Generally, carbon, silicon and manganese are added to stainless steel castings. Many people may feel a little confused about this. Why not add these elements? In fact, castings can be made without these elements, but the quality of castings made in this way is very poor, and the performance will be very low. This is because:

1. Carbon (C): The yield point and tensile strength of steel increase with the increase of carbon content, but the plasticity and impact property decrease. When carbon content exceeds 0.23%, the weldability of steel deteriorates. Therefore, the carbon content of low alloy structural steel used for welding generally does not exceed 0.20%. High carbon content also decreases the atmospheric corrosion resistance of steel, which is easy to rust in open-air material yard. In addition, carbon can increase the cold brittleness and aging sensitivity of stainless steel castings.

2. Silicon (Si): Silicon is added as reducing agent and deoxidizing agent in steelmaking process, so killed steel contains 0.15-0.30% silicon. If the content of silicon in steel exceeds 0.50-0.60%, silicon is an alloy element. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel. However, if the silicon content increases, the weldability of stainless steel castings will be reduced.

3. Manganese (Mn): In steelmaking process, manganese is a good deoxidizer and desulfurizer, generally containing 0.30-0.50% manganese in steel. When more than 0.70% of carbon steel is added, the "manganese steel" not only has enough toughness, but also has higher strength and hardness, which can improve the hardenability of steel and the hot working performance of stainless steel castings.