無損檢測試題教材系列

最新資料推薦 無損檢測試題教材系列之UT超聲檢測工藝規(guī)程（最通用版）NJBSTCo.,Ltd.QCD-013Rev.:0Page:1of12Title:ULTRASONICEXAMINATIONPROCEDUREULTRASONICEXAMINATIONPROCEDURE超聲波檢驗工藝規(guī)程CONTROLLED在控本口 UNCONTROLLED非在控本口 COPYNO副本編號：PREPAREDBY編制：DATE日期：REVIEWEDBY審核：DATE日期：APPROVEDBY批準(zhǔn)：DATE日期：NJBSTCo.,Ltd.QCD-013Rev.:0Page:2of12Title:ULTRASONICEXAMINATIONPROCEDUREDEMONSTRATIONCERTIFICATION更多資料：無損檢測招聘網(wǎng)piledinaccordancewiththerequirementsofASMECodeSectionVandSection伽Division1. 1.2Inaccordancewiththisprocedureapulse-echotypeofultrasonicinstrumentshallbeusedforCodeproductexamination.Singleprobe,anglebeamscanningshallbetheprincipalmethod,ifnecessary,straightbeamscanningmayalsobeused.1.3Thisprocedureisapplicableforultrasonicexaminationofbutt-welded,fullpenetratedjointinwrought(rolled,drawn,forgedorextruded)materialwiththicknessequaltoorgreaterthan5/16in.(8mm)detecting,locatingandevaluatingthereflectorsfromtheweldmetal,heataffectedzoneandbasemetaladjacenttheweld.1.4Ultrasonicexaminationofsinglesideweldedpartialpenetratedweldsandausteniticsteelweldsarenotconsideredtobewithinthescopeofthisprocedure.1.5Unlessotherprocedurehasbeenapprovedandacceptedthatmayspecifyparticularrequirements,ultrasonicexaminationrelatingtomethod,evaluation,anddetailedtechniqueandrequirementshallbeinaccordancewiththisprocedure.2.NDEPERSONNEL2.1NDEpersonnelshallbequalifiedandcertifiedaccordingtoNJBSTSWrittenPracticeQCD-011basedonSNTTC-IA(CurrentCodeAcceptedEdition).3.GENERALEXAMINATIONREQUIREMENTS3.1ExaminationcoverageThevolumeshallbeexaminedbymovingthesearchunitovertheexaminationsurfacesoastoscantheentireexaminationvolume.Eachpassofthesearchunitshalloverlapaminimumof10%ofthetransducer(piezo-electricelement)dimensionperpendiculartothedirectionofthescan.3.2SpeedofSearchUnitMovementsThespeedofsearchunitmovementforexaminationshallnotexceed6in./sec（150mm/sec.）3.3RecordingLevelAllreflectionsfromuncorrectedareashavingresponsesthatexceed50%ofreferencelevelshallberecorded.Thisrecordshalllocateeacharea,theresponselevel,thedimensions,thedepthbelowthesurface,andtheclassification.4.ULTRASONICINSTRUMENT,SEARCHUNITANDPARAMETERS4.1UltrasonicInstrumentApulse-echotypeofultrasonicinstrumentshallbeused.Thefollowinginstrumentsarerecommendedinexamination.InstrumentTypeCTS-261.適用范圍1.1本規(guī)程按ASME第V卷和第伽第1分冊要求編制。1.2按規(guī)程對規(guī)范產(chǎn)品的檢查用脈沖反射式超聲波探傷儀。以單斜探頭掃查為主要方法，必要時可輔以直探頭掃查。1.3本規(guī)程適用于板厚8mm鋼制壓力容器全焊透對接焊縫的超聲檢查（包括焊縫金屬和熱影響區(qū)）。1.4本規(guī)程不適用于單面焊部分焊透焊縫的檢查，也不適用于奧氏體鋼焊縫的的檢查。1.5除非其他程序經(jīng)批準(zhǔn)、有關(guān)具體要求經(jīng)認(rèn)可，UT有關(guān)方法、評定、要求應(yīng)按本規(guī)程。無損探傷人員2.1無損探傷人員應(yīng)按本公司根據(jù)SNT-TC-IA（現(xiàn)行版）制定的NDE人員培訓(xùn)、考試、資格鑒定和認(rèn)證的實施細(xì)則進(jìn)行資格鑒定和認(rèn)證。一般探傷要求3.1探測范圍 應(yīng)通過探頭在探測面的移動，使焊縫全體積均受超聲束掃查。探頭的掃查路徑應(yīng)至少重疊探頭橫向?qū)挾鹊?0%3.2探頭移動速度探傷時，探頭移動速度應(yīng)不大于150mm/s。3.3記錄水平 凡波高超過50%DAC基準(zhǔn)線而未予返修的訊號均應(yīng)記錄在案。超聲儀、探頭和參數(shù)4.1超聲儀應(yīng)使用下列脈沖反射式超聲儀：ManufacturedbyShantou,China儀器型號CTS26制造單位汕頭超聲儀器廠 NJBSTCo.,Ltd.QCD-013Rev.:0Page:4of12Title:ULTRASONICEXAMINATIONPROCEDURE4.2SearchUnitForstraightbeam,thediameteroftransducershallbe14mm-25mm.Foranglebeam,anangleshallbeselectedasappropriatefortheconfigurationbeingexamined.Thefollowingsearchunitsarerecommendedtobeusedinexamination: Therangeofangleisrecommendedasfollowing: 4.3FrequencyGenerally,thefrequencyof2.5MHzshallbeused.Forthethinnerplate,5MHzmaybeused.4.4ScreenHeightlinearityTheultrasonicinstrumentshallprovidelinearverticalpresentationwithin5%ofthefullscreenheightfor20%to80ofthecalibratedscreenheight(baselinetomaximumcalibratedscreenpoint(s)).TheprocedureforevaluatingscreenheightlinearityisprovidedinAppendixIofASMECodeSect.VSub.AArticle5andshallbeperformedatthebeginningofeachperiodofextendeduse(orevery3months,whicheverisless).4.5AmplitudeControlLinearityTheultrasonicinstrumentshallutilizeanamplitudecontrolaccurateoveritsusefulrangeto20%ofthenominalamplituderatio,toallowmeasurementofindicationsbeyondthelinearrangeoftheverticaldisplayonthescreen.TheprocedureforevaluatingamplitudecontrollinearityisgiveninASMESectV.Art.5.AppendixIIandshallbeperformedatthebeginningofeachperiodofextendeduse(orevery3months,whicheverisless).4.6CheckingandCalibrationofEquipmentTheproperfunctioningoftheexaminationequipmentshallbecheckedandtheequipmentshallbecalibratedbytheuseofthecalibrationstandardatthebeginningandendofeachexamination.,whenexaminationpersonnelarechanged,andatanytimethatmalfunctioningissuspectedasaminimum.Ifduringanycheckitisdeterminedthatthetestingequipmentisnotfunctioningproperly,4.2探頭直探頭直徑應(yīng)為14~25mm.斜探頭應(yīng)根據(jù)被檢工件厚度適當(dāng)選用(參照下表):探頭折射角與被檢壁厚關(guān)系：4.3頻率通常應(yīng)頻率2.5MHz,對薄板，可采用5MHz。4.4屏高線性超聲應(yīng)提供5%滿屏高的垂直線性（在20%至80%校正屏高的范圍內(nèi)）。屏高線性的測評方法按ASME第V卷A篇第5章附錄I,應(yīng)在每一周期開始（或每3個月，取兩者中時短者）測評一次。4.5波幅控制線性為能測量示波屏上超出垂直線性范圍的信號，超聲儀應(yīng)有在有用范圍內(nèi)可精確到標(biāo)稱波幅比20%的波幅控制器。評定波幅控制線性的方法，見ASME第V卷第5章附錄II。此評定應(yīng)在每一延長使用周期開始時進(jìn)行（或每3個月進(jìn)行一次，取兩者中較短的時間）。4.6設(shè)備校驗對探傷設(shè)備應(yīng)使用校正試塊于每次檢查開始和結(jié)束時進(jìn)行性能校驗，當(dāng)探傷人員更換時，或懷疑有故障時，也要校驗。校驗時發(fā)現(xiàn)探傷設(shè)備性能不佳時，所有產(chǎn)品均應(yīng)重新檢查（自設(shè)備上次有效校驗算起）。校正SearchUnittypeBeamAngle（）FrequencyManufacturedby2.5P8x124502.5MHzShantou,China2.5P8x125602.5MHzShantou,China2.5P8x126302.5MHzShantou,China2.5P8x126802.5MHzShantou,ChinaWallThickness(mm)BeamAngle()720-630KValue(tg)8-253.0-2.025-46680-5602.5-1.546630-4502.0-1.0探頭折射角()頻率制造單位2.5P8x124502.5MHz汕頭超聲儀器廠汕頭超聲儀器廠汕頭超聲儀器廠汕頭超聲儀器廠2.5P8x125602.5MHz2.5P8x126302.5MHz2.5P8x126802.5MHz壁厚(mm)折射角()K值(tg)8-25720-6303.0-2.025-46680-5602.5-1.546630-4502.0-1.0alloftheproductthathasbeentestedsincethelastvalidequipmentcalibrationshallbereexamined.5.CALIBRATION5.1BasicCalibrationBlockConfigurationNJBSTCo.,Ltd.QCD-0135.1基本校正試塊Rev.:0Page:5of12Title:ULTRASONICEXAMINATIONPROCEDUREThebasiccalibrationreflectorsshallbeusedtoestablishaprimaryreferenceresponseoftheequipment.Thebasiccalibrationreflectorsmaybelocatedeitherinthecomponentmaterialorinabasiccalibrationblock.GENERATENOTES:(a)Holesshallbedrilledandreamedminimumof3/2in.deep,essentiallyparalleltotheexaminationsurface.alternatively,theblockmaybeconstructedasshowninASMECodeSectionV,Article4,AppendixJ,Fig.J-10.(c)Curvedsurfaces:forcurvedsurfaces,twocurvedblocks,oneforeachrepresentativecurvature;ortwosetsofcalibrationreflectorsoriented90deg.fromeachothershallbeused.(d)Notchesmaybeprovidedasrequired.(e)Thetoleranceforholediametershallbe1/32in.Thetoleranceonnotchdepthshallbe+10and20%.Thetoleranceonholelocationthroughthethicknessshallbe1/8in.NOTE:(1)Foreachincreaseinweldthicknessof2in(50.8mm)orfraction應(yīng)使用能測定設(shè)備主要基準(zhǔn)性能的基本校正反射體。這些反射體可設(shè)定在基本校正試塊或試樣中。圖1基本校正試塊in.(mm) 說明：應(yīng)是鉆孔和鉸孔，深度至少為3/2(38mm)，基本平行于探測面。試塊也可按ASME第V卷，第4章附錄J，圖J-10制作。曲面：對曲面應(yīng)有兩個曲面校正試塊，各自具有所代表的曲率；兩組互成900的校正反射體。切槽按需設(shè)定?？讖饺菰S公差1/32(0.8mm),切槽深容許公差+10%、-20%，沿厚度方向孔位公差1/8in.(3.2mm)。注：厚度10in.(254mm以上)，厚度每增加2in(50.8mm)，孔徑應(yīng)增加1/16in.(1.6mm)ThicknessofWeld(T)焊縫厚度(T)1(25.4)1-2(25.4~50.8)2-4(50.8~101.6)4-6(101.6~127)ThicknessofBlock(T)試塊厚度(T)3/4(19.05)ortHoleDiameter孔徑3/32NotchSize切槽尺寸width=1/8to1/4(3.2~6.4)1-1/2(38.1)ort1/8(3.2)3(76.2)ort5(127)ort3/16(4.8)1/4Depth=2%Tor0.04(1.0)Whicheverisgreater.6-8(127~203.8)7(77.8)ort5/16(8.0)Intothebasemetal.8-10(203.2~254)10(254)9(228.6)ortt1(t+25.4)3/8(9.5)Note(1)Length=2(50.8)(min.)thereofover10in,(254mm),theholediametershallincrease1/16in.(1.6mm)5.2BasicCalibrationBlockMaterial5.2.1BlockSelection.Thematerialfromwhichtheblockisfabricatedshallbeofthesameproductform,andmaterialspecificationorequivalentP-Numbergroupingasoneofthematerialsbeingexamined.Forcalibrationblocksfordissimilarmetalwelds,thematerialselectionshallbebasedonthematerial5.2基本校正試塊材料5.2.1試塊材料選擇 制作試塊的材料應(yīng)與被檢材料中的一種具有相同的產(chǎn)品形式、材料規(guī)范或相當(dāng)?shù)腜號組。探測異種金屬焊縫時，所用校正試塊應(yīng)按進(jìn)行探傷的焊縫一側(cè)的材料。若探傷在焊縫兩側(cè)進(jìn)行，則校正反射體應(yīng)設(shè)在兩種材料中。被檢焊縫NJBSTCo.,Ltd.QCD-013Rev.:0Page:6of12Title:ULTRASONICEXAMINATIONPROCEDUREonthesideoftheweldfromwhichtheexaminationwillbeconducted:iftheexaminationwillbeconductedfrombothsides,calibrationreflectorsshallbeprovidedinbothmaterials.Wheretwoormorebasematerialthicknessesareinvolved,thecalibrationblockthicknessshallbedeterminedbytheaveragethicknessoftheweld.5.2.2Clad.Wherethecomponentmaterialisclad,theblockshallbecladbythesameweldingprocedureastheproductionpart.Wheretheautomaticmethodisimpractical,depositionofcladshallbebythemanualmethod.Itisdesirabletohavecomponentmaterialswhichhavebeencladbeforethedropoutsorprolongationsareremoved.5.2.3HeatTreatment.Thecalibrationblockshallreceiveatleasttheminimumtemperingtreatmentrequiredbythematerialspecificationforthetypeandgrade,andalsoapostweldheattreatmentofatleast2hr,ifthecalibrationblockcontainsweld(s).5.2.4SurfaceFinish.Thefinishonthesurfacesoftheblockshallberepresentativeofthesurfacefinishesonthecomponent.5.2.5BlockQuality.Thecalibrationblockmaterialshallbecompletelyexaminedwithastraightbeamsearchunit.Areasthatcontainanindicationexceedingtheremainingbackreflectionshallbeexcludedfromthebeampathsrequiredtoreachthevariouscalibrationreflectors.5.3CalibrationReflectors5.3.1BasicCalibrationReflectorsThecalibrationreflectorsarespecifiedinFig.15.3.2WeldsinMaterialswithDiameters20in.(508mm)andless.Thebasiccalibrationblockshallbecurvedformaterialswithdiameters20in.(508mm)andless.Exceptwhereotherwisestatedinthisprocedureasinglecurvedbasiccalibrationblockmaybeusedtocalibratetheexaminationonsurfacesintherangeofcurvaturefrom0.9to1.5timesthebasiccalibrationblockdiameter6.SYSTEMCALIBRATION(GENERAL)6.1AngleBeamCalibration(Transversalwave)asapplicablethecalibrationshallprovidethefollowingmeasurements: (a)sweeprangecalibration;(b)distance-amplitudecorrection(DAC);(C)positioncalibration;(d)echoamplitudemeasurementfromthetransversedrilledholeinthebasiccalibrationblock.6.2StraightBeamCalibrationThecalibrationshallprovidethefollowingmeasurements:(a)sweeprangecalibration;(b)distance-amplitudecorrection(DAC). 6.3CalibrationConfirmationCalibrationshallbeperformedpriortouseofthesysteminthethicknessrangeunderexamination. 涉及到兩種以上的壁厚時，校正試塊厚度應(yīng)按焊縫平均厚度確定。5.2.2堆焊層 當(dāng)部件材料有堆焊層時，試塊也應(yīng)有堆層，其堆焊層規(guī)程應(yīng)與產(chǎn)品零件一樣。若不能采用自動焊方法，則應(yīng)用手工焊方法堆焊。最好是采用切除的或延長部分未除去堆焊的部件材料。5.2.3熱處理校正試塊應(yīng)按材料牌號要求，至少作最低程度的回火處理。若校正試塊中含有焊縫，則還需作至少2小時的焊后熱處理。5.2.4表面粗糙度試塊表面粗糙度應(yīng)代表工件表面粗糙度。5.2.5試塊質(zhì)量。校正試塊材料應(yīng)使用直探頭作全面檢查。在聲束到達(dá)多種校正反射體的聲路中。不得有超過底波反射的信號存在。5.3校正反射體5.3.1基本校正反射體校正反射體按圖1規(guī)定。5.3.2直徑20in(508mm)的材料，基本試塊應(yīng)為曲面。除本規(guī)程另有說明外，一個單一曲面的基本校正試塊，可用來校正表面曲率范圍為0.9~1.5倍基本校正試塊直徑的檢驗。系統(tǒng)校驗6.1斜探頭校驗(橫波)應(yīng)作下列測定：(a)掃查范圍校正(b)距離-波幅校正(DAC)(C)位置校正(d)基本校正試塊中橫孔回波幅度的測定。6.2直探頭校驗應(yīng)作下列測定(a)掃查范圍校正:(b)距離-波幅校正(DAC)6.3校驗確認(rèn)使用儀器前，應(yīng)按被檢厚度范圍進(jìn)行校準(zhǔn)。NJBSTCo.,Ltd.QCD-013Rev.:0Page:7of12Title:ULTRASONICEXAMINATIONPROCEDURE6.3.1SweepRangeCorrection.IfapointontheDACcurvehasmovedonthesweeplinemorethan10%ofthesweepreadingor5%offullsweep,whicheverisgreater,correctthesweeprangecalibrationandnotethecorrectionintheexaminationrecord.Ifreflectorsarerecordedonthedatasheets,thosedatasheetsshallbevoidedandanewcalibrationshallberecorded.Allrecordedindicationssincethelastvalidcalibrationorcalibrationcheckshallbereexaminedwiththecorrectedcalibrationandtheirvaluesshallbechangedonthedatasheets.6.3.2DACCorrection Ifapointonthedistance-amplitudecorrection(DAC)curvehasdecreased20%or2dBofitsamplitude,alldatesheetssincethelastcalibrationorcalibrationcheckshallbemarkedvoid.Anareacoveredbythevoideddatashallbereexamined.Ifanypointofthedistanceamlitudecorrection(DAC)curvehasincreasedmorethan20%or2dBofitsamplitude,allrecordedindicationssincethelastvalidcalibrationorcalibrationcheckshallbereexaminedwiththecorrectedcalibrationandtheirvaluesshallbechangedonthedatasheets.EXAMINATION7.1Surfacepreparation7.1.1BaseMetalThebasemetaloneachsideoftheweldshallbefreeofweldspatter,surfaceirregularities,orforeignmatterthatmightinterferewiththeexamination.7.1.2WeldMetalWheretheweldsurfaceinterfereswiththeexamination,theweldshallbepreparedasneededtopermitexamination.7.2CouplantThecouplantusedinUTexaminationshouldbeassameasthatusedincalibration.TheNo.20motoroilorglycerinorpaste(C.M.C)shallberecommendedtouse.7.3ScanningRequirements7.3.1AngleBeamScanning7.3.1.1ScanningforReflectorsOrientedParalleltotheWeldTheanglebeamshallbedirectedatapproximaterightanglestotheweldaxisfromtwodirectionswherepossible.Thesearchunitshallbemanipulatedsothattheultrasonicenergypassesthroughtherequiredvolumesofweldandadjacentbasemetal.Thescanningshallbeperformedatagainsettingatleasttwotimestheprimaryreferencelevel.Evaluationshallbeperformedwithrespecttotheprimaryreferencelevel.7.3.1.2ScanningforReflectorsOrientedTransversetoWeldTheanglebeamshallbedirectedessentiallyparalleltotheweldaxis.ThesearchunitshallbemanipulatedsothattheanglebeampassesthroughtherequiredvolumesofweldandadjacentbasemetalspecifiedbythereferencingCodeSection.Thescanningshallbeperformedatagainsettingatleasttwotimestheprimaryreferencelevel.Evaluationshallbeperformedwithrespecttotheprimaryreferencelevel.Thesearchunitshallberotated180deg.andtheexaminationrepeated. 6.3.1掃描范圍校正如果DAC曲線上某一點沿掃描線的偏移超過掃描分格讀數(shù)10%或滿刻度5%（取其中較大者），則需修正掃描范圍的校正，并在檢驗記錄中注明這一數(shù)值。如果已將體記錄在數(shù)據(jù)表中，則這些數(shù)據(jù)表要作廢，并記錄新的校正。從上一有效的校正或校正核查以來所記錄的全部信號，均需用經(jīng)修正的校正重作檢驗，且數(shù)據(jù)表中的這些數(shù)值也要作修改。6.3.2DAC校正若DAC曲線上某一點其波幅減少20%或2dB，則從上一次校正或校正核查以來的所有數(shù)據(jù)表均應(yīng)標(biāo)注取消。應(yīng)進(jìn)行新的校準(zhǔn)和記錄，并對數(shù)據(jù)所包括區(qū)域重作檢驗。若DAC曲線上任何點其波幅增加大于20%或2dB，則從上一次有效校正或校正核查的所有記錄信號，應(yīng)重按修正的校準(zhǔn)檢驗，其數(shù)值也應(yīng)在數(shù)據(jù)表上更改。7.檢驗7.1表面準(zhǔn)備7.1.1母材 焊縫兩側(cè)母材應(yīng)無焊接飛濺、表面不規(guī)則或妨礙探傷的其他雜物。7.1.2焊縫若焊縫表面狀態(tài)妨礙探傷，應(yīng)作適當(dāng)修磨。7.2耦合焊縫UT用的耦合劑應(yīng)與試塊校驗時用的相同。推薦用20#機(jī)油或甘油或化學(xué)漿糊(C.M.C)。7.3掃查要求7.3.1斜探頭掃查7.3.1.1用斜射波探測平行于縫的反射體。斜聲束方向應(yīng)大致與焊縫軸線成直角。如有可能，要從兩個方向進(jìn)行。要適當(dāng)操作探頭，使超聲能量能經(jīng)過所需檢查的焊縫和鄰近母材金屬的體積。掃查中，應(yīng)將增益調(diào)整到比基準(zhǔn)靈敏度至少高一倍。應(yīng)參照靈敏度基準(zhǔn)作出評定。NJBSTCo.,Ltd.QCD-013Rev.:0Page:8of12Title:ULTRASONICEXAMINATIONPROCEDURE7.4StraightBeamThescanningoftheadjacentbasemetalshallbeperformedtodetectreflectorsthatmightaffectinterpretationofanglebeamresults,andisnottobeusedasacceptance-rejectionexamination.Locationsandareasofsuchreflectorsshallberecorded.7.5Theweldandbasemetalshallbescanned,whererequiredbythereferencingCodeSectiontotheextentpossiblewiththestraightbeamsearchunit.Thescanningshallbeperformedatagainsettingofatleasttwotimestheprimaryreferencelevel.8.EVALUATION8.1ExaminationUsingDACForexaminationusingadistanceamplitudecorrectioncurve(DAC),anyreflectorwhichcausesanindicationinexcessof20%ofDACshallbeinvestigatedtotheextentthatitcanbeevaluatedintermsoftheacceptancerejectionstandardsgivenin9ofthisprocedure.9.ACCEPTANCE-REJECTIONSTANDARDSAllimperfectionsthatproduceanindicationgreaterthan20%ofthereferencelevelshallbeinvestigatedtotheextentthattheoperatorcandeterminetheshape,identity,andlocationofallsuchimperfectionsandevaluatethemintermsoftheacceptancestandardsgivenin(a)and(b)below.(a)Imperfectionscharacterizedascracks,lackoffusion,orincompletepenetrationareunacceptableregardlessoflength.(b)Otherimperfectionsareunacceptableiftheindicationsexceedthereferencelevelamplitudeandhavethelengthswhichexceed: Wheretisthethicknessoftheweldexcludinganyallowablereinforcement.Forabuttweldhavingdifferentthicknessesattheweld,tisthethinnerofthesetwothicknesses.Ifafullpenetrationweldincludesafilletweld,thethicknessofthethroatofthefilletshallbeincludedint.10.RECORDSANDREPORTS10.1CalibrationRecordsInstrumentcalibrationsshallbeincludedintheultrasoniccalibrationrecords.Ultrasonicexaminationsystemcalibrationrequirementsandcalibrationblockidentityshallbeincludedintheultrasoniccalibrationrecords.10.2ExaminationRecordsForeachultrasonicexamination,thefollowinginformationshallbeidentifiedandrecorded:7.3.1.2用斜射波對焊縫橫向反射體作掃查。斜射波反射方向基本上與焊縫方向平行。要適當(dāng)操作探頭，以使超聲能量能通過ASME規(guī)范有關(guān)卷規(guī)定的焊縫和鄰近母材金屬的體積。掃查中，應(yīng)將增益調(diào)整到比基準(zhǔn)靈敏度高一倍。應(yīng)參照靈敏度基準(zhǔn)作出評定，應(yīng)將探頭轉(zhuǎn)過1800，并重新檢驗。7.4直探頭應(yīng)對鄰近的母材金屬進(jìn)行直射波掃查，以探測有可能影響斜射波檢驗結(jié)果辨認(rèn)的反射體，但此不作為驗收拒收的檢驗。應(yīng)對這些反射體的位置和區(qū)域作出記錄。7.5當(dāng)規(guī)范有要求時，應(yīng)在可能達(dá)到的范圍內(nèi)用直探頭對焊縫和母材金屬進(jìn)行掃查。掃查中，應(yīng)將增益調(diào)整到至少比基準(zhǔn)靈敏度高一倍。應(yīng)參照靈敏度基準(zhǔn)作出評定。評定8.1用DAC檢驗用DAC曲線時，凡信號超過20%DAC的任何反射體均應(yīng)對其定形、定性、定位，并按本規(guī)程第9條給出的驗收標(biāo)準(zhǔn)作出評定。驗收判廢標(biāo)準(zhǔn)凡信號超過參考基準(zhǔn)20%的缺陷均應(yīng)定形、定性、定位，并按以下驗收標(biāo)準(zhǔn)評定：定為裂紋、未熔合或未焊透的缺陷，無論長短，均不合格：若信號超過參考基準(zhǔn)波幅，且其長度超過下值的其他缺陷均不合格。其中t為不包括許可余高的焊縫厚