2019年, 第28卷, 第3期　
刊出日期：2019-09-28

  

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  Prediction of tensile strength of friction stir welded 6061 Al plates

  中国焊接. 2019, 28(3): 1-6. https://doi.org/10.12073/j.cw.20190617001

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  The present paper investigates the prediction of tensile strength after friction stir welding (FSW) using artificial neural network (ANN) in the MATLAB program. The experimental results are used to develop the mathematical model. The combined influence of welding speed, rotation speed, and axial force on the tensile strength of 6061 Al plates is simulated. Results of the tensile test are used to train and test the ANN model. A multi-layer solution is developed using the ANN model to predict tensile strength. Back propagation (BP) method is initially trained using 80% of the experimental data, then, testing is performed with the rest of the data. Results indicate that predicted values are close to the corresponding measured values.
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  Design and test of a protective structure for the double vertical explosive welding of large titanium/steel plate

  史长根, 孙泽瑞, 房中行, 赵林升, 史和生

  中国焊接. 2019, 28(3): 7-14. https://doi.org/10.12073/j.cw.20190223001

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  A comprehensive protective structure with rigidity and flexibility was put forward and designed in view of the quality and safety problems for the double vertical explosive welding of large titanium/steel cladding plate. The movement speed and displacement of the protective structure was calculated by establishing its physics model. The dynamics and stabilization properties were analyzed, and the protective structure parameters were optimized and devised. The comprehensive protective structure, which is composed of rigidity unit and flexibility wall, can bear the impact of detonation wave and the high-speed movement of the cladding plate. There are no damage and deformation in the protective structure and the cladding plate. The protective structure can be used many times. The bonding rate of the Ti/steel plate obtained was nearly 100%, and there is no deformation, surface cracks, and big wave and micro-defects. Therefore, the protective problems of the double vertical explosive welding can be solved effectively by the protective structure.
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  Study on microstructure and properties of 590 MPa class welding wire deposited metal on hull

  肖红军, 田志凌, 崔冰

  中国焊接. 2019, 28(3): 15-24. https://doi.org/10.12073/j.cw.20190505001

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  By means of metallographic microscope (OM), scanning electron microscope (SEM), back scattering electron diffraction (EBSD) and transmission electron microscope (TEM), the effect of Cu on microstructure transformation and mechanical properties of deposited metal of 590MPa class steel welding wire was studied. The results show that the microstructure of deposited metal is composed of acicular ferrite, lamellar bainite, granular bainite and residual austenite. With the increase of Cu content, the phase transition temperature of the deposited metal decreases, making the phase transition region of ferrite and pearlite shift to the right, expanding the phase transition region of bainite and shrinking the phase transition region of ferrite and pearlite. The microstructure of deposited metal changed, the content of M-A elements increased but the size decreased, and the ferrite-bainite biphasic microstructure was matched. The reduction of M-A component content in strips and blocks and the reduction of effective grain size will reduce the nucleation probability of microcracks, increase crack growth resistance, and improve the impact toughness of the deposited metal.
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  Cold cracking susceptibility of X100 pipeline steel

  严春妍, 姜心怡, 元媛, 纪秀林, 张可召

  中国焊接. 2019, 28(3): 25-33. https://doi.org/10.12073/j.cw.20190607001

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  The y-groove Tekken test has been performed to evaluate the cold cracking susceptibility of X100 pipeline steel. The impact of preheating state on the microstructure, distribution of hardness, and the stress-strain state in the welded joint was analyzed. The results show that X100 pipeline steel reveals a low susceptibility to cold cracking with cracking ratios below 20%. It is found that elevated preheating temperature leads to longer cooling time in the welded specimen and ultimately results in a lower cold cracking susceptibility. Preheating temperatures of up to 100 ℃ are favorable in decreasing the cold cracking susceptibility due to a relative fine microstructure and low M-A constituent amount in coarse grained heat affected zone, a low hardenability, and low-level residual stress and strain. However, excessive preheating temperatures of 150 ℃ and 200 ℃ lead to grain coarsening, higher M-A constituent amount, higher residual stress level and increasing strain level in the Tekken specimens. Preheating temperature above 150 ℃ is not favorable for decreasing the cold cracking susceptibility of X100 steel.
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  Filling technique for keyhole of friction stir spot welding based on the principles of resistance spot welding

  邓黎鹏, 柯黎明, 刘金合

  中国焊接. 2019, 28(3): 34-41. https://doi.org/10.12073/j.cw.20190626001

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  Keyhole at the end of a weld prepared by friction stir welding (FSW) is one of the major issues that impede the application of FSW. To address this issue, a keyhole filling technique was proposed in this paper, which is based on the principles of resistance spot welding (RSW). A three-phase secondary rectifier resistance spot welder was applied as the experimental instrument for filling the keyhole in the center of friction stir spot weld (FSSW). The test sheet is a 2024-T4 aluminium alloy with a thickness of 6.0mm. The experiments results show that the filled joint strength is improved by 26.12% since the area is increased for the plug in the keyhole. And there are two kinds of dimples in the tensile fracture—equiaxial dimples and long dimples. The filled joint involves the fusion welding zone (FWZ), pressure welding zone (PWZ), melted plug zone (MPZ), and plastic deformation zone (PDZ). The FWZ and the PWZ is the melting bond and diffusion bond between the plug and keyhole, respectively. The MPZ is the center part and the PDZ is upper or lower part of the plug.
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  Numerical analysis of influence of expansion joints on welding residual stress of an EGR cooler

  李军, 温树文, 张文锋, 张书彦

  中国焊接. 2019, 28(3): 42-47. https://doi.org/10.12073/j.cw.20190508001

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  The influence of expansion joints on the welding residual stress at the tube-plate junction of an exhaust gas recirculation (EGR) cooler was studied by numerical simulation method. The simulation results show that the expansion joints set on the housing of the EGR cooler mainly for the sake of protecting the tube-plate joints from bearing additional heating stress can also reduce the welding residual tensile stress. The expansion joints set on the EGR cooler can mitigate the tensile force acting on the edges of the main plates through its elastic extension, and thus reduce the magnitude of welding residual tensile stress at the tube-plate junction.
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  Effect of the heat input on microstructure and properties of submerged arc welded joint of 08Cr19MnNi3Cu2N stainless steel

  戴红, 夏希玮, 方乃文, 马青军, 常晶舒

  中国焊接. 2019, 28(3): 48-53. https://doi.org/10.12073/j.cw.20190509001

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  SAW308L submerged arc welding wire and SJ601A submerged arc welding flux were selected to weld the 12 mm 08Cr19MnNi3Cu2N low nickel and high nitrogen austenitic stainless steel plates with three different welding heat input, and microstructure, tensile properties, microhardness and corrosion properties of the welded joints were studied. The results show that no defects are found in the three groups of welded joints, and the welded joints have better performance.The tensile strength of 08Cr19MnNi3Cu2N stainless steel welded joints with different heat input is slightly lower than that of the base metal,and fracture occurs in the weld zone, and the hardness of the weld zone is lower than that of the base metal. The weld microstructure of stainless steel welded joints with different heat input is composed of austenite + δ ferrite, and ferrite is uniformly distributed in austenite. With the increase of the welding heat input, the ferrite content in the weld zone decrease gradually, the grain size in the thermal affected zone increase gradually, and the impact toughness reduce.
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  Microstructure and wear resistance of Fe-based and Co-based coating of AISI H13

  员霄, 王井, 朱青海, 陈志凯, 何冰

  中国焊接. 2019, 28(3): 54-60. https://doi.org/10.12073/j.cw.20190623001

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  Fe-based and Co-based cladding layers were prepared on the surface of AISI H13 hot die steel by laser cladding technology. The microstructure, hardness and abrasion resistance of the two cladding layers were studied by means of optical microscope, scanning electron microscope, rockwell hardness tester, and high temperature friction and wear tester. Also, the red hardness of the cladding layers was measured, after holding the layers at 600 ℃ for 1 hour by muffle furnace and repeated 4 times. The rockwell hardness values of the substrate, the Fe-based and the Co-based alloy coating measured were HRC 47, HRC 52 and HRC 48, respectively. The red hardness values of the substrate and the Fe-based cladding layer were decreased, while that of the Co-based cladding layer was increased. The Co-based cladding layer has the minimal wear loss weight and friction coefficient among them. The wear mechanisms of the substrate, the Fe-based layer and the Co-based layer attribute mainly to abrasive wear, adhesion wear, and both of them, respectively.
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  Thermal cycle and its influence on the microstructure of laser welded butt joint of 8 mm thick Ti-6Al-4V alloy

  田德勇, 颜廷艳, 高奇玉, 王飞云, 占小红

  中国焊接. 2019, 28(3): 61-66. https://doi.org/10.12073/j.cw.20190503001

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  Ti-6Al-4V alloy is extensively used in the manufacture of components in aviation. In the current study, the laser welding process is adopted to joint the Ti-6Al-4V alloy plate which has the thick of 8 mm. A three-dimensional finite element model is established to simulate the temperature distribution of laser welding process. The thermal cycle curves are produced on the strength of the simulation results. Meanwhile, the microstructure characteristics of the welded joint are investigated combined with simulation results. The results show that weld zone, heat affected zone and based metal experience similar thermal cycles process and the cooling rate has an important influence on the formation of microstructure. Moreover, the simulation results are well matched with experiment results.