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GB/T 4699.8-2025Ferrochromium, silicochromium, nitrogen-bearing ferrochromium and high nitrogen ferrochromium — Determination of silicon content — Silicomolybdenum blue spectrophotometric method, silicon potassium fluoride titrimetric method and perchloric acid dehydration gravimetric method (English PDF)

铬铁、硅铬合金、氮化铬铁和高氮铬铁硅含量的测定硅钼蓝分光光度法、氟硅酸钾滴定法和高氯酸脱水重量法

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Issued by

SAMR; SAC

Level / Type

National · Recommended

Issue date

August 29, 2025

Implementation date

March 1, 2026

Scope

GB/T 4699.8-2025 is the English-translated version of 铬铁、硅铬合金、氮化铬铁和高氮铬铁硅含量的测定硅钼蓝分光光度法、氟硅酸钾滴定法和高氯酸脱水重量法.

GB/T 4699.8-2025 is the Chinese national standard covering silicon in ferrochromium, silicochromium and the nitrided grades — three methods with different ranges, the molybdenum blue photometric one from 0.10 % to 6.00 % read at 680 nm after oxalic acid has removed the phosphorus and arsenic interference, the potassium fluorosilicate titration for the high-silicon silicochromium alloys, the perchloric acid dehydration gravimetric method that covers the whole span, and the sieve sizes for chips and powders. It replaces GB/T 5687.2-2007, under the China Iron and Steel Association. In force from 1 March 2026. Issued on 29 August 2025, it has been in force since 1 March 2026, replacing GB/T 5687.2-2007.

Document preview — GB/T 4699.8-2025

National Standard of the People's Republic of China

ICS: 77.100
Classification: H 11
Replacing: GB/T 5687.2-2007

Issued by: State Administration for Market Regulation; Standardization Administration of the PRC

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and Definitions
4 Method 1.Molybdenum Blue Spectrophotometry
4.1 Principle
4.2 Reagents and Materials
4.3 Instruments
4.4 Sampling

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

This document is Part 8 of GB/T 4699.GB/T 4699 has already published the following parts.

— Determination of carbon content in ferrochrome and silicon-chromium alloys by infrared absorption and gravimetric methods (GB/T 4699.4);

— Determination of Sulfur Content in Ferrochrome and Silicon-Chromium Alloys. Infrared Absorption Method and Combustion Neutralization Titration Method (GB/T 4699.6);

This document replaces GB/T 5687.2-2007 "Determination of Silicon Content in Ferrochrome, Silicon-Chromium Alloys and Ferrochrome Nitride - Dehydration by Perchloric Acid".

Compared with GB/T 5687.2-2007, the main technical changes in the "Law" are as follows, apart from structural adjustments and editorial modifications.

a) The scope of application has been revised to include the determination of silicon content in high-nitrogen ferrochrome (see Chapter 1, Chapter 1 of the 2007 edition);

b) Added Method 1.Silicate Molybdenum Blue Spectrophotometry, applicable to the determination of silicon content in ferrochrome, ferrochrome nitride, and high-nitrogen ferrochrome (see Chapter 4);

c) A second method has been added. potassium fluorosilicate titration, which is suitable for determining the silicon content in silicon-chromium alloys (see Chapter 5);

d) The sampling requirements in Method 3 have been modified, and sampling requirements for high-nitrogen ferrochrome samples have been added (see 6.4, Chapter 5 of the 2007 edition);

e) The allowed difference content in Method 3 has been modified (see 6.7, Chapter 8 of the 2007 edition);

f) A "Flowchart of the Experimental Analysis Result Acceptance Procedure" has been added (see Appendix A).

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the China Iron and Steel Association.

This document is under the jurisdiction of the National Technical Committee on Standardization of Pig Iron and Ferroalloys (SAC/TC318).

This document was drafted by: Jilin Ferroalloy Co., Ltd., Sichuan Chuantou Emei Ferroalloy (Group) Co., Ltd., and Qingdao Yuancheng.

Chuangzhi Technology Co., Ltd., CITIC (Liaoning) New Materials Technology Co., Ltd., Fangtongzhou Holdings Co., Ltd., Inner Mongolia Xintaiyuan New Materials Limited Liability Company, Ordos Xijin Mining and Metallurgy Co., Ltd., Hebei Jinxi Steel Group Co., Ltd., Metallurgical Industry Information Standards Research Institute Research Institute.

The main drafters of this document are: Zheng Haidong, Nie Shulan, Zhang Yunpeng, Wang Shuliang, Xu Wengao, Fang Yan, Ma Ning, Tang Huaying, Wu Lei, and Zhou Ruidong.

Wang Chao, Zhao Lixin, Pu Haiyan, Liu Huili, Cao Fawei, Zhang Li, Li Kunpeng, Liu Fei, Li Jinglin, Sun Fengxiao, Han Xuesong, Wang Hao, Wang Jing, Lu Chunsheng Cheng Zhaoyang.

This document was first published in 1985, revised for the first time in 2007, and this is the second revision.

Introduction

Because the testing of ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome involves many elements, the applicable range of these elements and...

The applicable methods differ. To ensure the convenience and accuracy of testing standards for ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome, we have developed specific methods for...

The analytical methods for different elements in ferrochrome, silicon-chromium alloy, ferrochrome nitride, and high-nitrogen ferrochrome have been supported by a national standard system.

GB/T 4699 Analytical methods for ferrochrome, silicon-chromium alloys, ferrochrome nitride and high-nitrogen ferrochrome are the standard analytical methods for ferrochrome, silicon-chromium alloys, ferrochrome nitride and high-nitrogen ferrochrome in China.

The basic standards for nitrogen, chromium, and ferric oxide testing consist of the following five parts. However, some parts have been obsolete, and this should be noted during use.

— Determination of Chromium Content in Ferrochromium, Silicon-Chromium Alloy, Ferrochromium Nitride, and High-Nitrogen Ferrochromium. Ammonium Persulfate Oxidation Titration and Potentiometric Titration (GB/T 4699.2). The purpose is to measure the chromium content in ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome, using a supersulfurized...

Ammonium acid oxidation titration and potentiometric titration.

— Determination of ferrochrome, silicon-chromium alloy, and ferrochrome nitride phosphorus content using bismuth-phosphorus-molybdenum blue spectrophotometry and molybdenum blue spectrophotometry (GB/T 4699.3). The purpose is to measure the silicon content in ferrochrome, silicon-chromium alloys, and ferrochrome nitride using bismuth-phosphorus-molybdenum blue spectrophotometry.

Molybdenum blue spectrophotometry and molybdenum blue spectrophotometry.

— Determination of Carbon Content in Ferrochrome and Silicon-Chromium Alloys. Infrared Absorption Method and Gravimetric Method (GB/T 4699.4). The purpose is to measure the carbon content of chromium.

The carbon content in iron and silicon-chromium alloys was determined using infrared absorption and gravimetric methods.

— Determination of Sulfur Content in Ferrochrome and Silicon-Chromium Alloys by Infrared Absorption Method and Combustion Neutralization Titration Method (GB/T 4699.6). The purpose is to...

The sulfur content in ferrochrome and silicon-chromium alloys was measured using infrared absorption and combustion neutralization titration methods.

— Determination of Silicon Content in Ferrochrome, Silicon-Chromium Alloy, Ferrochrome Nitride, and High-Nitrogen Ferrochrome. Silicate Molybdenum Blue Spectrophotometry and Potassium Fluorosilicate Titration The method involves dehydration by perchloric acid gravimetric method (GB/T 4699.8). The purpose is to determine the concentration of chromium in ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome.

The silicon content was determined by the perchloric acid dehydration gravimetric method.

Ferrochrome, silicon-chromium alloy, ferrochrome nitride, and high-nitrogen ferrochrome Determination of silicon content using the silicomolybdenum blue spectrophotometric method Potassium fluorosilicate titration and perchloric acid dehydration gravimetric method Warning---Personnel using this document should have formal laboratory work experience. 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 methods for determining ferrochrome and silicon-chromium alloys using the silicomolybdenum blue spectrophotometric method, potassium fluorosilicate titration method, and perchloric acid dehydration gravimetric method.

Silicon content in ferrochrome nitride and high-nitrogen ferrochrome.

This document applies to the determination of silicon content in ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome. Method 1.Silicon-molybdenum blue spectrophotometric method.

This method is suitable for determining the silicon content in ferrochrome, ferrochrome nitride, and high-nitrogen ferrochrome, with a determination range (mass fraction) of 0.10% to 6.00%. Method 2.Fluorine.

Potassium silicate titration is suitable for determining the silicon content in silicon-chromium alloys, with a determination range (mass fraction) of 30.00%~50.00%; Method 3.High The chloric acid dehydration gravimetric method is suitable for determining the silicon content in ferrochrome, silicon-chromium alloys, ferrochrome nitride, and high-nitrogen ferrochrome. The determination range (mass fraction) is as follows. 0.10%~60.00%.

2 Normative references

GB/T 4010

GB/T 6682

GB/T 8170

GB/T 12806

GB/T 12807

GB/T 12808

3 Terms and Definitions

This document does not contain any terms or definitions that need to be defined.

4 Method 1.Molybdenum Blue Spectrophotometry

4.1 Principle

The sample is dissolved in dilute hydrochloric acid and hydrogen peroxide or fused with alkali. Ammonium molybdate is added to react with silicon to form silicomolybdenum heteropolyacid. Oxalic acid is added to eliminate impurities such as phosphorus and arsenic.

To mitigate interference from the material, ferrous ammonium sulfate was used to reduce silicomolybdenum yellow to silicomolybdenum blue. The absorbance was measured at 680 nm using a spectrophotometer, and the silica content was calculated. The quality score.

4.2 Reagents and Materials

Unless otherwise specified, only reagents confirmed to be of analytical grade were used in the analysis, and the water used in the tests was of grade III or higher as specified in GB/T 6682.

Distilled water, deionized water, or water of equivalent purity. 4.2.1 Sodium peroxide, solid.

4.2.2 Anhydrous sodium carbonate, solid.

4.2.3 Chromium powder, omegaCr >99.9%.

4.2.4 Iron powder, omegaFe >99.9%. 4.2.5 Sulfuric acid, 1 1. 4.2.6 Sulfuric acid, 1 2. 4.2.7 Hydrochloric acid, 1 5.

4.2.8 Hydrogen peroxide, 30% (volume fraction).

4.2.9 Ammonium persulfate solution, 100 g/L. Prepare as needed.

4.2.10 Sodium sulfite solution, 100 g/L.

4.2.11 Ammonium molybdate solution, 50 g/L. Weigh 50 g of ammonium molybdate [(NH4)6Mo7O24-4H2O], place it in a 400 mL beaker, and add...

Dissolve in.200mL of water while warm, filter, cool to room temperature, add water to 1000mL, and mix well.

4.2.12 Oxalic acid-sulfuric acid mixed acid solution. Weigh 65g of oxalic acid (H2C2O4-2H2O), place it in a.2000mL Erlenmeyer flask, and add 500mL of [unclear text - possibly a typo, should be "500mL"]...

Add 600 mL of sulfuric acid (4.2.5) to water, and after it is completely dissolved, add 900 mL of water and mix well.

4.2.13 Ferrous ammonium sulfate solution, 100 g/L. Weigh 100 g of ferrous ammonium sulfate [(NH4)2Fe(SO4)2-6H2O] and place it in a 2000 mL solution of...

In a small flask, add 20 mL of sulfuric acid (4.2.5), then add 500 mL of water. After dissolving completely, add water to a final volume of 1000 mL and mix well.

4.2.14 Silicon standard solution.

a) Silicon standard stock solution, 1000 µg/mL.

Weigh 2.1395g of silica (purity greater than 99.9%) that has been pre-dried at 105°C for 1 hour and cooled to room temperature in a desiccator.

Place the mixture in a platinum crucible pre-filled with 6g of anhydrous sodium carbonate (4.2.2), stir well, and cover with a small amount of anhydrous sodium carbonate (4.2.2). Incubate at 950°C.

Heat in a high-temperature furnace until completely melted, then remove and cool. Place in a 400mL PTFE beaker, leach the molten material with hot water, and let it...

Dissolve the contents and rinse the crucible with water. After cooling, transfer the solution to a 1000mL plastic volumetric flask, dilute to the mark with water, and mix well. 1mL of this solution... Contains 1000µg of silicon.

b) Silicon standard solution, 80 µg/mL.

Aliquot 20.00 mL of silicon standard stock solution a) into a 250 mL plastic volumetric flask, dilute to the mark with water, and mix well. This solution 1 mL contains 80 µg of silicon.

4.3 Instruments

4.3.1 Use standard laboratory instruments and equipment in the analysis. Unless otherwise specified, single-mark volumetric flasks, graduated pipettes, and single-mark instruments shall be used.

Linear pipettes shall comply with the provisions of GB/T 12806, GB/T 12807 and GB/T 12808 respectively.

4.3.2 Nickel crucible, 30 mL in volume.

4.4 Sampling

4.4.1 Sampling shall be carried out in accordance with the provisions of GB/T 4010.

4.4.2 All ferrochrome nitride (powder sample) and high-nitrogen ferrochrome samples should pass through a 0.088 mm sieve.

4.4.3 All high-carbon ferrochrome and medium-carbon ferrochrome (powder samples) specimens should pass through a 0.125mm sieve.

4.4.4 All micro-carbon, low-carbon, and medium-carbon ferrochrome (shavings) and ferrochrome nitride (shavings) samples should pass through a 1.60 mm sieve, and samples should be taken from them. Sample on a 0.154mm sieve.

......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.

Referenced standards

Normative references

GB/T 4010 · GB/T 12806 · GB/T 12807

Editions of GB/T 4699.8

Edition	Title	Revision	Status
GB/T 4699.8-2025	Ferrochromium, silicochromium, nitrogen-bearing ferrochromium and high nitrogen ferrochromium - Determination of silicon content - Silicomolybdenum blue spectrophotometric method, silicon potassium fluoride titrimetric method and perchloric acid dehydrati	current edition	Current

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