ASTM_C_839_-_82_2015.pdf

Designation:C83982(Reapproved 2015)Standard Test Method forCompressive Stress of Porcelain Enamels by Loaded-BeamMethod1This standard is issued under the fixed designation C839;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.INTRODUCTIONMany methods and tests have been used in the industry to determine the relative compressive stressof porcelain enamel ground coats and cover coats.Three methods have been most commonly used.They are loaded-beam,warp,and split-ring methods.In the loaded-beam method the measure of stressis the load required to bring a specimen back to a plane after it has been bowed by controlledapplication of the enamel under test to one side of the specimen.The degree of the deflection of aspecimen from a plane caused by controlled application of enamel to one side is the indicatingmeasure of stress in the warp test.The indicating measurement in the split-ring test is the forcerequired to just open a split ring after controlled application of test enamel to the outside surface ofa ring.1.Scope1.1 This test method covers the measurement of the com-pressive stresses(Note 1)developed by fired porcelain enamelsusing the loaded-beam method.NOTE1Although some may interpret the calculations that are used inthis test method as indicating compressive load,it is commonly referred toas compressive stress within the porcelain enamel industry.1.2 This test method is limited to the use of the loaded-beammethod.However,this method includes charts(Fig.1 and Fig.2)that provide for conversion of loaded-beam test results towarp and ring stress values.1.3 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.1.4 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.2.Referenced Documents2.1 ASTM Standards:2A424 Specification for Steel,Sheet,for Porcelain Enameling3.Terminology3.1Description of Term Specific to This Standard3.2 compressive stress or stressa term used to designatethe degree of compression that exists in a porcelain enamel onsteel after processing.4.Significance and Use4.1 All porcelain enamel coatings or glass coatings are bynecessity under some degree of compression at room tempera-ture.The desired degree of compression or stress depends uponthe type of ware and the end use of the item.Some method ofdetermining relative compressive stress of enamels is neces-sary to establish the suitability of an enamel for a proposedapplication.5.Apparatus5.1 Furnace,suitable for simultaneous firing of at least six1 by 12-in.(25 by 305-mm)specimens in vertical hangingposition.5.2 Firing Rack,suitable for furnace.1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 onMaterials for Porcelain Enamel and Ceramic-Metal Systems.This test method was developed at the National Bureau of Standards under thesponsorship of the Porcelain Enamel Institute,Inc.,and was published as PEITechnical Publication No.T-30(1973).Current edition approved May 1,2015.Published June 2015.Originallyapproved in 1976.Last previous edition approved in 2010 as C839 82(2010).DOI:10.1520/C0839-82R15.2For 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 Metric Equivalentsin.mmin.mm0.020.510.102.540.041.020.123.050.061.520.143.560.082.03FIG.1 Conversion Chart for Loaded-Beam Stress to Warp StressFIG.2 Conversion Chart for Loaded-Beam Stress to Ring StressC839 82(2015)2 5.3 Loaded-Beam Test Apparatus(see Fig.3 and Fig.4).5.4 Metric Weights,slotted,1 to 500 g.5.5 Laboratory Balance,accurate to 10 mg with necessaryweights(1 to 100 g).5.6 Brushing Template,2116by 101516in.(52 by 278 mm)(see Fig.5 for one example of achieving the desired end result).5.7 Stencil Brush.5.8 Fluorescent Light Fixture with diffusion panel andadjustable support.6.Test Specimens6.1 Six specimens are required for each enamel tested.Metric Equivalentsin.mmin.mm146.3513444.45389.53211652.3971611.113111693.681212.74101.65815.884516109.540.86622.0858219.08125.4101516277.8111431.7512304.811238.116406.41111642.86FIG.3 Loaded-Beam Test ApparatusC839 82(2015)3 6.2 Specimens 1 by 12 in.(