Carbon plays a dual role in stainless steel, namely the beneficial side and the harmful side, depending on the requirements of use.

One is that carbon can reduce the corrosion resistance, plasticity, toughness and weldability of steel. This is due to the strong affinity between carbon and chromium, and it can form a series of complex compounds with chromium. The higher the carbon content in the steel, the more chromium carbide is formed. In this way, the chromium content in the solid solution is reduced, and the corrosion resistance of the steel is also reduced due to the reduction of the chromium content. The higher the carbon content in steel, the lower its corrosion resistance. For stainless steel, corrosion resistance is the main requirement, so the carbon content in stainless steel is generally very low, most of which are only 0.10% to 0.20%, and generally do not exceed 0.4%.

The second is that carbon can increase the hardness, wear resistance and strength of steel by increasing its content.

This is because the strength of stainless steel increases with the increase of carbon content in the steel. As the carbon content in the steel increases, the hardness of the steel after quenching will increase, and the wear resistance will increase accordingly. At the same time, the strength of the steel will also increase, but the plasticity and toughness will correspondingly decrease, and the corrosion resistance will also decrease.