稀土微合金化对5CrNiMo钢组织和性能的影响

以稀土为微合金化元素，在实际生产条件下用常规冶炼工艺，将稀土合金以瞬时密流工艺添加到5CrNiMo钢中，采用金相显微镜、扫描电镜等对5CrNiMo钢微观组织进行了系统研究，并进行了常规力学性能和成分检测。各项试验结果表明：加入微量的稀土元素后，5CrNiMo钢中硫含量降至0．009％和0．005％的高纯度钢数量级。退火组织、淬火组织和淬火后回火组织均显著细化，在硬度、强度相当的情况下，5CrNiMo钢的冲击功与不添加稀土元素的同炉次钢相比，分别提高14J和19J，增幅达5l％和68％。在试样表面达到相同龟裂程度时，试样所需的冷热循环周次比不加稀土的试样分别提高了35％和69％。

Effects of RE Microailoying on Microstructure and Properties of 5CrNiMo Steel

Using rare-earth as microalloying element, RE alloys is added to 5CrNiMo steels by instantaneous dense-flow technique under normal processing conditions with conventional smelting methods. The microstructure of 5CrNiMo steels is systematically studied by metallographic microscope and SEM, and mechanical properties and compositions are tested and analyzed. The results show that with little addition of RE elements, the content of S decreases to 0.009% and 0.005%, the value of standard of high-purity steel. The microstructures under heat treatment of anneal, quench and temper after quench are all conspicuously refinement. Compared with 5CrNiMo steels of the same heat without RE additions, the impact work of the steels increases by 51% and 68%, 14J and 19J respectively, while the hardness and strength remained stable. The times of cool-heat cycle operation needed of the samples without RE are increased by 35% and 69% with RE content to the same extent of crazing on the surface of the samples.