ASTM_C_336_-_71_2015.pdf

Designation:C33671(Reapproved 2015)Standard Test Method forAnnealing Point and Strain Point of Glass by FiberElongation1This standard is issued under the fixed designation C336;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the determination of the anneal-ing point and the strain point of a glass by measuring theviscous elongation rate of a fiber of the glass under prescribedcondition.1.2 The annealing and strain points shall be obtained byfollowing the specified procedure after calibration of theapparatus using fibers of standard glasses having knownannealing and strain points,such as those specified andcertified by the National Institute of Standards and Technology(NIST)2(see Appendix X1).1.3 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:3C338 Test Method for Softening Point of GlassC598 Test Method for Annealing Point and Strain Point ofGlass by Beam Bending3.Definitions3.1 annealing pointthat temperature at which internalstresses in a glass are substantially relieved in a matter ofminutes.4,5,6During a test in accordance with the requirementsof this method,the viscous elongation rate is measured by asuitable extensometer while the specimen fiber is cooling at arate of 4 6 1C/min.The elongation rate at the annealing pointis approximately 0.14 mm/min for a fiber of 0.65 mm diam-eter.63.2 annealing rangethe range of glass temperature inwhich stresses in glass articles can be relieved at a commer-cially desirable rate.For purposes of comparing glasses,theannealing range is assumed to correspond with the tempera-tures between the annealing point(AP)and the strain point(StP).3.3 strain pointthat temperature at which the internalstresses in a glass are substantially relieved in a matter ofhours.The strain point is determined by extrapolation of theannealing point data and is the temperature at which theviscous elongation rate is 0.0316 times that observed at theannealing point.4.Significance and Use4.1 This test method provides data useful for(1)estimatingstress release,(2)the development of proper annealingschedules,and(3)estimating setting points for seals.1This test method is under the jurisdiction of ASTM Committee C14 on Glassand Glass Products and is the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved Published May 2015.Originally approved in 1954.Last previous edition approved in 2010 as C336 71(2010).DOI:10.1520/C0336-71R15.2Available from National Institute of Standards and Technology(NIST),100Bureau Dr.,Stop 1070,Gaithersburg,MD 20899-1070,http:/www.nist.gov.Publi-cation 260.3For 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.4Littleton,J.T.,and Roberts,E.H.,“A Method for Determining the AnnealingTemperature of Glass,”Journal of the Optical Society of America,Vol 4,1920,p.224.5Lillie,H.R.,“Viscosity of Glass Between the Strain Point and MeltingTemperature,”Journal of American Ceramic Society,Vol 14,1931,p.502;“Re-Evaluation of Glass Viscosities at Annealing and Strain Points,”Journal ofAmerican Ceramic Society,Vol 37,1954,p.111.6McGraw,D.A.and Babcock,C.L.,“Effect of Viscosity and Stress Level onRate of Stress Release in Soda-Lime,Potash-Barium and Borosilicate Glasses,”Journal of the American Ceramic Society,Vol 42,1959,p.330.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 Accordingly,itsusageiswidespreadthroughoutmanufacturing,research,and development.It can be utilizedfor specification acceptance.5.Apparatus5.1 FurnaceThe furnace shall be 368 mm(1412-in.)longand approximately 114 mm(412in.)in diameter and shallcontain a copper core 305 mm(12 in.)long and 29 mm(118in.)in outside diameter,with inside diameter of 5.6 mm(732in.).It shall be constructed substantially as shown in Fig.1.5.1.1 Such a furnace will cool naturally at approximately4C(7F)/min at 500C(932F)and at a rate exceeding 3C(5.5F)/min at 400C(752F).5.2 Temperature Measuring and Indicating InstrumentsFor the measurement of temperature there shall be provided athermocouple,preferably platinum-platinum rhodium,insertedin the upper side hole of the copper core,as indicated in Fig.1,so that its junction is located mid