2015 Vol. 36 No. 11
2015, 36(11): 1-4.
Abstract：
The AgCuZnSn alloy is Cd-free and has high strength, makes it has a board application prospect in green manufacture, while the decrease in forming property induced which element limits its application. To overcome that weak point, a method to in-situ synthesis high strength Ag brazing alloy by using AgCuZn/ZnCuAgSn/AgCuZn composite sheet during the brazing process is proposed in the paper. The outer layer of the composite sheet is AgCuZn alloy, and the inner is ZnCuAgSn alloy. The melting points of the two alloys are close and melting point of the inner alloy is lower than the synthesized alloy, and the process ability of the composite sheet is better than the AgCuZnSn alloy with the same composition. Brazing of stainless steel using the composite brazing sheet was studied. It was found that the two alloys melt at the same time, and fused comprehensively after holding for a short time, forming high strength brazing seam. The strength of the obtained brazed joint is much higher than the joints brazed using common AgCuZn alloy.
The AgCuZnSn alloy is Cd-free and has high strength, makes it has a board application prospect in green manufacture, while the decrease in forming property induced which element limits its application. To overcome that weak point, a method to in-situ synthesis high strength Ag brazing alloy by using AgCuZn/ZnCuAgSn/AgCuZn composite sheet during the brazing process is proposed in the paper. The outer layer of the composite sheet is AgCuZn alloy, and the inner is ZnCuAgSn alloy. The melting points of the two alloys are close and melting point of the inner alloy is lower than the synthesized alloy, and the process ability of the composite sheet is better than the AgCuZnSn alloy with the same composition. Brazing of stainless steel using the composite brazing sheet was studied. It was found that the two alloys melt at the same time, and fused comprehensively after holding for a short time, forming high strength brazing seam. The strength of the obtained brazed joint is much higher than the joints brazed using common AgCuZn alloy.
2015, 36(11): 5-8.
Abstract：
Since to the feature of the magnetic control seam tracking signal is nonlinearly and not smooth, A signal extraction and analytical method of the system based on Hilbert Huang transform and Cohen nuclear magnetic control arc seam tracking sensor is propesed. The magnetic control to track the signal motivated by cycle is decomposed into several intrinsic mode functions from high frequency to low frequency component by using the empirical mode decomposition. On the basis of the Hilbert marginal spectrum of each component, using Cohen nuclear distribution of time-frequency transform to each component can effectively restrain cross terms and extract the real-time signal dynamic law reflecting magnetic control seam tracking. The test result manifest this method is contribute to reveal the time-frequency of interference source and frequency spectrum.
Since to the feature of the magnetic control seam tracking signal is nonlinearly and not smooth, A signal extraction and analytical method of the system based on Hilbert Huang transform and Cohen nuclear magnetic control arc seam tracking sensor is propesed. The magnetic control to track the signal motivated by cycle is decomposed into several intrinsic mode functions from high frequency to low frequency component by using the empirical mode decomposition. On the basis of the Hilbert marginal spectrum of each component, using Cohen nuclear distribution of time-frequency transform to each component can effectively restrain cross terms and extract the real-time signal dynamic law reflecting magnetic control seam tracking. The test result manifest this method is contribute to reveal the time-frequency of interference source and frequency spectrum.
2015, 36(11): 9-12.
Abstract：
This research is based on the low energy green welding technology and theory. The interaction mechanism between the low power laser and welding arc is expounded. The innovative ideas are proposed in low power pulse laser induced arc hybrid welding process. The energy-saving hybrid welding technology system is established. The results of the study show that the welding arc energy density is increased by the low-power laser induced effect, which is used to achieve the favorite hybrid between laser and arc heat sources. The low-power laser induced arc hybrid welding technology is used to join Mg alloy, Ti alloy and Steel successfully. The development of the low-power laser induced arc hybrid welding technology provides obviously effect on the low energy green welding manufacture.
This research is based on the low energy green welding technology and theory. The interaction mechanism between the low power laser and welding arc is expounded. The innovative ideas are proposed in low power pulse laser induced arc hybrid welding process. The energy-saving hybrid welding technology system is established. The results of the study show that the welding arc energy density is increased by the low-power laser induced effect, which is used to achieve the favorite hybrid between laser and arc heat sources. The low-power laser induced arc hybrid welding technology is used to join Mg alloy, Ti alloy and Steel successfully. The development of the low-power laser induced arc hybrid welding technology provides obviously effect on the low energy green welding manufacture.
2015, 36(11): 13-16.
Abstract：
Self-shielded flux cored wire for 9%Ni steel with Fe-Ni-Mn-Si alloy system was developed. This wire was welded by FCAW with no shielding gas. QLT heat treatment was carried out after welding. Mechanical properties, microstructure, and fracture morphology of welded joint were studied by tensile testing, low temperature impact testing,metallurgical analysis, and SEM. The results show that, The tensile strength of welded joint is 709 MPa,the yield strength is 580 MPa, elongation ratio is 26%, section shrinkage rate is 47%. The mechanical properties meet the requirement of the use of 9%Ni steel. The microstructure of the weld metal consists of fine grain ferrite and acicular ferrite. QLT heat treatment increased low temperature impact energy of weld metal from 48 J/cm2 to 100 J/cm2. It can significantly improve the low temperature toughness of the weld.
Self-shielded flux cored wire for 9%Ni steel with Fe-Ni-Mn-Si alloy system was developed. This wire was welded by FCAW with no shielding gas. QLT heat treatment was carried out after welding. Mechanical properties, microstructure, and fracture morphology of welded joint were studied by tensile testing, low temperature impact testing,metallurgical analysis, and SEM. The results show that, The tensile strength of welded joint is 709 MPa,the yield strength is 580 MPa, elongation ratio is 26%, section shrinkage rate is 47%. The mechanical properties meet the requirement of the use of 9%Ni steel. The microstructure of the weld metal consists of fine grain ferrite and acicular ferrite. QLT heat treatment increased low temperature impact energy of weld metal from 48 J/cm2 to 100 J/cm2. It can significantly improve the low temperature toughness of the weld.
2015, 36(11): 17-20.
Abstract：
The 3D finite element analysis models of 3D-TSV interconnect structure were developed. By using ANSYS, the finite element analysis of the stress distribution in the model was performed under the condition of thermal-structure coupling. The TSV height and the TSV diameter, the micro-bump height and the micro-bump diameter were selected as four key configuration parameters, combinations were designed. By using an L16(45) orthogonal array the 3D-TSV which have 16 different configuration parameters' levels. The maximum stress values within 3D-TSV were obtained. Variance analysis was performed based on the values of stress. The results show that the TSV height has highly significant impact on the stress of 3D-TSV under random vibration with 99% confidence. The TSV height, the TSV diameter, the micro-bump diameter and the micro-bump height affect the stress of 3D-TSV in a descending order. The single-factor analysis of variance shows that the stress and strain in TSV interconnect structure increase with the height of TSV.
The 3D finite element analysis models of 3D-TSV interconnect structure were developed. By using ANSYS, the finite element analysis of the stress distribution in the model was performed under the condition of thermal-structure coupling. The TSV height and the TSV diameter, the micro-bump height and the micro-bump diameter were selected as four key configuration parameters, combinations were designed. By using an L16(45) orthogonal array the 3D-TSV which have 16 different configuration parameters' levels. The maximum stress values within 3D-TSV were obtained. Variance analysis was performed based on the values of stress. The results show that the TSV height has highly significant impact on the stress of 3D-TSV under random vibration with 99% confidence. The TSV height, the TSV diameter, the micro-bump diameter and the micro-bump height affect the stress of 3D-TSV in a descending order. The single-factor analysis of variance shows that the stress and strain in TSV interconnect structure increase with the height of TSV.
2015, 36(11): 21-24.
Abstract：
Random vibration responses of QFP with different structure parameters were analyzed based on the ABAQUS software. The stress distributions of whole packaging and solder joints were obtained. The influence regularities of different lead widths, lead distances and lead heights on the stress field of QFP have been studied. The results indicate that, under the random vibration loading, the solder joints are weak components of QFP. The maximum stress focuses on the sharp corner of exterior part of the solder joints. Stress concentration areas locate at that position and the junction of lead with solder joint, which will be the most likely failure regions. The maximum stress of QFP is in direct proportion to the distance and height of lead and in inverse proportion to the width of lead.
Random vibration responses of QFP with different structure parameters were analyzed based on the ABAQUS software. The stress distributions of whole packaging and solder joints were obtained. The influence regularities of different lead widths, lead distances and lead heights on the stress field of QFP have been studied. The results indicate that, under the random vibration loading, the solder joints are weak components of QFP. The maximum stress focuses on the sharp corner of exterior part of the solder joints. Stress concentration areas locate at that position and the junction of lead with solder joint, which will be the most likely failure regions. The maximum stress of QFP is in direct proportion to the distance and height of lead and in inverse proportion to the width of lead.
2015, 36(11): 25-28.
Abstract：
To solve the quest of realizing synchronization, alternation and random phase control between the master and slave output in the twin-wire pulsed MIG welding, the 32-bit STM32F103ZET6 is adopted in the STM32 based power supply system for integrative twin-wire pulsed MIG welding. Synchronization, alternation and random phase control between two output is realized by single STM32F103ZET6 chip, whose integrated pulse width modulation (PWM) module produces PWM signal for phase-shift full-bridge soft-switching control, so that PWM control for the master and slave inverter is fully obtained by software, with high frequency invert and low frequency wave-form modulation achieved. The results show that the proposed power supply system meets the requirement of the design, as stable and high-speed welding process with little splash is acquired and the weld seam formation is decent.
To solve the quest of realizing synchronization, alternation and random phase control between the master and slave output in the twin-wire pulsed MIG welding, the 32-bit STM32F103ZET6 is adopted in the STM32 based power supply system for integrative twin-wire pulsed MIG welding. Synchronization, alternation and random phase control between two output is realized by single STM32F103ZET6 chip, whose integrated pulse width modulation (PWM) module produces PWM signal for phase-shift full-bridge soft-switching control, so that PWM control for the master and slave inverter is fully obtained by software, with high frequency invert and low frequency wave-form modulation achieved. The results show that the proposed power supply system meets the requirement of the design, as stable and high-speed welding process with little splash is acquired and the weld seam formation is decent.
2015, 36(11): 29-32.
Abstract：
Rotating arc GMAW welding method was used to weld low carbon steel. The effect of welding parameters including rotating frequency and welding speed were studied. The results show that welding spatter increases as the growth of the rotational frequency and the weld appearance is poor. When the rotating frequency is more than 70 r/min, the spatter significantly increased, welding process is unstable and the weld has a bad formation. The welding speed has no effect on spatter. The weld reinforcement increases at first, then stay a certain value as the rotating frequency increass, but decreases when welding speed increases. Rotating frequency and welding speed have little effect on weld width. Sectional area of the weld decreases with the increase in welding speed and rotation frequency has no contribution. Weld scales pattern spacing is inversely proportional to the rotating frequency, and proportional to the welding speed.
Rotating arc GMAW welding method was used to weld low carbon steel. The effect of welding parameters including rotating frequency and welding speed were studied. The results show that welding spatter increases as the growth of the rotational frequency and the weld appearance is poor. When the rotating frequency is more than 70 r/min, the spatter significantly increased, welding process is unstable and the weld has a bad formation. The welding speed has no effect on spatter. The weld reinforcement increases at first, then stay a certain value as the rotating frequency increass, but decreases when welding speed increases. Rotating frequency and welding speed have little effect on weld width. Sectional area of the weld decreases with the increase in welding speed and rotation frequency has no contribution. Weld scales pattern spacing is inversely proportional to the rotating frequency, and proportional to the welding speed.
2015, 36(11): 33-36.
Abstract：
In ultrasonic TOFD (time of flight diffraction) collected waves, the lateral wave brings about difficulty in identification of near surface defect signal. To solve this problem, a clutter suppression method using an adaptive filter is presented. Through iterative the parameters, the filter can adjust the reference signal to meet the changes of the clutter wave to be suppressed. Then the clutter wave can be removed and the near surface defect signal can be separated. The principle of clutter suppression method based on adaptive technology is described. The proposed method is studied by using computer simulation technique. Artificial defect collected waves are clutter suppression processed. The results show that the proposed method can effectively suppress clutter and extract near surface defect signal.
In ultrasonic TOFD (time of flight diffraction) collected waves, the lateral wave brings about difficulty in identification of near surface defect signal. To solve this problem, a clutter suppression method using an adaptive filter is presented. Through iterative the parameters, the filter can adjust the reference signal to meet the changes of the clutter wave to be suppressed. Then the clutter wave can be removed and the near surface defect signal can be separated. The principle of clutter suppression method based on adaptive technology is described. The proposed method is studied by using computer simulation technique. Artificial defect collected waves are clutter suppression processed. The results show that the proposed method can effectively suppress clutter and extract near surface defect signal.
Abstract：
Anodic bonding technology is a common method in MEMS packaging technology. Currently only glass and metal, the glass and semiconductor materials bonding can by realized. Test using the PEO as matrix, compound with a small amount of nano inorganic filler, the preparation of a new type of solid composite polymer electrolyte as a new anodic bonding materials, by means of DSC and XRD analysis means to study the interaction of PEO and inorganic filler and conductive mechanism, and then discusses the polymer solid electrolyte as a new type of packaging materials in the feasibility in application of anodic bonding,The results show that the addition of PEO can effectively inhibit the crystallization of PEO, and the bonding quality is good.
Anodic bonding technology is a common method in MEMS packaging technology. Currently only glass and metal, the glass and semiconductor materials bonding can by realized. Test using the PEO as matrix, compound with a small amount of nano inorganic filler, the preparation of a new type of solid composite polymer electrolyte as a new anodic bonding materials, by means of DSC and XRD analysis means to study the interaction of PEO and inorganic filler and conductive mechanism, and then discusses the polymer solid electrolyte as a new type of packaging materials in the feasibility in application of anodic bonding,The results show that the addition of PEO can effectively inhibit the crystallization of PEO, and the bonding quality is good.
2015, 36(11): 41-44.
Abstract：
An underwater welding robot system for large-scale structure is introduced for the environment of underwater welding and the system is composed of a robot mechanism, laser vision sensor, control system and welding system. The robot mechanism is composed of a pedrailed mobile platform and a torch adjustment mechanism and which can move flexibly for meeting the requirements of underwater welding. The components of sensor are selected and the optical path is also designed for the laser vision sensor to automatic welding seam identification. The PLC control system for the welding robot is designed and the coordinated control method is also adopted to achieve seam tracking accurately. And the underwater welding test platform is also completed. The results show that the robot operates steadily, reliably and the satisfactory welding quality is also obtained.
An underwater welding robot system for large-scale structure is introduced for the environment of underwater welding and the system is composed of a robot mechanism, laser vision sensor, control system and welding system. The robot mechanism is composed of a pedrailed mobile platform and a torch adjustment mechanism and which can move flexibly for meeting the requirements of underwater welding. The components of sensor are selected and the optical path is also designed for the laser vision sensor to automatic welding seam identification. The PLC control system for the welding robot is designed and the coordinated control method is also adopted to achieve seam tracking accurately. And the underwater welding test platform is also completed. The results show that the robot operates steadily, reliably and the satisfactory welding quality is also obtained.
2015, 36(11): 45-48.
Abstract：
For laser welded I-core steel sandwich plates, in the design formulas of the stiffness the influence of joint geometric parameters are not considered commonly. Therefore the accuracy is lack in practice. The three-point bending tests were investigated for the sandwich plates with six kinds of joint geometric parameter by self-designed device together with the finite element simulations. The aim is to research the effect of joint geometric parameters on the bending stiffness and shear stiffness. The results showed that the increase of weld width can significantly improve the bending stiffness and shear stiffness. However, when the weld width is greater than 60% thickness of core plates, the increase of stiffness became slow. The influence of root gap to the stiffness can be ignored. Based on these results, the corrected and simplified stiffness formula was offered for sandwich plate stiffness design considering joint geometry parameters.
For laser welded I-core steel sandwich plates, in the design formulas of the stiffness the influence of joint geometric parameters are not considered commonly. Therefore the accuracy is lack in practice. The three-point bending tests were investigated for the sandwich plates with six kinds of joint geometric parameter by self-designed device together with the finite element simulations. The aim is to research the effect of joint geometric parameters on the bending stiffness and shear stiffness. The results showed that the increase of weld width can significantly improve the bending stiffness and shear stiffness. However, when the weld width is greater than 60% thickness of core plates, the increase of stiffness became slow. The influence of root gap to the stiffness can be ignored. Based on these results, the corrected and simplified stiffness formula was offered for sandwich plate stiffness design considering joint geometry parameters.
2015, 36(11): 49-52.
Abstract：
Stencil printing process was optimized to obtain fine pitch flip chip solder bump. In order to evaluate the printing process, bump morphology were observed and bump heights were measured. Furthermore, shear force was tested by Pull-Shear Tester to investigate the effect of pad size on shear strength for the fine pitch solder bumps. Fracture surfaces were inspected and intermetallic compounds (IMC) at the surface and in the bump were separately detected and identified. It was found that bump height with small pad size was larger than that with large pad size as well as bump uniformity. Bump shear strength decreased with reducing pad size, which appeared size effect. This phenomenon was attributed to load condition difference during shear testing and IMC variation. Scallop IMC was observed at the bump interface with large pad size and needle like was found at the interface with small pad size, which possibly led to crack stress and decrease shear strength.
Stencil printing process was optimized to obtain fine pitch flip chip solder bump. In order to evaluate the printing process, bump morphology were observed and bump heights were measured. Furthermore, shear force was tested by Pull-Shear Tester to investigate the effect of pad size on shear strength for the fine pitch solder bumps. Fracture surfaces were inspected and intermetallic compounds (IMC) at the surface and in the bump were separately detected and identified. It was found that bump height with small pad size was larger than that with large pad size as well as bump uniformity. Bump shear strength decreased with reducing pad size, which appeared size effect. This phenomenon was attributed to load condition difference during shear testing and IMC variation. Scallop IMC was observed at the bump interface with large pad size and needle like was found at the interface with small pad size, which possibly led to crack stress and decrease shear strength.
Abstract：
The effect of welding current, welding time and electrode force on warping deformation of lap joint during resistance spot welding were investigated by using two-dimensional digital image correlation technique. The results show that the deformation changes differently at different phases of resistance spot welding process. Under identical conditions, increasing with the of the welding current or welding time, the warping deformation induced with nugget formation increased. With the electrode force increasing while the other conditions were identical, the warping deformation induced by nugget formation reduced while that induced by electrode impact increased. The two-dimensional digital image correlation technique was used for the first time researching the resistant spot welding process and it will provide [HJ1.15mm]new approach for the resistance spot welding process research and the weld quality improvement, which is of great significance for the development and improvement of the resistance spot welding process.
The effect of welding current, welding time and electrode force on warping deformation of lap joint during resistance spot welding were investigated by using two-dimensional digital image correlation technique. The results show that the deformation changes differently at different phases of resistance spot welding process. Under identical conditions, increasing with the of the welding current or welding time, the warping deformation induced with nugget formation increased. With the electrode force increasing while the other conditions were identical, the warping deformation induced by nugget formation reduced while that induced by electrode impact increased. The two-dimensional digital image correlation technique was used for the first time researching the resistant spot welding process and it will provide [HJ1.15mm]new approach for the resistance spot welding process research and the weld quality improvement, which is of great significance for the development and improvement of the resistance spot welding process.
2015, 36(11): 57-60.
Abstract：
The finite element simulation of the backing welding of the high strength steel plates was built by using MSC. Marc and the effects of the reserved groove gap on backing weld root fusion was investigated based on the welding temperature field. And the results of simulation were verified and supplemented by the experiments. The results showed that, under the low alloy high strength steel required welding heat input, when groove gap size was less than 2 mm, the backing weld root appears incomplete fusion defects. When the gap increases to 2-4 mm, the backing weld has single face welding-double face forming. When the gap increased to more than 5 mm, the heat resource could not reach to the base metal of the groove sidewall and the weld root appeard incomplete fusion, and was necessary to use swing welding with high heat input for good fusion.
The finite element simulation of the backing welding of the high strength steel plates was built by using MSC. Marc and the effects of the reserved groove gap on backing weld root fusion was investigated based on the welding temperature field. And the results of simulation were verified and supplemented by the experiments. The results showed that, under the low alloy high strength steel required welding heat input, when groove gap size was less than 2 mm, the backing weld root appears incomplete fusion defects. When the gap increases to 2-4 mm, the backing weld has single face welding-double face forming. When the gap increased to more than 5 mm, the heat resource could not reach to the base metal of the groove sidewall and the weld root appeard incomplete fusion, and was necessary to use swing welding with high heat input for good fusion.
2015, 36(11): 61-64,68.
Abstract：
Based on ABAQUS software, a thermal-elastic-plastic finite element method (FEM) was developed to simulate welding temperature field, residual stresses and deformation for multi-pass joints. The residual stresses and deformation in Q345 butt-welded joint with 16 mm thickness were simulated through using the developed computational approach. Meanwhile, experiments were carried out to measure the welding residual stresses and angular distortion in the butt-welded joint. Through comparing the measured data and the simulated result, it is found that both the residual stress and deformation predicted by FEM are in good agreement with the experimental results. In addition, the results show that the angular distortion and transverse shrinkage increase with the number of weld pass. The numerical results also suggest that the region with high tensile longitudinal stress slightly decreases when the number of weld pass changes from three to five, while the peak value of longitudinal residual stress is not sensitive to the number of weld pass.
Based on ABAQUS software, a thermal-elastic-plastic finite element method (FEM) was developed to simulate welding temperature field, residual stresses and deformation for multi-pass joints. The residual stresses and deformation in Q345 butt-welded joint with 16 mm thickness were simulated through using the developed computational approach. Meanwhile, experiments were carried out to measure the welding residual stresses and angular distortion in the butt-welded joint. Through comparing the measured data and the simulated result, it is found that both the residual stress and deformation predicted by FEM are in good agreement with the experimental results. In addition, the results show that the angular distortion and transverse shrinkage increase with the number of weld pass. The numerical results also suggest that the region with high tensile longitudinal stress slightly decreases when the number of weld pass changes from three to five, while the peak value of longitudinal residual stress is not sensitive to the number of weld pass.
Abstract：
The heat affected zone (HAZ) simulation test was done on two sorts of 12Cr1MoVG specimen. One of which was ferrite and pearlite for base metal and bainite for the other, by using Gleeble Thermal-force simulation machine. Then, for studying the reheat cracking susceptibility in the two different weld structures, the tensile test was done on the two different HAZ structures at different high temperatures slowly. The result showed that when HAZ structure is ferrite and bainite,its reheat cracking sensitive temperature range is 640-760 ℃ and the most sensitive point is 690 ℃ in our study. When HAZ structure is bainite,reheat cracking tendency is obvious after 650 ℃, especially at 690 ℃.Analysis result showed that when bainite exists in HAZ,its reheat cracking susceptibility is high. However, 5% to 8% ferrite exists in HAZ can reduce the reheat cracking sensitivity.
The heat affected zone (HAZ) simulation test was done on two sorts of 12Cr1MoVG specimen. One of which was ferrite and pearlite for base metal and bainite for the other, by using Gleeble Thermal-force simulation machine. Then, for studying the reheat cracking susceptibility in the two different weld structures, the tensile test was done on the two different HAZ structures at different high temperatures slowly. The result showed that when HAZ structure is ferrite and bainite,its reheat cracking sensitive temperature range is 640-760 ℃ and the most sensitive point is 690 ℃ in our study. When HAZ structure is bainite,reheat cracking tendency is obvious after 650 ℃, especially at 690 ℃.Analysis result showed that when bainite exists in HAZ,its reheat cracking susceptibility is high. However, 5% to 8% ferrite exists in HAZ can reduce the reheat cracking sensitivity.
2015, 36(11): 69-72.
Abstract：
The effects of the addition of Si on the microstructures and properties of SAl5356 aluminum alloy wire and its tensile properties of butt-welded joints with SAl5356 as the filler were investigated. Results showed that, when the content of Si ranged from 0 to 0.12%, the tensile strength of SAl5356 wire and its welded joint was improved slightly with the increase of Si content, while the plasticity was just the opposite. When the content of Si was higher than 0.12%, some coarse silicon rich phases were found in the microstructures of SAl5356 wire and its weld, and all properties, especially plasticity, dropped with the increase of Si content. In particular, when the Si content was above 0.2%, the coarse silicon rich phases were enriched at the grain boundaries, and forming fish-bone-shaped eutectic structure with α(Al) matrix, and their tensile properties dropped more obviously. The tensile strength of SAl5356 aluminum rod with Si content 0.25% was decreased 12% from its peak, while the elongation was decreased 45% from its peak. Therefore, to improve the performance of SAl5356 aluminum wire and its weld, Si content should not be more than 0.2%, and the optimum content of Si was less than 0.12%.
The effects of the addition of Si on the microstructures and properties of SAl5356 aluminum alloy wire and its tensile properties of butt-welded joints with SAl5356 as the filler were investigated. Results showed that, when the content of Si ranged from 0 to 0.12%, the tensile strength of SAl5356 wire and its welded joint was improved slightly with the increase of Si content, while the plasticity was just the opposite. When the content of Si was higher than 0.12%, some coarse silicon rich phases were found in the microstructures of SAl5356 wire and its weld, and all properties, especially plasticity, dropped with the increase of Si content. In particular, when the Si content was above 0.2%, the coarse silicon rich phases were enriched at the grain boundaries, and forming fish-bone-shaped eutectic structure with α(Al) matrix, and their tensile properties dropped more obviously. The tensile strength of SAl5356 aluminum rod with Si content 0.25% was decreased 12% from its peak, while the elongation was decreased 45% from its peak. Therefore, to improve the performance of SAl5356 aluminum wire and its weld, Si content should not be more than 0.2%, and the optimum content of Si was less than 0.12%.
Abstract：
Dissimilar barrier butt joints of SiC particles reinforced aluminum matrix composites with a volume fraction of 55% to 2024 aluminum alloy were fabricated by friction stir welding. Investigation of microstructure and mechanical properties of the joint was conducted. Results show that, a large amount of small SiC particles, with a strip-shaped distribution, was found in the advancing side in SAZ. Microstructure features of the weld in direction of weld thickness changed a lot in WNZ1, which at the lower side was the interval distribution of large SiC particles riched bands and small SiC particles riched bands. Grain size of the upper side was larger than that of the lower side in WNZ2, while grains surrounded by SiC particles were prone to grow larger. Bonding level of the material was different in different locations in IZ, which was affected also by debris fallen from the welding tool. A higher tensile strength was obtained in rotational speed of 750 r/min, 83.1% that of the composite base material. Fracture mode of the joints was detected to be the the matrices fracture and matrices segregation to SiC particles.
Dissimilar barrier butt joints of SiC particles reinforced aluminum matrix composites with a volume fraction of 55% to 2024 aluminum alloy were fabricated by friction stir welding. Investigation of microstructure and mechanical properties of the joint was conducted. Results show that, a large amount of small SiC particles, with a strip-shaped distribution, was found in the advancing side in SAZ. Microstructure features of the weld in direction of weld thickness changed a lot in WNZ1, which at the lower side was the interval distribution of large SiC particles riched bands and small SiC particles riched bands. Grain size of the upper side was larger than that of the lower side in WNZ2, while grains surrounded by SiC particles were prone to grow larger. Bonding level of the material was different in different locations in IZ, which was affected also by debris fallen from the welding tool. A higher tensile strength was obtained in rotational speed of 750 r/min, 83.1% that of the composite base material. Fracture mode of the joints was detected to be the the matrices fracture and matrices segregation to SiC particles.
2015, 36(11): 77-80.
Abstract：
By means of welding power system circuit model, thinking of the enthalpy changes on the wire tip, and energy balance on the droplet, the more precise CO2 short circuit transfer dynamic simulation model is put forward. Through this model, it explores changing trend of current waveform, and makes a comparison of characteristic parameters (average current, peak current, valley current, short circuit frequency, short circuit time and arcing time) between the practical measurement and the simulation under matching and mismatching welding parameters. And the related deviations of the characteristic parameters are analyzed. The results indicate that the model is basically consistented with practice. At last, this research will contribute to further development of simulation in short circuit transfer process.
By means of welding power system circuit model, thinking of the enthalpy changes on the wire tip, and energy balance on the droplet, the more precise CO2 short circuit transfer dynamic simulation model is put forward. Through this model, it explores changing trend of current waveform, and makes a comparison of characteristic parameters (average current, peak current, valley current, short circuit frequency, short circuit time and arcing time) between the practical measurement and the simulation under matching and mismatching welding parameters. And the related deviations of the characteristic parameters are analyzed. The results indicate that the model is basically consistented with practice. At last, this research will contribute to further development of simulation in short circuit transfer process.
Abstract：
The influence of heat treatment process on the interface thickness,interfacial bonding strength and the compounds change of Cu/Al-3.25Si cold-press joining was investigated by measuring the mechanical properties and observing microstructure. The results showed that the inter-layer thickness was firstly growing quickly with the increase of heat treatment temperature and holding time, and then it was growing slowly. The kinetics of the diffusion layer growth hasa index of 0.5-1. The interfacial shear strength is also growing quickly with the increase of heat treatment temperature and preservation time and then slowly. The intermetallic compounds is Cu9Al4, CuAl, CuAl2 from the copper side to the aluminum side under the optimum condition of 300 ℃×2 h.
The influence of heat treatment process on the interface thickness,interfacial bonding strength and the compounds change of Cu/Al-3.25Si cold-press joining was investigated by measuring the mechanical properties and observing microstructure. The results showed that the inter-layer thickness was firstly growing quickly with the increase of heat treatment temperature and holding time, and then it was growing slowly. The kinetics of the diffusion layer growth hasa index of 0.5-1. The interfacial shear strength is also growing quickly with the increase of heat treatment temperature and preservation time and then slowly. The intermetallic compounds is Cu9Al4, CuAl, CuAl2 from the copper side to the aluminum side under the optimum condition of 300 ℃×2 h.
Abstract：
An efficient X-ray radiography image analysis algorithm is developed for submerged-arc welding defects detection. The compress sensor theory is incorporated into the new algorithm, and the problem of defect detection is changed to a model recognition problem. The given X-ray image is represented by a linear combination of few model X-ray images. If a dictionary of model defect images and noise images are obtained, the coefficient vector can give important information for deciding the given image is defect or noise. Thus a sparse vector representation is sought by performing l0, l1 and l2 norm minimization. Finally, the sparse representations of the defect part and noisy part are compared in the context of a maximum likelihood ratio test which leads to the final classification. [JP2]Tested with 800 x-ray radiography images obtained from a factory production line, the proposed algorithm achieves a sensitivity 99% and specificity 98%.
An efficient X-ray radiography image analysis algorithm is developed for submerged-arc welding defects detection. The compress sensor theory is incorporated into the new algorithm, and the problem of defect detection is changed to a model recognition problem. The given X-ray image is represented by a linear combination of few model X-ray images. If a dictionary of model defect images and noise images are obtained, the coefficient vector can give important information for deciding the given image is defect or noise. Thus a sparse vector representation is sought by performing l0, l1 and l2 norm minimization. Finally, the sparse representations of the defect part and noisy part are compared in the context of a maximum likelihood ratio test which leads to the final classification. [JP2]Tested with 800 x-ray radiography images obtained from a factory production line, the proposed algorithm achieves a sensitivity 99% and specificity 98%.
2015, 36(11): 89-92.
Abstract：
The brazing process of Ti-22Al-25Nb alloy sheet was studied. The influences on the microstructure and the tensile strength of the matrix from the brazing process were studied in this paper. The strength of the brazing joints was tested. A few of short rod O phases were dissolved and lots of O phases were grown up in the matrix during the brazing process as the brazing temperature being 960 ℃. The grain size of the matrix was increased without phase transition. With heat preservation time by 15, 30 and 60 min extended gradually, the room temperature strength of the matrix was decreased from 1 257 to 1 100 MPa and the average room temperature elongation was increased from 2.9% up to 3.4%, 5.8% and 5.0%. The optimized brazing technology parameters of Ti2AlNb alloy plate is 960 ℃/30 min/furnace cooling with the higher shear strength of the brazed joints as 152 MPa.
The brazing process of Ti-22Al-25Nb alloy sheet was studied. The influences on the microstructure and the tensile strength of the matrix from the brazing process were studied in this paper. The strength of the brazing joints was tested. A few of short rod O phases were dissolved and lots of O phases were grown up in the matrix during the brazing process as the brazing temperature being 960 ℃. The grain size of the matrix was increased without phase transition. With heat preservation time by 15, 30 and 60 min extended gradually, the room temperature strength of the matrix was decreased from 1 257 to 1 100 MPa and the average room temperature elongation was increased from 2.9% up to 3.4%, 5.8% and 5.0%. The optimized brazing technology parameters of Ti2AlNb alloy plate is 960 ℃/30 min/furnace cooling with the higher shear strength of the brazed joints as 152 MPa.
Abstract：
Pre-brazed diamonds were fabricated by using diamonds and Ni-Cr composite brazing alloy, which were consisted of Ni-Cr alloy and A alloy. Brazing temperature was 1 050 ℃ and the holding time was 30 min. Abrasive composite segments consisting of the pre-brazed diamonds and metal matrix were sintered at the heating temperature of 810 ℃ for the dwell time of 4 min. The static compressive strength of the pre-brazed diamonds and the bending strength of the abrasive composite segments were measured. The interfacial microstructure of the pre-brazed diamonds and the composite segments fracture surface were characterized. Results obtained show that the chemical combination interface between diamonds and Ni-Cr composite alloy was developed when pre-brazing and the thermal damage to the diamonds was greatly reduced. The bending strength of the abrasive composite segments (10%-50%) was much higher than that of the conventional segments. In the composite segments the metallurgical bonding between the pre-brazed diamonds and metal matrix was formed and the diamonds were embedded firmly.
Pre-brazed diamonds were fabricated by using diamonds and Ni-Cr composite brazing alloy, which were consisted of Ni-Cr alloy and A alloy. Brazing temperature was 1 050 ℃ and the holding time was 30 min. Abrasive composite segments consisting of the pre-brazed diamonds and metal matrix were sintered at the heating temperature of 810 ℃ for the dwell time of 4 min. The static compressive strength of the pre-brazed diamonds and the bending strength of the abrasive composite segments were measured. The interfacial microstructure of the pre-brazed diamonds and the composite segments fracture surface were characterized. Results obtained show that the chemical combination interface between diamonds and Ni-Cr composite alloy was developed when pre-brazing and the thermal damage to the diamonds was greatly reduced. The bending strength of the abrasive composite segments (10%-50%) was much higher than that of the conventional segments. In the composite segments the metallurgical bonding between the pre-brazed diamonds and metal matrix was formed and the diamonds were embedded firmly.
Abstract：
Based on the theory of heat transfer and thermal elastoplastic finite element analysis, temperature field and stress field numerical simulations were calculated by ANSYS FEM software in variable polarity plasma arc welding of aluminum alloys. Combining heat source model which is Gaussian plus double ellipsoid was built. Temperature field and stress field were achieved accurately by loading different-size heat source models in positive and reverse polarity period alternatively. The values of residual stress were measured at different points in longitudinal and transversal directions after welding. The results show that the distribution law of residual stress, which was achieved in different directions on simulation model, was the same with theory analysis and the area of high stress was obviously smaller than that in TIG welding. The difference between actual residual stress and calculating residual stress is small. It proves that the calculation of numerical simulation is of great value on theory.
Based on the theory of heat transfer and thermal elastoplastic finite element analysis, temperature field and stress field numerical simulations were calculated by ANSYS FEM software in variable polarity plasma arc welding of aluminum alloys. Combining heat source model which is Gaussian plus double ellipsoid was built. Temperature field and stress field were achieved accurately by loading different-size heat source models in positive and reverse polarity period alternatively. The values of residual stress were measured at different points in longitudinal and transversal directions after welding. The results show that the distribution law of residual stress, which was achieved in different directions on simulation model, was the same with theory analysis and the area of high stress was obviously smaller than that in TIG welding. The difference between actual residual stress and calculating residual stress is small. It proves that the calculation of numerical simulation is of great value on theory.
Abstract：
With the same heat input, deposited metals were welded with 1 000 MPa grade solid welding wire as filler material by MAG (Metal Active Gas) and TIG welding methods, respectively. The effects of welding methods on microstructure and properties of deposited metals were studied by means of optical microscopy, transmission electron microscope (TEM) and fracture analysis etc. The results show that the deposition efficiency of MAG is significantly higher than TIG, and there is a clear "finger penetration" in MAG weld bead. The microstructure of primary weld region and reheated weld region of MAG deposited metal is significantly coarsing than TIG. TIG diposited metal has more refinement microstructure. The distribution is diversification and it includes more uniform distribution of retained austenite, which is one of the reasons for excellent low-temperature impact toughness. Besides, a large number of non-metallic inclusions in the MAG diposited metal, which is the initiation source of cleavage fracture. Therefore, non-metallic inclusion is another reason for deterioration low temperature impact toughness of MAG diposited metal. The results show that the integrated mechanical property of TIG diposited metal is much better than MAG, which is generated by the welding method for different microstructure type, morphology and characteristic of the non-metal inclusion.
With the same heat input, deposited metals were welded with 1 000 MPa grade solid welding wire as filler material by MAG (Metal Active Gas) and TIG welding methods, respectively. The effects of welding methods on microstructure and properties of deposited metals were studied by means of optical microscopy, transmission electron microscope (TEM) and fracture analysis etc. The results show that the deposition efficiency of MAG is significantly higher than TIG, and there is a clear "finger penetration" in MAG weld bead. The microstructure of primary weld region and reheated weld region of MAG deposited metal is significantly coarsing than TIG. TIG diposited metal has more refinement microstructure. The distribution is diversification and it includes more uniform distribution of retained austenite, which is one of the reasons for excellent low-temperature impact toughness. Besides, a large number of non-metallic inclusions in the MAG diposited metal, which is the initiation source of cleavage fracture. Therefore, non-metallic inclusion is another reason for deterioration low temperature impact toughness of MAG diposited metal. The results show that the integrated mechanical property of TIG diposited metal is much better than MAG, which is generated by the welding method for different microstructure type, morphology and characteristic of the non-metal inclusion.
Abstract：
A mock-up of control rod drive mechanism (CRDM) nozzle on the reactor pressure vessel (RPV) head was manufactured with J-type groove. The temperature during welding and the residual stress were measured. The segmented temperature heat source model and the thermal-mechanical coupling method were adopted to efficiently simulate the welding temperature field and residual stress field, and the simulated results were compared with the experimental ones. Based on the simulated results, the residual stress distribution characteristic in the J-weld was analyzed. The investigated results show that the proposed model and the simulation procedure can efficiently obtain the residual stress field in the J-weld between RPV head and the CRDM nozzle, the simulated results generally agree with the measured ones; the longitudinal stress in the J-weld is greater than the axial stress. The stresses on the outer and inner wall of the nozzle are non-uniform. In addition, the stresses in the weld and the nozzle at the up-hill and down-hill regions are larger than those at the side-hill region.
A mock-up of control rod drive mechanism (CRDM) nozzle on the reactor pressure vessel (RPV) head was manufactured with J-type groove. The temperature during welding and the residual stress were measured. The segmented temperature heat source model and the thermal-mechanical coupling method were adopted to efficiently simulate the welding temperature field and residual stress field, and the simulated results were compared with the experimental ones. Based on the simulated results, the residual stress distribution characteristic in the J-weld was analyzed. The investigated results show that the proposed model and the simulation procedure can efficiently obtain the residual stress field in the J-weld between RPV head and the CRDM nozzle, the simulated results generally agree with the measured ones; the longitudinal stress in the J-weld is greater than the axial stress. The stresses on the outer and inner wall of the nozzle are non-uniform. In addition, the stresses in the weld and the nozzle at the up-hill and down-hill regions are larger than those at the side-hill region.
2015, 36(11): 109-112.
Abstract：
A novel welding process with molten metal filler is invented to solve the problem of controlling the welding heat input and to suit the require of high-efficient manufacture. The design and principle of welding system and its elements are mainly introduced. Meanwhile, testing the system by overlaying weld using tin-lead alloy. The results show that the system accurately control welding heat input by output steady flow with required temperature and diameter, welding speed and air pressure. Therefore, the system could meet the requirement of welding process with molten metal filler, and the depth-to-width ratio of bead can reach 6 by using it.
A novel welding process with molten metal filler is invented to solve the problem of controlling the welding heat input and to suit the require of high-efficient manufacture. The design and principle of welding system and its elements are mainly introduced. Meanwhile, testing the system by overlaying weld using tin-lead alloy. The results show that the system accurately control welding heat input by output steady flow with required temperature and diameter, welding speed and air pressure. Therefore, the system could meet the requirement of welding process with molten metal filler, and the depth-to-width ratio of bead can reach 6 by using it.
