GB/T 26416.4-2022Chemical analysis method for rare earth ferroalloy—Part 4: Determination of iron content—Potassium dichromate titration (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 4 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.

This document replaces GB/T 26416.4-2010 "Methods for Chemical Analysis of Dysprosium-Fe Alloys Part 4: Determination of Iron Content Potassium Dichromate Content Compared with GB/T 26416.4-2010, except for structural adjustment and editorial changes, the main technical changes are as follows.

a) The measurement range (mass fraction) has been changed from "10.00%~30.00%" to "10.00%~90.00%" (see Chapter 1, Chapter 1 of the 2010 edition);

b) Changed some reagents and materials in the method summary (see Chapter 4, Chapter 2 of the 2010 edition);

c) Changed the sample preparation method and added the crushing process of the sample (see Chapter 7, Chapter 5 of the 2010 edition);

d) Changed the weighing amount of the sample from 5g to 1.0g (see 8.1, 6.1 of the 2010 edition);

e) The dissolution method of the sample has been changed, and the treatment steps for the insoluble sample have been added (see 8.4.1, 6.4.1 of the 2010 edition);

f) Increased the aliquot volume of samples with different iron contents (see Table 1);

g) The order of adding reagents has been changed (see 8.4.2, 6.4.2, 6.4.3 of the 2010 edition);

h) Changed "precision" and changed "permissible difference" to "reproducibility" (see Chapter 10, Chapter 8 of the 2010 edition).

Introduction

The rare earth ferroalloy 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. are used in iron and steel smelting. Chemical composition is an important assessment index of rare earth ferroalloys. GB/T 26416 integrates industry standards

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 Due to differences in objects and detection methods and substrates, etc., GB/T 26416 is proposed to be composed of 9 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 standards have clarified the scope of application, standardized reagents, materials, test equipment and procedures, and have been tested repeatedly by many laboratories.

The precision data given by the test and verification enhances the consistency and comparability of data between different laboratories, and establishes a standard for the quality verification of rare earth ferroalloys. Rigorous and standardized basis for standardization work.

This revision to GB/T 26416.4 adopts the potassium dichromate titration method to determine the iron content in rare earth iron alloys, which is applicable to all rare earth iron Determination of the iron content in the alloy, the recovery rate (mass fraction) of iron (Fe) is 98.8%~101.3%, and the relative standard deviation (RSD) is 0.13%~ 0.55%, which has the characteristics of simple method, easy operation, repeatability and reproducibility of measurement results. The precision data for this document are in the In 2020, it was determined by 7 laboratories on 5 samples with different levels of iron content, and each laboratory tested each level of iron The content was independently determined 11 times under repeatability conditions, and the joint test data were statistically analyzed according to GB/T 6379.2.

1 Scope

This document describes the rare earth iron alloys (lanthanum iron alloy, cerium iron alloy, neodymium iron alloy, dysprosium iron alloy, holmium iron alloy, gadolinium iron alloy, yttrium iron alloy Determination of iron content in gold, lanthanum-cerium-iron alloy).

This document is applicable to rare earth iron alloys (lanthanum iron alloy, cerium iron alloy, neodymium iron alloy, dysprosium iron alloy, holmium iron alloy, gadolinium iron alloy, yttrium iron alloy Determination of iron content in gold, lanthanum-cerium-iron alloy), measurement range (mass fraction). 10.00%~90.00%.

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 was dissolved with hydrochloric acid and hydrogen peroxide, most of the ferric iron was reduced to ferrous iron with stannous chloride, sulfur and phosphorus mixed acid was added, and sodium tungstate As an indicator, use titanium trichloride to reduce the remaining ferric iron to divalent to form "tungsten blue", and then add potassium dichromate solution dropwise to oxidize the excess trivalent iron. Titanium, using sodium diphenylamine sulfonate as indicator, titrate with potassium dichromate standard titration solution to purple as the end point, and calculate the iron content in the sample.

5 Reagents or Materials

Unless otherwise specified, in the analysis, only reagents confirmed to be of analytical grade or higher and distilled substances of grade two or higher in accordance with 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 Hydrochloric acid (rho=1.19g/mL).

5.2 Hydrogen peroxide solution [w(H2O2)>=30%].

5.3 Hydrochloric acid (19).

5.4 Sulfuric acid (5 95).

5.5 Sulphur-phosphorus mixed acid (3 3 5). Slowly pour 300mL of concentrated sulfuric acid (rho=1.84g/mL) into 500mL of water under constant stirring, and then Add 300mL phosphoric acid (rho=1.70g/mL), and mix well.