The temperature of molten steel slag produced by the steelmaking process is 1500°c~1700°c, and the total amount of energy contained is considerable. Therefore, the efficient recovery and utilization of sensible heat of steel slag has always been the focus of attention of the metallurgical field all over the world. However, at present, the average recovery rate of waste heat resources per ton of steel in China's iron and steel industry is less than 26%, while the sensible heat recovery rate of various molten slag (including steel slag) is only 1.6%. There are huge room and a broad market for improvement.
The effect of peak temperatures on the grain growth, microstructure transformation and Vickers hardness of the weld coarse grain heat-affected zone (CGHAZ) of SA508 Gr.4N steel for nuclear reactor pressure vessel was studied. The results show that different t8/5 time has no obvious effect on grain growth at the same peak temperature, but different peak temperatures have a great influence. The higher the peak temperature, the more obvious the effect on grain growth. The grain size distribution at different peak temperatures and t8/5 time conforms to the Gaussian normal distribution curve, and a grain growth model suitable for CGHAZ of SA508 Gr.4N steel has been established. The room temperature martensite structure can be obtained by treatment at different peak temperatures and t8/5 time. At the same peak temperature, there is no significant difference in martensite structure at different t8/5 time, and the size of martensite lath only increases with the increasing peak temperatures. At different peak temperatures and t8/5 time, grain size has less effect on the Vickers hardness, which is closely related to the room temperature microstructure of the material.
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