Surface hardening method of screw drill universal joint and related universal joints

Abstract

This invention discloses a surface hardening method for universal joints in screw drills and related universal joints. The method includes: performing heat treatment and finishing on a rough-machined universal joint blank to obtain the universal joint body; after preheating the universal joint body, spot welding a tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal to the wear-resistant contact surface at one end of the universal joint body; spraying nickel-tungsten carbide powder and nickel-coated boron carbide composite powder onto the wear-resistant contact surface to form a hardened layer on the wear-resistant contact surface; after cooling, grinding the sprayed surface to the design dimensions; inspecting the porosity of the ground sprayed surface, filling the porosity with nickel-tungsten carbide powder and nickel-coated boron carbide composite powder, heating and melting to seal the porosity; and after cooling, precision grinding the universal joint to the design dimensions. This invention greatly improves the wear resistance and impact fracture resistance of the universal joint, enabling it to be used in conjunction with other screw drill components resistant to 350℃ high temperatures to form screw drills resistant to 350℃ high temperatures.

Description

Technical Field

[0001] This invention relates to the field of drilling engineering equipment technology, and in particular to a surface hardening method for a screw drill universal joint and related universal joints. Background Technology

[0002] The universal joint, a key component in the transmission of screw drills, is currently manufactured using a heat treatment process that involves carburizing steel for an extended period followed by quenching and tempering to improve wear resistance. However, this prolonged high-temperature heating process results in coarse grains in the material, reduced impact resistance, and increased susceptibility to breakage. Furthermore, the universal joint exhibits insufficient resistance to corrosion and wear, leading to a generally short service life and making it a bottleneck in the overall lifespan of screw drills.

[0003] Current universal joint manufacturing technology cannot meet the demands of high-temperature drilling. Universal joint parts currently manufactured using heat treatment and surface hardening processes have a carburized wear layer. However, this carburized structure undergoes a microstructural transformation after several hours at temperatures exceeding 200°C, causing a decrease in hardness. When the temperature exceeds 250°C, the hardness of the carburized layer drops drastically, leading to a sharp decline in its wear resistance and resulting in wear and breakage of the universal joint. Therefore, universal joint parts produced using current carburizing, quenching, and tempering surface hardening processes cannot be used for extended periods in operating environments exceeding 200°C.

[0004] As drilling progresses to deeper and ultra-deeper formations, well temperatures often exceed 200°C, especially in geothermal drilling where temperatures are even higher. This places higher demands on the temperature resistance and wear resistance of downhole tools and screw drill components. For example, universal joint components are generally required to maintain sufficient strength, impact resistance, and wear resistance even under prolonged operating conditions at well temperatures below 350°C, ensuring a sufficiently long service life and high reliability. Summary of the Invention

[0005] The inventors of this invention have discovered that universal joints currently manufactured using existing processes are generally unable to meet the requirements of high-temperature well conditions exceeding 350°C.

[0006] In view of the above problems, the present invention is proposed to provide a surface hardening method for a screw drill universal joint and a related universal joint that overcomes or at least partially solves the above problems.

[0007] In a first aspect, embodiments of the present invention provide a surface hardening method for a universal joint of a screw drill bit, comprising:

[0008] The universal joint blank that has undergone rough machining is subjected to heat treatment and finishing to obtain the universal joint body.

[0009] After preheating the universal joint body, a tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal is spot-welded to the wear-resistant contact surface at one end of the universal joint body.

[0010] For the wear-resistant contact surface of the universal joint body after spot welding, nickel tungsten carbide powder and nickel-coated boron carbide composite powder are sprayed to form a hardened layer on the wear-resistant contact surface.

[0011] After cooling, grind the spray-welded surface to the design dimensions;

[0012] Inspect the pores of the spray-welded working surface after grinding, fill the pores with nickel tungsten carbide powder and nickel-coated boron carbide composite powder, and heat to melt and seal the pores.

[0013] After cooling, the universal joint is precision ground to the design dimensions.

[0014] In one embodiment, the tungsten-cobalt alloy block encased in the spot-welded nickel-based brazing filler metal, on the wear-resistant contact surface at one end of the universal joint body, includes:

[0015] Multiple tungsten-cobalt alloy blocks, each wrapped with nickel-based brazing filler metal, are spot-welded one by one to the wear-resistant contact surface at one end of the universal joint, so that the tungsten-cobalt alloy blocks are fixed to the wear-resistant contact surface in a uniformly distributed toothed manner.

[0016] In one embodiment, the arrangement density of multiple nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks does not exceed 50%, and the arrangement density is the ratio of the total area of ​​the nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks to the area of ​​the wear-resistant contact surface.

[0017] In one embodiment, the tungsten-cobalt alloy block wrapped with nickel-based solder is made by wrapping a YG8 alloy block with nickel-based solder.

[0018] A tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal is spot-welded, melting the bottom of the nickel-based brazing filler metal to weld it to the universal joint body, thus fixing the YG8 alloy block wrapped with nickel-based brazing filler metal to the wear-resistant contact surface of the universal joint.

[0019] In one embodiment, the wear-resistant contact surface of the universal joint body after spot welding is sprayed with a composite powder of nickel-tungsten carbide powder and nickel-coated boron carbide powder, including:

[0020] Heat the YG8 alloy block wrapped with nickel-based brazing filler metal to approximately 350°C;

[0021] A 0.12-0.15 mm thick layer of NiWC35 tungsten carbide dispersion spray welding powder is sprayed onto the surface and around the YG8 alloy block wrapped with nickel-based solder as a pre-protective layer.

[0022] Starting from one end of the spray-welded surface, the universal joint body is heated to 650℃-700℃;

[0023] Starting from one end of the spray-welded surface, spray NiWC35 tungsten carbide dispersed spray-welded powder and nickel-coated boron carbide composite powder into the gaps of the YG8 alloy block wrapped with nickel-based brazing filler metal up to the height of the YG8 alloy block wrapped with nickel-based brazing filler metal, and melt it to a molten mirror state. Repeat this process until the end of the spray-welded surface is reached.

[0024] During the spray welding process, the YG8 alloy block is not exposed to air, and the overall temperature of the universal joint body does not exceed 620℃.

[0025] In one embodiment, during spray welding, the powder feeding switch of the spray gun is intermittently turned on to feed powder. The nozzle of the spray gun is at an angle of 80-90° to the surface to be welded. The oxygen pressure used is 0.45-0.50 MPa, and the acetylene pressure used is about 0.04 MPa. The straight-line distance between the nozzle and the surface to be welded is about 20-25 mm, and the nozzle moving speed is 5-8 meters / minute.

[0026] In one embodiment, nickel-tungsten carbide powder and nickel-coated boron carbide composite powder are heated and melted by laser radiation to fill the pores. The universal joint after filling the pores is placed in a box-type resistance furnace or lime wool at about 200°C for slow cooling until the universal joint is cooled to room temperature and then taken out of the furnace.

[0027] In one embodiment, preheating the universal joint body includes:

[0028] The universal joint body is preheated in a box-type resistance furnace with an inert protective atmosphere. First, inert protective gas is introduced to purge the air in the furnace, and then the temperature is raised to 250-300℃ and held for 2 hours.

[0029] In one embodiment, the universal joint blank that has undergone rough machining is subjected to a quenching and tempering process, including:

[0030] The universal joint body is heated to 860℃±5℃ in a heating furnace and held at 860℃±5℃ for 1.5 hours. After holding, it is transferred to a rapid quenching oil or water-based quenching medium for rapid cooling to cool the universal joint body to room temperature.

[0031] Within 2 hours, the universal joint body is transferred back into the heating furnace and reheated to 630℃±5℃. After a 2-hour heat preservation process at 630℃±5℃, it is quickly transferred to a cooling water tank with a water temperature below 30℃ to cool to room temperature.

[0032] Secondly, embodiments of the present invention provide a universal joint for a screw drill bit, wherein the universal joint is manufactured by the surface hardening method for screw drill bit universal joints as described above.

[0033] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0034] The surface hardening method for universal joints in screw drills provided in this invention, along with the related universal joints, abandons the traditional method of improving wear resistance by carburizing steel. Instead, a tungsten-cobalt alloy block encased in nickel-based brazing filler metal is spot-welded to the wear-resistant contact surface. Then, nickel-tungsten carbide powder and a composite powder of nickel-coated boron carbide are sprayed onto the surface to form a hardened layer. This hardened layer possesses high-temperature resistance, corrosion resistance, and strength. The screw drill universal joint surface-treated using this method avoids the problem of rapid softening of the hardened layer when operating at temperatures exceeding 250°C. It also overcomes the problem of coarse grains and easy fracture in traditional universal joint base materials after prolonged high-temperature carburizing. This allows it to be used with other screw drill components resistant to 350°C to form 350°C-resistant screw drills, significantly improving the wear resistance and impact fracture resistance of the universal joint in the screw drill.

[0035] The embodiments of the present invention provide a more wear-resistant and longer-lasting universal joint for the exploration and development of high-temperature and ultra-high-temperature well screw drills, which has broad application prospects in the field of ultra-deep well exploration and development.

[0036] It can be further promoted and applied to long-life screw drills, which can significantly improve the service life of long-life screws and greatly improve the efficiency of drilling operations.

[0037] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0039] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0040] Figure 1A This is a schematic diagram of the overall structure of the universal joint in an embodiment of the present invention;

[0041] Figure 1B This is a schematic diagram of the cross-section of the universal joint AA in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the tooth arrangement in the AA cross-sectional view of an embodiment of the present invention;

[0043] Figure 3 This is a development diagram of the uniformly distributed teeth of the YG8 alloy block wrapped with nickel-based brazing filler metal in an embodiment of the present invention;

[0044] Figure 4 This is a structural diagram of the YG8 alloy block wrapped with nickel-based solder in an embodiment of the present invention;

[0045] Figure 5 This is a schematic cross-sectional view of the universal joint blank in an embodiment of the present invention;

[0046] Figure 6 This is a temperature curve diagram of the heat treatment process of the universal joint body in an embodiment of the present invention;

[0047] Figure 7 This is a partial schematic diagram of the spray welding of a YG8 alloy block wrapped with nickel-based brazing filler metal in an embodiment of the present invention. Detailed Implementation

[0048] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0049] This invention provides a surface hardening method for a universal joint of a screw drill bit, the method comprising the following steps:

[0050] S1. The universal joint blank that has undergone rough machining is subjected to heat treatment and finishing to obtain the universal joint body.

[0051] S2. After preheating the universal joint body, spot weld the tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal to the wear-resistant contact surface at one end of the universal joint body.

[0052] S3. Spray-weld nickel tungsten carbide powder and nickel-coated boron carbide composite powder onto the wear-resistant contact surface of the universal joint body after spot welding to form a hardened layer on the wear-resistant contact surface.

[0053] S4. After cooling, grind the spray-welded surface to the design dimensions.

[0054] S5. Inspect the pores of the spray-welded working surface after grinding, fill the pores with nickel tungsten carbide powder and nickel-coated boron carbide composite powder, and heat to melt to seal the pores.

[0055] S6. After cooling, the universal joint is precision ground to the design dimensions.

[0056] In step S2 above, the tungsten cobalt alloy block wrapped with nickel-based brazing filler metal is spot-welded to the wear-resistant contact surface at one end of the universal joint body. For example, multiple tungsten cobalt alloy blocks wrapped with nickel-based brazing filler metal can be spot-welded one by one to the wear-resistant contact surface at one end of the universal joint, so that the tungsten cobalt alloy blocks are fixed to the wear-resistant contact surface in a uniformly distributed toothed manner.

[0057] In one embodiment, the arrangement density of the multiple nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks does not exceed 50%, and the arrangement density is the ratio of the total area of ​​the nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks to the area of ​​the wear-resistant contact surface.

[0058] In one embodiment, the tungsten-cobalt alloy block wrapped with nickel-based solder is made by wrapping a YG8 alloy block with nickel-based solder.

[0059] A tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal is spot-welded, melting the bottom of the nickel-based brazing filler metal to weld it to the universal joint body, thus fixing the YG8 alloy block wrapped with nickel-based brazing filler metal to the wear-resistant contact surface of the universal joint.

[0060] Reference Figure 1A As shown, for example, a universal joint includes a wear-resistant contact surface 1-1, a universal joint body 1-2, and a tapered thread 1-3. (Refer to...) Figure 1B yes Figure 1A The cross-sectional view along the AA direction shows that the wear-resistant contact surface 1-1 is the surface where the spray-welded hardened layer is applied, i.e., the wear-resistant contact surface formed on the universal joint body 1-2. The wear-resistant contact surface 1-1 is composed of a YG8 alloy block 4-1 wrapped with nickel-based brazing filler metal, molten NiWC35 tungsten carbide dispersed spray-welded powder, and a composite powder 2-3 containing a trace amount of nickel-coated boron carbide. It is the wear-resistant working surface of the universal joint.

[0061] Figure 2 for Figure 1A The schematic diagram of the tooth arrangement in the AA cross-section shows that it consists of a YG8 alloy block 4-1 wrapped with uniformly distributed nickel-based brazing filler metal, a body contact surface 4-2, and a universal joint body 1-2. The tooth arrangement is formed by spot welding the YG8 alloy block 4-1 wrapped with nickel-based brazing filler metal to the surface of the body contact surface 4-2.

[0062] Figure 3 for Figure 2 The diagram shows the evenly distributed teeth of the YG8 alloy block 4-1 encased in nickel-based solder. It consists of the YG8 alloy block 4-1 encased in nickel-based solder and the body contact surface 4-2. The YG8 alloy block 4-1 encased in nickel-based solder is evenly fixed to the surface of the body contact surface 4-2 by spot welding.

[0063] Figure 4 This is a structural diagram of a YG8 alloy block 4-1 encased in nickel-based solder. It consists of a YG8 alloy block 5-2 and nickel-based solder 5-1. The YG8 alloy block 4-1 encased in nickel-based solder is arranged according to... Figure 3 During spot welding of the toothed pattern, the bottom part of the nickel-based brazing filler metal 5-1 melts and welds together with the contact surface 4-2 of the body, so that the YG8 alloy block 4-1 wrapped by the nickel-based brazing filler metal is fixed on the surface of the contact surface 4-2 of the body.

[0064] In one embodiment, step S3 above, which involves spraying nickel-tungsten carbide powder and nickel-coated boron carbide composite powder onto the wear-resistant contact surface of the universal joint body after spot welding, is specifically implemented through the following process:

[0065] Heat the YG8 alloy block wrapped with nickel-based brazing filler metal to approximately 350°C;

[0066] A 0.12-0.15 mm thick layer of NiWC35 tungsten carbide dispersion spray welding powder is sprayed onto the surface and around the YG8 alloy block wrapped with nickel-based solder as a pre-protective layer.

[0067] Starting from one end of the spray-welded surface, the universal joint body is heated to 650℃-700℃;

[0068] Starting from one end of the spray-welded surface, spray NiWC35 tungsten carbide dispersed spray-welded powder and nickel-coated boron carbide composite powder into the gaps of the YG8 alloy block wrapped with nickel-based brazing filler metal up to the height of the YG8 alloy block wrapped with nickel-based brazing filler metal, and melt it to a molten mirror state. Repeat this process until the end of the spray-welded surface is reached.

[0069] During the spray welding process, the YG8 alloy block is not exposed to air, and the overall temperature of the universal joint body does not exceed 620℃.

[0070] Figure 4 This is a structural diagram of a YG8 alloy block 4-1 encased in nickel-based solder. It consists of a YG8 alloy block 5-2 and nickel-based solder 5-1. The YG8 alloy block 4-1 encased in nickel-based solder is arranged according to... Figure 3 During spot welding of the toothed pattern, the bottom part of the nickel-based brazing filler metal 5-1 melts and welds together with the contact surface 4-2 of the body, so that the YG8 alloy block 4-1 wrapped by the nickel-based brazing filler metal is fixed on the surface of the contact surface 4-2 of the body.

[0071] In one embodiment, during spray welding, the powder feeding switch of the spray gun is intermittently turned on to feed powder. The angle between the nozzle of the spray gun and the surface to be welded is 80-90°. The oxygen pressure used is 0.45-0.50 MPa, and the acetylene pressure used is about 0.04 MPa. The straight-line distance between the nozzle and the surface to be welded is about 20-25 mm, and the nozzle moving speed is 5-8 meters / minute.

[0072] In one embodiment, in step S5 above, nickel tungsten carbide powder and nickel-coated boron carbide composite powder are heated and melted by laser radiation to fill the pores, and the universal joint after filling the pores is placed in a box-type resistance furnace or lime wool at about 200°C for slow cooling until the universal joint is cooled to room temperature and then taken out of the furnace.

[0073] In one embodiment, preheating the universal joint body in step S1 above can be achieved in the following way:

[0074] The universal joint body is preheated in a box-type resistance furnace with an inert protective atmosphere. First, inert protective gas is introduced to purge the air in the furnace, and then the temperature is raised to 250-300℃ and held for 2 hours.

[0075] In one embodiment, the universal joint blank that has undergone rough machining is subjected to quenching and tempering treatment, which can be achieved in the following way:

[0076] The universal joint body is heated to 860℃±5℃ in a heating furnace and held at 860℃±5℃ for 1.5 hours. After holding, it is transferred to a rapid quenching oil or water-based quenching medium for rapid cooling to cool the universal joint body to room temperature.

[0077] Within 2 hours, the universal joint body is transferred back into the heating furnace and reheated to 630℃±5℃. After a 2-hour heat preservation process at 630℃±5℃, it is quickly transferred to a cooling water tank with a water temperature below 30℃ to cool to room temperature.

[0078] For example, the base material is made of high-strength steel containing alloys such as chromium, nickel, and molybdenum, which is tempered to obtain sufficient mechanical properties and strength. A YG8 alloy block, approximately 1.6mm thick and with 10mm x 10mm sides, is uniformly distributed on about 50% of the friction working surface, encased in nickel-based brazing filler metal. NiWC35 tungsten carbide dispersed spray welding powder and a trace amount of nickel-coated boron carbide composite powder are then sprayed into the gaps around the YG8 alloy block to harden the gaps. During this process, the overall temperature of the base material is strictly controlled to not exceed the tempering temperature during the tempering process, ensuring that the mechanical properties and strength of the base material are not reduced while obtaining a wear-resistant hardened surface with sufficient wear and corrosion resistance. This method is suitable for 350℃ screw drill bits, significantly improving the wear resistance of the universal joint without reducing the overall impact resistance of the steel base material. The purpose of this invention is to significantly improve the service life of the universal joint of the screw drill bit, thereby significantly improving the overall service life of the screw drill bit and increasing the working efficiency of the screw drill bit used in high-temperature and complex working conditions.

[0079] Example 1:

[0080] The universal joint processing flow provided in Embodiment 1 of the invention is as follows:

[0081] 5.1 Rough turning of the body: The universal joint blank is rough turned into shape. Figure 5 The shape shown.

[0082] 5.2. Body conditioning treatment.

[0083] Description of the heat treatment process for universal joint body blanks 1-2:

[0084] High-strength universal joint body containing alloys such as chromium, nickel, and molybdenum 1-2 Figure 6The high-temperature heating furnace process (3-1) raises the temperature to 860℃±5℃, followed by a holding period of 1.5 hours at 860℃±5℃ (3-2), completing the austenitization transformation of the internal structure of the universal joint body 1-2. Then, it is rapidly transferred to a rapid quenching oil or water-based quenching medium for a rapid cooling process (3-3), quickly cooling the universal joint body 1-2 to room temperature, maximizing the transformation of the internal structure from austenite to martensite. Afterward, within a maximum of 2 hours, it is transferred to a tempering furnace, heated to 630℃±5℃ in process (3-4), and held at 630℃±5℃ for 2 hours (3-5), allowing the martensite structure to transform as completely as possible into troostite. Finally, it is rapidly transferred to a cooling water bath at a temperature below 30℃ for process (3-6) to cool to room temperature, reducing the segregation of impurities at grain boundaries and improving the impact toughness and strength of the workpiece.

[0085] 5.3. Finishing: The universal joint body is machined into the following shape: Figure 1A The shape shown.

[0086] 5.4 Surface hardening process.

[0087] 5.4.1 Degreasing and oil removal before welding: The surface of the universal joint body 1-2 must be strictly degreased and oil-removed before spray welding. 5.4.2 Preheating before welding: The universal joint body 1-2 is preheated using a box-type resistance furnace with an inert protective atmosphere. During operation, inert protective gas is first introduced to purge the air from the furnace, then the temperature is raised to 250-300℃ and held for 2 hours.

[0088] 5.4.3 Spot welding of cemented carbide: After the universal joint body 1-2 has been heated and removed from the box-type resistance furnace with an inert protective atmosphere, it should be quickly transferred to the welding operation station and welded as follows. Figure 3 Spot welding is performed using a uniformly distributed tooth arrangement as shown. The spot welding current is 750-850A. The YG8 alloy blocks 4-1, which are wrapped with nickel-based brazing filler metal, are spot welded one by one onto the contact surface 4-2 of the main body.

[0089] 5.4.4, Complete as follows Figure 2 and Figure 3 After spot welding the toothed area, NiWC35 tungsten carbide dispersed spray welding powder is applied.

[0090] 5.4.4.1 Spraying a protective layer.

[0091] NiWC35 tungsten carbide dispersed spray welding powder 6-1 was added to the powder canister of an oxy-acetylene flame torch with an alloy powder canister structure, and the flame was adjusted to a neutral flame.

[0092] The substrate surrounding the YG8 alloy block 4-1, which is wrapped with nickel-based brazing filler metal, is preheated to about 350°C.

[0093] Oxygen pressure 0.55-0.60 MPa, acetylene pressure 0.05-0.06 MPa, nozzle angle 80-90° to welding surface, distance between nozzle and welding surface approximately 170-180 mm, nozzle movement speed 6-8 m / min. A 0.12-0.15 mm thick layer of NiWC35 tungsten carbide dispersed welding powder 6-1 is sprayed onto and around the surface of the nickel-based brazing filler metal-coated YG8 alloy block 4-1. This tightly encapsulates and firmly welds the nickel-based brazing filler metal-coated YG8 alloy block 4-1 to the contact surface 4-2 of the main body.

[0094] Figure 7 A partial schematic diagram of the YG8 alloy block 4-1 coated with nickel-based brazing filler metal being sprayed. This includes the universal joint body 1-2, the YG8 alloy block 4-1 coated with nickel-based brazing filler metal, the body contact surface 4-2, and the NiWC35 tungsten carbide dispersed spraying powder 6-1.

[0095] In the above embodiments:

[0096] 1) During the spraying process, the YG8 alloy block 4-1 wrapped with nickel-based brazing filler metal must be kept tightly wrapped to prevent oxidation.

[0097] 2) During the spray welding process, the position of the flame core needs to be constantly moved to prevent the wrapped YG8 alloy block 5-2 from being exposed to the air and to prevent local overheating of the universal joint body 1-2.

[0098] 3) During operation, strictly control the overall temperature rise of YG8 alloy block 5-2 and universal joint body 1-2. The overall temperature of universal joint body 1-2 must not exceed 620℃. Strictly control the heating and cooling rate of the cemented carbide block to avoid excessive temperature difference between the inside and outside of YG8 alloy block 5-2, which may cause cracks in YG8 alloy block 5-2.

[0099] 5.4.4.2 Spray-welded hardened layer;

[0100] Replace the powder canister of the flame gun with NiWC35 tungsten carbide dispersion welding powder and a small amount of nickel-coated boron carbide composite powder 2-3.

[0101] Heat the workpiece from one end of the spray-welded surface to about 650℃-700℃.

[0102] Next, adjust the flame to a softer, neutral flame, intermittently turn on the powder feed switch to feed powder, keeping the nozzle 20-30mm away from the welding surface. Spray NiWC35 tungsten carbide dispersed welding powder and a trace amount of nickel-coated boron carbide composite powder 2-3 between the alloy blocks. Spray the NiWC35 tungsten carbide dispersed welding powder and the trace amount of nickel-coated boron carbide composite powder 2-3 up to the height 4-1 of the YG8 alloy block wrapped with nickel-based brazing filler metal, melting it to a molten mirror finish. At this point, immediately move the flame core to the next area to continue spraying powder and melting it, repeating this process until the end of the welding surface is reached.

[0103] In the above embodiments:

[0104] 1) Ensure that the YG8 alloy block 5-2 is sealed to prevent direct contact with air and oxidation.

[0105] 2) When powder spraying, the angle between the spray gun nozzle and the welding surface should be 80-90°, the flame should be adjusted to a relatively soft neutral flame, the oxygen pressure should be 0.45-0.50MPa, the acetylene pressure should be around 0.04MPa, and the gas flow rate should be slightly increased. The straight-line distance between the nozzle and the welding surface should be about 20-25mm, and the nozzle moving speed should be 5-8 meters / minute.

[0106] 3) It is necessary to strictly control the amount of powder fed into the spray gun and strictly control the thickness of the sprayed weld.

[0107] 4) During remelting, the nozzle should be 7-10mm away from the surface to be sprayed. The remelting time should be as short as possible. Once a molten mirror finish appears, move to the next area immediately and continue spraying powder and remelting.

[0108] 5) Minimize the temperature rise of YG8 alloy block 5-2 and the substrate as much as possible.

[0109] 6) During the spray welding process, continuously move the position of the flame core to prevent local overheating of the YG8 alloy block 5-2 and the universal joint body 1-2, and continuously stir the molten surface to remove slag and gas.

[0110] 7) During the spraying process, the overall temperature of the universal joint body 1-2 must not exceed 620℃.

[0111] 8) Strictly control the heating and cooling rates of the cemented carbide during operation to avoid excessive temperature differences between the inside and outside of the YG8 alloy block 5-2, which could cause cracks.

[0112] 9) Take precautions against wind during operation.

[0113] 5.5 After the spray welding is completed, quickly place it in a 200℃ box-type resistance furnace or lime wool for slow cooling.

[0114] 5.6. After the workpiece is cooled slowly to below 200°C, it is removed from the furnace and air-cooled.

[0115] 5.7 Use a diamond grinding wheel to grind the workpiece's spray-welding surface to the design dimensions.

[0116] 5.8 Inspect the porosity of the sprayed surface after grinding.

[0117] 5.9 Fill the pores on the sprayed surface with NiWC35 tungsten carbide dispersion spray welding powder and a small amount of nickel-coated boron carbide composite powder 2-3.

[0118] 5.10. Use laser radiation to heat and melt NiWC35 tungsten carbide dispersed spray welding powder and a small amount of nickel-coated boron carbide composite powder 2-3 to seal the pores, and quickly put the sealed workpiece into a 200℃ box-type resistance furnace for slow cooling. After slow cooling to room temperature, remove it from the furnace.

[0119] 5.11. Use a diamond grinding wheel to finely grind the sealing area and the entire working surface of the workpiece to the design dimensions.

[0120] Example 2:

[0121] The universal joint body is made of 30CrNi2MoV material, with the following material composition (by weight): C%: 0.28-0.33, Si%: 0.15-0.35, Mn%: 0.75-1.0, Cr%: 0.75-1.0, Ni%: 1.65-2.0, Mo%: 0.35-0.50, V%: 0.05-0.10, P%: ≤0.015, S%: ≤0.015.

[0122] The universal joint processing flow provided in Embodiment 2 of the invention is as follows:

[0123] 8.1 Rough turning of the body: The universal joint blank is rough turned into shape as follows Figure 5 The shape shown.

[0124] 8.2. Body conditioning and tempering:

[0125] After holding at 860℃ for 1.5 hours, the material is cooled to room temperature in a 50℃ water-based quenching medium. Immediately after this process, it is held at 630℃ for 2 hours and then rapidly cooled to room temperature in water. The surface hardness of the universal joint body 1-2 after tempering is 37-39 HRC.

[0126] 8.3. Finishing: The universal joint body is machined into the following shape: Figure 1A The shape shown.

[0127] 8.4 Surface hardening process.

[0128] 8.4.1 Degreasing before welding: Clean the universal joint body with alkaline water at 1-290℃ for 30 minutes, then dry for 15 minutes.

[0129] 8.4.2 Preheating before welding: The universal joint body 1-2 is preheated in a box-type resistance furnace under nitrogen protective atmosphere. During operation, nitrogen is first introduced to purge the air in the furnace, and then the temperature is raised to 300℃ and held for 2 hours.

[0130] 8.4.3 Spot welding of cemented carbide: After removing the universal joint body 1-2 from the nitrogen atmosphere-protected box-type resistance furnace, quickly transfer it to the welding operation station and proceed as follows. Figure 3Spot welding is performed using a uniformly distributed toothed pattern as shown. The spot welding current is 800A. The YG8 alloy blocks 4-1, which are wrapped with nickel-based brazing filler metal, are spot welded one by one onto the contact surface 4-2 of the main body. The toothed pattern occupies approximately 40% of the hardened surface area.

[0131] 8.4.4 Implement NiWC35 tungsten carbide dispersed spray welding powder.

[0132] 8.4.4.1. Spray a protective layer.

[0133] NiWC35 tungsten carbide dispersed spray welding powder 6-1 was added to the powder canister of an oxy-acetylene flame torch with an alloy powder canister structure, and the flame was adjusted to a neutral flame.

[0134] The substrate surrounding the YG8 alloy block 4-1, which is wrapped with nickel-based brazing filler metal, is preheated to about 350°C.

[0135] Oxygen pressure 0.60 MPa, acetylene pressure 0.05 MPa, nozzle angle 85° to welding surface, distance between nozzle and welding surface approximately 175 mm, nozzle movement speed 6-8 m / min. A layer of NiWC35 tungsten carbide dispersed welding powder 6-1, approximately 0.15 mm thick, is sprayed onto the surface and surrounding area of ​​the nickel-based brazing filler metal-coated YG8 alloy block 4-1. This tightly encapsulates and firmly welds the nickel-based brazing filler metal-coated YG8 alloy block 4-1 to the contact surface 4-2 of the main body.

[0136] 8.4.4.2 Spray-welded hardened layer.

[0137] Replace the powder canister of the flame gun with NiWC35 tungsten carbide dispersion welding powder and a small amount of nickel-coated boron carbide composite powder 2-3.

[0138] Heat the workpiece to about 700°C, starting from the spray-welded end.

[0139] The nozzle of the spray gun is at an angle of approximately 85° to the surface to be welded. The flame is adjusted to a relatively soft, neutral flame. The oxygen pressure is 0.50 MPa, and the acetylene pressure is approximately 0.04 MPa. The gas flow rate is slightly increased. The straight-line distance between the nozzle and the surface to be welded is approximately 20 mm, and the nozzle movement speed is approximately 8 meters per minute.

[0140] Intermittently turn on the powder feeding switch to feed powder, spraying NiWC35 tungsten carbide dispersed welding powder and a trace amount of nickel-coated boron carbide composite powder 2-3 between the alloy blocks. Spray the NiWC35 tungsten carbide dispersed welding powder and the trace amount of nickel-coated boron carbide composite powder 2-3 up to the height of the YG8 alloy block 4-1 covered with nickel-based brazing filler metal, while melting it to a molten mirror finish. At this point, immediately move the flame core to the next part to continue spraying powder and melting the powder, repeating this process until the end of the sprayed surface. During the spraying process, strictly control the overall temperature of the universal joint body 1-2 to not exceed 620℃, and the YG8 alloy block 5-2 must not be directly exposed to air.

[0141] 8.5 After the spray welding is completed, quickly place it in a 200℃ box-type resistance furnace or lime wool for slow cooling.

[0142] 8.6. After the workpiece is cooled slowly to below 200°C, it is removed from the furnace and air-cooled.

[0143] 8.7 Use a diamond grinding wheel to grind the workpiece's spray-welding surface to the design dimensions.

[0144] 8.8 Inspect the porosity of the surface after grinding and spraying.

[0145] 8.9 Fill the pores of the spray welding surface with NiWC35 tungsten carbide dispersion spray welding powder and a small amount of nickel-coated boron carbide composite powder 2-3.

[0146] 8.10. Using 1800W laser power and 2mm beam diameter laser radiation, heat the NiWC35 tungsten carbide dispersed spray welding powder and a small amount of nickel-coated boron carbide composite powder 2-3 until they melt and fill the pores. Then quickly put the sealed workpiece into a 200℃ box-type resistance furnace for slow cooling. After slow cooling to room temperature, remove it from the furnace.

[0147] 8.11. Use a diamond grinding wheel to finely grind the sealing area and the entire working surface of the workpiece to the design dimensions.

[0148] In the above embodiments:

[0149] 1. Under the premise of meeting the wear resistance requirements, the tungsten carbide sprayed layer should be as thin as possible to reduce the thermal impact of the thermal spraying process on the universal joint body. Generally, a final sprayed layer of 1.8mm is sufficient to meet the wear resistance requirements.

[0150] 2. During the spray welding process, ensure that the YG8 alloy block 5-2 is not exposed to air. If the YG8 alloy block 5-2 is exposed to air, it will cause surface decarburization or cracking.

[0151] 3. The density of the YG8 alloy block 4-1 wrapped with nickel-based brazing filler metal should not exceed 50%. If it exceeds 50%, the heat-affected zone of the universal joint body 1-2 will expand, reducing the strength of the universal joint body 1-2, reducing the impact resistance of the universal joint body 1-2, and increasing the risk of YG8 alloy block 5-2 breaking.

[0152] 4. The remelting time of the hardened layer should be as short as possible. After the molten mirror surface appears, it is necessary to move to the next part immediately and continue to spray powder and remelt. Otherwise, the remelted part will overheat, reduce the strength of the universal joint body 1-2, reduce the impact resistance of the universal joint body 1-2, and increase the risk of YG8 alloy block 5-2 breaking.

[0153] The surface hardening method for screw drill universal joints and related universal joints provided in this invention abandon the traditional method of improving wear resistance by carburizing steel. Instead, a tungsten-cobalt alloy block coated with nickel-based brazing filler metal is spot-welded to the wear-resistant contact surface. Then, nickel-tungsten carbide powder and a composite powder of nickel-coated boron carbide are sprayed onto the surface to form a hardened layer. This hardened layer possesses high-temperature resistance, corrosion resistance, and strength. Screw drill universal joints surface-treated using this method avoid the problem of rapid softening of the hardened layer when operating at temperatures exceeding 250°C. This overcomes the problem of coarse grains and easy fracture in traditional universal joint base materials after prolonged high-temperature carburizing. This allows it to be used with other screw drill components resistant to 350°C to form 350°C-resistant screw drills, significantly improving the wear resistance and impact fracture resistance of the universal joint.

[0154] The embodiments of the present invention provide a more wear-resistant and longer-lasting universal joint for the exploration and development of high-temperature and ultra-high-temperature well screw drills, which has broad application prospects in the field of ultra-deep well exploration and development.

[0155] It can be further promoted and applied to long-life screw drills, which can significantly improve the service life of long-life screws and greatly improve the efficiency of drilling operations.

[0156] The prototype was tempered at 620℃, and theoretically, the overall strength of the universal joint body will not decrease below 630℃. The tungsten carbide sprayed layer will not fail or soften below 350℃, fully meeting the requirements of screw drill bits for high-temperature well conditions below 350℃.

[0157] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A surface hardening method for a universal joint of a screw drill bit, characterized in that, include: The universal joint blank that has undergone rough machining is subjected to heat treatment and finishing to obtain the universal joint body; After preheating the universal joint body, a tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal is spot-welded to the wear-resistant contact surface at one end of the universal joint body; the tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal is made by a YG8 alloy block wrapped with nickel-based brazing filler metal; spot welding the tungsten-cobalt alloy block wrapped with nickel-based brazing filler metal melts the bottom of the nickel-based brazing filler metal to weld it together with the universal joint body, and fixes the YG8 alloy block wrapped with nickel-based brazing filler metal to the wear-resistant contact surface of the universal joint; For the wear-resistant contact surface of the universal joint body after spot welding, nickel tungsten carbide powder and nickel-coated boron carbide composite powder are sprayed to form a hardened layer on the wear-resistant contact surface. After cooling, grind the spray-welded surface to the design dimensions; Inspect the pores of the spray-welded working surface after grinding, fill the pores with nickel tungsten carbide powder and nickel-coated boron carbide composite powder, and heat to melt and seal the pores. After cooling, the universal joint is precision ground to the design dimensions. For the wear-resistant contact surfaces of the universal joint body after spot welding, nickel-tungsten carbide powder and nickel-coated boron carbide composite powder are sprayed onto them, specifically including: Heat the YG8 alloy block wrapped with nickel-based brazing filler metal to 350°C; A 0.12-0.15 mm thick layer of NiWC35 tungsten carbide dispersion spray welding powder is sprayed onto the surface and around the YG8 alloy block wrapped with nickel-based solder as a pre-protective layer. Starting from the end of the spray-welded surface, the universal joint body is heated to 650℃-700℃; Starting from one end of the spray-welded surface, spray NiWC35 tungsten carbide dispersed spray-welded powder and nickel-coated boron carbide composite powder into the gaps of the YG8 alloy block wrapped with nickel-based brazing filler metal up to the height of the YG8 alloy block wrapped with nickel-based brazing filler metal, and melt it to a molten mirror state. Repeat this process until the end of the spray-welded surface is reached. During the spray welding process, the YG8 alloy block is not exposed to air, and the overall temperature of the universal joint body does not exceed 620℃.

2. The method as described in claim 1, characterized in that, The tungsten-cobalt alloy block encased in the spot-welded nickel-based brazing filler metal extends to the wear-resistant contact surface at one end of the universal joint body, including: Multiple tungsten-cobalt alloy blocks, each wrapped with nickel-based brazing filler metal, are spot-welded one by one to the wear-resistant contact surface at one end of the universal joint, so that the tungsten-cobalt alloy blocks are fixed to the wear-resistant contact surface in a uniformly distributed toothed manner.

3. The method as described in claim 2, characterized in that, The arrangement density of multiple nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks does not exceed 50%, and the arrangement density is the ratio of the total area of ​​the nickel-based brazing filler metal-encapsulated tungsten-cobalt alloy blocks to the area of ​​the wear-resistant contact surface.

4. The method as described in claim 1, characterized in that, During spray welding, the powder feeding switch of the spray gun is turned on intermittently to feed powder. The nozzle of the spray gun is at an angle of 80-90° to the surface to be sprayed. The oxygen pressure used is 0.45-0.50 MPa, and the acetylene pressure used is 0.04 MPa. The straight-line distance between the nozzle and the surface to be sprayed is 20-25 mm, and the nozzle moving speed is 5-8 meters / minute.

5. The method as described in claim 1, characterized in that, The pores are filled by heating and melting nickel-tungsten carbide powder and nickel-coated boron carbide composite powder through laser radiation. The universal joint after filling the pores is placed in a 200°C box-type resistance furnace or lime wool for slow cooling until the universal joint is cooled to room temperature before being taken out of the furnace.

6. The method according to any one of claims 1-5, characterized in that, The preheating of the universal joint body includes: The universal joint body is preheated in a box-type resistance furnace with an inert protective atmosphere. First, inert protective gas is introduced to purge the air in the furnace, and then the temperature is raised to 250-300℃ and held for 2 hours.

7. The method according to any one of claims 1-5, characterized in that, The rough-machined universal joint blank undergoes quenching and tempering treatment, including: The universal joint body is heated to 860℃±5℃ in a heating furnace and held at 860℃±5℃ for 1.5 hours. After holding, it is transferred to a rapid quenching oil or water-based quenching medium for rapid cooling to cool the universal joint body to room temperature. Within 2 hours, the universal joint body is transferred back into the heating furnace and reheated to 630℃±5℃. After a 2-hour heat preservation process at 630℃±5℃, it is quickly transferred to a cooling water tank with a water temperature below 30℃ to cool to room temperature.

8. A universal joint for a screw drill bit, characterized in that, The universal joint is manufactured by the surface hardening method of the screw drill universal joint as described in any one of claims 1-7.

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