What is the P and S of the steel ?

The P index of the steel represents the phosphorus content, and S stands for sulphur content.
Phosphorus is strong in steel solid solution strengthening and cold work hardening effect. As alloy elements adding in low alloy structural steel can improve its strength and atmospheric corrosion resistance, but reduce the cold stamping performance.
The combination of phosphorus and sulfur and manganese can increase the cutting performance of the steel, increase the surface quality of the workpiece, and use it for easy cutting steel, so phosphorus content is also high for easy cutting steel.
Phosphorus dissolved in ferrite, although it can improve the strength and hardness of the steel, the biggest harm is serious segregation, increase the temper brittleness, significantly reduce the plasticity and toughness of steel, make the steel easy embrittlement during cold working, also known as "cold shortness" phenomenon. Phosphorus also has adverse effects on weldability. Phosphorus is a harmful element, should be controlled strictly, the general content is not more than 0.030% - 0.040%.
If Sulfur is heavy segregation in steel, it worsens the quality of steel. At high temperatures, it is a harmful element that reduces the plasticity of the steel, which is in the form of a low melting FeS.
The individual FeS melting point is 1190 ℃, and in the steel with iron forming eutectic, the eutectic temperature is more low, only about 988 ℃, when steel solidification, iron sulfide segregation centralized in the original grain boundary. During hot rolling in 1100-1100 ℃, the FeS will melt on the grain boundary, is greatly weakened the binding force between grains, causes the steel heat brittle phenomenon. Therefore, the sulfur should be strictly controlled, and the general content is 0.020%-0.050%. In order to prevent the brittleness caused by sulfur, it should be added enough manganese to form the high melting point MnS. If the sulfur content is high in steel, it will cause the SO2 in welding, the result is formed the air hole and porosity in the welding metal.
Shanghai Katalor offers various kinds of alloy steel, carbon steel and low alloy steel S235JR, S235J0, S235J2, S275JR, S275J0, S275J2, S355JR, S355J0, S355J2, if you need any alloy steel, please contact us in time.

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