Influence Mechanism of Mold Preheating Temperature on Thermal Fatigue Damage

Mold preheating temperature is a core process parameter affecting the thermal fatigue service life of aluminum alloy casting molds. Thermal fatigue damage is the main failure form of casting molds in mass production, manifested as surface crack, peeling and deformation, which directly reduces mold precision and casting quality. Industrial test data shows that mold temperature difference is the fundamental cause of thermal fatigue stress. When the mold preheating temperature is lower than 150℃, the instantaneous temperature difference between the mold cavity and 680℃ aluminum liquid exceeds 530℃, generating huge instantaneous thermal stress, leading to rapid expansion of micro cracks on the mold surface and accelerated thermal fatigue failure. When the preheating temperature is too high (exceeding 280℃), the mold steel is in a high-temperature state for a long time, resulting in tempering softening, decreased hardness and wear resistance, and accelerated aging damage. The industry-standard preheating temperature range of 180-220℃ can effectively control the temperature difference between mold and aluminum liquid within 500℃, balance internal and external thermal stress of the mold, and greatly reduce thermal fatigue risk. In addition to temperature value, preheating uniformity and holding time also play key roles. Controlling the mold surface temperature difference within 30℃ and maintaining 20-30 minutes of constant temperature preheating can ensure full heat conduction of the mold body, eliminate residual stress, and further stabilize the mold thermal fatigue resistance. Strict implementation of preheating process standards can extend mold service life by 35% on average.