23 Anthropology Essay Topics on Dorset Culture

23 Anthropology Essay Topics on Dorset Culture One of the cultures discussed during anthropology course is the Dorset culture. Since your instructor would want you to read more about it, you may be tasked with an essay on it. In order to make yours stand out from the rest of the class and ensure that you get a good grade as a result, use the following facts to support your essay. The timeline of the Dorset Culture is divided into four periods: The Early (beginning around 500 BCE) Middle Late (beginning around CE 800) Terminal (between CE 1000 to 1500) It is evident from various digging sites of the Dorset that the Thule migrated from east of Alaska during the Terminal period. The expression â€Å"Cape Dorset Culture† was coined by Diamond Jenness in 1925. While studying the mixed collections that came from the Hudson Strait Area and Cape Dorset on Baffin Island, Jenness deduced that the culture existed before the Thule. Dorset and later the Thule people were the civilization which the Norse encountered when they visited the area. Calling them skrà ¦ling, which means ‘primitive people’, the Norse noted that they were strong and gigantic in structure, but easily scared. The Dorset Culture existed in Foxe Basin, which is a shallow oceanic basin north of Hudson Bay. They primarily resided in the areas of Nunavik, Labrador, Newfoundland and Low Arctic of Nunavut. Common objects found at Dorset sites include snow knives. This indicates that this civilization had knowledge and experience in making snow houses, which are now known as Igloos. Dorset people had great interest in carved objects, especially bears, fish and birds carved from bone, wood, ivory. They are considered the pioneers in carving artwork as none of the artefacts dating before their arrival were carved with such finesse. The Newfoundland Museum houses a substantial collection dug from Dorset sites. The collection includes Polar Bears, Human Figures, Birds, Human Skull and many other artifacts. Most of these represent the Dorset’s beliefs, especially with regards to the supernatural. Nature aside, various archaeologists assume that the Dorset people’s artwork was mainly inspired from their spiritual beliefs. Although the Dorset people did trade with the Thule, they did not favor the idea of mingling with them and chose to remain isolated. Anthropologists assume that their art is what they used to differentiate themselves from the Thule. The Dorset Civilization descended from Paleo-Eskimos of the Pre-Dorset Culture in 2000-500 BCE. By comparison, the Dorset people had a more prosperous economy and lived in permanent snow and turf-made houses. The earlier Dorset people did not hunt land animals such as caribou or polar bear because they did not have proper hunting tools like the arrow and bow. They survived by hunting sea mammals like the seal, which they hunted by cutting holes in the ice. In the Nunavik region, the late Dorset populations mainly hunted all mammals except the large whales or fed on migratory birds. They were fond of collecting various species of plants as well. There is no genetic connection between the Dorset and the Thule people. This shows that intermarriage between the two cultures did not happen. However, there was trade of knowledge between them as the Thule engaged in seal-hole hunting after migrating. Seal-hole hunting was not part of the Thule’s tradition, which could mean that the Dorset people must have taught them this skill. According to some scholars, Sadlermiut were the last remnants of the Dorset culture, as their culture and dialect differed from the mainland Inuit. This theory came to light during a mitochondrial DNA research in 2002. Another similar research in 2012 showed no link between the Sadlermiut and the Dorset. The hunting technology of the Dorset Culture included small triangular end-blades which they hefted onto harpoon heads. The harpoons were then used to hunt seals as well as larger sea mammals such as the walrus and narwhals. The Dorset people used soapstones to make lamps and relied on seal oil to fuel them. They used these lamps for heating and illuminating their homes during long, cold and dark winter months. The Dorset people had ice-creepers which resemble the modern Alaskan ice-creeper. However, the Dorset Ice-creeper may have been inspired by a similar object before it was replaced altogether in that region. Traditionally settling on coasts, the Dorset civilization lived in small tent rings that often included axial features. Their houses were generally subterranean, and their tents were skin-covered in summer time. This shows that they were more inclined towards the sea than their descendants, the Palaeo-Eskimo, as most of their houses were exposed to headlands and outer islands. They also had structures that resemble long houses, which they used in periods of extreme winter. During this time, Dorset families gathered and lived under a single roof. Dorset people used to live in small, close-knit communities. Each village consisted of no more than 20 to 30 people. The Late Dorset flintknappers were capable of producing a wide number of lithic materials such as slate, basalt, agate, quartzite and soapstone. These were then used for making a variety of weapons and knife blades. The Dorset people often used driftwood for construction. It was rarely used, though, because it was not being brought in continuously due to long distances. It is believed that the Dorset people had transportation means to travel through sea as well as on land. There is evidence suggesting that they made sleds, which were either pulled by hand or animals. Some archaeologists also believe that the Dorset built Kayak-like Boats. A large number of bones found at Dorset sites were of various bird species. They were presumably captured by nets or on open water when they could not fly during molting season. The Dorset culture started to disappear from the Labrador around 1500 years ago. They disappeared entirely from Greenland and the Canadian arctic. Their initial displacement from outside of the island of Newfoundland may have been due to the Thule. Why did the Dorset People disappear is still under-debate. Thule people had a strong history of warfare and had better hunting weapons then them, which is probably why conflicts between the two civilizations may have eliminated the former. However, the Medieval Warm Period may have threatened the existence of the Dorset population beforehand. These should give sufficient insights for you to write an anthropology essay on Dorset culture. Additionally you may check our 20 topics and 1 sample essay on Dorset culture as well a complete guide to write an essay paper  in  anthropology. References: Michael Fortescue, Steven Jacobson Lawrence Kaplan (1994): Comparative Eskimo Dictionary; with Aleut Cognates (Alaska Native Language Center Research Paper 9) Robert McGhee (2005): The Last Imaginary Place: A Human History of the Arctic World Robert McGhee (2001): Ancient People of the Arctic Plummet Patrick, Lebel Serge (1997). Dorset Tip Fluting: A Second American Invention. Arctic Anthropology 34 (2): 132–162. Renouf M.A.P. (1999). Prehistory of Newfoundland Hunter-Gatherers: Extinctions or Adaptations?. World Archaeology 30 (3): 403–420 Bonvillain, Nancy. The Inuit. Chelsea House Publishers, 1995 britannica.com/topic/Dorset-culture

Sharknado Will Teach You All About Blogging

Sharknado Will Teach You All About Blogging Sharknado. It spawned 5,032 tweets per minute at its peak (about 84 tweets each second)for a movie about a hurricane that spawns tornadoes filled with sharks that bring down people, helicopters, and houses. What can you possibly learn from this movie about writing, beyond the fact that people will watch anything scripted for the SyFy channel? At first glance at the amazing poster, it seems pretty clear that there is little about blogging and content marketing in the movie. **SPOILER ALERT** The sharks dont win. Sure, they get in a few good bites, but in the end, the hero prevails and its messy.  In the interest of learning something meaningful from all of lifes experiences, even the ridiculous ones, can writers find anything of value from Sharknado and its messy heroic win? #Sharknado is a treasure trove of great writing advice. #NoReallyMost certainly. After watching Sharknado, you will realize that, as a writer, you need to: 1. Think on your feet. A change in the blogging schedule meant I had 40 minutes to write and publish a post. Those werent ideal conditions, but  I did it.  I cranked out the blog post, and sent it on to my team to peer review. Hayden responded back, after reviewing the post. I literally thought as I read: heres what 10+ years of blogging and disciplined writing gets you, he said, and it was the first time I realized that constant long-term blogging gives you the skills to think on your feet when you have to. Long-term practice makes it possible for you to think on your feet. It will happen. Youll have about 30 minutes to write a blog post. Can you do it?  Youd better have a process, the confidence, and the ability to write out of nowhere. Which leads to the next point 2. Maintain situational awareness. In Sharknado, the sharks were coming from every direction–air, land, water, living room–and the hero had to be aware of his surroundings to stay alive. In those moments when you have to think on your feet, youll need situational awareness. To pull off that last-minute blog post, I referred to a list of running ideas I am constantly tracking. Im always making note of blog ideas because in those intense moments,  youd better have something in the bank. And to get those things, youll have to be aware of how just about anything could be a blog post and bank those ideas.

Synthesis of Research Problem, Method, and Design-Hypothetical Designs Paper

Synthesis of Problem, Method, and Design-Hypothetical Designs - Research Paper Example These challenges, which include dishonesty and plausible misjudgments, threaten the quality of results obtained through this process. Certain measures have, however, been put in place, to ensure high quality, and error free results. There is little or no attention given to the efficiency and throughput of the crowdsourcing process or the integrity of the results obtained. It is argued that the numbers of task workers and tasks are always small, thereby, resulting in crowdsourcing techniques that are not conscious of the number of tasks, potential worker behavior and efficiency of the process. This research aims at proposing a crowdsourcing, result-improvement technique that is independent of task complexity and sizes and ensures result quality, integrity, as well as efficiency and throughput of the process. The hypothesis being studied in this case is that crowdsourcing result-improvement techniques that are task size and complexity independent ensures result integrity, quality, effi ciency as well as throughput. Hypothetical Designs Quantitative design This design will utilize experimental research method - methods that aim at maximizing replicability, generalizability, and objectivity of results; mostly concerned with prediction (Creswell, 2009). The focus will be to test several existing crowdsourcing techniques including r-Redundancy, v-Voting, and Vote Boosting techniques on a large number of tasks that will be handled by a large number of users. These techniques will be considered as experiment participants. The independent variable in this case would be the crowdsourcing techniques, including r-Redundancy, v-Voting, Vote Boosting techniques and the technique that this research will propose. The independent variables will be studied in two level; low task, less complex task level, and high number of tasks, and complex tasks level. Consequently, the dependent variables will be integrity, quality, efficiency as well as throughput. The experiment will be set in such a way that, the tasks set for testing, will have two definitive parameters including the accuracy of the tasks initial states and the number of options available per decision. 8 sets of 100,000 tasks with 3, 4, or 5 options and 75%, 85%, and 95% as the accuracy for the initial set tasks. There are about 4 to 10 decisions distributed normally. The user network or population tested also has two parameters including mean probability for committing errors and for dishonesty. Values of 3%, 6% and 20% are used for both dishonesty and making of errors. These probabilities were distributed exponentially over [0, 1] around their mean values. Simulations for about 40 input-aggregation functions with each one receiving one input are run repeatedly. For this experiment, the proposed quantitative hypothetical design is deemed to be extremely expensive even in the event that only few points in a parameter space are covered. Qualitative Design In this case, this research method will aim at understanding and discovering the perspectives, thoughts and experiences of previous researchers and participants in the same field in order to understand reality, purpose and meaning (Trochim & Donnelly, 2008). The focus will be to review and evaluate literature on previous and current research

Effect of Greek Financial Crisis on the British Economy Essay

Effect of Greek Financial Crisis on the British Economy - Essay Example During the early days of 2010 sovereign debt was a subject of attention for the whole world. Sovereign debt is the total debt owed by a sovereign country like Greece to its creditors. As a result of this crisis, there was a panic in the financial market worldwide and euro suffered a huge decline in its value. Greece was helped by the EU and IMF to provide them with loans that could rescue the situation. This can be a short term solution to the problem but the obligations of long term debt will still persist or may even get worse (Abboushi, â€Å"Abstract†). David Cameron in one of his statements warned that British economy will suffer more due to this euro zone crisis. It remains a threat to the future of euro. There had been a decline in the growth rate of employment, especially in public sector of UK. The investors are losing confidence in the market and the financial market in UK suffered a setback. A deep recession is on the cards if the situation is not handled carefully. More support for the banking sector is needed and the Government should be forced to take some emergency steps to help improve the financial system, before the crisis worsens further. Even though Britain is not a part of euro zone, still budgetary deficit concerns of the country should be addressed immediately. British banks already hold a considerable amount of debt in Greece, which can be an area of major concern. Moreover, with Greece defaulting to pay their debts, the problem can spread over nations like Spain and Italy where UK has a much larger investment. In addition to this, euro zone is one of the biggest trading partners of UK, so obviously this crisis can have an impounding effect on UK’s economy if other big European economies falter (PRLog, â€Å"How the Greek economy can affect us all†). 2. Changes in the NHS led by the UK Government UK government took a bold step towards reforming National Health Services (NHS) in the country. There had been many major changes in NHS structure due to this decision of UK government and it is for the first time in the history of NHS that such radical changes are taking place. Hospitals are no longer under NHS. General Practitioners (GPs) and not the management bodies now have a huge role and responsibility and are in charge of major part of the budget. This move resulted in abolition of all the 10 strategic health authorities as well as 152 primary care trusts which are the management bodies of NHS. Most of the budget of NHS is now in the hands of GPs only and they have the authority to plan out things accordingly. The GPs are now to decide on the spending of NHS. This new re-structuring of NHS gives way to the development of a new board which is independent of any kind of political influence. It is completely an independent body now and has control over its own accountability. Health of public is now the responsibility of local authorities. NHS industry is now more of a top-down design with GPs sit ting at the top level. The patients are now being provided with more information through ‘HealthWatch’, a new type of body specially designed for the purpose. The patients now have the option to choose the GP according to their own wish and get registered with them. Since its inception in the year 1948, NHS has never experienced such drastic changes. Now the question remains as to what benefits these changes will bring to the people and the

Microstructure-mechanical Property Relationships

Microstructure-mechanical Property Relationships Microstructure-mechanical property relationships in high strength low alloy steels for automotive applications Chapter 1 Introduction The production of steel is an ancient process which has evolved over time. Where and when Steel was first created is unknown and a topic of much debate, however most historians believe earliest production of steel originates from China from as early as 202BC. A later form of steel named Wootz Steel was later developed in India, which used wind power to fuel a furnace producing nearly pure steel. In the 11th century China developed steel further was the first country to mass produce steel. Two methods were developed. A berganesque method which produced inhomogeneous steel, and a process which that relied on partial decarbonisation through repeated forging under a cold blast, this was seen as the superior method, and one which lead on to the Bessemer process [1].The Bessemer process involved using a blast furnace to extract iron from its ore and is the basis of modern steel extraction. Steel is produced firstly by extracting iron from its ore. Iron extraction differs slightly from other metals as it can only be found naturally in oxide form. This means that a smelting process is required. This involves a reduction reaction followed by alloying with additional elements like carbon to stabilise and strengthen the steel. Iron smelting requires a high temperature which produces a ferrous material made of a combination of iron and steel. The addition of alloying elements such as carbon affect the materials properties greatly. Changing the temperature at which the iron is smelted affects the phase of the resultant steel, giving rise to the possibility of producing steels with varying properties which are suitable for a range of applications. In the automotive industry, body frames were originally made of hardwood. This was replaced in 1923 when the American Rolling Company developed steel sheet production. The wooden frames were inferior in energy absorption which was a big safety issue. Steel was also much easier to form than wood and did not warp over time. As the automobile has evolved over time, there has been an increasing public awareness of the environmental impact of the car. This has forced manufacturers to produce lighter cars which are more economical. This brought about the development of thin, highly formable sheet steel. The main competitor to steel in the automotive industry is Aluminium, which offers a much better strength to weight ratio and also a better resistance to corrosion. However steel is still the most commonly used material mainly due to lower production cost. Increasing competition from aluminium is forcing the development of modern steels. Steel naturally has a higher formability and elongation than aluminium which is one of the reasons it is used so extensively in the automotive sector. This can be seen in Figure 1.1: Figure 1.1- Yield strength vs total elongation of aluminium alloys and automotive steels [3] Ultra low carbon (ULC) steels are used commonly in the production of automobiles. Their, highy formability and suitability for hot dip galvanising make them very attractive to automobile producers[4]. Pressure is being put on the manufacturers to produce lightweight cars that minimise emissions without compromising safety. Metallic properties required to achieve this consist of a high tensile strength, high r- value, good ductility and also the ability to be made resistant to corrosion (either naturally or through the use of chemical surface treatment). Various high performance steels have been developed to meet these requirements, of these, one of the most important being HSLA steels. High strength low alloy steels provide a much better strength to weight ratio than conventional low carbon steels allowing for thinner grades to be used, saving weight. HSLA steels have a manganese content of up to 1.5%, as well as microalloying elements such as vanadium and titanium. HSLA steels are increasingly replacing traditional low carbon steels for many automotive parts. This is due to their ability to reduce weight without compromising strength and dent resistance. Typical applications include door-intrusion beams, chassis members, reinforcing and mounting brackets, steering and suspension parts, bumpers, and wheels [5]. High strength low alloy steel properties are determined by the way in which they are processed. High deep drawability, can be achieved through precipitation of elements by annealing to produce a strong {111} recrystallisation texture [7], producing highly formable steels which are very desirable for automotive applications. In this study, two grades of IFHS strips are studied. A titanium only stabilised steel grade and a titanium-vanadium stabilised steel grade. These have been treated using a Viking tube furnace and studied using a scanning electron microscope, Photoshop and Optilab Software. Both steel grades have been studied using carefully selected thermo mechanical heat treatment cycles. The heating variables are expected to cause varying effects to the mechanical properties and microstructure of the two materials. The addition of vanadium in one of the steel grades is also expected to influence the mechanical properties. With the data obtained from my experiments I hope to determine the optimum processing route for similar HSLA steels. Chapter 2 Aims Carry out selective batch annealing heat treatments on two microalloyed High Strength IF strip steels. Measure grain size evolution samples using scanning electron microscopy and quantitave optical microscopy techniques. Measure mechanical properties of obtained samples using hardness and tensile testing techniques Determine the optimum processing characteristics, resulting in optimum mechanical property characteristics. Chapter 3 Literature Review 3.1 AUTOMOTIVE STEELS Automotive manufacturers make use of many different metals in the production of cars, of which the most predominant being steel. This is for several reasons, steel is relatively easy to recycle in comparison with polymers and aluminium, and this is an issue which is growing in importance as the public are becoming more and more environmentally aware. Steel is also a very good material in terms of its practicality, as it is easily welded, has good formability, elongation and ductility. As the environmental impact of cars is becoming more and more important, stringent regulations regarding emissions are being forced upon manufacturers. One of the ways that manufacturers have chosen to meet these requirements is to make the cars lighter by switching from mild steel to high strength steel grades which enables components to have a thinner cross section, saving weight. The three main types of steels used in automobiles today are; Low strength (IF and mild steels), High strength (Carbon manganese, bake hardening, IFHS and HSLA) Advanced high strength steels (dual-phase, complex phase, transformation induced plasticity and matensitic steels) These steel types can be seen below on figure 3.1 comparing their elongation and strength. Figure 3.1: Classification of automotive steels [8]. 3.1.1 Mild Steels Mild steels are normally found in two different forms for automotive purposes. Drawn Quality and Aluminium killed. These are both cheap to manufacture are used for high volume parts. They are usually of a ferrite microstructure. [8] 3.1.2 Interstitial Free Steels IF steels are used for car body panels extensively due largely to their deep drawability. The high elongation achieved in comparison with other steel grades can be seen in figure 3.1.The main characteristic of IF steel is a low carbon and nitrogen content. These elements are removed from solution by adding specific elements for alloys. Commonly used elements for this microalloying process include Manganese, Sulphur, Titanium and Niobium. As well as a deep drawability, IF steel have low yield strength but a poor dent resistance which is undesirable for certain automotive applications [6] Bake Hardening Steels BH steels keep carbon in solution either during processing before it is precipitated or during the paint baking state [8]. This strengthens the steel through solid solution strengthening, resulting in steel with both high formability and high strength. 3.1.4 Carbon-Manganese Steels Carbon-manganese steels are solid solution strengthened and are used in strip form on automobile bodies, although they are becoming replaced by lighter steel grades. They offer high drawability and are relatively cheap to produce. [9] D.T.Llewellyn: Steel: Metallurgy and Applications, Butterworth-Heinemann Ltd, Great Britain, 1992. 3.1.5 High-Strength Low-Alloy (HSLA) Steels HSLA steels are strengthened through the addition of microallying elements. These react with the carbon and nitrogen within the steel to form carbides and nitrides. Common elements include Nb, V and Ti. The resultant steel has both high strength and a high formability due to very fine grain sizes [10] Dual-Phase (DP) Steels Dual-phase steels contain two phases within their microstructure. These are ferrite and martensite. This two phase structure is produced through a complex series of contolled heating and cooling. Martensite regions are produced by heating and rapidly cooling. It is the marteniste regions tha give the hardness to the material where as the ferrite regions are much softer. The structure of DP steels takes advantages of the properties of each of the phases, where the hard maternsite regions are surrounded by softer ferrite which reduces brittleness, shown in figure 3.2. DP steel has good ductility, low yield strength but high work hardening rate [8]. Figure 3.2: Microstructure of DP steel [8]. 3.1.7 Transformation-Induced Plasticity (TRIP) Steels TRIP steels consist of a mainly ferrite microstructure with a low austenite content within the matrix. An isothermal hold during production at an intermediate temperature is used to produce bainite [8]. Strength is increased by transformationing of austenite regions to harder martensite regions. TRIP steels have a good work hardening rate and good strength. Work hardening in TRIP steels continues at higher strain levels than those of DP steels so TRIP steels is a superior material from this aspect. Figure 3.3 shows the multi phase microstructure of TRIP steel. Figure 3.3: Microstructure of TRIP steel [8]. Martensitic (MS) Steel MS steels are mainly of a martensitic microstructure but contain small amounts of ferrite and bainite. During heat treatment the steel is rapidly cooled transforming austenite into martensite. This gives a very high tensile strength since martensite produces a very hard material, but the drawback is this also gives a low formability. In order to overcome this low formability further processing such as heat treatments must be undertaken. [11] 3.1.9 High Strength Interstitial Free (HS-IF) Steels HSIF steels are strengthened through the addition of microalloying elements. Commonly used alloying elements include P, B, Si, Mn, Ti, N. The combinations in which the microalloying elements are used have an effect on the properties of resultant steel allowing a range of requirements to be met. HSIF steels can produce nearly twice the potential yield strength as conventional IF steels, although there is a reduction in formability. 3.2 Microalloying Elements 3.2.1 Carbon Carbon is one of the most important interstitial elements within steel, giving very different mechanical properties as its percentage content is altered and therefore must be studied in depth. Carbon is an element commonly found in automotive steels due to its high strength properties. Although adding carbon increases strength, it also affects the formability, i.e. its deep drawability. A set of experiments were carried out to determine the effect of carbon content within steel. When analysing the tensile test results it was noted that the ultimate tensile strength, the proof stress and the yield stress all increased as the amount of carbon increased in the steel. The plastic region as well as the general elongation of the steel under tensile stress decreased as the carbon content increased. These are significant changes in the mechanical properties. Hardness and Tensile strength increase as carbon content approaches 0.85% C as shown in figure 3.4. The elongation percentage decreases as the carbon content increases. This suggests that the more carbon present in the material, the stronger and less ductile it becomes. Figure 3.4: Affect of Carbon content in Steel Yield Strength Carbon content influences the yield strength of steel because carbon molecules fit into the interstitial crystal lattice sites of the body-centred cubic arrangement of the iron molecules. The interstitial carbons make it more difficult for any dislocation to occur as it reduces mobility. This has a hardening effect on the metal. Phase diagram Using the phase diagram one can understand why the properties of steels change with differing carbon content. Figure 3.5: Phase Diagram The gamma phase, relates to an Austenite range which has a Face Centred Cubic (FCC) structure. The alpha phase relates to a ferritic Body Centered Cubic crystal structure. Ferrite is found extensively in automotive steels, its BCC structure is much less dense than the FCC of austenite which makes it easily formable and therefore relatively cheap to manufacture. Fe3C refers to cementite and the mixture of alpha (ferrite) + cementite is called pearlite. On the phase diagram steels only apply up to about 1.4% carbon. The eutectoid point is at 723 degrees and is where there are three phases in equilibrium. The eutectoid composition is Fe-0.83%C. The reaction that happens at the eutectoid point is: austenite > ferrite + cementite gamma > alpha + Fe3C High carbon content means a greater precense of austenite, whereas low carbon content will give less austenite and a more ferritic microstructure. The affect of these differing microstructures is reflected in their mechanical properties. This is because Ferrite is soft and ductile and Cementite is hard and brittle. It can be seen by looking at figure 3.5 that as the carbon content is increased, strength increases. This relationship occurs up to the eutectoid point after which it starts to reduce. This where cementite grain-boundaries are created. The figure below shows how the varying content of carbon in steel affects its properties and suitability for different applications. Figure 3.6 Carbon Steel Applications Lever rule The lever rule can be used to calculate expected proportions of the phases present in each of the tested carbon steel specimens. These values can then be compared to the values obtained through testing. Figure 3.7 Lever Rule Calculations: a = Ferrite a + Fe3C = Pearlite 0.1wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.1)   Ã‚   = 0.897   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8-0.02) % Pearlite= (0.1- 0.02)    = 0.103   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8- 0.02) 0.4wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.4)   Ã‚   = 0.513   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8-0.02) % Pearlite= (0.4- 0.02)    = 0.487   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8- 0.02) 0.8wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.8)    = 0   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   (0.8-0.02) % Pearlite= (0.8- 0.02)   = 1   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   (0.8- 0.02) These results suggest that as the carbon content increases the pearlite to ferrite ratio also increases. So the ratio of Pearlite to ferrite increases as carbon content is increased the material is made harder, stronger and more brittle but less ductile. These results obtained using the lever rule support the results obtained from the tensile test, showing the steel with the highest carbon content to be the least ductile and most brittle. The results are also supported by the findings from the hardness test which shows the steel with the highest carbon content to be the hardest. 3.2.2 Titanium The addition of Titanium to IFHS steels is particularly useful in the manufacturing of strip steels where good drawability is a requirement. The addition of Ti or Nb results in a lower Yield Strength/Tensile Strength ratio giving an increased formability. This can be seen in figure 3.8. When Titanium reacts with Carbon and Nitrogen it forms TiC and TiN, these precipitates work to delay recrystallisation of austenite, thus refining the grains to a favourable smaller size [12]. Figure 3.8: The effect of Titanium and Niobium on Yield Srength/UTS ratio [12] Titanium precipitates exist within steels and these affect the mechanical properties. TiN precipitates help to promote recrystallisation and encourage the {111} texture. TiS precipitates are commonly found in the austenite region as well as Ti4C2S2, Ti4C2S2 is formed by reacting with Carbon and in the highest regions of the austenite range there is little to no Carbon. These conditions are created at very high temperatures similar to those during hot rolling processes. This leaves the steel highly formable and suitable for deep drawability application such as car body panels. It is very difficult however to form Ti4C2S2 as it is less stable than TiS, although it can be encouraged through specific heat treatment processes. [13] 3.2.3 Vanadium Titanium is commonly added with Niobium to steels to increase formability through precipitation. However these additions can result in a retardation of recrystallisation meaning a higher temperature or longer soaking time is required for recyrstallisation to occur. Vanadium offers a replacement to Niobium in the form of carbides and nitrides, VC and VN, which does not cause such a drastic retardation of recyrstallisation. This is attractive to manufacturers as lower temperatures and shorter processing time during annealing are more cost effective. The effectiveness of Vandium in essentially lowering the recrystallisation temperature is shown in Figure 3.9. Figure 3.9: The effect of Ti + Nb, Ti + V and V stabilised steels on the Temperature for Complete Recrystallisation in 30 Seconds [44]. Figure 3.9 shows that the V only stabilised steel recrystallises at a lower temperature than the TiV and TiNb steels. 3.2.4 Sulphur Sulphur is found in all steels including Interstitial Free High Strength Steels. It acts as an interstitial elements and other elements to form precipitates such as TiS, MnS and Ti4C2S2. These precipitates have different effects on the mechanical properties of the material. In particular the precipitation of carbosulphides is beneficial to the steel as this causes the steel to form in the austenite range and helps to reduce the TiC formation which could occur during heat treatment processing and cause the material to become less likely to form the {111} texture.[13] Promoting Ti4C2S2 therefore encourages the formation of the favourable {111} texture, increasing the formability of the material. In order for Ti4C2S2 to develop, Sulphur, Carbon and Titanium must all be present, and processed in such a way as to form a reaction, which can difficult. 3.2.5 Niobium Niobium if found extensively in IFHS Steels reacting with carbon to form carbides such as NbC. Solute Niobium can be used to segregate austenite and ferrite grain boundaries and increase the strength of the austenite region [14]. As Niobium content increases the r-value decreases as well as the ductility. Generally Nb content is minimised as much as possible as the positive effect it has on strength in the austenite region is relatively small and is outweighed by the negative effect it has on ductility. Boron can be used instead of Niobium as it has a much greater effect on strength than Niobium. This can be seen in figure 3.9 Figure 3.9: Average Flow Stress vs. Temperature for B, C, and Nb and Mo solutes in steel [15]. 3.2.6 Phosphorus Phosphorus, P, is a common alloy of IFHS steel, offering increases in strength through solid solution hardening. Adding Phosphorus can also have a direct effect on the grains within a structure by increasing the Hall-Petch slope (described below). Adding P however can have a negative effect on the brittleness of the material. This can be particularly problematic during the cold working process where brittle fracture is a distinct possibility. The Hall-Petch relationship says that as the grain size decreases the yield strength of a material increases. This is due to the dislocations piling up at grain boundaries, which act as barriers to dislocation movement at low temperatures. If the grain size is large, then a high number of dislocations will pile up at the edge of the slip plane. When the stress exceeds a critical value the dislocations cross the boundary. So the larger the grain size, the lower the applied stress required to reach this critical stress at the grain boundary, meaning the larger the grain size, the lower the yield stress due to easier dislocation movement. This is true down to a grain size of 100nm. Below this size the yield strength remains constant or starts to decrease. This is effect is called the reverse Hall-Petch effect. Phosphorus along with Silicon and Manganese are added via solid solution strengthening to strengthen steel allowing for a thinner sheet of metal to be used for car body panels, and thus reducing the weight. Phosphorus is the most effective out of the three elements in terms of cost and strengthening effect. This can be seen below in figure 3.11 where the effects of P and S additions are compared. Figure 3.11: Comparison of Stress vs. Temperature between Phosphorus and Silicon microalloyed Steels [16]. Phosphorus is also found in the form of FeTiP precipitates. These precipitates have a negative affect on strength and drawability. The effects of these precipitates are greater in batch annealed steels than in continuous steels. This is due to the long soaking times required in batch annealing which provides optimum conditions and sufficient time for these precipitates to form [17]. 3.2.7 Manganese Manganese is added through solid solution strengthening to IFHS steels in a low concentration in order to react with the Sulphur to produce MnS precipitates. These MnS precipitates act to refine grain structure during processing when there is a transformation in phase between austenite and ferrite. Mn is to strengthen steels through solid solution strengthening. The effect of Mn is relatively small in the austenite range but compared to the ferrite range. This is due to a difference in Mn solubility between the austenite and ferrite ranges. Where Mn in ferrite is 10wt% higher than in austenite [18] Mn acts to stabilize the austenite region and slows down the rate of austenite transformation and also the temperature at which the transformation takes place. This lowering of transformation temperature between austenite and ferrite promotes finer grains through grain refinement. Mn can be found in oxide and sulphide forms as well as combinations of the two, oxysulphides. These oxides and sulphides act to deoxidise and desulphurise the steel. When in sulphide form, MnS helps to reduce embrittlement of steel without reducing hardness. When mixed with common impurities such as Al2O3, SiO2, MnO, CaO, CaS and FeS an increase in hardness and strength occurs [19]. When in the oxide form, MnO at the surface acts a barrier layer to prevent surface oxidisation and corrosion. 3.2.8 Silicon Silicon is a useful element and is used to increase the strength through solid solution strengthening, although there is a compromise as increasing Silicon content decreases ductility. Silicon is also found in oxide form, as silicon dioxide. Silicon dioxide is found with Manganese Oxide or as Silicomanganese to give a strong oxygen stabilisation and prevent corrosion of steel. [20]. 3.2.9 Aluminium Aluminium is used to deoxidise steel by reacting with oxygen within the steel to form Al2O3. These Aluminium Oxides are later removed leaving an oxygen free steel. However the low density of Aluminium means that oxidisation could occur at the steel interface resulting in corrosion. Aluminium content can have a negative effect on formability. This is due to the precipitation of AlN during recrystallisation preventing the {111} development and thus preventing the formation of finer grains. So minimising the amount of AlN in solid solution results in higher formability. A more stable alternative to AlN which is commonly used in IFHS steels is TiN. 3.3 Hardening and processing There are many different compositions of steel which offer various advantageous properties. The main reason for altering composition or alloying is to strengthen the material. This can be done in several ways; 3.3.1 Precipitation strengthening This process uses heat treatment to raise the yield strength of a material. As temperature changes during heat treatment processing, fine particles are produced due to differing melting points of impurities. These fine particles impede dislocation movement. This in turn reduces the ductility and plasticity of the material and increases its hardness. 3.2.2 Solid – solution strengthening Solid solution strengthening is a form of alloying. It is a commonly used technique to improve the strength of a material. Atoms of the alloying element are added to the crystal lattice of the base metal via diffusion. There are two ways in which this can occur, depending on the size of the alloying alloying element. These are via substitutional solid solution, and interstitial solid solution. Substitutional solid solution This takes place when the sizes of the alloying atoms are equal in size to the base atoms, (Differing in size by no more than 15% according to the Hume-Rothery rules) The alloying atoms replace the solvent atoms and assume their lattice positions. The solute atoms can produce a slight distortion of the crystal lattice, due to the size variation. The amount of distortion increases with the size of the solute atom. This distortion has an effect on microstructural properties. The formation of slip planes is altered making dislocation movement more difficult, meaning a higher stress is required to move the dislocations. This gives the material a higher strength. A generalisation associated with substitution is that large substitutional atoms put the structure under compressive stress, and small substitutional atoms give tensile stress. Interstitial solid solution This occurs when the alloying atoms are much smaller than the base atoms. The alloying atoms fit into spaces within the crystal lattice. This is the case with carbon in steel, where carbon is a solute in the iron solvent lattice. The carbon atoms are less than half the size of the iron atoms so an interstitial solid solution forms. 3.3.3 Processing The final properties of steel are greatly affected by the manner in which it is first made and then processed. Typical processes include steel making, casting, hot and cold rolling and annealing. Each individual process has a distinct affect on the properties of the steel. To make the steel free from interstitial elements, Ti and Nb are often added to react with interstitials after a process called vacuum degassing. Vacuum degassing is the name given to the process where a metal is melted within a vacuum and the gasses are evaporated out. Hot and cold rolling Hot rolling is the first process to take place after steel making. After steel has been cast into uniform slabs or billets it is the rolled under a high temperature to reduce its cross sectional thickness. The hot rolling process is undertaken at a temperature above that at which recrystallisation occurs. Hot rolling reduces allows recrysallisation to occur during processing (dynamic recrystallisation) and the material is left stress free due the new grain nucleation and equiaxed grains. Effect of hot working on microstructure: Hot working occurs at high temperatures, this means that there is often enough thermal energy present for recrsytallisation to occur during deformation. This is called dynamic recrystallisation and it occurs with most metals, apart from aluminium. Recrystallisation occurs during the working process and also as the metal is cooling. Dynamic recrystallisation occurs by new grains nucleating at existing grain boundaries. The amount of recyrstallisation depends on several factors. It depends on the strain rate, temperature and amount of strain on the metal. Generally, as strain within the metal increases, so does the amount of recrystallisation. Cold working is when steel is plastically deformed below its recrystallisation temperature. This process increases the yield strength due to the plastic deformation causing slight defects within the microstructure of the metal. These defects make it difficult for slip planes to move. The grain size of the metal is also reduced, making the material harder through a process called Hall petch hardening. Hall Petch hardening, also known as grain boundary strengthening, increases materials strength by altering the grain size. This is because grain boundaries act as barriers to dislocation movement. So altering the grain size, through hot and cold rolling at various temperatures and rates will have an effect on dislocation movement and yield strength. Cold working will increase the strength of the metal by making it increasingly difficult for slip to occur. However as more and more of the larger grains split to form smaller grains the ductility is greatly reduced as the material hardens. Eventually fracture would occur. To avoid this, the material is annealed. Cold working occurs at a temperature below 0.4 of the metals melting point. Some of the energy created by the process is expelled as heat but some energy is stored within the structure putting it into a high energy state. The energy is stored within the grain boundaries of the deformed crystals and within the stress fields of the dislocations created through the plastic deformation. The structure is highly stressed after cold working and would prefer to return to its former low energy state. It is howeve Microstructure-mechanical Property Relationships Microstructure-mechanical Property Relationships Microstructure-mechanical property relationships in high strength low alloy steels for automotive applications Chapter 1 Introduction The production of steel is an ancient process which has evolved over time. Where and when Steel was first created is unknown and a topic of much debate, however most historians believe earliest production of steel originates from China from as early as 202BC. A later form of steel named Wootz Steel was later developed in India, which used wind power to fuel a furnace producing nearly pure steel. In the 11th century China developed steel further was the first country to mass produce steel. Two methods were developed. A berganesque method which produced inhomogeneous steel, and a process which that relied on partial decarbonisation through repeated forging under a cold blast, this was seen as the superior method, and one which lead on to the Bessemer process [1].The Bessemer process involved using a blast furnace to extract iron from its ore and is the basis of modern steel extraction. Steel is produced firstly by extracting iron from its ore. Iron extraction differs slightly from other metals as it can only be found naturally in oxide form. This means that a smelting process is required. This involves a reduction reaction followed by alloying with additional elements like carbon to stabilise and strengthen the steel. Iron smelting requires a high temperature which produces a ferrous material made of a combination of iron and steel. The addition of alloying elements such as carbon affect the materials properties greatly. Changing the temperature at which the iron is smelted affects the phase of the resultant steel, giving rise to the possibility of producing steels with varying properties which are suitable for a range of applications. In the automotive industry, body frames were originally made of hardwood. This was replaced in 1923 when the American Rolling Company developed steel sheet production. The wooden frames were inferior in energy absorption which was a big safety issue. Steel was also much easier to form than wood and did not warp over time. As the automobile has evolved over time, there has been an increasing public awareness of the environmental impact of the car. This has forced manufacturers to produce lighter cars which are more economical. This brought about the development of thin, highly formable sheet steel. The main competitor to steel in the automotive industry is Aluminium, which offers a much better strength to weight ratio and also a better resistance to corrosion. However steel is still the most commonly used material mainly due to lower production cost. Increasing competition from aluminium is forcing the development of modern steels. Steel naturally has a higher formability and elongation than aluminium which is one of the reasons it is used so extensively in the automotive sector. This can be seen in Figure 1.1: Figure 1.1- Yield strength vs total elongation of aluminium alloys and automotive steels [3] Ultra low carbon (ULC) steels are used commonly in the production of automobiles. Their, highy formability and suitability for hot dip galvanising make them very attractive to automobile producers[4]. Pressure is being put on the manufacturers to produce lightweight cars that minimise emissions without compromising safety. Metallic properties required to achieve this consist of a high tensile strength, high r- value, good ductility and also the ability to be made resistant to corrosion (either naturally or through the use of chemical surface treatment). Various high performance steels have been developed to meet these requirements, of these, one of the most important being HSLA steels. High strength low alloy steels provide a much better strength to weight ratio than conventional low carbon steels allowing for thinner grades to be used, saving weight. HSLA steels have a manganese content of up to 1.5%, as well as microalloying elements such as vanadium and titanium. HSLA steels are increasingly replacing traditional low carbon steels for many automotive parts. This is due to their ability to reduce weight without compromising strength and dent resistance. Typical applications include door-intrusion beams, chassis members, reinforcing and mounting brackets, steering and suspension parts, bumpers, and wheels [5]. High strength low alloy steel properties are determined by the way in which they are processed. High deep drawability, can be achieved through precipitation of elements by annealing to produce a strong {111} recrystallisation texture [7], producing highly formable steels which are very desirable for automotive applications. In this study, two grades of IFHS strips are studied. A titanium only stabilised steel grade and a titanium-vanadium stabilised steel grade. These have been treated using a Viking tube furnace and studied using a scanning electron microscope, Photoshop and Optilab Software. Both steel grades have been studied using carefully selected thermo mechanical heat treatment cycles. The heating variables are expected to cause varying effects to the mechanical properties and microstructure of the two materials. The addition of vanadium in one of the steel grades is also expected to influence the mechanical properties. With the data obtained from my experiments I hope to determine the optimum processing route for similar HSLA steels. Chapter 2 Aims Carry out selective batch annealing heat treatments on two microalloyed High Strength IF strip steels. Measure grain size evolution samples using scanning electron microscopy and quantitave optical microscopy techniques. Measure mechanical properties of obtained samples using hardness and tensile testing techniques Determine the optimum processing characteristics, resulting in optimum mechanical property characteristics. Chapter 3 Literature Review 3.1 AUTOMOTIVE STEELS Automotive manufacturers make use of many different metals in the production of cars, of which the most predominant being steel. This is for several reasons, steel is relatively easy to recycle in comparison with polymers and aluminium, and this is an issue which is growing in importance as the public are becoming more and more environmentally aware. Steel is also a very good material in terms of its practicality, as it is easily welded, has good formability, elongation and ductility. As the environmental impact of cars is becoming more and more important, stringent regulations regarding emissions are being forced upon manufacturers. One of the ways that manufacturers have chosen to meet these requirements is to make the cars lighter by switching from mild steel to high strength steel grades which enables components to have a thinner cross section, saving weight. The three main types of steels used in automobiles today are; Low strength (IF and mild steels), High strength (Carbon manganese, bake hardening, IFHS and HSLA) Advanced high strength steels (dual-phase, complex phase, transformation induced plasticity and matensitic steels) These steel types can be seen below on figure 3.1 comparing their elongation and strength. Figure 3.1: Classification of automotive steels [8]. 3.1.1 Mild Steels Mild steels are normally found in two different forms for automotive purposes. Drawn Quality and Aluminium killed. These are both cheap to manufacture are used for high volume parts. They are usually of a ferrite microstructure. [8] 3.1.2 Interstitial Free Steels IF steels are used for car body panels extensively due largely to their deep drawability. The high elongation achieved in comparison with other steel grades can be seen in figure 3.1.The main characteristic of IF steel is a low carbon and nitrogen content. These elements are removed from solution by adding specific elements for alloys. Commonly used elements for this microalloying process include Manganese, Sulphur, Titanium and Niobium. As well as a deep drawability, IF steel have low yield strength but a poor dent resistance which is undesirable for certain automotive applications [6] Bake Hardening Steels BH steels keep carbon in solution either during processing before it is precipitated or during the paint baking state [8]. This strengthens the steel through solid solution strengthening, resulting in steel with both high formability and high strength. 3.1.4 Carbon-Manganese Steels Carbon-manganese steels are solid solution strengthened and are used in strip form on automobile bodies, although they are becoming replaced by lighter steel grades. They offer high drawability and are relatively cheap to produce. [9] D.T.Llewellyn: Steel: Metallurgy and Applications, Butterworth-Heinemann Ltd, Great Britain, 1992. 3.1.5 High-Strength Low-Alloy (HSLA) Steels HSLA steels are strengthened through the addition of microallying elements. These react with the carbon and nitrogen within the steel to form carbides and nitrides. Common elements include Nb, V and Ti. The resultant steel has both high strength and a high formability due to very fine grain sizes [10] Dual-Phase (DP) Steels Dual-phase steels contain two phases within their microstructure. These are ferrite and martensite. This two phase structure is produced through a complex series of contolled heating and cooling. Martensite regions are produced by heating and rapidly cooling. It is the marteniste regions tha give the hardness to the material where as the ferrite regions are much softer. The structure of DP steels takes advantages of the properties of each of the phases, where the hard maternsite regions are surrounded by softer ferrite which reduces brittleness, shown in figure 3.2. DP steel has good ductility, low yield strength but high work hardening rate [8]. Figure 3.2: Microstructure of DP steel [8]. 3.1.7 Transformation-Induced Plasticity (TRIP) Steels TRIP steels consist of a mainly ferrite microstructure with a low austenite content within the matrix. An isothermal hold during production at an intermediate temperature is used to produce bainite [8]. Strength is increased by transformationing of austenite regions to harder martensite regions. TRIP steels have a good work hardening rate and good strength. Work hardening in TRIP steels continues at higher strain levels than those of DP steels so TRIP steels is a superior material from this aspect. Figure 3.3 shows the multi phase microstructure of TRIP steel. Figure 3.3: Microstructure of TRIP steel [8]. Martensitic (MS) Steel MS steels are mainly of a martensitic microstructure but contain small amounts of ferrite and bainite. During heat treatment the steel is rapidly cooled transforming austenite into martensite. This gives a very high tensile strength since martensite produces a very hard material, but the drawback is this also gives a low formability. In order to overcome this low formability further processing such as heat treatments must be undertaken. [11] 3.1.9 High Strength Interstitial Free (HS-IF) Steels HSIF steels are strengthened through the addition of microalloying elements. Commonly used alloying elements include P, B, Si, Mn, Ti, N. The combinations in which the microalloying elements are used have an effect on the properties of resultant steel allowing a range of requirements to be met. HSIF steels can produce nearly twice the potential yield strength as conventional IF steels, although there is a reduction in formability. 3.2 Microalloying Elements 3.2.1 Carbon Carbon is one of the most important interstitial elements within steel, giving very different mechanical properties as its percentage content is altered and therefore must be studied in depth. Carbon is an element commonly found in automotive steels due to its high strength properties. Although adding carbon increases strength, it also affects the formability, i.e. its deep drawability. A set of experiments were carried out to determine the effect of carbon content within steel. When analysing the tensile test results it was noted that the ultimate tensile strength, the proof stress and the yield stress all increased as the amount of carbon increased in the steel. The plastic region as well as the general elongation of the steel under tensile stress decreased as the carbon content increased. These are significant changes in the mechanical properties. Hardness and Tensile strength increase as carbon content approaches 0.85% C as shown in figure 3.4. The elongation percentage decreases as the carbon content increases. This suggests that the more carbon present in the material, the stronger and less ductile it becomes. Figure 3.4: Affect of Carbon content in Steel Yield Strength Carbon content influences the yield strength of steel because carbon molecules fit into the interstitial crystal lattice sites of the body-centred cubic arrangement of the iron molecules. The interstitial carbons make it more difficult for any dislocation to occur as it reduces mobility. This has a hardening effect on the metal. Phase diagram Using the phase diagram one can understand why the properties of steels change with differing carbon content. Figure 3.5: Phase Diagram The gamma phase, relates to an Austenite range which has a Face Centred Cubic (FCC) structure. The alpha phase relates to a ferritic Body Centered Cubic crystal structure. Ferrite is found extensively in automotive steels, its BCC structure is much less dense than the FCC of austenite which makes it easily formable and therefore relatively cheap to manufacture. Fe3C refers to cementite and the mixture of alpha (ferrite) + cementite is called pearlite. On the phase diagram steels only apply up to about 1.4% carbon. The eutectoid point is at 723 degrees and is where there are three phases in equilibrium. The eutectoid composition is Fe-0.83%C. The reaction that happens at the eutectoid point is: austenite > ferrite + cementite gamma > alpha + Fe3C High carbon content means a greater precense of austenite, whereas low carbon content will give less austenite and a more ferritic microstructure. The affect of these differing microstructures is reflected in their mechanical properties. This is because Ferrite is soft and ductile and Cementite is hard and brittle. It can be seen by looking at figure 3.5 that as the carbon content is increased, strength increases. This relationship occurs up to the eutectoid point after which it starts to reduce. This where cementite grain-boundaries are created. The figure below shows how the varying content of carbon in steel affects its properties and suitability for different applications. Figure 3.6 Carbon Steel Applications Lever rule The lever rule can be used to calculate expected proportions of the phases present in each of the tested carbon steel specimens. These values can then be compared to the values obtained through testing. Figure 3.7 Lever Rule Calculations: a = Ferrite a + Fe3C = Pearlite 0.1wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.1)   Ã‚   = 0.897   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8-0.02) % Pearlite= (0.1- 0.02)    = 0.103   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8- 0.02) 0.4wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.4)   Ã‚   = 0.513   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8-0.02) % Pearlite= (0.4- 0.02)    = 0.487   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  (0.8- 0.02) 0.8wt%C Normalised Steel Tensile Specimen: % Ferrite = (0.8- 0.8)    = 0   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   (0.8-0.02) % Pearlite= (0.8- 0.02)   = 1   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   (0.8- 0.02) These results suggest that as the carbon content increases the pearlite to ferrite ratio also increases. So the ratio of Pearlite to ferrite increases as carbon content is increased the material is made harder, stronger and more brittle but less ductile. These results obtained using the lever rule support the results obtained from the tensile test, showing the steel with the highest carbon content to be the least ductile and most brittle. The results are also supported by the findings from the hardness test which shows the steel with the highest carbon content to be the hardest. 3.2.2 Titanium The addition of Titanium to IFHS steels is particularly useful in the manufacturing of strip steels where good drawability is a requirement. The addition of Ti or Nb results in a lower Yield Strength/Tensile Strength ratio giving an increased formability. This can be seen in figure 3.8. When Titanium reacts with Carbon and Nitrogen it forms TiC and TiN, these precipitates work to delay recrystallisation of austenite, thus refining the grains to a favourable smaller size [12]. Figure 3.8: The effect of Titanium and Niobium on Yield Srength/UTS ratio [12] Titanium precipitates exist within steels and these affect the mechanical properties. TiN precipitates help to promote recrystallisation and encourage the {111} texture. TiS precipitates are commonly found in the austenite region as well as Ti4C2S2, Ti4C2S2 is formed by reacting with Carbon and in the highest regions of the austenite range there is little to no Carbon. These conditions are created at very high temperatures similar to those during hot rolling processes. This leaves the steel highly formable and suitable for deep drawability application such as car body panels. It is very difficult however to form Ti4C2S2 as it is less stable than TiS, although it can be encouraged through specific heat treatment processes. [13] 3.2.3 Vanadium Titanium is commonly added with Niobium to steels to increase formability through precipitation. However these additions can result in a retardation of recrystallisation meaning a higher temperature or longer soaking time is required for recyrstallisation to occur. Vanadium offers a replacement to Niobium in the form of carbides and nitrides, VC and VN, which does not cause such a drastic retardation of recyrstallisation. This is attractive to manufacturers as lower temperatures and shorter processing time during annealing are more cost effective. The effectiveness of Vandium in essentially lowering the recrystallisation temperature is shown in Figure 3.9. Figure 3.9: The effect of Ti + Nb, Ti + V and V stabilised steels on the Temperature for Complete Recrystallisation in 30 Seconds [44]. Figure 3.9 shows that the V only stabilised steel recrystallises at a lower temperature than the TiV and TiNb steels. 3.2.4 Sulphur Sulphur is found in all steels including Interstitial Free High Strength Steels. It acts as an interstitial elements and other elements to form precipitates such as TiS, MnS and Ti4C2S2. These precipitates have different effects on the mechanical properties of the material. In particular the precipitation of carbosulphides is beneficial to the steel as this causes the steel to form in the austenite range and helps to reduce the TiC formation which could occur during heat treatment processing and cause the material to become less likely to form the {111} texture.[13] Promoting Ti4C2S2 therefore encourages the formation of the favourable {111} texture, increasing the formability of the material. In order for Ti4C2S2 to develop, Sulphur, Carbon and Titanium must all be present, and processed in such a way as to form a reaction, which can difficult. 3.2.5 Niobium Niobium if found extensively in IFHS Steels reacting with carbon to form carbides such as NbC. Solute Niobium can be used to segregate austenite and ferrite grain boundaries and increase the strength of the austenite region [14]. As Niobium content increases the r-value decreases as well as the ductility. Generally Nb content is minimised as much as possible as the positive effect it has on strength in the austenite region is relatively small and is outweighed by the negative effect it has on ductility. Boron can be used instead of Niobium as it has a much greater effect on strength than Niobium. This can be seen in figure 3.9 Figure 3.9: Average Flow Stress vs. Temperature for B, C, and Nb and Mo solutes in steel [15]. 3.2.6 Phosphorus Phosphorus, P, is a common alloy of IFHS steel, offering increases in strength through solid solution hardening. Adding Phosphorus can also have a direct effect on the grains within a structure by increasing the Hall-Petch slope (described below). Adding P however can have a negative effect on the brittleness of the material. This can be particularly problematic during the cold working process where brittle fracture is a distinct possibility. The Hall-Petch relationship says that as the grain size decreases the yield strength of a material increases. This is due to the dislocations piling up at grain boundaries, which act as barriers to dislocation movement at low temperatures. If the grain size is large, then a high number of dislocations will pile up at the edge of the slip plane. When the stress exceeds a critical value the dislocations cross the boundary. So the larger the grain size, the lower the applied stress required to reach this critical stress at the grain boundary, meaning the larger the grain size, the lower the yield stress due to easier dislocation movement. This is true down to a grain size of 100nm. Below this size the yield strength remains constant or starts to decrease. This is effect is called the reverse Hall-Petch effect. Phosphorus along with Silicon and Manganese are added via solid solution strengthening to strengthen steel allowing for a thinner sheet of metal to be used for car body panels, and thus reducing the weight. Phosphorus is the most effective out of the three elements in terms of cost and strengthening effect. This can be seen below in figure 3.11 where the effects of P and S additions are compared. Figure 3.11: Comparison of Stress vs. Temperature between Phosphorus and Silicon microalloyed Steels [16]. Phosphorus is also found in the form of FeTiP precipitates. These precipitates have a negative affect on strength and drawability. The effects of these precipitates are greater in batch annealed steels than in continuous steels. This is due to the long soaking times required in batch annealing which provides optimum conditions and sufficient time for these precipitates to form [17]. 3.2.7 Manganese Manganese is added through solid solution strengthening to IFHS steels in a low concentration in order to react with the Sulphur to produce MnS precipitates. These MnS precipitates act to refine grain structure during processing when there is a transformation in phase between austenite and ferrite. Mn is to strengthen steels through solid solution strengthening. The effect of Mn is relatively small in the austenite range but compared to the ferrite range. This is due to a difference in Mn solubility between the austenite and ferrite ranges. Where Mn in ferrite is 10wt% higher than in austenite [18] Mn acts to stabilize the austenite region and slows down the rate of austenite transformation and also the temperature at which the transformation takes place. This lowering of transformation temperature between austenite and ferrite promotes finer grains through grain refinement. Mn can be found in oxide and sulphide forms as well as combinations of the two, oxysulphides. These oxides and sulphides act to deoxidise and desulphurise the steel. When in sulphide form, MnS helps to reduce embrittlement of steel without reducing hardness. When mixed with common impurities such as Al2O3, SiO2, MnO, CaO, CaS and FeS an increase in hardness and strength occurs [19]. When in the oxide form, MnO at the surface acts a barrier layer to prevent surface oxidisation and corrosion. 3.2.8 Silicon Silicon is a useful element and is used to increase the strength through solid solution strengthening, although there is a compromise as increasing Silicon content decreases ductility. Silicon is also found in oxide form, as silicon dioxide. Silicon dioxide is found with Manganese Oxide or as Silicomanganese to give a strong oxygen stabilisation and prevent corrosion of steel. [20]. 3.2.9 Aluminium Aluminium is used to deoxidise steel by reacting with oxygen within the steel to form Al2O3. These Aluminium Oxides are later removed leaving an oxygen free steel. However the low density of Aluminium means that oxidisation could occur at the steel interface resulting in corrosion. Aluminium content can have a negative effect on formability. This is due to the precipitation of AlN during recrystallisation preventing the {111} development and thus preventing the formation of finer grains. So minimising the amount of AlN in solid solution results in higher formability. A more stable alternative to AlN which is commonly used in IFHS steels is TiN. 3.3 Hardening and processing There are many different compositions of steel which offer various advantageous properties. The main reason for altering composition or alloying is to strengthen the material. This can be done in several ways; 3.3.1 Precipitation strengthening This process uses heat treatment to raise the yield strength of a material. As temperature changes during heat treatment processing, fine particles are produced due to differing melting points of impurities. These fine particles impede dislocation movement. This in turn reduces the ductility and plasticity of the material and increases its hardness. 3.2.2 Solid – solution strengthening Solid solution strengthening is a form of alloying. It is a commonly used technique to improve the strength of a material. Atoms of the alloying element are added to the crystal lattice of the base metal via diffusion. There are two ways in which this can occur, depending on the size of the alloying alloying element. These are via substitutional solid solution, and interstitial solid solution. Substitutional solid solution This takes place when the sizes of the alloying atoms are equal in size to the base atoms, (Differing in size by no more than 15% according to the Hume-Rothery rules) The alloying atoms replace the solvent atoms and assume their lattice positions. The solute atoms can produce a slight distortion of the crystal lattice, due to the size variation. The amount of distortion increases with the size of the solute atom. This distortion has an effect on microstructural properties. The formation of slip planes is altered making dislocation movement more difficult, meaning a higher stress is required to move the dislocations. This gives the material a higher strength. A generalisation associated with substitution is that large substitutional atoms put the structure under compressive stress, and small substitutional atoms give tensile stress. Interstitial solid solution This occurs when the alloying atoms are much smaller than the base atoms. The alloying atoms fit into spaces within the crystal lattice. This is the case with carbon in steel, where carbon is a solute in the iron solvent lattice. The carbon atoms are less than half the size of the iron atoms so an interstitial solid solution forms. 3.3.3 Processing The final properties of steel are greatly affected by the manner in which it is first made and then processed. Typical processes include steel making, casting, hot and cold rolling and annealing. Each individual process has a distinct affect on the properties of the steel. To make the steel free from interstitial elements, Ti and Nb are often added to react with interstitials after a process called vacuum degassing. Vacuum degassing is the name given to the process where a metal is melted within a vacuum and the gasses are evaporated out. Hot and cold rolling Hot rolling is the first process to take place after steel making. After steel has been cast into uniform slabs or billets it is the rolled under a high temperature to reduce its cross sectional thickness. The hot rolling process is undertaken at a temperature above that at which recrystallisation occurs. Hot rolling reduces allows recrysallisation to occur during processing (dynamic recrystallisation) and the material is left stress free due the new grain nucleation and equiaxed grains. Effect of hot working on microstructure: Hot working occurs at high temperatures, this means that there is often enough thermal energy present for recrsytallisation to occur during deformation. This is called dynamic recrystallisation and it occurs with most metals, apart from aluminium. Recrystallisation occurs during the working process and also as the metal is cooling. Dynamic recrystallisation occurs by new grains nucleating at existing grain boundaries. The amount of recyrstallisation depends on several factors. It depends on the strain rate, temperature and amount of strain on the metal. Generally, as strain within the metal increases, so does the amount of recrystallisation. Cold working is when steel is plastically deformed below its recrystallisation temperature. This process increases the yield strength due to the plastic deformation causing slight defects within the microstructure of the metal. These defects make it difficult for slip planes to move. The grain size of the metal is also reduced, making the material harder through a process called Hall petch hardening. Hall Petch hardening, also known as grain boundary strengthening, increases materials strength by altering the grain size. This is because grain boundaries act as barriers to dislocation movement. So altering the grain size, through hot and cold rolling at various temperatures and rates will have an effect on dislocation movement and yield strength. Cold working will increase the strength of the metal by making it increasingly difficult for slip to occur. However as more and more of the larger grains split to form smaller grains the ductility is greatly reduced as the material hardens. Eventually fracture would occur. To avoid this, the material is annealed. Cold working occurs at a temperature below 0.4 of the metals melting point. Some of the energy created by the process is expelled as heat but some energy is stored within the structure putting it into a high energy state. The energy is stored within the grain boundaries of the deformed crystals and within the stress fields of the dislocations created through the plastic deformation. The structure is highly stressed after cold working and would prefer to return to its former low energy state. It is howeve

On the Sidewalk Bleeding Essay

In the short story â€Å"On the sidewalk bleeding,† by Evan Hunter, the author makes us feel sympathy for the main character by using a variety of techniques such as characterisation, plot structure and language. The story opens with the main character, Andy, who has just been stabbed because he is in a gang. . Unfortunately it is too late to change what had happened and as a result the reader feels immense pity for him when he dies. This short story includes the themes of regret and how gang violence causes loss of identity. Firstly the author makes the reader feel sympathetic towards Andy by using effective techniques to emphasise the agony and the painful phase that Andy is going through. The author says that Andy is in so much pain that no sound comes out of his mouth. The passage says, â€Å"There was no voice in his throat only the bubbling of blood between his lips.† In this quote, alliteration is used with the words â€Å"bubbling of blood.† The author uses this technique to highlight how much pain and terror gangs can create. This is also effective as it creates a gruesome image in the reader’s mind of Andy in his current situation. Therefore we feel sorry for Andy as he cannot even call for help. Another way the author makes us sympathise for Andy is how the author uses the idea of Andy being isolated from the rest of the world. Andy is lying in the alley far from help and he can hear music but nothing or no-one is able to help him. We see this when the writes says, â€Å"He watched the world passing,† and also the quote, â€Å"He could hear the faint noise of music now, from and long, long way off.† These two extracts from the passage illustrate that although Andy is dying the world is still moving and no one cares or even looks at Andy. Also it shows to us that Andy is isolated from society. At this point in the story Andy realises that being in a gang has detached him from the rest of the world and there is no going back. This relates to the theme of regret as Andy starts to regret the choices he made in life. The reader starts to feel even sorrier for Andy as he starts to repent what he has done but he can’t do anything to save himself now as it is to o late. Furthermore, throughout the story the author has created characters which pass by Andy but unfortunately for Andy they don’t help him for different reasons. When the third useless person comes into the alley, Andy is in hope that she will help him but sadly she doesn’t. The story says, â€Å"An old lady stopped at the other end of the alley like a queen.† In this quote the author uses a simile to show us how the old lady was acting and how she considered herself nothing less than a queen. This quote makes us sad as Andy has now had three attempts of surviving but all of them have slipped away just because he is in a gang. This also relates to the theme of how gangs cause loss of identity as if he wasn’t in a gang he would have had at least one chance of surviving out of the three. This again makes the reader sympathise towards Andy. Furthermore feel sorry for Andy by using personifying the jacket and the knife. Andy knows that he is dying and wants to be known as an individual and not a royal. The quote is, â€Å"Had they stabbed him, Andy or had they only stabbed the jacket and the title, and what good was the title if you were dying. † In this personification is used to emphasise that the guardians only stabbed Andy simply because he was a royal and show that the knife had no hatred towards Andy only the jacket and the title. The jacket symbolises the royals and the knife symbolises the guardians to indicate how much hatred is between the two gangs. Similarly this idea is further developed when Andy blames the jacket for him loosing his life. Andy begins to realise that if there was no jacket there wouldn’t have been a rumble in the first place. The short story says, â€Å"The jacket was a stupid meaningless thing, which was robbing him off his life.† The jacket and title has ruined his life and future. The word choice of â€Å"meaningless† shows that where once the title and the jacket was so important to Andy and how he was proud of it, but now the same jacket and title mean nothing to Andy but instead detests them. Also personification is used to make the knife and jacket seem like people. This suggests that objects are more important and this goes back to the theme of when you join a gang you lose your identity. The theme here shows that when you join a gang you are no longer an individual but you are a gang member instead. Finally Andy at the end of the story was ashamed of being called a royal and his new identity. Andy tries to tell the world that he not a royal but only Andy. The reader sees this when the writer says, â€Å"I’m Andy,’ he screamed wordlessly, ‘I’m Andy.’† Reputation of Andy’s name emphasises to us that he wants to be known as Andy and not a royal before he dies. Juxtaposition of â€Å"screamed wordlessly† is used to show that Andy is trying to scream but he only can in his mind as he is in too much pain to speak. By this point Andy is utterly helpless and can’t do anything. We feel pity towards Andy as he can’t even speak his feeling so there is no chance of him surviving. In conclusion the author has used many techniques of writer’s craft such personification and language to make the reader sympathise towards the main character Andy. Although not much action happens in the short story, the author still manages to make us feel sorry for Andy as Andy goes through his life and realises that he has done nothing major in his life expect make stupid mistake of joining a gang which leads him to losing his life.

Essay about Easy Access For Children on Pornography Sites

Easy Access For Children on Pornography Sites You just finished a days work, have arrived home, unlocked the door, step inside, and just as you are about to yell, anyone home, you hear hooting and hollering coming from the family room. As you enter the room you see your children and their friends glued to the computer screen, which is covered with explicit images not intended for the eyes of children. According to an article written by P.J.Huffstutter, Yahoo, MSN Criticized for Offering Easy Access to Pornography, (C1) these two large Internet companies, have made it possible for everyone of all ages to access these adult communities. They require no proof of age, making it far too easy for under-age children to freely view the†¦show more content†¦Yahoos search engine was even worse, not only was I not asked my age, but I also never received any warnings of adult content. When I completed the search they offered me over 900 different sites to visit, and the majority of these offered little to the imagination. I was bot h shocked and surprised to see such explicit content. No wonder parents are so upset and critical of these companies. Perhaps parents need to take more control and provide more guidance over what their children are surfing for, either by putting a block on anything requiring you to be 18yrs of age, or having them use the computer with an adult around. Although monitoring childrens activities would take a considerable amount of time and effort, it is one way to put a dent in the problem. Who is to say that the Internet companies should be held responsible, especially when some adults in the communities feel they have a right to their opinions and should be able to view any material they want. Not many of us like restrictions forced upon us. 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