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Duality of carbon content of stainless steel forgings

Dec. 07, 2020

The company’s main production of stainless steel forgings include stainless steel flanges and stainless steel pipe fittings

The role of carbon in stainless steel forgings mainly has two aspects:

On the one hand, carbon and chromium have a strong affinity, and it can form a series of complex carbides with chromium. The higher the carbon content in steel, the more chromium carbide is formed. When w(Cr) < 10%, it is mainly cementite type carbides (Fe, Cr) 3C; in high chromium steel, complex carbides (Cr, Fe) 7C3 or (Cr, Fe) 23C6 are formed. In this way, the chromium content in the solid solution is reduced, and the corrosion resistance of the steel is also reduced. The higher the carbon content in steel, the lower its corrosion resistance. For stainless steel forgings, corrosion resistance is the main requirement, so the carbon content in stainless steel is generally very low, most of which are only 0.10% ~ 0.20% (mass fraction), generally not more than 0.4% (mass fraction).

Duality of carbon content of stainless steel forgings

On the other hand, the strength of stainless steel forgings increases with the increase of carbon content in the steel. In some occasions where stainless steel is required to have high hardness and wear resistance; for example, rolling bearings, springs, molds and cutting tools made of stainless steel require high hardness and strength, so in martensitic stainless steel forgings, in order to produce Martensite Volume transformation, the carbon content in steel generally varies from 0.1% to 1.0% (mass fraction). As the carbon content in the steel increases, the hardness of the steel after quenching increases, and the wear resistance increases accordingly. At the same time, the strength of the steel also increases, while the plasticity decreases correspondingly and the corrosion resistance decreases. For this reason, it is necessary to increase the chromium content in steel accordingly to produce stainless steels such as 9Cr18, 85Cr17 and 90Cr18MoV.

Therefore, our company strictly guarantees the production quality of stainless steel forged flanges.