Influence of various trace elements on stainless steel

The term "stainless steel" does not simply refer to one type of stainless steel, but to more than one hundred industrial stainless steels, each of which has been developed to perform well in its specific application. The key to success is first to understand the purpose , and then determine the correct steel grade. There are usually only six steel grades related to building construction applications. They all contain 17 to 22% chromium, and the better grades also contain nickel. Adding molybdenum can further improve atmospheric corrosion. , especially the corrosion resistance of chloride-containing atmosphere. Therefore, trace elements play a decisive role in the performance of steel

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

(2) Sulfur: It is a harmful contaminant in steel. When steel with high sulfur content is subjected to pressure processing at high temperature, it is easy to be brittle, which is usually called hot brittleness;

(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. But on the other hand, the high content of sulfur and phosphorus in low carbon steel 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. The steel used for electrician 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 can improve the wear resistance of steel;

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

(8) Vanadium: It can refine the grain structure of steel and improve the strength, toughness and wear resistance of steel. When it melts into austenite at high temperature, it can increase the hardenability of steel; on the contrary, when it exists in the form of carbide, it will reduce its hardenability;

(9) Molybdenum: It can significantly improve the hardenability and thermal strength of steel, prevent temper brittleness, and improve remanence and coercive force;

(10) Titanium: It can refine the grain structure of steel, thereby improving the strength and toughness of steel. In stainless steel, titanium can eliminate or reduce the intergranular corrosion phenomenon of steel;

(11) Nickel: It can improve the strength and toughness of steel and improve hardenability. When the content is high, some physical properties of steel and alloys can be significantly changed, and the corrosion resistance of steel can be improved;

(12) Boron: When the steel contains a small amount of (0.001-0.005%) boron, the hardenability of the steel can be doubled;

(13) Aluminum: It can refine the grain structure of steel and inhibit the aging of low carbon steel. Improve the toughness of steel at low temperature, but also improve the oxidation resistance of steel, improve the wear resistance and fatigue strength of steel, etc.; (14) Copper: its prominent role is to improve the atmospheric corrosion resistance of ordinary low-alloy steel, especially It is more obvious when used in combination with phosphorus.