1、Designation: D4145 10 (Reapproved 2018)Standard 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 revi
2、sion. A number in 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 subs
3、trates that are deformed 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 v
4、alues given in parentheses 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 e
5、stablish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Princip
6、les for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.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 gaug
7、e or thickness (t) of the sheet to which thecoating has been 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
8、 die to achieve no fracture or removal of thecoating.3. Summary 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
9、10) aftereach bend in order to determine if the coating 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 int
10、o products by roll forming, brakebending, or other deformation 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 e
11、valuating the ability of a coating system towithstand the 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 thetemperature of the specimen when it is bent can affect theresults of this test and should be agreed
12、 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.
13、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 a
14、utomated 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 10 magnification forexamining the
15、 specimen for coating fracture and pickoff aftertesting. A stereomicroscope has been found useful for thispurpose.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, andApplications and is the direct responsibility ofSubcommittee D01.53 on Coil
16、Coated Metal.Current edition approved Sept. 1, 2018. Published September 2018. Originallyapproved in 1983. Last previous edition approved in 2010 as D4145 10. DOI:10.1520/D4145-10R18.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis
17、 international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TB
18、T) Committee.15.5 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 sufficient to make therequired number of bends.A 2 by 6-in. (50 by 150-mm) size isconvenient. The specimen s
19、hall 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 direction of thesheet, or as agreed upon between purchaser and seller.NOTE 1A triangle-shaped specimen (
20、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 direction with respect toand along the rolling or flow direction. A transverse bend is perpendicularto
21、 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 specimen 90 in a smooth andNOTE 1The above bends are expanded for clarity. They are actuallyflat against thems
22、elves in the test.FIG. 1 T-Bend Test in Which the Coated Specimen is BentAround ItselfFIG. 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 themselv
23、es in the test.FIG. 5 Triangular Specimen for T-Bend TestD4145 10 (2018)2uniform 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
24、 bend, which is called an OT bend. Take care to tightenthe vise sufficiently so that the apex of the bend is as flat as canbe reasonably achieved.6.1.4 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
25、 thetape flat; then, holding the specimen firmly, remove the tapewith a rapid 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 ex
26、ample,galvanized steel), examine the tape to determine whetherpickoff is 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
27、 (OT) bend to complete a 180 bend, and tighten in the viseas before. This 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 th
28、e t-bendat which no cracking or pickoff occurs is the designatedsuccessful 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
29、 specimen 180 around the die ina smooth and uniform manner.6.2.3 Examine 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
30、bent equal to the thickness of the die.6.3 Bending the Coated Specimen Around 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
31、. A wider specimen may be used, limited by diewidth. The specimen shall be 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
32、between purchaser and seller.6.3.2 Secure about 0.25 to 0.75 (6 to 20 mm) 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 ma
33、nner so that the coating is on theoutside of the specimen after it is bent.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 specime
34、n between the fixedV-shaped die and moveable wedge of the forming tool suffi-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 o
35、f the holding jig or forming tool and depress into thefixed V-shaped die 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)
36、. Examine and by taping for cracking andpickoff, as with the OT bend.6.3.6 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, tem
37、per and location within thecoil if the sample was coated on a coil line,7.1.2 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 o
38、f the sheet,7.1.5 The minimum T-bend with no pickoff nor paintfracture (cracking) 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 operator
39、s in each of five laboratoriestested panels coated with paints of different 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 crit
40、e-ria should be used to judge the acceptability of results at the95 % confidence 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.
41、9 3.32Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D01-1034. ContactASTM CustomerService at serviceastm.org.D4145 10 (2018)38.2.2 ReproducibilityTwo measurements obtained in dif-ferent laboratories, each the mean of measuremen
42、ts 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 10.69. Keywords9.1 coating flexibility; prepainted sheet; T-bend flexibilityASTM International takes no position respecti
43、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
44、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
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