What is Thermal Shock Cracking Failure in Hot Runners

As we discussed about the solution treatment process and performance control of stainless steel bolts for hot runners, thermal shock cracking failure in hot runners is the brittle cracking caused by the thermal stress exceeding the material strength limit under the repeated and drastic temperature cycles.

Causes of Core Failure: The temperature of the hot runner rises quickly from room temperature to more than 300°C or cools quickly when production stops, the temperature difference between the inside and outside of the component causes large alternating thermal stress. The fracture propagation is finally initiated at the stress concentration areas, such as the threaded holes and the runner corners, after the long-term cycling.

High-risk failure locations: Areas of stress concentration such as bolt mounting holes, nozzle roots and runner corners in the hot runner body. Also hot runner stainless steel fasteners tend to fracture failure at the same time.

Prevention and Optimization Solutions: Selection of 316 stainless steel or Inconel high-temperature alloy materials with good thermal shock resistance, strict solution treatment to eliminate the residual stress, and the establishment of stepped temperature zones in heating and cooling stages to avoid sudden temperature changes substantially reduce the probability of cracking.