2023年, 第32卷, 第1期　
刊出日期：2023-03-28

  

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  Research on the heat conduction mechanism of induction brazecoating

  龙伟民, 王梦凡, 刘大双, 张雷, 张冠星, 王鑫华, 王水庆

  中国焊接. 2023, 32(1): 1-6. https://doi.org/10.12073/j.cw.20221219001

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  Induction brazecoating technology is an important means to improve the surface properties of materials. In this paper, copper plate and corundum are selected as substrates for induction brazecoating respectively. The temperature variation of powder and paste coating is systematically studied, and the heat conduction mode and path in the brazecoating process are analyzed. The results show that rise of the coating temperature mainly depends on the heat absorption from the substrate. The liquid-solid interface conducts heat violently and advances step by step, which promotes the melting spread of metal filler metal. The powdery brazecoating material is in a free state, and there is a gas insulation film between the powder particles and the diamond, making it difficult for substrate to conduct heat to the coating. The binder not only assists forming, shell making and oxygen isolation, but also plays an important role during melting.
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  The effect of activating fluxes on the cathode spots in the activating TIG welding

  黄勇, 王伯洋, 郭建航, 刘永刚, 黄健康, 樊丁, 余淑荣

  中国焊接. 2023, 32(1): 7-17. https://doi.org/10.12073/j.cw.20230103001

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  The cathode spots are a common phenomenon in the TIG (tungsten inert gas) welding process. However, it is rarely observed in the activating TIG welding process. This research is mainly focused on the effect of activating flux on cathode spots in the activating TIG welding. The characteristics and behaviors of cathode spots were investigated in activating TIG welding by the high-speed camera and the spectrograph. Three kinds of oxide (TiO₂, SiO₂, MnO₂) and two halide (MnCl₂, CaF₂) activating fluxes are used in the activating TIG welding process. The results show that differ from the TIG welding, the oxide activating flux increases the number of cathode spots and decreases the velocity. The effect is the opposite for the halide activating flux. Moreover, the number of spots no longer varies with the current except TiO₂ activating flux. As the temperature of the weld pool surface increases the spot moves away from the center. But this rule is not valid when silica and manganese compounds activating fluxes are used. The variation of cathode spots is caused by the oxide film reformed and the distribution of weld slag. The formation mechanism of cathode spots might be the impact of ions on the cathode surface and the strong electric field formed near the cathode surface.
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  Fatigue crack propagation of 7050 aluminum alloy FSW joints after surface peening

  金玉花, 陈永昇, 马悦铭, 王希靖, 郭廷彪

  中国焊接. 2023, 32(1): 18-26. https://doi.org/10.12073/j.cw.20221205001

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  The surface composite modification of the 7050 aluminum alloy friction stir-welded joints was performed by shot peening(SP)/multiple rotation rolling(MRR) and MRR/SP, and the fatigue performance of the nugget zone(NZ) was investigated. The results demonstrated that the fatigue life of SP/MRR samples is longer than that of MRR/SP . On the plane 150 μm below the surface. The grains with high angle grain boundary account for 71.5% and 34.3% for MRR/SP and SP/ MRR samples , respectively. The crack propagation path of the MRR/SP is transgranular and intergranular, and it is intergranular for the MRR/SP. Multitudinous fatigue striations and some voids appeared at the fracture during the stable crack propagation stage.However, fatigue striations for SP/MRR are with smaller spacing, fewer holes, and smaller size under SP/MRR compared with fatigue fracture of MRR/SP. The differences in fatigue properties and fracture characteristics of the NZ are related to the microstructure after the two combined surface modifications.
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  Microstructure and properties of induction brazing nickel base/WC composite coating

  秦建, 杨骄, 刘攀, 刘大双, 卢洪波, 廖清泉, 常云峰

  中国焊接. 2023, 32(1): 27-34. https://doi.org/10.12073/j.cw.20221213001

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  BNi-2/WC composite wear-resisting coating was prepared on carbon steel by the method of induction brazing. The microstructure and phase composition of the composite coating were analyzed, and the bonding strength and wear-resisting performance of the coating were tested. During the process of induction brazing, the tungsten carbide partially dissolves and reacts with the filler metal alloy to form NiW compound phase, which realizes the metallurgical combination of tungsten carbide and filler metal alloy. The matrix of the filler metal alloy consists of Ni solid solution and Ni₃B/Ni₃Si eutectic phase, and the metallurgical diffusion reaction occurs between the filler metal alloy and the steel matrix. The mechanical analysis results show that the self-strength of the composite coating reaches 140 MPa and the bonding strength of the filler metal alloy to the steel matrix reaches 360 MPa. The dry sand rubber wheel wear testing machine showed that the coating weight loss was only 0.2824 g, which was only 1/5 of the weight loss of 65 Mn matrix under the same conditions.
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  Prediction and sensitivity analysis of the surface quality in Ni60/WC coatings

  杨江淮, 练国富, 陈昌荣, 冯美艳

  中国焊接. 2023, 32(1): 35-45. https://doi.org/10.12073/j.cw.20221007001

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  For laser cladding a large temperature gradient easily weakened the surface quality by generating cracks and irregular coating surfaces, which in turn affected the bearing capacity and corrosion resistance of coatings in the rapid heating and cooling process. The response surface methodology (RSM) was used to predict coating cracks by changing the powder ratio, energy density, and preheating temperature, which obtained the relevant mathematical model. After that, the sensitivity of the crack length to process parameters was analyzed based on the sensitivity analysis method. The effect of Ni60/WC composite powder process parameters on the surface quality was revealed in laser cladding. The crack length first decreased and then increased, and the Smooth decreased with the increased powder ratio. The crack length and Smooth increased with the increased energy density. The crack length decreased and Smooth increased with the increased preheating temperature. Sensitivity analysis showed that the crack length and Smooth were the most sensitive to the powder ratio. Therefore, the process parameters were reasonably selected to control the surface quality. The mathematical model and sensitivity analysis method in the work could improve the surface quality, which provided a theoretical basis for the prediction and control of laser cladding cracks.
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  Comprehensive study of microstructure and mechanical properties of friction stir welded 5182-O/HC260YD + Z lap joint

  邓建峰, 郭伟强, 徐晓霞, 王博, 灰辉, 窦思忠, 黄望业

  中国焊接. 2023, 32(1): 46-52. https://doi.org/10.12073/j.cw.20221210001

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  The welding of aluminum (Al) and steel has attracted more and more interest due to the weight reduction trend in vehicle and aerospace manufacturing industries. 5182-O/HC260YD + Z lap joint was produced by friction stir welding (FSW), and the microstructure and mechanical property of the joint were systemically characterized. The microstructure in horizontal direction of the Al and steel near interface was similar to their corresponding conventional friction stir welded joint. The joint was divided into stir zone of Al (ST-Al), stir zone of interface (ST-I), thermal-mechanically affected zone of steel (TMAZ-Fe) and base material of steel (BM-Fe) according to their distinct microstructure vertically. Three kinds of intermetallic compounds (IMCs) of FeAl₃, FeAl and Fe₃Al were formed at the interface. The horizontal micro hardness distribution exhibited a hat shape and “M” shape in Al and steel, respectively. The hardest region of the joint was located at the ST-I, with a hardness of 175 HV−210 HV. The joint was fractured along the hook structure, with an average shear strength of 73.9 MPa. Fractural morphology of Al and steel indicted a cleavage fracture mode.
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  Progress in weldability research of high entropy alloys

  刘爱国, 王超

  中国焊接. 2023, 32(1): 53-62. https://doi.org/10.12073/j.cw.20221216001

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  High entropy alloys usually show good weldability. The weldability problems of high entropy alloys are segregation, cracks, and hardening or softening of weld, etc. When an Al_xCoCrFeNi alloy is welded, Al and Ni will segregate to the interdendritic region in the weld, but the degree of segregation is less than that of the base metal. When an Al_xCoCrCu_xFeNi alloy or a CoCrCu_xFeNi alloy is welded, Cu tends to segregate to the interdendritic region in the weld. Increasing the cooling rate of the welding process, such as with laser welding, is conducive to reducing the segregation in the weld. The segregation in the weld and the heat affected zone, especially the segregation of Cu, will lead to the generation of hot cracks. Hot cracking is the main form of cracking in high entropy alloys joints. Welding will lead to changes in the hardness of the weld. The main factors affecting the hardness change are the grain sizes and the precipitations. With laser welding, if the base metal is cold rolled, the hardness of the weld will decrease. If the base metal is hot rolled and annealed or cast, the hardness of the weld will increase. With TIG welding, the hardness of the weld is usually lower than that of the base metal, unless the grain of the base metal is particularly coarse before welding. With friction stir welding, recrystallization and grain refinement occur in the stir zone, and the hardness of the stir zone will be significantly improved no matter the original base metal is cold rolled or cast.