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试验材料采用高强钢钢板,用细砂纸对钢板进行打磨,直至钢板表面光滑无锈,然后用无水丙酮清洗表面,处理后的钢板尺寸为150mm×29mm×8mm。焊丝材料为304奥氏体不锈钢,直径D=0.6mm。高强钢和焊丝化学成分如表 1所示。
Table 1. Chemical compositions (mass fraction) of base metal and filler wire
material C Si Mn Cr Ni Mo P base metal 0.0022~0.0035 0.0012~0.0025 0.0045~0.0070 0.0036~0.0060 <0.000025 <0.00025 — welding wire ≤0.0008 ≤0.01 ≤0.02 0.018~0.02 0.080~0.110 — ≤0.00045 -
激光器采用德国通快公司生产的HL4006D型号Nd:YAG固体激光器,额定输出功率P0=4kW,激光波长λ=1.06μm,光束质量因数为25mm·mrad,激光经220mm的透射聚焦镜聚焦后,获得直径为0.6mm的光斑。焊接时采用德国KUKA公司的六轴机械手臂夹持激光焊接接头和送丝接头按设定的轨迹运行,送丝机为济南焊达机械有限公司生产的WF-007A多功能自动氩弧焊填丝机,最大送丝速率为6m/min。试验设备如图 1所示。试验中采用平板堆焊的前送丝方式,保护气体为氩气,气体流量为20L/min,后置吹气方向与激光束夹角为60°,焊丝与激光束夹角为60°,光丝距为0mm。利用高速摄像系统对焊接过程进行实时观察,采集频率为5000frame/s。前送丝示意图如图 2所示。
离焦量对高强钢激光填丝焊熔滴过渡特性的影响
Effect of defocus on droplet transfer characteristics of high strength steel by laser welding with fill wire
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摘要: 为了研究离焦量对激光填丝焊熔滴过渡及相关特征的影响,获得稳定过渡模式,借助高速摄像系统观察了不同离焦量下的熔滴过渡行为,并将其分为液桥过渡、混合过渡和滴状过渡3种类型进行了分析。结果表明,离焦量为-1mm和+3mm时的液桥过渡模式可以保证焊接过程的稳定性,获得的焊缝质量良好,焊缝截面无气孔等缺陷;而离焦量为+5mm时的过渡模式为滴状过渡,此时焊接稳定性最差,焊接过程中匙孔会完全闭合,焊缝表面成形不规则,焊缝截面底部出现大的气孔。该研究结果对实际生产有指导作用。Abstract: In order to study effect of defocus on droplet transfer and related characteristics of laser welding with filler wire, and achieve stable droplet transfer mode, a high speed camera system was used to observe droplet transfer under different defocus parameters. Droplet transfer was divided into three kinds:liquid bridge transfer, mixed transfer and drop transfer. The results show that, liquid bridge transfer mode with defocus of -1mm and +3mm could improve the stability of welding process with good quality, such as the weld cross section without porosity. For the drop transfer mode with defocus of +5mm, the welding stability is the worst. During the welding process, keyhole is completely closed, the surface of weld bead is formed irregularly, and the large pores appear at the bottom of the weld corrosion-face. The research results have guiding effect on actual production.
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Key words:
- laser technique /
- defocus /
- laser welding with filler wire /
- droplet transfer /
- high speed camera
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Figure 9. Geometric profile and surface appearance of weld bead under different defocus
a—F=-5mm, P=3500W, v1=1.2m/min, v2=5m/min b—F=-3mm, P=3500W, v1=1.2m/min, v2=5m/min c—F=-1mm, P=3500W, v1=1.2m/min, v2=5m/min d—F=+1mm, P=3500W, v1=1.2m/min, v2=5m/min e—F=+3mm, P=3500W, v1=1.2m/min, v2=5m/min f—F=+5mm, P=3500W, v1=1.2m/min, v2=5m/min
Figure 10. Line chart of keyhole area under different defocus
a—F=-5mm, P=3500W, v1=1.2m/min, v2=5m/min b—F=-3mm, P=3500W, v1=1.2m/min, v2=5m/min c—F=-1mm, P=3500W, v1=1.2m/min, v2=5m/min d—F=+1mm, P=3500W, v1=1.2m/min, v2=5m/min e—F=+3mm, P=3500W, v1=1.2m/min, v2=5m/min f—F=+5mm, P=3500W, v1=1.2m/min, v2=5m/min
Table 1. Chemical compositions (mass fraction) of base metal and filler wire
material C Si Mn Cr Ni Mo P base metal 0.0022~0.0035 0.0012~0.0025 0.0045~0.0070 0.0036~0.0060 <0.000025 <0.00025 — welding wire ≤0.0008 ≤0.01 ≤0.02 0.018~0.02 0.080~0.110 — ≤0.00045 -
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