1、Designation: D4145 10Standard Test Method forCoating Flexibility of Prepainted Sheet1This standard is issued under the fixed designation D4145; 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
2、parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for determiningthe flexibility and adhesion of organic coatings (paints) onmetallic substrates that are de
3、formed by bending when thesheet is fabricated into building panels or other products.1.2 The metal substrate must be capable of passing this testwithout fracturing and with no excessive grain development.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in par
4、entheses 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-pri
5、ate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 T-bend, na description of the severity of a bend interms of the gauge or thickness (t) of the sheet to which thecoating has b
6、een applied; as used in this test method, theT-bend rating is the minimum number of thicknesses of metalaround which the coated sheet is bent (Fig. 1), or if bent arounda die, the number of thicknesses of metal equivalent to thediameter of the die to achieve no fracture or removal of thecoating.3. S
7、ummary of Test Method3.1 Prepainted panels are bent 180 around progressivelymore thicknesses of metal or larger diameter dies, the end pointbeing when failures no longer occur. The panels may beexamined with or without low magnification (5 to 103) aftereach bend in order to determine if the coating
8、fractured(cracked). If loss of adhesion or pickoff is to be determined,this examination shall occur after performing a tape pull-offtest.4. Significance and Use4.1 Organic coatings on precoated sheet are subjected tostresses when fabricated into products by roll forming, brakebending, or other defor
9、mation processes. These stresses canexceed the flexibility or adhesive strength of the coating,resulting in fracture of the coating which exposes the substrate,or in the loss of adhesion of the coating to the substrate. Thistest is a means of evaluating the ability of a coating system towithstand th
10、e stresses of fabrication.4.2 The bend direction, whether the axis of bend is trans-verse to or along the rolling direction of the metal, and the1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibilit
11、y ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved June 1, 2010. Published August 2010. Originallyapproved in 1983. Last previous edition approved in 2002 as D 4145 - 83 (2002).DOI: 10.1520/D4145-10.NOTE 1The above bends are expanded for clarity. They are actuallyflat against them
12、selves in the test.FIG. 1 T-Bend Test in Which the Coated Specimen is BentAround Itself1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.temperature of the specimen when it is bent can affect theresults of this test and should be agree
13、d upon between thesupplier and the user.5. Apparatus5.1 A means of holding one end of the specimen rigidlywhile making the bend is needed. Damage to the coating whilemaking the bend must be avoided. Various bending tools suchas a vise with smooth jaws or with smooth inserts, a bendforming tool (Fig.
14、 2), a brake press (Fig. 3) or a combination oftools have been found to be satisfactory.5.2 If the metal is not bent around itself as in Fig. 1, a seriesof bending dies with smoothly rounded ends may be used asguides around which the specimen is bent (Fig. 4).5.3 Bend Forming Tool.5.3.1 A manual or
15、automated operation forming tool ca-pable of facilitating the T-bending of a sample may be used.Anarbor press with an appropriate fixed V-shaped die and move-able wedge has been found to be satisfactory for this purpose.5.4 Magnifier.5.4.1 A magnifier capable of 5 to 103 magnification forexamining t
16、he specimen for coating fracture and pickoff aftertesting. A stereomicroscope has been found useful for thispurpose.5.5 Clear Adhesive Tape.6. Procedure6.1 Bending the Coated Specimen Around Itself:6.1.1 The coated specimen shall be at least 2 in. (50 mm)across the bend direction, by a length suffic
17、ient to make therequired number of bends. A 2 by 6-in. (50 by 150-mm) size isconvenient. The specimen shall be held at 75 6 10F (24 65.5C) temperature, or as agreed upon between purchaser andseller. The bend direction will be longitudinal or in the samedirection with respect to the rolling or flow d
18、irection of thesheet, or as agreed upon between purchaser and seller.NOTE 1A triangle-shaped specimen (Fig. 5) has been found conve-nient for making T-bend tests. This shape leaves a portion of each bendexposed for later examination and for a permanent record.NOTE 2A longitudinal bend is in the same
19、 direction with respect toand along the rolling or flow direction. A transverse bend is perpendicularto and across the rolling or flow direction.6.1.2 Secure between 0.25 and 0.75 in. (6 and 20 mm) ofone end of the specimen in a vise or holding jig as shown inFig. 1. Bend the free end of the specime
20、n 90 in a smooth anduniform manner so that the coating to be examined is on theoutside of the specimen after bending.6.1.3 Continue to bend the specimen until the bent end canbe inserted in the jaws of the vise. Tighten the vise to completethe 180 bend, which is called an OT bend. Take care to tight
21、enthe vise sufficiently so that the apex of the bend is as flat as canbe reasonably achieved.FIG. 2 Bend Forming Tool for Performing T-BendsFIG. 3 Brake PressFIG. 4 T-Bend Test Using a Die Around Which the Specimen isBentNOTE 1The above bends are expanded for clarity. They are actuallyflat against t
22、hemselves in the test.FIG. 5 Triangular Specimen for T-Bend TestD4145 1026.1.4 Examine the bend for cracks in the coating, visually orwith low power magnification, or both.6.1.5 Apply pressure-sensitive tape along the bend. Rub thetape flat; then, holding the specimen firmly, remove the tapewith a r
23、apid movement at an angle of approximately 90, orperpendicular to the bend surface. Examine the tape for coatingremoved from the surface of the specimen (that is, pickoff). Inthe case of a metallic coated steel specimen (for example,galvanized steel), examine the tape to determine whetherpickoff is
24、between the organic coating and the metallic surfaceor between the metallic coating and the base steel.6.1.6 Secure the bent end of the specimen in the vise andbend the free end 90. Continue to bend the free end around thefirst (OT) bend to complete a 180 bend, and tighten in the viseas before. This
25、 makes a 1T bend (Fig. 1). Examine the coatingand perform the tape test for cracking and pickoff, as with theOT bend.6.1.7 Repeat this procedure, making a 2T, 3T, etc., bendsuntil no cracking or pickoff occurs. The number of the t-bendat which no cracking or pickoff occurs is the designatedsuccessfu
26、l t-bend level.6.2 Bending the Coated Specimen Around a Die:6.2.1 The coated specimen shall be at least 2 in. (50 mm)across the bend direction.6.2.2 Secure the specimen and bending die in a vise orholding jig (Fig. 4). Bend the specimen 180 around the die ina smooth and uniform manner.6.2.3 Examine
27、the bend for cracking as in 6.1.4 and forpick-off or loss of adhesion, or both, as in 6.1.5.6.2.4 Express the T-bend at which no cracking or no pickoffoccurs as the number of specimen thicknesses around whichthe metal is being bent equal to the thickness of the die.6.3 Bending the Coated Specimen Ar
28、ound Itself Using aBend Forming Tool:6.3.1 The coated specimen shall be at least 2 in. (50 mm)across the bend direction, by a length sufficient to make therequired number of bends. A 2 by 10-in. (50 by 254-mm) sizeis convenient. A wider specimen may be used, limited by diewidth. The specimen shall b
29、e held at 75 6 10F (24 6 5.5C)temperature, or as agreed on between purchaser and seller. Thebend direction will be longitudinal or in the same directionwith respect to the rolling or flow direction of the sheet, or asagreed on between purchaser and seller.6.3.2 Secure about 0.25 to 0.75 (6 to 20 mm)
30、 of one end ofthe specimen, as shown in Fig. 1, to the step in the fixed portionof the holding jig or forming tool. Depress the free end of thespecimen into the fixed V-shaped die by the moveable wedgein a smooth and uniform manner so that the coating is on theoutside of the specimen after it is ben
31、t.6.3.3 Insert the bent end between the fixed V-shaped die andmoveable wedge of the forming tool. Depress the specimen, asin a vise in 6.1.3, to complete the 180 bend, which is called anOT bend. Take care to tighten the specimen between the fixedV-shaped die and moveable wedge of the forming tool su
32、ffi-ciently so that the apex of the bend is as flat as can bereasonably achieved.6.3.4 Examine the bend for cracking as in 6.1.4 or for lossof adhesion as in 6.1.5.6.3.5 Secure the bent end of the specimen in the fixedportion of the holding jig or forming tool and depress into thefixed V-shaped die
33、by the moveable wedge. Continue to bendthe free end around the first (OT) bend to complete a 180bend, and then tighten between the fixed V-shaped die andmoveable wedge of the forming tool as before. This makes a1T bend (Fig. 1). Examine and by taping for cracking andpickoff, as with the OT bend.6.3.
34、6 Repeat this procedure, making a 2T, 3T, etc., bendsuntil no cracking or pickoff occurs.7. Report7.1 Report the following information:7.1.1 Identification of the material, such as coil number,metal thickness, grade, alloy, temper and location within thecoil if the sample was coated on a coil line,7
35、.1.2 The coating system, coating thickness, application andcuring conditions,7.1.3 The temperature at which the specimen is bent,7.1.4 The bend directionwhether across (transverse) oralong (longitudinal) the rolling direction of the sheet,7.1.5 The minimum T-bend with no pickoff nor paintfracture (c
36、racking) or any observed metal failure or metalcracking, and7.1.6 Whether judged visually or under (what power of)magnification.8. Precision28.1 On the basis of an interlaboratory study of this testmethod, in which two operators in each of five laboratoriestested panels coated with paints of differe
37、nt flexibility andadhesion, the standard deviation was found to be:Standard DeviationAluminumGalvanizedSteelT-bend to no fracture 0.55 1.33T-bend to no pickoff 0.76 2.098.2 Based on these standard deviations, the following crite-ria should be used to judge the acceptability of results at the95 % con
38、fidence level:8.2.1 RepeatabilityMeasurements obtained by two opera-tors in a single laboratory should be considered suspect if theydiffer by more than:AluminumGalvanizedSteelT-bend to no fracture 0.4 1.8T-bend to no pickoff 0.9 3.38.2.2 ReproducibilityTwo measurements obtained in dif-ferent laborat
39、ories, each the mean of measurements made bytwo operators within a laboratory, should be considered suspectif they differ by more than:AluminumGalvanizedSteelT-bend to no fracture 2.5 10.1T-bend to no pickoff 1.8 10.62Supporting data have been filed at ASTM International Headquarters and maybe obtai
40、ned by requesting Research Report RR:D01-1034.D4145 1039. Keywords9.1 coating flexibility; prepainted sheet; T-bend flexibilityASTM 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
41、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 technical committee and must be reviewed every five years andif not re
42、vised, 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 at a meeting of theresponsible technical committee, which you
43、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 Drive, PO Box C700, West Conshohocken, PA 19428-2959,United S
44、tates. 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4145 104
