Selection of Welding Materials, Welding Processes, and Failure Prevention for Die Casting Mold Welding
Local cracks, erosion, and wear occur in the mold, and welding is the most commonly used repair method. If the welding material is selected incorrectly, it will crack again quickly after welding. Many repairs and rework are caused by mismatched welding materials.
1、 Principle of matching welding materials for overlay welding
Substrate H13: H13 welding wire is selected, with the same material, similar thermal expansion coefficient, and low welding stress; 8407 substrate priority 8407 special welding material; Ordinary hard surface welding materials are not recommended to be directly welded to the formed surface, as they are prone to cracking and peeling. The alloy wheel mold cavity is mostly H13/8407, matched with corresponding hot work mold steel welding wire.
2、 Pre treatment before welding (of utmost importance)
Cracks must be polished and cleaned until they completely disappear, and direct welding cannot be applied on the cracks; Polish all oil stains, residual release agents, and old coatings clean; Preheat H13 to 350-450 ℃ to reduce welding cold cracks; Insulation and slow cooling after welding to release welding stress. Directly welding without preheating is likely to crack immediately after welding.
3、 Welding layering and subsequent treatment
Multi layer and multi pass welding, low current, low penetration depth, reducing heat input; Grinding and polishing after welding, followed by nitriding or coating; The hardness of the welding repair area is different from that of the substrate, and the thermal fatigue resistance is weaker than that of the original base material, which belongs to repair rather than restoring a brand new state.
4、 Which positions are not suitable for welding
Large area cracking, crack depth exceeding 1.5mm, multiple interwoven cracks, and thin-walled areas near waterways have a very high recurrence rate after welding, and priority should be given to replacing inserts. Sharp corners and stress concentration areas are more prone to re cracking due to stress accumulation after welding.
5、 Key points for communication on foreign trade mold maintenance
Notify the customer in advance that welding is a repair and the lifespan will be lower than that of a brand new base material; Record the welding repair position and welding material model, and write them into the maintenance ledger; After welding repair, the original design lifespan cannot be directly promised. The logic of low pressure casting mold welding repair is consistent, but the heat load is low and the service life after welding is longer. Google's "die casting mold welding rod selection" is aimed at mold repair technicians.
FAQ
Can we use regular Cr12 welding material to weld H13 molds?
Not recommended, thermal expansion mismatch, short-term cracking and peeling.
What happens if the preheating temperature before welding is not enough?
Cold cracking, directly cracking during the cooling process after welding.
3. Do you want to temper after welding?
Suggest stress tempering to reduce residual welding stress.
Can nitriding still be done after welding?
Sure, but the welding material structure is different from the base material, resulting in a decrease in the uniformity of the nitride layer.
5. Is the erosion and welding of the gate durable?
In the short term, if there is severe erosion, it is safer to prioritize replacing the inserts.
6. Should small microcracks be welded?
Shallow microcracks can be polished and removed without welding; Deep cracks must be repaired by root cleaning and welding.
How is the dimensional stability after welding?
Welding poses a risk of deformation, with higher risks for small and thin-walled parts.
What will happen if the same position is repeatedly welded?
The matrix grains are coarse, and the toughness continues to decrease, making it increasingly prone to cracking.
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