1、Designation: C 632 88 (Reapproved 2006)Standard Test Method forReboiling Tendency of Sheet Steel for Porcelain Enameling1This standard is issued under the fixed designation C 632; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 the determination of whether asheet steel for porcelain enameling will reboil under
3、a given setof worse case conditions.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 o
4、f 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:2C 286 Terminology Relating to Porcelain Enamel andCeramic-Metal Systems3. Terminology3.1 Definitions:3.
5、1.1 ground coata porcelain enamel applied directly tothe base metal to function as an intermediate layer between themetal and the cover coat (see Terminology C 286).3.1.2 reboilinggas evolution occurring and recurring dur-ing repeated firing of the ground coat, sometimes a defect (seeTerminology C 2
6、86).3.1.3 slip (slurry) a suspension of finely divided materialin liquid (see Terminology C 286).3.2 Description of a Term Specific to This Standard:3.2.1 quarter linesimaginary lines parallel to the directionof rolling positioned at a distance from the sheet mill edge,equal to one quarter of the sh
7、eet width.4. Summary of Test Method4.1 Both surfaces of sheet steel sample plates are subjectedto a cleaning treatment and are then porcelain enameled with asheet-steel, ground-coat type finish. Subsequent reheating atvarious times is performed to reveal whether or not the steelwill cause reboiling.
8、 The presence or absence of reboiling isdetermined by visual inspection.5. Significance and Use5.1 The results of this test indicate whether or not a sheetsteel will cause reboiling under one given set of enamelingconditions and enable the enamel processor to establish apossible source of imperfecti
9、ons in the finished coating.5.2 This test method is normally used to test samples fromlots, coils, or lifts of sheet steel which for some reason,production problems, defects evident on enameled parts, orproduction experience are suspected of causing defects inenameled ware which have the appearance
10、of reboiling. It isoften used to establish whether a problem exists with the baresteel or other factors such as the porcelain enamel, processingcontamination, and so forth.6. Apparatus6.1 This test can be conducted in any laboratory equippedfor general porcelain enameling. It does not require facili
11、tiesfor metal surface preparation.7. Reagents and Materials7.1 Steel Sheet, sufficient in size to provide samples asdescribed in 8.1 and 8.1.1.7.2 Porcelain-Enamel, Ground-Coat Slip, obtained fromproduction milling or prepared in laboratory facilities.7.3 Acetone or Isopropyl Alcohol, reagent grade.
12、8. Sampling8.1 Shear sufficient material from within the quarter lines ofa selected steel sheet sample from a sheet, coil, or lift to betested to provide a minimum of five panels, each at least 2 in.(50 mm) square but not greater than 4 by 6 in. (100 by 150mm).8.1.1 Choose panels from rust-free area
13、s that do not containthe mill identification stamp.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.Current edition approved April 1, 2
14、006. Published April 2006. Originallyapproved in 1969. Last previous edition approved in 2000 as C 632 88 (2000).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
15、 standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.1.2 Identify each panel by a method that enables identityto be monitored after repeated enamel firings. Steel diestamping is the mo
16、st commonly used technique.8.1.3 Material sheared from the sheet or coil may be withinthe range of sizes given in 8.1 or may be sheared intospecimens of these sizes after application and firing of theground-coat enamel.9. Procedure9.1 Swab the cut-to-size steel panels with cheeseclothsoaked with a s
17、olvent such as acetone or isopropyl alcohol.9.1.1 Scrub the panels by hand with a portion of theground-coat enamel. Remove the excess enamel from thepanels by flushing with water if the panels are to be coated byspraying. Dry the panels thoroughly.9.1.2 Avoid contact with soils of any nature and sto
18、re thepanels in a desiccator until they are ready for enameling.9.2 Apply 24 g/ft2(2.6 g/dm2) of enamel slip to each surface(Note 1). Either dipping or spraying may be used, dependingupon the method for which the slip is designed. Dry thesurfaces adequately. Fire them at a temperature and forsuffici
19、ent time to fuse the ground-coat enamel to the basemetal. This time and temperature should be that recommendedby the porcelain enamel manufacturers for optimum adherence(maturing temperature).NOTE 1Thin fired coatings of 212 to 3 mils (0.06 to 0.08 mm) aredesirable so that reboil bubbles can be read
20、ily observed.9.3 Store the fired panels at room temperature for at least 16h, but not more than 48 h, prior to conducting the reboiling test.9.4 For determining reboiling, reheat the first panel for atime which is the median firing time expected in part produc-tion or that recommended by the frit su
21、pplier for optimumenamel properties. If no reboiling occurs, increase firing timefor subsequent panels 5 s longer than the previous panel. Firingtime should be increased to the point that reboiling occurs orthe maximum time expected under worse case productionconditions is met. Of course, one may de
22、termine maximumtime for reboil by decreasing firing time sequentially. Aminimum of five panels or a time spread of 25 s is to be used.9.4.1 The reboiling furnace should be operated at about 506 10F (27 6 5C) below the maturing temperature of theground-coat enamel.9.4.2 At the end of the reheat time
23、allotted for each panel,remove the panel from the furnace and air cool it to roomtemperature.10. Inspection10.1 Visually examine the series of panels for evidence ofreboiling. The presence of reboiling on any of the steel panelsis considered a failure.10.2 Reboiling is characterized by the emergence
24、 of bubbleson the enamel surface. These bubbles rise and subside rapidlyand may persist as areas of blistering if arrested in a state ofdevelopment by removal of the sample from the furnace andcooling to room temperature. The typical appearance of reboil-ing is shown in Fig. 1.11. Precision and Bias
25、11.1 No statement is made about either the precision or biasof this test method for measuring reboiling of sheet steel forporcelain enameling since the result merely states whetherthere is conformance to the criteria for success specified in theprocedure.ASTM International takes no position respecti
26、ng 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 rights, and the riskof infringement of such rights, are entirely their own responsibility.This stand
27、ard 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 revision of this standard or for additional standardsand should be addressed to ASTM Internation
28、al 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 you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.T
29、his 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).FIG. 1 Reboiling of Porcelain Enamel on SteelC 632 88 (2006)2
