Chemical Elements Affecting Steel Properties

Is there any effect of different chemical elements on the properties of steel? If so, how much influence? Let’s analyze and introduce the different reactions of various chemical elements to the properties of steel:

1. Carbon (C): The carbon content of steel increases, the yield point, and tensile strength increase, but the plasticity and impact resistance decrease. When the carbon content exceeds 0.23%, the welding performance of steel deteriorates, so it is used for welding. The carbon content of low-alloy structural steel generally does not exceed 0.20%. High carbon content also reduces the steel’s resistance to atmospheric corrosion, and high carbon steel in open-air stockyards is susceptible to corrosion; in addition, carbon can increase the cold brittleness and age sensitivity of steel.

2. Silicon (Si): During the steelmaking process, silicon is added as a reducing agent and a deoxidizing agent, so the killed steel contains 0.15 to 0.30% silicon. If the silicon content in 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. Adding 1.0-1.2% silicon to the quenched and tempered structural steel can increase the strength 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 extremely high magnetic permeability, is used for silicon steel sheets in the electrical industry. Increasing the amount of silicon will reduce the welding performance of steel.

3. Manganese (Mn): Manganese is a good deoxidizing agent and a desulfurizing agent in the steelmaking process. Generally, manganese contains 0.30-0.50% of manganese. Adding 0.70% or more to carbon steel is regarded as “manganese steel”. Compared with steel with ordinary steel content, it not only has sufficient toughness, but also has higher strength and hardness, improves the hardenability of steel, and improves the hot workability of steel. For example, 16Mn steel is 40% higher than the A3 yield point. 11-14% steel containing manganese has an extremely high abrasion resistance and is used in excavator buckets, ball mill liners, etc. Increasing the amount of manganese reduces the corrosion resistance of steel and reduces welding performance.

4. Phosphorus (P): In general, 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 of steel is usually required to be less than 0.045%, and the requirements of high-quality steel are lower.

5. Sulfur (S): Sulfur is also a harmful element under normal circumstances. 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 welding performance and reduces corrosion resistance. Therefore, the sulfur content is usually required to be less than 0.055%, and the quality steel is required to be less than 0.040%. Adding 0.08-0.20% sulfur to the steel can improve the machinability, which is usually called free-cutting steel.

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

Through the introduction of the influence of the six chemical elements on the properties of steel, we have learned that the influence of steel properties on different chemical elements is different.