Welding process of 37Mn5 oil casing pipe

Welding process of 37Mn5 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 experimental results of the test blocks welded by the above two welding processes are as follows:

Results of plan (1): Tensile test, base metal broken, qualified; impact values of 3 samples in the heat affected zone were 26, 47, 23, unqualified; four samples with side bends were 3.75mm each cracks, 4mm cracks, 1.38mm cracks, 0.89mm cracks, unqualified; experiments have proven that this process plan is unreasonable.

The results of the (2) plan: the tensile test, the base material was broken, and it was qualified; the impact values of the three samples in the heat-affected zone were 51, 40, and 40, which were qualified; the four side bending samples were all intact and qualified; Experiments prove that this process plan is reasonable. Post-weld heat treatment can improve the welding structure and performance, and is one of the important factors that determine whether 37Mn5 petroleum casing welding can obtain welded joints that meet technical requirements.

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