Effect Of Transition Zone Characteristics On Cold Forming Properties Of High Strength Steel Tailor Rolled Blank

Automobile light weighting has become one of the development trends of the automotive industry in recent years.Tailor rolled blank(TRB)is a special lightweight sheet for automobiles.It has been applied in body parts by designing flexibly multi-segment variable thickness according to the force of the parts.In this paper,the low-alloy high-strength steel HC340LA is used as raw material to analyze the reasons for the difference in the performance of TRB.The U-channel is taken as an example to simulate and analyze the cold forming performance of TRB.The characteristics of TRB mold design are proposed,and the variation of the springback parameters and the springback value are reduced by the optimization of the pressing parameters.All of these provide reference for the design and stamping adjustment of the TRB mold in actual production.The main research contents are as follows:(1)In order to obtain the mechanical properties of the transition zone,the transition zone is discretely processed.The 2.2mm thick plate of the raw material was rolled into six equal thickness plates of diferent thicknesses(1.0mm?1.2mm?1.4mm?1.6mm?1.8mm?2.0mm).The annealing and tensile tests were carried out respectively.These experiments can obtain mechanical properties of different thicknesses.The reason for the performance of TRB differentiated by OM and EBSD experiment was analyzed.Finally,the mechanical properties of continuous thickness are obtained through the interpolation method,which provides data for finite element simulation.(2)The finite element simulation and experimental verification of the U-channel of TRB were carried out.The sample size was 160mm×40 mm(RD × TD),and the thickness was 1 mm?2 mm?and TRB.Using the finite element simulation software ABAQUS to simulate the transverse bending experiment.The results show that the maximum error of the rebound amount is 6.5%,which proves the accuracy of the simulation.The experiments of the U-channel express that the thickness of the thick and thick plate is different due to the joint action of the transition zone,and provides the simulation parameters for the U-channel longitudinal bending.(3)The simulation analysis of the longitudinal bending U-channel of TRB was carried out.Using the control variable method to compare TRB with the equal thick blank and the tailor welded blank(TWB).It is concluded that the springback of TRB is different from the equal thick blank and TWB.A stamping mold with a die surface change with thickness is proposed.The average springback of the U-channel formed by the mold is reduced from 9.44 mm to 4.22 mm;the average offset of the transition zone is 0.030 mm,which is smaller than that of the TWBs 0.009mm.The effect of the transition zone characteristics of the TRB on the springback is further studied.The results show that when the thickness is 340mm,the average rebound amount is reduced by 54.5%.The smaller the slope of the difference is,the smaller the rebound amount will be.When considering the distribution of thick sections such as multi-section differential plates,the thin areas should be centered at the ends,and the transition areas should be evenly distributed.(4)The orthogonal experiment was carried out to analyze the order of influence of mold parameters on springback and the influence of different blanking force loading methods on springback was studied.The production of the TRB mold is simplified by combining the production cost and the forming precision.The integral binder is adjusted to the block presser binders,and the difference of the springback value of the TRB can be reduced from 5.84 mm to 2.97 mm.