ASTM C965-96(2017) Standard Practice for Measuring Viscosity of Glass Above the Softening Point.pdf

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1、Designation: C965 96 (Reapproved 2017)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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This i

6、nternational standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TB

7、T) Committee.2. Referenced Documents2.1 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 corre

8、sponding usefulworking ranges. See Terminology 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 measu

9、retorque.NOTE 1Spindles and crucibles manufactured 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 c

10、rucible also may beused.4.1.2 Procedure 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 tha

11、n 3Cwithin the crucible (in glass) are 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 wit

12、h Test MethodE220 in conjunction with a 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 F

13、ig. 3 preferably shall be fabricated from 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 th

14、e center of thelarge diameter portion) 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 C1

15、4.04 on Physicaland Mechanical Properties.Current edition approved Nov. 1, 2017. Published November 2017. Originallyapproved in 1981. Last previous edition approved in 2012 as C965 96 (2012).DOI: 10.1520/C0965-96R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM

16、 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 StatesThis international standard was

17、developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14.1.8 A measur

18、ement system is necessary for measurementof spindle torque 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 m

19、olten charge reach a level at some fixed distance (severalmillimetres) 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 d2L1h!/4 2 Vs# 1 2 0.0007! (1)where:h = distance between c

20、rucible floor and spindle tip, mm(generally greater than 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, = density of glass at room temperature, g/cm3, an

21、d = 0 to 300C thermal expansion coefficient, cm/cmC( 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

22、 air bubbles to be released. Thistemperature should 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 s

23、everal standard reference glasses (seeAppendix X1),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:/ (2)3See NIST Special Publication 260, NIST St

24、andard 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 CrucibleScheme (Procedure A)NOTE 1Details

25、 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 (2017)2where: = viscosity, = torque, and = angular velocityFo

26、r aperiodic return:t/ln2/1! (3)where:t = time to traverse 2to1angular displacement.6.3 Using the standard reference glasses, establish linearplots of versus / or versus t/ln(2/1), or both. By properselection of glasses the same viscosity can be attained atdifferent temperatures; this can be helpful

27、in establishingwhether temperature 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.Alinear regression ofthe calibration data is recommended.7. Pro

28、cedure7.1 Center the spindle 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 minut

29、es forthe glass line to stabilize. 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 meas

30、urement.7.3 Adjust the temperature 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.FIG

31、. 3 Two Types of CruciblesFIG. 4 Typical Platinum Alloy SpindleC965 96 (2017)37.4 Torque-temperature data are 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 ver

32、y stiff (largediameter) wire. An alternative to constant angular velocityrotation is to displace the spindle 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, 2and 1,(21), and measure the time required for the

33、spindle to pass from2to 1on 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 s

34、ometimes conve-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 / or t/ln(

35、2/1), orboth, 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:log10 5 A1B/T 2 To(4)where:T = temper

36、ature, C, 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 vi

37、scosity SRMs 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 st

38、atistics.Following 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

39、glasses are 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 sa

40、mples are shown in Table X1.1.4The sole 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

41、 International Headquarters. Your com-ments will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.TABLE 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 (1.3

42、6 kg)717a Borosilicate glass, 40 by 40 by 150-mmbar570 gViscosity (Pas) at Indicated Temperature, CSRM Nos. 10 10210310410510610710810910101011SofteningPoint, 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

43、489.2 464.5 602 432 392717a 1555 1256 1065 932 834A758A697A647A606A570A540A719 513 470ANot certified, for information only.C965 96 (2017)4ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this st

44、andard are 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 a

45、ndif not revised, 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,

46、 which you 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 19428-29

47、59,United 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 Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 96 (2017)5