Beam oscillating parameters on pore inhibition,recrystallization and grain boundary characteristics of laser-arc hybrid welded AZ31 magnesium alloy

Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of beam oscillation parameters on pore inhibition,microstructure,grain boundary characteristics and tensile properties were investigated.The results showed that the pore formation can be inhibited with oscillating frequency higher than 75 Hz and radius smaller than 0.5 mm.The columnar grains neighboring the fusion line can be broken by the beam oscillation behavior,while the grain growth was promoted with the increase of frequency or radius.It should be noted that the coincidence site lattice(CSL)boundaries were mainlyΣ13b andΣ29 boundaries,which were contributed by{10■2}tensile twins and{11■2}compression twins,respectively.The total fraction of CSL boundaries reached maximum at radius of 0.25 mm and frequency of 75 Hz,which was also confirmed as the optimized parameters.In this case,the elongation rate increased up to 13.2%,12.8%higher than that of the weld without beam oscillation.Finally,the pore formation and inhibition mechanisms were illustrated according to the state of melt flow and keyhole formation,the abnormal growth was discussed basing on secondary recrystallization,and the relationship among the pore formation,grain size,boundary characteristics and weld toughness were finally established.

Microstructure homogeneity and mechanical properties of laser-arc hybrid welded AZ31B magnesium alloy

Laser-arc hybrid welding of AZ31B magnesium alloy was carried out,the effects of welding parameters on weld formation,microstructure homogeneity and mechanical properties were investigated.The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores.The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center.It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone,with the difference mainly affected by laser power rather than welding current and welding speed.The welding parameters were optimized as laser power of 3.5 kW,welding current of 100 A and welding speed of 1.5 m/min.In this case,the weld was free of undercut and pores,and the tensile strength and elongation rate reached 252 MPa and 11.2%,respectively.Finally,the microstructure homogeneity was illustrated according to the heat distribution,and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.

Research on laser-arc hybrid welding technology for long-distance pipeline construction

In recent years, the research on pipeline laser-arc hybrid welding technology has been the important and difficult in the field of welding all over the world. China Petroleum Pipeline Research Institute Co. Ltd. has firstly developed pipeline laser-arc hybrid welding system in China, and executed the welding tests based on X70/X80 steel. Preliminary experiment results showed that hybrid welding could meet the requirements of related standards such as API1104,ASME,etc., the mechanical properties of girth seam are qualified in the case that there were no internal defects. With the development of high-power fiber laser and the continuous improvement of welding equipment, laser-arc hybrid welding technology for pipeline field welding will be available soon.

Stability of fiber laser-MIG hybrid welding of high strength aluminum alloy

The effect of fiber laser on MIG arc was investigated with 8 mm 7075-T6 high strength aluminum alloy as base material.The arc shape,droplet transfer form and electrical signal in the process of MIG welding and laser-MIG hybrid welding were analyzed.The stability of the hybrid welding process was evaluated by standard deviation analysis.The results show that with the increase of laser power,a large number of laser-induced plasma enters the arc column area,providing more conductive channels,which makes the heat of MIG arc more concentrated and the short circuit transition disappear.Due to the continuous effect of laser,the keyhole becomes a continuous electron emission source,and a stable cathode spot will be formed near the keyhole,which enhances the stability of MIG arc at the base current state.By using the method of standard deviation analysis,the voltage standard deviation of single MIG welding arc and laser-MIG hybrid arc within 4 seconds was calculated.The standard deviation of single MIG arc voltage was 1.05,and the standard deviation of MIG arc voltage in laser-MIG hybrid welding was 0.71–0.86,so the hybrid welding process was more stable.

Microstructure and properties of laser-arc hybrid welding of high-strength low-alloy steel

Laser-arc hybrid welding has the characteristics of optimal surface formation and greater penetration;it is extensively used in the welding of plates of medium thickness.However, for hybrid welding of lasers, the welding seam cooling rate is rapid;thus, the welding seam has a higher tendency to significantly harden, which has a negative impact on the weld quality of the high-strength low-alloy(HSLA) steel plates of medium thickness.In this study, laser-arc hybrid welding is performed on the BG890 QL HSLA steel produced by Baoshan Iron & Steel Co.,Ltd.,and the quenching tendency of the welded structure is examined.The results demonstrate that the specific growth direction of the columnar crystal structure of the laser-arc hybrid welded joint is obvious.However, at the center and top of the welded seam, there are equiaxed crystals.The impact properties at room temperature and-40 ℃ of the weld area are 58.0 J and 40.0 J,respectively, and those of the heat-affected zone(HAZ) are 147.0 J and 66.5 J,respectively.The impact performance can meet these requirements.Laser-arc hybrid welding of HSLA steel can yield strong and durable welds and the HAZ structure to meet the requirements of engineering applications.

Numerical simulation of temperature field in laser-arc hybrid welding of wear-resistant steel

Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.

Application and development in railway vehicles trend of new welding technologies manufacturing industry

This paper introduces the application of new automatic welding technologies in railway vehicles manufacturing industry, and presents the state of art of advanced friction stir welding technology, semi-penetration laser welding technology and laser-arc hybrid welding technology in manufacturing aluminum alloy body shell, stainless steel body shell and bogie. This paper also analyzes the application and development trend of three welding technologies in the future.

FEM Simulation of Distortion and Residual Stress Generated by High Energy Beam Welding with Considering Phase Transformation

A series of experiments was carried out so as to elucidate the effect of the phase transformation in the cooling process on welding distortion and residual stress generated by laser beam welding (LBW) and laser-arc hybrid welding (HYBW) on the high strength steel (HT780). Then, the experiments were simulated by 3D thermal elasticplastic analysis with FEM (Finite Element Method) which was performed with using the idealized mechanical properties considering the transformation superplasticity. From the results, the effects of the phase transformation on welding distortion and residual stress generated by LBW and HYBW were elucidated. Furthermore, the generality of the idealization of the mechanical properties was verified.

Laser welding process and strength enhancement of carbon fiber reinforced thermoplastic composites and metals dissimilar joint:A review

Carbon fiber reinforced thermoplastic composites(CFRTP)and metals hybrid structures have been widely used in aircraft lightweight manufacturing.However,due to the significant difference in physical and chemical properties between CFRTP and metals,there are lots of challenges to connect them with high quality.Laser welding has a good application prospect in CFRTP and metals connection,and a significant research progress has been made in the exploration of CFRTP-metal laser joining mechanism,joining process optimization,joining strength improvement and joining defects controlling.However,there are still some problems need to be solved for this technology application.In this paper,the research progress of CFRTP-metal laser joining was summarized in three major aspects:theoretical modeling and simulation analysis,process exploration and parameter optimization,joint performance improvement and process innovation.And,problems and challenges of this technology were discussed,and the outlook of this research was provided.

激光功率对2195铝锂合金光纤-半导体激光复合焊接形貌与气孔的影响

光纤-半导体激光复合焊接技术充分结合了光纤与半导体激光热源的优势,在激光加工领域拥有巨大的潜力.针对2195铝锂合金开展光纤-半导体激光复合焊接试验,并定量研究激光功率对焊接形貌与气孔的影响.结果表明,光纤激光功率显著影响焊缝熔深,半导体激光功率显著影响焊缝上熔宽.基于回归分析方法建立焊缝横截面积预测模型.此外,光纤与半导体激光均对焊缝气孔缺陷的控制起着重要的作用,较高的光纤激光功率有利于降低气孔缺陷.对于4 mm厚2195铝锂合金,采用光纤激光功率为3.0 k W、半导体激光功率为2.5~3.0 k W时,熔池温度高且光纤-半导体激光复合作用范围大,焊接接头气孔缺陷少.

Microstructure and mechanical properties of weld metal in laser and gas metal arc hybrid welding of 440-MPa-grade high-strength steel

Fiber laser and gas metal arc hybrid welding of 440-MPa-grade high-strength marine steel was carried out at different welding speeds.The influence of welding speed on the micro structure and mechanical properties of weld metal was investigated.The weld-metal microstructure mainly consisted of pre-eutectoid ferrite,side-plate ferrite,acicular ferrite and lath bainite at a low welding speed.With the increase in welding speed,acicular ferrite and lath bainite were the dominant weld-metal microstructures.All samples failed at the base metal during tensile tests,which indicates that there is no soft zone in the hybrid welds.The welding speed had a significant effect on the impact toughness of the weld metal.The impact absorbed energy of the weld metal increased from 35 to 105 J with the increase in welding speed from 0.8 to 2.0 m/min.Large amounts of acicular ferrite and lath bainite were formed in the weld metal at a high welding speed,which resulted in an excellent impact toughness.

工业纯钛光纤激光-MIG复合焊接工艺及性能

采用光纤激光与熔化极惰性气体保护电弧焊(MIG焊)复合焊接工业纯钛,分别对激光焊、MIG焊和复合焊接头的焊缝表面成形、横断面进行了观察,并进行了激光焊和复合焊接头的拉伸试验及杯突试验.结果表明,复合焊的电弧稳定性比MIG焊显著提高,焊接速度可提高7倍;复合焊与激光焊接头的抗拉强度高于母材;复合焊接头的杯突值优于激光焊接头的杯突值,这是因为复合焊焊缝的微观组织有利于接头的塑性.因此,采用光纤激光-MIG电弧复合焊接方法很好地实现了工业纯钛的高速焊接,焊缝成形良好,接头的塑性优于单一激光焊的塑性.

6009铝合金光纤激光-MIG电弧复合焊和光纤激光焊工艺对比研究

采用光纤激光-MIG复合焊和光纤激光焊分别对6009铝合金进行焊接,研究两种焊接方式下焊接接头的成型性、显微组织、拉伸性能、显微硬度、断口形貌的不同。研究表明:激光电弧复合焊的焊接速度是激光焊接的3倍;相比于激光焊,激光电弧复合焊焊缝中心显微组织更加细小;接头的抗拉强度达到母材的63%以上,而激光焊接的抗拉强度仅仅只有母材的38%;显微硬度试验表明:复合焊存在软化区,而激光焊接几乎没有软化区;断口分析表明:复合焊和激光焊的拉伸断口都是典型的韧窝状态,但是复合焊接的韧窝更加均匀。

5083铝合金光纤激光-TIG复合焊接工艺研究

采用IPG YLS-6000光纤激光器和Fronius MagicWave3000job数字化焊机,对4mm厚5083H116铝合金进行了复合焊接试验。研究了电源特性、电流大小和热源间距等工艺参数对光纤激光-钨极惰性气体保护焊(TIG)复合焊接焊缝成形的影响规律,并分析了焊接接头的缺陷、显微硬度及力学性能。结果表明,光纤激光-TIG复合焊接5083铝合金,能够明显改善焊缝成形,提高焊接过程稳定性,特别是与变极性TIG电弧复合效果更为显著;光纤激光与变极性TIG电弧复合焊接,采用激光在前的方式,电弧电流150A,且热源间距不大于4mm,可以得到具有明亮金属光泽和均匀鱼鳞纹的焊缝,焊缝无气孔和裂纹缺陷,其表面有少量的下凹;复合焊接接头抗拉强度为318MPa,达到母材强度的93%,延伸率为7.6%,高于单光纤激光焊接,断口分析为韧性断裂。

光纤激光-MIG复合焊接中厚板铝合金组织特征

研究了光纤激光-MIG复合焊接中厚板铝合金的焊缝组织。结果表明,光纤激光-MIG复合焊接可一次焊透8 mm厚铸造铝合金ZL114,焊缝中没有大的工艺气孔,也无热裂纹,但出现较多的冶金气孔。焊缝主要由α(Al)和Al-Si共晶组成,焊缝上部、中部和下部组织变化不明显,焊缝没有分层现象。焊缝较热影响区和母材组织细密,焊缝和热影响区的共晶组织类似,但焊缝和母材共晶组织明显不同,体现在共晶形态和Si含量的不同,但母材的共晶组织在一定的热循环条件下,可以转变为与焊缝类似的共晶组织,伴随的是枝晶数量的减少,枝晶在母材和焊缝中都占绝大部分。

活性激光电弧复合焊接法研究

为了进一步提高激光电弧复合焊接的熔深,提出活性激光电弧复合焊接法。在氧气的保护下,用小功率光纤激光在待焊焊件表面进行预熔处理,使表面熔化生成一层氧化层,然后用激光电弧复合焊接覆盖氧化层,达到增加熔深的目的。结果表明,激光预熔后进行激光电弧复合焊接,电弧明显收缩,熔深增加1.5倍左右,表面成形良好。激光预熔后,焊缝含氧量增加,熔池表面张力温度系数由负变正,使得复合焊接熔深增加。研究工艺参数对焊缝熔深和熔宽的影响,随着激光预熔功率的增加,熔深增加熔宽减小;随着电流的增加,熔深熔宽都增加,但激光预熔后的焊道增加更快。随着复合焊接速度的增加,熔深和熔宽都减小。随着复合焊接中激光功率的增加,熔深增加,对熔宽的影响较小。利用活性激光电弧复合焊接法,可以得到较为细小的焊缝组织,提高焊接接头的抗拉强度,能达到母材抗拉强度的95%,且面弯和背弯180°后未出现裂纹,表明接头具有良好的韧性。

光纤激光及其复合焊接研究进展

综述了大功率光纤激光在综合使用成本、材料和工艺适应性等方面与CO_2激光和Nd:YAG激光的比较优势,光纤激光焊接时光致等离子体行为及其与入射光束的相互作用特点,以及光纤激光及其复合焊接技术在航空航天和石油管道建设方面的应用研究进展。结果表明,与CO_2激光和Nd:YAG激光相比,光纤激光综合使用成本低、材料和工艺适应性强,光致等离子体处于弱电离状态,其对入射光纤激光束的吸收和偏转作用可以忽略不计,光纤激光应用于焊接时,光纤激光/电弧复合焊接技术的工艺适应性要优于单独光纤激光焊接。

400MPa球墨铸铁光纤激光-MIG电弧复合焊接头的断裂特征

采用填充308L不锈钢焊丝光纤激光-MIG电弧复合焊方法,焊接厚度为5mm的风电关键部件用400 MPa级球墨铸铁,获得了表面成形良好且熔透的焊缝,研究了MIG电弧热输入对接头拉伸性能和断裂特征的影响.结果表明,电弧热输入较小时,接头的拉伸性能差,断裂沿熔合线发生,断口为脆性断口;电弧热输入较大时,接头的拉伸性能较好,断裂自半熔化区顶部沿母材发生,断口顶部为脆性断口,底部为韧性断口.接头断裂特征的差异是由接头中焊缝和半熔化区底部莱氏体的量的不同导致的.基于以上研究,获得了抗拉强度为346.4 MPa、断后伸长率为5.4%,断裂发生在母材上的优质接头.

光纤激光-MIG复合焊参数对钛合金焊缝成形的影响

采用板面堆焊方法,在焊接电流为极小值和极大值的条件下,通过试验研究了光纤激光- MIG复合焊工艺参数对工业纯钛焊缝横截面形貌、熔宽和余高的影响。

高强度管线钢激光电弧复合焊接技术研究现状

伴随石油天然气开发规模逐渐增大,油气输送管线的铺设距离逐年增加,迫切需要通过提高油气管线钢的强度等级来降低管道材料投资费用和管线运营成本,因此,X100及以上等级的管线钢在油气管线工程中将得到广泛应用。介绍了油气管线钢激光电弧复合焊接技术的研究历程,对比使用不同激光器进行激光电弧复合焊时的优缺点,综述了最具有野外现场应用前景的光纤激光电弧复合焊接技术的研究现状及相关研究成果,表明其在提高高强度管线钢焊接质量、焊接速度和生产效率等方面具有的重要工程应用价值和良好的应用前景。