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(1) Selection of welding method: 80%Ar+20%CO2 gas shielded welding. Selection of welding data: ER55-G is used for welding wire, diameter Φ3.2mm. Welding parameters: current 250~320A, voltage 26~30V; welding speed 35~50cm/min; preheating temperature is 100℃, ensure that the interlayer temperature is not lower than preheating temperature, but it is not allowed to be higher than preheating temperature 30℃ . Post-weld treatment: air cooling, without any heat treatment.

(2) Selection of welding method: 80%Ar+20%CO2 gas shielded welding. Selection of welding data: ER55-G is used for welding wire, diameter Φ3.2mm. Welding parameters: current 250~320A, voltage 26~30V; welding speed 35~50cm/min; preheating temperature is 100℃, ensure that the interlayer temperature is not lower than preheating temperature, but it is not allowed to be higher than preheating temperature 30℃ . Post-welding treatment: tempering treatment, temperature 600±20℃, holding time 4h; heating rate 50℃/h, cooling rate 50℃/h.

The experimental results of the test blocks welded by the above two welding processes are as follows:

The results of the (1) plan: tensile test, breaking the base material, qualified; the impact values ​​of the three samples in the heat-affected zone are 26, 47, 23, failing; the four samples of side bending are 3.75mm respectively The cracks, 4mm cracks, 1.38mm cracks, 0.89mm cracks are unqualified; the experiment proves that this kind of process plan is unreasonable.

The results of the (2) plan: tensile test, breaking the base material, qualified; the impact value of the three samples in the heat-affected zone is 51, 40, 40, qualified; all four samples of side bending are intact and qualified; Experiments prove that this kind of process plan is reasonable. Post-weld heat treatment can improve the welding structure and performance, which is one of the important factors for whether 37Mn5 petroleum casing welding can obtain a welded joint that meets the technical requirements.

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