1、Designation: E2792 11Standard Test Method forDetermination of Hydrogen in Aluminum and AluminumAlloys by Inert Gas Fusion1This standard is issued under the fixed designation E2792; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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 hydro-gen in aluminum and aluminum alloys in concentrations
3、 from0.05 mg/kg to 1 mg/kg.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 practices and determine the applica-bility of regulatory limitations p
4、rior to use.2. Referenced Documents2.1 ASTM Standards:2E50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE177 Practice for Use of the Ter
5、ms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1914 Practice for Use of Terms Relating to the Develop-ment and Evaluation of Methods for Chemical Analysis3. Terminology3.1 DefinitionsFor definitions of terms u
6、sed in this testmethod, see Terminology E135 and E1914.4. Summary of Test Method4.1 The specimen, contained in a high-purity graphite cru-cible, is heated to just below the melting point to drive off thesurface hydrogen. The sample is then heated to just beyond themelting point under a flowing carri
7、er gas atmosphere. Hydro-gen present in the sample is released as molecular hydrogeninto the flowing gas stream. The released hydrogen is separatedfrom other liberated gases such as carbon monoxide andsubsequently measured in a thermal conductivity cell.4.2 Calibration is made using gas dosing with
8、either heliumor hydrogen or reference materials of known hydrogen content.4.3 This test method is written for use with commercialanalyzers equipped to carry out the above operations automati-cally.5. Significance and Use5.1 This test method is intended for the routine testing ofaluminum and aluminum
9、 alloys to qualitatively determine theconcentration of hydrogen in aluminum and aluminum alloys.It is not intended to verify compliance with compositionalspecifications because of the lack of certified reference mate-rials. It is assumed that all who use this test method will betrained analysts capa
10、ble of performing common laboratoryprocedures skillfully and safely. It is expected that the workwill be performed in a properly equipped laboratory.6. Interferences6.1 The elements ordinarily present in aluminum and alu-minum alloys do not interfere.7. Apparatus7.1 Fusion and Measurement ApparatusA
11、utomatic hy-drogen analyzer, consisting of an electrode furnace or induc-tion furnace; analytical gas stream; impurity removal systems;auxiliary purification systems and either a thermal conductivitycell hydrogen measurement system or an infrared hydrogenmeasurement system. Several models of commerc
12、ial analyzersare available and presently in use in industry. Each has its ownunique design characteristics and operational requirements.Consult the instrument manufacturers instructions for opera-tional details.7.2 Graphite Crucibles, machined from high-purity graph-ite. Use the crucible design(s) r
13、ecommended by the manufac-turer of the instrument.7.3 Quartz Crucibles, for analysis of steel reference mate-rials on some instrument types. Use the crucible design(s)recommended by the manufacturer of the instrument.1This test method is under the jurisdiction of ASTM Committee E01 onAnalytical Chem
14、istry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.04 on Aluminum and Magnesium.Current edition approved Nov. 1, 2011. Published December 2011. DOI:10.1520/E2791-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cus
15、tomer 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.7.4 Crucible Tongs, capable of han
16、dling recommended cru-cibles.8. Reagents and Materials8.1 Acetone, Low-Residue.8.2 Sodium Hydroxide on Clay (Commonly known as As-carite II).8.3 High-Purity Gas (99.99 %)Argon, nitrogen, and he-lium or hydrogen (Note 1).NOTE 1Carrier and dosing gases vary by instrument model andinclude high-purity a
17、rgon, nitrogen, helium or hydrogen. Gas purityrequirements shall be specified by the instrument manufacturer.8.4 Magnesium Perchlorate (commonly known as Anhy-drone).8.5 Molecular Sieve, as specified by the instrument manu-facturer.8.6 Schutze ReagentIodine pentoxide on granular silica,purity as spe
18、cified by the instrument manufacturer.8.7 Copper Wire, to convert CO to CO2in thermal conduc-tivity cell instruments. Characteristics should be specified bythe instrument manufacturer.8.8 Glass wool, used to pack reagents.8.9 OMIyPurifier TubeOrganolithium polymer used bysome instruments to remove O
19、2, water vapor, CO, CO2, mostsulfur compounds, most halogen compounds, alcohols, andphenols to less than 10 ppb from the carrier gas.9. Hazards9.1 Refer to Practices E50 for potential hazards presentwhen using this test method.9.2 Use care when handling hot crucibles and operatingelectrical equipmen
20、t to avoid personal injury by either burn orelectrical shock.10. Preparation of Apparatus10.1 Assemble the apparatus as recommended by the manu-facturer.10.2 Provide the manufacturers recommended electricalpower and gas requirements. Prepare the apparatus for opera-tion in accordance with the instru
21、ment manufacturers recom-mendations.10.3 Set the instrument to the operational mode in accor-dance with the instrument manufacturers recommendations.10.4 Test the furnace and analyzer to ensure that the gasstream meets manufacturers requirements for acceptable leakrate.10.5 Optimize the crucible pre
22、treatment power settings(commonly called outgas), the surface and analysis powersettings, crucible pretreatment time and analysis integrationtime for aluminum alloys.10.5.1 Most manufacturers offer application guidance onappropriate settings to achieve optimum performance foraluminum alloys. Refer t
23、o this application guidance literaturefor assistance in determining optimum settings.10.5.2 If the instrument is capable; optimize the cruciblepretreatment time and power settings to achieve a stable blank(see 12.2.2).10.5.3 If the instrument is capable; optimize the analysistime and power settings
24、to obtain the optimum signal to noiseratio for the analysis of aluminum alloys.10.5.4 It will not be necessary to optimize the analysisset-up routinely. Store the settings into the instrument hardwareor software for routine use.11. Sampling and Sample Preparation11.1 Samples can be taken either from
25、 molten aluminumduring casting or from the appropriate areas of finishedproduct.11.1.1 Samples from molten aluminum should be takenusing the procedure described by Ransley and Talbot.3Briefly,a ladle is used to pour molten metal into a copper sampler thatis designed to minimize porosity, cracks, voi
26、ds, pits, and otherdefects that may lead to erroneously high hydrogen results.11.1.2 Samples from Cast or Finished ProductSamplesfrom cast or finished product should be taken from an area thatrepresents the nominal concentration of hydrogen in the piecebeing sampled. Hydrogen may segregate in produc
27、t and mayalso accumulate around defects sometimes making it difficultto obtain a representative sample. It is incumbent on the user toinsure that the area selected for sampling is satisfactory. Acubical piece should be cut from the product using a saw witha clean blade. Carbide tipped blades are rec
28、ommended. Thesize of the cube needed depends on the final sample sizerequired for the instrument.11.2 Samples must be of an appropriate size to fit into thegraphite crucible. In general, the sample should be as close tothe maximum size for the crucible as possible.Asample size ofat least 4 grams is
29、recommended. Smaller samples may beanalyzed, however, the amount of hydrogen generated will besmaller and the detection limit will be higher. Smaller samplesalso have a higher surface to bulk hydrogen ratio and themethod parameters may not be ideal for separating the surfacehydrogen from the bulk hy
30、drogen.11.3 The sample should be machined using a lathe ormilling machine to the manufacturers recommended specifica-tions. A fine surface is important for obtaining accurate results.Rough surfaces may lead to excessively high surface readingsand may, in extreme cases, cause high bulk results. Diamo
31、ndtipped tool bits and use of alcohol lubricant during machiningmay be used to improve the surface finish. The average surfaceroughness for samples machined using a diamond tipped toolbit and alcohol lubricant is typically 40 micro inches to 50micro inches. Surface area of the sample will increase a
32、s thesurface roughness increases. Increased surface area will resultin higher surface hydrogen readings and in extreme cases mayaffect the bulk hydrogen analysis.11.4 Specimens must be handled with crucible tongs or in amanner that prevents surface contamination. Samples may berinsed in acetone if s
33、urface contamination is suspected.3C.E. Ransley and D.E.J. Talbot, 9The Routine Determination of the HydrogenContent of Aluminum and Aluminum Alloys by the Hot-Extraction Method9.Journal of the Institute of Metals, Vol. 84, 1955-1956, 445.E2792 11212. Calibration12.1 Calibration can be done by two d
34、ifferent methods; gasdosing or by the use of certified reference materials. Mostinstruments used for the analysis of hydrogen in aluminumalloys are calibrated by gas dosing due to the lack of certifiedreference materials for hydrogen in aluminum.12.2 Blank Determination Procedure:12.2.1 Both gas dos
35、e and reference material calibrationrequire an accurate blank determination. The blank value maybe included in the calibration curve or subtracted from allsubsequent determinations.12.2.2 Make at least three blank determinations using anempty graphite crucible following the manufacturers guide-lines
36、.12.2.3 If the average blank value exceeds 0.000 mg/kg 60.005 mg/kg then determine the cause, make necessary correc-tions, and repeat 12.2.2. Refer to the instrument manufacturersinstructions concerning the troubleshooting and correction ofblank determinations not meeting the above criterion.12.2.4
37、Enter the average blank value in into the instrumentsoftware following the manufacturers recommended practice.The software will automatically compensate for the blankvalue in subsequent calibration and sample analysis.12.3 Calibration by Gas DosingPrepare at least four gasdose determinations as dire
38、cted by the instrument manufac-turer. Gas doses should have a mass fraction of hydrogengreater than or approximately equal to the unknown sampleswithin the scope of this test method (0.05 mg/kg to 1.0 mg/kg).12.3.1 Follow the gas dose calibration procedure recom-mended by the manufacturer. Some inst
39、ruments have softwarecapabilities that allow multi-point gas dose calibration whichmay improve the accuracy and precision of the calibration overthe single-point calibration methodology. The gas dose proce-dure should be repeated before analysis of each group ofsamples or if the instrument has not b
40、een in use for four hoursand/or the carrier gas has been changed.12.4 Calibration Using Reference MaterialSince thereare no known reference materials for hydrogen in aluminumalloys the instrument may be calibrated with appropriate steel,nickel, titanium or other metal reference materials. Refer to t
41、hemanufacturers application specifications for the power andtime settings for each base metal. It is not necessary to performthe reference material calibration procedure each time that theanalysis procedure is performed. However, the calibration mustbe verified when a different lot of crucibles is u
42、sed or thesystem has not been in use for 4 hours, and/or the carrier gassupply has been changed. Verification should consist of ana-lyzing at least one aluminum control material or at least onesteel, nickel, titanium or other reference material (12.5) and atleast one linearity check reference materi
43、al (12.6).12.4.1 Prepare at least four approximately 1 g specimens ofa steel, nickel, titanium or other metal reference materials foreach concentration level to be included in the calibration. Thespecimens must be of an appropriate size to fit into the quartzor graphite crucible. The steel, nickel,
44、titanium or other metalreference materials should have mass fraction of hydrogengreater than or approximately equal to the unknown sampleswithin the scope of this test method (0.05 mg/kg to 1.0 mg/kg).12.4.2 Follow the calibration procedure recommended bythe manufacturer. If the instrument is capabl
45、e of this function-ality enter the mass fraction of the hydrogen content of thereference material into the instrument/software. Analyze atleast three of the reference material specimens prepared in12.4.1.12.4.3 Use the average instrument response obtained for thereference materials to set the calibr
46、ation slope in accordancewith the manufacturers recommendations.12.4.4 Confirm the stability of the instrument/calibration byanalyzing the fourth specimen of the hydrogen referencematerial (Note 2).NOTE 2Confirmation of the calibration does not ensure accuracy. Theaccuracy of this test method is lar
47、gely dependent upon the absence of biasin the hydrogen values assigned to the reference materials and upon thehomogeneity of these materials.12.5 Confirm the calibration by analyzing a specimen ofaluminum control material or with steel, nickel, titanium orother metal reference materials. If using al
48、uminum controlmaterial, the results should fall within control limits based onthe final product requirements. If using steel, nickel, titaniumor other metal reference materials the results should fall withinthe uncertainty provided on the certification documentation.Analternate procedure can be impl
49、emented where this valueshould agree with the certified value within the limits of aprediction interval calculated using Eq 1. The predictioninterval is defined as the range of values bounded by theanalysis value -p and the analysis value +p. If the predictioninterval does not encompass the certified value, determine andcorrect the cause, and repeat 12.3.1 or 12.4.1 and 12.4.2. Seethe instrument manufacturers instructions concerning thetroubleshooting and correcting of an errant calibration.p 5 t S1 11=nD s (1)where:p = one-half the prediction interval,n = number
