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45钢在冷轧过程中出现纵向局部开裂的现象。利用光学显微镜、显微硬度计、SEM和直读光谱等设备分析45钢圆钢和开裂管的化学成分、显微组织、断口形貌和显微硬度。利用冷轧45钢加工硬化函数曲线对轧制的钢管变形参数进行计算。结果表明,45钢圆钢在穿孔及轧制后发生明显加工硬化降低了韧性及塑性,冷轧钢管的变形量过大导致产生较大的内应力造成在轧制时开裂。采用再结晶退火可消除钢管加工硬化,合理设计钢管轧制变形量提高了钢管质量,避免了管体开裂。
45 steel in the cold-rolled longitudinal phenomenon of local cracking. The chemical composition, microstructure, fracture morphology and microhardness of 45 steel round bar and cracked pipe were analyzed by optical microscope, microhardness tester, SEM and direct reading spectrometer. The deformation parameters of rolled steel tube were calculated by using the work hardening curve of cold-rolled 45 steel. The results show that the obvious hardening of 45 steel bar after perforation and rolling reduces the ductility and plasticity. The excessive deformation of cold-rolled steel pipe results in large internal stress that causes cracking during rolling. The use of recrystallization annealing can eliminate work hardening, rational design of steel pipe rolling deformation to improve the quality of steel, to avoid the tube cracking.