The decisive role of chromium in stainless steel: There is only one element that determines the properties of stainless steel, which is chromium, and each stainless steel contains a certain amount of chromium. So far, there is no chromium-free stainless steel. The fundamental reason why chromium has become the main element that determines the performance of stainless steel is that the addition of chromium as an alloying element to steel promotes its internal contradictory movement to help resist corrosion damage.
The performance and structure of steel are largely determined by the content of carbon in steel and the form of its distribution. The influence of carbon in stainless steel is particularly significant. The influence of carbon on the structure of stainless steel is mainly manifested in two aspects. On the one hand, carbon is an element that stabilizes austenite and has a large effect (about 30 times that of nickel). On the other hand, because of the very affinity of carbon and chromium Large, forming a complex series of carbides with chromium. Therefore, in terms of strength and corrosion resistance, the role of carbon in stainless steel is contradictory.
There is also a difference between strength and corrosion resistance. 0Cr13~2Crl3 steel has better corrosion resistance but lower strength than 3Crl3 and 4Cr13 steel. It is mostly used to manufacture structural parts. The latter two steel grades can be high due to higher carbon content. The strength is mostly used to manufacture springs, knives and other parts that require high strength and wear resistance. For example, in order to overcome the intergranular corrosion of 18-8 chromium-nickel stainless steel, the carbon content of the steel can be reduced to less than 0.03%, or an element (titanium or niobium) with greater affinity than chromium and carbon can be added to prevent it from forming carbonization Chromium, for example, when high hardness and wear resistance become the main requirements, we can increase the carbon content of steel while appropriately increasing the chromium content, so as to meet the requirements of hardness and wear resistance, but also The corrosion resistance function of stainless steel 9Cr18 and 9Cr17MoVCo steel used in industry as bearings, measuring tools and blades, although the carbon content is as high as 0.85~0.95%, because their chromium content has been increased correspondingly, the corrosion resistance is still guaranteed Claim.