Classification of alloy structural steel

According to the carbon content, alloy structural steel is divided into low carbon alloy steel, medium carbon alloy steel and high carbon alloy steel. According to the strength, alloy structural steel is divided into general strength steel, high strength steel and ultra-high strength steel. But the definition of high-strength steel and ultra-high-strength steel is not clear. The fastener industry generally believes that high strength means that the tensile strength is not less than 104OMPa (that is, above 10.9), and most of them are obtained by quenching and tempering or isothermal quenching and tempering to obtain a sorbite structure. Comprehensive mechanical properties such as good plasticity and toughness, high fatigue strength and low cold-brittle transition temperature. Ultra-high-strength steel refers to steel with a nominal tensile strength of not less than 1470MPa. Generally, tempered martensitic structure is obtained by quenching and low-temperature tempering or bainite structure is obtained by isothermal quenching. It has high strength, fatigue resistance and suitable toughness. The choice of material form mainly considers the processing technology. Low-carbon alloy steel and riveting screw steel have good cold deformation plasticity, and are mainly formed by cold emblem, so coiled material should be selected; medium carbon alloy steel and ultra-high-strength steel have poor cold deformation plasticity, and cold tenderness is difficult, mainly hot tender. And mechanical processing is the main, it is more suitable to choose the bar. Storage requirements: Alloy steel has poor corrosion resistance without protection. During storage, avoid rain, keep humidity less than 75%, and temperature between 5°C and 35°C. When there is no coating on the surface, Anti-rust oil needs to be applied and checked every year. If the anti-rust oil evaporates, it needs to be repainted.