1、Designation: A 921/A 921M 93 (Reapproved 2005)Standard Specification forSteel Bars, Microalloy, Hot-Wrought, Special Quality, forSubsequent Hot Forging1This standard is issued under the fixed designationA 921/A 921M; the number immediately following the designation indicates the yearof original adop
2、tion 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 specification covers hot-wrought, special qualitymicroalloyed carb
3、on steel bars intended 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 includ
4、e microalloying elements 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 A 29/A 29M.1.4 Supplementary requirements
5、S1 to S6 are provided foruse 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 bracke
6、ts. 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 specifi-cation.1.6 Unless the order specifies the applicable “M” specifica-tion designation, the ma
7、terial shall be furnished to the inch-pound units.2. Referenced Documents2.1 ASTM Standards:2A 29/A 29M Specification for Steel Bars, Carbon andAlloy,Hot-Wrought, General Requirements forA 576 Specification for Steel Bars, Carbon, Hot-Wrought,Special QualityA 788 Specification for Steel Forgings, Ge
8、neral Require-mentsE45 Test Methods for Determining the Inclusion Contentof Steel3. 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 proper
9、ties. This enhancementof mechanical properties 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 mate
10、rial:4.1.1 Quantity (weight or number of bars),4.1.2 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 Addi
11、tions to the specification and SupplementaryRequirements, 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 A 29/A 29M, unless otherwise provided in thisspecificat
12、ion.6. Materials and Manufacture6.1 Melting PracticeThe steel shall be produced in accor-dance with the applicable methods for primary and secondarymelting outlined in Specification A 788.6.2 The steel shall be killed. Supplementary RequirementsS1 through S6 may be invoked upon agreement betweenprod
13、ucer and purchaser.6.3 The bars shall be special quality.6.4 The bars shall be hot-wrought, as wrought.1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel, and Related Alloys and is the direct responsibility of SubcommitteeA01.15 on Bars.Current edition appro
14、ved March 1, 2005. Published March 2005. Originallyapproved in 1993. Last previous edition approved in 1999 as A 921/A 921M -93(1999).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
15、rmation, 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 States.7. Metallurgical Requirements7.1 Grain SizeThe steel shall conform to the fine grainsize requirement of Specific
16、ation A 29/A 29M. The grainrefining element may be specified according to one of thefollowing types: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 A
17、 29/A 29M.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 A 576, with the addition of microalloying elements asprovided in 8
18、.3-8.5,or8.1.2 Base compositions using the ranges and limits shownin Specification A 576, with the addition of microalloyingelements as provided in 8.3-8.5NOTE 1For improved machinability, alternative sulfur ranges may bespecified by agreement between the purchaser and the producer. Addi-tional mach
19、inability-enhancing elements such as lead, bismuth, selenium,or tellurium may also be specified by agreement.8.2 Silicon analysis shall be 0.15/0.35 %. Silicon content upto 0.80 % maximum may be furnished by agreement betweenpurchaser and producer.8.3 Vanadium, columbium (niobium), or molybdenum may
20、be specified singly or in combination, subject to the limitsshown in Table 2. The elements and ranges specified shall beby agreement between the purchaser and the producer.8.4 Titanium may be added for refinement of the austeniticand the as-forged ferritic grain size, or as a precipitationstrengthen
21、er. When titanium is specified, the titanium limitsshall be as agreed upon between producer and purchaser. Thetitanium analysis shall be reported.8.5 Nitrogen may be specified as a supplement to vanadium,columbium, or titanium. When nitrogen is specified to supple-ment vanadium, the minimum ratio of
22、 vanadium to nitrogenshall be 4 to 1. The nitrogen content shall not exceed 0.03 %and shall be reported.8.6 Sampling for heat and product analysis shall be inaccordance with the requirements of Specification A 29/A 29M.9. Workmanship and Appearance9.1 The bars shall be free of visible pipe and condi
23、tioned asnecessary to remove any injurious surface imperfections.10. Certification and Test Reports10.1 When specified by the purchaser, a manufacturerscertification that the material was manufactured and tested inaccordance with this specification together with a report of theheat analysis for the
24、specified elements and for copper,chromium, nickel, molybdenum, vanadium, and columbiumshall be furnished. When the amount of an element present isless than 0.02 %, the heat analysis may be reported as 0.02 %,except for titanium, aluminum, and nitrogen. When specified,these elements shall be reporte
25、d to three decimal places.11. Keywords11.1 carbon steel bars; microalloyed steel; steel barsTABLE 1 Typical Chemical Compositions of Microalloyed Carbon SteelsNOTE 1These compositions are identical to those in Specification A 576, with the exception of the addition of vanadium.Grade DesignationChemi
26、cal Composition Limits, %CMNPSV10V40 0.370.44 0.600.90 0.040 max 0.050 max 0.020.2010V45 0.430.50 0.600.90 0.040 max 0.050 max 0.020.2011V37 0.320.39 1.351.65 0.040 max 0.080.13 0.020.2011V41 0.370.45 1.351.65 0.040 max 0.080.13 0.020.2015V24 0.190.25 1.351.65 0.040 max 0.050 max 0.020.2015V41 0.360
27、.44 1.351.65 0.040 max 0.050 max 0.020.20TABLE 2 Chemical Requirements(Microalloy Elements)ElementChemical Ranges and Limits, %Heat Analysis Product AnalysisVanadium 0.020.20 0.010.21Columbium (Niobium) 0.0050.07 0.0040.08Molybdenum 0.010.30 0.31 maxA 921/A 921M 93 (2005)2SUPPLEMENTARY REQUIREMENTSO
28、ne or more of the following supplementary requirements shall apply only when specified by thepurchaser.S1. Restricted Chemical CompositionS1.1 Restricted heat analysis limits or ranges or restrictedproduct analysis tolerances on one or more elements may bespecified by the purchaser if the manufactur
29、er agrees to meetthe requested restriction.S2. Restricted Incidental ElementsS2.1 The steel shall not exceed the limits for copper, nickel,chromium, molybdenum, or other elements as shown on thepurchase order.S3. Nonmetallic Inclusion RequirementS3.1 A microscopical examination of longitudinal secti
30、onsto determine the nature and frequency of nonmetallic inclu-sions shall be made as prescribed in Test Methods E45. Theacceptance limits shall be specified by the purchaser.NOTE S1In resulfurized steels, much of the sulfur is present as sulfideinclusions. For this reason, maximum sulfide inclusion
31、level should not bespecified.S4. Calcium TreatmentS4.1 The steel shall be calcium treated.S5. Thermal Treatment to Insure Cold ShearabilityS5.1 The bars shall be thermal treated to ensure coldshearability. The type of treatment shall be as agreed uponbetween the purchaser and producer.S6. CleaningS6
32、.1 The surface of the bars shall be descaled by pickling orshotblasting, or other suitable means.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determi
33、nation 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 wi
34、thdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that y
35、our comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).A 921/A 921M 93 (2005)3
