ASTM E21-2009 374 Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials《金属材料升温拉伸试验用标准试验方法》.pdf

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1、Designation: E 21 09Standard Test Methods forElevated Temperature Tension Tests of Metallic Materials1This standard is issued under the fixed designation E 21; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revisi

2、on. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover procedure and equipment

3、 forthe determination of tensile strength, yield strength, elongation,and reduction of area of metallic materials at elevated tempera-tures.1.2 Determination of modulus of elasticity and proportionallimit are not included.1.3 Tension tests under conditions of rapid heating or rapidstrain rates are n

4、ot included.1.4 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns,

5、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 Standards:2E4 Practices for Force Verification of Testin

6、g MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 8/E 8M Test Methods for Tension Testing of MetallicMaterialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE74 Practice of Calibration of Force-Measuring Instru-ments for Verifying

7、 the Force Indication of Testing Ma-chinesE83 Practice for Verification and Classification of Exten-someter SystemsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 220 Test Method for Calibration of Thermocouples ByComparison TechniquesE 633 Guide for Use of Thermocouples

8、in Creep andStress-Rupture Testing to 1800F (1000C) in AirE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 Definitions of terms relating to tension testing whichappear in Terminology E6, shall apply to the terms used

9、 in thistest method.3.2 Definitions of Terms Specific to This Standard:3.2.1 reduced section of the specimenthe central portionof the length having a cross section smaller than the ends whichare gripped. The cross section is uniform within tolerancesprescribed in 7.7.3.2.2 length of the reduced sect

10、ionthe distance betweentangent points of the fillets which bound the reduced section.3.2.3 adjusted length of the reduced section is greater thanthe length of the reduced section by an amount calculated tocompensate for strain in the fillet region (see 9.2.3).3.2.4 gage lengththe original distance b

11、etween gagemarks made on the specimen for determining elongation afterfracture.3.2.5 axial strainthe average of the strain measured onopposite sides and equally distant from the specimen axis.3.2.6 bending strainthe difference between the strain atthe surface of the specimen and the axial strain. In

12、 general itvaries from point to point around and along the reduced sectionof the specimen.3.2.7 maximum bending strainthe largest value of bend-ing strain in the reduced section of the specimen. It can becalculated from measurements of strain at three circumferentialpositions at each of two differen

13、t longitudinal positions.4. Significance and Use4.1 The elevated-temperature tension test gives a usefulestimate of the ability of metals to withstand the application ofapplied tensile forces. Using established and conventional1These test methods are under the jurisdiction of ASTM Committee E28 onMe

14、chanical Testing and are the direct responsibility of Subcommittee E28.04 onUniaxial Testing.Current edition approved April 1, 2009. Published May 2009. Originallyapproved in 1933. Last previous edition approved in 2005 as E 21 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org,

15、 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 19428-2959, United States.relationships i

16、t can be used to give some indication of probablebehavior under other simple states of stress, such as compres-sion, shear, etc. The ductility values give a comparativemeasure of the capacity of different materials to deform locallywithout cracking and thus to accommodate a local stressconcentration

17、 or overstress; however, quantitative relationshipsbetween tensile ductility and the effect of stress concentrationsat elevated temperature are not universally valid. A similarcomparative relationship exists between tensile ductility andstrain-controlled, low-cycle fatigue life under simple states o

18、fstress. The results of these tension tests can be considered asonly a questionable comparative measure of the strength andductility for service times of thousands of hours. Therefore, theprincipal usefulness of the elevated-temperature tension test isto assure that the tested material is similar to

19、 reference materialwhen other measures such as chemical composition andmicrostructure also show the two materials are similar.5. Apparatus5.1 Testing Machine:5.1.1 The accuracy of the testing machine shall be withinthe permissible variation specified in Practices E4.5.1.2 Precaution should be taken

20、to assure that the force onthe specimens is applied as axially as possible. Perfect axialalignment is difficult to obtain especially when the pull rodsand extensometer rods pass through packing at the ends of thefurnace. However, the machine and grips should be capable ofloading a precisely made spe

21、cimen so that the maximumbending strain does not exceed 10 % of the axial strain, whenthe calculations are based on strain readings taken at zero forceand at the lowest force for which the machine is beingqualified.NOTE 1This requirement is intended to limit the maximum contribu-tion of the testing

22、apparatus to the bending which occurs during a test. Itis recognized that even with qualified apparatus different tests may havequite different percent bending strain due to chance orientation of aloosely fitted specimen, lack of symmetry of that particular specimen,lateral force from furnace packin

23、g, and thermocouple wire, etc. The scantevidence available at this time3indicates that the effect of bending strainon test results is not sufficient, except in special cases, to require themeasurement of this quantity on each specimen tested.5.1.2.1 In testing of brittle material even a bending stra

24、in of10 % may result in lower strength than would be obtained withimproved axiality. In these cases, measurements of bendingstrain on the specimen to be tested may be specificallyrequested and the permissible magnitude limited to a smallervalue.5.1.2.2 In general, equipment is not available for dete

25、rmin-ing maximum bending strain at elevated temperatures. Thetesting apparatus may be qualified by measurements of axialitymade at room temperature using the assembled machine, pullrods, and grips used in high temperature testing. The specimenform should be the same as that used during the elevated-

26、temperature tests and designed so that only elastic strains occurthroughout the reduced section. This requirement may neces-sitate use of a material different from that used during theelevated-temperature test. See Practice E 1012 for recom-mended methods for determining specimen alignment.5.1.2.3 G

27、ripping devices and pull rods may oxidize, warp,and creep with repeated use at elevated temperatures. Increasedbending stresses may result. Therefore, grips and pull rodsshould be periodically retested for axiality and reworked whennecessary.5.1.3 The testing machine shall be equipped with a means o

28、fmeasuring and controlling either the strain rate or the rate ofcrosshead motion or both to meet the requirements in 9.6.5.1.4 For high-temperature testing of materials that arereadily attacked by their environment (such as oxidation ofmetal in air), the specimen may be enclosed in a capsule so that

29、it can be tested in a vacuum or inert gas atmosphere. Whensuch equipment is used, the necessary corrections must bemade to determine the actual forces seen by the specimen. Forinstance, compensation must be made for differences in pres-sures inside and outside of the capsule and for any variation in

30、the forces applied to the specimen due to sealing ring friction,bellows or other features.5.2 Heating Apparatus:5.2.1 The apparatus for and method of heating the speci-mens should provide the temperature control necessary tosatisfy the requirements specified in 9.4.5.2.2 Heating shall be by an elect

31、ric resistance or radiationfurnace with the specimen in air at atmospheric pressure unlessother media are specifically agreed upon in advance.NOTE 2The media in which the specimens are tested may have aconsiderable effect on the results of tests. This is particularly true when theproperties are infl

32、uenced by oxidation or corrosion during the test.5.3 Temperature-Measuring Apparatus:5.3.1 The method of temperature measurement must besufficiently sensitive and reliable to ensure that the temperatureof the specimen is within the limits specified in 9.4.4.5.3.2 Temperature should be measured with

33、thermocouplesin conjunction with the appropriate temperature indicatinginstrumentation.NOTE 3Such measurements are subject to two types of error. Ther-mocouple calibration and instrument measuring errors initially introduceuncertainty as to the exact temperature. Secondly both thermocouples andmeasu

34、ring instruments may be subject to variation with time. Commonerrors encountered in the use of thermocouples to measure temperaturesinclude: calibration error, drift in calibration due to contamination ordeterioration with use, lead-wire error, error arising from method ofattachment to the specimen,

35、 direct radiation of heat to the bead, heat-conduction along thermocouple wires, etc.5.3.3 Temperature measurements should be made with ther-mocouples of known calibration. Representative thermo-couples should be calibrated from each lot of wires used formaking base-metal thermocouples. Except for r

36、elatively lowtemperatures of exposure, base-metal thermocouples are sub-ject to error upon reuse, unless the depth of immersion andtemperature gradients of the initial exposure are reproduced.Consequently base-metal thermocouples should be verified bythe use of representative thermocouples and actua

37、l thermo-couples used to measure specimen temperatures should not beverified at elevated temperatures. Base-metal thermocouples3Subcommittee E28.10 on Effect of Elevated Temperature on Properties requestsfactual information on the effect of nonaxiality of loading on test results.E21092also should no

38、t be reused without clipping back to remove wireexposed to the hot zone and rewelding. Any reuse of base-metal thermocouples after relatively low-temperature use with-out this precaution should be accompanied by recalibrationdata demonstrating that calibration was not unduly affected bythe condition

39、s of exposure.5.3.3.1 Noble metal thermocouples are also subject to errorsdue to contamination, etc., and should be periodically annealedand verified. Thermocouples should be kept clean prior toexposure and during use at elevated temperatures.5.3.3.2 Measurement of the emf drift in thermocouplesduri

40、ng use is difficult. When drift is a problem during tests, amethod should be devised to check the readings of thethermocouples on the specimen during the test. For reliablecalibration of thermocouples after use the temperature gradientof the testing furnace must be reproduced during the recalibra-ti

41、on.5.3.4 Temperature-measuring, controlling, and recording in-struments should be verified periodically against a secondarystandard, such as a precision potentiometer and if necessaryre-calibrated. Lead-wire error should be checked with the leadwires in place as they normally are used.5.4 Extensomet

42、er System:5.4.1 Practice E83, is recommended as a guide for selectingthe required sensitivity and accuracy of extensometers. Fordetermination of offset yield strength at 0.1 % or greater, aClass B-2 extensometer may be used. The extensometer shouldmeet the requirements of Practice E83and should, in

43、addition,be tested to assure its accuracy when used in conjunction witha furnace at elevated temperature. One such test is to measureat elevated temperature the stress and strain in the elastic rangeof a metal of known modulus of elasticity. Combinations ofstress and temperature which will result in

44、 creep of thespecimen during the extensometer system evaluation should beavoided.NOTE 4If an extensometer of Class B-2 or better is attached to thereduced section of the specimen, the slope of the stress-strain curve willusually be within 10 % of the modulus of elasticity.5.4.2 Non-axiality of loadi

45、ng is usually sufficient to causesignificant errors at small strains when strain is measured ononly one side of the specimen.4Therefore, the extensometershould be attached to and indicate strain on opposite sides ofthe specimen. The reported strain should be the average of thestrains on the two side

46、s, either a mechanical or electricalaverage internal to the instrument or a numerical average oftwo separate readings.5.4.3 When feasible the extensometer should be attacheddirectly to the reduced section of the specimen. When neces-sary, other arrangements (discussed in 9.6.3) may be used byprior a

47、greement of the parties concerned. For example, specialarrangements may be necessary in testing brittle materialswhere failure is apt to be initiated at an extensometer knifeedge.5.4.4 To attach the extensometer to miniature specimensmay be impractical. In this case, separation of the specimenholder

48、s or crossheads may be recorded and used to determinestrains corresponding to the 0.2 % offset yield strength. Thevalue so obtained is of inferior accuracy and must be clearlymarked as “approximate yield strength.” The observed exten-sion should be adjusted by the procedure described in 9.6.3 and10.

49、1.3.5.4.5 The extensometer system should include a means ofindicating strain rate.NOTE 5The strain rate limits listed in 9.6 are difficult to maintainmanually by using equipment which has a pacer disk and a follower hand.Equipment that makes timing marks on the edge of the force-strain recordrequires some trial and error to set the machine controls to give thespecified rate during yielding. Such marks are, however, very useful indetermining the strain rate after test. Convenient pacers, recently offeredby several manufacturers, work on the principle of an indicating tach