1、Designation: C621 09 (Reapproved 2018)Standard Test Method forIsothermal Corrosion Resistance of Refractories to MoltenGlass1This standard is issued under the fixed designation C621; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the corro-sion resistance of refractories in contact with mol
3、ten glassunder static, isothermal conditions.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to ad
4、dress all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was dev
5、eloped in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Do
6、cuments2.1 ASTM Standards:2E220 Test Method for Calibration of Thermocouples ByComparison Techniques3. Significance and Use3.1 This test method provides a rapid, inexpensive methodfor comparing the corrosion resistance of refractories. Theisothermal conditions of this test method represent the mosts
7、evere static corrosion environment possible at the specifiedtest temperature. This test method is suitable for qualitycontrol, research and development applications, and for prod-uct value studies on similar materials. Tests run at a series oftemperatures are often helpful in determining the use tem
8、pera-ture limitations of a particular material. Melt-line corrosionresults are also a useful indication of relative resistance to bothupward and downward drilling corrosion mechanisms. Exami-nation of test specimens also provides information about thetendency for a particular refractory to form ston
9、es or otherglass defects.3.2 Because this test method is both isothermal and static,and since most glass-contact refractories operate in a dynamicsystem with a thermal gradient, test results do not directlypredict service in a furnace. The effects of differing thermalconductivities, refractory thick
10、ness, artificial cooling or insu-lation upon the refractory thermal gradient, and the erosiveaction of moving molten glass currents are not evaluated withthis test.4. Apparatus4.1 Glass-Melting Test Furnace, heated with some type ofelectrical resistor (Note 1) and having a chamber large enoughto rec
11、eive four crucible assemblies of the type used in the test(Fig. 1) is required. The zone of the furnace in which thecrucibles will rest should possess a maximum transversethermal gradient of 61.8 F (61 C). Fig. A1.1 shows aschematic drawing of a furnace that is satisfactory for this test.NOTE 1It ha
12、s been demonstrated that gas-fired furnaces show greatervariability and higher average corrosion with this test method and aretherefore generally unsuitable.4.2 Temperature-Control Instrumentation, capable of main-taining the desired temperature to 61.8 F (61 C).4.3 Thermocouple, for use as the temp
13、erature measuringdevice. The type of thermocouple chosen will depend on thenormal use temperature of the furnace. Since thermocouplesage with a consequent drift in the signal fed to the controlinstrument, check the couple before each test run with acalibrated thermocouple. Test Method E220 specifies
14、 calibra-tion procedures for thermocouples. If drift becomes severe,replace the thermocouple. Position the thermocouple hot junc-tion in the furnace to coincide with the level of the glass lineof the test samples.4.4 Platinum Crucibles (Fig. 1).1This test method is under the jurisdiction of ASTM Com
15、mittee C08 onRefractories and is the direct responsibility of Subcommittee C08.10 on Refractoriesfor Glass.Current edition approved Oct. 1, 2018. Published October 2018. Originallyapproved in 1968. Last previous edition approved in 2014 as C621 09 (2014).DOI: 10.1520/C0621-09R18.2For referenced ASTM
16、 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohock
17、en, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organiza
18、tion Technical Barriers to Trade (TBT) Committee.14.5 Sintered Zircon, or other refractory wafers (Annex A2).4.6 Zircon Cement (Annex A3).4.7 Measuring Microscope.4.8 Tongs, suitable for handling samples in the furnace (Fig.A1.6).4.9 Furnace, for preheating test specimens to about 1832 F(1000 C) (An
19、nex A1).4.10 Diamond Saw, and diamond hone, or diamond-coredrill.5. Test Specimens5.1 Sample SelectionA sample shall be comprised of oneor more specimens cut from the refractory unit being tested.Specimens should be as representative of the material beingtested as possible. In the testing of slip-ca
20、st and pressedrefractory products, take care to avoid cracks, checks, obviouscontaminants, etc. In the testing of fusion-cast materials, it isrecognized that wide variations in both chemistry and crystalsize occur within every casting. Therefore, a standard samplinglocation should be used and specif
21、ied. For flat-cast blocks, takethe specimen on the surface opposite the font scar (andperpendicular to this surface) and at least 3 in. (76 mm) froman end and a side of the casting. For voidless castings, take thespecimen from any cast surface near the top, saw-cut surface ofthe block. Take this spe
22、cimen at least 3 in. from any corner ofthe casting. Such specimens avoid edge and corner crystalli-zation effects and have chemistries similar to those represent-ing the bulk of the casting.5.2 Specimen Size and Preparation:5.2.1 The specimen shall be either 0.39 in. (9.9 mm) squareby 2.0 in. (51 mm
23、) long or cylinders 0.5 in. (13 mm) indiameter by 2.0 in. long. In either case, the specified dimen-sions shall be controlled within 0.002 in. (0.05 mm) along theentire length of the specimens.5.2.2 Prepare cylindrical specimens with a diamond-corebit. Specimens should be perfectly smooth (free of s
24、malloffsets, etc.) and free of metal marks from the drill along theirentire length. Grind square specimens to size, after diamondsawing, on a diamond hone to provide clean parallel faces.5.2.3 Do not grind the specimens with silicon carbidebecause of the potential contaminating effect.5.2.4 After gr
25、inding or drilling, dry the specimens to con-stant weight at 230 F (110 C) prior to corrosion testing.5.3 Pretest Specimen Measurements and Inspection:5.3.1 Make a bulk density measurement on the specimen.Calculate the volume of the specimen either from the specimendimensions or by water displacemen
26、t.5.3.2 Measure the specimen to the nearest 0.001 in.(0.03 mm) at two points, the anticipated glass line, and at alevel halfway between the glass line and the bottom of thespecimen. With square specimens, it is important that theorientation of these measurements be marked above the glassline so that
27、 corresponding measurements can be made after thetest.5.3.3 Make an inspection of the specimen prior to the test,noting color, evidence of porosity, and any irregularities orunusual features.5.4 Other Specimen Notes:5.4.1 Four or more specimens are usually tested concur-rently. It has been found hel
28、pful to include a control (orstandard) in each series of specimens. Ideally, the controlspecimens are taken from a single refractory block or shaperetained semi-permanently for that purpose. By using a controlspecimen, the variability between tests can be continuouslyscrutinized and the control spec
29、imen can serve as a comparisonstandard for the other specimen in the same test.5.4.2 Either round or square test specimens may be used,but never both in the same series of experiments, since datafrom the two types of specimen geometry are not directlycomparable.5.4.3 Specimen orientation within a te
30、st or series of testsshould be consistent. When applicable, cast or pressed surfacesshould comprise the sample bottom.6. Test Temperature and Duration6.1 Test temperatures should simulate those in the intendedservice.SI Equivalentsin. mm0.030 0.761364 512 133364 131732 1312114 32.8NOTE 1All undesign
31、ated dimensions are in inches.FIG. 1 Crucible AssemblageC621 09 (2018)26.2 For maximum reliability and reproducibility, the testtime should be of sufficient duration to produce a glass-line cutbetween 20 and 60 % of the original specimen thickness.7. Procedure7.1 Mounting SpecimensMount specimens wi
32、th the zirconwafers and zircon cement and center them in the crucible asshown in Fig. 1, so the bottom of the specimen will be1364 in.(5 mm) from the bottom of the crucible.7.1.1 Place a1364-in. (5-mm) ground wafer within and onthe bottom of the crucible while the specimens are beingcemented in plac
33、e to obtain accurate spacing of the distancebetween the end of the specimen and the bottom of thecrucible.7.2 PreheatHeat the mounted specimens, without thecrucibles, in the preheat furnace to about 1830 F (1000 C).Simultaneously heat the crucibles charged with glass equiva-lent to 0.5 in.3(8 cm3) t
34、o the selected testing temperature in thetest furnace. Preheating minimizes specimen breakage from thethermal shock of immersion in hot glass.7.3 Beginning the Test:7.3.1 Transfer the test specimens from the preheat furnacewith suitable tongs and insert them into the crucible filled withhot glass.7.
35、3.2 The time of the test begins when the furnace recoversto the preset test temperature.7.3.3 At this time, make checks of the control thermocoupleby probing the furnace with a calibrated thermocouple insertedthrough the hole provided in the center of the top and innerfurnace plugs.7.4 Terminating t
36、he TestAt the conclusion of the test,remove the crucibles from the furnace one at a time andquickly remove the specimen from the glass before the glassbecomes too viscous.7.5 Remove the support wafer and excess cement and cutthe corroded specimens in half lengthwise (Fig. 2) using a thindiamond blad
37、e (Note 2). Care should be taken on squarespecimens so that the cut is made parallel to the measurementsthat were made before the test. Establish the glass line and aline one-half the distance from glass line to the base of thespecimen. Since the thickness of the saw blade can obviouslyinfluence the
38、 final test measurements, it is necessary that bladethickness be a constant at least within a specified tolerance.Therefore, the thickness of the diamond blade is arbitrarilyspecified at 0.056 6 0.0005 in. (1.42 6 0.013 mm), whichcoincides with the thickness of the most commonly used bladein small l
39、aboratory saws. Measure both halves of the specimenwith a measuring microscope, with the specimen immersed inor coated with a liquid whose refractive index is the same asthat of the test glass.NOTE 2It has been established that measurement of the specimensbefore splitting can result in large errors.
40、7.5.1 In the event of loose reaction interfaces on the testspecimens, the measurement of remaining specimens thicknessshall be made from the first material tightly adhering to thespecimen. This is most important if corrosion values halfwaydown the specimen are to be reproducible. Therefore, amateria
41、l might have a deep reaction interface, but as long as theinterface remains an integral part of the specimen it is notreported as being corroded.8. Calculation and Report8.1 The calculations are not intended to show the reductionin cross-sectional area of the specimen, but the depth ofcorrosion.8.1.
42、1 Glass-line corrosion is calculated as follows:Gc5 G 2 g11g2!#/2where:Gc= glass-line corrosion,G = width or diameter of specimen at glass line,before test, mm, andg1and g2= width or diameter of the two halves of the cutspecimen at the glass line, after test, measuredon cut face, mm.8.1.2 Half-down
43、corrosion is calculated as follows:Hc5 H 2 h11h2!#/2where:Hc= half-down corrosion,H = width or diameter of specimen halfway betweenglass line and bottom of sample, before test,mm, andh1and h2= width or diameter of the two halves of the cutspecimen at the half-down level, after test,measured on cut f
44、ace, mm.8.2 An additional optional measurement on the unalteredportion of the sample above the support wafer made before andafter the test will reveal any unusual shrinkage or growthphenomena that may have had some bearing on the result.8.3 The test report should include the calculated resultsalong
45、with the glass used (and whether batch or cullet), thetesting temperature, duration of the test, source, orientation andbulk density of each specimen, and a statement indicatingeither round or square cross section. The corrosion may beFIG. 2 View of Cut Specimen to Indicate Measurement After TestC62
46、1 09 (2018)3reported in inches (millimetres) or as a percentage of theoriginal sample width.8.4 The use of commercially available platinum crucibles iscommon. These crucibles are typically larger in size andvolume than those specified in 4.4 (Fig. 1). As a result, somelaboratories also use larger gl
47、ass volumes and/or specimens. Aruggedness test has shown that, with the standard specimensize and equal immersion depths, larger glass volumes result ingreater corrosion in a given time at the test temperature. Largerspecimens, or specimens with rectangular cross sections, willalso affect the measur
48、ed corrosion cut in an unpredictablemanner. Such tests do not normally affect the relative rankingof tested materials. If non-standard crucibles and/or specimensizes are used, the crucible type, glass volume, immersiondepth, and specimen dimensions must be reported.9. Precision and Bias9.1 Precision
49、:9.1.1 Glass-line cuts obtained in one laboratory (from 40 %ZrO2fusion cast AZS in soda-lime glass at 2730 F (1500 C)for three days) were used to determine critical differences at the90 % confidence level. These involved both single and multipleoperators and furnaces with the following results:Sample Size Critical Difference, % of Grand Average1 0.6042 0.4274 0.3028 0.22212 0.17416 0.1519.1.2 The user is cautioned that other test temperatures, testschedules, and specimens of different compositions may yieldgreater or less precision than given abov
