ASTM_C_621_-_09_2014.pdf

Designation:C62109(Reapproved 2014)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,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 molten 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 address all of thesafety 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: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 mostsevere 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 tempera-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 stones or otherglass defects.3.2 Because this test method 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 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 receive 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 61.8F(61C).Fig.A1.1 shows aschematic drawing of a furnace that is satisfactory for this test.NOTE1It has 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 61.8F(61C).4.3 Thermocouple,for use as the temperature-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.Method E220 specifies calibrationprocedures for thermocouples.If drift becomes severe,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.1This test method is under the jurisdiction of ASTM Committee C08 onRefractories and is the direct responsibility of Subcommittee C08.10 on Refractoriesfor Glass.Current edition approved Sept.1,2014.Published November 2014.Originallyapproved in 1968.Last previous edition approved in 2009 as C621 09.DOI:10.1520/C0621-09R14.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.8 Tongs,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.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-cast and pressedrefractory products,take care to avoid crac