(1. 西北工業(yè)大學(xué) 凝固技術(shù)國(guó)家重點(diǎn)實(shí)驗(yàn)室 摩擦焊接陜西省重點(diǎn)實(shí)驗(yàn)室，西安 710072；
2. 中國(guó)電子科技集團(tuán)公司 第二十研究所，西安 710068)
摘 要: 選取半徑分別為100、75、50和25 mm的球面電極，采用三相次級(jí)整流點(diǎn)焊機(jī)進(jìn)行1 mm厚2A12鋁合金點(diǎn)焊試驗(yàn)。利用光學(xué)顯微鏡和掃描電鏡觀察焊后熔核的形貌、裂紋特征及顯微組織，利用低倍測(cè)量顯微鏡和拉伸試驗(yàn)機(jī)測(cè)試熔核的尺寸和拉剪力，研究球面電極半徑對(duì)2A12鋁合金點(diǎn)焊熔核裂紋的分布特征、形成機(jī)理以及熔核尺寸和拉剪力的影響。結(jié)果表明：球面電極半徑越大，熔核內(nèi)越容易產(chǎn)生裂紋，且熔核直徑總體上呈下降趨勢(shì)。當(dāng)電極半徑分別為75和100 mm時(shí)，在熔核中間區(qū)域產(chǎn)生貫穿整個(gè)熔核的沿晶縱向結(jié)晶裂紋，在熔核的熱影響區(qū)出現(xiàn)液化裂紋，熔核內(nèi)沒(méi)有橫向裂紋產(chǎn)生。
關(guān)鍵字: 高強(qiáng)鋁合金；電阻點(diǎn)焊；電極半徑；裂紋；熔核
（1. Shaanxi Key Laboratory of Friction Welding Technologies, State Key Laboratory of Solidification Processing,
Northwestern Polytechnical University, Xi’an 710072, China;
2. The 20th Research Institute, China Electronic Technology Corporation, Xi’an 710068, China）
Abstract:Selecting 100, 75, 50 and 25 mm as the radius of spherical electrode, spot welding experiment of the aluminum alloy 2A12 sheet with thickness of 1 mm was performed on the three-phase secondary rectification welding machine. Using optical microscopy and scanning electron microscopy, the microstructure and crack characteristics of the nugget were observed. The low-magnification measuring microscope and the tensile test machine were used to test the nugget diameter and the tensile-shear strength of the weld, and then the effect of spherical electrode radius on the crack distribution, formation mechanism, nugget diameter, and the tensile-shear strength of spot welding joint of the aluminum alloy 2A12 were investigated. The results show that as the spherical electrode radius increases, more likely the cracks occur in the nuggets, and nugget diameters present decreasing tendency. When the spherical electrode radii are 75 and 100 mm, respectively, the intergranular longitudinal solidification crack locates in the middle of the nugget, which almost transverse across the whole weld nugget, and liquation crack is visible in the heat-affected zone (HAZ), but there is no transverse crack in the nugget.
Key words: high-strength aluminum alloy; resistance spot welding; electrode radius; crack; nugget
