Research On Welding Property And Springback Prediction Of High-strength Laser Tailor Welded Blanks

In recent years, the study of tailor welded blanks are mainly in the analysis of metal forming properties, such as rupture, wrinkle and weld movement, but less in the base theory of forming properties, especially not enough in the face of quantitative analysis of weld and heat affected zone constitutive relationship model. At the same time, there is a little research about springback of TWB. There is a big distinguish about forming properties and springback situation between TWB and each base metal, it's because the thickness, material properties of base metal and the weld properties existing. In order to research the weld property about laser TWB, this article makes lots of experiment work on H340LAD+Z/DP600 different thick plates of high strength laser TWB with thickness of 1.7mm/2.4mm, such as microstructure, mechanical properties, etc. For the purpose of studying the springback of influence on S-shape beam laser TWB about model parameters and process parameters, this text makes a research on S-shape beam laser TWB springback prediction through the parametric design to analysis model.Base on the method of combining"rule of mixtures"and the relationship between flow stress and microhardness, this article establishes the weld and heat affected zone constitutive relationship model through analysis mechanical model. When making a microhardness test to the TWB specimen, its found that the value of microhardness test in the weld is large big than the value of base metal, and the HAZ microhardness test value presents a descending tendency of form weld to base metal. From the metallographic examination, its can be found that the laser TWB welding joint has a good forming shape, smooth appearance, the width of HAZ is narrow, just about 0.3mm, and the width of laser weld region is about 1.5mm. Comparison to the base metal, the grain size of HAZ is tiny, the microstructure is fine,. Because of the existence of a certain amount of lath martensite, the weld seam has the higher strength and better toughness.Through the tensile test on different thickness of laser TWB specimens and the base materials specimens, we got the Stress-strain curves about different weld locations TWB and base metal, and the extent of plastic deformation. From the experiment, the results show that strength of tensile for TWB is between the higher base metal and the lower base mental, the plastic formability is lower to all base metal, the forming property largely depend on the weak blank, the higher proportion, the higher formability. In the biaxial stretch forming, the deformation extent of H340LAD+Z is larger than DP600, the plastic deformation extent of weld region is very small, there is almost no plastic deformation exist. Necking fracture of TWB specimens occurred all in the side of weak boards, but not at the region of HAZ.This article cites the base metal constitutive relationship, through the tensile test, to the analysis of finite element simulation, and makes the parametric design of S-shaped beam of different thickness of laser TWB by finite element simulation model through adopting orthogonal experimental design. Research is about the model parameters determined by track angleθt, corner radius R g, slope angleθc, punch radius R p, die radius R d, and the process parameters determined by blank holder force F, which take influence on the springback of S-shaped beam TWB. And through the analysis of various factors, we got the law of TWB springback. Using the Range Analysis, we got the primary and secondary order of each factors, obtained the optimal combination level of factors which generates the least springback influence to Tailor-welded blank.