Method for improving temperature resistance and wear resistance of cardan shaft of screw drill

Abstract

The invention relates to the field of screw drill machinery, and particularly discloses a method for improving temperature resistance and wear resistance of a cardan shaft of a screw drill, the friction part of the cardan shaft is treated by salt bath nitriding and salt bath oxidation processes, the salt bath nitriding treatment temperature is 550-620 DEG C, the salt bath oxidation treatment time is longer than 3 hours, the salt bath oxidation treatment temperature is 350-450 DEG C, and the salt bath oxidation treatment time is 0.5-1 hour; or a diamond-like carbon coating is sprayed through a plasma-assisted chemical vapor deposition process, the hardness of the coating is larger than 750 HV, the temperature resistance is larger than 300 DEG C, and the thickness of the coating is 0.03-0.05 mm. According to the method, the temperature resistance and wear resistance of the cardan shaft of the screw drill can be improved, and the requirement for 300 DEG C deep well drilling can be met.

Description

Technical Field

[0001] This invention relates to the field of screw drill mechanical technology, specifically a method for improving the temperature and wear resistance of the universal joint of a screw drill. Background Technology

[0002] Screw drills are the most commonly used downhole power tools in oil and gas drilling. They mainly consist of bypass valves, motor assemblies, universal joint assemblies, and drive shaft assemblies. The universal joint is a key component in the transmission of screw drills, and commonly used universal joints are classified as ball joint universal joints, flexible shaft universal joints, and petal universal joints. The universal joint mainly converts the planetary motion of the screw motor into coaxial rotational motion. It bears high stress loads, and currently, the most common failure modes are fracture and excessive wear. The service life of the universal joint is relatively short, which directly affects the downhole service life of the screw drill.

[0003] Existing universal joints are designed to seal the injected lubricating oil, facilitating rotation and improving wear resistance. However, during downhole operations, seals made of materials such as nitrile rubber are often used to seal the lubricated joints. Ordinary nitrile rubber generally has a temperature resistance of no more than 175°C. Currently, with the increase in drilling depth, downhole temperatures are also rising. In the future, downhole temperatures in ultra-deep wells will exceed 175°C. Universal joints should meet the above-mentioned high-temperature requirements. In addition to safety margin requirements, they should generally meet the 300°C requirement. This high-temperature condition often leads to a decrease in shaft fatigue strength, which in turn causes the universal joint to fail. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the temperature and wear resistance of the universal joint of a screw drill bit, which can meet the requirements of deep well drilling at 300℃.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for improving the temperature and wear resistance of the universal joint of a screw drill bit.

[0007] The friction parts of the universal joint are treated by salt bath nitriding and salt bath oxidation processes. The salt bath nitriding treatment is carried out at a temperature of 550-620℃ for more than 3 hours, and the salt bath oxidation treatment is carried out at a temperature of 350-450℃ for 0.5-1 hour. Alternatively, a diamond-like carbon coating is sprayed by plasma-assisted chemical vapor deposition. The coating has a hardness >750HV, a temperature resistance >300℃, and a coating thickness of 0.03-0.05mm.

[0008] In a further embodiment, the universal joint includes a rotor connector, a movable seat, a movable shaft, a limiting pin, and a connecting rod. The rotor connector has a first mounting groove. One end of the movable seat is connected to the first mounting groove, and the other end of the movable seat has a second mounting groove. One end of the movable shaft is slidably connected to the second mounting groove, and the other end of the movable shaft is locked to one end of the connecting rod by the limiting pin.

[0009] In a further embodiment, the rotor connector has a forked notch near the movable shaft end, and one end of the movable shaft is spherical, which is enclosed in a second mounting groove and slidably connected to the second mounting groove. The bottom of the spherical notch is slidably connected to the second mounting groove. A cutting surface is provided on the side of the spherical notch to insert into the forked notch. The end of the connecting rod has a forked notch that mates with the forked notch on the rotor connector and a third mounting groove to accommodate the other end of the movable shaft. Corresponding pin holes are provided on the other end of the movable shaft and the forked notch of the connecting rod. The other end of the movable shaft extends out of the first mounting groove and is inserted into the third mounting groove. After the limiting pin is inserted into the corresponding pin hole, it is welded and locked.

[0010] In a further embodiment, the corresponding sidewalls of the fork-shaped notches of the connecting rod and the rotor joint are brazed with cemented carbide, with the cemented carbide block having a embedment depth of ≥2.5mm and a coverage rate of ≥50%.

[0011] In a further embodiment, the rotor joint is tempered to 34-40 HRC using a quenching and tempering process.

[0012] In a further embodiment, the movable seat is adjusted to 34-40 HRC through a heat treatment process.

[0013] In a further embodiment, the active shaft is adjusted to 34-40 HRC through a heat treatment process.

[0014] In a further embodiment, the connecting rod is adjusted to 34-40 HRC through a heat treatment process.

[0015] In a further embodiment, the friction surface of the movable seat used for sliding is made by spraying Ni 60 material, and the connection end with the movable shaft is ground into a standard smooth arc with a thickness ≥3mm and a hardness of 55-65HRC.

[0016] Alternatively, the material can be cleaned under vacuum conditions using plasma, and then a DLC coating can be applied using plasma-assisted chemical vapor deposition. The coating hardness is >750HV, the temperature resistance is >300℃, and the coating thickness is 0.03-0.05mm.

[0017] In a further embodiment, the sliding friction part of the movable shaft is coated with a wear-resistant self-lubricating coating with a hardness of 50-60 HRC and a coating thickness of 0.15-0.2 mm.

[0018] Alternatively, a DLC coating can be applied by plasma-assisted chemical vapor deposition (PCVD) with a hardness >750HV, a temperature resistance >300℃, and a thickness of 0.03-0.05mm.

[0019] The beneficial effects of this invention are:

[0020] This invention's universal joint is made entirely of metal and uses a plug-in structure to convert the planetary motion of the screw motor into concentric rotational motion. Through tempering, salt bath nitriding, and salt bath oxidation treatments, the universal joint's temperature resistance is improved, allowing for long-term use in ultra-high temperature environments exceeding 300°C. The easily worn contact surfaces are treated with a special process, resulting in enhanced wear resistance, torsional resistance, and shear resistance, with less susceptibility to fluid properties and a long service life. This invented high-temperature resistant universal joint can be used in high-torque screw drills and all-metal screw drills for deep and ultra-deep well drilling, effectively breaking rock, increasing mechanical drilling speed, reducing drilling costs, and shortening drilling cycles. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a high-temperature resistant universal joint;

[0023] Figure 2 This is a 3D diagram of the rotor joint;

[0024] Figure 3 This is a cross-sectional view of the fork-shaped notch at the rotor joint;

[0025] Figure 4 This is a 3D schematic diagram of the movable seat;

[0026] Figure 5 This is a three-dimensional schematic diagram of the movable axis;

[0027] Figure 6 This is a three-dimensional schematic diagram of the limit pin;

[0028] Figure 7 This is a 3D schematic diagram of the connecting rod;

[0029] Figure 8 This is a cross-sectional view of the fork-shaped notch on the connecting rod;

[0030] Figure 9 This is a 3D schematic diagram of a primary assembly;

[0031] Figure 10 This is an assembly diagram of the limit pin, connecting rod, and movable shaft. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] First Embodiment

[0034] like Figure 1 As shown, a universal joint for a screw drill includes: a rotor joint 1, a movable seat 2, a movable shaft 3, a limiting pin 4, and a connecting rod 5. The rotor joint 1 and the connecting rod 5 are connected by a plug-in structure, and wear-resistant treatment is added to the parts that are prone to wear and damage, so as to withstand the high-frequency vibration generated during drilling.

[0035] like Figure 2 The rotor connector 1 shown is configured such that one end 1-1 is used to connect to the screw, and the other end 1-2 is used to connect to the connecting rod 5. The end 1-2 connected to the connecting rod 5 mainly consists of, as shown in the figure... Figure 3 The forked notch 1-2-1 and the contact sidewall 1-2-2 shown are used. (See reference...) Figure 1 The rotor joint 1 shown is connected to the rotor of an eccentric planetary screw motor. The rotational torque generated by the screw motor rotor is sequentially transmitted through the rotor joint 1, the connecting rod 5 and the rotor joint 1, converting the eccentricity into concentric rotational motion, and transmitting the rotational torque to the drive shaft assembly.

[0036] like Figure 4 As shown, one end 2-1 of the movable seat 2 is inserted into the... Figure 1 In the first mounting groove 1-3 shown, the other end 2-2 of the movable seat is in direct contact with one end 3-1 of the movable shaft 3. The movable seat 2 bears the external axial thrust and has a certain buffering effect.

[0037] like Figure 5 As shown, one end 3-1 of the movable shaft 3-2 has a convex spherical part for inserting into the second mounting groove 2-3 to realize the movable shaft to rotate and slide in all directions. The other end 3-4 of the shaft body 3-2 has a pin hole 3-3. The main function of the movable shaft 3 is to connect the rotor joint 1 and the connecting rod 5 by cooperating with the limiting pin 4.

[0038] like Figure 6As shown, the limiting pin 4 is mainly composed of a pin body 4-1 and a limiting pin head 4-2. The pin body 4-1 is fitted with pin holes 5-2 and 3-3. The limiting pin head 4-2 is welded to the pin hole 5-2 as a whole using a spray welding process, so as to achieve a stable connection between the movable shaft 3 and the connecting rod 5.

[0039] like Figure 7 As shown, each of the forked notches 5-1 of the connecting rod 5 has a pin hole 5-2. The main function of the pin hole 5-2 is to connect the movable shaft 3 and the connecting rod 5. The connecting rod 5 mainly buffers the axial force from the drill bit, and the forked notches 5-1 mainly transmit the rotational torque to the drive shaft assembly. Figure 8 As shown, the side surface 5-1-2 of the fork body 5-1-1 of the fork-shaped notch 5-1 is provided with a wear-resistant protective layer 5-1-3 to increase the wear resistance when in contact with the side wall 1-2-2 of the fork-shaped notch 1-2-1 of the rotor joint 1.

[0040] To improve the temperature and wear resistance of the universal joint of the screw drill during parts processing, the rotor joint 1 can be made of 4330V material. An ultra-high temperature tempering process is used to adjust the overall hardness of the joint material to 34-40 HRC. At the fork-shaped notches 1-2, a diamond-like carbon (DLC) coating is sprayed using plasma-assisted chemical vapor deposition to form its wear-resistant protective layer 1-2-3. The treated area needs to be thoroughly cleaned under vacuum conditions to enhance coating adhesion. The coating used has a hardness >750 HV, a temperature resistance >300℃, a thickness of 0.03-0.05 mm, and uniform spray thickness. The movable seat 2 is tempered to 34-40 HRC. At the other end 2-2, the movable seat is ground into a standard smooth arc, cleaned under vacuum conditions using plasma, and then coated with a DLC coating using plasma-assisted chemical vapor deposition. The coating hardness >750 HV and temperature resistance >300℃. The coating thickness is 0.03-0.05mm, and the spraying thickness is uniform. The material of the movable shaft 3 joint needs to be tempered to 34-40HRC. During processing, one end 3-1 of the movable shaft is sprayed with DLC coating using plasma-assisted chemical vapor deposition. The coating hardness is >750HV, the temperature resistance is >300℃, the coating thickness is 0.03-0.05mm, and the spraying thickness is uniform. The shaft head is lubricated. The material of the connecting rod 5 joint needs to be tempered to 34-40HRC. The joint material is the body material 4330V. The side wall 5-1-2 boundary of the fork body 5-1-1 at the fork-shaped notch 5-1 is polished smooth. It is cleaned with plasma under vacuum conditions. The DLC coating is sprayed using plasma-assisted chemical vapor deposition. The coating hardness is >750HV, the temperature resistance is >300℃, the coating thickness is 0.03-0.05mm, and the spraying thickness is uniform. This forms the wear-resistant protective layer 5-1-3.

[0041] like Figure 1As shown, during the assembly of the universal joint, firstly, one end 2-1 of the movable seat 2 is rotated and inserted into the first mounting groove 1-3 of the rotor joint 1, connecting with the first mounting groove 1-3. Then, one end 3-1 of the movable shaft 3, with its cutting surface 3-5 parallel to the fork-shaped notch 1-2, is inserted and rotated 90° to obtain a preliminary assembly. Next, the pin hole 5-2 of the connecting rod 5 is aligned with the pin hole 3-3 of the movable shaft 3. The limiting pin 4 is inserted into the pin hole 5-2 and the pin hole 3-3. The pin head 4-2 is connected to the pin hole 5-2 by spray welding, thus fixing the limiting pin 4 and assembling the connecting rod 5. Similarly, the rotor joint 1, movable seat 2, and movable shaft 3 are assembled first on the other end. Then, through the mutual cooperation of the limiting pin 4, pin hole 5-2, and pin hole 3-3, the connecting rod 5 is assembled, thereby completing the assembly of the universal joint.

[0042] In actual operation, the rotor joints 1 at both ends of the connecting rod 5 are connected to the screw motor rotor on the top and the transmission shaft assembly on the bottom. The rotor joints 1 mainly receive and transmit the rotational torque of the screw motor, while the movable seat 2 bears the axial thrust from the outside. The rotor joints 1, the movable shaft 3, and the limit pin 4 work together to connect the rotor joints 1 and the connecting rod 5 to transmit the rotational torque, thereby completing the smooth transmission of power.

[0043] Second Embodiment

[0044] In the second embodiment, the parts identical to those in the first embodiment will not be described again. During parts processing, the rotor joint 1 is made of 4330V material and undergoes an ultra-high temperature tempering process to adjust the overall hardness of the joint material to 34-40 HRC. The fork-shaped notches 1-2 are treated with salt bath nitriding and salt bath oxidation processes to form a wear-resistant protective layer 1-2-3 on the surface. The salt bath nitriding treatment temperature is 550-620℃ for more than 3 hours, and the salt bath oxidation treatment temperature is 350-450℃ for 0.5-1 hour. The movable seat 2 body is tempered to 34-40 HRC. The other end 2-2 of the movable seat is ground into a standard smooth arc and treated with salt bath nitriding and salt bath oxidation processes to form a wear-resistant protective layer on the surface. The salt bath nitriding treatment temperature is 550-620℃ for [time missing]. For the first joint, the salt bath oxidation treatment should last for more than 3 hours at a temperature of 350-450℃ for 0.5-1 hours. The material of the movable shaft 3 joint needs to be tempered to 34-40HRC. During processing, one end 3-1 of the movable shaft is sprayed with a wear-resistant self-lubricating coating with a hardness of 50-60HRC and a coating thickness of 0.15-0.2mm. The material of the connecting rod 5 joint needs to be tempered to 34-40HRC. The joint material is the body material 4330V. The side 5-1-2 boundary of the fork-shaped notch 5-1 and the fork body 5-1-1 is polished smooth. The surface is treated with salt bath nitriding and salt bath oxidation processes to form a wear-resistant protective layer 5-1-3. The salt bath nitriding treatment temperature is 550-620℃ for more than 3 hours, and the salt bath oxidation treatment temperature is 350-450℃ for 0.5-1 hours.

[0045] Third Embodiment

[0046] In the third embodiment, the parts identical to those in the first embodiment will not be described again. During parts processing, the rotor connector 1 is made of 4330V material, and the material itself undergoes an ultra-high temperature tempering process to adjust the overall hardness of the connector material to 34-40 HRC. The brazing boundary at the side 1-2-2 of the fork body 1-2-1 is ground smooth. A wear-resistant protective layer 1-2-3 is formed by brazing hard alloy at the contact surface 1-2-2 using a special process. The hard alloy block has an embedding depth ≥2.5mm and a coverage rate ≥50%. The movable seat 2-1 needs to be tempered to 34-40 HRC. The other end 2-2 of the movable seat 2 is spray-welded with Ni 60 material using a spray welding process, ground into a standard smooth arc with a thickness ≥3mm and a hardness of 55-65 HRC. The material of the movable shaft 3 connector needs to be tempered to 34-40 HRC. During processing, one end 3-1 of the movable shaft 3 is sprayed with a wear-resistant self-lubricating coating with a hardness of 50-60 HRC and a coating thickness of 0.15-0.2 mm. The material of the limit pin 4 connector needs to undergo special treatment to achieve an overall hardness of 277-331 HB. The material of the connecting rod connector needs to be tempered to 34-40 HRC. The connector material is the body material 4330V. The brazing boundary at the side 5-1-2 of the fork-shaped notch fork body 5-1-1 is polished smooth. The side 5-1-2 needs to be brazed to embed a YG8 hard alloy block with a embedding depth ≥2.5 mm and a hard alloy coverage ≥50%.

[0047] In the above embodiments, the metal joint material used for the universal joint can be one or a combination of several alloy steels such as 40Cr, 40CrNi, 40CrNiMo, 35CrMo, 42CrMo, 42CrMoS, 12CrNi3, and 20CrMnTi. Among them, the alloy steels 40Cr, 40CrNi, 40CrNiMo, 35CrMo, 42CrMo, 42CrMoS, 12CrNi3, and 20CrMnTi need to be quenched and tempered before use, with a quenching and tempering hardness of 250-300HB. The alloy steel materials 12CrNi3 and 20CrMnTi need to be carburized before use. It can also be alloy materials such as titanium alloys and nickel alloys, which need to be solution-treated and aged. It can also be stainless steel such as 0Cr17NiCuNb, which needs to be solution-treated and aged.

[0048] In the above examples, the metal joint material used for the universal joint can also be alloy materials such as titanium alloy, aluminum alloy and nickel alloy, or stainless steel D410, 0Cr17NiCuNb and 1Cr18Ni9Ti.

[0049] The high-temperature resistant universal joint is made entirely of metal and uses a plug-in structure to convert the planetary motion of the screw motor into concentric rotational motion. The forked notch plug-in structure facilitates assembly and disassembly. The invented high-temperature resistant universal joint has extremely strong temperature resistance and can be used for a long time in deep well environments. The above-mentioned coating is applied to the wear-prone contact surfaces, which has stronger wear resistance, torsion resistance, and shear resistance, is less affected by fluid properties, and has a long service life. The invented high-temperature resistant universal joint can be used in high-torque screw drills and all-metal screw drills for drilling deep and ultra-deep wells. It can effectively break rocks, increase mechanical drilling speed, reduce drilling costs, shorten drilling cycles, and improve economic efficiency.

[0050] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," "longitudinal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings.

[0051] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0052] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit, characterized in that, The friction parts of the universal joint are treated by salt bath nitriding and salt bath oxidation processes. The salt bath nitriding treatment is carried out at a temperature of 550-620℃ for more than 3 hours, and the salt bath oxidation treatment is carried out at a temperature of 350-450℃ for 0.5-1 hour. Alternatively, a diamond-like carbon coating is sprayed by plasma-assisted chemical vapor deposition. The coating has a hardness >750HV, a temperature resistance >300℃, and a coating thickness of 0.03-0.05mm.

2. The method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 1, characterized in that, The universal joint includes a rotor connector (1), a movable seat (2), a movable shaft (3), a limiting pin (4), and a connecting rod (5). The rotor connector (1) has a first mounting groove (1-3). One end (2-1) of the movable seat (2) is connected to the first mounting groove (1-3). The other end (2-2) of the movable seat (2) has a second mounting groove (2-3). One end (3-1) of the movable shaft (3) is slidably connected to the second mounting groove (2-3). The other end (3-4) of the movable shaft (3) is locked to one end of the connecting rod (5) through the limiting pin (4).

3. The method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The rotor connector (1) has a forked notch (1-2) near the movable shaft (3). One end (3-1) of the movable shaft (3) is spherical, which is enclosed in the second mounting groove (2-3) and slidably connected to it. The bottom of the spherical notch is slidably connected to the second mounting groove (2-3). A cutting surface (3-5) is provided on the side of the spherical notch, which can be inserted into the forked notch. The end of the connecting rod (5) has a forked notch (1-2) on the rotor connector (1). The fork-shaped notch (5-1) for docking and the third mounting groove (5-2) for accommodating the other end (3-4) of the movable shaft (3) are provided with corresponding pin holes (3-3, 5-2) on the other end of the movable shaft (3) and the fork-shaped notch (5-1) of the connecting rod (5). The other end (3-4) of the movable shaft (3) extends out of the first mounting groove (1-3) and is inserted into the third mounting groove (5-2). After the limiting pin (4) is inserted into the corresponding pin hole (3-3, 5-2), it is welded and locked.

4. The method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 3, characterized in that, The corresponding sidewalls of the forked notches (1-2, 5-1) of the connecting rod (5) and the rotor joint (1) are brazed with cemented carbide, with the cemented carbide block buried at a depth of ≥2.5mm and the cemented carbide block coverage rate ≥50%.

5. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The rotor joint (1) is adjusted to 34-40 HRC by a heat treatment process.

6. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The active seat (2) is adjusted to 34-40 HRC through a heat treatment process.

7. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The active shaft (3) is adjusted to 34-40 HRC through a heat treatment process.

8. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The connecting rod (5) is adjusted to 34-40 HRC through a heat treatment process.

9. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The friction surface of the movable seat (2) for sliding is made of Ni60 material by spray welding, and the connection end with the movable shaft (3) is ground into a standard smooth arc with a thickness ≥3mm and a hardness of 55-65HRC. Alternatively, the material can be cleaned under vacuum conditions using plasma, and then a DLC coating can be applied using plasma-assisted chemical vapor deposition. The coating hardness is >750HV, the temperature resistance is >300℃, and the coating thickness is 0.03-0.05mm.

10. A method for improving the temperature and wear resistance of the universal joint of a screw drill bit according to claim 2, characterized in that, The sliding friction part of the movable shaft (3) is coated with a wear-resistant self-lubricating coating with a hardness of 50-60HRC and a coating thickness of 0.15-0.2mm. Alternatively, a DLC coating can be applied by plasma-assisted chemical vapor deposition (PCVD) with a hardness >750HV, a temperature resistance >300℃, and a thickness of 0.03-0.05mm.

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