Efficient and low-cost machining method for precise slender pipe

Abstract

The invention discloses an efficient and low-cost machining method for a precise slender pipe. The main technological process comprises the steps of blanking, thermal refining, correction, turning and drilling of a deep hole clamping connector, drilling of a deep hole, rough turning of an outer circle, deoiling, electrolysis of the deep hole, cleaning, chemical copper plating of the surface of an inner hole, cold burnishing of the inner hole, copper removal, stress relief annealing, abrasive particle fluid polishing and the like. By adopting the technical routes of drilling, electrolytic polishing, cold burnishing of an inner hole, high-temperature stress relief annealing and abrasive flow polishing of the inner hole, precise, efficient and low-cost machining of the slender pipe is realized by completely localizing universal technical equipment, the size precision of the inner hole reaches IT8 level, the surface roughness Ra value reaches within 0.2 mu m, and the engineering application value is remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical processing, in particular to a method for processing a precise and slender tube with high efficiency and low cost. Background Art

[0002] Deep hole machining has always been a challenge in the machining field. A typical example of a deep hole component is a slender tube component, primarily made of alloy steel. This series of slender tubes typically has an aspect ratio of 60 to 120, with an inner hole diameter of 5 to 15 mm. The required inner hole diameter accuracy is IT8, and the surface roughness Ra is within 0.2 μm. This means that for a deep hole with a diameter of approximately 6 mm, the error should be within 0 to 0.02 mm. This makes deep hole precision machining difficult, inefficient, and costly.

[0003] Traditionally, deep-hole machining of slender tubular components is typically achieved using processes such as "drill → reamer → honing," "drill → reamer → electrolysis," or "drill → reamer → extrusion." Among these methods, the "drill → reamer → honing" approach offers significant advantages for deep-hole machining dimensional accuracy and surface roughness. However, the microscopic grinding marks introduced by the grinding properties of the honing method itself can severely impact the quality of subsequent hard chromium electroplating within the deep hole, easily causing defects such as coarse surface crystals, impacting product quality. Honing also suffers from low efficiency and extremely high costs. Neither the "drill → reamer → electrolysis" nor the "drill → reamer → extrusion" approaches can simultaneously achieve satisfactory dimensional accuracy and surface roughness, resulting in low pass rates and a gradual decline in their acceptance.

[0004] In order to achieve precise, efficient and low-cost processing of deep holes in slender tube components, the present invention provides a precise, efficient and low-cost processing method for slender tubes. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a high-efficiency and low-cost processing method for precision slender tubes, which fully uses general technical equipment to achieve high-efficiency and low-cost processing of slender tubes. The inner hole size accuracy reaches IT8 level and the surface roughness Ra value reaches within 0.2μm, with significant engineering application value.

[0006] The object of the present invention is achieved like this: A high-efficiency and low-cost processing method for a precision slender tube comprises the following steps: S1, cutting Cut the steel raw materials into required specifications to obtain the blank bars of the workpiece; S2. Tempering treatment The workpiece is subjected to quenching and tempering heat treatment; S3. Calibration Straighten the workpiece; S4, processing and clamping interface According to the clamping interface requirements of the deep hole drilling machine, the blank bar material is clamped and processed; S5. Drilling deep holes On a deep hole drilling machine, the inner hole of the workpiece is drilled by a gun drill; S6, rough turning of outer circle With the inner hole of the workpiece as the positioning center, the workpiece is rough turned to make the cross section of the workpiece into a cylindrical structure with uniform cross-section; S7, degreasing and cleaning Remove iron chips and oil from the workpiece; S8, electrolytic deep hole The inner hole surface of the workpiece is used as the anode and other electrode materials are used as the cathode. The cylindrical cathode rod is placed at the axis of the inner hole of the workpiece. Under the action of current and electrolyte, the rough part of the inner hole surface of the workpiece is dissolved and removed by electrochemical means for fine processing. S9. Cleaning Neutralize and clean the workpiece; S10, chemical copper plating on inner hole surface Use copper sulfate solution to wipe the inner hole surface of the workpiece, evenly apply the copper sulfate solution on the inner hole surface of the workpiece, and through the replacement reaction, copper is precipitated and attached to the inner hole surface of the workpiece to form a copper layer; S11, cold extrusion inner hole The carbide material is squeezed through the inner hole of the workpiece by an interference fit punch. The extrusion action of the punch causes the inner hole of the workpiece to undergo plastic deformation and expand. During the extrusion process, the copper layer acts as a lubricant to prevent the extrusion deformation process from scratching the inner hole surface of the workpiece. S12, copper removal and cleaning The copper removal process is used to dissolve and remove the copper layer on the surface of the inner hole of the workpiece through chemical reaction; S13, stress relief annealing Use heat aging treatment to eliminate the internal residual stress caused by deformation during the extrusion process of the inner hole of the workpiece; S14, abrasive fluid polishing Abrasives are used to polish the inner hole of the workpiece in the form of fluid to eliminate the oxidation color / oxidation layer on the surface of the inner hole of the workpiece caused by stress relief annealing, and the inner hole of the workpiece is further polished.

[0007] Furthermore, the material of the slender tube workpiece is alloy steel, the inner hole diameter ranges from 5 to 15 mm, the aspect ratio is 60 to 120, the inner hole diameter dimensional accuracy is ≤0.02 mm, and the inner hole surface roughness is ≤0.2 μm.

[0008] Furthermore, in S6, two tops are used for double top positioning.

[0009] Furthermore, in S2, the heat treatment hardness is controlled at 250HB to 320HB, and the structure is uniform tempered troostite.

[0010] Furthermore, in S13, the stress relief annealing process is: using a vacuum furnace and an inert gas protective atmosphere, keeping the temperature at 20°C to 80°C lower than the tempering temperature of the workpiece for 4 hours, and the heating and cooling stage time is not less than 1 hour. During the heat treatment process, the workpieces are placed vertically and neatly.

[0011] Furthermore, in S14, the abrasive material should have a particle size of not less than 1000 mesh. Furthermore, in S3, the straightness of the workpiece is controlled within 0.5 mm; In S5, the workpiece inner hole size accuracy is controlled within 0 to 0.05 mm, and the surface roughness Ra value is controlled within 3.2 μm; In S8, the electrolytic removal thickness is controlled at 0.15-0.3 mm, and the current density is controlled at 900-1100 A / dm 2 , the inner hole diameter dimensional accuracy is controlled within 0~0.05mm, and the surface roughness Ra value is controlled within 0.4μm; In S11, the extrusion deformation expansion of the inner hole diameter is controlled within 0.05-0.10 mm, the dimensional accuracy of the inner hole diameter of the workpiece 1 after extrusion is controlled within 0-0.02 mm, and the surface roughness Ra value is controlled within 0.2 μm.

[0012] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention can control the dimensional accuracy of the diameter of the fine deep hole within 0.02 mm and the surface roughness Ra value within 0.2 μm, with stable quality, high efficiency and low cost.

[0013] The efficient and low-cost processing method for precision slender tubes provided by the present invention does not require the use of high-end technical equipment or imported equipment (radial precision forging machines, precision cold rolling mills, high-end honing equipment, etc.). It uses completely domestically produced general process equipment, materials and technologies to achieve precise, efficient and low-cost processing of slender tube components, and has good engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 FIG is a diagram of an elongated tubular member of the present invention; Figure 2 This is a schematic diagram of the inner pore electrolysis scheme of the present invention; Figure 3 This is a diagram of the inner hole extrusion scheme of the present invention; Figure 4 Flowchart of the present invention.

[0015] Reference numerals In the accompanying drawings, 1, slender tube component, 2, electrolysis cathode rod, 3, extrusion punch, 4, push rod, 1-1, inner hole surface of the slender tube. DETAILED DESCRIPTION

[0016] A high-efficiency and low-cost processing method for precision slender tubes, the process route is: cutting → tempering treatment → calibration → deep hole turning and clamping interface → deep hole drilling → rough turning of the outer circle → degreasing and cleaning → electrolytic deep hole drilling → cleaning → chemical copper plating on the inner hole surface → cold extrusion polishing of the inner hole → copper removal and cleaning → stress relief annealing → abrasive fluid polishing.

[0017] like Figure 1 As shown, the slender tube 1 is a slender tube component made of alloy steel material, with an inner hole diameter D ranging from 5 to 15 mm, an aspect ratio (L / D) ranging from 60 to 120, an inner hole diameter D dimensional accuracy ≤ 0.02 mm, and an inner hole surface roughness Ra value ≤ 0.2 μm.

[0018] The blanking in the process route is to cut the raw material (round steel) according to the product size specification requirements to obtain slender tube component blank bars of specified length.

[0019] The quenching and tempering treatment involves subjecting the slender tubular component blank to a heat treatment with a hardness controlled between 250HB and 320HB, resulting in a uniformly tempered bainite structure. This is done to demonstrate that alloy steel with a hardness between 250HB and 320HB exhibits superior machinability, enabling improved deep-hole drilling quality and higher efficiency.

[0020] Correction involves straightening the workpiece after quenching and tempering heat treatment. Due to the rapid changes in thermal and structural stresses within the workpiece during quenching and tempering heat treatment, slight deformation of the slender tubular component blank is inevitable, necessitating correction / straightening. Straightening is generally achieved through mechanical methods, such as a three-roll straightening machine, which uses rolling to rapidly straighten the slender tubular component blank, achieving a straightness of 0.5 mm.

[0021] The turning and drilling deep hole clamping interface is processed according to the subsequent deep hole drilling machine clamping interface requirements, and must meet the clamping, positioning and driving requirements during subsequent deep hole drilling.

[0022] The deep hole drilling is to drill the workpiece by a gun drill on a deep hole drilling machine. After drilling, the inner hole size accuracy of the workpiece should be controlled within 0 to 0.05 mm, and the surface roughness Ra value should be controlled within 3.2 μm. This process can be guaranteed by using the current common deep hole drilling machine and gun drill processing.

[0023] The rough turning process, described above, uses the inner hole of the slender tubular component as the center of positioning, typically using two centers for double positioning. This rough turning process results in a uniform cylindrical cross-section. This uniform cylindrical structure creates a uniform stress and residual stress field during subsequent extrusion and stress relief annealing, ensuring uniform and stable deformation and quality control during subsequent processing.

[0024] The degreasing and cleaning are to remove iron chips and oil from the workpiece, so that the surface of the workpiece is clean and is conducive to subsequent electrolytic processing.

[0025] like Figure 2 As shown, the electrolytic deep hole is a process in which the inner hole surface 1-1 of the slender tube member 1 is used as the anode, brass or other electrode materials are used as the cathode 2, and a common NaCl electrolyte is used. Other electrolytes can also be selected if necessary. The slender cylindrical cathode rod 2 is placed at the axis of the inner hole of the slender tube member 1. Under the action of current and electrolyte, the rough part of the inner hole surface 1-1 of the slender tube member 1 is dissolved and removed by electrochemical means. Generally, the electrolytic removal thickness should be controlled at 0.15 to 0.3 mm, and the current density should be controlled at 1000A / dm 2 This can effectively remove the drilling lines on the inner hole surface after drilling, the inner hole diameter dimensional accuracy is controlled within 0 ~ 0.05mm, the surface roughness Ra value can be controlled within 0.4μm, and the inner hole surface is basically smooth, but residual waviness can still be observed by visually peeking into the inner hole, which requires subsequent extrusion processing to eliminate.

[0026] The cleaning mentioned above is to neutralize and clean the workpiece, and anti-corrosion treatment should be carried out if necessary.

[0027] The electroless copper plating on the inner bore surface involves quickly wiping a cotton ball soaked in copper sulfate solution across the inner bore surface of the slender tubular component, evenly coating the surface with the solution. This process, through a displacement reaction, deposits copper onto the inner bore surface. This ensures copper's excellent ductility and lubricity, providing lubrication for subsequent extrusion and plastic deformation processes, preventing scratches on the inner bore surface of the slender tubular component. The resulting copper layer is very thin and does not affect the dimensions.

[0028] like Figure 3 As shown, the cold extrusion inner hole is to squeeze the carbide material extrusion punch 3 through the inner hole of the slender tube member 1 under the action of the push force of the push rod 4 or the pull force of the pull rod. The inner hole is plastically deformed and expanded by the extrusion action of the punch, thereby obtaining a deep hole with high precision and high surface quality. The inner hole diameter extrusion deformation expansion amount ( d 1- d2) The inner diameter of the slender tube component 1 after extrusion should be controlled at 0.05~0.10mm d The 2′ dimensional accuracy is controlled within 0-0.02 mm, and the surface roughness Ra value is controlled within 0.2 μm. The purpose of this is to use a smaller extrusion deformation of 0.05-0.10 mm, which can not only obtain better inner hole dimensional accuracy and surface roughness quality, but also minimize the internal residual stress of the slender tube components during the extrusion process, and reduce the range of the internal residual stress field, thereby minimizing the subsequent reduction of residual stress and deformation caused by turning.

[0029] The copper removal and cleaning is a process of removing the copper layer on the surface of the inner hole of the workpiece by chemical reaction. The copper removal process can adopt various existing processes, such as electrochemical method or chemical method.

[0030] The stress relief annealing is a process that uses a thermal aging treatment to eliminate the internal residual stress generated during the extrusion deformation of the inner hole of the slender tube component. The stress relief annealing process is to use a vacuum furnace, keep the temperature at 20℃ to 80℃, which is lower than the tempering temperature of the slender tube component, for 4 hours. The heating and cooling stages should both last for no less than 1 hour. During the heat treatment process, the workpieces should be placed vertically and neatly at intervals. The purpose of this is to use the inert gas protective atmosphere of the vacuum furnace to minimize the oxidation or decarburization of the workpiece surface, and to use high-temperature stress relief annealing to fully eliminate the residual stress inside the workpiece. The slow heating and cooling is conducive to the full diffusion of atoms inside the workpiece, and the timely release of residual stress. When the temperature changes, the residual stress value is promptly reduced to below the yield limit of the material at the changed temperature, thereby minimizing the deformation of the workpiece caused by the simultaneous reduction of residual stress during the stress relief process.

[0031] The abrasive fluid polishing is to use SiC or other material abrasives with a particle size of not less than 1000 mesh to polish the inner hole of the workpiece in the form of a fluid to eliminate the oxidation color / oxide layer on the surface of the inner hole of the workpiece caused by stress relief annealing, and further polish the inner hole to obtain a high-quality inner hole surface, thereby completing the preparation of precision slender tubes.

[0032] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A high-efficiency and low-cost processing method for precision slender tubes, characterized in that: The following steps are involved: S1, cutting Cut the steel raw materials into required specifications to obtain the blank bars of the workpiece; S2. Tempering treatment The workpiece is subjected to quenching and tempering heat treatment; S3. Calibration Straighten the workpiece; S4, processing and clamping interface According to the clamping interface requirements of the deep hole drilling machine, the blank bar material is clamped and processed; S5. Drilling deep holes On a deep hole drilling machine, the inner hole of the workpiece is drilled by a gun drill; S6, rough turning of outer circle With the inner hole of the workpiece as the positioning center, the workpiece is rough turned to make the cross section of the workpiece into a cylindrical structure with uniform cross-section; S7, degreasing and cleaning Remove iron chips and oil from the workpiece; S8, electrolytic deep hole The inner hole surface of the workpiece is used as the anode and other electrode materials are used as the cathode. The cylindrical cathode rod is placed at the axis of the inner hole of the workpiece. Under the action of current and electrolyte, the rough part of the inner hole surface of the workpiece is dissolved and removed by electrochemical means for fine processing. S9. Cleaning Neutralize and clean the workpiece; S10, chemical copper plating on inner hole surface Use copper sulfate solution to wipe the inner hole surface of the workpiece, evenly apply the copper sulfate solution on the inner hole surface of the workpiece, and through the replacement reaction, copper is precipitated and attached to the inner hole surface of the workpiece to form a copper layer; S11, cold extrusion inner hole The carbide material is squeezed through the inner hole of the workpiece by an interference fit punch. The extrusion action of the punch causes the inner hole of the workpiece to undergo plastic deformation and expand. During the extrusion process, the copper layer acts as a lubricant to prevent the extrusion deformation process from scratching the inner hole surface of the workpiece. S12, copper removal and cleaning The copper removal process is used to dissolve and remove the copper layer on the surface of the inner hole of the workpiece through chemical reaction; S13, stress relief annealing Use heat aging treatment to eliminate the internal residual stress caused by deformation during the extrusion process of the inner hole of the workpiece; S14, abrasive fluid polishing Abrasives are used to polish the inner hole of the workpiece in the form of fluid to eliminate the oxidation color / oxidation layer on the surface of the inner hole of the workpiece caused by stress relief annealing, and the inner hole of the workpiece is further polished.

2. The high-efficiency and low-cost processing method for precision slender tubes according to claim 1, characterized in that: The material of the slender tube workpiece is alloy steel, the inner hole diameter ranges from 5 to 15 mm, the aspect ratio is 60 to 120, the inner hole diameter dimensional accuracy is ≤0.02 mm, and the inner hole surface roughness is ≤0.2 μm.

3. The high-efficiency and low-cost processing method for precision slender tubes according to claim 1 is characterized by: In S6, two tops are used for double top positioning.

4. The high-efficiency and low-cost processing method for a precision slender tube according to claim 1 is characterized in that: In S2, the heat treatment hardness is controlled at 250HB~320HB, and the structure is uniform tempered troostite.

5. The high-efficiency and low-cost processing method for a precision slender tube according to claim 1 is characterized in that: In S13, the stress relief annealing process is: using a vacuum furnace and an inert gas protective atmosphere, keeping the temperature at 20℃~80℃ lower than the tempering temperature of the workpiece for 4 hours, and the heating and cooling stage time is not less than 1 hour. During the heat treatment process, the workpieces are placed vertically and neatly.

6. The high-efficiency and low-cost processing method for precision slender tubes according to claim 1, characterized in that: In S14, the abrasive material used should have a particle size of not less than 1000 mesh.

7. The high-efficiency and low-cost processing method for precision slender tubes according to claim 1 is characterized by: In S3, the straightness of the workpiece is controlled within 0.5 mm; In S5, the workpiece inner hole size accuracy is controlled within 0 to 0.05 mm, and the surface roughness Ra value is controlled within 3.2 μm; In S8, the electrolytic removal thickness is controlled at 0.15-0.3 mm, and the current density is controlled at 900-1100 A / dm 2 , the inner hole diameter dimensional accuracy is controlled within 0~0.05mm, and the surface roughness Ra value is controlled within 0.4μm; In S11, the extrusion deformation expansion of the inner hole diameter is controlled within 0.05-0.10 mm, the dimensional accuracy of the inner hole diameter of the workpiece 1 after extrusion is controlled within 0-0.02 mm, and the surface roughness Ra value is controlled within 0.2 μm.

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