ASTM_D_6745_-_11_2015.pdf

Designation:D674511(Reapproved 2015)Standard Test Method forLinear Thermal Expansion of Electrode Carbons1This standard is issued under the fixed designation D6745;the number immediately following the designation indicates the year oforiginal adoption or,in the case 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 test method covers the determination of the coef-ficient of linear thermal expansion(CTE)for carbon anodesand cathodes used in the aluminum industry,in baked form,byuse of a vitreous silica dilatometer.1.2 The applicable temperature range for this test methodfor research purposes is ambient to 1000 C.The recom-mended maximum use temperature for product evaluation is500 C.1.3 This test method and procedure is based on Test MethodE228,which is a generic all-encompassing method.Specificsdictated by the nature of electrode carbons and the purposes forwhich they are used are addressed by this procedure.1.4 Electrode carbons in the baked form will only exhibitprimarily reversible dimensional changes when heated.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E228 Test Method for Linear Thermal Expansion of SolidMaterials With a Push-Rod Dilatometer3.Terminology3.1 Definitions:3.1.1 linear thermal expansion,nthe change in length perunit length resulting from a temperature change.Linear ther-mal expansion is symbolically represented by L/L0,where Lis the length change of the specimen(L1L0),L0and L1arethe specimens lengths at reference temperature T0and testtemperature T1,respectively.Linear thermal expansion is oftenexpressed as a percentage or in parts per million(such asm/m).3.1.1.1 mean coeffcient of linear thermal expansion(CTE),nThe linear thermal expansion per change in temperature;the mean coefficient of linear thermal expansion is representedby:T15L/L0T51L0LT51L0L12 L0T12 T0(1)3.1.1.1 DiscussionThis has to be accompanied by thevalues of the two temperatures to be meaningful;the referencetemperature(T0)is 20 C,and the notation may then onlycontain a single number,such as 200,meaning the meancoefficient of linear thermal expansion between 20 C and200 C.3.2 Definitions of Terms Specific to This Standard:3.2.1 reference specimen,na particularly identified orpedigreed material sample,with well-characterized behaviorand independently documented performance.3.2.2 specimen,na representative piece of a larger body(anode,cathode,and so forth)that is considered to be fairlytypical of a portion or of the entire piece.3.2.3 vitreous silica dilatometer,na device used to deter-mine linear thermal expansion,by measuring the difference inlinear thermal expansion between a test specimen and thevitreous silica parts of the dilatometer.4.Summary of Test Method4.1 Arepresentative specimen is placed into a vitreous silicadilatometer and heated,while its linear expansion is continu-ously recorded.The change of the specimen length is recordedas a function of temperature.The coefficient of linear thermalexpansion is then calculated from these recorded data.5.Significance and Use5.1 Coefficients of linear thermal expansion are used fordesign and quality control purposes and to determine dimen-sional changes of parts and components(such as carbonanodes,cathodes,and so forth)when subjected to varyingtemperatures.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.05 on Properties of Fuels,Petroleum Coke and Carbon Material.Current edition approved Oct.1,2015.Published December 2015.Originallyapproved in 2001.Last previous edition approved in 2011 as D6745 11.DOI:10.1520/D6745-11R15.2For 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 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.Apparatus6.1 DilatometerThe dilatometer consists of the following:6.1.1 Specimen Holder and Push-rod,both made of vitreoussilica.The design of the device shall ensure that the push-rodload on the specimen by itself is not causing deformation.Theuse of pressure distribution quartz plates on top of thespecimen is permissible.NOTE1Dilatometers are usually constructed in horizontal or verticalconfigurations.3Vertical devices are preferred for very large