ASTM C598-93(2013)
(Test Method)Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
SIGNIFICANCE AND USE
4.1 This test method offers an alternate procedure to Test Method C336 for determining the annealing and strain points of glass. It is particularly recommended for glasses not adaptable to flame working. Also fewer corrections are necessary in data reduction.
SCOPE
1.1 This test method covers the determination of the annealing point and the strain point of a glass by measuring the rate of midpoint viscous bending of a simply loaded glass beam.2 However, at temperatures corresponding to the annealing and strain points, the viscosity of glass is highly time-dependent. Hence, any viscosities that might be derived or inferred from measurements by this procedure cannot be assumed to represent equilibrium structural conditions.
1.2 The annealing and strain points shall be obtained following a specified procedure after direct calibration of the apparatus using beams of standard glasses having known annealing and strain points such as those supplied and certified by the National Institute of Standards and Technology.3
1.3 This test method, as an alternative to Test Method C336 is particularly well suited for glasses that for one reason or another are not adaptable for flame working. It also has the advantages that thermal expansion and effective length corrections, common to the fiber elongation method, are eliminated.
1.4 The values stated in metric units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C598 − 93 (Reapproved 2013)
Standard Test Method for
Annealing Point and Strain Point of Glass by Beam
Bending
This standard is issued under the fixed designation C598; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 Thistestmethodcoversthedeterminationoftheanneal- 2.1 ASTM Standards:
ing point and the strain point of a glass by measuring the rate C336Test Method for Annealing Point and Strain Point of
of midpoint viscous bending of a simply loaded glass beam. Glass by Fiber Elongation
However, at temperatures corresponding to the annealing and
3. Terminology
strain points, the viscosity of glass is highly time-dependent.
Hence, any viscosities that might be derived or inferred from 3.1 Definitions:
measurements by this procedure cannot be assumed to repre- 3.1.1 annealing range—the range of glass temperature in
which stresses in glass articles can be relieved at a commer-
sent equilibrium structural conditions.
cially desirable rate. For purposes of comparing glasses, the
1.2 The annealing and strain points shall be obtained fol-
annealing range is assumed to correspond with the tempera-
lowing a specified procedure after direct calibration of the
tures between the annealing point (A. P.) and the strain point
apparatus using beams of standard glasses having known
(St. P.).
annealingandstrainpointssuchasthosesuppliedandcertified
3.1.2 annealing point—that temperature at which internal
by the National Institute of Standards and Technology.
stresses in a glass are substantially relieved in a matter of
1.3 This test method, as an alternative toTest Method C336
minutes. During a test in accordance with the requirements of
is particularly well suited for glasses that for one reason or
this test method, the midpoint rate of viscous deflection of the
another are not adaptable for flame working. It also has the
test beam is measured by an extensometer with suitable
advantages that thermal expansion and effective length
magnification during cooling at a rate of 4 6 1°C/min. The
corrections, common to the fiber elongation method, are
nominal deflection rate at the annealing point ideally is as
eliminated.
follows:
1.4 The values stated in metric units are to be regarded as
211 3
Deflectionrate, cm/min 5 2.67 310 L M /I (1)
~ !
c
the standard. The values given in parentheses are for informa-
tion only. where:
L = support span, cm;
1.5 This standard does not purport to address all of the
M = centrally applied load, g; and
safety concerns, if any, associated with its use. It is the
I = cross-section moment of inertia of test beam, cm (see
responsibility of the user of this standard to establish appro- c
Appendix X1).
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 3.1.3 strain point—that temperature at which internal
stresses in a glass are substantially relieved in a matter of
hours. The strain point is determined by extrapolation of the
This test method is under the jurisdiction of ASTM Committee C14 on Glass
annealing point data and is the temperature at which the
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
viscous deflection rate is 0.0316 times that observed at the
Physical and Mechanical Properties.
Current edition approved Oct. 1, 2013. Published October 2013. Originally
annealing point.
approved in 1967. Last previous edition approved in 2008 as C598–93(2008).
DOI: 10.1520/C0598-93R13.
2 4
Hagy, H. E., “Experimental Evaluation of Beam Bending Method of Deter- For referenced ASTM standards, visit the ASTM website, www.astm.org, or
8 15
mining GlassViscosities in the Range 10 to 10 Poises,” Journal of the American contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Ceramic Society, Vol 46, No. 2, 1963, pp. 95–97. Standards volume information, refer to the standard’s Document Summary page on
NIST Special Publication 260. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C598 − 93 (2013)
4. Significance and Use the length of the specimen beam and along the axis of the
furnace from the undeflected beam plane to a point 13 mm ( ⁄2
4.1 This test method offers an alternate procedure to Test
in.) below.
Method C336 for determining the annealing and strain points
5.1.2 Temperature Measuring and Indicating Instruments—
of glass. It is particularly recommended for glasses not
For the measurement of temperature, there shall be provided a
adaptable to flame working.Also fewer corrections are neces-
calibrated Type R or S thermocouple. The thermocouple shall
sary in data reduction.
be housed in a double-bore alumina tube with its junction
5. Apparatus
placed within 5 mm of the specimen near the axis of the
furnace. It is recommended that the thermocouple be refer-
5.1 The apparatus shall consist of a furnace, a means of
enced to 0°C by means of an ice bath and its emf measured
controlling its temperature and cooling rate, a specimen holder
with a calibrated potentiometer having a sensitivity of 61µV
andloadingrod,andameansofobservingtherateofmidpoint
andanaccuracyof 65µV.Precautionsshallbetakentoensure
viscous deflection of the glass beam.
that the ice bath is maintained at 0°C throughout the test.
5.1.1 Furnace—The furnace shall be electrically heated by
5.1.3 Furnace Control—Suitable means shall be provided
resistance-wire windings of either platinum-rhodium or 80-20
for idling the furnace, controlling the heating rate, and, in the
Ni-Cr alloys.Acutaway drawing of a typical furnace is shown
case of very hard glasses, limiting the cooling rate to not more
in Fig. 1. Dimensions and details of the furnace construction
than 5°C/min.Although commercially available programming
are not critical, but a cylindrical furnace of height of 255 mm
equipment provides excellent control, a variable transformer
(10 in.), outside diameter of 230 mm (9 in.), and inside
with manual control is an inexpensive and adequate technique.
diameter of 130 mm (5 in.) with a removable top plug is
recommended. The temperature distribution shall be such that 5.1.4 Specimen Holder and Loading Rod—A ceramic sup-
differencesintemperaturegreaterthan2°Cshallnotresultover port stand and a ceramic loading rod shall be provided for
A—Alumina muffle support stand E—Linearly variable differential transformer
B—Specimen beam (LVDT)
C—Thermocouple F—Zero-adjust mechanism for LVDT
D—Loading rod G—Weight
H—Laboratory jack
FIG. 1 Cutaway Drawing of Beam-Bending Apparatus
C598 − 93 (2013)
supportingthespecimenandapplyingtheloadtothespecimen, moments of inertia shall bracket the expected operating range
respectively. The thermal expansion characteristics of both but be limited to the maximum permissible variation as
stand and rod materials must be very similar so as to minimize specified in Section 6. Carry out tests keeping load, span, and
motion of the loading rod on cooling as a result of expansion cooling rate constant. Make a linear calibration plot as shown
differences (see Appendix X2). A rectangular alumina muffle in Fig. 2. Then use this calibration plot to determine the
makes a suitable support stand (Note 1). The side walls of this deflection rates at the annealing points of unknown glasses
muffle can be notched to define specimen position. The having similar annealing points. It is recommended that the
supporting surfaces of these notches shall be flat and lie in a apparatus be recalibrated periodically depending upon inci-
planeperpendiculartotheaxisofthefurnace.Theinsideedges dence of usage.
of these supporting surfaces define the support span once the
7.2 Annealing Point Measurement—Measure the deflection
specimen beam starts to deflect. A support span of about 50
rate of the glass under test in accordance with the standard
mm is recommended. A suitable loading rod can be provided
procedure as described in Section 8. Obtain a plot as in Fig. 3
by a single-crystal sapphire rod flame bent at one end in the
by following the procedure described in 9.1. Select from the
formofashepherds’crook. ThearrangementisshowninFig.
calibrationplotin7.1thedeflectionrateofthecalibratingglass
1.
having the same cross-section moment of inertia as the test
glass. Using the deflection rate thus obtained, determine the
NOTE1—Vitreoussilicaisasuitablematerialforbothsupportstandand
loading rod. It is not recommended for temperatures above 900°C.
corresponding temperature from the plot of the glass under
measurement. This temperature is the annealing point of the
5.1.5 Extensometer for Measuring Midpoint Deflection
glass under test.
—Themeansofobservingtherateofmidpointdeflectionofthe
beam should be such as
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