1、Designation: A768/A768M 05 (Reapproved 2010)Standard Specification forVacuum-Treated 12 % Chromium Alloy Steel Forgings forTurbine Rotors and Shafts1This standard is issued under the fixed designation A768/A768M; the number immediately following the designation indicates the yearof original adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scop
3、e1.1 This specification covers vacuum-treated 12 % chro-mium steel forgings for turbine rotors and shafts.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall b
4、e used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-pri
5、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A275/A275M Practice for Magnetic Particle Examinationof Steel ForgingsA370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA418/A418M
6、 Practice for Ultrasonic Examination of Tur-bine and Generator Steel Rotor ForgingsA472/A472M Specification for Heat Stability of SteamTurbine Shafts and Rotor ForgingsA788/A788M Specification for Steel Forgings, General Re-quirements3. Ordering Information3.1 In addition to the ordering information
7、 required bySpecification A788/A788M, the purchaser shall include withthe inquiry and order a detailed drawing, sketch, or writtendescription of the forging, including the mechanical testspecimen location.4. General Requirements4.1 Material supplied to this specification shall conform tothe requirem
8、ents of Specification A788/A788M which outlinesadditional ordering information, manufacturing requirements,testing and retesting methods and procedures, marking, certi-fication, product analysis variations, and additional supplemen-tary requirements.4.2 If the requirements of this specification are
9、in conflictwith the requirements of Specification A788/A788M, therequirements of this specification shall prevail.5. Manufacture5.1 The melting processes of Specification A788/A788Mshall be applicable except that the open-hearth or basic oxygenmethods of primary melting shall not be used, and the mo
10、ltensteel shall be vacuum degassed prior to or during pouring of theingot.5.1.1 If the ESR process is used, then the electrodes shallhave been produced from vacuum degassed primary heat(s).5.2 In addition to the requirements of Specification A788/A788M, it is important to maintain the axial center o
11、f theforging in common with the axial center of the original ingot.5.3 Heat Treatment:5.3.1 The heat treatment for mechanical properties shallconsist of quenching and tempering.1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the
12、direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved April 1, 2010. Published May 2010. Originallyapproved in 1979. Last previous edition approved in 2005 as A768/A768M 05.DOI: 10.1520/A0768_A0768M-05R10.2For referenced ASTM standards, visit the ASTM web
13、site, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Sta
14、tes.5.3.1.1 The preliminary heat treatment shall consist ofnormalizing well above the transformation temperature range.This operation may be performed before preliminary machin-ing (see 5.4.1).5.3.1.2 The quenching treatment shall be from above thetransformation range but below the normalizing tempe
15、raturedescribed in 5.3.1.1. This treatment shall be performed afterpreliminary machining (see 5.4.1). Austenitizing temperaturesshall be in accordance with Table 1.5.3.1.3 The final tempering temperature shall be in accor-dance with Table 1.5.3.1.4 After heat treatment and subsequent rough machin-in
16、g and boring (see 5.4.2 and 5.4.3), the forging shall bestress-relieved at a temperature not more than 100F 55Cbelow the final tempering temperature, but not less than 1100F595C.5.3.1.5 With the prior approval of the purchaser, the stress-relief temperature may approach, equal, or slightly exceed th
17、efinal tempering temperature as a means of adjusting finalstrength or toughness. If the stress relief temperature is within25F 15C of the final tempering temperature, or higher,additional tension tests must be obtained (see 7.1.3).5.3.1.6 The method of cooling during quenching and fromthe final temp
18、ering and stress relieving temperatures shall bereported.5.4 Machining:5.4.1 Preliminary Rough MachiningAll exterior surfacesof the forging shall be machined prior to heat treatment formechanical properties.5.4.2 Second Rough MachiningAfter heat treatment formechanical properties, all surfaces of th
19、e forging shall be roughmachined prior to stress relief and the stability test.5.4.3 Boring:5.4.3.1 Forgings shall be bored to permissible bore size andtolerance when required by the purchasers drawing.5.4.3.2 Forgings may be bored to limits agreed to by thepurchaser or indicated on the purchasers d
20、rawing, to removeobjectionable center conditions revealed by ultrasonic inspec-tion.5.4.3.3 Unless otherwise specified by the purchaser, themanufacturer may bore the forging at any time prior to stressrelief (see Supplementary Requirement S1).5.4.4 Machining to Purchasers Requirements forShipmentThe
21、 forging as shipped shall conform to the finishand dimension requirements specified on the purchasersdrawing or order.6. Chemical Composition6.1 The steel shall conform to the requirements for chemicalcomposition prescribed in Table 2.6.2 Product AnalysisThe manufacturer shall make a prod-uct analys
22、is from each forging. The chemical composition thusdetermined shall not vary from the requirements specified inTable 1 by more than the amounts prescribed in SpecificationA788/A788M.7. Mechanical Properties7.1 Tension Test:7.1.1 The steel shall conform to the tensile requirements ofTable 3.7.1.2 The
23、 number and location of tension test specimensshall be as specified on the forging drawings furnished by thepurchaser.7.1.3 Final acceptance tests shall be made after heat treat-ment of the forging for mechanical properties prior to stressrelief, unless the stress relief temperature is within 25F 15
24、Cof the tempering temperature, or higher, in which case checktests shall be made after the stress relief treatment and reportedto the purchaser. The purchaser may require check tests aftercompletion of all heating cycles, including stress relief and theheat stability tests.7.1.4 The yield strength p
25、rescribed in Table 3 shall bedetermined by the offset method of Test Methods and Defini-tions A370.7.2 Impact Test:7.2.1 The steel shall conform to the requirements for notchtoughness (both transition temperature and room temperatureimpact values) prescribed in Table 3.7.2.2 The notch toughness spec
26、imens shall be machinedfrom radial bars taken from the main body of the forging, asshown in the forging drawing. The specimens shall be CharpyV-notch, Type A, as shown in Test Methods and DefinitionsA370. The notch direction of the Charpy bars shall betangential.8. Nondestructive Tests8.1 General Re
27、quirements:8.1.1 The forgings shall be free of cracks, seams, laps,shrinkage, and other injurious imperfections.8.1.2 The purchaser may request ultrasonic, magnetic par-ticle, dye penetrant, etch, or other accepted nondestructiveinspection necessary to evaluate imperfections and to ensurecompliance
28、with this requirement.8.2 Ultrasonic Inspection:8.2.1 An ultrasonic inspection shall be made on the ma-chined forging at the manufacturers plant. This inspectionshall be made in accordance with Test MethodA418/A418M todemonstrate freedom from detrimental internal defects.8.2.2 The ultrasonic inspect
29、ion shall be made from allavailable surfaces prior to removal of test specimens thatwould interfere with complete testing of the forging.8.2.3 Forgings with recordable ultrasonic indications shallbe referred to the purchaser for evaluation based on the nature,frequency, and location of indications,
30、both stationary andTABLE 1 Heat Treating Temperature, F C, RequirementsGrade Austenitizing 1stTempering,min2ndTempering1 17251825 1125 1100940995 605 5952 19001940 1040 1010104010351060 560 5455603 17001800 1120 1100925980 605 5954 17001800 975 950925980 525 510A768/A768M 05 (2010)2traveling. If the
31、 ultrasonic indications are considered objection-able, it shall be determined by conventional or mutuallyacceptable inspection procedures whether the forging will berejected.8.3 Internal Inspection:8.3.1 Boring, when specified for internal periscopic inspec-tion, shall be in accordance with the draw
32、ings furnished by thepurchaser. The drawings shall specify the nominal dimensionsof the bore hole.8.3.2 If objectionable conditions are encountered during theinternal inspection of the bore hole, the manufacturer shallnotify the purchaser of the location and nature of the condition.Further action sh
33、all be taken only after mutual agreementbetween the manufacturer and purchaser.9. Stability Test9.1 Each forging shall be subjected to a heat stability test atthe manufacturers plant in accordance with the latest issue ofTest Method A472/A472M to determine the stability or free-dom from tendency to
34、distort during high temperature operat-ing conditions.9.2 The stability test shall be conducted after the forging hasbeen stress relieved in accordance with 5.3.1.4.NOTE 1If agreed to by the purchaser, the stress relief may beperformed as part of the stability test.9.3 Stability Test Requirements:9.
35、3.1 The purchasers drawings shall indicate the minimumportion of the forging to be included within the heatingchamber during the stability test.9.3.2 The purchasers drawings or order shall indicate theminimum stability test temperature.10. Retreatment10.1 If the results of the mechanical tests of an
36、y forging donot conform to the requirements specified, the manufacturermay retreat the forging one or more times, but not more thanthree additional times, without the approval of the purchaser.10.2 If bore core properties are specified under Supplemen-tary Requirement S1 and retemper is necessary af
37、ter boring,the remaining portions of the bore core shall be replaced in thebore during retemper.10.3 If complete retreatment, including normalizing orquenching, is necessary after boring, the feasibility of retreat-ing portions of the bore core in the bore of the forging shall bediscussed between ma
38、nufacturer and purchaser and a proce-dure agreed upon before treatment.11. Certification and Reports11.1 In addition to the certification requirements of Speci-fication A788/A788M, the following shall be reported:11.1.1 Product analysis results.12. Package Marking, Packaging, and Loading12.1 In addi
39、tion to the marking requirements in Specifica-tion A788/A788M, test specimens shall be identified withnumbers corresponding to the forging identification numbersand numbers corresponding to test location and type if speci-fied on the purchasers drawings or order.TABLE 2 Chemical RequirementsComposit
40、ion, % Grade 1 Grade 2 Grade 3 Grade 4Carbon 0.15 max 0.080.15 0.100.16 0.050.07Manganese 1.0 max 0.500.90 0.251.00 0.701.00Phosphorus 0.018 max 0.02 max 0.015 max 0.015 maxSulfur 0.015 max 0.015 max 0.012 max 0.012 maxSilicon 0.35 max 0.30 max 0.150.45 0.300.50Nickel 0.400.75 2.03.0 0.75 max 3.54.2
41、5Chromium 11.513.0 11.013.0 11.013.0 11.2512.25Molybdenum 0.50 max 1.52.0 0.20 max 0.300.50Vanadium . 0.250.40 . 0.03 maxColumbium . . 0.15 min .Aluminum . . . 0.03 maxNitrogen . 0.06 max . .TABLE 3 Tensile and Notch Toughness RequirementsGrade 1Grade 2Grade 3 Grade 4Class 1 Class 2 Class 1 Class 2
42、Class 1 Class 2Tensile strength, ksi MPa 90110 85 min 150 min 90110 105125 110140 120150620760 585 1035 620760 725860 760965 8251035Yield strength (0.2 % offset) ksiMPa, min70631070808595485 435 760 485 550 585 655minElongation, min, % 16 18 15 15 16 16 15Reduction of area, min, % 45 45 45 45 45 45
43、42FATT50, max, F C 175 140 25 140 175 60 8080 60 -4 60 80 15 25Room temperature impact, min, ft-lbJ15 20 50 15 15 35 2520 28 70 20 20 49 35A768/A768M 05 (2010)312.2 In addition, the axial bores of bored forgings shall beprotected and suitably plugged to prevent damage or corrosionduring shipment or
44、storage.SUPPLEMENTARY REQUIREMENTSThe following supplementary requirement shall apply only when specified by the purchaser in theinquiry, contract, and order. Details of this supplementary requirement shall be agreed upon betweenthe manufacturer and the purchaser.S1. Bore Core PropertiesS1.1 The pur
45、chaser may require the removal of the longi-tudinal bore core from the forging after heat treatment formechanical properties and subsequent approval of the usualsurface mechanical property tests.S1.1.1 The diameter of the longitudinal bore core shall besubject to agreement between the manufacturer a
46、nd the pur-chaser.S1.1.2 The purchaser may require mechanical tests ontension of impact specimens from locations in the longitudinalbore core as specified on the forging drawings furnished by thepurchaser.S1.1.3 The acceptable level of mechanical properties ob-tained from specimens from the longitud
47、inal bore core shall beas agreed upon between the manufacturer and the purchaser.S2. Magnetic Particle ExaminationS2.1 A magnetic particle examination of the completeexterior and bore surfaces of the machined forging shall bemade at the forging manufacturers plant. The examinationshall be performed
48、in accordance with the latest issue of TestMethod A275/A275M.S2.2 Forgings with either cracks or linear indications of anylength are subject to rejection unless they can be removed tothe purchasers satisfaction.ASTM International takes no position respecting the validity of any patent rights asserte
49、d in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn.
