High-temperature brazing connection method for hard alloy drill bit

Abstract

The invention relates to a high-temperature brazing connection method of a hard alloy drill bit, which belongs to the technical field of brazing, and comprises the following steps: welding: in an argon environment, synchronously heating a steel body drill bit groove and the hard alloy drill bit to 600-700 DEG C, keeping the temperature, intensively aligning a heat source at a position 2-5cm away from the butt joint of the steel body drill bit groove and the hard alloy drill bit, raising the temperature to 950 DEG C, and keeping the temperature for 5-10min; and removing the heat source, inserting into a gradient cooling medium filled with argon, cooling and taking out after the gradient cooling medium submerges the steel body drill bit groove and the hard alloy drill bit by 5cm, thereby completing the welding of the steel body drill bit groove and the hard alloy drill bit. Through the synergistic effect of the composite brazing filler metal and the composite brazing flux, bubbles at welding points are effectively reduced, so that the welding positions have high strength, uniform and continuous brazing seams are formed in the whole welding face, the welding points can bear high shearing force and can also bear certain impact and bending stress, and the welding quality is improved. Meanwhile, permeation corrosion of media such as cooling liquid and cutting fluid can be effectively prevented.

Description

Technical Field

[0001] This invention belongs to the field of brazing technology, specifically relating to a high-temperature brazing connection method for cemented carbide drill bits. Background Technology

[0002] Brazing is a welding method that uses a filler metal with a melting point lower than that of the base metal to fill the gaps between solid workpieces through capillary action to achieve a metal connection. Unlike fusion welding, the base metal does not melt during brazing. Compared to pressure welding, brazing does not require applying pressure to the workpiece, and the welded joint has less deformation and a smooth surface. It is suitable for precision and complex components and combinations of dissimilar materials.

[0003] However, due to the mismatch in thermal expansion coefficients between carbide drill bits and steel drill bit grooves, cracks are easily generated during welding. Once local tensile stress forms and exceeds its tensile strength limit, micro-cracks will initiate and rapidly propagate, causing carbide drill bits to easily break during use. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature brazing connection method for cemented carbide drill bits in order to solve the above-mentioned problems.

[0005] The present invention achieves the above objectives through the following technical solutions:

[0006] This invention provides a high-temperature brazing connection method for cemented carbide drill bits, comprising the following steps:

[0007] Preparation of composite brazing filler metal: Select industrial pure aluminum, tin ingot, zinc ingot, and oxygen-free copper ingot. Remove the surface oxide film by grinding with a wire brush. Melt the industrial pure aluminum at 700-750℃, introduce argon gas, raise the temperature to 950℃ and add the oxygen-free copper ingot. Stir at 90 rpm for 20 min. Cool down to 750℃ and add the tin and zinc ingots. Stir at 60 rpm for 5-10 min to obtain a molten alloy liquid. Spray the molten alloy liquid through an atomizing nozzle under argon atmosphere, cool, and obtain a 100-200 mesh pre-made powder. Stir at 60 rpm for 10 min, vacuum dry, and obtain the alloy powder as the composite brazing filler metal.

[0008] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at a speed of 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, ethanol solution was added, and the mixture was stirred at 360 rpm for 30 min to obtain composite flux.

[0009] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0010] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, and fix the steel body drill bit groove and the carbide drill bit with a clamp;

[0011] Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 600-700℃ and maintain the temperature. Concentrate the heat source 2-5cm away from the joint between the steel drill bit groove and the carbide drill bit, raise the temperature to 950℃, and maintain it for 5-10 minutes. Remove the heat source and insert the drill bit into a gradient cooling medium filled with argon gas, with the gradient cooling medium covering the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

[0012] As a further optimization of the present invention, the raw materials for preparing the composite solder, by weight, include: 30-45 parts of industrial pure aluminum, 6-12 parts of tin ingots, 25-35 parts of zinc ingots and 3-5 parts of oxygen-free copper ingots.

[0013] As a further optimization of the present invention, the raw materials for preparing the composite flux, by weight, include: 15-20 parts potassium fluoroborate, 3-8 parts boron anhydride and 10-25 parts ethanol solution.

[0014] As a further optimization of the present invention, the raw materials for preparing the gradient cooling medium, by weight, include: 5-15 parts lime powder, 20-25 parts diatomaceous earth, 6-18 parts vermiculite, 35-45 parts volcanic rock particles and 40-55 parts bamboo charcoal particles.

[0015] As a further optimization of the present invention, the method for preparing the gradient cooling medium is as follows: lime powder, diatomaceous earth, vermiculite, volcanic rock particles and bamboo charcoal particles are mixed and stirred at 60 rpm for 40 min to obtain the gradient cooling medium.

[0016] As a further optimization of the present invention, when the heat source is concentrated at a distance of 2-5 cm from the joint between the steel drill bit groove and the carbide drill bit, the temperature is increased at a rate of 5°C / s.

[0017] As a further optimization of the present invention, the ethanol solution is a 75% aqueous ethanol solution.

[0018] As a further optimization of the present invention, the thickness of the alloy powder spread on the weld surface of the steel body drill bit groove is 0.3-0.6mm; the weld is filled with composite flux, and the composite flux overflowing the weld is scraped off with a scraper during filling.

[0019] As a further optimization of the present invention, the particle size of lime powder is 50-150μm, the particle size of diatomite is 75μm-1mm, the particle size of vermiculite is 1-3mm, the particle size of volcanic rock particles is 3-8mm, and the particle size of bamboo charcoal particles is 2-5mm.

[0020] The beneficial effects of this invention are as follows: This invention uses the synergistic effect of composite brazing filler metal and composite flux to effectively reduce the generation of air bubbles at the welding point, resulting in higher strength at the weld. The entire welding surface forms a uniform and continuous brazing seam, and the welding point can not only withstand high shear force, but also withstand a certain amount of impact and bending stress. At the same time, it can effectively prevent the penetration and corrosion of media such as coolant and cutting fluid. The use of gradient cooling medium solves the most difficult problem in welding cemented carbide to steel. No cracks will be generated when welding steel drill bit grooves and cemented carbide drill bits, increasing shear strength. Detailed Implementation

[0021] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0022] Unless otherwise specified, all methods used in this invention are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products.

[0023] In this invention, the cemented carbide drill bit is made of YG8 (K30) cemented carbide; the steel body drill bit groove is made of 40Cr steel.

[0024] Example 1

[0025] The gradient cooling medium is prepared by mixing 5 parts lime powder, 20 parts diatomaceous earth, 6 parts vermiculite, 35 parts volcanic rock particles and 40 parts bamboo charcoal particles, stirring at 60 rpm for 40 min to obtain the gradient cooling medium (the particle size of lime powder is 50 μm, the particle size of diatomaceous earth is 75 μm, the particle size of vermiculite is 1 mm, the particle size of volcanic rock particles is 3 mm and the particle size of bamboo charcoal particles is 2 mm).

[0026] Preparation of composite brazing alloy: 30 parts of industrial pure aluminum, 6 parts of tin, 25 parts of zinc, and 3 parts of oxygen-free copper were selected. The surface oxide film was removed by grinding with a wire brush. The industrial pure aluminum was melted at 700℃, argon gas was introduced, the temperature was raised to 950℃ and oxygen-free copper was added, and the mixture was stirred at 90 rpm for 20 min. The temperature was lowered to 750℃ and tin and zinc were added, and the mixture was stirred at 60 rpm for 5 min to obtain a molten alloy liquid. Under an argon atmosphere, the molten alloy liquid was sprayed out through an atomizing nozzle and cooled to obtain a 100-mesh pre-made powder. The powder was stirred at 60 rpm for 10 min and then vacuum dried to obtain the alloy powder as the composite brazing alloy.

[0027] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at a speed of 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, and 75% ethanol aqueous solution was added. The mixture was stirred at 360 rpm for 30 min to obtain the composite flux.

[0028] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0029] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove, with a thickness of 0.3mm. Butt the welding surface of the carbide drill bit with it. Fill the weld with composite flux. Use a scraper to remove the composite flux that overflows the weld. Use a clamp to fix the steel body drill bit groove and the carbide drill bit.

[0030] Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 600℃ and maintain the temperature. Concentrate the heat source 2cm away from the joint between the steel drill bit groove and the carbide drill bit, and raise the temperature to 950℃ at a rate of 5℃ / s, and maintain it for 5 minutes. Remove the heat source and insert the drill bit into a gradient cooling medium filled with argon gas. The gradient cooling medium should cover the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

[0031] Example 2

[0032] The gradient cooling medium is prepared by mixing 9 parts lime powder, 22 parts diatomaceous earth, 12 parts vermiculite, 40 parts volcanic rock particles and 50 parts bamboo charcoal particles, stirring at 60 rpm for 40 min to obtain the gradient cooling medium (the particle size of lime powder is 100 μm, the particle size of diatomaceous earth is 85 μm, the particle size of vermiculite is 2 mm, the particle size of volcanic rock particles is 5 mm and the particle size of bamboo charcoal particles is 3 mm).

[0033] Preparation of composite brazing alloy: 35 parts of industrial pure aluminum, 8 parts of tin, 30 parts of zinc, and 4 parts of oxygen-free copper were selected. The surface oxide film was removed by grinding with a wire brush. The industrial pure aluminum was melted at 725℃, argon gas was introduced, the temperature was raised to 950℃, oxygen-free copper was added, and the mixture was stirred at 90 rpm for 20 min. The temperature was lowered to 750℃, tin and zinc were added, and the mixture was stirred at 60 rpm for 6 min to obtain a molten alloy liquid. Under argon atmosphere, the molten alloy liquid was sprayed out through an atomizing nozzle and cooled to obtain 150-mesh pre-made powder. The powder was stirred at 60 rpm for 10 min and vacuum dried to obtain the alloy powder as the composite brazing alloy.

[0034] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, and 75% ethanol aqueous solution was added. The mixture was stirred at 360 rpm for 30 min to obtain the composite flux.

[0035] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0036] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove with a thickness of 0.4mm, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, scrape off the composite flux overflowing the weld with a scraper, and fix the steel body drill bit groove and the carbide drill bit with a clamp.

[0037] Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 650℃ and maintain the temperature. Concentrate the heat source 3cm away from the joint between the steel drill bit groove and the carbide drill bit, and raise the temperature to 950℃ at a rate of 5℃ / s, and maintain it for 8 minutes. Remove the heat source and insert the drill bit into a gradient cooling medium filled with argon gas. The gradient cooling medium should cover the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

[0038] Example 3

[0039] The gradient cooling medium is prepared by mixing 15 parts lime powder, 25 parts diatomaceous earth, 18 parts vermiculite, 45 parts volcanic rock particles and 55 parts bamboo charcoal particles, and stirring at 60 rpm for 40 min to obtain the gradient cooling medium (the particle size of lime powder is 150 μm, the particle size of diatomaceous earth is 1 mm, the particle size of vermiculite is 3 mm, the particle size of volcanic rock particles is 8 mm and the particle size of bamboo charcoal particles is 5 mm).

[0040] Preparation of composite brazing alloy: 45 parts of industrial pure aluminum, 12 parts of tin, 35 parts of zinc, and 5 parts of oxygen-free copper were selected. The surface oxide film was removed by grinding with a wire brush. The industrial pure aluminum was melted at 750℃, argon gas was introduced, the temperature was raised to 950℃, and the oxygen-free copper was added. The mixture was stirred at 90 rpm for 20 min, then cooled to 750℃, and the tin and zinc were added. The mixture was stirred at 60 rpm for 10 min to obtain a molten alloy liquid. Under an argon atmosphere, the molten alloy liquid was sprayed out through an atomizing nozzle and cooled to obtain a 200-mesh pre-formed powder. The powder was stirred at 60 rpm for 10 min and then vacuum dried to obtain the alloy powder as the composite brazing alloy.

[0041] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, and 75% ethanol aqueous solution was added. The mixture was stirred at 360 rpm for 30 min to obtain the composite flux.

[0042] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0043] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove with a thickness of 0.6mm, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, scrape off the composite flux overflowing the weld with a scraper, and fix the steel body drill bit groove and the carbide drill bit with a clamp.

[0044] Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 700℃ and maintain the temperature. Concentrate the heat source 5cm away from the joint between the steel drill bit groove and the carbide drill bit, and raise the temperature to 950℃ at a rate of 5℃ / s, and maintain it for 10 minutes. Remove the heat source and insert the drill bit into a gradient cooling medium filled with argon gas. The gradient cooling medium should cover the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

[0045] Comparative Example 1

[0046] The cooling medium is prepared by mixing 9 parts lime powder, 22 parts diatomite, 12 parts vermiculite, 40 parts volcanic rock particles and 50 parts bamboo charcoal particles, stirring at 60 rpm for 40 min to obtain the cooling medium (the particle size of lime powder, diatomite, vermiculite, volcanic rock particles and bamboo charcoal particles are all 100 μm).

[0047] Preparation of composite brazing alloy: 35 parts of industrial pure aluminum, 8 parts of tin, 30 parts of zinc, and 4 parts of oxygen-free copper were selected. The surface oxide film was removed by grinding with a wire brush. The industrial pure aluminum was melted at 725℃, argon gas was introduced, the temperature was raised to 950℃, oxygen-free copper was added, and the mixture was stirred at 90 rpm for 20 min. The temperature was lowered to 750℃, tin and zinc were added, and the mixture was stirred at 60 rpm for 6 min to obtain a molten alloy liquid. Under argon atmosphere, the molten alloy liquid was sprayed out through an atomizing nozzle and cooled to obtain 150-mesh pre-made powder. The powder was stirred at 60 rpm for 10 min and vacuum dried to obtain the alloy powder as the composite brazing alloy.

[0048] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, and 75% ethanol aqueous solution was added. The mixture was stirred at 360 rpm for 30 min to obtain the composite flux.

[0049] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0050] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove with a thickness of 0.4mm, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, scrape off the composite flux overflowing the weld with a scraper, and fix the steel body drill bit groove and the carbide drill bit with a clamp.

[0051] Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 650℃ and maintain the temperature. Concentrate the heat source 3cm away from the joint between the steel drill bit groove and the carbide drill bit, and raise the temperature to 950℃ at a rate of 5℃ / s, and maintain it for 8 minutes. Remove the heat source and insert the drill bit into a cooling medium filled with argon gas, with the cooling medium covering the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

[0052] Comparative Example 2

[0053] Preparation of composite brazing alloy: 35 parts of industrial pure aluminum, 8 parts of tin, 30 parts of zinc, and 4 parts of oxygen-free copper were selected. The surface oxide film was removed by grinding with a wire brush. The industrial pure aluminum was melted at 725℃, argon gas was introduced, the temperature was raised to 950℃, oxygen-free copper was added, and the mixture was stirred at 90 rpm for 20 min. The temperature was lowered to 750℃, tin and zinc were added, and the mixture was stirred at 60 rpm for 6 min to obtain a molten alloy liquid. Under argon atmosphere, the molten alloy liquid was sprayed out through an atomizing nozzle and cooled to obtain 150-mesh pre-made powder. The powder was stirred at 60 rpm for 10 min and vacuum dried to obtain the alloy powder as the composite brazing alloy.

[0054] Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, and 75% ethanol aqueous solution was added. The mixture was stirred at 360 rpm for 30 min to obtain the composite flux.

[0055] Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed;

[0056] Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove with a thickness of 0.4mm, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, scrape off the composite flux overflowing the weld with a scraper, and fix the steel body drill bit groove and the carbide drill bit with a clamp.

[0057] Welding: In an argon atmosphere, the steel drill bit groove and the carbide drill bit are simultaneously heated to 650℃ and maintained at that temperature. The heat source is then concentrated at a point 3cm from the joint between the steel drill bit groove and the carbide drill bit, and the temperature is increased to 950℃ at a rate of 5℃ / s, and maintained for 8 minutes. The heat source is then removed, and the parts are allowed to cool naturally at room temperature of 20℃ to complete the welding of the steel drill bit groove and the carbide drill bit.

[0058] Performance testing

[0059] According to GB / T 11363 "Test Method for Strength of Brazed Joints", the weld strength of the cemented carbide drill bit welded in the steel body drill bit groove using the methods of Examples 1-3 and Comparative Examples 1-2 was tested. The test results are shown in the table below.

[0060] project Shear strength / MPa Example 1 320 Example 2 323 Example 3 318 Comparative Example 1 301 Comparative Example 2 286

[0061] As can be seen from the table above, the carbide drill bits welded into the steel body drill bit groove using the methods of Examples 1-3 have strong shear strength. When using the carbide drill bits, it can be guaranteed that the drill bits will eventually be scrapped due to normal wear, rather than being damaged prematurely due to welding failure.

[0062] Comparing Comparative Example 1 with Example 2, which has the best numerical value among the examples, it can be found that Example 2, which uses a gradient cooling medium with different particle sizes, has stronger shear strength at the weld than the weld cooled by the cooling medium with the same particle size in Comparative Example 1. This shows that using a gradient cooling medium with different particle sizes to cool the weld can ensure that the cooling temperature changes in a gradient, so that the weld can achieve better shear strength.

[0063] Comparing Comparative Example 2 with Example 2, it can be found that the weld joint in Comparative Example 2, which was naturally cooled at room temperature of 20°C, does not have the same shear strength as the weld joint in Example 2, which was cooled by a gradient cooling medium.

[0064] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A high-temperature brazing connection method for cemented carbide drill bits, characterized in that, Includes the following steps: Preparation of composite brazing filler metal: Select industrial pure aluminum, tin ingot, zinc ingot, and oxygen-free copper ingot. Remove the surface oxide film by grinding with a wire brush. Melt the industrial pure aluminum at 700-750℃, introduce argon gas, raise the temperature to 950℃ and add the oxygen-free copper ingot. Stir at 90 rpm for 20 min. Cool down to 750℃ and add the tin and zinc ingots. Stir at 60 rpm for 5-10 min to obtain a molten alloy liquid. Spray the molten alloy liquid through an atomizing nozzle under argon atmosphere, cool, and obtain a 100-200 mesh pre-made powder. Stir at 60 rpm for 10 min, vacuum dry, and obtain the alloy powder as the composite brazing filler metal. Preparation of composite flux: Potassium fluoroborate and boron anhydride were dried in a drying oven at 105℃, and then added to a mechanical ball mill for ball milling at a speed of 335 r / s for 160 h. The uniformly mixed powder was transferred to a container, ethanol solution was added, and the mixture was stirred at 360 rpm for 30 min to obtain composite flux. Sample preparation: Grind the welded surfaces of the steel body drill bit groove and the carbide drill bit with sandpaper until the metal is exposed; Assembly of parts to be welded: Spread alloy powder evenly on the welding surface of the steel body drill bit groove, butt the welding surface of the carbide drill bit with it, fill the weld with composite flux, and fix the steel body drill bit groove and the carbide drill bit with a clamp; Welding: In an argon atmosphere, simultaneously heat the steel drill bit groove and the carbide drill bit to 600-700℃ and maintain the temperature. Concentrate the heat source 2-5cm away from the joint between the steel drill bit groove and the carbide drill bit, raise the temperature to 950℃, and maintain it for 5-10 minutes. Remove the heat source and insert the drill bit into a gradient cooling medium filled with argon gas, with the gradient cooling medium covering the steel drill bit groove and the carbide drill bit by 5cm. After cooling, remove the drill bit to complete the welding of the steel drill bit groove and the carbide drill bit.

2. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, The raw materials for preparing the composite solder, by weight, include: 30-45 parts of industrial pure aluminum, 6-12 parts of tin ingots, 25-35 parts of zinc ingots, and 3-5 parts of oxygen-free copper ingots.

3. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, The raw materials for preparing the composite flux, by weight, include: 15-20 parts potassium fluoroborate, 3-8 parts boron anhydride, and 10-25 parts ethanol solution.

4. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, The raw materials for preparing the gradient cooling medium, by weight, include: 5-15 parts lime powder, 20-25 parts diatomaceous earth, 6-18 parts vermiculite, 35-45 parts volcanic rock particles, and 40-55 parts bamboo charcoal particles.

5. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 4, characterized in that, The gradient cooling medium is prepared by mixing lime powder, diatomaceous earth, vermiculite, volcanic rock particles and bamboo charcoal particles, stirring at 60 rpm for 40 min to obtain the gradient cooling medium.

6. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, When the heat source is concentrated and heated at a distance of 2-5 cm from the joint between the steel drill bit groove and the carbide drill bit, the temperature rises at a rate of 5℃ / s.

7. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, The ethanol solution used is a 75% aqueous ethanol solution.

8. The high-temperature brazing connection method for a cemented carbide drill bit according to claim 1, characterized in that, The thickness of the alloy powder spread on the welded surface of the steel body drill bit groove is 0.3-0.6mm; the weld is filled with composite flux, and the composite flux overflowing the weld is scraped off with a scraper during filling.

9. A high-temperature brazing connection method for a cemented carbide drill bit according to claim 5, characterized in that, The lime powder has a particle size of 50-150μm, the diatomaceous earth has a particle size of 75μm-1mm, the vermiculite has a particle size of 1-3mm, the volcanic rock particles have a particle size of 3-8mm, and the bamboo charcoal particles have a particle size of 2-5mm.