Etching agent for inspecting dissimilar steel welding joint structure and using method thereof

Abstract

The invention discloses an etching agent for inspecting a dissimilar steel welding joint structure and a using method thereof. The etching agent comprises the following components, by mass, of 1%-8% of ferric chloride, 1%-9% of sodium chloride, 8%-30% of concentrated nitric acid and 53%-90% of phosphoric acid. The use method of the etching agent sequentially comprises the following steps that according to the proportion, the reagents are weighed correspondingly and are uniformly stirred; the etching agent is dipped to wipe the polishing surface of a sample, when the polishing surface becomes gray, the sample is washed out and dried; the etched sample is placed under light field lighting of an optical microscope to be observed. According to the etching agent and the using method thereof, reagent composition is simple and safe, and the long-term stable effective effect is achieved; and through one-time etching, microscopic structure morphologies of all areas of T91 / 92 and the austenitic heat-resistant stainless steel welding joint can be simultaneously, clearly and truly displayed without false appearance, the structure details are completely displayed, and observation equipment is simple and does not have special requirements.

Description

technical field [0001] The invention belongs to the field of etchants for testing the microstructure of welded joints of T91 / 92 and austenitic heat-resistant stainless steel dissimilar steels. Background technique [0002] With the improvement of the parameters of thermal power generating units, different temperature zones use different grades of materials, which not only meet the requirements of use in design, but also reduce the manufacturing cost, which has obvious economic benefits. Therefore, in the current high-grade boiler manufacturing process, T91 / 92 is often welded with austenitic heat-resistant stainless steel such as S30432, TP347H / HFG, TP310HCbN, etc., for the manufacture of high-temperature superheater and reheater components of boilers. Welding of dissimilar steels is more complicated and difficult than that of the same type of steel, and the quality of welded joints has always been the focus of boiler manufacturers and power plants. Metallographic structure ...

AI Technical Summary

Problems solved by technology

[0004] (1) The chemical composition of each area of ​​the joint is very different;

[0005] (2) There are large differences in the tissue types of the joints in each region;

[0006] (3) The size of the composition transition zone in the joint is often small, and the potential difference between different regions is large

[0007] These factors make the electrochemical properties of dissimilar steel joints different in different regions, and the display method becomes more complicated and difficult compared with the same steel. sex clearly

The current practice is usually to use a variety of etchant to etch in stages to display the structure and morphology of each area of ​​the joint respectively, but there are problems such as corrosion film interference, over-corrosion, corrosion surface pollution, and corrosion artifacts caused by multiple corrosions. and other disadvantages, which greatly hinder the observation and analysis of the metallographic structure of dissimilar steel joints, and affect the quality of inspection

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