1, carbon (C) : the carbon content in the steel increases, the yield point and tensile strength increases, but the plasticity and impact are reduced, when the carbon content exceeds 0.23%, the welding performance of the steel deteriorates, so the low alloy structural steel used for welding, the carbon content generally does not exceed 0.20%. The high carbon content will also reduce the atmospheric corrosion resistance of the steel, and the high carbon steel in the open air yard is easy to rust; In addition, carbon can increase the cold brittleness and aging sensitivity of steel.
2, silicon (Si) : in the steelmaking process to add silicon as a reducing agent and deoxidizer, so the sedative steel contains 0.15-0.30% silicon. If the silicon content of the steel exceeds 0.50-0.60%, silicon is considered an alloying element. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel, so it is widely used as spring steel. When 1.0-1.2% silicon is added to the tempered structural steel, the strength can be increased by 15-20%. The combination of silicon and molybdenum, tungsten, chromium, etc., has the effect of improving corrosion resistance and oxidation resistance, and can manufacture heat-resistant steel. Low carbon steel containing 1-4% silicon, with very high magnetic permeability, used in the electrical industry to make silicon steel sheet. The increase of silicon will reduce the weldability of the steel.
3, manganese (Mn) : in the process of steelmaking, manganese is a good deoxidizer and desulfurizer, and the general steel contains 0.30-0.50% manganese. When more than 0.70% is added to carbon steel, it is considered as "manganese steel", which is not only sufficient toughness, but also has higher strength and hardness than the general steel, improving the quenching of steel and improving the thermal processing performance of steel, such as 16Mn steel is 40% higher than A3 yield point. Steel containing 11-14% manganese has extremely high wear resistance and is used in excavator buckets, ball mill linings, etc. The increase of manganese content weakens the corrosion resistance of steel and reduces the weldability.
4. Phosphorus (P) : under normal circumstances, phosphorus is a harmful element in steel, which increases the cold brittleness of steel, deteriorates the welding performance, reduces plasticity, and deteriorates the cold bending performance. 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. The steel produces hot brittleness, reduces the ductility and toughness of the steel, and causes cracks during forging and rolling. Sulfur is also detrimental to welding performance, reducing corrosion resistance. Therefore, the sulfur content is usually required to be less than 0.055%, and the high-quality steel is required to be less than 0.040%. Adding 0.08-0.20% sulfur to the steel can improve the 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 prevention and heat resistance at high temperatures. However, because nickel is a scarce resource, it should try to use other alloying elements instead of nickel-chromium steel.
8, molybdenum (Mo) : molybdenum can refine the grain of steel, improve hardenability and thermal strength, and maintain sufficient strength and creep resistance at high temperatures (long-term stress at high temperatures, deformation, called creep). Adding molybdenum to structural steel can improve mechanical properties. It can also inhibit the brittleness of alloy steel due to fire. It can improve redness in tool steel.
9, titanium (Ti) : titanium is a strong deoxidizer in steel. It can make the internal structure of the steel dense, refine the grain strength; Reduces aging sensitivity and cold brittleness. Improve welding performance. Intergranular corrosion can be avoided by adding appropriate titanium to chromium-18 nickel-9 austenitic stainless steel.
10, Vanadium (V) : Vanadium is an excellent deoxidizer for steel. Adding 0.5% vanadium to steel can refine grain structure and improve strength and toughness. The carbides formed by vanadium and carbon can improve the resistance to hydrogen corrosion at high temperature and pressure.
11, tungsten (W) : tungsten melting point is high, the ratio is significant, is a precious alloy element. Tungsten carbide forms with carbon Tungsten carbide has a high hardness and wear resistance. Adding tungsten to tool steel can significantly improve the red hardness and thermal strength, and can be used as cutting tools and forging dies.
12, niobium (Nb) : Niobium can refine the grain and reduce the overheating sensitivity and tempering brittleness of steel, improve strength, but the plasticity and toughness have decreased. Adding niobium to ordinary low alloy steel can improve the resistance to atmospheric corrosion and hydrogen, nitrogen and ammonia corrosion at high temperature. Niobium can improve welding performance. Adding niobium to austenitic stainless steel can prevent intergranular corrosion.
13, cobalt (Co) : Cobalt is a rare precious metal, mostly used in special steel and alloys, such as heat-strong steel and magnetic materials.
14, copper (Cu) : WisCO with Daye ore refined steel, often contains copper. Copper can improve strength and toughness, especially atmospheric corrosion performance. The disadvantage is that it is easy to produce hot brittleness during hot processing, and the plastic content of copper exceeds 0.5% is significantly reduced. When the copper content is less than 0.50%, the weldability is not affected.
15, aluminum (Al) : Aluminum is a commonly used deoxidizer in steel. Adding a small amount of aluminum to the steel can refine the grain and improve the impact toughness, such as 08Al steel for deep drawing sheet. Aluminum also has oxidation resistance and corrosion resistance, aluminum and chromium, silicon combined, can significantly improve the high temperature non-peeling performance of steel and high temperature corrosion resistance. The disadvantage of aluminum is that it affects the thermal processing performance, welding performance and cutting performance of steel.
16, boron (B) : Adding a trace amount of boron to steel can improve the densification and hot rolling performance of steel, improve strength.
17, nitrogen (N): nitrogen can improve the strength of steel, low temperature toughness and weldability, increase aging sensitivity.
18, rare earth (Xt) : Rare earth elements are 15 lanthanides in the periodic table with atomic numbers of 57-71. These elements are all metals, but their oxides are very much like "earth", so they are commonly called rare earths. The addition of rare earths to steel can change the composition, form, distribution and properties of inclusions in steel, thereby improving various properties of steel, such as toughness, weldability, and cold working performance. Adding rare earth to share steel can improve wear resistance.
