GB/T 26416.8-2023Chemical analysis methods for rare earth ferroalloy—Part 8: Determination of silicon content—Spectrophotometry (English PDF)

Foreword

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

This document is part 8 of GB/T 26416 "Methods for Chemical Analysis of Rare Earth Ferroalloys". GB/T 26416 has issued the following part.

--- Part 1. Determination of the total amount of rare earth;

--- Part 2. Determination of rare earth impurity content Inductively coupled plasma emission spectrometry;

--- Part 3. Determination of calcium, magnesium, aluminum, nickel, manganese content Inductively coupled plasma emission spectrometry;

--- Part 4. Determination of iron content Potassium dichromate titration method;

--- Part 5. Determination of oxygen content pulse-infrared absorption method;

--- Part 6. Determination of molybdenum, tungsten and titanium content Inductively coupled plasma emission spectrometry;

--- Part 7. Determination of carbon and sulfur content High-frequency-infrared absorption method;

--- Part 8. Photometric method for the determination of the amount of silicon;

--- Part 9. Determination of phosphorus content Bismuth phosphomolybdenum blue spectrophotometry.

Introduction

The rare earth iron alloy referred to in this document refers to the master alloy composed of iron and one or more rare earth elements, generally adopts molten salt electrolysis or fusion It is mainly used as an additive for magnetic materials such as NdFeB permanent magnet materials, magnetostrictive materials, optical and magnetic recording materials, or as a deoxidizer, Additives, etc.

XB/T 616-2012 "Chemical Analysis Methods of Gadolinium-Fe Alloys", XB/T 621-2016 "Chemical Analysis Methods of Holmium-Fe Alloys", XB/T 623-2018 "Cerium-Fe Alloy Chemical Analysis Method", XB/T 624-2018 "Yttrium-Fe Alloy Chemical Analysis Method", etc., established for all current implementations Large-scale production of rare earth iron alloys (including iron lanthanum, iron cerium, iron lanthanum cerium, iron neodymium, iron dysprosium, iron gadolinium, iron holmium and iron yttrium, etc.) production and application needs The standard of chemical analysis method for the assessment indicators, including the detection of the total amount of rare earth, the content of rare earth impurities, and the content of non-rare earth impurities. According to detection Different objects and detection methods and substrate differences, etc., GB/T 26416 consists of the following parts.

--- Part 1. Determination of the total amount of rare earth;

--- Part 2. Determination of rare earth impurity content Inductively coupled plasma emission spectrometry;

--- Part 3. Determination of calcium, magnesium, aluminum, nickel, manganese content Inductively coupled plasma emission spectrometry;

--- Part 4. Determination of iron content Potassium dichromate titration method;

--- Part 5. Determination of oxygen content pulse-infrared absorption method;

--- Part 6. Determination of molybdenum, tungsten and titanium content Inductively coupled plasma emission spectrometry;

--- Part 7. Determination of carbon and sulfur content High-frequency-infrared absorption method;

--- Part 8. Photometric method for the determination of the amount of silicon;

--- Part 9. Determination of phosphorus content Bismuth phosphomolybdenum blue spectrophotometry.

The above-mentioned parts have clarified the scope of application, standardized reagents, materials, test equipment and procedures, and have undergone many tests and tests in many laboratories.

The precision data provided by the verification enhances the consistency and comparability of data between different laboratories, and establishes a strict quality verification system for rare earth ferroalloys. Careful and standardized basis for standardization work.

This document uses molybdenum blue spectrophotometry to determine the silicon content in rare earth iron alloys. Compared with inductively coupled plasma emission spectrometry, this The method has the advantages of simple equipment, high sensitivity, low detection limit and wide detection range, and can be used as a referee test method. The essence of this document The density data was confirmed by 7 laboratories in 2021 on 7 samples with different levels of silicon content in 6 rare earth ferroalloys.

(level 1 is determined by 6 laboratories), and each laboratory independently tests the silicon content of each level under repeatability conditions.

Measured 11 times, the test data were statistically analyzed according to GB/T 6379.2.

1 Scope

This document describes the rare earth iron alloys (lanthanum-iron, cerium-iron, gadolinium-iron, dysprosium-iron, holmium-iron, yttrium-iron, lanthanum-cerium-iron Alloy) Determination of silicon content.

This document is applicable to rare earth iron alloys (lanthanum-iron alloy, cerium-iron alloy, gadolinium-iron alloy, dysprosium-iron alloy, holmium-iron alloy, yttrium-iron alloy, lanthanum-cerium-iron alloy Alloy) Determination of silicon content. Measuring range (mass fraction): 0.0050%~0.20%.

2 Normative references

The contents of the following documents constitute the essential provisions of this document through normative references in the text. Among them, dated references For documents, only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document.

GB/T 6682 Analytical laboratory water specifications and test methods

GB/T 8170 Numerical rounding off rules and expression and determination of limit values

3 Terms and Definitions

This document does not have terms and definitions that need to be defined.

4 Method Summary

The sample is dissolved in dilute acid. In dilute acid medium, silicon and ammonium molybdate form silicon-molybdenum heteropolyacid, and in sulfuric acid and oxalic acid medium, phosphorus and arsenic heteropolyacid are decomposed. Acid, use ascorbic acid to reduce silicomomolybdenum heteropoly acid to a blue low-valent complex, and measure the absorbance at a wavelength of 810nm in a spectrophotometer, using standard Curve method to calculate the corresponding silicon content.

5 Reagents

Unless otherwise specified, in the analysis, only the reagents confirmed as superior grade and above and the second grade and above distilled water conforming to the provisions of GB/T 6682 were used.

Distilled water or deionized water or water of equivalent purity, liquid reagents are stored in plastic bottles. Prefer certified standard solutions.

5.1 Pure iron (purity >99.98%).

5.2 Mixed acid. Add 180mL hydrochloric acid (rho=1.19g/mL) and 60mL nitric acid (rho=1.42g/mL) to 760mL deionized water, mix well.

5.3 Sulfuric acid solution (1 2).

5.4 Sulfuric acid solution (1 5).

5.5 Ammonium molybdate (50g/L).

5.6 Oxalic acid-sulfuric acid mixed acid. dissolve 1g oxalic acid in 100mL sulfuric acid solution (5.4).

5.7 Ascorbic acid (20g/L), prepared when used.