ASTM C372-94
(Test Method)Standard Test Method for Linear Thermal Expansion of Porcelain Enamel and Glaze Frits and Fired Ceramic Whiteware Products by the Dilatometer Method
Standard Test Method for Linear Thermal Expansion of Porcelain Enamel and Glaze Frits and Fired Ceramic Whiteware Products by the Dilatometer Method
SCOPE
1.1 This test method covers the determination of the linear thermal expansion of premelted frit (porcelain enamel and glaze) and ceramic whiteware products by the thermal dilatometer method. This test method is applicable to apparatus meeting the reproducibility and accuracy requirements of this test method, which are to produce percent linear expansion accuracy of +3% or better and coefficient of linear expansion accuracy of +5% or better.
1.2 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: C 372 – 94
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
Linear Thermal Expansion of Porcelain Enamel and Glaze
Frits and Fired Ceramic Whiteware Products by the
Dilatometer Method
This standard is issued under the fixed designation C 372; 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
where:
a5 mean coefficient of linear thermal expansion from
1.1 This test method covers the determination of the linear
temperature T to T , and
thermal expansion of premelted frit (porcelain enamel and
1 2
P 5 percent linear thermal expansion as defined in 3.1.2.
glaze) and ceramic whiteware products by the thermal dilatom-
3.1.2 percent linear thermal expansion—from temperature
eter method. This test method is applicable to apparatus
T to temperature T (T < T ):
meeting the reproducibility and accuracy requirements of this 1 2 1 2
test method, which are to produce percent linear expansion
L 2 L
2 1
P 5 3 100 1 A
accuracy of 63 % or better and coefficient of linear expansion L
accuracy of 65 % or better.
DL
5 3 100 1 A
1.2 This standard does not purport to address all of the
L
safety concerns, if any, associated with its use. It is the
where:
responsibility of the user of this standard to establish appro-
P 5 percent linear thermal expansion from temperature
priate safety and health practices and determine the applica-
T to T ,
bility of regulatory limitations prior to use. 1 2
L 5 sample length at T (T between 20 and 30°C),
0 0 0
L 5 sample length at T ,
2. Referenced Documents
1 1
L 5 sample length at T , and
2 2
2.1 ASTM Standards:
A 5 instrument correction.
E 220 Method for Calibration of Thermocouples by Com-
parison Techniques
4. Significance and Use
E 228 Test Method for Linear Thermal Expansion of Solid
4.1 Measurement of thermal expansion is useful for predict-
Materials with a Vitreous Silica Dilatometer
ing stress within joined materials or single materials under
E 230 Temperature-Electromotive Force (EMF) Tables for
conditions of changing or nonuniform temperature. It can also
Standardized Thermocouples
serve as an indicator of phase composition or changes in
E 691 Practice for Conducting an Interlaboratory Study to
structure.
Determine the Precision of a Test Method
5. Apparatus
3. Terminology
5.1 Thermal Dilatometer:
3.1 Definitions:
5.1.1 General Description—A thermal dilatometer is an
3.1.1 mean coeffıcient of linear thermal expansion—from
apparatus that provides means for varying the temperature of a
temperature T to temperature T (T < T ):
1 2 1 2
test specimen in a controlled manner, measuring the specimen
0.01 P
length, and measuring the temperature of the specimen for each
a, mm/mm·°C or in./in.·°C 5
T 2 T
2 1
reading of specimen length. There are several different types as
follows:
5.1.1.1 Manual—A manual dilatometer is one in which any
or all of the above are done by manual means and the corrected
This test method is under the jurisdiction of ASTM Committee C-21 on
percent linear thermal expansion curve is plotted by hand.
Ceramic Whitewares and Related Products and is the direct responsibility of
5.1.1.2 Recording—A recording dilatometer is an apparatus
Subcommittee C21.03 on Fundamental Properties.
Current edition approved July 15, 1994. Published September 1994. Originally by which the above are recorded by instrumental means but the
published as C 372 – 55 T. Last previous edition C 372 – 88.
final corrected percent linear thermal expansion curve is
Annual Book of ASTM Standards, Vol 14.03.
plotted by hand.
Annual Book of ASTM Standards, Vol 14.02.
C 372
5.1.1.3 Automatic Recording—An automatic recording specimen shall be ground flat and perpendicular to the axis of
dilatometer is a recording dilatometer with provision for the specimen.
automatically plotting the corrected percent linear thermal 6.3 Test specimens shall be conditioned in accordance with
expansion curve. the history of the specimen. Conditioning shall include drying,
5.1.2 Any generally accepted apparatus that is capable of annealing, or protection against moisture expansion, as may be
measuring the length changes produced by thermal expansion necessary.
may be used in this method. The accuracy of the expansion- 6.4 The length of the specimen shall be measured to within
measuring apparatus including transducer, electronic, mechani- an accuracy of 0.1 %.
cal or optical amplification and readout device must be
7. Calibration
60.0001 in. (60.003 mm) and should be reproducible to6
7.1 Periodic calibration of the thermal dilatometer is recom-
0.00005 in. (60.0013 mm). A dilatometer may use a direct
mended to assure the accuracy required by this method.
method of sighting on either of the two ends of the test
Procedures for calibrating the component parts of the dilatom-
specimen or suitable markings at the ends, by means of two
eter are given below. A less time-consuming method for
telescopes mounted on a measuring bank. Another method
standardizing a complete apparatus, especially the recording
transmits the change in length of the specimen to a sensitive
type, is also given. A calibration check of the components of
dial gage or transducer by means of members that are chemi-
the apparatus should be done on an annual basis and calibration
cally inert and free of phase transformations, having ground
of the complete instrument using a standard sample should be
and polished surfaces at points of contact with the test
done within 90 days preceding a report prepared under this
specimens.
method. The date of last calibration by either method should be
5.2 Scale or Caliper, capable of measuring the length of the
included on the report.
specimen with an accuracy of 60.0005 in. (60.010 mm) must
7.2 Calibration Procedures:
be used.
7.2.1 Dilatometer:
5.3 Furnace that is electrically heated and designed so that
7.2.1.1 If a direct sighting method is used, the dilatometer
the thermal gradient over the length of the test specimen shall
can be calibrated with a standard sample with a known length
be less than 3°C. This may be accomplished by electrical
that has been measured by a micrometer with an accuracy of
shuntings, individually controlled zones, or other methods.
60.0001 in. (0.003 mm). The reference sample should be made
5.4 Temperature-Measuring Device—Temperature mea-
from a material that has a very low thermal expansion, such as
surements shall be made by means of a thermocouple placed in
fused silica or invar. The dilatometer system can be calibrated
contact with the test specimen approximately at its mid-length.
by measuring the length of the sample using a movable
The thermocouple shall have the accuracy specified in Table 15
telescope and comparing it with the known value.
of Standard E 230. Type S or Type K thermocouples are
7.2.1.2 If a dial gage transducer system is used, the dilatom-
recommended for this method.
eter can be calibrated with a micrometer or thickness gage. Fix
5.5 Temperature-Indicating Device—The temperature-
the dial gage transducer and micrometer in position on the
indicating device may be a millivolt potentiometer, a calibrated
instrument itself or in a special fixture during calibration. The
meter or recorder, or other apparatus with a precision of 65°C
system can be calibrated by displacing the probe of the
and an accuracy specification equivalent to the precision.
transducer a known amount with the micrometer or thickness
gage and adjusting the instrument to give that value. Which-
6. Test Specimens
ever technique is used, the micrometer or thickness gage shall
6.1 For frit or dried slip samples, specimens shall be
be accurate to 60.0001 in. (0.003 mm).
prepared as follows:
7.2.2 Furnace—The thermal gradient that occurs over the
6.1.1 Frit should be crushed and screened through a 10-
sample length within the furnace should be determined by
mesh sieve to remove large lumps. Then, a refractory boat
simultaneously measuring the temperature at the center, and at
crucible shall be filled with the sample material. If it is desired
3 1
the ends of an alumina sample ⁄8 to ⁄2 in. (10 to 13 mm) in
to reuse the crucible, it should be first lined with powdered
diameter and equal in length to the standard size sample for
alumina as a parting agent. The crucible can be of any suitable
which the apparatus is intended. The thermocouples shall be
refractory material such as porcelain or alumina, but shall be
Type S or Type K. Thermocouple wire of 0.010-in. (0.25-mm)
unglazed. For frits that will be fired at less than 800°C, a metal
diameter or less should be used. The thermocouple beads
mold may be used, if desired.
should be in contact with the test sample surface. Bring
6.1.2 The test specimen shall be subjected to the same firing
thermocouple wires out of the furnace for termination. A
cycle used commercially in order to give a smooth surface on
common negative wire may be used for all three thermocouples
a bulk sample.
to reduce the number of leads brought from the furnace.
NOTE 1—The sample must be cooled slowly over several hours to
Reference the center thermocouple to 0°C and use for the
preserve structural integrity.
temperature reading in degrees Celsius. Connect the thermo-
6.2 For all samples, test specimens may be of any conve- couples in differential as shown in Fig. 1 so as to indicate the
nient length, provided the uniformity of the furnace has been temperature difference between the center and each end. With
determined over that length. The minimum thickness of the the specimen, sample tubes, and readout thermocouple in their
specimen shall be 0.2 in. (5.1 mm) and the maximum cross- normal measuring configuration mounted in the furnace, the
2 2
sectional area shall be 0.45 in. (2.9 cm
...
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