Stainless Steel Science | Talk About 400 Series Stainless Steel

Stainless steel science | talk about 400 series stainless steel

400 series stainless steel is an alloy of iron, carbon and chromium. Because it does not contain nickel, it is a nickel-free stainless steel, also known as stainless iron. 400 series stainless steel contains martensitic structure and iron, not only has normal magnetic properties, but also has a strong high-temperature oxidation resistance, compared with carbon steel, its physical and mechanical properties have been further improved. And most 400 series stainless steels can be heat treated.

Steel grade classification

We know that according to the different metallographic organization, stainless steel can be divided into ferrite, martensite and austenite three kinds, and 400 series stainless steel is mainly ferrite and martensite.
 

Ferritic stainless steel: Chromium content is generally 12% to 30%, usually does not contain nickel, sometimes contains a small amount of Mo, Ti, Nb and other elements, in the use of the state of the matrix structure of ferritic stainless steel. It has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance, excellent stress corrosion resistance, etc., and is widely used in the manufacture of parts resistant to atmospheric, water vapor, water and oxidizing acid corrosion. But at the same time, there are some disadvantages such as poor plasticity, post-welding plasticity and corrosion resistance. The application of off-furnace refining technology (AOD or VOD) can greatly reduce the gap elements such as carbon and nitrogen, making it widely used. The common 400 series stainless steel models are 430 and 409L.

Martensitic stainless steel: the chromium content is not less than 12%(generally 12%~18%), the carbon content is high, the use of the state of the structure of martensite, through heat treatment can adjust its mechanical properties of stainless steel. Generally speaking, it is a kind of hardened stainless steel. The common 400 series stainless steel models are 410, 420, 440, 436L.

Scope of application

400 series stainless steel has a wide range of applications, and some relevant application areas are displayed below.

Automobile exhaust system exhaust pipe, silencer, tail pipe, catalyst, etc., the main steel types are 409L, 444, 436L, 439, 441, 429.