1、Designation: E208 171Standard Test Method forConducting Drop-Weight Test to Determine Nil-DuctilityTransition Temperature of Ferritic Steels1This standard is issued under the fixed designation E208; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1NOTEEditorial c
3、hanges made throughout in March 2018.INTRODUCTIONThis drop-weight test was developed at the Naval Research Laboratory in 1952 and has been usedextensively to investigate the conditions required for initiation of brittle fractures in structural steels.Drop-weight test facilities have been established
4、 at several Naval activities, research institutions, andindustrial organizations in this country and abroad. The method is used for specification purposes byindustrial organizations and is referenced in several ASTM specifications and the ASME Boiler andPressure Vessel Code. This procedure was prepa
5、red to ensure that tests conducted at all locationswould have a common meaning. This test method was originally published as Department of the Navydocument NAVSHIPS-250-634-3.1. Scope*1.1 This test method covers the determination of the nil-ductility transition (NDT) temperature of ferritic steels,5
6、8 in.(15.9 mm) and thicker.1.2 This test method may be used whenever the inquiry,contract, order, or specification states that the steels are subjectto fracture toughness requirements as determined by thedrop-weight test.1.3 The values stated in inch-pound units are to be regardedas the standard.1.4
7、 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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.
8、5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to T
9、rade (TBT) Committee.2. Referenced Documents2.1 ASTM Adjuncts:Drop Weight Machine23. Terminology3.1 Definitions:3.1.1 ferriticthe word ferritic as used hereafter refers to all-Fe steels. This includes martensitic, pearlitic, and all othernonaustenitic steels.3.1.2 nil-ductility transition (NDT) temp
10、erature the maxi-mum temperature where a standard drop-weight specimenbreaks when tested according to the provisions of this method.4. Summary of Test Method4.1 The drop-weight test employs simple beam specimensspecially prepared to create a material crack in their tensilesurfaces at an early time i
11、nterval of the test. The test isconducted by subjecting each of a series (generally four toeight) of specimens of a given material to a single impact loadat a sequence of selected temperatures to determine themaximum temperature at which a specimen breaks. The impactload is provided by a guided, fre
12、e-falling weight with an energyof 250 to 1400 ftlbf (340 to 1900 J) depending on the yieldstrength of the steel to be tested. The specimens are preventedby a stop from deflecting more than a few tenths of an inch.1This test method is under the jurisdiction of the ASTM Committee E28 onMechanical Test
13、ing and is the direct responsibility of Subcommittee E28.07 onImpact Testing.Current edition approved Dec. 1, 2017. Published March 2018. Originallyapproved in 1963. Last previous edition approved in 2012 as E208 06(2012). DOI:10.1520/E0208-17E01.2Detail drawings for the construction of this machine
14、 are available from ASTMHeadquarters. Order ADJE0208. Original adjunct produced in 2002.*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 StatesThis international standard was de
15、veloped 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 (TBT) Committee.14.2 The usual te
16、st sequence is as follows: After the prepa-ration and temperature conditioning of the specimen, the initialdrop-weight test is conducted at a test temperature estimated tobe near the NDT temperature. Depending upon the results ofthe first test, tests of the other specimens are conducted atsuitable t
17、emperature intervals to establish the limits within10F (5C) for break and no-break performance. A duplicatetest at the lowest no-break temperature of the series isconducted to confirm no-break performance at this tempera-ture.4.3 In 1984, the method of applying the crack-starter weldbead was changed
18、 from a two-pass technique to the currentsingle-pass procedure, and the practice of repair-welding of thecrack-starter weld bead was prohibited. For steels whoseproperties are influenced by tempering or are susceptible totemper embrittlement, the nil-ductility transition (NDT) tem-perature obtained
19、using the single-pass crack-starter weld beadmay not agree with that obtained using the previous two-passcrack-starter weld bead, or when the crack-starter bead wasrepaired.5. Significance and Use5.1 The fracture-strength transitions of ferritic steels used inthe notched condition are markedly affec
20、ted by temperature.For a given “low” temperature, the size and acuity of the flaw(notch) determines the stress level required for initiation ofbrittle fracture. The significance of this test method is related toestablishing that temperature, defined herein as the NDTtemperature, at which the “small
21、flaw” initiation curve, Fig. 1,falls to nominal yield strength stress levels with decreasingtemperature, that is, the point marked NDT in Fig. 1.5.2 Interpretations to other conditions required for fractureinitiation may be made by the use of the generalized flaw-size,stress-temperature diagram show
22、n in Fig. 1. The diagram wasderived from a wide variety of tests, both fracture-initiationand fracture-arrest tests, as correlated with the NDT tempera-ture established by the drop-weight test. Validation of the NDTconcept has been documented by correlations with numerousservice failures encountered
23、 in ship, pressure vessel, machinerycomponent, forged, and cast steel applications.6. Apparatus6.1 The drop-weight machine is of simple design based onthe use of readily available structural steel products.2Theprincipal components of a drop-weight machine are a verticallyguided, free-falling weight,
24、 and a rigidly supported anvil whichprovides for the loading of a rectangular plate specimen as asimple beam under the falling weight. Fig. 2(a) illustrates atypical drop-weight machine built of standard structuralshapes.6.2 A rail, or rails, rigidly held in a vertical position and ina fixed relatio
25、nship to the base shall be provided to guide theweight. The weight shall be provided with suitable deviceswhich engage the rail, or rails, and ensure that it will dropfreely in a single, vertical plane. The weight may be raised byany convenient means. A weight-release mechanism, function-ing similar
26、ly to that shown in Fig. 2(b), shall be provided torelease the weight quickly without affecting its free fall. Theweight shall be made in one piece, or if made of several pieces,its construction shall be rigid to ensure that it acts as a unitwhen it strikes the specimen. The striking tup of the weig
27、htshall be a steel cylindrical surface with a radius of 1 in. (25.4mm) and a minimum hardness of HRC 50 throughout thesection. The weight shall be between 50 and 300 lb (22.7 and136 kg). The rails and hoisting device shall permit raising theweight various fixed distances to obtain potential energies
28、 of250 to 1400 ftlbf (340 to 1900 J).6.3 A horizontal base, located under the guide rails, shall beprovided to hold and position precisely the several styles ofanvils required for the standard specimens. The anvil guidesshall position the anvil with the center-line of the deflectionstops under the c
29、enter-line of the striking tup of the weight. Ingeneral, the base will also support the guide rails, but this is nota requirement. The base shall rest on the rigid foundation. Thebase-foundation system shall be sufficiently rigid to allow thenormal drop-weight energy (Table 1) to deflect a standardF
30、IG. 1 Generalized Fracture Analysis Diagram Indicating the Approximate Range of Flaw Sizes Required for Fracture Initiation at Vari-ous Levels of Nominal Stress, as Referenced by the NDT Temperature3, 4E208 1712specimen to the stop at temperatures above the NDT. The baseshall not jump or shift durin
31、g the test, and shall be secured tothe foundation if necessary to prevent motion.6.4 A guard screen, similar to that shown in Fig. 2(c), isrecommended to stop broken specimen halves of the verybrittle steels which break into two pieces with both halvesbeing ejected forcefully from the machine.6.5 Th
32、e general characteristics of two of the anvils requiredare illustrated in Fig. 3. The anvils shall be made in accordancewith the dimensions shown in Fig. 4. The anvil supports anddeflection stops shall be steel-hardened to a minimum hardnessof HRC 50 throughout their cross section. The space between
33、the two stops is provided as clearance for the crack-starter weldon the specimen. The deflection stops may be made in twoseparate pieces, if desired. The anvil-base system shall besufficiently rigid to allow the normal drop-weight energy(Table 1) to deflect the specimen to the stop at temperatureswe
34、ll above the NDT.6.6 A measuring system shall be provided to assure that theweight is released from the desired height for each test, withinthe limits of +10, 0 %.6.7 Modifications of the equipment or assembly details ofthe drop-weight machine shown in Fig. 2 are permittedprovided that the modified
35、machine is functionally equivalent.Fig. 5 illustrates a portable machine design used by anindustrial concern for drop-weight tests of materials used forpressure vessel components at different fabrication sites.(a) LeftComplete Assembly(b) Upper RightQuick Release Mechanism(c) Lower RightGuard Screen
36、FIG. 2 Drop-Weight Test ApparatusE208 17137. Precautions7.1 The drop-weight test was devised for measuring fractureinitiation characteristics of58-in. (15.9-mm) and thicker struc-tural materials. This test is not recommended for steels lessthan58-in. thick.7.2 This test method establishes standard s
37、pecimens andconditions to determine the NDT temperature of a given steel.The use of standard specimens with nonstandard test condi-tions or the use of nonstandard specimens shall not be allowedfor specification purposes.7.3 This test method employs a small weld bead depositedon the specimen surface,
38、 whose sole purpose is to provide abrittle material for the initiation of a small, cleavage crack-flawin the specimen base material during the test. AnomalousTABLE 1 Standard Drop-Weight Test ConditionsAType ofSpecimenSpecimen Size,in. (mm)Spanin. (mm)DeflectionStopin. (mm)Yield Strength Level Drop
39、Weight Energy forGiven Yield Strength LevelBksi (MPa) ftlbf (J)P-1 1 by 312 by 14(25by 89 by 356)12.0(305)0.300(7.62)30 to 5050 to 7070 to 9090 to 110110to130(210 to 340)(340 to 480)(480 to 620)(620 to 760)(760 to 900)600800100012001400(810)(1080)(1360)(1630)(1900)P-234 by2by5(19 by 51 by 127)4.0(10
40、2)0.060(1.52)30 to 6060 to 9090 to 120120 to 150150 to 180(210 to 410)(410 to 620)(620 to 830)(830 to 1030)(1030 to 1240)250300350400450(340)(410)(470)(540)(610)P-358 by2by5(16 by 51 by 127)4.0(102)0.075(1.90)30 to 6060 to 9090 to 120120 to 150150 to 180(210 to 410)(410 to 620)(620 to 830)(830 to 10
41、30)(1030 to 1240)250300350400450(340)(410)(470)(540)(610)AUsers should observe the precautions stated in 7.3 when testing high-strength quenched and tempered materials.BInitial tests of a given yield strength level steel shall be conducted with the drop-weight energy stated in this column. In the ev
42、ent that the crack-stater weld is not visiblycracked or insufficient deflection is developed, or both (no-test performance) an increased drop-weight energy shall be employed for other specimens of the given steel.Editorially corrected March 2018.FIG. 3 General Appearance of the Anvils Required for D
43、rop-Weight NDT TestsE208 1714behavior may be expected for materials where the heat-affectedzone created by deposition of the crack-starter weld is mademore fracture resistant than the unaffected plate. This conditionis developed for quenched and tempered steels of high hard-ness obtained by temperin
44、g at low temperatures. The problemmay be avoided by placing the crack-starter weld on thesesteels before conducting the quenching and tempering heattreatment. Except for other cases which may be readilyrationalized in metallurgical terms (for example, it is possibleto recrystallize heavily cold-work
45、ed steels in the heat-affectedzone and to develop a region of improved ductility), theheat-affected zone problem is not encountered with conven-tional structural grade steels of a pearlitic microstructure orquenched and tempered steels tempered at high temperatures todevelop maximum fracture toughne
46、ss.8. Test Specimens8.1 Identification of MaterialAll sample material andspecimens removed from a given plate, shape, forging, orcasting product shall be marked to identify their particularsource (heat number, slab number, etc.).Asimple identificationsystem shall be used which can be employed in con
47、junctionwith an itemized table to obtain all the pertinent information.8.2 OrientationThe drop-weight test is insensitive tospecimen orientation with respect to rolling or forging direc-tion. However, unless otherwise agreed to, all specimensspecified by the purchaser shall be of the same orientatio
48、n andit shall be noted in the test report.8.3 Relation to Other SpecimensUnless otherwise speci-fied by the purchaser, the specimens shall be removed from thematerial at positions adjacent to the location of other type testspecimens (for example, mechanical test specimens) requiredfor evaluation of
49、other material properties.8.4 Special Conditions for Forgings and CastingsWheredrop-weight testing of cast or forged material is specified, thesize and location of integrally attached pad projections orprolongations to be used for specimen fabrication shall beagreed to in advance by the purchaser. If the design of thecasting or forging does not allow an attached test-materialcoupon, the following requirements shall apply:8.4.1 Drop-weight specimens cast or forged separately tothe dimensions required for testing shall be allowed only wherethe product d
