Method for determining cobalt content in tungsten matrix while adding cobalt and/or other additives

Abstract

The invention relates to a method for determining the cobalt content in a tungsten matrix while separately adding cobalt or simultaneously adding other additives. The method is characterized in that a sample is slightly heated by mixture of nitric acid and hydrochloric acid to be decomposed rapidly until cobalt is completely decomposed into cobalt ions and the matrix tungsten and other additives almost retain the original states and exist in the precipitated form, only a small number of matrix tungsten and other additives are decomposed and the determination cannot be affected, the decomposed sample is filtered in a constant volume way to prepare cobalt solution, an appropriate amount of citric acid is added for complexing in order to completely eliminate the interference of a small amount of the decomposed matrix tungsten, an appropriate amount of solution is taken separately, a color is developed by the cobalt ions and an appropriate quantity of EDTA (ethylene diamine tetraacetic acid) and hydrogen peroxide under the acidity of pH being 1-3 to form a stable rose-bengal ternary complex, the color depth is proportional to the amount of cobalt, and the cobalt content is determined according to colorimetric results. The method can be implemented simply, rapidly and accurately, the detection accuracy is high, analysis errors, inadequacy in results and poor reproducibility can be avoided, and the influence of the experience of operators on the accuracy of results can be eliminated completely.

Description

Technical field [0001] The invention relates to a method for determining the content of cobalt in a tungsten matrix when cobalt and / or other additives are added. Background technique [0002] In some products in the tungsten product industry such as tungsten powder metallurgy and cemented carbide, cobalt is often added alone or other additives are added at the same time. The content of cobalt is between x% and xx%, generally less than 20%. The accuracy or uniformity of the cobalt content will directly affect the performance of the product and must be monitored. [0003] The current determination of the cobalt content in the above-mentioned products uses the classic method, namely the EDTA volumetric method (titration method). This method is used in the constant analysis of many elements, especially suitable for the constant titration of colorless divalent metal ions that can be quantitatively complexed with EDTA at room temperature. The color of the titration end point becomes sha...

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Problems solved by technology

[0041] As mentioned above, although the classic EDTA volumetric method (titration method) has many advantages and the analysis speed is also fast, it is not easy to master when this method is applied to the determination of cobalt. In this way, the results are often low and the reproducibility is not ideal

This is mainly based on the following reasons: (1) the red color of cobalt ion interferes with the observation of the end point, adding malachite green solution (3.6) is just to offset the red color interference of cobalt ion and facilitate the observation of the end point, but the effect is not very satisfactory; (2) at room temperature Lower cobalt and EDTA can not complete the quantitative reaction completely, must be heated to near boiling, and must be titrated while hot, and this brings inconvenience to operation, must wear gloves, bothersome and has certain danger; (3) along with titration, temperature Part of the complex dissociates into metal ions and EDTA, resulting in low results and poor reproducibility; (4) The reaction of cobalt and EDTA quantitative complexation is slow, and the color change at the titration end point is not sharp and difficult to observe (5) A small amount of decomposed main body tungsten and other ions further aggravate the insensitivity of the titration end point color mutation, making the end point more difficult to observe and judge

Therefore, the influence of the operator experience of this method is particularly large, which is a fatal shortcoming for an analytical method.

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