1. Carbon (C): The carbon content in the steel increases, the yield point and tensile strength increase, but the plasticity and impact decrease.

2. Silicon (Si): When adding silicon as a reducing agent and deoxidizer in the steelmaking process, silicon can significantly improve the elastic limit, yield point and tensile strength of steel. The combination of silicon and molybdenum, tungsten, chromium, etc. can improve corrosion resistance and oxidation resistance, and can manufacture heat-resistant steel. Low carbon steel with silicon content of 1-4% has extremely high magnetic permeability, and is used in electrical industry to make silicon steel sheets. An increase in the amount of silicon will reduce the weldability of the steel.

3. Manganese (Mn): In the process of steelmaking, manganese is a good deoxidizer and desulfurizer. Generally, manganese in steel is 0.30-0.50%. When more than 0.70% is added to carbon steel, it is considered "manganese steel", which not only has sufficient toughness, but also has high strength and hardness, which improves the hardenability of steel and improves the hot workability of steel. In stainless steel, it can increase the solubility of nitrogen and inhibit the harmful effects of sulfur. The increase of manganese content is not conducive to high temperature oxidation resistance and reduces the plasticity of steel.

4. Phosphorus (P): In general, phosphorus is a harmful element in steel, which increases the cold brittleness of steel, makes welding performance worse, reduces plasticity, and makes cold bending performance worse. Therefore, the phosphorus content in steel is usually required to be less than 0.045%, and the requirements for high-quality steel are lower.

5. Sulfur (S): Sulfur is also a harmful element under normal circumstances. It makes the steel hot brittle, reduces the ductility and toughness of the steel, and causes cracks during forging and rolling. Sulfur is also detrimental to weldability, reducing corrosion resistance. Therefore, high-quality steel is usually required to be less than 0.040%. Adding 0.08-0.20% sulfur to steel can improve machinability, usually called free-cutting steel.

6. Chromium (Cr): In structural steel and tool steel, chromium can significantly improve strength, hardness and wear resistance, but at the same time reduce plasticity and toughness. Chromium can also improve the oxidation resistance and corrosion resistance of steel, so it is an important alloying element of stainless steel and heat-resistant steel.

7. Nickel (Ni): Nickel can improve the strength of steel while maintaining good plasticity and toughness. Nickel has high corrosion resistance to acid and alkali, rust and heat resistance at high temperature.

8. Molybdenum (Mo): Molybdenum can refine the grains of steel, improve hardenability and thermal strength, and maintain sufficient strength and creep resistance at high temperatures (long-term stress at high temperature, deformation occurs, called creep). Molybdenum is added to structural steel to improve mechanical properties. The brittleness of alloy steel due to quenching can also be suppressed.

9. Titanium (Ti): Titanium is a strong deoxidizer in steel. It can make the internal structure of steel dense, refine grains, reduce aging sensitivity and cold brittleness. Improve welding performance. Adding appropriate titanium to the chromium 18 nickel 9 austenitic stainless steel can avoid intergranular corrosion.

10. Vanadium (V): Vanadium is an excellent deoxidizer for steel. Adding 0.5% vanadium to the steel can refine the microstructure and grains and improve the strength and toughness. Carbides formed by vanadium and carbon can improve the resistance to hydrogen corrosion under high temperature and high pressure.

11. Tungsten (W): Tungsten has a high melting point and a large specific gravity. Tungsten and carbon form tungsten carbide with high hardness and wear resistance. Adding tungsten to tool steel can significantly improve red hardness and thermal strength, and can be used for cutting tools and forging dies.

12. Niobium (Nb): Niobium can refine the grains and reduce the overheating sensitivity and temper brittleness of the steel, and improve the strength, but the plasticity and toughness decrease. Adding niobium to ordinary low alloy steel can improve the resistance to atmospheric corrosion and hydrogen, nitrogen and ammonia corrosion at high temperature. Niobium improves weldability. The addition of niobium to austenitic stainless steel can prevent intergranular corrosion.

13. Cobalt (Co): Cobalt is a rare precious metal, which is mostly used in special steels and alloys, such as heat-strength steels and magnetic materials.

14. Copper (Cu): Improve corrosion resistance in sulfuric acid medium, surface antibacterial properties, improve cold formability, and reduce thermoplasticity.

15. Aluminum (Al): Aluminum is a deoxidizer commonly used in steel. A small amount of aluminum is added to the steel to refine the grains and improve the impact toughness. Aluminum also has anti-oxidation and anti-corrosion properties. The combination of aluminum and chromium and silicon can significantly improve the high-temperature peeling properties and high-temperature corrosion resistance of steel. The disadvantage of aluminum is that it affects the hot workability, weldability and machinability of steel.

16. Boron (B): Adding a small amount of boron to the steel can improve the compactness and hot rolling properties of the steel and increase the strength.

17. Nitrogen (N): Nitrogen can improve the strength, low temperature toughness and weldability of steel, and increase aging sensitivity.