Corrosive agent for displaying alloy steel 32CrNi3MoVE grain boundary and corrosion method

Abstract

The invention relates to a corrosive agent and a corrosion method for displaying a 32CrNi3MoVE crystal boundary of alloy steel, which are characterized in that a common chemical product is used as an electrolytic corrosive agent after being simply proportioned, and the 32CrNi3MoVE steel quenched and tempered state original austenite crystal boundary is clearly displayed by a proper corrosion method. Chemical reagents used by the corrosive are economical and applicable, the corrosive is composed of alum, oxalic acid, dishwashing liquid, distilled water and the like which are existing in a laboratory, the proportioning of the corrosive is the key, the electrolytic corrosion method is simple to operate, alum can effectively display the grain boundary, oxalic acid provides a weak acid environment for oxidation reduction, and the corrosion effect is good. The dishwashing liquid slows down the corrosion rate of weak acid electrolyte to a metallographic specimen, weakens structure display, and improves the definition of crystal boundary display. The corroded sample is lightly polished in a polishing machine, and the corrosive agent ratio and the electrolytic corrosion method are combined to form an efficient novel corrosion method. The traditional corrosive agent capable of completely replacing saturated picric acid and a proper amount of detergent and the corrosion method effectively solve the problem of 32CrNi 3MoVE steel quenched and tempered state original austenite grain boundary display.

Description

Technical Field

[0001] The invention belongs to the technical field of metallographic detection, and in particular relates to an etchant and a corrosion method for displaying the grain boundary of alloy steel 32CrNi3MoVE. Background Art

[0002] The original austenite grain size has a very important influence on the performance of steel. How to quickly and clearly display the original austenite grain boundaries after heat treatment of steel is of great significance to the research of steel. 32CrNi3MoVE material belongs to medium carbon structural steel. After austenitization heating, it is quenched to obtain martensite structure, and the original austenite grain boundaries are retained. After high temperature tempering, the tempered bainite structure is obtained, and its original austenite grain boundaries are difficult to display. At present, the common original austenite grain boundary display technologies mainly include oxidation method, ferrite network method, cementite network method, ordinary chemical corrosion method, hot dip etching method and electrolytic corrosion method. Among them, the oxidation method is more complicated to operate, and oxidation will hinder the growth of austenite grains, so it cannot accurately reflect the true original austenite grain size during normal heat treatment. The ferrite network method and cementite network method are suitable for low alloy steel, but not for medium carbon structural steel. At present, the only corrosion method for the tempered austenite grains of medium-carbon structural steel is hot-dip etching, which uses a supersaturated picric acid solution to boil and then etch. This method can well display the tempered austenite grains of medium-carbon structural steel without showing the structure. However, picric acid is a raw material for making explosives and cannot be purchased normally on the market. Therefore, it is urgent to find a new corrosion method to replace picric acid corrosion. Summary of the invention

[0003] The present invention provides an etchant and a corrosion method for displaying the grain boundaries of alloy steel 32CrNi3MoVE, which solves the problem of displaying the original austenite grain boundaries of 32CrNi3MoVE steel in a quenched and tempered state. Commonly used chemicals and simple proportions are used as electrolytic etchants, and appropriate corrosion methods are used to clearly display the original austenite grain boundaries of 32CrNi3MoVE steel in a quenched and tempered state.

[0004] In order to solve the above technical problems, the present invention provides an electrolytic etchant for displaying the grain boundary of alloy steel 32CrNi3MoVE, characterized in that:

[0005] The components of the electrolytic corrosive agent are: saturated alum solution, oxalic acid, and detergent. The specific ratio is: 100ml saturated alum solution, 2-5g oxalic acid, and 2-5ml detergent.

[0006] A corrosion method based on an electrolytic corrosive agent for displaying the grain boundaries of alloy steel 32CrNi3MoVE, characterized in that it comprises the following steps:

[0007] (1) Cut metallographic specimens from alloy steel samples and perform rough grinding and chamfering;

[0008] (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpapers, respectively. During the grinding process, the grinding marks of this process were perpendicular to the grinding marks of the previous process, and the grinding marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles;

[0009] (3) After fine grinding, the sample is polished on the surface of metallographic velvet;

[0010] (4) Cleaning after polishing;

[0011] (5) The polished sample is used as the anode and the graphite plate is used as the cathode. The sample is placed in the electrolytic corrosive agent as described in claim 1 at a voltage of 3-5 V for 30 s to 50 s. When the polished surface of the sample completely turns light gray, the sample is taken out and rinsed with clean water. After the sample is lightly polished on a polishing machine to remove excess corrosion products on the surface, it can be observed.

[0012] Beneficial effects: The chemical reagents used in the corrosive agent of the present invention are economical and applicable, and are composed of alum, oxalic acid, detergent, distilled water, etc. available in the laboratory. The corrosive agent ratio is particularly critical, and the electrolytic corrosion method is simple to operate. Alum can effectively display the grain boundary, oxalic acid provides a weak acid environment for oxidation and reduction, and detergent slows down the corrosion rate of the weak acid electrolyte on the metallographic sample, weakens the organization display, and improves the clarity of the grain boundary display. The sample after corrosion is lightly polished in a polishing machine, and the corrosive agent ratio is combined with the electrolytic corrosion method to form an efficient new corrosion method. It can completely replace the traditional corrosive agent and corrosion method of saturated "picric acid + appropriate amount of detergent" and effectively solve the problem of displaying the original austenite grain boundary of 32CrNi3MoVE steel in the tempered state. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The metallographic image of the original austenite grain boundary of the 32CrNi3MoVE steel in the quenched and tempered state prepared in Example 1 of the present invention;

[0014] Figure 2 The metallographic image of the original austenite grain boundary of the 32CrNi3MoVE steel prepared in Example 2 of the present invention;

[0015] Figure 3 This is a metallographic diagram of the original austenite grain boundary of the 32CrNi3MoVE steel in the quenched and tempered state prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below.

[0017] The invention provides an electrolytic corrosive agent for displaying the grain boundary of alloy steel 32CrNi3MoVE, which is characterized by: the electrolytic corrosive agent comprises: saturated alum solution, oxalic acid and Liby detergent, and the specific proportion is: 100 ml of saturated alum solution, 2-5 g of oxalic acid and 2-5 ml of detergent.

[0018] Preparation method of electrolytic corrosive agent: add 100ml of saturated alum solution into a dry beaker, use a balance to measure 2-5g of oxalic acid and add it to the beaker, use a measuring cylinder to measure 2-5ml of detergent and add it to the beaker, and stir thoroughly.

[0019] A corrosion method based on an electrolytic etchant for displaying the grain boundaries of alloy steel 32CrNi3MoVE, characterized in that:

[0020] (1) A metallographic specimen of 15 mm × 15 mm × 15 mm was cut from the alloy steel sample, and its cross section was coarsely ground by 2 mm using 240# sandpaper, and the four sides of the cross section were chamfered.

[0021] (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpapers, respectively. During the grinding process, the grinding marks of this process were perpendicular to the grinding marks of the previous process, and the grinding marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles;

[0022] (3) After fine grinding, the sample is polished on the surface of metallographic velvet. The velvet can be attached to a polishing machine with a speed of less than 600 rpm. Diamond powder with a particle size of 1 to 3.5 μm can be used during polishing. The surface of the sample after polishing should be free of dirt and scratches visible to the naked eye.

[0023] (4) Rinse the polished surface with clean water, then with anhydrous ethanol and blow dry;

[0024] (5) Use the polished sample as the anode and the graphite plate as the cathode in the prepared electrolytic corrosive agent with an electrolytic voltage of 3-5 V and a time of 30s-50s. When the polished surface of the sample completely turns light gray, take it out, rinse it with clean water, and lightly polish it on a polishing machine to remove excess corrosion on the surface before observation.

[0025] (6) Use an optical microscope to observe, collect and grade the microscopic morphology of the original austenite grains.

[0026] Example 1 and Example 2 use the same electrolytic corrosive agent, and the components of the electrolytic corrosive agent are: saturated alum solution, oxalic acid, and Liby detergent. The specific ratio is: 100 ml of saturated alum solution, 5 g of oxalic acid, and 3 ml of Liby detergent.

[0027] Electrolytic corrosive agent mixing method: Add 100 ml of saturated alum solution into a dry beaker, use a balance to measure 5 g of oxalic acid and add it to the beaker, use a measuring cylinder to measure 3 ml of Liby dishwashing liquid and add it to the beaker, and stir thoroughly.

[0028] Example 1

[0029] (1) A metallographic specimen of 15 mm × 15 mm × 15 mm was cut from the sample, and its cross section was coarsely ground by 2 mm using 240# sandpaper, and the edges of the cross section were chamfered.

[0030] (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpaper. During the grinding process, the wear marks of this process were perpendicular to the wear marks of the previous process, and the wear marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles.

[0031] (3) After fine grinding, the sample is polished on the surface of metallographic velvet. The velvet can be attached to a polishing machine with a speed of less than 600 rpm. Diamond powder with a particle size of 3.5 μm can be used during polishing. The surface of the sample after polishing should be free of dirt and scratches visible to the naked eye.

[0032] (4) Rinse the polished surface with clean water, then with anhydrous ethanol and blow dry;

[0033] (5) Use the polished sample as the anode and the graphite plate as the cathode and place it in the electrolytic corrosive agent prepared in step 1. The electrolysis voltage is 4 V and the time is 40 s. After the polished surface of the sample completely turns light gray, take it out and rinse it with clean water. After that, lightly polish it on a polishing machine to remove excess corrosion products on the surface and observe it under a metallographic microscope.

[0034] Corrosion effect: The original austenite grain boundary morphology of the sample in Example 1 is clearly visible, and the original austenite grain size can be accurately rated.

[0035] Example 2

[0036] (1) A metallographic specimen of 15 mm × 15 mm × 15 mm was cut from the sample, and its cross section was coarsely ground by 2 mm using 240# sandpaper, and the edges of the cross section were chamfered.

[0037] (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpaper. During the grinding process, the wear marks of this process were perpendicular to the wear marks of the previous process, and the wear marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles.

[0038] (3) After fine grinding, the sample is polished on the surface of metallographic velvet. The velvet can be attached to a polishing machine with a speed of less than 600 rpm. Diamond powder with a particle size of 3.5 μm can be used during polishing. The surface of the sample after polishing should be free of dirt and scratches visible to the naked eye.

[0039] (4) Rinse the polished surface with clean water, then with anhydrous ethanol and blow dry;

[0040] (5) Use the polished sample as the anode and the graphite plate as the cathode and place it in the electrolytic corrosive agent prepared in step 1. The electrolysis voltage is 3.8 V and the time is 44 s. After the polished surface of the sample completely turns light gray, take it out and rinse it with clean water. After that, lightly polish it on a polishing machine to remove excess corrosion products on the surface and observe it under a metallographic microscope.

[0041] Corrosion effect: The original austenite grain boundary morphology of the sample in Example 2 is clearly visible, and the original austenite grain size can be accurately rated.

[0042] Example 3

[0043] (1) A metallographic specimen of 15 mm × 15 mm × 15 mm was cut from the sample, and its cross section was coarsely ground by 2 mm using 240# sandpaper, and the edges of the cross section were chamfered.

[0044] (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpaper. During the grinding process, the wear marks of this process were perpendicular to the wear marks of the previous process, and the wear marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles.

[0045] (3) After fine grinding, the sample is polished on the surface of metallographic velvet. The velvet can be attached to a polishing machine with a speed of less than 600 rpm. Diamond powder with a particle size of 3.5 μm can be used during polishing. The surface of the sample after polishing should be free of dirt and scratches visible to the naked eye.

[0046] (4) Rinse the polished surface with clean water, then with anhydrous ethanol and blow dry;

[0047] (5) Use the polished sample as the anode and the graphite plate as the cathode in the electrolytic corrosive prepared in step 1, with an electrolytic voltage of 4.5 V and a time of 33 s. After the polished surface of the sample completely turns light gray, take it out, rinse it with clean water, and lightly polish it on a polishing machine to remove excess corrosion products on the surface, and then observe it under a metallographic microscope.

[0048] Corrosion effect: The original austenite grain boundary morphology of the sample in Example 3 is clearly visible, and the original austenite grain size can be accurately rated.

[0049] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An electrolytic etchant for showing the grain boundaries of alloy steel 32CrNi3MoVE, Features: The ingredients are: saturated alum solution, oxalic acid, and detergent. The specific ratio is: 100 ml of saturated alum solution, 2-5 g of oxalic acid, and 2-5 ml of detergent.

2. The electrolytic corrosive agent for displaying the grain boundary of alloy steel 32CrNi3MoVE according to claim 1, Features: 100ml of saturated alum solution, 5g of oxalic acid, and 3ml of detergent.

3. The electrolytic corrosive agent for displaying the grain boundary of alloy steel 32CrNi3MoVE according to claim 1, Features: Add 100 ml of saturated alum solution into a dry beaker, use a balance to measure 5 g of oxalic acid and add it to the beaker, use a measuring cylinder to measure 3 ml of Liby dishwashing liquid and add it to the beaker, and stir thoroughly.

4. A corrosion method based on electrolytic etchant showing the grain boundaries of alloy steel 32CrNi3MoVE, It is characterized in that The following steps are involved: (1) Cut metallographic specimens from alloy steel samples and perform rough grinding and chamfering; (2) After rough grinding, the metallographic specimens were finely ground using 600#, 800#, 1000#, and 1500# metallographic water sandpapers, respectively. During the grinding process, the grinding marks of this process were perpendicular to the grinding marks of the previous process, and the grinding marks of the previous process were completely removed. The cross section was rinsed with clean water to remove the surface abrasive particles; (3) After fine grinding, the sample is polished on the surface of metallographic velvet; (4) Cleaning after polishing; (5) The polished sample is used as the anode and the graphite plate is used as the cathode. The sample is placed in the electrolytic corrosive agent as described in claim 1 at a voltage of 3-5 V for 30 s to 50 s. When the polished surface of the sample completely turns light gray, the sample is taken out and rinsed with clean water. After the sample is lightly polished on a polishing machine to remove excess corrosion products on the surface, it can be observed.

5. A corrosion method based on an electrolytic corrosive agent showing the grain boundaries of alloy steel 32CrNi3MoVE according to claim 4, It is characterized in that The size of the metallographic sample is 15 mm×15 mm×15 mm.

6. A method of corrosion based on electrolytic corrosive agent showing the grain boundary of alloy steel 32CrNi3MoVE according to claim 4, It is characterized in that In step (1), the cross section of the metallographic sample is coarsely ground by 2 mm using 240# sandpaper, and the cross section is chamfered all around.

7. A method for corrosion based on electrolytic corrosive agent for displaying grain boundaries of alloy steel 32CrNi3MoVE according to claim 4, It is characterized in that In step (3), the velvet is pasted on a polishing machine with a rotation speed of less than 600 rpm, and diamond powder with a particle size of 1 to 3.5 μm is used during polishing. The surface of the sample after polishing should be free of dirt and scratches visible to the naked eye.

8. A method of corrosion based on electrolytic corrosive agent for displaying grain boundaries of alloy steel 32CrNi3MoVE according to claim 4, It is characterized in that In step (4), the polished surface is rinsed with clean water and then with anhydrous ethanol and then blown dry.

9. A method for corrosion based on electrolytic corrosive agent for displaying grain boundaries of alloy steel 32CrNi3MoVE according to claim 4, It is characterized in that The optical microscope was used for observation, and the microstructure of the original austenite grains was collected and graded.

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