GB/T 21931.2-2025 PDF English
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| GB/T 21931.2-2025 | English | 320 |
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Ferronickels - Determination of sulfur content - Infrared absorption method after induction furnace combustion
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| GB/T 21931.2-2008 | English | 140 |
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Nickel, ferronickel and nickel alloys -- Determination of sulfur content -- Infrared absorption method after induction furnace combustion
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GB/T 21931.2-2025: Ferronickels - Determination of sulfur content - Infrared absorption method after induction furnace combustion
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT21931.2-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.100
CCS H 11
Replacing GB/T 21931.2-2008
Ferronickels - Determination of sulfur content -- Infrared
absorption method after induction furnace combustion
(ISO 7526.2020, MOD)
Issued on: JUNE 30, 2025
Implemented on: JANUARY 01, 2026
Issued by. State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword... 3
Introduction... 5
1 Scope... 6
2 Normative references... 6
3 Terms and definitions... 7
4 Principle... 7
5 Reagents and materials... 7
6 Instruments and equipment... 8
7 Sampling and sample preparation... 10
8 Analysis steps... 10
9 Precision... 13
10 Test report... 14
Annex A (informative) Comparison on structure number changes between this
document and ISO 7526.2020... 16
Annex B (informative) Technical differences between this document and ISO
7526.2020 and their reasons... 18
Annex C (informative) Characteristics of commercial high frequency induction furnace
infrared sulfur analyzer... 19
Annex D (normative) Flowchart of the procedure for accepting specimen analysis
results... 21
Annex E (informative) Common precision test information... 22
Ferronickels -- Determination of sulfur content -- Infrared
absorption method after induction furnace combustion
WARNING -- Personnel using this document should have practical experience in
formal laboratory work. This document does not address all possible safety issues.
Users are responsible for taking appropriate safety and health measures and
ensuring compliance with relevant national regulations.
1 Scope
This document specifies the determination of sulfur content in ferronickel. It adopts the
infrared absorption method in which an induction furnace is used.
This document applies to the determination of sulfur content in ferronickel. The
measurement range (mass fraction) is 0.002%~0.26%.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 6379.1, Accuracy (trueness and precision) of measurement methods and
results -- Part 1.General principles and definitions
GB/T 6379.2, Measurement methods and results -- Accuracy (trueness and precision)
-- Part 2.Determine the standard methods of measurement repeatability and
reproducibility of the basic method
GB/T 6379.3, Accuracy (trueness and precision) of measurement methods and
results -- Part 3.Intermediate measures of the precision of a standard measurement
method
GB/T 8170, Rules of rounding off for numerical values and expression and
judgement of limiting values
GB/T 25050, Ferronickel ingots or pieces -- Sampling for analysis
GB/T 25051, Ferronickel shot -- Sampling for analysis
3 Terms and definitions
There are no terms or definitions that require definition in this document.
4 Principle
The test material is heated and burned in an oxygen stream in an induction furnace.
Under the action of flux and accelerators, sulfur is converted into sulfur dioxide, which
is carried by the oxygen stream to an infrared absorption cell. Use an infrared detector
to measure its absorption of infrared light of a specific wavelength. The sulfur content
is determined by the change in infrared energy received by the detector.
5 Reagents and materials
5.1 Oxygen
The purity should be at least 99.5% (mass fraction). When organic contaminants are
suspected in the oxygen, an oxidizing agent (copper (II) oxide or platinum tube) heated
at 600°C should be used. Then, an appropriate carbon dioxide absorbing agent and a
water absorbent should be used for absorption and purification.
5.2 Alkali asbestos
Use inert ceramic that is impregnated with sodium hydroxide. Particle size is 0.7
mm~1.2 mm. It is used to absorb carbon dioxide.
5.3 Magnesium perchlorate [Mg(ClO₄)₂]
Particle size is 0.7 mm~1.2 mm. It is used for moisture absorption.
5.4 Glass wool
5.5 Flux and accelerators
5.5.1 General requirements
Adding a flux can make the small particles of the specimen stick together. It shall make
the induction effect in the furnace more effective. It shall produce a melt with good
fluidity. Adding an accelerator can.
a) Create a good coupling induction medium for refractory samples (fine-grained
samples, materials with complex compositions). It shall allow for induction
heating and melting of refractory samples;
b) Increase the combustion temperature;
c) When the specimen volume is small, adding an accelerator can increase the total
crucible content. It shall create a good coupling medium.
The flux and accelerator used should have a low sulfur content. It should be used
simultaneously during the calibration procedure. Various factors (oxygen, crucible, flux,
and accelerator) contribute to the sulfur blank value. When the sulfur content of the
sample to be measured is ≤0.05% (mass fraction), the blank value should not exceed
0.0005% (mass fraction). When the sulfur content of the sample to be measured is >0.05%
(mass fraction), the blank value should not exceed 0.001% (mass fraction).
NOTE. Certain materials act as both fluxes and accelerators.
5.5.2 Flux
Common fluxes are tin, copper plus tin, copper or tungsten.
5.5.3 Accelerator
Common accelerators are copper, iron, tungsten or nickel.
5.6 Steel or ferronickel certified reference samples
The sulfur content (mass fraction) is 0.001%~0.27%.
6 Instruments and equipment
6.1 Sulfur analyzer
6.1.1 High-frequency induction furnace infrared sulfur analyzers are available from a
variety of manufacturers. The instrument should be operated according to the
manufacturer's instructions. A pressure regulator is required to control the oxygen
pressure entering the instrument's combustion furnace, as specified by the manufacturer.
6.1.2 Use a quartz tube filled with alkali asbestos (5.2) and magnesium perchlorate (5.3)
to purify the oxygen. In standby mode, the flow rate should be maintained at
approximately 0.5 L/min.
6.1.3 Install a glass wool (5.4) filter between the high-frequency induction furnace
chamber and the analyzer. Replace it when necessary. Clean the furnace chamber,
furnace column, and filter screen regularly to remove oxide residues.
6.2 Ceramic crucible and crucible cover
A ceramic crucible is needed to hold the sample and other necessary additives for the
subsequent melting process. The crucible should be precisely sized and fit the support
so that the sample in the crucible is directly inside the heating induction coil.
Typical dimensions of a crucible are.
The crucible and crucible cover should comply with the instrument manufacturer's
specifications. They shall be able to withstand the combustion temperature in the
induction furnace. They shall not produce sulfur-containing chemicals to meet the blank
value requirements specified in the document.
To eliminate the effects of possible sulfur contamination in the crucible on the
measurement, calcinate the crucible in a high-temperature furnace with air or oxygen
for at least 1 h at 1100°C. After cooling, store in a desiccator or sealed container.
Alternatively, use a resistance furnace with a combustion tube and flow oxygen through
the tube. Precondition the crucible in a similar manner.
6.3 Crucible clamp
Capable of gripping the crucible (6.2).
Height
Outer diameter
Inner diameter
Wall thickness
Bottom thickness
Crucible cover
aperture more than 10 mm.
7 Sampling and sample preparation
7.1 Sampling shall be carried out in accordance with the provisions of GB/T 25050 or
GB/T 25051.Sample preparation shall be carried out according to the normal agreed
procedures. In case of any dispute, the supplier and the purchaser may negotiate
separately.
7.2 Laboratory samples are usually in the form of pellets, drill cuttings or milling
cuttings. No further processing is required.
7.3 Laboratory samples that have been ground or drilled and contaminated with oil or
grease should be cleaned with high-purity acetone and allowed to air dry.
7.4 If the particle sizes of laboratory samples vary greatly, the specimens should be
obtained after reduction.
8 Analysis steps
WARNING -- The primary risk of burns during this test lies in the pre-burning
and molten state of the crucible. Therefore, crucible clamps should be used
throughout the test and the burned crucible should be stored in a suitable
container. When using an oxygen cylinder, follow standard safety precautions.
Localized oxygen accumulation can cause fires, so ensure that oxygen is effectively
removed from the apparatus during the combustion process.
8.1 Instrument preparation and stabilization
8.1.1 Assemble and prepare the instrument according to the manufacturer's instructions.
Perform a leak test on the high-frequency furnace and analysis system to ensure that
the entire gas system is leak-free.
8.1.2 Before calibrating the instrument or performing a blank test, weigh several
samples similar to the specimen to be tested. Add appropriate flux and accelerators.
Burn these in the instrument's induction furnace to stabilize the instrument.
NOTE. No need to use pre-treated crucibles.
8.1.3 Run the instrument through several cycles with oxygen flowing in. Adjust the zero
point of the instrument if necessary.
8.2 Blank test and zero adjustment
8.2.1 Sulfur content ≤0.05%
For this range, weigh a certain mass of flux (5.5.2) to the nearest 0.005 g. Place it in a
ceramic crucible (6.2). Add a certain mass of low-sulfur standard sample (5.6). Then
weigh a certain mass of accelerator (5.5.3) to cover.
The type and mass of flux and accelerator used in the blank test should be consistent
with the sample determination method used (see 8.4.1). Record the mass of the standard
sample. Place the crucible and contents on the furnace base support. Follow the
manufacturer's instructions. Repeat the test three times. Average the results.
Subtract the sulfur content of the standard sample from the average result to obtain the
blank value. If the blank value is greater than 0.0005% (mass fraction) or its standard
deviation is greater than 0.0002% (mass fraction), determine the cause and repeat the
test after correction.
Enter the blank mean value into the analytical instrument according to the
manufacturer's instructions.
NOTE 1.The blank reading obtained is the blank value produced by the crucible, flux, and
accelerator. If the analytical instrument does not have an automatic blank correction, the blank value
should be manually subtracted from the result displayed by the instrument each time a result is
calculated.
NOTE 2.Another method is to record the readings of a blank test. Make corrections using a
calibration chart.
8.2.2 Sulfur content >0.05%
Blank correction is not necessary within this range, but a blank value check should be
performed. The blank value should not exceed 0.001% (mass fraction). If the blank
value exceeds 0.001% (mass fraction), determine the cause and repeat the test after
correction.
8.3 Calibration
8.3.1 Select a series of certified steel or ferronickel standard samples (5.6) for
calibration and verification. The sulfur content of the certified standard samples should
include at least the lowest value, the highest value, and the 1/4 highest value in each
measurement range.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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