高强钢B340LA与B1500HS钢激光拼焊板热冲压淬火性能

Characterization of hot stamping and quenching of laser tailor welded blanks of HSLA steel B340LA and boron steel B1500HS

用质子光谱仪、光学显微镜、维氏硬度计等手段研究低合金高强钢B340LA与超高强硼钢B1500HS激光拼焊板焊接后的热冲压淬火特性。结果表明,拼焊板母材B340LA钢随着冷却速度的增加其相变点发生偏移,维氏硬度略有增加。拼焊板母材B1500HS钢随着冷速的增加硬度迅速提高。光学显微镜观察,当冷速超过30 K/s时母材B1500HS钢基本转化为马氏体组织。通过维氏硬度计测量,发现焊缝至母材过渡区硬度值平滑过渡,保证母材及焊缝力学性能良好的连续性。由于热冲压淬火后母材及焊缝区域显微硬度平滑过渡,应力应变分别更趋均匀,可显著提高低合金高强钢与超高强硼钢激光拼焊板拉深成形性。

The characterization and mechanical properties of the laser tailor welded blanks of high strength low alloy steel B340LA and ultra-high strength boron steel B15OOHS were investigated by means of proton spectrometer, optical microscope and micro-hardness tester. The results show that the phase transformation temperature of parent material B340LA steel changes with the increasing of cooling rate in the quenching process while its mierohardness （ HVO. 1 ） increases to some degree simultaneously. The microhardness of boron steel BI50OHS increases dramatically as the eooling rate rises. Hardness measurement and metallographie observation indicate that the mierostructure of boron steel B15OOHS consists of full martensite when the cooling rate reaches 30 K/s. The distribution of microhardness from parent materials to weld seam is continuous and smooth. The smoothly distributed micro-hardness leads to uniformly distributed strain and stress in hot stamping, which improves the formability of TWBs.