英语专业英语书籍强烈推荐Word文档格式.docx

英语专业英语书籍强烈推荐Word文档格式.docx

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2ClassificationofWeldingProcesses

Mostweldingprocessesrequiretheapplicationofenergy（heatorpressure）toproduceasuitablebond.Thereforeweldingprocessesmaybeclassifiedandnamedaccordingtobythetypeofenergysourceemployed.Ifincludingbrazing,theclassificationofweldingprocessesislistedbelow

（1）Fusionwelding

1Oxyacetylenewelding（OAW）

2ArcWelding

Shieldedmetalarcwelding（SMAW）orManualmetalarcwelding（MMAW）

Gasmetalarcwelding（GMAW）,includes:

metalinertgasesarcwelding（MIG）andmetalactivegasesarcwelding（MAG）

Gastungstenarcwelding（GTAW）ortungsteninertgasarcweldng（TIG）

Fluxcoredarcwelding（FCAW）

Electrogaswelding（GMAW-EG;

FCAW-EG）

Plasmaarcwelding（PAW）

Submergedarcwelding（SAW）

3Electroslagwelding（ESW）

4Thermitwelding（TW）

5Laserbeamwelding（LBW）

6Elecrtonbeamwelding（EBW）

（2）Pressurewelding（resistancewelding）

1Spotwelding

2Seamwelding

3Buttwelding

4Coldpressurewelding

5Frictionwelding

6Ultrasonicwelding

7Explosionweldinginvacuum

8Diffusionwelding

9Highfrequencywelding

（3）Brazingwelding

Thiswayofclassifyingweldingprocessesiscalledfamily-treemethod.Infact,thereisnouniformmethodofnamingweldingprocesses.Manyprocessesarenamedaccordingtotheheatsourceorshieldingmethod,butcertainspecializedprocessesarenamedafterthetypeofjointproduced.Examplesarestud,spotandbuttwelding.Anoverallclassificationcannottakeaccountofthisbecausethesametypeofjointmaybeproducedbyavarietyofprocesses.Studweldingmaybedonebyarcorprojectionweldingandspotweldingbyelectricresistance,arcorelectron-beamprocesses.Buttweldingmaybyresistance,flashoranyofanumberofothermethods.Althoughincommonusagemanyprocesseshaveabbreviatednames,thefullnamesoftenfollowthepattern:

first,astatementofthetypeofshielding;

secondly,thetypeofheatorenergysource;

thirdly,thetypeofjoint（wherethisisofspecificandnotgeneralimportance）.

Itisoftennecessarywhenreferringtoprocessestomentionthewaytheyareused,particularlywhethertheoperationismanualorautomatic.Thepracticaloperationofweldingcanbedividedintothreemainparts:

（a）Thecontrolofweldingconditions,particularlyarclengthandelectrodeorfiller-wirefeedrateandtime.

（b）Themovementandguidingoftheelectrode,torchorweldingheadalongtheweldline.

（c）Thetransferorpresentationofpartsforwelding.

Processesaredescribedasmanual,semi-automatic,orautomatic,dependingontheextenttowhichthepartsmentionedaboveareperformedmanually.Manualweldingisunderstoodbethatinwhichtheweldingvariablesarecontinuouslycontrolledbytheoperatorandmeansforweldingheldintheoperator’shand.Semi-automaticweldingisthatinwhichthereisautomaticcontrolofweldingconditionssuchasarclength,rateoffiller-wireadditionandweldtime,butthemovementandguidingoftheelectrode,torchorweldingheadisdonebyhand.Withautomaticweldingatleastparts（a）and（b）oftheoperationmustbedonebythemachine.

3.METALSANDFERROUSMETALS

Metalsaredividedintotwogeneraltypes-ferrousandnonferrous.Ferrousmetalsarethosewhichcontainiron.Nonferrousmetalsarethosewhichdonotcontainiron.However,somenonferrousmetalsmaycontainasmallamountofironasanimpurity.

Steelandcastironarethemostcommonferrousmetalsingeneraluse.Steelisanalloycontainingchieflyiron,carbon,andcertainotherelementsinvaryingamounts.Awiderangeofphysicalpropertiesmaybeobtainedinsteelbycontrollingtheamountofcarbonandotheralloyingelementsandbysubjectingthesteeltovariousheattreatments.

Plaincarbonsteelsusuallycontain,besidesironandcarbon,smallamountsofsilicon,sulphur,phosphorous,andmanganese.Alloysteelsareformedbytheadditionofoneormoreofthefollowingelements:

nickel,chromium,molybdenum,vanadium,tungsten,manganese,silicon,andsmallamountsofotheralloyingelements.

Carbonisbyfarthemostimportantalloyingelementinsteel.Itistheamountofcarbonpresentwhichlargelydeterminesthemaximumhardnessobtainable.Thehigherthecarboncontent,thehigherthetensilestrengthandthegreaterthehardnesstowhichthesteelmaybeheat-treated.

Low-carbonsteelsareusuallyusedforlow-strengthpartsrequiringagreatdealofforming.Medium-carbonsteelsareusedforforgingsandotherapplicationswhereincreasedstrengthandacertainamountofductilityarenecessary.High-carbonsteelsareusedforhigh-strengthpartssuchassprings,tools,anddies.Thefollowinglistisaclassificationofferrousmaterialsaccordingtotheircarboncontent.

FerrousMaterialCarbonContent

WroughtironTraceto0.08%

Low-carbonsteel0.04to0.30%

Medium-carbonsteel0.30to0.60%

High-carbonsteel0.60to1.70%

Castiron1.70to4.50%

Wroughtironisalmostpureiron.Itisnotfrequentlyfoundintheschoolshopbecauseofitshighcost.Itforgeswell,caneasilybebenthotorcold,andcanbewelded.

Carbonsteelsareclassifiedbytheamountofcarbontheycontain.Thisamountisgiveninpoints（100pointsequals1percent）orbypercentage.

A.Low-carbonsteel,oftencalledsoftormildsteel,contains0.04to0.30percentcarbon（4to30points）.Thistypeofsteelisavailableasblack-ironsheet,bandiron,barsandrods.Becauseitiseasilywelded,machined,andformed,low-carbonsteelissuitableforproductsandprojectsinwhichaneasilyworkedmetalisneeded.

B.Medium-carbonsteelhas0.30to0.60percentcarbon（30to60points）.Itisusedformanystandardmachineparts.Intheschoolshopitisusedforprojectslikehammerheadsandclampparts.

C.High-carbonsteelcontains0.60to