The application of thick-walled steel pipe in the pipe welding process

Welded joints groove forms commonly used in the construction pipeline welding groove type for the API standard 30 ° V-groove, suitable for manual welding. But for the thick-walled steel pipe, this type of groove weld joint type filler metal volume, high labor intensity, and not suitable for automatic soldering, welding, usually semi-automatic welding with 23 ° V-groove, with a narrow gap welding composite groove patterns. Welding energy needs into account to determine the composition of the base metal, weld material type, for drug skin (cored flux) metallurgical reactions and the effect of shielding gas protection, preheat condition, interpass temperature control of the tube specifications , the wire (strip) in diameter, the heat affected zone embrittlement and softening tendencies, the desired microstructure and mechanical properties, as well as welding position, welding passes, each weld thickness, weld and form of such a transition droplet factor. Preheating and interpass temperature by slowing the purpose of preheating the base material and reducing the stress state of the cooling rate of the weld root to prevent cold cracking roots. Construction of the pipeline welding preheat temperature range should be considered the strength of the base material, organizational performance variation, diameter and wall thickness, and the amount of hydrogen welding materials and other factors.

For multilayer welding thick-walled steel pipe, but also consider the weld interpass temperature control to control the cooling rate near the weld zone. Interpass temperature and preheat temperature generally similar. Avoid overheating the seam zone near the premise that higher layer temperature prevents multi-layer welding cold cracks. Heat treatment after welding and heat treatment pipeline construction is generally not performed after the heat treatment after welding and heat treatment. But for construction in the alpine region, when the preheat and interpass temperature control is difficult to play a greater role, it is necessary to take some of welded joints and heat treatment after hot measures to ensure that the organization and performance of welded joints. In pipe welding construction process should take into account the high strength, thick-walled steel pipe is exposed to the impact of external stress. Taking into account the ambient temperature, humidity and wind speed on the environmental impact of different welding methods, to take the necessary measures to ensure the welding quality.