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ASTM A143 - A 143M - 07 (2014).pdf

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ASTM A143 - A 143M - 07 (2014).pdf

Designation A143/A143M − 07 Reapproved 2014Standard Practice forSafeguarding Against Embrittlement of Hot-Dip GalvanizedStructural Steel Products and Procedure for DetectingEmbrittlement1This standard is issued under the fixed designation A143/A143M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This practice covers procedures that can be followed tosafeguard against the possible embrittlement of steel hot-dipgalvanized after fabrication, and outlines test procedures fordetecting embrittlement. Conditions of fabrication may inducea susceptibility to embrittlement in certain steels that can beaccelerated by galvanizing. Embrittlement is not a commonoccurrence, however, and this discussion does not imply thatgalvanizing increases embrittlement where good fabricatingand galvanizing procedures are employed. Where history hasshown that for specific steels, processes and galvanizingprocedures have been satisfactory, this history will serve as anindication that no embrittlement problem is to be expected forthose steels, processes, and galvanizing procedures.1.2 This practice is applicable in either inch-pounds or SIunits. Inch-pounds and SI units are not necessarily exactequivalents. Within the text of this practice and whereappropriate, SI units are shown in brackets.1.3 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards2F606 Test Methods for Determining the Mechanical Proper-ties of Externally and Internally Threaded Fasteners,Washers, and Rivets Metric F0606_F0606M3. Terminology3.1 Definitions3.1.1 embrittlement, nthe loss or partial loss of ductility ina steel where an embrittled product characteristically fails byfracture without appreciable deformation; types of embrittle-ment usually encountered in galvanized steel are related toaging phenomena, cold working, and absorption of hydrogen.4. Factors in Embrittlement4.1 Embrittlement or loss of ductility in steel is oftenassociated with strain-aging. Strain-aging refers to the delayedincrease in hardness and strength, and loss of ductility andimpact resistance which occur in susceptible steels as a resultof the strains induced by cold working. The aging changesproceed slowly at room temperature, but proceed at an accel-erated rate as the aging temperature is raised and may occurrapidly at the galvanizing temperature of approximately 850F[455C].4.2 Hydrogen embrittlement may also occur due to thepossibility of atomic hydrogen being absorbed by the steel. Thesusceptibility to hydrogen embrittlement is influenced by thetype of steel, its previous heat treatment, and degree ofprevious cold work. In the case of galvanized steel, the acidpickling reaction prior to galvanizing presents a potentialsource of hydrogen. However, the heat of the galvanizing bath1This practice is under the jurisdiction of ASTM Committee A05 on Metallic-Coated Iron and Steel Products and is the direct responsibility of SubcommitteeA05.13 on Structural Shapes and Hardware Specifications.Originally Prepared by Subcommittee A05.10 on Embrittlement Investigation ofCommittee A05 on Corrosion of Iron and Steel and based on an investigation madeby Battelle Memorial Institute under American Society for Testing and Materials’sponsorship. See Proceedings, Am. Soc. Testing Mats., Vol 31, Part I, 1931, p. 211;also paper by Samuel Epstein, “Embrittlement of Hot-Dip Galvanized StructuralSteel,” see Proceedings, Am. Soc. Testing Mats., Vol 32, Part II, 1932, p. 293.Current edition approved Aug. 1, 2014. Published September 2014. Originallyapproved in 1932. Last previous edition approved in 2007 as A143/A143M – 07.DOI 10.1520/A0143_A0143M-07R14.2For 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 standard’s Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1partially expels hydrogen that may have been absorbed. Inpractice hydrogen embrittlement of galvanized steel is usuallyof concern only if the steel exceeds approximately 150 ksi[1100 MPa] in ultimate tensile strength, or if it has beenseverely cold worked prior to pickling.4.3 Loss of ductility of cold-worked steels is dependent onmany factors including the type of steel strength level, agingcharacteristics, thickness of steel, and degree of cold work,and is accentuated by areas of stress concentration such ascaused by notches, holes, fillets of small radii, sharp bends, etc.4.4 Low temperatures increase the risk of brittle failure ofall plain carbon steels including steel that has been galvanized.The rate at which this temperature loss of ductility occursvaries for different steels. The expected service temperatureshould thus be taken into account when selecting the steel.5. Steels5.1 Open-hearth, basic-oxygen, and electric-furnace steelsshall be used for galvanizing. Other materials that can begalvanized include continuous cast slabs, steel or iron castings,and wrought iron.6. Cold Working and Thermal Treatment6.1 For intermediate and heavy shapes, plates, andhardware, cold bend radii should not be less than that which isproven satisfactory by practice or by the recommendations ofthe steel manufacturer. These criteria generally depend on thedirection of grain, strength, and type of steel. A cold bendingradius of three times 3 the section thickness, or as recom-mended in AISC Manual of Steel Construction,3will ordinarilyensure satisfactory properties in the final product. Althoughsharper bending on thin sections can usually be tolerated,embrittlement may occur if cold bending is especially severe.If the design requires sharper bending than discussed herein,the bending should be done hot, or if done cold the materialshould be subsequently annealed or stress relieved as noted in6.3.6.2 Smaller shapes, including thickness up to1⁄4 in.[6.4 mm] may be cold worked by punching without subsequentannealing or stress-relieving. Shapes5⁄16 to11⁄16 in. [8 to18 mm] in thickness are not seriously affected as to service-ability by cold punching or if the punching is done under goodshop practice. The heavier shapes,3⁄4 in. [19 mm] and over,shall be reamed with at least1⁄16 in. [1.6 mm] of metal removedfrom the periphery of the hole after punching, or shall bedrilled, or thermally treated prior to galvanizing as noted in 6.3.6.3 Fabrication in accordance with the principles outlined in6.1 and 6.2 will normally obviate the need for thermaltreatment. However, if required, proper thermal treatment shallprecede galvanizing of the steel. For heavy cold deformationexemplified by cold rolling, sheared edges, punched holes, orcold-formed rods and bolts, subcritical annealing at tempera-tures from 1200 to 1300F [650 to 705C] should be employed.For less severe cold deformation typified by cold bending, rollforming, etc., it is advisable to limit the thermal treatment tostress relieving at a maximum of 1100F [595C] to avoidexcessive grain growth or alternatively to fully normalize thesteel at temperatures from 1600 to 1700F [870 to 925C]. Thetime at temperature should be approximately 1 h/in.[24 min⁄cm] of section thickness.6.4 Flame cut copes on structural beams shall have aminimum radius of 1 in. [2.5 cm].After cutting, the cut surfaceshall be ground to remove notches, grooves, and irregularsurface features to leave the surface smooth.7. Preparation for Galvanizing7.1 Hydrogen can be absorbed during pickling and in someinstances, as noted in 4.2, may contribute to embrittlement ofthe galvanized product. The likelihood of this, or of surfacecracking occurring, is increased by excessive picklingtemperature, prolonged pickling time, and poor inhibition ofthe pickling acid. Heating to 300F [150C] after pickling andbefore galvanizing in most cases results in expulsion ofhydrogen absorbed during pickling.7.2 Abrasive blast cleaning followed by flash pickling mayalso be employed when over-pickling is of concern or whenvery high strength steel, ultimate tensile strength higher than150 ksi [1100 MPa], must be galvanized. The abrasive blastcleaning does not generate hydrogen while it is cleaning thesurface of the steel. The flash pickling after abrasive blastcleaning is used to remove any final traces of blast mediabefore hot-dip galvanizing.8. Responsibility for Avoiding Embrittlement8.1 Design of the product and selection of the proper steel towithstand normal galvanizing operations without embrittle-ment are the responsibility of the designer. The fabricator shallbe responsible for employing suitable fabrication procedures.The galvanizer shall employ proper pickling and galvanizingprocedures.9. Testing for Embrittlement of Steel Shapes, SteelCastings, Threaded Articles, and Hardware Items9.1 Subject to base material and dimensional limitations, thetests given in 9.2, 9.3, 9.4,or9.5, or a combination thereof,shall apply. If one test specimen should be found embrittled bythese tests, two additional specimens should be tested. Failureof either the second or the third specimen shall be cause forrejection of the lot see Note 1 that the samples represent.NOTE 1A lot is a unit of production from which a sample may betaken for testing. Unless otherwise agreed upon by the manufacturer andthe purchaser, or established within this practice, the lot shall be asfollows For test at a manufacturer’s facility, a lot is one or more articlesof the same type and size comprising a single order or a single deliveryload, whichever is the smaller, or a smaller number of articles identified asa lot by the manufacturer, when these have been galvanized within a singleproduction shift. For test by purchaser after delivery, the lot consists of thesingle order or the single delivery load, whichever is the smaller, unlessthe lot identity, established in accordance with the above, is maintainedand clearly indicated in the shipment by the manufacturer.9.2 A bend test for embrittlement of galvanized steel hard-ware such as bolts, pole and tower steps, braces, rods,reinforcing bars, etc., consists of bending the article and3Available from American Institute of Steel Construction AISC, One EastWacker Drive, Suite 3100, Chicago, IL 60601-2001. 9thEdition.A143/A143M − 07 20142comparing the degree of bending to that which is obtained ona similar ungalvanized article. The article, before and aftergalvanizing, may be clamped in a vise and using a lever ifnecessary, bent until cracking of the base steel occurs, or to 90whichever is less. The galvanized article should withstand adegree of bending substantially the same as the ungalvanizedarticle. Flaking or spalling of the galvanized coating is not tobe construed as an embrittlement failure. For threaded articles,the test shall be made on the unthreaded portion.9.3 Small steel castings and steel hardware of such shape orsize that do not permit bending may be struck a sharp blowwith a 2-lb [1-kg] hammer and the results for both galvanizedand ungalvanized samples compared. If the article withstandssuch a blow in the ungalvanized condition, but after galvaniz-ing cracks under the blow, it shall be considered embrittled.9.4 A test for embrittlement of galvanized steel angles isdetailed as follows9.4.1 Test SpecimenA test specimen with a length deter-mined by the table in 9.4.2.1 and by Fig. 1 shall be cut from thesteel angle before galvanizing. A hole shall be made in the testspecimen at its midlength, using the same procedure as will beemployed in the fabricated material which the specimenrepresents, whether this be by punching, punching andreaming, or drilling. The dimensional values, diameter, andlocation of hole shall be not less than those employed in thestructural details. Care should be taken not to place the holenear stamped or rolled-in identification marks. The specimenshall then be galvanized. For determining the elongation afterfracture, a 2-in. [51-mm] gage length Fig. 1 shall be prick-punched in the middle of the edge of the vertical leg of thegalvanized angle along a line parallel to its length and centereddirectly under the hole. For specimens under1⁄2 in. [13 mm] inthickness, or those in which the distance from the edge of thehole to the edge of the angle is less than3⁄8 in. [10 mm], a 1-in.[25-mm] gage length shall be used.9.4.2 Procedure9.4.2.1 The test shall be made in a universal testingmachine, or by other means such as a press with the loadapplied slowly, until fracture of the galvanized test specimenoccurs. The length of the test specimen and the distancebetween the supports are shown in the following tableLeg of Angle, l, in. [mm]see Fig. 1Length BetweenSupports, L1,in. [mm]Minimum Length, L2,in. [mm]Up to 4 [102], incl 14 [356] 18 [457]Over 4 to 6 [102 to 152], incl 20 [508] 24 [610]Over 6 to 8 [152 to 203], incl 30 [762] 36 [914]9.4.2.2 After the test, the distance along the gage lengthfrom each punch mark to the corresponding edge of thefracture shall be measured to 0.01 in. [0.25 mm] with a flexiblescale and the percentage of elongation calculated from the sumof these distances.9.4.2.3 For determining the percentage reduction of thick-ness after fracture, the reduction shall be measured with aball-point micrometer at the three locations indicated in Fig. 2namely a, outer side of hole; b, inner side of hole; and c,middle of leg. The percentage reduction of thickness shall becalculated on the basis of the original thickness of the angleand the average of the three values at a, b, and c.9.4.2.4 The test shall be made upon galvanized specimenshaving a temperature not below 60F [16C] and not over 90F[32C] when tested.9.4.3 RequirementsThe elongation measured in accor-dance with 9.4.2.2 shall be not less than 5 with the followingexception when the specimen does not show 5 elongation,the reduction in thickness shall be measured in accordance with9.4.2.3. The sum of the percentage of elongation plus theaverage percentage reduction of thickness shall not be less than10.9.5 For hot-dip galvanized externally threaded fasteners, analternate test to 9.2 for embrittlement is detailed inTest MethodF606.10. Keywords10.1 coatings-zinc; galvanized coatings; steel products-metallic coated; zinc coatings-steel productsNOTE 12 in. 51 mm.FIG. 1 Specimen for Elongat

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