ASTM C598-93(2003)

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

SIGNIFICANCE AND USE
This test method offers an alternate procedure to Test Method C 336 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. 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 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.

General Information

• Status: Historical
• Publication Date: 09-Apr-2003
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaces: ASTM C598-93(1998) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 10-Apr-2003
• Replaced By: ASTM C598-93(2008) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Apr-2008
• Referred By: ASTM E438-92(2018) - Standard Specification for Glasses in Laboratory Apparatus
• Effective Date: 10-Apr-2003
• Referred By: ASTM F79-69(2019) - Standard Specification for Type 101 Sealing Glass
• Effective Date: 10-Apr-2003
• Referred By: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 10-Apr-2003
• Referred By: ASTM C770-16(2020) - Standard Test Method for Measurement of Glass Stress&#x2014;Optical Coefficient
• Effective Date: 10-Apr-2003
• 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-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-Apr-2003
• Referred By: ASTM F105-72(2019) - Standard Specification for Type 58 Borosilicate Sealing Glass
• Effective Date: 10-Apr-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C 598 – 93 (Reapproved 2003)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope Glass by Fiber Elongation
1.1 Thistestmethodcoversthedeterminationoftheanneal-
3. Terminology
ing point and the strain point of a glass by measuring the rate
2 3.1 Definitions:
of midpoint viscous bending of a simply loaded glass beam.
3.1.1 annealing range—the range of glass temperature in
However, at temperatures corresponding to the annealing and
which stresses in glass articles can be relieved at a commer-
strain points, the viscosity of glass is highly time-dependent.
cially desirable rate. For purposes of comparing glasses, the
Hence, any viscosities that might be derived or inferred from
annealing range is assumed to correspond with the tempera-
measurements by this procedure cannot be assumed to repre-
tures between the annealing point (A. P.) and the strain point
sent equilibrium structural conditions.
(St. P.).
1.2 The annealing and strain points shall be obtained fol-
3.1.2 annealing point—that temperature at which internal
lowing a specified procedure after direct calibration of the
stresses in a glass are substantially relieved in a matter of
apparatus using beams of standard glasses having known
minutes. During a test in accordance with the requirements of
annealing and strain points such as those supplied and certified
this test method, the midpoint rate of viscous deflection of the
by the National Institute of Standards and Technology.
test beam is measured by an extensometer with suitable
1.3 Thistestmethod,asanalternativetoTestMethodC336
magnification during cooling at a rate of 4 6 1°C/min. The
is particularly well suited for glasses that for one reason or
nominal deflection rate at the annealing point ideally is as
another are not adaptable for flame working. It also has the
follows:
advantages that thermal expansion and effective length correc-
211 3
tions, common to the fiber elongation method, are eliminated.
Deflectionrate,cm/min 5 ~2.67 310 L M!/I (1)
c
1.4 The values stated in metric units are to be regarded as
where:
the standard. The values given in parentheses are for informa-
L = support span, cm;
tion only.
M = centrally applied load, g; and
1.5 This standard does not purport to address all of the
I = cross-section moment of inertia of test beam, cm (see
c
safety concerns, if any, associated with its use. It is the
Appendix X1).
responsibility of the user of this standard to establish appro-
3.1.3 strain point—that temperature at which internal
priate safety and health practices and determine the applica-
stresses in a glass are substantially relieved in a matter of
bility of regulatory limitations prior to use.
hours. The strain point is determined by extrapolation of the
annealing point data and is the temperature at which the
2. Referenced Documents
viscous deflection rate is 0.0316 times that observed at the
2.1 ASTM Standards:
annealing point.
C336 Test Method forAnnealing Point and Strain Point of
4. Significance and Use
1 4.1 This test method offers an alternate procedure to Test
This test method is under the jurisdiction of ASTM Committee C14 on Glass
Method C336 for determining the annealing and strain points
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
Physical and Mechanical Properties.
of glass. It is particularly recommended for glasses not
Current edition approved Apr. 10, 2003. Published July 2003. Originally
adaptable to flame working.Also fewer corrections are neces-
approved in 1967. Last previous edition approved in 1993 as C598–93.
sary in data reduction.
Hagy, H. E., “Experimental Evaluation of Beam Bending Method of Deter-
8 15
mining GlassViscosities in the Range 10 to 10 Poises,” Journal of the American
Ceramic Society, Vol 46, No. 2, 1963, pp. 95–97.
3 4
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.
C 598 – 93 (2003)
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
andanaccuracyof 65µV.Precautionsshallbetakentoensure
andloadingrod,andameansofobservingtherateofmidpoint
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.Acutaway 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
supportingthespecimenandapplyingtheloadtothespecimen,
differencesintemperaturegreaterthan2°Cshallnotresultover
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 planeperpendiculartotheaxisofthefurnace.Theinsideedges
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
C 598 – 93 (2003)
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.
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
(LVDT) is suitable for this purpose but any device (optical,
FIG. 2 Graphical Calibration Plot of Deflection Rate Versus
capacitative, or other) may be used, provided that length
Reciprocal of Moment of Inertia of Standard Glass Test Beams
changes are reliably measured as specified. The arrangement
with the LVDT is shown on Fig. 1. The core of the LVDT is
attached to the end of the loading rod, whereas the coils are
7.2 Annealing Point Measurement—Measure the deflection
attached to the leg of the furnace platform. A screw arrange-
rate of the glass under test in accordance with the standard
ment is provided in the coil attachment assembly to move the
procedure as described i
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