A corrosive agent and method for displaying as-cast dendritic morphology of high-carbon high-manganese steel

Abstract

The application provides a corrosion agent and a method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel, the corrosion agent is prepared from a nitric acid solution, anhydrous ethanol, ferric chloride, cupric chloride and water, the volume ratio of the nitric acid solution, the volume of the anhydrous ethanol, the volume of the water, the mass of the ferric chloride and the mass of the cupric chloride is (8-10) ml:(80-82) ml:(10-20) ml:(2-3) g:(1.5-2.5) g, and the corrosion method comprises the following steps: (1) sample preparation; (2) sample corrosion. The corrosion agent and the method can clearly and effectively etch out the dendritic structure, and can also clearly etch out the austenite grain boundary, so that the dendritic structure and the grain can be observed in the same mirror, the dendritic structure is qualitatively evaluated, the method can be used for the quality evaluation of the as-cast structure of the high-carbon high-manganese steel under the continuous casting process, and thus plays a certain guiding role in the optimization of the continuous casting production process of the high-carbon high-manganese steel and the as-cast quality control.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel production, and particularly relates to a corrosion agent and method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel. BACKGROUND

[0002] High-manganese steel is mainly divided into two categories: one is wear-resistant steel, and the other is non-magnetic steel. Here, the wear-resistant steel is mainly involved, which has a Mn content of 10% to 15% and a C content as high as 0.90% to 1.25%. After proper composition design adjustment, high-manganese steel has excellent wear resistance under strong impact and abrasive wear conditions, and is therefore often used in mining, building materials, thermal power and other mechanical equipment to make wear-resistant parts. The as-cast performance of high-manganese steel is good, but the production efficiency is relatively low. After high-manganese steel is produced by continuous casting, the production efficiency is greatly improved. Under the continuous casting production process, the as-cast solidification structure morphology is a basic factor for determining the internal and external quality. By observing the solidification structure of high-manganese steel continuous casting billets and studying the morphological characteristics, the interdendritic spacing and other related data can be measured, which provides a lot of valuable technical information for in-depth understanding of the solidification characteristics of high-manganese steel, improvement of the solidification conditions of the casting billets in the continuous casting process, and improvement of the quality of the casting billets.

[0003] However, the conventional nitric acid alcohol etchant cannot effectively etch the austenite grain boundaries, and it is also difficult to clearly etch the dendrites. There are few reports on methods that can clearly etch the grain boundaries and dendrites at the same time for high-manganese steel used as wear-resistant steel.

[0004] Patent application with publication number CN112481616A discloses a high-manganese steel metallographic etchant and its configuration method and etching method. Dilute hydrochloric acid and CrO3 aqueous solution are mixed in a volume ratio of 1:2 to form a mixed solution as the etchant, which can etch the austenite grain boundaries and twin boundaries of high-manganese steel with a Mn content of 15% to 30%, but cannot etch the dendrites. Patent application with publication number CN108693103A discloses a method for etching and measuring the dendrites of high-carbon steel casting billets. The main components of the etchant are picric acid, cuprous chloride, dishwashing liquid and water, with mass concentrations of (0.3% to 0.5%) : (0.1% to 0.2%) : (1% to 2%). This etchant can effectively etch the dendrites of high-carbon steel casting billets, but cannot etch the grain boundaries at the same time. In addition, picric acid, also known as yellow powder, is highly toxic and explosive. For example, in the existing technology “Research on Microsegregation Behavior of High-Manganese Steel” (China Metal Bulletin, 2021), the sample is etched with 20% nitric acid alcohol, and the dendritic morphology and austenite grain boundaries can be observed. However, the steel described in the literature is high-manganese TWIP steel, with a C content of up to 0.6% and a high Al content of 3.54%, which is not suitable for the high-carbon high-manganese steel described in the present method.

[0005] Therefore, it is urgent to provide a corrosion agent and method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel, which is used for quality evaluation of the as-cast structure under the continuous casting process of high-carbon high-manganese steel, so as to achieve the purpose of optimizing the solidification of the casting blank and improving the quality of the casting blank in the continuous casting process. SUMMARY

[0006] The purpose of the present application is to provide a corrosion agent and method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel, which can clearly and effectively etch out the dendritic structure and clearly etch out the austenite grain boundary, facilitate the observation of the dendritic structure and the grain, and qualitatively evaluate the dendritic structure. The method has the advantages of convenience, efficiency and accuracy, and can be used for quality evaluation of the as-cast structure under the continuous casting process of high-carbon high-manganese steel, thereby playing a certain guiding role in the optimization of the continuous casting production process of high-carbon high-manganese steel and the control of the as-cast quality.

[0007] In order to achieve the above-mentioned purpose of the application, the technical scheme provided by the present application is as follows:

[0008] A corrosion agent for displaying the as-cast dendritic morphology of high-carbon high-manganese steel is prepared from a nitric acid solution, anhydrous ethanol, ferric chloride, copper chloride and water.

[0009] In the corrosion agent, the volume ratio of the nitric acid solution, the volume of the anhydrous ethanol, the volume of the water, the mass of the ferric chloride and the mass of the copper chloride is (8-10) ml:(80-82) ml:(10-20) ml:(2-3) g:(1.5-2.5) g.

[0010] The mass concentration of the nitric acid solution is 63%-68%.

[0011] In the chemical composition of the high-carbon high-manganese steel, C is 0.90%-1.25%, Mn is 10.0%-15.0%, Si is 0.30%-1.0%, S is ≤0.05%, P is ≤0.10%, and Fe is the balance.

[0012] A method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel comprises the following steps:

[0013] (1) Sample preparation: according to the requirements of metallographic observation, the high-carbon high-manganese steel sample to be measured is ground and polished, washed and dried for standby;

[0014] (2) Sample corrosion: the sample treated in step (1) is immersed in the above-mentioned corrosion agent, taken out after 25-30 seconds, first washed with a large amount of water to remove the surface residual corrosion agent, then wiped with a cotton ball dipped in 2-3 g of detergent, and then sequentially washed with water and anhydrous ethanol, and dried with a hair dryer.

[0015] The method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel provided by the application, wherein the specific operation of step (1) is: polishing the high-carbon high-manganese steel sample with 180#, 400#, 800# and 1000# water sandpaper in sequence, then polishing to a mirror surface with 2.5 μm metallographic polishing agent, and then washing with clean water and anhydrous ethanol, and drying with a hair dryer for standby use.

[0016] The method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel provided by the application, wherein the step (2) is carried out at an ambient temperature of 15-20℃.

[0017] The method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel provided by the application, wherein in the step (2), the corroded surface of the high-carbon high-manganese steel sample is completely immersed in the etchant and gently shaken.

[0018] The technical scheme of the application has the following beneficial technical effects:

[0019] The etchant provided by the application does not need to add picric acid, the components are easy to obtain, the configuration is simple, the time consumption is less, the effect is stable, and the reproducibility is good.

[0020] The etchant provided by the application can clearly and effectively etch out the dendritic structure, and can also clearly etch out the austenite grain boundary, which is convenient for mirror observation of the dendritic structure and the grain, and qualitative evaluation of the dendritic structure.

[0021] The technical scheme provided by the application can be used for quality evaluation of the as-cast structure under the continuous casting process of high-carbon high-manganese steel, thereby playing a certain guiding role in optimization of the continuous casting production process of high-carbon high-manganese steel and control of the as-cast quality. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The metallographic image of the metallographic sample prepared for the embodiment 1 of the application;

[0023] Figure 2 The metallographic image of the metallographic sample prepared for the embodiment 2 of the application;

[0024] Figure 3 The metallographic image of the metallographic sample prepared for the embodiment 3 of the application;

[0025] Figure 4 The metallographic image of the metallographic sample prepared for the embodiment 4 of the application. IMPLEMENTATION

[0026] The technical scheme in the application will be described clearly and completely in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application. Example 1

[0027] The chemical composition of the high-carbon high-manganese steel sample to be tested in this example is shown in Table 1.

[0028] The etchant used in this example was prepared from 8 ml of nitric acid solution, 80 ml of anhydrous ethanol, 10 ml of distilled water, 2 g of ferric chloride, and 1.5 g of copper chloride; the mass concentration of the nitric acid solution was 65%.

[0029] The method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel is as follows:

[0030] (1) The high-carbon high-manganese steel sample was polished with 180#, 400#, 800#, and 1000# water sandpaper in sequence, and then polished to a mirror surface with 2.5 μm metallographic polishing agent. After that, the sample was washed with water and anhydrous ethanol, and dried with a hair dryer, ready for use.

[0031] (2) The sample treated in step (1) was immersed in the prepared etchant at an ambient temperature of 20°C, and gently shaken. After 30 s, the sample was taken out, rinsed with a large amount of water to remove the residual etchant on the surface, and then wiped with a cotton ball soaked with 2-3 g of dishwashing liquid. After wiping clean, the sample was rinsed with water and anhydrous ethanol in sequence, and then tilted and dried with a hair dryer to obtain a metallographic sample.

[0032] The metallographic structure of the above metallographic sample was observed under a metallographic microscope at 25 times magnification, and is shown in Figure 1 From Figure 1 the austenite grain boundaries and the intersecting dendrites of the high-carbon high-manganese steel can be clearly seen, and the secondary dendrite arm spacing can be measured. Example 2

[0033] The chemical composition of the high-carbon high-manganese steel sample to be tested in this example is shown in Table 1.

[0034] The etchant used in this example was prepared from 9 ml of nitric acid solution, 81 ml of anhydrous ethanol, 16 ml of distilled water, 2.7 g of ferric chloride, and 2.1 g of copper chloride; the mass concentration of the nitric acid solution was 68%.

[0035] The method for displaying the as-cast dendritic morphology of high-carbon high-manganese steel is as follows:

[0036] (1) The high-carbon high-manganese steel sample was polished with 180#, 400#, 800#, and 1000# water sandpaper in sequence, and then polished to a mirror surface with 2.5 μm metallographic polishing agent. After that, the sample was washed with water and anhydrous ethanol, and dried with a hair dryer, ready for use.

[0037] (2) Under an ambient temperature of 18°C, immerse the sample treated in step (1) into the prepared etchant, gently shake it, and take it out after 28 seconds. First, rinse off the residual etchant on the surface with plenty of water, then wipe it with a cotton ball dipped in 2-3g of detergent. After wiping it clean, rinse it with water and anhydrous ethanol in sequence. Then tilt the sample and blow it dry with a hair dryer to obtain the metallographic sample.

[0038] The metallographic sample was observed under a metallographic microscope at 25x magnification, and its metallographic structure was as follows: Figure 2 .Depend on Figure 2 The austenite grain boundaries and intersecting dendrites of high-carbon, high-manganese steel can be clearly seen, and the secondary dendrite spacing can be measured. Example 3

[0039] The chemical composition of the high-carbon, high-manganese steel sample to be tested in this embodiment is shown in Table 1.

[0040] In this embodiment, the corrosive agent is prepared by mixing 10 ml of nitric acid solution, 82 ml of anhydrous ethanol, 20 ml of distilled water, 3 g of ferric chloride, and 2.5 g of copper chloride; wherein the mass concentration of the nitric acid solution is 64%.

[0041] The method for displaying the dendritic morphology of cast high-carbon, high-manganese steel is as follows:

[0042] (1) The high carbon high manganese steel sample was polished with 180#, 400#, 800# and 1000# water sandpaper in sequence, and then polished to mirror surface with 2.5μm metallographic polishing agent. After that, it was cleaned with water and anhydrous ethanol, and dried with a hair dryer for later use.

[0043] (2) Under an ambient temperature of 15℃, immerse the sample treated in step (1) into the prepared etchant, gently shake it, and take it out after 25s. First, rinse off the residual etchant on the surface with plenty of water, then wipe it with a cotton ball dipped in 2-3g of detergent. After wiping it clean, rinse it with water and anhydrous ethanol in sequence. Then tilt the sample and blow it dry with a hair dryer to obtain the metallographic sample.

[0044] The metallographic sample was observed under a metallographic microscope at 25x magnification, and its metallographic structure was as follows: Figure 3 .Depend on Figure 3 The austenite grain boundaries and intersecting dendrites of high-carbon, high-manganese steel can be clearly seen, and the secondary dendrite spacing can be measured. Example 4

[0045] The chemical composition of the high-carbon, high-manganese steel sample to be tested in this embodiment is shown in Table 1.

[0046] In this embodiment, the corrosive agent is prepared by mixing 10 ml of nitric acid solution, 80 ml of anhydrous ethanol, 14 ml of distilled water, 2.3 g of ferric chloride, and 1.7 g of copper chloride; wherein the mass concentration of the nitric acid solution is 63%.

[0047] The method for displaying the dendritic morphology of cast high-carbon, high-manganese steel is as follows:

[0048] (1) The high carbon high manganese steel sample was polished with 180#, 400#, 800# and 1000# water sandpaper in sequence, and then polished to mirror surface with 2.5μm metallographic polishing agent. After that, it was cleaned with water and anhydrous ethanol, and dried with a hair dryer for later use.

[0049] (2) Under an ambient temperature of 20°C, immerse the sample treated in step (1) into the prepared etchant, gently shake it, and take it out after 25 seconds. First, rinse off the residual etchant on the surface with plenty of water, then wipe it with a cotton ball dipped in 2-3g of detergent. After wiping it clean, rinse it with water and anhydrous ethanol in sequence. Then tilt the sample and blow it dry with a hair dryer to obtain the metallographic sample.

[0050] The metallographic sample was observed under a metallographic microscope at 25x magnification, and its metallographic structure was as follows: Figure 4 .Depend on Figure 4 The austenite grain boundaries and intersecting dendrites of high-carbon, high-manganese steel can be clearly seen, and the secondary dendrite spacing can be measured.

[0051] Table 1. Chemical composition (wt%) of the high-carbon manganese steel samples in each embodiment.

[0052]

[0053] As can be seen from the above embodiments, the technical solution provided by the present invention can clearly and effectively etch out cast dendrites and austenite grain boundaries, which facilitates simultaneous observation of dendrites and grains under a microscope and qualitative evaluation of dendritic structure. It has the advantages of being convenient, efficient and accurate.

[0054] The technical solution of this invention can be used for quality assessment of the as-cast microstructure in the continuous casting process of high carbon and high manganese steel, thereby providing guidance for the optimization of the continuous casting production process and the control of as-cast quality of high carbon and high manganese steel.

[0055] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation are within the scope of protection claimed by the present invention.

Claims

1. Use of an etchant to simultaneously reveal the as-cast dendritic morphology and austenite grain boundaries in a high-carbon high-manganese steel, characterized in that, The corrosion agent is prepared by nitric acid solution, anhydrous ethanol, ferric chloride, cupric chloride and water; The ratio of the volume of the nitric acid solution, the volume of the anhydrous ethanol, the volume of the water, the mass of the ferric chloride and the mass of the cupric chloride in the corrosion agent is (8-10) ml:(80-82) ml:(10-20) ml:(2-3) g:(1.5-2.5) g; The chemical composition of the high-carbon high-manganese steel includes C: 0.90%-1.25%, Mn: 10.0%-15.0%, Si: 0.30%-1.0%, S≤0.05%, P≤0.10% and Fe in residual amount.

2. The use of a etchant according to claim 1 for simultaneously showing the as-cast dendritic morphology and the austenite grain boundaries of high carbon high manganese steel, characterized in that, The mass concentration of the nitric acid solution is 63%-68%.

3. The use of a caustic agent according to claim 1 for simultaneously showing the as-cast dendritic morphology and the austenite grain boundaries of high carbon high manganese steel, characterized in that, The method for simultaneously displaying the as-cast dendritic morphology and the austenite grain boundary of the high-carbon high-manganese steel comprises the following steps: (1) sample preparation: according to the requirements of metallographic observation, the high-carbon high-manganese steel sample is ground and polished on the surface to be measured, washed and dried for standby; (2) sample corrosion: the sample treated in step (1) is immersed in the corrosion agent, taken out after 25-30 seconds, first washed with a large amount of water to remove the residual corrosion agent on the surface, then wiped with a cotton ball dipped with 2-3 g of dishwashing liquid, washed with water and anhydrous ethanol in sequence, and dried with a hair dryer.

4. The use of a caustic agent according to claim 3 for simultaneously showing the as-cast dendritic morphology and the austenite grain boundaries of high carbon high manganese steel, characterized in that, The specific operation of step (1) is that the high-carbon high-manganese steel sample is polished with 180#, 400#, 800# and 1000# water sandpaper in sequence, then polished with 2.5 μm metallographic polishing agent to mirror surface, and then washed with water and anhydrous ethanol, and dried with a hair dryer for standby.

5. The use of a caustic agent according to claim 3 for simultaneously showing the as-cast dendritic morphology and the austenite grain boundaries of high carbon high manganese steel, characterized in that, Step (2) is carried out at an environmental temperature of 15-20 °C.

6. The use of a etchant according to claim 3, which simultaneously shows the as-cast dendrite morphology and the austenite grain boundary of high carbon high manganese steel, characterized in that, In step (2), the corrosion surface of the high-carbon high-manganese steel sample is completely immersed in the corrosion agent and gently shaken.

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