Research On Warm Blanking Of Ultra-high Strength Steel By Numerical Simulation

As one of the most effective ways to reduce automobile weight and improve the impactsafety, hot stamping technology of ultra-high strength steel has gained a wide attentionnowadays. However, the high strength and hardness achieved in the hot stamping parts makeit difficult to trim or punch in conventional blanking way. There are such problems as largeblanking fore, sever wear and sometimes unexpected tool failure. At present, laser cuttingtechnology is generally employed by manufacturer, in spite of its long cycle time, highproduction cost, and even poor product quality.The primary principle of warm blanking is to compound blanking process in hot stamping,so that the sheet can be trimmed or punched with high ductility and low hardness. Using ofwarm blanking technology can improve product quality, shorten cycle time and reduce theproduction cost, compared with conventional blanking and laser cutting. At present, there islittle study on this technology, and an all-around and in-depth research has been made in thispaper.Based on the software of DEFORM-3D, the numerical simulation for warm blanking wasperformed with the trimming process of22MnB5cap-type part taken as an example. Duringblanking process, material following behavior, stress and strain distribution in the shearingzone were analyzed. And during quenching process, temperature field at different time wasshown, changes of dimension and sheared surface before and after quenching were discussedrespectively. Then, effectiveness of the warm blanking was described, comparing withconventional cold blanking. It turned out that blanking force and work in warm blanking aresignificantly less than that in cold blanking. Besides, sheared surface quality is improved, toolwear depth is reduced, and thus the tool life is enhanced in warm blanking way. Due to the phenomenon of thermal expansion and contraction, the sheet shrank after quenching. Toguarantee the dimension accuracy, modified design formulas for tool was provided.Influence of blanking temperature, clearance and blanking speed on warm blanking wereresearched from four aspects of blanking force and work, sheared surface, dimensionaccuracy and tool wear. The main conclusions are as follows. Blanking force and workdecrease with the blanking temperature, clearance and speed increase. The higher temperature,smaller clearance and larger speed assures smoother sheared surface. Dimension accuracybecomes lower with higher blanking temperature, but hardly changes with clearance andblanking speed. In addition, the tool wear depth decreases as blanking temperature andclearance increasing, but as speed decreasing. Based on the above laws, optimal processingparameters with blanking temperature above650℃, clearance about10%and speed between70and90mm/s are determined.