9NiCrMoV钢淬火过程传热系数仿真分析与试验

Simulation analysis and experimental of heat transfer coefficient of 9NiCrMoV steel during quenching

船用中厚钢板在淬火过程中因截面冷速差异极易造成表面至心部组织性能不均匀,导致心部韧性波动或不达标。要明确不同冷速对组织性能的影响以调控钢材的性能,冷速的定量化测定就极为重要。鉴于实际测量工业厚板淬火冷速难度很大,可通过实验室小样物理模拟9NiCrMoV船用厚板钢不同厚度部位,对其进行不同冷速淬火处理,对比相同淬火工艺处理后的试样和工业厚板不同部位的组织性能,从而反推出厚板不同部位的淬火冷速和综合传热系数。试验采用在试样内部封装热电偶外接高频数据采集仪的办法,精确计算了实验室小样的淬火冷速。结果表明:尺寸为20 mm×20 mm×230 mm的试样在850和800℃淬火时冷速最大值分别可达85和64℃/s,通过DEFORM反传热模型确定的综合传热系数分别为12000 W/(m^(2)·℃)和8000 W/(m^(2)·℃)。

During the quenching process of marine medium and thick steel plate,due to the difference of section cooling rate,it is very easy to cause uneven microstructure and properties from the surface to the center,resulting in fluctuation of the toughness of the center or failure to meet the standard.The quantitative measurement of cooling rate is very important to understand the influence of different cooling rate on microstructure and properties in order to control the properties of steel.In view of the great difficulty in actually measuring the quenching cooling rate of industrial thick plate,the small samples in the laboratory were used to simulate different thickness part of 9NiCrMoV marine thick plate steel,and then quenching treatments with different cooling rates were carried out.Comparing the microstructure and properties of the small samples with those of the different parts of industrial thick plate treated by the same quenching process,the quenching cooling rate and comprehensive heat transfer coefficient of different parts of the 9NiCrMoV marine thick plate steel can be deduced.The quenching cooling rate of the laboratory samples was accurately calculated by encapsulating thermocouples in the samples and connecting them with high-frequency data acquisition instrument outside.The results show that the maximum cooling rates of the samples with the size of 20 mm×20 mm×230 mm after quenching at 850℃and 800℃are 85℃/s and 64℃/s,respectively,and the comprehensive heat transfer coefficients determined by DEFORM inverse heat transfer model are 12000 W/(m^(2)·℃)and 8000 W/(m^(2)·℃),respectively.