Transactions of Materials and Heat Treatment

Title：Defect analysis and mechanism discussion on forged automobile MR crankshaft

Authors： Ma Qiang Liu Jun Meng Qingyu

Unit： Baoshan Iron & Steel Co. Ltd.

KeyWords： forging MR crankshaft crack folding overheating

ClassificationCode：TG316

year,vol(issue):pagenumber：2017,42(10):26-32

Abstract：

Crack and folding defects existing on one end of automobile MR crankshaft flange processed by induction heating and forging for continuous casting microalloyed steels with C0.40%-Mn0.68%-S0.022%-V0.049% were found at the forging flash and the vertical plane respectively, and the above defects were analyzed and discussed by metallographic microscope, scanning electron microscopy combined with electronic probe and other means. The results show that there are decarburization of 0.2 mm near the crack with the same depth as the forged condition, the crack is characterized by intergranular fracture with widmannstatten structure around, the inclusions of (Mn, Fe)S present intergranular and intracrystalline widmannstatten precipitate morphology, and the microstructure of folding defect is similar to that of the crack. Furthermore, the causes of crack defects are the surface transverse cracks caused by the local overheating of material in the induction heating process and extended by external forging forces. However, the folding is formed by metal material merging into a stream in the final forging because of different flow rates of forging material caused by the uneven distribution of bar temperature making the material bending or sinking at the end.

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作者简介：马强（1982-），男，硕士，工程师，E-mail：maqiang@baosteel.com

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