Effect of Heat Treatment and Thermal Stress Cycle on Plastic Mould Material M238

Yong, Chen Yien (2013) Effect of Heat Treatment and Thermal Stress Cycle on Plastic Mould Material M238. Final Year Project (Other), Tunku Abdul Rahman University College.

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Abstract

The objective of this project is to study the effect of heat treatment and thermal stress cycles on die material M238. It also investigate the number of cycles to cause a die to crack, to observe the change in microstructure, hardness value and mechanical properties of the die material after go through the specified thermal cycles. From the result obtained, it shows that the best hardening temperature and holding time is 8500C for 15 minutes. The best tempering temperature and holding time is 5800C for 30 minutes respectively to obtain desired hardness and toughness value. After tempering, it was put in the thermal stress cycles from 25 to 4000C for 500 cycles and 25 to 5000C for 100 cycles followed by quenched in water. The maximum temperature used was much higher than temperature usually used in the injection moulding industry, the reason of using high temperature to 4000C and 5000C is to induce thermal stress into the specimen in the short time. The effect is to obtain long term effect in the shortest possible time. Various testing are performed to this material M238 to investigate the changes of hardness and toughness after go through accelerated thermal stress cycles. First is the hardness test, to check the changes of hardness after the thermal stress cycles. Next is the Charpy impact test to investigate the changes of toughness, after the thermal stress cycles. Besides that, the dimension of the specimen is measured to investigate the dimension stability after gone through thermal stress cycles.