1、Designation: E1941 10 (Reapproved 2016)Standard Test Method forDetermination of Carbon in Refractory and Reactive Metalsand Their Alloys by Combustion Analysis1This standard is issued under the fixed designation E1941; the number immediately following the designation indicates the year oforiginal ad
2、option or, in the case 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.1. Scope1.1 This test method applies to the determination of carbonin refractory a
3、nd reactive metals and their alloys in quantitiesfrom 20 g to 500 g. This corresponds to mass fractionsranging from 0.004 wt % to 0.100 wt % for a 0.5 g sample (seeNote 1).NOTE 1Actual quantitative range might vary from manufacturer tomanufacturer and according to sample mass. Samples of higher mass
4、 mayallow for proportionally lower detection limits provided complete com-bustion of the sample is assured.1.2 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 a
5、nd health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in Section 9.2. Referenced Documents2.1 ASTM Standards:2E50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, a
6、ndRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, see Termi
7、nology E135.4. Summary of Test Method4.1 The metal specimen, contained in a single-use ceramiccrucible, is ignited (combusted) in an oxygen atmosphere in aninduction furnace. The carbon in the specimen is oxidized tocarbon dioxide or carbon monoxide, or both, and is eventuallycarried to the analyzer
8、/detector. The amount of carbon presentis electronically processed and is displayed by the analyzerreadout.4.2 This test method is written for use with commerciallyavailable analyzers equipped to carry out the above operationsand calibrated using commercially available reference materi-als of known
9、carbon content.5. Significance and Use5.1 This test method is intended to test for compliance withcompositional specifications. It is assumed that all who use thismethod will be trained analysts capable of performing commonlaboratory procedures skillfully and safely. It is expected thatthe work will
10、 be performed in a properly equipped laboratory.6. Interferences6.1 The elements ordinarily present in these alloys do notinterfere. Halides that are present in some sponge type sampleswill cause low carbon recovery.7. Apparatus7.1 Combustion Furnace and Measurement Apparatus, au-tomatic carbon dete
11、rminator, consisting of an induction fur-nace; a dust/debris removal trap; an analytical gas streampurification system; an infrared detection system; and anautomatic readout (see Note 2).NOTE 2Several models of commercial carbon determinators areavailable and presently in use in industry. Each has i
12、ts own unique designcharacteristics and operational requirements. Consult the instrumentmanufacturers instruction manuals for operational details.7.2 Oxygen Tank and Regulator.7.3 Ceramic Crucibles and Lids, that meet or exceed theinstrument manufacturers specifications. Use of lids is op-tional. If
13、 they are used, they should have holes in them.7.4 Crucible Tongs, capable of handling recommended cru-cibles.7.5 Balance, capable of weighing to the nearest milligram.7.6 Furnace, capable of reaching and sustaining a tempera-ture of at least 700 C.1This test method is under the jurisdiction of ASTM
14、 Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.06 on Ti, Zr, W, Mo, Ta, Nb, Hf, Re.Current edition approved Dec. 1, 2016. Published December 2016. Originallyapproved in 1998. Last previous edition approved in 2010 as
15、E1941 10. DOI:10.1520/E1941-10R16.2For 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 standards Document Summary page onthe ASTM website.Copyright ASTM Internationa
16、l, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides
17、and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.18. Reagents8.1 Acetone (A.C.S. Reagent, or other suitable, degreasingreagents).8.2 Copper Accelerator, low carbon (see Note 3).8.3 High Purity Iron Chip Accelerator, low carbon (seeNote 3).8.4 Mag
18、nesium Perchlorate (Anhydrone), purity as speci-fied by equipment manufacturer.8.5 Oxygen, high purity (as specified by equipment manu-facturer).8.6 Tin Accelerator, low carbon (see Note 3).8.7 Tungsten Accelerator, low carbon (see Note 3).8.8 Sodium Hydroxide on Clay Base, commonly known asAscarite
19、 III (purity as specified by equipment manufacturer).8.9 Reference Materials, with known carbon content.NOTE 3The total carbon content of all accelerators used must besufficiently low to allow for blanking as described in Section 12.9. Hazards9.1 For hazards to be observed in the use of certain reag
20、entsand equipment in this test method, refer to Practices E50.9.2 Use care when handling hot crucibles and operatingfurnaces to avoid personal injury by either burn or electricalshock.10. Preparation of Apparatus10.1 Make a minimum of two determinations to conditionthe instrument as directed in Sect
21、ion 12 before attempting tocalibrate the system or determine the blank.10.2 Crucible and Lid PreparationCommercially avail-able crucibles and lids (Note 4) often contain levels of carbonsufficient to adversely affect results. To minimize this problem,crucibles and lids may be heat treated prior to u
22、se to removecontamination. Heating to 700 C to 800 C for at least 2 h orto 900 C to 1000 C for at least 1 h. has been determined to beeffective. Other heating conditions may be specified if there isdata supporting the effectiveness of the time and temperatureused on removing contaminants. Remove the
23、 crucibles and lidsfrom the furnace and allow them to cool (see Note 5). Use ofa desiccator or other covered container for storage is recom-mended to minimize the potential for contamination. Handleprepared crucibles only with clean crucible tongs.NOTE 4The use of lids is optional. If they are used,
24、 they should beprepared and stored in the same manner as the crucibles. If they are notused, references to them in this standard may be ignored.NOTE 5Crucibles and lids must be used within a specified time periodof being removed from the furnace. Four hours has been found to be anacceptable period,
25、but a longer time may be specified by the test facilityif supporting data are kept on file. If crucibles or lids, or both, are not usedwithin the specified time period after removing them from the furnace,they shall be reheated as described in 10.2.11. Sample Preparation11.1 The sample selected shal
26、l be representative of thematerial to be analyzed.11.2 Nibble, drill, shear, or machine a clean sample so thatpieces are uniform in size and will fit into the ceramic cruciblewithout extending over the rim.11.3 If necessary, wash the pieces in acetone or othersolvents (Note 6) to remove any oil, gre
27、ase, or cutting fluidcontamination. For heavier contamination, the sample may bewashed in a soap solution or in a sonic cleaner, or both, andrinsed with a solvent. Decant the solvent and dry the sample.Care should be taken to ensure complete removal of solvents orcleaners, especially from porous sam
28、ples, which may trapcleaning liquids, biasing results. Store the clean dried samplesin a manner that minimizes the potential for contamination.NOTE 6Other solvents may be alternative organic solvents, inorganicsolvents or inorganic acids that are capable of removing oil, grease ormachining fluids.12
29、. Calibration12.1 Calibration Reference MaterialsThe calibration ref-erence materials (RMs) will consist of one or more commercialRMs of known carbon content (the high RM value shouldslightly exceed that of the unknown). Use appropriateaccelerators, for example one scoop (approximately 1 g) ofiron c
30、hip accelerator and one scoop (approximately 1.5 g) ofcopper accelerator (Note 7) in a prepared crucible, plus aprepared crucible lid.NOTE 7Users of simultaneous carbon-sulfur determinators should beaware that copper accelerator will have a negative effect on the sulfurresult caused by the formation
31、 of copper sulfide. Other acceleratorcombinations that allow for complete combustion without the use ofcopper may be used if data supporting the effectiveness of the alternateaccelerators is available. The combination of 3 parts iron, 3 parts tungsten,and 2 parts tin has been found effective for car
32、bon and sulfur.12.2 Crucible BlankThe crucible blank will consist of acrucible and lid prepared the same way as those used forsamples, containing the same accelerator as that used forsamples.12.2.1 Prepare four crucible blanks as described in 12.2.12.2.2 Follow the blank calibration procedure as det
33、ailed inthe manufacturers instruction manual, using at least 3 blanks.12.2.3 Analyze one additional blank to verify the blankcalibration. The blank value should be within 5 g of theadjusted zero.12.2.4 Prepare at least three specimens of a referencematerial for each calibration point as directed in
34、Section 11 and12.1. Calibrate the instrument in a manner consistent with theinstructions in the manufacturers operating manual.12.2.5 Prepare at least one additional RM specimen tovalidate the calibration. The obtained value shall agree with thecertificate value within the range given by the publish
35、eduncertainty or it shall agree within the limits of a predictioninterval calculated using Eq 1. The prediction interval isdefined as the range of values bounded by the analysis value pand the analysis value +p. If the prediction interval does notencompass the certified value, determine and correct
36、the cause,and repeat calibration (Note 8). Either acceptance limit crite-rion is acceptable for routine operation.NOTE 8See the instrument manufacturers instructions concerning thetroubleshooting and correcting of errant calibration.E1941 10 (2016)2p 5 tS111=nDs (1)where:p = one-half the prediction
37、interval,n = number of replicates used in 12.2.4,t = students t chosen for the 95 % confidence level for nreplicate measurements (for example: t = 4.30 whenn = 3, 3.18 when n = 4, 2.78 when n = 5), ands = standard deviation of n replicates in 12.2.4 (Note 9).NOTE 9Here, s should be comparable to Sm,
38、 the repeatability standarddeviation, given in Table 1.Ifs Sm, there is evidence that therepeatability of the particular instrument is not acceptable for use with thistest method. The user should determine and correct the cause, and repeat12.2.1 through 12.2.3.12.2.6 One or more continuing calibrati
39、on verificationsmust be performed prior to and upon completion of a period ofcontinuous operation, and throughout this period with a pre-determined minimum frequency to be established by eachindividual test facility. The acceptance range for the verifica-tion material may be the limits stated on the
40、 certified value forthe reference material, or may be calculated using Eq 1 and thes and n values for multiple analyses of the verification material.If a continuing calibration verification indicates an out ofcalibration condition, stop analysis. Results must be supportedby acceptable preceding and
41、subsequent verifications to bereported.12.2.7 It is the responsibility of the user to document thefrequency of blank determination (12.2.2), routine calibrationand confirmation (12.2.4) and the conditions under whichblank determination and/or recalibration beyond this frequencyis required (examples
42、may include changing reagents, begin-ning use of a new batch of crucibles, changing gas cylinders ora personnel shift change).13. Procedure13.1 Make any pre-operational instrument checks as recom-mended by the instrument manufacturer.13.2 Set the analyzer to the operate mode.13.3 Prepare a specimen
43、as directed in Section 11 and placeit in a prepared crucible (see 10.2), add accelerator, and coverwith an optional prepared lid (see 10.2) (see Note 4).13.4 Enter the specimen mass as recommended by themanufacturer. If specimen identification feature is provided bymanufacturer, enter identification
44、.13.5 Place the crucible plus specimen on the inductionfurnace pedestal and close the furnace.13.6 Start the analysis cycle, referring to the manufacturersrecommended procedure.14. Calculation14.1 The carbon reading (result) will be direct if the blankand specimen weight have been correctly entered
45、in theappropriate portion of the analyzer (see Note 10).NOTE 10If the analyzer does not offer these functions, calculate thecarbon content by Eq 2 for single standard (one reference material and oneblank) calibrations, or Eq 3 for linear (two or more reference materials andone blank) calibrations:ca
46、rbon, mg/kg 5 A 2 B!/C (2)where:A = g of carbon in specimen,B = g of carbon in blank, andC = specimen weight (in g).Y 5 mX 5 b (3)where:Y = measurement response,m = slope,X = mass fraction of carbon in the calibration material, andb = Y intercept.Calculation of the calibration function shall be done
47、 using alinear least squares regression. Some manufacturers recom-mend the use of a curve weighting factor where the Calibrationmaterial value is derived as 1/X. It is acceptable to use this typeof curve weighting.TABLE 1 Carbon in Refractory and Reactive Metals and Their AlloysMetal IdentityCarbonf
48、ound, ppmMinimumSD (SM,Practice E1601)Repro-ducibilitySD (SR,Practice E1601)Repro-ducibilityIndex (R,Practice E1601)Rrel%Zirconium 3500701 24 3 6 17 71660b 346 7 15 42 12SRM 360a 151 6 10 27 18Titanium #1 654 8 32 90 14#2 72 3 9 27 37SRM 176 132 6 19 52 40Hafnium 420b 194 12 26 74 38Niobium 752 19 3
49、 7 19 100SP5943 327 4 13 36 11Molybdenum 5657 22 4 7 20 905654 38 3 10 27 72Tungsten C-6 56 3 10 28 50C-3 111 3 9 24 21Tantalum A 119 3 7 20 17B37 82 60Nine laboratories contributed results for all the samples included in this study.E1941 10 (2016)314.2 Since most modern commercially available instru-ments calculate mass fractions directly, including correctionsfor blank and sample mass, manual calculations by the analystare not required. If the analyzer does not compensate for blankand sample mass values, then use the following equation:carbon,
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