ASTM C336-71(1995)e1

Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation

SCOPE
1.1 This test method covers the determination of the annealing point and the strain point of a glass by measuring the viscous elongation rate of a fiber of the glass under prescribed condition.  
1.2 The annealing and strain points shall be obtained by following the specified procedure after calibration of the apparatus using fibers of standard glasses having known annealing and strain points, such as those specified and certified by the National Institute of Standards and Technology (NIST) (see Appendix X1).  
1.3  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: 31-Dec-1999
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaced By: ASTM C336-71(2000) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Jan-2000
• Referred By: ASTM C770-16(2020) - Standard Test Method for Measurement of Glass Stress—Optical Coefficient
• Effective Date: 01-Jan-2000
• Referred By: ASTM F105-72(2019) - Standard Specification for Type 58 Borosilicate Sealing Glass
• Effective Date: 01-Jan-2000
• Referred By: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 01-Jan-2000
• 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: 01-Jan-2000
• Referred By: ASTM C598-93(2019) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Jan-2000
• Referred By: ASTM F79-69(2019) - Standard Specification for Type 101 Sealing Glass
• Effective Date: 01-Jan-2000

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: C 336 – 71 (Reapproved 1995)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Annealing Point and Strain Point of Glass by Fiber
Elongation
This standard is issued under the fixed designation C 336; 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.
This standard has been approved for use by agencies of the Department of Defense.
e NOTE—Section 12 was added editorially in September 1995.
1. Scope suitable extensometer while the specimen fiber is cooling at a
rate of 4 6 1°C/min. The elongation rate at the annealing point
1.1 This test method covers the determination of the anneal-
is approximately 0.14 mm/min for a fiber of 0.65-mm diam-
ing point and the strain point of a glass by measuring the
eter.
viscous elongation rate of a fiber of the glass under prescribed
3.2 annealing range—the range of glass temperature in
condition.
which stresses in glass articles can be relieved at a commer-
1.2 The annealing and strain points shall be obtained by
cially desirable rate. For purposes of comparing glasses, the
following the specified procedure after calibration of the
annealing range is assumed to correspond with the tempera-
apparatus using fibers of standard glasses having known
tures between the annealing point (AP) and the strain point
annealing and strain points, such as those specified and
(StP).
certified by the National Institute of Standards and Technology
3.3 strain point—that temperature at which the internal
(NIST) (see Appendix X1).
stresses in a glass are substantially relieved in a matter of
1.3 This standard does not purport to address all of the
hours. The strain point is determined by extrapolation of the
safety concerns, if any, associated with its use. It is the
annealing point data and is the temperature at which the
responsibility of the user of this standard to establish appro-
viscous elongation rate is 0.0316 times that observed at the
priate safety and health practices and determine the applica-
annealing point.
bility of regulatory limitations prior to use.
4. Significance and Use
2. Referenced Documents
4.1 This test method provides data useful for (1) estimating
2.1 ASTM Standards:
stress release, (2) the development of proper annealing sched-
C 338 Test Method for Softening Point of Glass
ules, and (3) estimating setting points for seals. Accordingly, its
C 598 Test Method for Annealing Point and Strain Point of
usage is widespread throughout manufacturing, research, and
Glass by Beam Bending
development. It can be utilized for specification acceptance.
3. Definitions
5. Apparatus
3.1 annealing point—that temperature at which internal
5.1 Furnace—The furnace shall be 368-mm (14 ⁄2-in.) long
stresses in a glass are substantially relieved in a matter of
, ,
4 5 6 and approximately 114 mm (4 ⁄2 in.) in diameter and shall
minutes. During a test in accordance with the requirements
contain a copper core 305 mm (12 in.) long and 29 mm (1 ⁄8
of this method, the viscous elongation rate is measured by a
in.) in outside diameter, with inside diameter of 5.6 mm ( ⁄32
in.). It shall be constructed substantially as shown in Fig. 1.
5.1.1 Such a furnace will cool naturally at approximately
This test method is under the jurisdiction of ASTM Committee C-14 on Glass
4°C (7°F)/min at 500°C (932°F) and at a rate exceeding 3°C
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
Physical and Mechanical Properties.
(5.5°F)/min at 400°C (752°F).
Current edition approved Oct. 25, 1971. Originally published as C 336 – 54 T.
5.2 Temperature Measuring and Indicating Instruments—
Last previous edition C 336 – 69.
2 For the measurement of temperature there shall be provided a
National Institute of Standards and Technology Publication 260.
Annual Book of ASTM Standards, Vol 15.02. thermocouple, preferably platinum-platinum rhodium, inserted
Littleton, J. T., and Roberts, E. H., “A Method for Determining the Annealing
in the upper side hole of the copper core, as indicated in Fig.
Temperature of Glass,” Journal of the Optical Society of America, Vol 4, 1920, p.
224.
Lillie, H. R., “Viscosity of Glass Between the Strain Point and Melting
Temperature,” Journal of American Ceramic Society, Vol 14, 1931, p. 502; McGraw, D. A. and Babcock, C. L., “Effect of Viscosity and Stress Level on
“Re-Evaluation of Glass Viscosities at Annealing and Strain Points,” Journal of Rate of Stress Release in Soda-Lime, Potash-Barium and Borosilicate Glasses,”
American Ceramic Society, Vol 37, 1954, p. 111. Journal of the American Ceramic Society, Vol 42, 1959, p. 330.
C 336
FIG. 1 Apparatus for Determination of Annealing Point and Strain Point of Glass
1, so that its junction is located midway in the length of the in the following sections it will be assumed that this technique
core. The thermocouple wire shall not be allowed to directly has been used, although any other equally sensitive and precise
contact the copper; this can be ensured by placing a 6-mm method of following the temperature of the thermocouple may
( ⁄4-in.) length of ceramic tube in the bottom of the hole ahead be used.
of the couple. The cold junction of the thermocouple shall be 5.3 Furnace Control—Suitable means shall be provided for
maintained in an ice bath during tests. idling the furnace, controlling its heating rate, and, in the case
5.2.1 The temperature-indicating instrument, preferably a of very hard glasses, limiting the cooling rate to not more than
potentiometer, shall be of such quality and sensitivity as to 5°C (9°F)/min. A variable transformer is a convenient device
permit reading the thermocouple emf to an amount correspond- for this purpose. The transformer can also be employed as a
ing to 0.1°C (0.2°F), equivalent to about 1 μV for a platinum switch for interrupting the furnace current.
couple or to about 4 μV for a base-metal couple. 5.4 Device for Measuring Elongation—The means of ob-
5.2.2 Provision shall be made for reading temperatures serving the rate of elongation of the fiber should be such as to
accurately at predetermined moments. One means of accom- indicate reliably over a range of about 6-mm ( ⁄4-in.) change in
plishing this is to maintain the potentiometer setting at an fiber length with an uncertainty not greater than about 0.01 mm
electromotive force corresponding to a known temperature, (0.0004 in.). A convenient method is shown in Fig. 1, where the
near the annealing point and inferring the temperature from the arm of the optical lever, N, bears upon a platform, L, incorpo-
deflection of a sensitive galvanometer, previously calibrated rated in the loading linkage. The fulcrum of the lever should be
for the purpose. It is convenient to adjust the galvanometer mounted on a rigid (but height-adjustable) member, substan-
shunt to a sensitivity of about 3°C (5.5°F)/cm of deflection and tially free of vibration. With an optical lever arm about 38 mm
to somewhat less than critical damping. This technique for (1 ⁄2 in.) long and a scale distance of about 1 m (40 in.), the
reading temperature changes is one of the preferred methods; multiplying factor is about 50. Readings can be made to 0.5
C 336
mm on the scale and, if the scale is 508 mm in length, a
sufficient range is attained. The scale is curved with its center
of curvature at the mirror location. The system may be
calibrated by mounting a micrometer screw in place of the
platform, L.
5.4.1 Any other extensometer arrangement, such as a lin-
early variable differential transformer (LVDT) or a travelling
microscope, is suitable for measuring elongation, provided that
length changes are reliably measured as specified.
5.5 Micrometer Calipers, with a least count of 0.005 mm,
for measuring specimen fiber diameters.
6. Test Specimen
6.1 Drawing the Fiber—Draw a suitable fiber from 2 cm
(more or less) of glass in any form such as a fragment, cane,
flat strip, or tubing. Stick the piece to handles of glass or other
FIG. 2 Calibration
suitable material, such as refractory or metal, and then work it
into a ball, using a flame adjustment found suitable for the
8.1.2 Long Fiber, Independent Support—An alternative
particular kind of glass. When the ball is in a uniform state of
long fiber method is that shown in Fig. 3, in which the top of
proper temperature, and while it is still in the fire, slightly
the fiber is supported independently of the furnace. This
elongate it into a pear shape. Then, remove the ball from the
method requires the application of a correction for thermal
fire, and draw it down to a convenient length.
expansion.
6.2 Measurement of Fiber Dimensions—Measure the fiber
8.2 Method B:
with micrometer calipers at 51-mm (2-in.) intervals, and select
8.2.1 Short Fiber, Independent Support—The short fiber
a 508-mm (20-in.) length that is substantially circular in cross
method of support and loading is as shown in Fig. 4, in which
section, has a diameter of 0.65 6 0.10 mm (0.025 6 0.004 in.),
the short fiber is supported independently of the furnace
an
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