铝合金压铸模具热疲劳寿命试验研究

压铸模具是压铸的关键部件之一,其经受周期性的加热与冷却,易产生热疲劳。针对这种现象,研究压铸模具热疲劳的过程,不同工艺对热疲劳寿命的影响规律,探索预测压铸模具热疲劳寿命的方法。研究开发自约束冷热疲劳方法的热疲劳试验机,试样在铝液中加热,在脱模剂中冷却,试样内部通冷却水冷却,实现在压铸条件下的模具热疲劳试验。采用开发的热疲劳试验机对H13钢试样进行热疲劳寿命试验研究,在试验过程中测量试样的温度变化,每隔3 000～4 000次测量残余应力,观察裂纹,经过几万次的循环后可以得到应力变化曲线和基于温差的模具热疲劳寿命曲线。研究水冷对试样的温度、应力、裂纹以及热疲劳寿命的影响。同时,针对试验过程进行传热数值模拟,得到不同工艺条件下的模具温差。试验和数值模拟相结合讨论如何提高模具的热疲劳寿命。

Study on the Thermal Fatigue Life of H13 Steel for

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.