Metallographic Sample Preparation Method for High Silicon Steel

Abstract

The present application discloses a metallographic sample preparation method for high-silicon steel, comprising the steps of sampling, mounting, water grinding, rough polishing, fine polishing, and surface treatment. In the fine polishing step, the polishing liquid adopts an oil-based diamond suspension + a lubricant, and the sample surface does not contact water during the entire fine polishing process. The diamond particle size in the oil-based diamond suspension is 1-5 μm, the concentration is 2-5 g / L, the pH is 6.5-7.5, the pressure P3 of the polishing disk is 20-29 N, the rotation speed W3 of the polishing disk is 350-450 rpm, the rotation speed R3 of the grinding and polishing head holding the sample is 200-300 rpm, the polishing time t3 is 1-3 min, and satisfies: 21≤P3+[(W3+R3)×0.01+t3]×[C]≤35. In the surface treatment step, the sample surface does not contact water throughout the entire process.

Description

Technical Field

[0001] The present application belongs to the technical field of steel material test sample preparation, and specifically relates to a method for preparing a metallographic sample of high-silicon steel. Background Art

[0002] Inclusions are crucial indicators in the performance analysis of steel materials. The presence of inclusions can significantly affect the properties of steel, such as reducing its toughness, fatigue strength, and corrosion resistance. Therefore, accurately counting and analyzing the number, size, composition, and distribution of inclusions is crucial for evaluating and optimizing the performance of steel materials.

[0003] Especially for high-silicon steel samples such as spring steel and silicon steel, inclusions are a crucial performance indicator and play a key role in the final performance of the product. For example, inclusions in spring steel have a significant impact on fatigue performance, while inclusions in silicon steel affect magnetic properties. Inclusion analysis has become an important means to improve the performance of high-silicon steel samples.

[0004] High-silicon steel samples are typically graded or counted for inclusions using a metallographic microscope or scanning electron microscope (SEM). However, during metallographic sample preparation, it was discovered that high-silicon steel samples are highly susceptible to oxidation. The contrast of the oxidized area is close to the inclusion identification range, making it difficult to distinguish between oxidation products and inclusions when counting inclusions under metallographic microscope observation, thus affecting the efficiency and accuracy of inclusion counting.

[0005] Currently, the commonly used preparation methods for high-silicon steel samples are electrolytic polishing and extraction replication. Although these methods can solve the oxidation problem of high-silicon steel samples to a certain extent, they have problems such as complex procedures, unstable effects, and poor versatility, and cannot be widely promoted and applied. Summary of the Invention

[0006] The purpose of this application is to provide a method for preparing metallographic samples of high-silicon steel.

[0007] To achieve one of the above-mentioned application objectives, an embodiment of the present application provides a method for preparing a metallographic sample of high-silicon steel, comprising the steps of sampling, mounting, water grinding, rough polishing, fine polishing, and surface treatment performed in sequence;

[0008] In the water grinding step, 2 to 3 passes of water grinding are performed, the pressure P1 of the grinding disc is 40 to 50 N, the rotation speed W1 of the grinding disc is 250 to 350 rpm, the rotation speed R1 of the grinding head holding the sample is 100 to 200 rpm, the water grinding time t1 of each pass is 2 to 10 minutes, and the following conditions are satisfied: 41≤P1+[(W1+R1)×0.01+t1]×[C]≤60;

[0009] In the rough polishing step, the pressure P2 of the polishing disk is 30-39 N, the rotation speed W2 of the polishing disk is 250-350 rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 100-200 rpm, the polishing time t2 is 2-8 min, and the following conditions are satisfied: 31≤P2+[(W2+R2)×0.01+t2]×[C]≤50;

[0010] In the fine polishing step, the polishing liquid adopts an oil-based diamond suspension + lubricant, the sample surface does not contact water during the entire fine polishing process, the diamond particle size in the oil-based diamond suspension is 1-5 μm, the concentration is 2-5 g / L, the pH is 6.5-7.5, the pressure P3 of the polishing disk is 20-29 N, the rotation speed W3 of the polishing disk is 350-450 rpm, the rotation speed R3 of the grinding and polishing head holding the sample is 200-300 rpm, the polishing time t3 is 1-3 min, and satisfies: 21≤P3+[(W3+R3)×0.01+t3]×[C]≤35;

[0011] During the surface treatment step, the sample surface does not contact water at all;

[0012] Wherein, [C] is the percentage of C content in the sample.

[0013] As a further improvement of one embodiment of the present application, in the surface treatment step, a paper towel is used to wipe the surface of the finely polished sample clean in one direction, and then placed in a drying oven for drying. The surface smoothness of the paper towel is 150~200s.

[0014] As a further improvement of one embodiment of the present application, in the fine polishing step, the lubricant is DP-Lubricant Blue lubricant manufactured by Struers, Denmark.

[0015] As a further improvement of one embodiment of the present application, in the fine polishing step, 1 to 1.5 mL of lubricant is added to the polishing disc before fine polishing. During the fine polishing process, the polishing liquid is added by adding 0.2 to 0.4 mL of oil-based diamond suspension and 0.2 to 0.4 mL of lubricant to the polishing disc every 15 seconds.

[0016] As a further improvement of an embodiment of the present application, in the fine polishing step, the polishing disk uses a metal-based synthetic fiber disk with a particle size of 3 μm, and the water content of the metal-based synthetic fiber polishing disk is ≤0.1%.

[0017] As a further improvement of one embodiment of the present application, in the rough polishing step, the polishing liquid adopts diamond suspension + water, the diamond particle size in the diamond suspension is 7~11μm, the concentration is 1~3g / L, and the pH is 8.0~9.0.

[0018] As a further improvement of an embodiment of the present application, in the rough polishing step, the polishing disk uses a metal-based synthetic fiber disk with a particle size of 9 μm.

[0019] As a further improvement of an embodiment of the present application, in the rough polishing step, after the rough polishing is completed, the sample surface is rinsed with water and blown dry with cold air.

[0020] As a further improvement of one embodiment of the present application, in the water grinding step, the grinding wheel adopts a metal-based diamond grinding wheel with a particle size number of 200#~1000#.

[0021] As a further improvement of an embodiment of the present application, the chemical composition of the high-silicon steel is, by mass percentage, C<1%, 1%≤Si≤3.5%.

[0022] Compared with the prior art, the beneficial effects of the present application are as follows: the metallographic sample preparation method of high silicon steel of the present application controls the sample surface not to contact water during the water grinding, rough polishing and fine polishing steps, and at the same time limits the polishing liquid in the fine polishing step to use an oil-based diamond suspension to ensure that the sample surface does not contact water during the fine polishing step, thereby preventing the surface oxidation of the prepared sample. Further limiting the various parameters of the oil-based diamond suspension can ensure that the sample surface is flat, smooth and not corroded, avoid the generation of deep scratches that affect the analysis of inclusions, improve the surface quality of the sample, and reduce surface scratches, improve polishing efficiency, sample preparation efficiency and the effective detection rate of inclusions; in addition, the lubricant can not only improve the polishing efficiency and cleanliness, but also avoid the introduction of water, further avoiding the oxidation of the sample surface; further combined with the water grinding, rough polishing and fine polishing steps, the key parameters in the metallographic sample preparation process such as the rotation speed, pressure, and polishing time of each component are limited and associated with the C content in the steel sample, so that the key parameters can be controlled according to the C content in the steel sample, which increases the scope of application, avoids the trouble of separate research and setting parameters for different steel samples, and improves the sample preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a metallographic photograph of a metallographic sample of high silicon steel of Example 1 of the present application;

[0024] Figure 2 This is a metallographic photograph of a metallographic sample of high silicon steel of Example 2 of the present application;

[0025] Figure 3 This is a metallographic photograph of a metallographic sample of high silicon steel of Example 3 of the present application;

[0026] Figure 4 This is a metallographic photograph of a metallographic sample of high silicon steel in the comparative example of this application. DETAILED DESCRIPTION

[0027] The technical solution of the present application is further introduced below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0028] The present application provides a metallographic sample preparation method for high-silicon steel to reduce surface oxidation of the sample and ensure the surface quality of the sample. The process is simple and efficient, with wide applicability, and can provide reliable guarantees for subsequent inclusion analysis.

[0029] Among them, the so-called high-silicon steel refers to steel in which the mass percentage of Si in its chemical composition is 1%~3.5%.

[0030] The preparation method comprises the steps of sampling, sample mounting, water grinding, rough polishing, fine polishing and surface treatment which are carried out in sequence.

[0031] In the water grinding step, 2 to 3 passes of water grinding are performed, the pressure P1 of the grinding disc is 40 to 50 N, the rotation speed W1 of the grinding disc is 250 to 350 rpm, the rotation speed R1 of the grinding and polishing head holding the sample is 100 to 200 rpm, the water grinding time t1 of each pass is 2 to 10 min, and satisfies: 41≤P1+[(W1+R1)×0.01+t1]×[C]≤60.

[0032] In the rough polishing step, the pressure P2 of the polishing disk is 30~39N, the rotation speed W2 of the polishing disk is 250~350rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 100~200rpm, the polishing time t2 is 2~8min, and satisfies: 31≤P2+[(W2+R2)×0.01+t2]×[C]≤50.

[0033] In the fine polishing step, the polishing liquid adopts an oil-based diamond suspension + lubricant, the sample surface does not contact water during the entire fine polishing process, the diamond particle size in the oil-based diamond suspension is 1~5μm, the concentration is 2~5g / L, the pH is 6.5~7.5, the pressure P3 of the polishing disk is 20~29N, the rotation speed W3 of the polishing disk is 350~450rpm, the rotation speed R3 of the grinding and polishing head clamping the sample is 200~300rpm, the polishing time t3 is 1~3min, and satisfies: 21≤P3+[(W3+R3)×0.01+t3]×[C]≤35.

[0034] Where [C] is the percentage of carbon in the sample. For example, if the carbon content in a steel sample is 0.2%, then [C] is 0.2.

[0035] The three equations above only limit the values ​​of the pressure, speed, and time parameters and are not related to the units. The values ​​of each parameter are determined based on the aforementioned units. For example, if P1 is 40N, W1 is 300rpm, R1 is 100rpm, and t1 is 5min, then in the equation 41≤P1+[(W1+R1)×0.01+t1]×[C]≤60, P1 is 40, W1 is 300, R1 is 100, and t1 is 5.

[0036] The oil-based diamond suspension, composed of diamond micropowder uniformly dispersed in an oily liquid medium, exhibits high hardness, wear resistance, and chemical stability. In the oil-based diamond suspension, limiting the diamond particle size ensures a smooth sample surface, avoiding deep scratches that can affect inclusion analysis. Limiting the concentration ensures polishing efficiency, as the number of diamond particles per unit volume affects sample preparation efficiency. A controlled pH value ensures a smooth sample surface and prevents corrosion during polishing.

[0037] During the surface treatment step, the sample surface does not contact water at all.

[0038] Thus, the metallographic sample preparation method of high-silicon steel of the present application, during water grinding, rough polishing, and fine polishing, controls the sample surface from contacting water in the fine polishing step and the surface treatment step, and limits the polishing liquid in the fine polishing step to an oil-based diamond suspension to ensure that the sample surface does not contact water in the fine polishing step, thereby preventing oxidation of the prepared sample surface. Further limiting the various parameters of the oil-based diamond suspension can ensure that the sample surface is flat and smooth and not corroded, avoid the generation of deep scratches that affect inclusion analysis, improve the surface quality of the sample, reduce surface scratches, and improve polishing efficiency, sample preparation efficiency, and the effective detection rate of inclusions. In addition, the lubricant can not only improve the polishing efficiency and cleanliness, but also avoid the introduction of water, further avoiding sample surface oxidation. Further, in combination with the water grinding, rough polishing, and fine polishing steps, the key parameters in the metallographic sample preparation process, such as the rotation speed, pressure, and polishing time of each component, are limited and associated with the C content in the steel sample, so that the key parameters can be controlled according to the C content in the steel sample, thereby increasing the scope of application, avoiding the trouble of separately studying and setting parameters for different steel samples, and improving sample preparation efficiency.

[0039] After analysis and testing of inclusions in the samples using a scanning electron microscope, the effective detection rate of inclusions in the high-silicon steel metallographic samples prepared using the above method was ≥95%.

[0040] Preferably, in the surface treatment step, the surface of the sample after fine polishing is wiped clean along one direction with a paper towel, and then placed in a drying oven for drying, and the surface smoothness of the paper towel is 150~200s.

[0041] The surface smoothness of the paper towel is tested with reference to the standard GB / T456-2002 Test for Smoothness of Paper and Paper Materials, and the Buick method is used to test the surface smoothness of the paper towel.

[0042] Specifically, smoothness is quantified by measuring the time it takes for air to leak out when a semi-vacuum is formed between a paper towel and a standard glass plate; the longer the time, the smoother the surface.

[0043] By wiping the surface of the sample after fine polishing with a paper towel and limiting the surface smoothness of the paper towel, not only can the particles left on the sample surface during the fine polishing step be wiped clean to avoid surface scratches, but also the oxidation of the sample surface caused by liquid flushing can be avoided, thereby improving the surface quality of the sample and increasing the effective detection rate of inclusions.

[0044] Preferably, the paper towel is a wettable paper towel, which has high flexibility and will not break even when wet, thereby improving the cleanliness of the sample surface after wiping and avoiding surface scratches.

[0045] Preferably, during the fine polishing step, the lubricant is DP-Lubricant Blue lubricant manufactured by Struers, Denmark. This lubricant is water-free, which not only prevents the introduction of moisture into the lubricant during the fine polishing process but also provides better lubrication of the polishing disc, thereby allowing the sample to be polished to a smooth surface under the action of the suspension.

[0046] Preferably, in the fine polishing step, 1 to 1.5 mL of lubricant is added to the polishing disc before fine polishing, and during fine polishing, the polishing liquid is added by adding 0.2 to 0.4 mL of oil-based diamond suspension and 0.2 to 0.4 mL of lubricant to the polishing disc every 15 seconds. By adding the lubricant before fine polishing and adding the oil-based diamond suspension and lubricant at intervals during fine polishing, not only can the polishing disc be lubricated, reducing the friction between the polishing disc and the sample surface, but also the introduction of moisture during the fine polishing step can be avoided, thereby avoiding oxidation of the sample surface and improving the flatness and polishing efficiency of the sample surface.

[0047] Specifically, in the fine polishing step, a fully automatic grinding and polishing machine is used for fine polishing, and the oil-based diamond suspension and lubricant are automatically added by the fully automatic grinding and polishing machine, so that the addition amount can be accurately controlled.

[0048] Preferably, during the fine polishing step, the polishing disc is a metal-based synthetic fiber disc with a particle size of 3 μm and a water content of 0.1% or less. By controlling the water content of the polishing disc, water is prevented from entering the fine polishing process. The particle size of the polishing disc must match the particle size of the oil-based diamond suspension to achieve an excellent polishing effect.

[0049] Preferably, during the rough polishing step, the polishing liquid comprises a diamond suspension + water, wherein the diamond particle size in the diamond suspension is 7-11 μm, the concentration is 1-3 g / L, and the pH is 8.0-9.0. By limiting the parameters of the diamond suspension during the rough polishing step, it is possible to ensure that the sample achieves an ideal polished surface during the rough polishing step. Limiting the diamond particle size ensures consistent polishing marks on the sample surface and avoids deep scratches. Limiting the concentration ensures polishing efficiency, as the number of particles per unit volume affects sample preparation efficiency. Limiting the pH value ensures a smooth sample and prevents corrosion during the polishing process.

[0050] The diamond suspension is made by uniformly dispersing diamond powder in a liquid medium, and the liquid medium can be aqueous or oily.

[0051] Preferably, during the rough polishing step, a metal-based synthetic fiber polishing disc with a grit size of 9 μm is used. Compared to fine polishing, the grit size of the polishing disc during the rough polishing step is larger. Furthermore, the grit size of the polishing disc should match the particle size of the diamond suspension to achieve optimal polishing results.

[0052] In the rough polishing step, after the rough polishing is completed, the sample surface is rinsed with water and blown dry with cold air. The water rinse can effectively remove a large amount of large particle debris generated by the rough polishing, and does not affect the anti-oxidation treatment in the subsequent fine polishing and surface treatment steps, thereby improving efficiency and saving costs.

[0053] Specifically, a hair dryer may be used to blow out cold air to dry the surface of the sample after being rinsed with water.

[0054] Preferably, in the water grinding step, a metal-based diamond grinding wheel with a grit number of 200# to 1000# is used. The smaller the grit number, the coarser the abrasive particles of the grinding wheel. During water grinding, the abrasive particles of the grinding wheel are adjusted from coarse to fine, i.e., from small to large grit numbers.

[0055] Wherein, in the water grinding step, an automatic grinding and polishing machine is used for water grinding.

[0056] In the rough polishing step, a fully automatic grinding and polishing machine is used for rough polishing.

[0057] In the fine polishing step, a fully automatic grinding and polishing machine is used for fine polishing.

[0058] The mounting step refers to embedding the sample into a resin or plastic matrix to form a sample with a regular shape.

[0059] Preferably, in the mounting step, a sample with a diameter of 30 mm or 40 mm is formed.

[0060] Specifically, the mounting step can adopt a hot mounting method, in which thermoplastic plastic (such as bakelite powder, polyvinyl chloride) is molded by heating and pressurizing to wrap the sample; or a cold mounting method can be adopted, in which the sample is wrapped by curing resin at room temperature.

[0061] The above metallographic sample preparation method can be applied to high-silicon steel with a C content of <1%, and has a wide range of applications.

[0062] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of the present application. They are not intended to limit the scope of protection of the present application. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present application should be included in the scope of protection of the present application.

[0063] The beneficial effects of the present application are further illustrated below through specific examples and comparative examples. Of course, the examples are only a part of the many variations of the present application, not all of them.

[0064] Example 1

[0065] This embodiment uses the above-mentioned metallographic sample preparation method of high-silicon steel, which specifically includes the following steps:

[0066] (1) Sampling

[0067] Non-oriented silicon steel with a grade of 25WV1300 and a thickness of 0.25 mm was selected, wherein the C content was 0.002% and the Si content was 3.3%.

[0068] Since the thickness of non-oriented silicon steel is relatively thin, the specifications of the samples are: length 15mm and width 10mm.

[0069] (2) Mounting

[0070] The hot mounting method was used to form samples with a diameter of 30 mm.

[0071] (3) Water mill

[0072] The automatic grinding and polishing machine performs two passes of water grinding. The grinding discs for the two passes of water grinding are metal-based diamond grinding discs with grit numbers of 220# and 600# respectively. The pressure P1 of the grinding disc is 45N, the rotation speed W1 of the grinding disc is 300rpm, the rotation speed R1 of the grinding and polishing head holding the sample is 150rpm, the water grinding time t1 of each pass is 4min, and P1+[(W1+R1)×0.01+t1]×[C]=45.

[0073] (4) Rough polishing

[0074] A fully automatic grinding and polishing machine was used for rough polishing. After rough polishing, the sample surface was rinsed with water and dried with cold air.

[0075] The polishing disc is a metal-based synthetic fiber disc with a particle size of 9 μm, and the polishing liquid is a diamond suspension + water. The diamond particle size in the diamond suspension is 9 μm, the concentration is 2 g / L, and the pH is 8.5.

[0076] The pressure P2 of the polishing disk is 35N, the rotation speed W2 of the polishing disk is 300rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 150rpm, the polishing time t2 is 5min, and P2+[(W2+R2)×0.01+t2]×[C]=35.

[0077] (5) Fine polishing

[0078] Fine polishing was performed using a fully automatic grinder-polisher. The polishing discs used were metal-based synthetic fiber discs with a 3μm particle size and a water content of ≤0.1%. The polishing fluid consisted of an oil-based diamond suspension combined with a lubricant. The diamond particles in the oil-based diamond suspension were 3μm in size, at a concentration of 3g / L and a pH of 7.0. Both the oil-based diamond suspension and lubricant were added automatically by the fully automatic grinder-polisher. The sample surface remained free of water during the entire fine polishing process. The lubricant used was DP-Lubricant Blue, manufactured by Struers, Denmark.

[0079] Before fine polishing, 1.2 mL of lubricant was added to the polishing disc. During fine polishing, 0.3 mL of oil-based diamond suspension and 0.3 mL of lubricant were added to the polishing disc every 15 s.

[0080] Among them, the pressure P3 of the polishing disk is 25N, the rotation speed W3 of the polishing disk is 360rpm, the rotation speed R3 of the grinding and polishing head clamping the sample is 220rpm, the polishing time t3 is 2min, and P3+[(W3+R3)×0.01+t3]×[C]=25.

[0081] (6) Surface treatment

[0082] The sample surface does not come into contact with water during the entire process.

[0083] Specifically, a wet paper towel with a surface smoothness of 150s was used to wipe the surface of the finely polished sample clean along a fixed direction, and then placed in a drying oven for drying.

[0084] The surface of the metallographic sample obtained by the above preparation method is clean, free of oxidation and artificial pollution, and the metallographic photos are as follows: Figure 1 shown.

[0085] After analyzing and testing the inclusions in the samples using a scanning electron microscope, it was found that the effective detection rate of inclusions was 95%.

[0086] Example 2

[0087] This embodiment uses the above-mentioned method for preparing metallographic samples of high-silicon steel, which specifically includes the following steps:

[0088] (1) Sampling

[0089] We selected 55SiCr spring steel wire rod with a C content of 0.55% and a Si content of 1.4%. The diameter of the spring steel wire rod was 19 mm, and a sample of 10 mm in length was taken from the center of the longitudinal section of the wire rod.

[0090] (2) Mounting

[0091] The hot mounting method was used to form samples with a diameter of 30 mm.

[0092] (3) Water mill

[0093] The automatic grinding and polishing machine performs two passes of water grinding. The grinding discs for the two passes of water grinding are metal-based diamond grinding discs with grit numbers of 220# and 600# respectively. The pressure P1 of the grinding disc is 48N, the rotation speed W1 of the grinding disc is 300rpm, the rotation speed R1 of the grinding and polishing head holding the sample is 160rpm, the water grinding time t1 of each pass is 5min, and P1+[(W1+R1)×0.01+t1]×[C]=53.

[0094] (4) Rough polishing

[0095] A fully automatic grinding and polishing machine was used for rough polishing. After rough polishing, the sample surface was rinsed with water and dried with cold air.

[0096] The polishing disc is a metal-based synthetic fiber disc with a particle size of 9 μm, and the polishing liquid is a diamond suspension + water. The diamond particle size in the diamond suspension is 9 μm, the concentration is 2 g / L, and the pH is 8.5.

[0097] The pressure P2 of the polishing disk is 36N, the rotation speed W2 of the polishing disk is 320rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 160rpm, the polishing time t2 is 5min, and P2+[(W2+R2)×0.01+t2]×[C]=41.

[0098] (5) Fine polishing

[0099] Fine polishing was performed using a fully automatic grinder-polisher. The polishing discs used were metal-based synthetic fiber discs with a 3μm particle size and a water content of ≤0.1%. The polishing fluid consisted of an oil-based diamond suspension combined with a lubricant. The diamond particles in the oil-based diamond suspension were 3μm in size, at a concentration of 3g / L and a pH of 7.0. Both the oil-based diamond suspension and lubricant were added automatically by the fully automatic grinder-polisher. The sample surface remained free of water during the entire fine polishing process. The lubricant used was DP-Lubricant Blue, manufactured by Struers, Denmark.

[0100] Before fine polishing, 1.2 mL of lubricant was added to the polishing disc. During fine polishing, 0.3 mL of oil-based diamond suspension and 0.3 mL of lubricant were added to the polishing disc every 15 s.

[0101] Among them, the pressure P3 of the polishing disk is 26N, the rotation speed W3 of the polishing disk is 380rpm, the rotation speed R3 of the grinding and polishing head clamping the sample is 230rpm, the polishing time t3 is 2min, and P3+[(W3+R3)×0.01+t3]×[C]=30.

[0102] (6) Surface treatment

[0103] The sample surface does not come into contact with water during the entire process.

[0104] Specifically, a wet paper towel with a surface smoothness of 150s was used to wipe the surface of the finely polished sample clean along a fixed direction, and then placed in a drying oven for drying.

[0105] The surface of the metallographic sample obtained by the above preparation method is clean, free of oxidation and artificial pollution, and the metallographic photos are as follows: Figure 2 shown.

[0106] After analyzing and testing the inclusions in the samples using a scanning electron microscope, the effective detection rate of inclusions was found to be 97%.

[0107] Example 3

[0108] This embodiment uses the above-mentioned metallographic sample preparation method of high-silicon steel, which specifically includes the following steps:

[0109] (1) Sampling

[0110] High-strength cable steel wire rod with a grade of 96Si was selected, containing 0.96% C and 1.2% Si. The spring steel wire rod had a diameter of 5.5 mm and was sampled at the center of its longitudinal cross-section, with a length of 20 mm.

[0111] (2) Mounting

[0112] The hot mounting method was used to form samples with a diameter of 30 mm.

[0113] (3) Water mill

[0114] The automatic grinding and polishing machine performs two passes of water grinding. The grinding discs for the two passes of water grinding are metal-based diamond grinding discs with grit numbers of 220# and 600# respectively. The pressure P1 of the grinding disc is 48N, the rotation speed W1 of the grinding disc is 320rpm, the rotation speed R1 of the grinding and polishing head holding the sample is 180rpm, the water grinding time t1 of each pass is 6min, and P1+[(W1+R1)×0.01+t1]×[C]=58.

[0115] (4) Rough polishing

[0116] A fully automatic grinding and polishing machine was used for rough polishing. After rough polishing, the sample surface was rinsed with water and dried with cold air.

[0117] The polishing disc is a metal-based synthetic fiber disc with a particle size of 9 μm, and the polishing liquid is a diamond suspension + water. The diamond particle size in the diamond suspension is 9 μm, the concentration is 2 g / L, and the pH is 8.5.

[0118] The pressure P2 of the polishing disk is 36N, the rotation speed W2 of the polishing disk is 320rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 180rpm, the polishing time t2 is 6min, and P2+[(W2+R2)×0.01+t2]×[C]=46.

[0119] (5) Fine polishing

[0120] Fine polishing was performed using a fully automatic grinder-polisher. The polishing discs used were metal-based synthetic fiber discs with a 3μm particle size and a water content of ≤0.1%. The polishing fluid consisted of an oil-based diamond suspension combined with a lubricant. The diamond particles in the oil-based diamond suspension were 3μm in size, at a concentration of 3g / L and a pH of 7.0. Both the oil-based diamond suspension and lubricant were added automatically by the fully automatic grinder-polisher. The sample surface remained free of water during the entire fine polishing process. The lubricant used was DP-Lubricant Blue, manufactured by Struers, Denmark.

[0121] Before fine polishing, 1.2 mL of lubricant was added to the polishing disc. During fine polishing, 0.3 mL of oil-based diamond suspension and 0.3 mL of lubricant were added to the polishing disc every 15 s.

[0122] Among them, the pressure P3 of the polishing disk is 26N, the rotation speed W3 of the polishing disk is 400rpm, the rotation speed R3 of the grinding and polishing head clamping the sample is 240rpm, the polishing time t3 is 2min, and P3+[(W3+R3)×0.01+t3]×[C]=34.

[0123] (6) Surface treatment

[0124] The sample surface does not come into contact with water during the entire process.

[0125] Specifically, a wet paper towel with a surface smoothness of 150s was used to wipe the surface of the finely polished sample clean along a fixed direction, and then placed in a drying oven for drying.

[0126] The surface of the metallographic sample obtained by the above preparation method is clean, free of oxidation and artificial pollution, and the metallographic photos are as follows: Figure 3 shown.

[0127] After analyzing and testing the inclusions in the samples using a scanning electron microscope, the effective detection rate of inclusions was found to be 96%.

[0128] Comparative Example

[0129] The metallographic sample preparation method of this embodiment specifically includes the following steps:

[0130] (1) Sampling

[0131] We selected 55SiCr spring steel wire rod with a C content of 0.55% and a Si content of 1.4%. The diameter of the spring steel wire rod was 19 mm, and a sample of 10 mm in length was taken from the center of the longitudinal section of the wire rod.

[0132] (2) Mounting

[0133] The hot mounting method was used to form samples with a diameter of 30 mm.

[0134] (3) Water mill

[0135] The automatic grinding and polishing machine performs two passes of water grinding. The grinding discs for the two passes of water grinding are metal-based diamond grinding discs with grit numbers of 220# and 600# respectively. The pressure P1 of the grinding disc is 48N, the rotation speed W1 of the grinding disc is 300rpm, the rotation speed R1 of the grinding and polishing head holding the sample is 160rpm, the water grinding time t1 of each pass is 5min, and P1+[(W1+R1)×0.01+t1]×[C]=53.

[0136] (4) Rough polishing

[0137] A fully automatic grinding and polishing machine was used for rough polishing. After rough polishing, the sample surface was rinsed with water and dried with cold air.

[0138] The polishing disc is a metal-based synthetic fiber disc with a particle size of 9 μm, and the polishing liquid is a diamond suspension + water. The diamond particle size in the diamond suspension is 9 μm, the concentration is 2 g / L, and the pH is 8.5.

[0139] The pressure P2 of the polishing disk is 36N, the rotation speed W2 of the polishing disk is 320rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 160rpm, the polishing time t2 is 5min, and P2+[(W2+R2)×0.01+t2]×[C]=41.

[0140] (5) Fine polishing

[0141] Fine polishing was performed using a fully automatic grinder-polisher. The polishing discs were metal-based synthetic fiber discs with a 3μm particle size and were rinsed with water. The polishing fluid consisted of a diamond suspension with a 3μm particle size, a concentration of 3g / L, and a pH of 7.0. The diamond suspension was automatically added via the fully automatic grinder-polisher. During the fine polishing process, 0.3mL of the diamond suspension was added to the disc every 15 seconds.

[0142] Among them, the pressure P3 of the polishing disk is 26N, the rotation speed W3 of the polishing disk is 380rpm, the rotation speed R3 of the grinding and polishing head clamping the sample is 230rpm, the polishing time t3 is 2min, and P3+[(W3+R3)×0.01+t3]×[C]=30.

[0143] (6) Surface treatment

[0144] The polished sample surface was cleaned with water and then dried with a hair dryer.

[0145] The surface of the metallographic sample obtained by the above preparation method is severely oxidized, and the metallographic photos are as follows Figure 4 shown.

[0146] After analyzing and testing the inclusions in the samples using a scanning electron microscope, it was found that the effective detection rate of inclusions was 45%.

[0147] It can be seen that the metallographic sample preparation method of high-silicon steel of the present application can effectively prevent the surface oxidation of the metallographic sample of high-silicon steel, and is applicable to steel of different categories and grades, and has a wide range of applications.

[0148] It should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a metallographic sample of high silicon steel, characterized in that: It includes the steps of sampling, mounting, water grinding, rough polishing, fine polishing and surface treatment in sequence; In the water grinding step, 2 to 3 passes of water grinding are performed, the pressure P1 of the grinding disc is 40 to 50 N, the rotation speed W1 of the grinding disc is 250 to 350 rpm, the rotation speed R1 of the grinding head holding the sample is 100 to 200 rpm, the water grinding time t1 of each pass is 2 to 10 minutes, and the following conditions are satisfied: 41≤P1+[(W1+R1)×0.01+t1]×[C]≤60; In the rough polishing step, the pressure P2 of the polishing disk is 30-39 N, the rotation speed W2 of the polishing disk is 250-350 rpm, the rotation speed R2 of the grinding and polishing head holding the sample is 100-200 rpm, the polishing time t2 is 2-8 min, and the following conditions are satisfied: 31≤P2+[(W2+R2)×0.01+t2]×[C]≤50; In the fine polishing step, the polishing liquid adopts an oil-based diamond suspension + lubricant, the sample surface does not contact water during the entire fine polishing process, the diamond particle size in the oil-based diamond suspension is 1-5 μm, the concentration is 2-5 g / L, the pH is 6.5-7.5, the pressure P3 of the polishing disk is 20-29 N, the rotation speed W3 of the polishing disk is 350-450 rpm, the rotation speed R3 of the grinding and polishing head holding the sample is 200-300 rpm, the polishing time t3 is 1-3 min, and satisfies: 21≤P3+[(W3+R3)×0.01+t3]×[C]≤35; During the surface treatment step, the sample surface does not contact water at all; Wherein, [C] is the percentage of C content in the sample; in the above relationship, only the numerical values ​​of the pressure, speed, and time parameters are limited, and the units are irrelevant. The values ​​of each parameter are determined based on the above units.

2. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the surface treatment step, a paper towel is used to wipe the surface of the finely polished sample clean in one direction, and then placed in a drying oven for drying. The surface smoothness of the paper towel is 150-200s.

3. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the fine polishing step, the lubricant used is DP-Lubricant Blue lubricant manufactured by Struers, Denmark.

4. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the fine polishing step, 1 to 1.5 mL of lubricant is added to the polishing disc before fine polishing. During the fine polishing process, the polishing liquid is added by adding 0.2 to 0.4 mL of oil-based diamond suspension and 0.2 to 0.4 mL of lubricant to the polishing disc every 15 seconds.

5. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the fine polishing step, the polishing disc is a metal-based synthetic fiber disc with a particle size of 3 μm, and the water content of the metal-based synthetic fiber polishing disc is ≤0.1%.

6. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the rough polishing step, the polishing liquid is a diamond suspension + water, the diamond particle size in the diamond suspension is 7-11 μm, the concentration is 1-3 g / L, and the pH is 8.0-9.

0.

7. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the rough polishing step, the polishing disk is a metal-based synthetic fiber disk with a particle size of 9 μm.

8. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the rough polishing step, after the rough polishing is completed, the sample surface is rinsed with water and blown dry with cold air.

9. The method for preparing a metallographic sample of high silicon steel according to claim 1, wherein: In the water grinding step, the grinding disc adopts a metal-based diamond grinding disc with a particle size of 200#~1000#.

10. The method for preparing a metallographic sample of high silicon steel according to claim 1, characterized in that: The chemical composition of the high silicon steel is, by mass percentage, C<1%, 1%≤Si≤3.5%.

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