1、Designation:A921/A921M93(Reapproved 2016)Standard Specification forSteel Bars,Microalloy,Hot-Wrought,Special Quality,forSubsequent Hot Forging1This standard is issued under the fixed designation A921/A921M;the number immediately following the designation indicates the yearof original adoption or,in
2、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 hot-wrought,special qualitymicroalloyed carbon steel bars inten
3、ded for use as hot forgingstock.The bars shall be hot-wrought,as-wrought,unlessthermal treatment is necessary to ensure cold shearability.1.2 The bars shall be furnished to chemical compositiononly.Chemical composition is based on standard carbon steelgrades modified to include microalloying element
4、s such ascolumbium(niobium),vanadium,or molybdenum.Desiredmechanical properties are developed in the subsequent hotforging and controlled cooling operations.1.3 Sections and sizes of bar steel available are covered inSpecification A29/A29M.1.4 Supplementary Requirements S1 to S6 are provided foruse
5、when additional controls or requirements are desired.These shall apply only when specified on the purchase order.1.5 The values stated in either inch-pound units or SI unitsare to be regarded separately as standard.Within the text andtables,SI units are shown in brackets.The values stated in eachsys
6、tem are not exact equivalents;therefore,each system mustbe used independently of the other.Combining values from thetwo systems may result in nonconformance with the specifi-cation.1.6 Unless the order specifies the applicable“M”specifica-tion designation,the material shall be furnished to the inch-
7、pound units.2.Referenced Documents2.1 ASTM Standards:2A29/A29M Specification for General Requirements for SteelBars,Carbon and Alloy,Hot-WroughtA576 Specification for Steel Bars,Carbon,Hot-Wrought,Special QualityA788/A788M Specification for Steel Forgings,General Re-quirementsE45 Test Methods for De
8、termining the Inclusion Content ofSteel3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 microalloyed steelsmicroalloyed steels are carbonsteels to which small quantities of certain elements are addedin order to enhance mechanical properties.This enhancementof mechanical properti
9、es results from control of the tempera-ture and cooling rate during the final hot-working process.4.Ordering Information4.1 Orders for material supplied to this specification shouldinclude the following,as required,to describe adequately thedesired material:4.1.1 Quantity(weight or number of bars),4
10、.1.2 Name of material(hot-rolled microalloyed steel bars),4.1.3 Dimensions,4.1.4 ASTM specification number and date of issue,4.1.5 Grade designation or chemical composition limits(see8.1 8.5),4.1.6 Type(see 7.1)to designate grain refiner,4.1.7 Additions to the specification and SupplementaryRequirem
11、ents,if required,and,4.1.8 End use.5.General Requirements5.1 Material furnished under this specification shall con-form to the applicable requirements of the current edition ofSpecification A29/A29M,unless otherwise provided in thisspecification.6.Materials and Manufacture6.1 Melting PracticeThe ste
12、el shall be produced in accor-dance with the applicable methods for primary and secondarymelting outlined in Specification A788/A788M.6.2 The steel shall be killed.Supplementary RequirementsS1 through S6 may be invoked upon agreement betweenproducer and purchaser.1This specification is under the jur
13、isdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.15 on Bars.Current edition approved Sept.1,2016.Published September 2016.Originallyapproved in 1993.Last previous edition approved in 2011 as A921/A921M-93(2011).DOI:10.152
14、0/A0921_A0921M-93R16.2For 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.Copyright ASTM International,100 Barr Harbor
15、Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.3 The bars shall be special quality.6.4 The bars shall be hot-wrought,as wrought.7.Metallurgical Requirements7.1 Grain SizeThe steel shall conform to the fine grainsize requirement of Specification A29/A29M.The grain refin-ing elemen
16、t may be specified according to one of the followingtypes:7.1.1 Type AAluminumThe total aluminum analysisshall be 0.020%or greater,and shall be reported.7.1.2 Type BThe grain refining element shall be specifiedin accordance with 5.1.2.3 of Specification A29/A29M.8.Chemical Composition8.1 Typical examples of chemical compositions are shownin Table 1.Other compositions may be specified using one ofthe following methods:8.1.1 Base compositions selected from Table 1 of Specifi-cation A576,with the a
