Stainless steel sulfur and phosphorus elements
The sulfur content of steel shall not exceed 0.05%; the phosphorus content in general steel shall be limited to less than 0.0%.
Therefore, sulfur and phosphorus content is a very important indicator. Carbon structural steel and high-quality carbon structural steel are divided according to it: steel with sulfur and phosphorus content not exceeding 0.04% is called high-quality steel; sulfur content does not exceed 0.03%. Steel with a phosphorus content of no more than 0.035% is called high-grade high-quality steel; steel with a sulfur and phosphorus content of no more than 0.025% is called super-quality steel.
Common stainless steel models
Commonly used stainless steel models are often represented by numbers and symbols. There are 200 series, 300 series, and 400 series. It is represented by element symbols plus numbers, such as 1Cr18Ni9, 0Cr18Ni9, 00Cr18Ni9, 1Cr17, 3Cr13, 1Cr17Mn6Ni5N, etc., and the numbers indicate the corresponding element content.
200 series: chromium-nickel-manganese austenitic stainless steel
300 series: chromium-nickel austenitic stainless steel
301: Good ductility, used for molding products. Can also be hardened by machine speed. Good weldability. Wear resistance and fatigue strength are better than 304 stainless steel.
302: The corrosion resistance is the same as that of 304, and the strength is better due to the relatively high carbon content.
302B: It is a stainless steel with high silicon content, which has high resistance to high temperature oxidation.
303: It is sharpened by adding a small amount of sulfur and phosphorus.
303Se: It is also used to make parts that require hot heading, because this stainless steel has good hot workability under such conditions.
304: that is, 18/8 stainless steel. The GB grade is 0Cr18Ni9. 309: Compared with 304, it has better temperature resistance.
304L: It is a variant of 304 stainless steel with a lower carbon content, used in occasions that require welding. The lower carbon content minimizes the precipitation of carbides in the heat-affected zone near the weld, which can lead to intergranular corrosion (weld attack) in stainless steels in some environments.
304N: It is a nitrogen-containing stainless steel, and nitrogen is added to increase the strength of the steel.
305 and 384: High nickel content, low work hardening rate, suitable for various occasions that require high cold formability.
308: Used to make welding rods.
309, 310, 314 and 330: The content of nickel and chromium is relatively high, in order to improve the oxidation resistance and creep strength of steel at high temperature. 30S5 and 310S are variants of 309 and 310 stainless steel, the difference is that the carbon content is lower, in order to minimize the precipitation of carbides near the weld. 330 stainless steel has a particularly high resistance to carburization and thermal shock resistance.
316 and 317: contain aluminum, so the resistance to pitting corrosion in marine and chemical industrial environments is much better than 304 stainless steel. Among them, the variants of 316 stainless steel include low-carbon stainless steel 316L, nitrogen-containing high-strength stainless steel 316N, and free-cutting stainless steel 316F with high sulfur content.
321, 347 and 348: are stainless steels stabilized with titanium, niobium plus tantalum, and niobium respectively, suitable for welding components used at high temperatures. 348 is a stainless steel suitable for the nuclear power industry, which has certain restrictions on the combined amount of tantalum and cobalt.
400 Series: Ferritic and Martensitic Stainless Steels
408: Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni
409: The cheapest model (British and American), usually used as a car exhaust pipe, is a ferritic stainless steel (chrome steel)
410: Martensitic (high-strength chromium steel), good wear resistance and poor corrosion resistance. 416: The addition of sulfur improves the processing properties of the material.
420: "Knife grade" martensitic steel, similar to the earliest stainless steels such as Brinell high chromium steels. Also used for surgical knives, can be made very shiny
430: Ferritic stainless steel, for decoration, such as for automotive accessories. Good formability, but poor temperature resistance and corrosion resistance
440: High-strength cutting tool steel with slightly higher carbon content. After proper heat treatment, a higher yield strength can be obtained, and the hardness can reach 58HRC. It is among 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)
500 series: heat resistant chromium alloy steel
600 series: martensitic precipitation hardening stainless steel
630: The most commonly used precipitation hardening stainless steel model, usually also called 17-4; 17%Cr, 4%Ni