Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

The dynamic effects of metal vapour in gas metal arc welding

Abstract: Numerical simulations for the dynamic effects of metal vapour in gas metal arc welding (GMAW) suggest that vapour from the welding droplet at the tip of the welding wire has a significant influence on the plasma properties. It is found that for the evaporation rates calculated for arcs in pure argon, the dynamic effects of metal vapour markedly cool down the plasma in the central region of the arc, leading to the formation of a low temperature zone centred on the arc axis, in agreement with experimental measurements in the literature. Radiation effects, omitted in this paper, may produce further cooling of the plasma gas. The results highlight major deficiencies in the common approach to modelling the GMAW process and suggest that accurate description of GMAW must include the influence of metal vapour on the plasma.

Elucidation of phenomena in high-power fiber laser welding and development of prevention procedures of welding defects

Abstract: Fiber lasers have been receiving considerable attention because of their advantages of high power, high beam quality and high efficiency, and are expected as one of the desirable heat sources for high-speed and deep-penetration welding. In our researches, therefore, the effects of laser powers and their densities on the weld penetration and the formation of sound welds were investigated in welding of Type 304 austenitic stainless steel, A5052 aluminum alloy or high strength steel plates with four laser beams of about 0.12 to 1 mm in focused spot diameter, and their welding phenomena were observed with high-speed video cameras and X-ray transmission real-time imaging system. It was found that the laser power density exerted a remarkable effect on the increase in weld penetration at higher welding speeds, but on the other hand at low welding speeds deeper-penetration welds could be produced at higher power. Laser-induced plume behavior and its effect on weld penetration, and the mechanisms of spattering, underfilling, porosity and humping were elucidated, sound welds without welding defects could be produced under the improved welding conditions. In addition, importance of the development of focusing optics and the removal of a plume during remote welding will be emphasized in terms of the stable production of constant deep-penetration welds and the reduction in welding defects in high power laser welding.

Studies on Effects of Welding Parameters on the Mechanical Properties of Welded Low-Carbon Steel

Abstract: In this work, the effect of heat input on the mechanical properties of low-carbon steel was studied using two welding processes: Oxy-Acetylene Welding (OAW) and Shielded Metal Arc Welding (SMAW). Two different edge preparations on a specific size, 10-mm thick low-carbon steel, with the following welding parameters: dual welding voltage of 100 V and 220 V, various welding currents at 100, 120, and 150 Amperes and different mild steel electrode gauges of 10 and 12 were investigated. The tensile strength, hardness and impact strength of the welded joint were carried out and it was discovered that the tensile strength and hardness reduce with the increase in heat input into the weld. However, the impact strength of the weldment increases with the increase in heat input. Besides it was also discovered that V-grooved edge preparation has better mechanical properties as compared with straight edge preparation under the same conditions. Microstructural examinations conducted revealed that the cooling rate in different media has significant effect on the microstructure of the weldment. Pearlite and ferrite were observed in the microstructure, but the proportion of ferrite to pearlite varied under different conditions.

Effect of arc current on microstructure and wear characteristics of a Ni-based coating deposited by PTA on gray cast iron

Abstract: The plasma transferred arc (PTA) technique is currently used to coat the edges of moulds for the glass industry with nickel-based hardfacing alloys. However the hardness and wear performance of these coatings are significantly affected by the procedure adopted during the deposition of coatings. The aim of the present investigation is to study the effect of arc current on the microstructure, hardness and wear performance of a nickel-based hardfacing alloy deposited on gray cast iron, currently used in molds for the glass industry. Microstructure, hardness and wear assessments were used to characterize the coatings. Electron probe micro analysis (EPMA) mapping, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) and X-ray diffraction (XRD) were used to characterize the microstructure of the deposits. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was also studied. The typical microstructure of the coatings consists of dendrites of Ni–Fe, in the FCC solid solution phase, with interdendritic phases rich in Cr–B, Ni–Si and Fe–Mo–C. Increasing the arc current reduces the proportion of porosity and hardness of the coatings and modifies their composition due to the increasing dilution of the cast iron. The partial melted zone (PMZ) had a typical white cast iron plus martensite microstructure, while the heat affected zone (HAZ) had only a martensite structure. The wear tests showed decreasing wear resistance with decreasing hardness of the coatings. PWHT reduces the hardness of the PMZ and HAZ but does not significantly alter the hardness of the bulk coating.