ASTM C839-1982(2005) Standard Test Method for Compressive Stress of Porcelain Enamels by Loaded-Beam Method《用负载梁法测定搪瓷的压缩应力标准试验方法》.pdf

1、Designation: C 839 82 (Reapproved 2005)Standard Test Method forCompressive Stress of Porcelain Enamels by Loaded-BeamMethod1This standard is issued under the fixed designation C 839; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,

2、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.INTRODUCTIONMany methods and tests have been used in the industry to determine the relative compressive stressof porc

3、elain 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 en

4、amel 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

5、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.NOTE 1Although some may interpret the calculations that are used

6、 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-

7、beam test results towarp and ring stress values.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 reg

8、ulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 424 Specification for Steel, Sheet, for Porcelain Enamel-ing3. Terminology3.1 Description of Term Specific to This Standard3.2 compressive stress or stressa term used to designatethe degree of compression that exists in a

9、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 metho

10、d 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

11、 for furnace.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,2116 by 101516 in. (52 by 278 mm)(see Fig. 5 for one example of achieving the desired end res

12、ult).5.7 Stencil Brush.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 Standa

13、rds under thesponsorship of the Porcelain Enamel Institute, Inc., and was published as PEITechnical Publication No. T-30 (1973).Current edition approved Sept. 15, 2005. Published September 2005. Originallyapproved in 1976. Last previous edition approved in 1999 as C 839 82 (1999).2For referenced AST

14、M 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho

15、cken, PA 19428-2959, United States.Metric Equivalentsin. mm in. mm0.02 0.51 0.10 2.540.04 1.02 0.12 3.050.06 1.52 0.14 3.560.08 2.03FIG. 1 Conversion Chart for Loaded-Beam Stress to Warp StressFIG. 2 Conversion Chart for Loaded-Beam Stress to Ring StressC 839 82 (2005)25.8 Fluorescent Light Fixture

16、with diffusion panel andadjustable support.6. Test Specimens6.1 Six specimens are required for each enamel tested.6.2 Specimens 1 by 12 in. (25 by 305 mm) shall be cut byshearing from flat sheets of 20-gage Commercial Quality TypeII enameling iron (see Specification A 424) with thickness0.036 6 0.00

17、2 in. (0.91 6 0.05 mm). The 12-in. dimensionshould be cut perpendicular to the direction of rolling of sheet.Care should be exercised to prevent formation of burrs duringshearing. Burrs that are formed may be removed by carefullyfiling edges or by lightly touching edges to a sanding belt.Since oppos

18、ing sides of the sheet may produce slightlydifferent results, one side of the sheet should be scribed in sucha manner that the scribe mark will appear about 1 in. from oneMetric Equivalentsin. mm in. mm14 6.35 134 44.4538 9.53 2116 52.39716 11.11 31116 93.6812 12.7 4 101.658 15.88 4516 109.540.866 2

19、2.0 858 219.081 25.4 101516 277.81114 31.75 12 304.8112 38.1 16 406.411116 42.86FIG. 3 Loaded-Beam Test ApparatusC 839 82 (2005)3end of the resulting strips after shearing. A14 -in. (6.35-mm)diameter hole should be punched in one end of the specimenfor hanging purposes during drying and firing. The

20、center ofthe hole should be on the center line716 in. (11 mm) from theend of the specimen. Specimens should be numbered foridentification during the testing procedure. They may bepermanently identified by metal stamping on the scribed sidewhile being supported on an anvil (see Fig. 6).7. Procedure7.

21、1 Application of Ground Coat to Test Strips:7.1.1 Subject the specimens to a pickle procedure normalfor ground coat application. Pickle in a suspended verticalposition to prevent distortion.7.1.2 Measure and record metal thickness of the test speci-mens.7.1.3 Apply a medium high-temperature ground c

22、oat (1520to 1540F (825 to 840C) by spraying. With scribed sides up,first spray the back sides of strips to give 1.5 g dry weight perstrip. Dry and cool. Reverse the strips and spray a like amounton the face side. Dry and cool. Use a relatively dry spray toavoid formation of beads on the edges of the

23、 strips (Note 2).7.1.4 Fire the strips in a vertical hanging position at theoptimum time and temperature for the ground coat. Thepreferred procedure is to fire multiples of six simultaneously.Cool in a suspended position, avoiding drafts or forced cooling.7.1.5 Weigh and record the weight of each st

24、rip to thenearest 0.01 g.7.1.6 Place each strip on the test apparatus with the scribedside down.7.1.7 Measure and record the ground coat residual load,which is the weight in grams required to cause the strip to justrest on the three knife edges of the fixture. Discard any stripshaving zero or negati

25、ve stress (reverse bow) or having positiveload of more than 50 g.FIG. 4 Loaded-Beam Test ApparatusNOTE 1See Fig. 3 for metric equivalents.FIG. 5 Brushing TemplateC 839 82 (2005)4NOTE 2More consistently uniform and usable specimens will result ifa spraying technique is developed whereby a few hundred

26、ths of a gramless enamel is applied to the back than to the face. This practice reducesthe possibility of developing a concavity in the strip as viewed from theface side.7.2 Application of Test Enamel:7.2.1 Apply test enamel to the face side of six ground-coated specimens by spraying. Apply the enam

27、el to yield a dryweight of 30 g/ft2(323 g/m2,or212 g per strip). Use arelatively dry spray to avoid formation of beads along edges.After drying and cooling, use a template to brush back 11116 in.(43 mm) from each end of strip, leaving 858 in. (179 mm) ofcover coat on the strip. Wipe the edges and ba

28、ck of strips witha felt pad and dust with a soft-bristled brush or wool duster.7.2.2 Fire panels, again in a vertical hanging position, atoptimum temperature and time for the test enamel as covercoat. Cool in a vertical position, avoiding forced cooling.Rapid cooling produces greater residual compre

29、ssive stresses.7.2.3 Weigh each strip to the nearest 0.01 g and record.7.3 Measurement of Load:7.3.1 Center each coated strip individually over the threeknife edges of the fixture with face side upward and punchedhole to left. Stops or blocks may be of aid in centering thestrips on knife edges.7.3.2

30、 Centrally load the strip with slotted weights over thecenter knife edge until the strip just touches the central knifeedge. A strong diffuse light source behind the test fixturefacilitates observation of the end point.7.3.3 Measure and record the uncorrected compressive loadof each of the cover-coa

31、ted test strips. The load, in grams,required to cause the strip to just touch the central knife edgeis the uncorrected compressive load.7.3.4 Corrected load is uncorrected compressive load minusresidual ground coat load (see 7.1.7).8. Calculation8.1 Calculate the corrected load, L, by subtracting th

32、eresidual ground coat load from the uncorrected compressiveload.8.2 Calculate the compressive stress, Sc, for each testspecimen as follows:Sc5 L 31.80W30.036Ti(1)orSc5 L 31.80W30.914Tm(2)where:Sc= compressive stress of the specimen, gf/in. (or gf/mm),L = corrected load for cover-coated strip, gf,1.8

33、0 = calculated fired weight of enamel on 858 -in. (219-mm) length of strip equivalent to 30 g/ft2(323 g/m2)(dry),W = actual fired weight of test enamel on strip to thenearest 0.01 g,Ti= actual metal thickness, in., andTm= actual metal thickness, mm.8.3 Determine the average of the six compressive st

34、ressvalues and report as the compressive stress of the testedenamel.8.4 If the end use of the test data requires a statisticalcomparison of samples, the standard deviation and statisticalerror of the six specimens comprising one lot may be calcu-lated by the root-mean-square method. The compressive

35、stressof the enamel may then be reported as the numerical average ofthe test values together with their statistical error (see Appen-dix X1 for an example of data treatment).9. Conversion of Test Results9.1 Conversion charts may be used to make approximateconversions of results of the loaded-beam te

36、st method in termsof other test methods (or vice versa if necessary). Fig. 1provides for conversion of loaded-beam test results to warpvalues. Fig. 2 may be used to convert loaded-beam results toring-stress values.10. Precision and Accuracy10.1 The precision and accuracy of this test method arebeing

37、 developed.NOTE 1Wipe all bisque cover coat enamel from sides, ends, and back of ground coated test sample before firing cover coat.NOTE 2See Fig. 3 for metric equivalents.FIG. 6 Detail of Test SpecimenC 839 82 (2005)5APPENDIX(Nonmandatory Information)X1. EXAMPLE OF DATA TREATMENTX1.1 Table X1.1 pro

38、vides sample values for six specimensto illustrate the application of formulas necessary for themeasurement of compressive stress.X1.2 The following compressive stress values for indi-vidual specimens are calculated by applying the formula:Sc= L 3 (1.80/W) 3 (0.036/Ti) (see Section 8):Specimen No. C

39、ompressive Stress (Sc)1 5252 5243 4964 5105 4886 481_Mean 504X1.3 Calculate the statistical error of the determination asfollows:e 5 1.05 s (X1.1)where:e = statistical error of the mean value for the samples at the95 % confidence level, ands = standard deviation of the six individual values from the

40、average of all six.NOTE X1.1The factor 1.05 applies only when the number of speci-mens is six and the confidence level is 95 %. For larger or smallernumbers of specimens, use the “a” values for that number shown in Table2, Part 2, of STP 15 D.3X1.4 Calculate the standard deviation, s, as follows:s 5

41、(Sc2(Sc!2nn 2 1(X1.2)where:n = number of specimens,(Sc2= sum of the squares of the stress values of the sixindividual specimens, and(Sc)2= square of the sum of the six stress values.X1.5 The following calculations are involved in applyingEq X1.2:Specimen ScSc21 525 275 6252 524 274 5763 496 246 0164

42、 510 260 1005 488 238 1446 481 231 361_ _(Sc= 3 024 1 525 822 = (Sc2Mean Sc= 504s 51 525 822 29 144 57665(X1.3)51 525 822 2 1 524 096551 72655 =345.2s 5 18.6X1.6 Applying Eq X1.1, e = 1.05 3 18.6 = 19.5.X1.7 Compressive stress value for example Enamel A thusbecomes 504 6 19.5.3Special Technical Publ

43、ication 15 D, available from American Society forTesting and Materials, 1916 Race St., Philadelphia, PA 19103.TABLE X1.1 Sample ValuesEnamel Specimen No.Application (g),WResidualLoadFinal Load Corrected Load, L Metal Thickness, TiA 1 1.76 1 486 485 0.0342 1.71 12 482 4703 1.80 7 475 4684 1.82 30 517

44、 4875 1.77 5 458 4536 1.75 5 447 442C 839 82 (2005)6ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rig

45、hts, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for

46、 revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing

47、 you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C 839 82 (2005)7