1、Designation: C 598 93 (Reapproved 2008)Standard Test Method forAnnealing Point and Strain Point of Glass by BeamBending1This standard is issued under the fixed designation C 598; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、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 anneal-ing point and the strain point of a glass by measuring
3、 the rateof midpoint viscous bending of a simply loaded glass beam.2However, at temperatures corresponding to the annealing andstrain points, the viscosity of glass is highly time-dependent.Hence, any viscosities that might be derived or inferred frommeasurements by this procedure cannot be assumed
4、to repre-sent equilibrium structural conditions.1.2 The annealing and strain points shall be obtained fol-lowing a specified procedure after direct calibration of theapparatus using beams of standard glasses having knownannealing and strain points such as those supplied and certifiedby the National
5、Institute of Standards and Technology.31.3 This test method, as an alternative to Test Method C 336is particularly well suited for glasses that for one reason oranother are not adaptable for flame working. It also has theadvantages that thermal expansion and effective length correc-tions, common to
6、the fiber elongation method, are eliminated.1.4 The values stated in metric units are to be regarded asthe standard. The values given in parentheses are for informa-tion only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibi
7、lity 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:4C 336 Test Method for Annealing Point and Strain Point ofGlass by Fiber Elongation3. Terminology3
8、.1 Definitions:3.1.1 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 (A. P.) and the s
9、train point(St. P.).3.1.2 annealing pointthat temperature at which internalstresses in a glass are substantially relieved in a matter ofminutes. During a test in accordance with the requirements ofthis test method, the midpoint rate of viscous deflection of thetest beam is measured by an extensomete
10、r with suitablemagnification during cooling at a rate of 4 6 1C/min. Thenominal deflection rate at the annealing point ideally is asfollows:Deflection rate, cm/min 5 2.67 3 10211L3M!/Ic(1)where:L = support span, cm;M = centrally applied load, g; andIc= cross-section moment of inertia of test beam, c
11、m4(seeAppendix X1).3.1.3 strain pointthat temperature at which 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 deflection rate is 0.0316 times that observ
12、ed at theannealing point.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 April 1, 2008. Published December 2008. Originallyapproved in 19
13、67. Last previous edition approved in 2003 as C 598 93 (2003).2Hagy, H. E., “Experimental Evaluation of Beam Bending Method of Deter-mining Glass Viscosities in the Range 108to 1015Poises,” Journal of the AmericanCeramic Society, Vol 46, No. 2, 1963, pp. 9597.3NIST Special Publication 260.4For refer
14、enced 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
15、 Conshohocken, PA 19428-2959, United States.4. Significance and Use4.1 This test method offers an alternate procedure to TestMethod C 336 for determining the annealing and strain pointsof glass. It is particularly recommended for glasses notadaptable to flame working. Also fewer corrections are nece
16、s-sary in data reduction.5. Apparatus5.1 The apparatus shall consist of a furnace, a means ofcontrolling its temperature and cooling rate, a specimen holderand loading rod, and a means of observing the rate of midpointviscous deflection of the glass beam.5.1.1 FurnaceThe furnace shall be electricall
17、y heated byresistance-wire windings of either platinum-rhodium or 80-20Ni-Cr alloys. A cutaway drawing of a typical furnace is shownin Fig. 1. Dimensions and details of the furnace constructionare not critical, but a cylindrical furnace of height of 255 mm(10 in.), outside diameter of 230 mm (9 in.)
18、, and insidediameter of 130 mm (5 in.) with a removable top plug isrecommended. The temperature distribution shall be such thatdifferences in temperature greater than 2C shall not result overthe length of the specimen beam and along the axis of thefurnace from the undeflected beam plane to a point 1
19、3 mm (12in.) below.5.1.2 Temperature Measuring and Indicating InstrumentsFor the measurement of temperature, there shall be provided acalibrated Type R or S thermocouple. The thermocouple shallbe housed in a double-bore alumina tube with its junctionplaced within 5 mm of the specimen near the axis o
20、f thefurnace. It is recommended that the thermocouple be refer-enced to 0C by means of an ice bath and its emf measuredwith a calibrated potentiometer having a sensitivity of 61Vand an accuracy of 65 V. Precautions shall be taken to ensurethat the ice bath is maintained at 0C throughout the test.5.1
21、.3 Furnace ControlSuitable means shall be providedfor idling the furnace, controlling the heating rate, and, in thecase of very hard glasses, limiting the cooling rate to not morethan 5C/min. Although commercially available programmingequipment provides excellent control, a variable transformerwith
22、manual control is an inexpensive and adequate technique.5.1.4 Specimen Holder and Loading RodA ceramic sup-port stand and a ceramic loading rod shall be provided forAAlumina muffle support stand ELinearly variable differential transformerBSpecimen beam (LVDT)CThermocouple FZero-adjust mechanism for
23、LVDTDLoading rod GWeightHLaboratory jackFIG. 1 Cutaway Drawing of Beam-Bending ApparatusC 598 93 (2008)2supporting the specimen and applying the load to the specimen,respectively. The thermal expansion characteristics of bothstand and rod materials must be very similar so as to minimizemotion of the
24、 loading rod on cooling as a result of expansiondifferences (see Appendix X2). A rectangular alumina mufflemakes a suitable support stand (Note 1). The side walls of thismuffle can be notched to define specimen position. Thesupporting surfaces of these notches shall be flat and lie in aplane perpend
25、icular to the axis of the furnace. The inside edgesof these supporting surfaces define the support span once thespecimen beam starts to deflect. A support span of about 50mm is recommended. A suitable loading rod can be providedby a single-crystal sapphire rod flame bent at one end in theform of a s
26、hepherds crook.5The arrangement is shown in Fig.1.NOTE 1Vitreous silica is a suitable material for both support standand loading rod. It is not recommended for temperatures above 900C.5.1.5 Extensometer for Measuring Midpoint DeflectionThe means of observing the rate of midpoint deflection of thebea
27、m should be such as to indicate reliably over a range of atleast 2.5 mm. The graduated scale of the extensometer shallpermit direct reading to 0.025 mm and estimates of 0.0025mm. Its accuracy shall be such that the error of indication willnot exceed 60.005 mm for any length change. To ensure thisacc
28、uracy, the extensometer shall be precalibrated. A linearlyvariable differential transformer (LVDT) is suitable for thispurpose but any device (optical, capacitative, or other) may beused, provided that length changes are reliably measured asspecified. The arrangement with the LVDT is shown on Fig. 1
29、.The core of the LVDT is attached to the end of the loading rod,whereas the coils are attached to the leg of the furnaceplatform. A screw arrangement is provided in the coil attach-ment assembly to move the coils vertically for zeroing pur-poses.5.1.6 Micrometer Calipers, with an accuracy of at leas
30、t 0.01mm, for measuring specimen dimensions.6. Preparation of Test Specimen6.1 Specimens may either be flame drawn or centerlessground into cylindrical form or diamond-saw cut and millground into rectangular form. Nonuniformity of any dimensionalong the length of the specimen shall not exceed 2 %. F
31、or asupport span of 50 mm, the cross-section moment of inertiashall be between 2 3 104cm4and 10 3 104cm4.7. Calibration and Measurement with Standard Glass7.1 CalibrationDetermine the deflection rates at the an-nealing point using test beams of a calibrating glass6whichcover a range of cross-section
32、 moments of inertia. Determinethe deflection rates by following the standard proceduredescribed in Section 8 and in 9.1. The range of cross-sectionmoments of inertia shall bracket the expected operating rangebut be limited to the maximum permissible variation asspecified in Section 6. Carry out test
33、s keeping load, span, andcooling rate constant. Make a linear calibration plot as shownin Fig. 2. Then use this calibration plot to determine thedeflection rates at the annealing points of unknown glasseshaving similar annealing points. It is recommended that theapparatus be recalibrated periodicall
34、y depending upon inci-dence of usage.7.2 Annealing Point MeasurementMeasure the deflectionrate of the glass under test in accordance with the standardprocedure as described in Section 8. Obtain a plot as in Fig. 3by following the procedure described in 9.1. Select from thecalibration plot in 7.1 the
35、 deflection rate of the calibrating glasshaving the same cross-section moment of inertia as the testglass. Using the deflection rate thus obtained, determine thecorresponding temperature from the plot of the glass undermeasurement. This temperature is the annealing point of theglass under test.7.3 S
36、train Point DeterminationObtain the strain point byextrapolation of the straight-line plot in 7.2. (See Fig. 3.)Divide the midpoint deflection rate at the annealing point by31.6 to obtain the midpoint deflection rate at the strain point.From the plot in 7.2 (Fig. 3), select the temperature corre-spo
37、nding to this deflection rate. This temperature is the strainpoint of the glass under test.8. Procedure8.1 With the furnace at least 25C (45F) below the esti-mated annealing point, remove the top plug and place thespecimen beam across the support stand at the notch points.Carefully engage the loadin
38、g rod to the specimen and center itusing long calipers. Replace the top plug.8.2 Apply a weight to the hook on the end of the LVDT coreas shown in Fig. 1. Adjust the total applied load consisting ofthe loading rod, LVDT core, hooks and fixtures, and weightaccording to the cross-section moment of ine
39、rtia of the test5Flame bent sapphire hooks, available from Insaco Inc., PO Box 422, Quaker-town, PA, 18951, have been found suitable for this purpose.6Calibrating glasses known as standard reference materials (SRMs) are availablefrom the National Institute of Standards and Technology (NIST). See Tab
40、le 1 ofNIST Special Publication 260, SRM Program, NIST, Gaithersburg, MD 20899.Glass SRMs are available and their certified values are listed in the back of Vol15.02, 1999 ASTM Annual Book of Standards.FIG. 2 Graphical Calibration Plot of Deflection Rate VersusReciprocal of Moment of Inertia of Stan
41、dard Glass Test BeamsC 598 93 (2008)3specimen. The appropriate total load may be approximatedfrom Fig. 4, which shows this load plotted as a function ofcross-section moment of inertia.8.3 Adjust the position of the extensometer to the lower endof its measuring range. Then start heating the furnace a
42、t aconvenient rate, preferably at about 5C/min. Stop heating andestablish a cooling rate of 4 6 1C/min when the specimenmidpoint deflection rate in centimetres per minute reaches:4 3 10210L3M!/Ic(2)Reset the extensometer to the lower end of its range.NOTE 2This deflection rate, corresponding to a vi
43、scosity of 1012P,guarantees erasure of previous thermal history.8.4 Immediately after cooling has been established, takereadings of both the extensometer and potentiometer alter-nately at 30-s intervals so that each will be read at 1-minintervals. Continue readings until the temperature is 10Cbelow
44、the annealing point. Such a temperature will generallybe reached when the extensometer indicates a deflection ratethree times less than that expected at the annealing point. If theextensometer goes off range during the test, reset it to the lowerend of the range by means of the vertical zeroing scre
45、w. Totalbeam deflections greater than 10 mm are excessive.9. Interpretation of Results9.1 Plotting DataTake the change in extensometer read-ings during each 1-min interval as the rate of midpointdeflection at the temperature recorded for the middle of thatminute. Plot it logarithmically against its
46、corresponding tem-perature, using standard-form 3-cycle graph paper with 85-mm(3.33-in.) length cycles and linear scale 381 mm (15 in.) longwith 300 divisions. The relation should be substantially linear;draw a straight line to represent the plotted points as in Fig. 3.9.2 Annealing and Strain Point
47、sDetermine the midpointviscous deflection rate of the test beam corresponding to theannealing and strain points as described in Section 7. From thegraph relating deflection rate to temperature, determine thetemperatures corresponding to these deflection rates. Thesetemperatures will be the annealing
48、 and strain points.10. Report10.1 Report the following information:10.1.1 Identification of the glass tested,10.1.2 Manufacturing source and date,10.1.3 Calibration reference,10.1.4 Annealing point,10.1.5 Strain point, and10.1.6 Date of test and name of operator.11. Precision and Bias11.1 This proce
49、dure in general will yield annealing points to62C (standard deviation) of standard values. A rigid test ofthe apparatus is to calibrate with one NIST SRM and thenmeasure other NIST SRMS based on this calibration. If theother standard glasses values are within 2C of certification,excellent performance has been established. If errors arise thatincrease as the difference in annealing points increases, atemperature measurement or distribution problem may exist.This should be corrected. If attempts to correct such a situationare unsuccessful
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