A method for preparing a diffusion-multiphase eutectic of high-strength alloy steel

Abstract

The application provides a preparation method of a diffusion multi-element joint of high-strength alloy steel, and belongs to the technical field of alloy steel. The high-strength alloy steel has a tensile strength of at least 2000 MPa, and comprises the following steps: preparing an alloy ingot according to requirements, wherein the mass percentage of the diffusion element in the alloy ingot is less than 1.0%; cutting and polishing the alloy ingot, and then assembling and vacuum welding the alloy ingot with a sealing sleeve according to a preset arrangement, wherein the alloy ingot is subjected to quenching treatment before polishing; and subjecting the assembled multi-element joint to hot isostatic pressing and annealing treatment to obtain a sample. The quenching treatment of the alloy ingot before polishing makes the surface roughness Ra value of the prepared sample 0.03+ / -0.01 microns, and the surface flatness less than 0.05 mm, thereby meeting the requirements of subsequent processes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alloy steel, and particularly relates to a preparation method of a diffusion multi-element alloy. BACKGROUND

[0002] High-strength steel has a wide range of applications in many industries due to its extremely high strength, toughness and wear resistance. For example, high-strength steel is required as a structural material in the fields of automobile manufacturing, aerospace, construction and energy, and must have high strength, high toughness, corrosion resistance and other characteristics in these fields. However, the hydrogen embrittlement problem of high-strength steel is still a serious challenge.

[0003] The hydrogen embrittlement performance of steel depends on its chemical composition and microstructure. By controlling the content and distribution of multiple elements in the steel, the mechanical properties and corrosion resistance of the steel can be adjusted. Traditional steel preparation methods such as casting, heat treatment and alloying cannot accurately control the distribution of multiple elements, making it difficult to achieve gradient composition changes, and the content of the element to be diffused in the steel for hydrogen embrittlement performance measurement is low, basically below 1wt%. Therefore, new preparation methods need to be developed to meet the special requirements of high-strength steel materials.

[0004] In recent years, improving the hydrogen embrittlement sensitivity of high-strength steel through alloy design and adding specific micro-alloying elements has gradually become an important research direction. By adding micro-alloying elements (such as vanadium, titanium, niobium, etc.) or special alloying elements (such as nickel, molybdenum, etc.), the resistance of high-strength steel to hydrogen embrittlement can be effectively improved. These alloying elements can form stable compounds with hydrogen atoms or provide effective hydrogen trapping sites, thereby slowing down the diffusion and aggregation of hydrogen at grain boundaries. However, the selection and composition of multiple alloying elements in the current high-strength steel hydrogen embrittlement research field is still a relatively difficult and complex problem. Traditionally, this selection and composition is based on empirical rules, trial and error methods and experimental results, which requires a lot of time and effort.

[0005] The high-throughput alloy preparation method is the key to expand the alloy design space and accelerate the alloy research. The high-throughput test, automatic alloy preparation technology can efficiently synthesize and evaluate a large number of alloy samples, and accelerate the search for high hydrogen embrittlement resistance high strength steel alloy components. The use of diffusion multi-element section to prepare high-throughput test samples to realize rapid search for the best element hydrogen embrittlement resistance ratio becomes a new technology. The diffusion multi-element section preparation method uses atomic diffusion at high temperature to control the gradient distribution of multiple elements in the material by adjusting the diffusion rate and temperature gradient. This method can accurately control the content and variation range of multiple elements in high strength steel materials. However, the following problems need to be overcome when applying diffusion multi-element section to the study of hydrogen embrittlement resistance of high strength steel: first, the alloy steel has high strength, usually more than 2000MPa, and the content of the diffused element is low, how to successfully prepare the diffusion multi-element section; second, for the study of hydrogen embrittlement resistance, the diffusion distance should be at least 300μm to effectively study the effect of elements on hydrogen embrittlement, corrosion and fatigue performance, how to ensure that the diffusion distance is more than 300μm; finally, the high strength alloy steel has high hot isostatic pressing pressure, and the processing process is easy to produce pressure cracking and affect the success rate. SUMMARY

[0006] To solve the above problems, the present application provides a diffusion multi-element section preparation method for high strength alloy steel. The alloy ingot is quenched before grinding and polishing to make the surface roughness Ra value of the prepared sample 0.03±0.01μm, and the surface flatness within 0.05mm, meeting the subsequent process requirements.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a diffusion multi-element section preparation method for high strength alloy steel, the tensile strength of which is at least 2000MPa, comprising: preparing alloy ingots as required, the mass percentage of the diffused element in the alloy ingot being less than 1.0%; assembling and welding the alloy ingot after cutting, grinding and polishing according to the preset arrangement and sealing sleeve, the alloy ingot being quenched before grinding and polishing; hot isostatic pressing and annealing the assembled multi-element section to obtain a sample.

[0009] Further, the mass percentage of the diffused element is less than 0.6%.

[0010] Further, the grinding and polishing include physical polishing and chemical mechanical polishing in sequence, and the alloy ingot is vacuum annealed before chemical mechanical polishing.

[0011] Further, the physical polishing comprises polishing the quenched alloy ingot to 5000 mesh by using sandpaper, polishing to a surface roughness of 2.5-1.0 μm by using diamond polishing paste, and polishing to a surface roughness of 0.2-0.4 μm by using vibration polishing.

[0012] Further, the vibration polishing process is as follows: using boron carbide as abrasive material, a particle size of 50-100 μm, a slurry ratio of 0.6-0.8, polishing for 10-15 min at a frequency of 3000-5000 Hz and an amplitude of 1-1.5 mm.

[0013] Further, after chemical mechanical polishing, the surface roughness of the alloy ingot is 0.02-0.04 μm.

[0014] Further, the chemical mechanical polishing process is as follows: using 15-25 wt% silica suspension, adjusting the pH value to 7-9, adding 0.1-0.5 wt% hydroxyethyl cellulose with a density of 0.6-0.7 g / ml, and polishing for at least 4 h.

[0015] Further, the alloy ingot comprises a base of 36MnB5, Ti, Nb, V, Cr, Mo, C small ingots arranged on both sides of the base, and the small ingots are formed by adding less than 1.0% by mass of the element to be diffused on the basis of the same composition as the base.

[0016] Further, the Ti, Cr, C small ingots are located on one side of the base, and the C small ingot is located between the Ti and Cr small ingots; the Nb, Mo, V small ingots are located on the other side of the base, and the Mo small ingot is located between the Nb and V small ingots.

[0017] Further, the sealing sleeve is made of the same material as the base of the alloy ingot.

[0018] The technical scheme provided by the embodiment of the present application has the following beneficial effects: the diffusion multi-element section preparation method of high-strength alloy steel provided by the present application is suitable for steel with a tensile strength of 2000 MPa or more and a mass percentage of the element to be diffused of less than 1.0%, and the present application proposes quenching treatment before polishing, which further improves the hardness and wear resistance of the alloy steel, so that the surface roughness Ra of the prepared sample is 0.03±0.01 μm and the surface flatness is within 0.05 mm during subsequent polishing, so as to ensure the diffusion rate and uniformity of the elements. If the sample surface is uneven, such as the flatness being greater than 0.05 mm, the sample surface has protrusions, depressions or other uneven defects, and during the hot isostatic pressing process, the pressure will act unevenly on the sample surface, which will cause local stress concentration and further cause the formation of cracks, thereby affecting the success rate of sample preparation; finally, the diffusion multi-element section prepared by the technical scheme provided by the present application satisfies a diffusion distance of 300 μm or more. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the assembly of the multi-unit section in an embodiment of the present invention;

[0021] Figure 2 This is an EMPA image of the diffusion-multi-element V ingot prepared in Example 1 of the present invention and the matrix gradient composition sample;

[0022] Figure 3 The trend of nanoindentation hardness variation between the diffusion-multi-element V ingot prepared in Example 1 of this invention and the matrix gradient region.

[0023] Explanation of the symbols in the attached diagram: 1. Cap; 2. Cover. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] This invention discloses a method for preparing diffusion-dependent multi-element joints of high-strength alloy steel, wherein the high-strength alloy steel has a tensile strength of at least 2000 MPa. The method includes: preparing an alloy ingot as required, wherein the mass percentage of the element to be diffused in the alloy ingot is less than 1.0%; cutting, grinding, and polishing the alloy ingot, assembling it with a sealing sleeve according to a preset arrangement, and vacuum welding it; quenching the alloy ingot before grinding and polishing; and subjecting the assembled multi-element joints to hot isostatic pressing and annealing to obtain a sample.

[0026] The preparation method of the high-strength alloy steel diffusion multi-element joint provided by the application is suitable for a steel grade with a tensile strength of 2000 MPa or more and a mass percentage of the diffusion element of less than 1.0%, and the quenching treatment is performed before polishing, so that the hardness and wear resistance of the alloy steel are further improved, the surface roughness Ra of the prepared sample is 0.03±0.01 μm in the subsequent polishing process, and the surface flatness is within 0.05 mm, so as to ensure the diffusion rate and uniformity of the element. If the surface of the sample is uneven, for example, the flatness is greater than 0.05 mm, and the sample surface has protrusions, depressions or other uneven defects, the pressure will be unevenly applied to the surface of the sample during the hot isostatic pressing process, local stress concentration will be caused, and then cracks will be formed, thereby affecting the success rate of sample preparation; and finally the prepared diffusion multi-element joint satisfies the diffusion distance of 300 μm or more.

[0027] It should be noted that the vacuum degree of the vacuum welding is 0.02 Pa or less, and the surface flatness is the difference between the highest point and the lowest point of the surface.

[0028] Specifically, the mass percentage of the diffusion element is less than 0.6%.

[0029] Specifically, the polishing includes physical polishing and chemical mechanical polishing in sequence, and the alloy ingot is subjected to vacuum annealing treatment before the chemical mechanical polishing. The vacuum annealing treatment is adopted to reduce the hardness of the alloy steel organization, so as to facilitate the removal of the stress layer caused by the mechanical polishing through the chemical mechanical polishing, and to avoid the influence on the element diffusion, especially for the content of the diffusion element in the application being less than 1 wt%. The annealing temperature adopted in the application is below the austenite transformation temperature, and the heat preservation time is at least 1 h.

[0030] Specifically, the physical polishing includes polishing the quenched alloy ingot to 5000 mesh by using sandpaper, polishing the surface roughness to 1.0-2.5 μm by using diamond polishing paste, and polishing the surface roughness to 0.2-0.4 μm by using vibration polishing. On the one hand, the quenching process is adopted before the grinding and polishing to improve the hardness of the high-strength alloy steel, but it should be noted that unreasonable subsequent polishing process will still cause poor surface flatness. The above processes are organically combined to prepare the sample with the surface roughness Ra of 0.03±0.01 and the surface flatness within 0.05 mm, so as to meet the requirements of the subsequent process.

[0031] Specifically, the vibration polishing process is as follows: boron carbide is used as the abrasive, the average particle size is 50-100 μm, the abrasive liquid ratio is 0.6-0.8, the frequency is 3000-5000 Hz, the amplitude is 1-1.5 mm, and the polishing time is 10-15 min.

[0032] Specifically, the surface roughness of the alloy ingot after chemical mechanical polishing is 0.02-0.04 μm.

[0033] Specifically, the chemical mechanical polishing process is as follows: 15-25 wt% silica suspension is used, the pH value is adjusted to 7-9, 0.1-0.5 wt% hydroxyethyl cellulose with a density of 0.6-0.7 g / ml is added, and polishing is performed for at least 4 h. Chemical mechanical polishing removes the stress layer caused by mechanical polishing on one hand, avoiding affecting element diffusion; on the other hand, hydroxyethyl cellulose coats silica, satisfying the condition that the polishing ability is not affected while preventing silica particles from remaining on the polished surface, affecting element diffusion. Preferably, the chemical mechanical polishing in the embodiment of the present application is performed in a vibrating manner, and the vibration frequency is preferably 2000-3000 Hz.

[0034] Specifically, the alloy ingot comprises a 36MnB5 base, Ti, Nb, V, Cr, Mo and C small ingots arranged on both sides of the base, and the small ingots are formed by adding less than 1.0% by mass of the to-be-diffused elements on the basis of the same composition as the base. In the present application, 0.5 wt% of the corresponding to-be-diffused elements are added in the smelting process of the small ingots. The tensile strength of the 36MnB5 base used in the present application is at least 2000 MPa, and the hardness of the small ingots of various elements is higher than that of the 36MnB5 base.

[0035] The composition of the 36MnB5 used in the present application is shown in Table 1.

[0036] Table 1 Composition of high-strength alloy steel 36MnB5

[0037] Element C Mo Cr Nb V Ti Content / % 0.36 0.01 0.18 0.001 0.002 0.037

[0038] Specifically, as shown in Figure 1 the Ti, Cr and C small ingots are arranged on one side of the base, and the C small ingot is arranged between the Ti and Cr small ingots; the Nb, Mo and V small ingots are arranged on the other side of the base, and the Mo small ingot is arranged between the Nb and V small ingots. Through the above arrangement, on one hand, the detection zone formed by the diffusion of the to-be-diffused elements from the small ingots to the base can be detected, and on the other hand, the detection zones formed by the diffusion of the Ti and Cr small ingots with the C small ingot and the diffusion of the Nb and V small ingots with the Mo small ingot can be detected, thereby improving the throughput of the test.

[0039] In order to detect the absence of cracks and other defects in the sample prepared by the present application, five samples are taken in the thickness direction of the prepared sample, specifically as Figure 1 in the thickness direction of the middle package, i.e. the direction perpendicular to the two covers, and the samples are uniformly taken, and then polished and examined by light microscopy.

[0040] In the embodiment of the present application, the size of each sample is: 36MnB5 base: 15*5*7mm; Ti, Nb, V, Cr, Mo, C small ingot: 5*5*7mm; multi-element node cover size: 21*21*7mm, the internal hollow size: 15*15*7mm; cover size (2): 21*21*3mm.

[0041] Specifically, the sealing sleeve is the same as the base material of the alloy ingot. By setting the sealing sleeve to be the same as the base material of the alloy ingot, the strength of the sealing sleeve is prevented from being low, and relative sliding between the base and the small ingot during hot isostatic pressing leads to failure of preparation of the diffusion multi-element node.

[0042] For high-strength steel 36MnB5, a heat preservation treatment is adopted to heat the temperature to an austenite transformation temperature and preserve for a certain time, and then quenching treatment is performed, the austenite transformation temperature is determined based on a phase diagram, and the preservation temperature can be set by using existing experience, which will not be described here. The quenching treatment is to put the preserved high-strength steel into water.

[0043] The hot isostatic pressing process is to keep the temperature at 1000-1200℃ and the pressure at least 120MPa for 2.5h. The annealing process is to keep the temperature at 800-1000℃ for 30-35 days.

[0044] In order to better illustrate the embodiments of the present application, the present application will be further described in detail through specific examples.

[0045] Example 1

[0046] The embodiment of the present application provides a preparation method of 36MnB5 diffusion multi-element node, which comprises:

[0047] S1, preparing an alloy ingot according to requirements, including a 36MnB5 base and Ti, Nb, V, Cr, Mo and C small ingots, wherein the mass percentage of the diffusion elements of the Ti, Nb, V, Cr, Mo and C small ingots is 0.5%.

[0048] S2, after cutting, polishing and polishing the alloy ingot, assembling and sealing welding with a sealing sleeve according to a preset arrangement, the alloy ingot is subjected to quenching treatment before polishing and polishing.

[0049] The alloy ingot is cut into a required size and is quenched, after the quenching is finished, the alloy ingot is polished to 5000 meshes, is polished to a surface roughness of 2.5 microns by using a diamond polishing paste, is polished in a grinding liquid with boron carbide as an abrasive, an average particle size of 50 microns, a material liquid ratio of 0.6, a frequency of 3000 Hz, an amplitude of 1 mm for 10 min, the surface roughness is measured to be 0.4 microns, a 15wt% silicon dioxide suspension is used, the pH value is adjusted to 7, 0.1wt% hydroxyethyl cellulose with a density of 0.6g / ml is added, and polishing is performed for 4h, the surface roughness is measured to be 0.04 microns, and the surface flatness is 0.04mm.

[0050] According to the arrangement mode of Figure 1 , the small ingot, the base body and the sealing sleeve are assembled and sealing welded.

[0051] S3, the assembled multi-element node is subjected to hot isostatic pressing and annealing treatment to obtain a sample.

[0052] The assembled multi-element node is kept at a temperature of 1100 DEG C and a pressure of 120 MPa for 2.5h. The annealing process is kept at 900 DEG C for 30 days, and the sample is obtained.

[0053] As shown in Figure 2 , the V element diffused from the V small ingot into the base body has a significant diffusion trend within a distance of about 500 microns.

[0054] As shown in Figure 3 , the mechanical test results of the gradient sample by nanoindentation and microindentation methods can be seen that within the diffusion range, different hardnesses are caused by different component gradients, which proves that the mechanical properties and other characteristics of the steel can be adjusted by preparing the high-strength steel gradient component sample.

[0055] Through light microscopy, the prepared sample has no cracks in the five samples in the thickness direction, and there is no silicon dioxide at the interface between the small ingot and the base body.

[0056] Example 2

[0057] The embodiment of the present application provides a 36MnB5 diffusion multi-element node preparation method, comprising:

[0058] S1, preparing an alloy ingot according to requirements, including a 36MnB5 base body and Ti, Nb, V, Cr, Mo and C small ingots, wherein the mass percentage content of the diffused elements of the Ti, Nb, V, Cr, Mo and C small ingots is 0.5%.

[0059] S2, after the alloy ingot is cut, polished and polished, the alloy ingot is assembled and sealing welded according to a preset arrangement and a sealing sleeve, and the alloy ingot is quenched before polishing and polishing.

[0060] The alloy ingot is cut to the required size and quenched, and after quenching, the alloy ingot is polished to 5000 mesh, polished to a surface roughness of 2.0 microns with diamond polishing paste, polished in a grinding fluid with boron carbide as the abrasive, an average particle size of 80 microns, a material liquid ratio of 0.7, a frequency of 4000 Hz, an amplitude of 1.2 mm, and polished for 12 minutes. The surface roughness is measured to be 0.3 microns, and a 20wt% silica suspension is used to adjust the pH to 8, and 0.3wt% hydroxyethyl cellulose with a density of 0.6g / ml is added, and polished for 4 hours. The surface roughness is measured to be 0.03 microns, and the surface flatness is 0.035mm.

[0061] According to the arrangement mode of Figure 1 The small ingot, the base and the sealing sleeve are assembled and sealed welded.

[0062] S3, the assembled multi-element node is subjected to hot isostatic pressing and annealing treatment to obtain a sample.

[0063] The assembled multi-element node is maintained at a temperature of 1000 DEG C and a pressure of 120 MPa for 2.5 hours. The annealing process is maintained at 800 DEG C for 31 days, and the sample is obtained.

[0064] The V element diffused from the V small ingot into the base has a significant diffusion trend within a distance of about 550 microns. Through optical inspection, the prepared sample has no cracks in the thickness direction of the five samples, and there is no silicon dioxide at the interface between the small ingot and the base.

[0065] Example 3

[0066] The embodiment of the present application provides a 36MnB5 diffusion multi-element node preparation method, comprising:

[0067] S1, an alloy ingot is prepared according to requirements, including a 36MnB5 base and Ti, Nb, V, Cr, Mo and C small ingots, wherein the mass percentage content of the diffused elements of the Ti, Nb, V, Cr, Mo and C small ingots is 0.5%.

[0068] S2, after the alloy ingot is cut, polished and polished, it is assembled and sealed welded according to the preset arrangement and the sealing sleeve. The alloy ingot is quenched before polishing and polishing.

[0069] The alloy ingot is cut into the required size and quenched. After quenching, the alloy ingot is polished to 5000 mesh, polished to a surface roughness of 1.0 μm using a diamond polishing paste, polished in a grinding fluid with boron carbide as the abrasive, an average particle size of 100 μm, a material liquid ratio of 0.8, a frequency of 5000 Hz, an amplitude of 1.5 mm, and a polishing time of 15 min. The surface roughness is measured to be 0.2 μm. A 25 wt% silica suspension is used, the pH value is adjusted to 9, 0.5 wt% hydroxyethyl cellulose with a density of 0.7 g / ml is added, and the polishing is performed for 4 h. The surface roughness is measured to be 0.02 μm and the surface flatness is 0.04 mm.

[0070] According to the arrangement mode of Figure 1 , the small ingot, the base and the sealing sleeve are assembled and seal welded.

[0071] S3, the assembled multi-element joint is subjected to hot isostatic pressing and annealing treatment to obtain a sample.

[0072] The assembled multi-element joint is maintained at a temperature of 1200℃ and a pressure of 120 MPa for 2.5 h. The annealing process is to maintain at 1000℃ for 30 days to obtain the sample.

[0073] The V element diffused from the V small ingot into the base has a significant diffusion trend within a distance of about 650 μm. Through optical microscope inspection, the prepared sample has no cracks in the five samples in the thickness direction, and there is no silicon dioxide at the interface between the small ingot and the base.

[0074] Example 4

[0075] Different from Example 1, in step S2 of the present embodiment, after the vibration polishing is completed, the alloy ingot is subjected to vacuum annealing treatment, and then polished using a 15 wt% silica suspension, the pH value is adjusted to 7, 0.1 wt% hydroxyethyl cellulose with a density of 0.6 g / ml is added, and the polishing is performed for 4 h. The surface roughness is measured to be 0.04 μm and the surface flatness is 0.04 mm. According to the arrangement mode of Figure 1 , the small ingot, the base and the sealing sleeve are assembled and seal welded.

[0076] The V element diffused from the V small ingot into the base has a significant diffusion trend within a distance of about 600 μm. Through optical microscope inspection, the prepared sample has no cracks in the five samples in the thickness direction, and there is no silicon dioxide at the interface between the small ingot and the base.

[0077] Comparative Example 1

[0078] Compared with Example 1, in step S2 of the comparative example, the alloy ingot was polished to 5000 mesh, and polished to a surface roughness of 3.0 μm using a diamond polishing paste; using boron carbide as the abrasive, with an average particle size of 50 μm, a slurry with a solid-liquid ratio of 0.6, polishing at a frequency of 3000 Hz and an amplitude of 1 mm for 10 min, the measured surface roughness was 0.4 μm, using a 15 wt% silica suspension, adjusting the pH value to 7, adding 0.1 wt% hydroxyethyl cellulose with a density of 0.6 g / ml, and polishing for 4 h, the measured surface roughness was 0.06 μm.

[0079] The V element diffused from the V ingot into the matrix had a clear diffusion trend within a distance of about 500 μm.

[0080] Through optical microscopy, one of the five samples prepared in the thickness direction had a crack at the edge position, and there was no silica at the interface between the ingot and the matrix.

[0081] Comparative Example 2

[0082] Compared with Example 1, in step S2 of the comparative example, the alloy ingot was polished to 5000 mesh, and polished to a surface roughness of 0.8 μm using a diamond polishing paste; using boron carbide as the abrasive, with an average particle size of 50 μm, a slurry with a solid-liquid ratio of 0.6, polishing at a frequency of 3000 Hz and an amplitude of 1 mm for 10 min, the measured surface roughness was 0.4 μm, using a 15 wt% silica suspension, adjusting the pH value to 7, adding 0.1 wt% hydroxyethyl cellulose with a density of 0.6 g / ml, and polishing for 4 h, the measured surface roughness was 0.07 μm.

[0083] The V element diffused from the V ingot into the matrix had a clear diffusion trend within a distance of about 500 μm.

[0084] Through optical microscopy, one of the five samples prepared in the thickness direction had a crack at the edge position, and there was no silica at the interface between the ingot and the matrix.

[0085] Comparative Example 3

[0086] Compared with Example 3, in step S2 of the comparative example, the alloy ingot was cut to the required size and quenched, after quenching, the alloy ingot was polished to 5000 mesh, polished to a surface roughness of 1.0 μm using diamond polishing paste, polished in a grinding liquid with boron carbide as the abrasive, an average particle size of 100 μm, a liquid-to-solid ratio of 0.8, a frequency of 5000 Hz, an amplitude of 1.5 mm, and a polishing time of 20 min. The surface roughness was measured to be 0.18 μm. Polishing was performed for 4 h using a 25 wt% silica suspension, with a pH value of 9, and 0.5 wt% hydroxyethyl cellulose with a density of 0.7 g / ml. The surface roughness was measured to be 0.02 μm, and the surface flatness was 0.051 mm.

[0087] The V element diffused from the V ingot into the base had a clear diffusion trend within a distance of about 500 μm. Through optical microscopy, one of the five samples in the thickness direction of the prepared sample had a tiny crack, and there was no silica at the interface between the ingot and the base.

[0088] Comparative Example 4

[0089] Compared with Example 3, in step S2 of the comparative example, the alloy ingot was cut to the required size and quenched, after quenching, the alloy ingot was polished to 5000 mesh, polished to a surface roughness of 2.5 μm using diamond polishing paste, polished in a grinding liquid with boron carbide as the abrasive, an average particle size of 50 μm, a liquid-to-solid ratio of 0.6, a frequency of 3000 Hz, an amplitude of 1 mm, and a polishing time of 10 min. The surface roughness was measured to be 0.5 μm. Polishing was performed for 4 h using a 15 wt% silica suspension, with a pH value of 7, and 0.1 wt% hydroxyethyl cellulose with a density of 0.6 g / ml. The surface roughness was measured to be 0.05 μm, and the surface flatness was 0.052 mm.

[0090] The V element diffused from the V ingot into the base had a clear diffusion trend within a distance of about 500 μm. Through optical microscopy, one of the five samples in the thickness direction of the prepared sample had a tiny crack, and there was no silica at the interface between the ingot and the base.

[0091] Comparative Example 5

[0092] Compared with Example 1, in step S2 of the comparative example, the can and the cover were made of stainless steel with a strength of 300 MPa.

[0093] The V element diffused from the V ingot into the base had a clear diffusion trend within a distance of about 200 μm. Through optical microscopy, slippage occurred between the V ingot and the base during the hot isostatic pressing process, resulting in a short diffusion distance.

[0094] Comparative Example 6

[0095] In step S2 of the comparative example, no hydroxyethyl cellulose was added in the chemical mechanical polishing compared with the example 1.

[0096] The V element diffused from the small ingot to the base has a significant diffusion trend within a distance of about 450 μm. A small amount of silicon dioxide exists at the interface between the small ingot and the base as detected by SEM.

[0097] Comparative example 7

[0098] In step S2 of the comparative example, no quenching treatment was performed on the alloy ingot before polishing compared with the example 1. The surface roughness of the alloy ingot after polishing is 0.1 mm.

[0099] The prepared sample has cracks in five samples in the thickness direction as detected by light microscopy, and no silicon dioxide exists at the interface between the small ingot and the base.

[0100] It can be known from the example 1, the comparative examples 1, 2, 3 and 4 that when the surface roughness at different stages of the polishing process is not within the range protected by the present application, the surface flatness is poor, thereby increasing the stress between the small ingot and the base and generating cracks, and the sample fails to be prepared. The main reason is that when the treatment intensity of a step is too high or too low, the polishing effect on different regions of the polished surface of the alloy ingot is greatly different, resulting in poor surface flatness. Only when the polishing intensity of each step is controlled to a certain extent, the flatness of the entire polished surface can be improved.

[0101] It can be known from the comparison between the example 1 and the comparative example 5 that for high-strength steel with a strength of 2000 MPa or more, using a high-strength can and cover is beneficial to the stability of the assembled diffusion multi-element joint and reduces the probability of slipping.

[0102] It can be known from the comparison between the example 1 and the comparative example 6 that if no hydroxyethyl cellulose is added in the chemical mechanical polishing, the hydroxyethyl cellulose coats the silicon dioxide particles, the silicon dioxide is adsorbed on the polished surface of the alloy ingot, and the diffusion of the diffused elements in the small ingot is affected.

[0103] The comparison between the example 1 and the comparative example 7 shows that when no heat treatment is performed on the alloy ingot before polishing, the hardness of the alloy ingot is low, the surface flatness after polishing is poor, and thus the diffusion multi-element joint prepared has many cracks.

[0104] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a diffusion multiphase joint of a high-strength alloy steel having a tensile strength of at least 2000 MPa, characterized in that, The application relates to a method for preparing a multi-element sample. The alloy ingot is cut, polished and assembled with a sealing sleeve according to a preset arrangement, and vacuum welding is performed; the alloy ingot is quenched before polishing and polishing. The assembled multi-element sample is subjected to hot isostatic pressing and annealing treatment to obtain a sample. The polishing and polishing include physical polishing and chemical mechanical polishing, and the alloy ingot is subjected to vacuum annealing treatment before chemical mechanical polishing. The alloy ingot comprises a 36MnB5 base body, Ti, Nb, V, Cr, Mo and C small ingots arranged on two sides of the base body, and the small ingots are formed by adding less than 1.0% of a diffusible element in mass percentage on the basis of the same composition as the base body. The sealing sleeve is made of the same material as the base body of the alloy ingot. The mass percentage of the diffusible element is less than 0.6%.

2. The method for preparing diffusion-multi-component joints of high-strength alloy steel according to claim 1, characterized in that, The physical polishing includes polishing the quenched alloy ingot to 5000 meshes by using sandpaper, polishing to a surface roughness of 1.0-2.5 microns by using diamond polishing paste, and polishing to a surface roughness of 0.2-0.4 microns by using vibration polishing.

3. The method for preparing diffusion-multi-component joints of high-strength alloy steel according to claim 1, characterized in that, The vibration polishing process is as follows: boron carbide is used as abrasive, the average particle size is 50-100 microns, the abrasive liquid ratio is 0.6-0.8, the polishing is performed in a grinding liquid at a frequency of 3000-5000 Hz and an amplitude of 1-1.5 mm for 10-15 min.

4. The method for preparing diffusion-multi-component joints of high-strength alloy steel according to claim 3, characterized in that, After chemical mechanical polishing, the surface roughness of the alloy ingot is 0.02-0.04 microns.

5. The method for preparing diffusion-multi-component joints of high-strength alloy steel according to claim 1, characterized in that, The chemical mechanical polishing process is as follows: 15-25 wt% of silica suspension is used, the pH value is adjusted to 7-9, 0.1-0.5 wt% of hydroxyethyl cellulose with a density of 0.6-0.7 g / ml is added, and polishing is performed for at least 4 h.

6. The method of claim 5, wherein the diffusion multi- composition joint of high-strength alloy steel is characterized by, The Ti, Cr and C small ingots are arranged on one side of the base body, and the C small ingot is arranged between the Ti and Cr small ingots; the Nb, Mo and V small ingots are arranged on the other side of the base body, and the Mo small ingot is arranged between the Nb and V small ingots.

7. The method of claim 1, wherein the diffusion-multipledelta of high-strength alloy steel is prepared by the steps of: ​

Images