Welding process of oil casing pipe:
(1) Selection of welding method: 80%Ar+20%CO2 gas shielded welding.
Selection of welding materials: ER55-G is used as the welding wire, with a diameter of Φ3.2mm.
Welding parameters: current 250~320A, voltage 26~30V;
Welding speed: 35~50cm/min; preheating temperature is 100℃, ensuring that the interlayer temperature is not lower than the preheating temperature, but it is not allowed to be 30℃ higher than the preheating temperature.
Post-weld treatment: air cooling without any heat treatment.
(2) Selection of welding method: 80%Ar+20%CO2 gas shielded welding.
Selection of welding materials: ER55-G is used as the welding wire, with a diameter of Φ3.2mm.
Welding parameters: current 250~320A, voltage 26~30V;
Welding speed: 35~50cm/min; preheating temperature is 100℃, ensuring that the interlayer temperature is not lower than the preheating temperature, but it is not allowed to be 30℃ higher than the preheating temperature.
Post-weld treatment: tempering treatment, temperature 600±20℃, holding time 4h; heating rate 50℃/h, cooling rate 50℃/h.
The test blocks welded by the above two welding processes have the following experimental results:
The results of the first (1) plan: tensile test, broken base material, qualified; impact value of 3 samples in heat affected zone 26, 47, 23, unqualified; four samples of side bending have 3.75mm Cracks, 4mm cracks, 1.38mm cracks, 0.89mm cracks, failed; the experiment proved that this process plan is unreasonable.
The results obtained from the plan (2): tensile test, broken base material, qualified; impact value of three samples in heat affected zone 51, 40, 40, qualified; all four samples of side bending are qualified, qualified; Experiments prove that this process plan is reasonable. Post-weld heat treatment can improve the performance of the welded structure, which is one of the important factors for whether the 37Mn5 petroleum casing can be welded to meet the technical requirements.
