ASTM C832-00(2010)
(Test Method)Standard Test Method of Measuring Thermal Expansion and Creep of Refractories Under Load
Standard Test Method of Measuring Thermal Expansion and Creep of Refractories Under Load
SIGNIFICANCE AND USE
The thermal expansion under load and the 20 to 50 h creep properties of a refractory are useful in characterizing the load bearing capacity of a refractory that is uniformly heated. Directly applicable examples are blast furnace stoves and glass furnace checkers.
SCOPE
1.1 This test method covers the procedure for measuring the linear change of refractory specimens that are subjected to compressive stress while being heated and while being held at elevated temperatures.
1.2 This test method does not apply to materials whose strength depends on pitch or carbonaceous bonds unless appropriate atmospheric control is used (see 7.3).
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.4 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: C832 − 00(Reapproved 2010)
Standard Test Method of
Measuring Thermal Expansion and Creep of Refractories
Under Load
This standard is issued under the fixed designation C832; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope higher the temperature at maximum dilation, the more refrac-
tory the product and the better it is able to resist deformation at
1.1 This test method covers the procedure for measuring the
elevated temperatures.
linear change of refractory specimens that are subjected to
compressive stress while being heated and while being held at
3.1.3 20 to 50 h creep—thepercentdeformationbetweenthe
elevated temperatures.
20 and 50 h can be used to rank products in terms of relative
1.2 This test method does not apply to materials whose load bearing capacity at a particular temperature. Relative
strength depends on pitch or carbonaceous bonds unless rankings of various products may differ at different tempera-
appropriate atmospheric control is used (see 7.3).
tures.
1.3 The values stated in inch-pound units are to be regarded
4. Summary of Test Method
as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only
4.1 Test specimens sawed from samples of refractory brick
and are not considered standard.
or from prefabricated samples of monolithic refractories are
1.4 This standard does not purport to address all of the
placed in a furnace and subjected to a prescribed compressive
safety concerns, if any, associated with its use. It is the
stress. Sensors are positioned for continuously measuring the
responsibility of the user of this standard to establish appro-
linear change of the specimens parallel to the direction of the
priate safety and health practices and determine the applica-
compressive stress. The temperature and linear change of the
bility of regulatory limitations prior to use.
specimens are continuously recorded while heating the furnace
at a controlled rate for thermal expansion under load testing.
2. Referenced Documents
The time and linear change of the specimens are also continu-
2.1 ASTM Standards:
ously recorded while at soak temperature for 20 to 50 h of
E691 Practice for Conducting an Interlaboratory Study to
creep testing.
Determine the Precision of a Test Method
4.2 The user should be aware that other mechanisms,
3. Terminology besides those related to creep, may be activated. This is
especially true as temperatures approach 1650°C. When other
3.1 Definitions of Terms Specific to This Standard:
material responses are activated, such as corrosion, oxidation,
3.1.1 maximum dilation—the percent expansion where the
sintering, etc., strong caution should be exercised when inter-
thermal-expansion rate equals the creep-deformation rate. It
preting and identifying creep mechanisms.
can be used in estimating thermal-expansion relief when used
in conjunction with the temperature at maximum dilation.
4.3 Since materials tend to exhibit faster creep rates during
3.1.2 temperature at maximum dilation—in addition to es-
the initial stage of deformation, the user should be cautioned
timating thermal-expansion relief, it can be used to rank
when extrapolating measured creep rates beyond the normal
products in terms of relative refractoriness. In general, the
50 h test time. The material must be in the secondary creep
stage in order to extrapolate to longer times.
This test method is under the jurisdiction of ASTM Committee C08 on
5. Significance and Use
Refractories and is the direct responsibility of Subcommittee C08.01 on Strength.
Current edition approved Nov. 1, 2010. Published November 2010. Originally
5.1 The thermal expansion under load and the 20 to 50 h
approved in 1976. Last previous edition approved in 2005 as C832 – 00 (2005).
DOI: 10.1520/C0832-00R10.
creep properties of a refractory are useful in characterizing the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
load bearing capacity of a refractory that is uniformly heated.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Directly applicable examples are blast furnace stoves and glass
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. furnace checkers.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C832 − 00 (2010)
6. Interferences length of the specimen can cause fluctuations in strain mea-
surements or changes in creep rate (see 7.1 and 7.2).
6.1 Chemical Interactions with Test Environment—The test
environment (vacuum, inert gas, ambient air, etc.), including
7. Apparatus
moisture content (percent relative humidity), may have a
stronginfluenceonbothcreepstrainrateandcreeprupturelife. 7.1 Electrically Heated Furnace, with a setting space suffi-
cient to contain one or more specimens of the size specified in
In particular, refractories susceptible to slow crack growth or
oxidation will be strongly influenced by the test environment. Section 8. The specimens should be equally heated on at least
two opposite sides, and the temperature difference between
Testing should be conducted in environments that are either
representative of service conditions or inert to the refractories specimens in a multiple-position furnace and between the top
and bottom ends of single specimens should be no more than
being tested depending on the performance being evaluated.
18°F (10°C). See Figs. 1-5 for sketches of five typical furnace
6.2 Specimen Surface Preparation—Surface preparation of
arrangements.
specimens can introduce machining flaws that may affect the
creep strain rate and creep rupture life. Machining damage 7.2 Temperature Controllers,thatcontrolheatingatarateof
imposed during specimen preparation will most likely result in 100 6 9°F/h (55 6 5°C/h) over the temperature range from
premature failure of the specimen, but may also introduce 500 to 3000°F (260 to 1650°C) and can control soak tempera-
flaws that can grow by slow crack growth. Surface preparation tures within 69°F (65°C).
can also lead to residual stresses, which can be released during
7.3 Air Atmosphere, unless otherwise specified. If pitch or
the test.
carbonaceous-bonded materials are tested, specify the atmo-
6.3 Specimen/Extensometer Chemical Interactions—If the sphere used when reporting results.
strain measurement technique relies on physical contact be-
7.4 Linear Measuring Device, that records the difference in
tween the extensometer components (contacting probes or
length dimension of each specimen parallel to the direction of
optical method flags) and the specimen, then the flag attach-
stress and yields the desired precision and reproducibility.
ment methods and extensometer contact materials must be
7.5 Recorders, that display linear change readings to
chosen with care to ensure that no adverse chemical reactions
60.0005 in. (0.013 mm).
occur during testing. This should not be a problem if the probe
or specimen materials are mutually chemically inert. The user 7.6 Loading Devices, that apply at least 100 psi (689 kPa)
1 1
should also be aware that impurities or second phases in the compressive stress within 61%, on a 1 ⁄2 by 1 ⁄2-in. (38 by
probes and flags or specimens may be mutually chemically 38-mm) cross section.
reactive and could influence the results.
8. Specimen Preparation
6.4 Temperature Variations—Creep strain is related to tem-
1 1 1
perature through an exponential function. Thus, fluctuations in 8.1 Cut or form specimens nominally 1 ⁄2 by 1 ⁄2 by 4 ⁄2 in.
test temperature or changes in temperature profile along the (38 by 38 by 114 mm) (Note 1) with the 4 ⁄2-in. dimension
FIG. 1 Specimen Furnace Arrangement
C832 − 00 (2010)
FIG. 2 Specimen Furnace Arrangement
surfacesofthespecimenisrecommendedtobewithin0.001in.
1 1 1
(0.03mm).Onlythe1 ⁄2by1 ⁄2-in.(38by38-mm)andone1 ⁄2
by 4 ⁄2-in. (38 by 114-mm) surfaces may be original.
8.3 Measure all dimensions to the nearest 0.001 in. (0.03
mm) as follows:
8.3.1 Length—Average five measurements which include
four taken at ⁄4 in. (6 mm) on the diagonal from each corner
and one at the center of the faces.
8.3.2 Width and Depth—Averagethreemeasurementswhich
include one taken at the center of the faces and two from the
quarter points.
8.3.3 Calculate the cross-sectional area of each specimen
and use to determine the precise loading per specimen.
9. Calibration
9.1 Calibrate each loading and measuring position sepa-
rately. Follow the procedure given in Section 10 and determine
the “machine output” curves for each position using a speci-
men of known thermal expansion. Calibration shall be done on
each new furnace and after replacement of any parts of the
measuring or loading devices. Fused magnesium oxide (MgO)
orisostaticallypressedandfiredMgOof99 %minimumpurity
and 3.18 g/cm minimum bulk density is recommended for
standardization. Volume stable 90 % plus aluminum oxide
(Al O ), fused silica (SiO ), or sapphire may also be used if
2 3 2
reliable thermal expansion data are available. Make these runs
FIG. 3 Specimen Furnace Arrangement
with the loading mechanism blocked so that the specimen is
essentially under zero stress.
perpendicular to the pressing direction of a brick, the ramming
9.2 Make a minimum of three runs and record the measure-
direction of a plastic, or the position of the vibrator used in
ments of linear change continuously with a computer/data
forming a castable. The 4 ⁄2-in. dimension may be parallel to
acquisition system or on a strip chart or X-Y recorder or, if
the length or width of the original shape.
done manually, at 100°F (55°C) intervals up to 2000°F
NOTE 1—Specimens of different geometry (for example, cylin
...
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