A method for extracting carbides from wear-resistant steel

Abstract

The present invention discloses a method for extracting carbides from wear-resistant steel, belonging to the field of metal electrochemistry technology. The present invention achieves the purpose of extracting pure and complete carbides from steel by improving the electrolyte and method. An electrolyte containing tartaric acid is selected to react with metal ions in the solution to inhibit the formation of iron hydroxide. The acidic environment can effectively dissolve sulfide inclusions and reduce the impact of impurities on the purity of carbides. An H-type electrolytic cell is used, and a filter membrane is used to physically separate the cathode and the anode, effectively preventing the iron precipitated on the cathode from mixing into the carbides and affecting the analysis of the carbides. The method can successfully obtain carbides from the wear-resistant steel matrix by selecting a suitable electrolyte and an electrolytic extraction device. The extraction device is simple, and the obtained carbides are purer and more complete, which can realize the analysis of the phase, morphology and particle size distribution of the carbides.

Description

Technical Field

[0001] The invention belongs to the technical field of metal electrochemistry, and particularly relates to a method for extracting carbides from wear-resistant steel. Background Art

[0002] Wear-resistant steel forms carbides in the matrix by adding strong carbide elements, and its comprehensive mechanical properties are improved by the precipitation strengthening mechanism; however, factors such as the number, morphology and size of carbides will affect the mechanical properties of steel, so it is necessary to study the carbides in steel; the three-dimensional carbide morphology cannot be observed only through metallographic microscopes and scanning electron microscopes, and carbides are not evenly distributed in the matrix. The number and size of carbides obtained by image statistics are very random, and reducing this randomness requires a lot of work for statistics; therefore, it is of great significance to use electrolytic extraction to extract carbides from the matrix for research.

[0003] Utilizing the electrolytic potential difference between the steel matrix and the carbide, the steel sample is used as the anode and the platinum electrode as the cathode. After applying a constant voltage, the steel matrix begins to dissolve in an ionic state, while the carbide in the matrix is ​​retained due to the relatively high electrolytic potential, attached to the surface of the matrix or dispersed in the solution; however, during the electrolysis process, the iron ion content increases, easily forming iron hydroxide, and a reduction reaction easily occurs on the cathode surface to produce iron. At the same time, some inclusions are difficult to dissolve during the electrolysis process, and are easily mixed into the carbide during the collection process and collected together, which has the problem of affecting the purity of the carbide. Summary of the Invention

[0004] The object of the present invention is to provide a method for extracting carbides from wear-resistant steel, which specifically comprises the following process steps:

[0005] (1) Prepare the electrolyte using tartaric acid, potassium chloride and deionized water.

[0006] (2) Prepare the wear-resistant steel sample as the electrolytic sample required for electrolytic extraction, remove the oxide on the surface of the wear-resistant steel sample using 240-2000 mesh sandpaper, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 5-10 minutes, then dry it and weigh the sample.

[0007] (3) Use an H-type replaceable membrane electrolytic cell and install three electrodes. Fix two nylon filter membranes at the flange mouth. Use flange clamps to fix the flange mouths at both ends. Connect the working electrode to the positive pole of the power supply as the anode and the platinum electrode as the cathode. Use constant voltage polarization mode for electrolytic extraction.

[0008] (4) Place the sample after electrolysis in a container filled with anhydrous ethanol, and then place it in an ultrasonic dispersion, repeating 2 to 3 times; transfer the anhydrous ethanol containing carbides to a filtration device; transfer the electrolyte containing carbides at the working electrode end to the filtration device; use anhydrous ethanol to wash the residual carbides on the container, electrolytic cell and nylon filter membrane at the working electrode end into the filtration device.

[0009] (4) The remaining sample surface is cleaned and dried, and the weight of the sample after electrolytic extraction is weighed; the anode mud produced during the electrolysis process is filtered out, and it is rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide is placed in a drying oven for drying, and the obtained carbide is collected and weighed.

[0010] Preferably, in step (1) of the present invention, every 500 mL of electrolyte is prepared according to the ratio of 25-30 g of tartaric acid, 15-20 g of potassium chloride, and the balance being deionized water.

[0011] Preferably, the temperature of the electrolytic cell in step (3) of the present invention is maintained at room temperature, the voltage of the constant voltage polarization mode is set to 3.4 to 3.8 V, and the electrolysis time is set to 6 to 12 h.

[0012] Preferably, the nylon filter membrane used in step (3) and step (5) of the present invention has a pore size of 0.05 μm.

[0013] Preferably, the electrolyte used in the present invention needs to be prepared and used immediately, and the purity of tartaric acid and potassium chloride is analytical grade.

[0014] Preferably, the steel sample used in step (2) is a thin block steel sample with a size of 10 mm×15 mm×2 mm, and a platinum sheet electrode clamp is used to fix the steel sample and use it as a working electrode.

[0015] Preferably, each H-type electrolytic cell in step (3) has a capacity of 100 mL and an inner diameter of the flange opening of 15 mm.

[0016] Preferably, the H-type electrolytic cell in step (3) isolates the working electrode from the platinum electrode, and the iron generated by reduction on the platinum electrode is separated by a nylon filter membrane, effectively preventing the carbide from being contaminated by iron. The installation process of using this device is simple and quick.

[0017] Preferably, two nylon filter membranes are used in the flange port in step (3) in an overlapping manner to facilitate the collection of carbides that are free on the filter membrane.

[0018] Preferably, the vacuum pump used for filtration in step (4) has an air flow rate of 15 L / min.

[0019] Preferably, the drying temperature of the drying oven in step (4) is 80° C. and the drying time is 15 minutes.

[0020] Preferably, when collecting carbides in step (4), the carbides of each part are collected on the filter membrane to obtain all the carbides of the electrolyzed part of the sample, which can be used for analyzing the content of the carbides.

[0021] Beneficial effects of the present invention:

[0022] The electrolyte of the present invention has simple components, is economical and environmentally friendly, can not only destroy the passivation film on the surface of the steel sample and reduce current attenuation, but also react with iron ions to prevent the formation of precipitates during the electrolysis process that affect the purity of the collected carbides. In addition, the ionized hydrogen ions make the electrolyte acidic, and a small amount of manganese sulfide inclusions in the steel will decompose in this acidic environment and react with tartaric acid to avoid being collected as carbides.

[0023] In summary, the present invention reduces the addition of reagents and obtains pure carbide by optimizing the electrolyte composition; the present invention also simplifies the operating steps and reduces the carbide loss during the transfer process by optimizing the extraction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the electrolytic extraction device used in the present invention.

[0025] Figure 2 Schematic diagram of the filtration device used in the present invention.

[0026] Figure 3 This is an electron microscope image of the carbide in Example 1.

[0027] Figure 4 This is the XRD pattern of the carbide in Example 1.

[0028] Figure 5 This is the particle size distribution diagram of the carbide in Example 1.

[0029] Figure 6 This is an electron microscope image of the carbide in Example 2.

[0030] Figure 7 This is the XRD pattern of the carbide in Example 2.

[0031] Figure 8 This is the particle size distribution diagram of the carbide in Example 2.

[0032] Figure 9 This is an electron microscope image of the carbide in Example 3.

[0033] Figure 10 This is the XRD pattern of the carbide in Example 3.

[0034] Figure 11 This is the particle size distribution diagram of the carbide in Example 3.

[0035] Figure 12 This is the XRD pattern of the carbide in Comparative Example 1.

[0036] Figure 13 This is the XRD pattern of the carbide in Comparative Example 2. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0038] Example 1

[0039] This embodiment uses austenitic wear-resistant steel as the working electrode for electrolytic extraction, and specifically includes the following steps:

[0040] (1) Preparation of electrolyte: The electrolyte is prepared according to the ratio of 30 g tartaric acid, 20 g potassium chloride, and 500 mL deionized water.

[0041] (2) Use 240-2000 grit sandpaper to remove oxides from the surface of the wear-resistant steel sample, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 minutes, dry the sample and weigh and record the sample weight. Prepare eight samples with a total mass of 16.7274 g.

[0042] (3) Install a working electrode and a reference electrode at one end of a 100 mL H-type replaceable membrane electrolytic cell, install a platinum sheet electrode at the other end, fix two nylon filter membranes at the flange port, and use flange clamps to fix the flange ports at both ends; after the installation is completed, pour the electrolyte prepared in step (1) into the cell to immerse the three electrodes and the flange connection port; connect the working electrode to the positive pole of the power supply as the anode, and the platinum sheet electrode as the cathode, and keep the temperature of the electrolyte at room temperature; use a constant voltage polarization mode for electrolytic extraction, set the voltage to 3.8 V, the electrolysis time to 8 h, and start electrolysis.

[0043] (4) After all samples are electrolyzed, the samples are placed in a beaker filled with anhydrous ethanol and ultrasonically dispersed. This process is repeated 2 to 3 times. The anhydrous ethanol containing carbides in the beaker is transferred to a filtration device, and the electrolyte containing carbides at the working electrode end is transferred to a filtration device. Anhydrous ethanol is used to wash the residual carbides on the beaker, electrolytic cell, and nylon filter membrane at the working electrode end into the filtration device. The remaining sample surface is cleaned and dried. The total weight of the sample after electrolytic extraction is weighed to be 12.3457 g.

[0044] The anode mud produced during the electrolysis process was filtered and rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide was placed in a drying oven for drying. The carbide was collected and weighed, and its total mass was 0.1832 g. The morphology of the collected carbide is as follows: Figure 3 , XRD results are as follows Figure 4 , the particle size distribution diagram is as follows Figure 5 It can be seen from the figure that the carbides obtained by electrolytic extraction from austenitic wear-resistant steel are VC and NbTiC2, and the size distribution is about 100 to 2000nm.

[0045] Example 2

[0046] This embodiment uses bainite wear-resistant steel as the working electrode for electrolytic extraction, which specifically includes the following steps:

[0047] (1) Prepare the electrolyte according to the ratio of 28 g tartaric acid, 15 g potassium chloride, and 500 mL deionized water.

[0048] (2) Use 240-2000 grit sandpaper to remove oxides from the surface of the wear-resistant steel sample, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 minutes, dry the sample and weigh and record the sample weight. Prepare eight samples with a total mass of 16.9574 g.

[0049] (3) Install a working electrode and a reference electrode at one end of a 100 mL H-type replaceable membrane electrolytic cell, install a platinum sheet electrode at the other end, fix two nylon filter membranes at the flange port, and use flange clamps to fix the flange ports at both ends; after installation, pour the electrolyte prepared in step (1) into the cell to immerse the three electrodes and the flange connection port; connect the working electrode to the positive pole of the power supply as the anode, and the platinum sheet electrode as the cathode, and keep the temperature of the electrolyte at room temperature; use a constant voltage polarization mode for electrolytic extraction, set the voltage to 3.4 V, the electrolysis time to 12 h, and start electrolysis.

[0050] (4) After all samples are electrolyzed, the samples are placed in a beaker filled with anhydrous ethanol and ultrasonically dispersed. This process is repeated 2 to 3 times. The anhydrous ethanol containing carbides in the beaker is transferred to a filtration device, and the electrolyte containing carbides at the working electrode end is transferred to a filtration device. Anhydrous ethanol is used to wash the residual carbides on the beaker, electrolytic cell, and nylon filter membrane at the working electrode end into the filtration device. The remaining sample surface is cleaned and dried. The total weight of the sample after electrolytic extraction is weighed to be 12.6065 g.

[0051] The anode mud produced during the electrolysis process was filtered and rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide was placed in a drying oven for drying. The carbide obtained was collected and weighed, and its total mass was 0.1878 g. The morphology of the collected carbide is as follows: Figure 6 , XRD results are as follows Figure 7 , the particle size distribution diagram is as follows Figure 8 ,It can be seen from the figure that the carbide obtained by electrolytic extraction from bainitic wear-resistant steel is TiC, and its size distribution is about 300 to 2000 nm.

[0052] Example 3

[0053] This embodiment uses martensitic wear-resistant steel as the working electrode for electrolytic extraction, which specifically includes the following steps:

[0054] (1) Prepare the electrolyte according to the ratio of 25 g tartaric acid, 15 g potassium chloride, and 500 mL deionized water.

[0055] (2) Use 240-2000 grit sandpaper to remove oxides from the surface of the wear-resistant steel sample, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 minutes, dry the sample and weigh and record the sample weight. Prepare eight samples with a total mass of 16.5961 g.

[0056] (3) Install a working electrode and a reference electrode at one end of a 100 mL H-type replaceable membrane electrolytic cell, install a platinum sheet electrode at the other end, fix two nylon filter membranes at the flange port, and use flange clamps to fix the flange ports at both ends; after installation, pour the electrolyte prepared in step (1) into the cell to immerse the three electrodes and the flange connection port; connect the working electrode to the positive pole of the power supply as the anode, and the platinum sheet electrode as the cathode, and keep the temperature of the electrolyte at room temperature; use a constant voltage polarization mode for electrolytic extraction, set the voltage to 3.4 V, the electrolysis time to 12 h, and start electrolysis.

[0057] (4) After all samples are electrolyzed, the samples are placed in a beaker filled with anhydrous ethanol and ultrasonically dispersed. This process is repeated 2 to 3 times. The anhydrous ethanol containing carbides in the beaker is transferred to a filtration device, and the electrolyte containing carbides at the working electrode end is transferred to a filtration device. Anhydrous ethanol is used to wash the residual carbides on the beaker, electrolytic cell, and nylon filter membrane at the working electrode end into the filtration device. The remaining sample surface is cleaned and dried. The total weight of the sample after electrolytic extraction is weighed to be 11.9149 g.

[0058] The anode mud produced during the electrolysis process was filtered and rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide was placed in a drying oven for drying. The carbide was collected and weighed, and its total mass was 0.2254 g. The morphology of the collected carbide is as follows: Figure 9 , XRD results are as follows Figure 10 , the particle size distribution diagram is as follows Figure 11 ,It can be seen from the figure that the carbides obtained by electrolytic extraction from martensitic wear-resistant steel are M7C3 type carbides, with a size distribution of about 500 to 1000 nm.

[0059] Comparative Example 1

[0060] This embodiment uses austenitic wear-resistant steel as the working electrode for electrolytic extraction, which specifically includes the following steps:

[0061] (1) Prepare the electrolyte according to the ratio of 15 g tartaric acid, 20 g potassium chloride, and 500 mL deionized water.

[0062] (2) Use 240-2000 grit sandpaper to remove oxides from the surface of the wear-resistant steel sample, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 minutes, dry the sample and weigh and record the sample weight. Prepare eight samples with a total mass of 17.2147 g.

[0063] (3) In a 100 mL H-type replaceable membrane electrolytic cell, a working electrode and a reference electrode were installed at one end, and a platinum electrode was installed at the other end. Two nylon filter membranes were fixed at the flange port, and the flange ports at both ends were fixed with flange clamps. Three electrodes were connected, with the working electrode as the anode and the platinum electrode as the cathode. The temperature of the electrolyte was maintained at room temperature. Electrolytic extraction was performed using a constant voltage polarization mode, with the voltage set to 3.8 V and the electrolysis time set to 8 h. After completion, the electrolyte was poured in and the electrolysis was started after the three electrodes and the flange connection port were immersed.

[0064] (4) After all samples are electrolyzed, the samples are placed in a beaker filled with anhydrous ethanol and ultrasonically dispersed. This process is repeated 2 to 3 times. The anhydrous ethanol containing carbides in the beaker is transferred to a filtration device, and the electrolyte containing carbides at the working electrode end is transferred to a filtration device. Anhydrous ethanol is used to wash the residual carbides on the beaker, electrolytic cell, and nylon filter membrane at the working electrode end into the filtration device. The remaining sample surface is cleaned and dried. The total weight of the sample after electrolytic extraction is weighed to be 12.4961 g.

[0065] The anode mud produced during the electrolysis process was filtered and rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide was placed in a drying oven for drying. The obtained carbide was collected and weighed, and its total mass was 0.2154 g. The XRD results are shown in FIG. Figure 12 ,It can be seen from the figure that in addition to carbides, MnS also exists in the powder obtained by electrolytic extraction of austenitic wear-resistant steel.

[0066] By comparison, it can be seen that insufficient amount of tartaric acid cannot dissolve MnS inclusions in austenitic wear-resistant steel.

[0067] Comparative Example 2

[0068] This embodiment uses austenitic wear-resistant steel as the working electrode for electrolytic extraction, which specifically includes the following steps:

[0069] (1) Prepare the electrolyte according to the ratio of 5 g tartaric acid, 20 g potassium chloride, and 500 mL deionized water.

[0070] (2) Use 240-2000 grit sandpaper to remove oxides from the surface of the wear-resistant steel sample, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 minutes, dry the sample and weigh and record the sample weight. Prepare eight samples with a total mass of 17.8436 g.

[0071] (3) Install the working electrode and reference electrode at one end of a 100 mL H-type replaceable membrane electrolytic cell, and a platinum electrode at the other end. Fix two nylon filter membranes at the flange port, and use flange clamps to fix the flange ports at both ends. Connect the three electrodes, with the working electrode as the anode and the platinum electrode as the cathode. Maintain the electrolyte at room temperature and perform electrolytic extraction using the constant voltage polarization mode. Set the voltage to 3.8 V and the electrolysis time to 8 h. After completion, pour the electrolyte into the cell, immerse the three electrodes and the flange connection port, and then start electrolysis.

[0072] (4) After all samples are electrolyzed, the samples are placed in a beaker filled with anhydrous ethanol and ultrasonically dispersed. This process is repeated 2 to 3 times. The anhydrous ethanol containing carbides in the beaker is transferred to a filtration device, and the electrolyte containing carbides at the working electrode end is transferred to a filtration device. Anhydrous ethanol is used to wash the residual carbides on the beaker, electrolytic cell, and nylon filter membrane at the working electrode end into the filtration device. The remaining sample surface is cleaned and dried. The total weight of the sample after electrolytic extraction is weighed to be 14.2023 g.

[0073] The anode mud produced during the electrolysis process was filtered and rinsed with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. The nylon filter membrane containing the carbide was placed in a drying oven for drying. The obtained carbide was collected and weighed, and its total mass was 0.1675 g. The XRD results are as follows: Figure 13 ,It can be seen from the figure that in addition to carbides, MnS also exists in the powder obtained by electrolytic extraction of austenitic wear-resistant steel.

[0074] By comparison, it can be seen that insufficient amount of tartaric acid cannot dissolve MnS inclusions in austenitic wear-resistant steel.

[0075] Excessive tartaric acid will destroy the carbide.

[0076] The obtained electron microscope images of the carbides show that the electrolyte used in the present invention can obtain complete carbides, and the carbides will not be destroyed in this acidic environment.

[0077] By collecting complete and pure carbides and performing particle size analysis and mass fraction calculation, the carbides in the steel can be quantitatively analyzed. The following table shows the mass percentages of the carbides collected in the examples.

[0078] Table 1 Carbide mass fractions of Examples and Comparative Examples

[0079]

[0080] The XRD test results show that the present invention can effectively extract carbides from austenite, bainite and martensite wear-resistant steels. No peaks of inclusions and iron are observed in the XRD diagram of the embodiment, indicating that the electrolyte in the present invention can dissolve inclusions well and inhibit the generation of impurities, and the extraction device has a good physical isolation effect on the iron generated on the cathode; the XRD diagram of the comparative example clearly shows the appearance of the MnS peak, indicating that impurities are generated in the comparative example. The tartaric acid used in the present invention can dissolve inclusions at an appropriate dosage, effectively improving the purity of the extracted carbides.

Claims

1. A method for extracting carbides from wear-resistant steel, characterized in that: The method comprises the following process steps: (1) Prepare the electrolyte using tartaric acid, potassium chloride and deionized water; (2) Prepare the wear-resistant steel sample as the electrolytic sample required for electrolytic extraction. Use 240-2000 grit sandpaper to remove the oxide on the surface of the wear-resistant steel sample. Place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 5-10 minutes. Then dry it and weigh the sample. (3) Use an H-type replaceable membrane electrolytic cell and install three electrodes. Fix two nylon filter membranes at the flange port. Use flange clamps to fix the flange ports at both ends. Connect the working electrode to the positive pole of the power supply as the anode and the platinum electrode as the cathode. Use constant voltage polarization mode for electrolytic extraction. (4) Place the sample after electrolysis in a container filled with anhydrous ethanol, and then place it in an ultrasonic dispersion, repeating 2 to 3 times; transfer the anhydrous ethanol containing carbides to a filtration device; transfer the electrolyte containing carbides at the working electrode end to the filtration device; Use anhydrous ethanol to wash the residual carbides on the nylon filter membrane of the container, electrolytic cell and working electrode into the suction filtration device; (5) Clean and dry the remaining sample surface, and weigh the sample weight after electrolytic extraction; filter out the anode mud produced during the electrolysis process, and rinse it with anhydrous ethanol 4 to 5 times during the filtration process to obtain pure carbide on the nylon filter membrane. Place the nylon filter membrane containing carbide in a drying oven to dry, and collect and weigh the obtained carbide; In step (1), every 500 mL of electrolyte is prepared according to the ratio of 25-30 g of tartaric acid, 15-20 g of potassium chloride, and the balance is deionized water; The temperature of the electrolytic cell in step (3) was maintained at room temperature, the voltage of the constant voltage polarization mode was set to 3.4-3.8 V, and the electrolysis time was set to 6-12 h.

2. The method for extracting carbides from wear-resistant steel according to claim 1, characterized in that: The nylon filter membrane used in step (3) and step (5) has a pore size of 0.05 μm.

3. The method for extracting carbides from wear-resistant steel according to claim 1, characterized in that: The electrolyte in step (1) needs to be prepared and used immediately, and the purity of tartaric acid and potassium chloride should be analytical grade.

4. The method for extracting carbides from wear-resistant steel according to claim 1, characterized in that: The steel sample in step (2) has a size of 10 mm × 15 mm × 2 mm and is fixed with a platinum electrode clamp as a working electrode.

5. The method for extracting carbides from wear-resistant steel according to claim 1, characterized in that: The capacity of each H-type electrolytic cell in step (3) is 100 mL.

6. The method for extracting carbides from wear-resistant steel according to claim 1, characterized in that: When installing the three electrodes in step (3), the working electrode and the reference electrode need to be installed in the same electrolytic cell, and the platinum electrode needs to be installed in another electrolytic cell.

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