What are the repair processes for thermal shock cracks in hot runners?

Based on the above analysis, appraisal, repair feasibility and precautions of secondary repair for thermal shock cracks of hot runners, the following repair techniques are suitable for different damage degrees:

Shallow Microcrack Argon Arc Welding Repair Process 1. Clean the cracked region using grinder. Argon arc welding with minimal current and heat input. Special welding wire of the same composition. After each weld hammering between layers should be done to relieve stress. This is the most popular mainstream restoration procedure and is appropriate for superficial microcracks that have not pierced the runner.

Laser Cladding Repair Process High-energy laser beam is used to concurrently melt a particular alloy welding wire and the substrate in the fractured area. The heat input is quite low and the welding deformation is nearly insignificant. It is suitable for repair of microcracks of high-precision small-sized precision hot runner nozzle components.

Laser Cladding Repair procedure: This procedure uses a high energy laser to melt a particular alloy welding wire and the substrate at the same time in the cracked area. The heat input is very minimal and welding deformation is hardly negligible . It is suitable for the repair of microcracks in high-precision small-sized precision hot runner nozzle components.

General Stress Relieve Strengthen Repair Process: For hot runner plates with micro fractures spread in several regions, after welding repair, put the plate into heat treatment furnace and maintain at 600-650℃ for 2-4 hours then slow cooling. This entirely removes latent stress built up over years and stops crack growth in later working situations.

Inlay-Filling Repair Process: For local and small-area penetrating cracks, a regular groove is machined in the crack area, and an insert of the same material is placed and subsequently sealed by welding. This procedure can be applied for localized penetrating small cracks that cannot be directly mended by welding so as to avoid entire scrapping.

Different techniques are employed according to the crack depth, position and hot runner material to enhance the service life after repair.