1、Designation:A31971(Reapproved 2015)Standard Specification forGray Iron Castings for Elevated Temperatures for Non-Pressure Containing Parts1This standard is issued under the fixed designation A319;the number immediately following the designation indicates the year oforiginal adoption or,in the case
2、of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers three classes of gray ironsuitable for castings exposed to temperatures e
3、ncountered insuch service as grate bars,stoker links,stoker parts,oil stillfurnace parts,firebox parts,ingot molds,glass molds,causticpots,and metal melting pots.NOTE1This specification is general,covering cast irons normallyused for the above types of service,at temperatures as high as 1400F(760C).
4、It is not intended to imply that all three classes are suitablethroughout this entire temperature range without regard to actual servicestresses.Some are suitable for long service at the lower temperatures only,unless low stresses are involved.1.2 The three classes of gray iron covered by this speci
5、fi-cation are as follows:1.2.1 Class I,possessing superior resistance to thermalshock,1.2.2 Class II,possessing average resistance to thermalshock and a moderately good tensile strength(tensile strengthsabove 30 000 psi(207 MPa)may be expected),and1.2.3 Class III,possessing a higher tensile strength
6、 thaneither Classes I or II(tensile strengths as high as 40 000 psi(276 MPa)may be expected).1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered st
7、andard.2.Referenced Documents2.1 ASTM Standards:2A48/A48M Specification for Gray Iron Castings3.Manufacture3.1 The melting procedure shall be optional with thefoundry.4.Physical Requirements4.1 Some of the gray cast irons described in this specifica-tion are deliberately made of a soft,low-strength
8、iron forresistance to thermal shock,and strength requirements areunnecessary.For applications in which a strength requirementis essential,room temperature tensile strengths may be speci-fied up to those prescribed for Class 40 in SpecificationA48/A48M.5.Machinability5.1 All machinable castings shall
9、 be limited in hardness atsuch locations on the castings as designated by the purchaser.The maximum hardness at the locations on castings that are tobe machined shall be a matter of agreement between themanufacturer and the purchaser.6.Chemical Composition6.1 It is the intention of this specificatio
10、n to classify theseirons in accordance with their carbon content equivalentcalculated as follows:Carbon content equivalent5 C10.3Si1P!(1)where:C=carbon content,%,Si=silicon content,%,andP=phosphorus content,%,6.2 The carbon content equivalent and the minimum carboncontent for the various classes sha
11、ll be as prescribed in Table 1.Table 2 prescribes the allowable silicon ranges predicated onthe basis of various permissible carbon contents.It is recom-mended that embrittling impurities be held to the followingmaximum limits:Phosphorus,max,%Sulfur,max,%0.600.156.3 The three basic classes may be al
12、loyed with chromium.When chromium is present as an alloying element,each classshall be subdivided into types designated as follows:TypeChromium,%A0.200.40B0.410.65C0.660.95D0.961.201This specification is under the jurisdiction of ASTM Committee A04 on IronCastings and is the direct responsibility of
13、 Subcommittee A04.01 on Grey and WhiteIron Castings.Current edition approved Nov.1,2015.Published November 2011.Originallyapproved in 1948.Last previous edition approved in 2011 as A319 71(2011).DOI:10.1520/A0319-71R15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM
14、 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 Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.4 All irons may be alloyed to incre
15、ase the strength and toimprove and stabilize the structure for elevated-temperatureservice.The alloying elements,which,in addition tochromium,are commonly added to improve these properties,are copper,molybdenum,nickel,and vanadium.Any combi-nation of these alloying elements that assists in resisting
16、oxidation or surface deterioration or in stabilizing the structureor retaining strength at elevated temperatures,may be used.NOTE2The provisions of this specification permit the purchaser toselect a grade of cast iron suitable for his service and to define the productas,for example:Castings Class II,Type B,plus|Cz|Cz alloys.All surfaces marked“f”(for finish)with HBN 250,max.7.Product Analysis7.1 When alloying elements are agreed upon between themanufacturer and the purchaser,the purchaser may ma
