Local weld‑repair extends H13 insert service‑life, yet improper welding introduces residual‑stress, cracking and hardness drop. Standard procedure is required for LPDC, gravity and CPC counter‑pressure casting mold on‑site mold maintenance.
Pre‑weld preparation: completely remove damaged zone. Micro‑crack shall be fully milled away; residual invisible micro‑crack under weld‑bead will propagate under cyclic thermal‑mechanical‑load after only 600‑900 casting cycles for EV structural‑part mold.
Pre‑heating requirement for H13 weld‑repair: pre‑heat insert substrate up to 380‑420 ℃ before welding operation. Localised cold‑welding without pre‑heat generates welding‑heat‑affected‑zone cold‑crack for CPC counter‑pressure casting mold inserts.
Select matched H13 welding consumable. Mismatched filler‑metal creates hardness discontinuity; different thermal‑expansion coefficient generates new interface stress during cyclic casting for gravity casting mold maintenance work.
Multi‑layer welding: control single‑layer weld‑bead thickness below 2.5 mm. Avoid thick single‑pass welding which accumulates huge welding‑residual‑stress inside repaired H13 insert for LPDC casting mold aluminum wheel mold repair.
Post‑weld stress‑relief tempering is mandatory step. Immediately perform stress‑relief tempering at 540‑570 ℃ after weld‑repair; skipping this procedure leaves high residual‑stress and raises insert‑fracture risk under counter‑pressure load.
After stress‑relief, multi‑point hardness test on welding zone and heat‑affected zone. Hardness deviation over ±3 HRC versus base‑material specification indicates unqualified weld‑repair for aluminum casting mold maintenance acceptance.
Weld‑repair location shall avoid high‑stress thin‑wall zones. Repeated welding repair on same position accumulates residual‑stress; more than two weld‑repair cycles on identical area triggers insert replacement assessment for EV structural‑part mold.
Post‑weld surface processing: grinding and polishing must remove decarburized layer on weld‑bead surface. Remaining decarburized layer brings low‑hardness zone, accelerating aluminum sticking and thermal‑crack initiation during mass‑production for CPC counter‑pressure casting mold.
Nitriding after weld‑repair: welding zone loses original nitriding protection. Local re‑nitriding treatment is required; ordinary overall nitriding may cause over‑brittleness on non‑weld original insert surface for gravity casting mold.
Defect misjudgement risk: surface crack after weld‑repair is frequently attributed to casting thermal‑load; in fact it originates from insufficient pre‑heat or omitted post‑weld stress‑relief during mold repair workshop operation.
Cross‑border project note: overseas mold‑repair vendors often skip post‑weld stress‑relief to shorten lead‑time. Technical specification must explicitly enforce pre‑heat, matched filler‑metal and mandatory post‑weld tempering requirement in purchase documents.
FAQ
Q: What pre‑heating temperature range for H13 insert local weld‑repair work?
A: Pre‑heat substrate to 380‑420 ℃ to prevent welding cold‑crack generation.
Q: What maximum single‑pass weld‑bead thickness recommended for multi‑layer welding?
A: Restrict single‑layer bead thickness below 2.5 mm to control residual‑stress build‑up.
Q: What mandatory post‑weld tempering temperature for stress‑relief of repaired H13 insert?
A: Stress‑relief tempering at 540‑570 ℃ must be performed right after welding.
Q: What hardness‑deviation threshold marks unqualified weld‑repair zone?
A: Hardness deviation over ±3 HRC compared with base‑material specification is unacceptable.
Q: How many repair‑weld cycles on identical area shall trigger insert replacement evaluation?
A: More than two weld‑repair operations on same location suggests insert replacement.
Q: What surface layer must be fully removed after weld‑repair grinding work?
A: Weld‑bead surface decarburized layer shall be completely eliminated by grinding & polishing.
Q: What risk will happen if applying full‑part nitriding after local weld‑repair?
A: Original non‑weld insert surface may suffer over‑nitriding and become excessively brittle.
