1、Designation: E208 17Standard 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 cas
2、e 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.INTRODUCTIONThis
3、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 at several Naval activities, research institutions, a
4、ndindustrial 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 prepared to ensure that tests conducted at all locationswou
5、ld 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,58 in.(15.9 mm) and thicker.1.2 This test method may be
6、 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 This standard does not purport to address all of thes
7、afety 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.1.5 This international standard was developed in accor-d
8、ance 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 Trade (TBT) Committee.2. Referenced Documents2.1 ASTM A
9、djuncts: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) temperature the maxi-mum temperature where a standard drop
10、-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 interval of the test. The test isconducted by subjectin
11、g 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, free-falling weight with an energyof 250 to 1400 ft lbf (
12、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 Testing and is the direct responsibility of Subcommittee
13、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/E0208-17.2Detail drawings for the construction of this machine are available from ASTMHeadquarters. Order ADJE0208. Or
14、iginal 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 developed in accordance with internationally recognized pr
15、inciples 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 test sequence is as follows: After the prepa-ration and te
16、mperature 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 temperature intervals to establish the limits within10F (
17、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 from a two-pass technique to the currentsingle-pass pro
18、cedure, 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 using the single-pass crack-starter weld beadmay not agr
19、ee 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 affected by temperature.For a given “low” temperature, the si
20、ze 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 flaw” initiation curve, Fig. 1,falls to nominal yield st
21、rength 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 shown in Fig. 1. The diagram wasderived from a wide variety
22、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 in ship, pressure vessel, machinerycomponent, forged, a
23、nd 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, and a rigidly supported anvil whichprovides for the loa
24、ding 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 relationship to the base shall be provided to guide theweight.
25、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 similarly to that shown in Fig. 2(b), shall be provided torelea
26、se 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 weightshall be a steel cylindrical surface with a radius of
27、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 of250 to 1400 ft lbf (340 to 1900 J).6.3 Ahorizontal ba
28、se, 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 center-line of the striking tup of the weight. Ingeneral,
29、 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 standardFIG. 1 Generalized Fracture Analysis Diagram Indicating t
30、he Approximate Range of Flaw Sizes Required for Fracture Initiation at Vari-ous Levels of Nominal Stress, as Referenced by the NDT Temperature3, 4E208 172specimen to the stop at temperatures above the NDT. The baseshall not jump or shift during the test, and shall be secured tothe foundation if nece
31、ssary 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 The general characteristics of two of the anvils requiredar
32、e 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 betweenthe two stops is provided as clearance for the crack-star
33、ter 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 temperatureswell above the NDT.6.6 A measuring system shall be provided
34、 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 machine is functionally equivalent.Fig. 5 illustrates a p
35、ortable 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 ScreenFIG. 2 Drop-Weight Test ApparatusE208 1737. Precautions7.
36、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 specimens andconditions to determine the NDT temperature of
37、 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, whose sole purpose is to provide abrittle material for th
38、e initiation of a small, cleavage crack-flawin the specimen base material during the test. Anomalousbehavior may be expected for materials where the heat-affectedzone created by deposition of the crack-starter weld is madeTABLE 1 Standard Drop-Weight Test ConditionsAType of SpecimenSpecimen Size,in.
39、 (mm)Span, in. (mm)Deflection Stop,in. (mm)Yield Strength Level,ksi (MPa)Drop-Weight Energy for GivenYield Strength LevelBft lbf (J)P-1 1 by 312 by 14(25.4 by 89 by 356)12.0(305)0.300(7.62)30 to 50 (210 to 340)50 to 70 (340 to 480)70 to 90 (480 to 620)90 to 110 (620 to 760)110 to 130 (760 to 900)600
40、800100012001400(810)(1080)(1360)(1630)(1900)P-234 by2by5(19 by 51 by 127)4.0(102)0.060(1.52)30 to 60 (210 to 410)60 to 90 (410 to 620)90 to 120 (620 to 830)120 to 150 (830 to 1030)150 to 180 (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 6
41、0 (210 to 410)60 to 90 (410 to 620)90 to 120 (620 to 830)120 to 150 (830 to 1030)150 to 180 (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 le
42、vel steel shall be conducted with the drop-weight energy stated in this column. In the event 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 stee
43、l.FIG. 3 General Appearance of the Anvils Required for Drop-Weight NDT TestsE208 174more fracture resistant than the unaffected plate. This conditionis developed for quenched and tempered steels of high hard-ness obtained by tempering at low temperatures. The problemmay be avoided by placing the cra
44、ck-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-worked steels in the heat-affectedzone and to develop a region of impro
45、ved 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 toughness.8. Test Specimens8.1 Identification of MaterialAll sample materi
46、al 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 conjunctionwith an itemized table to obtain all the pertinent informat
47、ion.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 orientation andit shall be noted in the test report.8.3 Relation to Other Spe
48、cimensUnless 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 other material properties.8.4 Special Conditions for Forgings and C
49、astingsWheredrop-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 theAnvil Dimension UnitsSpecimen TypeToleranceP-1 P-2 P-3S, Span in.mm12.03054.01004.01000.051.5D, Deflection stop in.mm0.307.600.0601.500.0751.900.0020.05A, Anvil length not criticalB, Anvil width not criticalC, Anvil thickness in.mm1.5 min38 min1.5 min38 min1.5 min38 minE, Sup
