钢是含碳量小于2.11％的铁碳合金,按化学组成可分为碳钢和合金钢两大类.含碳量小于0.25％的叫低碳钢,含碳量为0.25～0.60％的叫中碳钢,含碳量大于0.60％的叫高碳钢;合金元素含量小于5％的叫低合金钢,5～10％的叫中合金钢,大于10％的叫高合金钢。按用途分为结构钢、工具钢、特殊性能钢三大类。结 Steel is an iron-carbon alloy with a carbon content of less than 2.11%, which can be divided into two categories of carbon steel and alloy steel by chemical composition: carbon steel with a carbon content of less than 0.25% is called low-carbon steel with a carbon content of 0.25-0.60% Medium carbon steel, carbon content greater than 0.60% is called high carbon steel; alloy content less than 5% called low alloy steel, 5-10% called medium alloy steel, more than 10% called high alloy steel. Use divided into structural steel, tool steel, special performance steel three categories. Knot