High-Speed Tandem Pulsed GTAW of Thin Stainless Steel Plate
Compared with single GTA and tandem GTA welded joints, the mechanical properties of three different weld joints were studied
BY H. JIANG, G. QIN, C. FENG, AND X. MENG
A novel high-speed welding process with tandem pulsed gas tungsten arcs, which employed two pulse arcs with a 180-deg phase to regulate the behavior of the weld pool and obtain a high-quality weld bead with low welding heat input, was proposed. The effects of pulse welding current parameters>were studied through a statistical design of experiment. The welding speed of a 1.2-mm-thick 304 austenite stainless steel plate can reach up to 3.0 m/min without sacrificing weld appearance qual- ity. The grain structure, mechanical properties, and heat input of tandem pulsed gas tungsten arc welding (GTAW–P) were analyzed and compared with those of single and tan- dem GTAW. Good mechanical properties of the welded joint were obtained by tandem GTAW–P. Compared with the sin- gle and tandem GTAW, the heat input of tandem GTAW–P was decreased by 17.5 and 14.5%, respectively. The main arc at pulse peak obtained sufficient penetration, and the as- sisting arc at pulse background reduced the unnecessary heat input. When the main arc reached pulse background, the assisting arc at pulse peak heated the trailing region of the molten pool continuously to ensure reflow of the metal and suppressed the generation of weld defects.
Thin Stainless Steel Plate
Low Heat Input
作者：H. JIANG, G. QIN, C. FENG, AND X. MENG
Laser Heat Treatment of Low-Alloy Ultrahigh-Strength Steel Laser-Welded Joints
Laser heat treatment was performed to improve the bending property of laser- welded joints of low-alloy ultrahigh-strength steel with minimized strength loss
BY C. LUO, Y. CAO, L. ZHAO, AND J. SHAN
The poor bending property of laser-welded joints limits the application of low-alloy ultrahigh-strength steel (LAUHSS). In this work, two stages of laser heat treatment (LHT) were per- formed to enhance the face- and back-bending property of joints with minimized strength loss. The microstructures and mechanical properties were evaluated, and the influence mechanism of LHT on the bending property was discussed. The first LHT aimed to improve the back-bending property, after which the joints were comprised of the austenized and tempering zones. In the tempering zone, the original inhomogeneous microstructures transformed into similar tempered martensite. This smoothed out the steep hardness gradient to relatively uniform values. In the austenized zone, austeniza- tion occurred and the hardness valley still existed around the sides of the zone. The mechanical property test results showed the back-bending angle could be improved from 30 deg to more than 90 deg, while the face-bending angle showed unsatisfactory results with more than 1280 MPa ten- sile strength. The second LHT was performed based on the first LHT to improve the face-bending property of joints. With lower power in the second LHT, the dual-phase microstruc- tures in the austenized zone tempered. Additionally, the hard- ness distributions of joints tended to be more uniform with- out valleys. A more than 90-deg face-bending angle and about 1205 MPa tensile strength were obtained. After LHT, the range of plastic deformation during the bending process ex- panded instead of concentrating in the hardness valley zone, which led to a larger relative bending radius and less tensile stress on the bending surface. This is beneficial for the im- provement of the bending property.
Low-Alloy Ultrahigh-Strength Steel
Relative Bending Radius
Laser Heat Treatment
作者：C. LUO, Y. CAO, L. ZHAO, AND J. SHAN
Spot Weld Strength Modeling and Processing Maps for Hot-Stamping Steels
A methodology was developed for modeling the link between nugget size and strength, as well as resistance spot welding and expulsion, in commercial hot stamping
BY A. MOHAMADIZADEH, E. BIRO, M. WORSWICK, N. ZHOU, S. MALCOLM, C. YAU, Z. JIAO, AND K. CHAN
This research focuses on developing a novel methodology for modeling the link between nugget size and strength, as well as resistance spot welding (RSW) parameters and expulsion, in commercial hot-stamping Usibor® 1500 and Ductibor® 500. The RSW process was simulated for more than 250 different sets of welding time, current, and electrode force, resulting in the creation of 3D processing maps for both materials. The predictions were evaluated by measurements, and 3D nonlinear regression methods were used to explain the variations in strength as the function of welding parameters. A substantial amount of effort was devoted to taking the effect of expulsion into the numerical models so that the shear-tension strength of the spot welds would be predictable based on the occurrence and extent of expulsion during RSW. The results indicated that the occurrence of ex- pulsion may decrease the strength of the spot weld up to 10 kN (2248 lbf) in Usibor (45%) and leads to 4 kN (899 lbf) strength loss (23%) in Ductibor. The models can estimate the strength of the spot weld with ± 1 kN (224 lbf) error.
Resistance Spot Welding
作者：A. MOHAMADIZADEH, E. BIRO, M. WORSWICK, N. ZHOU, S. MALCOLM, C. YAU, Z. JIAO, AND K. CHAN
本文针对商业热冲压板Usibor® 1500和Ductibor® 500提出了一种模拟熔核尺寸与焊接强度、电阻点焊参数与喷溅关系的方法，并对两种母材下250余种不同焊接时间、电路和电极力等焊接参数下的电阻点焊进行了3D加工云图进行了构建。通过实际测量对预测结果进行了评估，并采用三维非线性回归方法解释了焊接强度随焊接参数的变化规律。文中在喷溅的数值模型建立方面开展了大量工作，以期根据储能电阻点焊过程中发生的喷溅程度来预测焊接的剪切强度。试验结果表明，喷溅使Usibor(45%)点焊强度降低10kn (2248 lbf)， Ductibor (899 lbf)强度损失4kn(23%)。该模型的点焊强度预测精度达到±1kn (224 lbf)以内。
本文摘自：Welding Journal 《焊接杂志》2019年8月刊