Q345船舶钢激光-MAG复合焊及激光填丝焊工艺试验研究

发布时间：2018-06-01 18:33

本文选题：Q345船舶钢 + 激光-电弧复合焊　；参考：《南京理工大学》2016年硕士论文

【摘要】：激光焊在能量密度高,焊接速度快,焊缝深宽比大,热影响区小,呈现窄的热影响区和小的热变形,而且焊接时无需真空。目前船舶行业普遍采用的是手工焊接,采用激光焊来提高焊接质量、焊接智能化迫在眉睫。激光填丝焊和复合焊接技术可以降低装配精度、改善焊缝冶金特性、提高接头机械性能。本文针对9mm厚Q345船舶钢进行激光电弧复合焊、激光填丝焊工艺研究,为船舶钢激光焊提供技术参考。激光填丝焊和复合焊需要调节焊接工艺参数,包括送丝速度、离焦量、激光功率、光丝距、焊接速度、电流值等,来获得良好质量的焊缝。离焦量决定了热影响区的大小。填丝焊光丝距需控制在-1 mm至+1 mm,而复合焊由于激光和电弧的共同作用,光丝距在2mm至3mm时成型良好。激光功率增大,熔深熔宽增大;焊接速度增大,熔深熔宽减小。这是因为激光功率和焊接速度决定了功率密度,从而决定了熔深熔宽。复合焊中的电流值在150 A到220 A之间,复合焊成型良好。填丝焊中,送丝速度也影响激光能量在熔化焊丝和促进熔池中的分配。激光填丝焊和复合焊改善了自熔焊的错边容限和间隙适应性。填丝焊错边容限为1.3 mm,间隙适应值为0.9 mm;复合焊的错边容限为1.8 mm,间隙适应值为1.4 mm。激光填丝焊和激光电弧复合焊接在生产实际中有更好的应用前景。传统焊接方式中,Q345易产生气孔和热裂纹。由于激光焊线能量大,热影响区小,冷却速度快,经过精密的焊前处理,在合理的工艺参数下,选用氩氧混合保护气体,可以获得无气孔、无热裂纹的焊缝。复合焊与填丝焊的接头都是由焊缝区、热影响区、母材而组成。对于复合焊,焊缝微观组织由部分魏氏体和贝氏体组成；热影响区有明显的羽毛状上贝氏体和板条马氏体；热影响区中的不完全结晶区有在晶界处重新形核长大的趋势。而填丝焊的组织相对与复合焊较为细小,因为填丝焊在单激光热源作用下,熔池停留的时间较短。填丝焊、复合焊拉伸试样均断于母材；填丝焊和复合焊的显微硬度均是母材小于热影响区,热影响区小于焊缝区。填丝焊最大硬度为340 HV,比复合焊大6%左右；填丝焊焊缝的冲击功为55J,比复合焊大12%。试样正弯曲角度与背弯曲角度能达到180。。拉伸和冲击断口均分布有等轴韧窝,焊接接头均为韧性断裂。经盲孔法测试的残余应力值均不高。
[Abstract]:Laser welding has high energy density, high welding speed, large ratio of weld depth to width, small heat affected zone, narrow heat affected zone and small thermal deformation, and there is no need for vacuum in welding. At present, manual welding is widely used in the shipbuilding industry. It is urgent to use laser welding to improve welding quality. Laser wire filling welding and composite welding technology can reduce the assembly accuracy, improve the metallurgical characteristics of weld and improve the mechanical properties of joints. In this paper, laser arc composite welding and laser wire filling welding for 9mm thick Q345 ship steel are carried out, which provides a technical reference for laser welding of ship steel. The welding parameters including wire feeding speed, defocusing, laser power, optical wire distance, welding speed, current value and so on need to be adjusted to obtain good quality weld seam by laser wire filling welding and composite welding, which include wire feeding speed, defocusing amount, laser power, optical wire distance, welding speed, current value and so on. The amount of defocus determines the size of the heat affected zone. The distance between filler wire and wire should be controlled between 1 mm and 1 mm, while the distance between 2mm and 3mm is well formed due to the combined effect of laser and arc. The laser power increases the penetration width increases and the welding speed increases and the penetration width decreases. This is because laser power and welding speed determine the power density, thus determining the penetration width. The current value in the composite welding is between 150 A and 220 A, and the composite welding is well formed. The feeding speed also affects the distribution of laser energy in the melting wire and the melting pool. Laser wire filling welding and composite welding can improve the tolerance and clearance adaptability of self-fusion welding. The error margin tolerance and clearance fitness of filler wire welding are 1.3 mm and 0.9 mm, respectively, and that of composite welding are 1.8 mm and 1.4 mm respectively. Laser wire filling welding and laser arc welding have better application prospect in production practice. In the traditional welding mode, Q345 is easy to produce porosity and hot crack. Due to the large energy of laser welding line, small heat affected zone and fast cooling rate, through precise pre-welding treatment and under reasonable technological parameters, the welding seam without porosity and heat crack can be obtained by selecting argon and oxygen mixed protective gas. The joint of composite welding and filler wire welding is composed of weld zone, heat affected zone and base metal. For the composite welding, the microstructure of the weld is composed of a part of Weieldite and bainite, the heat affected zone has obvious feathery upper bainite and lath martensite, and the incomplete crystallization zone in the heat affected zone has the tendency of renucleating at the grain boundary. The microstructure of filler wire welding is smaller than that of composite welding because the retention time of weld pool is shorter under the action of single laser heat source. The microhardness of filler wire welding and composite welding is smaller than heat affected zone and heat affected zone is smaller than weld zone. The maximum hardness of filler wire welding is 340 HVV, which is about 6% greater than that of composite welding, and the impact power of filler wire welding weld is 55 J, which is 12% larger than that of composite welding. The positive bending angle and the back bending angle of the sample can reach 180. The tensile fracture and impact fracture are equiaxed dimples, and the welded joints are ductile fracture. The residual stress measured by blind hole method is not high.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U671.8

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