Research: Features of Stainless Steel Chemical Compositions and Differences among Various Stainless Steel Grades (Ⅱ)

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Austenitic-ferrite duplex stainless steel

Austenitic-ferrite duplex stainless steel is also a type of stainless steel, which contains two phases of almost equal proportion, i.e., half of austenite and half of ferritic. In the case of low C content, Cr content is 18%-28% and Ni content 3%-10%. Some duplex steels also contain Mo, Cu, Si, Nb, Ti, N and other alloying elements. This grade of stainless steel features both austenite and ferritic stainless steel.

books of duplex stainless steel

Compared with ferrite, duplex stainless steel has a higher plasticity and toughness, free from room temperature brittleness, with its intergranular corrosion resistance and welding performance improved remarkably. Meanwhile it also maintains its properties of ferrite stainless: the steel 475 ℃ brittleness and high thermal conductivity, super-plasticity and other properties. Compared with austenitic stainless steel, it features high strength with intergranular corrosion resistance and chloride corrosion resistance improved significantly. Duplex stainless steel has excellent pitting corrosion resistance and it is also a kind of nickel- saving stainless steel.

0Cr26Ni5Mo2, also named 329, features high strength, excellent intergranular corrosion resistance and chloride stress corrosion resistance. It is widely used in oil refining, fertilizer, papermaking, petroleum, Chemical industry, etc.

1Cr18Ni11Si4A1Ti is harnessed to manufacture components and equipment capable of resisting high temperature concentrated nitric acid media

00Cr18Ni5Mo3Si2 features double phases of ferritic steel and austenite steel, with high resistance to stress cracking corrosion(SCC). Its pitting corrosion resistance is equivalent to that of 00cr17nil3m0. Its high strength makes it suitable for chloride-containing environment. It is used for oil refining, fertilizer, papermaking, petroleum, chemical industry, heat exchangers and condensers, etc.

Ferritic stainless steel

Ferritic steel is a type of steel containing less than 0.10% carbon, 11%-30% chrome roughly, always nickel-free. At times it is also composed of a small amount of elements such as Mo, Ti, and Nb. It is magnetic and not capable of hardening through heating. This grade of steel was classified as one stainless steel group, capable of resisting oxidation and corrosion, specifically stress cracking corrosion (SCC).

This grade of steel features large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance, etc. It is usually used for manufacturing parts resistant to atmospheric, steam, water, and oxidizing acids. This grade of steel also has its disadvantages, such as poor plasticity and obviously reduced plasticity and corrosion resistance after welding, confining its applications. However, the application of off-furnace refining technology (AOD or VOD) significantly reduces the interstitial elements such as carbon and nitrogen, thus making this type of steel widely used. It is usually used for interior decoration, heavy oil burner parts, household appliances, and household appliances parts.

Ferrite type 0Crl3Al (also named 405) will not show significant hardening after cooling off from high temperature. It is used as steam turbine materials, parts for quenching, composite steel, etc.

00Cr12 is of less carbon content than 0Crl3, featuring good bending performance on the welding section, good processability, and high temperature oxidation resistance.It is applied for vehicle exhaust treatment device, boiler combustion chamber, nozzle.

1Cr17, also named 430, features good oxidation resistance and excellent resistance to stress cracking corrosion.

Y1Cr17 features better cutting performance than 1Cr17, and is used for automatic lathes, bolts, nuts, etc.

1Cr17Mo, also named 434 is an improved version of steel 1Cr17, with better salt solution resistance. It is generally used as exterior decoration material for cars.

00Cr30Mo2 is a grade of steel with high O-Mo contents and extremely low C, N content, featuring good corrosion resistance, good resistance to halide stress cracking corrosion and pitting corrosion. It is used for devices related to organic acids such as acetic acid, lactic acid, and caustic alkali.

00Cr27Mo2 features the similar performance, use, corrosion resistance and soft magnetic properties like 00Cr30M02.

Martensitic stainless steel

Martensitic stainless steel is a hardenable stainless steel group which mechanical properties can be changed by heat treatment. The common grades are built around 1Cr13, such as 2Cr13, 3Cr13, 4Crl and so on. It can be hardened after quenching, and different tempering temperatures can present different toughness combinations. It is mainly used for steam turbine blades, cutlery, surgical instruments, etc. In terms of chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. In perspective of the structure and strengthening mechanism, it can be classified into 1) martensitic stainless steel, 2) Semi-Martensitic PHSS (precipitation-hardening stainless steel) and 3) maraging steel.

Martensitic 1Cr12, also named 403 is a good heat-resistant stainless steel used for steam turbine blades and high-stress components.

1Cr13, also named 410 features high hardness and good corrosion resistance in the quenched state.

1Cr13Mo is a high-strength steel grade of higher corrosion resistance than 1Crl3, used for turbine blades, high temperature parts

Y1Cr13 stainless steel features the best cutting performance, suitable for automatic lathe use.

2Cr13, also named 420, features good corrosion resistance and high hardness post quenching, used for steam turbine blade

3Cr13 is of higher hardness than 2Cr13 in the quenched state, used for cutting tool, nozzle, seat, valve, etc.

3Cr13Mo features high hardness and high wear resistance, used for hot oil pump shafts, valve, valve bearings, medical pile springs and other parts.

Y3Cr13 is an improved steel grade of 3Crl with enhanced cutting performance.

1Cr17Ni12 is used for parts, cellars and equipment that require high strength and high resistance to nitric acid and organic acids.

7Cr17, also named 440A, is used for parts, cellars and equipment that require high strength and high resistance to nitric acid and organic acids.

8Cr17 is of higher hardness than 7Cr17 and higher toughness than 11Cr17 in hardened state, used for tool, valve etc.

11Cr7 is known for its highest hardness among all stainless steels and heat-resistant steels, used for nozzles and bearings.

Y11Cr17 is an improved steel grade of 11Cr17 with enhanced cutting performance, used for automatic lathe.

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