A0800_A0800M-01(2006)奥氏体合金钢铸件中铁素体含量的估算.pdf

Designation:A 800/A 800M 01(Reapproved 2006)Standard Practice forSteel Casting,Austenitic Alloy,Estimating Ferrite ContentThereof1This standard is issued under the fixed designationA 800/A 800M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers procedures and definitions forestimating ferrite content in certain grades of austenitic iron-chromium-nickel alloy castings that have compositions bal-anced to create the formation of ferrite as a second phase inamounts controlled to be within specified limits.Methods aredescribed for estimating ferrite content by chemical,magnetic,and metallographic means.1.2 The grades covered by this practice are:CF-3,CF-3A,CF-8,CF-8A,CF-3M,CF-3MA,CF-8M,CF-8C,CG-8M,andCH-10.1.3 The values stated in either inch-pound units or SI unitsare to be regarded separately as standard.Within the text,theSI units are shown in brackets.The values stated in eachsystem are not exact equivalents;therefore,each system mustbe used independently of the other.Combining values from thetwo systems may result in nonconformance with the practice.1.4 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Documents2.1 ASTM Standards:2A 351/A 351M Specification for Castings,Austenitic,forPressure-Containing PartsA 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA 799/A 799M Practice for Steel Castings,Stainless,In-strument Calibration,for Estimating Ferrite ContentA 941 Terminology Relating to Steel,Stainless Steel,Re-lated Alloys,and FerroalloysE 38 Methods for Chemical Analysis of Nickel-Chromiumand Nickel-Chromium-Iron AlloysE 353 Test Methods for Chemical Analysis of Stainless,Heat-Resisting,Maraging,and Other Similar Chromium-Nickel-Iron AlloysE 562 Test Method for Determining Volume Fraction bySystematic Manual Point Count2.2Constitution Diagrams:Schoefer Diagram for Estimating Ferrite Content of Stain-less Steel Castings(1980 revision)3Schaeffler Diagram for Estimating Ferrite Content of Stain-less Steel Weld Metal4DeLong Diagram for Estimating Ferrite Content of StainlessSteel Weld Metal52.3American Welding Society Specification:AWS A 4.2,Procedures for Calibrating Magnetic Instru-ments to Measure the Delta Ferrite Content of AusteniticStainless Steel Weld Metal63.Terminology3.1 Definitions:3.1.1 ferritethe ferromagnetic,body-centered,cubic-microstructural constituent of variable chemical composition iniron-chromium-nickel alloys.This may be formed upon solidi-fication from the molten metal(delta ferrite)or by transforma-tion from austenite or sigma phase on cooling in the solid state(alpha ferrite).3.1.2 ferrite contentthe proportion of total volume of aniron-chromium-nickel alloy present as the ferrite phase.3.1.3 ferrite numberthe ferrite content expressed as anarbitrary number based on the magnetic response of the alloyin a weld deposit.3.1.4 ferrite percentagethe ferrite content expressed as avolume percent.1This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel,and Related Alloys and is the direct responsibility of SubcommitteeA01.18 on Castings.Current edition approved March 1,2006.Published April 2006.Originallyapproved in 1982.Last previous edition approved in 2001 as A 800/A 800M 01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Appendix of this practice.4Metal Progress Data Book,American Society for Metals,Mid June 1977,p.161.5Welding Journal,American Welding Society,Vol 38,No.7,July 1973,p.293s.6Available from American Welding Society(AWS),550 NW LeJeune Rd.,Miami,FL 33126.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.3.1.5 heat treatmentthe definitions in Terminology A 941are applicable to this practice.4.Significance and Use4.1 The tensile and impact properties,the weldability,andthe corrosion resistance of iron-chromium-nickel alloy castingsmay be influenced beneficially or detrimentally by the ratio ofthe amount of ferrite to the amount of austenite in themicrostructure.The ferrite content may be limited by purchaseorder requirements or by the design construction codes gov-erning the equipment in which the castings will be used.Thequantity of ferrite in the structure is fundamentally a functionof the chemical composition of the alloy and its thermalhistory.Because of segregation,the chemical composition,and,therefore,the ferrite content,may differ from point topoint on a casting.Determination of the ferrite content by anyof the procedures described in the following practice is subjectto varying degrees of imprecision which must be recognized insetting realistic limits on the range of ferrite content specified.Sources of error include the following:4.1.1 In Determinations from Chemical CompositionDeviations from the actual quantity of each element present inan alloy because of chemical analysis variance,althoughpossibly minor in each case,can result in substantial differencein the ratio of total ferrite-promoting to total austenite-promoting elements.Therefore,the precision of the ferritecontent estimated from chemical composition depends on theaccuracy of the chemical analysis procedure.4.1.2 In Determinations from Magnetic ResponsePhasesother than ferrite and austenite may be formed at certaintemperatures and persist at room temperature.These may soalter the magnetic response of the alloy that the indicatedferrite content is quite different from that of the same chemicalcomposition that has undergone different thermal treatment.Also,because the magnets or probes of the various measuringinstruments are small,different degrees of surface roughness orsurface curvature will vary the magnetic linkage with thematerial being measured.4.1.3 InDeterminationsfromMetallographicExaminationMetallographic point count estimates of ferritepercentage may vary with the etching technique used foridentification of the ferrite phase and with the number of gridpoints chosen for the examination,as explained in Test MethodE 562.4.2 The estimation of ferrite percent by chemical composi-tion offers the most useful and most common method of ferritecontrol during melting of the metal.4.3 For most accurate estimate of ferrite percent,a quanti-tative metallographic method should be used.5.Ordering Information5.1 Orders for material to this practice should include thefollowing as required:5.1.1 ApplicableASTM product specification or other docu-ment covering product requirements,5.1.2 Alloy grade,5.1.3 Required ferrite content range,in volume percent,ofthe castings after final heat treatment.Also,if desired by thepurchaser,required ferrite content range,in ferrite number,forweld deposits(Note 1)as deposited,and5.1.4 Supplementary requirements,if any,desired.NOTE1There may be a substantial decrease in the ferrite content ofweld deposits after solution heat treatment in comparison with theas-deposited value.6.General Caution6.1 In specifying ferrite content as required in 5.1.3,thepurchaser should not set limits that conflict with applicablematerial specification requirements:for example,a maximumlimit of 10%ferrite for Grade CF-3A in Specification A 351/A 351M for which the minimum tensile strength requirement is77 ksi 530 MPa.6.2 When Supplementary Requirement S1 is specified,thepurchaser should set ferrite content limits that are compatiblewith the measuring instrument to be used.7.Estimation of Ferrite Content7.1 Estimation in the base metal of the casting by chemicalcomposition in accordance with the Schoefer diagram(seeAppendix X1):7.1.1 A chemical analysis of the heat from which thecastings are poured shall include the following elementswhether or not required by the chemical requirements of theproduct specification:carbon,manganese,silicon,chromium,nickel,molybdenum,columbium,and nitrogen.7.1.1.1 Upon written agreement between the purchaser andthe producer,an estimated nitrogen content may be reportedinstead of an amount determined by analysis of the specificheat if actual chemical analyses have been made for nitrogen ina sufficient number of heats of the same alloy type,producedby the same melting practice,to establish the average nitrogencontent to be expected.7.1.2 The ferrite content of the casting shall be estimatedfrom the central line of the diagram at the composition ratio of“chromium equivalent”(Cre)to“nickel equivalent”(Nie)determined from the following formula:Cr%!1 1.5Si%!1 1.4Mo%!1 Cb%!2 4.99!/Ni%!130C%!1 0.5Mn%!1 26N 2 0.02%!1 2.77!5Cre!/Nie!7.1.3 When a product analysis is made by the purchaser,itshall include the elements listed in 7.1.1.If a comparison ismade of ferrite content estimated from a product analysisperformed by the purchaser,with that estimated from the heatanalysis(see 7.1.1),the reproducibility data in the precisionstatements of Test Methods E 353 shall be used as a guide.7.1.3.1 Methods E 38 or Test Methods E 353,as applicable,shall be used as referee chemical analysis methods.7.2 Estimation in weld deposits by chemical composition inaccordance with the Schaeffler or DeLong diagrams:7.2.1 The ferrite content shall be estimated(a)from thedeposit chemical analysis included on the electrode manufac-turers certified material test report,or(b)from chemicalanalysis of a weld deposit pad made by the casting manufac-turer.A 800/A 800M 01(2006)27.3 Estimation of ferrite content in heat,product,or weldmetal may be made by the magnetic response or metallo-graphic methods by imposition of Supplementary Require-ments S1 or S2,respectively.8.Acceptance Standards8.1 Conformance with the required ferrite content rangespecified in 5.1.3 as indicated by the estimation procedure of7.1 and 7.2 shall be the basis for acceptance of materialsupplied under this practice unless other methods of estimationare ordered as supplementary requirements,in which case thesupplementary requirement shall be the basis of acceptance.8.2 If lack of conformance with the ferrite content rangespecified in 5.1.3 is indicated by a product analysis made by thepurchaser(7.1.3)and by a referee analysis as provided in7.1.3.1,rejection of material shall be subject to the tests of 7.3as established by written agreement between the manufacturerand the purchaser.9.Certification9.1 The manufacturers certification shall be furnished tothe purchaser stating that the material was sampled and testedin accordance with the specification(including year date)andwas found to meet the requirements.9.2 The test report shall contain the results of the actualchemical analyses required by 7.1.1 and 7.2.1 and the indicatedferrite content range.The estimates of ferrite content frommagnetic measurements(S1)or from point counts(S2),orboth,if ordered by the purchaser,also shall be reported.9.3 The test report shall be signed by an authorized agent ofthe manufacturer.9.4 The test report shall be furnished within five workingdays of shipment of the castings.10.Keywords10.1 austenite;austenitic stainless steel;ferrite;SchoeferDiagram;steel castingsSUPPLEMENTARY REQUIREMENTSThe following supplementary requirements are for use when desired by the purchaser.They shallnot apply unless specified in the order,in which event the specified methods of ferrite contentestimation shall be employed by the manufacturer before shipment of the castings.S1.Estimation of Ferrite Content by Measurement ofMagnetic ResponseS1.1 The ferrite content of the heat from which the castingsare poured shall be estimated from measurements made byprimary or secondary instruments calibrated in accordancewith the requirements of PracticeA 799/A 799M.All measure-ments shall be made on material after the solution heattreatment required by the applicable product specification,or,if any subsequent solution heat treatment is employed,thenafter the final solution heat treatment.S1.1.1 Location of measurementsbase metal:S1.1.1.1 Measurements shall be made on the unstrainedends of tension test specimens from the same heat as thecastings represented.Measurements may be made either beforeor after performance of the tension test.If a tension test is notrequired by the applicable product specification,measurementsmay be made on a specimen cut from a keel block of a designin Fig.3 of Test Methods and Definitions A 370.S1.1.1.2 When further specified,measurements shall bemade on the base metal of the castings,or a specified sampleof castings(not on weld repairs or other weld deposits),inlocations designated on the design drawing or as otherwiseagreed in writing between the purchaser and the manufacturer.S1.2 The ferrite content of weld deposits shall be estimatedfrom measurements made by primary or secondary instrumentscalibrated in accordance with the requirements of SpecificationAWS A4.2.All measurements shall be made on weld depositsas deposited.S1.2.1 Location of measurementsweld deposits:S1.2.1.1 Measurements shall be made on a weld pad depos-ited in accordance with the electrode specification.S1.2.1.2 When further specified,measurements shall bemade on repair or fabrication welds on castings in locations asagreed in writing between the purchaser and manufacturer.S1.3 Number of MeasurementsSix measurements shall bemade at random in each designated location.For instrumentshaving probes making two contacts with the surface beingmeasured,a“measurement”shall consist of a pair of readingstaken with the probe oriented on perpendicular axes.S1.4 Surface Condition:S1.4.1 The instrument magnet or probe and the surface to bemeasured shall be dry and cleaned prior to testing to removeany scale,grease,lint,or dirt that could affect the accuracy ofmeasurement.S1.4.2 Measurements shall be made more than 0.25 in.6.350 mm from the edge of a surface.When measurementsare made on a curved surface the radius of curvature must begreater than 0.375 in.9.525 mm.S1.5 Acceptance Criteria:S1.5.1 The average of the ferrite contents estimated frommeasurements in each designated location shall be within thelimits stated in the order,and not more than two individualmeasurements shall indicate ferrite contents less than or inexcess of these limits.S1.5.1.1 If ferrite contents are estimated with an instrumentthat indicates for each measurement a value between an upperand a lower limit,more than one-half of all measurements shallbe within the limits stated in the order.S1.5.2 Should the requirements of S1.5.1 not be met,areferee esti