1、Designation: C 326 09Standard Test Method forDrying and Firing Shrinkages of Ceramic Whiteware Clays1This standard is issued under the fixed designation C 326; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of linearshrinkage of ceramic whiteware clays, both unfired and fired.1.2 The values s
3、tated 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.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its
4、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 The purpose of this test is to obtain values of shrinkageafter drying and firing of clays
5、 or bodies or both, under variousprocessing conditions to enable designers to determine theproper size of mold or die so as to produce a predeterminedsize of fired ware.3. Test Specimens3.1 Test specimens shall be round bars approximately 0.75in. (19 mm) in diameter by 5 in. (127 mm) in length.3.2 T
6、est specimens may be prepared either by casting orplastic forming, as circumstances require. At least ten speci-mens shall be prepared. For cast specimens the molds may beeither one-piece, or two- or more-part molds; in either instancesufficient space shall be provided to allow solid casting without
7、piping. Where plastic-forming is employed, the clay-watermass shall be brought to a consistency that permits the makingof specimens rigid enough to allow careful handling withoutdistortion immediately after the test specimen is made. Plastic-formed test specimens shall be made either by extrusion or
8、 bypressing in a suitable metal mold. Where a vacuum pugmill isused, a vacuum of not less than 25 in. (635 mm) Hg shall bemaintained during the forming operation. Where no vacuumattachment is used, the plastic clay shall be thoroughly hand-wedged to eliminate entrapped air as a preliminary to formin
9、gtest pieces.3.3 The test specimens, cast or plastic-formed, shall besuitably identified and marked with shrinkage reference lines 4in. (102 mm) apart on the long axis of the specimen. Theshrinkage reference lines may conveniently be made with agage with knife edges at zero and 4 in. (102 mm) and ma
10、rkingmust be done as soon as the bars can be handled withoutdistortion.3.4 The marked specimens shall then be placed on a lightlyoiled pallet with semi-circular grooves 0.40 in. (10.2 mm) indiameter and allowed to dry at 68 to 100F (20 to 40C) for24h. The purpose of the semi-circular (half round) gr
11、ooves is tomaintain straightness of the bars during drying. During thispreliminary drying period, the bars shall be turned 90 severaltimes at 2-h intervals to eliminate possible warping in thevertical direction. After the initial drying period, the specimensshall be placed in a drying oven at 200 to
12、 230F (100 to 110C)and further dried for 24 h.3.5 The drying shrinkage of the test specimens should bedetermined in accordance with Sections 4 and 5. The speci-mens can now be fired according to a suitable firing scheduleto the desired temperature and the procedures of Sections 4 and5 applied to det
13、ermine the total shrinkage.3.6 The test bars must be clearly identified as to whetherthey were cast or extruded, and shrinkage data likewiseidentified because of slight differences in shrinkage betweencast and extruded bars.4. Shrinkage Measurement4.1 Measure the distance between shrinkage reference
14、marks on dried or fired specimens to the closest 0.004 in. (0.1mm) with calipers of suitable accuracy. Record the average ofat least ten measurements (one measurement on each of thegroup of ten or more specimens).5. Calculation5.1 Calculate the linear drying shrinkage as a percentage ofplastic lengt
15、h, as follows:Sd5Lp2 LdLp3 100 (1)where:Sd= linear drying shrinkage, %,Lp= plastic length of test specimen, andLd= dry length of test specimen.1This test method is under the jurisdiction ofASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC2
16、1.04 on Raw Materials.Current edition approved Jan. 1, 2009. Published January 2009. Originallyapproved in 1953. Last previous edition approved in 2003 as C 326 03.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
17、t Conshohocken, PA 19428-2959, United States.5.2 Calculate the total linear shrinkage after drying andfiring of clay shrinkage specimens as a percentage of plasticlength, as follows:St5Lp2 LfLp3 100 (2)where:St= total linear shrinkage after drying and firing, %,Lp= plastic length of test specimen, a
18、ndLf= fired length of test specimen.5.3 When desired, volume shrinkage may be calculatedfrom linear shrinkage, as follows:Volume shrinkage, % 5 1 2 1 2 S/100!3# 100 (3)where:S = linear shrinkage, %.5.4 The shrinkage factor is used to convert fired sizes toplastic sizes or mold sizes. Calculate as fo
19、llows:Shrinkage factor 5 Lp/Lf(4)where:Lp= plastic length of test specimen, andLf= fired length of test specimen.6. Precision and Bias6.1 The direction of flow in forming influences the orienta-tion of the clay particles and the shrinkage. The shrinkagevalue should be related to the method of formin
20、g as well as thedimension of the ware.6.2 When the original reference points are 100 mm apart,the precision of the shrinkage measurement is 6 0.1 %.6.3 Measurements of drying shrinkage on one dimension ofspecimens all formed by the same method should yield astandard deviation of 0.1 % or less.6.4 Me
21、asurement of total linear shrinkage after drying andfiring on one dimension of specimens should yield a standarddeviation of 0.25 % or less.7. Keywords7.1 clay; drying shrinkage; firing shrinkageSUMMARY OF CHANGESCommittee C21 has identified the location of selected changes to this standard since th
22、e last issue (C 32603)that may impact the use of this standard.(1) Addition of 1.2 describing the use of units in this testmethod, with renumbering of the subsequent subsection of theScope.ASTM International takes no position respecting the validity of any patent rights asserted in connection with a
23、ny 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 standard is subject to revision at any time by the responsible technica
24、l 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 International Headquarters. Your comments will receive careful consideration
25、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.This standard is copyrighted by ASTM International, 100 Barr Harbor
26、 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).C326092
