Analysis method for chemically and quantitatively separating carbide phases M6C and MC in high-speed steel

Abstract

The invention provides an analysis method for chemically and quantitatively separating carbide phases M6C and MC in high-speed steel, and belongs to the technical field of metallurgical analysis and physical and chemical phase analysis. According to the method, the M6C phase and the MC phase are quantitatively extracted and separated, so that the content and the element composition of each phase are accurately measured. The method comprises the following steps: firstly, extracting all carbide phases in the steel through an electrolysis technology, then selectively dissolving and separating the carbide phases by using various separating solutions based on the difference of the different carbide phases in chemical properties, and carrying out reflux treatment on the obtained M6C and MC phases by using a 5% complexing agent and a 20% weak oxidant solution, so that the M6C phase is selectively dissolved while the MC phase is kept insoluble, and collecting, filtering and cleaning to obtain a pure carbide MC phase. Respectively dissolving the separated precipitates, fixing the volume, and measuring by adopting an inductively coupled plasma spectrometry. According to the method, accurate quantitative analysis of carbide phases M6C and MC in high-speed steel is realized, the technical problem that the carbide phases are difficult to separate is solved, and a reliable method is provided for material research and quality control of the high-speed steel.

Description

Technical Field

[0001] This invention relates to the fields of metallurgical analysis and physicochemical phase analysis, specifically to an analytical method for the quantitative chemical separation of carbide phases M6C and MC in high-speed steel. Background Technology

[0002] High-speed steel (HSS) is an alloy tool steel with high hardness, excellent heat resistance, and wear resistance, making it an indispensable key material in the machinery manufacturing industry. Due to its high carbon content and various carbide-forming elements, carbides are the main precipitated phases in HSS microstructure, and their quantity, type, and distribution play a decisive role in the material's final service life and performance. Among various carbides, the MC phase has the highest hardness and melting point, significantly contributing to improving the steel's high-temperature hardness and wear resistance. Simultaneously, the MC phase readily precipitates in a finely dispersed morphology, helping to refine grains and produce a precipitation strengthening effect, thereby improving the steel's strength and toughness while maintaining high hardness. Therefore, quantitative analysis of various carbide phases in HSS is of great significance for material design and performance optimization.

[0003] However, in existing technologies, especially when M6C and MC phases coexist, accurate quantitative analysis faces significant challenges. Traditional phase analysis methods, such as X-ray diffraction, while capable of phase identification, suffer from poor quantitative accuracy and, most critically, cannot provide specific elemental composition information for each phase. Due to the very similar chemical properties of the M6C and MC phases, selective dissolution and separation using conventional chemical separation methods are difficult to achieve, making it impossible to obtain independent content and composition data for each phase separately. This technical bottleneck severely restricts a deeper understanding of the relationship between the microstructure and properties of high-speed steel. Therefore, developing a new analytical method capable of effectively separating and accurately determining the content and elemental composition of the M6C and MC phases has become a critical technical problem urgently needing to be solved in this field.

[0004] There are currently no related patent reports in China. Therefore, this patent can quantitatively extract, separate and determine the content and elemental composition of carbide phases M6C and MC in high-speed steel, which is of great significance for optimizing the microstructure and improving the performance of high-speed steel. Summary of the Invention

[0005] The purpose of this invention is to quantitatively separate M6C and MC phases by controlling their redox potentials and considering the differences in the solid-solid elements and their responses to weak oxidizing media. The two phases are placed in a reflux flask with an aqueous solution of a weak oxidizing agent (in the presence of a complexing agent) and heated under reflux, allowing M6C to completely transfer into the solution. Phase separation requires that the separated phase completely dissolve while the retained phase remains completely insoluble. Specifically, the washed precipitate is transferred to a reflux flask with 100 mL of an aqueous solution containing 5% complexing agent and 20% weak oxidizing agent. The mixture is refluxed for 3–4 hours, during which M6C gradually transfers into the solution. The elemental content of the MC phase is measured from the precipitate, and the composition of the M6C phase is calculated using the differential method, thus achieving quantitative chemical analysis of the content and elemental composition of the M6C and MC phases.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: an analytical method for the chemical quantitative separation of carbide phases M6C and MC in high-speed steel, specifically comprising the following steps: (1) Extraction of precipitated phases: The carbide phases in the high-speed steel sample were extracted by electrolysis to obtain phases including M6C, MC, and M. 23 C6 phase and M7C3 phase precipitate powder (A); (2) Chemical separation of the precipitated phase: including the following sub-steps: a. Dissolve M 23 C6 phase and M7C3 phase, retain MC phase and M6C phase: The precipitated phase powder (A) is heated and refluxed with separation liquid 1 to obtain the residual MC phase and M6C phase powder (B); b. Dissolve the MC and M6C phases, retaining M. 23 C6 phase and M7C3 phase: The precipitated phase powder (A) and separation liquid 2 were kept at a boiling water bath to obtain the residual M. 23 C6 phase and M7C3 phase powder (C); c. Dissolve the M6C phase and retain the MC phase: Heat the precipitated phase powder (B) and separation liquid 3 under reflux to obtain the residual MC phase powder (D); (3) Preparation and determination of test solution: Dissolve the precipitate powders (A), (B), (C) and (D) obtained in steps (1) and (2) respectively with mixed acid, and after adjusting the volume, determine the concentration of each element by ICP-AES method and calculate the mass percentage of each element in the precipitate in the steel. (4) Calculation of the amount of precipitated phase: Based on the measurement results, the content and elemental composition of M6C phase and MC phase are calculated by the differential method. The amount of M6C phase is obtained by subtracting the amount of powder (D) from the amount of powder (B), and the amount of MC phase is obtained by the amount of powder (D).

[0007] Specifically, the elemental content in each test solution was determined by ICP-AES, and the content and composition of the M6C phase were calculated by the differential method, thus realizing the chemical quantitative analysis of the content and elemental composition of the M6C and MC phases.

[0008] (1) M 23 C6 phase and M7C3 phase = C The amount of residue (C) obtained after separation is M. 23 The amounts of C6 phase and M7C3 phase.

[0009] (2) MC phase = D The amount of residue (D) obtained after separation is the amount of MC phase.

[0010] (3) M6C phase = B–D The amount of the separated residue (B) minus the amount of the separated residue (D) is the amount of the M6C phase.

[0011] Preferably, the electrolytic extraction in step (1) uses a neutral KCl electrolyte, the electrolytic environment temperature is 0℃~5℃, the anodic current density is 0.025~0.030A / cm², and the electrolysis time is 1 hour.

[0012] Preferably, after electrolysis in step (1), the precipitated phase is rinsed with citric acid solution and deionized water, wherein the concentration of citric acid solution is 10 g / L.

[0013] Preferably, the separation solution 1 in step (2)a is made by dissolving 30 mL of hydrochloric acid and 1 g of citric acid in water, diluting it to 100 mL and mixing it.

[0014] Preferably, the separation solution 2 in step (2)b is made by dissolving 30 mL of hydrogen peroxide and 5 mL of sulfuric acid in water, diluting it to 100 mL and mixing it well, and adding 5-10 mL of hydrogen peroxide every half hour during the heat preservation process.

[0015] Preferably, the separation liquid 3 in step (2)c is an aqueous solution containing 20% ​​weak oxidant and 5% complexing agent.

[0016] Preferably, the mixed acid in step (3) is aqua regia and hydrofluoric acid, wherein the amount of aqua regia used is 20 mL and the amount of hydrofluoric acid used is 2 mL.

[0017] Preferably, the volume adjustment in step (3) uses a 100mL or 250mL polyethylene volumetric flask, and the volume is selected according to the amount of precipitated phase.

[0018] More preferably, the heating reflux time in steps (2)a and (2)c is 3 to 4 hours, keeping the solution at a gentle boil.

[0019] More preferably, the difference method in step (4) further includes calculating M. 23 The amounts of C6 and M7C3 phases are obtained from the amount of powder (C).

[0020] Compared with the prior art, the present invention achieves the following technical effects: This invention provides an analytical method for the chemical quantitative separation of carbide phases M6C and MC in high-speed steel. This method is advanced and scientific in the extraction and separation of precipitated phases, playing a crucial role in analyzing the content and elemental composition of various carbides in high-speed steel. By combining chemical phase separation with differential methods, the method achieves quantitative separation and precise determination of M6C and MC carbide phases with extremely similar chemical properties in high-speed steel. This overcomes the limitations of traditional X-ray diffraction methods, which can only provide semi-quantitative analysis of phase content and cannot obtain elemental composition. This method exhibits good selectivity and high accuracy, enabling the precise chemical composition of each phase and its mass fraction in the steel, providing crucial data support for optimizing the microstructure and improving the performance of high-speed steel. Attached Figure Description

[0021] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0022] Figure 1 The images show the X-ray diffraction analysis results of the precipitated phases of the annealed high-speed steel powder before and after separation in Example 1.

[0023] Figure 2 The images show the X-ray diffraction analysis results of the heat-treated powdered high-speed steel in Example 2 before and after phase separation. Detailed Implementation

[0024] The following are specific embodiments of the present invention, described in conjunction with the accompanying drawings, to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments. Specific details, such as particular configurations, are provided in the following description merely to aid in a comprehensive understanding of the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention.

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0026] Unless otherwise specified, the materials, practices, and experimental equipment involved in the embodiments of this invention are all commercially available products in the relevant chemical and biotechnology fields.

[0027] Example 1: Taking annealed powder high-speed steel as an example: 1. Extraction of the precipitated phase: (1) Electrolytic extraction of MC phase, M6C phase and M7C3 phase (A) a. After weighing the sample on an electronic balance, suspend the high-speed steel sample in an electrolytic cell containing 600 mL of electrolyte. The electrolysis environment temperature is 0℃~5℃, and the anode current density through the sample is 0.025~0.030 A / cm². 2 After electrolysis for 1 hour, the sample is removed. Using a glass rod with a latex tube attached to one end and deionized water, the precipitated phase on the anode surface of the sample is rinsed into a glass beaker to clean the sample surface. The sample is then rinsed with anhydrous ethanol, dried, and weighed. b. Connect the vacuum pump to the glass core filter device, place 4 layers of filter paper on the core, and use a clamp to connect it to the suction cup with a 0.22 μ polycarbonate filter membrane attached to the bottom. Turn on the vacuum pump to completely transfer the precipitated phase in the glass beaker to the filter device for suction filtration. Rinse the precipitated phase three times with citric acid solution and deionized water respectively to clean the precipitated phase. c. Transfer the filter membrane with the precipitated phase to a beaker, and use a glass rod with a latex tube attached to one end and deionized water to rinse the precipitated phase adhering to the filter beaker into the same beaker.

[0028] 2. Chemical separation of the precipitated phase: (1) Dissolve the M7C3 phase, retain the MC and M6C phases (B) a. Place the extracted precipitate powder (A) into a 250 mL ground glass joint reflux flask, add 100 mL of separation solution 1, connect the water condenser, turn on the cooling water, place the reflux flask on a hot plate and heat it under reflux for 3-4 hours, keeping the solution at a gentle boil during the process. After the process is complete, let it cool slightly, remove the reflux flask, and turn off the cooling water. b. Connect the vacuum pump to the glass frit filter device, place 4 layers of filter paper on the frit, and use a clamp to connect it to the suction cup with a 0.22 μm polycarbonate filter membrane attached to the bottom. Turn on the vacuum pump to completely transfer the solution and residual precipitate in the reflux bottle to the filter device for suction filtration, and rinse it clean with citric acid solution and deionized water.

[0029] (2) Dissolve the MC phase and M6C phase, and retain the M7C3 phase (C). a. Place the extracted precipitate powder (A) in a 200 mL beaker, add 100 mL of separation liquid 2, and place the beaker in a boiling water bath for 3 hours, adding 5-10 mL of hydrogen peroxide every half hour. b. Connect the vacuum pump to the glass frit filter device, place 4 layers of filter paper on the frit, and use a clamp to connect it to the suction cup with a 0.22 μm polycarbonate filter membrane attached to the bottom. Turn on the vacuum pump and transfer the solution and residual precipitated phase in the beaker to the filter device for suction filtration. Rinse thoroughly with citric acid solution and deionized water.

[0030] (3) Dissolve the M6C phase and retain the MC phase (D). a. Place the extracted precipitate powder (B) in a 250 mL ground glass joint reflux flask, add 100 mL of separation liquid 3, connect the water condenser, turn on the cooling water, place the reflux flask on a hot plate and heat it under reflux for 3 to 4 hours, keeping the solution at a gentle boil during the process. After the process is completed, let it cool slightly, remove the reflux flask, and turn off the cooling water. b. Connect the vacuum pump to the glass frit filter device, place 4 layers of filter paper on the frit, and connect it to the suction cup with a 0.22μ polycarbonate filter membrane attached to the bottom using a clamp. Turn on the vacuum pump and transfer the solution and residual precipitated phase in the reflux bottle to the filter device for suction filtration. Rinse thoroughly with citric acid solution and deionized water.

[0031] 3. Preparation and determination of the test solution: Powders (A), (B), (C), and (D) were transferred to 100 mL polytetrafluoroethylene (PTFE) beakers, respectively. Using a glass rod with a latex tube attached to one end and a small amount of deionized water, the precipitated phase adhering to the filter beaker was washed into the PTFE beaker. 20 mL of aqua regia and 2 mL of hydrofluoric acid were added, and the mixture was heated at low temperature to dissolve. After cooling, the solution was transferred to a 100 mL or 250 mL polyethylene volumetric flask (depending on the amount of precipitated phase) and diluted to the mark with deionized water. The concentrations of each element in the solution were determined using ICP-AES, and the mass percentage of each element in the precipitated phase relative to the steel was calculated.

[0032] 4. Calculation of the amount of precipitated phase: (1) M7C3 phase = C The amount of residue (C) obtained after separation is the amount of M7C3 phase.

[0033] (2) MC phase = D The amount of residue (D) obtained after separation is the amount of MC phase.

[0034] (3) M6C phase = BD The amount of the separated residue (B) minus the amount of the separated residue (D) is the amount of the M6C phase.

[0035] The X-ray diffraction analysis results of the precipitated phases of annealed high-speed steel powder before and after separation are attached. Figure 1 .

[0036] Table 1 Content of various precipitates in annealed powdered high-speed steel

[0037] Example 2: Taking heat-treated powder high-speed steel as an example: 1. Extraction of the precipitated phase: (1) Electrolytic extraction of MC phase and M6C phase (E) a. After weighing the sample on an electronic balance, suspend the high-speed steel sample in an electrolytic cell containing 600 mL of electrolyte. The electrolysis environment temperature is 0℃~5℃, and the anode current density through the sample is 0.025~0.030 A / cm². 2 After electrolysis for 1 hour, the sample is removed. Using a glass rod with a latex tube attached to one end and deionized water, the precipitated phase on the anode surface of the sample is rinsed into a glass beaker to clean the sample surface. The sample is then rinsed with anhydrous ethanol, dried, and weighed. b. Connect the vacuum pump to the glass core filter device, place 4 layers of filter paper on the core, and use a clamp to connect it to the suction cup with a 0.22 μ polycarbonate filter membrane attached to the bottom. Turn on the vacuum pump to completely transfer the precipitated phase in the glass beaker to the filter device for suction filtration. Rinse the precipitated phase three times with dilute citric acid solution and deionized water respectively to clean the precipitated phase. c. Transfer the filter membrane with the precipitated phase to a beaker, and use a glass rod with a latex tube attached to one end and deionized water to rinse the precipitated phase adhering to the filter beaker into the same beaker.

[0038] 2. Chemical separation of the precipitated phase: (1) Dissolve the M6C phase and retain the MC phase (F). a. Place the extracted precipitate powder (E) in a 250 mL ground glass joint reflux flask, add 100 mL of separation solution 3, connect the water condenser, turn on the cooling water, place the reflux flask on a hot plate and heat it under reflux for 3 to 4 hours, keeping the solution at a gentle boil during the process. After the process is completed, let it cool slightly, remove the reflux flask, and turn off the cooling water. b. Connect the vacuum pump to the glass frit filter device, place 4 layers of filter paper on the frit, and connect it to the suction cup with a 0.22μ polycarbonate filter membrane attached to the bottom using a clamp. Turn on the vacuum pump and transfer the solution and residual precipitated phase in the reflux bottle to the filter device for suction filtration. Rinse thoroughly with citric acid solution and deionized water.

[0039] 3. Preparation and determination of the test solution: Powders (E) and (F) were transferred to 100 mL polytetrafluoroethylene (PTFE) beakers respectively. Using a glass rod with a latex tube attached to one end and a small amount of deionized water, the precipitated phase adhering to the filter beaker was washed into the PTFE beaker. 20 mL of aqua regia and 2 mL of hydrofluoric acid were added, and the mixture was heated at low temperature to dissolve. After cooling, the solution was transferred to a 100 mL or 250 mL polyethylene volumetric flask (depending on the amount of precipitated phase) and diluted to the mark with deionized water. The concentrations of each element in the solution were determined using ICP-AES, and the mass percentage of each element in the precipitated phase relative to the steel was calculated.

[0040] 4. Calculation of the amount of precipitated phase: (1) MC phase = F The amount of residue (F) obtained after separation is the amount of MC phase.

[0041] (2) M6C phase = EF The amount of M6C phase is the total amount of precipitated phase (E) obtained by electrolysis minus the amount of residue (F) obtained by separation.

[0042] The X-ray diffraction analysis results of the precipitated phases of heat-treated powder high-speed steel before and after separation are attached. Figure 2 .

[0043] Table 2 Content of various precipitates in heat-treated powder high-speed steel

[0044] Those skilled in the art to which this application pertains may make various modifications or additions to the specific embodiments described, or adopt similar methods to replace them, without departing from the inventive concept of this application or exceeding the scope defined by the appended claims.

Claims

1. An analytical method for the quantitative chemical separation of carbide phases M6C and MC in high-speed steel, characterized in that: Includes the following steps: (1) Extraction of precipitated phases: The carbide phases in the high-speed steel sample were extracted by electrolysis to obtain phases including M6C, MC, and M. 23 C6 phase and M7C3 phase precipitate powder (A); (2) Chemical separation of the precipitated phase: including the following sub-steps: a. Dissolve M 23 C6 phase and M7C3 phase, retain MC phase and M6C phase: The precipitated phase powder (A) is heated and refluxed with separation liquid 1 to obtain the residual MC phase and M6C phase powder (B); b. Dissolve the MC and M6C phases, retaining M. 23 C6 phase and M7C3 phase: The precipitated phase powder (A) and separation liquid 2 were kept at a boiling water bath to obtain the residual M. 23 C6 phase and M7C3 phase powder (C); c. Dissolve the M6C phase and retain the MC phase: Heat the precipitated phase powder (B) and separation liquid 3 under reflux to obtain the residual MC phase powder (D); (3) Preparation and determination of test solution: Dissolve the precipitate powders (A), (B), (C) and (D) obtained in steps (1) and (2) respectively with mixed acid, and after adjusting the volume, determine the concentration of each element by ICP-AES method and calculate the mass percentage of each element in the precipitate in the steel. (4) Calculation of the amount of precipitated phase: Based on the measurement results, the content and elemental composition of M6C phase and MC phase are calculated by the differential method. The amount of M6C phase is obtained by subtracting the amount of powder (D) from the amount of powder (B), and the amount of MC phase is obtained by the amount of powder (D).

2. The analytical method according to claim 1, characterized in that: The electrolytic extraction in step (1) uses a neutral KCl electrolyte, the electrolysis environment temperature is 0℃~5℃, the anode current density is 0.025~0.030A / cm², and the electrolysis time is 1 hour.

3. The analytical method according to claim 1, characterized in that: After electrolysis in step (1), the precipitated phase is rinsed with citric acid solution and deionized water, wherein the concentration of citric acid solution is 10 g / L.

4. The analytical method according to claim 1, characterized in that: In step (2)a, the separation solution 1 is made by dissolving 30 mL of hydrochloric acid and 1 g of citric acid in water, diluting it to 100 mL and mixing.

5. The analytical method according to claim 1, characterized in that: In step (2)b, the separation solution 2 is made by dissolving 30 mL of hydrogen peroxide and 5 mL of sulfuric acid in water, diluting it to 100 mL and mixing it well, and adding 5-10 mL of hydrogen peroxide every half hour during the heat preservation process.

6. The analytical method according to claim 1, characterized in that: The separation liquid 3 mentioned in step (2)c is an aqueous solution containing 20% ​​weak oxidant and 5% complexing agent.

7. The analytical method according to claim 1, characterized in that: The mixed acid mentioned in step (3) is aqua regia and hydrofluoric acid, wherein the amount of aqua regia used is 20 mL and the amount of hydrofluoric acid used is 2 mL.

8. The analytical method according to claim 1, characterized in that: The volumetric flask used in step (3) is a 100 mL or 250 mL polyethylene volumetric flask, and the volume is selected according to the amount of precipitated phase.

9. The analytical method according to claim 1, characterized in that: The heating reflux time in steps (2)a and (2)c is 3 to 4 hours, keeping the solution at a gentle boil.

10. The analytical method according to claim 1, characterized in that: The difference method described in step (4) also includes calculating M. 23 The amounts of C6 and M7C3 phases are obtained from the amount of powder (C).

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