1、Designation: C965 96 (Reapproved 2012)Standard Practice forMeasuring Viscosity of Glass Above the Softening Point1This standard is issued under the fixed designation C965; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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 practice covers the determination of the viscosityof glass above the softening point through the use of a platin
3、umalloy spindle immersed in a crucible of molten glass. Spindletorque, developed by differential angular velocity betweencrucible and spindle, is measured and used to calculateviscosity. Generally, data are taken as a function of temperatureto describe the viscosity curve for the glass, usually in t
4、herange from 1 to 106Pas.1.2 Two procedures with comparable precision and accu-racy are described and differ in the manner for developingspindle torque. Procedure A employs a stationary crucible anda rotated spindle. Procedure B uses a rotating crucible incombination with a fixed spindle.1.3 This st
5、andard 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
6、 ASTM Standards:2C162 Terminology of Glass and Glass ProductsE220 Test Method for Calibration of Thermocouples ByComparison Techniques3. Significance and Use3.1 This practice is useful in determining the viscosity-temperature relationships for glasses and corresponding usefulworking ranges. See Term
7、inology C162.4. Apparatus4.1 The apparatus shall consist of an electrically heatedfurnace equipped with a temperature controller, temperaturemeasuring equipment, a platinum alloy spindle, a crucible, adevice to rotate spindle or crucible, and equipment to measuretorque.NOTE 1Spindles and crucibles m
8、anufactured from 90 % Pt10 % Rhor 80 % Pt20 % Rh alloys have been found satisfactory for this purpose.4.1.1 Procedure A employs an electrically heated tube-typefurnace with a fixed support for the crucible as shown in Fig.1. A platinum alloy resistance-heated crucible also may beused.4.1.2 Procedure
9、 B employs a similar furnace but with aremovable, rotatable crucible support as shown in Fig. 2.4.1.3 Furnaces other than resistance-wound muffle typesmay be used provided they give uniform and stable tempera-ture conditions. Temperature differences greater than 3Cwithin the crucible (in glass) are
10、excessive for high precisionmeasurements.4.1.4 A temperature controller shall be provided for main-taining the glass temperature within 62C of a specifiedtemperature.4.1.5 Temperatures shall be measured with Type R or Sthermocouples calibrated in accordance with Test MethodE220 in conjunction with a
11、 calibrated potentiometer or solidstate instrumentation capable of 0.5C accuracy.An immersionthermocouple is recommended but a thermocouple in air maybe used provided measurements show equivalency.4.1.6 A crucible to contain the glass similar to those shownin Fig. 3 preferably shall be fabricated fr
12、om a platinum alloy,but a refractory material may be used provided it does notcontaminate the glass.4.1.7 A platinum alloy spindle with the geometry shown inFig. 4 is recommended. An alternative design has a hollowshaft to house the thermocouple (junction at the center of thelarge diameter portion)
13、which has the advantage of proximity,but the disadvantage of possible electrical disconnection duringtorque measurement.1This practice is under the jurisdiction of ASTM Committee C14 on Glass andGlass Products and is the direct responsibility of Subcommittee C14.04 on Physicaland Mechanical Properti
14、es.Current edition approved March 1, 2012. Published March 2012. Originallyapproved in 1981. Last previous edition approved in 2007 as C965 96(2007). DOI:10.1520/C0965-96R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
15、Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.8 A measurement system is necessary for measurementof spindle torque
16、 to an accuracy of 1 %.5. Preparation of Test Glass5.1 Select a mass of glass that is free of foreign material.Break or cut glass into pieces, each weighing about 10 to 50 g,and place the correct quantity into the crucible that will makethe molten charge reach a level at some fixed distance (several
17、millimetres) above the point where the spindle narrows down.The weight of glass required can be approximated satisfactorilywith the following expression for a cylindrical crucible:WT5 pd2L 1 h!/4 2 Vs#r 1 2 0.0007a! (1)where:h = distance between crucible floor and spindle tip, mm(generally greater t
18、han 10 mm to avoid end effects)WT= glass charge weight at room temperature, g,d = inside diameter of crucible, mm,L = immersed portion of spindle, mm,Vs= volume of immersed portion of spindle, mm3,r = density of glass at room temperature, g/cm3, anda = 0 to 300C thermal expansion coefficient, cm/cmC
19、(3 107).Avoid very small pieces of glass in the charge as they tendto make the molten glass seedy.5.2 Place the filled crucible in proper position in the furnaceand heat to a temperature that lowers the viscosity of glasssufficiently to allow trapped air bubbles to be released. Thistemperature shoul
20、d be below the original melting temperatureto avoid reboil. If reboil occurs, allow additional time for theglass to clear. Hold at this temperature at least 20 min beforestarting measurements.6. Calibration and Viscosity Determination6.1 The use of several standard reference glasses (seeAppendix X1)
21、,3available from the National Institute of Stan-dards and Technology, is recommended. These provide a widerange of temperatures and viscosities for calibration.6.2 For constant angular velocity rotation:hV/v (2)where:h = viscosity,V = torque, andv = angular velocityFor aperiodic return:3See NIST Spe
22、cial Publication 260, NIST Standard Reference Materials,National Institute of Standards and Technology, Gaithersburg, MD.1Furnace Winding2Crucible3Spindle4Shaft5Viscometer (providing both rotation and torque measurement)6ThermocoupleFIG. 1 General Arrangement for Rotating Spindle, Fixed CrucibleSche
23、me (Procedure A)NOTE 1Details are the same as in Fig. 1 except that the viscometer isreplaced by a torque measuring device, and the crucible is mounted on aremovable rotatable stand.FIG. 2 General Apparatus Arrangement for Rotating CrucibleScheme (Procedure B)C965 96 (2012)2ht/ln u2/u1! (3)where:t =
24、 time to traverse u2tou1angular displacement.6.3 Using the standard reference glasses, establish linearplots of h versus V/v or h versus t/ln(u2/u1), or both. Byproper selection of glasses the same viscosity can be attained atdifferent temperatures; this can be helpful in establishingwhether tempera
25、ture errors are present. Nonlinearity of theseplots indicate a problem in the apparatus which must becorrected. These linear plots, once well-established, are used toderive viscosity of unknown test glasses. A linear regression ofthe calibration data is recommended.7. Procedure7.1 Center the spindle
26、 over the crucible with a preset fixturethat assures concentric alignment and lower the spindle into themolten glass. The displacement between spindle end andcrucible floor shall be sufficient to minimize end effects(generally 1 cm or more will suffice). Allow a few minutes forthe glass line to stab
27、ilize. Connect the torque-measuringsystem.7.2 Depending on whether Procedure A or Procedure B isbeing employed, start rotation of either spindle or crucible.Measure and record the torque after it has stabilized. Measureand record the temperature at the time of torque measurement.7.3 Adjust the tempe
28、rature controller to change the tempera-ture for the next set of readings. Allow sufficient time fortemperature stabilization, and repeat 7.2. Torque readings maybe taken on cooling or heating providing that data so taken arein agreement with steady-state measurements.7.4 Torque-temperature data are
29、 repeated to provide suffi-cient data to describe the viscosity-temperature relationship.7.5 With a steel wire suspension as the torque measurementmember, viscosities above 103Pas require very stiff (largediameter) wire. An alternative to constant angular velocityrotation is to displace the spindle
30、some 30 to 40 from the rest(0) position and allow the wire suspension to drive the spindleback to null. Select two angles relative to null, u2and u1,(u2TABLE 3FIG. 3 Two Types of CruciblesFIG. 4 Typical Platinum Alloy SpindleC965 96 (2012)3u1), and measure the time required for the spindle to pass f
31、romu2to u1on return to null. This is called aperiodic return.7.6 After all measurements have been taken, raise thetemperature so the spindle can be easily raised out of the melt.After clinging molten glass has dripped back into the crucible,remove the spindle from the furnace. It is sometimes conve-
32、nient to remove the crucible when hot and pour the moltenglass out, especially if the crucible is reusable.8. Calculation8.1 Take the average of the torque or time readings depend-ing whether the mode of observation is constant angularvelocity or aperiodic return. Calculate V/v or t/ln(u2/u1), orbot
33、h, and from the calibration function calculate the viscosity.8.2 Plot derived viscosities as a function of temperature anddraw a smooth curve to fit the data. For most glasses the datacan be fitted to the following expression for mathematicalsmoothing:log10h5A 1 B/T 2 To(4)where:T = temperature, C,
34、andA, B, and To= adjustable constants.9. Report9.1 Report the following information:9.1.1 Designation of glass, source, and date,9.1.2 Viscosity-temperature plot and mathematical fit ifderived, and9.1.3 Date of test and name of operator.10. Precision and Bias10.1 Proper calibration with viscosity SR
35、Ms eliminatesbias and makes the accuracy of measurement equal to theuncertainty of the values given in the SRM certificates.10.2 Precision will vary from laboratory to laboratory andapparatus to apparatus. It can be established by multipledeterminations for the same glass using standard statistics.F
36、ollowing best practices, the standard deviation for a singleapparatus would not be expected to exceed a few (5) percent.11. Keywords11.1 concentric cyclinders method; glass; viscosityAPPENDIX(Nonmandatory Information)X1. STANDARD SAMPLES FOR VISCOSITY DETERMINATIONSX1.1 Standard reference glasses ar
37、e available as viscositystandards for the calibration and standardization of instrumentsof the rotating cylinder, fiber elongation, beam-bending, andparallel-plate types. A certificate listing the certified propertyvalues is issued with each sample of standard reference glass.4Available samples are
38、shown in Table 1:TABLE 1 X1.1 Standard SamplesSRMNos.Unit of Issue710a Soda-lime silica glass, Type 523/586 2 lb (0.90 kg)711 Lead-silica glass, Type 617/366 3 lb (1.36 kg)717a Borosilicate glass, 40 by 40 by 150-mmbar570 gViscosity (Pas) at Indicated Temperature, CSRM Nos. 10 1021031041051061071081
39、0910101011SofteningPoint, CAnnealingPoint, CStrain Point,C710a 1464 1205 1037 918 . . . . . . . 731 545 504711 1327.1 1072.8 909.0 794.7 710.4 645.6 594.3 552.7 518.2 489.2 464.5 602 432 392717a 1555 1256 1065 932 834A758A697A647A606A570A540A719 513 470_ANot certified, for information only.4The sole
40、 source of supply of the samples known to the committee at this timeis Standard Reference Materials Program, National Institute of Standards andTechnology, Gaithersburg, MD 20899. If you are aware of alternative suppliers,please provide this information to ASTM International Headquarters. Your com-m
41、ents will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.C965 96 (2012)4ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are
42、 expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not r
43、evised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you
44、 may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United
45、States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C965 96 (2012)5
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