Drill rod pressure block, rotary drilling rig drill rod and preparation method of gradient wear-resistant layer

Abstract

This invention discloses a drill rod pressure block, a rotary drilling rig drill rod, and a method for preparing a gradient wear-resistant layer. The drill rod pressure block is fixed to the outer side of the drill rod cylinder to bear the downward pressure of the drive sleeve. It includes a substrate and a gradient wear-resistant layer fixed to the upper end of the substrate. The upper end profile of the substrate is consistent with the lower end profile of the gradient wear-resistant layer. The upper end profile of the gradient wear-resistant layer is planar. The gradient wear-resistant layer includes a second coating with a gradually increasing radial thickness gradient from the outer side of the drill rod cylinder and a first coating with a constant thickness. The first coating is located outside the second coating. Advantages: It solves the technical problem of uneven pressure distribution during service, which leads to inconsistent wear progress on the bearing surface of the rotary drilling rig drill rod pressure block; the functional gradient wear-resistant coating cladding method and path using a combination of ultra-high speed and high speed laser cladding significantly reduces the depth of the tempering softening zone caused by secondary heating during the preparation process; the dedicated tooling can accurately position the pressure block, making clamping simple and efficient.

Description

Technical Field

[0001] This invention relates to a drill rod pressure block, a rotary drilling rig drill rod, and a method for preparing a gradient wear-resistant layer, belonging to the field of mechanical equipment technology. Background Technology

[0002] Rotary drilling rigs, as important equipment in the field of engineering machinery, rely primarily on the drill rod to transmit power loads to the drill bucket, rotating forward to achieve the purpose of breaking up rock and soil. The drill rod typically consists of multiple seamless steel pipe sleeves of varying diameters. Each section has a drive key and a pressure block welded around its outer circumference to transmit torque, axial pressure, and other loads. Under harsh conditions such as hard rock, the drill rod will be subjected to enormous reaction impact loads. Therefore, to improve efficiency during construction, a large driving load needs to be applied to the bearing surface of the pressure block, with a theoretical load per unit area of ​​approximately 40 MPa. However, because the drive key, which applies the driving load, needs to move up and down, there is a radial gap between it and the drill rod sleeve. Simultaneously, during construction, the drill rod is subjected to irregular lateral loads, causing lateral relative movement between it and the drive key, affecting the interaction area between the drive key and the pressure block, and increasing the surface load on the pressure block. Although the pressure block undergoes overall quenching treatment, under heavy loads, its surface still experiences uneven wear and severe crushing failures, thus affecting the operating efficiency and safety of the rotary drilling rig. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing a drill rod pressure block, a rotary drilling rig drill rod, and a gradient wear-resistant layer.

[0004] To solve the above technical problems, the present invention provides a drill pipe pressure block, which is fixed on the outer side of the drill pipe cylinder to bear the downward pressure of the drive sleeve. It includes a base and a gradient wear-resistant layer fixed on the upper end of the base, wherein the upper end profile of the base is consistent with the lower end profile of the gradient wear-resistant layer.

[0005] The upper surface of the gradient wear-resistant layer is a plane;

[0006] The gradient wear-resistant layer includes a second coating with a gradually increasing radial thickness from the outer side of the drill pipe cylinder to the outside, and a first coating with a constant thickness, with the first coating located outside the second coating; the radial direction refers to the diameter direction of the cross-section of the drill pipe cylinder.

[0007] Furthermore, the outer surface of the drill rod pressure block, which is composed of the matrix and the gradient wear-resistant layer, is an arc surface.

[0008] Furthermore, the thickness of the first coating is H1, and the width is 2B1-D; the width of the second coating is 2D-2B1, and the gradient thickness H is expressed as: H=H1+(Smax-S) / (Smax-Smin)*(H2-H1).

[0009] Where B1 is the width of the area where the drive key of the drive sleeve interacts with the pressure block when the drive sleeve is coaxial with the drill pipe body; D is the width of the pressure block;

[0010] S represents the effective area of ​​the driving key relative to the pressure block when they are in any position during construction.

[0011] S=δ*π*(2(R+D)*BB 2 );

[0012] Smax is the maximum effective area of ​​the driving key relative to the pressure block when the driving key is in any position during construction.

[0013] Smax=δ*π*(2R*D+D 2 );

[0014] Smin is the minimum effective working area of ​​the driving key relative to the pressure block when it is in any position during construction.

[0015] Smin=δ*π*(2(R+D)*(2B1-D)-(2B1-D) 2 );

[0016] Where δ represents the ratio of the arc angle of the pressure block to 360°, expressed as: δ=θ / 360°, where θ is the arc angle of the drill pipe pressure block, and B is the width of the area where the drive key interacts with the pressure block at any position.

[0017] Furthermore, the substrate is made of alloy steel that has undergone quenching treatment.

[0018] A rotary drilling rig drill rod includes a drill rod pressure block.

[0019] A method for preparing a gradient wear-resistant layer, comprising:

[0020] The base of multiple drill pipe pressure blocks is evenly distributed along the circumference and fixed on a tooling that matches its inner surface to form a multi-lobed structure.

[0021] The tooling after fixing the drill rod pressure block is clamped on the turntable. The rotation speed of the turntable is calculated based on the laser cladding linear velocity and the diameter of the arc-shaped plane of the drill rod pressure block. The turntable rotation speed and the cladding head feed speed are adjusted in real time according to the change of the diameter of the cladding area to ensure that the cladding linear velocity and overlap rate of the cladding layer are consistent along the direction from the outer diameter to the inner diameter, so as to obtain a cladding layer with consistent thickness.

[0022] Based on the thickness of different regions of the gradient wear-resistant layer and the thickness of a single cladding layer, the number of cladding layers of the gradient wear-resistant layer is determined. The laser spot scanning path moves from the outer side of the drill rod pressure block to the inner side of the drill rod pressure block. After the previous cladding layer is completed, the laser is turned off and then moved to the outer side of the pressure block to start the preparation of the next cladding layer.

[0023] The first cladding layer of the gradient wear-resistant layer is prepared using an ultra-high-speed laser cladding process; each subsequent cladding layer is prepared using a high-speed laser cladding process until all cladding layers are completed.

[0024] Furthermore, during the cladding process, the angle θ between the laser beam and the surface of the area to be clad is maintained at 80°-90°.

[0025] Furthermore, the parameters of the ultra-high-speed laser cladding process include: coating thickness 0.3-0.4 mm, laser power 4000-4500 W, cladding linear speed 20-24 mm / s, overlap rate 65%-75%, powder feed rate 45-50 g / min, protective gas flow rate 15-20 L / min, and powder feeding gas flow rate 10-12 L / min; the powder is iron-based high-speed laser cladding powder.

[0026] The parameters of the high-speed laser cladding process include: coating thickness 0.7-0.8mm, laser power 4500-4700W, cladding line speed 9-10mm / s, overlap rate 65%-75%, powder feeding rate 48-54g / min, protective gas flow rate 14-16L / min, and powder feeding gas flow rate 6-9L / min.

[0027] The powder is an iron-based high-speed laser cladding powder.

[0028] Furthermore, the composition of the iron-based high-speed laser cladding powder is as follows: C: 2-2.6%, Cr: 5-7%, V: 5.5-7%, Si: 0.9-1%, B: 0.3-0.6%, Fe balance, the powder particles are spherical, and the powder particle size is 20-53 micrometers.

[0029] Furthermore, the tooling includes: a cylinder, a side stop block, a lower stop block, and an outer stop block;

[0030] Side blocks and bottom blocks are fixed to the surface of the cylinder respectively; the side profile of the side block is consistent with the side profile of the drill rod pressure block; the bottom block is a cylinder, and the outer block passes through the cylinder and is connected by bolts; the inner side of the outer block is an arc surface, and the arc diameter is consistent with the outer diameter of the drill rod pressure block.

[0031] The side stop, lower stop, and outer stop, along with the surface of the cylinder, form a groove for inserting the drill rod pressure block. The left and right sides of the drill rod pressure block fit seamlessly with the side stop on both sides. By tightening the bolts, the outer stop presses the drill rod pressure block.

[0032] The beneficial effects achieved by this invention are as follows:

[0033] This invention solves the technical problem of inconsistent wear processes on the bearing surface of the drill rod pressure block caused by uneven pressure distribution during service, by combining a second coating with a gradually increasing radial thickness gradient from the outer side of the drill rod cylinder and a first coating with a constant thickness as part of the bearing of the drill rod pressure block, and in conjunction with the bearing substrate.

[0034] This invention utilizes a functional gradient wear-resistant coating cladding method and path combining ultra-high-speed and high-speed laser cladding to significantly reduce the depth of the tempering softening zone caused by secondary heating during the preparation process.

[0035] This invention, by setting up a multi-lobed combined cladding fixture structure for the drill pipe pressure block, can accurately position the pressure block, is simple to clamp, and is highly efficient. Attached Figure Description

[0036] Figure 1-1 This is a schematic diagram of the components at the pressure point of the drill rod of a rotary drilling rig;

[0037] Figure 1-2 yes Figure 1-1 A schematic diagram of the vertical cross-section;

[0038] Figure 1-3 yes Figure 1-2 Enlarged view of the circled area;

[0039] Figure 2 This is a schematic diagram of the wear-resistant coating structure on the bearing surface of the pressure block;

[0040] Figure 3 This is a schematic diagram of the drill pipe pressure block structure;

[0041] Figure 4 This is a schematic diagram of the tooling loading or overall structure;

[0042] Figure 5 This is a schematic diagram of the laser cladding path on the surface of the pressure block;

[0043] Figure 6 This involves an analysis of the laser cladding angle on the surface of the pressure block.

[0044] Figure 7-1 It is a three-dimensional schematic diagram of the tooling structure;

[0045] Figure 7-2 This is a top view of the tooling structure;

[0046] Figure 8 This is a schematic diagram of the bearing surface structure of the pressure block. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0048] A drill pipe pressure block with a wear-resistant coating structure having a radially gradient thickness on the bearing surface.

[0049] like Figure 1-1 , Figure 1-2 and Figure 1-3 The diagram shown illustrates the force analysis of the bearing surface of the pressure block 3 during operation. The pressure block 3 is welded to the drill rod cylinder 1. During construction, the hydraulic cylinder applies a downward force F to the surface of each pressure block 3 via the drive sleeve 2, thereby driving the drill rod downwards for drilling. Figure 1-2 and Figure 1-3 As can be seen, the radius of the drill pipe body 1 is R, and the thickness of the pressure block 3 is D. During construction, the drive sleeve 2 needs to move up and down, so there is a gap between the drive key 4 of the drive sleeve and the drill pipe body 1.

[0050] When the drive sleeve 2 is coaxial with the drill pipe cylinder 1, the width of the interaction area between the drive key 4 and the pressure block is B1, and the contact area S1 between the drive key 4 and the drill pipe is:

[0051] S1=δ*(π*(R+D) 2 -π*(R+D-B1) 2 )=δ*π*(2(R+D)*B1-B1 2 );

[0052] Where δ=θ / 360, θ is the arc angle of the pressure block.

[0053] The force per unit area of ​​the bearing surface of the pressure block is:

[0054] F / S1=F / (δ*π*(2(R+D)*B1-B1 2 )).

[0055] However, during actual construction, due to external eccentric loads and other effects, the drive sleeve 2 and the drill pipe cylinder 1 are mostly in a non-axial state, which leads to changes in the contact area between the drive key and the drill pipe, and the width B of their interaction area varies within the range of (2B1-D,D).

[0056] Based on the force per unit area on the bearing surface of the pressure block, and considering the properties of the wear-resistant coating material and the coating preparation process, the thickness of coating 1 near the outer arc of the pressure block is designed to be H1, and the width is designed to be 2B1-D. The width of coating 2 is designed to be 2D-2B1, and the minimum thickness is H2. According to the force distribution law per unit area on the bearing surface of the pressure block in the diameter direction, the thickness of the intermediate transition section of the coating is...

[0057] H=H1+(Smax-S) / (Smax-Smin)*(H2-H1);

[0058] Where S is the effective area of ​​the driving key relative to the pressure block when it is in any position during construction, S=δ*π*(2(R+D)*BB 2 );

[0059] Smax is the maximum effective area of ​​the driving key relative to the pressure block when the driving key is in any position during the construction process. Smax = δ*π*(2(R+D)*DD) 2 )=δ*π*(2R*D+D 2 );

[0060] Smin is the minimum effective working area of ​​the driving key relative to the pressure block when the driving key is in any position during the construction process. Smin=δ*π*(2(R+D)*(2B1-D)-(2B1-D) 2 ).

[0061] Based on the above analysis, the thickness value H2n of coating 2 at 1mm intervals along the diameter direction is obtained. Finally, a curve is fitted based on the thickness value at each point, which is the substrate contour curve before cladding on the bearing surface of the pressure block, as shown in the figure. Figure 2 As shown.

[0062] To balance the wear process of the pressure block's bearing surface, a wear-resistant coating structure with radially varying thickness was designed for the bearing surface. For example... Figure 3 As shown, the interface between the gradient wear-resistant layer 5 and the substrate 6 has a "straight line-circular arc" combined structure. The gradient wear-resistant layer 5 includes coating 1 51 and coating 2 52. The upper surface is flat, and its thickness is distributed in a gradient along the diameter direction. The coating 1 51 has the largest thickness near the outer side of the arc of the pressure block, and the thickness of coating 2 52 along the diameter direction of the pressure block transitions in an arc.

[0063] (2) The preparation method of the gradient wear-resistant layer 5 is as follows:

[0064] To improve the overall service life of the pressure block, the substrate 6 is generally made of alloy steel and undergoes overall quenching treatment to enhance the wear resistance of the extruded block. However, during the preparation of the wear-resistant coating, secondary heating causes softening of the substrate near the interface between the substrate and the coating, thus affecting the wear resistance of the substrate. To solve the above problems, this invention utilizes ultra-high-speed-high-speed composite laser cladding technology and specialized tooling to achieve efficient preparation of multi-lobed combined planar surface wear-resistant coatings. Combined with a functionally graded wear-resistant coating cladding path, the depth of the tempering softening zone caused by secondary heating during the preparation process can be significantly reduced, achieving efficient and high-quality preparation of the wear-resistant coating.

[0065] like Figure 4 As shown, multiple pressure blocks are evenly distributed along the circumference and fixed on a special tooling. The upper surface of the base of all pressure blocks forms a multi-lobed arc-shaped plane 12, whose outer diameter and inner diameter are the outer diameter and inner diameter of the pressure block, respectively.

[0066] The gradient wear-resistant layer 5 is prepared using iron-based high-speed laser cladding powder, with the following main components: C: 2-2.6%, Cr: 5-7%, V: 5.5-7%, Si: 0.9-1%, B: 0.3-0.6%, and Fe as the balance. The powder particles are spherical with a particle size of 20-53 micrometers. The cladding layer prepared from this material exhibits excellent wear resistance and impact resistance. To reduce heat input to the substrate during laser cladding, the first layer of the wear-resistant coating is prepared using an ultra-high-speed laser cladding process. The coating thickness is 0.3-0.4 mm, the laser power is 4000-4500 W, the cladding linear speed is 20-24 mm / s, the overlap rate is 65%-75%, the powder feed rate is 45-50 g / min, the protective gas flow rate is 15-20 L / min, and the powder feeding gas flow rate is 10-12 L / min. After the first cladding layer is prepared, high-speed laser cladding technology is used to prepare the coating. This reduces the number of coating layers and the probability of interlayer defects. Compared with ordinary laser cladding, it can significantly reduce the heat input to the substrate. The preparation process parameters are: coating thickness 0.7-0.8mm, laser power 4500-4700W, cladding linear speed 9-10mm / s, overlap rate 65%-75%, powder feed rate 48-54g / min, protective gas flow rate 14-16L / min, and powder feed gas flow rate 6-9L / min.

[0067] During the preparation of the gradient wear-resistant layer 5, a special fixture is clamped onto a vertical turntable. The rotational speed of the turntable is calculated based on the high-speed laser cladding linear velocity and the diameter of the multi-lobed arc-shaped plane. Simultaneously, the turntable rotation speed and the cladding head feed speed can be adjusted in real time according to changes in the diameter of the cladding area, ensuring that the cladding linear velocity and overlap rate of the wear-resistant coating are consistent along the direction from the outer diameter to the inner diameter, thus obtaining a cladding layer of uniform thickness. The laser cladding path of the gradient wear-resistant coating on the pressure block surface is as follows: Figure 5As shown, the number of wear-resistant cladding layers in different regions is determined based on the thickness of different areas of the cladding layer and the thickness of a single cladding layer. The laser spot scanning path moves from the outer side of the pressure block to the inner side of the pressure block. After the previous cladding layer is completed, the laser is turned off and then moves back to the outer side of the pressure block to begin preparing the next cladding layer. Figure 6 As shown, during the cladding process, the angle θ between the laser beam and the surface of the area to be clad is maintained at 80°-90°.

[0068] like Figure 7-1 and Figure 7-2 The diagram shows a special tooling for ultra-high-speed laser cladding of a wear-resistant coating on the surface of a pressure block. This tooling 7 has a side stop 71 and a lower stop 72 welded to the surface 74 of the cylinder. The left side structure of the side stop 71 is identical to the side structure of the pressure block. The lower stop 72 is a cylinder with threaded holes, allowing the outer stop 73 to be fixed to it using bolts 75. The inner arc surface of the outer stop 73 has the same arc diameter as the outer diameter of the pressure block. Before cladding, the pressure blocks 3 are inserted into their respective slots. Due to the wedge-shaped structure of the lower end face of the pressure block 3, under the action of gravity and the lower stop 72, the side of the pressure block 3 automatically and seamlessly engages with the side stop of the tooling. Then, the bolts 75 are tightened to press the pressure block against the outer stop 73, thus completely fixing the pressure block 3. The cylinder diameter, the spacing between adjacent side stops, and the inner arc structure of the outer stop 73 can be customized according to the actual dimensions of the pressure block. This tooling has a simple structure, is easy to operate, and can effectively ensure the quality of the wear-resistant coating of the pressure block.

[0069] Example:

[0070] The dynamic load of a rotary drilling rig is mainly transmitted to the drill bit via the drill rod. The outer surface of the drill rod is typically welded with key components such as drive keys and pressure blocks at 120° intervals to transmit torque and downward pressure. Currently, pressure blocks are generally made of integrally quenched 27SiMn, but under harsh working conditions such as hard rock, they will experience wear and crushing failures after 350 hours of feedback, requiring shutdown for maintenance and component replacement, severely impacting the operating efficiency and reliability of the rotary drilling rig. To address these problems, this invention proposes a gradient wear-resistant coating structure and its preparation method to strengthen the bearing surface of the pressure block on the rotary drilling rig drill rod. The known dimensions are: drill rod cylinder radius R = 254 mm; pressure block thickness D = 25 mm; surface force F of a single pressure block = 100 kN; the interaction area width B1 between the drive key and the pressure block when the drive sleeve is coaxial with the drill rod cylinder = 19 mm; and the arc angle θ of the pressure block = 30.7°. Based on the above information, the width B of the interaction area between the driving key and the bearing surface of the pressure block varies from 13 to 25 mm. Furthermore, Smax can be calculated as follows:

[0071] 30.7 / 360*3.14*(2*254*25+25*25)=3568.065mm 2

[0072] The effective working area S and its coating thickness when the drive key is in any position relative to the pressure block during construction are:

[0073] B 13 14 15 16 17 18 19 20 21 22 23 24 25 S 1897.2 2039.4 2181 2322.1 2462.7 2602.7 2742.3 2881.2 3019.7 3157.6 3294.9 3431.8 3568.1

[0074] Based on the requirements of the coating material and its preparation process, the thickness H1 of coating 1 on the outer side of the pressure block arc is designed to be 4mm, and the width is designed to be 13mm. The minimum thickness H2 of coating 2 is designed to be 1mm, and the width is 12mm. The thickness H of the intermediate transition section is:

[0075] B 13 14 15 16 17 18 19 20 21 22 23 24 25 H 4 3.7 3.5 3.2 3 2.7 2.5 2.2 2 1.7 1.5 1.2 1

[0076] Based on the coating thickness values ​​obtained at different locations from the above analysis, the following can be fitted: Figure 8 The pressure block wear-resistant coating structure is shown. To reduce the softening phenomenon of heat-affected zone during the preparation of wear-resistant coatings, this invention proposes an efficient preparation method and laser cladding path for a "multi-lobed" combined planar surface wear-resistant coating.

[0077] The wear-resistant coating is prepared using iron-based high-speed laser cladding powder, with the following main components: C: 2.5%, Cr: 6%, V: 6%, Si: 1%, B: 0.6%, and Fe balance. The powder particles are spherical with a particle size of 20-53 micrometers. The cladding layer prepared from this material can reach a hardness of 66 HRC and exhibits excellent wear resistance. To reduce the heat input to the substrate, the first layer of the wear-resistant coating is prepared using an ultra-high-speed laser cladding process. The coating consists of one layer with a thickness of 0.3 mm. The laser power is 4500 W, the cladding linear speed is 20 mm / s, the overlap rate is 75%, the powder feed rate is 45 g / min, the protective gas flow rate is 15 L / min, and the powder feeding gas flow rate is 10 L / min. After the first cladding layer was prepared, it was fabricated using high-speed laser cladding technology. The process parameters were: coating thickness 0.8 mm, laser power 4700 W, cladding linear speed 10 mm / s, overlap rate 75%, powder feed rate 50 g / min, protective gas flow rate 16 L / min, and powder feeding gas flow rate 9 L / min. During the cladding process, the angle θ between the laser beam and the surface of the area to be clad was maintained at 80-90°. Furthermore, based on the thickness of different areas of the cladding layer and the thickness of a single cladding layer, the number of ultra-high-speed laser cladding wear-resistant coating layers was determined to be 1 layer, and the number of high-speed laser cladding wear-resistant coating layers was determined to be 5 layers.

[0078] Based on the size of the pressure blocks, the ultra-high-speed laser cladding fixture clamps 11 blocks at a time, with an angle of 32.7° between adjacent pressure blocks. After the pressure blocks are clamped and fixed, the fixture is held on a vertical turntable. The rotational speed of the turntable and the feed speed of the cladding head are calculated based on the high-speed laser cladding linear velocity and the diameter of the multi-lobed arc-shaped plane. Simultaneously, the turntable rotational speed and the feed speed of the cladding head can be adjusted in real time according to the change in the diameter of the cladding area, ensuring that the laser cladding linear velocity and overlap rate of the wear-resistant coating are consistent along the direction from the outer diameter to the inner diameter, thus obtaining a cladding layer of uniform thickness. The laser spot scanning path moves from the outer side of the pressure block to the inner side. After the previous layer of cladding is completed, the laser is turned off, and the laser moves back to the outer side of the pressure block to begin preparing the next cladding layer. During the cladding process, the angle θ between the laser beam and the surface of the area to be clad is maintained at 80°-90°.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A drill pipe pressure block, fixed to the outer side of the drill pipe cylinder, for bearing the downward pressure of the drive sleeve, characterized in that, It includes a substrate and a gradient wear-resistant layer fixed to the upper end of the substrate, wherein the upper end profile of the substrate is consistent with the lower end profile of the gradient wear-resistant layer; The upper surface of the gradient wear-resistant layer is a plane; The gradient wear-resistant layer includes a second coating with a gradually increasing radial thickness from the outer surface of the drill pipe cylinder to the outside, and a first coating with a constant thickness, with the first coating located outside the second coating; the radial direction refers to the diameter direction of the cross-section of the drill pipe cylinder. The thickness of the first coating is H1, and the width is 2B1-D; the width of the second coating is 2D-2B1, and the gradient thickness H is expressed as: H=H1+(Smax-S) / (Smax-Smin)*(H2-H1). Where B1 is the width of the area where the drive key of the drive sleeve interacts with the pressure block when the drive sleeve is coaxial with the drill pipe body; D is the width of the pressure block; S represents the effective area of ​​the driving key relative to the pressure block when they are in any position during construction. S=δ*π*(2(R+D)*BB 2 ); Smax is the maximum effective area of ​​the driving key relative to the pressure block when the driving key is in any position during construction. Smax=δ*π*(2R*D+D 2 ); Smin is the minimum effective working area of ​​the driving key relative to the pressure block when it is in any position during construction. Smin=δ*π*(2(R+D)*(2B1-D)-(2B1-D) 2 ); Where δ represents the ratio of the arc angle of the pressure block to 360°, expressed as: δ=θ / 360°, where θ is the arc angle of the drill pipe pressure block, and B is the width of the area where the drive key interacts with the pressure block at any position.

2. The drill pipe pressure block according to claim 1, characterized in that, The outer surface of the drill rod pressure block, which is composed of the matrix and the gradient wear-resistant layer, is an arc surface.

3. The drill pipe pressure block according to claim 1, characterized in that, The substrate is made of alloy steel that has undergone quenching treatment.

4. A drill rod for a rotary drilling rig, characterized in that, Includes the drill pipe pressure block as described in any one of claims 1-3.

5. A method for preparing a gradient wear-resistant layer based on claim 1, characterized in that, include: The base of multiple drill pipe pressure blocks is evenly distributed along the circumference and fixed on a tooling that matches its inner surface to form a multi-lobed structure. The tooling after fixing the drill rod pressure block is clamped on the turntable. The rotation speed of the turntable is calculated based on the laser cladding linear velocity and the diameter of the arc-shaped plane of the drill rod pressure block. The turntable rotation speed and the cladding head feed speed are adjusted in real time according to the change of the diameter of the cladding area to ensure that the cladding linear velocity and overlap rate of the cladding layer are consistent along the direction from the outer diameter to the inner diameter, so as to obtain a cladding layer with consistent thickness. Based on the thickness of different regions of the gradient wear-resistant layer and the thickness of a single cladding layer, the number of cladding layers of the gradient wear-resistant layer is determined. The laser spot scanning path moves from the outer side of the drill rod pressure block to the inner side of the drill rod pressure block. After the previous cladding layer is completed, the laser is turned off and then moved to the outer side of the pressure block to start the preparation of the next cladding layer. The first cladding layer of the gradient wear-resistant layer is prepared using an ultra-high-speed laser cladding process; each subsequent cladding layer is prepared using a high-speed laser cladding process until all cladding layers are completed.

6. The preparation method according to claim 5, characterized in that, During the cladding process, the angle θ between the laser beam and the surface of the area to be clad is maintained at 80°-90°.

7. The preparation method according to claim 5, characterized in that, The parameters of the ultra-high-speed laser cladding process include: coating thickness 0.3-0.4 mm, laser power 4000-4500 W, cladding linear speed 20-24 mm / s, overlap rate 65%-75%, powder feed rate 45-50 g / min, protective gas flow rate 15-20 L / min, and powder feeding gas flow rate 10-12 L / min; the powder is iron-based high-speed laser cladding powder. The parameters of the high-speed laser cladding process include: coating thickness 0.7-0.8mm, laser power 4500-4700W, cladding line speed 9-10mm / s, overlap rate 65%-75%, powder feeding amount 48-54g / min, protective gas flow rate 14-16L / min, and powder feeding gas flow rate 6-9L / min. The powder is an iron-based high-speed laser cladding powder.

8. The preparation method according to claim 7, characterized in that, The composition of the iron-based high-speed laser cladding powder is as follows: C: 2-2.6%, Cr: 5-7%, V: 5.5-7%, Si: 0.9-1%, B: 0.3-0.6%, Fe balance. The powder particles are spherical with a particle size of 20-53 micrometers.

9. The preparation method according to claim 5, characterized in that, The tooling includes: a cylinder, a side stop block, a lower stop block, and an outer stop block; Side blocks and bottom blocks are fixed to the surface of the cylinder respectively; the side profile of the side block is consistent with the side profile of the drill rod pressure block; the bottom block is a cylinder, and the outer block passes through the cylinder and is connected by bolts; the inner side of the outer block is an arc surface, and the arc diameter is consistent with the outer diameter of the drill rod pressure block. The side stop, lower stop, and outer stop, along with the surface of the cylinder, form a groove for inserting the drill rod pressure block. The left and right sides of the drill rod pressure block fit seamlessly with the side stop on both sides. By tightening the bolts, the outer stop presses the drill rod pressure block.

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