A method for observing and analyzing inclusions in steel

Abstract

The present invention discloses a method for observing and analyzing inclusions in steel. This method proposes precise process conditions for separating non-metallic inclusions from steel, achieving a high extraction rate and preserving the observed three-dimensional morphology of inclusions. This facilitates better analysis of their characteristics and provides a basis for improving the technology for controlling inclusions in steel.

Description

Technical Field

[0001] The invention belongs to the technical field of inclusion analysis in steel, and particularly relates to a method for observing and analyzing inclusions in steel. Background Art

[0002] Cylinder steel pipes are primarily used in the manufacture of hydraulic transmission equipment for vehicles, construction machinery, lifting and transportation machinery, mining machinery, and other machinery, such as hydraulic and pneumatic steel cylinders, hydraulic struts, and oil pump barrels. With the rapid development of cylinder steel pipes, machining technology has also been continuously upgraded in terms of both process and efficiency. The optimization of cold-drawn cylinder machining methods from honing to cutting and rolling has placed higher demands on steel pipe quality, increasing the incidence of surface defects in cylinder barrels. These defects are primarily caused by non-metallic inclusions in the steel.

[0003] Inclusions in steel include Al₂O₃, a deoxidation product of the molten steel; larger aluminates and silicates; entanglements in continuous casting mold slag, tundish covering agent slag, ladle slag entanglements; and magnesia-alumina spinel inclusions formed when MgO enters the molten steel due to the dissolution and shedding of refractory materials and reacts with Al₂O₃. These inclusions are hard, resistant to deformation, and difficult to melt. Since the cutting and skiving process of cold-drawn cylinders involves point-to-point contact, the tool tip encounters inclusions and detaches them from the matrix, easily leading to point defects. Therefore, analyzing the morphology, composition, size, and quantity of various inclusions in steel can help identify their sources, assess their impact on surface quality, and elucidate the mechanisms by which inclusions cause surface defects. This helps advance inclusion control technology for cold-drawn cylinder steel and improve its surface quality.

[0004] Metallographic method, acid dissolution method and aqueous solution electrolysis method are three commonly used methods for detecting and extracting inclusions in steel.

[0005] Although the metallographic method is convenient, it can only observe the morphology of a certain cross section of the inclusion, making it difficult to determine the true size and three-dimensional morphology of the inclusion, and the judgment of the inclusion size and morphology is prone to "misjudgment". Although the acid dissolution method can quickly dissolve inclusions into the solution, it is easy to dissolve small inclusions in the steel, and it is also easy to dissolve chemically unstable inclusions, such as calcium-containing and magnesium-containing inclusions, resulting in the loss of some inclusion data in the steel. The aqueous solution electrolysis method uses an acidic aqueous solution as the electrolyte. This method can further accelerate the dissolution rate of the steel sample, but it has the following disadvantages: the acidic solution easily destroys the morphology of inclusions and it is difficult to extract small particle inclusions. It is only suitable for analyzing large inclusions larger than 50μm in steel, and it is difficult to accurately evaluate the large number of small and medium-sized inclusions in the steel. Summary of the Invention

[0006] In order to overcome the defects of the prior art, the present invention provides a method for observing and analyzing inclusions in steel. The method can obtain a full range of inclusions with a wide size range, which is convenient for observing and analyzing the true size and three-dimensional morphology of inclusions within different particle size ranges. The size and three-dimensional morphology of various types of non-metallic inclusions in steel, such as Al2O3, SiO2, Ti2O3, CaO, MgO, Al2O3-MgO, CaO-SiO2, Al2O3-SiO2, Al2O3-SiO2-MgO, Al2O3-SiO2-CaO and Al2O3-SiO2-CaO-MgO, CaS, MnS, TiN, AlN, Nb (C, N), can be clearly and completely characterized.

[0007] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0008] According to a first aspect of an embodiment of the present invention, the present invention provides a method for observing and analyzing inclusions in steel, comprising the following steps:

[0009] 1) Steel sample preparation: Cut the sample from the steel to be analyzed, polish the surface, and clean it with ultrasonic vibration to remove surface dirt;

[0010] 2) Pre-electrolysis: The steel sample is pre-electrolyzed with an electrolyte to obtain a pre-electrolyzed sample. The pre-electrolysis time is 20 to 60 minutes, the pre-electrolysis current is 0.03 to 0.18 A, and the pre-electrolysis time and the pre-electrolysis current satisfy the following relationship:

[0011] 2eN A ×0.01×10 -3 ·ρ Fe ·S / M Fe <I·t<2eN A ×0.05×10 -3 ·ρ Fe ·S / M Fe

[0012] Where, I is the pre-electrolysis current, A; t is the pre-electrolysis time, s; M Fe is the molar mass of iron, kg·mol -1 ; S is the electrolysis area, m 2 ρ Fe is the sample density, kg·m -3 , N A is Avogadro's constant 6.02×10 23 ;

[0013] 3) Electrolysis: Electrolyze the pre-electrolyzed sample using the electrolyte, collect the electrolyte containing anode mud, control the electrolyte temperature to be 0-5° C., the electrolysis time to be 1-15 h, the electrolysis current to be 0.03-0.18 A, and the electrolysis time and the electrolysis current to satisfy the following relationship:

[0014] 2eN A ×0.05×10 -3 ·ρ Fe ·S / M Fe <I·t<2eN A ×0.5×10 -3 ·ρ Fe ·S / M Fe

[0015] Where I is the electrolysis current, A; t is the electrolysis time, s; M Fe is the molar mass of iron, kg·mol -1 ; S is the electrolysis area, m 2 ρ Fe is the density of the steel sample, kg·m -3 , N A is Avogadro's constant 6.02×10 23 ;

[0016] 4) The electrolytic solution is sequentially subjected to ultrasonic vibration cleaning, magnetic separation, membrane filtration, vacuum drying, and gold spraying. The filter membrane containing inclusions is observed under an electron microscope to analyze the three-dimensional morphology, composition, and quantity of the inclusions in the steel sample.

[0017] In some preferred embodiments, in step 1), the steel sample is a square electrolytic sample with a length of 20 to 50 mm, a width of 5 to 20 mm, and a thickness of 1 to 5 mm; or, the steel sample is a round electrolytic sample with a diameter of 10 to 50 mm and a thickness of 1 to 50 mm.

[0018] In some preferred embodiments, the electrolyte is a mixture of (80-98)% anhydrous methanol, (1-10)% triethanolamine, and (1-10)% tetramethylammonium chloride by weight, and is placed in a refrigerator at 0-4°C for storage. The present invention has found that when the weight ratio of anhydrous methanol is less than 80%, or the weight ratio of triethanolamine is less than 1%, or the weight ratio of tetramethylammonium chloride is less than 1%, the weight ratio of one of the three active ingredients in the electrolyte is too low, resulting in an electrolytic corrosion rate that is too slow, making it difficult to perform effective electrolytic corrosion. When the weight ratio of anhydrous methanol is greater than 98%, or the weight ratio of triethanolamine is greater than 10%, or the weight ratio of tetramethylammonium chloride is greater than 1%, the weight ratio of one of the three active ingredients in the electrolyte is too high. Since the sum of the weight ratios of the three is 100%, the weight ratios of the other two active ingredients are too low, which also results in an electrolytic corrosion rate that is too slow, making it difficult to perform effective electrolytic corrosion.

[0019] In some preferred embodiments, in steps 2) and 3), the steel sample is fixed at the anode in the electrolysis device and connected to the positive electrode on the power supply through a wire, and the metal Pt sheet is fixed at the cathode in the electrolysis device and connected to the negative electrode on the power supply through a wire.

[0020] In some preferred embodiments, the method further comprises: before the electrolysis step, ultrasonically cleaning the pre-electrolyzed sample with ethanol.

[0021] In some preferred embodiments, argon gas is introduced into the electrolyte in steps 2) and 3). During the electrolysis process, unelectrolyzed inclusions or magnetic compounds on the surface of the steel sample tend to adhere to the steel sample. The introduction of argon gas allows these small particles to be promptly dispersed into the electrolyte, thereby improving electrolysis efficiency, preventing inclusions from adhering to each other, and facilitating the production of dispersed, independent inclusions. In some specific embodiments, argon gas is introduced into the steel sample at a rate of 0.2 L / min throughout the pre-electrolysis and electrolysis processes.

[0022] In some preferred embodiments, the pore size of the filter membrane is 0.05 to 1.0 μm. Since the size range of the inclusions to be observed is 1 to 500 μm, a filter membrane with a size smaller than 1.0 μm can just intercept all inclusions larger than 1 μm. However, if the pore size of the filter membrane is smaller than 0.05 μm, filtration becomes difficult, and the separation of the electrolyte and inclusion particles becomes more difficult.

[0023] In some preferred embodiments, the vacuum drying temperature is 60-100° C., and the time is 2-4 hours.

[0024] In some preferred embodiments, the gold spraying time is 30 to 90 seconds.

[0025] The technical ideas of the present invention are as follows:

[0026] The present invention conducts a pre-electrolysis for a certain period of time before the steel sample is electrolyzed, the purpose of which is to dissolve and remove incomplete inclusions caused by wire cutting. Through extensive research, it has been found that the product of the pre-electrolysis time and the pre-electrolysis current I·t needs to be controlled within a reasonable range. The I·t value is less than 2eN A ×0.01×10 -3 ·ρ Fe ·S / M Fe The electrolytic thickness of the steel sample is too low, making it difficult to electro-dissolve and remove the remaining incomplete inclusions; the I·t value is greater than 2eN A ×0.05×10 -3 ·ρ Fe ·S / M Fe, causing intact slag coils or inclusions in the steel sample to fall off, resulting in failure to observe the slag coils and inclusions. When the I·t value of the pre-electrolysis is within a specific range, incomplete inclusions can be effectively removed while ensuring that intact slag coils or inclusions in the steel sample do not fall off. This facilitates the subsequent electrolysis process, retaining only intact inclusions in the steel sample for observation and analysis, improving the accuracy of statistical characteristics such as the three-dimensional morphology and size of the inclusions.

[0027] In addition, the product of electrolysis time and current I·t needs to be controlled within a reasonable range. A ×0.05×10 -3 ·ρ Fe ·S / M Fe When the electrolytic thickness of the steel sample is too thin, only some very small inclusions in the steel can be observed, and it is difficult to dissolve and remove the larger inclusions in the steel, resulting in the inability to accurately observe and analyze the three-dimensional morphology, size and quantity of the inclusions. A ×0.5×10 -3 ·ρ Fe ·S / M Fe When the I·t value of the electrolysis is within a specific range, the complete inclusions with a size of 1 to 500 μm can be effectively separated, improving the accuracy of the statistics of the three-dimensional morphology and size of the inclusions.

[0028] The embodiments of the present invention have the following advantages:

[0029] The present invention provides an effective inclusion extraction and analysis method for extracting inclusions of varying types and sizes from steel and characterizing their size, composition, three-dimensional morphology, and quantity. Compared to electrolytic extraction methods using water electrolyte, the present invention allows all types and sizes of inclusions in steel to enter the electrolyte without being completely dissolved, providing a reliable inclusion extraction method for statistical analysis of all types and sizes of inclusions.

[0030] The present invention uses a specific non-aqueous electrolyte for electrolysis. The pre-electrolysis and electrolysis currents and times are set according to the sample size and the size range of the inclusions being analyzed. This allows for the intact extraction of inclusions within the desired size range from the steel. The extracted inclusions are comprehensive, encompassing a wide range of sizes, and exhibit a low dissolution rate. The extracted inclusions are then sprayed with gold for microscopic observation and energy spectrum analysis. Due to the complete inclusion extraction method, the three-dimensional morphology, composition, size, and quantity of inclusions of various types and sizes can be clearly observed and analyzed, revealing the formation mechanisms of various inclusion types, providing a basis for improving surface defects in steel pipes and supporting the optimization of steelmaking processes.

[0031] The present invention adopts magnetic separation to separate the electrolyte after the steel sample is electrolyzed, thereby improving the separation rate of magnetic compound particles dispersed in the electrolyte and inclusions, and effectively improving the observation and analysis efficiency of inclusions.

[0032] The method of the present invention is simple and easy to implement, has low cost, short processing cycle and is suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other implementation drawings based on the provided drawings without inventive effort.

[0034] Figure 1 Schematic diagram of a non-aqueous electrolysis device.

[0035] Figure 2 The three-dimensional morphology and composition scan of the non-metallic inclusions observed in Example 1.

[0036] Figure 3 The three-dimensional morphology and composition scan of the non-metallic inclusions observed in Example 2.

[0037] Figures 4 to 6 The three-dimensional morphology and composition scan of the non-metallic inclusions observed in Example 3.

[0038] Figure 7 The three-dimensional morphology and composition surface scan of the non-metallic inclusions observed in the comparative example. DETAILED DESCRIPTION

[0039] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0040] Example 1

[0041] This embodiment provides a method for observing and analyzing inclusions in a 27SiMn steel ingot for a silicon-deoxidized cold-drawn cylinder. The composition of the steel sample is shown in Table 1. The method comprises the following steps:

[0042] (1) The steel samples were processed into thin steel samples with a size of 28 mm × 10 mm × 2 mm, and the surfaces of the samples were polished with 60#, 200#, and 800# sandpaper in sequence to make the surface smooth. Then, ultrasonic vibration cleaning was performed in an ethanol solution to remove oil stains on the surface of the steel samples.

[0043] (2) Evenly mix 82% anhydrous methanol, 2% triethanolamine and 16% tetramethylammonium chloride in a weight ratio to prepare an electrolyte. Figure 1 As shown, the thin steel sample to be electrolyzed served as the anode, and the thin Pt sheet served as the cathode. Insulated copper wires connected the thin steel sample to the anode of the power supply, and the thin Pt sheet to the cathode. The pre-electrolysis current was controlled at 0.05 A, and the duration was 1.2 h. The electrolyte composition and pre-electrolysis conditions are shown in Table 2. Argon was introduced at a flow rate of 0.2 L / min during the pre-electrolysis process. After the pre-electrolysis, the steel sample was placed in a small beaker containing an appropriate amount of ethanol and ultrasonically cleaned twice for 3 minutes each time. After cleaning, it was dried with a hair dryer. The steel sample was weighed and found to have a mass of m1 = 4322.74 mg.

[0044] (3) The pre-electrolyzed steel sample is pressed Figure 1 The sample was placed in an electrolysis apparatus, an appropriate amount of electrolyte was added, and the electrolysis current was controlled at 0.05 A for 15 hours. The electrolyte composition and electrolysis conditions are shown in Table 2. Argon gas was introduced at a flow rate of 0.2 L / min during the electrolysis process. After the electrolysis, the steel sample surface was cleaned with ethanol, and the cleaning solution was poured into the electrolyte containing anode mud. The electrolyte was then oscillated in an ultrasonic cleaner twice, each for 3 minutes. The cleaned steel sample surface was then air-dried. The mass of the sample after electrolysis was weighed and found to be m² = 3997.56 mg. The calculated mass of the electrolyzed steel sample, m = 325.18 mg.

[0045] (4) The electrolyte is subjected to two magnetic separations to separate the dispersed magnetic compounds and inclusions in the electrolyte as much as possible. The electrolyte obtained after the magnetic separation is vacuum filtered with a filter membrane with a pore size of 0.45 μm, and inclusions with a particle size greater than 0.45 μm are retained on the filter membrane. The filter membrane with retained inclusions obtained above is dried in a vacuum drying oven at 100°C for about 2 hours, and then the dried filter membrane is sprayed with gold for 60 seconds. Finally, the three-dimensional morphology, size and composition of different types of inclusions are analyzed using a scanning electron microscope equipped with an energy dispersive spectrometer. Figure 2 The three-dimensional morphology of different types of inclusions observed and the corresponding composition surface scanning results are shown. S1 is Al2O3-SiO2, S2 is Al2O3-SiO2-CaO, and S3 is CaS. The inclusion size is about 20μm.

[0046] Example 2

[0047] This embodiment provides a method for observing and analyzing inclusions in the surface layer of a 25Mn steel ingot of a certain aluminum deoxidation cold-drawn cylinder. The composition of the steel sample is shown in Table 1. The method comprises the following steps:

[0048] (1) The steel samples were processed into thin steel samples with a size of 25 mm × 10 mm × 2 mm, and the surfaces of the samples were polished with 60#, 200#, and 800# sandpaper in sequence to make the surface smooth. Then, ultrasonic vibration cleaning was performed in an ethanol solution to remove oil stains on the surface of the steel samples.

[0049] (2) Mix 96% anhydrous methanol, 2% triethanolamine and 2% tetramethylammonium chloride in a weight ratio to prepare an electrolyte. Figure 1 As shown, the thin steel sample to be electrolyzed served as the anode, and the thin Pt sheet served as the cathode. The sample was connected to the anode of the power supply, and the Pt sheet to the cathode, using insulated copper wires. The pre-electrolysis current was controlled at 0.07 A, and the duration was 1.2 h. The pre-electrolysis solution composition and pre-electrolysis conditions are shown in Table 2. Argon was introduced at a flow rate of 0.2 L / min during the pre-electrolysis process. After the pre-electrolysis, the steel sample was placed in a small beaker containing an appropriate amount of ethanol and ultrasonically cleaned twice for 3 minutes each time. After cleaning, it was dried with a hair dryer. The steel sample was weighed to a mass of m1 = 3604.94 mg.

[0050] (3) The pre-electrolyzed steel sample is pressed Figure 1 The sample was placed in an electrolysis apparatus, an appropriate amount of electrolyte was added, and the electrolysis current was controlled at 0.07 A for 8 hours. The electrolyte composition and electrolysis conditions are shown in Table 2. Argon gas was introduced at a flow rate of 0.2 L / min during the electrolysis process. After the electrolysis, the steel sample surface was cleaned with ethanol, and the cleaning solution was poured into the electrolyte containing anode mud. The electrolyte was then oscillated in an ultrasonic cleaner twice, each for 3 minutes. The cleaned steel sample surface was then air-dried. The mass of the sample after electrolysis was weighed and found to be m² = 3277.25 mg. The calculated mass of the electrolyzed steel sample, m = 327.69 mg.

[0051] (4) The electrolyte is subjected to two magnetic separations to separate the dispersed magnetic compounds and inclusions in the electrolyte as much as possible. The electrolyte obtained after the magnetic separation is vacuum filtered with a filter membrane with a pore size of 0.45 μm, and inclusions with a particle size greater than 0.45 μm are retained on the filter membrane. The filter membrane with retained inclusions obtained above is dried in a vacuum drying oven at 100°C for about 2 hours, and then the dried filter membrane is sprayed with gold for 60 seconds. Finally, the three-dimensional morphology, composition and size of different types of inclusions are analyzed by a scanning electron microscope equipped with an energy dispersive spectrometer. Figure 3 The three-dimensional morphology of the different types of inclusions observed and the corresponding composition surface scan results are shown. S4 is CaO-CaS, S5 is SiO2, S6 is Al2O3, and S7 is Al2O3-SiO2-MgO-CaO, with sizes ranging from 10-30μm.

[0052] Example 3

[0053] This embodiment provides a method for observing and analyzing inclusions in a 25Mn steel ingot for an aluminum deoxidation cold drawing cylinder. A sample is taken from the center of the 25Mn steel ingot for aluminum deoxidation cold drawing cylinder and analyzed. The composition of the steel sample is shown in Table 1. The method comprises the following steps:

[0054] (1) The steel samples were processed into thin steel samples with a size of 25 mm × 10 mm × 2 mm, and the surfaces of the samples were polished with 60#, 200#, and 800# sandpaper in sequence to make the surface smooth. Then, ultrasonic vibration cleaning was performed in an ethanol solution to remove oil stains on the surface of the steel samples.

[0055] (2) Mix 87% anhydrous methanol, 9% triethanolamine and 4% tetramethylammonium chloride in a weight ratio to prepare an electrolyte. Figure 1 As shown, the thin steel sample to be electrolyzed served as the anode, and the thin Pt sheet served as the cathode. Insulated copper wires connected the thin steel sample to the anode of the power supply, and the thin Pt sheet to the cathode. The pre-electrolysis current was controlled at 0.14 A, and the duration was 0.5 h. The electrolyte composition and pre-electrolysis conditions are shown in Table 2. Argon was introduced at a flow rate of 0.2 L / min during the pre-electrolysis process. After the pre-electrolysis, the steel sample was placed in a small beaker containing an appropriate amount of ethanol and ultrasonically cleaned twice for 3 minutes each time. After cleaning, it was dried with a hair dryer. The steel sample mass was weighed to m1 = 3593.94 mg.

[0056] (3) The pre-electrolyzed steel sample is pressed Figure 1 The sample was placed in an electrolysis apparatus, an appropriate amount of electrolyte was added, and the electrolysis current was controlled at 0.14 A for 6 hours. The electrolyte composition and electrolysis conditions are shown in Table 2. Argon gas was introduced at a flow rate of 0.2 L / min during the electrolysis process. After the electrolysis, the steel sample surface was cleaned with ethanol, and the cleaning solution was poured into the electrolyte containing anode mud. The electrolyte was then oscillated in an ultrasonic cleaner twice, each for 3 minutes. The cleaned steel sample surface was then air-dried. The mass of the sample after electrolysis was weighed and found to be m² = 3267.25 mg. The calculated mass of the electrolyzed steel sample, m = 326.69 mg.

[0057] (4) The electrolyte is subjected to two magnetic separations to separate the dispersed magnetic compounds and inclusions in the electrolyte as much as possible. The electrolyte obtained after the magnetic separation is vacuum filtered with a filter membrane with a pore size of 0.45 μm, and inclusions with a particle size greater than 0.45 μm are retained on the filter membrane. The filter membrane with retained inclusions obtained above is dried in a vacuum drying oven at 100°C for about 2 hours, and then the dried filter membrane is sprayed with gold for 60 seconds. Finally, the three-dimensional morphology and composition of different types of inclusions are analyzed by a scanning electron microscope equipped with an energy dispersive spectrometer. Figures 4 to 6The three-dimensional morphology of different types of inclusions observed and the corresponding surface scan components. Figure 4 CaO-SiO2, Figure 5 is CaO, Figure 6 It is Al2O3-SiO2-MgO-CaO, and the size of inclusions is 10-100μm.

[0058] Comparative Example

[0059] In this comparative example, the electrolytic steel sample was selected from the surface layer sample of 25Mn steel ingot, and the specific treatment process was basically the same as that of Example 3. The composition of the steel sample is shown in Table 1. The difference is:

[0060] The current was controlled to 0.25A and the electrolysis time was 12h, replacing the 0.14A in Example 3. The other reaction conditions were the same as those in Example 3. The mass of the steel sample after cleaning and pre-electrolysis was m1 = 3593.74mg; Figure 1 The steel sample was placed in an electrolysis device for electrolysis. After the electrolysis was completed, the surface of the cleaned steel sample was blown dry, and the mass of the steel sample after electrolysis was weighed to be m2 = 3067.25 mg.

[0061] The mass of the electrolytic steel sample was calculated to be m = 526.49 mg. The electrolyte was subjected to two magnetic separations to separate the dispersed magnetic compounds and inclusions in the electrolyte as much as possible. The electrolyte obtained after the magnetic separation was vacuum filtered using a filter membrane with a pore size of 0.45 μm, and inclusions with a particle size > 0.45 μm were retained on the filter membrane. The filter membrane with retained inclusions obtained above was dried in a vacuum drying oven at 100 ° C for about 2 hours, and then the dried filter membrane was sprayed with gold for 60 seconds. Finally, the three-dimensional morphology and composition of different types of inclusions were analyzed by a scanning electron microscope equipped with an energy dispersive spectrometer. Figure 7 The three-dimensional morphology and corresponding surface scan compositions of the different types of inclusions observed are shown below. S8 is Al2O3-SiO2-CaO, S9 is CaO-SiO2Al2O3, and S10 is Al2O3-SiO2. The inclusion size is 5-10μm.

[0062] Compared with the results of Example 3, the I·t value of the steel sample in the comparative example is not within the reasonable range, as shown in Table 3. When the charge is too high, the electrolytic corrosion of the steel sample increases, and the three-dimensional morphology of the observed inclusions becomes blurred. This is because the high current causes the non-metallic inclusions in the steel to dissolve, and the size of the detected inclusions becomes smaller.

[0063] Based on the above examples and comparative examples, see the following table:

[0064] Table 1

[0065]

[0066] Table 2

[0067]

[0068] Table 3

[0069]

[0070] Table 4

[0071]

[0072]

[0073] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for observing and analyzing inclusions in steel, characterized in that: The steps include: 1) Steel sample preparation: Cut the sample from the steel to be analyzed, polish the surface, and clean it with ultrasonic vibration to remove surface dirt; 2) Pre-electrolysis: The steel sample is pre-electrolyzed with an electrolyte to obtain a pre-electrolyzed sample. The pre-electrolysis time is 20 to 60 minutes, the pre-electrolysis current is 0.03 to 0.18 A, and the pre-electrolysis time and the pre-electrolysis current satisfy the following relationship: 2eN A ×0.01×10 -3 ·ρ Fe ·S / M Fe <I·t<2eN A ×0.05×10 -3 ·ρ Fe ·S / M Fe Where, I is the pre-electrolysis current, A; t is the pre-electrolysis time, s; M Fe is the molar mass of iron, kg·mol -1 ; S is the electrolysis area, m 2 ρ Fe is the sample density, kg·m -3 , N A is Avogadro's constant 6.02×10 23 ; 3) Electrolysis: Electrolyze the pre-electrolyzed sample using the electrolyte, collect the electrolyte containing anode mud, control the electrolyte temperature to be 0-5° C., the electrolysis time to be 1-15 h, the electrolysis current to be 0.03-0.18 A, and the electrolysis time and the electrolysis current to satisfy the following relationship: 2eN A ×0.05×10 -3 ·ρ Fe ·S / M Fe <I·t<2eN A ×0.5×10 -3 ·ρ Fe ·S / M Fe Where, I is the electrolysis current, A; t is the electrolysis time, s; M Fe is the molar mass of iron, kg·mol -1 ; S is the electrolysis area, m 2 ρ Fe is the sample density, kg·m -3 , N A is Avogadro's constant 6.02×10 23 ; 4) The electrolytic solution is sequentially subjected to ultrasonic vibration cleaning, magnetic separation, membrane filtration, vacuum drying, and gold spraying. The filter membrane containing inclusions is observed under an electron microscope to analyze the three-dimensional morphology, composition, and quantity of the inclusions in the steel sample.

2. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: In step 1), the steel sample is a square electrolytic sample with a length of 20 to 50 mm, a width of 5 to 20 mm, and a thickness of 1 to 5 mm; or, the steel sample is a round electrolytic sample with a diameter of 10 to 50 mm and a thickness of 1 to 50 mm.

3. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: The electrolyte is prepared by mixing (80-98)% of anhydrous methanol, (1-10)% of triethanolamine and (1-10)% of tetramethylammonium chloride in weight percentage, and is refrigerated in a refrigerator at 0-4° C. for later use.

4. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: In steps 2) and 3), the steel sample is fixed on the anode of the electrolytic device and connected to the positive electrode of the power supply through a wire, and the metal Pt sheet is fixed on the cathode of the electrolytic device and connected to the negative electrode of the power supply through a wire.

5. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: The method further comprises: before the electrolysis step, using ethanol to perform ultrasonic cleaning on the pre-electrolyzed sample.

6. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: In steps 2) and 3), argon gas is introduced into the electrolyte.

7. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: The pore size of the filter membrane is 0.05-1.0 μm.

8. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: The vacuum drying temperature is 60-100° C., and the time is 2-4 hours.

9. The method for observing and analyzing inclusions in steel according to claim 1, characterized in that: The time of the gold spraying is 30 to 90 seconds.

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