Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded aust...Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.展开更多
Penetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars,while their fatigue performances and the difference between them are not completely u...Penetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars,while their fatigue performances and the difference between them are not completely understood.In this study,the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated.The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance,and their hardness was lower than that of the plates.The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes,whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes.The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture,respectively,and the primary cracks were initiated at welding fusion lines on the lap surface.There were long plastic ribs on the penetration plate fracture,but not on the non-penetration plate fracture.The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa,respectively,which can be used as reference stress for the fatigue design of the laser welded structures.The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.展开更多
A study was performed with the objectives of understanding lap welding phenomena of Zn-coated steels with a Nd:YAG laser as well as obtaining a fundamental knowledge of monitoring signals for the formation judgment of...A study was performed with the objectives of understanding lap welding phenomena of Zn-coated steels with a Nd:YAG laser as well as obtaining a fundamental knowledge of monitoring signals for the formation judgment of sound or bad weld beads. The behavior of a molten pool and a reflected beam was simultaneously observed through a high-speed video together with the monitoring of reflected beam intensity.The effect of a gap between sheets on porosity formation and bead appearances was confirmed,and characteristic monitoring signals were obtained according to the gaps.In the case of no gap,spatters were frequently generated,and a reflected beam was fluctuated intensively at low frequencies.On the other hand,in welding sheets with a wide gap,lap welds were not produced and the high frequency signals of a reflected beam were detected.Moreover,sound welds were produced in the sheets with a proper gap,and a moderate reflected beam was monitored.From these results,it was found that monitoring of a reflected beam was beneficial to the judgment of sound,under-filled or incomplete lap welds.展开更多
It is difficult to gain effective Ti-Al fusion welding joints due to their differences in thermal properties and the appearance of brittle Ti-Al Intermetallic Compounds(IMCs).The experiments of laser fusion welding fo...It is difficult to gain effective Ti-Al fusion welding joints due to their differences in thermal properties and the appearance of brittle Ti-Al Intermetallic Compounds(IMCs).The experiments of laser fusion welding for TC4 titanium and 7075 aluminum alloy were carried out,temperature field and ductility/brittleness,as well as chemical potential of elements,were calculated,and the effect of adding Nb foil on mechanical properties of the weld was also investigated.The results suggested that Nb atoms tend to diffuse toward Al side,which is conducive to the participation of Nb in the metallurgical reaction and contributes to forming the Ti-Nb-Al IMC layer at the interface.As the thickness of Nb foil increases,the tensile-shear force of joint climbs first but then declines,and reaches the highest value of 1663 N with 0.10 mm-thickness Nb foil,representing 58.38%enhancement compared with the non-added one.Adding Nb foil slows down the heat transfer as a blocker,and thus both the melting amount of Al and the mixing area of Ti and Al decrease.In addition,Nb alloying reduces the brittleness of the Ti-Al compound.Hence,the joint properties of titanium/aluminum are improved with the addition of Nb foil.展开更多
This paper presents an experimental design approach to process parameter optimization for the laser lap welding of SUS301L austenitic stainless steels using Nd:YAG laser in order to reduce the welding deformations of ...This paper presents an experimental design approach to process parameter optimization for the laser lap welding of SUS301L austenitic stainless steels using Nd:YAG laser in order to reduce the welding deformations of the back of the welding seams while ensuring mechanical properties of welding joints.To determine the optimal laser-welding parameters,a set of mathematical models were developed relating welding parameters to each of the weld characteristics.These were validated both statistically and experimentally.In order to reduce experimental error and the number of specimens,the part of orthogonal experiments were used in this study.The quality criteria set for the weld to determine optimal parameters were the maximization of weld width and the minimization of weld depth.Laser power,welding speed,the laser irradiation angle,the focused distance and shield gas of 3.5kW,7.0m/min,70°,0mm and N2 with the flow of 30L/min,respectively,with a fiber diameter of 600μm were identified as the optimal set of process parameters.展开更多
文摘Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.
基金Supported by Scientific Research and Development Projects of China Railway Corporation(Grant No.2017J011-C).
文摘Penetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars,while their fatigue performances and the difference between them are not completely understood.In this study,the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated.The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance,and their hardness was lower than that of the plates.The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes,whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes.The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture,respectively,and the primary cracks were initiated at welding fusion lines on the lap surface.There were long plastic ribs on the penetration plate fracture,but not on the non-penetration plate fracture.The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa,respectively,which can be used as reference stress for the fatigue design of the laser welded structures.The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.
文摘A study was performed with the objectives of understanding lap welding phenomena of Zn-coated steels with a Nd:YAG laser as well as obtaining a fundamental knowledge of monitoring signals for the formation judgment of sound or bad weld beads. The behavior of a molten pool and a reflected beam was simultaneously observed through a high-speed video together with the monitoring of reflected beam intensity.The effect of a gap between sheets on porosity formation and bead appearances was confirmed,and characteristic monitoring signals were obtained according to the gaps.In the case of no gap,spatters were frequently generated,and a reflected beam was fluctuated intensively at low frequencies.On the other hand,in welding sheets with a wide gap,lap welds were not produced and the high frequency signals of a reflected beam were detected.Moreover,sound welds were produced in the sheets with a proper gap,and a moderate reflected beam was monitored.From these results,it was found that monitoring of a reflected beam was beneficial to the judgment of sound,under-filled or incomplete lap welds.
基金supported by the National Natural Science Foundation of China(No.52174360)the Natural Science Foundation of Hunan Province of China(No.2020JJ4207).
文摘It is difficult to gain effective Ti-Al fusion welding joints due to their differences in thermal properties and the appearance of brittle Ti-Al Intermetallic Compounds(IMCs).The experiments of laser fusion welding for TC4 titanium and 7075 aluminum alloy were carried out,temperature field and ductility/brittleness,as well as chemical potential of elements,were calculated,and the effect of adding Nb foil on mechanical properties of the weld was also investigated.The results suggested that Nb atoms tend to diffuse toward Al side,which is conducive to the participation of Nb in the metallurgical reaction and contributes to forming the Ti-Nb-Al IMC layer at the interface.As the thickness of Nb foil increases,the tensile-shear force of joint climbs first but then declines,and reaches the highest value of 1663 N with 0.10 mm-thickness Nb foil,representing 58.38%enhancement compared with the non-added one.Adding Nb foil slows down the heat transfer as a blocker,and thus both the melting amount of Al and the mixing area of Ti and Al decrease.In addition,Nb alloying reduces the brittleness of the Ti-Al compound.Hence,the joint properties of titanium/aluminum are improved with the addition of Nb foil.
基金Foundation of the Education Ministry for Returned Chinese Scholars,China for financially supporting this research under Contract No.20080003
文摘This paper presents an experimental design approach to process parameter optimization for the laser lap welding of SUS301L austenitic stainless steels using Nd:YAG laser in order to reduce the welding deformations of the back of the welding seams while ensuring mechanical properties of welding joints.To determine the optimal laser-welding parameters,a set of mathematical models were developed relating welding parameters to each of the weld characteristics.These were validated both statistically and experimentally.In order to reduce experimental error and the number of specimens,the part of orthogonal experiments were used in this study.The quality criteria set for the weld to determine optimal parameters were the maximization of weld width and the minimization of weld depth.Laser power,welding speed,the laser irradiation angle,the focused distance and shield gas of 3.5kW,7.0m/min,70°,0mm and N2 with the flow of 30L/min,respectively,with a fiber diameter of 600μm were identified as the optimal set of process parameters.
基金Project(51675104)supported by the National Natural Science Foundation of ChinaProject(202002020068)supported by the Guangzhou Municipal Special Fund Project for Scientific and Technological Innovation and Development,ChinaProject(2017KCXTD010)supported by the Innovation Team Project,Department of Education of Guangdong Province,China。
