Cause analysis and mechanism study of fracture splitting drop-dregs of C70S6 material connecting rod
The chemical composition,metallographic structure,macro and micro morphology of fracture splitting,and mechanical properties of C70S6 material connecting rod were detected and analyzed by spark discharge atomic emission spectrometer,metallographic microscope,scanning electron microscope(SEM)and universal tensile testing machine.The fracture splitting drop-dregs cause and mechanism of connecting rod big head hole were analyzed.The results showed that the fracture splitting drop-dregs position was mainly near billet parting plane,and the grain size at the parting plane of drop-dregs connecting rod was Grade 6.5.The content of ferrite was 7.0％(mass fraction,the same below),and the grain size difference of the whole fracture splitting surface was Grade 3.5.The edge of dropped steel slag showed obvious char-acteristics of ductile fracture.The grain size at the parting plane of no drop-dregs connecting rod was Grade 5,and the ferrite content was 5.0％.The grain size difference of fracture splitting surface was Grade 0.5,and the microstructure uniformity was good.The microstructure showed the characteristics of brittle cleavage.The comprehensive analysis showed that the microstructure of connecting rod billet was not uniform,the local grains were fine,and the overall grade difference was large,resulting in the high lo-cal plasticity of billet material,which was the root cause of the chip loss.By adjusting the production and heat treatment process of the bar for forging connecting rod,the grain size of microstructure was coars-ened,the grain size difference and ferrite content was reduced.Consequently,the problem of drop-dregs loss was completely eliminated.
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万方数据
