SPECIFICATION FOR ALLOY STEEL BOLTING MATERIALS FOR LOW-TEMPERATURE SERVICESA-320/SA-320M(Identical with ASTM Specification A 320/A 320M-99.)1.Scope1.1This specification covers alloy steel bolting mate-rials for pressure vessels,valves,flanges,and fittings for low-temperature service.The term “bolting material”as used in this specification covers rolled,forged,or strain hardened bars,bolts,screws,studs,and stud bolts.The bars shall be hot-wrought.The material may be further processed by centerless grinding or by cold drawing.Austenitic stainless steel may be solution annealed or annealed and strain-hardened.When strain-hardened austenitic stainless steel is ordered,the pur-chaser should take special care to ensure that Appendix X1is thoroughly understood.1.2Several grades are covered,including both ferritic and austenitic steels designated L7,B8,etc.Selection will depend on design,service conditions,mechanical properties,and low-temperature characteristics.The me-chanical requirements of Table 1indicate the diameters for which the minimum mechanical properties apply to the various grades and classes,and Table 2stipulates the requirements for Charpy impact energy absorption.The manufacturer should determine that the material can conform to these requirements before parts are manufactured.For example,when Grade L43is speci-fied to meet the Table 2impact energy values at −150°F [−101°C],additional restrictions (such as procuring a steel with lower P and S contents than might normally be supplied)in the chemical composition for AISI 4340are likely to be required.NOTE 1—The committee formulating this specification has included several grades of material that have been rather extensively used for the present purpose.Other compositions will be considered for inclusion by the committee from time to time as the need becomes ers should note that hardenability of some of the grades mentioned may restrict the maximum size at which the required mechanical properties are obtainable.5081.3Nuts for use with this bolting material are covered in Section 9and the nut material shall be impact tested.1.4Supplementary Requirements (S1,S2,and S3)of an optional nature are provided.They shall apply only when specified in the inquiry,contract and order.1.5This specification is expressed in both inch-pound units and in SI units.However,unless the order specifies the applicable “M”specification designation (SI units),the material shall be furnished to inch-pound units.1.6The values stated in either inch-pound units or SI units are to be regarded separately as standard.Within the text,the SI units are shown in brackets.The values stated in each system are not exact equivalents;therefore,each system must be used independently of the bining values from the two systems may result in nonconformance with the specification.2.Referenced Documents2.1ASTM Standards:A 29/A 29M Specification for Steel Bars,Carbon and Alloy,Hot-Wrought and Cold-Finished,General Re-quirements forA 194/A 194M Specification for Carbon and Alloy Steel Nuts for Bolts for High-Pressure and High-Tempera-ture ServiceA 276Specification for Stainless Steel Bars and Shapes A 370Test Methods and Definitions for Mechanical Test-ing of Steel ProductsA 751Test Methods,Practices,and Terminology for Chemical Analysis of Steel ProductsE 18Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic MaterialsPART A—FERROUS MATERIAL SPECIFICATIONS SA-320/SA-320ME566Practice for Electromagnetic(Eddy-Current)Sort-ing of Ferrous MetalsF436Specification for Hardened Steel Washers2.2ANSI Standards:B1.1Unified Inch Screw Threads(UN and UNR Thread Form)B18.2.1Square and Hex Bolts and ScrewsB18.3Hexagon Socket and Spline Socket ScrewsB18.22.1Plain Washers2.3AIAG Standard:AIAG B-502.00Primary Metals Identification Tag Ap-plication Standard3.Ordering Information3.1The inquiry and order for material under this specification shall include the following as required to describe the material adequately:3.1.1Specification designation latest issue,and analysis by grade as selected from Table3;3.1.2Heat-treated condition(that is,for the austen-itic stainless steels,solution treated(Class1);solution treated afterfinishing(Class1A),and annealed-and strain-hardened(Class2);3.1.3Quantity(number of pieces or weight);3.1.4Description of items required(bars,bolts, screws,or studs);3.1.5Dimensions(diameter,length of point,overall length,finish,shape,and threads);3.1.6Nuts and washers,if required by purchaser,in accordance with Section9;3.1.7End use;3.1.8Supplementary requirements,if any;and3.1.9Special requirements,in accordance with4.3.1,4.3.2,4.3.3,7.3,10.1,11.1,and14.1.4.Materials and Manufacture4.1Process—The steel shall be produced by anyof the following primary processes:open-hearth,basic-oxygen,electric-furnace,or vacuum-induction melting (VIM).The primary melting may incorporate separate degassing or refining.The molten steel may be vacuum-treated prior to or during pouring of the ingot.The basic-oxygen process shall be limited to steels containing not over6%chromium.5094.2Discard—A sufficient discard shall be made to secure freedom from injurious piping and undue segregation.4.3Heat Treatment:4.3.1The bolting material shall be allowed to cool to room temperature after rolling or forging.Grades L7,L7A,L7B,L7C,L7M,L43,L1,L70,L71,L72, and L73shall be reheated to above the upper critical temperature and liquid quenched and tempered.Grades B8,B8C,B8M,B8T,B8F,B8P,B8LN,and B8MLN shall receive a carbide solution treatment.Products made from such material are described as Class 1. This shall consist of holding the material for a sufficient time at a temperature at which the chromium carbide will go into solution and then cooling in air or in a liquid medium at a rate sufficient to prevent reprecipitation of the carbide.Material thus treated is described as Class 1.If specified in the purchase order,material shall be solution treated in thefinished condition;material so treated is described as Class1A.4.3.2When increased mechanical properties are desired,the austenitic bolting materials shall be solution annealed and strain hardened if specified in the purchase order;material so treated is identified as Class2.4.3.3If scale-free brightfinish is required,this shall be specified in the purchase order.4.3.4For L7M bolting,thefinal heat treatment, which may be the tempering or stress-relieving operation conducted at1150°F[620°C]minimum,shall be done after machining or rolling of the threads.5.Chemical Composition5.1Heat Analysis—An analysis of each heat of steel shall be made by the manufacturer to determine the percentages of the elements specified in Table3. This analysis shall be made from a test ingot taken during the pouring of the heat.The chemical composi-tion thus determined shall be reported to the purchaser or the purchaser’s representative,and shall conform to the requirements prescribed in Table3.5.2Product Analysis—An analysis may be made by the purchaser from samples representing the bolting material.The chemical composition thus determined shall conform to the requirements prescribed in Table3.5.3The steel shall not contain an unspecified element for the ordered grade to the extent that the steel conforms to the requirements of another grade for which that element is a specified element.Furthermore,SA-320/SA-320M2001SECTION IIelements present in concentrations greater than0.75 weight/percent shall be reported.Chemical analysis shall be performed in accordance with Test MethodsA751.6.Mechanical Requirements6.1Tensile Properties:6.1.1The material shall conform to the require-ments as to tensile properties prescribed in Table1at room temperature after heat treatment(see4.3.1).6.1.2Number of Tests:6.1.2.1For heat-treated bars,one tension test and one impact test consisting of three specimens shallbe made for each diameter of each heat representedin each tempering charge.In the continuous type treat-ment,a charge shall be defined as6000lb[2700kg].6.1.2.2For studs,bolts,screws,etc.,one tension test and one set of three impact specimens shall be made for each diameter of each heat involved in the lot.Each lot shall consist of the following:Diameter,in.[mm]Lot Size,lb[kg]11⁄8[30]and under1500[680]or fraction thereofOver11⁄8[30]to13⁄4[45],incl4500[2040]or fraction thereofOver13⁄4[45]to21⁄2[65],incl6000[2700]or fraction thereofOver21⁄2[65]100pieces or fraction thereof6.1.2.3Tension and impact tests are not requiredto be made on bolts,screws,studs,or stud bolts which are fabricated from heat-treated bars furnishedin accordance with the requirements of this specification and tested in accordance with6.1.2.1,provided theyare not given a subsequent heat treatment.6.1.3Test Specimens—Tension test specimens taken fromfinished bolts,screws,studs,or stud bolts shall be machined to the form and dimensions and shall be taken from positions shown in Annex A3on Steel Fasteners,paragraph A3.2.1.7of Test Methods and Definitions A370.Tension test specimens frombar stock are covered by Test Methods and DefinitionsA370in Annex A1,“Steel Bar Products.”6.1.4Test Method—Tension tests shall be madein accordance with Test Methods and Definitions A 370including applicable parts of Annex A3,“Steel Fasteners.”Speed of testing shall meet the requirementsof Test Methods and Definitions A370section,“Speedof Testing.”5106.2Impact Properties:6.2.1Requirements:6.2.1.1Material of Grades L7,L7A,L7B,L7C, L7M,L43,L70,L71,L72,and L73shall show a minimum impact energy absorption of20ft·lbf[27 J]and of Grade L1a minimum impact energy absorption of40ft·lbf[54J]at the test temperature when tested by the procedure specified in the applicable portions of Sections19to28of Test Methods and Definitions A370.The temperature of the coolant used for chilling the test specimens shall be controlled within±3°F [1.5°C].Impact tests are not required for carbide solution treated or strain hardened Grades B8,B8F,B8P,B8M, B8T,B8LN,and B8MLN for temperatures above −325°F[−200°C];for carbide solution treated Grades B8,B8P,B8C,and B8LN above−425°F[−255°C]; for all ferritic and austenitic steel grades of bolting1⁄2 in.[12.5mm]and smaller in diameter.All other material furnished under this specification shall be tested.Test temperatures for ferritic grades are listed in Table4. Exceptions to this requirement are permissible,and the impact tests may be made at specified temperatures different than those shown in Table4,provided the test temperature is at least as low as the intended service temperature and the bolting is suitably marked to identify the reported test temperature.When impact testing is required for austenitic grades,test criteria shall be agreed upon between the supplier and purchaser.6.2.1.2The impact test requirements for standard and subsize Charpy test specimens are prescribed in Table2.6.2.2Number of Tests:6.2.2.1The test requirements for heat-treated bars are given in6.1.2.1.6.2.2.2For test requirements on studs,bolts, screws,etc.,see6.1.2.2and6.1.2.3.6.2.2.3Impact tests are not required to be made on heat-treated bars,bolts,screws,studs,and stud bolts 1⁄2in.[12.5mm]and under in diameter.6.2.3Test Specimens:6.2.3.1The impact test specimen shall have the form and dimensions shown in Fig.10of Test Methods and Definitions A370for the Charpy V-notch specimen, Type A.The notch shall be located on the test specimen surface which most closely approaches a radial direction. The base of the notch shall be as nearly as practicable perpendicular to the surface of the bar.PART A—FERROUS MATERIAL SPECIFICATIONS SA-320/SA-320M6.2.3.2For sections1in.[25mm]or less in diameter,test specimens shall be taken at the axis;for sections over1in.[25mm]in diameter,midway between the axis and the surface.6.3Hardness Requirements:6.3.1The hardness shall conform to the require-ments prescribed in Table1with testing performed in accordance with Test Methods and Definitions A370.6.3.2The maximum hardness of Grade L7M shallbe235HB or99HRB(conversion in accordance with Table2B of Test Methods and Definitions A370). Minimum hardness shall not be less than200HB or93HRB.Conformance to this hardness shall be ensuredby testing the hardness of each stud or bolt by Brinellor Rockwell B methods as described in the sectionson Brinell Test,Portable Hardness Test,and Rockwell Test of Test Methods and Definitions A370.6.3.2.1The use of100%electromagnetic testingfor hardness as an alternative to100%indentation hardness testing is permissible when qualified by sam-pling using indentation hardness testing.Each lot testedfor hardness electromagnetically shall be100%exam-ined in accordance with Practice E566.Following electromagnetic testing for hardness,a random sampleof a minimum of100pieces in each purchase lot(asdefined in6.1.2.2)shall be tested by indentation hard-ness methods.All samples must meet hardness require-ments to permit acceptance of the lot.If any one sample is outside of the specified maximum or minimum hardness,the lot shall be rejected and either reprocessed and resampled,or tested100%by indentation hardness methods.6.3.2.2In the event a controversy exists relativeto minimum strength,tension tests shall prevail over hardness readings.Products which have been tested and found acceptable shall have a line under the grade symbol.6.3.2.3Surface preparation for indentation hard-ness testing shall be in accordance with Test MethodsE18.Hardness tests shall be performed on the endof the bolt or stud.When this is impractical,the hardness test shall be performed elsewhere.7.Workmanship,Finish,and Appearance7.1Bolts,screws,studs,and stud bolts shall be pointed and shall have a workmanlikefinish.Points shall beflat and chamfered or rounded at option ofthe manufacturer.Length of points on studs and stud511bolts shall be not less than one nor more than two complete threads as measured from the extreme end parallel to the axis.Length of studs and stud bolts shall be measured fromfirst thread tofirst thread. 7.2Standard permissible variations for dimensions of bars shall be as prescribed in Table5.Aside from the tolerances given in Table5,additional tolerances for the basic materials are given in Specifications A 29/A29M and A276.7.3Bolt heads shall be in accordance with the dimensions of ANSI B18.2.1.Unless otherwise specified in the purchase order,the Heavy Hex Screws Series should be used,except the maximum body diameter and radius offillet may be the same as for the Heavy Hex Bolt Series.Socket-head fasteners shall be in accordance with ANSI B18.3.8.Retests8.1If the results of the mechanical tests of any test lot do not conform to the requirements specified,the manufacturer may retreat such lot not more than twice, in which case two additional tension tests and one additional impact test consisting of three specimens shall be made from such lot,all of which shall conform to the requirements specified.9.Nuts and Washers9.1Bolts,studs,and stud bolts of Grades L7,L7A, L7B,L7C,L43,L1,L70,L71,L72,and L73shall be equipped with ferritic alloy nuts conforming to Grade 4or Grade7of Specification A194/A194M or a grade of steel similar to the studs.Grade7M nuts at a hardness not exceeding235HB(or equivalent)shall be used with Grade L7M bolts,studs,and stud bolts. All nut materials,including those which may be supplied under Specification A194/A194M,shall be subject to the impact requirements of this specification in the following manner:impact tests shall be made on test specimens taken from the bar or plate from the heat of steel used for manufacturing the nuts,and heat treated with the nut blanks.9.2Bolts,studs,and stud bolts of Grades B8,B8C, B8T,B8P,B8F,B8M,B8LN,and B8MLN shall be equipped with austenitic alloy nuts conforming to Grades8,8C,8T,8F,8M,8LN,and8MLN for Specification A194/A194M.Impact tests are not required for Grades8F,8M,8T,and8MLN for tempera-SA-320/SA-320M2001SECTION IItures above−325°F[−200°C]and for Grades8,8P,8C,and8LN above−425°F[−255°C].9.3If the purchaser requires nuts with a Charpy impact energy absorption of not less than20ft·lbf [27J]at temperatures below−150°F[−100°C],he may require that the nuts conform to Grades8,8C,8M,8P,8T,8F,8LN,or8MLN of Specification A194/A 194M.9.4Washers for use with ferritic steel bolting shall conform to Specification F436.9.5Washers for use with austenitic steel bolting shall be made of austenitic steel as agreed upon betweenthe manufacturer and purchaser.9.6Washer dimensions shall be in accordance with requirements of ANSI B18.22.1,unless otherwise speci-fied in the purchase order.10.Threads10.1All alloy steel bolts,studs,and stud bolts,unless otherwise specified,shall be threaded in accordance with ANSI B1.1,Class2Afit,sizes1in.[25mm] and smaller in diameter with the Coarse Thread Series, and11⁄8in.[29mm]and larger in diameter with the8Pitch Thread Series.10.2Where practical,all threads shall be formed after heat treatment.Class1A,Grades B8A,B8CA,B8MA,B8PA,B8FA,B8TA,B8LNA,and B8MLNAare to be solution-treated in thefinished condition.11.Inspection11.1The inspector representing the purchaser shall have free entry,at all times while work on the contractof the purchaser is being performed,to all parts ofthe manufacturer’s works that concern the manufactureof the material ordered.The manufacturer shall affordthe inspector all reasonable facilities to satisfy him thatthe material is being furnished in accordance with this specification.All tests(except product analysis)and inspection shall be made at the place of manufacture prior to shipment,unless otherwise specified,and shallbe so conducted as not to interfere unnecessarily withthe operation of the works.51212.Rejection and Rehearing12.1Rejection:12.1.1Unless otherwise specified in the order,any rejection based on tests made in accordance with5.2 shall be reported to the manufacturer within30days from the receipt of samples by the purchaser.12.1.2Material that shows defects subsequent to its acceptance at the manufacturer’s works shall be rejected,and the manufacturer shall be notified. 12.2Rehearing—Samples tested in accordance with 5.2that represent rejected material shall be preserved for2weeks from the date of the test report.In case of dissatisfaction with the results of the tests,the manufacturer may make claim for a rehearing within that time.13.Certification13.1When agreed upon in writing between the manufacturer and the purchaser,a certification that the material conforms to the requirements of this specifica-tion shall be the basis of acceptance of the material. Otherwise,the manufacturer shall report to the purchaser or the purchaser’s representative the results of the chemical analyses and mechanical tests made in accord-ance with the specification.The specification designation included on test reports shall include year of issue and revision letter,if any.14.Product Marking14.1Grade and manufacturer’s symbols shall be applied to one end of studs3⁄8in.[10mm]in diameter and larger and to the heads of bolts1⁄4in.[6mm]in diameter and larger.(If the available area is inadequate, the grade symbol may be marked on one end and the manufacturer’s identification symbol marked on the other end.)The identification symbol shall be as shown in Table3.In the case of Class2,Grades B8,B8C, B8M,B8P,B8F,and B8T strain hardened as provided in Table1,a line shall be stamped under the grade symbol in order to distinguish it from Class1and Class1A bolting which has not been strain hardened. In the case of Class1A,the marking B8A,B8CA, B8MA,B8PA,B8FA,B8TA,B8LNA,and B8MLNA identifies the material as being in the solution-treated condition in thefinished state.Grade L7M which has been100%evaluated in conformance with this specification shall have a line under the grade symbolPART A—FERROUS MATERIAL SPECIFICATIONS SA-320/SA-320Mto distinguish it from L7M produced to previous revi-sions not requiring100%hardness testing.14.2For bolting materials,including threaded bars, that are furnished bundled and tagged or boxed,the tags and boxes shall carry the grade symbol for the material identification and the manufacturer’s identifica-tion mark or name.14.3Nuts from materials that have been impact tested shall be marked with the letter“L.”14.4For purposes of identification marking,the manufacturer is considered the organization that certifiesthe fastener was manufactured,sampled,tested,and inspected in accordance with the specification and the results have been determined to meet the requirementsof this specification.51314.5Bar Coding—In addition to the requirements in14.1,14.2,14.3,and14.4,bar coding is acceptable as a supplementary identification method.Bar coding should be consistent with AIAG Standard B-502.00. If used on small items,the bar code may be applied to the box or a substantially applied tag.15.Keywords15.1additional elements;austenitic stainless steel; bolts–steel;chromium-molybdenum steel;fasteners–steel;markings onfittings;nickel-chromium-molybde-num alloy steel;pressure vessel service;stainless steel bolting material;starting material;steel bars–alloy;steel bolting material;steelflanges;steel valves;temperature service applications–low。
