ML40Cr盘条冷镦性能研究

Research of ML40Cr wire rod cold heading property

分别采用轧制坯和连铸坯生产φ16 mm ML40Cr冷镦钢盘条,连铸坯盘条冷镦后试样全部合格,轧制坯盘条经1/4冷镦后1个试样出现斜裂纹。对2种坯料生产的盘条夹杂物进行分析,夹杂物级别相对较低且相差不大;连铸坯和轧制坯盘条金相组织均为珠光体+铁素体;晶粒度均为9.5～10级,分布均匀;连铸坯生产的16 mmML40Cr盘条带状组织为3级,存在较轻微的枝晶组织,轧制坯生产的盘条带状组织为2.5级,盘条中存在较明显的方框形偏析。分析表明:连铸坯中的方框形偏析经加热、轧制后难以消除,盘条中晶粒细小,使得钢的变形抗力增大,增加了盘条的开裂倾向。

Diameter 16 mm ML40Cr cold heading steel wire rod is produced by adopting rolling billet and continuous cast- ing separately, the specimens are all qualified after continuous casting wire rod is cold headed, inclined crack occurs in one specimen after rolling block wire rod is 1/4 cold headed. The inclusions of wire rod produced with two kinds of billets are analyzed, inclusions grade is low and difference is small. Microstructure of continuous casting and rolling billet is p^arlite and ferrite. Grain size is 9.5 -10 grade and distribution is even. The band structure of diameter 16 mm MIAOCr wire rod produced with continuous casting is 3 grade, slight dendritic structure exists. The band structure of wire rod produced with rolling billet is 2. 5 grade, obvious box shaped segregation exists in wire rod. Analyzed result shows that box shaped segre- gation in continuous casting cann＇ t be removed after heating and rolling, grain size of wire rod is small, which enlarge the deformation resistance of steel and increase the cracking tendency of wire rod.