The determination of carbon element by microcomputer carbon and sulfur analyzer is one of the main elements of industrial steel. The performance and organization of steel are largely determined by the content and distribution of carbon in steel. The influence of carbon in stainless steel is particularly significant . The effect 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 the degree of effect is very large (about 30 times that of nickel). On the other hand, due to the affinity of carbon and chromium Large, formed with chromium—a series of complex carbides. Therefore, from the aspects of strength and corrosion resistance, the role of carbon in stainless steel is contradictory.
Recognizing the law of this influence, we can choose stainless steels with different carbon contents from different application requirements.
For example, the most widely used and the most basic stainless steel in the industry-the standard chromium content of the five steel grades 0Crl3 ~ 4Cr13 is 12-14%, which is only after the factor of carbon forming chromium carbide with chromium is taken into account The purpose of the decision is to combine the carbon and chromium to form chromium carbide, the chromium content in the solid solution should not be lower than the minimum chromium content of 11.7%.
For these five steel grades, due to the different carbon content, the strength and corrosion resistance are also different. The corrosion resistance of 0Cr13 ~ 2Crl3 steel is better but the strength is lower than 3Crl3 and 4Cr13 steel. They are mostly used for manufacturing structural parts. The two steel grades can obtain high strength due to their high carbon content. They are mostly used to manufacture springs, knives and other parts that require high strength and wear resistance. For another 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 with greater affinity for chromium and carbon (titanium or niobium) can be added to prevent it from forming carbonization. Chromium, when high hardness and wear resistance become the main requirements, we can increase the carbon content of the steel while appropriately increasing the chromium content, so as to meet both the hardness and wear resistance requirements, and give consideration Corrosion resistance function, industrially used as bearings, measuring tools and blades with stainless steel 9Cr18 and 9Cr17MoVCo steel, although the carbon content is as high as 0.85 ~ 0.95%, because their chromium content has also increased accordingly, so the corrosion resistance is still guaranteed Claim.
In general, the carbon content of stainless steels currently used in industry is relatively low. Most stainless steels have a carbon content of 0.1 to 0.4%, and acid-resistant steels have a carbon content of 0.1 to 0.2%. Stainless steels with a carbon content of more than 0.4% account for only a small part of the total number of steel grades. This is because under most conditions of use, stainless steels always aim at corrosion resistance. In addition, the lower carbon content is also due to certain technological requirements, such as easy welding and cold deformation.
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