Effects of Chemical Elements on Stainless Steel Pipes (Part One)

1. Carbon(C): When the carbon content in the stainless steel pipes is increased, yield and tensile strength of stainless steel pipes will be increased, but the plasticity and impact strength will be reduced. When the carbon content is more than 0.23%, stainless steel pipes will have the deteriorated welding performance, so the carbon content in the low-alloy structural steel for welding is generally less than 0.20%. The high carbon content will decrease the stainless steel pipe's resistance to atmospheric corrosion, which will make the stainless steel pipe with the high carbon content easy to rust in the open field. In addition, the carbon can increase the cold brittleness and aging sensitivity of stainless steel pipes.
2. Silicon(Si): Usually, the silicon is added into the steel in the steelmaking process as a reducing agent and deoxidizer, so the killed steel contains the silicon from 0.15% to 0.30%. If the silicon content in the stainless steel pipe exceeds 0.60%, silicon will belong to the alloy elements. Silicon can significantly improve the elastic limit, the yield point and the tensile strength of the stainless steel pipe, which makes it widely used for the spring steel. For the stainless steel pipe made of the quenched and tempered structural steel, by adding 1.0% to 1.2% silicon, the strength of the stainless steel pipe can be increased by 15% to 20%. If the silicon is used combined with the molybdenum, tungsten, chromium and other chemical elements, it can improve the corrosion resistance and oxidation resistance of the stainless steel pipe and can be used to manufacture the heat-resistant stainless steel pipe. The low-carbon steel with the silicon content from 1% to 4% has the high magnetic permeability, and can be used to manufacture the silicon steel sheet for the electrical industry. Increasing silicon content will decrease the welding performance of the stainless steel pipe.

3. Manganese(Mn): Manganese is a good deoxidizer as well as desulfurizing agent in the steelmaking processes. The manganese content in the ordinary steel is usually between 0.30% and 0.50%. If the manganese content in the carbon steel is more than 0.70%, the steel can be called the manganese steel which has higher strength and hardness than the ordinary steel. When the manganese content in the stainless steel pipe is increased, the corrosion resistance and welding performance of the stainless steel pipe are decreased.
4. Phosphorus(P): In general, phosphorus is a harmful element in steel, and it will increase the cold brittleness, reduce the plasticity and deteriorate the welding and cold bending performance of stainless steel pipes. So usually it is required that the phosphorus content in the stainless steel pipe should be less than 0.045%, and the high quality stainless steel pipe even have higher requirements on the phosphorus content.

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