As critical equipment that withstands high temperatures, high pressures, and corrosive media, the quality of pressure vessel welding is directly related to operational safety and service life. Welding is not only the core process in pressure vessel manufacturing, but also the most prone to defects. To ensure quality, multiple process factors must be controlled.

The selection of welding consumables is crucial. Pressure vessels are typically made of carbon steel, stainless steel, and alloy steel. Different materials require different welding processes and consumables. Poor compatibility between the welding consumables and the parent metal can easily lead to insufficient weld strength or cracking. Therefore, strictly selecting qualified welding rods, welding wires, and shielding gases in accordance with design requirements is the primary prerequisite for ensuring welding quality.

Controlling welding process parameters determines the density and mechanical properties of the weld. Factors such as current, voltage, welding speed, and interpass temperature must be properly adjusted. Excessive current can easily cause burn-through and spatter, while too low current can lead to incomplete fusion and porosity. Proper heat input can also effectively prevent microstructural embrittlement and residual stress.

Pre-weld preparation and preheating are also crucial. Before welding, remove oil, rust, and moisture from the weld surface to reduce porosity and slag inclusions. For high-strength steel or thick-walled pressure vessels, preheating measures should be implemented based on the material's characteristics to prevent cold cracking. Interpass temperatures should also be controlled to ensure weld continuity and stability.

The welding environment and operator skill are equally important. Working in high humidity, low temperatures, or windy environments can easily lead to porosity and cracking, necessitating shielding and moisture-proofing measures. The welder's skill level directly impacts the weld joint's form and internal quality. Therefore, welds must be performed by qualified welders with relevant qualifications and verified by a process qualification.

Post-weld heat treatment is crucial for stress relief and improved weld microstructure. Tempering or full heat treatment after welding, especially for high-pressure and large-scale pressure vessels, can effectively improve joint toughness and corrosion resistance.

Factors affecting pressure vessel welding quality primarily include consumables selection, process parameters, pre-weld preparation, environmental conditions, welder skill, and post-weld heat treatment. Only by strictly controlling these critical links can weld reliability and the overall safety of the pressure vessel be ensured.