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General principal of heat treatment of steel
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Summary
This report looks at how heat tempering, solution annealing and cold work hardening, can change the properties of stainless steel. There are three main grades of stainless steel, these grades are ferritic, Austenitic and Martensitic. These grades have different ways of hardening. There are other grades of Stainless Steels that don’t fit in with the other grades, these are known as special stainless steels and are prescription hardenable.
Introduction
Stainless steels are used in every day applications such as oil and gas, medical equipment, cutlery, boats and many more. The discovery of stainless steel is not very well known, as Germany, Britain, Poland, France, America and Sweden have all claimed that they discovered Stainless
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He used steel alloys which had chromium in them. He then started experimenting with steel that used different chromium values between 6% and ranging all the way up to 15%, with varying amounts of carbon. During these experiments he created a steel that contained 0.24% carbon and 12.8% chromium. He argued that this was the first ever stainless steel.
Categories of stainless steel Stainless steel is normally classed as stainless steel if it contains 10% and above chromium. There are some steels that only contain 8% chromium and are classed as stainless steels. Stainless steel is used for its properties such as, erosion resistance and corrosion resistance. Some stainless steels such as type 422, have impact toughness and strength, with temperatures below 650 degrees
Compared to alloy steels, stainless steel is harder to forge. This is due to it needing a higher pressure to create a forged component, even though its done at the same temperature as steel alloys. There are three groups of stainless steel that are mainly looked at when forging, austenitic, ferritic and martensitic. These aren’t the only groups of stainless steels, there are many special types that do not come under these categories. There is a group of steel alloys that are in the forging category but considered special stainless steel, due to the heat resistant
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these are stainless steel that a prescription hardenable (PH) such as 15-5PH, PH-13-8Mo and 17-4PH these alloys are used for forging. The alloys include Cr-Ni in their make-up, like austenitic materials. They have added metals such as aluminium, copper, titanium and columbium when other properties are required. These allow the stainless steels to be solution treated and age cycled, giving the material more strength. These materials, when in the annealed condition, are “soft martensitic” and are then made into “hard martensitic” by sub-zero cooling or age cycling. This gives the material properties of corrosion resistance and very good tensile and yield strengths. There is a grade of stainless steel called duplex. Duplex is almost twice as strong as 304- type stainless. This kind of stainless steel is normally used in nuclear components. Duplex has a higher chromium than prescription hardening types of stainless steel, it also contains less carbon but has similar nickel to PH grades of stainless steel. Other materials can be added to change the properties of
We use metals to construct all kinds of structures, from bridges to skyscrapers to elevators. The strength as well as durability of materials that are crafted out of metal make the materials ideal not only for construction but also for many other applications.
The stainless steel columns seem to have been made by casting and then polished to achieve their current look. Casting is an artistic manufacturing process by which hot liquid materials are poured into a mould and allowed to sit until cooled and solidified. Then the Mould is taken off of the art piece or broken off the art in some cases. This method is used because of the difficulty that would arise from having to figure out how to manipulate materials such as steel or aluminum that are very hard to work
These include, high strength, low weight, high chemical resistance and high cut resistance. This material does not corrode or rust and is also unaffected when placed in or under water.
A huge fascination of arsenic started in the 19th century when people got word of a province in southeastern Austria where people ate arsenic. Women would eat arsenic to help gain weight and fix their complexion to look more beautiful and men would eat arsenic because they believed it helped them breath easier when they were climbing high up in the mountains. One doctor by the name of Dr. Robert Craig MacLagan, was particularly interested in this and visited the town to see for himself what was really occurring. He observed the people and tested their urine to prove that they have been indeed ingesting arsenic. He wrote about the things he witnessed in the Edinburgh Medical Journal. The men in the town would eat 6 grains/dose at least twice a week, sometimes eating it on their bread or just drinking it with their water. As a result many Victorians began self-medicating themselves with arsenic.
Review the effects of arsenic as a soil pollutant on human health. You need to consider the major sources of arsenic (both natural & man-made), pathways for uptake by people and the impacts on human health.
Since all metals have different densities and makeups I think that the heat capacity will greatly vary. The makeup of iron is very different than aluminum so the heat capacity will be quite different. Also, a lot of metals are not completely pure and that will also have some effect on the heat capacity.
By adding up to 2%,of carbon it makes the steel tough and strong. Although it’s tough and strong, it is able to bend. To make sure that the metal doesn’t rust, it has a zinc coating on it. Iron is 26 on the periodic table,and considered an “transition metal,” meaning that it is ductile and malleable, and conduct electricity and heat. ... “Some other elements that are similar to iron are cobalt and nickel. They are the only elements known to produce a magnetic field.” Zinc is 30 on the periodic table and it is also a transition metal like iron. “The first iron used by humans is likely to have come from meteorites.” A meteorite is a meteor that survives its passage through the earth's atmosphere such that part of it strikes the ground. More than 90 percent of meteorites are of rock, while the remainder consist wholly or partly of iron and nickel. Meteors are believed to have been from the asteroid belt of Mars and
A wide variety of coating alloys and wrought alloys can be prepared that give the metal greater strength, castability, or resistance to corrosion or high temperatures. Some new alloys can be used as armor plate for tanks, personnel carriers, and other military vehicles.
The beginnings of modern processing of iron can be traced back to central Europe in the mid-14th century BC. Pure iron has limited use in today’s world. Commercial iron always contains small amounts of carbon and other impurities that change its physical properties, which are much improved by the further addition of carbon and other alloying elements. This helps to prevent oxidation, also known as rust.
Stainless steel is a type of alloy that has a very strong lattice structure (an arrangement/ shape of the crystals or other objects) which in some case can be more beneficial than others depending on the type of application it may be used for. In many cases this structure will make the material more suited to being used in engineering applications such as tools for instance a hammer (stainless steel alloys) , also they can be used for gears, engines, electrical motors and hydraulic systems because the structure makes the material so strong. So when the arrangement of the structure is as above it makes the overall material even stronger which makes it a good for all the applications stated above. I believe its strength and durability are its main properties as these are commonly needed in the engineering industry, although it is also very well known to be used for its corrosion resistance as it is resistant to many types of corrosion. It is used for these properties because the components such as gears need to be strong in order to keep transferring and altering the rotary motion and torque exhibited in the machine that it may be used in, durable to withstand any loads or pressure put onto it and also corrosion resistance to give the components a bigger life span and increase its rate of work throughout its required use.
BIBLIOGRAPHY Advantages to Aluminum. http://www.kaiserextrusion.com/advantage.html. November 28, 2000. Aluminum Facts. http://www.epa.gov/seahome/housewaste/src/alum.htm. November,28 2000. Bowman, Kenneth A. World Book Encyclopedia. "Aluminum." Chicago: World Book, Inc., 1992. Cobb, Cathy. Creations of Fire. New York: Plenum Press, 1995 Geary, Don. The Welder's Bible. Pensilvania: Tab Books, 1993. Knapp PhD, Brian. Aluminum. Connecticut: Grolier, 1996. Newmark, Dr. Ann. Chemistry. London: Dorling Kindersley, 1993. Walker, John R. Modern Metalworking. Illinois: The Goodheart-Willcox Company, Inc., 1985.
The basis for the understanding of the heat treatment of steels is the Fe-C phase diagram. Because it is well explained in earlier volumes of Metals Handbook and in many elementary textbooks, the stable iron-graphite diagram and the metastable Fe-Fe3 C diagram. The stable condition usually takes a very long time to develop, especially in the low-temperature and low-carbon range, and therefore the metastable diagram is of more interest. The Fe-C diagram shows which phases are to be expected at equilibrium for different combinations of carbon concentration and temperature. We distinguish at the low-carbon and ferrite, which can at most dissolve 0.028 wt% C at 727 oC and austenite which can dissolve 2.11 wt% C at 1148 oC. At the carbon-rich side we find cementite. Of less interest, except for highly alloyed steels, is the d-ferrite existing at the highest temperatures. Between the single-phase fields are found regions with mixtures of two phases, such as ferrite + cementite, austenite + cementite, and ferrite + austenite. At the highest temperatures, the liquid phase field can be found and below this are the two phase fields liquid + austenite, liquid + cementite, and liquid + d-ferrite. In heat treating of steels the liquid phase is always avoided. Some important boundaries at single-phase fields have been given special names. These include: the carbon content at which the minimum austenite temperature is attained is called the eutectoid carbon content. The ferrite-cementite phase mixture of this composition formed during cooling has a characteristic appearance and is called pearlite and can be treated as a microstructural entity or microconstituent. It is an aggregate of alternating ferrite and cementite particles dispersed with a ferrite matrix after extended holding close to A1. The Fe-C diagram is of experimental origin. The knowledge of the thermodynamic principles and modern thermodynamic data now permits very accurate calculations of this diagram.
There are many different types of alloys; some are so common that they carry on a life beyond their metal bases. For example, 65-90% of copper mixed with 10-35% of zinc create the well known alloy brass, which provides increased resistance to corrosion in things like instruments and
In the other hand, the Hardening processes consist of quenching and tempering. They help in developing the appropriate bulk and surface properties. Martensite can be found in the structure of hardened or quenched steel. Martensite is a hard but brittle structure which needs tempering. After tempering, the toughness is increased and the brittleness is reduced, then it will have broad use throughout engineering field. Their principal use is to render the part fit for final use.