Function and Utility of Various Main Elements in Stainless Steel
Nickel Ni: The main role in stainless steel is that it changes the crystal structure of the steel. Nickel is an excellent corrosion-resistant material, which can improve the strength of the steel and keep the steel in good plasticity and toughness.
Carbon C: Increased carbon content increases strength. However, for materials with high requirements on corrosion resistance, stainless steel with low carbon content (below 0.03%) should be used. Carbon can significantly improve the strength of steel, which does have an adverse effect on corrosion resistance.
Chromium Cr: Chromium is the basic component of stainless steel, and stainless steel requires a chromium content greater than 12% to remain passive. Increasing the chromium content is extremely effective in improving the corrosion resistance of steel to oxidizing acids, and also improves pitting corrosion resistance. The combination of chromium and oxygen can form a corrosion-resistant Cr2O3 passive film, which is one of the basic elements for maintaining corrosion resistance of stainless steel.
The increase of chromium content can improve the repair ability of the passive film of steel. Generally, the chromium content in stainless steel must be above 12%.
Phosphorus and sulfur (P, S): are harmful elements in stainless steel, which will adversely affect the corrosion resistance and punch ability of stainless steel.
Copper Cu: In terms of corrosion resistance, it increases the corrosion resistance to non-oxidizing acids, reduces the sensitivity to pitting corrosion, has good plasticity, and has excellent cold workability.