(1. 湖南大學(xué) 汽車車身先進(jìn)設(shè)計制造國家重點實驗室，長沙 410082；
2. 湖南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410082)
摘 要: 通過雙相鋼/鋁合金有無添加Mn粉激光焊接的對比，揭示鋼上、鋁下激光搭接焊時Mn粉的作用。對焊接過程進(jìn)行金屬蒸氣/等離子體形貌分析及光譜采集，發(fā)現(xiàn)添加Mn粉激光焊接時，金屬蒸氣/等離子體顏色明亮，光譜相對強度和金屬蒸氣/等離子體的電子密度增加；焊縫EDS分析發(fā)現(xiàn)，添加Mn粉時，熔池內(nèi)部Fe、Al混合寬度減小，鋁側(cè)熔池兩側(cè)的Al含量增多；剪切試驗發(fā)現(xiàn)，添加Mn粉焊接接頭的平均抗剪強度提高，斷口呈現(xiàn)混合斷裂特征。由于添加Mn粉加快鋼/鋁層間熱量傳遞，受熱分解產(chǎn)生的金屬蒸氣在排出過程中，產(chǎn)生強烈向下的反沖作用力，使下層鋁合金板材中的焊接匙孔加深，同時，金屬蒸氣改善下層鋁合金的高反射率狀況，促進(jìn)鋁合金吸收激光能量，導(dǎo)致焊接熔深增加。此外，熔池流動行為發(fā)生改變，下層Al向上層鋼側(cè)的擴散受到抑制，熔融態(tài)Al向熔寬兩側(cè)遷移，在減弱熔池內(nèi)部Fe、Al混合程度、降低鋼/鋁界面Fe-Al化合物層厚度的同時，上、下板結(jié)合處的焊接熔寬加大，因此添加Mn粉改善鋼/鋁焊接接頭的力學(xué)性能。
關(guān)鍵字: 激光搭接焊；鋼/鋁異種金屬；Mn粉；焊縫成形
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:Through comparison analysis of the laser welding of dual phase steel to aluminum alloy with and without Mn powder addition, Mn powder effect on dissimilar metals in steel-on-aluminum overlap configuration were discussed. By collecting and analyzing the metallic vapor/plasma shape and welding spectra, it is found that the color of metallic vapor/plasma induced by laser welding with Mn powder addition is bright, the relative intensity of spectra and electron density of metallic vapor/plasma increases. In addition, the mixing of Fe and Al in the molten pool decreases based on EDS analysis of joints, however, the content of Al on both sides of weld width increases. The results of the shearing experiments show that the average shear strength of welded joint increases compared to that without powder addition, and the failure mode is a mixed fracture. The welding keyhole of the lower Al plates becomes deeper by the reversed impact during the discharge of steam due to the decompose of Mn powder. Meanwhile, heat transfer between steel and aluminum is speeded up, the metallic vapor can decrease the reflectivity and increase the laser energy absorption of the lower aluminum alloy, thus, increasing the depth of the welding joints. What’s more, the flow behavior of the molten pool changes, the molten Al removes to both side of the welding joint, which leads to the width increase of the welding joints, thus the diffusion from the lower Al to the upper steel side is suppressed, and the size of Fe-Al intermetallic compound in aluminum/steel interface is reduced. Therefore, it can improve the mechanical properties of steel/aluminum welding joint with Mn powder addition.
Key words: laser lap welding; steel/l alloy dissimilar metal; Mn powder; weld molding
