Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavio...Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavior using high speed photographic equipment. A stable autogenous CO2 laser welding process and greater penetration are generated at the root pass because of strong reduction of the plasma volume. According to the waveforms of welding current and arc voltage, and the interaction between the arc and the laser induced plasma, a suitable groove angle is obtained. Laser-double MIG hybrid welding process is studied and the optimum distances between the laser and two arcs are determined. By using autogenous CO2 laser welding, CO2 laser-MIG hybrid welding and laser-double MIG hybrid welding, 28 mm thick steel plates are welded with four passes. The welds produced are assessed by X-ray. No crack is found and there is only a small amount of pores. The experimental results show that the multipuss welding procedures proposed can realize the joining of thick section steels with high efficiency and good quality.展开更多
Thanks to the fantastic development of power, transportation, chemical engineering, architecture and other fields, there has been an increasing demand for new type of section steel with large sections used for constru...Thanks to the fantastic development of power, transportation, chemical engineering, architecture and other fields, there has been an increasing demand for new type of section steel with large sections used for construction frame, such as type-H, type-T, and type-C section steel. New types of section steel usually are long and with large cross section. Therefore, for the sake of the cost, steel plate welding structure is used home and abroad. During the welding process, welding distortion seems unavoidable. Presently, proper welding machinery, technique and standards are adopted to minimize the distortion. Angular distortion is corrected with oil press and angular distortion corrector, while horizontal distortions like sickle curve and arch are mainly done with flame. Flame correction is of great labor intensity and is also time and material consuming. Besides, the correction is affected by the operators’ skill and mood, which, to some extent, limits the productivity. In this paper, a new technique of section steel distortion correction with high efficiency and adaptability and yet low investment and cost will be proposed for the development of new-type section steel. The correction principles and capability calculation should be done some research on, which will be introduced. The practice done on section steel with a wing edge of 40～60 mm, proves satisfactory: compared with oil-press correction, continual mangling correction saves equipment investment by three quarters, installed capacity by three quarters and investment by three quarters and with a much higher efficiency. Particularly in the distortion correction of heavy welding structures, mangling correction stands out from the crowd. Mangling correction proves to be the best solution to the continual horizontal distortion correction of welding section steel.展开更多
缆式焊丝熔化极气体保护电弧焊(gas metal arc welding,GMAW)中存在的焊缝截面侧偏现象会导致焊接接头熔合不良,基于熔滴受力分析和最小电压理论对焊缝截面侧偏现象的变化规律进行机理分析.结果表明,电流是影响截面侧偏的关键因素,由于...缆式焊丝熔化极气体保护电弧焊(gas metal arc welding,GMAW)中存在的焊缝截面侧偏现象会导致焊接接头熔合不良,基于熔滴受力分析和最小电压理论对焊缝截面侧偏现象的变化规律进行机理分析.结果表明,电流是影响截面侧偏的关键因素,由于缆式焊丝独特的绞合结构引起电弧旋转,进而导致出现熔滴受力不均的现象,熔滴过渡方向与焊丝轴线存在夹角,在熔滴冲击力的作用下导致焊缝截面出现侧偏现象,随着电流的增加,电弧对熔滴的拘束增强,熔滴过渡方向逐渐趋于轴线,因而焊缝截面侧偏的趋势随着电流增加而减小.展开更多
Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly devel...Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction industry.This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face design.The built-up columns were filled with ordinary concrete of good strength.Finite element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression.Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box configurations.The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.展开更多
In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to ...In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.展开更多
文摘Laser multipass welding techniques for thick section steels have been developed using a new type of UV combined narrow groove. The shape and sizes at the bottom of groove are determined by analyzing the plasma behavior using high speed photographic equipment. A stable autogenous CO2 laser welding process and greater penetration are generated at the root pass because of strong reduction of the plasma volume. According to the waveforms of welding current and arc voltage, and the interaction between the arc and the laser induced plasma, a suitable groove angle is obtained. Laser-double MIG hybrid welding process is studied and the optimum distances between the laser and two arcs are determined. By using autogenous CO2 laser welding, CO2 laser-MIG hybrid welding and laser-double MIG hybrid welding, 28 mm thick steel plates are welded with four passes. The welds produced are assessed by X-ray. No crack is found and there is only a small amount of pores. The experimental results show that the multipuss welding procedures proposed can realize the joining of thick section steels with high efficiency and good quality.
文摘Thanks to the fantastic development of power, transportation, chemical engineering, architecture and other fields, there has been an increasing demand for new type of section steel with large sections used for construction frame, such as type-H, type-T, and type-C section steel. New types of section steel usually are long and with large cross section. Therefore, for the sake of the cost, steel plate welding structure is used home and abroad. During the welding process, welding distortion seems unavoidable. Presently, proper welding machinery, technique and standards are adopted to minimize the distortion. Angular distortion is corrected with oil press and angular distortion corrector, while horizontal distortions like sickle curve and arch are mainly done with flame. Flame correction is of great labor intensity and is also time and material consuming. Besides, the correction is affected by the operators’ skill and mood, which, to some extent, limits the productivity. In this paper, a new technique of section steel distortion correction with high efficiency and adaptability and yet low investment and cost will be proposed for the development of new-type section steel. The correction principles and capability calculation should be done some research on, which will be introduced. The practice done on section steel with a wing edge of 40～60 mm, proves satisfactory: compared with oil-press correction, continual mangling correction saves equipment investment by three quarters, installed capacity by three quarters and investment by three quarters and with a much higher efficiency. Particularly in the distortion correction of heavy welding structures, mangling correction stands out from the crowd. Mangling correction proves to be the best solution to the continual horizontal distortion correction of welding section steel.
文摘缆式焊丝熔化极气体保护电弧焊(gas metal arc welding,GMAW)中存在的焊缝截面侧偏现象会导致焊接接头熔合不良,基于熔滴受力分析和最小电压理论对焊缝截面侧偏现象的变化规律进行机理分析.结果表明,电流是影响截面侧偏的关键因素,由于缆式焊丝独特的绞合结构引起电弧旋转,进而导致出现熔滴受力不均的现象,熔滴过渡方向与焊丝轴线存在夹角,在熔滴冲击力的作用下导致焊缝截面出现侧偏现象,随着电流的增加,电弧对熔滴的拘束增强,熔滴过渡方向逐渐趋于轴线,因而焊缝截面侧偏的趋势随着电流增加而减小.
文摘Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction industry.This paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face design.The built-up columns were filled with ordinary concrete of good strength.Finite element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial compression.Analytical approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box configurations.The obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.
文摘In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.
