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Stainless steel, also known as inox steel in metallurgy is a steel alloy with a minimum of 10.5% chromium content by mass. Stainless steel does not easily corrode or stain with water as compared to ordinary steel, but still it is not fully stain-proof, most notably under low oxygen, high salinity, or poor circulation environments. Stainless steel is very much different from carbon steel by the amount of chromium present, and because of that unprotected carbon steel rusts readily when exposed to air and moisture. It also contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion by blocking oxygen diffusion to the steel surface and blocks corrosion from spreading into the metal's internal structure, and due to the similar size of the steel and oxide ions they bond very strongly and remain attached to the surface Well, there are different grades and surface finishes of stainless steel suiting the nature and environment of the alloy to be endure. Stainless steel is generally used at the places where both the properties of steel like, resistance and corrosion are required. Also there are some alleys of stainless steel which tries to cone over some discrepancies, of which i am going to discuss the few of it. First alloy is Stainless Steel 15-5, which is a precipitation hardening martensitic stainless steel. It is also available in various standards like UNS S15500, AMS 5659 and ASTM A564. This alloy of stainless steel constitutes Iron Fe(75%), Chromium Cr(14.48%), Nickel Ni(4.5%), Copper Cu(3.5%), Manganese Mn(≤1%), Silicon Si(≤1), Nb + Ta(0.3), Carbon C(≤0.07%), Phosphorous P(≤0.4%) and Sulfur S(≤0.03%). Stainless steel 15-5 PH, also known as XM-12 or UNS S15500 is basically a modification of 17-4 PH developed in 1960. 15-5 PH has more redefined structure than 17-4 PH formed after re-melting price makes it tougher than others. The 15-5PH has low temperature hardening, good fabrication properties and excellent corrosion resistance, which tends to make it suitable for many industries. It also can be easily machined in the solution-annealed state or in final heat treat condition. We can also increase the strength and ductility of 15-5 PH by heating the material at different temperatures. The 15-5 PH can be used for the applications requiring better corrosion resistance and transverse properties compared to other similar martenstic grades like making valves, aircraft parts, gears and pump parts. It can be also used for marine gas turbine compressor sections, hollow shafts, paper mill equipment, engine parts, aircraft components, fittings, fasteners and nuclear reactor components. One such stainless steel alloy is 17-4 PH (Precipitation Hardening), which is also known as Type 630, a chromium-copper precipitation hardening stainless steel basically used for the applications requiring high strength and a moderate level of corrosion resistance. In 17-4 PH high strength is maintained to approximately 600 degrees Fahrenheit (316 degrees Celsius). The alloy 17-4 PH has Cu and Nb/Cb additions. It has great strength, hardness (up to 572°F / 300°C), and corrosion resistance. We can easily optimize the mechanical properties with heat treatment which will yield very high strength up to 1100-1300 MPa (160-190 ksi). But this grade is not suitable for use at temperatures above 572°F (300°C) or at very low temperatures. It also has adequate resistance to atmospheric corrosion or in diluted acids or salts where its corrosion resistance is equivalent to Alloy 304 or 430. This alloy is widely used in food industry, pulp and paper industry, aerospace industry (turbine blades, etc.) and in manufacturing of mechanical components. Commonly alloy steels are designated by AISI four-digit numbers with a great responsiveness to mechanical and heat treatments than carbon steels. The compositions can be compromises of limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va in the carbon steels. The AISI 4130 steel alloy contains chromium and molybdenum as strengthening agents. It has low carbon content with an ease to welding. The chemical composition of AISI 4130 is Iron, chromium, manganese, carbon, silicon, molybdenum and phosphorous. Hence, market is full of various kinds of stainless steel alloys which are highly compatible in all applications in several of industries like Flight Metals.
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15-5 PH, 17-4 PH, 4130 Steel,
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