NationalStandardofthePeoplesRepublicofChinaGB700-88Carbonstructuralsteels(extract)5Technicalrequirements5.1 Typeandchemicalcomposition5.1.1 Steeltypeandchemicalcomposition(meltinganalysis)shallaccordwithTable1.Table1TypeGradeChemicalcomposition,%DeoxidizationmethodCMnSiSPmaximumQ195一0.060.120.250.500.300.050).045F、b、ZQ215A0.090.150.250.550.300.0500.045二、b、ZB0.045Q235A0.140.220.300.651)0.300.0500.045二、b、ZB0.120.200.300.701)0.045C0.180.350.800.040).040ZD0.170.035).035TZQ255A0.180.280.400.700.300.0500.0451ZB0.045Q275-0.280.380.500.800.350.050).045ZNote:1)ForQ235A.BboilingsteeltheupperlimitofMnContentis0.60%.5.1.1.1 ForboilingsteeltheSishallbenotmorethan0.07%,forsolidsteeltheSishallbenotmorethan0.17%,forsolidsteeltheminimumcontentofSiis0.12%.5.1.1.2 Dgradesteelshallhasadequateelementswhichcouldcomeintobeingcrystalpattern,forinstanceAlsshallnotlessthan0.015%orAltisnotlessthan0.020%.5.1.1.3 ForcontentsofimpuritiesCr,Ni,Cushallallbenotmorethan0.30%,forOxygenconvertersteelNshallnotmorethan0.008%,itcouldnotmakeanalysisincasethesupplierpromised.ForAgradesteelthecontentofCumaynotmorethan0.35%incasethedemanderaccepted,meanwhilethesuppliershallfinishCuanalysisofsteelandindicatethecontentintheQualityCertificate.5.1.1.4 ResidualcontentofAsofsteelshallnotmorethan0.080%.Forsteelthatformedfrompig-ironsmeltingwithmineralrichofAs,theAscontentcouldbenegotiatedbybothsupplieranddemander.IncasethereisnoAsintherawmaterial,theAsanalysisisnotnecessary.5.1.1.5 ForcontentofC,MnofalltypesofAgradesteelandotherclasssteel,thelowerlimitisnotconditionsofdelivery,andthecontentofC,Mn(meltinganalysis)shallbeindicatedintheQualityCertificate,howeverthepriorbasisisthemechanicalpropertiesofsteelshallaccordwiththisstandard.5.1.1.6 Thesuppliershallguaranteethechemicalcomposition(meltinganalysis)accordwiththetable1whiletheysupplythesteelingot(includingcontinuouscastingblank)andbilletsteel.Tomakethepropertiesofrolledsteelcomplywiththisstandard,thechemicalcompositionofalltypesofA,Bgradesteelcouldbeadjustedaccordingtothedemandersrequirementswhichcouldsignotheragreements.5.1.2 Thechemicalcompositiontoleranceoffinishedsteelandbilletsteelshallaccordwithtable1ofstandardGB222.Itshallnotguaranteethechemicalcompositiontoleranceoffinishedsteelwhichmadefromboilingsteel,sodoesthebilletsteel.5.2 SmeltingmethodSteelshallbesmeltedbyoxygenconverter,openhearthfurnace,orelectricfurnaceandindicatedinthecontract.Thesmeltingmethodgenerallydeterminedbythesupplier.5.3 DeliverystatusItgenerallydeliverythesteelwithhotrolledsteelstatus(includingcontrolledrolling).Incasethedemanderrequire,normalizingtreatmentstatusisacceptedunderthenegotiation(Agradesteelexcluded).5.4 Mechanicalproperties5.4.1Tensiletestandimpacttestshallaccordwithtable2,bendtestshallaccordwithtable3.Table2StretchingtestImpacttestYieldpointO-s,N/mm2Elongation65,%CharpyTypeGradeThickness(Diameter),mmTensileThickness(Diameter),mmTemperatureV-Notch164060100150strengtho-N/mm2164060100150CImpactTest40601001504060100150JTable3TypeSampledirectionColdbendtestB=2a180Thickness(Diameter),mm6060100100200thediameterofcurvecenterdQ195ongitudinal0-ateral0.5aQ215ongitudinal0.5a1.5a2aaterala2a2.5aQ235ongitudinala2a2.5aateral1.5a2.5a3aQ2552a3a3.5aQ2753a4a4.5aNote:“ B” is the width of the sample,is the thickness ofathesteel(diameter).5.4.1.1 TheyieldpointoftypeQ195isforreference,itisnotconditionsofdelivery.5.4.1.2 Itshalluselateralsamplesofsteelsheetandsteelstripwhilecarryingoutthestretchingandbendingtests,percentageofelongationcouldbe1%lessthanthatoftable2(absolutevalue),however,structuralsteelshalluselongitudinalsamples.5.4.1.3 ThecoldbendtestofalltypesofAgradesteelisonlycarriedoutthedemanderrequired.Theupperlimitoftensilestrengthcouldnotberegardedasconditionsofdelivery.