Heat treatment heating and cooling rates
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In one particular period of time (about 0.3 hours) on the heat treatment cooling rate curve of that equipment, the cooling rate reached 350°C/h; however, the cooling rate from 620°C to 400°C was 175°C/h. The process requires a cooling rate of 55–280°C/h. Is such a cooling rate acceptable?
I don’t understand what you mean by the cooling rate reaching 350°C/h within 0.3 hours. In which temperature range is this occurring? If it’s below 400°C, then the material has already been taken out of the furnace; it’s impossible for the temperature to drop that quickly
At temperatures below 400°C, no requirement is placed on the cooling rate.
Before 400°C, it took only 0.3 hours to drop from 600°C to 500°C. Subsequently, the cooling rate slowed down, with an average cooling rate of 175°C/h from 620°C to 400°C. I’m not sure if it’s clear enough.
The cooling rate in certain local temperature ranges exceeds the allowed limit; the cooling rate can only meet the requirements when calculated based on the overall cooling time. The furnace’s cooling measures are inadequate, or cooling occurs too rapidly during certain periods.
Is this okay? Due to my limited knowledge, I was unable to find any relevant standards or technical specifications.
First, you need to know what goal you want to achieve with this heat treatment Is it to eliminate welding residual stresses, improve mechanical properties, restore the material’s mechanical properties, or carry out degassing treatment? Do different purposes require different cooling rates?
Stress-relief heat treatment requires a cooling rate of 55~280°C/h.