1、Designation: C 832 00 (Reapproved 2005)Standard Test Method ofMeasuring Thermal Expansion and Creep of RefractoriesUnder Load1This standard is issued under the fixed designation C 832; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the procedure for measuring thelinear change of refractory specimens that are s
3、ubjected tocompressive stress while being heated and while being held atelevated temperatures.1.2 This test method does not apply to materials whosestrength depends on pitch or carbonaceous bonds unlessappropriate atmospheric control is used (see 7.3).1.3 The values stated in inch-pound units are to
4、 be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
5、the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Termi
6、nology3.1 Definitions of Terms Specific to This Standard:3.1.1 maximum dilationthe percent expansion where thethermal-expansion rate equals the creep-deformation rate. Itcan be used in estimating thermal-expansion relief when usedin conjunction with the temperature at maximum dilation.3.1.2 temperat
7、ure at maximum dilationin addition toestimating thermal-expansion relief, it can be used to rankproducts in terms of relative refractoriness. In general, thehigher the temperature at maximum dilation, the more refrac-tory the product and the better it is able to resist deformation atelevated tempera
8、tures.3.1.3 20 to 50 h creepthe percent deformation betweenthe 20 and 50 h can be used to rank products in terms ofrelative load bearing capacity at a particular temperature.Relative rankings of various products may differ at differenttemperatures.4. Summary of Test Method4.1 Test specimens sawed fr
9、om samples of refractory brickor from prefabricated samples of monolithic refractories areplaced in a furnace and subjected to a prescribed compressivestress. Sensors are positioned for continuously measuring thelinear change of the specimens parallel to the direction of thecompressive stress. The t
10、emperature and linear change of thespecimens are continuously recorded while heating the furnaceat a controlled rate for thermal expansion under load testing.The time and linear change of the specimens are also continu-ously recorded while at soak temperature for 20 to 50 h ofcreep testing.4.2 The u
11、ser should be aware that other mechanisms,besides those related to creep, may be activated. This isespecially true as temperatures approach 1650C. When othermaterial responses are activated, such as corrosion, oxidation,sintering, etc., strong caution should be exercised when inter-preting and ident
12、ifying creep mechanisms.4.3 Since materials tend to exhibit faster creep rates duringthe initial stage of deformation, the user should be cautionedwhen extrapolating measured creep rates beyond the normal50 h test time. The material must be in the secondary creepstage in order to extrapolate to long
13、er times.5. Significance and Use5.1 The thermal expansion under load and the 20 to 50 hcreep properties of a refractory are useful in characterizing theload bearing capacity of a refractory that is uniformly heated.Directly applicable examples are blast furnace stoves and glassfurnace checkers.6. In
14、terferences6.1 Chemical Interactions with Test EnvironmentThe testenvironment (vacuum, inert gas, ambient air, etc.), includingmoisture content (percent relative humidity), may have astrong influence on both creep strain rate and creep rupture life.In particular, refractories susceptible to slow cra
15、ck growth or1This test method is under the jurisdiction of ASTM Committee C08 onRefractories and is the direct responsibility of Subcommittee C08.01 on Strength.Current edition approved Dec. 1, 2005. Published December 2005. Originallyapproved in 1976. Last previous edition approved in 2000 as C 832
16、 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO
17、Box C700, West Conshohocken, PA 19428-2959, United States.oxidation will be strongly influenced by the test environment.Testing should be conducted in environments that are eitherrepresentative of service conditions or inert to the refractoriesbeing tested depending on the performance being evaluate
18、d.6.2 Specimen Surface PreparationSurface preparation ofspecimens can introduce machining flaws that may affect thecreep strain rate and creep rupture life. Machining damageimposed during specimen preparation will most likely result inpremature failure of the specimen, but may also introduceflaws th
19、at can grow by slow crack growth. Surface preparationcan also lead to residual stresses, which can be released duringthe test.6.3 Specimen/Extensometer Chemical InteractionsIf thestrain measurement technique relies on physical contact be-tween the extensometer components (contacting probes oroptical
20、 method flags) and the specimen, then the flag attach-ment methods and extensometer contact materials must bechosen with care to ensure that no adverse chemical reactionsoccur during testing. This should not be a problem if the probeor specimen materials are mutually chemically inert. The usershould
21、 also be aware that impurities or second phases in theprobes and flags or specimens may be mutually chemicallyreactive and could influence the results.6.4 Temperature VariationsCreep strain is related to tem-perature through an exponential function. Thus, fluctuations intest temperature or changes i
22、n temperature profile along thelength of the specimen can cause fluctuations in strain mea-surements or changes in creep rate (see 7.1 and 7.2).7. Apparatus7.1 Electrically Heated Furnace, with a setting space suffi-cient to contain one or more specimens of the size specified inSection 8. The specim
23、ens should be equally heated on at leasttwo opposite sides, and the temperature difference betweenspecimens in a multiple-position furnace and between the topand bottom ends of single specimens should be no more than18F (10C). See Figs. 1-5 for sketches of five typical furnacearrangements.7.2 Temper
24、ature Controllers, that control heating at a rate of100 6 9F/h (55 6 5C/h) over the temperature range from500 to 3000F (260 to 1650C) and can control soak tempera-tures within 69F (65C).7.3 Air Atmosphere, unless otherwise specified. If pitch orcarbonaceous-bonded materials are tested, specify the a
25、tmo-sphere used when reporting results.7.4 Linear Measuring Device, that records the difference inlength dimension of each specimen parallel to the direction ofstress and yields the desired precision and reproducibility.7.5 Recorders, that display linear change readings to60.0005 in. (0.013 mm).7.6
26、Loading Devices, that apply at least 100 psi (689 kPa)compressive stress within 61%, on a 112 by 112-in. (38 by38-mm) cross section.8. Specimen Preparation8.1 Cut or form specimens nominally 112 by 112 by 412 in.(38 by 38 by 114 mm) (Note 1) with the 412-in. dimensionperpendicular to the pressing di
27、rection of a brick, the rammingdirection of a plastic, or the position of the vibrator used informing a castable. The 412-in. dimension may be parallel tothe length or width of the original shape.NOTE 1Specimens of different geometry (for example, cylindrical)may be used upon agreement between the p
28、arties concerned.8.2 Grind or sand both 112 by 112-in. (38 by 38-mm)surfaces so that they are nominally plane and perpendicular tothe length dimension. The parallelness tolerance on the loadingsurfaces of the specimen is recommended to be within 0.001 in.FIG. 1 Specimen Furnace ArrangementC 832 00 (
29、2005)2(0.03 mm). Only the 112 by 112-in. (38 by 38-mm) and one 112by 412-in. (38 by 114-mm) surfaces may be original.8.3 Measure all dimensions to the nearest 0.001 in. (0.03mm) as follows:8.3.1 LengthAverage five measurements which includefour taken at14 in. (6 mm) on the diagonal from each cornera
30、nd one at the center of the faces.8.3.2 Width and DepthAverage three measurementswhich include one taken at the center of the faces and two fromthe quarter points.8.3.3 Calculate the cross-sectional area of each specimenand use to determine the precise loading per specimen.9. Calibration9.1 Calibrat
31、e each loading and measuring position sepa-rately. Follow the procedure given in Section 10 and determinethe “machine output” curves for each position using a speci-men of known thermal expansion. Calibration shall be done oneach new furnace and after replacement of any parts of themeasuring or load
32、ing devices. Fused magnesium oxide (MgO)or isostatically pressed and fired MgO of 99 % minimum purityand 3.18 g/cm3minimum bulk density is recommended forstandardization. Volume stable 90 % plus aluminum oxide(Al2O3), fused silica (SiO2), or sapphire may also be used ifreliable thermal expansion dat
33、a are available. Make these runswith the loading mechanism blocked so that the specimen isessentially under zero stress.9.2 Make a minimum of three runs and record the measure-ments of linear change continuously with a computer/dataacquisition system or on a strip chart or X-Y recorder or, ifdone ma
34、nually, at 100F (55C) intervals up to 2000F(1095C) and 50F (28C) intervals above 2000F whileheating in accordance with 10.5. Reposition the specimen aftereach run to ensure that all random errors due to handling arerepeated each time. To ensure that the error for these runs is nogreater than 60.05 %
35、 expansion at a probability level of 0.95,the standard deviation of the machine output cannot exceed0.02 percentage points.9.3 If MgO is chosen as the calibration standard, use theexpansion data listed for MgO in Table 1.9.4 Obtain correction factors at the selected temperaturelevels from the algebr
36、aic difference between the averagemachine output in percent and the applicable true-expansionpercentage for the calibration standard. The algebraic sum ofFIG. 2 Specimen Furnace ArrangementFIG. 3 Specimen Furnace ArrangementC 832 00 (2005)3the correction factors and the machine output of an unknowny
37、ields the expansion data in percent for the unknown.10. Procedure10.1 After leveling the hearth setters, place each specimenin the furnace with its longitudinal axis in alignment with thecenterline of the loading device. To protect the bottom of theload plunger, place a14-in. (6-mm) thick slab of al
38、umina orsilicon carbide on top of the specimen. A slab works best if itis larger than the specimen, such as one that is approximatelyequal in length and width to the cross section of the plunger. Ifchemical reaction between specimen and furnace loading partsis expected, use a piece of 1-mil (25.4-m)
39、 thick platinum foilbetween the top and bottom of the specimen and the furnaceparts (Note 2). Do not use setting powder. The top of eachspecimen shall be level and parallel to the bottom setter.NOTE 2As testing temperatures approach 1650C, spacers of Al2O3,SiC, or Pt may not be suitable due to chemi
40、cal reaction with the specimenor creep of the spacer. Under these conditions, the measured dilation maybe significantly affected.10.2 Position linear measuring devices and check for free-dom of movement of sensor rods, dials, plungers, linearlyvariable differential transformers (LVDTs), and operatio
41、n ofrecording equipment.10.3 Apply loads on each specimen in the amount necessaryto provide the desired stress as determined by the specimencross-sectional area. The stress level used must accompany testresults. Use a stress of 25 psi (172 kPa) unless otherwisespecified. Stress levels other than 25
42、psi (172 kPa) may be usedupon agreement between the interested parties.10.4 Use a calibrated thermocouple, preferably connected toa program controller, for measuring and controlling furnacetemperature. For accuracy in measuring specimen temperature,it is recommended that a grounded, insulated, and c
43、alibratedthermocouple be placed so that the hot junction is within12 in.(6 mm) of the midpoint of every specimen (Note 3).NOTE 3Control of the temperature is essential for accurate results. Itis recommended that access ports be provided to periodically check thetemperature of each specimen with a ca
44、librated thermocouple to ensurethat the desired temperature is obtained throughout the test.10.5 Heating control may be manual, but an electricallydriven program controller is preferred. Heat the furnace at arate of 1006 9F/h (55 6 5C/h) to the desired soak tempera-ture.10.6 For thermal expansion un
45、der load testing, continuouslyrecord the measurements of linear change with a computer/dataacquisition system or on a strip chart or X-Y recorder, ormanually at intervals of 100F (55C) during heating. Attemperatures above 2000F (1095C), take readings at 50F(28C) intervals.10.7 Continue heating until
46、 one of the following occurs:10.7.1 Linear thermal expansion ceases, and a maximumdilation level is identifiable, and 20 to 50 h creep testing is notdesired, or10.7.2 The specimen fails.FIG. 4 Specimen Furnace ArrangementC 832 00 (2005)410.8 For 20 to 50-h creep testing, hold the specimen at thedesi
47、red soak temperature for 50 h. Continuously record themeasurement of linear change with a computer/data acquisitionsystem or on a strip chart or X-Y recorder, or manually atintervals of 5 h.10.9 Convert linear measurements to percent and record tothe nearest 0.001 %. Test at least two specimens. Eac
48、h speci-men is considered a test result and replicates must be tested inthe same furnace.11. Report11.1 For the thermal expansion under load test, report theaverage and standard deviation for the temperature and linearchange at the maximum level of expansion where the creep rateequals the expansion
49、rate. This point is called the maximumdilation point. Report temperature to the nearest 9F (5C) andexpansion to the nearest 0.001 %. Base results on at least twospecimens.11.2 For the 20 to 50 h creep test, report the average andstandard deviation for the creep between 20 and 50 h. Baseresults on at least two specimens.12. Precision and Bias12.1 Interlaboratory DataAn interlaboratory round robinwas conducted in 1983 in which four laboratories each testedtwo specimens from five different types of refractory materials.Each la
