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试验中采用的材料为SUS301L奥氏体不锈钢,上下板厚均为0.6mm,牌号:022Cr17Ni7,抗拉强度大于820MPa,屈服强度大于480MPa,试样尺寸大小为60mm×120mm,相关物理参量如表 1所示。
Table 1. Related physical parameters of SUS301L austenitic stainless steel
boiling point/℃ melting point/℃ latent heat of phase change/(J·kg-1) density/(kg·m-3) Poisson’s ratio 3073 1447 2.6×105 7800 0.3 试验中采用IPG公司的光纤激光器。焊接试验分成两部分,首先采用单一因素实验,研究不同激光焊接工艺参量(保护气体流量、离焦量、激光功率、焊接速率)对截面处焊缝熔深熔宽的影响;然后通过正交试验优化焊接工艺参量对使用优化后焊接工艺参量的焊件进行宏观形貌与微观组织的观测, 并进行力学性能的分析。
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保护气体流量的选择会影响到激光焊接的质量,过多的保护气不仅造成了浪费,而且会带走焊接过程中很大一部分的能量,直接降低焊接效率;相反,过少的保护气,无法有效地将工件上方聚集的等离体子及时吹走[10]。采用单一变量法,保护气体采用氩气,取工艺参量为:激光功率1150W、焊接速率38mm/s、离焦量0mm,由于此功率参量下所有试件均焊透,因此用束腰宽代替原本下板熔深数据。图 4为3种不同保护气体流量上板熔宽及束腰宽度。
由图 4可知,随着氩气流量的增大,单位时间内热量损失增加,焊件从激光中得到的热量不断减少,上板熔宽呈递减趋势。焊缝束腰宽度在保护气体流量为25L/min时数值最小,呈V字型变化。
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薄板的焊接通常为正离焦。进行负离焦焊接时,下板容易被焊透从而在焊缝背部的中间位置形成凸起,在地铁车顶上应用时,影响外观[11]。本文中取零离焦时,焊缝完整且连续,没有咬边、凹陷、变形等明显缺陷。因此在本小节试验中,离焦量分别取0mm, +1mm, +2mm, 其余焊接工艺参量为:激光功率1150W,焊接速率38mm/s,保护气体流量25L/min。图 5为3种不同离焦量下上板熔宽及下板熔深。
由图 5分析可知,离焦量增加的过程中,下板熔深随之减小,上板熔宽有所下降但是变化不大,结合图中数据分析得出: 离焦量对焊缝熔深的影响略大于熔宽。
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焊接速率大小通常负相关于焊缝熔深,影响焊纹密度,热输入量的合理配置能够很好地规避焊缝不连续等缺陷,保证焊接质量[12]。在激光功率1050W、离焦量0mm、保护气体流量25L/min下,焊接速率分别取为36mm/s, 38mm/s, 40mm/s。图 6为3种不同速率下上板熔宽及下板熔深。
由图 6可知,焊接速率与上板熔宽和下板熔深呈负相关性。在36mm/s的焊接速率下,下板熔深占比超过98%,焊件几近焊穿,处于临界状态。在3种速率下,焊缝形貌都良好,深度达到要求,下板均为焊透。
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激光功率过小,焊件可能会无法焊透,焊缝过窄,影响到接头力学性能;激光功率过大,热量的迅速吸收造成温度梯度的增大,在焊件内部会存在较大的残余应力,导致焊件的变形[13-14]。取焊接工艺参量为:焊接速率36mm/s、离焦量0mm、保护气体流量25L/min,激光功率大小分别为950W, 1050W, 1150W。图 7为3种不同激光功率下焊缝熔深、熔宽数据变化图。
由图 7可知,随着激光功率的增加,作用在焊件上的功率密度逐渐增大,工件获得能量增多,上板往下传递的热量随之增加,焊缝熔深熔宽也逐渐增大。当功率增大到1150W之后,下板焊透。
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由单因素实验结果可确定焊接工艺参量范围:激光功率950W~1050W,焊接速率36mm/s~40mm/s,离焦量0mm~2mm,保护气体流量20L/min~30L/min。正交试验共4个因素,每个因素均为3个水平,如表 2所示。以三水平四因素正交表设计正交试验,如表 3所示。表 3中实验结果为上板熔宽以及下板熔深占比。
Table 2. Orthogonal test factors and level table
factor laser power A/W welding speed B/(mm·s-1) defocusing amout C/mm shielding gas flow D/(L·min-1) level 1 950 36 0 20 level 2 1050 38 1 25 level 3 1150 40 2 30 Table 3. Orthogonal test table
experimentnumber factor A factor B factor C factor D result 1 result 2 laser power/W welding speed/(mm·s-1) defocusing amout/mm shielding gas flow/(L·min-1) upper plate welding width/μm percentage of lower plate welding depth/% 1 1 1 1 1 1204.7 42.38 2 1 2 2 2 1208.2 27.72 3 1 3 3 3 968.8 0.00 4 2 1 2 3 1298.9 100.00 5 2 2 3 1 1247.9 26.98 6 2 3 1 2 1217.0 81.57 7 3 1 3 2 1333.2 100 8 3 2 1 3 1327.0 100 9 3 3 2 1 1292.8 100 对上板熔宽以及下板熔深制正交分析表,分析得出结果为:激光功率对上板熔深和下板熔宽影响最大,离焦量对下板熔深影响更加明显,而焊接速率对上板熔宽影响明显,保护气体流量影响最小。最优工艺参量水平为A2B1C2D2, 即激光功率1050W,焊接速率36mm/s,离焦量1mm,保护气体流量25L/min。
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激光焊接功率1050W、焊接速率36mm/s、离焦量1mm、保护气体流量25L/min时,仿真与试验焊缝界面重叠对比如图 8所示。从图 8中看出,焊缝上表面几乎完全重合,包括焊缝中央凸起的部分,二者的熔宽、熔深数据基本一致,实验下板焊缝熔深略大于仿真结果, 两个焊缝截面图的轮廓变化趋势也基本保持一致。综上所述,仿真结果十分接近于实验结果,SUS301L不锈钢的激光焊接仿真对于实际焊接过程有指导意义。
地铁车顶用SUS301L不锈钢激光焊接工艺参量优化
Study on the parameter optimization of laser welding of SUS301L stainless steel for metro roof
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摘要: 为了研究地铁车顶SUS301L不锈钢叠焊工艺中对熔宽熔深的技术需求, 运用数值模拟技术分析了各项焊接工艺参量对熔宽熔深的显著影响, 采用正交实验法则对工艺参量进行了优化设计, 取得了激光焊接SUS301L不锈钢薄板的工艺参量。结果表明, SUS301L不锈钢薄板激光焊接在激光焊接功率为1050W、焊接速率为36mm/s、离焦量为1mm、保护气体流量为25L/min时, 熔宽和下板熔深分别为1216.4μm和407.4μm; 在最优工艺参量条件下, 焊缝表面呈银白色, 连续且完整, 焊缝区为等轴晶与柱状晶, 焊缝平均拉剪强度为2559.96kN; 仿真结果与试验结果具有较好的一致性, 表明所建立仿真模型的正确性。该研究为后期工艺数据库的搭建提供了参考。
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关键词:
- 激光技术 /
- 激光叠焊 /
- 正交试验 /
- SUS301L不锈钢板 /
- 工艺参量优化
Abstract: In order to meet the technical requirements for the penetration and width of SUS301L stainless steel laser lap welding for subway roof, the influence of welding parameters on the penetration and width was analyzed using numerical simulation technology. The design of parameters were optimized through orthogonal test which obtained the process parameters of laser welding SUS301L stainless steel sheet. The results show that the optimal parameters of laser welding of SUS301L stainless steel sheet is that the laser welding power of 1050W, welding speed of 36mm/s, defocusing amount of 1mm, the flow rate of shielding gas of 25L/min. With the optimal parameters, the width and penetration are respectively 1216.4μm and 407.4μm. The good consistency between the simulation results and the experiment results shows that the correctness of the simulation model can be established in this paper, which can provide reference for the construction of the later process database. Under the optimal welding parameters, the surface of the weld is silvery, continuous and complete, the weld area is isomer and column crystals, and the average shear strength of the weld is 2559.96kN. -
Table 1. Related physical parameters of SUS301L austenitic stainless steel
boiling point/℃ melting point/℃ latent heat of phase change/(J·kg-1) density/(kg·m-3) Poisson’s ratio 3073 1447 2.6×105 7800 0.3 Table 2. Orthogonal test factors and level table
factor laser power A/W welding speed B/(mm·s-1) defocusing amout C/mm shielding gas flow D/(L·min-1) level 1 950 36 0 20 level 2 1050 38 1 25 level 3 1150 40 2 30 Table 3. Orthogonal test table
experimentnumber factor A factor B factor C factor D result 1 result 2 laser power/W welding speed/(mm·s-1) defocusing amout/mm shielding gas flow/(L·min-1) upper plate welding width/μm percentage of lower plate welding depth/% 1 1 1 1 1 1204.7 42.38 2 1 2 2 2 1208.2 27.72 3 1 3 3 3 968.8 0.00 4 2 1 2 3 1298.9 100.00 5 2 2 3 1 1247.9 26.98 6 2 3 1 2 1217.0 81.57 7 3 1 3 2 1333.2 100 8 3 2 1 3 1327.0 100 9 3 3 2 1 1292.8 100 -
[1] HUANG Zh Y. Research on manufacturing technology of stainless steel roof steel structure for urban rail passenger cars[D]. Changchun: Jilin University, 2019: 21-27(in Chinese). [2] YANG L, YANG B, YANG G W, et al. Analysis of fatigue characteristics of spot welded joints of stainless steel carbody[J]. Transactions of the China Welding Institution, 2020, 41(7): 18-24(in Chin-ese). [3] HAN X H, ZHANG Zh Y, LI G Q. Application and prospect of laser welding technology in stainless steel rail passenger car manufacturing[J]. Electirc Welding Machine, 2018, 48(3): 1-8(in Chinese). [4] WANG C Y, GAO X D, MA N J, et al. Magneto-optical imaging detection of laser welding defecs lander multi-directinal magnetic field excitation. Laser Technology, 2020, 44(5): 592-599(in Chin-ese). [5] LIU L X, ZHONG Y M, MA Ch P, et al. Research on residual stress of laser welding joint of SUS301L austenitic stainless steel for subway[J]. Hot Working Technology, 2013, 42(13): 186-188(in Chin-ese). [6] HARISH K, GANESH P, RAKESH K, et al. Laser welding of 3mm thick laser-cut AISI 304 stainless steel sheet[J]. Journal of Materials Engineering and Performance, 2006, 15(1): 23-31. doi: 10.1361/105994906X83385 [7] TIAN M. Research on laser welding process of stainless steel for rail trains[D]. Wuhan: Huazhong University of Science and Technology, 2015: 47-55(in Chinese). [8] CHEN L, ZHOU L Z, TANG Ch, et al. Study of laser butt welding of SUS301L stainless steel and welding joint analysis[J]. International Journal of Advanced Manufacturing Technology, 2014, 73(9/12): 1695-1704. doi: 10.1007/s00170-014-5928-y [9] DUAN W, ZHOU L H. Simulation study of laser welding of aluminum alloy sheet based on Simufact Welding[J]. Hot Working Technology, 2018, 47(15): 168-171 (in Chinese). [10] ZHANG L J, ZHANG J X, WANG R, et al. The effect of side blowing gas on the CO2 laser welding process of stainless steel sheet[J]. Applied Laser, 2005, 25(4): 217-221 (in Chinese). [11] GAN H Y. The influence of process parameters on the forming properties of laser welding of stainless steel sheet[J]. Applied Laser, 2015, 35(2): 221-223(in Chinese). doi: 10.3788/AL20153502.0221 [12] SHU L S, WANG B, BAI H Q, et al. The influence of process parameters on laser welding deformation of 304 thin steel plate[J]. Hot Working Technology, 2019, 48(17): 117-121(in Chinese). [13] WANG H X, SHI Ch Y, WANG Ch Sh, et al. Non-penetrating laser lap welding process of SUS301L stainless steel for railway passenger car[J]. Hot Working Technology, 2009, 38(19): 136-139 (in Chinese). [14] BAI Ch M. Research on non-penetration laser overlap welding process of austenitic stainless steel[D]. Changchun: Changchun University of Science and Technology, 2019: 23-37 (in Chinese). [15] ZHAO X, YANG Zh B, WANG F. Process analysis and performance study of laser tailor welding of SUS 301L stainless steel[J]. Welding Technology, 2019, 48(6): 43-46 (in Chinese). [16] YANG X W. Research on the influence of welding process factors on the structure and performance of laser welding joints for stainless steel rail cars[D]. Changchun: Jilin University, 2019: 29-34 (in Chinese).