ASTM C336-71(2000)

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
• 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 C336-71(1995)e1 - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Jan-2000
• Replaced By: ASTM C336-71(2005) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Sep-2005
• 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 C770-16(2020) - Standard Test Method for Measurement of Glass Stress&#x2014;Optical Coefficient
• 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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C336–71(Reapproved2000)
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.
4,5,6
1. Scope minutes. During a test in accordance with the requirements
of this method, the viscous elongation rate is measured by a
1.1 This test method covers the determination of the anneal-
suitable extensometer while the specimen fiber is cooling at a
ing point and the strain point of a glass by measuring the
rate of 4 6 1°C/min.The elongation rate at the annealing point
viscous elongation rate of a fiber of the glass under prescribed
is approximately 0.14 mm/min for a fiber of 0.65-mm diam-
condition.
eter.
1.2 The annealing and strain points shall be obtained by
3.2 annealing range—the range of glass temperature in
following the specified procedure after calibration of the
which stresses in glass articles can be relieved at a commer-
apparatus using fibers of standard glasses having known
cially desirable rate. For purposes of comparing glasses, the
annealing and strain points, such as those specified and
annealing range is assumed to correspond with the tempera-
certified by the National Institute of Standards and Technology
tures between the annealing point (AP) and the strain point
(NIST) (see Appendix X1).
(StP).
1.3 This standard does not purport to address all of the
3.3 strain point—that temperature at which the 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 elongation rate is 0.0316 times that observed at the
2. Referenced Documents annealing point.
2.1 ASTM Standards:
4. Significance and Use
C 338 Test Method for Softening Point of Glass
4.1 This test method provides data useful for (1) estimating
C 598 Test Method for Annealing Point and Strain Point of
3 stress release, (2) the development of proper annealing sched-
Glass by Beam Bending
ules,and(3)estimatingsettingpointsforseals.Accordingly,its
3. Definitions usage is widespread throughout manufacturing, research, and
development. It can be utilized for specification acceptance.
3.1 annealing point—that temperature at which internal
stresses in a glass are substantially relieved in a matter of
5. Apparatus
5.1 Furnace—The furnace shall be 368-mm (14 ⁄2-in.) long
and approximately 114 mm (4 ⁄2 in.) in diameter and shall
This test method is under the jurisdiction of ASTM Committee C-14 on Glass
contain a copper core 305 mm (12 in.) long and 29 mm (1 ⁄8
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
in.) in outside diameter, with inside diameter of 5.6 mm ( ⁄32
Physical and Mechanical Properties.
in.). It shall be constructed substantially as shown in Fig. 1.
Current edition approved Oct. 25, 1971. Originally published as C 336 – 54 T.
Last previous edition C 336 – 69.
National Institute of Standards and Technology Publication 260.
Annual Book of ASTM Standards, Vol 15.02.
Littleton, J. T., and Roberts, E. H., “A Method for Determining the Annealing
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;
“Re-Evaluation of Glass Viscosities at Annealing and Strain Points,” Journal of
American Ceramic Society, Vol 37, 1954, p. 111.
McGraw, D. A. and Babcock, C. L., “Effect of Viscosity and Stress Level on
Rate of Stress Release in Soda-Lime, Potash-Barium and Borosilicate Glasses,”
Journal of the American Ceramic Society, Vol 42, 1959, p. 330.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C336–71 (2000)
FIG. 1 Apparatus for Determination of Annealing Point and Strain Point of Glass
5.1.1 Such a furnace will cool naturally at approximately electromotive force corresponding to a known temperature,
4°C (7°F)/min at 500°C (932°F) and at a rate exceeding 3°C near the annealing point and inferring the temperature from the
(5.5°F)/min at 400°C (752°F). deflection of a sensitive galvanometer, previously calibrated
5.2 Temperature Measuring and Indicating Instruments— for the purpose. It is convenient to adjust the galvanometer
For the measurement of temperature there shall be provided a shunt to a sensitivity of about 3°C (5.5°F)/cm of deflection and
thermocouple, preferably platinum-platinum rhodium, inserted to somewhat less than critical damping. This technique for
in the upper side hole of the copper core, as indicated in Fig. reading temperature changes is one of the preferred methods;
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
permitreadingthethermocoupleemftoanamountcorrespond- 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
5.2.2 Provision shall be made for reading temperatures observing the rate of elongation of the fiber should be such as
accurately at predetermined moments. One means of accom- to indicate reliably over a range of about 6-mm ( ⁄4-in.) change
plishing this is to maintain the potentiometer setting at an in fiber length with an uncertainty not greater than about 0.01
C336–71 (2000)
mm (0.0004 in.). A convenient method is shown in Fig. 1,
where the arm of the optical lever, N, bears upon a platform, L,
incorporated in the loading linkage. The fulcrum of the lever
should be mounted on a rigid (but height-adjustable) member,
substantially free of vibration. With an optical lever arm about
38 mm (1 ⁄2 in.) long and a scale distance of about 1 m (40 in.),
the multiplying factor is about 50. Readings can be made to 0.5
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.
FIG. 2 Calibration
5.5 Micrometer Calipers, with a least count of 0.005 mm,
for measuring specimen fiber diameters.
8. Procedure
6. Test Specimen
8.1 Method A:
8.1.1 Long Fiber, Furnace Support—The recommended
6.1 Drawing the Fiber—Draw a suitable fiber from 2 cm
method of fiber support and loading is as shown in Fig. 1,in
(more or less) of glass in any form such as a fragment, cane,
which the top of a long fiber is supported on the furnace top
flat strip, or tubing. Stick the piece to handles of glass or other
itself and the fiber extends entirely through the furnace to the
suitable material, such as refractory or metal, and then work it
lever platform, L, or to the attachment of the load.
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
sect
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