Etching agent and detecting method for macroscopic structure and defects of steel

Abstract

A corrosion reagent for detecting steel macrostructure and defects, and a detection method; the corrosion reagent is divided into three sub-reagents in order of use, a first sub-reagent comprising 5%-10% H2SO4, 20%-25% HNO3, and 65%-75% H2O, a second sub-reagent comprising 25%-35% HNO3 and 65%-75% H2O, and a third sub-reagent comprising 3%-5% HNO3 and 95%-97% H2O. The detection method comprises the following steps: pretreatment; corroding with the first sub-reagent for 20-30 minutes; corroding with the second sub-reagent for 10-20 minutes; corroding with the third sub-reagent for 3-5 minutes; and scanning and imaging. The method enables the metallurgical defects and microstructure of a steel ingot to be clearly shown without heat erosion, and has low requirements for surface smoothness and flatness of a sample, and is particularly suitable for macrostructure and defect detection for heavy casting and forging.

Description

technical field [0001] The invention belongs to the technical field of metal structure detection, and in particular relates to a steel macrostructure and defect corrosion reagent and a detection method. Background technique [0002] my country's current energy and power, metallurgical machinery, petrochemical, shipbuilding and other major technical equipment and major engineering constructions urgently need supporting high-quality large-scale castings and forgings. The large-scale castings and forgings industry is an indispensable strategic industry for my country to become an industrial power. The traditional casting and forging manufacturing process relies on experience, casting and forging is difficult to form, defect prevention, and performance control. However, the characterization of the macrostructure and defects of large-scale casting and forging is the main basis for research and optimization of casting and forging processes. Classification societies require inspect...

AI Technical Summary

Problems solved by technology

[0004] However, the sample size of large castings and forgings is very large, and the general size is more than 1.0m×1.0m×0.8m. If such a large cross-section sample is etched with hot acid, the size of the hot acid tank needs to be 2.0m×2.0m ×1.6m, the amount of acid solution is large, the acid smoke will cause serious pollution to the environment, and the cost of heating devices, hoisting equipment and test sites is very high

At the same time, due to the large size of the test surface of the sample, there is no suitable equipment to process the surface of the sample, making it difficult for the surface finish to meet the requirements of the existing GB226 standard

At present, the fastest way to process the surface of the sample is: after the experimental face milling cutter, the roughness is not higher than Ra3.2μm; and such a processing roughness, the existing standard cold acid etching method cannot The tissue is etched out; and after the surface of the sample is manually polished, although the smoothness of the local area is improved, the uneven surface leads to poor surface uniformity, and the surface flatness decreases, accompanied by original machining traces; therefore, It is difficult to make metallographic samples with good smoothness and flatness for large castings and forgings, which cannot meet the requirements of existing detection methods

[0005] In summary, the existing hot acid etching method consumes a large amount of acid solution, causes serious environmental pollution, and the cost of equipment and site is very high, so it cannot be applied to the macrostructure and defect detection of large castings and forgings; and the surface of large castings and forgings Difficult to process, poor surface finish and flatness, and cannot be applied to the existing cold acid etching method

Images