冷却速率越大或预变形处理以后的试样在熔化过程中更容易发生二次枝晶臂之间的合并。
The more the increase of cooling rate or pre-deformation, the more the secondary dendrite arms are easy to coarsen.
对含有内部裂纹的45钢试样采取了不同温度一次加热正火处理和二次加热正火处理，研究了其内部裂纹愈合的可能性。
The possibility of inner microcrack healing was studied by normalizing the 45 steel samples containing inner crack for one time and two times respectively.
结果表明：在焊缝区域内存在着局部未熔区以及铸造疏松组织和二次裂纹等缺陷，这是导致试样低应力断裂的根本原因。
The results show that the partial unmelted region, casting defect structure and secondary crack form in the welding seam, which result in the low stress breakage of the samples.
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