2021年, 第30卷, 第3期　
刊出日期：2021-09-28

  

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  Microstructure and property of bonds obtained by vacuum brazing using Al-Si-Ti-Cu-In filler metal

  李娟, 常子恒, 李玉松, 赵宏龙, 张英哲, 周念, 秦庆东

  中国焊接. 2021, 30(3): 1-6. https://doi.org/10.12073/j.cw.20210516001

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  Aluminium matrix composites with 70% volume fractions of SiC particles, as the reinforcements, were brazed in the vacuum furnace using Al-Si-Ti-Cu-In alloy as filler metal. The microstructure and constituent of the joints were examined by means of SEM and EDS. Meanwhile, welded joints were submitted to shear test. The result shows that high quality joints were acquired, which mainly contains honeycomb Al base phase, Ti, In rich phase and annular Si rich phase. The brazing process sincludes five stages: (1) particles cohere; (2) liquid flows and particles rearrange; (3) the sintering neck grows; (4) second liquid flows and pores fill; (5) closed pores englobe and narrow. The reducing of the sintering body’s and pores’ free surface energy drove the sintering process to continue. The maximum shear strength was 90 MPa. The fracture belongs to mixing fracture with the characteristic of both the cleavage fracture and the micro void accumulation fracture.
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  Stability of fiber laser-MIG hybrid welding of high strength aluminum alloy

  韩永全, 韩蛟, 陈岩, 姚青虎, 王鹏

  中国焊接. 2021, 30(3): 7-11. https://doi.org/10.12073/j.cw.20210522001

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  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.
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  Narrow gap space contributes to chemical metallurgy of self-shielded arc welding

  刘大双, 魏萍, 龙伟民, 吴玉程, 黄文斌

  中国焊接. 2021, 30(3): 12-19. https://doi.org/10.12073/j.cw.20210607003

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  The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding. The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30 V and current of 260 A. The deposition efficiency keeps over 90 % for both 12 mm and 8 mm narrow gap welding. For 12 mm narrow gap welding, when the voltage is 28 V and the current is 264 A (or 286 A), no pores are found in the narrow gap weld. In the continuous welding process, manganese vapor, aluminum vapor and CO continuously generate to form gasbag and occupy the narrow gap space, thus protecting the droplet and molten pool from the invasion of air.
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  Corrosion behavior of aluminum/steel dissimilar metals friction stir welding joint

  莫淑娴, 董少康, 朱浩, 焦忆楠, 王军

  中国焊接. 2021, 30(3): 20-30. https://doi.org/10.12073/j.cw.20210504001

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  The corrosion performance of aluminum/steel contact and aluminum/steel FSW joint in 3.5 wt.% NaCl solution were analyzed using potentiostatic tests. The post-corrosion microstructure of the welding joint was characterized by optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the localized corrosion of FSW joint of Al/steel dissimilar metals mainly initiated at the interface transition zone (ITZ). Precipitation of intermetallic compounds (IMCs) and Fe-rich phase particles in ITZ accelerated the corrosion of the FSW joint. This phenomenon has been attributed to distinct corrosion potentials between IMCs and steel, aluminum base metal. The corrosion resistance sequence of IMCs in ITZ is Fe₃Al > FeAl > Fe₂Al₅.
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  Fine microstructure characterization of titanium alloy laser narrow gap welded joint

  高福洋, 穆壮壮, 马照伟, 杜志博

  中国焊接. 2021, 30(3): 31-38. https://doi.org/10.12073/j.cw.20210514001

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  In this paper, the microstructure of narrow gap laser welded joint of 45 mm Ti6321 titanium alloy was characterized. The microstructure characteristics of Laser self-fusion and laser-multi-pass-narrow-gapfilling layer were observed by metallographic microscope, and the phase morphology was analyzed by transmission electron microscope. The results show that the joint was obtained using the laser-multi-pass-narrow-gap welding, and no volumetric defect is observed. The weld grain of self fusion welded bead tends to be equiaxed with lots of needle α’, and the width of weld metal needle α’ was 0.4 μm. The heat affected zone is columnar crystal with lamellar α, and The width of heat affected zonelamellarα was 2–4 μm with a large number of dislocation tangles. The weld grains of laser-multi-pass-narrow-gap filler bead are coarse columnar grains with staggered acicular α’, and the width of acicular α’ in weld metal is less than 1 μm with number of dislocations. The heat affected zone is thick lamellar microstructure with a width of 2–4 μm with a large number of dislocation entanglement and packing. The microstructure evolution law is related with heating temperature and cooling rate.
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  A bibliometric analysis on friction stir welding

  中国焊接. 2021, 30(3): 39-48. https://doi.org/10.12073/j.cw.20210613001

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  Friction stir welding (FSW), as a growing welding technology, from its genesis in 1991, was attended by many researchers in interdisciplinary fields of science and engineering. The current paper presents a bibliometric analysis of the subject and can be addressed as guidance for the researchers who want to explore this field of welding technology. The research growth of FSW, most productive and influential authors, disciplines, leader journals, countries, and institutions are investigated. The highly influential papers in two historical periods and top keywords are also introduced. This paper summarizes the growth structure of FSW during the last 26 years and provides concise bibliometry.
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  Numerical simulation of residual stress and deformation for submerged arc welding of Q690D high strength low alloy steel thick plate

  朱梓坤, 韩阳, 张舟, 张义, 周龙早

  中国焊接. 2021, 30(3): 49-58. https://doi.org/10.12073/j.cw.20210306001

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  The finite element simulation software SYSWELD is used to numerically simulate the temperature field, residual stress field, and welding deformation of Q690D thick plate multi-layer and multi-pass welding under different welding heat input and groove angles. The simulation results show that as the welding heat input increases, the peak temperature during the welding process is higher, and the residual stress increases, they are all between 330–340 MPa, and the residual stress is concentrated in the area near the weld. The hole-drilling method is used to measure the actual welding residual stress, and the measured data is in good agreement with the simulated value. The type of post-welding deformation is angular deformation, and as the welding heat input increases, the maximum deformation also increases. It shows smaller residual stress and deformation when the groove angle is 40° under the same heat input. In engineering applications, under the premise of guaranteeing welding quality, smaller heat input and 40° groove angle should be used.
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  Aluminium-based moderate temperature filler metals for vacuum brazing of 6061 aluminium alloy

  张国清, 李彬, 王炜, 黄晓猛, 元琳琳

  中国焊接. 2021, 30(3): 59-64. https://doi.org/10.12073/j.cw.20210301001

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  Four kinds of aluminum based moderate temperature filler metals used for vacuum brazing of 6061 aluminum alloy were prepared by rapid solidification-isothermal rolling. The effects of alloy elements content on the melting characteristics of filler metals was studied by Differential Scanning Calorimetry (DSC). The microstructures of the filler metals and brazed joints were observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results show that with the increase of Cu content into the filler metals,the liquid phase temperature gradually is decreased. Microstructure characterzation of the brazed joints shows the eutectic structure of (α+β) and (α+θ) decrease gradually, θ-CuAl₂(Ni) gradually increases and transforms from small fishbone shapes to block shapes. Peak shear strength of 83 MPa for the 6061 aluminum joint with Al-9.5Si-10Cu-2Ni-0.5Mg was achieved after brazing at 575℃ for 2 min.