ASTM_A_940_-_A_940M_-_06_2016.pdf

Designation:A940/A940M06(Reapproved 2016)Standard Specification forVacuum Treated Steel Forgings,Alloy,Differentially HeatTreated,for Turbine Rotors1This standard is issued under the fixed designation A940/A940M;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers vacuum treated,alloy steelforgings,differentially heat treated for turbine rotors.1.2 Differential heat treatment of a rotor forging involvessubjecting two portions of the forging concurrently to twodifferent austenitizing temperatures followed by two differentcooling rates for normalizing and quenching,and thentempering,to achieve creep resistance in the high pressure(HP)portion and high toughness in the low pressure(LP)portion.21.3 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 be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.2.Referenced Documents2.1 ASTM Standards:3A275/A275M Practice for Magnetic Particle Examination ofSteel ForgingsA370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA418/A418M Practice for Ultrasonic Examination of Tur-bine and Generator Steel Rotor ForgingsA470/A470M Specification for Vacuum-Treated Carbon andAlloy Steel Forgings for Turbine Rotors and ShaftsA472/A472M Specification for Heat Stability of Steam Tur-bine Shafts and Rotor ForgingsA788/A788M Specification for Steel Forgings,General Re-quirementsE139 Test Methods for Conducting Creep,Creep-Rupture,and Stress-Rupture Tests of Metallic Materials3.Ordering Information3.1 In addition to the ordering information required bySpecification A788/A788M,the purchaser shall include withthe inquiry and order a detailed drawing,sketch,or writtendescription of the forging,including the mechanical testlocations,the portion of the forging to be included in theheating chamber during the stability test,and the minimumstability test temperature.3.2 The purchaser shall specify if check tests for mechanicalproperties are required after stress relief or heat stability tests.3.3 Supplementary RequirementsSupplementary require-ments are provided.These requirements shall apply only whenspecified in the purchase order.4.General Requirements4.1 Material supplied to this specification shall conform tothe requirements of Specification A788/A788M,which out-linesadditionalorderinginformation,manufacturingrequirements,testing and retesting methods and procedures,marking,certification,product analysis variations,and addi-tional supplementary requirements.4.2 If the requirements of this specification are in conflictwith the requirements of Specification A788/A788M,therequirements of this specification shall prevail.5.Manufacture5.1 Melting processes of Specification A788/A788M shallbe applicable,except that the open hearth or basic oxygenmethods of primary melting shall not be used and the moltensteel shall be vacuum treated during processing.Except forvacuum stream degassed ingots,the hydrogen content shall bedetermined.The acceptable hydrogen limit as well as the stagein processing when sampling,the sample preparation proce-dure and the method of analysis shall be established betweenthe manufacturer and the purchaser.5.1.1 If the ESR process is used,the electrodes shall havebeen produced from vacuum treated primary heat(s).1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.06 on Steel Forgings and Billets.Current edition approved March 1,2016.Published April 2016.Originallyapproved in 1995.Last previous edition approved in 2011 as A940/A940M 06(2011).DOI:10.1520/A0940_A0940M-06R16.2Symposium on Steel Forgings,ASTM STP 903,ASTM International,WestConshohocken,PA,1984,pp.5986.3For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.2 In addition to the requirements of Specification A788/A788M,it is important to maintain the axial center of theforging in common with the axial center of the original ingot.5.3 Differential Heat TreatmentThe heat treatment formechanical properties shall consist of normalizing and temper-ing of the creep resistant portion,HP portion,and quenchingand tempering of the high toughness portion,LP portion.5.3.1 The preliminary heat treatment shall consist of nor-malizing well above