Different determination methods and comparative analysis on continuous cooling transformation curves of hypoperitectic steels
The accurate measurement of the continuous cooling transformation curves is crucial for revealing the high-temperature phase transformation of steels and formulating the heat treatment process.Taking the low-alloy hypoperitectic steel slabs as an example,the CCT curves were measured by Gleeble thermal simulation testing machine and thermal dilatometer in the cooling rate range of 0.1-50℃/s according to the dilatation method and a comparative analysis was conducted based on the phase structure and JMatPro calculation results.The results show that the temperature distribution of the experimental sample in Gleeble is not uniform due to its electrical current heating practice and sample size,in which there is a room-temperature zone,a transition zone and a high-temperature zone.Among them,the cooling rate in the transition zone is approximately air cooling rate,which affects the expansion amount obtained for the experimental sample at the given temperature.The sample of the thermal dilatometer is small,the temperature during the heating process is consistent,the measured phase transformation temperature is basically consistent,and the CCT curve obtained is relatively stable and reliable.It is pointed out accordingly that the phase transformation temperature and phase content of target steels in the continuous casting process can be quickly obtained through JMatPro software calculation along with a following experimental thermal dilatometer correction,which can provide efficient and accurate theoretical guidance for the formulation of production practice.
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