There are two classifications of stainless steel: one is divided into chrome stainless steel and chrome-nickel stainless steel according to the characteristics of alloy elements; the other is divided into M stainless steel, F stainless steel, and A stainless steel according to the organization state of the steel in the normalized state. , A-F duplex stainless steel.

 

一 、 Martensitic stainless steel

 

Typical martensitic stainless steels include 1Cr13 ~ 4Cr13 and 9Cr18, etc.

 

1Cr13 steel has good processing performance. Can be deep drawn, bent, crimped and welded without preheating. 2Crl3 does not require preheating before cold deformation, but requires preheating before welding. 1Crl3 and 2Cr13 are mainly used to make corrosion-resistant structural parts such as steam turbine blades, while 3Cr13 and 4Cr13 are mainly used to make medical equipment surgical knives and wear-resistant parts; 9Crl8 can be used for corrosion-resistant bearings and cutters.

 

2.Ferritic stainless steel

 

The Cr content of ferrite stainless steel is generally 13% ~ 30% and the carbon content is less than 0.25%. Other alloying elements are sometimes added. The metallurgical structure is mainly ferrite. There is no α <= & gt; γ transformation during heating and cooling, and it cannot be strengthened by heat treatment. Strong oxidation resistance. At the same time, it also has good hot workability and certain cold workability. Ferritic stainless steel is mainly used to make components that require higher corrosion resistance and lower strength. It is widely used in the production of nitric acid, nitrogen fertilizer and other equipment and chemical pipelines.

 

Typical ferritic stainless steels are Crl7, Cr25 and Cr28.

 

 

 

According to the composition, it can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening series (600 series).

 

200 series: chromium-manganese-nickel

 

201,202, etc .: Manganese-nickel substitutes have relatively poor corrosion resistance, and are widely used as cheap substitutes for the 300 series in China

 

300 series: chrome-nickel austenitic stainless steel

 

301: Good ductility, used for molded products. It can also be hardened by mechanical processing. Good weldability. Abrasion resistance and fatigue strength are better than 304 stainless steel.

 

302: Corrosion resistance is the same as 304, and the strength is better because the carbon content is relatively high.

 

303: It is easier to cut than 304 by adding a small amount of sulfur and phosphorus.

 

304: universal model; that is, 18/8 stainless steel. Products such as: corrosion-resistant containers, tableware, furniture, railings, medical equipment. The standard composition is 18% chromium plus 8% nickel. It is a non-magnetic stainless steel that cannot be modified by heat treatment. The GB grade is 0Cr18Ni9.

 

304 L: The same characteristics as 304, but low carbon, so it is more resistant to corrosion and easy to heat treatment, but has poor mechanical properties. It is suitable for welding and difficult to heat treatment products.

 

304 N: It has the same characteristics as 304 and is a nitrogen-containing stainless steel. Nitrogen is added to increase the strength of the steel.

 

309: Has better temperature resistance than 304, with a temperature resistance up to 980 ° C.

 

309 S: With a large amount of chromium and nickel, it has good heat resistance and oxidation resistance. Products such as: heat exchangers, boiler components, and jet engines.

 

310: Excellent high temperature oxidation resistance, the highest operating temperature is 1200 ° C.

 

316: After 304, the second most widely used steel grade is mainly used in the food industry, clocks and jewelry, pharmaceutical industry and surgical equipment. The addition of molybdenum element makes it obtain a special structure with corrosion resistance. Because it has better resistance to chloride corrosion than 304, it is also used as "marine steel". SS316 is usually used in nuclear fuel recovery equipment. 18/10 grade stainless steel usually also meets this application level.

 

316 L: Low carbon, so it is more resistant to corrosion and easy to heat treatment. Products such as: chemical processing equipment, nuclear power generators, refrigerant storage tanks.

 

321: Similar to 304 except that the addition of titanium reduces the risk of corrosion of the material weld.

 

347: Add stabilizing element niobium, suitable for welding aircraft parts and chemical equipment.

 

400 series: ferritic and martensitic stainless steel, no manganese, can replace 304 stainless steel to a certain extent

 

408: Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.

 

409: The cheapest model (British and American), usually used as car exhaust pipe, is a ferritic stainless steel (chrome steel).

 

410: Martensite (high-strength chromium steel), good wear resistance and poor corrosion resistance.

 

416: The addition of sulfur improves the processability of the material.

 

420: "Blade grade" martensitic steel, similar to the earliest stainless steel of Brinell high chromium steel. Also used in surgical knives, it can be made very bright.

 

430: Ferritic stainless steel, for decoration, for example, for car accessories. Good moldability, but poor temperature resistance and corrosion resistance.

 

440: High-strength cutting tool steel with slightly higher carbon content. After proper heat treatment, it can obtain higher yield strength and hardness can reach 58HRC, which is among the hardest stainless steels. The most common application example is the "razor blade". There are three commonly used models: 440A, 440B, 440C, and 440F (easy to process).

 

500 series: heat-resistant chrome alloy steel.

 

600 series: Martensitic precipitation hardened stainless steel