4 welding process 2004

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1、WeldingProcessesTWICourseRef:D73WeldingProcessTWIWeldingProcessesWeldingWeldingtermsProcessthatproducecoalescenceofworkpiecesbyusingpressureorwithoutundercertaintemperature.BS499prt1WeldingtermsAunionbetweenpiecesofmetalatfacesrenderedplasticorliquidbyheat,pressureorboth.WeldingProcesses

2、ALLIEDWELDINGPROCESSFUSIONWELDINGSOLIDSTATEWELDINGRESISTANCEWELDINGBRAZING&SOLDERINGOXYFUELWELDINGLASERWELDINGFusionWeldingFactorsThefouressentialfactorsforfusionwelding1.Fusionisachievedbymeltingusingahighintensityheatsource2.Theweldingprocessmustbecapableofremovinganyoxideandcontaminat

3、ionfromthejoint3.Atmospherecontaminationmustbeavoided4.TheweldedjointmustpossessthemechanicalpropertiesrequiredbythespecificationbeingadaptedManualMetalArcProcess(MMA)SHEILDEDMETALARCWELDING(SMAW)ManualMetalArcProcess(MMA)ParentmaterialElectricArcGasshield(Co2)MoltenweldpoolSolidifiedsla

4、gPenetrationBuildupofweldmetalElectrodecoveringElectrodecorewire(RimmingSteel)SHEILDEDMETALARCWELDING(SMAW)WeldingMachineElectrodeHolderWorkCableReturnCable+ClampPowerSourceWorkPieceEarthBasicMMAEquipmentDiagramWeldingVariablesWeldercontrolsArclengthAngleofelectrodeSpeedoftravelTYPEOFPOL

5、ARITYDIRECTCURRENT(STRAIGHTPOLARITY–ve&REVERSEPOLARITY+ve)ALTERNATINGCURRENTWeldingPowerSourcesDroopingorConstantCurrentCharacteristic20804060130140120100180160200106050403020807090100NormalOperatingVoltageRangeLargevoltagevariation,e.g.+10v(duetochangesinarclength)Smallamperagechangere

6、sultinginvirtuallyconstantcurrente.g.+5A.VoltageAmperageO.C.V.Strikingvoltage(typical)forarcinitiationWeldingPowerSourcesDroopingorConstantCurrentCharacteristicAsthewelderincreasesthearcgap,morevoltsarerequiredforthearctobridgetheincreasedarcgap.LargearcgapRequiresmorevoltsAsthewelderre

7、ducesthearcgap,lessvoltsarerequiredforthearctobridgethereducedarcgap.SmallarcgapRequireslessvoltsManualMetalArc(MMA)ThethreemainelectrodecoveringtypesusedinMMAweldingRutile-generalpurpose(E6013)Basic-lowhydrogen(E7018/7016)Cellulose-deeppenetration/fusion(E6010/6011)FUNCT