Chemical etching agent for displaying metallurgical structure of INVAR steel and soldered joints thereof and preparation method thereof

Abstract

The invention relates to a chemical etching agent for displaying the metallurgical structure of INVAR steel and soldered joints thereof and a preparation method thereof. One part of the chemical etching agent comprises the following components: 3-10g of chromium trioxide CrO3, 30-100ml of hydrochloric acid HCL (analytically pure) and 30-100ml of water H2O. The method comprises the following steps: (1) weighing required raw materials based on the prescription of each part of etching agent; and (2) firstly adding the chromium trioxide to water, stirring until the chromium trioxide is completely dissolved to form a mixed solution, then slowly adding the analytically pure hydrochloric acid to the mixed solution, and uniformly stirring to obtain the required chemical etching agent. The chemical etching agent for displaying the metallurgical structure of the INVAR steel and the soldered joints thereof has the advantages of good etching effect, high etching speed and high efficiency, can be stored for long, and has extremely high popularization and application value for the metallographic examination of the INVAR steel and the soldered joints thereof.

Description

technical field [0001] The invention relates to a chemical etchant, in particular to a chemical etchant for displaying the metallographic structure of INVAR steel and its welded joints and a preparation method thereof. Background technique [0002] Metallographic inspection is a commonly used test method in modern industry, and it is an important means to control the quality of mechanical products, research and development of new materials, new processes and new products. It refers to the process of observing the metallographic structure of metal materials through a microscope and making qualitative identification and quantitative measurement, such as determining the size, shape and distribution characteristics, grain size, inclusion type and quantity of each constituent phase in the alloy, and The organization of the surface treatment layer, etc. It can provide qualitative or quantitative test results on the matrix structure, grain size, and second equivalent parameters of...

AI Technical Summary

Problems solved by technology

Due to the special material of INVAR steel, commonly used chemical etchants cannot make it show metallographic structure; while the foreign technical document GTT No.96Contatinment System for LNG Carrier (External document N o 1096-1)) The INVAR steel etchant formulation provided: 50 milliliters of distilled water, 50 milliliters of 94%-95% alcohol, 50 milliliters of hydrochloric acid, 20 grams of copper sulfate containing 5 crystal waters, in practical application, there are the following deficiencies : 1. The erosion speed is slow, and the erosion time needs more than ten minutes or even longer

2. The corrosive agent has a short validity period and cannot be used for a long time. It is necessary to always use a new reagent

3. The erosion result is unstable, and the metallographic structure that can be clearly observed cannot be stably obtained