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在拔制无缝钢管过程中,冷拔顶头承受大的挤压和剪切应力。要求顶头外表面应有较高的硬度和耐磨性,心部有较高的强度和韧性。45钢顶头多采用车削成型-表面渗碳(渗层1.8~2.3mm)-淬火+低温回火-精磨-镀铬及抛光的工艺。金工车间在加工φ69(外径)顶头时,经镀铬和抛光后顶头外表面,出现网状微裂纹(图1),废品率高达30%。为此我们对顶头外表面裂纹进行了检验与分析,找出了产生原因及消除缺陷的方法。金相观察表明,横向未经腐蚀的试样,
In the drawing of seamless steel pipe, cold drawn head to withstand large squeeze and shear stress. Require the outer surface of the head should have a higher hardness and wear resistance, the heart has a higher strength and toughness. 45 steel head more turning shape - surface carburizing (infiltration layer 1.8 ~ 2.3mm) - quenching and tempering - refining - chrome and polishing process. Metalworking shop in processing φ69 (diameter) head, chrome and polished head after the outer surface, mesh crazing (Figure 1), rejection rate of up to 30%. To this end, we test and analyze the crack on the outer surface of the head, find out the causes and ways to eliminate the defects. Metallographic observation shows that the horizontal unetched sample,