Why is carbon content of stainless steel low?
[stainless steel contains low carbon content] stainless steel contains very high Cr. Cr and carbon combine to form carbides, Cr23C6 or Cr7C3, which contain very high Cr. That is, the formation of these carbides is at the expense of a large amount of Cr. It is conceivable that once the content of Cr in the matrix drops a lot, the corrosion resistance will decrease. For austenitic stainless steel, due to the precipitation of Cr carbide, its intergranular corrosion resistance has deteriorated significantly, which is called sensitization.Martensitic stainless steels contain relatively large amounts of carbon.
This is because the main alloying elements of martensite chromium stainless steel is iron, chromium and carbon, such as Cr is greater than 13%, there is no gamma phase, such as single-phase alloy ferritic alloy, in any heat treatment system does not produce martensite, therefore must join the forming elements of austenite, Fe-Cr two alloy, to expand, C and N are effective elements, C, N elements adding alloy allows higher CR content. Chromium is one of the most important essential elements in martensitic chromium stainless steels, except chromium. In fact, martensitic chromium stainless steel is a kind of iron, chromium and carbon three element alloy C.However, the corrosion resistance of martensitic stainless steel mainly depends on the content of chromium, but the carbon in the steel due to the formation of stable chromium carbide with chromium, but also indirectly affect the corrosion resistance of steel. Therefore, in 13%Cr steel, the lower carbon content, the higher corrosion resistance. In 1Cr13, 2Cr13, 3Cr13 and 4Cr13 four kinds of steel, the corrosion resistance and strength of the order is just the opposite. In addition, carbon has an effect on the mechanical properties of stainless steel matrix.
The corrosion resistance of stainless steel decreases with the increase of carbon content. Therefore, the carbon content of most stainless steel is lower, the maximum is not more than 1.2%, and some steel's Omega C (carbon content) is even less than 0.03% (such as 00Cr12). The main alloying element in stainless steel is Cr (chromium), and the steel has corrosion resistance only when the Cr content reaches a certain value. Therefore, stainless steel in general Cr (chromium) content of at least 10.5%. Stainless steel also contains Ni, Ti, Mn, N, Nb, Mo, Si, Cu and other elements.
