ASTM A143 A143M-2007 Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement《热浸镀锌结构钢产品的脆性.pdf

1、Designation: A 143/A 143M 07Standard Practice forSafeguarding Against Embrittlement of Hot-Dip GalvanizedStructural Steel Products and Procedure for DetectingEmbrittlement1This standard is issued under the fixed designation A 143/A 143M; the number immediately following the designation indicates the

2、 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 (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Dep

3、artment 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 embrittlem

4、ent 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, pr

5、ocesses 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

6、necessarily exactequivalents. Within the text of this practice and where appro-priate, 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-pria

7、te safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F 606 Test Methods for Determining the Mechanical Prop-erties of Externally and Internally Threaded Fasteners,Washers, Direct Tension Indicators, and Rive

8、ts3. Terminology3.1 Definition:3.1.1 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 wo

9、rking, 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 re

10、sultof 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 850F455C.4.2 Hydrogen embrittlement may also occur due to thepo

11、ssibility 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 potentials

12、ource of hydrogen. However, the heat of the galvanizing bathpartially expels hydrogen that may have been absorbed. Inpractice hydrogen embrittlement of galvanized steel is usuallyof concern only if the steel exceeds approximately 150 ksi1100 MPa in ultimate tensile strength, or if it has beenseverel

13、y 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,

14、 fillets of small radii, sharp bends, etc.1This 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 Em

15、brittlement Investigation ofCommittee A05 on Corrosion of Iron and Steel and based on an investigation madeby Battelle Memorial Institute under American Society for Testing and Materialssponsorship. See Proceedings, Am. Soc. Testing Mats., Vol 31, Part I, 1931, p. 211;also paper by Samuel Epstein, “

16、Embrittlement of Hot-Dip Galvanized StructuralSteel,” see Proceedings , Am. Soc. Testing Mats., Vol 32, Part II, 1932, p. 293.Current edition approved May 1, 2007. Published June 2007. Originallyapproved in 1932. Last previous edition approved in 2003 as A 143/A 143M - 03.2For referenced ASTM standa

17、rds, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA

18、 19428-2959, United States.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 ac

19、count 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

20、heavy shapes, plates, and hard-ware, 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 (33

21、) 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

22、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 to14 in. 6.4mm may be cold worked by punching without subsequentannealing or stress-relieving

23、. Shapes516 to1116 in. 8 to 18mm in thickness are not seriously affected as to serviceabilityby cold punching or if the punching is done under good shoppractice. The heavier shapes,34 in. 19 mm and over, shall bereamed with at least116 in. 1.6 mm of metal removed fromthe periphery of the hole after

24、punching, or shall be drilled, orthermally 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.

25、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

26、 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. 24min/cm of section thickness.6.4 Flame cut co

27、pes 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

28、noted in 4.2, may contribute to embrittlement ofthe galvanized product. The likelihood of this, or of surfacecracking occurring, is increased by excessive pickling tempera-ture, prolonged pickling time, and poor inhibition of thepickling acid. Heating to 300F 150C after pickling andbefore galvanizin

29、g 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 abrasiv

30、e 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

31、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 Embrittlemen

32、t 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

33、 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 establis

34、hed within this practice, the lot shall be asfollows: For test at a manufacturers 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, whe

35、n 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 s

36、hipment 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 andcomparing the degree of bending to that which is obtained ona similar ungalvanized article. The art

37、icle, 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

38、 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 blow3Available from American Institute of St

39、eel Construction (AISC), One EastWacker Drive, Suite 3100, Chicago, IL 60601-2001. 9thEdition.A 143/A 143M 072with 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 crack

40、s under the blow, it shall be considered embrittled.9.4 A test for embrittlement of galvanized steel angles isdetailed as follows:9.4.1 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 ma

41、de 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 and ream-ing, or drilling. The dimensional values, diameter, and locationof hole shall be not less than those employed i

42、n the structuraldetails. Care should be taken not to place the hole near stampedor rolled-in identification marks. The specimen shall then begalvanized. For determining the elongation after fracture, a2-in. 51-mm gage length (Fig. 1) shall be prick-punched inthe middle of the edge of the vertical le

43、g of the galvanizedangle along a line parallel to its length and centered directlyunder the hole. For specimens under12 in. 13 mm inthickness, or those in which the distance from the edge of thehole to the edge of the angle is less than38 in. 10 mm, a 1-in.25-mm gage length shall be used.9.4.2 Proce

44、dure:9.4.2.1 The test shall be made in a universal testing ma-chine, or by other means such as a press with the load appliedslowly, until fracture of the galvanized test specimen occurs.The length of the test specimen and the distance between thesupports are shown in the following table:Leg of Angle

45、, l, in. mm(see Fig. 1)Length BetweenSupports, L1,in. mmMinimum Length, L2,in. mmUp to 4 102, incl 14 356 18 457Over 4 to 6 102 to 152, incl 20 508 24 610Over 6 to 8 152 to 203, incl 30 762 36 9149.4.2.2 After the test, the distance along the gage lengthfrom each punch mark to the corresponding edge

46、 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 thre

47、e locations indicated in Fig. 2:namely 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

48、 galvanized specimenshaving a temperature not below 60F 16C and not over 90F32C 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

49、 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 Section 9.2 for embrittlement is detailed in TestMethod F 606.10. Keywords10.1 coatings-zinc; galvanized coatings; steel products-metallic coated; zinc coatings-steel productsASTM International takes no position respecting the validity of any patent rights asserted in