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实验材料选用1.5mm厚的CR340冷轧热镀锌钢板,镀层为双面镀锌,镀锌量为60g/m2。钢板化学成分如表 1所示,力学性能如表 2所示,图 1为CR340基体组织金相图。实验前用激光切割制成120mm×60mm×1.5mm的试板,并用酒精擦除材料表面油污[17]。
Table 1. Chemical composition of CR340 sheet(mass fraction)
C Si Mn Nb P S Al Fe 0.0012 0.0015 0.005 0.00015 0.00035 0.00025 0.00015 balance Table 2. Mechanical properties of CR340 sheet
yield strength/MPa tensile strength/MPa elongation after fracture/% 270 400 11 -
利用模数为1.0mm的右斜30°直纹滚花刀在层叠接合面处,对上下镀锌板分别辊压出交错排布的排气通道,并利用OLS4000激光共聚焦显微镜观察并测量排气通道的3维形貌。可以发现,在压力作用下,刀齿在镀锌板表面挤压出一道道主排气通道,并在主排气通道的两边形成隆起,于是在主排气通道与主排气通道之间由隆起堆叠出的微小空间形成次排气通道;由主排气通道和次排气通道形成的复合排气通道在焊缝中心实现了排气通道的全覆盖。通过控制辊压力的大小来控制辊压深度,实验前测量主、次排气通道的深度。图 2为排气通道。其中,图 2a为位置示意图,图 2b为实际辊压效果,图 2c为局部放大,图 2d为表面3维形貌,图 2e为截面形状,图 2f为主、次排气通道。
实验中采用零间隙层叠搭接焊接头形式,重叠宽度10mm,预先在层叠面处辊压一定结构的排气通道,焊缝轨迹位于重叠面中心位置,如图 3所示。实验中用到的激光焊接系统,包括由中国武汉锐科生产的RFL-C3300型光纤激光器,波长为1080nm,经聚焦直径为200nm焊接头聚焦后得到直径为0.3mm的激光光斑。焊接时,工件固定装夹,由FANUC M-20iA六轴机械手带动焊接头运动来完成焊接。焊接完成后并对焊缝宏观形貌、飞溅情况、接头微观组织及力学性能进行分析研究。
在金相试样制取中,沿垂直于焊缝的方向截取试样尺寸为20mm×15mm×3mm的试样,按照标准金相制作方法依次进行打磨、抛光,制取金相样件,腐蚀液选择硝酸酒精溶液(质量分数为0.04),腐蚀时间为15s左右[18]。利用Leica DMC4500金相显微镜对制得的金相样件进行观察;利用HV-1000Z型显微硬度计测量焊接接头显微硬度,加载载荷和加载时间分别25g和10s。
参照GB/T2651-2008《焊接接头拉伸试验》标准, 利用线切割制做拉伸试样[19],采用WDW3100型电子万能实验机进行拉伸测试,同参量下样件拉伸3次取平均值。
基于排气通道的车身镀锌板激光叠焊工艺
Laser welding process of body galvanized sheet based on exhaust passage
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摘要: 为了解决汽车工业中车身镀锌板激光层叠搭接焊的问题,提出一种在镀锌板层叠接合面辊压一定排气通道的工艺方法,使之在零间隙下可获得一个较好的焊接效果。实验中对比了有无排气通道下,零间隙层叠搭接的焊接质量,从焊缝表面形貌、飞溅产生、焊缝组织、接头显微硬度及接头力学性能等方面进行了分析。结果表明,辊压得到主排气通道深度为125.0μm、次排气通道深度为32.6μm的复合排气通道,在激光功率为2500W、扫描速率为25mm/s时, 可以获得外观成形及力学性能均满意的搭接接头。该研究对提高车身镀锌板激光叠焊工艺是有帮助的。Abstract: In order to solve the problem of laser laminated lap welding of galvanized sheet for automobile body, a process of rolling a certain exhaust passage on the laminated joint surface of galvanized sheet was put forward, so that a better welding effect could be obtained under zero clearance. The welding quality of zero-gap laminated joints with and without exhaust channels was compared and analyzed from the aspects of weld surface morphology, splash generation, weld microstructure, micro-hardness, and mechanical properties of joints. The results show that the composite exhaust channel with the main exhaust channel depth of 125.0μm and the secondary exhaust channel depth of 32.6μm can be obtained by rolling, and the lap joint with satisfactory appearance and mechanical properties can be obtained at laser power of 2500W and scanning speed of 25mm/s. The research is helpful to improve the laser overlay welding process of body galvanized sheet.
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Key words:
- laser technique /
- laser welding /
- exhaust passage /
- galvanized sheet /
- organizational performance
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Table 1. Chemical composition of CR340 sheet(mass fraction)
C Si Mn Nb P S Al Fe 0.0012 0.0015 0.005 0.00015 0.00035 0.00025 0.00015 balance Table 2. Mechanical properties of CR340 sheet
yield strength/MPa tensile strength/MPa elongation after fracture/% 270 400 11 -
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