Research On Wear Resistance Characteristics Of Hot Blanking Dies For High Strength Steels

With gradual development of auto lightweight,the application of AHSS(Advanced High Strength Steels)is getting more and more widely.Hot stamping process of AHSS has become a key technology as its unique advantages.However,hot stamping parts of high strength steels are mostly needed subsequent cutting,trimming,etc.While traditional cold punching process is difficult to be conducted due to high strength,and laser cutting may involve secondary positioning problem,high cost and low efficiency.Therefore,a new hot blanking technology of high strength steels is proposed.This technology can complete blanking and trimming during the process of hot stamping and quenching.The die of this process has complex structure,expensive materials,high processing difficulty and accuracy.So,the service life of hot blanking dies is an important index to evaluate products cost and economic benefit.Die wear is the most important factor that affects die life.Therefore,it is of great significance to research the wear characteristics of hot blanking dies for high strength steels.In this thesis,the wear behavior of B1500HS high strength steel die was investigated,and the main content is as follows:The wear mechanism of AHSS hot blanking dies was studied by means of theoretical analysis.What’s more,a suitable calculation model of wear loss for hot blanking dies was established.Based on this model,several factors that influence the wear of AHSS hot blanking dies were put forward,providing a basis for numerical simulation and experimental research.Through the finite element analysis software ABAQUS,the B1500HS hot blanking process numerical simulation research was conducted.Based on the theories of die wear,the modified Archard model was coupled into the simulations,and the wear loss were calculated under several different process parameters and die structure parameters.Through comparison,the influences of these parameters on wear loss of hot blanking dies were analyzed.The results showed that the die clearance,sheet metal temperature and cutting rate parameters had significant effect on the die wear.The wear loss was also different with different trimming contour.Either too big or too small of the die clearances were not conducive to improve the wear resistance performance,and when the blank temperature increased,abrasion of the die reduced,but when cutting rate grew,die wear aggravated.Considering the factors of wear accumulation between each time hot blanking in continuous production,3000 times hot blanking tests of high strength steels have been carried out.The experimental wear behaviors under different die clearances and trimming contour were obtained.And it showed a good agreement with the simulated results.What’s more,the reasonable die clearance and suitable die material were determined combined the forming quality of hot blanking parts and die wear.