SU1057856A1 - Reagent for revealing boundaries and sizes of grains in steel - Google Patents

Abstract

REACTIVE FOR DETERMINING GRANTS AND DIMENSIONS OF STEEL GRAINS containing hydrofluoric acid and hydrogen peroxide, characterized in that, in order to make it possible to determine the boundaries and sizes of grains in chromium-nickel-molybdenum steel, it additionally contains a supersaturated aqueous solution of picnic, a new acid with traceable the ratio of components, about. P1 Hydrofluoric acid (d 0,92) 1-5 Hydrogen peroxide

Description

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The invention relates to analytical chemistry, namely to methods for determining grain sizes in steel, mainly in chromium-nickel-molybdenum steels, grade 18X2H4MA. A reagent is known for detecting boundaries and determining grain sizes (metallographic analysis) of heat-treated steel X12M G13 containing components, wt. h, i. Alcohol solution (5-10%) picric acid; 6 Alcohol solution (2-4%) nitric acid.4 However, this reagent does not clearly reveal the boundaries and grain sizes to 18X2H4MA chromium nickel molybdenum steel, .. due to inconsistencies in the ratios of the content of components in the reagent and its composition and, as a result, after etching the microsections, only certain areas and traces of boundaries are observed in the specified reagent, the microstructure of the steel is etched, making it difficult to assess the grain size and its nature. The closest in technical essence and the achieved result to the proposed is a reagent for detecting the boundaries and sizes of grains in alloyed steel .2, containing components, about. Hydrofluoric acid Up to 10 Hydrogen peroxide 60 Water30 However, this reagent is not suitable for metallographic studies of a 18X2H4MA brand chromo-nickel-molybdenum. After etching, in this reagent, the grain boundaries on steel 18X2H4MA are etched unevenly, which is why they are not knocked down, and the microstructure is intensively etched. There are etched areas that look like dark spots, which reduces the clarity of the resulting image. These drawbacks make it difficult to determine the grain size. The purpose of the invention is to make it possible to determine the boundaries and sizes of grains in chromium nickel molybdenum steel. The goal is achieved by the fact that the reagent for detecting the boundaries and grain sizes in steel containing hydrofluoric acid, hydrogen peroxide, additionally contains a supersaturated aqueous solution of picric acid in the following ratio of components, ob, i, Hydrofluoric acid (d 0.92) .1-5 Hydrogen peroxide (30%) 30-50 Peres: A saturated aqueous ac solution of picric acid - 40-80 to obtain a reagent - pre-prepared a supersaturated aqueous solution of picric acid, in which 100 g of water, heated to 60 ° C, dissolve 3 g of powdered picric acid and hold for 24 hours to ripen the supersaturated solution. Making sure that the supersaturated solution of picric acid has matured (there is a slight precipitate at the bottom of the vessel and there are no bubbles, air on the walls), hydrogen peroxide is introduced into it alternately, and then hydrofluoric acid in the amounts indicated in the reagent, the maturation of the succinated aqueous solution of picric acid acids are needed to remove air bubbles from the solution, the oxygen of which is the oxidizing agent of the surface of the scif during etching. The introduction of supersaturated aqueous solution of picric acid into the reagent m reagent effect on grain boundaries, and accelerates the process of etching. When the content in the reagent is less than 40 vol. H of a supersaturated aqueous solution of picric acid, the etching reaction is violent, resulting in the etching of grain boundaries to unequal depth and, therefore, their isolation is lacking, the microstructure is etched. When the content in the reagent is more than 60 vol.h, supersaturated aqueous solution of picric acid, the etching reaction of the polished section slows down and the laboriousness of detecting grain boundaries increases. Adding hydrogen peroxide to the reagent contributes to a clearer etching of the grain boundaries. With a peroxide content of less than 30 and more than 50 ob.ch. grain boundaries are etched to unequal depth, their isolation is lacking, the clarity of the overall etching pattern is reduced. Hydrofluoric acid in the reagent in the range of 1-5 ob.h. significantly affects the rate, the reaction of Splint etching and the nature of the resulting image. When its content is less than 1 ob.h. the etching reaction takes place in the field, the revealed boundaries are not closed, etched slightly, more than 5 parts by vol. - very rapid etching, etching occurs, apart from the grain boundaries - microstructures, sections of the surface of the thin section are etched.

Example 1. A thin section is prepared from chromium-nickel-molybdenum steel 18X2H4MA. 1-2 minutes are etched in a freshly prepared reagent containing, vol., {Hydrofluoric acid (C1 0.92) 1; 3b% hydrogen peroxide solution 30; supersaturated aqueous solution of picric acid 40. After light polishing, a metallographic examination of a thin section on an MIM microscope is carried out.

The use of etching reagent with the above-mentioned content of components makes it possible to clearly reveal the grain boundaries.

Example 2. A chromium-nickel-molybdenum steel section was etched in a reagent, containing, ob.ch.

hydrofluoric acid 5; 30% hydrogen peroxide solution 50; supersaturated aqueous solution of picric acid 80. After polishing, a metallographic examination of a thin section under a microscope is carried out. ,

The use of a reagent with the aforementioned content of components makes it possible to clearly reveal the grain boundaries, the microstructure, the orientation of the structural components relative to the grain boundaries.

Thus, the use of the proposed reagent allows to determine the grain size, grain boundaries and reveal the microstructure, as well as the orientation of the structural components relative to the grain boundaries in chromium-nickel-molybdenum steel 18X2H4WA.

Claims (1)

A reagent for detecting grain boundaries in steel containing hydrofluoric acid and hydrogen peroxide, characterized in that, in order to provide the possibility of determining the boundaries and grain sizes in chromium-nickel-molybdenum steel, it additionally contains a supersaturated aqueous solution of picric acid with the following ratio of components, about. h "Hydrofluoric acid (d = 0.92) 1-5 Hydrogen peroxide (30%) 30-50 A supersaturated aqueous solution of picric acid 40-80 S ω from SL * 4 00 SL