Abstract: Die, crucial for die casting, is susceptible thermal fatigue because of endless cycles of heating and cooling. For this phenomenon，it is necessary to study the process of casting mold thermal fatigue and the influence of different processes on the casting mold thermal fatigue life, and to explore methods to predict the thermal fatigue life of casting mold. A thermal fatigue testing device is developed based on self-restraint thermal fatigue method. The test condition is similar to the actual working condition with heating of the specimen by aluminum melt pool, cooling by lubricant oil and internal circulation of cooling water. By adopting the developed device the thermal fatigue life of popular used H13 steel is studied. During the test the specimen temperature is measured continuously, the residual stress and cracks are measured or observed at intervals of 3 000～4 000 cycles. The curves of stress variation and the mold thermal fatigue life based on temperature difference are obtained. The influence of internal cooling on temperature, stress, crack and thermal fatigue life of specimens is studied. In addition, numerical simulation of the heat transfer during the test is carried out, and the temperature difference can be accurately acquired. Together with the measured results, how to improve the thermal fatigue life of the mold is discussed.

Key words: Aluminum alloy, Casting die, H13 steel, Numerical simulation, Thermal fatigue life