APPLICATION OF NUCLEAR REACTOR COOLING TECHNOLOGY THAT USES LIQUID SODIUM TO METALLIC HEAT-TREATMENT PROCESS

为了提高钠淬火过程中相变、变形和应力的预测精度，对钢筒和钢盘进行了淬火试验。通过将测量结果与热处理工艺分析程序模拟的结果进行比较，验证了分析的准确性。两种热处理工艺分析程序(GRANTAS、DEFORM-HT)计算的冷却曲线、硬度、变形量的测量值与分析值吻合较好。钠冷工艺模拟结果表明，钢件表面在第一冷却阶段均匀快速冷却，在表面附近形成硬质马氏体层，表面硬度均匀，变形小，无裂纹。此外，在较低温度区域(低于ms点)的冷却速度可以通过钠淬火来控制。此外，还证实了均匀快速淬火对零件表面产生了残余压应力。对带键槽的钢轴等非轴对称形状零件进行了淬火试验和淬火过程模拟。通过对复杂形状钢件进行淬火处理，证实了钠淬火对控制变形和裂纹的实际应用效果。

The quenching experiment of steel cylinder and steel disc was executed to improve the prediction accuracy of the phase transformation, distortion and stress during sodium quenching. Analytical accuracy was verified by comparing measured results with the result simulated with the heat-treatment process analysis code. It was confirmed that these measurement values and analytical values of cooling curves, hardness, distortion of steel specimens calculated by two heat-treatment process analysis codes (GRANTAS, DEFORM-HT), showed a good agreement. The simulation result of sodium quenching process showed that hard martensite layer near the surface of steel parts created by uniform rapid cooling on whole surface of steel parts in the first cooling stage results in uniform surface hardness, lower distortion, no cracking. In addition, the cooling rate in the lower temperature region (lower than Ms point) can be controlled by sodium quenching. Moreover, it was confirmed that the compressive residual stress was generated to surfaces of parts by uniform and rapid quenching. The quenching experiment and the simulation of quenching process of nonaxisymmetric shaped parts such as the steel axes with a key groove etc. was are executed. It was confirmed that sodium quenching is effective for practical use to control of the distortion and the cracking by hardening the complex shaped steel parts.