ASTM C372-94(2001)
(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: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.
1. Scope
where:
a = 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 = percent linear thermal expansion as defined in 3.1.2.
glaze)andceramicwhitewareproductsbythethermaldilatom-
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 3100 1 A
accuracy of 63% or better and coefficient of linear expansion L
accuracy of 65% or better.
1.2 This standard does not purport to address all of the
DL
5 3100 1 A
safety concerns, if any, associated with its use. It is the L
responsibility of the user of this standard to establish appro-
where:
priate safety and health practices and determine the applica-
P = percent linear thermal expansion from temperature
bility of regulatory limitations prior to use.
T to T ,
1 2
L = sample length at T (T between 20 and 30°C),
2. Referenced Documents 0 0 0
L = sample length at T ,
1 1
2.1 ASTM Standards:
L = sample length at T , and
2 2
E220 Method for Calibration of Thermocouples by Com-
A = instrument correction.
parison Techniques
E228 Test Method for Linear Thermal Expansion of Solid
4. Significance and Use
Materials with a Vitreous Silica Dilatometer
4.1 Measurementofthermalexpansionisusefulforpredict-
E230 Temperature-Electromotive Force (EMF) Tables for
ing stress within joined materials or single materials under
Standardized Thermocouples
conditions of changing or nonuniform temperature. It can also
E691 Practice for Conducting an Interlaboratory Study to
serve as an indicator of phase composition or changes in
Determine the Precision of a Test Method
structure.
3. Terminology
5. Apparatus
3.1 Definitions:
5.1 Thermal Dilatometer:
3.1.1 mean coeffıcient of linear thermal expansion—from
5.1.1 General Description—A thermal dilatometer is an
temperature T to temperature T (T < T ):
1 2 1 2
apparatus that provides means for varying the temperature of a
0.01 P
test specimen in a controlled manner, measuring the specimen
a,mm/mm·°Corin./in.·°C 5
T 2 T
2 1 length,andmeasuringthetemperatureofthespecimenforeach
readingofspecimenlength.Thereareseveraldifferenttypesas
follows:
ThistestmethodisunderthejurisdictionofASTMCommitteeC21onCeramic
5.1.1.1 Manual—Amanual dilatometer is one in which any
Whitewares and Related Products and is the direct responsibility of Subcommittee
oralloftheabovearedonebymanualmeansandthecorrected
C21.03 on Methods for Whitewares and Environmental Concerns.
Current edition approved July 15, 1994. Published September 1994. Originally
percent linear thermal expansion curve is plotted by hand.
published as C372–55T. Last previous edition C372–88.
Annual Book of ASTM Standards, Vol 14.03.
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.
C372
5.1.1.2 Recording—Arecording dilatometer is an apparatus 6.2 For all samples, test specimens may be of any conve-
bywhichtheabovearerecordedbyinstrumentalmeansbutthe nient length, provided the uniformity of the furnace has been
final corrected percent linear thermal expansion curve is determined over that length. The minimum thickness of the
plotted by hand. specimen shall be 0.2 in. (5.1 mm) and the maximum cross-
2 2
sectional area shall be 0.45 in. (2.9 cm ). The ends of the
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
measuringapparatusincludingtransducer,electronic,mechani-
an accuracy of 0.1%.
cal or optical amplification and readout device must be
60.0001 in. (60.003 mm) and should be reproducible to
7. Calibration
60.00005 in. (60.0013 mm). A dilatometer may use a direct
method of sighting on either of the two ends of the test
7.1 Periodiccalibrationofthethermaldilatometerisrecom-
specimen or suitable markings at the ends, by means of two
mended to assure the accuracy required by this method.
telescopes mounted on a measuring bank. Another method
Procedures for calibrating the component parts of the dilatom-
transmits the change in length of the specimen to a sensitive
eter are given below. A less time-consuming method for
dial gage or transducer by means of members that are chemi-
standardizing a complete apparatus, especially the recording
cally inert and free of phase transformations, having ground
type, is also given. A calibration check of the components of
and polished surfaces at points of contact with the test
theapparatusshouldbedoneonanannualbasisandcalibration
specimens.
of the complete instrument using a standard sample should be
5.2 Scale or Caliper, capable of measuring the length of the
done within 90 days preceding a report prepared under this
specimen with an accuracy of 60.0005 in. (60.010 mm) must
method.Thedateoflastcalibrationbyeithermethodshouldbe
be used.
included on the report.
5.3 Furnace that is electrically heated and designed so that
7.2 Calibration Procedures:
the thermal gradient over the length of the test specimen shall
7.2.1 Dilatometer:
be less than 3°C. This may be accomplished by electrical
7.2.1.1 If a direct sighting method is used, the dilatometer
shuntings, individually controlled zones, or other methods.
can be calibrated with a standard sample with a known length
5.4 Temperature-Measuring Device—Temperature mea-
that has been measured by a micrometer with an accuracy of
surementsshallbemadebymeansofathermocoupleplacedin
60.0001in.(0.003mm).Thereferencesampleshouldbemade
contact with the test specimen approximately at its mid-length.
from a material that has a very low thermal expansion, such as
ThethermocoupleshallhavetheaccuracyspecifiedinTable15
fused silica or invar. The dilatometer system can be calibrated
of Standard E230. Type S or Type K thermocouples are
by measuring the length of the sample using a movable
recommended for this method.
telescope and comparing it with the known value.
5.5 Temperature-Indicating Device—The temperature- 7.2.1.2 Ifadialgagetransducersystemisused,thedilatom-
indicatingdevicemaybeamillivoltpotentiometer,acalibrated
eter can be calibrated with a micrometer or thickness gage. Fix
meter or recorder, or other apparatus with a precision of 65°C the dial gage transducer and micrometer in position on the
and an accuracy specification equivalent to the precision.
instrument itself or in a special fixture during calibration. The
system can be calibrated by displacing the probe of the
6. Test Specimens transducer a known amount with the micrometer or thickness
gage and adjusting the instrument to give that value. Which-
6.1 For frit or dried slip samples, specimens shall be
ever technique is used, the micrometer or thickness gage shall
prepared as follows:
be accurate to 60.0001 in. (0.003 mm).
6.1.1 Frit should be crushed and screened through a 10-
7.2.2 Furnace—The thermal gradient that occurs over the
mesh sieve to remove large lumps. Then, a refractory boat
sample length within the furnace should be determined by
crucible shall be filled with the sample material. If it is desired
simultaneously measuring the temperature at the center, and at
to reuse the crucible, it should be first lined with powdered
3 1
the ends of an alumina sample ⁄8 to ⁄2 in. (10 to 13 mm) in
alumina as a parting agent.The crucible can be of any suitable
diameter and equal in length to the standard size sample for
refractory material such as porcelain or alumina, but shall be
which the apparatus is intended. The thermocouples shall be
unglazed. For frits that will be fired at less than 800°C, a metal
Type S or Type K. Thermocouple wire of 0.010-in. (0.25-mm)
mold may be used, if desired.
diameter or less should be used. The thermocouple beads
6.1.2 Thetestspecimenshallbesubjectedtothesamefiring
should be in contact with the test sample surface. Bring
cycle used commercially in order to give a smooth surface on
thermocouple wires out of the furnace for termination. A
a bulk sample.
commonnegativewiremaybeusedforallthreethermocouples
to reduce the number of leads brought from the furnace.
NOTE 1—The sample must be cooled slowly over several hours to
preserve structural integrity. Reference the center thermocouple to 0°C and use for the
C372
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. With full-scale temperature range. If the values do not agree within
the specimen, sample tubes
...
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