YG20/45钢激光熔钎焊焊缝界面显微组织与元素扩散研究

Study on Microstructure and Element Diffusion in Laser Weld of YG20/45 Steel

针对YG20/45钢异种金属焊接时,存在焊缝接头脆性高及焊缝连接性能差等缺点,课题组提出以Cu/Invar/Ni复合层为中间层进行激光熔钎焊焊接,研究焊缝区域微观组织、化学成分及元素扩散规律。试验结果表明:母材硬质合金中的WC晶粒棱角在焊接试验中会溶解,部分晶粒聚集但不长大,从而降低了焊接接头的脆性;在焊缝过渡区Invar合金和硬质合金中的元素发生扩散反应,其中Invar合金中的Fe和Ni元素补充硬质合金流失的Co元素,形成粘结相,提高了焊接母材的连接性;硬质合金和45钢之间加Cu/Invar/Ni复合层,激光钎焊接头宏观形貌都较好,在母材厚为4 mm时,试验采用激光功率为1 700 W,激光扫描速度为0.1 m/s,离焦量-3 mm时可以获得冶金性良好的焊接接头。

Aiming at the disadvantages of high brittleness of welded joint and poor weld connection performance in the dissimilar metal welding of YG20/45 steel, the laser fusion brazing welding with Cu/Invar/Ni composite layer as the intermediate layer was proposed to study the microstructure, chemical composition and element diffusion law in the weld area. The test results show that the WC grain edges and corners in the base metal cemented carbide will dissolve in the welding test, and some grains gather but do not grow up, which reduces the brittleness of the welded joint. In the weld transition zone, the elements in Invar alloy and cemented carbide have diffusion reaction. The Fe and Ni elements in Invar alloy supplement the co elements lost in cemented carbide to form a bonding phase, which improves the connectivity of welding base metal. When Cu/Invar/Ni composite layer is added between cemented carbide and 45 steel, the macro morphology of laser brazed joint is better. When the base metal is 4 mm thick, the laser power is 1 700 W, the laser scanning speed is 0.1 m/s, and the defocus amount is-3 mm, the welded joint with good metallurgical properties can be obtained.