ASTM E1251-94(1999)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E 1251 – 94 (Reapproved 1999)
Standard Test Method for
Optical Emission Spectrometric Analysis of Aluminum and
Aluminum Alloys by the Argon Atmosphere, Point-to-Plane,
Unipolar Self-Initiating Capacitor Discharge
This standard is issued under the fixed designation E 1251; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.3 This standard does not purport to address all of the
safety problems, if any, associated with its use. It is the
1.1 This test method provides for the optical emission
responsibility of the user of this standard to establish appro-
spectrometric analysis of aluminum and aluminum alloys, in
priate safety and health practices and determine the applica-
cast or wrought form, for the following elements in the
bility of regulatory limitations prior to use. Specific safety
concentration ranges indicated:
hazard statements are given in 8.2 and Section 10.
Element Concentration, Range, %
2. Referenced Documents
Silicon 0.001 to 24.0
Copper 0.001 to 20.0
2.1 ASTM Standards:
Magnesium 0.001 to 11.0
E 135 Terminology Relating to Analytical Chemistry for
Zinc 0.001 to 10.0
Tin 0.001 to 7.5
Metals, Ores, and Related Materials
Nickel 0.001 to 4.0
E 158 Practice for Fundamental Calculations to Convert
Iron 0.001 to 3.5
Intensities into Concentrations in Optical Emission Spec-
Lithium 0.005 to 3.0
Manganese 0.001 to 2.0
trochemical Analysis
Cobalt 0.001 to 2.0
E 172 Practice for Describing and Specifying the Excitation
Silver 0.001 to 1.5
Source in Emission Spectrochemical Analysis
Chromium 0.001 to 1.0
Zirconium 0.001 to 1.0
E 227 Test Method for Optical Emission Spectrometric
Lead 0.002 to 0.7
Analysis of Aluminum and Aluminum Alloys by the
Bismuth 0.001 to 0.7
Point-to-Plane Technique
Cadmium 0.001 to 0.5
Beryllium 0.0001 to 0.5
E 305 Practice for Establishing and Controlling Spectro-
Titanium 0.001 to 0.5
chemical Analytical Curves
Antimony 0.001 to 0.5
E 380 Practice for Use of the International System of Units
Vanadium 0.001 to 0.15
Strontium 0.0001 to 0.07
(SI) (the Modernized Metric System)
Gallium 0.001 to 0.05
E 406 Practice for Using Controlled Atmospheres in Spec-
Sodium 0.0001 to 0.05
Boron 0.0001 to 0.05 trochemical Analysis
Barium 0.0001 to 0.05
E 607 Test Method for Optical Emission Spectrometric
Calcium 0.001 to 0.05
Analysis of Aluminum and Aluminum Alloys by the
Phosphorus 0.0001 to 0.01
Point-to-Plane Technique, Nitrogen Atmosphere
1.2 This test method is suitable primarily for the control
E 716 Practices for Sampling Aluminum and Aluminum
analysis of chill-cast specimens. Other forms may be analyzed,
Alloys for Spectrochemical Analysis
provided that (1) they are sufficiently massive to prevent undue
E 876 Practice for Use of Statistics in the Evaluation of
heating, (2) they permit machining flat surfaces having a 4
Spectrometric Data
minimum diameter of approximately 15 mm, and (3) reference
materials of similar metallurgical condition and chemical
3. Terminology
composition are available.
3.1 Definitions—For definitions of terms used in this test
method, refer to Terminology E 135.
This test method is under the jurisdiction of ASTM Committee E-1 on
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
responsibility of Subcommittee E01.04 on Aluminum and Magnesium. Annual Book of ASTM Standards, Vol 03.05.
Current edition approved Jan. 15, 1994. Published March 1994. Originally Annual Book of ASTM Standards, Vol 14.02 (excerpts in all other volumes).
e1 4
published as E 1251 – 88. Last previous edition E 1251 – 88 (1992) . Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1251
3.2 Definitions of Terms Specific to This Standard: digital counts by means of a computer. The ratios of the
3.2.1 alloy-type calibration—the grouping of alloys of simi- voltages of the analytical lines to the voltage of the internal
lar composition for the purpose of calibration so as to permit standard line are converted into concentrations either manually
standardization with a minimum number of reference materi- by graphs, tables, or X-Y recorders, or by a computer in
als, for example, high silicon-aluminum casting alloys, Ameri- accordance with Practice E 158.
can Aluminum Association alloy numbers 308 to 380, may be 4.2 Two alternative procedures for calibration may be em-
standardized with 380 standardant. ployed. The two procedures can give the same precision,
3.2.2 standardization—See Terminology E 135. Two types accuracy, and detection limits.
of standardization are commonly used, as follows 4.2.1 The first procedure, Binary Calibration, is used when
3.2.2.1 two-point standardization——adjustment of a gain there is a need to analyze almost the entire range of aluminum
control of a channel for an individual spectral line in a manner alloys. This procedure employs calibration curves for each
that reproduces the readings that the high and low standardants element that cover the entire concentration range that has to be
displayed during the collection of calibration data. In computer determined in all alloys. Fifty or more binary calibrants may be
applications, correction is done mathematically by applying a required for calibration. Type reference materials are used to
slope and intercept correction, that is, a multiplication to adjust the concentrations read from the binary curves in order
correct the amount of difference between the high and low to report the correct concentrations for specific alloys.
standardant readings followed by the addition or subtraction of 4.2.2 The second procedure, Alloy-Type Calibration,is
a constant to finally restore readings to expected values. more appropriate for analyzing only a relatively few alloys of
3.2.2.2 single-point standardization—adjustment of a chan- similar composition. It employs an analytical curve for each
nel for an individual spectral line using a single standardant. element that covers a relatively limited concentration range.
Usually the single standardant is a high reference material used Calibration may require only 5 to 20 calibrants.
to set the gain. If the analytical interest is just in low
5. Significance and Use
concentrations near the detection limit, a low standardant is
used and either a gain or a background control may be 5.1 The physical and chemical properties of high-purity
aluminum and aluminum alloys depend on chemical composi-
adjusted.
tion, which must be determined and controlled. Accurate,
4. Summary of Test Method
high-speed analysis of aluminum, before it is poured from the
4.1 A unipolar self-initiating capacitor discharge is pro- furnace, can prevent scrapped heats and minimize the cost of
duced in an argon atmosphere between a prepared flat surface expensive alloying metals.
of the specimen and the tip of a semi-permanent thoriated- 5.2 This test method is applicable to chill-cast specimens
tungsten or other counter electrode. The radiant energies of prepared for routine production control. It can be applied to
selected analytical lines and an internal standard line are other types of specimens if there are appropriate reference
converted into electrical currents by photomultipliers. The materials, or if the specimens are remelted.
currents are integrated during the exposure time either by
6. Interferences
charging integrating capacitors and measuring the cumulative
voltages at the end of the exposure, or by interrogating the 6.1 Known line interferences due to other elements are
capacitors during the exposure and converting the voltages into listed in Table 1.
TABLE 1 Analytical Lines and Concentration Ranges
Recommended High-
Interferences
Wavelength In Air, Background Detection
Element Concentration Concentration
A,B,C D E,F
˚
A Equivalent, % Limit, %
H
G ˚
Element, l,A, and k, %
Range, % Index, %
Silicon I 2881.58 0.001–1.5 0.01 0.0001 1.5 Cr 2881.93
I 2516.12 0.001–1.5 0.006 0.0001 1.5
B
I 3905.53 0.05–24 0.25 0.01 >24 Cr 3905.66 0.09
I 2124.15 0.05–24 0.5 0.05 >24
Iron II 2382.04 0.001–1.5 0.015 0.0008 1.0
II 2599.40 0.001–1.5 0.005 0.0004
I 2599.57
B I
I 3749.49 0.001–3.5 0.0001
I 4415.12 0.01–3.5 0.0004
I 4383.55 0.005–3.5 0.05
Copper I 3273.96 0.001–1.5 0.005 <0.0001 0.7 Fe 2961.28
F
I 2961.17 0.05–20 0.40 0.01 >20
F
II 2247.00 0.01–5 0.03 0.0005 5
F
I 5105.54 0.05–20 0.32 0.01 >20
B F
Manganese I 4030.76 0.001–2 0.028 0.0001
II 2593.73 0.0005–0.5 0.004 0.00005 0.2
F
II 2933.06 0.001–2 0.006 0.0002 >1.1
B
II 3460.33 0.01–2
Magnesium II 2795.53 0.0005–0.3 0.0006 0.00003 0.04
E 1251
Recommended High-
Interferences
Wavelength In Air, Background Detection
Element Concentration Concentration
A,B,C D E,F
˚
A Equivalent, % Limit, % H
G ˚
Element, l,A, and k, %
Range, % Index, %
I 2852.13 0.0005–0.3 0.008 <0.0001 0.25
I 2776.69 0.05–11 0.08 0.01 >11
B F
I 3832.31 0.01–11 0.015 0.002 >11
F
I 5183.62 0.01–11 0.02 0.002 >11
Chromium I 4254.35 0.001–1 0.015 <0.0001
F
II 2677.16 0.001–1 0.004 0.0005
II 2766.54 0.005–1
Nickel I 3414.76 0.001–2 0.02 <0.0001 >2.5
F
I 3101.88 0.005–4 0.05 0.001 >5
F
II 2316.04 (2nd) 0.001–2 0.015 0.0005 <2.5
F
Zinc I 2138.56 (2nd) 0.0005–0.1 0.035 0.0001 0.05
I 3345.02 0.001–10.0 0.065 0.0004 >8
F
I 4810.53 0.01–10 0.07 0.001 >10
I 4722.16 0.01–10 0.26 0.0015 >10
Titanium II 3349.04 0.0005–0.5 0.004 <0.0001
II 3372.80 0.001–0.5 0.002 <0.0001
F
I 3635.45 0.0005–0.05 0.030 0.0003
F
Vanadium I 3183.41 0.001–0.15 0.06 0.0003
II 3102.30 0.001–0.15 0.014 <0.0001
Lead I 4057.82 0.002–0.7 0.04 0.0001 Mn 4057.92 0.01
I 2833.06 0.002–0.7 0.07 0.002
Tin I 3175.02 0.001–7.5 0.04 0.0001 >10
Bismuth I 3067.72 0.001–0.7 0.04 0.0002
Gallium I 2943.64 0.001–0.05 0.015 <0.0001
B
I 4172.06 0.001–0.05
F
Boron I 2497.73 (2nd) 0.0001–0.05 0.002 0.0001 Fe 2497.82 0.001
Mn 2497.78 0.007
I 2089.59 (2nd) 0.0001–0.05 Mo 2089.52 0.13
Beryllium I 2348.61 0.0001–0.05 0.001 0.00003
II 3130.42 0.0005–0.05 0.0035 0.0001
I 3321.34 0.0001–0.05 0.0001
Sodium I 5889.95 0.0001–0.05 0.0015 <0.0001
B
Calcium II 3933.67 0.001–0.05 0.001 0.00005 Fe 3933.61
F
Zirconium II 3391.98 0.001–1 0.02 0.001
B
II 3496.21 0.001–1 0.006 <0.0001
B
Cobalt I 3453.51 0.0001–2 <0.0001
Cadmium I 2288.02 0.001–0.3 0.05 <0.0001 As 2288.12
I 4799.92 0.005–2 0.15 0.003
Lithium I 6707.84 0.0001–0.02 0.0005 <0.00005 Sb 3232.50
I 3232.61 0.01–3 Fe 3232.79
Antimony I 2311.47 (2nd) 0.001–0.5 0.17 0.0002 Co 2311.66 0.6
I 2598.06 0.001–0.5 0.0002 Fe 2598.37
B
Strontium II 4215.52 0.0001–0.1 0.0004 0.0001
Barium II 4554.04 0.0001–0.1 0.0004 0.0001
I,J
Phosphorous I 1782.31 (2nd) 0.0001–0.1 0.084 0.0001
Silver I 3280.68 0.0005–0.1
I 3382.89 0.0001–0.1 >10
I 4668.48 0.05–1.5
Aluminum I 2567.99 70–100
I 2660.39 70–100
I 2372.08 70–100
A
I 5 atom line, II 5 ion line.
B
Useful analytical lines with improved signal to background ratios due to the complete removal of C-N background by the argon atmosphere.
C
Second (2nd) indicates that the second order shall be used, where available.
D
Background Equivalent—The concentration at which the signal due to the element is equal to the signal due to the background.
E
In this test method, the detection limit was measured by calculating the standard deviation of ten concentration printouts of a specimen between three and ten times
the expected detection limit.
F
See footnote E. For the values marked with an F, the available data was for a concentration greater than ten times but less than 100 times the expected detection
limit.
G
High-Concentration Index—The concentration at which the tangent to the calibration curve plotted on log-log paper drops from 45° theoretical to 37°, that is, the
response of I /I as ordinate versus% a as abscissa has dropped from approximately 1.0 to 0.75. It is recommended that a second, less sensitive line with close to 45°
a s
response be employed before this concentration is reached.
H
Interference Factor, k—The apparent increase in the concentration of the element being determined, expressed in percent, due to 1.0 % of the interfering element.
I
The detection limit for iron is determined more by possible segregation in the specimen and by contamination during machining than by spectrochemical sensitivity.
J
˚
If phosphorous is to be determined, the most sensitive line appears to be 1782.31 A in the second order and this requires a vacuum spectrometer. Optimum results
˚
are obtained by using as an internal standard a background channel profiled off the peak of phosphorous 1782 A in the first order. The ratio of P1782.31 A
˚
(2nd)/background near 1782 A (1st) is plotted against % P. Even with this compensation for variability in background, alloys with highly different compositions of major
alloying elements, particularly silicon, require separate reference materials and analytical curves.
E 1251
7. Apparatus counter electrode, but the flow rate shall not confine the
discharge to an area less than 5 mm in diameter, to provide
7.1 Specimen Preparation Equipment:
adequate sampling of the specimen. The argon, with most of
7.1.1 Specimen Molds for aluminum and methods for
the metal dust, shall be exhausted to the atmosphere from the
pouring specimens are described in Practice E 716. Chill-cast
back or side of the chamber.
specimens, poured as described therein, shall be used in this
7.4 Gas Flow System, to supply pure argon gas (99.995 %)
test method.
to the excitation chamber. The gas shall be delivered by a flow
7.1.2 Lathe, capable of machining a smooth, flat surface on
system as described in Practice E 406 from either high-purity
the reference materials and specimens. A variable-speed cutter,
compressed gas, or liquid argon bottles, or from a welding
a cemented-carbide tool, and an automatic cross-feed are
grade supply that has been purified to the required 99.995 %
recommended.
level. The system shall include: a two-stage regulator of
7.1.3 Milling Machine—A vertical milling machine with
all-metal construction with two pressure gages; copper tubing
fly-cutter and vise for holding the specimen can be used as an
with all-metal seals; a solenoid and valve operated automati-
alternative to the lathe.
cally by the control system, to start the full argon flow for the
7.2 Excitation Source, capable of producing a unipolar
pre-flush and stop it at the end of the exposure; and a needle
self-initiating capacitor discharge, utilizing the parameters
valve to maintain a very slo
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