65Mn/Q235双金属复合管的热处理工艺优化及其耐磨性

Heat Treatment Process Optimization and Wear Resistance of 65Mn/Q235 Bimetal Composite Pipe

采用金相显微镜、扫描电子显微镜、洛氏硬度计、显微硬度计和磨粒磨损试验机,分析了65Mn/Q235双金属复合管在使用过程中失效的原因,并对其热处理工艺进行了优化。结果表明:65Mn钢中存在大量的未溶碳化物和层片状珠光体,导致其韧性降低、焊缝硬度较低,使65Mn/Q235双金属复合管在服役过程中因耐磨性不足而失效。采用优化的热处理工艺即840℃保温10~30 min油冷后,65Mn/Q235双金属复合管的组织为均匀细小的马氏体,未溶碳化物和层片状珠光体基本消除,焊缝硬度得到提高,耐磨性明显改善。

Causes of the failure of 65Mn/Q235 bimetal composite pipes in service were analyzed by using metallographic microscope,scanning electron microscope,Rockwell hardness tester,microhardness tester,and abrasive wear testing machine,and their heat treatment process was optimized.The results showed that there were a large amount of undissolved carbides and lamellar pearlites in 65Mn steel,which led to a decrease in its toughness and lower hardness of the weld,resulting in the failure of 65Mn/Q235 bimetal composite pipes in service due to insufficient wear resistance.After an optimized heat treatment process,that is,holding at 840℃for 10 to 30 min and cooling in oil,was used,the microstructure of 65Mn/Q235 bimetal composite pipe was uniform and fine martensites,undissolved carbide and lamellar pearlite were basically eliminated,the hardness of the weld was increased,and its wear resistance was improved significantly.