What main alloying elements are used in alloy structural steel and their functions?

Manganese improves hardenability and eliminates harmful iron sulfide impurities inside the matrix. Chromium boosts tensile strength, wear resistance and corrosion resistance of finished parts. Nickel significantly enhances low-temperature impact toughness to prevent brittle fracture under cold working environments. Molybdenum restricts temper brittleness during heat treatment and stabilizes strength under long-term moderate high-temperature loads. Silicon refines grain structure and elevates elastic limit. Every element is added within fixed narrow ranges to avoid performance defects and meet standard mechanical indicators for structural service.