CN102773323B - Strong force rotary pressing molding method of nanocrystalline/superfine crystal carbon steel cylindrical piece - Google Patents

Abstract

The invention discloses a powerful spinning forming method for a nanocrystalline/ultrafine-grained carbon steel cylindrical part. The method is based on the size of the metal cylindrical part, the principle of constant material volume in the deformation process, and 85-90% of workpiece production According to the requirements of the total thickness reduction rate, prefabricated non-welded cylindrical or cup-shaped blanks; then the blanks are set on the mandrel, and the wall thickness reduction rate reaches 60-70% after multiple passes of staggered spinning ; Then put the workpiece into an inert gas protection furnace for recrystallization treatment; finally, put the workpiece on the mandrel again, and through multi-pass spinning deformation, the total wall thickness reduction rate reaches 85-90%. The invention aims at low-carbon steel thin-walled cylindrical parts not only having high-precision external dimensions, but also having ultrafine-grained/nano-sized microscopic grain structures on the whole rather than on the surface, thus having good overall mechanical properties.

Description

Power Spinning Forming Method of Nanocrystalline/Ultrafine Grained Carbon Steel Cylindrical Parts

technical field

The invention relates to a nano/ultra-fine crystal material, in particular to a powerful spinning forming method for a nano-crystal/ultra-fine crystal carbon steel cylinder, belonging to the field of plastic forming of metal materials.

Background technique

Ultrafine crystal/nano material is an important development direction of nano science and technology. The characteristic dimension of grains of ultra-fine-grained materials is below the micron level (100nm to 1000nm), and the characteristic dimension of grains of nanomaterials is on the order of nanometers (1nm to 100nm). Due to the extremely fine grains, a large number of central atoms located in the grain boundaries and defects in the grains, and its own quantum size effect, small size effect, surface effect and macroscopic quantum tunneling effect, ultrafine grain/nanomaterials and the same composition Compared with conventional micron crystal materials, it has many exotic properties in catalysis, optics, magnetism, mechanics, etc., so it has become a research hotspot in the field of materials science and condensed matter physics, and it has gradually been paid attention to and popularized in the processing of mechanical parts. .

The preparation method of nanocrystalline/ultrafine crystalline materials is mainly to prepare bulk materials with extremely small grain size, and then use this material to process the required parts. The preparation of such bulk materials is generally limited by technology, and only small-sized blanks can be obtained, so only small-sized parts can be processed.

In order to solve the problem of grain refinement of large-sized parts, combined with the fact that the surface of mechanical parts is relatively easy to be damaged during actual work, the surface ultra-fine grain/nanoization technology has been formed, that is, the parts are processed first by conventional methods. Then only the ultra-fine grain/nano treatment is performed on the surface of the part, and the material grains within most of the volume of the part are still above the conventional micron level.

For the low-carbon steel thin-walled cylindrical metal parts widely used in actual engineering, due to the small thickness, the service environment of the inner and outer surfaces of the parts and the interior of the material is very close, and the surface nanotechnology can no longer meet the use requirements. If the size of the part is large and it is desired to obtain a microstructure with ultra-fine grains/nano-grains, nano-bulk materials cannot be used to process larger parts, and the parts processed by conventional methods cannot only be superficially superficial. Fine-grained/nano-sized treatment.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a microstructure that can not only obtain the overall nanocrystalline/ultrafine grain, but also directly process a larger-sized carbon steel thin-walled cylindrical part that meets the requirements of the product shape. Methods.

The purpose of the present invention is achieved through the following technical solutions:

A method for powerful spinning forming of nanocrystalline/ultrafine-grained carbon steel cylindrical parts, comprising the steps of:

(1) According to the wall thickness and part length of metal cylindrical parts, according to the principle of constant material volume and the requirement of a total thickness reduction rate of 85-90% in the wall of carbon steel cylindrical parts during the deformation process, prefabricated without welds Cylindrical or cup-shaped blank; the material of the carbon steel cylindrical part is low carbon steel;

(2) Put the blank on the mandrel, and undergo multi-pass three-rotor stagger spinning deformation, so that the wall thickness reduction rate reaches 60-70%; control the axial stagger of the three-rotor wheel to 1.5- 2.5mm, the radial misalignment is 0.1~0.3mm;

(3) Put the workpiece into an inert gas protection furnace with a temperature of 400-450°C to heat up to the recrystallization holding temperature of 550-600°C, keep it warm for 0.8-1 hour, and then take it out of the furnace to cool;

(4) Set the workpiece on the spinning mandrel again, and through multi-pass three-roller staggered spinning deformation, the total wall thickness reduction rate reaches 85-90%, and then trims to meet the size requirements of the part.

In order to further realize the purpose of the present invention, when designing the size of the blank, a trimming allowance of 30-50 mm is added in the length direction of the part.

The carbon content of the carbon steel is preferably 0.1%-0.25%.

The cooling in step (3) is preferably cooling with water.

The three-roller staggered-pitch spinning deformation is formed by using a frame-roller-seat spinning machine, and the three spinners with numbers 1, 2, and 3 are distributed symmetrically at 120° around the center hole of the frame. There is a through hole in the center of the frame, and the center point of the frame through hole is located on the same horizontal line as the main shaft of the machine tool. The distances from the center point of the three rotary wheels with labels 1, 2, and 3 are R1, R2, and R3 respectively, and the radial stagger distance between the rotary wheels with labels 1 and 2 respectively is e12=R1－R2, and the labels are respectively The radial stagger distance between the rotary wheels 2 and 3 is e23=R2－R3; the installation positions of the three rotary wheels are staggered in the direction of the machine tool spindle, and S12 is the axial stagger between the rotary wheels labeled 1 and 2. S23 is the axial stagger distance between the 2 and 3 rollers.

Recrystallization description of step (3): During the heating and holding process of step (3), due to the plastic deformation of the workpiece, under the appropriate temperature and holding time, there will be no strain in the microstructure of the deformed metal. New grains of ─ recrystallization core. The new grains continue to grow until the original deformed structure disappears completely, and the properties of the metal also change significantly. This process is called recrystallization (different from the crystallization process in which liquid solidifies into a solid). The recrystallization temperature is not fixed, and is affected by many factors, mainly the chemical composition of the material, the degree of deformation, etc. Generally, the recrystallization temperature is greater than 0.4 times the melting point of the material, and the accurate recrystallization temperature mainly depends on experiments.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention can obtain the microstructure of ultra-fine crystal/nano material that runs through the whole material instead of the surface;

2. The present invention can obtain practical parts with ultra-fine crystal/nano-materials instead of blanks of materials;

3. The present invention can obtain ultra-fine crystal/nano material parts with large size;

4. Compared with the material microstructure obtained by conventional spinning, the ultra-fine grain/nano microstructure obtained by the present invention has better mechanical and chemical properties.

Description of drawings

Fig. 1 is a structural schematic diagram of a metal thin-walled cylindrical part of the present invention.

Fig. 2 is a schematic view of the frame wheel seat used in the present invention.

Fig. 3 is a schematic diagram of the position of the rotary wheel when Fig. 1 is projected in the direction A.

Fig. 4 is a diagram of a tubular blank used in the present invention.

Fig. 5 is a diagram of a cup blank used in the present invention.

Fig. 6 is a schematic diagram of the normal spinning process of the staggered spinning of the tubular blank.

Fig. 7 is a schematic diagram of the cup-shaped rough blank center spinning reverse spinning process.

Fig. 8 is a flowchart of the forming method of the present invention.

Fig. 9 is a photograph of the original crystal phase of the rough material 20 steel used in the present invention.

Fig. 10 is a temperature change curve of the recrystallization treatment of the present invention.

Fig. 11 is a transmission electron microscope photo of 20 steel of the present invention after spinning forming and recrystallization treatment.

Detailed ways

The present invention will be further described below in conjunction with the drawings and examples, but the protection scope of the present invention is not limited to the range expressed in the examples.

The profile of the part to be processed in the present invention is shown in Figure 1, which is a low-carbon steel metal thin-walled cylindrical part. The frame spinning machine is used for spinning forming. Figure 2 shows the frame spinning wheel seat, in which the three spinning wheels labeled 1, 2, and 3 are distributed symmetrically at 120° around the center hole of frame 0. , There is a through hole in the center of the frame, which is used to pass through the spinning mandrel and the workpiece, so the center Z point of the frame through hole is on the same level as the machine tool spindle. The distances from the center Z point of the three rotary wheels with labels 1, 2, and 3 are R1, R2, and R3 respectively. The distances can be adjusted according to the needs to obtain the radial offset of the rotary wheels, where the labels are 1, The radial stagger distance e ₁₂ between the rollers of 2 = R1-R2, the radial stagger distance between the rollers marked 2 and 3 respectively e ₂₃ = R2-R3; Figure 3 shows three rollers Schematic diagram of the staggered installation positions in the direction of the main shaft of the machine tool. S ₁₂ is the axial stagger distance between the rollers marked 1 and 2, and S ₂₃ is the axial stagger distance between the rollers marked 2 and 3. The amount of disclination can be adjusted as needed.

Since there is a certain offset in the radial and axial directions of the three rollers, this spinning forming method is called offset spinning. During spinning, the three spinning wheels that have adjusted the axial and radial offsets move to the left at the same time, and contact the workpiece successively. By adjusting the radial positions R1, R2, and R3 of the rollers, the designed total thickness reduction of the workpiece and the respective reductions undertaken by each roller are realized.

As shown in Figures 6 and 7, the tubular part spinning mandrel 4 has a cylindrical shape, and is fixedly connected to the main shaft of the machine tool through the flange at the end, the tubular blank shown in Figure 4 or the cup blank shown in Figure 5 Set on the mandrel 4, the blank, the mandrel and the machine tool spindle rotate together. For the convenience of expression, the three rotary wheels in Fig. 6 and Fig. 7 are respectively drawn at the same circumferential angular position. The frame wheel seat is installed on the workbench of the machine tool, and can move with the workbench along the direction of the main axis of the machine tool, that is, move along the longitudinal direction of the mandrel 4 .

When spinning the tubular blank shown in Figure 4, first put the blank on the mandrel 4, and then adjust the three rotary wheels to the appropriate position in the radial and axial directions to achieve the designed offset, as shown in the figure 6. Since the mandrel and the blank rotate around the main axis Z, when the wheel base moves to the left and the three wheels contact the blank in turn, the three wheels rotate successively and apply pressure to the workpiece to deform the workpiece and reduce its thickness. In order to prevent slippage between the blank and the mandrel during the deformation process, a retaining ring 5 with teeth at the end is fixed at the root of the mandrel 4, and when the blank is pressed against the retaining ring 5 to the left, the teeth of the retaining ring will The workpiece is bitten tightly so that it can rotate synchronously with the mandrel. Since the axial movement direction V of the three rollers _{is opposite} to the flow direction V in which the deformed material is extruded, this spinning forming of the tubular blank is also called reverse rotation.

When spinning the cup-shaped blank shown in Figure 5, first put the blank on the mandrel 4, and then adjust the three rotary wheels to the appropriate position in the radial and axial directions to achieve the designed offset, as shown in the figure 7. Since the mandrel and the blank rotate around the main axis Z, when the wheel base moves to the left and the three wheels contact the blank in turn, the three wheels rotate successively and apply pressure to the workpiece to deform the workpiece and reduce its thickness. The workpiece is clamped by the tail top 6 and the mandrel 4, and rotates synchronously with the mandrel. Since the axial movement direction V of the three rollers is _exactly the same as the flow direction V in which the deformed material is extruded, the spinning forming of this cup-shaped blank is also called positive rotation.

The present invention utilizes the above-mentioned forward rotation and reverse rotation methods to process cylindrical parts.

Example 1

A low-carbon steel metal thin-walled cylindrical part, the material is 10 steel (0.1% carbon content), the shape is shown in Figure 1, in which the diameter of the inner cavity of the cylindrical part is d=68mm, the wall thickness δ=0.6mm, and the length l=1000mm. In addition to shape requirements, it is also necessary to obtain an ultrafine-grained microstructure with a grain size of less than 1 μm.

1. Since the specifications can be purchased in the market as The seamless steel pipe, the diameter of the inner cavity of the cylindrical part is d=68mm, and the wall thickness is Δ=4mm. If the seamless steel pipe of this specification is used to form the part, the wall thickness should be reduced from 4mm to 0.6mm, and the thinning rate is 85%. Therefore, the part is planned to be processed by the seamless steel pipe blank (as shown in Figure 4) through multi-pass spinning forming and recrystallization treatment (as shown in Figure 8). The blank tube raw material is in an annealed state, and its grain shape is equiaxed, which is basically similar to that shown in Figure 9, and the grain size is 30-50 μm.

Lengthen the part by 30mm as the trimming allowance, and determine the length of the seamless steel pipe blank according to the principle of constant volume as

2. Design a spinning mandrel with a diameter of 68mm and a length of 1100mm, install it on the spindle of the machine tool, and set the specification as A seamless steel pipe blank with a length of L=150mm is set on the mandrel. The three-rotation wheel is reverse-rotated and staggered for spinning (as shown in Figure 6). The axial stagger is s ₁₂ =s ₂₃ =2.5mm; the radial stagger is e ₁₂ =e ₂₃ =0.3mm. Due to the good plasticity of the material, a wall thickness reduction rate of 70% can be achieved through two passes of spinning: the first spin forming reduces the wall thickness of the workpiece from 4mm to 2.4mm (thinning rate is 40%), That is to say, in the case of satisfying the amount of misalignment, adjust R3 to the radius of the mandrel plus the wall thickness of the workpiece: R3=34+2.4=36.4 (mm), and complete a spinning forming. The second spinning forming reduces the wall thickness of the workpiece from 2.4mm to 1.2mm (the total thinning rate is 70%), that is, R3=34+1.2=35.2 (mm), and the second spinning forming is completed.

3. According to the 70% thinning rate of the material, combined with the test, the recrystallization temperature is determined to be 560°C. Put the workpiece in an inert gas shielded furnace at T ₁ =430°C and heat it up to T ₂ =560°C, keep it warm for t=0.8 hours, and then take it out of the furnace for water cooling, as shown in Figure 10. The furnace temperature when the workpiece enters the furnace is determined to be 430°C instead of room temperature. The main purpose is to reduce the time the workpiece takes up in the furnace and ensure better temperature uniformity inside the workpiece during the process of heating up to 560°C.

4. Set the workpiece on the spinning mandrel again, adjust the radial offset of the three-wheel to e ₁₂ =e ₂₃ =0.2mm, and reduce the wall thickness of the workpiece from 1.2mm to 0.6mm (the total thinning rate is 85%), that is, adjust R3 to R3=34+0.6=34.6 (mm) to complete the third spin forming.

Due to the first two passes of spinning forming, the original relatively coarse equiaxed grains are elongated into elongated fibrous structures, and the material atoms have accumulated a large deformation internal energy. When undergoing the above heat treatment, the atoms Rearrangement completes recrystallization, thereby obtaining fine equiaxed grains, which is similar to Figure 11, and it can be seen that the grain size is basically smaller than 1um. After the final spinning forming, the fine equiaxed grains are further elongated into a fibrous structure, thereby obtaining an extremely small size in the transverse direction of the fiber, that is, the characteristic dimension of the grain of the part is extremely small. The reduction of the grain size is conducive to obtaining excellent material properties.

At this time, the total length of the workpiece is 1030mm, and 15mm allowance is cut off at both ends to obtain a part that meets the shape requirements, and the characteristic dimension of the grain of the part reaches 100-800nm, which is an ultra-fine grain microstructure.

Example 2

A low-carbon steel metal thin-walled cylindrical part, the material is 10 steel (0.1% carbon content), the shape is shown in Figure 1, in which the diameter of the inner cavity of the cylindrical part is d=69mm, the wall thickness δ=0.6mm, and the length l=1000mm. In addition to shape requirements, it is also necessary to obtain an ultrafine-grained microstructure with a grain size of less than 1 μm.

1. The inner diameter of the part is d=69mm, and there is no similar seamless steel pipe on the market. The part is planned to use a cup-shaped part (as shown in Figure 5) formed by deep drawing of the steel plate as the spinning blank, and then spin through multiple passes. Press forming and recrystallization treatment method processing (as shown in Figure 8). The blank tube raw material is in an annealed state, its grain shape is equiaxed, and its grain size is 30-50 μm, as shown in FIG. 9 .

The wall thickness of the cup-shaped blank is determined to be Δ=4mm according to the requirement of a total thinning rate of 85%. Therefore, a steel plate with a thickness of the cup-shaped blank of Δ=4mm can be selected, and a disc with a diameter of 220mm is designed according to the principle of constant volume. The cup-shaped blank is obtained by ordinary drawing forming method, as shown in Figure 5, where the inner diameter d=69mm, the wall thickness of the cup-shaped blank is Δ=4mm, and the depth L=150mm.

2. Design a spinning mandrel with a diameter of 69 mm and a length of 1100 mm, install it on the spindle of the machine tool, and put the cup-shaped blank obtained by the above-mentioned deep drawing on the mandrel. Using the three-rotor wheel positive rotation offset spinning deformation (as shown in Figure 7), the axial offset is s ₁₂ =s ₂₃ =2mm; the radial offset is e ₁₂ =e ₂₃ =0.3mm. Since the steel plate has undergone deep drawing, the plasticity has decreased. Compared with Example 1, the spinning wall thickness reduction rate before recrystallization treatment is reduced to 60%: the first spin forming adjusts R3 to R3=34.5 +2.6 (mm), reduce the wall thickness of the workpiece from 4mm to 2.6mm (thinning rate is 35%), adjust R3 to R3=34.5+1.6 (mm) in the second spinning forming, and reduce the wall thickness of the workpiece by 2.6mm thinned to 1.6mm (60% total thinning).

3. After testing, the recrystallization treatment temperature of the workpiece is 550°C. Compared with Example 1, the recrystallization temperature has decreased because the material has undergone deep drawing deformation, although the wall thickness of the cup-shaped blank during spinning The thinning rate is smaller than that of Example 1, but the cumulative deformation has increased, the internal stress and energy of the material are higher, and the atomic mobility is enhanced, resulting in a decrease in the recrystallization temperature. Therefore, put the workpiece in an inert gas shielded furnace with a temperature of T ₁ =400°C and continue to heat up to T ₂ =550°C, keep it warm for t=0.9 hours, and then take it out of the furnace for water cooling, as shown in Figure 10. The grains of the material after heat treatment are shown in Figure 11.

4. Set the workpiece on the spinning mandrel again, adjust R3 to R3=34.5+0.6 (mm), and reduce the wall thickness of the workpiece from 1.6mm to 0.6mm (the total thinning rate is 85%).

At this time, the total length of the workpiece is 1034mm. Cut off the mouth of the workpiece by 20mm and the bottom of the workpiece by 14mm (including cutting off the bottom of the cup) to obtain a part that meets the shape requirements, and the characteristic dimension of the grain of the part reaches 80-900nm. It is nano/ultrafine grain microstructure.

Example 3

A low-carbon steel metal thin-walled cylindrical part, the material is 25 steel (0.25% carbon content), the shape is shown in Figure 1, the inner diameter of the wall cylindrical part d=140mm, the wall thickness δ=0.5mm, Length l=500mm. In addition to shape requirements, it is also necessary to obtain an ultrafine-grained microstructure with a grain size of less than 1 μm.

1. Since the specifications can be purchased in the market as seamless steel pipe, the inner diameter of the seamless steel pipe is d=140mm, and the wall thickness of the seamless steel pipe is Δ=5mm. If the seamless steel pipe of this specification is used to form the part, the wall thickness should be reduced from 5mm to 0.5mm, and the thinning rate is 90%. Therefore, the part is planned to be processed by the seamless steel pipe blank (as shown in Figure 4) through multi-pass spinning forming and recrystallization treatment (as shown in Figure 8). The blank tube raw material is in an annealed state, its grain shape is equiaxed, and its grain size is basically similar to that shown in Fig. 9 .

Due to the large diameter and thin wall thickness of the part, the quality of the mouth part during spinning is relatively poor, so the trimming allowance after forming is increased to 50mm, and the length of the blank is determined according to the principle of constant volume.

2. Design a spinning mandrel with a diameter of 140mm and a length of 600mm, install it on the spindle of the machine tool, and set the specification as A seamless steel pipe blank with a length of L=53.5mm is set on the mandrel. Adopt three-rotation wheel anti-rotation and staggered pitch spinning (as shown in Figure 6), the axial staggered amount is s ₁₂ =s ₂₃ =1.5mm; the radial staggered amount is e ₁₂ =e ₂₃ =0.2mm. Compared with Example 1, the carbon content of the material has increased, and the plasticity has decreased, so it is determined that the total wall thickness reduction rate before recrystallization treatment is 60%. Adjust R3 to R3=70+3.25 (mm) for the first spinning forming, and reduce the wall thickness of the workpiece from 5mm to 3.25mm (35% thinning rate), and adjust R3 to R3 for the second spinning forming =34.5+2 (mm), reduce the wall thickness of the workpiece from 3.25mm to 2mm (the total thinning rate is 60%).

3. After testing, the recrystallization temperature of the workpiece is 600°C, so put the workpiece into an inert gas protection furnace with a temperature of T ₁ =450°C and continue heating to T ₂ =600°C, keep it warm for t=1 hour, and then Out of the furnace water cooling, as shown in Figure 10. The grain size of the material after heat treatment is similar to that shown in Figure 11.

4. Set the workpiece on the spinning mandrel again, adjust the radial offset of the three-rotor wheel to e ₁₂ =e ₂₃ =0.1mm, first adjust R3 to R3=34.5+1.1 (mm), and adjust the wall thickness of the workpiece Thinning from 2mm to 1.1mm (the total thinning rate is 78%), then adjust R3 to R3=34.5+0.5 (mm), and reduce the workpiece wall thickness from 1.1mm to 0.5mm (the total thinning rate is 90%) %).

At this time, the total length of the workpiece is 650mm, and the two ends are cut off with a margin of 25mm to obtain a part that meets the shape requirements, and the characteristic dimension of the grain of the part reaches 100-1000nm, which is an ultra-fine grain microstructure.

In the implementation process of the present invention, the focus is to ensure that a large workpiece wall thickness reduction rate is obtained in the deformation process, and to arrange a recrystallization process in the multi-pass spinning deformation process to pull the crystal grains in the deformation process. The growth and thinning are organically combined with the grain nucleation and growth suppression during the recrystallization process, so as to obtain metal thin-walled cylindrical parts that meet high performance requirements. The recrystallization treatment temperature is affected by many factors, such as the more impurity elements in the steel, the higher the recrystallization temperature; the greater the deformation of the material, the lower the recrystallization temperature, etc. It is often necessary to determine the recrystallization temperature of the workpiece through experiments.

Claims (5)

1. a powerful spinning forming method of nanocrystalline/ultrafine-grained carbon steel cylindrical parts, is characterized in that comprising the steps: (1) According to the wall thickness and part length of metal cylindrical parts, according to the principle of constant material volume and the requirement of a total thickness reduction rate of 85-90% in the wall of carbon steel cylindrical parts during the deformation process, prefabricated without welds Cylindrical or cup-shaped blank; the material of the carbon steel cylindrical part is low carbon steel; (2) Put the blank on the mandrel, and undergo multi-pass three-rotor stagger spinning deformation, so that the wall thickness reduction rate reaches 60-70%; control the axial stagger of the three-rotor wheel to 1.5- 2.5mm, the radial misalignment is 0.1~0.3mm; (3) Put the workpiece into an inert gas protection furnace with a temperature of 400-450°C to heat up to the recrystallization holding temperature of 550-600°C, keep it warm for 0.8-1 hour, and then take it out of the furnace to cool; (4) Set the workpiece on the spinning mandrel again, and through multi-pass three-roller staggered spinning deformation, the total wall thickness reduction rate reaches 85-90%, and then trims to meet the size requirements of the part. 2. The powerful spinning forming method of nanocrystalline/ultrafine-grained carbon steel tubular parts according to claim 1, characterized in that: when designing the blank size, a trimming allowance of 30-50 mm is added in the length direction of the part. 3. The powerful spinning forming method of nano-crystalline/ultra-fine-grained carbon steel cylindrical parts according to claim 1, characterized in that: said carbon steel is low-carbon steel with a carbon content of 0.1%-0.25%. 4. The powerful spinning forming method of nanocrystalline/ultrafine-grained carbon steel cylindrical parts according to claim 1, characterized in that: the cooling in the step (3) is water cooling. 5. The powerful spinning forming method of nanocrystalline/ultra-fine-grained carbon steel cylindrical parts according to claim 1, characterized in that: the three-roller staggered-pitch spinning deformation uses frame-roller seat type spinning The machine is used for spinning forming, and the three rotary wheels with the labels 1, 2, and 3 are distributed symmetrically at 120° around the center hole of the frame. There is a through hole in the center of the frame, and the center point of the through hole of the frame is located at the same position as the spindle Horizontal line; the distances from the center point of the three rotary wheels with labels 1, 2, and 3 are R1, R2, and R3 respectively, and the radial stagger distance between the rotary wheels with labels 1 and 2 is e12=R1-R2, The radial offset e23=R2－R3 between the rotary wheels with labels 2 and 3 respectively; the installation positions of the three rotary wheels are staggered in the direction of the main shaft of the machine tool, and S12 is the axis between the rotary wheels with labels 1 and 2 The disclination distance, S23 is the axial discrepancy distance between the 2nd and 3rd rollers.