Cardan shaft assembly of screw drill

Abstract

The screw drill cardan shaft assembly comprises a connecting rod, the two ends of the connecting rod are each provided with a movable shaft, and each movable shaft can be connected into a rotor connector in a universal rotation mode; and the side wall of each rotor joint can be inserted into the side wall of the connecting rod in a shifting fork manner. Through shifting fork type insertion connection of the rotor connector and the connecting rod, plane planetary motion of the screw motor rotor is converted into concentric rotation motion, transmission of rotation torque is achieved, the screw drill and the drill bit are matched to effectively break rocks, the mechanical drilling speed is increased, it is guaranteed that the screw drill meets underground application conditions, and the tripping frequency is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of screw drill tools, and in particular to a universal shaft assembly of a screw drill tool. Background Art

[0002] Screw drill bits are the most commonly used downhole power tools for oil and gas drilling. They are mainly composed of a bypass valve, a motor assembly, a universal shaft assembly and a drive shaft assembly. The universal shaft assembly is a key component of the screw drill bit transmission and is subject to large stress loads. Currently, most failures are caused by fracture and wear transition. The life of the universal shaft assembly directly affects the downhole service life of the screw drill bit.

[0003] With the development of oil and gas exploration and development, more and more attention has been focused on deep wells and ultra-deep wells. However, as the depth increases, the development environment of oil and gas becomes more complex. The compaction effect increases the hardness of the formation rock, which is resistant to abrasion and difficult to drill in hard rock. The development of ultra-deep wells places higher demands on the universal shaft assembly of the screw drill. The wear resistance is relatively poor, which places higher demands on the material of the core components of the universal shaft assembly. Therefore, in response to the development needs of ultra-deep wells, it is urgent to develop a universal shaft assembly that is wear-resistant, shear-resistant, torsion-resistant, and has a long service life to ensure that the screw drill meets the applicable conditions underground and reduce the number of trips.

[0004] Therefore, the inventor, relying on his many years of experience and practice in related industries, proposes a universal shaft assembly for a screw drill to overcome the defects of the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a universal shaft assembly for a screw drill, which overcomes the problems existing in the prior art. By means of a fork-type plug-in connection between a rotor joint and a connecting rod, the planar planetary motion of the screw motor rotor is converted into a concentric rotational motion, thereby realizing the transmission of rotational torque. The screw drill and the drill bit can cooperate to effectively break rocks, increase the mechanical drilling speed, ensure that the screw drill meets the applicable conditions underground, and reduce the number of trips.

[0006] The object of the present invention is achieved in this way. A universal shaft assembly of a screw drill comprises a connecting rod, wherein movable shafts are respectively arranged at both ends of the connecting rod, and each movable shaft can be universally rotatably connected to a rotor joint; and the side wall of each rotor joint can be fork-connected to the side wall of the connecting rod.

[0007] In a preferred embodiment of the present invention, the rotor joint includes a joint body, a joint fork is arranged at the first end of the joint body, and the joint fork includes a circumferentially spaced first substrate, both sides of the first substrate respectively constitute a first contact surface, and a first carbide block is arranged on each of the first contact surfaces.

[0008] In a preferred embodiment of the present invention, the connecting rod includes a rod body, and rod forks are respectively arranged at both ends of the rod body, and the rod fork includes a second substrate spaced circumferentially, and the two sides of the second substrate respectively constitute a second contact surface, and a second carbide block is arranged on each of the second contact surfaces; each of the second substrates can be inserted between two of the first substrates, and each of the second carbide blocks respectively abuts against each of the first carbide blocks along the circumference of the connecting rod.

[0009] In a preferred embodiment of the present invention, the movable shaft includes a shaft body, a shaft head is arranged at the first end of the shaft body, a spherical end face is arranged at the shaft head, and a cutting plane is arranged on the side wall of the shaft head; a first connecting blind hole is arranged inwardly at the first end of the joint body, a movable seat is arranged at the bottom of the first connecting blind hole, and a spherical contact surface is arranged on the end face of the movable seat; the shaft head is inserted into the first connecting blind hole, and the spherical end face is spherically abutted against the spherical contact surface.

[0010] In a preferred embodiment of the present invention, a limit groove is provided on the side wall of the second end of the shaft body; a second connecting blind hole is provided at the end of the connecting rod, the second end of the shaft body is inserted into the second connecting blind hole, a limit hole is provided on the side wall of the connecting rod, and limit pins are inserted into the limit hole and the limit groove.

[0011] In a preferred embodiment of the present invention, the limiting pin comprises a pin body, a pin head is arranged at the end of the pin body, and the pin head passes through the limiting hole and is inserted into the limiting groove.

[0012] In a preferred embodiment of the present invention, a tapered threaded portion is provided at the second end of each of the rotor joints.

[0013] In a preferred embodiment of the present invention, the first substrate is made of high-strength alloy steel 4330V, and the hardness of the first substrate is adjusted to 34-40HRC; the burial depth of the first cemented carbide block is ≥2.5mm, and the coverage rate of the first cemented carbide block on the first contact surface is ≥50%.

[0014] In a preferred embodiment of the present invention, the second substrate is made of high-strength alloy steel 4330V, and the hardness of the second substrate is adjusted to 34-40HRC; the burial depth of the second cemented carbide block is ≥2.5mm, and the coverage rate of the second cemented carbide block on the second contact surface is ≥50%.

[0015] In a preferred embodiment of the present invention, the hardness of the movable shaft is adjusted to 34-40HRC, and the shaft head is sprayed with a wear-resistant self-lubricating coating with a coating thickness of 0.15-0.2mm and a coating hardness of 50-60HRC.

[0016] In a preferred embodiment of the present invention, the hardness of the movable seat is adjusted to 34-40HRC, the spherical contact surface is spray-welded with a Ni60 material layer, the thickness of the Ni60 material layer is ≥3mm, and the hardness of the Ni60 material layer is 55-65HRC.

[0017] In a preferred embodiment of the present invention, the hardness of the limit pin is 277-331HB.

[0018] In a preferred embodiment of the present invention, the first cemented carbide block and the second cemented carbide block are YG8 cemented carbide blocks.

[0019] As described above, the screw drill universal shaft assembly provided by the present invention has the following beneficial effects:

[0020] The screw drill universal shaft assembly provided by the present invention converts the planar planetary motion of the screw motor rotor into concentric rotational motion through the fork-type plug-in connection between the rotor joint and the connecting rod, thereby realizing the transmission of rotational torque; the connecting rod transmits the torque through the concentric rotational motion, and at the same time buffers the axial force from the drill bit; the present invention transmits high torque through the rotor joint → connecting rod → rotor joint, and the screw drill and the drill bit cooperate to effectively break rocks, improve the mechanical drilling speed, ensure that the screw drill meets the applicable conditions downhole, and reduce the number of tripping and drilling; the present invention can be used in high-torque screw drills and all-metal screw drills to drill deep wells and ultra-deep wells, reduce drilling costs, and shorten drilling cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0022] in:

[0023] Figure 1 : It is a structural schematic diagram of the screw drill universal shaft assembly of the present invention.

[0024] Figure 2 : is a schematic diagram of the rotor joint of the present invention.

[0025] Figure 3 :for Figure 2 Middle AA section view.

[0026] Figure 4 : is a schematic diagram of a movable seat of the present invention.

[0027] Figure 5 : is a schematic diagram of the movable axis of the present invention.

[0028] Figure 6 : is a schematic diagram of a limit pin of the present invention.

[0029] Figure 7: is a schematic diagram of a connecting rod of the present invention.

[0030] Figure 8 :for Figure 7 Middle BB section view.

[0031] Fig. 9 : It is a cross-sectional view of the connection state of the rotor joint, movable seat and movable shaft of the present invention.

[0032] Fig.10 : It is an external view of the connection state of the rotor joint, movable seat and movable shaft of the present invention.

[0033] Fig.11 : It is a schematic diagram of the assembly of the limit pin of the present invention.

[0034] Fig.12 : It is an external view of the screw drill universal shaft assembly of the present invention after assembly.

[0035] In the figure:

[0036] 1. Rotor joint;

[0037] 11. Joint body; 12. Joint fork; 121. First base body; 122. First cemented carbide block; 13. Tapered thread portion;

[0038] 2. Movable seat;

[0039] 21. Spherical contact surface;

[0040] 3. Movable axis;

[0041] 31. shaft body; 32. shaft head; 321. cutting plane; 322. spherical end surface; 33. limiting groove;

[0042] 4. Limit pin;

[0043] 41. Pin body; 42. Pin head;

[0044] 5. Connecting rod;

[0045] 51. Rod body; 52. Rod fork; 521. Second base body; 522. Second cemented carbide block; 53. Limiting hole. DETAILED DESCRIPTION

[0046] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0047] The specific embodiments of the present invention described herein are only used to explain the purpose of the present invention and cannot be understood as limiting the present invention in any way. Under the guidance of the present invention, technicians can conceive of any possible variations based on the present invention, which should be considered to belong to the scope of the present invention. It should be noted that when an element is referred to as "arranged on" another element, it can be directly on the other element or there can also be a central element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a central element at the same time. The terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, or it can be the internal communication of two elements, it can be directly connected, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation method.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0049] like Figures 1 to 12 As shown, the present invention provides a screw drill universal shaft assembly, including a connecting rod 5, with movable shafts 3 respectively arranged at both ends of the connecting rod 5, each movable shaft 3 can be universally rotatably connected to a rotor joint 1; and the side wall of each rotor joint 1 can be forked and plugged into the side wall of the connecting rod 5.

[0050] The two rotor joints 1 are respectively connected to the screw motor rotor (existing technology) and the drive shaft assembly (existing technology). The rotor joint 1 is connected to the connecting rod 5 by plugging and unplugging. The rotor joint receives the rotational torque from the screw motor rotor. Through fork-type plug-in, the planar planetary motion (existing technology, eccentric rotation) of the screw motor rotor is converted into concentric rotational motion, thereby realizing the transmission of the rotational torque backward to the connecting rod 5.

[0051] Eccentric rotation is the movement form of the screw motor, which is the component connected to the upper part of the rotor joint. The concentric rotation movement is mainly realized by the fork of the rotor joint and the connecting rod through the plug-in action.

[0052] The main function of the connecting rod 5 is to transmit the torque through concentric rotational motion and to buffer the axial force from the drill bit (playing a buffering role on the external axial thrust).

[0053] The screw drill universal shaft assembly of the present invention is a symmetrical structure, and the rotor joint 1 and the connecting rod 5 are connected through a plug-in structure to complete torque transmission.

[0054] The screw drill universal shaft assembly provided by the present invention converts the planar planetary motion of the screw motor rotor into concentric rotational motion through the fork-type plug-in connection between the rotor joint and the connecting rod, thereby realizing the transmission of rotational torque; the connecting rod transmits the torque through the concentric rotational motion, and at the same time buffers the axial force from the drill bit; the present invention transmits high torque through the rotor joint → connecting rod → rotor joint, and the screw drill and the drill bit cooperate to effectively break rocks, improve the mechanical drilling speed, ensure that the screw drill meets the applicable conditions downhole, and reduce the number of tripping and drilling; the present invention can be used in high-torque screw drills and all-metal screw drills to drill deep wells and ultra-deep wells, reduce drilling costs, and shorten drilling cycles.

[0055] Further, if Figure 1 , Figure 2 , Figure 3 As shown, the rotor joint 1 includes a joint body 11, a joint fork 12 is arranged at the first end of the joint body 11, and the joint fork 12 includes a circumferentially spaced first substrate 121, and both sides of the first substrate 121 respectively constitute a first contact surface, and each first contact surface is provided with a first cemented carbide block 122. The cemented carbide blocks are embedded in the first contact surface to enhance the wear resistance and improve the service life, and it is also conducive to the realization of transmitting large torque.

[0056] When processing parts, the material of the first base 121 of the joint fork 12 is high-strength alloy steel 4330V, and the base material itself adopts ultra-high temperature quenching and tempering process, and the overall hardness of the first base 121 material is adjusted to 34-40HRC, and the boundary between the first base 121 and the first contact surface is polished and smooth, and the first contact surface is inlaid with the first cemented carbide block 122 by brazing process to enhance wear resistance. The first cemented carbide block 122 is a YG8 cemented carbide block, the burial depth of the first cemented carbide block 122 is ≥2.5mm, and the coverage rate of the first cemented carbide block 122 on the first contact surface is ≥50%.

[0057] Further, if Figure 7 , Figure 8As shown, the connecting rod 5 includes a rod body 51, and rod forks 52 are respectively arranged at both ends of the rod body 51. The rod forks 52 include second bases 521 spaced apart in the circumferential direction. The two sides of the second base 521 respectively constitute second contact surfaces, and second carbide blocks 522 are arranged on each second contact surface. The second contact surface is inlaid with carbide blocks to enhance wear resistance and service life, and is also conducive to the transmission of large torque; each second base 521 can be inserted between two first bases 121, and each second carbide block 522 is respectively pressed against each first carbide block 122 along the circumferential direction of the connecting rod 5. The rod body 51 mainly buffers the axial force from the drill bit, and transmits torque together with the rod fork 52.

[0058] The material of the connecting rod 5 (rod body 51 and second substrate 521) is high-strength alloy steel 4330V, and the rod body 51 and second substrate 521 are tempered to 34-40HRC; the boundary between the second substrate 521 and the second contact surface is polished and smooth, and the second contact surface needs to be inlaid with a YG8 cemented carbide block (second cemented carbide block 522) by brazing to enhance the overall wear resistance of the rod fork 52. The buried depth of the second cemented carbide block 522 is ≥2.5mm, and the coverage rate of the second cemented carbide block 522 on the second contact surface is ≥50%.

[0059] Further, if Figure 5 , Fig. 9 , Fig.10 As shown, the movable shaft 3 includes a shaft body 31, a shaft head 32 is provided at the first end of the shaft body 31, and a spherical end surface 322 is provided at the shaft head 32; a cutting plane 321 is provided on the side wall of the shaft head 32, and the cutting plane 321 is used as a reference during assembly; a first connecting blind hole is provided inwardly at the first end of the joint body 11, such as Figure 1 , Figure 4 As shown, a movable seat 2 is provided at the bottom of the first connecting blind hole, and a spherical contact surface 21 is provided on the end surface of the movable seat 2; the shaft head 32 is inserted into the first connecting blind hole, and the spherical end surface 322 is spherically abutted against the spherical contact surface 21. The spherical end surface 322 of the movable shaft 3 and the spherical contact surface 21 of the movable seat 2 are spherically contacted to realize the rotation of the movable shaft 3 in all directions, achieving the purpose of universal rotation. The movable seat 2 is in direct contact with the shaft head 32 of the movable shaft 3, which mainly plays a certain buffering role on the axial thrust during the drilling process.

[0060] The main function of the movable seat 2 is to bear the axial thrust from the drill bit during the drilling process and to buffer the thrust.

[0061] The material of the movable shaft 3 needs to be tempered to adjust the hardness to 34-40HRC, and the shaft head is sprayed with a wear-resistant self-lubricating coating with a coating thickness of 0.15-0.2mm and a coating hardness of 50-60HRC to enhance the wear resistance of the shaft head during use.

[0062] The movable seat 2 needs to adopt the tempering process to adjust the hardness to 34-40HRC, spray-weld the Ni60 material layer on the spherical contact surface, and grind it into a standard smooth arc. The thickness of the Ni60 material layer is ≥3mm, and the hardness of the Ni60 material layer needs to reach 55-65HRC.

[0063] The screw drill universal shaft assembly of the present invention adopts a reinforced design at the contact parts of the components that are prone to wear and damage, including the joint fork 12 of the rotor joint 1, the spherical contact surface 21 of the movable seat 2, the shaft head 32 of the movable shaft 3, and the rod fork 52 of the connecting rod 5. The design mainly includes embedding carbide blocks at the joint fork 12 and the rod fork 52, spraying Ni60 alloy material on the spherical contact surface 21 of the movable seat 2 by a spray welding process, and spraying a wear-resistant self-lubricating coating on the shaft head 32 of the movable shaft 3. The contact parts of the components withstand the high-frequency vibration generated during the drilling process, thereby improving the wear resistance and extending the service life.

[0064] Further, if Figure 5 As shown, a limiting groove 33 is provided on the side wall of the second end of the shaft body 31; a second connecting blind hole is provided at the end of the connecting rod 5, and the second end of the shaft body is inserted into the second connecting blind hole. A limiting hole 53 is provided on the side wall of the connecting rod 5, and limiting pins are inserted into the limiting hole 53 and the limiting groove 33 to realize the connection between the movable shaft 3 and the connecting rod 5.

[0065] The movable shaft 3 is connected to the rotor joint 1 and the connecting rod 5 by cooperating with the limit pin 4, ensuring that the rotor joint 1 and the connecting rod 5 will not be separated when they are matched through the plug-in structure, and also ensuring that the movable shaft 3 will not fall off during universal motion.

[0066] Further, if Figure 6 As shown, the limit pin 4 includes a pin body 41, and a pin head 42 is provided at the end of the pin body 41. The pin head 42 passes through the limit hole 53 and is inserted into the limit groove 33. The base material of the limit pin 4 needs to be specially treated as a whole, and the overall hardness reaches 277-331HB. The pin head 42 is welded to the limit hole 53 as a whole by a spray welding process, so as to realize the stable connection between the movable shaft 3 and the connecting rod 5.

[0067] Further, if Figure 1 , Figure 2 As shown, a tapered threaded portion 13 is provided at the second end of each rotor joint 1, and the tapered threaded portions 13 of the two rotor joints 1 are respectively connected to the screw motor rotor (existing technology) and the transmission shaft assembly (existing technology).

[0068] When assembling the universal shaft assembly of the screw drill of the present invention, first assemble one end of the rotor joint 1 with the movable seat 2 and the movable shaft 3 (such as Fig. 9 , Fig.10As shown), the movable seat 2 is embedded in the first connecting blind hole of the rotor joint 1, and the cutting plane 321 of the shaft head 32 of the movable shaft 3 is installed parallel to the joint fork 12. When the shaft head 32 contacts the spherical contact surface 21 of the movable seat 2, the movable shaft 3 is rotated 90° to obtain the following Fig.10 The primary assembly is shown.

[0069] like Fig.11 As shown, the limiting hole 53 of the connecting rod is then aligned with the limiting groove 33 of the movable shaft, the limiting pin 4 is inserted into the limiting hole 53 and the limiting groove 33, and the limiting pin 4 and the limiting hole 53 are connected as a whole by a spray welding process, so as to fix the limiting pin 4 and assemble the connecting rod 5. The other end of the rotor joint 1 is also assembled with the rotor joint 1, the movable seat 2, and the movable shaft 3, and then the connecting rod 5 is assembled through the mutual cooperation of the limiting pin 4, the limiting hole 53, and the limiting groove 33, as shown. Fig.12 As shown, the assembly of the screw drill universal shaft assembly is completed.

[0070] As described above, the screw drill universal shaft assembly provided by the present invention has the following beneficial effects:

[0071] The screw drill universal shaft assembly provided by the present invention converts the planar planetary motion of the screw motor rotor into concentric rotational motion through the fork-type plug-in connection between the rotor joint and the connecting rod, thereby realizing the transmission of rotational torque; the connecting rod transmits the torque through the concentric rotational motion, and at the same time buffers the axial force from the drill bit; the present invention transmits high torque through the rotor joint → connecting rod → rotor joint, and the screw drill and the drill bit cooperate to effectively break rocks, improve the mechanical drilling speed, ensure that the screw drill meets the applicable conditions downhole, and reduce the number of tripping and drilling; the present invention can be used in high-torque screw drills and all-metal screw drills to drill deep wells and ultra-deep wells, reduce drilling costs, and shorten drilling cycles.

[0072] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A universal shaft assembly for a screw drill, It is characterized in that It comprises a connecting rod, and movable shafts are respectively arranged at both ends of the connecting rod, and each movable shaft can be universally rotatably connected to a rotor joint; and the side wall of each rotor joint can be forked and plugged to connect the side wall of the connecting rod.

2. The screw drill universal shaft assembly according to claim 1, It is characterized in that The rotor joint comprises a joint body, a joint fork is arranged at the first end of the joint body, the joint fork comprises a first substrate spaced circumferentially, both sides of the first substrate respectively constitute first contact surfaces, and a first cemented carbide block is arranged on each of the first contact surfaces.

3. The screw drill universal shaft assembly as claimed in claim 2, It is characterized in that The connecting rod includes a rod body, and rod forks are respectively arranged at both ends of the rod body. The rod fork includes a second substrate spaced circumferentially, and the two sides of the second substrate respectively constitute a second contact surface, and a second cemented carbide block is arranged on each of the second contact surfaces; each of the second substrates can be inserted between two of the first substrates, and each of the second cemented carbide blocks respectively abuts against each of the first cemented carbide blocks along the circumference of the connecting rod.

4. The screw drill universal shaft assembly as claimed in claim 2, It is characterized in that The movable shaft includes a shaft body, a shaft head is arranged at the first end of the shaft body, a spherical end face is arranged at the shaft head, and a cutting plane is arranged on the side wall of the shaft head; a first connecting blind hole is arranged inwardly at the first end of the joint body, a movable seat is arranged at the bottom of the first connecting blind hole, and a spherical contact surface is arranged on the end face of the movable seat; the shaft head is inserted into the first connecting blind hole, and the spherical end face is spherically abutted against the spherical contact surface.

5. The screw drill universal shaft assembly as claimed in claim 4, It is characterized in that A limiting groove is arranged on the side wall of the second end of the shaft body; a second connecting blind hole is arranged on the end of the connecting rod, the second end of the shaft body is inserted into the second connecting blind hole, a limiting hole is arranged on the side wall of the connecting rod, and limiting pins are inserted into the limiting hole and the limiting groove.

6. The screw drill universal shaft assembly according to claim 5, It is characterized in that The limiting pin comprises a pin body, a pin head is arranged at the end of the pin body, and the pin head passes through the limiting hole and is inserted into the limiting groove.

7. The screw drill universal shaft assembly according to claim 1, It is characterized in that A tapered threaded portion is provided at the second end of each of the rotor joints.

8. The screw drill universal shaft assembly as claimed in claim 2, It is characterized in that The first substrate is made of high-strength alloy steel 4330V, and the hardness of the first substrate is adjusted to 34-40HRC; the embedding depth of the first hard alloy block is ≥2.5mm, and the coverage rate of the first hard alloy block on the first contact surface is ≥50%.

9. The screw drill universal shaft assembly according to claim 3, It is characterized in that The second substrate is made of high-strength alloy steel 4330V, and the hardness of the second substrate is adjusted to 34-40HRC; the embedding depth of the second hard alloy block is ≥2.5mm, and the coverage rate of the second hard alloy block on the second contact surface is ≥50%.

10. The screw drill universal shaft assembly according to claim 4, It is characterized in that The hardness of the movable shaft is adjusted to 34-40HRC, and the shaft head is sprayed with a wear-resistant self-lubricating coating with a coating thickness of 0.15-0.2mm and a coating hardness of 50-60HRC.

11. The screw drill universal shaft assembly according to claim 4, It is characterized in that The hardness of the movable seat is adjusted to 34-40HRC, the spherical contact surface is spray-welded with a Ni60 material layer, the thickness of the Ni60 material layer is ≥3mm, and the hardness of the Ni60 material layer is 55-65HRC.

12. The screw drill universal shaft assembly according to claim 5, It is characterized in that The hardness of the limit pin is 277-331HB.

13. The screw drill universal shaft assembly according to claim 3, It is characterized in that The first cemented carbide block and the second cemented carbide block are YG8 cemented carbide blocks.

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