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Four common welding defects in boiler pressure vessels
The welding quality directly affects the performance and safety of the boiler structure. Poor welding quality of the boiler may lead to leakage or even explosion accidents, causing significant losses to people's lives and property. Therefore, exploring the causes of welding defects in boilers, mastering their preventive measures, and effectively improving the welding quality of boilers are of great significance for ensuring the safe operation of boilers.
2018.05.03
I. Overview In the manufacturing of pressure vessels, when submerged arc welding is used to join the longitudinal weld seams of cylindrical shells, cracks—hereinafter referred to as end-terminal cracks—often occur at or near the ends of these longitudinal welds. Many researchers have already studied this issue and concluded that the primary cause of end-terminal cracks is as follows: As the welding arc approaches the end of the longitudinal weld seam, the weld undergoes axial expansion and deformation, while simultaneously experiencing lateral tensile deformation perpendicular to the axial direction. Moreover, during the rolling and fabrication processes, the cylindrical shell itself experiences cold-work hardening stresses and assembly stresses. During welding, due to the restraint effect of the end-positioning welds and arc-starting plates, significant stresses accumulate at the weld’s end terminal.
2018.05.03
A Brief Analysis of Common Problems and Countermeasures in Gas-Shielded Welding
With the continuous improvement of welding technology in Chinese enterprises, gas-shielded welding processes have been steadily developing thanks to their advantages such as high quality, efficiency, energy savings, low costs, and minimal environmental pollution. In recent years, following the CO2 welding technology promotion and application exchange conferences, gas-shielded welding technology has been vigorously promoted and applied in the mechanical and metal structures industry, laying a solid foundation for the sustained, stable, and robust development of CO2 welding technology. Gas-shielded welding not only meets the demands of automation but also drives enterprise advancement and industrial upgrading, thus becoming the dominant welding method in many mechanical manufacturing and construction enterprises. However, in the...
2018.05.03
The Influence of Welding Parameters and Processes on Weld Beads
I. The Influence of Welding Current, Arc Voltage, and Welding Speed on the Weld Bead 1. Welding Current: When the welding current increases (with other conditions remaining unchanged), the weld penetration and reinforcement height both increase, while the weld width remains unchanged (or slightly increases). The reasons are as follows: ① After the current increases, both the arc force and the heat input on the workpiece increase, causing the heat source to shift downward and resulting in greater weld penetration. The relationship between weld penetration and current is approximately linear. ② As the current increases, the amount of wire melted increases nearly proportionally. Since the weld width remains roughly constant, the reinforcement height consequently increases. ③ After the current increases, the diameter of the arc column expands; however, the depth to which the arc penetrates into the workpiece also increases, thereby limiting the range of movement of the arc spot.
2018.05.03
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