关键词: 喷淋淬火, 冷却速度, 力学性能, 静态CCT曲线, 黑匣子试验

Abstract: Water spray quenching of NM500 steel plate with different process parameters was carried out by using quenching machine. The hardness, low temperature impact properties and microstructure of the NM500 steel plate under different quenching processes were studied, and the cooling rate at different positions of the steel plate under the optimal quenching process was measured by black box test. The results indicate that with a constant total water volume for the quenching machine, adopting a double-slot quenching method, distributing more water to slot 1 and appropriately reducing the roll speed, the instantaneous cooling capacity of the steel plate can be significantly enhanced, thereby achieving higher hardness and low temperature impact property. Further verification through microstructure observation, CCT curve of the NM500 steel and on-site black box test confirms that when using the optimal quenching process, the cooling rates of the steel plate surface, quarter thickness and core is close to martensitic critical cooling rate of the NM500 steel, resulting in a fully martensitic structure from the surface to the core of the steel plate.

Key words: water spray quenching, cooling rate, mechanical properties, static CCT curve, black box test