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The continuous cooling transformation (CCT) behavior of a Ti attached steel was studied through thermal simulation tests, and the influences of different cooling rates on the microstructure and transformation were investigated. The results show that the microstructure changes with the cooling rate, and the CCT curve of studied steel is plotted, which indicates that the solid-state phase transformation mainly consists of four regions. The CCT diagram made it possible to predict the microstructures of studied steel with different cooling rates.

The CCT curve of a C-Si-Mn steel was investigated. The hot simulation tests at different cooling rates were conducted on Gleeble-1500 simulator and microstructures were observed. Based on transformation temperatures recorded by dilation curves and microstructures, the CCT curve diagram for tested steel was plotted. The effects of cooling rate on microstructure and transformation temperature were studied. The results provide the theoretical basis for determination of hot processing and heat treatment technology of C-Si-Mn steels.

The precipitation in continuously casting slabs of a Ti-Nb microalloyed steel was studied. The samples were taken from different places along cross section of slabs and the precipitations were observed by TEM. The results show that the centre area of slab contains more precipitates of Ti-Nb and carbonitrides more uniformly distribute in the centre along thickness direction. Moreover, the precipitates in the middle are more than those in the edge along width direction of slab. Some large carbonitrides exist in the middle of slab because the temperature in the middle is higher during slab cooling resulting in the large precipitates. The study provides the basis for understanding the precipitation in slabs of Ti-Nb microalloyed steels.