ASTM_C_1276_-_94_2005.pdf

Designation:C 1276 94(Reapproved 2005)Standard Test Method forMeasuring the Viscosity of Mold Powders Above TheirMelting Point Using a Rotational Viscometer1This standard is issued under the fixed designation C 1276;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers measurement of the viscosity ofmold powders above their melting point through the use of aplatinum spindle immersed in a platinum crucible containingthe molten mold flux.Developed by differential angularvelocity between the crucible and spindle,spindle torque ismeasured and used to calculate the viscosity.Data are gener-ally taken as a function of temperature to describe theviscosity-temperature relationship for the molten mold flux.1.2 This test method uses a high-temperature furnace andmeasurements on molten material.Personal protection equip-ment to wear include high-temperature resistant insulatinggloves,coveralls,and a full-face shield.1.3 The values stated in inch-pound units are to be regardedas the standard.The values given in parentheses are forinformation only.1.4 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.A specific warningstatement is given in Note 1.2.Referenced Documents2.1 ASTM Standards:2C 965 Practice for Measuring of Viscosity of Glass Abovethe Softening PointC 1095 Practice for Calculating Precision Data on Refrac-tories(C08)from Interlaboratory Test Results3E 220 Test Method for Calibration of Thermocouples byComparison TechniquesE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Significance and Use3.1 The viscosity of a molten mold flux is a very importantproperty for the correct functioning of a mold powder.Thisprocedure is designed for producers and users of mold powdersto develop the viscosity-temperature relationships of the mol-ten mold flux for quality control or specification purposes,orboth.Practice C 965 was developed for glasses that aresignificantly higher in viscosity than mold powders.Also,sample preparation is very different for the glass productscovered.NOTE1Warning:Use caution when discharging molten sample intowater since this can cause an explosion.4.Apparatus4.1 Electrically Heated Furnace,equipped with a tempera-ture controller,temperature measuring equipment,a spindle,acrucible,a device to rotate the spindle,and equipment tomeasure the torque or viscosity.4.1.1 Any electrically heated furnace capable of providing auniform and stable temperature in the testing zone of thefurnace can be used.The furnace must be capable of maintain-ing a temperature 180F(82C)above the maximum testtemperature.The atmosphere in the furnace should be air oroxidizing.4.2 Thermocouple,calibrated in accordance with TestMethod E 220.It is preferred that the thermocouple be im-mersed in the molten mold flux,in which case only the baremetal of the thermocouple should be immersed,since immer-sion of the thermocouple sheath may result in a reactionbetween the sheath and the molten flux.Alternatively,thethermocouple can be placed outside the crucible containing themolten mold flux,providing that the temperature differencebetween the flux and the position where the thermocouple isplaced is no more than 9F(5C).4.3 Spindle and Crucible,platinum or a platinum alloy.4Thespindle is attached to the rotating device using platinumextension wires inside the furnace and other suitable wiresoutside the furnace,for example,stainless steel.4.3.1 The dimensions of the crucible and spindle shall besuch that,when the crucible is filled with molten mold flux,the1This 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 March 1,2005.Published March 2005.Originallyapproved in 1994.Last previous edition approved in 1999 as C 1276-94(1999).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.3Withdrawn.4An alloy such as zirconia grain-stabilized(ZGS)platinum has been usedsuccessfully.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.Copyright by ASTM Intl(all rights reserved);Thu Apr 16 08:44:17 EDT 2009Downloaded/printed byLaurentian University pursuant to License Agreement.No further reproductions authorized.body of the spindle can be immerse