Key points of welding process for medium carbon steel
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If the weldment is too large and the overall preheating is difficult, local preheating may be performed. The heating range of the local preheating is 150 to 200 mm on both sides of the welded joint.
(2) Basic welding rods are preferred when welding rod conditions permit.
(3) The groove shape shall be welded as far as possible to the U-groove type. If it is a casting defect, the shape of the groove excavated by the shovel should be rounded. The purpose is to reduce the proportion of the base metal melted into the weld metal to reduce the carbon content in the weld and prevent cracks.
(4) Welding process parameters Since the proportion of the base metal melted into the first layer of weld metal is up to 30%, the first layer weld should be welded with small current and slow welding speed as much as possible to reduce the melting of the base metal. deep.
(5) Post-weld heat treatment After welding, it is better to immediately perform stress-relieving heat treatment on the weldment, especially for large-thickness weldments, high-rigidity structural members, and weldments working under severe conditions (dynamic load or impact load). The tempering temperature for stress relief is 600 to 650 °C.
If the stress relief heat treatment cannot be performed after welding, the post heat treatment should be performed immediately.