Why air-cooled and furnace-cooled materials cooled for a duration of 1 hour or 60 minutes.

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Expert Solution

It depends on the thickness of the materials. generally, we used to consider one hour for a single inch (optimized by trial and error). But, it can be varied as because the treatment is totally operated by manual. So, better set your holding time +/- 10 minute extra. For your sample, It will be around - > 1 hours. One thing you have to be careful, while you will open the furnace door at a said temperature temperature will fall down. So calculate the holding time after the temperature will reach the same, or one thing you can do, set the temperature above your required one (say 20 deg C). By this temperature drop will be in your limited required values. I have done austenizing on three austenitic structural materials followed by the same rules.

For 1 inch (i.e. 25.4 mm) thickness it takes 1hour to fully austenitize the sample. As far as other transformations are considered, for patenting (isothermal pearlite transformation) holding time can be decided by trial and error otherwise you have to go through rigorous phase transformation calculations. Moreover time it takes for austenite to get fully converted in to pearlite also depends on its grain size. Bainitic tranformation is very fast in low alloyed steels but in heavily alloyed steel it depends on the chemical composition.

samet mamat answered 2 hours ago

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