1、Designation:C82981(Reapproved 2015)Standard Practices forMeasurement of Liquidus Temperature of Glass by theGradient Furnace Method1This standard is issued under the fixed designation C829;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revis
2、ion,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 These practices cover procedures for determining theliquidus temperature(Note 1)of a glass(Note 1)by establ
3、ish-ing the boundary temperature for the first crystallinecompound,when the glass specimen is held at a specifiedtemperature gradient over its entire length for a period of timenecessary to obtain thermal equilibrium between the crystallineand glassy phases.NOTE1These terms are defined in Terminolog
4、y C162.1.2 Two methods are included,differing in the type ofsample,apparatus,procedure for positioning the sample,andmeasurement of temperature gradient in the furnace.Bothmethods have comparable precision.Method B is preferred forvery fluid glasses because it minimizes thermal and mechanicalmixing
5、effects.1.2.1 Method A employs a trough-type platinum container(tray)in which finely screened glass particles are fused into athin lath configuration defined by the trough.1.2.2 Method B employs a perforated platinum tray onwhich larger screened particles are positioned one per hole onthe plate and
6、are therefore melted separately from each other.21.3 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 regul
7、atory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3C162 Terminology of Glass and Glass Products2.2 Other Document:NIST Certificate for Liquidus Temperature,SRM 77343.Significance and Use3.1 These practices are useful for determining the maximumtemperature at which crystallizati
8、on will form in a glass,and aminimum temperature at which a glass can be held,forextended periods of time,without crystal formation andgrowth.4.Apparatus4.1 The apparatus for determining the liquidus temperatureshall consist essentially of an electrically heated gradientfurnace,a device for controll
9、ing the furnace temperature,temperature measuring equipment,and other items listed.4.1.1 Furnace:4.1.1.1 Method AHorizontal temperature gradient,electri-cally heated furnace,tube type,as illustrated in Figs.1-3 anddescribed in A1.1.4.1.1.2 Method BAn alternative furnace detail employingpregrooved Al
10、2O3cores and dual windings,as illustrated inFigs.4 and 5,and described in A1.2.4.1.1.3 Equivalent temperature gradient conditions may alsobe obtained with furnaces having multiple windings equippedwith separate power and control,or a tapped winding shuntedwith suitable resistances.For high precision
11、,temperaturegradients in excess of 10C/cm should be avoided.4.1.2 Furnace Temperature Control:4.1.2.1 Method AA suitable temperature controller shallbe provided to maintain a fixed axial temperature distributionover the length of the furnace.4.1.2.2 Method BArheostat shall be used to supply powerto
12、the outer winding.Aseparate rheostat and controller shall beused for the inner core winding.The basic furnace temperaturelevel is achieved by controlling power to both inner and outercore windings.The slope of the gradient is achieved byadjusting power input to the outer core winding only.Theestabli
13、shed temperature gradient is then maintained by control-ling power to the inner core winding only.1These practices are under the jurisdiction of ASTM Committee C14 on Glassand Glass Productsand are the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition
14、approved May 1,2015.Published May 2015.Originallyapproved in 1976.Last previous edition approved in 2010 as C829 81(2010).DOI:10.1520/C0829-81R15.2From NBS Research Paper RP2096,Vol 44,May 1950,by O.H.Grauer and E.H.Hamilton,with modification and improvement by K.J.Gajewski,Ford MotorCo.,Glass Resea
15、rch and Development Office(work unpublished).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.4Available from Natio
16、nal Institute of Standards and Technology(NIST),100Bureau Dr.,Stop 1070,Gaithersburg,MD 20899-1070,http:/www.nist.gov.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.1.3 Temperature-Measuring Equipment Furnace tem-peratures shall be measured with calibrated Type R or Sthermocouples in conjunction with a calibrated potentiometer,or other comparable instrumentation,capable of measurementswithin 0.5C.In addition to control thermocouple
