The Failure Analysis Of Induction Hardening Crack For Non Quenched And Tempered Steel Crankshaft

As the key component of the engine,the non-quenched and tempered steel crankshaft is very demanding for the comprehensive performance of the finished product.In the production of non quenched and Tempered Steel Crankshafts for heavy truck 7L engines,there has been a problem of induction quenching cracks in production,and the rate of waste products fluctuates greatly.Because the induction hardening process is close to the last process of crankshaft production,the loss of cracks will increase the production cost.If there is leak detection in the detection process,there will be great quality risk for the whole machine.This article first carries on the statistical analysis to the crack location of WD07 crankshaft during induction hardening occurs,determine the location of most crack,and the crack location by means of traditional method and macro analysis method,preliminary determine the structure of box type cracks and segregation of raw materials and molding mold resistance design of the retaining wall position.Followed by DEFORM roll forging,the pre forging and finish forging process was simulated,and the effects of forging crack factors such as forging temperature,forging die fillet,material box type segregation,material flow rate by using the DEFORM numerical simulation,quantitative analysis of die fillet change caused by the effect of stress,strain,velocity caused by the influence of the crack,material box type horizontal and vertical segregation in the crack,puts forward improvement measures and improvement direction.Finally,according to the actual production confirmation,we can confirm that by improving the raw material segregation and improving the transition fillet of the mould,the ratio of induced quenching crack will be reduced,but a certain number of cracks will still appear.After further analysis,it is found that the carbon content and sulfur content of the material are in the upper limit of the ratio of the crankshaft induction hardening crack.The increase of C element,induction quenching martensite is obtained when the lattice distortion effect due to the increase of C,the stress also increased;S in the material mainly in the form of sulfides,the microstructure and morphology of sulfide as a separate individual,because of lower sulfide bearing material distortion ability,reduce the crack critical value,at the same time due to the presence of sulfide,crack conduction more easily,so the control box type and segregation of carbon and sulfur content become the key to solve the crack from the material aspect.