GB/T 41496-2022 English PDF (GBT41496-2022)

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GB/T 41496-2022: Ferroalloys一Determination of moisture of lots一Gravimetric method
GB/T 41496-2022
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.100
CCS H 11
Ferroalloys - Determination of moisture of lots - Gravimetric
method
ISSUED ON: APRIL 15, 2022
IMPLEMENTED ON: NOVEMBER 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions... 4 
4 Principles ... 5 
5 Instruments ... 5 
6 Sampling and sample preparation ... 5 
7 Samples ... 5 
8 Analytical procedures ... 6 
9 Calculation and representation of results ... 7 
10 Tolerance ... 9 
11 Test report ... 10 
Appendix A (Normative) Flow chart of the procedure for accepting the analytical results
of the measurement sample ... 11 
Ferroalloys - Determination of moisture of lots - Gravimetric
method
Caution - Persons using this document shall have practical experience in formal
laboratory work. This document does not address all possible security issues. It is
the user's responsibility to take appropriate safety and health measures AND to
ensure compliance with the conditions, which are stipulated by relevant national
laws and regulations.
1 Scope
This document specifies a method for the gravimetric determination of the moisture
content of ferroalloys.
This document is applicable to the determination of moisture content, between 0.010%
and 1.00%, in the delivery batch of iron alloys and nickel-iron ingots or blocks, that are
not easily chemically changed, during the drying process, in GB/T 4010.
2 Normative references
The contents of the following documents constitute essential provisions of this
document through normative references in the text. Among them, for dated references,
only the version corresponding to the date applies to this document; for undated
references, the latest version (including all amendments) is applicable to this document.
GB/T 4010 Ferroalloys sampling and preparation of samples for chemical analysis
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 28296 Pig iron containing nickel
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Lots
Ferroalloys of the same specification, in one delivery.
Note: The lots may consist of one or more batches.
4 Principles
Weigh a certain mass of ferroalloy test samples. Place them in a drying oven, at 105 °C
± 5 °C, to dry it, until the mass is constant. Calculate the mass fraction of moisture, as
relative to the mass lost as relative to the initial mass.
5 Instruments
5.1 Drying tray: A stainless metal tray, which has a smooth and clean surface, AND can
hold a specified number of measurement samples, whose thickness does not exceed
31.5 mm (or can hold a whole nickel-iron ingot or several pieces of non-fragile iron
alloy).
5.2 Drying oven: It has the function of electric heating and blasting; the temperature
can be controlled at 105 °C ± 5 °C.
5.3 Balance: The measuring range is more than 5000 g; the sensitivity is 0.1 g.
6 Sampling and sample preparation
The sampling and preparation of samples, for the determination of moisture in the lots
of ferroalloys, shall be carried out, in accordance with the provisions of GB/T 4010. If
the content of nickel-containing pig iron and nickel-iron ingots or blocks is different,
the sampling for the determination of moisture in the lots shall be in accordance with
the provisions of GB/T 25050 and GB/T 28296.
7 Samples
7.1 Samples of fragile alloys for determination of moisture
Fragile alloys include high-carbon ferrochromium, ferrosilicon, ferrotitanium,
ferromanganese, ferromolybdenum, ferrotungsten, manganese-silicon alloy, silicon-
chromium alloy, ferrovanadium, ferroboron, ferroniobium, and other ferroalloys, which
can be directly crushed, by jaw crusher.
The moisture determination shall be carried out, immediately after the sample
preparation is completed. The minimum mass of the sample, which is required for
moisture determination, is as shown in Table 1.
Spread the measurement sample in the weighed drying tray (5.1). The thickness of the
fragile alloy sample layer shall not exceed 31.5 mm; immediately measure the total
mass. Record the mass of the drying tray AND the total mass of the drying tray and the
test sample; calculate the initial mass of the measurement sample AND a value of 0.02%
of the initial mass of the measurement sample. Place the drying tray (5.1), which
contains the measurement sample, in the drying oven (5.2), which was set at 105 °C;
keep this temperature for not less than 2 h. Take out the drying tray, which contains the
test sample, from the drying oven. Weigh it immediately, to avoid the re-absorption of
moisture. Alternatively, in a container with a sealed lid, weigh the measurement sample,
after cooling in air.
Put the drying tray, which contains the measurement sample, into the drying oven again,
to continue to heat for 30 min. Repeat the weighing.
Repeat the above procedure, until reaching the constant weight (the mass difference
between the last two consecutive weighing is not greater than 0.02% of the initial mass
of the measurement sample).
9 Calculation and representation of results
9.1 Calculations for the determination of sample moisture
The moisture content of each measurement sample is calculated, according to formula
(1) AND rounded off according to GB/T8170; the test result is rounded off to the third
decimal place.
Where:
ωi - Determination result of moisture content of the ith measurement sample,
expressed in mass fraction (%);
m1 - The initial mass of the measurement sample, in grams (g);
m2 - The mass of the measurement sample after drying, in grams (g).
9.2 Calculation of the moisture content of lots
9.2.1 The moisture content of the lots shall be calculated, according to one of the
formulas (2) ~ (5) as needed, rounded off according to GB/T 8170, reported to the
second decimal place.
9.2.2 When the moisture content is measured, by the use of the bulk sample, which is
taken out from the lots, the average moisture content ( ) of the whole batch of
Where:
k - The number of parts of unequal mass of ferroalloy in the lots;
mi - The mass of the ith part, in grams (g);
ωi’’ - The determination result of moisture content of the ith part, expressed in mass
fraction (%). For the number of samples for parallel determination, it may refer to
the 2nd ~ 3rd row in Table 2;
i - 1, 2, 3, …, k.
9.2.5 When the moisture content of each incremental sample is measured, the moisture
content of the lots shall be calculated, according to the arithmetic mean ( ) of all the
incremental sample results, which are obtained in 9.1, according to formula (5). The
moisture content result of each incremental sample is calculated to the third decimal
place; the moisture content result of whole batch is reported to the second decimal place.
Where:
n - Number of incremental samples;
ωi‴ - The determination result of moisture content of the ith incremental sample,
expressed in mass fraction (%);
i - 1, 2, 3, …, n.
Note: For non-fragile alloys, it usually use this method for the determination of moisture
content.
10 Tolerance
The tolerances for two parallel tests in the laboratory of fragile ferroalloys are as sho...