First, preheat Preheating helps to reduce the maximum hardness of heat-affected zone of medium carbon steel and prevent cold crack, which is the main technological measure of welding carbon steels, and preheating can improve joint plasticity and reduce residual stress after welding.
Usually, the preheating temperature of 35 and 45 steel is higher than the 150~250℃ carbon content or because of the thick and stiffness, the crack tendency is high, the preheating temperature can be raised to 250~400℃.
If the solder is too large, the overall preheating difficulties, can be local preheating, local preheating of the heating range of the two sides of the welding 150~200mm.
Basic electrodes are preferred when conditions permit.
III. Groove Form Weld the welding parts as much as you like with a U-shaped groove.
If the casting defect, shovel dug the groove profile should be smooth, the purpose is to reduce the base material into the weld metal in the proportion to reduce the carbon content in the weld, to prevent cracks.
IV. Welding Process Parameters
As the ratio of the base material to the first weld metal is up to 30%, the first weld seam should be used as small current and slow welding speed to reduce the penetration depth of the base material.
V. Heat treatment after welding After welding, it is best to remove the stress heat treatment of the welding parts immediately, especially for the welded parts with large thickness, high rigidity structure and severe conditions (dynamic load or impact load). The tempering temperature of eliminating stress is 600~650℃. If the welding can not be done to eliminate stress heat treatment, should be immediately after heat treatment.