1、Designation: E2792 13Standard 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 graphitecrucible, is heated to just below the melting point to drive offthe surface hydrogen. The sample is then heated to just beyondthe melting point under a flowing carrier
7、 gas atmosphere.Hydrogen present in the sample is released as molecularhydrogen into the flowing gas stream. The released hydrogen isseparated from other liberated gases such as carbon monoxideand subsequently measured in a thermal conductivity cell.4.2 Calibration is made using gas dosing with eith
8、er 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 all
9、oys 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 capable
10、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 ApparatusAutom
11、atic hydro-gen analyzer, consisting of an electrode furnace or inductionfurnace; 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 commercial an
12、alyzersare 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) recomme
13、nded by the manufac-turer of the instrument.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 E01.04 on Aluminum and Magnesium.Current edition approved April 1, 2013. Publis
14、hed June 2013. Originallyapproved in 2011. Last previous edition approved in 2011 as E2792-11. DOI:10.1520/E2791-13.2For 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
15、the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.3 Quartz Crucibles, for analysis of steel reference mate-rials on some instrument types. Use the crucible design(s)recommended by
16、 the manufacturer of the instrument.7.4 Crucible Tongs, capable of handling recommended cru-cibles.8. Reagents and Materials8.1 AcetoneReagent Grade or ACS certified grade orhigher purity.8.2 Ethyl AlcoholReagent Grade orACS certified grade orhigher purity.8.3 Isopropyl AlcoholReagent Grade or ACS c
17、ertifiedgrade or higher purity.8.4 Sodium Hydroxide on Clay (Commonly known as As-carite II).8.5 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 argon, nitrogen, helium or hydrogen. Gas purityre
18、quirements shall be specified by the instrument manufacturer.8.6 Magnesium Perchlorate (commonly known as Anhy-drone).8.7 Molecular Sieve, as specified by the instrument manu-facturer.8.8 Schutze ReagentIodine pentoxide on granular silica,purity as specified by the instrument manufacturer.8.9 Copper
19、 Wire, to convert CO to CO2in thermal conduc-tivity cell instruments. Characteristics should be specified bythe instrument manufacturer.8.10 Glass wool, used to pack reagents.8.11 OMIPurifier TubeOrganolithium polymer used bysome instruments to remove O2, water vapor, CO, CO2, mostsulfur compounds,
20、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 equipment to avoid personal injury by either burn orele
21、ctrical 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 instrument manufacturers recom-mendations.10.3 Set th
22、e 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 pretreatment power settings(commonly called outgas
23、), 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 to this application guidance literaturefor assis
24、tance 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 to obtain the optimum signal to noiseratio for
25、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 molten aluminumduring casting or from the appr
26、opriate 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, voids, pits, and otherdefects that may lead to err
27、oneously 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 product and mayalso accumulate around defects sometim
28、es 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 recommended. Thesize of the cube needed depends on
29、 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 recommended. Smaller samples may beanalyzed, ho
30、wever, 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 hydrogen.11.3 The sample should be machined using
31、 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. Diamondtipped tool bits and use of ethyl alcohol or
32、isopropyl alcohollubricant during machining may be used to improve the surface3C.E. Ransley and D.E.J. Talbot, “The Routine Determination of the HydrogenContent of Aluminum and Aluminum Alloys by the Hot-Extraction Method“.Journal of the Institute of Metals, Vol. 84, 1955-1956, 445.E2792 132finish.
33、The average surface roughness for samples machinedusing a diamond tipped tool bit and alcohol lubricant istypically 40 micro inches to 50 micro inches. Surface area ofthe sample will increase as the surface roughness increases.Increased surface area will result in higher surface hydrogenreadings and
34、 in extreme cases may affect the bulk hydrogenanalysis.11.4 Specimens must be handled with crucible tongs or in amanner that prevents surface contamination. Samples may berinsed in acetone, ethyl alcohol, or isopropyl alcohol if surfacecontamination is suspected.12. Calibration12.1 Calibration can b
35、e done by two different 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
36、.1 Both gas dose 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 manufactur
37、ers guide-lines.12.2.3 If the average blank value exceeds 0.000 mg/kg 60.005 mg/kg then determine the cause, make necessarycorrections, and repeat 12.2.2. Refer to the instrument manu-facturers instructions concerning the troubleshooting andcorrection of blank determinations not meeting the abovecri
38、terion.12.2.4 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 determin
39、ations as directed 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 manufactu
40、rer. Some instruments 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 instru
41、ment has not been in use for four hoursand/or the carrier gas has been changed.12.4 Calibration Using Reference MaterialSince there areno known reference materials for hydrogen in aluminum alloysthe instrument may be calibrated with appropriate steel, nickel,titanium or other metal reference materia
42、ls. Refer to themanufacturers 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
43、crucibles is used 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 re
44、ference material (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 s
45、teel, nickel, 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 instru
46、ment is capable 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
47、set the calibration 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
48、 method is largely 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 material
49、s. If using aluminum 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 implemented 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 pred
