High-air-pressure down-hole hammer air cylinder and preparation method thereof

Abstract

The invention relates to a preparation method of a high-air-pressure down-hole hammer air cylinder. The preparation method comprises the following steps that firstly, hardening and tempering are conducted, wherein a blank is subjected to quenching and high-temperature tempering treatment, and a blank base body is obtained; 2, semi-finish machining is conducted, specifically, the workblank base body obtained through hardening and tempering is machined, the working procedures sequentially comprise finish turning of one end, finish turning of the other end, finish turning of an outer circle, drilling and milling of an exhaust hole and drilling and milling of an inclined exhaust hole, and the air cylinder base body obtained after semi-finish machining is obtained; step 3, vacuum quenching; fourthly, vacuum tempering is conducted; 5, finish machining is conducted, specifically, the air cylinder base body subjected to vacuum tempering is machined, and the working procedures sequentially comprise inner hole rough grinding, outer circle accurate grinding, outer circle hard turning and inner hole accurate grinding; and sixthly, honing is conducted. The overall deformation of the workpiece is strictly controlled through quenching and tempering pretreatment and vacuum heat treatment, the roundness of the inner hole of the final product can be stably smaller than 0.01 mm, and the coaxiality of the inner circle and the outer circle is smaller than 0.015 mm.

Description

Technical Field

[0001] This invention relates to the field of down-the-hole impactors, and more specifically to a method for preparing a high-pressure down-the-hole impactor cylinder. Background Technology

[0002] High-pressure down-the-hole hammers are widely used in mining, tunneling, foundation construction, and other engineering fields. The cylinder, as the key moving component and pressure-bearing chamber of the hammer, directly determines the hammer's working efficiency, energy consumption, and service life due to its internal quality, dimensional accuracy, and surface properties.

[0003] The traditional manufacturing process for down-the-hole impactor cylinders typically involves: blanking, machining, heat treatment, chamfering, end face grinding, precision turning of the outer diameter, precision grinding of the inner diameter, and precision grinding of the outer diameter again. This traditional process struggles to effectively eliminate accumulated machining stress, leading to inconsistent dimensional accuracy in the final product (especially the roundness of the inner hole and the coaxiality of the inner and outer diameters). Roundness is often difficult to control within 0.015mm, and coaxiality is also difficult to guarantee. Insufficient precision results in problems such as poor piston movement, air leakage, and uneven wear during impactor operation, thereby reducing impact power, increasing energy consumption, and shortening the overall lifespan of the machine. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a method for manufacturing a high-pressure down-the-hole impactor cylinder, aiming to improve machining accuracy and ensure the roundness of the cylinder's inner bore and the coaxiality of the inner and outer bores. The specific technical solution is as follows: A method for manufacturing a high-pressure down-the-hole impactor cylinder includes the following steps: Step 1, tempering: Quenching and high-temperature tempering are performed on the raw material to obtain the blank matrix; Step 2, Semi-finishing: The blank base obtained by quenching and tempering is machined. The process includes precision turning one end, precision turning the other end, precision turning the outer circle, drilling and milling the exhaust hole, and drilling and milling the oblique exhaust hole to obtain the semi-finished cylinder base. Step 3, Vacuum quenching: The semi-finished cylinder base is heated and vacuum quenched; Step 4, Vacuum Tempering: Heat the vacuum-quenched cylinder base to perform vacuum tempering; Step 5, Finishing: The cylinder base after vacuum tempering is machined, and the process includes rough grinding of the inner hole, finish grinding of the outer circle, hard turning of the outer circle, and finish grinding of the inner hole in sequence. Step 6, Honing: Honing the inner hole of the cylinder base after low-temperature tempering to obtain the high-pressure down-the-hole impactor cylinder.

[0005] Furthermore, the raw material for the rough material is 40CrMnMo seamless steel pipe. Step one specifically includes heating the rough material to 830-870℃, holding it at that temperature for 2-3 hours, and then rapidly cooling it in quenching oil; tempering the quenched rough material at 650-700℃ at high temperature, holding it at that temperature for 0.5-1 hours, then cooling it to 50-70℃ in the furnace, and then air cooling it after removing it from the furnace.

[0006] Furthermore, in step two, when finishing one end, the outer circle of the blank base is clamped, the inner hole of that end is machined using a boring tool, and then the outer circle and end face of that end are machined using an external turning tool; when finishing the other end, the machined outer circle is clamped, the inner hole of that end is machined using a boring tool, and the transition of the inner hole is made with an arc; when finishing the outer circle, the inner hole of the cylinder is supported by an internal support jaw, and the other end is held by a center, and the outer circle is machined using an external turning tool; drilling and milling the exhaust hole is performed on a 4-axis machining center; drilling and milling the inclined exhaust hole is performed on a 5-axis machining center.

[0007] Furthermore, step three specifically includes holding the temperature at 630–670°C for 1–3 hours in a vacuum environment of less than 50 Pa, then holding it at 830–870°C for 2–4 hours, followed by vacuum quenching for 20–40 minutes and quenching oil temperature of 40–55°C.

[0008] Furthermore, step four specifically includes maintaining the temperature at 200–240°C for 2–4 hours in a vacuum environment of less than 50 Pa, and then rapidly cooling it down with nitrogen at 2 atmospheres.

[0009] Furthermore, in step five, when rough grinding the inner hole, an internal grinding machine and a 46-60# white fused alumina grinding wheel are used for grinding; when fine grinding the outer diameter, an external grinding machine and a 46-60# brown fused alumina grinding wheel are used for grinding. During installation, the tapered mandrel is inserted into the rough-ground inner hole as a reference and clamped using a two-center method; when hard turning the outer diameter, it is clamped on a CNC lathe using a one-clamp-one-center method for machining; when fine grinding the inner hole, a deep hole internal grinding machine or an internal grinding machine is used, and a 46-60# white fused alumina grinding wheel is used for fine grinding. During installation, a four-jaw chuck is used to clamp one end of the cylinder's outer diameter, and a center rest supports the other end of the outer diameter.

[0010] Furthermore, the honing head uses 300-500# diamond oil stone.

[0011] A high-pressure down-the-hole impactor cylinder is manufactured by the above-described preparation method.

[0012] The beneficial effects of this invention are as follows: Through tempering pretreatment and vacuum heat treatment, the overall deformation of the workpiece is strictly controlled, resulting in a final product with a stable inner hole roundness of less than 0.01 mm and an inner and outer circle coaxiality of less than 0.015 mm. Vacuum heat treatment avoids decarburization and oxidation, resulting in uniform surface hardness. Furthermore, the subsequent honing process provides excellent surface finish and oil retention characteristics, significantly enhancing wear resistance. High precision and high surface quality ensure smooth piston movement and reliable sealing within the impactor, reducing internal leakage and abnormal wear, thereby greatly improving the impact efficiency and service life of the impactor. Attached Figure Description

[0013] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the high-pressure down-the-hole impactor cylinder described in the embodiment.

[0015] In the diagram: 1. Exhaust vent; 2. Slanted exhaust vent; 3. Inner hole. Detailed Implementation

[0016] Example 1: Taking 40CrMnMo seamless steel pipe as the raw material as an example, this invention provides a high-pressure down-the-hole impactor cylinder, such as... Figure 1 As shown, the cylinder includes an exhaust port 1, an oblique exhaust port 2, and an inner hole 3. The inner hole 3 is divided into multiple segments according to its diameter, and its manufacturing method is as follows: Step 1, Tempering: Cut the steel pipes to size to obtain raw materials. Quench and temper the raw materials to obtain the blank base. Specifically, put the raw materials into a heating furnace, heat to 830℃, hold for 2 hours, and then cool rapidly in quenching oil. After quenching, put the raw materials into a heating furnace and temper at 650℃ for 0.5 hours. Then cool to 50℃ with the furnace and then remove from the furnace and air cool.

[0017] Step 2, Semi-finishing: The blank base obtained from quenching and tempering is machined. The process includes, in sequence, finishing turning one end, finishing turning the other end, finishing turning the outer diameter, drilling and milling exhaust hole 1, and drilling and milling the oblique exhaust hole 2, to obtain the semi-finished cylinder base. Specifically, when finishing turning one end, the outer diameter of the blank base is clamped, and the inner hole of that end is machined using a φ40 boring tool. Then, the outer diameter and end face of that end are machined using an external turning tool, with an overall surface roughness not exceeding Ra6.3. When finishing turning the other end, the machined outer diameter is clamped, and the runout of the outer diameter is required to be less than 0.2mm. The inner hole of that end is machined using a φ40 boring tool, with an overall surface roughness not exceeding Ra6.3. The inner hole is made of different... The cylinder consists of a diameter section, with the inner hole 3 connected and the transition point being a circular arc with an arc size of R2-R6. When precision turning the outer diameter, an internal support jaw is used to support the cylinder inner hole, and the other end is held by a center. An external turning tool is used to machine the outer diameter, and the overall roughness is no greater than Ra3.2. Drilling and milling the exhaust hole 1 is performed on a 4-axis machining center, using a drill bit and a milling cutter to drill the hole, and a chamfering cutter is used to chamfer the inside and outside of the hole, with the overall roughness no greater than Ra6.3. Drilling and milling the inclined exhaust hole 2 is performed on a 5-axis machining center, using a drill bit and a milling cutter to drill and mill the hole, and a chamfering cutter is used to chamfer the inside and outside of the hole, with the overall roughness no greater than Ra6.3.

[0018] Step 3, Vacuum quenching: Heat the semi-finished cylinder base to 830℃ for vacuum quenching; specifically, in a vacuum environment of less than 50Pa, hold at 630℃ for 1 hour, then hold at 830℃ for 2 hours, and then perform vacuum quenching for 20 minutes with a quenching oil temperature of 40℃.

[0019] Step 4, Vacuum Tempering: Heat the vacuum-quenched cylinder base to 200℃ for vacuum tempering; specifically, in a vacuum environment of less than 50Pa, hold at 200℃ for 2 hours, and then use nitrogen gas at 2 atmospheres for rapid cooling. After tempering, the workpiece hardness is 51.2HRC.

[0020] Step 5, Finishing: The cylinder base after vacuum tempering is machined, with the following steps in sequence: rough grinding of the inner hole 3, finish grinding of the outer diameter, hard turning of the outer diameter, and finish grinding of the inner hole 3 again. Specifically, for rough grinding of the inner hole 3, an internal grinding machine and a 46-60# white corundum wheel are used to achieve a surface roughness of Ra1.6. For finish grinding of the outer diameter, an external grinding machine and a 46-60# brown corundum wheel are used. During installation, a 1:3000 tapered mandrel is inserted into the rough-ground inner hole 3 as a reference. When clamping with two centers, the surface roughness is Ra0.8. When hard turning the outer diameter, the machine is clamped on a CNC lathe using a one-clamp-one-center method. The chuck pressure during clamping is <0.5MPa, and the runout of the outer diameter after clamping is <0.05 to prevent clamping deformation. When fine grinding the inner hole 3, a deep hole internal grinding machine or an internal grinding machine is used with a 46-60# white corundum grinding wheel for fine grinding. During installation, one end of the cylinder's outer diameter is clamped by a four-jaw chuck, and the other end of the outer diameter is supported by a center rest. The surface roughness is Ra0.4.

[0021] Step Six: Honing Treatment: The inner hole 3 of the cylinder base after low-temperature tempering is honed to obtain the high-pressure down-the-hole impactor cylinder. Specifically, the honing head uses 300-500# diamond oil stone with a roughness < Ra0.2.

[0022] The cylinder obtained in this embodiment has an outer roundness of 0.008 mm, an inner roundness of 0.009 mm, and a coaxiality of φ0.012 mm between the inner and outer circles.

[0023] Example 2: Taking 40CrMnMo seamless steel pipe as the raw material as an example, this invention provides a high-pressure down-the-hole impactor cylinder, the preparation method of which is as follows: Step 1, Tempering: Cut the steel pipes to size to obtain raw materials. Quench and temper the raw materials to obtain the blank base. Specifically, put the raw materials into a heating furnace, heat to 850℃, hold for 2.5 hours, and then cool rapidly in quenching oil. After quenching, put the raw materials into a heating furnace and temper at 660℃ for 0.6 hours. Then, cool them to 60℃ with the furnace and then remove them from the furnace and air cool.

[0024] Step 2, Semi-finishing: The blank base obtained from quenching and tempering is machined. The process includes, in sequence, finishing turning one end, finishing turning the other end, finishing turning the outer diameter, drilling and milling exhaust hole 1, and drilling and milling the oblique exhaust hole 2, to obtain the semi-finished cylinder base. Specifically, when finishing turning one end, the outer diameter of the blank base is clamped, and the inner hole of that end is machined using a φ40 boring tool. Then, the outer diameter and end face of that end are machined using an external turning tool, with an overall surface roughness not exceeding Ra6.3. When finishing turning the other end, the machined outer diameter is clamped, and the runout of the outer diameter is required to be less than 0.2mm. The inner hole of that end is machined using a φ40 boring tool, with an overall surface roughness not exceeding Ra6.3. The inner hole 3 is formed by... Composed of different diameter segments, the inner hole 3 transitions with an arc, the arc size being R2-R6; when precision turning the outer diameter, an inner support jaw is used to support the inner hole of the cylinder, and the other end is held by a center, and an outer diameter turning tool is used to machine the outer diameter, with an overall roughness not greater than Ra3.2; drilling and milling of the exhaust hole 1 is performed on a 4-axis machining center, using a drill bit and a milling cutter to drill the hole, and a chamfering cutter to chamfer the inside and outside of the hole, with an overall roughness not greater than Ra6.3; drilling and milling of the inclined exhaust hole 2 is performed on a 5-axis machining center, using a drill bit and a milling cutter to drill and mill the hole, and a chamfering cutter to chamfer the inside and outside of the hole, with an overall roughness not greater than Ra6.3.

[0025] Step 3, Vacuum quenching: Heat the semi-finished cylinder base to 840℃ for vacuum quenching; specifically, in a vacuum environment of less than 50Pa, hold at 660℃ for 1.5 hours, then hold at 840℃ for 3 hours, and then perform vacuum quenching for 30 minutes at a quenching oil temperature of 45℃.

[0026] Step 4, Vacuum Tempering: Heat the vacuum-quenched cylinder base to 220℃ for vacuum tempering; specifically, in a vacuum environment of less than 50Pa, hold at 220℃ for 3 hours, and then use nitrogen gas at 2 atmospheres for rapid cooling. The hardness of the workpiece after tempering is 53.2HRC.

[0027] Step 5, Finishing: The cylinder base after vacuum tempering is machined, with the following steps in sequence: rough grinding of the inner hole 3, finish grinding of the outer diameter, hard turning of the outer diameter, and finish grinding of the inner hole 3 again. Specifically, for rough grinding of the inner hole 3, an internal grinding machine and a 46-60# white corundum wheel are used to achieve a surface roughness of Ra1.6. For finish grinding of the outer diameter, an external grinding machine and a 46-60# brown corundum wheel are used. During installation, a 1:3000 tapered mandrel is inserted into the rough-ground inner hole 3 as a reference. When clamping with two centers, the surface roughness is Ra0.8. When hard turning the outer diameter, the machine is clamped on a CNC lathe using a one-clamp-one-center method. The chuck pressure during clamping is <0.5MPa, and the runout of the outer diameter after clamping is <0.05 to prevent clamping deformation. When fine grinding the inner hole 3, a deep hole internal grinding machine or an internal grinding machine is used with a 46-60# white corundum grinding wheel for fine grinding. During installation, one end of the cylinder's outer diameter is clamped by a four-jaw chuck, and the other end of the outer diameter is supported by a center rest. The surface roughness is Ra0.4.

[0028] Step 6, Honing treatment: Honing is performed on the inner hole 3 of the cylinder base after low temperature tempering to obtain the cylinder body of the high wind pressure down-the-hole impactor. The honing head is made of 300-500# diamond oil stone with a roughness < Ra0.2.

[0029] The cylinder obtained in this embodiment has an outer roundness of 0.006 mm, an inner roundness of 0.007 mm, and a coaxiality of φ0.013 mm between the inner and outer circles.

[0030] Example 3: Taking 40CrMnMo seamless steel pipe as the raw material as an example, this invention provides a high-pressure down-the-hole impactor cylinder, the preparation method of which is as follows: Step 1, Heat treatment: Cut the steel pipes to size to obtain raw materials. Quench and temper the raw materials to obtain the blank base. Specifically, put the raw materials into a heating furnace, heat to 870℃, hold for 3 hours, and then cool rapidly in quenching oil. After quenching, put the raw materials into a heating furnace, temper at 700℃, hold for 1 hour, cool with the furnace to 70℃, and then remove from the furnace and air cool.

[0031] Step 2, Semi-finishing: The blank base obtained from quenching and tempering is machined. The process includes, in sequence, finishing turning one end, finishing turning the other end, finishing turning the outer diameter, drilling and milling exhaust hole 1, and drilling and milling the oblique exhaust hole 2, to obtain the semi-finished cylinder base. Specifically, when finishing turning one end, the outer diameter of the blank base is clamped, and the inner hole of that end is machined using a φ40 boring tool. Then, the outer diameter and end face of that end are machined using an external turning tool, with an overall surface roughness not exceeding Ra6.3. When finishing turning the other end, the machined outer diameter is clamped, and the runout of the outer diameter is required to be less than 0.2mm. The inner hole of that end is machined using a φ40 boring tool, with an overall surface roughness not exceeding Ra6.3. The inner hole 3 is formed by... Composed of different diameter segments, the inner hole 3 transitions with an arc, the arc size being R2-R6; when precision turning the outer diameter, an inner support jaw is used to support the inner hole of the cylinder, and the other end is held by a center, and an outer diameter turning tool is used to machine the outer diameter, with an overall roughness not greater than Ra3.2; drilling and milling of the exhaust hole 1 is performed on a 4-axis machining center, using a drill bit and a milling cutter to drill the hole, and a chamfering cutter to chamfer the inside and outside of the hole, with an overall roughness not greater than Ra6.3; drilling and milling of the inclined exhaust hole 2 is performed on a 5-axis machining center, using a drill bit and a milling cutter to drill and mill the hole, and a chamfering cutter to chamfer the inside and outside of the hole, with an overall roughness not greater than Ra6.3.

[0032] Step 3, Vacuum quenching: Heat the semi-finished cylinder base to 870℃ for vacuum quenching; specifically, in a vacuum environment of less than 50Pa, hold at 670℃ for 3 hours, then hold at 870℃ for 4 hours, and then perform vacuum quenching for 40 minutes with a quenching oil temperature of 55℃.

[0033] Step 4, Vacuum Tempering: Heat the vacuum-quenched cylinder base to 240℃ for vacuum tempering; specifically, in a vacuum environment of less than 50Pa, hold at 240℃ for 4 hours, and then use nitrogen gas at 2 atmospheres for rapid cooling. The hardness of the workpiece after tempering is 54.1HRC.

[0034] Step 5, Finishing: The cylinder base after vacuum tempering is machined, with the following steps in sequence: rough grinding of the inner hole 3, finish grinding of the outer diameter, hard turning of the outer diameter, and finish grinding of the inner hole 3 again. Specifically, for rough grinding of the inner hole 3, an internal grinding machine and a 46-60# white corundum wheel are used to achieve a surface roughness of Ra1.6. For finish grinding of the outer diameter, an external grinding machine and a 46-60# brown corundum wheel are used. During installation, a 1:3000 tapered mandrel is inserted into the rough-ground inner hole 3 as a reference. When clamping with two centers, the surface roughness is Ra0.8. When hard turning the outer diameter, the machine is clamped on a CNC lathe using a one-clamp-one-center method. The chuck pressure during clamping is <0.5MPa, and the runout of the outer diameter after clamping is <0.05 to prevent clamping deformation. When fine grinding the inner hole 3, a deep hole internal grinding machine or an internal grinding machine is used with a 46-60# white corundum grinding wheel for fine grinding. During installation, one end of the cylinder's outer diameter is clamped by a four-jaw chuck, and the other end of the outer diameter is supported by a center rest. The surface roughness is Ra0.4.

[0035] Step 6, Honing treatment: Honing is performed on the inner hole 3 of the cylinder base after low temperature tempering to obtain the cylinder body of the high wind pressure down-the-hole impactor. The honing head is made of 300-500# diamond oil stone with a roughness < Ra0.2.

[0036] The cylinder obtained in this embodiment has an outer circle roundness of 0.008mm, an inner hole roundness of 0.01mm, and a coaxiality of φ0.01mm between the inner hole and the outer circle.

[0037] 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 preparing a cylinder for a high-pressure down-the-hole impactor, characterized in that, Includes the following steps: Step 1, tempering: Quenching and high-temperature tempering are performed on the raw material to obtain the blank matrix; Step 2, Semi-finishing: The blank base obtained by quenching and tempering is machined. The process includes precision turning one end, precision turning the other end, precision turning the outer circle, drilling and milling the exhaust hole, and drilling and milling the oblique exhaust hole to obtain the semi-finished cylinder base. Step 3, Vacuum quenching: The semi-finished cylinder base is heated and vacuum quenched; Step 4, Vacuum Tempering: Heat the vacuum-quenched cylinder base to perform vacuum tempering; Step 5, Finishing: The cylinder base after vacuum tempering is machined, and the process includes rough grinding of the inner hole, finish grinding of the outer circle, hard turning of the outer circle, and finish grinding of the inner hole in sequence. Step 6, Honing: Honing the inner hole of the cylinder base after low-temperature tempering to obtain the high-pressure down-the-hole impactor cylinder.

2. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: The raw material for the rough material is 40CrMnMo seamless steel pipe. Step one specifically includes heating the rough material to 830-870℃, holding it at that temperature for 2-3 hours, and then rapidly cooling it in quenching oil; quenching the rough material and then tempering it at 650-700℃ for 0.5-1 hours, then cooling it in the furnace to 50-70℃, and finally removing it from the furnace and air cooling it.

3. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: In step two, when finishing one end, the outer circle of the blank base is clamped, the inner hole of that end is machined using a boring tool, and then the outer circle and end face of that end are machined using an external turning tool; When finishing the other end, clamp the machined outer circle and use a boring tool to machine the inner hole at that end, with the transition of the inner hole being a rounded arc. When precision turning the outer diameter, the inner bore of the cylinder is supported by an internal support jaw, and the other end is held by a center. The outer diameter is machined using an external turning tool. The drilling and milling of the ventilation holes were performed on a 4-axis machining center. The drilling and milling of the inclined ventilation holes is performed on a 5-axis machining center.

4. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: Step 3 specifically includes holding the temperature at 630–670°C for 1–3 hours in a vacuum environment of less than 50 Pa, then holding it at 830–870°C for 2–4 hours, followed by vacuum quenching for 20–40 minutes and quenching oil temperature of 40–55°C.

5. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: Step four specifically includes maintaining the temperature at 200–240°C for 2–4 hours in a vacuum environment of less than 50 Pa, and then rapidly cooling it down with nitrogen gas at 2 atmospheres.

6. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: In step five, when rough grinding the inner hole, an internal grinding machine and a 46-60# white corundum grinding wheel are used for grinding; When fine grinding the outer diameter, use an external cylindrical grinding machine and a 46-60# brown corundum grinding wheel for grinding. When installing, insert the tapered mandrel into the rough-ground inner hole as a reference and clamp it with two centers. When machining the outer diameter, the machine is clamped on a CNC lathe using a clamping and supporting method. When fine grinding the inner hole, use a deep hole internal grinding machine or an internal grinding machine, and use a 46-60# white corundum grinding wheel for fine grinding. During installation, use a four-jaw chuck to hold one end of the cylinder's outer diameter, and a center support to support the other end's outer diameter.

7. The method for preparing a high-pressure down-the-hole impactor cylinder according to claim 1, characterized in that: The honing head uses 300-500# diamond oil stone.

8. A high-pressure down-the-hole impactor cylinder, characterized in that: It is prepared by any of the preparation methods described in claims 1-7.

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