A slightly overheated hot runner cannot be repaired because overheating causes irreversible damage such as grain boundary oxidation, voids, or localized melting. Even if the damage seems minor, the structural integrity and load-bearing capacity of the material are permanently lost.
1. Why can't it be repaired?
Complete destruction of grain boundary bonding: Oxygen has formed a continuous oxide network along the grain boundaries, preventing metal atoms from recombining.
Extreme embrittlement: The plasticity of the overheated area approaches zero; any processing (such as welding or repair welding) will trigger new intergranular cracks.
Irreversible damage: Microscopic defects will rapidly propagate under thermal cycling or load, posing a risk of sudden fracture.
Engineering consensus: Overheating = permanent failure; regardless of severity, repair and use are prohibited.
2. Correct Handling Method: Direct Replacement
Immediate Shutdown: Stop production immediately upon discovering signs of overheating (e.g., surface discoloration, micro-cracks, blistering);
Replace with New Part: Remanufacture using anti-overheating materials such as PM-H13 or H13+Ti;
Trace the Root Cause: Check for inaccurate temperature control system, thermocouple drift, and excessive heating parameters.
Safety Principle: Avoid complacency; slightly overheated parts may experience penetrating fractures within hours during service.
3. Preventive Recommendations
Strict Temperature Control: H13 steel operating temperature ≤ 600°C, heat treatment not exceeding 1150°C;
Dual Thermocouple Monitoring: Achieve redundant temperature measurement, automatic alarm and power-off for overheating;
Regular Metallographic Inspection: Inspect every 6–12 months, shortening to 3–6 months under high-load conditions.
