Processing technology of large-diameter super-long combined pipe body

Abstract

The invention relates to a processing technology of a large-diameter super-long combined pipe body, which comprises the following steps of: carrying out semi-finish machining on a single pipe body quenched and tempered blank until the allowance of 5mm is reserved on the single side of the outer circle of an inner hole, heating by using a pit furnace, carrying out semi-finish machining, then carrying out stress relief tempering on the pipe body, carrying out finish machining on the pipe body by using a deep hole drilling and boring machine and a numerical control lathe until the allowance of 2.5 mm is reserved on the single side of the inner hole and the single side of the outer circle; an inner hole is used as a benchmark for outer circle finish machining of a workpiece after finish machining, a connecting thread sleeve is used for assembling a first pipe body and a second pipe body after forming, a deep hole drilling and boring machine is used for three-cutter pull boring type floating boring and honing inner hole forming of the whole workpiece after connection, and errors caused by assembly and connection after traditional single pipe body finish machining are avoided. According to the method, a method that a certain allowance is reserved for assembling after a single branch pipe body is subjected to semi-finish machining, and an inner hole is integrally pulled and bored in a floating mode after assembling and connecting is adopted, so that pipe body machining with high-precision requirements such as roughness and straightness of the inner hole of the large-diameter super-long combined pipe body is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of mechanical manufacturing technology and relates to a processing technology for producing high-precision ultra-long tube products with high inner diameter by using an integral floating boring method after assembly, thus avoiding the precision errors caused by traditional assembly errors. Background Technology

[0002] Currently, in the development of various types of high-chamber-pressure, high-life, high-strength, and corrosion-resistant ultra-long tube launching systems, the main component of the launching device is the ultra-long tube. The material is generally PCrNi3Mo1V, PCrNi3MoVA, or PCrNi3MoVQE(Ⅲ), with a total length of approximately 16000mm and an aspect ratio greater than 100. This structure consists of a 9600mm long tube 1, a 6640mm long tube 2, and an 850mm long intermediate connecting sleeve. The overall shape... This type of tube, characterized by a thicker middle section and extremely long, thinner ends with a step difference of up to 200mm, relies on the simultaneous engagement of three extra-long mating stops at both ends of the middle connection point, with a clearance of 0.1mm. After assembly, the inner bore roundness must be no greater than 0.05mm, the surface roughness Ra no greater than 0.4um, and the coaxiality no greater than 0.05mm. Simultaneously, it must allow a 1500mm long inspection sample column with a clearance of 0.2~0.3mm to pass smoothly through the inner bore. This type of extra-long tube demands high precision in terms of inner bore roughness and straightness. Therefore, traditional single-tube precision machining followed by assembly introduces errors, causing the sample column to jam within the inner bore, requiring repeated disassembly and inspection, and making it difficult to guarantee the sample column's smooth passage through the assembled tube. This traditional single-tube precision machining and assembly technique cannot guarantee the smooth passage of the sample column through the inner bore; therefore, a suitable process for manufacturing this type of extra-long tube needs to be designed. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a processing technology for a large-diameter ultra-long combined pipe body that is semi-finished with a certain margin before assembly, and then finely machined as a whole after assembly, so as to meet the design requirement that the ultra-long pipe body test sample column can pass smoothly through the inner cavity.

[0004] The objective of this invention is achieved as follows: A processing technology for large-diameter, ultra-long composite pipes involves semi-finishing the tempered billet using a deep-hole drilling and boring machine and a CNC lathe, leaving a 5mm finishing allowance on each side of the inner hole and outer diameter. The semi-finished pipe is then subjected to stress-relief tempering using a pit furnace for heating. The pipe is then finished again using a deep-hole drilling and boring machine and a CNC lathe, leaving a 2.5mm finishing allowance on each side of the inner hole and outer diameter. The finished workpiece is then shaped by finishing the outer diameter using the inner hole as a reference. After the outer diameter is shaped, the first and second pipes are assembled and connected using connecting threaded sleeves. The assembled workpiece is then subjected to three-stage broaching and floating boring on a deep-hole drilling and boring machine, followed by honing to ensure the required inner hole roughness and straightness, thus forming the ultra-long composite pipe. The specific implementation steps are as follows: Step 1) Use a deep hole drilling and boring machine and a CNC lathe to semi-finish the heat-treated tube blank, and machine it until a 5mm finishing allowance is left on each side of the inner hole and the outer circle; Step 2) Use a pit furnace to hoist and heat the semi-finished tube body to remove internal stress and prevent deformation after finishing. The heating temperature should be 25° lower than the performance tempering temperature of the workpiece. Since the tube body material is PCrNi3Mo1V, PCrNi3MoVA, or PCrNi3MoVQE(Ⅲ), its performance tempering temperature is 540°C~560°C. Therefore, a stress-relief tempering temperature of 500°C is selected, and the holding time is not less than 8 hours. After taking it out of the furnace, let it cool naturally to room temperature. Step 3) Use a deep hole drilling and boring machine and a CNC lathe to finish the tube body, leaving a 2.5mm finishing allowance on each side of the inner hole and outer circle; Step 4) Insert centering plugs at both ends, mount on a CNC lathe, set the speed, travel speed, and cutting amount, and precision machine the outer circle to ensure that the dimensions of the mating parts of the two tubes meet the design clearance requirements; Step 5) Assemble the first tube body, the second tube body, and the connecting screw sleeve on the installation platform; align the outer circle of the small end of the first tube body with the large end of the second tube body, level and center the whole, connect the connecting screw sleeve to the first tube body with 1-2 threads, insert the positioning straight end of the small end of the first tube body into the large end of the second tube body to ensure the coaxiality of the two tube bodies. After the two tube bodies are spliced ​​in place, apply pre-tightening to the connecting screw sleeve using a pre-tightening tool, and use an endoscope to observe the splicing position of the two tube bodies to ensure that there are no gaps at the splice. Step 6) Using a deep hole drilling and boring machine, after alignment, perform three passes of floating boring of the inner hole, leaving a honing allowance of 0.4~0.5mm. After the first pass of boring the inner hole, use a test specimen with a length of 1550mm and the actual measured inner hole size ΦD (-0.145 / -0.245) to check the straightness of the inner hole after boring, ensuring that the specimen passes smoothly through the inner bore and guaranteeing the straightness requirements of the inner hole for each subsequent pass; Step 7) Use a horizontal deep hole honing machine to perform overall honing of the inner hole to ensure that the inner hole roughness, straightness and dimensions meet the design requirements; Step 8) Measure the inner hole size of the tube body after honing. Use a sample column with a length of 1550 mm and a gap of 0.2~0.3 mm, and an outer diameter equal to the measured inner hole size ΦD (-0.145 / -0.245) mm after honing, to check the straightness of the inner hole. Ensure that the sample column passes smoothly through the inner bore after final honing to achieve the high precision requirements of inner hole straightness and roughness Ra not greater than 0.4 μm.

[0005] The beneficial effects of this invention are as follows: Through a series of reasonable process designs, this invention mainly focuses on the machining of inner holes of ultra-long parts using a multi-blade broaching floating boring method on a deep hole drilling and boring machine. Based on the traditional method of ensuring accuracy after precision machining of a single tube body and subsequent assembly, this invention utilizes the overall floating broaching boring method after assembly to produce ultra-long tube body products with high precision inner holes, thus avoiding the accuracy errors caused by traditional assembly errors. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of the structure of the first tube.

[0007] Figure 2 This is a schematic diagram of the second tube.

[0008] Figure 3 This is a schematic diagram of the connecting threaded sleeve.

[0009] Figure 4 This is an assembly diagram of the present invention.

[0010] Figure 1 The tube body is made of PCrNi3Mo1V material, with a total length of 6640mm. The tolerance of the outer circle and inner hole diameter is no greater than 0.05mm, the inner hole roughness Ra is no greater than 0.4um, and the coaxiality of the inner and outer circles is no greater than 0.05mm.

[0011] Figure 2 The tube body is made of PCrNi3Mo1V material, with a total length of over 9520mm. The tolerance of the outer circle and inner hole diameter is no greater than 0.05mm, the inner hole roughness Ra is no greater than 0.4um, and the coaxiality of the inner and outer circles is no greater than 0.05mm.

[0012] Figure 3 The tube body is made of PCrNi3Mo1V material, with a total length of 850mm. The inner diameter tolerance is no greater than 0.05mm, the inner cylindricity is no greater than 0.05mm, and the coaxiality of the inner and outer circles is no greater than 0.05mm. Detailed Implementation

[0013] This invention discloses a processing technology for large-diameter, ultra-long composite pipes. The process involves semi-finishing the tempered billet using a deep-hole drilling and boring machine and a CNC lathe, leaving a 5mm finishing allowance on each side of the inner hole and outer diameter. After semi-finishing, the pipe is subjected to stress-relieving tempering using a pit furnace. It is then finished again using the same deep-hole drilling and boring machine and CNC lathe, leaving a 2.5mm finishing allowance on each side of the inner hole and outer diameter. The finished workpiece is then shaped by finishing the outer diameter using the inner hole as a reference. After the outer diameter is shaped, the first and second pipes are assembled and connected using connecting threaded sleeves. The assembled workpiece is then subjected to three-stage broaching and floating boring on a deep-hole drilling and boring machine, followed by honing to ensure the required inner hole roughness and straightness. This process completes the machining of the ultra-long composite pipe. The specific implementation steps are as follows: Step 1) Use a deep hole drilling and boring machine and a CNC lathe to semi-finish the heat-treated tube blank, and machine it until a 5mm finishing allowance is left on each side of the inner hole and the outer circle; Step 2) Use a pit furnace to hoist and heat the semi-finished tube body to remove internal stress and prevent deformation after finishing. The heating temperature should be 25° lower than the performance tempering temperature of the workpiece. Since the tube body material is PCrNi3Mo1V, PCrNi3MoVA, or PCrNi3MoVQE(Ⅲ), its performance tempering temperature is 540°C~560°C. Therefore, a stress-relief tempering temperature of 500°C is selected, and the holding time is not less than 8 hours. After taking it out of the furnace, let it cool naturally to room temperature. Step 3) Use a deep hole drilling and boring machine and a CNC lathe to finish the tube body, leaving a 2.5mm finishing allowance on each side of the inner hole and outer circle; Step 4) Insert centering plugs at both ends, mount on a CNC lathe, set the speed, travel speed, and cutting amount, and precision machine the outer circle to ensure that the dimensions of the mating parts of the two tubes meet the design clearance requirements; Step 5) Assemble the first tube body, the second tube body, and the connecting screw sleeve on the installation platform; align the outer circle of the small end of the first tube body with the large end of the second tube body, level and center the whole, connect the connecting screw sleeve to the first tube body with 1-2 threads, insert the positioning straight end of the small end of the first tube body into the large end of the second tube body to ensure the coaxiality of the two tube bodies. After the two tube bodies are spliced ​​in place, apply pre-tightening to the connecting screw sleeve using a pre-tightening tool, and use an endoscope to observe the splicing position of the two tube bodies to ensure that there are no gaps at the splice. Step 6) Using a deep hole drilling and boring machine, after alignment, perform three passes of floating boring of the inner hole, leaving a honing allowance of 0.4~0.5mm. After the first pass of boring the inner hole, use a test specimen with a length of 1550mm and the actual measured inner hole size ΦD (-0.145 / -0.245) to check the straightness of the inner hole after boring, ensuring that the specimen passes smoothly through the inner bore and guaranteeing the straightness requirements of the inner hole for each subsequent pass; Step 7) Use a horizontal deep hole honing machine to perform overall honing of the inner hole to ensure that the inner hole roughness, straightness and dimensions meet the design requirements; Step 8) Measure the inner hole size of the tube body after honing. Use a sample column with a length of 1550 mm and a gap of 0.2~0.3 mm, and an outer diameter equal to the measured inner hole size ΦD (-0.145 / -0.245) mm after honing, to check the straightness of the inner hole. Ensure that the sample column passes smoothly through the inner bore after final honing to achieve the high precision requirements of inner hole straightness and roughness Ra not greater than 0.4 μm.

[0014] Example 1: A PCrNi3Mo1V ultra-long composite tube is assembled from three parts: tube 1 (total length 6640mm), tube 2 (total length 9520mm), and connecting threaded sleeve (total length 850mm). After assembly, the maximum outer diameter of the composite tube is Φ420mm, the inner diameter is Φ154.94 (+0.1 / 0)mm, and the total length is 15645mm. The requirements are that there is no gap at the joint between the two tubes, the overall inner diameter roundness is not greater than 0.05mm, the roughness Ra is not greater than 0.4um, and the coaxiality is not greater than 0.05mm. At the same time, the test sample column with a length of 10 times the diameter (length 1550mm) and a diameter of Φ154.94d9 (-0.145 / -0.245) can pass smoothly through the inner bore.

[0015] The specific processing steps are as follows: 1. Use a deep hole drilling and boring machine and a CNC lathe to semi-finish the two tube bodies, leaving a 5mm finishing allowance on each side of the inner hole and outer circle: inner hole Φ145mm, outer circle Φ230~Φ441mm (5mm is reserved on each side of the outer circle of each step).

[0016] 2. Use a pit furnace to heat the semi-finished tube body at a temperature of 480-500℃ and a holding time of 10 hours. After removing it from the furnace, allow it to cool naturally to room temperature to fully remove the internal stress of the workpiece.

[0017] 3. Use a deep hole drilling and boring machine and a CNC lathe to finish the two pipe bodies respectively, leaving a 2.5mm finishing allowance on each side of the inner hole and the outer circle: inner hole Φ: 149.5mm, outer circle Φ225~Φ436mm (2.5mm is reserved on each side of the outer circle of each step).

[0018] 4. Install centering plugs at both ends of the two pipes respectively, mount them on a CNC lathe, top the plugs and clamp the workpieces, set the speed to 70 r / min, axial feed 0.3 mm / r, and make two feeds of 1.7 mm and 0.8 mm to finish turning the outer diameters ΦD1, ΦD2, ΦD3, ΦD4, ΦD5, ΦD6, ΦD7 and ΦD8. Then, use a polishing wheel with 600 grit sandpaper to finish polishing the outer diameter of the pipes. Finally, check that the cylindricity of the outer diameter is 0.05 mm and the coaxiality is 0.05 mm, which meets the design requirements of the drawings.

[0019] 5. Assembly: On the installation platform, using a string line or infrared level, place pipe body 1 and pipe body 2 on the platform. After leveling with the level, ensure a full fit at the stop of pipe body 1 and pipe body 2 to ensure smooth operation. Then, place pipe body 1 and the connecting sleeve on the installation platform, level them, and fit them together. Next, place pipe body 2 and the connecting sleeve on the installation platform, level them, and fit them together. Finally, use the connecting sleeve to assemble pipe body 1 and pipe body 2 as a whole. First, place pipe body 1, pipe body 2, and the connecting sleeve on the installation platform. After leveling and aligning pipe body 1 and the connecting sleeve, connect them with 1-2 threads. Align the outer circle of the small end of pipe body 1 with the large end of pipe body 2. After leveling and centering, use a depth gauge to measure the edge distance or a flexible arm to check the coaxiality of the two pipes. Insert the locating stop of the small end of pipe body 1 into pipe body 2. Slowly push the locating stop of the small end of pipe body 1 into pipe body 2 until pipe body 2 and the locating stop of the connecting sleeve are engaged. After closing, use a hexagonal wrench to slowly tighten the connecting sleeve. At this time, the threaded end of tube body 1 will slowly disengage from the connecting sleeve, and tube body 2 will gradually screw into the connecting sleeve. When the threads of tube body 1 and the connecting sleeve have retracted to 155mm from the hexagonal end face of the sleeve to the relief groove of the tube body 1 thread (the thread length of tube body 1 is 165mm, and the relief groove is 20mm; at this point, tube body 1 and the connecting sleeve are connected by approximately 1-2 turns), use a hexagonal wrench to tighten the connecting sleeve, and then... 1 and 2 converge towards the middle. The threads at both ends of the connecting screw sleeve are simultaneously connected to both pipe body 1 and pipe body 2. The end face of the connecting screw sleeve is 35mm from the outer diameter thread relief groove of pipe body 1 (relief groove 20mm, thread reserved 1-2 turns), and the end face of the connecting screw sleeve is 50mm from the outer diameter thread relief groove of pipe body 2 (relief groove 20mm, thread reserved 3 turns). At this time, the mating end faces of the two pipe bodies are spliced ​​in place. Use an endoscope to observe the splicing position of the two pipe bodies to ensure that there is no gap at the splicing point.

[0020] 6. Using a deep hole drilling and boring machine, perform three passes of floating boring into the inner hole, starting from the large end, to Φ152.1 (+0.1 / 0), Φ153.4±0.1, and Φ154.5±0.1 respectively, leaving a honing allowance of 0.4~0.5mm. After the first pass of boring into the inner hole to Φ152.1 (+0.1 / 0), use a 1550mm long sample post with a diameter of Φ152.1 (-0.145 / -0.245) to check the straightness of the inner hole after the first pass, ensuring the straightness requirement of the inner hole for each subsequent pass.

[0021] 7. Use a horizontal deep hole honing machine to hone the inner hole to Φ154.94 (+0.1 / 0), ensuring that the inner hole roughness Ra≤0.4.

[0022] 8. Measure the inner bore size of the honed tube. Use a 154.94 (-0.145 / -0.245) diameter and 1550 mm length mandrel to check the straightness of the inner bore. Ensure that the mandrel passes smoothly through the inner bore and that the straightness of the inner bore meets the design requirements.

[0023] Processing according to the above requirements avoids the errors caused by the traditional single-branch precision machining and assembly connection, which leads to the sample column getting stuck in the inner cavity, requiring repeated disassembly and inspection, and making it difficult to ensure that the sample column can pass smoothly through the inner cavity of the assembled tube. This method successfully adopts the method of semi-precision machining of single-branch tubes with a certain allowance for assembly, and then floating and boring the inner hole of the whole after assembly connection, which ensures the high precision requirements of the inner hole roughness and straightness of the large-diameter ultra-long combined tube.

Claims

1. A processing technology for a large-diameter, ultra-long composite pipe body, characterized in that: The tube blank was semi-finished using a deep hole drilling and boring machine and a CNC lathe, leaving a 5mm finishing allowance on each side of the inner hole and outer diameter. After semi-finishing, the tube was subjected to stress-relieving tempering using a pit furnace. It was then finished again using the same deep hole drilling and boring machine and CNC lathe, leaving a 2.5mm finishing allowance on each side of the inner hole and outer diameter. The finished workpiece was then shaped by finishing the outer diameter using the inner hole as a reference. After the outer diameter was shaped, the first and second tubes were assembled and connected using connecting threaded sleeves. The assembled workpiece was then subjected to three-stage broaching and floating boring on a deep hole drilling and boring machine, followed by honing to ensure the required inner hole roughness and straightness. This process was used to shape the extra-long composite tube. The specific implementation steps are as follows: Step 1) Use a deep hole drilling and boring machine and a CNC lathe to semi-finish the heat-treated tube blank, and machine it until a 5mm finishing allowance is left on each side of the inner hole and the outer circle; Step 2) Use a pit furnace to hoist and heat the semi-finished tube body to remove internal stress and prevent deformation during the finishing process. The heating temperature should be 25°~30° lower than the performance tempering temperature of the workpiece. Since the tube body material is PCrNi3Mo1V or PCrNi3MoVA or PCrNi3MoVQE(Ⅲ), its performance tempering temperature is 540°C~560°C. Therefore, a stress-relief tempering temperature of about 500°C is selected, and the holding time is not less than 8 hours. After taking it out of the furnace, let it cool naturally to room temperature. Step 3) Use a deep hole drilling and boring machine and a CNC lathe to finish the tube body, leaving a 2.5mm finishing allowance on each side of the inner hole and outer circle; Step 4) Insert centering plugs at both ends, mount on a CNC lathe, set the speed, travel speed, and cutting amount, and precision machine the outer circle to ensure that the dimensions of the mating parts of the two tubes meet the design clearance requirements; Step 5) Assemble the first tube body, the second tube body, and the connecting screw sleeve on the installation platform; align the outer circle of the small end of the first tube body with the large end of the second tube body, level and center the whole, connect the connecting screw sleeve to the first tube body with 1-2 threads, insert the positioning straight end of the small end of the first tube body into the large end of the second tube body to ensure the coaxiality of the two tube bodies. After the two tube bodies are spliced ​​in place, apply pre-tightening to the connecting screw sleeve using a pre-tightening tool, and use an endoscope to observe the splicing position of the two tube bodies to ensure that there are no gaps at the splice. Step 6) Using a deep hole drilling and boring machine, after alignment, perform three passes of floating boring of the inner hole, leaving a honing allowance of 0.4~0.5mm. After the first pass of boring the inner hole, use a test specimen with a length of 1550mm and the actual measured inner hole size ΦD (-0.145 / -0.245) to check the straightness of the inner hole after boring, ensuring that the specimen passes smoothly through the inner bore and guaranteeing the straightness requirements of the inner hole for each subsequent pass; Step 7) Use a horizontal deep hole honing machine to perform overall honing of the inner hole to ensure that the inner hole roughness, straightness and dimensions meet the design requirements; Step 8) Measure the inner hole size of the tube body after honing. Use a sample column with a length of 1550mm (10 times the diameter), a gap of 0.2~0.3mm, and an outer diameter equal to the measured inner hole size ΦD (-0.145 / -0.245)mm after honing to check the straightness of the inner hole. Ensure that the sample column passes smoothly through the inner bore after final honing to achieve the high precision requirements of inner hole straightness and roughness Ra not exceeding 0.4um.

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