Preparation method of explosively welded composite plate made of CoCrNi medium entropy alloy and Q235B steel

Abstract

The present invention discloses a method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate. The CoCrNi medium entropy alloy plate is annealed, and then sand, anvil, Q235B hot-rolled steel plate, support column, medium entropy alloy plate, kraft paper, and explosive are laid in sequence from bottom to top on the explosion field. Then, the explosive is explosively welded to obtain a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate. The explosive has a detonation velocity of 2500-3000 m / s and a velocities of 18-22 mm. The present invention achieves metallurgical bonding of the CoCrNi medium entropy alloy and the Q235B steel plate. The resulting composite plate has an interface bonding rate greater than 99.2%, a yield strength greater than 420 MPa, a tensile strength greater than 500 MPa, an elongation after fracture greater than 35%, and an interface shear strength greater than 200 MPa. The present invention has a simple process and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of preparation of metal-based composite materials, and specifically provides a method for preparing a composite plate made of explosively welded CoCrNi medium-entropy alloy and Q235B steel, belonging to the field of metal composite material processing. Background Art

[0002] The equiatomic CoCrNi medium-entropy alloy is a new structural material developed in recent years. It boasts high strength, high toughness, and excellent resistance to friction, wear, corrosion, radiation, and high temperatures, showing significant potential for application in transportation, aerospace, and other fields. However, the alloy's high Co content also results in high costs. Q235B steel is one of the most widely used steels due to its extremely low manufacturing cost. However, its relatively low mechanical properties and corrosion resistance limit its application to applications requiring less demanding material properties.

[0003] Dissimilar metal layered composites have attracted widespread attention due to their ability to combine the advantages of various metal materials, and their scope of application is constantly expanding. Combining CoCrNi medium-entropy alloys with Q235B not only significantly reduces costs but also maintains high mechanical properties and corrosion resistance for the overall material. For layered metal composite sheets, the most commonly used composite methods are solid-liquid composite, rolling composite, and explosive composite. However, the melting point difference between CoCrNi medium-entropy alloys and Q235B steel is not large, making them unsuitable for solid-liquid composite. The significant differences between the two materials in mechanical properties, work hardening ability, and oxidation resistance also make rolling composites unsuitable. Explosive welding, as an important method for preparing dissimilar metal layered composites, can theoretically achieve composite bonding of all metal materials. However, the explosion process is significantly affected by multiple factors and the parameters of each factor. Currently, there are no relevant technical reports on the explosive composite of CoCrNi medium-entropy alloys and Q235B steel.

[0004] Therefore, developing a technology for explosive welding of CoCrNi medium entropy alloy and Q235B steel is a key issue that needs to be solved urgently in the field of composite plate manufacturing technology. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention aims to provide a method for preparing explosively welded composite plates made of a CoCrNi medium-entropy alloy and Q235B steel. The method utilizes a cast steel anvil as a backing plate, Q235B steel as a substrate, the CoCrNi medium-entropy alloy as a composite plate, and kraft paper as a barrier between the explosive and the composite plate. A self-made high-strength explosive is employed to achieve the metallurgical connection of the plates. The method is simple, convenient, and suitable for industrial production.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The present invention discloses a preparation method of a CoCrNi medium-entropy alloy and Q235B steel explosively welded composite plate. The method comprises the following steps: annealing the CoCrNi medium-entropy alloy plate, laying sand, anvils, Q235B hot-rolled steel plates, support columns, medium-entropy alloy plates, kraft paper, and explosives in sequence from bottom to top on an explosion field, and then performing explosive welding to obtain the CoCrNi medium-entropy alloy and Q235B steel explosively welded composite plate. The explosive has a detonation velocity of 2500-3000 m / s and a velocities of 18-22 mm.

[0008] The preparation method of the present invention first performs a complete annealing treatment on the CoCrNi medium-entropy alloy to improve the plasticity of the alloy, and Q235B steel is selected as a hot-rolled steel plate with good plasticity and medium strength. Based on the above properties of the two, it can be ensured that they are easy to combine during the explosion process without cracking. Then, Q235B steel is used as a substrate, the CoCrNi medium-entropy alloy is used as a composite plate, and kraft paper is used as an interlayer between the explosive and the composite plate. Finally, the explosive provided by the present invention is used for explosion welding to obtain a composite material with metallurgical bonding, wherein the detonation velocity is controlled within the range of the present invention, so that the composite interface of the two plates in the present invention can be a small wavy bonding interface, thereby improving the bonding strength. The high intensity of the explosive can cause the substrate and the composite plate to undergo severe work hardening during the explosion process, thereby improving the strength of the material and compensating for the material strength loss caused by the complete annealing of the CoCrNi medium-entropy alloy before explosive composite. The preparation method of the present invention fully utilizes the excellent work hardening ability of the soft CoCrNi medium-entropy alloy, ensuring that the final composite plate can achieve high strength even without heat treatment.

[0009] As a preferred embodiment, the length × width × thickness of the Q235B hot-rolled steel plate is: (500~800) mm × (400~600) mm × (10~40) mm, and the length × width × thickness of the CoCrNi medium entropy alloy plate is: (510~810) mm × (410~610) mm × (2~5) mm, and the length and width of the CoCrNi medium entropy alloy plate are both greater than the length and width of the Q235B hot-rolled steel plate.

[0010] In the present invention, the high-cost medium-entropy alloy plate is selected as a thin plate, and the low-cost Q235B hot-rolled steel plate is used as a thick plate. In the process of explosive composite, the Q235B hot-rolled steel plate is used as the base plate and the medium-entropy alloy plate is used as the composite plate, which has better support.

[0011] As a preferred solution, the surface roughness Ra of the CoCrNi medium entropy alloy plate and the Q235B hot-rolled steel plate is ≤3 μm. In actual operation, the surface of the base plate and the composite plate is polished before use to remove surface oil and oxides to ensure that the surface roughness Ra is ≤3 μm.

[0012] As a preferred solution, the CoCrNi medium entropy alloy plate is annealed at a temperature of 1000-1100° C. for 1-2 hours.

[0013] By completely softening and annealing the medium entropy alloy plate within the above parameters, the alloy is given good plasticity, ensuring that the explosion process can easily achieve metallurgical bonding of the material without cracking.

[0014] In the present invention, commercially available Q235B hot-rolled steel plates are used, which have good plasticity and medium strength and do not require heat treatment.

[0015] In industrial applications, a flat hard soil site is selected as the blasting site, and a layer of sand is laid on the hard soil as the foundation;

[0016] As a preferred solution, the thickness of the sand is 20~25mm.

[0017] As a preferred solution, the anvil is made of cast steel and has a thickness of 50-55 mm.

[0018] In the present invention, due to the use of high-strength explosives, the explosion process not only has a greater impact on the base plate and the composite plate, but also has a greater impact on the anvil plate. Based on the properties of Q235B hot-rolled steel plate, a cast steel anvil plate with good rigidity is placed under the soft base plate in industrial production to avoid serious bending and deformation of the composite plate during the explosion process.

[0019] During the actual operation, the anvil should be parallel to the ground and must not be tilted. The upper surface of the anvil should be cleaned and kept smooth, and the Q235B hot-rolled steel plate should be placed in the center area of ​​the anvil.

[0020] Preferably, the length and width of the anvil are both 1000-3000 mm. The anvil should be parallel to the ground and not tilted, and the upper surface of the anvil should be clean.

[0021] As a preferred solution, support columns are arranged at the four corners of the surface of the Q235B hot-rolled steel plate, and the CoCrNi medium-entropy alloy plate is placed above the support columns to ensure that the center position of the CoCrNi medium-entropy alloy plate and the center position of the Q235B hot-rolled steel plate are on the same axis, and the four sides are parallel to the four sides of the Q235B hot-rolled steel plate.

[0022] Further preferably, the support column has a diameter of 10-12 mm and a height of 6-8 mm.

[0023] As a preferred solution, the CoCrNi medium entropy alloy plate is surrounded by wooden strips on all sides, and the upper surface of the wooden strips is controlled to be higher than the surface of the CoCrNi medium entropy alloy plate to serve as an explosive pool. The depth of the explosive pool is 50-70 mm.

[0024] During industrial applications, kraft paper is placed in the explosive pool to isolate the explosive from direct contact with the composite plate, and to act as a buffer and protect the plate surface during explosion. Then, the explosive pool on the kraft paper is evenly filled with low-detonation-velocity and high-intensity mixed explosives, ensuring that the thickness of the explosives is uniform during the filling process.

[0025] As a preferred embodiment, the explosives are composed of the following ingredients by mass: 55-65% antimony-free rock ammonium nitrate explosive, 5-15% calcium carbonate powder, 5-10% sodium chloride, 5-10% silicon carbide powder, 5-10% perlite powder, 5-10% sawdust, and 5-10% chromium powder.

[0026] The explosive components of the present invention use antimony-free rock ammonium nitrate as a basic explosive. Calcium carbonate, sodium chloride, and silicon carbide powder are added to the basic explosive to reduce the detonation velocity of the explosive. Perlite powder and wood chips are added to improve the fluffiness of the explosive, which is beneficial for detonation. Chromium powder is added to increase the explosive strength. Through the synergistic effect of the above explosive components, an explosive with a detonation velocity of 2500-3000 m / s and a strength of 18-22 mm is obtained. The use of the explosive of the present invention can not only obtain a detonation velocity adapted to the plate, but also control the amplitude of the composite interface waveform, form a small-wave bonding interface, and improve the bonding strength. In addition, the high-strength explosive can cause the base plate and the composite plate to undergo severe work hardening during the explosion process, thereby compensating for the material strength loss caused by complete annealing before explosive bonding.

[0027] In industrial applications, explosives must be prepared, dried, and evenly mixed within one hour before use. Then, they must be sieved through a 40-mesh sieve, and the -40-mesh mixed powder must be selected as the explosive to be used. Water must be added to the mixed explosives to a minimum of 5% by volume, and the mixture must be thoroughly mixed before laying.

[0028] As a preferred solution, the mesh size of the explosive is -40 mesh, and the density of the explosive is 0.8~0.9g / cm 3 .

[0029] As a preferred solution, a detonator is installed in the explosives, positioned centrally along the short sides of the Q235B steel plate and the CoCrNi medium-entropy alloy plate. A lead is then connected to the detonator, which is then connected to a remote detonation device. The detonator is then detonated by the detonator via the lead, completing the explosive welding process and producing an explosively welded composite plate of the CoCrNi medium-entropy alloy and Q235B steel. The inventors have discovered that placing the detonator on the short side improves the yield rate.

[0030] In a further preferred embodiment, three quarters of the detonator is buried in the explosive.

[0031] In industrial production, the board surface after explosive compounding needs to be cleaned and leveled, and the cracked and collapsed parts of the edges need to be removed. Finally, ultrasonic testing is used to ensure that the entire board surface is well bonded.

[0032] The CoCrNi medium-entropy alloy and Q235B steel explosively welded composite plate prepared by the present invention has an interface bonding rate greater than 99.2%, a yield strength greater than 420 MPa, a tensile strength greater than 500 MPa, an elongation after fracture greater than 35%, and an interface shear strength greater than 200 MPa.

[0033] Principles and advantages

[0034] This invention achieves metallurgical bonding of a CoCrNi medium-entropy alloy and Q235B steel through explosive welding, providing a method for preparing high-performance bimetallic composite plates suitable for industrial production. During explosive welding, the selection of various welding parameters has a crucial impact on the performance of the resulting composite plate. Through multiple experiments, the present invention has identified appropriate process parameters for explosive welding of a CoCrNi medium-entropy alloy and Q235B steel.

[0035] Before explosive welding, the selected CoCrNi medium-entropy alloy is fully annealed to improve the plasticity of the alloy; Q235B steel is selected as hot-rolled steel plate, which has good plasticity and medium strength. Based on the performance characteristics of these two materials, it is guaranteed that the explosion process is easy to combine without cracking. In industrial production, a cast steel anvil with good rigidity is placed under the soft substrate to avoid severe bending and deformation of the composite plate during the explosion process. By controlling the detonation velocity of the explosives, the composite interface is combined in a small wave shape; the use of high-strength explosives can cause the substrate and composite plate to undergo severe work hardening during the explosion, thereby improving the strength of the material and compensating for the material strength loss caused by the complete annealing of the CoCrNi medium-entropy alloy before explosive composite. This technology fully utilizes the excellent work hardening ability of the soft CoCrNi medium-entropy alloy to ensure that the final composite plate can achieve a high strength without heat treatment.

[0036] The present invention obtains a composite plate of CoCrNi medium-entropy alloy and Q235B steel by explosive welding for the first time. The composite plate has an interface bonding rate greater than 99.2%, a yield strength greater than 420 MPa, a tensile strength greater than 500 MPa, an elongation after fracture greater than 35%, and an interface shear strength greater than 200 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Process structure of explosive welding of CoCrNi medium entropy alloy and Q235B steel;

[0038] Figure 2 Explosion welding samples of the CoCrNi medium entropy alloy and Q235B steel obtained in Example 1;

[0039] Figure 3 The interface morphology of the explosively welded composite plate of the CoCrNi medium entropy alloy and Q235B steel obtained in Example 1 shows a small wavy bonding interface. DETAILED DESCRIPTION

[0040] The following are preferred embodiments of the present invention, but not all embodiments. Without departing from the principle of this process innovation, any equivalent process transformation made by utilizing the contents of the present invention specification, or directly or indirectly applied in other related technical fields, shall be deemed to be within the scope of patent protection of this invention.

[0041] Example 1

[0042] CoCrNi medium entropy alloy plates and commercially available hot-rolled Q235B steel plates that had been fully softened and annealed at 1000°C for 2 hours were selected as raw materials, and the following steps were followed:

[0043] S1. Cut a Q235B steel plate with a length × width of 500 mm × 400 mm and a thickness of 10 mm, and a CoCrNi medium-entropy alloy plate with a length × width of 510 mm × 410 mm and a thickness of 2 mm. Grind one side of each alloy plate with an abrasive belt to remove surface oil and oxides, ensuring a surface roughness Ra ≤ 3 μm.

[0044] S2. Select a flat hard soil site as the blasting site and lay a 20mm layer of sand on the hard soil as the foundation.

[0045] S3. Place a cast steel anvil parallel to the ground with dimensions of 1000 mm x 1500 mm x 50 mm on the foundation and clean its surface.

[0046] S4. Place a 10 mm thick Q235B steel plate with the polished surface facing up on the center area of ​​the cast steel anvil.

[0047] S5. Arrange four aluminum alloy columnar support columns with a diameter of 12 mm and a height of 6 mm at the four corners of the Q235B steel plate surface.

[0048] S6. Place a 2 mm thick CoCrNi medium-entropy alloy sheet with the polished surface facing downward on a support column. Ensure that the center of the medium-entropy alloy and the center of the Q235B steel substrate are coaxial, and that the four sides are parallel to the four sides of the substrate.

[0049] S7. Surround the medium-entropy alloy with wooden strips, with the upper surface of the wooden strips 50 mm higher than the surface of the medium-entropy alloy, to serve as an explosive pool.

[0050] S8. Lay a layer of kraft paper at the bottom of the explosives pool to prevent direct contact between the explosives and the composite plate.

[0051] S9. Evenly spread the homemade high-strength mixed explosive in the explosive pool above the kraft paper, and arrange the detonating cap in the center of one of the short sides to ensure that three-quarters of the detonating cap is buried in the explosive. In this embodiment, the composition of the explosive is: 55% antimony-free rock ammonium nitrate explosive, 10% calcium carbonate powder, 10% sodium chloride, 5% silicon carbide powder, 5% perlite powder, 10% wood chips, and 5% chromium powder. All powders are dried and mixed evenly within 1 hour before use, and then sieved through a 40-mesh sieve, and the -40-mesh mixed powder is selected as the stand-by explosive. Before use, add 5% by volume of water to the mixed explosive and mix it evenly. The detonation velocity of the mixed explosive is 2500m / s, the strength is 18mm, and the density is: 0.8g / cm 3 .

[0052] S10. Detonating the detonator through the connecting wire and the detonator to obtain a CoCrNi medium-entropy alloy and Q235B steel composite plate.

[0053] The resulting explosively welded plates were surface cleaned, leveled, and their cracked and collapsed edges removed, and finally ultrasonically inspected.

[0054] The interface bonding rate of the CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate prepared by this process is 99.5%, the yield strength is 438 MPa, the tensile strength is 515 MPa, the elongation after fracture is 36.7%, and the interface shear strength is 212 MPa.

[0055] Example 2

[0056] CoCrNi medium entropy alloy plates that had been completely softened and annealed at 1000°C for 2 hours and commercially available hot-rolled Q235B steel plates were selected as raw materials and the following steps were followed:

[0057] S1. Cut a Q235B steel plate with a length × width of 600 mm × 500 mm and a thickness of 30 mm, and a CoCrNi medium-entropy alloy plate with a length × width of 610 mm × 510 mm and a thickness of 3 mm. Grind one side of each alloy plate with an abrasive belt to remove surface oil and oxides, ensuring a surface roughness Ra ≤ 3 μm.

[0058] S2. Select a flat hard soil site as the blasting site and lay a 20mm layer of sand on the hard soil as the foundation.

[0059] S3. Place a cast steel anvil parallel to the ground with dimensions of 1000 mm x 1500 mm x 50 mm on the foundation and clean its surface.

[0060] S4. Place a 30 mm thick Q235B steel plate with the polished surface facing up on the center area of ​​the cast steel anvil.

[0061] S5. Arrange four aluminum alloy columnar support columns with a diameter of 12 mm and a height of 6 mm at the four corners of the Q235B steel plate surface.

[0062] S6. Place a 3 mm thick CoCrNi medium-entropy alloy sheet with the polished surface facing downward on a support column. Ensure that the center of the medium-entropy alloy and the center of the Q235B steel substrate are coaxial, and that the four sides are parallel to the four sides of the substrate.

[0063] S7. Surround the medium-entropy alloy with wooden strips, with the upper surface of the wooden strips 60mm above the surface of the medium-entropy alloy, to serve as an explosive pool.

[0064] S8. Lay a layer of kraft paper at the bottom of the explosives pool to prevent direct contact between the explosives and the composite plate.

[0065] S9. Evenly spread the homemade high-strength mixed explosive in the explosive pool above the kraft paper, and arrange the detonating cap in the center of one of the short sides to ensure that three-quarters of the detonating cap is buried in the explosive. In this embodiment, the composition of the explosive is: 60% antimony-free rock ammonium nitrate explosive, 15% calcium carbonate powder, 5% sodium chloride, 5% silicon carbide powder, 5% perlite powder, 5% wood chips, and 5% chromium powder. All powders are dried and mixed evenly within 1 hour before use, and then sieved through a 40-mesh sieve, and the -40-mesh mixed powder is selected as the stand-by explosive. Before use, add 5% by volume of water to the mixed explosive and mix it evenly. The detonation velocity of the mixed explosive is 2700m / s, the strength is 18mm, and the density is: 0.83g / cm 3 .

[0066] S10. Detonating the detonator through the connecting wire and the detonator to obtain a CoCrNi medium-entropy alloy and Q235B steel composite plate.

[0067] The resulting explosively welded plates were surface cleaned, leveled, and their cracked and collapsed edges removed, and finally ultrasonically inspected.

[0068] The interface bonding rate of the CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate prepared by this process is 99.6%, the yield strength is 435 MPa, the tensile strength is 512 MPa, the elongation after fracture is 37.1%, and the interface shear strength is 213 MPa.

[0069] Example 3

[0070] CoCrNi medium entropy alloy plates and commercially available hot-rolled Q235B steel plates that had been fully softened and annealed at 1000°C for 2 hours were selected as raw materials, and the following steps were followed:

[0071] S1. Cut a Q235B steel plate with a length × width × width of 800 mm × 600 mm and a thickness of 40 mm, and a CoCrNi medium-entropy alloy plate with a length × width of 810 mm × 610 mm and a thickness of 5 mm. Grind one side of each alloy plate with an abrasive belt to remove surface oil and oxides, ensuring a surface roughness Ra ≤ 3 μm.

[0072] S2. Select a flat hard soil site as the blasting site and lay a 20mm layer of sand on the hard soil as the foundation.

[0073] S3. Place a cast steel anvil parallel to the ground with dimensions of 1000 mm x 1500 mm x 50 mm on the foundation and clean its surface.

[0074] S4. Place a 40 mm thick Q235B steel plate with the polished surface facing up on the center area of ​​the cast steel anvil.

[0075] S5. Arrange four aluminum alloy columnar support columns with a diameter of 12 mm and a height of 6 mm at the four corners of the Q235B steel plate surface.

[0076] S6. Place a 5 mm thick CoCrNi medium-entropy alloy sheet with the polished surface facing downward on a support column. Ensure that the center of the medium-entropy alloy and the center of the Q235B steel substrate are coaxial, and that the four sides are parallel to the four sides of the substrate.

[0077] S7. Surround the medium-entropy alloy with wooden strips, with the upper surface of the wooden strips 70mm above the surface of the medium-entropy alloy, to serve as an explosive pool.

[0078] S8. Lay a layer of kraft paper at the bottom of the explosives pool to prevent direct contact between the explosives and the composite plate.

[0079] S9. Evenly spread the homemade high-strength mixed explosive in the explosive pool above the kraft paper, and arrange the detonating cap in the center of one of the short sides to ensure that three-quarters of the detonating cap is buried in the explosive. In this embodiment, the composition of the explosive is: 60% antimony-free rock ammonium nitrate explosive, 10% calcium carbonate powder, 5% sodium chloride, 5% silicon carbide powder, 5% perlite powder, 5% wood chips, and 10% chromium powder. All powders are dried and mixed evenly within 1 hour before use, and then sieved through a 40-mesh sieve, and the -40-mesh mixed powder is selected as the stand-by explosive. Before use, add 5% by volume of water to the mixed explosive and mix it evenly. The detonation velocity of the mixed explosive is 3000m / s, the strength is 22mm, and the density is: 0.9g / cm 3 .

[0080] S10. Detonating the detonator through the connecting wire and the detonator to obtain a CoCrNi medium-entropy alloy and Q235B steel composite plate.

[0081] The resulting explosively welded plates were surface cleaned, leveled, and their cracked and collapsed edges removed, and finally ultrasonically inspected.

[0082] The interface bonding rate of the CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate prepared by this process is 99.2%, the yield strength is 421 MPa, the tensile strength is 503 MPa, the elongation after fracture is 35.2%, and the interface shear strength is 202 MPa.

[0083] Example 4

[0084] CoCrNi medium entropy alloy plates and commercially available hot-rolled Q235B steel plates that had been fully softened and annealed at 1000°C for 2 hours were selected as raw materials, and the following steps were followed:

[0085] S1. Cut a Q235B steel plate with a length × width of 700 mm × 500 mm and a thickness of 20 mm, and a CoCrNi medium-entropy alloy plate with a length × width of 710 mm × 510 mm and a thickness of 4 mm. Grind one side of each alloy plate with an abrasive belt to remove surface oil and oxides, ensuring a surface roughness Ra ≤ 3 μm.

[0086] S2. Select a flat hard soil site as the blasting site and lay a 20mm layer of sand on the hard soil as the foundation.

[0087] S3. Place a cast steel anvil parallel to the ground with dimensions of 1000 mm x 1500 mm x 50 mm on the foundation and clean its surface.

[0088] S4. Place a 20 mm thick Q235B steel plate with the polished surface facing up on the center area of ​​the cast steel anvil.

[0089] S5. Arrange four aluminum alloy columnar support columns with a diameter of 12 mm and a height of 6 mm at the four corners of the Q235B steel plate surface.

[0090] S6. Place a 4 mm thick CoCrNi medium-entropy alloy sheet with the polished surface facing downward on a support column. Ensure that the center of the medium-entropy alloy and the center of the Q235B steel substrate are coaxial, and that the four sides are parallel to the four sides of the substrate.

[0091] S7. Surround the medium-entropy alloy with wooden strips, with the upper surface of the wooden strips 65mm above the surface of the medium-entropy alloy, to serve as an explosive pool.

[0092] S8. Lay a layer of kraft paper at the bottom of the explosives pool to prevent direct contact between the explosives and the composite plate.

[0093] S9. Evenly spread the homemade high-strength mixed explosive in the explosive pool above the kraft paper, and arrange the detonating cap in the center of one of the short sides to ensure that three-quarters of the detonating cap is buried in the explosive. In this embodiment, the composition of the explosive is: 65% antimony-free rock ammonium nitrate explosive, 10% calcium carbonate powder, 5% sodium chloride, 5% silicon carbide powder, 5% perlite powder, 5% wood chips, and 5% chromium powder. All powders are dried and mixed evenly within 1 hour before use, and then sieved through a 40-mesh sieve, and the -40-mesh mixed powder is selected as the stand-by explosive. Before use, add 5% by volume of water to the mixed explosive and mix it evenly. The detonation velocity of the mixed explosive is 2700m / s, the strength is 18mm, and the density is: 0.82g / cm 3 .

[0094] S10. Detonating the detonator through the connecting wire and the detonator to obtain a CoCrNi medium-entropy alloy and Q235B steel composite plate.

[0095] The resulting explosively welded plates were surface cleaned, leveled, and their cracked and collapsed edges removed, and finally ultrasonically inspected.

[0096] The interface bonding rate of the CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate prepared by this process is 99.5%, the yield strength is 423 MPa, the tensile strength is 508 MPa, the elongation after fracture is 35.9%, and the interface shear strength is 210 MPa.

[0097] Example 5

[0098] CoCrNi medium entropy alloy plates that had been completely softened and annealed at 1000°C for 2 hours and commercially available hot-rolled Q235B steel plates were selected as raw materials and the following steps were followed:

[0099] S1. Cut a Q235B steel plate with a length × width of 800 mm × 400 mm and a thickness of 35 mm, and a CoCrNi medium-entropy alloy plate with a length × width of 810 mm × 410 mm and a thickness of 2.5 mm. Grind one side of each alloy plate with an abrasive belt to remove surface oil and oxides, ensuring a surface roughness Ra ≤ 3 μm.

[0100] S2. Select a flat hard soil site as the blasting site and lay a 20mm layer of sand on the hard soil as the foundation.

[0101] S3. Place a cast steel anvil parallel to the ground with dimensions of 1000 mm x 1500 mm x 50 mm on the foundation and clean its surface.

[0102] S4. Place a 35mm thick Q235B steel plate with the polished surface facing up on the center area of ​​the cast steel anvil.

[0103] S5. Arrange four aluminum alloy columnar support columns with a diameter of 12 mm and a height of 6 mm at the four corners of the Q235B steel plate surface.

[0104] S6. Place a 2.5 mm thick CoCrNi medium-entropy alloy sheet with the polished surface facing downward on a support column. Ensure that the center of the medium-entropy alloy and the center of the Q235B steel substrate are coaxial, and that the four sides are parallel to the four sides of the substrate.

[0105] S7. Surround the medium-entropy alloy with wooden strips, with the upper surface of the wooden strips 60mm above the surface of the medium-entropy alloy, to serve as an explosive pool.

[0106] S8. Lay a layer of kraft paper at the bottom of the explosives pool to prevent direct contact between the explosives and the composite plate.

[0107] S9. Evenly spread the homemade high-strength mixed explosive in the explosive pool above the kraft paper, and arrange the detonating cap in the center of one of the short sides to ensure that three-quarters of the detonating cap is buried in the explosive. In this embodiment, the composition of the explosive is: 58% antimony-free rock ammonium nitrate explosive, 5% calcium carbonate powder, 5% sodium chloride, 10% silicon carbide powder, 10% perlite powder, 5% wood chips, and 7% chromium powder. All powders are dried and mixed evenly within 1 hour before use, and then sieved through a 40-mesh sieve, and the -40-mesh mixed powder is selected as the stand-by explosive. Before use, add 5% by volume of water to the mixed explosive and mix it evenly. The detonation velocity of the mixed explosive is 2800m / s, the strength is 20mm, and the density is: 0.88g / cm 3 .

[0108] S10. Detonating the detonator through the connecting wire and the detonator to obtain a CoCrNi medium-entropy alloy and Q235B steel composite plate.

[0109] The resulting explosively welded plates were surface cleaned, leveled, and their cracked and collapsed edges removed, and finally ultrasonically inspected.

[0110] The interface bonding rate of the CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate prepared by this process is 99.3%, the yield strength is 430 MPa, the tensile strength is 512 MPa, the elongation after fracture is 36.2%, and the interface shear strength is 215 MPa.

[0111] Comparative Example 1

[0112] Other conditions were the same as those in Example 1, except that the CoCrNi medium-entropy alloy was not annealed before explosive cladding. That is, the composite plate material was a hard CoCrNi medium-entropy alloy. Since the hard medium-entropy alloy has high strength and poor plasticity, it cannot withstand strong plastic deformation during the explosive cladding process. Therefore, after the explosion, the strong impact force generated by the explosives caused the medium-entropy alloy composite plate to be cracked, and the cladding failed.

[0113] Comparative Example 2

[0114] Other conditions were the same as in Example 1, except that an 80-mesh sieve was used for screening the mixed explosive. Since calcium carbonate and sodium chloride in the explosive components are prone to agglomeration, when a sieve finer than 40 mesh was used for screening, a large amount of agglomerated calcium carbonate and sodium chloride in the mixed explosive was screened out, resulting in a reduction in the content of calcium carbonate and sodium chloride in the explosive components after screening. The reduction in the content of these two components will cause the detonation velocity of the explosive to increase. Therefore, after screening with an 80-mesh sieve, the detonation velocity of the explosive was 3250 m / s, which exceeded the suitable detonation velocity range of the explosive shown in the present invention. After explosive composite, the interface was large and wavy, and the molten zone content was much higher than that in Example 1. The yield strength of the composite plate was only 400 MPa, the tensile strength was only 480 MPa, and the interface shear strength was only 165 MPa. The performance of the composite plate was lower than that of Example 1.

[0115] Comparative Example 3

[0116] Other conditions were the same as in Example 1, except that the explosive composition was changed to: 70% antimony-free rock ammonium nitrate explosive, 10% sodium chloride, 5% silicon carbide powder, 5% perlite powder, and 10% wood chips. This explosive composition omitted calcium carbonate, which reduces detonation velocity, and chromium powder, which increases brute force. With this composition ratio, the explosive had a detonation velocity of 3200 m / s and a brute force of 13 mm. The increased detonation velocity easily formed a large wavy interface, which facilitated the formation of a large melting zone. The reduced brute force reduced the force exerted during the explosion, resulting in a lower interfacial bonding rate. When explosive compounding was performed using this explosive composition, the interfacial bonding rate was only 28%.

Claims

1. A method for preparing a composite plate of CoCrNi medium entropy alloy and Q235B steel by explosive welding, characterized in that: The CoCrNi medium entropy alloy plate is annealed, and then sand, anvils, Q235B hot-rolled steel plates, support columns, medium entropy alloy plates, kraft paper, and explosives are laid in order from bottom to top on the explosion field. Then, explosive welding is performed to obtain a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate. The explosive has a detonation velocity of 2500-3000 m / s and a strength of 18-22 mm. The annealing temperature is 1000-1100°C and the annealing time is 1-2 hours; The thickness of the sand is 20-25 mm; The anvil is made of cast steel and has a thickness of 50-55 mm. The length and width of the anvil are both 1000-3000 mm; The explosive has the following composition by mass percentage: 55-65% antimony-free rock ammonium nitrate explosive, 5-15% calcium carbonate powder, 5-10% sodium chloride, 5-10% silicon carbide powder, 5-10% perlite powder, 5-10% sawdust, and 5-10% chromium powder; The mesh size of the explosive is -40 mesh, and the density of the explosive is 0.8~0.9g / cm 3 .

2. The method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate according to claim 1, characterized in that: The length × width × thickness of the Q235B hot-rolled steel plate is: 500-800 mm × 400-600 mm × 10-40 mm, and the length × width × thickness of the CoCrNi medium-entropy alloy plate is: 510-810 mm × 410-610 mm × 2-5 mm, and the length and width of the CoCrNi medium-entropy alloy plate are both greater than the length and width of the Q235B hot-rolled steel plate; The surface roughness Ra of the CoCrNi medium entropy alloy plate and the Q235B hot-rolled steel plate are both ≤3 μm.

3. The method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate according to claim 1 or 2, characterized in that: Support columns are arranged at the four corners of the surface of the Q235B hot-rolled steel plate, and the CoCrNi medium entropy alloy plate is placed above the support columns, ensuring that the center position of the CoCrNi medium entropy alloy plate and the center position of the Q235B hot-rolled steel plate are on the same axis, and the four sides of the CoCrNi medium entropy alloy plate are parallel to the four sides of the Q235B hot-rolled steel plate; The support column has a diameter of 10-12 mm and a height of 6-8 mm.

4. The method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate according to claim 1 or 2, characterized in that: The CoCrNi medium entropy alloy plate is surrounded by wooden strips on all sides, and the upper surface of the wooden strips is controlled to be higher than the surface of the CoCrNi medium entropy alloy plate to serve as an explosive pool. The depth of the explosive pool is 50-70 mm.

5. The method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate according to claim 1 or 2, characterized in that: A detonator is installed in the explosive, the detonator being installed at the center position of the short side direction of the Q235B steel plate and the CoCrNi medium entropy alloy plate, and then a lead is connected to the detonator, and finally the connecting lead is connected to a remote control detonating device. The detonator is detonated by a detonator through the connecting lead to complete the explosive welding, thereby obtaining an explosively welded composite plate of the CoCrNi medium entropy alloy and the Q235B steel; and three-quarters of the detonator is buried in the explosive.

6. The method for preparing a CoCrNi medium entropy alloy and Q235B steel explosively welded composite plate according to claim 1 or 2, characterized in that: The CoCrNi medium-entropy alloy and Q235B steel explosively welded composite plate has an interface bonding rate greater than 99.2%, a yield strength greater than 420 MPa, a tensile strength greater than 500 MPa, an elongation after fracture greater than 35%, and an interface shear strength greater than 200 MPa.

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