Corrosive agent for high-manganese non-magnetic steel and method for corroding the same

Abstract

The application discloses a kind of high-manganese non-magnetic steel etchant and its corrosion method, belong to chemical technology field.The high-manganese non-magnetic steel etchant of the application includes the following volume fraction components: concentrated hydrochloric acid 6-8 parts, concentrated nitric acid 1-4 parts, anhydrous ethanol 10-38 parts.The etchant of the application can avoid the shortcomings that conventional aqua regia solution needs to be configured and placed for a long time, is volatile and not easy to store, can be used immediately and can be stored and reused within 1-2 months.Meanwhile, the metallographic surface after immersion etching has fewer black spots and clear grain boundaries compared to conventional aqua regia solution immersion etching, and can be well rated for grain size.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a corrosive agent and its corrosion method for high-manganese non-magnetic steel. Background Technology

[0002] High-manganese non-magnetic steel is commonly used in the manufacture of non-magnetic drill collars for drilling, generator retaining rings, and other workpieces. It is a high-strength, high-toughness, and corrosion-resistant austenitic stainless steel. After the workpiece leaves the factory, its metallographic structure is not easily corroded during metallographic inspection. The elemental contents of high-manganese non-magnetic steel are shown in the table below.

[0003] Table 1. Elemental content of high-manganese non-magnetic steel

[0004]

[0005] Currently, aqua regia solution with a hydrochloric acid to nitric acid ratio of 3:1 is generally used to etch high-manganese non-magnetic steel. Disadvantages: the aqua regia solution needs to stand for 3-4 hours after preparation for the etching effect to be noticeable; the reaction rate is too fast, making the etching effect difficult to control; aqua regia is extremely unstable and will become ineffective after 2-3 days. Ferric chloride hydrochloric acid solution is also a common metallographic etching agent for non-magnetic steel, with a ratio of 5g:50mL:100mL for ferric chloride, hydrochloric acid, and water, which can be prepared and used immediately. However, the etching effect of ferric chloride hydrochloric acid solution on factory-made workpieces is not ideal, and the grain boundary structure cannot be fully revealed. There are also reports of preparing a stainless steel metallographic etching agent by adding hydrofluoric acid, water, and ferric chloride to the aqua regia solution formula, with an etching time of 3-10 minutes, but the metallographic etching agent ratio is complex. Therefore, there is an urgent need for a high-manganese non-magnetic steel etchant with good corrosion effect, simple preparation, good stability, and easy storage. Summary of the Invention

[0006] To address the problems existing in the prior art, the purpose of this invention is to provide a corrosive agent and a corrosion method for high-manganese non-magnetic steel.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A corrosive agent for high-manganese non-magnetic steel comprises the following components in parts by volume:

[0009] 6-8 parts concentrated hydrochloric acid, 1-4 parts concentrated nitric acid, and 10-38 parts anhydrous ethanol.

[0010] In one specific embodiment, the etchant for the high-manganese non-magnetic steel comprises the following components in parts by volume:

[0011] 7.5 parts concentrated hydrochloric acid, 2.5 parts concentrated nitric acid, and 15 parts anhydrous ethanol.

[0012] The preparation method of the etchant for high-manganese non-magnetic steel includes the following steps:

[0013] First add concentrated hydrochloric acid, then concentrated nitric acid, stirring constantly; finally add anhydrous ethanol, let stand, and stir constantly until the corrosive agent cools to room temperature, then pour it into a brown reagent bottle for storage.

[0014] The application of the etchant for high-manganese non-magnetic steel prepared by the above method in the corrosion of high-manganese non-magnetic steel.

[0015] A method for corroding high-manganese non-magnetic steel, using a corrosive agent for high-manganese non-magnetic steel prepared by the above method.

[0016] In one specific embodiment, the method for corroding high-manganese non-magnetic steel comprises the following steps:

[0017] After grinding and polishing, the surface of the high-manganese non-magnetic steel metallographic sample is immersed in the etchant for high-manganese non-magnetic steel prepared by the above method for 5 to 10 minutes. When the sample surface turns silver-gray or brownish-blue, the sample is removed and the etchant on the sample surface is rinsed with clean water. Then, the sample surface is gently wiped with a water-soaked degreased cotton ball.

[0018] In one specific embodiment, the surface grinding method of the high-manganese non-magnetic steel metallographic sample involves grinding with 120-mesh, 400-mesh, 800-mesh, and 2000-mesh sandpaper in sequence, and finally mechanically polishing with 9μm and 6μm diamond suspensions in sequence.

[0019] Advantages of the technical solution of this invention:

[0020] Currently, the commonly used metallographic etching agent for non-magnetic steel is aqua regia solution, with a hydrochloric acid to nitric acid ratio of 3:1. However, this etchant is too corrosive, the etching rate is too fast, it is difficult to control the degree of etching, and the surface of the etched sample is prone to having many black spots and impurities, which are difficult to clean. At the same time, aqua regia solution has disadvantages such as being volatile, difficult to store, and requiring a long time to stand after preparation before use.

[0021] The etchant of this invention avoids the drawbacks of conventional aqua regia solutions, such as the need for long-term storage after preparation, easy volatility, and difficulty in preservation. It can be prepared and used immediately and can be stored and reused within 1-2 months. At the same time, the metallographic surface after etching produces fewer black spots and clearer grain boundaries compared to conventional aqua regia solutions, allowing for better grain size rating.

[0022] The concentrated hydrochloric acid and concentrated nitric acid in this invention have extremely strong oxidizing properties, while anhydrous ethanol has reducing properties. After being mixed and prepared, the oxidizing ability of the corrosive agents is reduced, which can effectively control the corrosion process and will not cause great harm to the human body like aqua regia. Attached Figure Description

[0023] Figure 1The effect of corrosive agent etching of high-manganese non-magnetic steel in Example 1 is shown in the figure.

[0024] Figure 2 Example 2: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0025] Figure 3 Example 3: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0026] Figure 4 Example 4: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0027] Figure 5 Example 5: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0028] Figure 6 Example 6: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0029] Figure 7 Example 7: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0030] Figure 8 Example 8: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0031] Figure 9 Example 9: Effect diagram of corrosion of high-manganese non-magnetic steel by corrosive agent;

[0032] Figure 10 The effect of the corrosive agent eroding high-manganese non-magnetic steel in Comparative Example 1;

[0033] Figure 11 The effect of the corrosive agent eroding high-manganese non-magnetic steel in Comparative Example 2;

[0034] Figure 12 The effect of etching 06Cr19Ni9NbN austenitic stainless steel with corrosive agent in Example 3 is shown in the figure.

[0035] Figure 13 Example 3: Effect image of corrosion of high-manganese non-magnetic steel after one month of exposure to corrosive agent;

[0036] Figure 14 The effect of the corrosive agent in Example 3 etching high-manganese non-magnetic steel after being placed for 2 months. Detailed Implementation

[0037] Unless otherwise stated, the terms used in this invention generally have the meanings commonly understood by those skilled in the art.

[0038] The present invention will now be described in further detail with reference to specific embodiments and data. These embodiments are merely illustrative and are not intended to limit the scope of the invention in any way.

[0039] In the following examples, the concentrated hydrochloric acid has an analytical grade concentration of 36-38% by mass; the concentrated nitric acid has an analytical grade concentration of 65-68% by mass; the anhydrous ethanol has an analytical grade concentration of ≥99.7% by mass; and the ferric chloride has an analytical grade concentration of ≥99.0% by mass.

[0040] Example 1

[0041] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0042] 6 mL concentrated hydrochloric acid, 2.5 mL concentrated nitric acid, and 16.5 mL anhydrous ethanol;

[0043] The preparation method is as follows:

[0044] First add concentrated hydrochloric acid, then concentrated nitric acid, and stir continuously with a glass rod. Finally, add anhydrous ethanol, let it stand, and stir continuously with a glass rod until the temperature of the corrosive agent drops to room temperature. Then pour it into a brown reagent bottle to obtain the final product.

[0045] Example 2

[0046] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0047] 7.5 mL concentrated hydrochloric acid, 4 mL concentrated nitric acid, 13.5 mL anhydrous ethanol;

[0048] The preparation method is the same as in Example 1.

[0049] Example 3

[0050] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0051] 7.5 mL concentrated hydrochloric acid, 2.5 mL concentrated nitric acid, 15 mL anhydrous ethanol;

[0052] The preparation method is the same as in Example 1.

[0053] Example 4

[0054] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0055] 6 mL concentrated hydrochloric acid, 4 mL concentrated nitric acid, and 38 mL anhydrous ethanol;

[0056] The preparation method is the same as in Example 1.

[0057] Example 5

[0058] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0059] 7 mL concentrated hydrochloric acid, 3.5 mL concentrated nitric acid, and 22.5 mL anhydrous ethanol;

[0060] The preparation method is the same as in Example 1.

[0061] Example 6

[0062] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0063] 7.5 mL concentrated hydrochloric acid, 4 mL concentrated nitric acid, 28 mL anhydrous ethanol;

[0064] The preparation method is the same as in Example 1.

[0065] Example 7

[0066] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0067] 8 mL concentrated hydrochloric acid, 2 mL concentrated nitric acid, and 10 mL anhydrous ethanol;

[0068] The preparation method is the same as in Example 1.

[0069] Example 8

[0070] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0071] 6 mL concentrated hydrochloric acid, 1 mL concentrated nitric acid, and 15 mL anhydrous ethanol;

[0072] The preparation method is the same as in Example 1.

[0073] Example 9

[0074] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0075] 8 mL concentrated hydrochloric acid, 2 mL concentrated nitric acid, and 20 mL anhydrous ethanol;

[0076] The preparation method is the same as in Example 1.

[0077] Comparative Example 1

[0078] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0079] 3 mL concentrated hydrochloric acid, 1 mL concentrated nitric acid;

[0080] First add concentrated hydrochloric acid, then concentrated nitric acid, and stir continuously with a glass rod. After standing, stir continuously with a glass rod until the temperature of the corrosive agent drops to room temperature, then pour it into a brown reagent bottle to obtain the product.

[0081] Comparative Example 2

[0082] A corrosion agent for high-manganese non-magnetic steel is formulated from the following components:

[0083] 50 mL concentrated hydrochloric acid, 100 mL water, 5 g ferric chloride;

[0084] First add concentrated hydrochloric acid, then add water, and stir continuously with a glass rod. After standing, add the weighed ferric chloride and stir continuously with a glass rod until the ferric chloride is completely dissolved in the solution. Pour the solution into a brown reagent bottle to obtain the final product.

[0085] Example 10

[0086] A method for corroding high-manganese non-magnetic steel is as follows:

[0087] After sampling the high-manganese non-magnetic steel, the surface to be inspected needs to be ground sequentially with 120-grit, 400-grit, 800-grit, and 2000-grit sandpaper. Then, the surface to be inspected is mechanically polished to a scratch-free mirror finish with 9μm and 6μm diamond suspensions. After that, the sample is placed in a beaker, and then the etching agent is poured into the beaker to immerse the sample for etching. After that, it is left for 5 to 10 minutes. When the sample surface turns silver-gray or brownish-blue, the sample is removed and the etching agent on the sample surface is rinsed off with clean water. The sample surface is then gently wiped with a water-soaked degreased cotton ball. Finally, the sample surface is rinsed with alcohol and dried with a hair dryer.

[0088] After etching the high-manganese non-magnetic steel with the etchant from Example 1 for 8 minutes, the surface to be inspected was placed under a metallographic microscope for photographing. The metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows: Figure 1 As shown.

[0089] After etching the high-manganese non-magnetic steel with the etchant of Example 2 for 2 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 2 As shown, when the etchant of Example 2 is used for etching, the etchant solution boils immediately after standing for 5 minutes, turns reddish-brown, and is extremely unstable.

[0090] After etching the high-manganese non-magnetic steel with the etchant of Example 3 for 6 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 3 As shown.

[0091] After etching the high-manganese non-magnetic steel with the etchant of Example 4 for 9 minutes, the surface to be inspected was placed under a metallographic microscope for photographing. The metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows: Figure 4 As shown.

[0092] After etching the high-manganese non-magnetic steel with the etchant of Example 5 for 7 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 5 As shown.

[0093] After etching the high-manganese non-magnetic steel with the etchant of Example 6 for 5 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 6 As shown.

[0094] After etching the high-manganese non-magnetic steel with the etchant of Example 7 for 2 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 7 As shown. When etched with the etchant of Example 7, the etchant solution boiled immediately after standing for 10 minutes, turned green, and was unstable.

[0095] After etching the high-manganese non-magnetic steel with the etchant of Example 8 for 10 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 8 As shown.

[0096] After etching the high-manganese non-magnetic steel with the etchant of Example 9 for 6 minutes, the surface to be inspected was placed under a metallographic microscope for photographing, and the metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows. Figure 9 As shown.

[0097] After wiping the high-manganese non-magnetic steel with the etchant from Comparative Example 1 for 30 seconds, the surface to be inspected was photographed under a metallographic microscope to observe the metallographic surface of the high-manganese non-magnetic steel after etching. Figure 10 As shown.

[0098] After wiping the high-manganese non-magnetic steel with the etchant from Comparative Example 2 for 1 minute, the surface to be inspected was placed under a metallographic microscope for photographing. The metallographic surface of the high-manganese non-magnetic steel after etching was observed as follows: Figure 11 As shown.

[0099] After etching 06Cr19Ni9NbN austenitic stainless steel with the etchant of Example 3 for 6 minutes, the surface to be inspected was photographed under a metallographic microscope to observe the metallographic surface of the high-manganese non-magnetic steel after etching. Figure 12 As shown.

[0100] The etchant used in Example 3 was left to stand for one month before being used to etch high-manganese non-magnetic steel. After 8 minutes, the surface to be inspected was photographed under a metallographic microscope to observe the metallographic surface of the high-manganese non-magnetic steel after etching. Figure 13 As shown.

[0101] The etchant used in Example 3 was left to stand for 2 months before being used to etch high-manganese non-magnetic steel. After 13 minutes, the surface to be inspected was photographed under a metallographic microscope to observe the metallographic surface of the high-manganese non-magnetic steel after etching. Figure 14 As shown.

[0102] Depend on Figures 1 to 14It can be seen that the etchants in Examples 2 and 7 have good etching effects, but both etchants are unstable. When aqua regia (Comparative Example 1) is used to etch high-manganese non-magnetic steel, there are many black spots on the metallographic surface. When ferric chloride hydrochloric acid aqueous solution is used to etch high-manganese non-magnetic steel, the grain boundaries are not clear. In summary, the etchant in Example 3 has the best etching effect on high-manganese non-magnetic steel. When the etchant in Example 3 is used to etch 06Cr19Ni9NbN austenitic stainless steel, the etchant in Example 3 has a poor etching effect on 06Cr19Ni9NbN austenitic stainless steel for the same etching time. The etchant in Example 3 still has a good etching effect after being placed for 1 month and 2 months, but the etching time is prolonged.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A corrosive agent for high-manganese non-magnetic steel, characterized in that, It consists of the following components in parts by volume: 7.5 parts concentrated hydrochloric acid, 2.5 parts concentrated nitric acid, and 15 parts anhydrous ethanol.

2. The method for preparing the etchant for high-manganese non-magnetic steel according to claim 1, characterized in that, The steps are as follows: First add concentrated hydrochloric acid, then concentrated nitric acid, stirring constantly; finally add anhydrous ethanol, let stand, and stir constantly until the corrosive agent cools to room temperature, then pour it into a brown reagent bottle for storage.

3. The application of the etchant for high-manganese non-magnetic steel prepared by the method of claim 2 in the corrosion of high-manganese non-magnetic steel.

4. A method for corroding high-manganese non-magnetic steel, characterized in that, The etchant for high-manganese nonmagnetic steel prepared using the method described in claim 2.

5. The method for corroding high-manganese non-magnetic steel according to claim 4, characterized in that, The steps are as follows: After grinding and polishing, the surface of the high-manganese non-magnetic steel metallographic sample is immersed in the etchant for high-manganese non-magnetic steel prepared by the method described in claim 2 for 5 to 10 minutes. When the sample surface turns silver-gray or brownish-blue, the sample is removed and the etchant on the sample surface is rinsed with clean water. Then, the sample surface is gently wiped with a water-soaked degreased cotton ball.

6. The method for corroding high-manganese non-magnetic steel according to claim 5, characterized in that, The surface grinding method of the high-manganese non-magnetic steel metallographic sample is to grind it sequentially with 120-mesh, 400-mesh, 800-mesh, and 2000-mesh sandpaper, and finally to mechanically polish it sequentially with 9μm and 6μm diamond suspensions.

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