Energy recovery unit bearing cylinder inner flow channel corrosion-resistant layer cladding process

Abstract

The application discloses a kind of energy recovery unit with corrosion-resistant layer cladding process in cylinder inner channel, first, cast steel is used to complete cylinder casting, rough machining cylinder outer circle, inner hole, taper hole, various stages of vane hole, after rough machining, first stress relief heat treatment is carried out, to obtain cylinder blank;Then cylinder blank is carried out semi-finishing cladding surface and first flaw detection, after the second half of cylinder blank or entire flow passage is cladded, second heat treatment and second flaw detection, to obtain cylinder intermediate body;Finally, semi-finishing outer circle, vane hole and inner channel processing are carried out to cylinder intermediate body, third flaw detection is carried out, whether to repair welding is determined according to flaw detection result, after finishing, to obtain corrosion-resistant cylinder for energy recovery unit;The application adopts cast steel, and a layer of corrosion-resistant layer is cladded in the second half of cylinder or entire flow passage to realize corrosion prevention, with the advantages of low cost and good protection effect.

Description

Technical Field

[0001] This invention relates to the technical field of blast furnace gas residual pressure recovery turbine power generation devices (TRT), specifically to a corrosion-resistant layer cladding process for the inner flow channel of an energy recovery unit. Background Technology

[0002] The blast furnace gas pressure recovery turbine power generation unit (TRT) is a secondary energy recovery device that converts the internal energy of the high-temperature and high-pressure gas generated by the blast furnace into mechanical energy or electrical energy, thereby realizing the recycling of energy.

[0003] With improvements in blast furnace smelting technology, the temperature of the gas entering the TRT unit has gradually decreased from 120–150℃ to 90–120℃. This has led to condensation of the gas in the latter half of the TRT unit, producing acidic liquid rich in Cl. - SO4 2- Plasma media severely corrodes the original cylinder material (cast steel or cast iron), affecting the unit's lifespan. Currently, the method used in production is to replace the integral cylinder with cast stainless steel to improve the overall lifespan of the unit. However, the current measures have the following disadvantages: 1) Using cast stainless steel as the integral material results in high manufacturing costs, and corrosion is more likely to occur in the later stages of the unit, making integral casting with stainless steel wasteful; 2) Stainless steel generally has good resistance to H2SO4 corrosion, but it is prone to intergranular corrosion in HCl environment, so its corrosion resistance is poor in the acidic liquid formed by high-temperature coal gas condensation. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a corrosion-resistant layer cladding process for the inner flow channel of the bearing cylinder of an energy recovery unit. The substrate is made of cast steel, and a corrosion-resistant layer is clad in the rear half or the entire flow channel of the bearing cylinder to achieve corrosion protection. This process has the advantages of low cost and good protection effect.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A welding process for the corrosion-resistant layer of the inner flow channel of an energy recovery unit includes the following steps:

[0007] Step 1) Casting of the bearing cylinder is completed using cast steel. The outer circle, inner hole, tapered hole, and stationary blade holes of each stage of the bearing cylinder are roughly machined. After the rough machining is completed, the first heat treatment is performed to relieve stress and obtain the bearing cylinder blank.

[0008] Step 2) The cylinder blank is semi-finished and the cladding surface is inspected for the first time to ensure that there are no defects exceeding the standard. Then, the second half or the entire flow channel of the cylinder blank is clad and the second heat treatment is completed to relieve stress and the second flaw inspection is performed to obtain the cylinder intermediate body.

[0009] Step 3) The intermediate body of the bearing cylinder is semi-finished for outer diameter, stationary blade hole and inner flow channel. Then the third flaw detection is carried out. After completion, the finishing is carried out to obtain the corrosion-resistant bearing cylinder for energy recovery unit.

[0010] In step 1), when rough machining the outer circle, inner hole, tapered hole, and stationary blade holes of the bearing cylinder, leave a 5-10mm allowance on each side. Leave a 5-10mm allowance on each side of both ends of the bearing cylinder. Machin the inner hole at the 10mm allowance on the right end face as a straight hole.

[0011] In step 2), during semi-finishing, the inner wall cladding area is first processed to the finishing size, and then the cladding layer thickness is further processed downwards, and finally processed downwards by 2-3 mm.

[0012] The cladding in step 2) specifically involves:

[0013] 2.1) Surface pretreatment: The surface of the cylinder blank is degreased using an organic solvent; the organic solvent is alcohol or acetone.

[0014] 2.2) The cladding material uses high-temperature alloy powder with the following composition: Cr: 20-23%, Co: 0.5-1%, Mo: 8-10%, Nb: 3.15-4.15%, C: ≤0.1%, Fe≤5%, Ni: balance;

[0015] Cladding parameter control: Set the parameters of laser power, scanning speed, powder feeding speed, overlap rate, and spot diameter according to the required cladding layer thickness; after cladding, the cladding layer thickness is 0.5-2mm greater than the final required thickness, and the surface of the cylinder is flat overall;

[0016] Deformation control measures:

[0017] (1) Segmented cladding: Clamping is carried out in segments according to the size of the cladding area. The cladding is carried out in a circular manner from right to left or from the middle outwards in a symmetrical manner to ensure that the unclad parts do not overheat.

[0018] (2) When drilling the bottom layer, the laser power is controlled at 1700-1900w and the scanning speed is 15-25mm / s to reduce heat input;

[0019] (3) A ring-shaped anti-deformation fixture is set on the outer periphery of the right side of the cylinder, and the un-melted part inside is supported by steel pipes at the mid-section.

[0020] The cladding parameters in step 2.2) are: laser power: 1500~2400w; overlap rate: ≥40%; powder feeding speed: 15~30g / min; scanning speed: 15~25mm / s; spot diameter: 2~4mm.

[0021] In step 2), a 7-axis robotic arm with a reach of 1.7m is used for cladding, and its control accuracy is not less than 0.03mm.

[0022] The stress-relieving process of the second heat treatment in step 2) is as follows: hold at 600-640℃ for 1-3 hours, cool with the furnace to 150-200℃, and then furnace cool.

[0023] In step 2), the cladding metal is multi-layered. Each layer of cladding metal needs to be polished and subjected to a second flaw detection using a penetrant method. It is required to meet the requirements of NB / T 47013.5 and not allow any crack defects. It must be qualified at level II and the circular defect must be ≤Φ3mm.

[0024] In step 3), the cladding layer after finishing meets the design size requirements and the local thinning amount is not less than 10%.

[0025] If the result of the third flaw detection in step 3) is unqualified, the defect shall be repaired by welding using the original cladding method and cladding parameters, or by welding using argon arc welding.

[0026] In step 3), after the upper and lower split surfaces of the bearing cylinder are exposed to light and flat, the upper and lower bearing cylinders are placed on the worktable and aligned with their large end faces. The upper bearing cylinder is used as a reference for dial indicator marking, and the difference is marked at the corresponding point on the lower bearing cylinder for alignment during machining.

[0027] In step 3), the inner hole is clad as required, with a single-sided allowance of 0.3-0.5 mm. Before machining the inner hole, the cutting parameters are optimized, including a feed rate of 0.4-0.6 mm and a rotation speed of 25-30 r / min, to ensure that the dimensions and surface roughness of the finished inner hole meet the requirements.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) Because the present invention uses cylinder casting, its manufacturing cost is significantly reduced compared to using cast stainless steel for the whole body;

[0030] 2) Because this invention clads the latter half or the entire flow channel of the cylinder blank to prepare a corrosion-resistant layer, compared to existing stainless steel which has good resistance to H2SO4 but poor corrosion resistance in HCl environments, this invention provides better protection, especially in environments containing Cl. - It exhibits better corrosion resistance in acidic environments;

[0031] 3) Due to the control of cladding parameters in this invention: the parameters of laser power, scanning speed, powder feeding speed, overlap rate, and spot diameter are set according to the cladding layer thickness requirements; after cladding is completed, the cladding layer thickness should be 0.5-2mm greater than the final required thickness, so the surface of the bearing cylinder is generally flat.

[0032] 4) Because the present invention adopts deformation control measures for cladding, the cladding is carried out in sections according to the size of the cladding area, and the cladding is carried out in a circular manner from right to left to ensure that the uncladding area does not overheat; the laser power for the bottom layer is controlled at 1700-1900w and the scanning speed is 15-25mm / s to reduce heat input; an annular anti-deformation fixture is set on the outer periphery of the right side of the bearing cylinder, and the uncladding area inside is supported by a steel pipe at the middle parting surface in a cross shape, so the cladding deformation is small and the cladding quality is good.

[0033] 5) Since the cladding metal of this invention is multi-layer cladding, the surface of each layer of cladding metal needs to be polished and subjected to a second flaw detection using a penetrant method. It is required to meet the requirements of NB / T 47013.5 and not allow crack defects. It must be qualified at level II and the circular defect must be ≤Φ3mm. Therefore, the cladding quality is good.

[0034] 6) Because this invention uses a 7-axis robotic arm with a reach of 1.7m for cladding, its control accuracy is not less than 0.03mm, so the cladding accuracy is high;

[0035] 7) Because the present invention welds the inner hole as required, leaving a 0.3-0.5mm allowance on each side, and then selects the cutting tool and optimizes the cutting parameters to ensure that the dimensions and roughness of the finished inner hole meet the requirements, the dimensional accuracy is high.

[0036] In summary, the present invention uses cast steel as the base material and clads a corrosion-resistant layer on the rear half of the cylinder or the entire flow channel to achieve corrosion protection, which has the advantages of low cost and good protection effect. Attached Figure Description

[0037] Figure 1 This is a flowchart of an embodiment of the present invention.

[0038] Figure 2 This is a structural diagram of the bearing cylinder according to Embodiment 1 of the present invention. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0040] Example 1, referring to Figure 1 A welding process for the corrosion-resistant layer of the inner flow channel of an energy recovery unit includes the following steps:

[0041] Step 1) The bearing cylinder is cast using ZG200-400 cast steel. The outer circle, inner hole, tapered hole, and stationary blade holes of each stage of the bearing cylinder are rough machined. After the rough machining is completed, the first heat treatment is performed to relieve stress and obtain the bearing cylinder blank.

[0042] In this embodiment, when rough machining the outer circle, inner hole, tapered hole, and stationary blade holes of the bearing cylinder, a 10mm allowance is left on each side. The allowance on each side of both ends of the bearing cylinder is 10mm. The inner hole at the 10mm allowance on the right end face is machined into a straight hole for subsequent datum alignment.

[0043] Step 2) The bearing cylinder blank undergoes semi-finishing of the cladding surface and first flaw detection. After ensuring that there are no defects exceeding the standard on the cladding surface, the second half or the entire flow channel of the bearing cylinder blank is clad, and the second heat treatment to relieve stress and the second flaw detection are completed to obtain the bearing cylinder intermediate body.

[0044] In this embodiment, during semi-finishing, the cladding area is first machined to the finishing size, then the cladding layer thickness is further machined down by 5mm, and finally down by 3mm; a 7-axis robotic arm with a reach of 1.7m is used for cladding, and its control accuracy is not less than 0.03mm;

[0045] The cladding process specifically involves:

[0046] 2.1) Surface pretreatment: The surface of the bearing cylinder blank is degreased with alcohol, and cladding is carried out as soon as possible after degreasing;

[0047] 2.2) The cladding material is Ni-based high-temperature alloy powder with the following measured composition: Cr: 21.56%, Co: 0.76%, Mo: 8.2%, Nb: 3.25%, C: 0.008%, Fe: 3.0%, Ni: balance;

[0048] Cladding parameter control: Set parameters such as laser power, scanning speed, powder feeding speed, overlap rate, and spot diameter according to the cladding layer thickness requirements; to ensure the final thickness of the cladding layer, after cladding, the thickness of the cladding layer should be 0.5mm greater than the final required thickness, and there should be no grooves on the surface of the cylinder, and the surface should be flat.

[0049] Deformation control measures:

[0050] (1) Segmented cladding: Clamping is carried out in segments according to the size of the cladding area, and cladding is carried out in a circular manner from right to left to ensure that the unclad parts do not overheat.

[0051] (2) The laser power for the bottom layer is controlled at 1800w, and the scanning speed is 20mm / s to reduce heat input;

[0052] (3) A ring-shaped anti-deformation fixture is set on the outer periphery of the right side of the cylinder, and the un-melted part inside is supported by steel pipes at the mid-section.

[0053] The cladding parameters in step 2.2) are: laser power: 2000w; overlap rate: ≥40%; powder feeding speed: 20g / min; scanning speed: 23mm / s; spot diameter: 3mm;

[0054] The second heat treatment process is as follows: hold at 620℃ for 2 hours, then cool in the furnace to 200℃ and then furnace cool.

[0055] The cladding metal is multi-layered. Each layer of cladding metal needs to be polished and tested for flaws using penetrant testing. The flaw detection is carried out according to the NB / T 47013 standard dye penetrant testing. Cracks are not allowed. Level II is qualified and circular defects are required to be ≤Φ3mm. If defects are detected during the process, they should be repaired immediately.

[0056] Step 3) The intermediate body of the bearing cylinder is semi-finished for machining the outer circle, stationary blade hole and inner flow channel. Then, a third flaw detection is performed. Based on the flaw detection results, it is decided whether to repair welding. After completion, fine machining is performed to obtain the corrosion-resistant bearing cylinder for the energy recovery unit.

[0057] In this embodiment, the repair welding is carried out on the defects according to the cladding method and cladding parameters. When the bearing cylinder is disassembled, it is difficult to repair the defects using the original process. Therefore, argon arc welding is used to repair the local defects. After finishing, the local thinning of the cladding layer is not less than 10%.

[0058] Reference Figure 2 In this embodiment, after the upper and lower center surfaces of the bearing cylinder are exposed to light and flat, the upper bearing cylinder and the lower bearing cylinder are respectively placed on the worktable and aligned with the large end faces. The upper bearing cylinder is used as the reference for dialing, and the difference is marked at the corresponding point on the lower bearing cylinder for alignment during machining.

[0059] The inner hole is clad as required, with a 0.5mm allowance on each side. Before machining the inner hole, the cutting parameters are optimized, including a feed rate of 0.5mm and a rotation speed of 28r / min. After finishing, the inner hole size and surface roughness are measured to ensure that the finished inner hole size and surface roughness meet the requirements.

[0060] Corrosion resistance test of this embodiment: After corrosion with 5% H2SO4 for 1 week, the average corrosion rate was 0.20 g / year, the corrosion-resistant layer thinning was 0.87 mm / year, and no intergranular corrosion occurred; after corrosion with 5% HCl for 1 week, the average corrosion rate was 0.81 g / year, the corrosion-resistant layer thinning was 0.35 mm / year, and no intergranular corrosion occurred.

[0061] Example 2, the cladding parameters in step 2) of Example 1 are changed to: laser power: 1500w; overlap rate: ≥50%; powder feeding speed: 15g / min; scanning speed: 15mm / s; spot diameter: 2mm; the second heat treatment process is changed to: holding at 600℃ for 1h, cooling to 150℃ in the furnace and then furnace cooling; other steps remain unchanged, and the cladding layer thickness is 2mm.

[0062] Corrosion resistance test of this embodiment: After corrosion with 5% H2SO4 for 1 week, the average corrosion rate was 0.28 g / year, the corrosion-resistant layer thinning was 0.70 mm / year, and no intergranular corrosion occurred; after corrosion with 5% HCl for 1 week, the average corrosion rate was 0.46 g / year, the corrosion-resistant layer thinning was 0.35 mm / year, and no intergranular corrosion occurred.

[0063] Example 3: The cladding parameters in step 2) of Example 1 are changed to: laser power: 2400w; overlap rate: ≥40%; powder feeding speed: 30g / min; scanning speed: 25mm / s; spot diameter: 4mm; the second heat treatment process is changed to: heat treatment at 640℃ for 3h, followed by furnace cooling to 180℃; other steps remain unchanged.

[0064] Corrosion resistance test in this embodiment: The sample was corroded with 5% HCl for 1 week, with an average corrosion rate of 0.81 g / year and a corrosion-resistant layer thinning of 0.35 mm / year. No intergranular corrosion occurred.

Claims

1. A welding process for the corrosion-resistant layer of the inner flow channel of a bearing cylinder in an energy recovery unit, characterized in that, Includes the following steps: Step 1) The bearing cylinder is cast using cast steel. The outer circle, inner hole, conical hole, and stationary blade holes of each stage of the bearing cylinder are rough machined. After the rough machining is completed, the first heat treatment is performed to relieve stress and obtain the bearing cylinder blank. Step 2) The cylinder blank is semi-finished and the cladding surface is inspected for the first time to ensure that there are no defects exceeding the standard. Then, the second half or the entire flow channel of the cylinder blank is clad and the second heat treatment to relieve stress and the second flaw inspection are completed to obtain the cylinder intermediate body. The cladding process specifically involves: 2.1) Surface pretreatment: The surface of the cylinder blank is degreased using an organic solvent; the organic solvent is alcohol or acetone. 2.2) The cladding material uses high-temperature alloy powder with the following composition: Cr: 20-23%, Co: 0.5-1%, Mo: 8-10%, Nb: 3.15-4.15%, C: ≤0.1%, Fe≤5%, Ni: balance; Cladding parameter control: Set the parameters of laser power, scanning speed, powder feeding speed, overlap rate, and spot diameter according to the required cladding layer thickness; after cladding, the cladding layer thickness is 0.5-2mm greater than the final required thickness, and the surface of the cylinder is flat overall; Deformation control measures: (1) Segmented cladding: According to the size of the cladding area, segmented cladding is carried out, and cladding is carried out in a circular manner from right to left or from the middle outward in a symmetrical manner to ensure that the uncladding parts do not overheat; (2) When drilling the bottom layer, control the laser power to be 1700-1900w and the scanning speed to be 15-25mm / s to reduce heat input; (3) A ring-shaped anti-deformation fixture is set on the outer periphery of the right side of the bearing cylinder, and the un-melted part inside is supported by steel pipes at the mid-section. Step 3) Perform semi-precision machining of the outer diameter, stationary blade hole and inner flow channel of the intermediate body of the bearing cylinder, followed by a third flaw detection, and then precision machining to obtain the corrosion-resistant bearing cylinder for the energy recovery unit.

2. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that, The cladding parameters in step 2.2) are: laser power: 1500~2400w; overlap rate: ≥40%; powder feeding speed: 15~30g / min; scanning speed: 15~25mm / s; spot diameter: 2~4mm.

3. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: In step 2), the cladding metal is multi-layered. Each layer of cladding metal needs to be polished and subjected to a second flaw detection using a penetrant method. It is required to meet the requirements of NB / T 47013.5 and not allow any crack defects. It must be qualified at level II and the circular defect must be ≤Φ3mm.

4. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: In step 2), a 7-axis robotic arm with a reach of 1.7m is used for cladding, and its control accuracy is not less than 0.03mm.

5. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: The second heat treatment stress relief process in step 2) is as follows: hold at 600-640℃ for 1-3 hours, cool with the furnace to 150-200℃, and then furnace cool.

6. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: In step 3), the cladding layer after finishing meets the design size requirements and the local thinning amount is not less than 10%; if the third flaw detection result is unqualified in step 3), the defect is repaired by welding using the original cladding method and cladding parameters, or by welding using argon arc welding.

7. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: In step 3), after the upper and lower split surfaces of the bearing cylinder are exposed to light and flat, the upper and lower bearing cylinders are placed on the worktable and aligned with their large end faces. The upper bearing cylinder is used as a reference for dial indicator marking, and the difference is marked at the corresponding point on the lower bearing cylinder for alignment during machining.

8. The welding process for the corrosion-resistant layer of the inner flow channel of the bearing cylinder in an energy recovery unit according to claim 1, characterized in that: In step 3), the inner hole is clad as required, with a single-sided allowance of 0.3-0.5mm. Before machining the inner hole, the cutting parameters are optimized, including a feed rate of 0.4-0.6mm and a rotation speed of 25-30r / min, to ensure that the dimensions and surface roughness of the finished inner hole meet the requirements.

9. The welding process for the corrosion-resistant layer of the inner flow channel of an energy recovery unit according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1) The bearing cylinder is cast using ZG200-400 cast steel. The outer circle, inner hole, tapered hole, and stationary blade holes of each stage of the bearing cylinder are rough machined. After the rough machining is completed, the first heat treatment is performed to relieve stress and obtain the bearing cylinder blank. When rough machining the outer circle, inner hole, tapered hole, and stationary blade holes of the bearing cylinder, leave a 10mm allowance on each side. Leave a 10mm allowance on each side of both ends of the bearing cylinder. Machin the inner hole at the 10mm allowance on the right end face as a straight hole for subsequent datum alignment. Step 2) The cylinder blank is semi-finished and the cladding surface is inspected for the first time to ensure that there are no defects exceeding the standard. Then, the second half or the entire flow channel of the cylinder blank is clad and the second heat treatment to relieve stress and the second flaw inspection are completed to obtain the cylinder intermediate body. During semi-finishing, the cladding area is first machined to the finishing size, then the cladding layer thickness is further machined down by 5mm, and finally down by 3mm; a 7-axis robotic arm with a reach of 1.7m is used for cladding, and its control accuracy is not less than 0.03mm; The cladding process specifically involves: 2.1) Surface pretreatment: The surface of the bearing cylinder blank is degreased with alcohol, and cladding is carried out as soon as possible after degreasing; 2.2) The cladding material is Ni-based high-temperature alloy powder with the following measured composition: Cr: 21.56%, Co: 0.76%, Mo: 8.2%, Nb: 3.25%, C: 0.008%, Fe: 3.0%, Ni: balance; Cladding parameter control: Set the parameters of laser power, scanning speed, powder feeding speed, overlap rate, and spot diameter according to the cladding layer thickness requirements; to ensure the final thickness of the cladding layer, after cladding, the thickness of the cladding layer should be 0.5mm greater than the final required thickness, and there should be no grooves on the surface of the cylinder, and the surface should be flat. Deformation control measures: Segmented cladding: Clamping is performed in segments according to the size of the cladding area, and cladding is carried out sequentially from right to left in a circular manner to ensure that the unclad parts do not overheat. (2) The laser power for the bottom layer is controlled at 1800w, and the scanning speed is 20mm / s to reduce heat input; (3) A ring-shaped anti-deformation fixture is set on the outer periphery of the right side of the bearing cylinder, and the un-melted part inside is supported by steel pipes at the mid-section. The cladding parameters in step 2.2) are: laser power: 2000w; overlap rate: ≥40%; powder feeding speed: 20g / min; scanning speed: 23mm / s; spot diameter: 3mm; The second heat treatment process is as follows: hold at 620℃ for 2 hours, then cool in the furnace to 200℃ and then furnace cool. The cladding metal is multi-layered. Each layer of cladding metal needs to be polished and tested for flaws using penetrant testing. The flaw detection is carried out according to the NB / T 47013 standard dye penetrant testing. Cracks are not allowed. Level II is qualified and circular defects are required to be ≤Φ3mm. If defects are detected during the process, they should be repaired immediately. Step 3) The intermediate body of the bearing cylinder is semi-finished for machining the outer circle, stationary blade hole and inner flow channel. Then, a third flaw detection is performed. Based on the flaw detection results, it is decided whether to repair welding. After completion, fine machining is performed to obtain the corrosion-resistant bearing cylinder for the energy recovery unit. Repair welding is performed on defects according to the cladding method and parameters. When the bearing cylinder is disassembled, it is difficult to repair defects using the original process, so argon arc welding is used for local repair welding; after finishing, the local thinning of the cladding layer should not be less than 10%. After the upper and lower center surfaces of the bearing cylinder are exposed to light and flat, the upper and lower bearing cylinders are placed on the worktable and aligned with the large end faces. The upper bearing cylinder is used as a reference for dial indicator, and the difference is marked at the corresponding point on the lower bearing cylinder for alignment during machining. The inner hole is clad as required, with a 0.5mm allowance on each side. Before machining the inner hole, the cutting parameters are optimized, with a cutting depth of 0.5mm and a tool speed of 28r / min. After finishing, the inner hole dimensions and surface roughness are measured to ensure that the finished inner hole dimensions and surface roughness meet the requirements.

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