ASTM E2792-11
(Test Method)Standard Test Method for Determination of Hydrogen in Aluminum and Aluminum Alloys by Inert Gas Fusion
Standard Test Method for Determination of Hydrogen in Aluminum and Aluminum Alloys by Inert Gas Fusion
SIGNIFICANCE AND USE
This test method is intended for the routine testing of aluminum and aluminum alloys to qualitatively determine the concentration of hydrogen in aluminum and aluminum alloys. It is not intended to verify compliance with compositional specifications because of the lack of certified reference materials. It is assumed that all who use this test method will be trained analysts capable of performing common laboratory procedures skillfully and safely. It is expected that the work will be performed in a properly equipped laboratory.
SCOPE
1.1 This test method applies to the determination of hydrogen in aluminum and aluminum alloys in concentrations from 0.05 mg/kg to 1 mg/kg.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E2792 − 11
StandardTest Method for
Determination of Hydrogen in Aluminum and Aluminum
Alloys by Inert Gas Fusion
This standard is issued under the fixed designation E2792; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Hydrogen present in the sample is released as molecular
hydrogenintotheflowinggasstream.Thereleasedhydrogenis
1.1 This test method applies to the determination of hydro-
separated from other liberated gases such as carbon monoxide
gen in aluminum and aluminum alloys in concentrations from
and subsequently measured in a thermal conductivity cell.
0.05 mg/kg to 1 mg/kg.
4.2 Calibration is made using gas dosing with either helium
1.2 This standard does not purport to address all of the
orhydrogenorreferencematerialsofknownhydrogencontent.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.3 This test method is written for use with commercial
priate safety and health practices and determine the applica-
analyzers equipped to carry out the above operations automati-
bility of regulatory limitations prior to use.
cally.
5. Significance and Use
2. Referenced Documents
5.1 This test method is intended for the routine testing of
2.1 ASTM Standards:
aluminum and aluminum alloys to qualitatively determine the
E50 Practices for Apparatus, Reagents, and Safety Consid-
concentration of hydrogen in aluminum and aluminum alloys.
erations for Chemical Analysis of Metals, Ores, and
It is not intended to verify compliance with compositional
Related Materials
specifications because of the lack of certified reference mate-
E135 Terminology Relating to Analytical Chemistry for
rials. It is assumed that all who use this test method will be
Metals, Ores, and Related Materials
trained analysts capable of performing common laboratory
E177 Practice for Use of the Terms Precision and Bias in
procedures skillfully and safely. It is expected that the work
ASTM Test Methods
will be performed in a properly equipped laboratory.
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
6. Interferences
E1914 Practice for Use of Terms Relating to the Develop-
6.1 The elements ordinarily present in aluminum and alu-
ment and Evaluation of Methods for Chemical Analysis
minum alloys do not interfere.
3. Terminology
7. Apparatus
3.1 Definitions—For definitions of terms used in this test
7.1 FusionandMeasurementApparatus—Automatichydro-
method, see Terminology E135 and E1914.
gen analyzer, consisting of an electrode furnace or induction
furnace; analytical gas stream; impurity removal systems;
4. Summary of Test Method
auxiliary purification systems and either a thermal conductivity
4.1 The specimen, contained in a high-purity graphite
cell hydrogen measurement system or an infrared hydrogen
crucible, is heated to just below the melting point to drive off
measurement system. Several models of commercial analyzers
the surface hydrogen. The sample is then heated to just beyond
are available and presently in use in industry. Each has its own
the melting point under a flowing carrier gas atmosphere.
unique design characteristics and operational requirements.
Consult the instrument manufacturer’s instructions for opera-
tional details.
This test method is under the jurisdiction of ASTM Committee E01 on
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
7.2 Graphite Crucibles, machined from high-purity graph-
responsibility of Subcommittee E01.04 on Aluminum and Magnesium.
ite. Use the crucible design(s) recommended by the manufac-
Current edition approved Nov. 1, 2011. Published December 2011. DOI:
turer of the instrument.
10.1520/E2791-11.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
7.3 Quartz Crucibles, for analysis of steel reference mate-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
rials on some instrument types. Use the crucible design(s)
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. recommended by the manufacturer of the instrument.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2792 − 11
7.4 Crucible Tongs, capable of handling recommended cru- 10.5.2 If the instrument is capable; optimize the crucible
cibles. pretreatment time and power settings to achieve a stable blank
(see 12.2.2).
8. Reagents and Materials
10.5.3 If the instrument is capable; optimize the analysis
8.1 Acetone, Low-Residue.
time and power settings to obtain the optimum signal to noise
ratio for the analysis of aluminum alloys.
8.2 Sodium Hydroxide on Clay (Commonly known as As-
10.5.4 It will not be necessary to optimize the analysis
carite II).
set-uproutinely.Storethesettingsintotheinstrumenthardware
8.3 High-Purity Gas (99.99 %)—Argon, nitrogen, and he-
or software for routine use.
lium or hydrogen (Note 1).
NOTE 1—Carrier and dosing gases vary by instrument model and 11. Sampling and Sample Preparation
include high-purity argon, nitrogen, helium or hydrogen. Gas purity
11.1 Samples can be taken either from molten aluminum
requirements shall be specified by the instrument manufacturer.
during casting or from the appropriate areas of finished
8.4 Magnesium Perchlorate (commonly known as Anhy-
product.
drone).
11.1.1 Samples from molten aluminum should be taken
8.5 Molecular Sieve, as specified by the instrument manu- 3
using the procedure described by Ransley and Talbot. Briefly,
facturer.
a ladle is used to pour molten metal into a copper sampler that
8.6 Schutze Reagent—Iodine pentoxide on granular silica, is designed to minimize porosity, cracks, voids, pits, and other
purity as specified by the instrument manufacturer. defects that may lead to erroneously high hydrogen results.
11.1.2 Samples from Cast or Finished Product—Samples
8.7 Copper Wire, to convert CO to CO in thermal conduc-
from cast or finished product should be taken from an area that
tivity cell instruments. Characteristics should be specified by
represents the nominal concentration of hydrogen in the piece
the instrument manufacturer.
being sampled. Hydrogen may segregate in product and may
8.8 Glass wool, used to pack reagents.
also accumulate around defects sometimes making it difficult
™
8.9 OMI Purifier Tube—Organolithium polymer used by
to obtain a representative sample. It is incumbent on the user to
some instruments to remove O , water vapor, CO, CO , most
insure that the area selected for sampling is satisfactory. A
2 2
sulfur compounds, most halogen compounds, alcohols, and
cubical piece should be cut from the product using a saw with
phenols to less than 10 ppb from the carrier gas.
a clean blade. Carbide tipped blades are recommended. The
size of the cube needed depends on the final sample size
9. Hazards
required for the instrument.
9.1 Refer to Practices E50 for potential hazards present
11.2 Samples must be of an appropriate size to fit into the
when using this test method.
graphite crucible. In general, the sample should be as close to
9.2 Use care when handling hot crucibles and operating
themaximumsizeforthecrucibleaspossible.Asamplesizeof
electrical equipment to avoid personal injury by either burn or
at least 4 grams is recommended. Smaller samples may be
electrical shock.
analyzed, however, the amount of hydrogen generated will be
smaller and the detection limit will be higher. Smaller samples
10. Preparation of Apparatus
also have a higher surface to bulk hydrogen ratio and the
method parameters may not be ideal for separating the surface
10.1 Assemble the apparatus as recommended by the manu-
facturer. hydrogen from the bulk hydrogen.
10.2 Provide the manufacturer’s recommended electrical
11.3 The sample should be machined using a lathe or
power and gas requirements. Prepare the apparatus for opera-
milling machine to the manufacturers recommended specifica-
tion in accordance with the instrument manufacturer’s recom-
tions.Afine surface is important for obtaining accurate results.
mendations.
Rough surfaces may lead to excessively high surface readings
and may, in extreme cases, cause high bulk results. Diamond
10.3 Set the instrument to the operational mode in accor-
tipped tool bits and use of alcohol lubricant during machining
dance with the instrument manufacturer’s recommendations.
may be used to improve the surface finish.The average surface
10.4 Test the furnace and analyzer to ensure that the gas
roughness for samples machined using a diamond tipped tool
stream meets manufacturer’s requirements for acceptable leak
bit and alcohol lubricant is typically 40 micro inches to 50
rate.
micro inches. Surface area of the sample will increase as the
10.5 Optimize the crucible pretreatment power settings surface roughness increases. Increased surface area will result
(commonly called outgas), the surface and analysis power
in higher surface hydrogen readings and in extreme cases may
settings, crucible pretreatment time and analysis integration affect the bulk hydrogen analysis.
time for aluminum alloys.
10.5.1 Most manufacturers offer application guidance on
appropriate settings to achieve optimum performance for
C.E. Ransley and D.E.J. Talbot, "The Routine Determination of the Hydrogen
aluminum alloys. Refer to this application guidance literature
Content of Aluminum and Aluminum Alloys by the Hot-Extraction Method".
for assistance in determining optimum settings. Journal of the Institute of Metals, Vol. 84, 1955-1956, 445.
E2792 − 11
11.4 Specimens must be handled with crucible tongs or in a each concentration level to be included in the calibration. The
manner that prevents surface contamination. Samples may be specimens must be of an appropriate size to fit into the quartz
rinsed in acetone if surface contamination is suspected. or graphite crucible. The steel, nickel, titanium or other metal
reference materials should have mass fraction of hydrogen
greater than or approximately equal to the unknown samples
12. Calibration
within the scope of this test method (0.05 mg/kg to 1.0 mg/kg).
12.1 Calibration can be done by two different methods; gas
12.4.2 Follow the calibration procedure recommended by
dosing or by the use of certified reference materials. Most
the manufacturer. If the instrument is capable of this function-
instruments used for the analysis of hydrogen in aluminum
ality enter the mass fraction of the hydrogen content of the
alloys are calibrated by gas dosing due to the lack of certified
reference material into the instrument/software. Analyze at
reference materials for hydrogen in aluminum.
least three of the reference material specimens prepared in
12.2 Blank Determination Procedure:
12.4.1.
12.2.1 Both gas dose and reference material calibration
12.4.3 Use the average instrument response obtained for the
require an accurate blank determination. The blank value may
reference materials to set the calibration slope in accordance
be included in the calibration curve or subtracted from all
with the manufacturer’s recommendations.
subsequent determinations.
12.4.4 Confirm the stability of the instrument/calibration by
12.2.2 Make at least three blank determinations using an
analyzing the fourth specimen of the hydrogen reference
empty graphite crucible following the manufacturer’s guide-
material (Note 2).
lines.
NOTE 2—Confirmation of the calibration does not ensure accuracy. The
12.2.3 If the average blank value exceeds 0.000 mg/kg 6
accuracy of this test method is largely dependent upon the absence of bias
0.005 mg/kg then determine the cause, make necessary
in the hydrogen values assigned to the reference materials and upon the
corrections, and repeat 12.2.2. Refer to the instrument manu-
homogeneity of these materials.
facturer’s instructions concerning the troubleshooting and
12.5 Confirm the calibration by analyzing a specimen of
correction of blank determinations not meeting the above
aluminum control material or with steel, nickel, titanium or
criterion.
other metal reference materials. If using aluminum control
12.2.4 Enter the average blank value in into the instrument
material, the results should fall within control limits based on
software following the manufacturers recommended practice.
the final product requirements. If using steel, nickel, titanium
The software will automatically compensate for the blank
or other metal reference materials the results should fall within
value in subsequent calibration and sample analysis.
theuncertaintyprovidedonthecertificationdocumentation.An
12.3 Calibration by Gas Dosing—Prepare at least four gas
alternate procedure can be implemented where this value
dose determinations as directed by the instrument manufac-
should agree with the certified value within the limits of a
turer. Gas doses should have a mass fraction of hydrogen
prediction interval calculated using Eq 1. The prediction
greater than or approximately equal to the unknown samples
interval is defined as the range of values bounded by the
within the scope of this test method (0.05 mg/kg to 1.0 mg/kg).
analysis value -p and the analysis value +p. If the prediction
12.3.1 Follow the gas dose calibration procedure recom-
interval does not encompass the certified value, determine and
mended by the manufacturer. Some instruments have software
correct the cause, and repeat 12.3.1 or 12.4.1 and 12.4.2. See
capabilities that allow multi-point gas dose calibration which
the instrument manufacturer’s instructions concerning the
may improve the accuracy and precision of the calibration over
troubleshooting and correcting of an errant calibration.
the single-point calibration methodology. The gas dose proce-
dure should be repeated before analysis of each group of
p 5 t· 11 ·s (1)
S D
samples or if the instrument has not been in use for four hours
=n
and/or the carrier gas has been changed.
where:
12.4 CalibrationUsingReferenceMaterial—Sincethereare
p = one-half the prediction interval,
no known reference materials for hydrogen in aluminum alloys
n = number of replicates used in 12.4.2,
the instrument may be calibrated with appropriate steel, nickel,
t = student’s t chosen for the 95 % confidence level for n
titanium or other metal reference materials. Refer to the
replicate measurements (for example: n = 3 (degrees of
manufacturer’s application specifications for the power and
freedom = 2) t = 4.303; n =4 (degree
...
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