Corrosive agent and method for revealing G20CrNi4 granular bainite structure

Abstract

The application provides a corrosion agent and method for displaying G20CrNi4 granular bainite structure, the corrosion agent is prepared by 2%-4% nitric acid alcohol solution, hydrochloric acid and ferric chloride in the proportion of 100ml:0.3-0.7ml:0.4g-0.6g; the method for displaying granular bainite structure comprises sample preparation, corrosion agent preparation, granular bainite structure corrosion and metallographic microscope observation. The corrosion agent provided by the application is simple to prepare, the method for displaying granular bainite structure is stable and reliable, simple to operate, and can realize corrosion and clear display of granular bainite structure of carburizing bearing steel.

Description

Technical Field

[0001] This invention belongs to the field of detection technology, specifically relating to a corrosive agent and method for displaying granular bainitic structure of G20CrNi4. Background Technology

[0002] Metallic materials have always been widely used. With economic development, users have increasingly higher requirements for the performance and internal and external quality of steel. Microstructure is a crucial indicator of steel product quality, directly determining product performance. Microstructural inspection is the most commonly used method in modern steel enterprises to inspect the internal quality of steel materials. Its principle is to select appropriate corrosive agents based on different microstructures, ensuring accurate and reliable microstructural visualization, and allowing the test results to reflect the quality of the steel.

[0003] For polished samples, different etching methods and etching times are used. Different components are etched to varying degrees, resulting in different microstructures. The observation and judgment of the microstructure are closely related to the accuracy and clarity of its appearance. Finding the most suitable etchant and display method for each microstructure or steel grade is an important measure for steel inspection, and can better guide production personnel to improve processes.

[0004] Currently, ferrite and pearlite microstructures are the most commonly examined. Due to their simple microstructures and low visibility requirements, single etchants are commonly used. However, the visibility of granular bainite microstructure in carburized bearing steel G20CrNi4 is still in the exploratory stage. The original method uses nitric acid alcohol to visualize granular bainite microstructure. Although bainite microstructure can be observed, island-like structures cannot be clearly observed, and the boundaries of the island-like structures are unclear. Their morphology, distribution, and arrangement cannot be clearly visualized. There is an urgent need to find an etchant and visualization method that can clearly visualize granular bainite microstructure, thus ensuring the production and application of carburized bearing steel G20CrNi4. Summary of the Invention

[0005] The purpose of this invention is to provide a etchant and method for displaying the granular bainitic structure of G20CrNi4. The provided etchant is simple to prepare, the display method is stable and reliable, and the operation is simple, which can achieve clear display of the granular bainitic structure of carburized bearing steel.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] A etchant for displaying granular bainitic structure of G20CrNi4 is prepared by mixing a 2%–4% nitric acid alcohol solution, hydrochloric acid, and ferric chloride in a ratio of 100 ml: 0.3–0.7 ml: 0.4 g–0.6 g.

[0008] The preparation process of the corrosive agent of the present invention is as follows: Prepare 100 ml of 2% to 4% nitric acid alcohol solution, add 0.3 to 0.7 ml of hydrochloric acid to it, mix and stir evenly, then add 0.4 g to 0.6 g of ferric chloride to it, and stir to dissolve.

[0009] The present invention also provides a method for displaying granular bainitic microstructure of G20CrNi4, comprising the following steps:

[0010] (1) Sample preparation: The sample is processed into a size of (15~20)mm×(10~15)mm×(10~15)mm, and the sample is ground and polished. The surface roughness requirement is the same as that of the metallographic sample.

[0011] (2) Preparation of corrosive agent: Prepare 100 ml of 2% to 4% nitric acid alcohol solution, add 0.3 to 0.7 ml of hydrochloric acid, mix and stir evenly, then add 0.4 g to 0.6 g of ferric chloride and stir to dissolve;

[0012] (3) Corrosion of granular bainite structure: Place the prepared sample into the corrosive agent described in step (2) with the corrosion surface facing down, and the corrosion time is 20-40 seconds; after corrosion, take out the sample, rinse and dry it.

[0013] (4) It can be observed with a metallographic microscope.

[0014] Furthermore, the rinsing in step (3) of the present invention is first rinsed with water and then rinsed with ethanol.

[0015] The hydrochloric acid used in this invention is of analytical grade.

[0016] The technical solution of this invention has the following beneficial effects:

[0017] The method of this invention can clearly display the granular bainitic structure of carburized bearing steel G20CrNi4, as well as the distribution, arrangement and morphology of island structures within the granular bainitic structure. Based on the distribution, arrangement and morphology of the island structures, reliable data can be provided for process adjustment, thus ensuring the production of high-quality new carburized bearing steel.

[0018] The etchant provided by this invention is simple to prepare, and the method for displaying granular bainite and island structures is stable, reliable, and easy to operate. It can achieve corrosion and clear display of granular bainite structures in carburized bearing steel. Attached Figure Description

[0019] Figure 1 This is the granular bainitic structure shown in Example 1.

[0020] Figure 2 This is the granular bainitic structure shown in Example 2.

[0021] Figure 3 This is the granular bainitic structure shown in Example 3. Implementation

[0022] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. Example 1

[0023] A method for displaying the granular bainitic microstructure of φ150mm carburized bearing steel G20CrNi4 includes the following steps:

[0024] (1) Sample preparation: The continuous casting billet was processed into a size of about 10mm×10mm×20mm. The 10mm×20mm corrosion surface was ground smooth with an 80# grinding wheel, and then smoothed with 500# and 800# wet sandpaper in sequence. It was then polished with diamond polishing spray at 7μm and set aside for use.

[0025] (2) Preparation of corrosive agent: Use a 200ml beaker, add 97ml of alcohol, add 3ml of nitric acid to the 97ml of alcohol, stir evenly, then add 0.7ml of hydrochloric acid, mix and stir evenly, and then add 0.4g of ferric chloride;

[0026] (3) Corrosion of granular bainite structure: Wear protective gloves, place the prepared sample in the prepared corrosive agent, immerse the entire test surface of the sample in the corrosive agent, and do not touch the corrosive agent container. Gently shake it twice, and the corrosion time is 20 seconds. After corrosion, take out the sample, rinse it with water and ethanol in sequence, and then use a powerful hair dryer to dry it quickly.

[0027] (4) A clear granular bainite structure can be obtained by placing the sample under a metallographic microscope, see [reference needed]. Figure 1 . Example 2

[0028] A method for displaying the granular bainitic structure of φ85mm carburized bearing steel G20CrNi4 includes the following steps:

[0029] (1) Sample preparation: The continuous casting billet was machined into a size of about 10mm×15mm×20mm. The etched surface was smoothed with an 80# grinding wheel of 15mm×20mm. Then, it was smoothed with 500# and 800# wet sandpaper in sequence. Finally, it was polished with diamond polishing spray at 7μm and set aside for use.

[0030] (2) Preparation of corrosive agent: Use a 250ml beaker, add 98ml of alcohol, add 2ml of nitric acid to the 98ml of alcohol, stir evenly, then add 0.3ml of hydrochloric acid, mix and stir evenly, and then add 0.5g of ferric chloride;

[0031] (3) Corrosion of granular bainite structure: Wear protective gloves, place the prepared sample in the prepared corrosive agent, immerse the entire test surface of the sample in the corrosive agent, and do not touch the corrosive agent container. Gently shake it twice, and the corrosion time is 30 seconds. After corrosion, take out the sample, rinse it with water and ethanol in sequence, and then use a powerful hair dryer to dry it quickly.

[0032] (4) A clear granular bainite structure can be obtained by placing the sample under a metallographic microscope, see [reference needed]. Figure 2 . Example 3

[0033] A method for displaying the granular bainitic structure of φ210mm carburized bearing steel G20CrNi4 includes the following steps:

[0034] (1) Sample preparation: The continuous casting billet was machined into a size of about 10mm×15mm×15mm. The etched surface was ground smooth with a 10mm×15mm 80# grinding wheel, and then smoothed with 500# and 800# wet sandpaper in sequence. It was then polished with diamond polishing spray at 7μm and set aside for use.

[0035] (2) Preparation of corrosive agent: Use a 250ml beaker, add 96ml of alcohol, add 4ml of nitric acid to 96ml of alcohol, stir evenly, then add 0.5ml of hydrochloric acid, mix and stir evenly, and then add 0.6g of ferric chloride;

[0036] (3) Corrosion of granular bainite structure: Wear protective gloves, place the prepared sample in the prepared corrosive agent, immerse the entire test surface of the sample in the corrosive agent, and do not touch the corrosive agent container. Gently shake it twice, and the corrosion time is 22s. After corrosion, take out the sample, rinse it with water and ethanol in sequence, and then use a powerful hair dryer to dry it quickly.

[0037] (4) A clear granular bainite structure can be obtained by placing the sample under a metallographic microscope, see [reference needed]. Figure 3 .

Claims

1. A etchant that displays a granular bainitic structure of G20CrNi4, characterized in that, It is prepared by mixing 2%–4% nitric acid alcohol solution, hydrochloric acid, and ferric chloride in a ratio of 100 ml: 0.3–0.7 ml: 0.4 g–0.6 g; the hydrochloric acid is of analytical grade.

2. The etchant that displays a granular bainitic structure of G20CrNi4 as described in claim 1, characterized in that, The preparation process of the corrosive agent is as follows: Prepare 100 ml of 2% to 4% nitric acid alcohol solution, add 0.3 to 0.7 ml of hydrochloric acid, mix and stir evenly, then add 0.4 g to 0.6 g of ferric chloride and stir to dissolve.

3. A method for displaying granular bainitic microstructure of G20CrNi4, characterized in that: The method includes the following steps: (1) Sample preparation: The sample is processed into a size of (15~20)mm×(10~15)mm×(10~15)mm, and the sample is ground and polished. (2) Preparation of corrosive agent: Prepare 100 ml of 2% to 4% nitric acid alcohol solution, add 0.3 to 0.7 ml of hydrochloric acid, mix and stir evenly, then add 0.4 g to 0.6 g of ferric chloride and stir to dissolve; (3) Corrosion of granular bainite structure: Place the prepared sample in the prepared etchant with the etched surface facing down, and etch for 20-40 seconds; after etching, take out the sample, rinse and dry it. (4) The sample can be observed under a metallographic microscope.

4. The method for displaying granular bainitic microstructure of G20CrNi4 as described in claim 3, characterized in that: The rinsing in step (3) involves rinsing with water and then with ethanol in sequence.

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