An unqualifed six-cylinder heavy truck crankshaft has been studied to investigate the cause of magnetic particle testing defects on the rod journals.Large-sized long-striped MnS inclusions are regarded as the major ca...An unqualifed six-cylinder heavy truck crankshaft has been studied to investigate the cause of magnetic particle testing defects on the rod journals.Large-sized long-striped MnS inclusions are regarded as the major cause for the magnetic particle testing failure because they have been detected in situ under the magnetic particle indications.Through the observation of macroscopic structures of the rod journals and corresponding counterweight blocks,it is found that for the 1#and 3#rod journals,the center metal of the original hot-rolled bar has been extruded to the inboard edge of the rod journals and large-sized long-striped MnS inclusions are exposed on the surface after fash removal,leading to the failure of magnetic particle testing.As for the 2#rod journal,the center metal of the original bar has not been extruded to the surface and MnS inclusions on the rod journal surface are small in size,few in number,resulting in passing the magnetic particle testing.If the quality of the hot-rolled bars fuctuates,it is more recommended to apply magnetic particle testing on samples at the center of bars before forging to evaluate the severity of defects caused by the long-striped MnS inclusions for fear of the scrap of the fnal crankshafts.展开更多
In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundr...In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Based on the analysis, a new casting technology of the chain wheel was designed and used in the casting production successfully.展开更多
基金The authors are grateful to the financial support provided by the National Natural Science Foundation of China(Grant Nos.51874034 and 51674024).
文摘An unqualifed six-cylinder heavy truck crankshaft has been studied to investigate the cause of magnetic particle testing defects on the rod journals.Large-sized long-striped MnS inclusions are regarded as the major cause for the magnetic particle testing failure because they have been detected in situ under the magnetic particle indications.Through the observation of macroscopic structures of the rod journals and corresponding counterweight blocks,it is found that for the 1#and 3#rod journals,the center metal of the original hot-rolled bar has been extruded to the inboard edge of the rod journals and large-sized long-striped MnS inclusions are exposed on the surface after fash removal,leading to the failure of magnetic particle testing.As for the 2#rod journal,the center metal of the original bar has not been extruded to the surface and MnS inclusions on the rod journal surface are small in size,few in number,resulting in passing the magnetic particle testing.If the quality of the hot-rolled bars fuctuates,it is more recommended to apply magnetic particle testing on samples at the center of bars before forging to evaluate the severity of defects caused by the long-striped MnS inclusions for fear of the scrap of the fnal crankshafts.
文摘In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature gradient results in a wider mushy zone at the S/L interface that causes the defects and MT thin lines on the surface of the chain wheel casting. Based on the analysis, a new casting technology of the chain wheel was designed and used in the casting production successfully.
