1、Designation: A 920/A 920M 07Standard Specification forSteel Bars, Microalloy, Hot-Wrought, Special Quality,Mechanical Properties1This standard is issued under the fixed designation A 920/A 920M; the number immediately following the designation indicates the yearof original adoption or, in the case o
2、f 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. Scope*1.1 This specification covers hot-wrought, special qualitymicroalloyed carbon steel bars intende
3、d for use in applicationswhere as-rolled mechanical properties are desired. A typicalend use is hydraulic cylinder shafts.1.2 The bars shall be furnished to chemical composition andmechanical properties as provided herein. Chemical composi-tion is based on standard carbon steel grades modified toinc
4、lude microalloying elements such as columbium (niobium),vanadium, or molybdenum. Three strength classes are avail-able, designated 75 520, 80 550, and 100 690, correspond-ing to the minimum yield strength in ksi.1.3 Sections and sizes of bar steels available are covered inSpecification A 29/A 29M.1.
5、4 Supplementary Requirements S1 to S5 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,
6、 SI 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 specifi-cation.1.6 Unless the order specifies the applicable “M” speci
7、fica-tion designation, the material 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 370 Test Methods and Definitions for Mechanical Testingof Steel ProductsA 576 Spec
8、ification for Steel Bars, Carbon, Hot-Wrought,Special QualityE45 Test Methods for Determining the Inclusion Contentof Steel3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 microalloyed steels, ncarbon steels to which smallquantities of certain elements are added in order to enh
9、ancemechanical properties.3.1.1.1 DiscussionThis enhancement of mechanical prop-erties results from control of the temperature and cooling rateduring the hot-rolling process.4. Ordering Information4.1 Orders for material supplied to this specification shouldinclude the following, as required, to des
10、cribe adequately thedesired material: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 (seeSection 8),4.1.6 Class,4.1.7 Type (
11、see 7.1) to designate grain refiner,4.1.8 Additions to the specification and SupplementaryRequirements, if required, and,4.1.9 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 29
12、M, unless otherwise provided herein.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 576.6.2 The steel shall be killed. Supplementary RequirementsS1 through S5 may be in
13、voked upon agreement betweenproducer and purchaser.6.3 The bars shall be special quality.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 approved Nov. 1, 200
14、7. Published December 2007. Originallyapproved in 1993. Last previous edition approved in 2002 as A 920/A 920M 02a.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 t
15、he standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.4 The bars shall be hot-wrought, as wrought, unlessotherwise sp
16、ecified.7. Metallurgical Requirements7.1 Grain SizeThe steel shall conform to the fine grainsize requirement of Specification A 29/A 29M. The grainrefining element may be specified according to one of thefollowing types:7.1.1 Type A, AluminumThe total aluminum analysis shallbe 0.020 % or greater, an
17、d shall be reported.7.1.2 Type BThe grain refining element shall be specifiedin accordance with 5.1.2.3 of Specification A 29/A 29M.7.2 MicrostructureThe microstructure shall consist of aminimum of 90 % ferrite-pearlite or 90 % bainite as agreedupon between the purchaser and producer.8. Chemical Com
18、position8.1 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 8.3 to 8.5,or8.1.2 Base co
19、mpositions using the ranges and limits shownin Table 2 of Specification A 576, with the addition ofmicroalloying elements as provided in 8.3 to 8.5.NOTE 1For improved machinability, alternative sulfur ranges may bespecified upon agreement between the purchaser and the producer.Additional machinabili
20、ty-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 upon agreement be-tween purchaser and producer.8.3 Vanadium, columbium (niobium), or molybdenum maybe
21、specified singly or in combination, subject to the limitsshown in Table 2. The elements and ranges specified shall beupon agreement between the purchaser and the producer.8.4 Titanium shall be added when specified for refinementof the ferritic-pearlitic (or bainitic) or austenitic grain size.When ti
22、tanium is specified, the titanium limits shall be asagreed upon between producer and purchaser. The titaniumcontent shall be reported.8.5 Nitrogen may be specified as a supplement to vanadium,columbium, or titanium. If specified, the nitrogen content shallnot exceed 0.030 % and shall be reported.8.6
23、 Sampling for heat and product analysis shall be inaccordance with the requirements of Specification A 29/A 29M.9. Mechanical Properties9.1 The material as represented by the test specimens shallconform to the requirements of Table 3 for the class specified.9.2 Test specimens shall be prepared from
24、the material inthe as-rolled condition, unless otherwise specified.9.3 Test specimens shall be taken longitudinally and may betested in full thickness or they may be machined to thedimensions shown in Figs. 4 or 5 of Test Methods andDefinitions A 370. If the test specimens are selected conform-ing t
25、o the dimensions of Fig. 5, they shall be machined from aposition midway between the center and surface of the bar.9.4 Two tension tests shall be made from each heat, unlessthe finished material from a heat is less than 50 tons (45 mg),when one tension test will be sufficient.10. Workmanship and App
26、earance10.1 The bars shall be free of visible pipe and conditionedas necessary to remove any injurious surface imperfections.11. Certification and Test Reports11.1 When specified by the purchaser, a manufacturerscertification that the material was manufactured and tested inaccordance with this speci
27、fication together with a report of theheat analysis for the 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 aluminum, titanium,
28、and nitrogen. When specified,these elements shall be reported to three decimal places.11.2 The report shall include the results of any mechanicaltests performed in accordance with this specification, includingsupplementary requirements, if any.TABLE 1 Typical Chemical Compositions of Microalloyed Ca
29、rbon SteelsNOTEThese compositions are identical to those in Specification A 576, with the exception of the addition of vanadium.Base Grade Designation Chemical 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 0.3
30、20.39 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 0.360.44 1.351.65 0.040 max 0.050 max 0.020.20TABLE 2 Chemical Requirements(Microalloy Elements)Element Chemical Ranges and Limits, %Heat Analysis Pr
31、oduct AnalysisVanadium 0.020.20 0.010.21Columbium (Niobium) 0.0050.07 0.0040.08Molybdenum 0.010.30 0.31 maxA 920/A 920M 07212. Keywords12.1 carbon steel bars; microalloyed steel; steel barsSUPPLEMENTARY REQUIREMENTSOne or more of the following supplementary requirements shall apply only when specifi
32、ed 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 manufacturer agrees to meetthe requested restriction.S2. Restricted Incidental ElementsS2.1 Th
33、e 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 sectionsto determine the nature and frequency of nonmetallic inclu-sions shall be made as
34、 prescribed in Test Methods E45. Theacceptance limits shall be specified by the purchaser.NOTE S1.1In resulfurized steels, much of the sulfur is present assulfide inclusions. For this reason, maximum sulfide inclusion level shouldnot be specified.S4. Calcium TreatmentS4.1 The steel shall be calcium
35、treated.S5. CleaningS5.1 The surface of the bars shall be descaled by pickling orshotblasting, or other suitable means.S6. Restricted Mechanical Property RequirementsS6.1 Restricted mechanical property requirements to beagreed upon between purchaser and producer.SUMMARY OF CHANGESCommittee A01 has i
36、dentified the location of selected changes to this standard since the last issue(A 920/A 920M 02a) that may impact the use of this standard. (Approved Nov. 1, 2007.)(1) Changed Nitrogen percentage to 0.030 % in 8.5.ASTM International takes no position respecting the validity of any patent rights ass
37、erted 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 b
38、y the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will rece
39、ive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your 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 Inte
40、rnational, 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).TABLE 3 Mechanical Property RequirementsClass Yield Strength, min Tensile Strength, min Elongation, %, minksi MPa ksi MPa in 8 in. (200 mm) in 2 in. (50 mm)75 75 520 100 690 7 1080 80 550 100 690 6 9100 100 690 115 790 5 7A 920/A 920M 073
