Medium carbon steel welding process points
Date:2019-07-26 Views:243Time Label:Medium carbon steel welding process points
Preheating is beneficial to reduce the maximum hardness of the heat affected zone of medium carbon steel and prevent cold cracks. This is the main process measure for welding medium carbon steel. Preheating can also improve joint plasticity and reduce post-weld residual stress. Generally, 35 and 45 steels have a preheating temperature of 150 to 250 ° C or a high carbon content or a large thickness and rigidity. When the crack tends to be large, the preheating temperature can be raised to 250 to 400 ° C.
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.
Second, the electrode
Basic electrodes are preferred when conditions permit.
Third, the groove form
Weld the weldment as much as possible into a U-shaped groove for welding. In the case of casting defects, 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.
Fourth, welding process parameters
Since the proportion of the base metal melted into the first layer of weld metal is up to about 30%, the first layer weld should be welded with a small current and a slow welding speed to reduce the penetration of the base metal.
Five, post-weld heat treatment
Immediately after welding, the weldment is subjected to stress-relieving heat treatment, especially for large-thickness weldments, high-rigidity structural members, and weldments operating under severe conditions (dynamic or impact loads). 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.