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    大直徑P91鋼管淬火裂紋分析

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

    • 摘要: 分析一種大直徑厚壁P91鋼管的外表面裂紋，通過觀察裂紋的宏觀和微觀形貌，發(fā)現(xiàn)裂紋無氧化脫碳和夾雜，斷口呈脆性斷裂，符合淬火應力開裂的特征。經(jīng)現(xiàn)場調查分析，認為裂紋是熱處理過程中冷卻不均勻形成的，是一種淬火裂紋。通過改變鋼管水淬時的冷卻條件，如清理淬火槽內氧化鐵皮，使水淬時鋼管不相互接觸，同時加強槽內水的循環(huán)或采用外淋+內噴鋼管旋轉裝置進行冷卻等，可避免P91鋼管在熱處理生產(chǎn)過程中的冷卻不均勻，從而杜絕淬火裂紋。

       

      Abstract: 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 conformance 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.

       

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