THE EFFECT OF PRIOR PARTIAL TRANSFORMATION OF AUSTENITE ON SUBSEQUENT ISOTHERMAL TRANSFORMATION AT LOWER TEMPERATURES

摘要

An investigation of the effects of prior partial transformation at one temperature upon subsequent transformation at a lover temperature showed that the effects were not the same in the three steels studied. The product initiated at a high temperature did not continue to grow at the lover reaction temperature in an SAE 4340 steel and a 1.0 per cent chromium-O.50 per cent carbon steel. That is, a new induction period preceded the start of the re¬action at the lover temperature. Data for a eutectoid steel, which contained 0.80 per cent chromium and 0.75 per cent carbon, suggested that, when large percentages of transformation product were formed at the higher tempera¬ture, the particles continued to grow at the lover temperature, provided the products formed at the two temperatures were similar.