ASTM C598-93(1998)

Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending

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.  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.  
1.3 This test method, as an alternative to Test Method C 336 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 problems, 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.

General Information

• Status: Historical
• Publication Date: 09-Oct-1998
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaced By: ASTM C598-93(2003) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 10-Apr-2003
• Referred By: ASTM C336-71(2020) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 10-Oct-1998
• Referred By: ASTM F105-72(2019) - Standard Specification for Type 58 Borosilicate Sealing Glass
• Effective Date: 10-Oct-1998
• Referred By: ASTM E438-92(2018) - Standard Specification for Glasses in Laboratory Apparatus
• Effective Date: 10-Oct-1998
• Referred By: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 10-Oct-1998
• Referred By: ASTM F79-69(2019) - Standard Specification for Type 101 Sealing Glass
• Effective Date: 10-Oct-1998
• Referred By: ASTM C770-16(2020) - Standard Test Method for Measurement of Glass Stress&#x2014;Optical Coefficient
• Effective Date: 10-Oct-1998
• Referred By: ASTM C1350M-96(2019) - Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range (Approximately 10⁸ Pa&#xb7;s to Approximately 10¹³ Pa&#xb7;s) by Beam Bending (Metric)
• Effective Date: 10-Oct-1998

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 598 – 93 (Reapproved 1998)
Standard Test Method for
Annealing Point and Strain Point of Glass by Beam
Bending
This standard is issued under the fixed designation C 598; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This test method covers the determination of the anneal- 3.1 Definitions:
ing point and the strain point of a glass by measuring the rate 3.1.1 annealing range—the range of glass temperature in
of midpoint viscous bending of a simply loaded glass beam. which stresses in glass articles can be relieved at a commer-
However, at temperatures corresponding to the annealing and cially desirable rate. For purposes of comparing glasses, the
strain points, the viscosity of glass is highly time-dependent. annealing range is assumed to correspond with the tempera-
Hence, any viscosities that might be derived or inferred from tures between the annealing point (A. P.) and the strain point
measurements by this procedure cannot be assumed to repre- (St. P.).
sent equilibrium structural conditions. 3.1.2 annealing point—that temperature at which internal
1.2 The annealing and strain points shall be obtained fol- stresses in a glass are substantially relieved in a matter of
lowing a specified procedure after direct calibration of the minutes. During a test in accordance with the requirements of
apparatus using beams of standard glasses having known this test method, the midpoint rate of viscous deflection of the
annealing and strain points such as those supplied and certified test beam is measured by an extensometer with suitable
by the National Institute of Standards and Technology. magnification during cooling at a rate of 4 6 1°C/min. The
1.3 This test method, as an alternative to Test Method C 336 nominal deflection rate at the annealing point ideally is as
is particularly well suited for glasses that for one reason or follows:
another are not adaptable for flame working. It also has the
211 3
Deflection rate, cm/min 5 ~2.67 3 10 L M!/I (1)
c
advantages that thermal expansion and effective length correc-
tions, common to the fiber elongation method, are eliminated.
where:
1.4 The values stated in metric units are to be regarded as L = support span, cm;
M = centrally applied load, g; and
the standard. The values given in parentheses are for informa-
I = cross-section moment of inertia of test beam, cm (see
tion only.
c
Appendix X1).
1.5 This standard does not purport to address all of the
3.1.3 strain point—that temperature at which internal
safety concerns, if any, associated with its use. It is the
stresses in a glass are substantially relieved in a matter of
responsibility of the user of this standard to establish appro-
hours. The strain point is determined by extrapolation of the
priate safety and health practices and determine the applica-
annealing point data and is the temperature at which the
bility of regulatory limitations prior to use.
viscous deflection rate is 0.0316 times that observed at the
2. Referenced Documents
annealing point.
2.1 ASTM Standards:
4. Significance and Use
C 336 Test Method for Annealing Point and Strain Point of
4.1 This test method offers an alternate procedure to Test
Glass by Fiber Elongation
Method C 336 for determining the annealing and strain points
of glass. It is particularly recommended for glasses not
This test method is under the jurisdiction of ASTM Committee C-14 on Glass
adaptable to flame working. Also fewer corrections are neces-
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
sary in data reduction.
Physical and Mechanical Properties.
Current edition approved Nov. 15, 1993. Published January 1994. Originally
issued as C 598 – 67 T. Last previous edition C 598 – 88.
Hagy, H. E., “Experimental Evaluation of Beam Bending Method of Deter-
8 15
mining Glass Viscosities in the Range 10 to 10 Poises,” Journal of the American
Ceramic Society, Vol 46, No. 2, 1963, pp. 95–97.
NIST Special Publication 260.
Annual Book of ASTM Standards, Vol 15.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 598 – 93 (1998)
5. Apparatus furnace. It is recommended that the thermocouple be refer-
enced to 0°C by means of an ice bath and its emf measured
5.1 The apparatus shall consist of a furnace, a means of
with a calibrated potentiometer having a sensitivity of 61μV
controlling its temperature and cooling rate, a specimen holder
and an accuracy of 65 μV. Precautions shall be taken to ensure
and loading rod, and a means of observing the rate of midpoint
that the ice bath is maintained at 0°C throughout the test.
viscous deflection of the glass beam.
5.1.3 Furnace Control—Suitable means shall be provided
5.1.1 Furnace—The furnace shall be electrically heated by
for idling the furnace, controlling the heating rate, and, in the
resistance-wire windings of either platinum-rhodium or 80-20
case of very hard glasses, limiting the cooling rate to not more
Ni-Cr alloys. A cutaway drawing of a typical furnace is shown
than 5°C/min. Although commercially available programming
in Fig. 1. Dimensions and details of the furnace construction
equipment provides excellent control, a variable transformer
are not critical, but a cylindrical furnace of height of 255 mm
with manual control is an inexpensive and adequate technique.
(10 in.), outside diameter of 230 mm (9 in.), and inside
diameter of 130 mm (5 in.) with a removable top plug is 5.1.4 Specimen Holder and Loading Rod—A ceramic sup-
recommended. The temperature distribution shall be such that port stand and a ceramic loading rod shall be provided for
differences in temperature greater than 2°C shall not result over supporting the specimen and applying the load to the specimen,
the length of the specimen beam and along the axis of the respectively. The thermal expansion characteristics of both
furnace from the undeflected beam plane to a point 13 mm ( ⁄2 stand and rod materials must be very similar so as to minimize
in.) below. motion of the loading rod on cooling as a result of expansion
5.1.2 Temperature Measuring and Indicating Instruments— differences (see Appendix X2). A rectangular alumina muffle
For the measurement of temperature, there shall be provided a makes a suitable support stand (Note 1). The side walls of this
calibrated Type R or S thermocouple. The thermocouple shall muffle can be notched to define specimen position. The
be housed in a double-bore alumina tube with its junction supporting surfaces of these notches shall be flat and lie in a
placed within 5 mm of the specimen near the axis of the plane perpendicular to the axis of the furnace. The inside edges
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
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 598 – 93 (1998)
of these supporting surfaces define the support span once the
specimen beam starts to deflect. A support span of about 50
mm is recommended. A suitable loading rod can be provided
by a single-crystal sapphire rod flame bent at one end in the
form of a shepherds’ crook. The arrangement is shown in Fig.
1.
NOTE 1—Vitreous silica is a suitable material for both support stand
and loading rod. It is not recommended for temperatures above 900°C,
however.
5.1.5 Extensometer for Measuring Midpoint
Deflection—The means of observing the rate of midpoint
deflection of the beam should be such as to indicate reliably
over a range of at least 2.5 mm. The graduated scale of the
extensometer shall permit direct reading to 0.025 mm and
estimates of 0.0025 mm. Its accuracy shall be such that the
error of indication will not exceed 60.005 mm for any length
change. To ensure this accuracy, the extensometer shall be
precalibrated. A linearly variable differential transformer
FIG. 2 Graphical Calibration Plot of Deflection Rate Versus
(LVDT) is suitable for this purpose but any device (optical,
Reciprocal of Moment of Inertia of Standard Glass Test Beams
capacitative, or other) may be used, provided that length
changes are reliably measured as specified. The arrangement
with the LVDT is shown on Fig. 1. The core of the LVDT is
having similar annealing points. It is recommended that the
attached to the end of the loading rod, whereas the coils are
apparatus be recalibrated periodically depending upon inci-
attached to the leg of the furnace platform. A screw arrange-
dence of usage.
ment is provided in the coil attachment assembly to move the
7.2 Annealing Point Measurement—Measur
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