1、Designation: C 621 09Standard Test Method forIsothermal Corrosion Resistance of Refractories to MoltenGlass1This standard is issued under the fixed designation C 621; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 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 molten glassunder s
3、tatic, 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 address all of the
4、safety concerns, if any, associated with its use. It is theresponsibility of 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 220 Test Method for Calibr
5、ation 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 mostsevere static corrosion environment possible at the spe
6、cifiedtest 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 tempera-ture limitations of a particular material. Melt-l
7、ine 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 stones or otherglass defects.3.2 Because this test method
8、is both isothermal and staticand 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 thickness, artificial cooling or insu-lation upon the refrac
9、tory 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 receive four crucible assemblies of the type used in the t
10、est(Fig. 1) is required. The zone of the furnace in which thecrucibles will rest should possess a maximum transversethermal gradient of 61.8F (61C). Fig. A1.1 shows aschematic drawing of a furnace that is satisfactory for this test.NOTE 1It has been demonstrated that gas-fired furnaces show greaterv
11、ariability 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 61.8F (61C).4.3 Thermocouple, for use as the temperature-measuringdevice. The type of thermocouple chosen wi
12、ll 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. Method E 220 specifies calibrationprocedures for thermocouples. If drift becomes seve
13、re, replacethe thermocouple. Position the thermocouple hot junction inthe furnace to coincide with the level of the glass line of the testsamples.4.4 Platinum Crucibles (Fig. 1).4.5 Sintered Zircon, or other refractory wafers (Annex A2).4.6 Zircon Cement (Annex A3).4.7 Measuring Microscope.4.8 Tongs
14、, suitable for handling samples in the furnace (Fig.A1.6).4.9 Furnace, for preheating test specimens to about 1832F(1000C) (Annex A1).4.10 Diamond Saw, and diamond hone, or diamond-coredrill.1This test method is under the jurisdiction of ASTM Committee C08 onRefractories and is the direct responsibi
15、lity of Subcommittee C08.10 on Refractoriesfor Glass.Current edition approved March 1, 2009. Published March 2009. Originallyapproved in 1968. Last previous edition approved in 2001 as C 621 84 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servi
16、ce 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 Box C700, West Conshohocken, PA 19428-2959, United States.5. Test Specimens5.1 Sample SelectionA sample
17、 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-cast and pressedrefractory products, take care to avoid cracks, checks, obviouscontaminants, etc. In the testing
18、 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 specified. For flat-cast blocks, takethe specimen on the surface opposite the font scar (andperpendicular to this su
19、rface) 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 specimen at least 3 in. from any corner ofthe casting. Such specimens avoid edge and corner crystalli-zation effe
20、cts 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) long or cylinders 0.5 in. (13 mm) indiameter by 2.0 in. long. In either case the specified dimensionsshall b
21、e controlled within 0.002 in. (0.05 mm) along the entirelength of the specimens.5.2.2 Prepare cylindrical specimens with a diamond-corebit. Specimens should be perfectly smooth (free of smalloffsets, etc.) and free of metal marks from the drill along theirentire length. Grind square specimens to siz
22、e, 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 grinding or drilling, dry the specimens to con-stant weight at 230F (110C) prior to corrosion testing.5.3 Pretest S
23、pecimen 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 displacement.5.3.2 Measure the specimen to the nearest 0.001 in. (0.03mm) at two points, the anticipated glass line, and at a
24、levelhalfway between the glass line and the bottom of the specimen.With square specimens it is important that the orientation ofthese measurements be marked above the glass line so thatcorresponding measurements can be made after the test.5.3.3 Make an inspection of the specimen prior to the test,no
25、ting 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 helpful to include a control (orstandard) in each series of specimens. Ideally the controlspecimens are taken from a s
26、ingle refractory block or shaperetained semi-permanently for that purpose. By using a controlspecimen the variability between tests can be continuouslyscrutinized, and the control specimen can serve as a compari-son standard for the other specimen in the same test.5.4.2 Either round or square test s
27、pecimens 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 test or series of testsshould be consistent. When applicable, cast or pressed surfacesshould comprise the sample bot
28、tom.6. Test Temperature and Duration6.1 Test temperatures should simulate those in the intendedservice.6.2 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 Moun
29、ting SpecimensMount specimens with the zir-con wafers and zircon cement and center them in the crucibleas shown in Fig. 1, so the bottom of the specimen will be1364in. (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 s
30、pecimens are beingcemented in place to obtain accurate spacing of the distancebetween the end of the specimen and the bottom of thecrucible.SI Equivalentsin. mm0.030 0.761364 512 133364 131732 1312114 32.8NOTE 1All undesignated dimensions are in inches.FIG. 1 Crucible AssemblageC6210927.2 PreheatHea
31、t the mounted specimens, without thecrucibles, in the preheat furnace to about 1830F (1000C).Simultaneously heat the crucibles charged with glass equiva-lent to 0.5 in.3(8 cm3) to the selected testing temperature in thetest furnace. Preheating minimizes specimen breakage from thethermal shock of imm
32、ersion 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.7.3.2 The time of the test begins when the furnace recoversto the preset test temperature.7.3.3 At this time make checks of
33、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 the TestAt the conclusion of the test,remove the crucibles from the furnace one at a time andquickly remove the specimen fro
34、m 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 blade (Note 2). Care should be taken on squarespecimens so that the cut is made parallel to the measurementsthat were made bef
35、ore 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 final test measurements, it is necessary that bladethickness be a constant at least within a specified tolerance.Therefor
36、e, 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 laboratory saws. Measure both halves of the specimenwith a measuring microscope, with the specimen immersed inor coated wit
37、h 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.7.5.1 In the event of loose reaction interfaces on the testspecimens, the measurement of remaining specimens thicknessshal
38、l 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, amaterial might have a deep reaction interface, but as long as theinterface remains an integral part of the specimen it is notrepo
39、rted 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.8.1.1 Glass line corrosion is calculated as follows:Gc5 G 2 g11 g2!# /2where:Gc= glass line corrosion,G = width or diameter of
40、 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, mea-sured on cut face mm.8.1.2 Half-down corrosion is calculated as follows:Hc5 H 2 h11 h2!# /2where:Hc= half-down corrosion,H = width or diameter of specimen h
41、alf way be-tween glass line and bottom of sample, beforetest, mm, andh1and h2= width or diameter of the two halves of the cutspecimen at the half-down level, after test,measured on cut face mm.8.2 An additional optional measurement on the unalteredportion of the sample above the support wafer made b
42、efore 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 with the glass used (and whether batch or cullet), thetesting temperature, duration of the test, source, orientatio
43、n andbulk density of each specimen, and a statement indicatingeither round or square cross-section. The corrosion may bereported 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 lar
44、ger in size andvolume than those specified in 4.4 (Fig. 1). As a result, somelaboratories also use larger glass 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
45、 test temperature. Largerspecimens, or specimens with rectangular cross sections, willalso affect the measured 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 typ
46、e, glass volume, immersiondepth, and specimen dimensions must be reported.FIG. 2 View of Cut Specimen to Indicate Measurement After TestC6210939. Precision and Bias9.1 Precision:9.1.1 Glass-line cuts obtained in one laboratory (from 40 %ZrO2fusion cast AZS in soda-lime glass at 2730F (1500C)for thre
47、e 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 oth
48、er test temperatures, testschedules, and specimens of different compositions may yieldgreater or less precision than given above.9.2 Bias:9.2.1 No justifiable statement on bias is possible since thetrue value of a glass-line cut cannot be established.10. Keywords10.1 corrosion; crucible; finger; gla
49、ss; glass-line cut; iso-thermal; metal-line cut; refractory; staticANNEXES(Mandatory Information)A1. TEST FURNACEA1.1 Fig. A1.1 shows a schematic drawing of a furnacesuitable for this test. This furnace is a platinum wound, verticaltube-type, resistance furnace. Drawings of refractory partsother than cores and insulation are given in Figs. A1.2-A1.5.(See TableA1.1 for SI equivalents.). The inner winding core is4 in. (114.9 mm) outside diameter by 15 in. (381 mm) long.The core is grooved for 39 turns of 5060 mil (1.27 to1.52-mm) platinum wire and
