ASTM C372-94(2001)e1
(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.
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:C372–94 (Reapproved 2001)
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 C372; 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.
e NOTE—7.2.4.1 was editorially corrected in February 2007.
0.01 P
1. Scope
a,mm/mm·°Corin./in.·°C 5
T 2 T
2 1
1.1 This test method covers the determination of the linear
thermal expansion of premelted frit (porcelain enamel and
where:
glaze)andceramicwhitewareproductsbythethermaldilatom-
a = mean coefficient of linear thermal expansion from
eter method. This test method is applicable to apparatus
temperature T to T , and
1 2
meeting the reproducibility and accuracy requirements of this
P = percent linear thermal expansion as defined in 3.1.2.
test method, which are to produce percent linear expansion
3.1.2 percent linear thermal expansion—from temperature
accuracy of 63% or better and coefficient of linear expansion
T to temperature T (T < T ):
1 2 1 2
accuracy of 65% or better.
L 2 L
2 1
1.2 This standard does not purport to address all of the P 5 3100 1 A
L
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
DL
5 3100 1 A
priate safety and health practices and determine the applica-
L
bility of regulatory limitations prior to use.
where:
2. Referenced Documents
P = percent linear thermal expansion from temperature
2.1 ASTM Standards: T to T ,
1 2
E220 Method for Calibration of Thermocouples by Com- L = sample length at T (T between 20 and 30°C),
0 0 0
L = sample length at T ,
parison Techniques
1 1
L = sample length at T , and
E228 Test Method for Linear Thermal Expansion of Solid 2 2
A = instrument correction.
Materials with a Vitreous Silica Dilatometer
E230 Temperature-Electromotive Force (EMF) Tables for
4. Significance and Use
Standardized Thermocouples
4.1 Measurementofthermalexpansionisusefulforpredict-
E691 Practice for Conducting an Interlaboratory Study to
3 ing stress within joined materials or single materials under
Determine the Precision of a Test Method
conditions of changing or nonuniform temperature. It can also
3. Terminology serve as an indicator of phase composition or changes in
structure.
3.1 Definitions:
3.1.1 mean coeffıcient of linear thermal expansion—from
5. Apparatus
temperature T to temperature T (T < T ):
1 2 1 2
5.1 Thermal Dilatometer:
5.1.1 General Description—A thermal dilatometer is an
ThistestmethodisunderthejurisdictionofASTMCommitteeC21onCeramic apparatus that provides means for varying the temperature of a
Whitewares and Related Products and is the direct responsibility of Subcommittee
test specimen in a controlled manner, measuring the specimen
C21.03 on Methods for Whitewares and Environmental Concerns.
length,andmeasuringthetemperatureofthespecimenforeach
Current edition approved July 15, 1994. Published September 1994. Originally
readingofspecimenlength.Thereareseveraldifferenttypesas
published as C372–55T. Last previous edition C372–88.
Annual Book of ASTM Standards, Vol 14.03.
follows:
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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C372–94 (2001)
NOTE 1—The sample must be cooled slowly over several hours to
5.1.1.1 Manual—Amanual dilatometer is one in which any
preserve structural integrity.
oralloftheabovearedonebymanualmeansandthecorrected
percent linear thermal expansion curve is plotted by hand.
6.2 For all samples, test specimens may be of any conve-
5.1.1.2 Recording—Arecording dilatometer is an apparatus
nient length, provided the uniformity of the furnace has been
bywhichtheabovearerecordedbyinstrumentalmeansbutthe determined over that length. The minimum thickness of the
final corrected percent linear thermal expansion curve is
specimen shall be 0.2 in. (5.1 mm) and the maximum cross-
2 2
plotted by hand. sectional area shall be 0.45 in. (2.9 cm ). The ends of the
specimen shall be ground flat and perpendicular to the axis of
5.1.1.3 Automatic Recording—An automatic recording
dilatometer is a recording dilatometer with provision for the specimen.
6.3 Test specimens shall be conditioned in accordance with
automatically plotting the corrected percent linear thermal
expansion curve. the history of the specimen. Conditioning shall include drying,
annealing, or protection against moisture expansion, as may be
5.1.2 Any generally accepted apparatus that is capable of
necessary.
measuring the length changes produced by thermal expansion
6.4 The length of the specimen shall be measured to within
may be used in this method. The accuracy of the expansion-
an accuracy of 0.1%.
measuringapparatusincludingtransducer,electronic,mechani-
cal or optical amplification and readout device must be
7. Calibration
60.0001 in. (60.003 mm) and should be reproducible to
7.1 Periodiccalibrationofthethermaldilatometerisrecom-
60.00005 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-
theapparatusshouldbedoneonanannualbasisandcalibration
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.Thedateoflastcalibrationbyeithermethodshouldbe
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.
60.0001in.(0.003mm).Thereferencesampleshouldbemade
5.4 Temperature-Measuring Device—Temperature mea-
from a material that has a very low thermal expansion, such as
surementsshallbemadebymeansofathermocoupleplacedin
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
ThethermocoupleshallhavetheaccuracyspecifiedinTable15
telescope and comparing it with the known value.
of Standard E230. Type S or Type K thermocouples are
7.2.1.2 Ifadialgagetransducersystemisused,thedilatom-
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
indicatingdevicemaybeamillivoltpotentiometer,acalibrated
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
3 1
crucible shall be filled with the sample material. If it is desired 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 Thetestspecimenshallbesubjectedtothesamefiring thermocouple wires out of the furnace for termination. A
cycle used commercially in order to give a smooth surface on commonnegativewiremaybeusedforallthreethermocouples
a bulk sample. to reduce the number of leads brought from the furnace.
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C372–94 (2001)
Reference the center thermocouple to 0°C and use for the 100°C intervals. The results plotted in 7.2.5.2 must agree with
temperature reading in degrees Celsius. Connect the thermo- the accepted values for the platinum or reference standard
couples in differential as shown in Fig. 1 so as to indicate the within 61% of the expansion value of platinum over the
temperature difference between the center and each end. W
...
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