2022年, 第31卷, 第4期　
刊出日期：2022-12-28

  

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  Effect of TiC addition on the microstructure and wear resistance of induction brazed nickel-based coating in air

  龙伟民, 孙华为, 刘大双, 秦建, 张雷, 卢洪波

  中国焊接. 2022, 31(4): 1-6. https://doi.org/10.12073/j.cw.20221017001

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  The nickel-based coating with different TiC addition was fabricated onto 45 steel substrate by using induction brazed technology in air. The effect of TiC addition on the microstructure and wear resistance of induction brazing coating was studied. The results show that the microstructure of brazing coating is strengthened and refined by adding TiC. With the increase of the amount of TiC added, the amount of TiC in the Ni-based matrix is increased, and the matrix structure is obviously refined. This is because the high melting point TiC particles can be used as heterogeneous nucleation cores, thus refining the Ni based matrix structure. Moreover, the wear resistance of brazing coating is improved due to the addition of TiC.
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  From statistical analysis to process optimization during cladding using a Nd:YAG laser

  亚伟, Pathiraj B., 于兴华

  中国焊接. 2022, 31(4): 7-22. https://doi.org/10.12073/j.cw.20220518001

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  Application of statistical methods to optimize the process parameters was achieved by employing full factorial design of experiments, which was accomplished by cladding using stepwise ramped laser power. The correlations between clad geometry and dilution (clad characteristics) and the main process parameters laser power (P_l), cladding speed (v_c), the powder feed rate ($ \dot{\mathit{m}} $) were obtained through application of variance analysis technique (ANOVA). The obtained correlations between the main processing parameters and the clad characteristics are discussed and a statistical model was developed. The desirability investigations using the developed statistical model were performed by considering the clad geometry, aspect ratio, dilution and hardness. Optimal parameters for cladding Stellite 6 on AISI 420 steel substrate and for cladding Nucalloy 488V on S355 J2 steel substrate were obtained. The optimal processing parameters can be applied to clad other materials with similar chemical compositions.
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  High-strength friction stir welding of selective laser melted AlSi10Mg alloys

  王伟, 李鹏, 孟祥晨, 谢聿铭, 冒冬鑫, 张泽宇, 黄永宪

  中国焊接. 2022, 31(4): 23-27. https://doi.org/10.12073/j.cw.20220912001

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  Selective laser melted AlSi10Mg alloys with eutectic network structures were successfully joined by friction stir welding. Sound butt-lap joints have been achieved. A novel enlarged pin was designed to overcome kissing bonding defects and increase interfacial bonding area. The hook defect in a conventional butt-lap joint was avoided due to the limitation of the upward flow of interfacial materials, and the interfacial joining width was 2.5 times of the plate thickness. The eutectic Si network structure was broken into the re-dispersed rich-Si phases, improving joint performance. The ultimate tensile strength reached 83.1% of the matrix, higher than those of conventional melting techniques.
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  Analysis of bending mechanism in multi-scanning laser bending process based on plastic strain development

  王超, 吴春彪, 徐本连, 金載雄

  中国焊接. 2022, 31(4): 28-36. https://doi.org/10.12073/j.cw.20221005001

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  By using multi-pass straight-line scan strategies, a larger bending angle can be achieved. There is, however, a limited understanding of the variation in bending angle per pass during multi-pass under various process parameters. In multi-pass laser scanning, the bending angle cannot always linearly increase with scanning passes and this phenomenon can be observed mostly in low heat input. Strain hardening is the common explanation for this phenomenon. However, it could not explain why this bending angle reduction phenomenon occurs at low heat input scanning rather than at high heat input scanning. In this study, this phenomenon is discussed based on strain development in experiments and numerical simulation. The different growing mechanism of plastic strain is analyzed to reveal the effects of laser power and scanning velocity. Furthermore, the opposite bending trend that occurred at larger laser power is discussed in comparison to the plastic strain development. The study shows that relatively larger heat input below 6.7 J/mm can help to avoid the bending angle reduction phenomenon and the opposite bending trend is highly dependent on the larger laser power. For achieving the expected cumulative bending angle in multi-pass laser bending, it is recommended to decrease the scanning velocity at a relatively low laser power level while increase the scanning velocity at a high level of laser power.
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  The comparison of multi-layer narrow-gap laser and arc welding of S32101 duplex stainless steel

  李军兆, 温凯, 孙清洁, 刘一搏, 孔玢, 曾宪山

  中国焊接. 2022, 31(4): 37-47. https://doi.org/10.12073/j.cw.20221012001

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  Multi-layer narrow-gap welding of thick S32101 duplex stainless steel was conducted using laser welding with beam wobble process. The phase transition, grain size, phase proportion and crystal texture of welded joint were also studied and compared with gas metal arc welding process. The microhardness and tensile strength were measured and fracture surface was analyzed to evaluate the mechanical properties of welded joints. The results showed that beam wobble technology improved the misalignment of laser beam and filler wire in narrow groove and helped to avoid incomplete fusion defects. Compared to arc welding process, the groove size and heat input were reduced, while welding efficiency was increased. The faster cooling rate and lower temperature gradient of laser wobble welding favored grain refinement, while the austenite content in weld zone decreased. Both the beam wobble and swing arc were conducive to stir weld pool, optimizing the weld microstructure and joint formation. The microstructural variance in various weld passes was caused by the heat input and heat dissipation ability. The microhardness of laser welded joint was lower, while the tensile strength and elongation percentage were higher. The fracture surface of arc welded joint was featured with shallower dimples and cleavage steps.
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  Effect of process parameters on interfacial microstructure and mechanical properties of Al/Cu friction stir lap welding joints

  王晨霁, 刘松, 朱浩, 曹志龙, 董少康

  中国焊接. 2022, 31(4): 48-58. https://doi.org/10.12073/j.cw.20220922001

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  In this study, friction stir lap welding (FSLW) was performed for the welding test of 6061 aluminium alloy and T2 pure copper. The effect of process parameters containing rotation rate and travel speed on interfacial microstructure evolution and mechanical properties of Al/Cu dissimilar joints were explored. The experiments were carried out under the rotation rates of 600, 900 and 1200 r/min and with the travel speeds of 30, 70 and 100 mm/min. The characteristic of interface transition zones (ITZs) and the species of intermetallic compounds (IMCs) were investigated. The Al/Cu interface showed a layered structure composed of Al-Cu IMCs, which will affect the mechanical property. The layer consisting of Al₂Cu was formed at lower heat input, and as heat input increased the Al₄Cu₉ phase started to form. Excessive heat input will increase the thickness of the interface and raise the brittleness of the joints. The thickness of the IMCs layers changed from 0.89 μm to 3.96 μm as the heat input increased. The maximum value of tensile shear loading of 4.65 kN was obtained at the rotation rate of 900 r/min and travel speed of 100 mm/min with the interface thickness of 2.89 μm. The fracture mode of the joints was a mix of ductile and brittle fracture.
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  Thermal simulation of single thermal cycle for high strength steel pipe

  夏培培, 杨柳青, 吴林恩, 谷云龙, 徐晓林, 由宗彬

  中国焊接. 2022, 31(4): 59-66. https://doi.org/10.12073/j.cw.20220909001

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  Single thermal cycle simulation tests were carried out for X80 high strength steel pipes from three steel mills by a Gleeble 3500HS thermal simulation test machine, and coincidence degree of the thermal simulation curve with the set curve under heat inputs of 6–30 kJ/cm was observed; The relationship between different heat inputs and microstructure, impact toughness and hardness of steel pipe CGHAZ (coarse grain heat affected zone) was studied by metallographic examination, impact test and hardness test. The results show that with the increase of heat input, original austenite grain size increases gradually, the lath bainite ratio decreases and the granular bainite ratio increases. The impact toughness of C steel pipe is lower than those of A and B steel pipe, and the impact toughness of CGHAZ from the three steel pipes show different trends: for A steel pipe CGHAZ, impact toughness increases first and then decreases, with the highest value of 270–320 J under 20–25 kJ/cm; for B steel pipe CGHAZ, impact toughness decreases slightly; for C steel pipe CGHAZ, impact toughness increases, with the highest value of 260–300 J under 25 kJ/cm. As the heat input increases, the hardness of three X80 steel pipes CGHAZ shows a decreasing trhighend, and C steel pipe has the largest decreasing range.