1、Designation: E1941 10Standard 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 adoption or, in the
2、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 and reactive metals
3、 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 mayallow for prop
4、ortionally 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 and health practice
5、s 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, andRelated Material
6、sE135 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 Terminology E135.4. Sum
7、mary 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/detector. The amo
8、unt 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 carbon content.5.
9、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 be performed in a
10、 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 determinator, consisti
11、ng 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 its own unique desi
12、gncharacteristics 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 they are used, th
13、ey should have holes in them.1This test method is under the jurisdiction of ASTM 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, 2010. Published Febru
14、ary 2011. Originallyapproved in 1998. Last previous edition approved in 2004 as E1941 04. DOI:10.1520/E1941-10.2For 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 s
15、tandards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.4 Crucible Tongs, capable of handling recommended cru-cibles.7.5 Balance, capable of weighing to the nearest milligram.7.6 Furnace, c
16、apable of reaching and sustaining a tempera-ture of at least 700 C.8. 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 Magnesium Perchlorate (Anhydrone), purit
17、y 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 III (purity as specified by equipmen
18、t 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 reagentsand equipment in this test method
19、, 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 Section 12 before attempting tocalibrate
20、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 use to removecontamination. Heating to
21、 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 crucibles and lidsfrom the furnace a
22、nd 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, they should beprepared and stored in
23、 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, but a longer time may be specified by
24、 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 shall be representative of thematerial to
25、 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, grease, or cutting fluidcontamination. F
26、or 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 samples, which may trapcleaning liquids,
27、 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. Calibration12.1 Calibration Referen
28、ce 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 appropriate accel-erators, for example one scoop (approximately 1 g) of iron chipaccelerator and one scoop (appr
29、oximately 1.5 g) of copperaccelerator (Note 7) in a prepared crucible, plus a preparedcrucible 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 of copper sulfide. Other accelerat
30、orcombinations 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 carbon and sulfur.12.2 Crucible BlankT
31、he 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 detailed inthe manufacturers instructi
32、on 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 Section 11 and12.1. Calibrate the i
33、nstrument 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 publisheduncertainty or it shall agree wit
34、hin 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 the cause,E1941 102and repeat calib
35、ration (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.p 5 t S1 11=nD s (1)where:p = one-half the prediction interval,n = number of replicates used
36、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, the repeatability standarddeviation, g
37、iven in Table 1.Ifs Sm, there is evidence that the repeat-ability of the particular instrument is not acceptable for use with this testmethod. The user should determine and correct the cause, and repeat12.2.1 through 12.2.3.12.2.6 One or more continuing calibration verificationsmust be performed pri
38、or 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 certified value forthe reference mat
39、erial, 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 subsequent verifications to bereporte
40、d.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 may include changing reagents, begin-
41、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 as directed in Section 11 and placeit
42、 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.13.5 Place the crucible plus specime
43、n 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 in theappropriate portion of the anal
44、yzer (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:carbon, mg/kg 5 A B! / C (2)where:A = g
45、 of carbon in specimen,B = g of carbon in blank, andC = specimen weight (in g).TABLE 1 Carbon in Refractory and Reactive Metals and Their AlloysMetal IdentityCarbonfound, ppmMinimumSD (SM,Practice E1601)Repro-ducibilitySD (SR,Practice E1601)Repro-ducibilityIndex (R,Practice E1601)Rrel%Zirconium 3500
46、701 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 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
47、 7 20 17B37 82 60Nine laboratories contributed results for all the samples included in this study.E1941 103Y 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 using al
48、inear 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.14.2 Since most modern commercially available instru-ments calculate mass fractions directly, i
49、ncluding 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, % 5FA B! 3CDG(4)where:A = digital volt meter (DVM) reading for specimen,B = DVM reading for blank,C = mass compensator setting, andD = specimen mass, g.15. Precision and Bias15.1 PrecisionNine laboratories cooperated in testing15 samples representing 7 different matrices. The data obtainedis presented in Table 1. The testing and statis
