Strain aging embrittlement of 20 steel thick-wall high pressure pipes is an important factor which has a great effect on the pipe long-term operating safety. Lots of heat treatments which were commonly used in engineering were adopted to eliminate or prevent the strain aging brittleness. The effect of the treatments was evaluated by Charpy V-notch impact absorption energy. Microstructure and fracture of specimen morphologies were observed by optical microscopy, scanning electron microscopy and transmission electron microscopy. Microstructure change of materials after different heat treatments was also discussed. The results show that the strain aging embrittlement comes into being in rolling process and is enhanced during the bend-forming process of the pipes. Different heat treatments have different effects to eliminate or prevent the strain aging brittleness, among which normalizing plus high temperature tempering is most effective. The deformation degree has a significant effect on recovering the impact properties of materials and whether aging or not after pre-deformation does not have significant effect on the heat treatment efficiency.%以Charpy V型缺口冲击吸收能量为应变时效脆化评价指标,研究采用工程中常用的热处理方法对应变时效脆化避免和消除的效果,使用光学显微镜、SEM和TEM观察试样组织形貌,探讨了各种热处理下的材料微观组织变化.结果表明:采用的20钢厚壁高压管轧制过程中已发生应变时效脆化,后续的预制更加加重了管子的应变时效脆化程度;不同热处理方法避免和消除应变时效脆化效果不同,其中以正火加高温回火效果最佳;变形度对恢复材料的冲击性能影响显著,预变形后是否时效对热处理的效果没有显著影响.
展开▼
