Tool steels are utilized on a wide variety of application including forming, shearing, cutting and molding (manufacturing the tools, dies, and molds) where (due to their remarkable properties) high wear resistance, hardness, strength, toughness, heat resistance and other properties are preferred for optimum performance. In addition to alloying, tools steels are considered special because they are very difficult to manufacture and require careful manufacturing in every processing step. The very high alloy content and special microstructure that make them desirable for severe applications also make them difficult to manufacture [ , ].
High-carbon, high-chromium (AISI D series) cold-work tool steels are of the main groups of tool steels which are identified with their high wear resistance and exceptional nondeforming properties. The excellent wear resistance of D-type cold-work tool steels is the result of their high chromium (~12wt.%) and high carbon (1.5 to 2.35wt.%) contents.
Generally, the high-carbon, high-alloy tool steels are particularly difficult to process by the conventional ingot metallurgy route. The main challenge is that the relatively slow cooling of the conventional static cast ingot allows the formation of coarse eutectic carbide structures, which are difficult to break down during hot working [1, ]. For overcoming these problems some new processing methods such as powder metallurgy (PM) and spray forming have been developed for production of the most highly alloyed tool steels, such as high-carbon, high-chromium (AISI D series) and high-speed (AISI T and M series) [1, , , ]. These techniques offer the possibility to produce steels with higher homogeneity, lack of segregations, finer microstructure and uniform d...
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The high temperature application of Austenitic Stainless Steel is somewhat limited because at higher temperatures it undergoes a phenomenon called Sensitization. According to Ghosh et al. [1], it refers to the precipitation of carbides and nitrides at the grain boundaries. Precipitation of Chromium rich carbides (Cr23C6) and nitrides at the grain boundaries result when the Austenitic stainless steel is heated and held in the temperature range of 500-8500C (773K-1123K). This precipitation of carbides taking place at the grain boundary is because of their insolubility at these temperature ranges. This leads to Chromium depreciated regions around the grain boundaries. So the change in microstructure is takes place and the regions with low Chromium contents become susceptible to Intergranular Corrosion (IGC) and Intergranular Stress Corrosion Cracking (Alvarez et al.) [1, 2]. Along with carbides and nitrides there is formation of chi phase. The chi phase, which is a stable intermetallic compound, consists of Fe, Cr, and Mo of type M18C. Some studies reveal that sensitization may lead to formation of Martensite. In addition to the altered microstructure, mechanical properties of the Austenitic Stain...
Continuous casting is a casting process that is used in the manufacturing industry to produce molten steel at the temperature of 1,600OC and converted into particular size of slabs. This modern casting process is used in many steel manufactures as it has superior quality of castings, less loss of material, cost reduction and high productivity rate over the cast ingot production [1].
The heat input rate is one of the most important variables in fusion welding, since it governs heating rates, cooling rates and weld pool size. In the welding of steel, this is important relationship since increased cooling rates increase the risk of hydrogen-induced cracking. The other metallurgical feature that is directly affected by the heat input rate is grain size in the heat affected zone (HAZ) and in the weld metal. In steel welding it is necessary to seek a heat input rate that gives the optimum combination of grain size and cooling rate [11]. Before the actual welding is done, all the earlier steps such as layout, plate edge preparation, fit up and alignment should be well planned with regard to achieving...
The metal’s hardness along with its great tensile strength and ability to withstand extremely high temperatures make it ideal for use in the filaments in incandescent light bulbs, cathode-ray tubes, X-ray tubes, vacuum tube filaments, and rocke...
The machinability of copper and copper alloys is improved by lead, sulfur, tellurium, and zinc while it deteriorates when tin and iron are added. Lead in brass alloys with concentrations around 2 wt%, improves machinability by acting as a microscopic chip breaker, and tool lubricant, while they increase the brittleness of the alloy [17]. Lead additions are used to improve machinability. The lead is insoluble in the solid brass and segregates as small globules that help the swarf to break up in to small pieces and may also help to lubricate the cutting tool action. The addition of lead is however, affect cold ductility which may control both the way in which material is produced and the extent to which it can be post-formed after machining
Nucor is the second largest steel producer (2nd in assets, 1st in profits) in the United States. Its profits of $123 million have made it one of the most efficient firms in the steel industry. Nucor achieved that position by focusing on the manufacturing segment known as mini-mills - the relatively small, electrically-powered mills that melt down scrap steel to manufacture products. This process saves on costly labor, raw materials, and the capital-intensive machinery necessary to produce steel from iron ore. A major concern of mini-mill steel manufacturers is maintaining quality, since their raw material consists of scrap steel of varying quality, containing a variety of alloys and impurities. Another concern it the recent rising price of scrap steel.
The aim of this study is to observe, understand and draw conclusions on the formation of the oxide scale of the selected stainless steel at high rolling temperature and its associated factors.
The element diffusion from the tool through the tool-chip interface leads to composition change of tool substrate, which may increase the possibility of mechanical damage of the cutting edge also the high strength of titanium at elevated temperature contributes to the high compressive stresses ...
If work-hardening is performed at elevated temps it is said to be hot-worked. In contrast cold-working is done right around room temperature. In both situations the work hardening increases the strength and hardness because of plastic deformation. This causes atoms in a crystal to become disordered, which means that the atoms have moved into a disordered structure. This then raises the strength and hardness by impairing the easy movement of dislocations. Cold working was done at first along with harness testing, once familiarized with all of this testing relationships between hardness, microstructure, and degree of work hardening of brass were
Niobium is added to steel in its production. The addition of Niobium when added to steel allows for the metal to harden. This allows for a stronger steel to be used in both pipes and cars. However Niobium also acts as a brilliant superalloy and is commonly used in rocket assemblies, gas turbines, and jet engines. Niobium plays a vital role in the nozzle of rockets. The Apollo rockets are a most notable case, there rocket nozzles were made up of a Niobium alloy known as C-103. However uses of Niobium are also found in superconducting magnets. These magnets are helpful in the medical devices such as MRI scanners. It is also present in particle accelerators. Most notably, the LHC uses 600 tonnes of niobium
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.
Maraging steels of different compositions have been prepared by means of induction furnace electro slag remelting technique using titanium and chromium instead of cobalt which is a high expensive strategic element, also nickel content was reduced to 10-13%. Mass attenuation coefficients, half value layers and effective atomic numbers have been determined for the prepared samples at photon energies 238, 583, 661, 911, 1173, 1332 and 2614keV. The results are compared with the corresponding theoretical calculations. In addition, the hardness has been determined for the investigated steels. High nitrogen free nickel steel and carbon steel samples have been also investigated for the sake of comparison. The achieved results reveal the superiority of cobalt-free maraging steels comparing with the other investigated high nitrogen free nickel and carbon steels to be used as a proper shielding material in the nuclear domain. Among the investigated cobalt-free maraging steels, a steel of constituent's "0.05%C-13.26%Ni-2.15%Cr-4.3%Mo-0.02%Ti-0.01%V" has the best attenuation properties. The obtained results are useful for potential applications of these alloys in industrial and nuclear applications.
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.
Metals possess many unique fundamental properties that make them an ideal material for use in a diverse range of applications. Many common place things know today are made from metals; bridges, utensils, vehicles of all modes of transport, contain some form of metal or metallic compound. Properties such as high tensile strength, high fracture toughness, malleability and availability are just some of the many advantages associated with metals. Metals, accompanied by their many compounds and alloys, similar properties, high and low corrosion levels, and affects, whether negative or positive, are a grand force to be reckoned with.
In summary, the rate of cooling from the austenite phase is the main determinant of final structure and properties.