Research on Stamping Forming Properties of the Steel Sheets Used for Car Body

摘要

The microstructures and macro texture of DC04 steel sheets using for car body were observed by optical microscopy,XRD and other instruments.The tensile properties,strain hardening exponent n and plastic strain ratio r value of the steel sheets were tested using the tensile testing machine.The rigid punch test and the cup drawing test were done by TE-SMF sheet metal composite molding machine.The relationship between the microstructures and the forming properties of the DC04 steel sheets in different process conditions such as hot rolling,cold rolling and annealing was studied.It was found that the microstructures of hot rolled steel sheets were equiaxed ferrite,the average grain size is 23.94μm; the microstructures after cold rolled is stretched,flattened fiber structure; after annealing,the equiaxed ferrite of average grain size 18.24μm was got by the recovery,recrystallization and grain growth.The most annealing texture is {111} surface texture with a little {100} texture.It suggested that the sample has good stamping formability.The tensile test results of the annealing steel sheets showed that the tensile curve has no obvious yield point,the yield strength Rp0.2 of 147 MPa,the tensile strength Rm of 289MPa,the elongation A80 of 80％,the yield ratio of 0.51,the strain hardening exponent n value of 0.21,the plastic strain ratio r value of 3.07.The lower yield ratio,higher n value and r value,the better stamping properties were guaranteed.The rigid punch test and cupping test results of steel sheets also proved this phenomenon.