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针对火车车厢中梁用钢YQ450NQR1高强耐候钢的腿部拉裂问题,运用金相显微镜、扫描电镜和能谱仪对拉裂裂纹形貌进行分析;设计裂纹脱碳模拟试验,探明裂纹两侧发生脱碳的工艺条件并判定裂纹产生工序;通过对铸坯原料进行低倍检测明确与拉裂相对应的连铸坯质量缺陷,并结合检测结果对铸坯缺陷产生原因进行分析。研究结果表明,腿部拉裂缺陷是由严重的铸坯边部皮下网状裂纹造成的,而钢水在结晶器中冷却不均匀、残余元素含量高以及氮含量波动范围过大是造成皮下网状裂纹的主要原因。通过采取措施,YQ450NQR1钢腿部拉裂率由原来的0.5%~3.5%稳定控制在1%以下。
Aiming at the problem of the leg crack of YQ450NQR1 high-strength weather-proof steel for the railcar in the train car, the crack shape of the crack was analyzed by means of optical microscope, scanning electron microscope and energy dispersive spectrometer. The crack decarburization simulation test was designed to detect the occurrence of crack on both sides of the crack Carbon process conditions and determine the crack generation process; through the raw material of the slab at a low detection to determine the quality of the continuous casting slab defects, and combined with the test results cast slab defects were analyzed. The results show that the leg rupture defects are caused by serious subcutaneous mesh cracks on the edge of the slab. However, the molten steel is unevenly cooled in the crystallizer, the residual element content is high and the fluctuation range of nitrogen content is too large. The main reason for cracks. By taking measures, YQ450NQR1 steel leg rupture rate from the original 0.5% ~ 3.5% stable control in less than 1%.