A couple years ago, a friend and I did an experiment with some 52100 flat bar. The bar was .140 x 3/4 and we used 3 pieces of 4", 6", and 8" steel. They were put into a heat treat oven that was digitally controlled and the temperature set on 1500 degree F. The short piece was removed after one hour and quenched, the 6" piece was removed after 6 hours and quenched, and the last piece was removed after 23 hours and quenched. All 3 pieces were broken and the grain compared. There was no difference in grain size, only in the oxidation of the outside from the length of time that they were in the oven.
I think that 52100 is supposed to start growning grain at about 1750. It could very well start before that but I know it won't at 1500. I believe that time will have some effect on steels at the higher temperatures but it has to reach a temperature that the grain will start to grow before it can increase in grain size.
I have also put a blade in the forge and closed it up for the night when the forge was still extremely hot. The result was that after the 2 normalizings that I had done on the blade, the high temperature ruined the blade by causing large grain growth "after" I had reduced it. Lesson learned on that bowie, it broke with large grains showing.
I think that 52100 is supposed to start growning grain at about 1750. It could very well start before that but I know it won't at 1500. I believe that time will have some effect on steels at the higher temperatures but it has to reach a temperature that the grain will start to grow before it can increase in grain size.
I have also put a blade in the forge and closed it up for the night when the forge was still extremely hot. The result was that after the 2 normalizings that I had done on the blade, the high temperature ruined the blade by causing large grain growth "after" I had reduced it. Lesson learned on that bowie, it broke with large grains showing.
