A multi-layer annular sandwich-type impregnated diamond drill bit and its preparation method

Abstract

The present invention discloses a multi-layer annular sandwich-type impregnated diamond drill bit and a preparation method thereof. The multi-layer annular sandwich-type impregnated diamond drill bit comprises an annular sandwich-type working layer with a multi-layer structure. The annular sandwich-type working layer is composed of a wear-resistant layer and a weakening layer alternating along the annular sandwich-type working layer. The preparation method comprises the following steps: 3D printing the wear-resistant layer filamentary material and the weakening layer filamentary material together to obtain an annular sandwich-type working layer green body; degreasing the green body to obtain a degreased annular sandwich-type working layer green body; assembling the degreased annular sandwich-type working layer green body, a non-working layer, and a drill bit rigid body and then sintering the resulting product. During the drilling process of the diamond drill bit of the present invention, the weakening layer wears ahead of time, causing grooves to appear in the working layer, and the working surface automatically forms multiple groups of blade-like morphologies, resulting in high drilling efficiency. The drill bit adopts a fused wire manufacturing process, which meets the requirements of ultra-thinness and high precision of the wear-resistant layer and the weakening layer, saves manufacturing time, and achieves high efficiency and low cost in manufacturing.

Description

Technical Field

[0001] The invention mainly belongs to the fields of mechanical processing and powder metallurgy, and particularly relates to a multi-layer annular sandwich-type impregnated diamond drill bit and a preparation method thereof. Background Art

[0002] Because traditional processes make it difficult to manufacture ultra-thin and complex working layer lip structures, if extreme strata or complex conditions are encountered during drilling, ordinary drill bits will have low drilling efficiency or a short lifespan, significantly increasing construction costs and hindering the improvement and development of drilling technology. This structure designs the drill bit working layer into a multi-layer ring shape, in which both the wear-resistant layer and the weakening layer are thin layers. When the drill bit is working, the weakening layer wears out in advance, forming annular grooves on the lip surface, making the working surface have multiple sets of blade-like structures, reducing the contact area and increasing the drill bit pressure ratio, which is beneficial for drilling extreme strata. At the same time, the formation of multiple sets of grooves greatly promotes the discharge of rock cuttings and the cooling of the matrix, increasing the lifespan of the drill bit and improving drilling efficiency. The present invention adopts a fused filament manufacturing process in the preparation of the wear-resistant layer and the weakening layer, using two different filaments for simultaneous printing and integrated molding to obtain a green body, breaking the limitations of traditional processes, reducing manufacturing time, and achieving high efficiency and low cost in manufacturing. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the first object of the present invention is to provide a multi-layer annular sandwich-type diamond-impregnated drill bit.

[0004] The second object of the present invention is to provide a method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a multi-layer annular sandwich impregnated diamond drill bit, which comprises an annular sandwich working layer with a multi-layer structure. The annular sandwich working layer is divided into N layers along the radial direction of the annular sandwich working layer, and is composed of wear-resistant layers and weakened layers alternating with each other, wherein the outermost layer and the innermost layer are both wear-resistant layers, and are thicker than the other layers; the wear-resistant layer is composed of a metal matrix A and diamonds C dispersed in the metal matrix A, wherein the metal matrix A, The composition, by mass percentage, is: 20% to 70% tungsten carbide, 15% to 30% copper, 4% to 15% nickel, 4% to 6% manganese, 2% to 15% cobalt, and 2% to 8% tin; the weakened layer is composed of a metal matrix B and diamonds D dispersed in the metal matrix B, wherein the metal matrix B, by mass percentage, is: 30% to 75% copper, 5% to 20% tungsten carbide, 8% to 15% nickel, 4% to 15% cobalt, and 3% to 6% tin.

[0007] The annular sandwich-type working layer of the multi-layer annular sandwich-type diamond-impregnated drill bit provided by the present invention adopts a multi-layer structure, in which wear-resistant layers and weakened layers are alternately composed. Through the composition arrangement of the present invention, the weakened layer wears out in advance during operation, forming grooves, and the diamond working surface automatically forms multiple groups of blade-like structures to reduce the contact area, increase the drill bit specific pressure, and make it easier to crush rock, thereby facilitating the drilling of hard rock and improving drilling efficiency.

[0008] In the present invention, by controlling the formula of the wear-resistant layer and the weakened layer, the wear resistance of the wear-resistant layer is made as stronger as possible than that of the weakened layer. If the formula is unreasonable, the wear-resistant layer may have too low strength, which may lead to problems such as low drill efficiency and short life. If the strength of the weakened layer is too high, it will be difficult for the weakened layer to fall off, which may also cause low efficiency. If the strength of the weakened layer is too low, the drill performance will be poor, which will also cause low work efficiency.

[0009] In a preferred embodiment, N is 11 to 17. The inventors have discovered that controlling the number of layers within this range results in a multi-layered annular sandwich-type diamond-impregnated drill bit with optimal performance. In this case, after the weakened layer wears away, the wear-resistant layer cuts in like a blade, increasing the drill bit's specific pressure and making it easier to drill in hard formations.

[0010] In a preferred embodiment, the thickness of the outermost layer and the innermost layer of the annular sandwich working layer is 0.5 to 2 mm, preferably 1 to 1.75 mm, and the thickness of the remaining layers is 0.1 to 1 mm, preferably 0.5 to 1 mm.

[0011] The inventors have found that controlling the thickness of each layer within the above range ultimately leads to the highest drilling efficiency.

[0012] In the present invention, the thickness of each layer in the annular sandwich working layer refers to the distance formed between the inner diameter and the outer diameter of each layer in the radial direction.

[0013] In a preferred solution, in the wear-resistant layer, the mass ratio of the metal matrix A to the diamond C is 2 to 20:1, preferably 10 to 12:1.

[0014] In a preferred solution, the metal matrix A, by mass percentage, comprises the following components: 50% to 56% tungsten carbide, 23% to 27% copper, 6% to 7% nickel, 5% to 6% manganese, 6% to 7% cobalt, and 2% to 4% tin. In a preferred solution, in the weakened layer, the mass ratio of the metal matrix A to the diamond C is 4 to 40:1; preferably 6 to 12:1.

[0015] In a preferred embodiment, the metal matrix B comprises, by mass percentage, 65% to 70% copper, 12% to 15% tungsten carbide, 8% to 12% nickel, 4% to 5% cobalt, and 4% to 5% tin.

[0016] In a preferred embodiment, the multi-layer annular sandwich-type diamond-impregnated drill bit is composed of a drill bit rigid body, a non-working layer arranged on the drill bit rigid body, and an annular sandwich-type working layer arranged on the non-working layer.

[0017] In the present invention, the non-working layer is also composed of a metal matrix and diamonds, wherein the formula can be a conventional formula in the prior art.

[0018] In a preferred solution, the annular sandwich working layer has an axial height of 4 to 10 mm.

[0019] In a preferred solution, the annular sandwich working layer has a plurality of water inlets or water troughs evenly distributed in the circumferential direction.

[0020] The present invention provides a preparation method for a multi-layer annular sandwich impregnated diamond drill bit. The method comprises the following steps: mixing metal matrix powder, diamond powder, and a binder according to a designed ratio to obtain a wear-resistant layer mixture; kneading, granulating, and drawing the wear-resistant layer mixture to obtain a wear-resistant layer filament; mixing metal matrix powder, diamond powder, and a binder according to a designed ratio to obtain a weakened layer mixture; kneading, granulating, and drawing the weakened layer mixture to obtain a weakened layer filament; 3D printing the wear-resistant layer filament and the weakened layer filament together to obtain an annular sandwich working layer green body; degreasing the green body to obtain a degreased annular sandwich working layer green body; assembling the degreased annular sandwich working layer green body, a non-working layer, and a drill bit rigid body and then sintering the assembled body to obtain a multi-layer annular sandwich impregnated diamond drill bit.

[0021] In a preferred embodiment, the particle size of the metal matrix powder is ≤75 μm, and the particle size of the diamond powder is ≤830 μm.

[0022] In a preferred solution, in the wear-resistant layer mixture, the mass ratio of (metal matrix powder+diamond powder):binder=4-9:1.

[0023] In a preferred solution, in the weakened layer mixture, the mass ratio of (metal matrix powder + diamond powder): binder = 4 to 9:1.

[0024] In a preferred embodiment, the binders in the wear-resistant layer mixture and the weakening layer mixture are composed as follows by mass percentage: 30% to 65% of polyvinyl alcohol, 10% to 25% of polyethylene terephthalate, 7% to 14% of hydroxyethyl methacrylate, 7% to 14% of acrylamide, 7% to 14% of polyethylene carboxyl polymer, 7% to 14% of epoxy resin, 3% to 5% of dibutyl phthalate, 3% to 5% of polyvinyl chloride, and 3% to 5% of N,N'-methylenebisacrylamide.

[0025] The binder of the present invention uses solid components as the main material, and the metal powders are bonded together through the molecular forces of the bonding system, namely van der Waals attraction and hydrogen bonding. The composition of the binder is controlled within the scope of the present invention, so that the prepared filaments have good flexibility, fluidity and uniformity, so that green blanks with uniform performance can be obtained by printing.

[0026] In a preferred solution, in the process of obtaining the wear-resistant layer filamentary material and the weakened layer filamentary material, the mixing temperature is 170-210° C., and the wire drawing speed is 1-5 rpm.

[0027] In a preferred solution, the diameters of the wear-resistant layer filaments and the weakening layer filaments are both 0.5-1 mm.

[0028] In the present invention, by first preparing the filamentous material and then performing melt extrusion molding, the uniformity of the material extruded from the nozzle can be fully guaranteed.

[0029] The preferred method is to place the wear-resistant layer filament and the weakening layer filament into corresponding feed ports of a dual-nozzle FDM printer for simultaneous 3D printing. Using dual nozzles to simultaneously print the two filaments improves the integrity of the drill bit, ultimately resulting in the best possible performance.

[0030] In a preferred embodiment, during the 3D printing process, the printing layer thickness is 0.1 mm to 0.5 mm, the printing speed is 30 mm / s to 60 mm / s, the printing platform temperature is 70°C to 120°C, the nozzle diameter is 0.2 mm to 0.8 mm, and the nozzle temperature is 120°C to 230°C.

[0031] In the actual operation process, the printing parameters are set first, and the model of the annular sandwich working layer is drawn on the computer. The model is imported into the slicing software to set the printing parameters, and then it is imported into the melt extrusion molding printer for printing. The wear-resistant layer filament material and the weakening layer filament material are placed in the double-nozzle FDM printer, and the corresponding printing models are matched in turn to print out the green body of the annular sandwich working layer.

[0032] In a preferred embodiment, the annular sandwich working layer green body is first placed in an organic solvent for solvent degreasing, and then subjected to thermal degreasing in a vacuum environment.

[0033] Further preferably, the organic solvent is at least one selected from n-hexane, n-heptane, trichloroethylene, carbon tetrachloride and trichloroethane.

[0034] Further preferably, the temperature of the solvent degreasing is 35° C. to 75° C., and the solvent degreasing time is 6 h to 10 h.

[0035] In a preferred embodiment, the thermal degreasing process is to use a heating rate of 8 to 12°C / min throughout the entire process, first heating to 180 to 220°C, keeping warm for 50 to 70 minutes, then heating to 430 to 470°C, keeping warm for 80 to 100 minutes, and then heating to 610 to 650°C, keeping warm for 90 to 110 minutes.

[0036] In the thermal debinding process of the present invention, based on the differences in the pyrolysis temperature ranges of different components of the binder, a gradient heating mode is adopted for step-by-step debinding, which can effectively ensure the integrity of the green body and the removal effect of the binder in the green body, and avoid the occurrence of debinding defects.

[0037] The preferred solution is that the sintering process is: heating the temperature to 280-320°C at a heating rate of 50-70°C / min, and controlling the sintering pressure to 50-70 kg / cm 2 Then, the temperature is raised to 480-520°C at a heating rate of 60-80°C / min, and the sintering pressure is controlled at 60-80 kg / cm 2 Then, the temperature is raised to 830-870°C at a heating rate of 80-120°C / min, and the sintering pressure is controlled at 80-120 kg / cm 2 Then, heat up to 950℃~980℃ at 120℃~150℃ / min and keep warm for 3~10min, and control the sintering pressure at 120Kg~180Kg / cm 2 , then cool to below 400℃ and release the pressure.

[0038] In the present invention, by controlling the sintering process within the above range, the performance of the obtained drill bit is optimized.

[0039] In the actual operation process, after complete cooling, the mold is demoulded and the threads, nozzles, water tanks, etc. are processed to obtain a multi-layer annular sandwich impregnated diamond drill bit.

[0040] Principles and advantages

[0041] The multi-layer annular sandwich-type diamond-impregnated drill bit disclosed herein has a multi-layered annular working layer, composed of alternating thin wear-resistant layers and weakened layers. During drilling, the weakened layers wear out prematurely, forming annular grooves. This automatically creates multiple blade-like structures on the working surface, making it easier to cut and crush rock, thereby improving rock crushing efficiency. The multiple grooves also provide excellent channels for flushing fluid, greatly facilitating the removal of rock cuttings and cooling the drill bit, thereby extending the life of the drill bit. Furthermore, the present invention utilizes a fused filament manufacturing process to simultaneously produce the thin wear-resistant layer and weakened layer, ultimately achieving the integrated molding of the multi-layer annular sandwich-type green body, saving manufacturing time and reducing manufacturing costs.

[0042] The present invention has the following advantages:

[0043] 1. When the multi-layer annular sandwich-type diamond-impregnated drill bit of the present invention is in operation, the weakened layer wears ahead to form annular grooves, giving the working surface a multiple-group blade-like structure. This reduces the contact area, increases the drill bit's specific pressure, and makes it easier to crush rock, thereby facilitating the drilling of hard rock. Simultaneously, the formation of multiple groups of grooves greatly promotes the discharge of rock cuttings and the cooling of the drill bit matrix, thereby increasing the life of the drill bit. In addition to elastic and plastic contact, the interface between the drill bit's working layer and the rock also experiences a strong cutting mechanical action, greatly improving drilling efficiency.

[0044] 2. Traditional processes are unable to manufacture ultra-thin complex structures. The present invention adopts the fused filament manufacturing process to prepare the wear-resistant layer and the weakening layer. Two different filaments are used for simultaneous printing and integrated molding to obtain a green body, which breaks the limitations of traditional processes, reduces manufacturing time, and achieves high efficiency and low cost in manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 , is a schematic diagram of a multi-layer annular sandwich-type impregnated diamond drill bit;

[0046] Figure 1 In the figure, 1-annular sandwich working layer, 2-non-working layer, 3-drill bit steel body.

[0047] Figure 2 , a top view of the annular sandwich working layer;

[0048] Figure 2 In the middle, 4-wear-resistant layer; 5-weakened layer; 6-sprue and water channel. DETAILED DESCRIPTION

[0049] like Figure 1 and Figure 2 As shown, the multi-layer annular sandwich impregnated diamond drill bit is composed of three parts: a multi-layer annular sandwich working layer (1), a non-working layer (2), and a drill bit rigid body (3). The multi-layer annular sandwich working layer (1) is formed by 3D printing by combining a thin wear-resistant layer (5) and a weakened layer (4) at intervals. When the drill bit is working, the weakened layer wears ahead to form grooves, automatically forming multiple groups of blade-like working lip surfaces. The multi-layer annular sandwich working layer (1), the non-working layer (2), and the drill bit rigid body (3) are hot-pressed and sintered into a whole by powder metallurgy.

[0050] Example 1

[0051] The drill bit has an outer diameter and inner diameter of Φ76 / 49mm. The outermost and innermost wear-resistant layers are 1.75mm thick. The thin wear-resistant layer is 1.0mm thick, and the weakened layer is 0.5mm thick. The drill bit has eight wear-resistant layers (including inner and outer layers) and seven weakened layers. The drill bit is designed with eight nozzles and water troughs. The wear-resistant layer formula: The mass ratio of metal matrix powder to diamond powder is 10:1, of which the metal matrix powder accounts for 56% tungsten carbide powder, 23% copper powder, 6% nickel powder, 6% manganese powder, 6% cobalt powder, and 3% tin powder.

[0052] Weakened layer formula: The ratio of metal matrix powder to diamond powder is 6:1, of which copper powder accounts for 65% of the metal matrix powder, tungsten carbide powder accounts for 15%, nickel powder accounts for 10%, cobalt powder accounts for 5%, and tin powder accounts for 5%.

[0053] The manufacturing process is as follows:

[0054] ① Refining: Mix the powder materials required for each structural layer with the binder in proportion, then put the mixed materials into the internal mixer for internal mixing and granulation, and finally put the granular materials into the wire drawing machine to obtain the filamentous materials required for printing the wear-resistant layer and the weakening layer.

[0055] The ratio of the binder is: the mass ratio of powder material to binder is 6:1; the composition of the binder is: polyvinyl alcohol accounts for 43%, polyethylene terephthalate accounts for 18%, hydroxyethyl methacrylate accounts for 8%, acrylamide accounts for 8%, polyethylene carboxyl polymer accounts for 7%, epoxy resin accounts for 7%, dibutyl phthalate accounts for 3%, polyvinyl chloride accounts for 3%, and N,N'-methylenebisacrylamide accounts for 3%.

[0056] ② Printing: A multi-layer annular sandwich-type diamond-impregnated drill bit working layer model was created on a computer. The model was imported into the slicing software of a dual-nozzle FDM printer to set the printing parameters. Two filaments were placed into the corresponding feed ports of the dual-nozzle FDM printer and printed to obtain a green body. The printing layer thickness was 0.2 mm, the printing speed was 50 mm / s, the printing platform temperature was 95°C, the nozzle diameter was 0.4 mm, and the nozzle temperature was 200°C.

[0057] ③ Degreasing: In the first stage, solvent degreasing is adopted to place the multi-layer annular sandwich working layer green body into a digital display constant temperature water bath for degreasing; in the second stage, thermal degreasing is adopted to place the multi-layer annular sandwich working layer green body into a degreasing furnace for degreasing.

[0058] The specific implementation method of the degreasing process is as follows: the solvent used in the first stage of solvent degreasing is a mixed solvent of n-heptane, trichloroethylene, carbon tetrachloride and trichloroethane, the temperature of this stage is 50°C, and the degreasing time is 8 hours; in the second stage of thermal degreasing, it includes three insulation processes under vacuum, the temperature of the first insulation stage is 200°C, and the insulation time is 60 minutes; the temperature of the second insulation stage is 450°C, and the insulation time is 90 minutes; the temperature of the third insulation stage is 630°C, and the insulation time is 100 minutes; the whole process adopts a heating rate of 10°C / min.

[0059] ④ Sintering: The degreased multi-layer annular sandwich working layer is placed in a mold, assembled with the non-working layer and the drill bit rigid body, and then placed in a sintering furnace for sintering. The sintering process is carried out under a protective atmosphere, with multiple insulation sections and gradual temperature increase.

[0060] The specific implementation of the sintering process is as follows: when the sintering temperature is lower than 300℃, the heating rate is 60℃ / min, and the sintering pressure is 60Kg / cm 2 Then the temperature was raised to 500℃ at a heating rate of 70℃ / min and the sintering pressure was 70Kg / cm 2 Then the temperature was raised to 840℃ at a heating rate of 100℃ / min and the sintering pressure was 100Kg / cm 2 Then, the temperature was raised to 980℃ at a heating rate of 130℃ / min and kept at 980℃ for 5min. The sintering pressure was 150Kg / cm 2 , then stop heating and cool naturally. After the temperature drops below 400℃, release the pressure. After complete cooling, demould and process the threads, nozzles, water tanks, etc. to obtain a multi-layer annular sandwich impregnated diamond drill bit with a service life of 110m and a drilling speed of 6.5m / h.

[0061] Example 2

[0062] The drill bit's outer and inner diameters are Φ101 / 83mm. The outermost and innermost wear-resistant layers are 1.0mm thick; the thin wear-resistant layer is 0.8mm thick, and the weakened layer is 0.5mm thick. There are a total of seven wear-resistant layers (including the inner and outer layers) and six weakened layers. The drill bit is designed with 10 nozzles and troughs. The wear-resistant layer formula: The metal matrix powder to diamond powder ratio is 12:1, with tungsten carbide powder accounting for 50% of the metal matrix powder, copper powder accounting for 27%, nickel powder accounting for 7%, manganese powder accounting for 6%, cobalt powder accounting for 7%, and tin powder accounting for 3%.

[0063] Formula of the weakened layer: The ratio of metal matrix powder to diamond powder is 5:1, wherein the copper powder accounts for 70% of the metal matrix powder, the tungsten carbide powder accounts for 12%, the nickel powder accounts for 10%, the cobalt powder accounts for 4%, and the tin powder accounts for 4%.

[0064] The manufacturing process is as follows:

[0065] ① Refining: Mix the powder materials required for each structural layer with the binder in proportion, then put the mixed materials into the internal mixer for internal mixing and granulation, and finally put the granular materials into the wire drawing machine to obtain the filamentous materials required for printing the wear-resistant layer and the weakening layer.

[0066] The ratio of the binder is: the mass ratio of the powder material to the binder is 6:1; the composition of the binder is: polyvinyl alcohol accounts for 48%, polyethylene terephthalate accounts for 15%, hydroxyethyl methacrylate accounts for 7%, acrylamide accounts for 7%, polyvinyl carboxyl polymer accounts for 7%, epoxy resin accounts for 7%, dibutyl phthalate accounts for 3%, polyvinyl chloride accounts for 3%, and N,N'-methylenebisacrylamide accounts for 3%.

[0067] ② Printing: A multi-layer annular sandwich-type diamond-impregnated drill bit working layer model was created on a computer. The model was imported into the slicing software of a dual-nozzle FDM printer to set the printing parameters. Two filaments were placed into the corresponding feed ports of the dual-nozzle FDM printer and printed to obtain a green body. The printing layer thickness was 0.2 mm, the printing speed was 50 mm / s, the printing platform temperature was 95°C, the nozzle diameter was 0.4 mm, and the nozzle temperature was 200°C.

[0068] ③ Degreasing: In the first stage, solvent degreasing is adopted to place the multi-layer annular sandwich working layer green body into a digital display constant temperature water bath for degreasing; in the second stage, thermal degreasing is adopted to place the multi-layer annular sandwich working layer green body into a degreasing furnace for degreasing.

[0069] The specific implementation method of the degreasing process is as follows: the solvent used in the first stage of solvent degreasing is a mixed solvent of n-heptane, trichloroethylene, carbon tetrachloride and trichloroethane, the temperature of this stage is 50°C, and the degreasing time is 8 hours; in the second stage of thermal degreasing, it includes three insulation processes under vacuum, the temperature of the first insulation stage is 200°C, and the insulation time is 60 minutes; the temperature of the second insulation stage is 450°C, and the insulation time is 90 minutes; the temperature of the third insulation stage is 630°C, and the insulation time is 100 minutes; the whole process adopts a heating rate of 10°C / min.

[0070] ④ Sintering: The degreased multi-layer annular sandwich working layer is placed in a mold, assembled with the non-working layer and the drill bit rigid body, and then placed in a sintering furnace for sintering. The sintering process is carried out under a protective atmosphere, with multiple insulation sections and gradual temperature increase.

[0071] The specific implementation of the sintering process is as follows: when the sintering temperature is lower than 300℃, the heating rate is 60℃ / min, and the sintering pressure is 60Kg / cm 2Then the temperature was raised to 500℃ at a heating rate of 70℃ / min and the sintering pressure was 70Kg / cm 2 Then the temperature was raised to 850℃ at a heating rate of 100℃ / min and the sintering pressure was 100Kg / cm 2 Then, the temperature was raised to 970℃ at a heating rate of 130℃ / min and kept at 970℃ for 6min. The sintering pressure was 150Kg / cm 2 , then stop heating and cool naturally. After the temperature drops below 400℃, release the pressure. After complete cooling, demould and process the threads, nozzles, water tanks, etc. to obtain a multi-layer annular sandwich impregnated diamond drill bit with a service life of 100m and a drilling speed of 6m / h.

[0072] Comparative Example 1

[0073] All other conditions were the same as in Example 1, except that the annular sandwich working layer was not separated into layers, and instead, the wear-resistant layer was prepared using the same formulation to obtain a monolithic annular sandwich working layer. The blade-like structure could not be formed, significantly reducing the efficiency of the drill bit, increasing the drill bit pressure, and affecting the ability to mine hard formations.

[0074] Comparative Example 2

[0075] All other conditions were the same as in Example 1, except that the weakening layer formulation contained 40% copper powder, 40% tungsten carbide powder, 12% nickel powder, 4% cobalt powder, and 4% tin powder in the metal matrix powder. As a result, the weakening layer was difficult to remove and the blade-like structure formed slowly, seriously affecting the operating efficiency of the drill bit.

Claims

1. A multi-layer annular sandwich-type impregnated diamond drill bit, characterized by: The multi-layer annular sandwich impregnated diamond drill bit is composed of a drill bit rigid body, a non-working layer arranged on the drill bit rigid body, and an annular sandwich working layer arranged on the non-working layer; The annular sandwich working layer is divided into N layers along the radial direction of the annular sandwich working layer, and is composed of wear-resistant layers and weakened layers alternatingly, wherein the outermost layer and the innermost layer are both wear-resistant layers, and the thickness of each layer is greater than that of the other layers; Said N is 11 to 17; The thickness of the outermost layer and the innermost layer of the annular sandwich working layer is 0.5 to 2 mm, and the thickness of the remaining layers is 0.1 to 1 mm; The wear-resistant layer is composed of a metal matrix A and diamonds C dispersed in the metal matrix A. In the wear-resistant layer, the mass ratio of the metal matrix A to the diamonds C is 2 to 20:

1. The metal matrix A, in terms of mass percentage, comprises the following components: 50% to 56% tungsten carbide, 23% to 27% copper, 6% to 7% nickel, 5% to 6% manganese, 6% to 7% cobalt, and 2% to 4% tin. The weakened layer is composed of a metal matrix B and diamonds D dispersed in the metal matrix B. In the weakened layer, the mass ratio of the metal matrix B to the diamonds D is 4 to 40:

1. The metal matrix B, in terms of mass percentage, comprises the following components: 65% to 70% copper, 12% to 15% tungsten carbide, 8% to 12% nickel, 4% to 5% cobalt, and 4% to 5% tin. The annular sandwich working layer has an axial height of 4 to 10 mm; The annular sandwich working layer has a plurality of water inlets or water grooves evenly distributed in the circumferential direction.

2. The method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit according to claim 1, characterized in that: A wear-resistant layer mixture is obtained by mixing metal matrix powder, diamond powder and binder according to a designed proportion, and the wear-resistant layer mixture is then mixed, granulated and drawn to obtain a wear-resistant layer filamentary material. A weakened layer mixture is obtained by mixing metal matrix powder, diamond powder and binder according to a designed proportion, and the weakened layer mixture is then mixed, granulated and drawn to obtain a weakened layer filamentary material. The wear-resistant layer filamentary material and the weakened layer filamentary material are 3D printed together to obtain an annular sandwich type working layer green billet, and the green billet is degreased to obtain a degreased annular sandwich type working layer green billet. The degreased annular sandwich type working layer green billet, the non-working layer and the drill bit rigid body are assembled and sintered to obtain a multi-layer annular sandwich type impregnated diamond drill bit.

3. The method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit according to claim 2, characterized in that: The particle size of the metal matrix powder is ≤75 μm, and the particle size of the diamond powder is ≤830 μm; In the wear-resistant layer mixture, the mass ratio of (metal matrix powder + diamond powder): binder is 4 to 9:1; In the weakening layer mixture, the mass ratio is (metal matrix powder + diamond powder): binder = 4 to 9:

1.

4. The method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit according to claim 2, characterized in that: The binders in the wear-resistant layer mixture and the weakening layer mixture are composed of the following compositions by mass percentage: 30% to 65% polyvinyl alcohol, 10% to 25% polyethylene terephthalate, 7% to 14% hydroxyethyl methacrylate, 7% to 14% acrylamide, 7% to 14% polyvinyl carboxyl polymer, 7% to 14% epoxy resin, 3% to 5% dibutyl phthalate, 3% to 5% polyvinyl chloride, and 3% to 5% N,N'-methylenebisacrylamide.

5. The method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit according to claim 2, characterized in that: In the process of obtaining the wear-resistant layer filament material and the weakened layer filament material, the mixing temperature is 170-210°C, and the drawing speed is 1-5 rpm; The diameters of the wear-resistant layer filaments and the weakened layer filaments are both 0.5 to 1 mm; During the 3D printing process, the printing layer thickness is 0.1 mm to 0.5 mm, the printing speed is 30 mm / s to 60 mm / s, the printing platform temperature is 70°C to 120°C, the nozzle diameter is 0.2 mm to 0.8 mm, and the nozzle temperature is 120°C to 230°C.

6. The method for preparing a multi-layer annular sandwich-type impregnated diamond drill bit according to claim 2, characterized in that: The annular sandwich working layer green body is first placed in an organic solvent for solvent degreasing, and then subjected to thermal degreasing in a vacuum environment; The organic solvent is selected from at least one of n-hexane, n-heptane, trichloroethylene, carbon tetrachloride and trichloroethane; The temperature of the solvent degreasing is 35°C to 75°C, and the time of the solvent degreasing is 6h to 10h; The thermal degreasing process is as follows: the temperature is first raised to 180-220°C, kept warm for 50-70 minutes, then raised to 430-470°C, kept warm for 80-100 minutes, and then raised to 610-650°C, kept warm for 90-110 minutes, with a heating rate of 8-12°C / min throughout the process.

7. The method for preparing a multi-layer annular sandwich-type diamond-impregnated drill bit according to claim 2, characterized in that: The sintering process is as follows: heating the temperature to 280-320°C at a heating rate of 50-70°C / min, and controlling the sintering pressure at 50-70 kg / cm 2 Then, the temperature is raised to 480~520℃ at a heating rate of 60℃~80℃ / min, and the sintering pressure is controlled at 60Kg~80Kg / cm 2 Then, the temperature is raised to 830~870℃ at a heating rate of 80℃~120℃ / min, and the sintering pressure is controlled at 80Kg~120Kg / cm 2 Then, heat up to 950℃~980℃ at 120℃~150℃ / min and keep warm for 3~10min, and control the sintering pressure at 120Kg~180Kg / cm 2 , then cool to below 400℃ and release the pressure.

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