45号钢的正火工艺

On the normalization of 45 steel

韶钢炼轧厂生产的 45号钢在常规生产检验中发现材料规格对力学性能初检合格率有影响 .为此 ,随机抽取16、18、2 8、3 0mm 4个规格、11个炉号的 45号钢进行正火工艺试验 ,探讨了正火工艺对 45号钢力学性能的影响 .结果表明 :直径小于 2 5mm的 45号钢 ,正火工艺采用GB/T699- 1999标准推荐的工艺执行 ,即 85 0℃×40min ,力学性能达到标准要求 ;直径大于或等于 2 5mm的 45号钢 ,正火工艺采用 880℃× 3 0～ 60min也可达标 .金相检验表明 :这两种工艺处理试样的金相组织均为块状铁素体和大小均匀的珠光体 。

Routine inspections and tests showed that the mechanical properties of the 45 steel bar produced by the Continuous Casting and Rolling Plant of SISG Co. varied with its size. To investigate this phenomenon, steel bars in diameters of 16, 18, 28 and 30 mm were randomly sampled from 11 heats and normalized with different procedures. It was found that bars in diameter smaller than 25 mm normalized with the procedure recommended by GB/T699-1999 Standard, i.e. heating at 850(C for 40min, followed by air cooling, could meet the requirements for mechanical property, while those in diameter larger than 25mm had to be normalized by heating at 880 ℃ for 30～60 min in order to meet the requirements. Metallography of the normalized steel bars demonstrated that a microstructure composed of massive ferrite and evenly_sized pearlite was generated by the normalization, which possessed the required strength and ductility.