| Latent heat was released in metal phase transformation. Latent heat could influence structural transformation of metallic materials, which could also impact the burst size of latent heat. The impacts between latent heat and structural transformation were mutual. Austenite phase transformation in the air-cooling process after rolling was studied to describe austenite phase transformation exactly. The impacts of latent heat in austenite phase transformation were analyzed in more depth.The law of temperature dropping in 40Cr and low-Nb cores was determined directly by thermocouple in laboratory on the basis of researching the round steel surface state of temperature dropping by air cooling after rolling. The purpose of experiments was ruling out the impacts of anti-heat in surface by core, reflecting the influences of latent heat more accurately. A number of parameters were got by experiments, including curves of temperature dropping and cooling rate in core, temperatures of beginning and ending in metal phase transformation which were contrasted with transformation points in CCT of 40Cr.The round steel 40Cr transient temperature field model was established by finite element method. The design condition of the model was air cooling process after round steel hot rolling in actual products. The model used 40Cr as Research Object, considering calorific losses caused by Heat conduction, radiation, convection and so on, the release of latent heat in phase transformations etc. The temperature distribution and cooling rate of rolling cross-section in the whole cooling were calculated, receiving rules of internal temperature changes over time in two conditions with latent heat and no latent heat of round steel, which laid the foundation for latent heat analysis.Phase transition enthalpies were calculated by anti-algorithm. The result was compared to experimental results calculated with a comprehensive thermal analysis instrument (DSC), and the metallurgical structure in test pieces cooling in constant-speed was examined. Impacts of volume fraction in items caused by latent heat in the conditions of latent heat and no latent heat were calculated on the basis of temperature field simulation. |
