GB/T 7143-2025 Methods for chemical analysis of silica sand for foundry English, Anglais, Englisch, Inglés, えいご
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ICS 25.120.20
CCS J 31
National Standard of the People's Republic of China
GB/T 7143-2025
Replaces GB/T 7143-2010
Methods for chemical analysis of silica sand for foundry
铸造用硅砂化学分析方法
(English Translation)
Issue date: 2025-02-28 Implementation date: 2025-09-01
Issued by the State Administration for Market Regulation
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Preparation of test samples
5 Test methods
Methods for chemical analysis of silica sand for foundry
1 Scope
This document describes the specimen preparation and test methods for the chemical composition analysis method of silica sand for foundry.
This document is applicable to the determination of chemical composition such as silica, alumina, iron oxide, titanium oxide, calcium oxide, magnesium oxide, potassium oxide and sodium oxide content of natural silica sand, selected quartz sand and artificial quartz sand for foundry.
Note: The measurement methods listed in this document are selected according to specific circumstances.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions 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 601 Chemical reagent - Preparations of reference titration solutions
GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods
GB/T 2684 Test methods for foundry sands and molding mixtures
GB/T 5611 Foundry terminology
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values
GB/T 21114-2019 Refractories - Chemical analysis by X-ray fluorescence(XRF) - Fused cast-bead method
3 Terms and definitions
The terms and definitions defined in GB/T 5611 are applicable to this document.
4 Preparation of test samples
4.1 The sample shall be representative and homogeneous and free from foreign impurities.
4.2 The measurement sample is divided by the quartering method (if the particles are too large, they should be crushed to less than 0.8 mm first, and the iron introduced in the crushing process should be removed with a magnet, and then divided). Finally, about 20g of a sample is obtained and ground until all passes through a 75μm sieve (i.e. No. 200 sieve). Put the above sample in a weighing bottle, dry it at 105 °C ~ 110 °C for 2 hours, then put it in a desiccator, and cool it for later use.
5 Test methods
5.1 General
5.1.1 Unless otherwise specified, the standard solutions, preparations and preparations used in the analysis are prepared according to the provisions of GB/T 601 and GB/T 603. Use reagents confirmed to be analytical purity and third-grade water according to GB/T 6682. For the reagents used in the test, if the concentration is not indicated, the original concentration is the factory.
5.1.2 All test methods need to be measured twice in parallel, and the average value is used as the final test result; The judgment of test results shall be carried out according to the rounded value comparison method in GB/T 8170.
5.2 Determination of silica content
5.2.1 Determination of silicon dioxide content by hydrochloric acid one-step dehydration - Molybdenum blue spectrophotometric combined method
5.2.1.1 Principle
The sample is melted and decomposed with sodium carbonate, the frit is dissolved with hydrochloric acid, evaporated and dried up to dehydrate silicic acid, added hydrochloric acid to dissolve soluble salts, filtered and burned into silica, and then treated with hydrofluoric acid to make silicon escape in the form of silicon tetrafluoride. The quality difference before and after hydrofluoric acid treatment is the amount of silica in the precipitate.
5.2.1.2 Reagents and materials
The reagents and materials used in the test mainly include:
a) Anhydrous sodium carbonate;
b) Hydrochloric acid;
c) Hydrofluoric acid;
d) Ethanol solution: 95%;
e) Hydrochloric acid: 1+1;
f) Hydrochloric acid: 1+11;
g) Hydrochloric acid: 5+95;
h) Sulfuric acid: 1+1;
i) Potassium thiocyanate solution: 5%;
j) Silver nitrate solution: 1%;
k) Potassium fluoride solution: 2%;
l) Boric acid solution: 2%;
m) Potassium hydroxide solution: 20%, stored in a plastic bottle;
n) Ammonium molybdate solution: 5%;
o) Ascorbic acid solution: 2%, prepared fresh before use;
p) Silicon dioxide standard solution: 0.1mg/mL. Accurately weigh 0.1000g of silicon dioxide (primary standard reagent) pre-calcined at 1000℃ for 1 hour into a platinum crucible. Add 2g of anhydrous sodium carbonate, mix uniformly, heat at low temperature initially, then gradually raise the temperature to 1000℃ until a transparent melt is obtained. Cool, transfer to a plastic beaker, leach with boiling water and rinse the crucible with water. Cool to room temperature, transfer to a 1000mL volumetric flask, dilute to the mark with water, shake well, and store in a plastic bottle. Each milliliter of this solution is equivalent to 0.1mg of silicon dioxide;
q) p-Nitrophenol indicator ethanol solution: 5g/L.
5.2.1.3 Instruments
The main instruments used in the test are as follows:
a) Analytical balance: accuracy of 0.0001g;
b) Platinum crucible: 30mL~100mL;
c) High-temperature box-type resistance furnace;
d) Single-mark pipette: 5mL, 10mL, 25mL, Class A;
