ASTM_C_768_-_99.pdf

Designation:C 768 99Standard Practice forDrip Slag Testing Refractory Materials at High Temperature1This standard is issued under the fixed designation C 768;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 practice describes a procedure for comparing thebehavior of refractories to the action of molten slag drippedonto test specimens within a heated furnace.No numericresults are obtained from this practice.Numeric evaluation oftest results is the responsibility of the of the test operator.1.2 The values stated in inch-pound units are to be regardedas the standard.The values given in parentheses are forinformation only.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.Significance and Use2.1 This practice outlines a procedure which,when appro-priate evaluation methods are added,can be useful in thedevelopment of new products or in the selection of products tobe used in contact with a particular slag composition.2.2 Since the entire test specimen is at the test temperature,penetration of the slag into the sample is promoted and mayexceed that observed when the temperature gradient,typical ofmost refactory applications,is present.The test slag is con-stantly renewed so that a high rate of corrosion is maintained.2.3 Oxidation of carbon-containing materials may occur asthe entire sample is not covered by slag.A reference refractoryspecimen should be used for comparison.3.Apparatus3.1 The apparatus shall consist of a suitable electricallyheated furnace which is capable of attaining and holdingtemperatures up to 2950F(1620C).Afurnace chamber 15 by20 by 12-in.(381 by 510 by 305-mm)deep is suggested.3.1.1 As an alternative,a furnace of suitable size using gasor oil as a fuel may also be used.Care should be exercised indesigning the burners and their placement to avoid excessiveturbulence and velocity of gases across the test specimens.3.2 The furnace should be equipped with water-cooled feedtubes of approximately58-in.(16-mm)inside diameter posi-tioned so the melting slag will be directed onto the inclinedfaces of the test specimens.The tubes should be located aminimum of 512in.(140 mm)apart,terminate about 1 in.(25mm)inside the furnace wall,and be mounted at an angle ofapproximately 10 with the horizontal(low ends inside thefurnace)(Fig.1).3.3 The bottom of the furnace should be constructed toprovide a base for the specimen supports and a sand pit toreceive the spent slag.3.4 A device,with a variable-speed drive,should be pro-vided to feed slag in the form of preformed rods at a constantrate.The rate of feed for each slag composition should beestablished so that melting takes place beyond the end of themullite tubes.3.5 Above a furnace temperature of 1470F(800C),thefurnace atmosphere within the test furnace shall contain aminimum of 0.5%oxygen with 0%combustibles.NOTE1If reducing conditions within electrically heated furnaces aredesired,coke breeze can be used in the furnace bottom instead of sand.3.6 It is recommended that the furnace temperature becontrolled with a platinum-rhodium/platinum thermocoupleconnected to a program controller-recorder.The thermocoupleshould be located as near as possible to the specimens butpositioned to avoid being contaminated by slag.If desired,aradiation pyrometer sighted on an unslagged surface of aspecimen may be used.4.Test Specimens and Support4.1 Prepare two specimens for each test run.4.2 The test specimen should have a thickness of 212or 3 in.(64 or 76 mm)and an original 412by 412-in.(114 by 114-mm)surface that will receive the molten slag.The thickness of oneend of the specimen shall be cut at a 30 angle to permitmounting it near the furnace wall(Fig.2).If the tester desiresto test a cut surface of a specimen,this fact should be reportedunder Section 8.4.3 Asupport brick,compatible with the test specimen,shallbe provided for each specimen.The top of the support shallalso be cut on an angle of 30.The side of the support oppositethe wall shall be provided with a V-shaped notch about 3 in.1This practice is under the jurisdiction ofASTM Committee C-8 on Refractoriesand is the direct responsibility of Subcommittee C08.04 on Chemical Behaviors.Current edition approved Oct.10,1999.Published November 1999.Originallypublished as C 768 73.Last previous edition C 768 85(1995).1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.(76 mm)wide and 1 in.(25 mm)deep cut into its length tominimize slag attack of the support(Fig.3).5.Slag Rods5.1 The