Manufacturing method of small-caliber nickel-copper alloy seamless heat exchange tube

Abstract

The invention relates to a manufacturing method of a small-caliber nickel-copper alloy seamless heat exchange tube. The manufacturing method comprises the steps that S1, a UNS N04400 round steel material is subjected to peeling, PT inspection, shearing, centering, grinding, heating, perforating, water cooling and inspection; s2, a hot-punched blank is only cleaned, and inspection is conducted after point grinding is conducted after internal and external polishing; s3, the obtained pipe blank is subjected to first-pass intermediate product cold rolling, deoiling, straightening, pipe cutting, grinding, inspecting and cleaning; s4, second-pass intermediate product cold rolling, deoiling, heat treatment, straightening, pipe cutting, grinding, inspection and cleaning are conducted; S5, finished product cold rolling is conducted; s6, deoiling a finished product; s7, heat treatment of a finished product; s8, straightening a finished product; s9, performing ultrasonic vortex treatment, water pressure treatment and pipe cutting on a finished product; and S10, finished product surface inspection, size inspection, cleaning, mark spraying and finishing procedures are carried out. The method has the advantages of high one-time inspection qualification rate, yield and dimensional precision of products, good inner and outer surface quality, stable structure performance and high practicability.

Description

Technical Field

[0001] The invention relates to the technical field of material processing, in particular to a method for manufacturing a small-caliber nickel-copper alloy seamless heat exchange tube. Background Art

[0002] UNS N04400 alloy is a nickel-copper alloy material, which not only has excellent mechanical properties and welding properties, but also has excellent corrosion resistance. In many corrosive environments, the corrosion resistance of N04400 alloy is better than that of general austenitic stainless steel and duplex stainless steel. UNS N04400 alloy has a wide range of applications, including petrochemical, atomic energy industry, ocean-going ships and other fields. Especially with the rapid development of China's industry, more and more equipment is used under harsh conditions such as strong acid and strong alkali, which puts higher requirements on the corresponding pipes. Therefore, the development of UNS N04400 seamless pipe products has broad application prospects.

[0003] At present, there are several major difficulties in the manufacturing of N04400 nickel-copper alloy seamless heat exchange tubes, which lead to the problems of long manufacturing cycle, low one-time inspection pass rate, low material yield rate, low dimensional accuracy, and poor internal and external surface quality of the final finished tubes. Specifically, they include: First, the perforation is difficult and the perforation quality is poor. Internal and external cracks, head marks, roller marks, guide plate marks, steel sticking and other defects often occur. In particular, some small steel sticking defects are not easy to find with the naked eye, which is a great challenge to the quality of rough pipe spot grinding and is time-consuming and labor-intensive. Second, it is not acid-resistant, the grinding and repair of rough pipes and intermediate products is large, the manufacturing cycle is long, and it is difficult to guarantee the delivery time. Third, in the ASME SB-163-2021 standard, the outer diameter tolerance of UNS N04400 alloy seamless pipes with an outer diameter of ≤15.9 is from negative zero to positive 0.13, the tolerance band is small, and the outer diameter accuracy requirements are extremely high.

[0004] Based on this, a production process for N04400 nickel-copper alloy seamless heat exchange tubes that can overcome the above-mentioned difficulties has been developed, and the development of N4400 nickel-copper alloy seamless heat exchange tubes with a short product manufacturing cycle, a high one-time inspection pass rate, a high yield rate, high dimensional accuracy, good inner and outer surface quality, and physical and chemical properties that meet standard technical requirements has become a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of long manufacturing cycle, low qualified rate and yield rate, low dimensional accuracy and poor surface quality of existing nickel-copper alloy seamless heat exchange tubes, and to provide a manufacturing method for small-diameter nickel-copper alloy seamless heat exchange tubes, which can improve the product's one-time inspection qualified rate and yield rate, enhance dimensional accuracy, improve the quality of internal and external surfaces, ensure stable organizational performance, strong practicality, and facilitate mass production.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for manufacturing a small-caliber nickel-copper alloy seamless heat exchange tube, the specific steps are as follows: S1: UNS N04400 round steel is selected, and the UNS N04400 round steel is subjected to peeling, PT inspection, shearing, centering, grinding, heating, perforation, water cooling and inspection to obtain UNS N04400 hot perforated blank; S2: The UNS N04400 hot perforated billet is only cleaned, and the cleaned billet is polished inside and outside and then spot-grinded, and then inspected. The unqualified ones are repaired and re-inspected. Specifically, the UNS N04400 hot perforated billet is cleaned, polished inside and outside + spot-grinded + inspected. During the inspection, endoscopes are used one by one, and PT is randomly inspected; S3: The tube blank obtained in S2 is subjected to the first pass of intermediate product cold rolling, and after the cold rolling, the intermediate product is degreased, the intermediate product is straightened, the intermediate product is cut, the intermediate product is ground, the intermediate product is inspected, and the intermediate product is cleaned, wherein: (1) During the first pass of cold rolling of the intermediate product, the cold rolling deformation is controlled at 60%~70%, the rolling speed is controlled at ≤60 times / min, the feed amount is ≤3mm / time, the Q value is ≥1.20, the outer diameter deviation after rolling is controlled at ±0.5%Dmm, and the wall thickness deviation is controlled at ±5%Smm; (2) The specific process of degreasing the first intermediate product is: degreasing in an alkali tank → rinsing → soaking in a hot water tank → rinsing → inspection; (3) The specific process of the first intermediate product grinding and inspection is: endoscope inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection; S4: The tube blank obtained in S3 is subjected to a second pass of intermediate product cold rolling, and after the cold rolling, the intermediate product is degreased, heat treated, straightened, cut, ground, inspected and cleaned, wherein: (1) During the second pass of cold rolling of the intermediate product, the cold rolling deformation is controlled at 55%~65%, the rolling speed is controlled at ≤100 times / min, the feed amount is ≤2.5mm / time, the Q value is ≥0.95, the outer diameter deviation after rolling is controlled at ±0.5%Dmm, and the wall thickness deviation is controlled at ±5%Smm; (2) The specific process of degreasing the second intermediate product is: soaking in an alkali tank → soaking in a clean water tank → wiping the outer surface → felting the inner wall with wool balls → inspection; (3) The second intermediate product heat treatment is carried out in a bright furnace. The furnace atmosphere is pure hydrogen or ammonia decomposition. The heat treatment temperature of the intermediate product is controlled at 920±10℃, and the holding time is ≥ wall thickness × 2.5 min; (4) The specific process of the second intermediate product grinding and inspection is: endoscope inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection; S5: The steel pipe obtained in S4 is subjected to cold rolling of finished products. During the cold rolling of finished products, the cold rolling deformation is 60% to 70%, the rolling speed is controlled at ≤120 times / min, the feed amount is ≤1.5mm / time, the Q value is ≥0.7, and during the cold rolling of finished products, the outer diameter deviation after rolling is controlled at ±0.04mm, and the wall thickness deviation is controlled at ±0.05mm; S6: Degreasing the steel pipe obtained in S5, including soaking in an alkali tank → soaking in a clean water tank → wiping the outer surface → felting the inner wall with wool balls → inspection; S7: The steel pipe obtained in S6 is subjected to finished product heat treatment. The finished product heat treatment is carried out in a bright furnace. The atmosphere in the furnace is pure hydrogen. The heat treatment temperature is controlled to be 920±10℃, and the insulation time is ≥ wall thickness × 3 min. After the finished product is heat treated, all processes including the transportation process are covered with rubber rings for protection. S8: straightening the steel pipe obtained in S7; S9: subjecting the steel pipe obtained in S8 to finished product ultrasonic eddy current, water pressure, and pipe cutting, and taking samples for physical and chemical tests during pipe cutting; S10: The steel pipes obtained in S9 are subjected to finished product surface inspection, dimension inspection, cleaning, spray marking and finishing processes, and finally packaged and put into storage.

[0007] Furthermore, in step S3, during the first intermediate product degreasing, the components of the solution in the alkali cylinder are controlled to be degreased in a mass ratio of: degreasing agent: water = 1:6, the alkali cylinder temperature is 70-80°C, and the alkali cylinder immersion time is 60-90 minutes.

[0008] Furthermore, in the steps S3 and S4, when the intermediate product is straightened, the straightening control speed is ≤6m / min, the curvature after straightening is ≤1.0mm / m, and the outer diameter deviation after straightening is ±0.02mm.

[0009] Furthermore, in the steps S3 and S4, when the intermediate products are ground and inspected, the intermediate products are first inspected by endoscopy, and those with poor endoscopy results are internally polished at designated spots. After all FBs are qualified, external rough polishing + spot grinding + external fine polishing + spot grinding are performed, followed by visual inspection.

[0010] Furthermore, in steps S4 and S5, when degreasing the second intermediate product and the finished pipe, the mass ratio of the solution in the alkali cylinder is: degreasing agent: water = 1:5.5, the temperature of the alkali cylinder is 40-60°C, the soaking time in the alkali cylinder is 30-40 minutes, and the inner wall is cleaned with wool ball felt for 3-5 times.

[0011] Furthermore, in step S8, when straightening the finished pipe, a plastic roller or nylon roller straightener is used as the straightening machine, the speed is controlled to be ≤8m / min, the curvature after straightening is ≤0.5mm / m, the outer diameter deviation after straightening is ±0.01mm, the rubber rings are peeled off one by one before straightening, and the rubber rings are put on one by one after straightening, and they are manually lifted to a special protective blanking rack to replace mechanical blanking and avoid scratches and bruises.

[0012] Furthermore, in step S9, the first ultrasonic qualified rate is ≥95%, the first eddy current qualified rate is 100%, the rubber rings are peeled off one by one before flaw detection, and silicone plugs are stuffed at both ends. After flaw detection, the rubber rings are put on one by one, and they are manually lifted to a special protective blanking rack to replace mechanical blanking and avoid scratches and bruises.

[0013] Furthermore, in step S8, the water pressure qualified rate is ≥100%, the pipe cutting underlength rate is ≤0.25%, the rubber rings are peeled off one by one before the water pressure, and the rubber rings are put on one by one after the water pressure, the pipes are manually tilted for 30 seconds to pour out most of the water in the pipes, and then lifted to a special protective blanking rack, and the residual water in the inner hole of the pipe is cleaned within 30 minutes after the water pressure; the rubber rings are peeled off one by one before cutting the pipes, and the rubber rings are put on one by one after cutting the pipes, and the internal and external burrs are cleaned and manually lifted to a special protective blanking rack.

[0014] Furthermore, in step S9, the surface inspection includes visual inspection and dimensional inspection, and the qualified rate is ≥96%. The dimensional accuracy control of the finished tube includes: outer diameter ±0.04mm, wall thickness ±0.05mm, the inner and outer surfaces of the finished tube are smooth, and the inner and outer wall roughness Ra≤0.6.

[0015] Furthermore, the room temperature tensile test of the manufactured finished pipe shows that: yield strength is ≥210 MPa, tensile strength is ≥500 MPa, and elongation after fracture is ≥50%.

[0016] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The present invention treats N04400 hot perforated blanks by directly polishing inside and outside and spot grinding after cleaning without pickling. When degreasing the intermediate product, it is also degreased only by soaking in an alkali cylinder and a clean water cylinder. Since N04400 is extremely resistant to acid corrosion, it is not recommended to put it in an acid cylinder in the production process. By controlling the alkali cylinder ratio, increasing the proportion of the degreasing agent, strictly controlling the alkali cylinder temperature and extending the cylinder time, the degreasing quality is ensured and the risk of carburization during heat treatment is avoided. When specifying the method for degreasing the finished product, degreasing is carried out by degreasing in an alkali cylinder, soaking in a clean water cylinder, wiping the outer surface with acetone and cleaning the inner wall with a wool ball felt soaked in acetone. The alkali cylinder ratio, temperature and time, and the inner and outer wall cleaning method are strictly controlled to ensure the degreasing quality of the finished pipe and ensure that the finished product has no risk of carburization during bright heat treatment. (2) The present invention adopts three cold rolling passes, wherein the first pass is intermediate cold rolling, and the cold rolling deformation is controlled at 60% to 70%, the second pass is intermediate cold rolling, and the cold rolling deformation is controlled at 55% to 65%, and the third pass is finished cold rolling, and the cold rolling deformation is controlled at 60% to 70%, so that the grains are fully broken and a finer grain size can be obtained after heat treatment. The first pass of intermediate cold rolling ensures the surface quality by strictly controlling the feed amount and controls the Q value to make the deformation more uniform, thereby improving the dimensional accuracy; similarly, the finished cold rolling also ensures the surface quality and dimensional accuracy by strictly controlling the feed amount and Q value; (3) The present invention adopts continuous rolling process to produce N04400 nickel-copper alloy tube. Since 400 is soft in material, continuous rolling process can be tried under the condition of ensuring the performance of finished products. Continuous rolling process can greatly improve production efficiency, reduce the labor cost of internal and external grinding and repair of intermediate products, save manufacturing cost, shorten delivery time, and directly perform second cold rolling after degreasing without heat treatment. The second intermediate product solid solution heat treatment adopts bright furnace, the atmosphere in the furnace is pure hydrogen or ammonia decomposition, and the heat treatment temperature is 920±10℃. N04400 is not acid-resistant, and this pass is bright, which can eliminate work hardening on the one hand and reduce the grinding amount after oxidation in oxidizing atmosphere on the other hand. The third finished product solid solution heat treatment adopts bright furnace, the atmosphere in the furnace is pure hydrogen, and the heat treatment temperature is 920±10℃. While obtaining good organization and comprehensive mechanical properties, the surface color of heat exchange tube is bright and the consistency of overall color is guaranteed. (4) The present invention specifies the straightening machine model, straightening speed, straightness and outer diameter deviation range after straightening, especially the straightening of finished products requires the use of plastic rollers or nylon rollers straightening machines, and specifies the straightening speed ≤ 8 m / min. While ensuring the curvature, the risk of iron rod straightening scratches and marks can be avoided, the quality of finished product straightening can be ensured, and the straightening, especially the outer diameter deviation range of the finished product after straightening, is strictly specified to effectively avoid the risk of outer diameter deviation caused by straightening, thereby improving dimensional accuracy; (5) The present invention provides a method for grinding and repairing hot-perforated billets and intermediate steel pipes. The hot-perforated billets are subjected to internal and external polishing + local spot grinding. During spot grinding, all remaining defects due to external polishing are required to be spot ground clean, especially steel sticking and guide plate marks that are not polished cleanly. The purpose of re-inspection and random inspection of hot-perforated billets is to avoid residual cracks on the outer surface. The purpose of endoscopy of each hot-perforated billet is to more accurately and efficiently treat its inner wall defects and avoid the inner wall defects from being transferred to the next cold rolling process and causing the defects to extend. The external rough polishing + local spot grinding + external fine polishing of the intermediate products can effectively ensure the quality of the outer surface of the intermediate products, thereby ensuring the outer surface quality of the finished cold-rolled products. The purpose of endoscopy of each intermediate product during grinding and repair is to ensure the quality of the inner wall of the finished cold-rolled products and reduce the risk of endoscopy failure due to ultrasonic internal damage and inner wall defects, thereby improving the final ultrasonic qualified rate, surface inspection qualified rate and final yield rate. (6) The present invention strictly limits the optimization of the continuous rolling process of UNS N04400 nickel-copper alloy seamless heat exchange tube, thereby ensuring a high first-time inspection pass rate, high material yield rate, high dimensional accuracy, good internal and external surface quality, stable mechanical properties, strong practicality, and conducive to batch production; (7) The first ultrasonic qualified rate of the N04400 nickel-copper alloy seamless heat exchange tube prepared by the method of the present invention is ≥95%, the first eddy current qualified rate is 100%, the first surface inspection qualified rate, i.e., visual inspection + dimensional inspection qualified rate is ≥96%, and the comprehensive first inspection qualified rate, i.e., ultrasonic qualified rate × eddy current qualified rate × surface inspection qualified rate is ≥91%; (8) The yield rate of N04400 nickel-copper alloy seamless heat exchange tubes prepared by the method of the present invention is ≥83%; the prepared N04400 nickel-copper alloy seamless heat exchange tubes can meet the following dimensional accuracy: outer diameter ±0.04mm, wall thickness ±0.05mm; the inner and outer surfaces of the prepared seamless heat exchange tubes are smooth and the color is consistent, and the inner and outer wall roughness Ra≤0.6; the room temperature tensile test of the finished tubes (delivered in the stress-relieved state): yield strength ≥210Mpa, tensile strength ≥500MPa, elongation after fracture ≥50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the UNS N04400 cold rolling parameter table in this embodiment; Figure 2 This is the table of dimensional accuracy and actual measured dimensions of the UNS N04400 technical requirements in this embodiment; Figure 3 This is the main control requirements table for the first intermediate product degreasing process of UNS N04400 in this embodiment; Figure 4 This is the main control requirements table for the degreasing process of the second intermediate product and finished product pipe in this embodiment; Figure 5 This is the UNS N04400 heat treatment parameter table in this embodiment; Figure 6 This is the UNS N04400 straightening parameter table in this embodiment; Figure 7 This is the UNS N04400 pipe cutting requirements table in this embodiment; Figure 8 This is the UNS N04400 grinding and repair operation requirements table in this embodiment; Fig. 9 This is a record sheet of ultrasonic, eddy current, water pressure, visual and dimensional inspections of finished pipes in this embodiment; Fig.10 This is the UNS N04400 yield rate calculation table in this embodiment; Fig.11This is a table of room temperature tensile properties of the UNS N04400 finished pipe in this embodiment. DETAILED DESCRIPTION Example

[0018] To make the present invention more clear, a method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube of the present invention is further described below in conjunction with the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] A method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube, the finished product specification is φ15.875×1.829×7242mm, the technical requirements must meet ASME SB163-2021, NB / T47019.1+47019.9-2021 standards, the outer diameter tolerance is 15.875 (-0~+0.13), and the wall thickness tolerance is 1.829 (-0~+0.36), specifically comprising the following steps: S1: Select UNS N04400 round steel material, and perform peeling, PT inspection, shearing, centering, grinding, heating, perforation, water cooling and inspection on it. The perforation specification is φ80×9mm.

[0020] S2: Only UNS N04400 φ80×9mm hot-pierced billets are cleaned, and the cleaned billets are polished inside and outside, then spot-grinded and inspected. Unqualified ones are repaired and re-inspected. Specifically: After cleaning, the hot-pierced billets are polished inside and outside + spot-grinded + inspected. During the inspection, endoscopes are used one by one, and PT is randomly inspected.

[0021] S3: The qualified φ80×9mm tube obtained in S2 is subjected to the first pass of intermediate product cold rolling, and the rolling specification is φ51×4.5. After cold rolling, the intermediate product needs to be degreased, straightened, cut, ground, inspected and cleaned, including: During the first pass of cold rolling of the intermediate product, the cold rolling deformation is 67%, the rolling speed is 60 times / min, the feed amount is 3mm / time, the Q value is 1.28, the outer diameter deviation after rolling is controlled within ±0.25mm, and the wall thickness deviation is controlled within ±0.20mm; The specific process of degreasing the intermediate product is: degreasing in an alkali tank → rinsing → soaking in a hot water tank → rinsing → inspection; The specific process of intermediate product grinding and inspection is: endoscopic inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection.

[0022] S4: The φ51×4.5 tube blank obtained in S3 is subjected to the second pass of intermediate product cold rolling, and the rolling specification is φ32×2.9. After cold rolling, the intermediate product needs to be degreased, heat treated, straightened, cut, ground, inspected and cleaned, among which: During the second pass of cold rolling of the intermediate product, the cold rolling deformation is 60%, the rolling speed is 100 times / min, the feed amount is 2.5mm / time, the Q value is 0.97, the outer diameter deviation after rolling is controlled within ±0.15mm, and the wall thickness deviation is controlled within ±0.15mm; The specific process of degreasing the intermediate product is: soaking in an alkali tank → soaking in a clean water tank → wiping the outer surface → felting the inner wall with wool balls → inspection; The heat treatment of intermediate products is carried out in a bright furnace. The atmosphere in the furnace is pure hydrogen or ammonia decomposition. The heat treatment temperature of the intermediate products is controlled at 920±10℃ and the holding time is 8min. The specific process of intermediate product grinding and inspection is: endoscopic inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection.

[0023] S5: cold rolling the steel pipe obtained in S4; The finished product specification is φ15.875×1.829, the finished product rolling specification is φ15.93×1.95, the cold rolling deformation during the finished product rolling is 68%, the rolling speed is 120 times / min, the feed amount is 1.5mm / time, and the Q value is 0.74; When the finished product is cold rolled, the outer diameter deviation after rolling is controlled within ±0.04mm and the wall thickness deviation is controlled within ±0.05mm.

[0024] S6: degreasing the steel pipe obtained in S5; The specific steps for degreasing finished pipes are: soak in an alkali tank → soak in a clean water tank → wipe the outer surface → felt the inner wall with wool balls → inspect.

[0025] S7: subjecting the steel pipe obtained in S6 to finished product heat treatment; The finished product heat treatment is carried out in a bright furnace with a pure hydrogen atmosphere; When heat treating the finished product, the heat treatment temperature is controlled at 920±10℃ and the insulation time is 6min. Rubber rings are put on each product for protection during all processes from heat treatment to packaging, including the transportation process.

[0026] S8: Straighten the steel pipe obtained in S7.

[0027] S9: subjecting the steel pipe obtained in S8 to finished product ultrasonic eddy current, water pressure and pipe cutting, and taking samples for physical and chemical tests during pipe cutting.

[0028] S10: The steel pipes obtained in S9 are subjected to finished product surface inspection, dimension inspection, cleaning, spray marking and finishing processes, and finally packaged and put into storage.

[0029] In this embodiment, the cold rolling process of UNS N04400 nickel-copper alloy seamless heat exchange tube is formulated by strictly controlling the cold rolling deformation of intermediate products and finished products, selecting a reasonable rolling speed and a relatively small feed amount to ensure the quality of the inner and outer surfaces, and controlling the Q value to ensure the uniformity of the structure in the wall thickness direction, thereby improving the dimensional accuracy and the quality of the inner wall. For specific cold rolling parameters, see Figure 1 The technical requirements for dimensional accuracy and actual dimensions are shown in the table. Figure 2 The table shown, from Figure 2 It can be seen from the table that the dimensional accuracy of intermediate quality control and finished pipes in each pass meets the internal control requirements, and the dimensional accuracy of finished pipes is higher than ASMESB163-2021 and NB / T47019.1+47019.9-2021 standards.

[0030] In this embodiment, the specific process of degreasing the intermediate product of UNS N04400 nickel-copper alloy seamless heat exchange tube is: degreasing in an alkali cylinder → flushing → soaking in a hot water cylinder → flushing → inspection. The main control requirements for degreasing the intermediate product are shown in Figure 3 The table shown in the figure shows that the steps for degreasing finished pipes are as follows: degreasing by soaking in an alkali tank → degreasing by soaking in a clean water tank → wiping the outer surface → taping the inner wall with cloth strips → inspection. The main control requirements for degreasing finished pipes are shown in Figure 4 As shown in the table, the degreasing agents are all degreasing agents in the prior art. The inner and outer surfaces of the pipes obtained by degreasing according to the above method are clean and free of oil stains, and there is no risk of carburization during heat treatment.

[0031] In this embodiment, the second intermediate heat treatment and finished product heat treatment of UNS N04400 nickel-copper alloy seamless heat exchange tube are carried out in a bright furnace. The atmosphere in the second intermediate furnace is pure hydrogen or ammonia decomposition, and the atmosphere in the finished product heat treatment furnace is pure hydrogen. The heat treatment system is as follows: Figure 5 Table shown.

[0032] In addition, the second intermediate product heat treatment is bright heat treatment, the atmosphere in the furnace is pure hydrogen or ammonia decomposition, the furnace has 5 temperature zones, T01~T02 is the heating zone, T03~T05 is the insulation zone, the heat treatment temperature is 920℃, the insulation time is 8min, and the cooling method is water jacket cooling.

[0033] The finished product heat treatment is bright heat treatment, the atmosphere in the furnace is pure hydrogen, the furnace has 5 temperature zones, T01~T02 is the heating zone, T03~T05 is the insulation zone, the heat treatment temperature is 920℃, the insulation time is 6min, and the cooling method is water jacket cooling.

[0034] In this embodiment, the straightening parameters for intermediate and finished products of UNS N04400 nickel-copper alloy heat exchange tubes are shown in Figure 6The table shown specifies the straightening machine model, straightening speed, straightness and outer diameter deviation range after straightening. In particular, the straightening of finished products requires the use of plastic rollers or nylon roller straightening machines, and the straightening speed is specified to be ≤8m / min. This ensures the curvature while avoiding the risk of iron rod straightening scratches and marks, thereby ensuring the quality of finished straightening products. Strict regulations on straightening, especially the outer diameter deviation range after straightening of finished products, can effectively avoid the risk of outer diameter deviation caused by straightening, thereby improving dimensional accuracy.

[0035] In this embodiment, the requirements for cutting intermediate and finished products of UNS N04400 nickel-copper alloy seamless heat exchange tubes are as follows: Figure 7 As shown in the table, by strictly controlling the amount of flat heads and strictly adhering to the center cutting method, manual measurement is required to mark the middle position before cutting the pipe, and visual inspection is not allowed. This can reduce the risk of intermediate and finished pipes being under-lengthened, and improve the final product inspection pass rate and final yield rate.

[0036] In this embodiment, the inspection and grinding operation requirements for the perforated billet and intermediate quality tube of UNS N04400 nickel-copper alloy heat exchange tube are as follows: Figure 8 As shown in the table, the perforated billet is polished inside and outside + spot grinding. During spot grinding, all the remaining defects from external polishing are required to be spot ground clean, especially the steel sticking and the guide plate marks that are not polished cleanly. The re-inspection and random inspection of hot perforated billets is to avoid that there are no cracks remaining on the outer surface. The endoscope of each hot perforated billet is to treat the inner wall defects more accurately and efficiently, and to avoid the inner wall defects from flowing to the next cold rolling process and causing the defects to extend. External rough polishing + local spot grinding + external fine polishing of intermediate products can effectively ensure the quality of the outer surface of the intermediate products, thereby ensuring the outer surface quality of the finished cold-rolled products. Endoscopes are performed one by one during the grinding and repair of intermediate products to ensure the quality of the inner wall of the finished cold-rolled products, reduce the risk of endoscope failure due to ultrasonic internal damage and inner wall defects, thereby improving the final ultrasonic qualification rate, surface inspection qualification rate and final yield rate.

[0037] In this embodiment, the ultrasonic, eddy current, water pressure, tube cutting, visual and dimensional inspection of the finished product of UNS N04400 nickel-copper alloy seamless heat exchange tube are shown in Fig. 9 As shown in the table, it can be seen from the parameters shown in the table that the ultrasonic pass rate of N04400 nickel-copper alloy seamless heat exchange tubes produced under this production method is as high as 95.69%, the eddy current and water pressure pass rates are both 100.00%, the tube cutting underlength rate is 0.21%, the visual (including endoscope) + size inspection pass rate is as high as 96.49%, and the one-time inspection pass rate is as high as 91.95%.

[0038] Before flaw detection, peel off the rubber rings one by one, plug the two ends with customized silicone plugs, put on the rubber rings one by one after flaw detection, and manually lift them to a special protective blanking rack; peel off the rubber rings one by one before water pressure, put on the rubber rings one by one after water pressure, manually tilt the pipe for 30 seconds to pour out most of the water in the pipe, and then lift it to a special protective blanking rack. Mechanical blanking is prohibited to avoid scratches and bruises. Clean the residual water in the inner hole of the pipe within 30 minutes after water pressure; the pipe cutting condition must be kept clean and a full set of protective work must be done. Peel off the rubber rings one by one before pipe cutting, put on the rubber rings one by one after pipe cutting, remove the burrs inside and outside, and then manually lift it to a special protective blanking rack. Mechanical blanking is prohibited to avoid scratches and bruises.

[0039] UNS N04400 nickel-copper alloy seamless heat exchange tube yield statistics see Fig.10 As shown in the table, 57.99 tons of round steel were collected for hot-punching billets, and 3,634 pieces of finished products with a diameter of 15.875×1.829×7242mm were put into storage, weighing 18.82 tons, with a yield rate of 78.71%.

[0040] According to the room temperature tensile test method of finished pipe: ASTM E8, the test results are as follows Fig.11 From the table shown, it can be seen that the N04400 nickel-copper alloy seamless heat exchange tube manufactured by the method of the present invention has excellent mechanical properties. The yield strength under 12 furnace batch numbers is 218~235Mpa, which is much higher than the ASME SB163-2021 standard requirement of ≥193Mpa, and the tensile strength of 12 furnace batch numbers is 515~544Mpa, which is much higher than the standard requirement of ≥483Mpa. The elongation after break is 50%~52%, which is higher than the standard requirement of ≥35%.

[0041] Then, expansion test was carried out according to the test requirements of ASTM B829-19. The expansion test results of all 12 batches of N04400 nickel-copper alloy heat exchange tubes showed: no cracks.

[0042] The present invention solves the problems of low first-time inspection pass rate, low material yield rate, low dimensional accuracy and poor inner and outer surface quality by strictly limiting the process optimization of UNS N044000 alloy seamless heat exchange tubes. It can be seen from Tables 9-11 that the products produced by the method have a high first-time inspection pass rate, a high material yield rate, high dimensional accuracy, good inner and outer surface quality, stable mechanical properties, strong practicability, and are conducive to batch production.

[0043] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for manufacturing a small-caliber nickel-copper alloy seamless heat exchange tube, characterized in that: S1: UNS N04400 round steel is selected, and the UNS N04400 round steel is subjected to peeling, PT inspection, shearing, centering, grinding, heating, perforation, water cooling and inspection to obtain UNS N04400 hot perforated blank; S2: The UNS N04400 hot perforated billet is only cleaned, and the cleaned billet is polished inside and outside and then spot-grinded, and then inspected. The unqualified ones are repaired and re-inspected. Specifically, the UNS N04400 hot perforated billet is cleaned, polished inside and outside + spot-grinded + inspected. During the inspection, endoscopes are used one by one, and PT is randomly inspected; S3: The tube blank obtained in S2 is subjected to the first pass of intermediate product cold rolling, and after the cold rolling, the intermediate product is degreased, the intermediate product is straightened, the intermediate product is cut, the intermediate product is ground, the intermediate product is inspected, and the intermediate product is cleaned, wherein: (1) During the first pass of cold rolling of the intermediate product, the cold rolling deformation is controlled at 60%~70%, the rolling speed is controlled at ≤60 times / min, the feed amount is ≤3mm / time, the Q value is ≥1.20, the outer diameter deviation after rolling is controlled at ±0.5%Dmm, and the wall thickness deviation is controlled at ±5%Smm; (2) The specific process of degreasing the first intermediate product is: degreasing in an alkali tank → rinsing → soaking in a hot water tank → rinsing → inspection; (3) The specific process of the first intermediate product grinding and inspection is: endoscope inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection; S4: The tube blank obtained in S3 is subjected to a second pass of intermediate product cold rolling, and after the cold rolling, the intermediate product is degreased, heat treated, straightened, cut, ground, inspected and cleaned, wherein: (1) During the second pass of cold rolling of the intermediate product, the cold rolling deformation is controlled at 55%~65%, the rolling speed is controlled at ≤100 times / min, the feed amount is ≤2.5mm / time, the Q value is ≥0.95, the outer diameter deviation after rolling is controlled at ±0.5%Dmm, and the wall thickness deviation is controlled at ±5%Smm; (2) The specific process of degreasing the second intermediate product is: soaking in an alkali tank → soaking in a clean water tank → wiping the outer surface → felting the inner wall with wool balls → inspection; (3) The second intermediate product heat treatment is carried out in a bright furnace. The furnace atmosphere is pure hydrogen or ammonia decomposition. The heat treatment temperature of the intermediate product is controlled at 920±10℃, and the holding time is ≥ wall thickness × 2.5 min; (4) The specific process of the second intermediate product grinding and inspection is: endoscope inspection → external rough polishing → local spot grinding → external fine polishing → local spot grinding → surface inspection; S5: The steel pipe obtained in S4 is subjected to cold rolling of finished products. During the cold rolling of finished products, the cold rolling deformation is 60% to 70%, the rolling speed is controlled at ≤120 times / min, the feed amount is ≤1.5mm / time, the Q value is ≥0.7, and during the cold rolling of finished products, the outer diameter deviation after rolling is controlled at ±0.04mm, and the wall thickness deviation is controlled at ±0.05mm; S6: Degreasing the steel pipe obtained in S5, including soaking in an alkali tank → soaking in a clean water tank → wiping the outer surface → felting the inner wall with wool balls → inspection; S7: The steel pipe obtained in S6 is subjected to finished product heat treatment. The finished product heat treatment is carried out in a bright furnace. The atmosphere in the furnace is pure hydrogen. The heat treatment temperature is controlled to be 920±10℃, and the insulation time is ≥ wall thickness × 3 min. After the finished product is heat treated, all processes including the transportation process are covered with rubber rings for protection. S8: straightening the steel pipe obtained in S7; S9: subjecting the steel pipe obtained in S8 to finished product ultrasonic eddy current, water pressure, and pipe cutting, and taking samples for physical and chemical tests during pipe cutting; S10: The steel pipes obtained in S9 are subjected to finished product surface inspection, dimension inspection, cleaning, spray marking and finishing processes, and finally packaged and put into storage.

2. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1, characterized in that: In the step S3, during the first pass of degreasing the intermediate product, the components of the solution in the alkali cylinder are controlled to be degreased in a mass ratio of: degreasing agent: water = 1:6, the alkali cylinder temperature is 70-80°C, and the alkali cylinder soaking time is 60-90 minutes.

3. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the steps S3 and S4, when the intermediate product is straightened, the straightening control speed is ≤6m / min, the curvature after straightening is ≤1.0mm / m, and the outer diameter deviation after straightening is ±0.02mm.

4. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the steps S3 and S4, when the intermediate products are ground and inspected, the intermediate products are first inspected by endoscope, and the ones with poor endoscope are polished at designated spots. After all FBs are qualified, external rough polishing + spot grinding + external fine polishing + spot grinding are performed and then visual inspection is performed.

5. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the steps S4 and S5, when the second intermediate product and the finished pipe are degreased, the mass ratio of the solution in the alkali cylinder is: degreaser: water = 1:5.5, the temperature of the alkali cylinder is 40-60°C, the soaking time of the alkali cylinder is 30-40min, and the inner wall is beaten with wool ball felt until it is clean, the number of times is 3-5 times.

6. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the step S8, when the finished pipe is straightened, a plastic roller or nylon roller straightener is used as the straightening machine, the speed is controlled to be ≤8m / min, the curvature after straightening is ≤0.5mm / m, the outer diameter deviation after straightening is ±0.01mm, the rubber rings are peeled off one by one before straightening, and the rubber rings are put on one by one after straightening, and they are manually lifted to a special protective blanking rack.

7. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the step S9, the first ultrasonic qualified rate is ≥95%, the first eddy current qualified rate is 100%, the rubber rings are peeled off one by one before flaw detection, the two ends are plugged with silicone plugs, and the rubber rings are put on one by one after flaw detection, and they are manually lifted to the special protective blanking rack.

8. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In the step S8, the water pressure qualified rate is ≥100%, the pipe cutting underlength rate is ≤0.25%, the rubber rings are peeled off one by one before the water pressure, and the rubber rings are put on one by one after the water pressure, the pipes are manually tilted for 30 seconds to pour out most of the water in the pipes, and then lifted to a special protective blanking rack, and the residual water in the inner hole of the pipe is cleaned within 30 minutes after the water pressure; the rubber rings are peeled off one by one before cutting the pipes, and the rubber rings are put on one by one after cutting the pipes, and the internal and external burrs are cleaned and manually lifted to a special protective blanking rack.

9. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: In step S9, the surface inspection includes visual inspection and dimensional inspection, and the qualified rate is ≥96%. The dimensional accuracy control of the finished tube includes: outer diameter ±0.04mm, wall thickness ±0.05mm, the inner and outer surfaces of the finished tube are smooth, and the inner and outer wall roughness Ra≤0.

6.

10. The method for manufacturing a small-diameter nickel-copper alloy seamless heat exchange tube according to claim 1 or 2, characterized in that: The room temperature tensile test of the manufactured finished pipe shows that the yield strength is ≥210 MPa, the tensile strength is ≥500 MPa, and the elongation after fracture is ≥50%.

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