大直径P91钢管淬火裂纹分析  

Analysis of Quench-caused Crack of Large-sized P91 Steel Tube

作　　者：田研[1] 彭先明[1] 左国锋 周勇[1] TIAN Yan;PENG Xianming;ZUO Guofeng;ZHOU Yong(Hengyang Valin Steel Tube Co.,Ltd.,Hengyang 421001,China)

机构地区：[1]衡阳华菱钢管有限公司,湖南衡阳421001

出　　处：《钢管》2020年第3期34-37,共4页Steel Pipe

摘　　要：分析一种大直径厚壁P91钢管的外表面裂纹,通过观察裂纹的宏观和微观形貌,发现裂纹无氧化脱碳和夹杂,断口呈脆性断裂,符合淬火应力开裂的特征。经现场调查分析,认为裂纹是热处理过程中冷却不均匀形成的,是一种淬火裂纹。通过改变钢管水淬时的冷却条件,如清理淬火槽内氧化铁皮,使水淬时钢管不相互接触,同时加强槽内水的循环或采用外淋+内喷钢管旋转装置进行冷却等,可避免P91钢管在热处理生产过程中的冷却不均匀,从而杜绝淬火裂纹。Analyzed in the essay is the outer surface crack of the large-sized,heavy-wall P91 steel tube.It is identified via observation of the macro and micro morphologies of the crack that the crack is free of any oxidation/decarbonization and inclusion,and the fracture is of the brittle fracture,which is in confoimance with the characteristic of the quench-caused cracking.Based on relevant on-the-site investigation,it is regarded that the crack is of a quench-caused type as formed due to uneven cooling during the heat treatment process.Accordingly actions aiming at improving the cooling conditions for the steel tube during the quenching operation as below need to be taken to have the steel tube avoiding uneven cooling during the heat treatment operation so as to completely stop the said quench-caused crack.Such actions include cleaning the primary scale in the quenching tank to get the tubes avoid touching to each other during the quench operation,and strengthening the circulation of the water in the tank or adopting the external showing+internal spraying tube-rotation device to cool the tube,etc.

关 键 词：P91 淬火裂纹 脱碳 马氏体转变 

分 类 号：TG157[金属学及工艺—热处理]