UNS S31803双相不锈钢焊接三通开裂失效分析-豆柴文库

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UNSS31803双相不锈钢焊接三通开裂失效分析
Abstract
ThepresentpaperdiscussesthefailureanalysisofUNSS31803duplexstainlesssteelweldingteecracking.Thestudyhighlightsthecausesandcharacteristicsofthefailureandpresentsrecommendationstoavoidsuchfailuresinthefuture.Theanalysisisbasedontheexaminationofthefailedcomponents,themetallographic,andthemechanicaltesting.
Introduction
UNSS31803duplexstainlesssteeliswidelyusedinthepetrochemicalandoilandgasindustriesduetoitsexcellentcorrosionresistanceandmechanicalproperties.However,weldingofduplexstainlesssteelisproblematicduetosensitizationandprecipitationofsecondaryphases.TheprimaryobjectiveofthepresentstudyistounderstandtherootcausesandmechanismsbehindthefailureofUNSS31803duplexstainlesssteelweldingtee.
MaterialsandMethods
ThefailedweldingteewasobtainedfromapetrochemicalplantinChina.Thefailedteewascutandexaminedvisuallyandunderamicroscope.Themetallographicsampleswerepreparedandetchedwith5%oxalicacidsolutiontovisualizethemicrostructure.Themechanicalpropertieswereevaluatedusingatensiletestingmachineandahardnesstester.
ResultsandDiscussion
Visualinspectionofthefailedteeindicatedthatthefailureoccurredduetoacrackthatpropagatedthroughthewallthicknessofthetee.ThecrackhadabutterflyshapeandpropagatedfromtheHAZ(heat-affectedzone)totheweldmetal.Thecrackwaslocatedattheintersectionoftherunandthebranchofthetee.ThemicrostructureexaminationofthefracturedsurfaceshowedthatthecrackinitiatedatthetopsurfaceoftheHAZ(heat-affectedzone)closetothefusionline.ThemicrostructureoftheHAZexhibitedasignificantamountofdeltaandsigmaphases,indicatingthatthematerialhadbeensensitizedduringtheweldingprocess.
Themechanicaltestingresultsshowedthattheultimatetensilestrength(UTS)oftheweldedteewassignificantlylowerthanthebasemetal.ThehardnessoftheHAZwasalsohigherthanthebasemetal,indicatingsensitization.Theresultsindicatethatthecrackingresultedfromacombinationoffactors,includingsensitization,residualweldingstresses,andstrainhardening.
Conclusion
Insummary,thefailureanalysisofUNSS31803duplexst