焊接参数对铝合金激光——MIG电弧复合焊缝熔深的影响

以5A06(LF6)铝合金为研究对象,研究了铝合金激光-MIG电弧复合焊(HYBRID焊)时焊接参数的变化对焊缝熔深的影响规律,并将焊接参数的变化对激光-MIG电弧复合焊、MIG电弧焊、激光焊的焊缝熔深的影响进行了综合比较分析.结果表明,若以等效于激光焊熔深的MIG电弧功率为分界线,可以把MIG电弧的功率分成高、低能量两个区,当激光与低能量电弧区的电弧复合时,激光对焊缝的熔深起主导作用,HYBRID焊的熔深大于该区的MIG电弧焊;当激光与高能量电弧区的电弧复合时,电弧对焊缝的熔深起主导作用,HYBRID焊缝主要体现为MIG焊缝的特点,加入激光的优势主要体现在增加焊接速度方面,即高速焊时也可获得良好的焊缝成形.     

Factors controlling the magnesium weld morphology in deep penetration welding by a CO2 laser

In laser welding with power density beyond 10⁴ W · mm⁻², the formation of plasma cavities, commonly referred to as keyholes, leads to deep penetration welds with high aspect ratios. In this paper, the morphologies of keyhole welds produced with a 6 kW CW CO₂ laser on two die-cast magnesium alloys, AZ91 and AM50, are compared. It was found that the two magnesium alloys responded differently to laser welding. Though irregular weld cross-section profiles were consistently observed on each materials, bead dimensions often varied with the welding variables in contrasting ways. For both alloys, important characteristics of the weld beads such as depth, width, crown height (hump), and surface ripples were analyzed as a function of the welding parameters, most particularly the heat input. Results show that the use of heat input, a variable grouping two welding parameters into one, was often inadequate in characterizing the bead morphology. Several explanations are given, including base metal vaporization, but the process of bremsstralung absorption explains it well and rationalizes many observed characteristics of laser weld morphology.     

High quality welding of stainless steel with 10 kW high power fibre laser

Abstract

The objectives of this research are to investigate penetration characteristics, to clarify welding phenomena and to develop high quality welding procedures in bead on plate welding of type 304 austenitic stainless steel plates with a 10 kW fibre laser beam. The penetration depth reached 18 mm at the maximum at 5 mm s^?1. At 50 mm s^?1 or lower welding speeds, however, porosity was generated at any fibre laser spot diameter. On the other hand, at 100 mm s^?1 or higher welding speeds, underfilling and humping weld beads were formed under the conventionally and tightly focused conditions respectively. The generation of spatters was influenced mainly by a strong shear force of a laser induced plume and was greatly reduced by controlling direction of the plume blowing out of a keyhole inlet. The humping formation was dependent upon several dynamic or static factors, such as melt volume above the surface, strong melt flow to the rear molten pool on the top surface, solidification rate and narrow molten pool width and corresponding high surface tension. Its suppression was effective by producing a wider weld bead width under the defocused laser beam conditions or reduction of melt volume out of keyhole inlet under the full penetration welding conditions. Concerning porosity, X-ray transmission in situ observation images demonstrated that pores were formed not only from the tip of the keyhole but also at the middle part because of high power density. The keyhole behaviour was stabilised using a nitrogen shielding gas, resulting in porosity prevention. Consequently, to produce high quality welds in 10 kW high power fibre laser welding, the reduction procedures of welding defects were required on the basis of understanding their formation mechanism, and 10 kW fibre laser power could produce sound deeply penetrated welds of 18 mm depth in a nitrogen shielding gas.     

几种常见合金的激光扫描焊接特性及研究现状

激光扫描焊接是一种高效的新型激光焊接技术,具有独特的激光束定位方式、扫描范围广、灵活性高、工作距离长等优点,相比于传统激光焊接,其多点焊接的特性能在很大程度上提升焊接效率.概述了激光扫描焊接技术的工作原理和分类,重点阐述铝合金、镁合金、钛合金、铜及铜合金、铝-钢异质合金几种常用合金的激光扫描焊接特性及研究现状.扫描激光...     

Effect of laser spot weld energy and duration on melting and absorption

Abstract

To facilitate pulse Nd–YAG laser spot weld development, it is common practice to adjust the pulse energy, duration, and focus spot size. An accurate understanding of the effect of these parameters on melting, weld appearance, and heat input is thus required. Calorimetric measurements of the net heat input to 304 stainless steel workpieces for laser spot welds have been completed. A pulse Nd–YAG laser was used with varying pulse energies from 1 to 5·5 J, and pulse durations of 2·2 and 7·0 ms. Measurements showed the absorption for spot welds produced using the pulsed Nd–YAG laser to vary from 38 to 67% and to be relatively insensitive to beam intensity. Analysis of the continuous point source equation for conduction heat flow in solids was used to predict the weld size for the pulse energy and duration measured in the experiment. Calculations of the weld pool volume from the weld metallography were used to determine the melting for each spot weld. Comparisons of the measured weld size with the three-dimensional model predicted size indicated that the observed weld pools are larger than is expected from the measured workpiece energy. Analysis of the experimental data and the theoretical model has revealed a substantial increase in melting for short duration pulses versus long duration pulses of the same energy. The benefit of laser spot welding parameter optimisation is hence indicated.     

激光/等离子电弧复合热源能量参数对钛合金焊缝成形的影响

在对钛合金激光/等离子电弧复合焊与单一激光焊的焊缝成形进行比较的基础上,研究了激光在复合等离子电弧后主要焊接工艺参数对焊缝成形的影响.结果表明,随激光功率增大和焊接速度降低,复合焊与单一激光焊焊缝的横截面形貌均由钉形向近X形转变.与单一激光焊相比,复合焊焊缝的余高和咬边较大.激光/等离子电弧"协同效应"随激光功率和焊接速度变化而不同,从而影响复合焊焊缝的熔宽和熔宽比.随焊接电流从零增大到60 A,焊缝熔宽略有增大,而焊缝熔宽比基本保持不变.     

Correlation between laser-wire distance and Nd：YAG laser ＋ P-GMA hybrid welding heat input parameters

In laser+P-GMA hybrid welding,laser-wire distance is an important parameter to describe the distance from laser spot to the center of the pulsed gas metal arc.The experiments results show that the optimal laser-wire distance with the deepest weld penetration increases with welding current and laser power being increased and decreases with welding speed being increased.Welding current,laser power and welding speed determine the hybrid welding heat input in laser+arc hybrid welding process,so there is a correlation between the optimal laser-wire distance and the hybrid heat input welding parameters for the deepest weld penetration: the optimal laser-wire distance increases with the heat input being increased.The positive correlation between the optimal laser-wire distance and the hybrid welding heat input is induced by the characteristics of the limited influence of P-GMA welding process on laser transmission and the dependence of weld penetration of hybrid welding on laser power.     

Optimization of Ti6Al4V titanium alloy laser–arc hybrid weld parameters

This article reports the results of a study aimed at using statistical methods to optimize the parameters for laser–arc hybrid butt welding of Ti6Al4V titanium alloy sheets with a thickness of 3.0 mm. The study has examined the effects of the hybrid welding process parameters, such as laser beam power, arc pulse frequency, arc length, arc current, wire speed, laser and arc relative positions, and weld speed. Microstructure has been studied using light microscopy and morphological analysis of weld bead cross sections. This article reports the results of energy and morphological tests.     

Arc characteristics of laser-TIG double-side welding

Abstract

Based on the experiments of laser-TIG double-side welding (LTDSW) for aluminium alloys, the influence of laser radiation on the arc behaviours of the opposite side was investigated. Generally, with the variation of laser power, there are three typical arc shapes: arc column convergence, arc root constriction and arc expansion. An important point to notice is that the laser keyhole preheating will induce the arc column convergence in the LTDSW. The arc voltage in the LTDSW is lower than that in TIG welding over the entire range of the experimental currents. Moreover, with increasing welding current, the difference in arc voltage between TIG welding and LTDSW is diminished because of the self-stabilisation of the arc burning at high currents. The complex transformation of arc behaviours has a great effect on the arc current density and its stability. The laser generated hot spot or laser induced plasma will have a higher temperature and greater electron density than neighbouring regions, and will offer the line of least resistance or the lowest potential drop. Hence, it is very reasonable that the arc voltage should descend under the influence of laser radiation, and the arc electrons should compress and root to the hot spot or plasma zone.     

Nd:YAG激光+CMT电弧复合热源横焊工艺参数对焊缝成形的影响

以304不锈钢为对象,借助焊缝成形参数来评价YAG激光+CMT电弧复合热源横焊焊缝的成形特征,研究了Nd:YAG激光+CMT复合热源横焊过程中焊接工艺参数对焊缝成形的影响.结果表明,在CMT电弧焊接中加入激光可以改善横焊焊缝成形;在激光能量和焊接电流一定时,光丝间距存在一个最佳匹配,使得Nd:YAG激光+CMT复合热源横焊焊缝成形良好;与其它复合热源焊接相对比激光功率对熔深影响较大,对横焊焊缝成形的影响程度与焊接电流有关;焊接速度对横焊焊缝成形影响显著;离焦量对横焊焊缝成形影响较小;电弧功率对横焊焊缝的偏离度影响显著.     

钛合金激光穿透焊的焊缝成形(Ⅰ)

在对钛合金激光穿透焊焊缝成形特征分析的基础上研究了激光焊主要工艺参数对焊缝成形的影响 ,同时对比研究了CO2 激光和YAG激光穿透焊时焊缝成形的差异。研究结果表明 ,在穿透焊条件下 ,CO2 激光和YAG激光焊接钛合金焊缝都具有钉形和近X形两种典型的截面形貌。焊缝成形与焊接热输入及激光功率密度有密切联系。随焊接热输入和激光功率密度的增大 ,焊缝截面由钉形向近X形转变。在采用同样工艺规范获得近X形焊缝成形时 ,YAG激光焊缝的对称度显著高于CO2 激光焊缝。通过调整激光功率、焊接速度和离焦量等激光焊工艺参数 ,可以对焊缝成形进行有效控制 ,提高焊接接头质量。     

热塑性塑料PP半导体激光焊接工艺

随着产品轻量化的发展要求,塑料激光焊接以其优良的焊接质量、易于控制、可焊接微小零件等诸多优点成为人们研究的热点.利用波长为808 nm的半导体激光器,采用吸收剂Clearweld对聚丙烯(PP)进行了激光透射焊接,讨论了激光功率、焊接速度、夹紧力和吸收剂等工艺因素对其焊接质量的影响.结果表明,在有夹紧力夹持、且激光光斑大小一定的情况下,焊接热输入存在一个最佳范围以获得良好的焊缝成形和接头强度.     

Process and joint characterizations of laser-MIG hybrid welding of AZ31 magnesium alloy

High power laser-metal inert gas (MIG) hybrid welding of AZ31 Mg alloys was studied. Microstructure and fracture surface of welded joints were observed by optical microscope and scanning electron microscope. The mechanical properties of welded joints were evaluated by tensile test. Under the optimal welding parameters, the stable process and sound joints were obtained. The tensile strength efficiency of welded joints recovered 84-98% of the substrate. It was found that the arc was compressed and stabilized by the laser beam during the hybrid welding. The compressed extent of arc column increased with laser power, and the process stability could be improved by increasing laser power and arc current or slowing welding speed. The arc stabilized mechanism in laser-MIG hybrid welding of Mg alloys was summarized in two factors. First, the laser keyhole fixes the arc root and improves the igniting ability of the arc. Second, the electromagnetic force is downward and increased by the laser-arc interaction, which prevents the overheating of the droplet and smoothes droplet transfer from the wire to the weld pool.     

Fibre laser welding of aluminium alloy

The objectives of this research are to investigate the effects of various welding conditions on penetration and defect formation, to clarify their welding phenomena and to develop the procedure of reduction of the defect. Fibre laser bead-on-plate welding was performed on several aluminium alloys, in particular A5083, at the power of 6 or 10 kW and several power densities from 0.4 kW/mm². It was found that the weld beads were narrower and deeper with an increase in the laser power density. For example, fully penetrated weld beads in 10 mm thick plates were produced at the laser power density of 640 kW/mm² and the welding speed of 10 m/min. However, convex–concave bead surfaces were formed. Moreover, in the case of the high power density, no porosity and many pores were present at high and low welding speeds, respectively. On the other hand, in the case of the ultra-high power density, few pores were generated in high speed welding. These reasons were interpreted by observing keyhole behaviour, bubble formation and the molten pool geometry during high power fibre laser welding with a high-speed video camera and microfocused X-ray transmission in situ observation method. Moreover, the porosity in the weld bead was reduced and prevented by the utilization of nitrogen gas instead of Ar gas, or the forward inclination angle of 40° (50° from the right angle) in Ar shielding gas.     

Use of magnetic arc oscillation for grain refinement of gas tungsten arc welds in α–β titanium alloys

Abstract

In an effort to refine the weld metal grain structure in α–β titanium alloys, gas tungsten arc welding was carried out, during which transverse oscillations of the arc were induced through the use of an alternating external magnetic field. At optimum values of oscillation amplitude and frequency in both the alloys investigated, considerable refinement of the fusion zone grain structure was achieved. This could be attributed to factors that include enhanced fluid flow, reduced temperature gradients, and a continually changing weld pool size and shape owing to the action of the imposed magnetic field. The reduction in the prior β grain size was shown to result in a notable increase in fusion zone tensile ductility. Post-weld annealing increased ductility in all cases, but the magnetically treated material continued to show a higher elongation than that of the untreated material even after post-weld heat treatment.     

Effect of power source characteristic on CO2 short circuiting arc welding

Abstract

Some problems are reported concerning the observation of the weld pool and effects of the power source characteristic on arc stability in CO₂ short circuiting arc welding. First, the effect of a power source with a constant voltage characteristic on CO₂ short circuiting arc welding is investigated by analysing the behaviour of the voltage and the current. From the results of this analysis, the cause of spatter generation is identified. A new power source characteristic is then proposed to improve the stability and the self-regulation of the arc. By adjusting the power source characteristic, the metal transfer can be stabilised in the CO₂ short circuiting arc welding process, i.e. the present authors have developed a power source having a non-linear characteristic. Its performance is verified by carrying out experiments.     

Study of laser MIG hybrid welded AZ31 magnesium alloy

Abstract

The laser metal inert gas (MIG) hybrid welded AZ31 magnesium alloy is discussed in weld shape, microstructure characteristics and mechanical properties in comparison of single laser and arc welding. The stable MIG arc, reliable droplet transfer and regular weld that are hardly obtained in single MIG welding can be obtained in hybrid welding by laser arc synergic effects. The ultimate tensile strength and elongation of hybrid weld are far higher than those of laser weld and reach 97·8 and 87·5% of base metal respectively. Under this experimental condition, the efficiency of hybrid welding is 1·20 times faster than that of single laser welding. Between the wide upper part (arc zone) and the narrow lower part (laser zone), obvious difference is observed. Arc zone has coarser grain size and wider partial melted zone than laser zone. Finally, the porosity reduction mechanism of hybrid weld is discussed according to the weld pool shape and the acting forces on it.     

厚板钛合金等离子—钨极氩弧复合焊接接头组织与性能

针对16 mm厚TA2钛合金板材进行等离子打底+钨极氩弧焊盖面的复合焊(plasma-tungsten inert gas welding,P-T复合焊),采用小孔型等离子焊实现不开坡口单面焊双面成形。结果表明,焊缝的组织为少量锯齿形α-Ti+针状马氏体,未发现成分偏析与聚集、夹杂物及裂纹等缺陷。热影响区及熔合线为锯齿形α-Ti+板条马氏体组织。焊缝的抗拉强度达到486 MPa,与母材相当,且断裂位置位于热影响区。在较优的工艺参数下进行焊接,焊缝及热影响区的维氏硬度分别为175 HV和170 HV,均高于母材。因此P-T组合焊接能实现钛合金厚板焊接,在厚板钛合金焊接中具有广泛的应用前景。创新点： 首次采用等离子打底和氩弧焊盖面的复合焊接方法实现16 mm厚钛板无缺陷焊接。     

Keyhole stability in disc laser welding of AZ31B and AZ61A magnesium alloys and weld metal properties

Abstract

To confirm the process potential and limitations of laser welding of magnesium alloys, a newly developed disc laser of 16 kW in maximum power was used to weld thin plates of AZ31B and AZ61A alloys. Melting characteristics and weld metal properties were studied under different process parameters. The very high power density of the applied beam caused the keyhole and the molten pool to be unstable. Underfill was the main welding defect limiting the process window and its formation was closely related to the keyhole instability. A process diagram indicating areas of sound and defected welds could be constructed. Sound welded joints could be obtained for AZ31B alloy with similar mechanical properties as that of the base material. The brittle intermetallics network present along the grain boundaries in AZ61A weld metals required a higher energy input to alleviate its detrimental effect on the mechanical properties of the welded joints.