(1) Carbon; The higher the carbon content, the higher the hardness of steel, but the worse its plasticity and toughness

(2) Sulfur; It is a harmful impurity in steel. Steel with high sulfur content is easy to embrittle during pressure processing at high temperature, which is usually called thermal embrittlement

(3) Phosphorus; It can significantly reduce the plasticity and toughness of steel, especially at low temperature. This phenomenon is called cold brittleness. In high-quality steel, sulfur and phosphorus should be strictly controlled. On the other hand, low carbon steel contains high sulfur and phosphorus, which can make it easy to cut, which is beneficial to improve the machinability of steel

(4) Manganese; It can improve the strength of steel, weaken and eliminate the adverse effects of sulfur, and improve the hardenability of steel. High alloy steel (high manganese steel) with high manganese content has good wear resistance and other physical properties

(5) Silicon; It can improve the hardness of steel, but the plasticity and toughness decrease. Electrical steel contains a certain amount of silicon, which can improve the soft magnetic properties

(6) Tungsten; It can improve the red hardness and thermal strength of steel, and improve the wear resistance of steel

(7) Chromium; It can improve the hardenability and wear resistance of steel, and improve the corrosion resistance and oxidation resistance of steel

In order to improve the corrosion resistance of steel pipes, general steel pipes (black pipes) are galvanized. Galvanized steel pipe is divided into hot-dip galvanizing and electric steel zinc. The hot-dip galvanizing layer is thick and the cost of electric galvanizing is low, so there is galvanized steel pipe.