Electrochemical in-situ etching method for non-metallic inclusions for hypereutectoid steel rail steel

Abstract

The invention provides an electrochemical in-situ etching method for non-metallic inclusions for hypereutectoid rail steel, which comprises the following steps: a) performing electrochemical in-situ etching on a sample to be etched in electrolyte, taking out the sample, and sequentially cleaning and drying to obtain a sample to be detected; the electrolyte comprises: 1%-1.5% of lithium chloride; 78%-84% of an alcoholic solution; 15%-20% of acetylacetone; and b) detecting the to-be-detected sample obtained in the step a) to obtain morphology characteristics, size information and in-situ distribution evolution rules of the inclusions. According to the electrochemical in-situ etching method for the non-metallic inclusions for the hypereutectoid rail steel, the specific electrolyte is matched with the specific process steps, overall good interaction is achieved, three-dimensional in-situ etching of the non-metallic inclusions in the hypereutectoid rail steel is successfully achieved, and the electrochemical in-situ etching method for the non-metallic inclusions in the hypereutectoid rail steel is obtained by combining with conventional metallographic detection. Component and content information of the non-metallic inclusion can be analyzed more comprehensively, and an important scientific basis is provided for analysis and research of the non-metallic inclusion and development of a control process technology.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and more specifically to an electrochemical in-situ etching method for non-metallic inclusions in hypereutectoid rail steel. Background Art

[0002] Rails are key components of railway transportation, affecting the high speed, efficiency and safety of railway transportation. With the continuous development of railway transportation, the quality requirements of rails are increasing. Among them, non-metallic inclusions in rails are important quality indicators. This is mainly because non-metallic inclusions block the continuity of the matrix structure in the rails, exist as heterogeneous phases, and are easy to deteriorate the mechanical properties of the rails after reaching a certain size. For example, hard Al2O3 will deteriorate the plasticity, toughness and fatigue resistance of the rails, and easily cause the rails to peel off. Large-sized long strips of MnS inclusions are the main cause of rust, and MnS is a plastic inclusion. It is easy to deform into long strips of MnS inclusions during the rolling process. Such long strips of MnS are the main reason for the increase or even exceeding of the rating results of Class A inclusions, and are also one of the main reasons for the failure of ultrasonic testing. It can be seen from this that for rails, which are an important part of railway transportation, the control of non-metallic inclusions is important. Therefore, many scholars have carried out a lot of research. In addition, with the changes in the service environment of rails, the requirements for the mechanical properties of rails are also constantly increasing, and the development of new high-end heavy rail products is also extremely urgent. Hypereutectoid rails have attracted much attention due to their excellent mechanical properties. They are mainly used in heavy-load freight lines and have high strength, wear resistance and excellent fatigue resistance.

[0003] As we all know, the study of non-metallic inclusions in steel requires theoretical research from the aspects of thermodynamics and kinetics, and also requires industrial testing in close combination with on-site equipment and process conditions to accurately adjust the actual production process. In the process of precise adjustment of the actual production process, the comprehensive and accurate analysis of the industrial test results is the key to process research. Incomplete or inaccurate test results often lead to inaccurate production process research, and even lead to misjudgment of results, making it difficult to effectively break through related process research. Therefore, the study of non-metallic inclusions in heavy rail steel requires comprehensive and accurate detection of non-metallic inclusions.

[0004] At present, there are many studies on non-metallic inclusions in steel, and there are also many studies on non-metallic inclusions in heavy rail steel. Most of the related research focuses on the research of inclusion control process and equipment technology. Metallographic detection and large sample electrolysis are mostly used for the detection of non-metallic inclusions. In recent years, Aspex scanning statistics and industrial CT scanning have been developed. Among them, two-dimensional detection often finds it difficult to obtain the complete morphology of inclusions, and even the observation information of some inclusions is seriously missing, which is only the "tip of the iceberg" of actual information; secondly, it leads to the lack of detection information of the chemical composition of non-metallic inclusions. Due to the complex formation process of non-metallic inclusions in steel, some inclusions evolve layer by layer at different stages. Two-dimensional detection leads to deviations in the detection results of their chemical composition content, which ultimately leads to misjudgment of the source of inclusions and their formation and evolution behavior mechanism. For the three-dimensional detection of inclusions, the electrolysis method is currently mainly used, including: partial acid etching method, small sample electrolysis method and large sample electrolysis method. The relevant technology obtains more comprehensive inclusion information than two-dimensional detection. However, due to the different chemical compositions of different steel types, their acid corrosion resistance varies to varying degrees, and the detection results vary greatly.

[0005] To this end, scholars have carried out a lot of technical research, such as:

[0006] CN118032905A discloses a non-aqueous quantitative electrolytic analysis method for strip defects on the surface of a hot-rolled plate, comprising the following steps: 1) using a hot-rolled plate sample containing strip defects as an anode and a stainless steel sheet as a cathode, and using an electrolyte having the following components in percentage by volume: 10-20% triethanolamine, 0.5-1% tetramethylammonium chloride, and 79-89.5% methanol; the chemical composition mass percentages of the hot-rolled plate include: C≤0.003%, Si≤0.2%, Mn≤0.2%, P≤0.02%, S≤0.02%, and the remainder includes Fe and other unavoidable impurities; 2) setting the electrolysis current and electrolysis time, and performing a constant amount of electrolysis on the strip defects, and the electrolysis thickness h-(Fe) is 20-30 μm; wherein: M-(Fe) is the molar mass of Fe, in kg / mol; ρ-(Fe) is the density of the substrate iron, 7800 kg / m 3 ; S is the electrolysis area, unit m 2 ; I is the electrolysis current, unit A; t is the electrolysis time, unit s; e is the electron charge, 1.6×10 -19 C; NA is Avogadro's constant, 6.02×10 23 / mol; at the same time, the electrolysis time and current must satisfy the following relationship: 5.49×10 4 ×S <I×t<8.24×10 5 ×S; 3) After electrolysis reveals the inclusions in the defect strip, the microscopic morphology and energy spectrum analysis of the hot-rolled strip defects containing inclusions are carried out.

[0007] CN117871202A discloses a method for extracting inclusions from an iron-based high-temperature alloy for steam turbine blades and an electrolysis device, comprising: workpiece preparation: cutting a block workpiece from an inclusion-rich region in a steam turbine blade by mechanical processing; placing the cut workpiece in an ultrasonic cleaning machine for vibration cleaning; preparing an electrolyte: using aqueous solution electrolysis, the electrolyte is mixed by mass in the following proportions: 1% ferric chloride, 1% sodium chloride, and the remainder is distilled water; preparing an acid solution: using chemical separation, the acid solution is: saturated oxalic acid and 10% concentrated nitric acid solution; aqueous solution electrolysis: connecting the workpiece obtained in the first step with the electrolysis device for Ionization: constant voltage method is adopted during electrolysis, the electrolysis temperature is controlled at about 20°C in a water bath, the voltage is constant at 10V, and the electrolyte is replaced every 180 minutes of electrolysis until the workpiece is completely electrolyzed; physical separation and cleaning: the electrolysis product and the liquid are separated by a centrifuge at a speed of 5000r / s for 5 minutes; the electrolysis product is repeatedly washed with deionized water and dried to obtain the electrolysis product; chemical separation: the electrolysis product obtained in the fifth step is placed in a saturated oxalic acid and 10% concentrated nitric acid solution and soaked for 12 hours; cleaning and collection: the acidolysis product obtained in the sixth step is repeatedly rinsed with deionized water and dried to finally obtain inclusions in the high-temperature alloy.

[0008] CN117457104A is specifically a research method for the influence of alloying elements on the formation and evolution behavior of manganese-containing inclusions in medium-high manganese steel, comprising the following steps: S1. placing iron-containing materials with low element composition in a corundum crucible in the constant temperature zone of a vertical tube furnace, and the outer layer of the corundum crucible is protected by a graphite crucible; S2. introducing high-purity argon gas from the bottom of the tube furnace for a period of time to keep the furnace tube at a positive pressure; S3. heating the iron-containing materials to a certain temperature to melt, and keeping the temperature for a period of time to obtain molten iron; S4. adding alloying materials to the molten iron, homogenizing it for a period of time, and then cooling it to room temperature with the furnace to obtain a medium-high manganese steel sample; S5. sampling the obtained steel sample for chemical composition analysis; S6. cutting a cubic metallographic sample with a size of 10mm×10mm×10mm at the longitudinal and transverse 1 / 2 position of the steel sample, grinding and polishing, and using a scanning electron microscope equipped with an energy spectrum to analyze the two-dimensional morphology, size, distribution and chemical composition of manganese-containing inclusions. S7. The polished surface of the electrolytic metallographic sample in a non-aqueous solution was used to observe the three-dimensional morphology of manganese-containing inclusions in situ with a scanning electron microscope. S8. The thermodynamic calculation software FactSage was used to select the FTmisc, FToxyd and FSstel databases. The precipitation time, precipitation temperature and precipitation amount of different inclusion phases during the solidification of medium-high manganese steel were calculated under the ScheilGulliver cooling mode. The liquidus and solidus temperatures of medium-high manganese steel were calculated using the equilibrium cooling module to reveal the formation mechanism of manganese-containing inclusions under the action of different alloying elements. S9. According to the equilibrium Gibbs free energy change of MnS generation and the Voller-Beckermann microsegregation model, the relationship between the solid phase ratio, the equilibrium activity product and actual activity product of Mn and S, and the precipitation temperature was calculated, and the influence of different alloying elements on the precipitation and evolution behavior of MnS inclusions was discussed.

[0009] However, the above-mentioned prior arts do not involve the electrochemical in-situ corrosion technology of non-metallic inclusions in hypereutectoid rail steel. Summary of the invention

[0010] In view of this, the purpose of the present invention is to provide an electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel, which not only retains the in-situ information of non-metallic inclusions in hypereutectoid heavy rail steel, but also can more comprehensively present the three-dimensional morphology of non-metallic inclusions. By combining with conventional metallographic detection, the composition and content information of non-metallic inclusions can be more comprehensively analyzed, providing an important scientific basis for the analysis and research of non-metallic inclusions and the development of control process technology.

[0011] The present invention provides a method for electrochemical in-situ corrosion of non-metallic inclusions for hypereutectoid rail steel, comprising the following steps:

[0012] a) electrochemically etching the sample to be etched in situ in an electrolyte, and then taking it out, washing and drying it in sequence to obtain a sample to be tested; the electrolyte comprises:

[0013] Lithium chloride 1%~1.5%;

[0014] Alcohol solution 78%~84%;

[0015] Acetylacetone 15%~20%;

[0016] b) Testing the sample obtained in step a) to obtain the morphological characteristics, size information and in-situ distribution evolution law of the inclusions.

[0017] Preferably, the smelting chemical composition of the sample to be etched in step a) is composed of the following elements, in mass percentage: C 0.85%~1.00%, Si 0.60%~0.70%, Mn 0.70%~0.90%, P≤0.015%, S≤0.010%, Cr 0.20%~0.40%, V 0.05%~0.08%, and the rest is Fe and other inevitable impurities.

[0018] Preferably, the sample to be corroded in step a) is a regular sample with a volume of (4-6) mm×(15-25) mm×(35-45) mm, and the surface to be observed is (15-25) mm×(35-45) mm; before use, the surface to be observed of the sample to be corroded is polished with 150-200 mesh, 250-300 mesh, 350-450 mesh, 750-850 mesh and 1100-1300 mesh sandpaper in sequence, further polished with polishing paste, rinsed with alcohol, blown dry, and set aside.

[0019] Preferably, the alcohol solution in step a) is a methanol solution and / or an ethanol solution.

[0020] Preferably, the pH of the electrolyte in step a) is 8-9.

[0021] Preferably, the electrochemical in-situ etching equipment in step a) comprises a constant temperature electrolytic cell containing an electrolyte; a corrosion-resistant conductive steel sheet and a sample to be etched are placed in the electrolyte, wherein the corrosion-resistant conductive steel sheet is connected to the cathode of the power supply, and the sample to be etched is connected to the anode of the power supply via a platinum electrode.

[0022] Preferably, the electrolyte temperature of the electrochemical in-situ etching in step a) is -12°C to -8°C, and the current density is 0.05A / cm 2 ~0.07A / cm 2 , the leaching time is 560s~580s.

[0023] Preferably, the cleaning method in step a) is cleaning with anhydrous ethanol.

[0024] Preferably, the drying method in step a) is oven drying; the oven drying temperature is 40° C. to 60° C., and the time is 30s to 40s.

[0025] Preferably, the detection method in step b) is EBSD metallographic inclusion detection.

[0026] The present invention provides an electrochemical in-situ corrosion method for non-metallic inclusions for hypereutectoid rail steel, comprising the following steps: a) electrochemically in-situ corrosion is performed on a sample to be corroded in an electrolyte, and after being taken out, it is successively cleaned and dried to obtain a sample to be tested; the electrolyte comprises: 1% to 1.5% lithium chloride; 78% to 84% alcohol solution; 15% to 20% acetylacetone; b) testing the sample to be tested obtained in step a) to obtain morphological characteristics, size information and in-situ distribution evolution law of the inclusions. Compared with the prior art, the electrochemical in-situ etching method for non-metallic inclusions in hypereutectoid rail steel provided by the present invention adopts a specific electrolyte in combination with specific process steps to achieve overall good interaction, and successfully realizes the three-dimensional in-situ etching of non-metallic inclusions in hypereutectoid rail steel, which not only retains the in-situ information of non-metallic inclusions in hypereutectoid heavy rail steel, but also can more comprehensively present the three-dimensional morphology of non-metallic inclusions. By combining with conventional metallographic detection, the composition and content information of non-metallic inclusions can be more comprehensively analyzed, providing an important scientific basis for the analysis and research of non-metallic inclusions and the development of control process technology.

[0027] At the same time, the electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel provided by the present invention has simple process, concise equipment, easy operation, significant effect, and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure and connection of the electrolysis equipment in an embodiment of the present invention;

[0029] Figure 2 This is a photo of a typical result of in-situ etching of non-metallic inclusions in Example 1 of the present invention;

[0030] Figure 3 This is a typical photo of the in-situ corrosion results of non-metallic inclusions in Example 2 of the present invention;

[0031] Figure 4 This is a photo of a typical result of in-situ etching of non-metallic inclusions in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The present invention provides a method for electrochemical in-situ corrosion of non-metallic inclusions for hypereutectoid rail steel, comprising the following steps:

[0034] a) electrochemically etching the sample to be etched in situ in an electrolyte, and then taking it out, washing and drying it in sequence to obtain a sample to be tested; the electrolyte comprises:

[0035] Lithium chloride 1%~1.5%;

[0036] Alcohol solution 78%~84%;

[0037] Acetylacetone 15%~20%;

[0038] b) Testing the sample obtained in step a) to obtain the morphological characteristics, size information and in-situ distribution evolution law of the inclusions.

[0039] Generally speaking, the alloy components and content in steel will significantly affect the corrosion resistance of the steel, and in order to better retain the information of inclusions in the steel, the characteristics of non-metallic inclusions in the steel also need to be fully considered. It can be seen that in the process of electrochemical corrosion, the electrochemical corrosion reagent formula and the key electrolysis process parameters need to be scientifically developed. In addition, the in-situ information of inclusions is also extremely critical for inclusion research, that is, it is necessary to maintain the in-situ distribution information of inclusions. On this basis, the present invention provides a method for electrochemical in-situ corrosion of non-metallic inclusions for hypereutectoid rail steel.

[0040] The present invention firstly performs electrochemical in-situ etching on the sample to be etched in an electrolyte, and then takes it out, cleans it and dries it in sequence to obtain the sample to be tested.

[0041] In the present invention, the sample to be corroded, i.e., the rail steel, belongs to hypereutectoid rail steel, and the non-metallic inclusions therein mainly include MnS, and Ca, Si, Al, and Mg composite oxides; the smelting chemical composition of the sample to be corroded, in terms of mass percentage, is preferably composed of the following elements: C 0.85%~1.00%, Si 0.60%~0.70%, Mn 0.70%~0.90%, P≤0.015%, S≤0.010%, Cr 0.20%~0.40%, V 0.05%~0.08%, and the rest is Fe and other inevitable impurities.

[0042] In the present invention, the sample to be corroded is preferably a regular sample with a volume of (4-6) mm×(15-25) mm×(35-45) mm, more preferably 5 mm×20 mm×40 mm, which is processed by cutting equipment, and its surface to be observed is preferably (15-25) mm×(35-45) mm, more preferably 20 mm×40 mm; before use, the surface to be observed of the sample to be corroded is preferably polished with 150-200 mesh, 250-300 mesh, 350-450 mesh, 750-850 mesh and 1100-1300 mesh sandpaper in sequence, further polished with polishing paste, rinsed with alcohol, blown dry, and set aside; more preferably, the surface to be observed of the sample to be corroded is polished with 180 mesh, 280 mesh, 400 mesh, 800 mesh and 1200 mesh sandpaper in sequence, further polished with polishing paste, rinsed with alcohol, blown dry, and set aside.

[0043] The present invention adopts in-situ electrolytic corrosion, and the electrolyte is a non-aqueous electrolyte, comprising:

[0044] Lithium chloride 1%~1.5%;

[0045] Alcohol solution 78%~84%;

[0046] Acetylacetone 15%~20%.

[0047] In the present invention, the alcohol solution is preferably a methanol solution and / or an ethanol solution, more preferably a methanol solution. The present invention has no particular restrictions on the sources of the lithium chloride, alcohol solution, and acetylacetone, and commercially available products known to those skilled in the art can be used.

[0048] In the present invention, the pH of the electrolyte is preferably 8-9, that is, a weakly alkaline chemical reagent.

[0049] In the present invention, the electrochemical in-situ etching equipment preferably includes a constant temperature electrolytic cell containing an electrolyte; a corrosion-resistant conductive steel sheet and a sample to be etched are placed in the electrolyte, wherein the corrosion-resistant conductive steel sheet is connected to a cathode of a power supply, and the sample to be etched is connected to an anode of a power supply via a platinum electrode; on this basis, the electrochemical in-situ etching process is preferably specifically as follows:

[0050] The observed surface (target detection surface) of the sample to be corroded is placed horizontally with the surface facing downward, facing the corrosion-resistant conductive steel sheet, so as to promote the electrolysis product to separate from the target detection surface of the sample and improve the corrosion uniformity and cleanliness of the corrosion surface. At the same time, during the corrosion process, the temperature is set by the constant temperature pool to keep the corrosion environment (electrolyte) temperature preferably at -12℃~-8℃; the electrolysis current density i is preferably set to 0.05A / cm by adjusting the DC regulated power supply. 2 ~0.07A / cm 2 , more preferably 0.06A / cm2; the leaching time t is preferably controlled to be 560s~580s.

[0051] In the present invention, the cleaning method is preferably cleaning with anhydrous ethanol.

[0052] In the present invention, the drying method is preferably oven drying; the temperature of the oven drying is preferably 40° C. to 60° C., and the time is preferably 30s to 40s.

[0053] After obtaining the sample to be tested, the present invention detects the obtained sample to be tested to obtain the morphological characteristics, size information and in-situ distribution evolution law of the inclusions.

[0054] In the present invention, the detection method is preferably EBSD metallographic inclusion detection, and the conventional research and analysis EBSD metallographic inclusion detection technical means well known to those skilled in the art can be used to obtain the inclusion morphology characteristics, size information and in-situ distribution evolution law.

[0055] The present invention provides an electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel, comprising the following steps: a) electrochemically in-situ corroding a sample to be corroded in an electrolyte, taking it out and successively cleaning and drying it to obtain a sample to be tested; the electrolyte comprises: 1%-1.5% lithium chloride; 79%-83% alcohol solution; 15%-20% acetylacetone; b) testing the sample to be tested obtained in step a) to obtain morphological characteristics, size information and in-situ distribution evolution law of inclusions. Compared with the prior art, the electrochemical in-situ etching method for non-metallic inclusions in hypereutectoid rail steel provided by the present invention adopts a specific electrolyte in combination with specific process steps to achieve overall good interaction, and successfully realizes the three-dimensional in-situ etching of non-metallic inclusions in hypereutectoid rail steel, which not only retains the in-situ information of non-metallic inclusions in hypereutectoid heavy rail steel, but also can more comprehensively present the three-dimensional morphology of non-metallic inclusions. By combining with conventional metallographic detection, the composition and content information of non-metallic inclusions can be more comprehensively analyzed, providing an important scientific basis for the analysis and research of non-metallic inclusions and the development of control process technology.

[0056] At the same time, the electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel provided by the present invention has simple process, concise equipment, easy operation, significant effect, and broad application prospects.

[0057] In order to further illustrate the present invention, the following examples are provided for detailed description.

[0058] Example 1

[0059] This embodiment is a hypereutectoid rail steel produced by a certain enterprise, and its smelting chemical composition (mass percentage) is composed of the following elements: C 0.85%~0.91%, Si 0.60%~0.65%, Mn 0.70%~0.75%, P≤0.008%, S≤0.005%, Cr0.20%~0.30%, V 0.05%~0.07%, and the rest is Fe and other inevitable impurities.

[0060] The key technical parameters involved in the present invention are actually implemented as follows:

[0061] (1) Equipment preparation, the key equipment consists of: DC regulated power supply, temperature control device, platinum electrode, and electrolytic cell (see Figure 1 as shown).

[0062] (2) Electrolyte preparation: (a) Key characteristics of electrochemical in situ etching reagent: This chemical reagent is a non-aqueous electrolyte with a final pH value of 9, that is, a weakly alkaline chemical reagent; (b) Main components of the chemical reagent: lithium chloride (molecular formula LiCl, white crystals), methanol, acetylacetone; (c) Key principle: Lithium chloride is dissolved in an organic solvent to form a complex, which acts as a conductive salt during the electrolysis process and promotes charge transfer between electrodes; (d) Reagent component content: 1% lithium chloride, 18% acetylacetone, 81% methanol solution.

[0063] (3) Sample preparation: The steel ingot sample was made into a regular sample with a volume of 5 mm × 20 mm × 40 mm using a cutting machine, and the observation surface was 20 mm × 40 mm. The observation surface of the sample was polished with 180, 280, 400, 800 and 1200 grit sandpaper in turn, and further polished with polishing paste, rinsed with alcohol, and blown dry for electrochemical leaching.

[0064] (4) In-situ corrosion of non-metallic inclusions in the sample, corrosion environment (electrolyte) temperature -12 °C, current density i = 0.06A / cm 2 , leaching time t=580s.

[0065] (5) Sample post-treatment: The samples were cleaned with anhydrous ethanol and dried in a drying oven (50°C, 30s~40s).

[0066] (6) Result observation: The samples that have completed in-situ etching are subjected to conventional research and analysis EBSD metallographic inclusion detection to understand the morphological characteristics, size information and in-situ distribution evolution of the inclusions in the sample; photos of typical inclusion detection results Figure 2 shown.

[0067] The test results show that the overall size of non-metallic inclusions increases gradually from the surface of the ingot to the center of the ingot, specifically from an average of 1.2 μm at 10 mm from the surface to an average of 13.7 μm at 100 mm from the surface; the number density decreases gradually, specifically from 24 particles / 100 mm at 10 mm from the surface to 13.7 μm at 100 mm from the surface. 2 Reduced to an average of 12 particles / 100mm at a distance of 100mm from the surface 2 .

[0068] Example 2

[0069] This embodiment is a hypereutectoid rail steel produced by a certain enterprise, and its smelting chemical composition (mass percentage) is composed of the following elements: C 0.95%~1.00%, Si 0.67%~0.70%, Mn 0.85%~0.90%, P≤0.015%, S≤0.010%, Cr0.35%~0.40%, V 0.07%~0.08%, and the rest is Fe and other inevitable impurities.

[0070] The key technical parameters involved in the present invention are actually implemented as follows:

[0071] (1) Equipment preparation, the key equipment consists of: DC regulated power supply, temperature control device, platinum electrode, and electrolytic cell (see Figure 1 as shown).

[0072] (2) Electrolyte preparation: (a) Key characteristics of electrochemical in situ etching reagent: This chemical reagent is a non-aqueous electrolyte with a final pH value of 8, that is, a weakly alkaline chemical reagent; (b) Main components of the chemical reagent: lithium chloride (molecular formula LiCl, white crystals), methanol, acetylacetone; (c) Key principle: Lithium chloride is dissolved in an organic solvent to form a complex, which acts as a conductive salt during the electrolysis process and promotes charge transfer between electrodes; (d) Reagent component content: 1.5% lithium chloride, 15% acetylacetone, 83.5% methanol solution.

[0073] (3) Sample preparation: The steel ingot sample was made into a regular sample with a volume of 5 mm × 20 mm × 40 mm using a cutting machine, and the observation surface was 20 mm × 40 mm. The observation surface of the sample was polished with 180, 280, 400, 800 and 1200 grit sandpaper in turn, and further polished with polishing paste, rinsed with alcohol, and blown dry for electrochemical leaching.

[0074] (4) In-situ corrosion of non-metallic inclusions in the sample, corrosion environment (electrolyte) temperature -8 °C, current density i = 0.06 A / cm 2 , leaching time t=560s.

[0075] (5) Sample post-treatment: The samples were cleaned with anhydrous ethanol and dried in a drying oven (50°C, 30s~40s).

[0076] (6) Result observation: The samples that have completed in-situ etching are subjected to conventional research and analysis EBSD metallographic inclusion detection to understand the morphological characteristics, size information and in-situ distribution evolution of the inclusions in the sample; photos of typical inclusion detection results Figure 3 shown.

[0077] The test results show that the overall size of non-metallic inclusions increases gradually from the rail surface to the center of the rail waist, specifically from an average of 5.2μm at 10mm from the rail tread (top surface of the rail head) to an average of 31.9μm at 30mm from the rail tread; the number density decreases gradually, specifically from 55 particles / 100mm at 5mm from the rail tread. 2 Reduced to an average of 19 / 100mm at 30mm from the rail tread 2 .

[0078] Example 3

[0079] This embodiment is a hypereutectoid rail steel produced by a certain enterprise, and its smelting chemical composition (mass percentage) is composed of the following elements: C 0.90%~0.96%, Si 0.64%~0.68%, Mn 0.75%~0.85%, P≤0.012%, S≤0.009%, Cr0.30%~0.35%, V 0.06%~0.08%, and the rest is Fe and other inevitable impurities.

[0080] The key technical parameters involved in the present invention are actually implemented as follows:

[0081] (1) Equipment preparation, the key equipment consists of: DC regulated power supply, temperature control device, platinum electrode, and electrolytic cell (see Figure 1 as shown).

[0082] (2) Electrolyte preparation: (a) Key characteristics of electrochemical in situ etching reagent: This chemical reagent is a non-aqueous electrolyte with a final pH value of 8, that is, a weakly alkaline chemical reagent; (b) Main components of the chemical reagent: lithium chloride (molecular formula LiCl, white crystals), methanol, acetylacetone; (c) Key principle: Lithium chloride is dissolved in an organic solvent to form a complex, which acts as a conductive salt during the electrolysis process and promotes charge transfer between electrodes; (d) Reagent component content: 1.3% lithium chloride, 20% acetylacetone, 78.7% methanol solution.

[0083] (3) Sample preparation: The steel ingot sample was made into a regular sample with a volume of 5 mm × 20 mm × 40 mm using a cutting machine, and the observation surface was 20 mm × 40 mm. The observation surface of the sample was polished with 180, 280, 400, 800 and 1200 grit sandpaper in turn, and further polished with polishing paste, rinsed with alcohol, and blown dry for electrochemical leaching.

[0084] (4) In-situ corrosion of non-metallic inclusions in the sample, corrosion environment (electrolyte) temperature -10 °C, current density i = 0.06A / cm 2 , leaching time t=570s.

[0085] (5) Sample post-treatment: The samples were cleaned with anhydrous ethanol and dried in a drying oven (50°C, 30s~40s).

[0086] (6) Result observation: The samples that have completed in-situ etching are subjected to conventional research and analysis EBSD metallographic inclusion detection to understand the morphological characteristics, size information and in-situ distribution evolution of the inclusions in the sample; photos of typical inclusion detection results Figure 4 shown.

[0087] The test results show that the overall size of non-metallic inclusions increases gradually from the surface of the ingot to the center of the ingot, specifically from an average of 0.8 μm at 10 mm from the surface to an average of 11.2 μm at 100 mm from the surface; the number density decreases gradually, specifically from 21 particles / 100 mm at 10 mm from the surface to 11.2 μm at 100 mm from the surface. 2 The average number of particles decreased to 13 / 100mm at a distance of 100mm from the surface. 2 .

[0088] The above embodiments illustrate that by adopting the electrochemical in-situ etching method for non-metallic inclusions in hypereutectoid rail steel provided by the present invention, three-dimensional in-situ etching of non-metallic inclusions in hypereutectoid rail steel is successfully achieved; the sample etched by this method retains the in-situ information of non-metallic inclusions in the steel, and more comprehensively analyzes the three-dimensional morphology, size and quantity distribution and other information of non-metallic inclusions in different parts of the hypereutectoid rail steel; the three-dimensional morphological characteristics of non-metallic inclusions are more comprehensive than two-dimensional detection, and after combining with general technical means such as EBSD, information such as the chemical composition of non-metallic inclusions is more comprehensively detected; the relevant results more comprehensively and accurately support the formation and evolution analysis of non-metallic inclusions in hypereutectoid rail steel and the development of control process technology.

[0089] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for electrochemical in-situ corrosion of non-metallic inclusions in hypereutectoid rail steel, comprising the following steps: a) electrochemically etching the sample to be etched in situ in an electrolyte, and then taking it out, washing and drying it in sequence to obtain a sample to be tested; the electrolyte comprises: Lithium chloride 1%~1.5%; Alcohol solution 78%~84%; Acetylacetone 15%~20%; b) Testing the sample obtained in step a) to obtain the morphological characteristics, size information and in-situ distribution evolution law of the inclusions.

2. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The smelting chemical composition of the sample to be etched in step a) is composed of the following elements, in terms of mass percentage: C 0.85%~1.00%, Si 0.60%~0.70%, Mn 0.70%~0.90%, P≤0.015%, S≤0.010%, Cr 0.20%~0.40%, V 0.05%~0.08%, and the rest is Fe and other inevitable impurities.

3. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The sample to be corroded in step a) is a regular sample with a volume of (4-6) mm×(15-25) mm×(35-45) mm, and the surface to be observed is (15-25) mm×(35-45) mm; before use, the surface to be observed of the sample to be corroded is polished with 150-200 mesh, 250-300 mesh, 350-450 mesh, 750-850 mesh and 1100-1300 mesh sandpaper in sequence, further polished with polishing paste, rinsed with alcohol, blown dry, and set aside.

4. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The alcohol solution in step a) is a methanol solution and / or an ethanol solution.

5. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The pH of the electrolyte in step a) is 8-9.

6. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The electrochemical in-situ etching equipment in step a) comprises a constant temperature electrolytic cell containing an electrolyte; a corrosion-resistant conductive steel sheet and a sample to be etched are placed in the electrolyte, wherein the corrosion-resistant conductive steel sheet is connected to the cathode of the power supply, and the sample to be etched is connected to the anode of the power supply through a platinum electrode.

7. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The electrolyte temperature of the electrochemical in-situ etching in step a) is -12°C to -8°C, and the current density is 0.05A / cm 2 ~0.07A / cm 2 , the leaching time is 560s~580s.

8. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The cleaning method in step a) is cleaning with anhydrous ethanol.

9. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The drying method in step a) is oven drying; the oven drying temperature is 40°C to 60°C and the time is 30s to 40s.

10. The electrochemical in-situ corrosion method for non-metallic inclusions in hypereutectoid rail steel according to claim 1, characterized in that: The detection method in step b) is EBSD metallographic inclusion detection.

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