Based on our previous discussion of the solution treatment process and high-temperature performance of stainless steel bolts in hot runners, the following methods can be used to determine if thermal shock cracking has occurred in hot runners:
Visual Inspection: Directly observe the surface of the hot runner plate and nozzles to check for fine linear cracks extending from high-temperature stress concentration points. These cracks are often distributed along areas of temperature gradient in the hot runner.
Penetration Testing: Spray a colored penetrant onto the surface of the hot runner to be inspected. After wiping it clean, spray a developer. Cracks will show clear red marks, accurately detecting microcracks invisible to the naked eye.
Operating Condition Verification: Check for recent operations such as rapid temperature increases from room temperature to above 300°C within a short period, or sudden cooling with cold water at high temperatures. These drastic temperature fluctuations are the core cause of thermal shock cracking.
Evidence of Production Anomalies: If unexplained leakage or abnormal fluctuations in injection pressure occur during injection molding, after ruling out factors such as loose bolts, the malfunction is most likely caused by thermal shock cracking inside the hot runner.
The above methods can quickly and accurately determine whether thermal shock cracking has occurred in the hot runner, preventing the malfunction from escalating and affecting production.
