1、Designation: A920/A920M 07A920/A920M 14Standard Specification forSteel Bars, Microalloy, Hot-Wrought, Special Quality,Mechanical Properties1This standard is issued under the fixed designation A920/A920M; the number immediately following the designation indicates the yearof original adoption or, in t
2、he 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. Scope*Scope1.1 This specification covers hot-wrought, special quality microalloyed carbon stee
3、l bars intended for use in applications whereas-rolled mechanical properties are desired. A typical end use is hydraulic cylinder shafts.1.2 The bars shall be furnished to chemical composition and mechanical properties as provided herein. Chemical compositionis based on standard carbon steel grades
4、modified to include microalloying elements such as columbium (niobium), vanadium, ormolybdenum. Three strength classes are available, designated 75 520, 80 550, and 100 690, corresponding to the minimumyield strength in ksi.1.3 Sections and sizes of bar steels available are covered in Specification
5、A29/A29M.1.4 Supplementary Requirements S1 to S5 are provided for use when additional controls or requirements are desired. Theseshall apply only when specified on the purchase order.1.5 The values stated in either inch-poundSI units or SIinch-pound units are to be regarded separately as standard. W
6、ithin thetext and tables, SI units are shown in brackets. The values stated in each system aremay not be exact equivalents; therefore, eachsystem mustshall be used independently of the other. Combining values from the two systems may result in nonconformancenon-conformance with the specification. st
7、andard.1.6 Unless the order specifies the applicable “M” specification designation, the material shall be furnished to the inch-poundunits.2. Referenced Documents2.1 ASTM Standards:2A29/A29M Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-WroughtA370 Test Methods and Def
8、initions for Mechanical Testing of Steel ProductsA576 Specification for Steel Bars, Carbon, Hot-Wrought, Special QualityE45 Test Methods for Determining the Inclusion Content of Steel3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 microalloyed steels, ncarbon steels to which s
9、mall quantities of certain elements are added in order to enhancemechanical properties.3.1.1.1 DiscussionThis enhancement of mechanical properties results from control of the temperature and cooling rate during the hot-rolling process.1 This specification is under the jurisdiction ofASTM Committee A
10、01 on Steel, Stainless Steel and RelatedAlloys and is the direct responsibility of Subcommittee A01.15on Bars.Current edition approved Nov. 1, 2007Oct. 1, 2014. Published December 2007October 2014. Originally approved in 1993. Last previous edition approved in 20022007as A920/A920M 02a.A920/A920M 07
11、. DOI: 10.1520/A0920_A0920M-07.10.1520/A0920_A0920M-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This d
12、ocument is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions
13、as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Uni
14、ted States14. Ordering Information4.1 Orders for material supplied to this specification should include the following, as required, to describe adequately the desiredmaterial: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
15、ASTM specification number and date of issue,4.1.5 Grade designation or chemical composition limits (see Section 87),4.1.6 Class,4.1.7 Type (see 7.1) to designate grain refiner,4.1.7 Additions to the specification and Supplementary Requirements, if required, and,4.1.8 End use.5. General Requirements5
16、.1 Material furnished under this specification shall conform to the applicable requirements of the current edition ofSpecification A29/A29M, unless otherwise provided herein.6. Materials and Manufacture6.1 Melting PracticeThe steel shall be produced in accordance with the applicable methods for prim
17、ary and secondary meltingoutlined in Specification A576.6.2 The steel shall be killed. Supplementary Requirements S1 through S5 may be invoked upon agreement between producerand purchaser.6.3 The bars shall be special quality.6.4 The bars shall be hot-wrought, as wrought, unless otherwise specified.
18、7. Metallurgical Requirements7.1 Grain SizeThe steel shall conform to the fine grain size requirement of Specification A29/A29M. The grain refiningelement may be specified according to one of the following types:7.1.1 Type A, AluminumThe total aluminum analysis shall be 0.020 % or greater, and shall
19、 be reported.7.1.2 Type BThe grain refining element shall be specified in accordance with 5.1.2.3 of Specification A29/A29M.7.2 MicrostructureThe microstructure shall consist of a minimum of 90 % ferrite-pearlite or 90 % bainite as agreed uponbetween the purchaser and producer.7. Chemical Compositio
20、n7.1 Typical examples of chemical compositions are shown in Table 1. Other compositions may be specified using one of thefollowing methods:7.1.1 Base compositions selected from Table 1 of Specification A576, with the addition of microalloying elements as providedin 8.37.3 to 8.57.5, or7.1.2 Base com
21、positions using the ranges and limits shown in Table 2 of Specification A576, with the addition of microalloyingelements as provided in 8.37.3 to 8.57.5.NOTE 1For improved machinability, alternative sulfur ranges may be specified upon agreement between the purchaser and the producer. Additionalmachi
22、nability-enhancing elements such as lead, bismuth, selenium, or tellurium may also be specified by agreement.7.2 Silicon analysis shall be 0.15/0.35 %. Silicon content up to 0.80 % maximum may be furnished upon agreement betweenpurchaser and producer.TABLE 1 Typical Chemical Compositions of Microall
23、oyed Carbon SteelsNOTE 1These compositions are identical to those in Specification A576, with the exception of the addition of vanadium.Base Grade Designation Chemical Composition Limits, %C Mn P S V10V40 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
24、.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 0.360.44 1.351.65 0.040 max 0.050 max 0.020.20A920/A920M 1427.3 Vanadium, columbium (niobium), or molybdenum may be specified singly or i
25、n combination, subject to the limits shownin Table 2. The elements and ranges specified shall be upon agreement between the purchaser and the producer.7.4 Titanium shall be added when specified for refinement of the ferritic-pearlitic (or bainitic) or austenitic grain size. Whentitanium is specified
26、, the titanium limits shall be as agreed upon between producer and purchaser. The titanium content shall bereported.7.5 Nitrogen may be specified as a supplement to vanadium, columbium, or titanium. If specified, the nitrogen content shall notexceed 0.030 % and shall be reported.7.6 Sampling for hea
27、t and product analysis shall be in accordance with the requirements of Specification A29/A29M.8. Mechanical Properties8.1 The material as represented by the test specimens shall conform to the requirements of Table 3 for the class specified.8.2 Test specimens shall be prepared from the material in t
28、he as-rolled condition, unless otherwise specified.8.3 Test specimens shall be taken longitudinally and may be tested in full thickness or they may be machined to the dimensionsshown in Figs. 4 or 5 of Test Methods and Definitions A370. If the test specimens are selected conforming to the dimensions
29、 ofFig. 5, they shall be machined from a position midway between the center and surface of the bar.8.4 Two tension tests shall be made from each heat, unless the finished material from a heat is less than 50 tons (45 mg),45mg, when one tension test will be sufficient.9. Workmanship and Appearance9.1
30、 The bars shall be free of visible pipe and conditioned as necessary to remove any injurious surface imperfections.10. Certification and Test Reports10.1 When specified by the purchaser, a manufacturers certification that the material was manufactured and tested inaccordance with this specification
31、together with a report of the heat analysis for the specified elements and for copper, chromium,nickel, molybdenum, vanadium, and columbium shall be furnished. When the amount of an element present is less than 0.02 %,the heat analysis may be reported as 0.02 %, except for aluminum, titanium, and ni
32、trogen. When specified, these elements shallbe reported to three decimal places.10.2 The report shall include the results of any mechanical tests performed in accordance with this specification, includingsupplementary requirements, if any.TABLE 2 Chemical Requirements(Microalloy Elements)Element Che
33、mical 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 maxA920/A920M 14311. Keywords11.1 carbon steel bars; microalloyed steel; steel barsSUPPLEMENTARY REQUIREMENTSOne or more of the following supplementary re
34、quirements shall apply only when specified by thepurchaser.S1. Restricted Chemical CompositionS1.1 Restricted heat analysis limits or ranges or restricted product analysis tolerances on one or more elements may be specifiedby the purchaser if the manufacturer agrees to meet the requested restriction
35、.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 Amicroscopical examination of longitudinal sections to determine the nature and frequency
36、of nonmetallic inclusions shallbe made as prescribed in Test Methods E45. The acceptance limits shall be specified by the purchaser.NOTE S1.1In resulfurized steels, much of the sulfur is present as sulfide inclusions. For this reason, maximum sulfide inclusion level should not bespecified.S4. Calciu
37、m TreatmentS4.1 The steel shall be calcium treated.S5. CleaningS5.1 The surface of the bars shall be descaled by pickling or shotblasting, or other suitable means.S6. Restricted Mechanical Property RequirementsS6.1 Restricted mechanical property requirements to be agreed upon between purchaser and p
38、roducer.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 7TABLE 3 Mechanical Property RequirementsClass Yield Strength, min Tens
39、ile Strength, min Elongation, %, minksi MPa ksi MPa in 8 in. 200 mm in 2 in. 50 mm75 75 520 100 690 7 1080 80 550 100 690 6 9100 100 690 115 790 5 7A920/A920M 144SUMMARY OF CHANGESCommittee A01 has identified the location of selected changes to this standard since the last issue(A920/A920M 02a) that
40、 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 asserted in connection with any item mentionedin this standard. Users of this standard are expressly advis
41、ed 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 r
42、eapproved 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 receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If y
43、ou 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individua
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