Tham khảo tài liệu 'modeling and simulation for material selection and mechanical design part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Figure 29 Simulation of temperature and progress of transformation of mass C steel under different cooling conditions on run-out table of a hot-strip mill. a of 1670kJ m2hK for water cooling. In this calculation the finish rolling temperature is 1123 K the coiling temperature is 873 K and transformation is completed before coiling. The traveling time through the run-out table can be shortened from to about 5 sec by increasing the heat transfer coefficient up to 5020kJ m2hK as shown in Fig. 30 b . The figure however shows the undesirable situation where the temperature of steel drops to about 800 K which is below the bainite-start temperature about 823 K for C steel and bainite which deteriorates the quality of steel might appear. This situation can be avoided by changing the cooling condition. Figure 30 c shows the suitable cooling condition in which the water cooling is stopped just before the transformation start and restarted at about 20 transformation. Copyright 2004 by Marcel Dekker Inc. All Rights Reserved. Figure 31 Temperature changes of steel at two different positions in the direction of width on the run-out table. Figure 32 Temperature change of steel at two different positions in the direction of width on the run-out table. Cooling condition was modified from that in Fig. 31. Copyright 2004 by Marcel Dekker Inc. All Rights Reserved. Distance from the edge cm Figure 33 Changes in the index of hardness Ae1 TP 1 2 in which TP is the mean pearlite transformation temperature along the width under two different conditions. axis Ae1 TP Ỵ 7 where TP is the mean transformation temperature of pearlite representing hardness of pearlite because the pearlite hardness depends on the lamella spacing of pearlite which depends upon the under-cooling from Ae1 temperature. Conditions A and B in Fig. 33 correspond to those in Figs. 31 and 32. This result indicates that the fluctuations of properties due to the variation of temperature along the width can .
