High-altitude ball nose drill bit and method of making same

Abstract

The present application relates to the technical field of hard alloy material, and particularly relates to a high-altitude ball tooth drill bit and a preparation method thereof. The drill bit comprises a drill steel body and hard alloy ball teeth pressed into tooth holes, the hard alloy ball teeth mainly have a super-large WC powder as a framework, and WC-Co-Cr composite particles formed by fine-grained WC, Co and Cr3C2 are introduced; during preparation, the composite particles are first obtained, then the composite particles are low-energy mixed into the super-large WC framework powder, and the drill bit is prepared through drying, pressing, degreasing sintering, grinding and heating and pressing assembly. By retaining a discrete fine-grained WC enrichment area and controlling sintering magnetic saturation, the risk of continuous expansion of thermal cracks along the coarse WC grain boundary can be reduced, so that the ball teeth have wear resistance, impact resistance and use stability under high-altitude working conditions.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide materials technology, and in particular to a high-altitude ball tooth drill bit and its preparation method. Background Technology

[0002] In high-altitude mining and engineering rock drilling operations, ball-tooth drill bits typically need to operate continuously in environments with low air pressure, low temperature, large diurnal temperature variations, and strong abrasive effects from drying rock powder. As components that directly bear impact, wear, and thermal cycling, the state of the cemented carbide material in the ball teeth directly affects the drill bit's chipping, wear, and operational stability. In the current manufacturing of ultra-large grain cemented carbide mining alloys, wear resistance and toughness are often balanced by increasing the tungsten carbide grain size, adjusting the cobalt binder phase content, or changing the sintering process.

[0003] However, while ultra-large grain WC-Co cemented carbide is beneficial for improving the wear life of mining ball teeth, under high-altitude rock drilling conditions, the tooth crown heats up due to friction, and is then cooled by the low-temperature environment and flushing medium. This makes the area near the coarse WC grain boundaries prone to becoming a region of concentrated thermal stress. Simply increasing the cobalt phase content may weaken the wear resistance of the tooth crown; simply extending the grinding process or increasing the sintering strength may cause excessive dispersion of the fine-grained components, continuous cobalt pooling, or deviation of the carbon potential from the appropriate range, thereby inducing decarburized phases, free carbon, or localized structural inhomogeneity. Therefore, existing ball tooth materials still face the challenge of stably balancing a wear-resistant skeleton, a thermal crack-resistant structure, and a stable sintering carbon potential. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a high-altitude ball tooth drill bit and its preparation method, so as to solve the problem that it is difficult to simultaneously achieve the wear-resistant skeleton and hot crack suppression structure in existing ultra-large grain WC-Co mining ball teeth under stable carbon potential.

[0005] To achieve the above objectives, the present invention provides a method for preparing a high-altitude ball tooth drill bit, comprising the following steps: S1. Fine WC powder, Co powder, Cr3C2 powder and acetylene black are wet-milled in anhydrous ethanol, and paraffin ethanol solution is added to obtain WC-Co-Cr composite particle slurry. S2. Spray granulation, sieving and air classification of the WC-Co-Cr composite particle slurry to remove fine powder smaller than 10μm, and necking treatment of the classified particles to obtain WC-Co-Cr composite particles with D50 of 20.6-27.8μm and D90 of 34.8-43.5μm. S3. After wet mixing of the ultra-large WC powder, Co powder, and acetylene black, remove the grinding balls, then add the WC-Co-Cr composite particles and paraffin ethanol solution, and perform paddle-type low-speed mixing, drying, and granulation to obtain ball-tooth pressed powder; wherein, based on a total mass of 100 parts of non-volatile powder, the ultra-large WC powder is 83.30-84.95 parts, the Co powder is 6.60-7.45 parts, the WC-Co-Cr composite particles are 7.55-10.05 parts, and the acetylene black is 0.02-0.05 parts; S4. Press the ball tooth powder into a ball crown blank, and then sinter it under cold isostatic pressing and vacuum pressure to obtain a sintered ball tooth with a magnetic saturation rate of 82-88%. S5. After grinding, cleaning and drying, the sintered ball teeth are pressed into the heated drill bit steel body tooth hole, and after cooling, the high-altitude ball tooth drill bit is obtained.

[0006] Preferably, in step S1, based on a total mass of 100 parts of premixed solids, the fine WC powder comprises 65.90-66.48 parts, the Co powder comprises 30.50-31.44 parts, the Cr3C2 powder comprises 2.42-2.92 parts, and the acetylene black comprises 0.22-0.25 parts; the wet milling speed is 65-72 r / min, and the wet milling time is 7-8.5 h.

[0007] Preferably, in step S2, the inlet temperature of the spray granulation is 154-165℃, the outlet temperature is 82-86℃, and the rotation speed of the atomizing disc is 9800-11200 r / min; the neck connection treatment includes holding at 610-640℃ for 40-50 min in a hydrogen atmosphere, then switching to an argon atmosphere and holding at 760-800℃ for 25-35 min.

[0008] Preferably, in step S3, the ultra-large WC powder, Co powder, and acetylene black are wet-mixed at 45 r / min for 3 h and then the grinding balls are removed; the blade linear velocity of the paddle-type low-speed post-mixing is 0.30-0.45 m / s, and the mixing time is 30-45 min; the drying is vacuum drying at 68℃ and -0.085 MPa for 5 h; and the granulation is granulation through a 60-mesh sieve.

[0009] Preferably, in step S4, the pressing includes molding and cold isostatic pressing. The molding pressure is 210 MPa and the holding time is 8 s. The cold isostatic pressing pressure is 170 MPa and the holding time is 3 min. The vacuum pressure sintering includes: heating to 380℃ and holding for 60 min, then heating to 520℃ and holding for 90 min; evacuating to 6 Pa and then heating to 900℃ and holding for 45 min, then heating to 1280℃ and holding for 30 min; continuing to heat to 1435-1445℃ and holding for 60-65 min, and from the temperature reaching 1400℃, argon gas is introduced and the pressure is increased to 5.0-5.8 MPa.

[0010] Preferably, in step S5, the continuous contact time of a single tooth during grinding is controlled to be within 3 seconds, and the grinding fluid temperature is 18°C; after grinding, ultrasonic cleaning is performed for 10 minutes and drying is carried out at 80°C for 40 minutes; the drill bit steel body is a 42CrMo drill bit steel body, the tooth hole area of ​​the drill bit steel body is heated to 430-450°C, and the sintered ball tooth is pressed into the tooth hole within 32-35 seconds.

[0011] Furthermore, the present invention also provides a high-altitude ball tooth drill bit, which is prepared by the aforementioned method.

[0012] Preferably, the high-altitude ball tooth drill bit includes a drill bit body and cemented carbide ball teeth pressed into the tooth holes of the drill bit body, wherein discrete fine-grained WC enrichment regions formed by the WC-Co-Cr composite particles are distributed in the cemented carbide ball teeth.

[0013] Preferably, the cemented carbide ball teeth, calculated based on a total mass of 100 parts of non-volatile powder, include: 83.30-84.95 parts of ultra-large WC powder, 4.98-6.66 parts of fine WC powder, 9.45-9.83 parts of Co (converted amount), 0.18-0.29 parts of Cr3C2 (converted amount), and 0.040-0.073 parts of acetylene black (converted amount); the metallographic porosity of the cemented carbide ball teeth is Al2, Bo0, and Co0, and no η phase or free carbon is observed.

[0014] Preferably, the drill bit body is a 42CrMo drill bit body, the room temperature diameter of the tooth hole is 11.93-11.94 mm, the effective depth of the tooth hole is 13.0 mm, and the tooth body diameter of the cemented carbide ball tooth is 12.0 mm.

[0015] The beneficial effects of this invention are: This invention uses an ultra-large WC framework as the main wear-resistant phase in cemented carbide ball teeth, and first forms composite particles of fine WC, Co, and Cr3C2 before mixing them with the ultra-large WC framework powder. This arrangement prevents the fine-grained components from being completely and uniformly dispersed through conventional co-milling, but rather retains them as discrete fine-grained WC-rich regions after sintering. This facilitates the formation of crack deflection and stress dispersion sites near the coarse WC grain boundaries, thereby reducing the tendency for hot cracks to propagate continuously along the coarse grain boundaries. This microstructure is suitable for the manufacturing of ultra-large grain cemented carbide mining alloys, and can improve the crack resistance stability of ball teeth under high-altitude temperature difference cycling while maintaining the wear-resistant framework of the tooth crown.

[0016] This invention controls the formation of WC-Co-Cr composite particles, slight necking, and low-energy post-mixing to maintain a certain size of the composite particles during pressing and sintering. Compared with full co-milling of fine-particle components or subsequent high-energy mixing, this method helps to reduce the excessive fragmentation of fine-particle enrichment areas, avoids the formation of continuous cobalt pools or local weak areas, and maintains a better balance between hardness, transverse fracture strength, and impact toughness in cemented carbide ball teeth.

[0017] This invention also controls the final magnetic saturation rate within a suitable carbon potential window, making it less likely for significant decarburized phases or free carbon defects to appear in the sintered structure. When the carbon potential is too low, a brittle η phase is easily formed; when the carbon potential is too high, free carbon and localized cobalt phase anomalies are likely to occur. Constraining the final sintering state through magnetic saturation rate helps stabilize the grain boundary bonding and binder phase state of the WC-Co cemented carbide ball teeth. The ball teeth produced in this way, when used in high-altitude ball tooth drill bits, maintain good wear resistance, impact resistance, and stability during embedded use under conditions of dry, highly abrasive conditions, low-temperature drilling start-up, and thermal cycling. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0019] Unless otherwise stated, the following examples and comparative examples used the following raw materials: Ultra-large WC powder was sourced from HC Stark Tungsten Powder Company, model WC MAS 900, with a D50 of 8.60 μm, a D90 of 13.40 μm, a total carbon mass fraction of 6.12%, a free carbon mass fraction of 0.018%, and an oxygen mass fraction of 0.08%; fine WC powder was sourced from HC Stark Tungsten Powder Company, model WCDS 100, with a D50 of 1.10 μm, a D90 of 2.05 μm, a total carbon mass fraction of 6.13%, and an oxygen mass fraction of 0.12%; Co powder was sourced from Umicore, model CO6105, with a D50 of 1.30 μm and an oxygen mass fraction of 0.32%; Cr3C2 powder was sourced from Hägner GmbH, model Cr3C2. 160, D50 is 0.75μm, purity is 99.6%; acetylene black is from Thermo Fisher Scientific, model is 50% compressed acetylene black, D50 is 0.70μm, ash content is 0.03%.

[0020] Example 1: (1) 6.30 kg of fine WC powder, 2.94 kg of Co powder, 0.272 kg of Cr3C2 powder and 0.022 kg of acetylene black were added to a cemented carbide-lined roller mill jar, along with 6.41 kg of anhydrous ethanol and 38 kg of WC-Co grinding balls. The mixture was wet-milled at 70 r / min for 8 h. 0.87 kg of a 12 wt% paraffin ethanol solution was added and the mixture was rolled for another 20 min to obtain a WC-Co-Cr composite particle slurry. (2) Spray granulation of the slurry obtained in step (1) with an inlet temperature of 160℃, an outlet temperature of 84℃, and an atomizing disc rotation speed of 10500 r / min; the sprayed powder is passed through a 250-mesh sieve to remove coarse particles, and then through airflow classification to remove fine powder smaller than 10μm, retaining WC-Co-Cr composite particles with D50 of 24.0μm and D90 of 39.0μm; the composite particles are then subjected to a hydrogen flow rate of 1.5m 3 Under the condition of / h, the temperature was raised to 630℃ and held for 45min, then switched to argon and raised to 790℃ and held for 30min. After cooling, 8.77kg of slightly necked WC-Co-Cr composite particles were weighed and set aside. (3) Add 84.21 kg of super-large WC powder, 7.00 kg of Co powder and 0.02 kg of acetylene black to a wet mixing drum, add 38.00 kg of anhydrous ethanol and 120 kg of WC-Co grinding balls, and wet mix at 45 r / min for 3 h; stop the wet mixing drum and remove the grinding balls, add 8.77 kg of WC-Co-Cr composite particles weighed in step (2), and then add 15 kg of paraffin ethanol solution with a mass fraction of 12 wt%. Use a paddle type low-speed mixing with a paddle linear velocity of 0.38 m / s and mix for 40 min to obtain the post-mixed slurry. (4) The post-mixed slurry was vacuum dried at 68℃ and -0.085MPa for 5h, and then granulated through a 60-mesh sieve to obtain spherical tooth pressing powder; the pressing powder was loaded into a spherical tooth mold, and the molding pressure was 210MPa and the pressure was held for 8s to obtain a spherical crown tooth blank with a tooth body diameter of 12.0mm, a tooth height of 20.0mm, and a tooth crown radius of 6.0mm; the tooth blank was cold isostatically pressed at a pressure of 170MPa and held for 3min to obtain a cold isostatically pressed tooth blank; (5) Place the cold isostatic pressing tooth blank in a vacuum pressure sintering furnace, raise it to 380℃ at 1.2℃ / min and hold for 60min, then raise it to 520℃ at 0.8℃ / min and hold for 90min; evacuate to 6Pa, raise it to 900℃ at 4℃ / min and hold for 45min, then raise it to 1280℃ at 5℃ / min and hold for 30min; continue to raise it to 1440℃ and hold for 60min, start filling with argon gas from the temperature of 1400℃ and pressurize it to 5.5MPa, and maintain 5.5MPa during the 1440℃ holding stage; after the holding is completed, cool it to 900℃ at 4℃ / min, and then cool it with the furnace to below 120℃ before taking it out of the furnace to obtain sintered spherical teeth; (6) The sintered ball teeth are subjected to external cylindrical grinding and crown grinding. The continuous contact time of a single tooth is controlled within 3 seconds, and the grinding fluid temperature is 18℃. After grinding, the teeth are ultrasonically cleaned for 10 minutes and dried at 80℃ for 40 minutes to obtain cemented carbide ball teeth. (7) Take a 42CrMo drill bit steel body with a room temperature diameter of 11.94 mm and an effective depth of 13.0 mm. Heat the drill bit steel body to 430°C and press the cemented carbide ball tooth obtained in step (6) into the tooth hole within 35 seconds. Cool it to room temperature to obtain a high-altitude ball tooth drill bit.

[0021] Example 2: The difference between this embodiment and Embodiment 1 is as follows: In step (1), the fine WC powder is 5.45 kg, Co powder is 2.60 kg, Cr3C2 powder is 0.20 kg, acetylene black is 0.020 kg, anhydrous ethanol is 5.80 kg, and WC-Co grinding balls are 35 kg, and wet grinding is carried out at 65 r / min for 7 h; In step (2), the inlet temperature is 154℃, the outlet temperature is 82℃, the atomizing disc speed is 9800 r / min, and WC-Co-Cr composite particles with D50 of 20.6 μm and D90 of 34.8 μm are retained. The mixture was kept at 620℃ in hydrogen for 45 minutes and then at 780℃ in argon for 30 minutes. After cooling, 7.55 kg of WC-Co-Cr composite particles were weighed. In step (3), the amount of ultra-large WC powder was 84.95 kg, Co powder was 7.45 kg, acetylene black was 0.05 kg, the blade linear velocity was 0.34 m / s, and the mixture was mixed for 35 minutes. In step (5), the highest sintering temperature was 1435℃, the temperature was kept for 65 minutes, and the argon pressure was 5.0 MPa. The other conditions were the same as in Example 1, and a high-altitude ball tooth drill bit was obtained.

[0022] Example 3: The difference between this embodiment and Embodiment 1 is as follows: In step (1), the fine WC powder is 7.25 kg, Co powder is 3.35 kg, Cr3C2 powder is 0.32 kg, acetylene black is 0.025 kg, anhydrous ethanol is 7.20 kg, and WC-Co grinding balls are 42 kg, and wet grinding is performed at 72 r / min for 8.5 h; In step (2), the inlet temperature is 165℃, the outlet temperature is 86℃, the atomizing disc speed is 11200 r / min, and WC-Co-Cr composite particles with D50 of 27.8 μm and D90 of 43.5 μm are retained. The particles were kept at 640℃ in hydrogen for 50 min and then at 800℃ in argon for 30 min. After cooling, 10.05 kg of WC-Co-Cr composite particles were weighed. In step (3), the amount of ultra-large WC powder was 83.30 kg, Co powder was 6.60 kg, acetylene black was 0.05 kg, the blade linear velocity was 0.45 m / s, and the mixture was mixed for 45 min. In step (5), the highest sintering temperature was 1445℃, the temperature was kept for 60 min, and the argon pressure was 5.8 MPa. The other conditions were the same as in Example 1, and a high-altitude ball tooth drill bit was obtained.

[0023] Example 4: The difference between this embodiment and Embodiment 1 is that in step (2), after the spray powder is classified, WC-Co-Cr composite particles with D50 of 22.8 μm and D90 of 37.2 μm are retained, and the composite particles are subjected to a hydrogen flow rate of 1.5 m³ / h. 3 Under the condition of / h, the temperature is raised to 610℃ and held for 40min, then switched to argon and raised to 760℃ and held for 25min. After cooling, 8.60kg of slightly necked WC-Co-Cr composite particles are weighed; in step (3), the amount of ultra-large WC powder is 84.35kg, Co powder is 7.02kg, acetylene black is 0.03kg, the blade linear velocity is 0.30m / s, and the mixture is mixed for 30min; the other conditions are the same as in Example 1, and a high-altitude ball tooth drill bit is obtained.

[0024] Example 5: The difference between this embodiment and Embodiment 1 is as follows: In step (1), the fine WC powder is 6.80 kg, Co powder is 3.12 kg, Cr3C2 powder is 0.285 kg, and acetylene black is 0.024 kg; in step (2), WC-Co-Cr composite particles with D50 of 25.8 μm and D90 of 41.2 μm are retained, and the particles are kept at 635℃ in hydrogen for 45 min and at 790℃ in argon for 35 min. After cooling, the WC particles are weighed. -Co-Cr composite particles 9.35kg; in step (3), the amount of super large WC powder is 84.00kg, Co powder is 6.60kg, acetylene black is 0.05kg, the blade linear velocity is 0.42m / s, and the mixture is mixed for 45min; in step (7), the room temperature diameter of the tooth hole is 11.93mm, the tooth hole area of ​​the drill bit steel body is heated to 450℃, and the cemented carbide ball tooth is pressed in within 32s; the remaining conditions are the same as in Example 1, and a high-altitude ball tooth drill bit is obtained.

[0025] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that: WC-Co-Cr composite particles were not prepared. Instead, 84.21 kg of ultra-large WC powder, 5.80 kg of fine WC powder, 9.70 kg of Co powder, 0.25 kg of Cr3C2 powder, and 0.04 kg of acetylene black were added to a cemented carbide-lined roller mill jar at one time. 45.00 kg of anhydrous ethanol and 158 kg of WC-Co grinding balls were added. After wet grinding at 70 r / min for 8 hours, 15.87 kg of a 12 wt% paraffin ethanol solution was added, and the milling continued for 40 minutes. Then, the drill bit was prepared according to the drying, pressing, sintering, grinding, and pressing steps of Example 1.

[0026] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that: Cr3C2 powder is not added in step (1), and fine WC powder is used to make up the mass; the other conditions are the same as in Example 1.

[0027] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the amount of Cr3C2 powder used in step (1) is 0.55 kg, and the amount of ultra-large WC powder is reduced accordingly; the other conditions are the same as in Example 1.

[0028] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that: in step (2), the spray powder is not subjected to hydrogen and argon heat treatment after sieving and airflow classification, and 8.70 kg of WC-Co-Cr composite particles are directly weighed for step (3); the other conditions are the same as in Example 1.

[0029] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that: after adding WC-Co-Cr composite particles in step (3), the grinding ball is not removed, and wet grinding is continued at 70 r / min for 3 h, and then a paraffin ethanol solution with a mass fraction of 12 wt% is added; the other conditions are the same as in Example 1.

[0030] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that 0.02 kg of acetylene black is not added in step (3); the other conditions are the same as in Example 1.

[0031] Comparative Example 7: The difference between Comparative Example 7 and Example 1 is that the amount of acetylene carbon black added in step (3) is 0.12 kg, and the amount of ultra-large WC powder is reduced accordingly; the other conditions are the same as in Example 1.

[0032] Comparative Example 8: The difference between Comparative Example 8 and Example 1 is that: in step (7), the tooth hole area of ​​the 42CrMo drill bit steel body is not heated, and the cemented carbide ball tooth is pressed into the tooth hole with a diameter of 11.94 mm at room temperature; the other conditions are the same as in Example 1.

[0033] Performance testing (1) Hardness: Carbide Rockwell hardness A scale test was conducted according to GB / T3849.1-2015. A test plane was prepared on the side of the ground ball tooth body. Three points were measured for each sample and the average value was taken.

[0034] (2) Transverse fracture strength: According to GB / T3851-2015, standard strips were prepared from the same batch of pressed powder. The drying, dewaxing and sintering regimes of the strips were consistent with those of the corresponding ball teeth. The average value of the results was taken.

[0035] (3) Room temperature impact toughness: Tested according to GB / T1817-2017. Standard impact samples were prepared from the same batch of pressed powder, and the sintering regime was consistent with that of the corresponding ball teeth. The results are expressed in J / cm. 2 count.

[0036] (4) Magnetic saturation rate: The magnetic saturation MS was measured according to GB / T23369-2009 and calculated as magnetic saturation rate = measured MS / theoretical MS × 100%.

[0037] (5) Total length of indentation cracks: According to the indentation test caliber of GB / T33819-2017, after applying load to the polished surface, the total length of the cracks at the four corners of the indentation is measured. Five indentations are measured for each sample and the average value is taken.

[0038] (6) Metallographic structure: According to GB / T3488.1-2024 and GB / T3488.4-2022, observe the porosity, non-combined carbon defects, decarburized phase and fine WC enrichment area distribution.

[0039] (7) High and low temperature cycling: After the sample is kept at -30℃ for 1 hour, it is raised to 65℃ and kept for 1 hour as one cycle, and the cycle is repeated 50 times. After the cycle, the impact toughness is determined according to step (3). The retention rate is equal to the impact toughness after the cycle / the impact toughness before the cycle × 100%.

[0040] (8) Drilling wear: The same granite rock sample was used for laboratory drilling wear test. The uniaxial compressive strength of the rock sample was 170-190 MPa. The impact frequency, axial load, rotation speed and flushing conditions were kept consistent. The average wear height of the ball tooth crown after drilling 100m was recorded, and the cumulative drilling depth when the crown cracked or the tooth was lost was taken as the failure depth.

[0041] (9) Pushing force: The assembled drill bit is loaded along the axial direction of the ball tooth, and the maximum load when a single tooth is pushed out of the tooth hole is measured. Three teeth are tested for each sample and the average value is taken.

[0042] Table 1. Material performance test results Table 2. Performance test results for high and low temperature cycling and drilling applications. As shown in Tables 1 and 2, the magnetic saturation rates of Examples 1-5 were all within the range of 82-88%, no η phase or free carbon was observed in the metallographic structure, the hardness remained at 86.8-87.4 HRA, the transverse fracture strength was 2875-3065 MPa, and the impact toughness was 18.1-19.9 J / cm. 2 The total length of the indentation crack was 0.74-0.88 mm. These results indicate that, in the presence of the ultra-large WC framework phase, pre-forming and retaining WC-Co-Cr composite particles of a certain size is beneficial for balancing hardness, flexural strength, and impact toughness.

[0043] After high and low temperature cycling, the impact toughness retention rate of Examples 1-5 was 95.6-96.5%, the wear height after 100m was 0.35-0.44mm, and the cumulative drilling depth was 225-252m. Example 2 had a lower amount of composite particles and Cr3C2, resulting in a slightly higher wear height; Example 3 had a higher amount of composite particles and Cr3C2, resulting in higher impact toughness but also an increased wear height; Example 5, after adjusting the ball tooth and steel body embedding parameters, achieved a pushing force of 18.9kN and a cumulative drilling depth of 252m.

[0044] Compared with the examples, Comparative Examples 1, 4, and 5 correspond to overall high-energy mixing, composite particles without slight necking, and high-energy ball milling after the addition of composite particles, respectively. All of these examples showed adverse changes in transverse fracture strength, impact toughness, total indentation crack length, and drilling depth, indicating that the formation of composite particles, appropriate reinforcement, and low-energy post-mixing affect the final ball tooth state. Comparative Examples 2 and 3 correspond to Cr3C2 deficiency and excess, respectively. The former showed more obvious local coarsening, while the latter showed increased hardness but decreased impact toughness and cumulative drilling depth, indicating that the amount of Cr3C2 should be controlled in conjunction with the state of the composite particles.

[0045] Comparative Examples 6 and 7 exhibited magnetic saturation rates lower and higher than those of the Examples, respectively, and showed η-phase or free carbon and localized Co pools, respectively. Their cycle retention rate and cumulative drilling depth were significantly lower than those of the Examples. The ball tooth body performance of Comparative Example 8 was close to that of Example 1, but the ejection force after room temperature pressing was reduced to 10.2 kN, and the cumulative drilling depth was 167 m, indicating that heating and pressing the tooth hole of the 42CrMo drill bit body is beneficial to improving the ball tooth's embedding stability.

[0046] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a high-altitude ball-tooth drill bit, characterized in that, Includes the following steps: S1. Fine WC powder, Co powder, Cr3C2 powder and acetylene black are wet-milled in anhydrous ethanol, and paraffin ethanol solution is added to obtain WC-Co-Cr composite particle slurry. S2. Spray granulation, sieving and air classification of the WC-Co-Cr composite particle slurry to remove fine powder smaller than 10μm, and necking treatment of the classified particles to obtain WC-Co-Cr composite particles with D50 of 20.6-27.8μm and D90 of 34.8-43.5μm. S3. After wet mixing of the ultra-large WC powder, Co powder, and acetylene black, remove the grinding balls, then add the WC-Co-Cr composite particles and paraffin ethanol solution, and perform paddle-type post-mixing, drying, and granulation to obtain ball-tooth pressed powder; wherein, based on a total mass of 100 parts of non-volatile powder, the ultra-large WC powder is 83.30-84.95 parts, the Co powder is 6.60-7.45 parts, the WC-Co-Cr composite particles are 7.55-10.05 parts, and the acetylene black is 0.02-0.05 parts; S4. Press the spherical tooth powder into a spherical crown tooth blank, and then sinter it under cold isostatic pressing and vacuum pressure to obtain a sintered spherical tooth with a magnetic saturation rate of 82-88%. S5. After grinding, cleaning and drying, the sintered ball teeth are pressed into the heated drill bit steel body tooth hole, and after cooling, the high-altitude ball tooth drill bit is obtained.

2. The method for preparing a high-altitude ball-tooth drill bit according to claim 1, characterized in that, In step S1, based on a total mass of 100 parts of premixed solids, the fine WC powder comprises 65.90-66.48 parts, the Co powder comprises 30.50-31.44 parts, the Cr3C2 powder comprises 2.42-2.92 parts, and the acetylene black comprises 0.22-0.25 parts; the wet milling speed is 65-72 r / min, and the wet milling time is 7-8.5 h.

3. The method for preparing a high-altitude ball-tooth drill bit according to claim 1, characterized in that, In step S2, the inlet temperature of spray granulation is 154-165℃, the outlet temperature is 82-86℃, and the rotation speed of the atomizing disc is 9800-11200r / min; the neck treatment includes holding at 610-640℃ for 40-50min in a hydrogen atmosphere, then switching to an argon atmosphere and holding at 760-800℃ for 25-35min.

4. The method for preparing a high-altitude ball-tooth drill bit according to claim 1, characterized in that, In step S3, the ultra-large WC powder, Co powder and acetylene black are wet-mixed at 45 r / min for 3 h and then the grinding balls are removed; the blade linear velocity of the paddle-type low-speed post-mixing is 0.30-0.45 m / s and the mixing time is 30-45 min; the drying is vacuum drying at 68℃ and -0.085 MPa for 5 h; and the granulation is granulation through a 60 mesh sieve.

5. The method for preparing a high-altitude ball-tooth drill bit according to claim 1, characterized in that, In step S4, the pressing includes molding and cold isostatic pressing. The molding pressure is 210 MPa and the holding time is 8 s. The cold isostatic pressing pressure is 170 MPa and the holding time is 3 min. The vacuum pressure sintering includes: heating to 380℃ and holding for 60 min, then heating to 520℃ and holding for 90 min; evacuating to 6 Pa and then heating to 900℃ and holding for 45 min, then heating to 1280℃ and holding for 30 min; continuing to heat to 1435-1445℃ and holding for 60-65 min, and from the temperature reaching 1400℃, argon gas is introduced and the pressure is increased to 5.0-5.8 MPa.

6. The method for preparing a high-altitude ball-tooth drill bit according to claim 1, characterized in that, In step S5, the continuous contact time of a single tooth during grinding is controlled to be within 3 seconds, and the grinding fluid temperature is 18℃; after grinding, ultrasonic cleaning is performed for 10 minutes and drying is carried out at 80℃ for 40 minutes; the drill bit steel body is a 42CrMo drill bit steel body, the tooth hole area of ​​the drill bit steel body is heated to 430-450℃, and the sintered ball tooth is pressed into the tooth hole within 32-35 seconds.

7. A high-altitude ball-tooth drill bit, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The high-altitude ball-tooth drill bit according to claim 7, characterized in that, The high-altitude ball tooth drill bit includes a drill bit body and cemented carbide ball teeth pressed into the tooth holes of the drill bit body. The cemented carbide ball teeth have discrete fine-grained WC enrichment regions formed by the WC-Co-Cr composite particles.

9. The high-altitude ball-tooth drill bit according to claim 7 or 8, characterized in that, The cemented carbide ball teeth, calculated based on a total non-volatile powder mass of 100 parts, include: 83.30-84.95 parts of ultra-large WC powder, 4.98-6.66 parts of fine WC powder, 9.45-9.83 parts of Co, 0.18-0.29 parts of Cr3C2, and 0.040-0.073 parts of acetylene black. The metallographic porosity of the cemented carbide ball teeth is A02, B00, and C00, and no η phase or free carbon is observed.

10. The high-altitude ball-tooth drill bit according to claim 8, characterized in that, The drill bit body is made of 42CrMo drill bit steel, the room temperature diameter of the tooth hole is 11.93-11.94 mm, the effective depth of the tooth hole is 13.0 mm, and the tooth body diameter of the carbide ball tooth is 12.0 mm.

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