The five elements commonly used in steel that affect the welding performance of steel are carbon, silicon, manganese, phosphorus, and sulfur.

1. Carbon: As the carbon content in 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 the steel deteriorates. Therefore, the carbon content of low-alloy structural steel used for welding generally does not exceed 0.2%. High carbon content will also reduce the steel's resistance to atmospheric corrosion. High-carbon steel in open-air material yards is prone to rust. In addition, carbon can increase the cold brittleness and aging sensitivity of steel.
2. Silicon: Silicon is added as a reducing agent and deoxidizer during the steelmaking process, so calm steel contains 0.3% silicon. If the silicon content in steel exceeds 0.6%, silicon is considered an alloying element. Silicon can significantly increase the elastic limit, yield point, and tensile strength of steel, so it is widely used as spring steel. Adding 1.2% silicon to quenched and tempered structural steel can increase the strength by 15-20%.
3. Manganese: In the steelmaking process, manganese is a good deoxidizer and desulfurizer. Generally, steel contains 0.3-0.5% manganese. When more than 0.7% is added to carbon steel, it is called "manganese steel". Compared with ordinary steel, the steel has not only sufficient toughness, but also higher strength and hardness, improves the hardenability of steel, and improves the hot processing performance of steel.
4. Phosphorus: Phosphorus is a harmful element in steel, which increases the cold brittleness of steel, deteriorates welding performance, reduces plasticity, and deteriorates cold bending performance. Therefore, the phosphorus content in steel is usually required to be less than 0.045%, and the requirement for high-quality steel is lower.
5. Sulfur: Sulfur is also a harmful element under normal circumstances. It makes steel hot and brittle, reduces the ductility and toughness of steel, and causes cracks during forging and rolling. Sulfur is also not good for welding performance and reduces corrosion resistance.

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