Welding Science (Brazil)

Dissimilar material welding enables the integration of the superior properties of different materials, thereby achieving optimal structural performance and economic efficiency while meeting specific service requirements. The presence of solid-solution strengthening elements such as Ti, Co, and Al, and trace elements such as P and S, in GH3030 nickel-based superalloy leads to their segregation and the formation of intermetallic compounds in the welded joint, resulting in deterioration of joint performance. High-entropy alloys (HEAs), with their high-entropy effect and delayed diffusion effect working synergistically, can effectively suppress compositional segregation caused by uneven elemental diffusion and the formation of intermetallic compounds at interfaces, thereby improving the quality of welded joints and demonstrating great potential for dissimilar material joining. Therefore, in this study, fiber laser welding was used to effectively join AlCoCrFeNi2.1 eutectic high-entropy alloy and GH3030 nickel-based superalloy, with the expectation to improve welded joint element segregation, suppressing the formation of intermetallic compounds, and enhance the welded joint quality and its performance. The AlCoCrFeNi2.1/GH3030 joint exhibits an average yield strength of 1.31 GPa, which is significantly higher than that of the GH3030/GH3030 joint (1.07 GPa). In addition, the AlCoCrFeNi2.1/GH3030 joint shows a higher average work-hardening exponent of 0.337 compared with 0.30 for the GH3030/GH3030 joint, indicating improved plasticity. The results showed that under appropriate welding process parameters, the hardness of the weld zone, transitioning from the nickel-based superalloy to the eutectic high-entropy alloy, exhibited a stable increasing trend, and the joint exhibits good plasticity, with brittle fracture being unlikely.

Abstract Through the analysis of the magnetic field around the arc, the feasibility of controlling the arc shape and performance by the external axial magnetic field is clarified. Combined with the derived mathematical expression of the alternating axial magnetic field generated by the energized solenoid, the magnetic field and its distribution were simulated with COMSOL Multiphysics and MATLAB software, and the effects of the magnetic head structure and parameters on the magnetic field and its distribution were determined. A magnetic head was designed and manufactured according to the simulation results, and the welding process experiments were carried out. The experimental results show that the high-frequency axial magnetic field can significantly compress the arc and improve the welding penetration.

To weld is an indispensable step in the industrial sector and different materials and processes can be used to carry it out.The joining of parts through heat, arc flash, pressure or explosion emits gases and fine particles that remain in suspension in the work environment.With a view to avoiding the exposure of workers to the harmful effects resulting from the welding process, rules were drawn up in Brazil and abroad determining the use of protective equipment and establishing standard operating procedures.The first objective of this article was to gather and analyze these standards, followed by a literature review on the harmful effects of welding fumes on human health.The injuries caused by exposure indicate inadequate or absent use of protective equipment, it is necessary to understand the causes.

Abstract Experiments have been conducted to investigate the influence of the cusp external magnetic field (EMF) on deposition rate of two-electrode tungsten insert gas (T-TIG) welding. T-TIG arc parameters such as arc shape, arc voltage, arc pressure and arc plasma information were acquired respectively. Results showed compared to TIG, a higher welding current could be allowed for T-TIG, due to its low arc pressure characteristic. Under the effect of the cusp EMF, the arc shape was compressed along x-axis of T-TIG, while elongated along y-axis of T-TIG. Besides, the peak arc pressure of T-TIG was not significantly increased by the cusp EMF. Moreover, with the action of the cusp EMF, the maximum values of the electron temperature (Te) and electron density (Ne) of T-TIG were not significantly increased, but along y-axis, the increments of the two parameters were gradually increased and their distributions were widened. Therefore, more arc energy was allocated on y-axis of T-TIG by the cusp EMF, which could improve the preheating and the melting of the filler wire along y-axis, so the deposition rate of T-TIG could be increased by 17.6% under the effect of the cusp EMF.

Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable. In this study, a tin-based solder alloy was developed for this special tin-plating process. For this new solder alloy, the molten solder's antioxidant performance, the morphology of inter-metallic compounds (IMCs) at the solder/copper interface and the dissolution rate of outer conductor during tin-plating process were studied. The results indicate that when the addition of P element in the pure tin solder up to 35ppm, the static oxidation rate of pure tin decreased to 12.1g/m2 from 26.5g/m2, while the dynamic oxidation rate decreased from 8.9g/m2 to 5.6g/m2, which can significantly reduce the amounts of the oxidized slag from tinned tank during the continuous operating; By adding 0.1%Co, 0.05%Ni, the morphology of IMCs changed from scallop-shape to a uniform plate-shape, which can improve the interfacial bonding strength and flexibility; Adding 0.7%Cu can reduce the dissolution of the outer copper conductor during tin-plating process.

Magnetic Pulse Welding (MPW) is not only one of the most useful welding processes for the dissimilar metal joining which uses cylindrical materials such as a pipe, but also a new technology for metal welding by means of repulsive force on account of the interaction between magnetic part of working coil and current induced in an outer pipe. Since the factors effected on quality of MPW are the charged voltage, the gap between inner pipe and outer pipes and a thickness of an outer pipe, the this study was focused on the investigation of the effect of process parameters and development of the mathematical model for the prediction on a quality of joint using Response Surface Method (RSM). To achieve the objective, the MPW equipment manufactured by WELDMATE CO., LTD. has been employed and applied for the materials such as the Al 1070, SM45C for Al and steel pipe respectively. After the sequent experiment, leakage test has been done to verify efficiency of the welding. The experimental values have been shown the good agreement with the predicted ones, indicating suitability of mathematical model employed. It is concluded that the gap between outer pipe and inner rod is one of major process parameters for influence on quality of joint while Al/steel pipe welding using the MPW.

The pore and crack formations in the weld bead during underwater wet welding are the main cause of failure to reach the required mechanical properties of the weld metal. These defects are closely associated with the decomposition of the water molecule under electric arc conditions. In this paper, the thermodynamic calculations of the complex process of the water decomposition under the conditions of high electric arc temperatures at a pressure of 1 atm of steam are discussed. The values of the partial pressures of the five main products of the vaporizations and decomposition of the water (H2O(g), H2, O2, H and O) are calculated for temperatures between 1870 and 4000 K. Due to the fact that atomic hydrogen is mainly responsible for pore formation in the weld metal, its partial pressure as a function of partial pressures of atomic oxygen and steam (water vapour) is expressed. Hydrogen solubility values in the liquid metal under the conditions of underwater wet welding at depths of 50 and 100 m, and a comparison between the thermodynamic calculation and porosity measurement results at depths of 50 and 100 m, are presented.

The worn surface of a modified aluminium-silicon eutectic alloy are examined in order to determine the nature of surface damages. Furthermore, an attempt is made to relate the surface features to the mechanism by which the wear particles are formed. Oblique sections of worn materials are used to examine the extent of subsurface changes through both microhardness measurements and metallography observation. The results indicate that both wear features and mechanism are different when the binary eutectic AL/Si alloys are compared to the modified materials.