1.Carbon (C)
The carbon content in the steel increases, while the yield point and tensile strength increase, but the plasticity and impact property decrease. When the carbon content exceeds 0.23%, the welding performance of the steel deteriorates. Therefore, the carbon content of low alloy structural steel used for welding generally does not exceed 0.20%. High carbon content will also reduce the atmospheric corrosion resistance of steel, and the high carbon steel in the open pit is easy to rust; In addition, carbon can increase the cold brittleness and aging sensitivity of steel.
2. Silicon (Si)
silicon is added as reducing agent and deoxidizer during steelmaking, so killed steel contains 0.15-0.30% silicon. If the silicon content in steel exceeds 0.50-0.60%, silicon is considered as an alloy element. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel, so it is widely used as spring steel. The strength of quenched and tempered structural steel can be increased by 15-20% by adding 1.0-1.2% silicon. Silicon combined with molybdenum, tungsten and chromium can improve corrosion resistance and oxidation resistance, and can be used to make heat-resistant steel. Low carbon steel containing 1-4% silicon has very high magnetic permeability. It is used in the electrical industry to make silicon steel sheets. The increase of silicon content will reduce the weldability of steel.
