How many grades of stainless steel are there? Characteristics and applications of different grades

There are many types of stainless steel. Stainless steel can be classified according to its composition:
2XX series - chromium-nickel series austenitic stainless steel
3XX series - chromium-nickel series austenitic stainless steel
4XX series - high chromium series ferritic steel and martensitic steel
5XX series - low chromium heat-resistant steel series martensitic steel
6XX series - precipitation hardening steel

The most commonly used series are 2XX/3XX/4XX. Each large series is divided into many small grades, such as 201, 202, 304, 316, 416, etc.

Introduction to the characteristics and applications of commonly used grades of stainless steel in each series:
200 series stainless steel belongs to low-nickel and high-manganese stainless steel, with a nickel content of 4% to 6% and a manganese content of about 8%. It is a nickel-saving stainless steel. Since its resistance to intergranular corrosion and pitting corrosion is significantly lower than that of 300 series stainless steel, the biggest advantage of 200 series stainless steel is that it is cheaper than 300 series stainless steel. Under the premise of weak corrosion, 202 stainless steel can almost completely replace 304 stainless steel. In addition, 200 series stainless steel has the non-magnetic characteristics of austenitic steel and its appearance is similar to 304. There are often inferior products on the market that are sold as "304";

202 stainless steel: Under the premise of weak corrosion, 202 stainless steel can almost completely replace 304 stainless steel. It is widely used in building decoration, municipal engineering, highway guardrails, hotel facilities, shopping malls, glass handrails, public facilities and other places;

301 stainless steel: Good ductility, used for molded products, can also be hardened through processing, good weldability, wear resistance and fatigue strength are better than 304 stainless steel;

302 stainless steel: Corrosion resistance is the same as 304, corresponding to the domestic grade 1Cr18Ni9, has a relatively high carbon content and better strength, and is often used in architectural decorative parts;

303 stainless steel: It is a free-cutting stainless steel containing sulfur and selenium. It is used in places where easy cutting and high surface finish are required. It is most suitable for automatic lathes, bolts and nuts;

304 stainless steel: It is the most common material among stainless steels. Its density is 7.93 g/cm3. It is also called 18/8 stainless steel in the industry. It can withstand high temperatures of 800 degrees. It has good processing performance and high toughness. It is widely used in industry, furniture decoration industry, food and medical industry;

309 stainless steel: It has better temperature resistance than 304. The factory produces more 309S stainless steel, which has better corrosion resistance and high temperature resistance; it can withstand high temperatures of 980°C and is mainly used in boilers, chemical industry and other industries. Compared with 309S, 309 does not contain sulfur S;

316 stainless steel: After 304, the second most widely used steel grade, due to the addition of Mo element greatly improves its corrosion resistance and high temperature strength. The high temperature resistance can reach 1200-1300 degrees, and it can be used under harsh conditions; Corrosion resistance: The corrosion resistance is better than 304 stainless steel, and it has good corrosion resistance in the production process of pulp and paper. Moreover, 316 stainless steel is also resistant to erosion by the ocean and corrosive industrial atmosphere. The national standard grade of 316 stainless steel (06Cr17Ni12Mo2) has good oxidation resistance. It is best not to use 316 stainless steel continuously within the range of 427℃-857℃ (800℉-1575°F), but when 316 stainless steel is used continuously outside this temperature range, it has good heat resistance;

316L stainless steel: It has better resistance to carbide precipitation than 316 stainless steel and can be used in the above temperature range. The biggest difference in use is that 316L has ultra-low carbon, so when welding, 316L carbon is not easy to precipitate and combine into chromium carbide, which can reduce the corrosion of the welded part;

321 stainless steel: Except that the risk of rusting of the material weld is reduced due to the addition of elements, other properties are similar to 304;

408 stainless steel: Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni;

409 stainless steel: The cheapest model (British and American), usually used as automobile exhaust pipes, belongs to ferritic stainless steel (chrome steel);

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

416 stainless steel: The addition of sulfur improves the processing performance of the material, easy-to-cut martensitic stainless steel, can be strengthened by heat treatment, 416 has better strength and cutting processability than 304 and 316, small friction coefficient, low carbon content, good corrosion resistance, but not as good as 304 and 316;

420 stainless steel: "Tool-grade" martensitic steel, with certain wear resistance and corrosion resistance, high hardness, similar to Brinell high-chromium steel, the earliest stainless steel. Also used for surgical knives, can be made very bright. 420 stainless steel is suitable for all kinds of precision machinery, bearings, electrical equipment, instruments, meters, transportation vehicles, household appliances, etc. It is mostly used to manufacture parts resistant to atmospheric, steam, water and oxidizing acid corrosion;

430 stainless steel: ferritic stainless steel is a general steel with good corrosion resistance, better thermal conductivity than austenite, smaller thermal expansion coefficient than austenite, heat fatigue resistance, added stabilizing elements, and good mechanical properties of welds. 430 stainless steel is used for automotive accessories, architectural decoration, fuel burner parts, household appliances, and household appliance parts;

430F stainless steel: a steel with easy-to-cut properties added to 430 steel, mainly used for automatic lathes, bolts and nuts;

440 stainless steel: high-strength cutting tool steel, slightly higher carbon content, can obtain higher yield strength after proper heat treatment, hardness can reach 58HRC, and is one of the hardest stainless steels. The most common application example is "razor blades". There are three commonly used models: 440A, 440B, 440C, and 440F (easy to process);

443 stainless steel: a type of ferritic stainless steel, now generally used to replace 304, with the same anti-rust ability and processing performance as 304. It is currently being promoted in the fields of electrical appliances, utensils, kitchen equipment, elevators, ovens, etc.;

500 series: heat-resistant chromium alloy steel;

600 series: martensitic precipitation hardening stainless steel;

630: the most commonly used precipitation hardening stainless steel model, also commonly called 17-4; 17%Cr, 4%Ni.