Measures to prevent welding cold cracks in heat-resistant steel
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Measures to prevent welding cold cracks in heat-resistant steel
The three key factors for cold cracking are: diffused hydrogen, hardenability, and constraint. Measures to prevent cold cracks: Use low-hydrogen welding materials, dry the electrodes and fluxes, clean the wire and the welding area, and control the sources of hydrogen. Appropriate welding wire energy; excessive wire energy can cause coarsening of grains in the near-weld zone ； Too low a wire energy can cause hardening in the heat-affected zone, thereby increasing the tendency for cold cracks. Preheating can reduce the cooling rate, effectively preventing cold cracks. For multi-layer welding, it is also necessary to maintain the interlayer temperature at or above the preheating temperature. Post-weld heat treatment can allow diffused hydrogen to escape fully, and it is an effective measure to prevent cold cracks. Post-weld heat treatment.
Measures to prevent welding cold cracks in heat-resistant steel include: ① Reducing the hydrogen content in the weld, such as using low-hydrogen electrodes and thoroughly drying the welding materials； ②Appropriate preheating and post-heating ； ③Choose raw materials with a lower carbon equivalent ； ④Reduce restraint stress and avoid stress concentration (see hydrogen in metals).
Generally, these include: 1. Selecting appropriate welding materials and baking them as required before use； 2. Carry out pre-welding preheating and post-welding heat treatment in accordance with the welding process ； 3. During operation, strictly control the input of wire energy!
Welding requirements for heat-resistant steel: 1. Select appropriate welding materials; for shielded metal arc welding, R307 can be used； 2. Preheating before welding ； 3. Low wire energy welding parameters to prevent the formation of excessive martensitic hardened structures ； 4. Higher interlayer temperature, 180~300 degrees ； 5. Perform tempering treatment after welding.