ASTM_B_926_-_09.pdf

Designation:B92609Standard Method forPinhole Determination in Aluminum and Aluminum AlloyPlain Foil by Means of a Light Table1This standard is issued under the fixed designation B926;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.1.Scope*1.1 This method covers the identification and counting ofpinholes,including roll holes,in plain foil using a light table,and inspector with normal 20/20 or corrected 20/20 vision,anda darkened inspection area.1.2 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.1.3 This method may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B881 Terminology Relating to Aluminum-and Magnesium-Alloy Products3.Terminology3.1 DefinitionsRefer to Terminology B881 for definitionsof product terms used in this specification.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrationdetermination of the values of the sig-nificant parameter(s)by comparison with a value(s)indicatedby a reference instrument or by a set of reference standards.3.2.2 pinholeany small void in the foil that will permit thetransmission of light.Classification criteria for pinholes limitsthese voids to those that are too small in size to be clearlyvisible to the unaided eye(1 visual inspection).3.2.3 roll holethe producers classification of a pinholecaused by an imperfection on any type of roll the foil contactsduring production.The distinguishing feature of a roll hole(s)is the repeatability of this void on a regular interval.Thisinterval is directly proportional to the circumference of the rollcausing the void(this interval will also increase proportionallyto subsequent thickness reductions).4.Summary of Method4.1 This method contains guidelines for determining thenumber of pinholes present in the area with the highest pinholeconcentration in a sample of foil.4.2 A full width sample is placed on the light table,and thepinholes are counted in a sample of known area(five or moresquare feet).5.Significance and Use5.1 Foil in thickness of about 0.002 in.(0.05 mm)andheavier is virtually free of pinholes.With decrease in thickness,the number of pinholes may increase.5.2 This method is provided to develop and maintainuniformity in the methods of evaluating pinholes in aluminumfoil.The pinhole data provides assessments of process capa-bility and quality levels of the foil as well.6.Apparatus6.1 A light table which provides illumination between 1500and 1800 lux light intensity with a smooth and uniforminspection surface on which the foil is examined.The lighttable must be in a black booth or in an area where the lights areturned off to provide darkness of less than 50 lux.The lighttable should be able to accommodate the widest width of foilto be examined.The usual construction of the light tableconsists of a shallow box painted white on the inside with rowsof fluorescent lights and with a frosted or milk glass coveringto provide uniform light diffusion.6.2 One or more counting frames(grids)that have openingsof one square foot(one square decimeter for SI counts).6.3 Sheet of foil to be tested.6.4 Calibration of the necessary light intensities can beaccomplished using a standard light meter.1This test method is under the jurisdiction of ASTM Committee B07 on LightMetals and Alloys and is the direct responsibility of Subcommittee B07.03 onAluminum Alloy Wrought Products.Current edition approved Dec.1,2009.Published January 2010.Originallyapproved in 2003.Last previous edition approved in 2003 as B926 03.DOI:10.1520/B0926-09.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.Procedure7.1 Test a full-width representative sample with a minimumof five square feet.Examine the full width of the sheet.The foilgage should be within tolerance.7.2 Place the foil sample on the light table carefully to avoidwrinkling/creasing with the long direction of the bulbs perpen-dicular to the rolling direction of the foil and turn the lights onin the light table and off in t