A method of manufacturing a seamless pipe for small-bore uns s32750 umbilical

Abstract

The application discloses a manufacturing method of seamless pipe for small-bore UNS S32750 umbilical cable, and belongs to the technical field of material processing, which comprises the following steps: (1) hot piercing of round steel; (2) pickling of the hot-pierced blank; (3) performing incoming inspection, inner and outer surface grinding and re-inspection on the pipe blank; (4) performing multi-pass intermediate product cold rolling, and after the cold rolling, the intermediate product needs to be deoiled, heat treated, straightened, cut, ground and inspected; (5) performing head rolling, finished product cold drawing and head cutting; (6) performing finished product deoiling; (7) performing finished product heat treatment; (8) performing finished product straightening; (9) performing finished product ultrasonic vortex, water pressure, back straightening, fixed cutting, cleaning, end branch-by-branch PT and outer throwing, and sampling and performing physical and chemical tests during pipe cutting; and (10) performing finished product surface inspection, size inspection, cleaning, mark spraying and finishing processes on the obtained steel pipe, and finally performing packaging and warehousing, and the method has high first-time inspection qualified rate and high yield.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a seamless tube, specifically a method for manufacturing a seamless tube for small-diameter UNS S32750 umbilical cables, belonging to the field of materials processing technology. Background Technology

[0002] Deep-sea umbilical cables consist of many tubes. Typically, the innermost tube (inner tube) is the hydraulic fluid delivery tube, and the cable and optical fiber are located between the inner tube and the outer protective layer (outer tube). The steel tubes in the umbilical cable are generally S32750 (SAF2507) super duplex stainless steel tubes, with specifications ranging from Φ6.3 to Φ50.8 mm. The minimum yield strength of S32750 stainless steel is 550 MPa, and its tensile strength is 800–1000 MPa. Before manufacturing the umbilical cable, each seamless steel tube, several meters long, is butt-welded and coiled into a roll, with each roll typically several kilometers long, sometimes exceeding 20 kilometers, for transport to the cable manufacturer. Once installed underwater, sometimes at depths exceeding 2000 meters, these umbilical cables are difficult to repair, making their quality paramount. With the growth of global energy demand and the accelerated development of marine resources, the demand for submarine cable laying will reach an all-time high. However, research on key technologies for umbilical cables is still limited, which to some extent restricts the development of deep-sea oil and gas fields.

[0003] Currently, patent CN119406965A discloses a manufacturing method for UNS N06690 alloy seamless heat exchange tubes, which includes: (i) peeling, PT inspection, shearing, centering, grinding, heating, piercing, water cooling, and inspection of round steel materials; (ii) pickling the hot-pierced billet, followed by incoming material inspection and grinding of the inner and outer surfaces; (iii) performing two-pass intermediate cold rolling, after which intermediate degreasing, intermediate heat treatment, intermediate straightening, intermediate tube cutting, pickling, intermediate grinding, and intermediate inspection are required; (iv) performing finished product cold rolling; and (v) entering... (vi) Degreasing the finished product; (vii) Heat treatment of the finished product; (viii) Straightening of the finished product; (viii) Ultrasonic eddy current test, water pressure test, and pipe cutting of the finished product, and taking samples for physical and chemical tests during pipe cutting; (ix) The obtained steel pipe undergoes surface inspection, dimensional inspection, cleaning, marking and finishing processes, and finally packaging and warehousing. Its room temperature tensile test: yield strength 280-320 MPa, tensile strength 640-680 MPa, elongation after fracture ≥55%; Patent CN117696621B A UNS The manufacturing method of N08810 alloy seamless heat exchange tubes includes the following steps: (i) inspecting the incoming steel material and grinding the inner and outer surfaces; (ii) performing a single-pass intermediate cold rolling, followed by intermediate degreasing, intermediate heat treatment, intermediate straightening, intermediate tube cutting, pickling, intermediate grinding, and intermediate inspection; (iii) performing finished product cold rolling; (iv) performing finished product degreasing; (v) performing finished product heat treatment; (vi) performing finished product straightening; (vii) performing finished product ultrasonic eddy current, hydrostatic, and tube cutting, with samples taken for physical and chemical tests during tube cutting; (viii) performing finished product surface inspection, dimensional inspection, cleaning, marking, and finishing processes on the obtained steel tubes, and finally packaging and warehousing; the above two patents involve intermediate cold rolling. The process employs a single-pass, two-pass cold rolling method, but with fewer cold rolling passes, the grains are not sufficiently broken down. This results in insufficiently fine grains after heat treatment, leading to uneven deformation and affecting dimensional accuracy. Furthermore, the degreasing and heat treatment times for intermediate products are not adjusted according to the billet size; only simple degreasing is performed. While this completes the degreasing process to some extent, it results in excessive surface oil, prolonged degreasing time, extended soaking time, reduced production efficiency, and a large required amount of degreasing agent, increasing costs and failing to meet future clean production trends. The sole use of a roller hearth furnace during heat treatment easily generates oxide scale, and polishing small-diameter pipes is costly, time-consuming, and labor-intensive, with various performance aspects requiring improvement.

[0004] Based on this, developing a manufacturing method for a small-diameter seamless tube for UNS S32750 umbilical cables that can overcome the above-mentioned difficulties, and producing a small-diameter seamless tube for UNS S32750 umbilical cables with a high first-pass yield, high yield, high dimensional accuracy, good internal and external surface quality, and physical and chemical properties that meet the standard technical requirements has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for manufacturing seamless tubes for small-diameter UNSS32750 umbilical cables. The products manufactured by this method have a high first-pass yield, high yield, high dimensional accuracy, good inner and outer surface quality, stable microstructure and properties, strong practicality, and are conducive to mass production.

[0006] To solve the above technical problems, the present invention provides a method for manufacturing a seamless tube for small-diameter UNS S32750 umbilical cables, specifically including the following steps:

[0007] (a) After peeling, cutting, centering, and surface grinding of UNS S32750 round steel, hot piercing is performed at a piercing temperature of 1170℃ and a holding time of 20min. After piercing, the billet is water-cooled and then inspected for dimensions and inner and outer surfaces.

[0008] (ii) Pickling the UNS S32750 hot-pierced billet. The pickling solution is composed of HF: 1.5-2.5% by mass, HNO3: 8-12%, and the balance is tap water. The sum of the above components is 100%. The temperature of the pickling tank is 45-55℃, the pickling time is 5-6 hours, and pickling is stopped when there is no oxide scale on the inner and outer surfaces.

[0009] (iii) The tube blanks after pickling in step (ii) are inspected upon arrival and the inner and outer surfaces are ground. Specifically, the tube blanks are inspected first, ground, and then re-inspected. During the re-inspection, each endoscope is randomly selected for PT.

[0010] (iv) The tube blank obtained in step (iii) is subjected to multiple passes of intermediate cold rolling. After each pass of cold rolling, intermediate degreasing, intermediate heat treatment, intermediate straightening, intermediate tube cutting, intermediate grinding, and intermediate inspection are required, including:

[0011] When cold rolling intermediate products, the mill model, cold rolling deformation, rolling speed, and feed rate are controlled as follows:

[0012] The rolling mill model is LG60, the cold rolling deformation is controlled at 55%-65%, the rolling speed is ≤60 times / min, and the feed rate is ≤3mm / time;

[0013] The rolling mill model is LG40, the cold rolling deformation is controlled at 55%-65%, the rolling speed is ≤100 times / min, and the feed rate is ≤2.5mm / time;

[0014] The rolling mill model is LG30, the cold rolling deformation is controlled at 50%-60%, the rolling speed is ≤100 times / min, and the feed rate is ≤2mm / time;

[0015] The rolling mill model is LD30, the cold rolling deformation is controlled at 35%-50%, the rolling speed is ≤60 times / min, and the feed rate is ≤2mm / time;

[0016] For intermediate cold-rolled products, the Q value is controlled to be ≥1, and the deviations in outer diameter and wall thickness after rolling are controlled as follows:

[0017] The rolling mill model is LG60, with the outer diameter deviation controlled within ±0.5%Dmm and the wall thickness deviation controlled within ±5%Smm;

[0018] The rolling mill model is LG40, with the outer diameter deviation controlled within ±0.4%Dmm and the wall thickness deviation controlled within ±4%Smm;

[0019] The rolling mill model is LG30, with the outer diameter deviation controlled within ±0.3%Dmm and the wall thickness deviation controlled within ±3%Smm;

[0020] The rolling mill model is LD30, and the cold-rolled outer diameter deviation is controlled within ±0.05mm, and the wall thickness deviation is controlled within ±0.05mm;

[0021] The specific process for removing oil from intermediate products is as follows:

[0022] If the intermediate product wall thickness is ≥3mm, the oil removal process for the intermediate product is as follows: oil scraping machine → oil removal in alkali tank → rinsing → hot water tank soaking → oil removal in acid tank → rinsing → inspection.

[0023] If the wall thickness of the intermediate product is <3mm, the oil removal process of the intermediate product is as follows: oil scraping machine → immersion in alkali tank → immersion in hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → inspection.

[0024] intermediate product heat treatment:

[0025] If the intermediate product has a wall thickness ≥3mm, it should be processed in a roller hearth furnace with a slightly oxidizing atmosphere. The heat treatment temperature should be 1090±10℃, and the holding time should be as follows:

[0026] If the wall thickness of the intermediate steel pipe is ≥3 mm or 6 mm, the heat preservation time should be ≥ wall thickness × 2.5 min.

[0027] If 13mm or more is greater than the wall thickness of the intermediate steel pipe and 6mm or more, the heat preservation time shall be greater than or equal to the wall thickness × 2min.

[0028] If the intermediate product wall thickness is <3, it should be processed in a bright furnace with a pure hydrogen atmosphere. The heat treatment temperature is 1090±10℃, and the holding time is as follows:

[0029] If 3mm > the wall thickness of the intermediate steel pipe is ≥ 2.5mm, the heat preservation time should be ≥ wall thickness × 3min.

[0030] If 2.5mm > the wall thickness of the intermediate steel pipe (≥ 2mm), the heat preservation time should be ≥ wall thickness × 3.5min.

[0031] If 2mm > the wall thickness of the intermediate steel pipe is ≥ 1.5mm, the heat preservation time should be ≥ wall thickness × 4min.

[0032] If 1.5mm > the wall thickness of the intermediate steel pipe is ≥ 1mm, the heat preservation time should be ≥ wall thickness × 5min.

[0033] If 1mm is greater than the wall thickness of the intermediate steel pipe, the heat preservation time is 6 minutes.

[0034] (v) Roll the steel pipe obtained in step (iv) into a head, cold draw the finished product, and cut the head;

[0035] When cold-drawing the finished product, a polycrystalline outer mold is selected as the cold-drawing die. The mold specification is the outer diameter specification of the finished product. The increase in outer diameter and wall thickness during cold drawing is 0.02-0.03mm. Therefore, the outer diameter deviation of the finished product is -0.02~+0.08mm, and the wall thickness deviation is -0.02~+0.08mm, which just meets the subsequent polishing dimensional requirements. After polishing, the outer diameter of the finished product is reduced by 0.02-0.03mm, and the wall thickness is reduced by 0.01-0.02mm. This can greatly improve the final dimensional accuracy and the pass rate of dimensional inspection.

[0036] (vi) The steel pipe obtained in step (v) is degreased;

[0037] The specific steps for degreasing the finished pipe are as follows: scraping oil with an oil scraper → soaking in an alkaline tank → soaking in a hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → inspection;

[0038] (vii) Perform finished product heat treatment on the steel pipe obtained in step (vi);

[0039] The heat treatment of the finished products is carried out in a bright furnace with a pure hydrogen atmosphere.

[0040] The heat treatment temperature for the finished product is controlled at 1070±10℃, and the holding time is as follows:

[0041] If 3mm > the wall thickness of the intermediate steel pipe is ≥ 2.5mm, the heat preservation time should be ≥ wall thickness × 3min.

[0042] If 2.5mm > the wall thickness of the intermediate steel pipe (≥ 2mm), the heat preservation time should be ≥ wall thickness × 3.5min.

[0043] If 2mm > the wall thickness of the intermediate steel pipe is ≥ 1.5mm, the heat preservation time should be ≥ wall thickness × 4min.

[0044] If 1.5mm > the wall thickness of the intermediate steel pipe is ≥ 1mm, the heat preservation time should be ≥ wall thickness × 5min.

[0045] If 1mm is greater than the wall thickness of the intermediate steel pipe, the heat preservation time is 6 minutes.

[0046] (viii) Straighten the steel pipe obtained in step (vii);

[0047] (ix) The steel pipes obtained in step (viii) are subjected to ultrasonic eddy current test, water pressure test, back straightening, fixed cutting, cleaning, PT test and external polishing of the ends one by one, and samples are taken for physical and chemical tests during pipe cutting.

[0048] (x) The steel pipes obtained in step (ix) are subjected to surface inspection, dimensional inspection, cleaning, marking and finishing processes, and finally packaged and put into storage.

[0049] The technical solution further defined in this invention is:

[0050] Furthermore, in the aforementioned manufacturing method of seamless tubes for small-diameter UNS S32750 umbilical cables, the intermediate degreasing process in step (iv) adopts the following steps: oil scraping with an oil scraper → degreasing in an alkaline tank → rinsing → soaking in a hot water tank → degreasing in an acid tank → rinsing → inspection. The composition of the solution in the alkaline tank is controlled by the following mass ratio: degreasing agent: water = 1:20; alkaline tank temperature: 50-60℃; alkaline tank soaking time: 30-40min. The composition of the solution in the acid tank is controlled by the following mass percentage: HF: 1%, HNO3: 10-15%, with the remainder being tap water. The sum of all the above components is 100%; acid tank temperature: 55-60℃; acid washing time: 40-60min.

[0051] The intermediate product degreasing process involves: scraping oil with an oil scraper → soaking in an alkaline tank → soaking in a hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → during inspection: the solution in the alkaline tank is prepared by a mass ratio of degreasing agent to water of 1:8; the alkaline tank temperature is 40-60℃; the alkaline tank soaking time is 15-25 minutes; the hot water tank temperature is 70-80℃; the hot water tank soaking time is 10-20 minutes; after removing the product from the hot water tank, the outer surface is wiped with a cotton cloth soaked in acetone, and the inner wall is cleaned with wool felt balls, repeated 2-4 times.

[0052] In the aforementioned method for manufacturing seamless tubing for small-diameter UNS S32750 umbilical cables, the straightening parameters are controlled as follows during the intermediate product straightening process in step (iv):

[0053] If the outer diameter of the intermediate steel pipe is >57mm, the straightening control speed should be ≤10m / min, the curvature after straightening should be ≤2mm / m, and the outer diameter deviation after straightening should be ±0.05%Dmm; (take the integer multiple of 0.01 larger than the value).

[0054] If the outer diameter of the intermediate product is 32mm or less and the outer diameter of the steel pipe is 57mm or less, the straightening control speed is ≤8m / min, the curvature after straightening is ≤1.5mm / m, and the outer diameter deviation after straightening is ±0.05%Dmm; (take the integer multiple of 0.01 larger than the value).

[0055] If the outer diameter of the intermediate steel pipe is <32mm, the straightening control speed should be ≤10m / min, the curvature after straightening should be ≤1.0mm / m, and the outer diameter deviation after straightening should be ±0.05%Dmm. (Take a multiple of 0.01 larger than the value)

[0056] Technical effects: By specifying the requirements for straightening speed, straightness, and the range of outer diameter deviation after straightening, this invention ensures the curvature while avoiding the risk of straightening damage and marks caused by iron rod straightening, thus guaranteeing straightening quality. Strictly specifying the range of outer diameter deviation after straightening can effectively avoid the risk of outer diameter deviation caused by straightening, thereby improving dimensional accuracy.

[0057] In the aforementioned manufacturing method of seamless tubes for small-diameter UNS S32750 umbilical cables, if the wall thickness of the intermediate product is ≥3mm during heat treatment, and the intermediate product is placed in a roller hearth furnace, pickling is performed after the intermediate product is cut and before the intermediate product is ground. The composition of the solution in the pickling tank is as follows by mass ratio: HF: 5-8%, HNO3: 10-15%, and the balance is tap water. The sum of the above components is 100%. The temperature of the pickling tank is controlled at 50-55℃, and the pickling time is 6-8h. After pickling for 6h, the pickling status of the inner and outer surfaces of the steel pipe is checked every 20 minutes. Pickling is stopped when there is no oxide scale on the inner and outer surfaces.

[0058] Technical benefits: This invention specifies a method for pickling intermediate products, including strict control of the acid tank ratio, temperature, and time to ensure pickling quality. S32750 intermediate products picked using this method have no oxide scale residue on either the inner or outer walls, and show no tendency for over-acidification. This significantly improves the inspection efficiency of endoscopes, reduces the polishing cost of internal oxide scale removal, and only requires rework of defective endoscopes' inner bores, thus improving production efficiency and shortening the overall production cycle of intermediate products.

[0059] In the aforementioned manufacturing method of seamless tube for small-diameter UNS S32750 umbilical cable, during the intermediate product grinding and inspection in step (iv), the grinding adopts a combination of local spot grinding and overall external polishing. External polishing is performed using a flap wheel, while local spot grinding is performed using a polishing machine equipped with a flower-shaped flap wheel.

[0060] Inspection is conducted visually and with each endoscope individually. Endoscopes that fail inspection are internally polished using an automatic internal polishing machine with a cross-shaped polishing head made of sandpaper. Before the finished product is cold-drawn, the intermediate product is inspected using visually, with each endoscope individually, and with ultrasonic testing of the intermediate product.

[0061] Technical effects: This invention specifies a method for intermediate product grinding and inspection. By ensuring the quality of intermediate product grinding, the quality of the next cold rolling process is controlled, preventing piercing defects and cold working defects from being properly ground and extending into the next cold rolling process. The inspection of intermediate products with an endoscope is to ensure the quality of the inner wall is controlled, reduce the frequency of internal damage alarms during ultrasonic testing of finished products, and improve the ultrasonic pass rate of the final product. The addition of an ultrasonic process to the intermediate product inspection before the finished product cold drawing is to ensure the quality of the finished product cold drawing and prevent defects missed by manual visual inspection and endoscopic inspection from flowing to the finished product stage.

[0062] In the aforementioned manufacturing method of seamless tube for small-diameter UNS S32750 umbilical cable, during the degreasing of the finished tube in step (vi), the solution in the alkali tank is in the following mass ratio: degreasing agent: water = 1:8. The alkali tank temperature is 40-60℃, and the alkali tank soaking time is 25-35 minutes. The hot water tank temperature is 70-80℃, and the hot water tank soaking time is 20-30 minutes. After the hot water tank is removed, the outer surface is wiped with a cotton cloth soaked in acetone, and the inner wall is cleaned with wool felt. This is repeated 3-5 times.

[0063] Technical advantages: This invention employs an oil scraper to scrape oil from both intermediate and finished product tubes before immersion in an alkaline tank. On one hand, this allows for the recovery and reuse of rolling oil after filtration, thus saving costs. On the other hand, oil removal after scraping reduces the proportion of degreasing agent in the alkaline tank and shortens the immersion time, significantly improving the efficiency of oil removal.

[0064] In the aforementioned method for manufacturing seamless tubes for small-diameter UNS S32750 umbilical cables, in step (viii), the straightening machine speed is controlled to be ≤10m / min during the straightening of the finished tube, the curvature after straightening is ≤1.0mm / m, and the outer diameter deviation after straightening is ±0.01mm.

[0065] Technical effects: This invention specifies the requirements for straightening speed, straightness, and the range of outer diameter deviation after straightening. The finished product straightening is specified to use a plastic roller straightening machine, and the straightening speed is specified to be ≤10m / min. This ensures the curvature while avoiding the risk of straightening damage and marks caused by iron rod straightening, thus guaranteeing the quality of the finished product straightening. Strictly specifying the range of outer diameter deviation after straightening can effectively avoid the risk of outer diameter deviation caused by straightening, thereby improving dimensional accuracy.

[0066] In the aforementioned manufacturing method of seamless tube for small-diameter UNS S32750 umbilical cable, the first ultrasonic pass rate in step (nine) is ≥92%, the first eddy current pass rate is 95%, and the end PT pass rate is 100%.

[0067] In the aforementioned method for manufacturing seamless tubes for small-diameter UNS S32750 umbilical cables, the surface roughness Ra of the inner and outer walls in step (x) is inspected to be ≤1.6μm.

[0068] In the aforementioned manufacturing method of seamless tube for small-diameter UNS S32750 umbilical cable, the finished tube is tested at room temperature with the following tensile test results: yield strength ≥710MPa, tensile strength ≥950MPa, and elongation after fracture ≥35%; the finished tube is tested with the following hardness: hardness 270-290HV.

[0069] The beneficial effects of this invention are:

[0070] This invention employs multi-pass cold rolling, ensuring the cold rolling quality of the inner and outer surfaces of the steel pipe by strictly controlling the mill model, feed rate, rolling speed, and deformation. The control of the mill model, cold rolling deformation, rolling speed, and feed rate is as follows:

[0071] The rolling mill model is LG60, the cold rolling deformation is controlled at 55%-65%, the rolling speed is ≤60 times / min, and the feed rate is ≤3mm / time;

[0072] The rolling mill model is LG40, the cold rolling deformation is controlled at 55%-65%, the rolling speed is ≤100 times / min, and the feed rate is ≤2.5mm / time;

[0073] The rolling mill model is LG30, the cold rolling deformation is controlled at 50%-60%, the rolling speed is ≤100 times / min, and the feed rate is ≤2mm / time;

[0074] The rolling mill model is LD30, the cold rolling deformation is controlled at 35%-50%, the rolling speed is ≤60 times / min, and the feed rate is ≤2mm / time;

[0075] While ensuring surface quality, by controlling the Q value to be ≥1, the deformation is made more uniform, thereby improving dimensional accuracy;

[0076] The finished product cold drawing uses a polycrystalline die. The polycrystalline die material has good mechanical properties and stability, can withstand large mechanical loads, and has a high surface finish on both the inner and outer surfaces. This results in a tube with good inner and outer surface quality, low roughness, and is less prone to burring. By studying the changes in outer diameter and wall thickness after cold drawing, adjusting the outer diameter and wall thickness of the previous cold rolling stage, and using a suitable polycrystalline die, high dimensional accuracy can be achieved. This invention uses finished product cold drawing instead of cold rolling. While the dimensional accuracy of finished product cold drawing is not as good as cold rolling, its efficiency is higher. Furthermore, due to the smaller deformation during cold drawing, it is easier to achieve the desired results. Each grinding process eliminates defects completely, eliminating the risk of cold-rolled defects and the risk of small cracks growing larger as cold rolling progresses. As long as the quality of the previous grinding process and the inner and outer surface quality of the finished cold-drawn tube are well controlled, the quality of the finished tube can be well controlled. This combined rolling and drawing process has been maturely applied to the production of small-diameter duplex steel heat exchange tubes, and the ultrasonic qualification rate is relatively stable. Adding an ultrasonic test after the grinding process before cold drawing can more effectively control the quality of the finished product. Of course, strengthening the quality control of grinding and endoscopic inspection can also achieve the same control effect. This invention effectively improves the efficiency of cold drawing.

[0077] This invention specifies a method for degreasing intermediate products, including pre-scraping with an oil scraper followed by degreasing, strictly controlling the ratio of solutions in the alkali tank and acid tank, as well as the temperature and time, to ensure degreasing quality and avoid the risk of nitriding during heat treatment. It also specifies a method for degreasing the finished product, including pre-scraping with an oil scraper followed by degreasing in an alkali tank, immersion in a hot water tank, wiping the outer surface with acetone, and cleaning the inner wall with acetone-soaked cloth strips. Strict control of the alkali tank ratio, temperature, time, and cleaning methods for both the inner and outer walls ensures the quality of degreasing in the finished product tubes and guarantees that there is no risk of nitriding during the bright heat treatment of the finished product.

[0078] This invention specifies that if the intermediate product wall thickness is ≥3mm, the solution heat treatment of the intermediate product shall be carried out in a roller hearth furnace with a slightly oxidizing atmosphere and a heat treatment temperature of 1090±10℃. This eliminates cold rolling work hardening, ensures good plasticity of the seamless tube, and facilitates subsequent cold rolling forming. The holding time of the intermediate product is determined according to the wall thickness (if 6mm or ≥ steel pipe intermediate product wall thickness ≥ 3mm, the holding time ≥ wall thickness × 2.5min; if 13mm or ≥ steel pipe intermediate product wall thickness > 6mm). For intermediate products with a wall thickness of 3mm or less, the holding time should be ≥ wall thickness × 2min. Generally, the larger of the two values ​​should be used. If the wall thickness of the intermediate product is < 3mm, the solution heat treatment should be performed using a bright finish, with a pure hydrogen atmosphere in the furnace and a heat treatment temperature of 1090±10℃. This eliminates cold rolling work hardening, ensures good plasticity of the seamless pipe, and facilitates subsequent cold rolling forming. The holding time for the intermediate product depends on the wall thickness (if 3mm > intermediate product wall thickness ≥ 2.5mm, holding time ≥ wall thickness × 3min; if 2.5mm > intermediate product wall thickness ≥ 2mm, holding time ≥ wall thickness × 3.5min; if 2mm > intermediate product wall thickness ≥ 1.5mm, holding time ≥ wall thickness × 4min; if 1.5mm > intermediate product wall thickness ≥ 1mm, holding time ≥ wall thickness × 5min; if 1mm > intermediate product wall thickness, holding time is 6min). Generally, the larger of the two values ​​should be used. For integer values, a slightly longer holding time is required, resulting in a more uniform and porous oxide scale that is easier to remove with acid washing. The solution heat treatment of the finished product is carried out in a bright furnace with a pure hydrogen atmosphere at a heat treatment temperature of 1090±10℃. The holding time of the finished product is determined according to the wall thickness (if 3mm > steel pipe intermediate product wall thickness ≥ 2.5mm, holding time ≥ wall thickness × 3min; if 2.5mm > steel pipe intermediate product wall thickness ≥ 2mm, holding time ≥ wall thickness × 3.5min; if 2mm > steel pipe intermediate product wall thickness ≥ 1.5mm, holding time ≥ wall thickness × 4min; if 1.5mm > steel pipe intermediate product wall thickness ≥ 1mm, holding time ≥ wall thickness × 5min; if 1mm > steel pipe intermediate product wall thickness, holding time is 6min). The purpose is to obtain good microstructure and comprehensive mechanical properties while ensuring the surface color of the heat exchange tube is bright and the overall color consistency is good.

[0079] This invention specifies methods for grinding hot-pierced billets and intermediate steel pipes. The PT (Pre-Test) of hot-pierced billets is to ensure that there are no cracks left on the outer surface. The endoscope is used for each hot-pierced billet to more accurately and efficiently treat internal wall defects and prevent internal wall defects from flowing to the next cold rolling process and causing defect extension. The endoscope is used for each intermediate product during grinding to ensure the quality of the inner wall of the finished cold-rolled product, reduce the risk of endoscope failure due to ultrasonic internal damage and internal wall defects, and thus improve the final ultrasonic pass rate, surface inspection pass rate and final yield.

[0080] This invention solves the problems of low first-pass yield, low yield, low dimensional accuracy, and poor internal and external surface quality by strictly optimizing the seamless tube process for small-diameter UNS S32750 umbilical cables. The products produced by this method have a high first-pass yield, high yield, high dimensional accuracy, good internal and external surface quality, stable mechanical properties, and strong practicality, which is conducive to mass production.

[0081] The seamless tube for small-diameter UNS S32750 umbilical cable prepared by the method of the present invention has a first ultrasonic pass rate of ≥93%, a first eddy current pass rate of ≥96%, a first surface inspection (visual inspection + dimensional inspection) pass rate of ≥96%, and a comprehensive first inspection pass rate (ultrasonic pass rate × eddy current pass rate × surface inspection pass rate) of ≥86%, with a high overall pass rate.

[0082] The yield (round steel → finished tube) of small-diameter UNS S32750 umbilical cable seamless tube prepared by the method of this invention is ≥72%; the prepared UNS S32750 umbilical cable seamless tube can meet the following dimensional accuracy: outer diameter ±0.10mm, wall thickness ±0.10mm; the prepared UNS S32750 umbilical cable seamless tube has smooth inner and outer surfaces and consistent color, and inner and outer wall roughness Ra≤1.6; its finished tube has a room temperature tensile test: yield strength ≥710MPa, tensile strength ≥950MPa, elongation after fracture ≥35%; the hardness test of the manufactured finished tube is 270-290HV. Attached Figure Description

[0083] Figure 1 The image shows the metallographic structure of a seamless tube manufactured using the manufacturing method of small-diameter UNS S32750 seamless tube for umbilical cables in an embodiment of the present invention.

[0084] Figure 2 This image shows non-metallic inclusions in a seamless tube manufactured using the manufacturing method of small-diameter UNS S32750 seamless tube for umbilical cables, as described in an embodiment of the present invention.

[0085] Figure 3This is a test diagram of a flattening test performed on a seamless tube manufactured using the manufacturing method of small-diameter UNS S32750 seamless tube for umbilical cables according to an embodiment of the present invention.

[0086] Figure 4 for Figure 3 Top view;

[0087] Figure 5 This is a test diagram of the flaring test performed on a seamless tube manufactured using the manufacturing method of small-diameter UNS S32750 seamless tube for umbilical cables according to an embodiment of the present invention.

[0088] Figure 6 for Figure 5 Top view. Detailed Implementation

[0089] The present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0090] Example 1

[0091] This embodiment provides a method for manufacturing a seamless tube for small-diameter UNS S32750 umbilical cables, with finished product specifications of φ14.7×1×12500mm. The technical requirements must meet the ISO-13628-5:2009 standard and the technical agreement attached to the contract. The method specifically includes the following steps:

[0092] (a) After peeling, cutting, centering, and surface grinding of UNS S32750φ75 round steel, hot piercing is performed. The piercing specification is φ80×7mm, the piercing temperature is 1170℃, and the holding time is 20min. After piercing, the tube blank is water-cooled. After cooling, the tube blank is inspected for dimensions and inner and outer surfaces.

[0093] (ii) Pickling the UNS S32750φ80×7 hot-pierced blank. The pickling solution is HF: 1.5-2.5% by mass, HNO3 concentration: 8-12%, and the balance is tap water. The sum of the above components is 100%. The temperature of the pickling tank is 45-55℃, the pickling time is 5-6 hours, and the pickling is stopped when there is no oxide scale on the inner and outer surfaces.

[0094] (III) The UNS S32750 φ80×7 tube blanks after pickling in step (II) are subjected to incoming material inspection and internal and external surface grinding, including initial inspection + grinding + re-inspection of the tube blanks. During the re-inspection, each endoscope is used and a PT is performed on a random sample. Specifically, the defects of the tube blanks and their grinding methods are preliminarily identified. For tube blanks with external surface heat perforation defects, spot grinding + external polishing is performed. For some tube blanks with internal hole defects, internal polishing is performed. After the tube blanks are ground, they are re-inspected. During the re-inspection, a PT is performed on a random sample. Only those that pass the re-inspection can be transferred. Unqualified products are ground a second time.

[0095] (iv) The tube blank obtained in step (iii) is subjected to multiple passes of intermediate cold rolling. After each pass of cold rolling, intermediate degreasing, intermediate heat treatment, intermediate straightening, intermediate tube cutting, intermediate pickling (if the intermediate heat treatment is bright heat treatment, the pickling process is not required in this pass), intermediate grinding and intermediate inspection are required. The specific cold rolling parameters are shown in Table 1.

[0096] For intermediate cold-rolled products, the Q value (relative wall reduction rate) should be ≥1, and the deviations in outer diameter and wall thickness after rolling should be controlled as follows:

[0097] The rolling mill model is LG60, with the outer diameter deviation controlled within ±0.5%Dmm and the wall thickness deviation controlled within ±5%Smm;

[0098] The rolling mill model is LG40, with the outer diameter deviation controlled within ±0.4%Dmm and the wall thickness deviation controlled within ±4%Smm;

[0099] The rolling mill model is LG30, with the outer diameter deviation controlled within ±0.3%Dmm and the wall thickness deviation controlled within ±3%Smm;

[0100] The rolling mill model is LD30, with the outer diameter deviation controlled within ±0.05mm and the wall thickness deviation controlled within ±0.05mm;

[0101] The deviations of the outer diameter and wall thickness are taken as integer multiples of 0.05, where D represents the outer diameter and S represents the wall thickness;

[0102] For intermediate products with a wall thickness ≥3mm, the specific degreasing process is as follows: scraping oil with an oil scraper → degreasing in an alkaline tank → rinsing → soaking in a hot water tank → degreasing in an acid tank → rinsing → inspection;

[0103] If the wall thickness of the intermediate product is ≥3mm, the heat treatment of the intermediate product shall be carried out in a roller hearth furnace with a slightly oxidizing gas atmosphere. The heat treatment temperature shall be 1090±10℃, and the holding time shall be as follows:

[0104] If the wall thickness of the intermediate steel pipe is ≥3 mm, the heat preservation time is ≥2.5 min (generally, take the larger integer value).

[0105] If 13mm ≥ the wall thickness of the intermediate steel pipe > 6mm, the heat preservation time ≥ the wall thickness × 2min (generally take the larger integer value).

[0106] If the wall thickness of the intermediate product is <3mm, the oil removal process of the intermediate product is as follows: oil scraping machine → immersion in alkali tank → immersion in hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → inspection.

[0107] For intermediate products with a wall thickness <3mm, heat treatment is carried out in a bright furnace with a pure hydrogen atmosphere. The heat treatment temperature is 1090±10℃, and the holding time is as follows:

[0108] If 3mm > the wall thickness of the intermediate steel pipe is ≥ 2.5mm, the heat preservation time is ≥ wall thickness × 3min (generally, take the larger integer value).

[0109] If 2.5mm > the wall thickness of the intermediate steel pipe is ≥ 2mm, the heat preservation time is ≥ wall thickness × 3.5min (generally, take the larger integer value).

[0110] If 2mm > the wall thickness of the intermediate steel pipe is ≥ 1.5mm, the heat preservation time is ≥ wall thickness × 4min (generally, take the larger integer value).

[0111] If 1.5mm > the wall thickness of the intermediate steel pipe is ≥ 1mm, the heat preservation time is ≥ the wall thickness × 5min (generally, take the larger integer value).

[0112] If 1mm is greater than the wall thickness of the intermediate steel pipe, the heat preservation time is 6 minutes (generally, the larger integer value is taken).

[0113] (v) Roll the steel pipe obtained in step (iv) into a head, cold draw the finished product, and cut the head;

[0114] When cold-drawing the finished product, a polycrystalline outer mold is selected as the cold-drawing die. The mold specification is the outer diameter specification of the finished product. The increase in outer diameter and wall thickness during cold drawing is 0.02-0.03mm. Therefore, the outer diameter deviation of the finished product is controlled within -0.02~+0.08mm, and the wall thickness deviation is controlled within -0.02~+0.08mm, which just meets the subsequent polishing dimensional requirements. After polishing, the outer diameter of the finished product is reduced by 0.02-0.03mm, and the wall thickness is reduced by 0.01-0.02mm. This can greatly improve the final dimensional accuracy and the pass rate of dimensional inspection.

[0115] (vi) The steel pipe obtained in step (v) is degreased;

[0116] The specific steps for degreasing the finished pipe are as follows: scraping oil with an oil scraper → soaking in an alkaline tank → soaking in a hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → inspection;

[0117] (vii) Perform finished product heat treatment on the steel pipe obtained in step (vi);

[0118] The heat treatment of the finished products is carried out in a bright furnace with a pure hydrogen atmosphere.

[0119] The heat treatment temperature for the finished product is controlled at 1070±10℃, and the holding time is as follows:

[0120] If 3mm > the wall thickness of the intermediate steel pipe is ≥ 2.5mm, the heat preservation time is ≥ wall thickness × 3min (generally, take the larger integer value).

[0121] If 2.5mm > the wall thickness of the intermediate steel pipe is ≥ 2mm, the heat preservation time is ≥ wall thickness × 3.5min (generally, take the larger integer value).

[0122] If 2mm > the wall thickness of the intermediate steel pipe is ≥ 1.5mm, the heat preservation time is ≥ wall thickness × 4min (generally, take the larger integer value).

[0123] If 1.5mm > the wall thickness of the intermediate steel pipe is ≥ 1mm, the heat preservation time is ≥ the wall thickness × 5min (generally, take the larger integer value).

[0124] If 1mm is greater than the wall thickness of the intermediate steel pipe, the heat preservation time is 6 minutes (generally, the larger integer value is taken).

[0125] (viii) Straighten the steel pipe obtained in step (vii);

[0126] (ix) The steel pipes obtained in step (viii) are subjected to ultrasonic eddy current test, water pressure test, back straightening, fixed cutting, cleaning, PT test and external polishing of the ends one by one, and samples are taken for physical and chemical tests during pipe cutting.

[0127] (x) The steel pipes obtained in step (ix) are subjected to surface inspection, dimensional inspection, cleaning, marking and finishing processes, and finally packaged and put into storage.

[0128] In this embodiment, the cold rolling process of UNS S32750 seamless tube for umbilical cable strictly controls the cold rolling deformation of intermediate products, selects a reasonable rolling speed and a relatively small feed amount to ensure the quality of its inner and outer surfaces, and controls the Q value to ensure the uniformity of the structure in the wall thickness direction, thereby improving dimensional accuracy and inner wall quality. Specific cold rolling parameters are shown in Table 1 below, and the technical requirements for dimensional accuracy and actual dimensions are shown in Table 2.

[0129] Table 1. Cold Rolling Parameters of UNS S32750

[0130]

[0131] Table 2 UNS S32750 Technical Requirements: Dimensional Accuracy and Actual Measured Dimensions

[0132]

[0133] As can be seen from Table 2, the dimensional accuracy of intermediate and finished tubes in each process meets the internal control requirements, and the dimensional accuracy of finished tubes is higher than the requirements of ISO-13628-5:2009 standard.

[0134] The specific degreasing process for the intermediate seamless tubes (wall thickness S≥3) for UNS S32750 umbilical cables is as follows: oil scraping with an oil scraper → degreasing in an alkaline tank → rinsing → soaking in a hot water tank → degreasing in an acid tank → rinsing → inspection. The main control requirements for degreasing the intermediate tubes are shown in Table 3. The specific steps for degreasing the intermediate tubes (wall thickness S<3) and the finished tubes are as follows: oil scraping with an oil scraper → soaking in an alkaline tank → soaking in a hot water tank → wiping the outer surface → applying wool felt balls to the inner wall → inspection. The main control requirements for degreasing are shown in Table 4. The tubes obtained by degreasing according to the above methods have clean inner and outer surfaces without oil stains, and there is no risk of nitriding during heat treatment.

[0135] Table 3. Main Control Requirements for Degreasing Process of UNS S32750 Intermediate Product (Wall Thickness S≥3)

[0136]

[0137] Table 4. Main Control Requirements for Degreasing Process of Intermediate (Wall Thickness S < 3) and Finished Products in UNS S32750

[0138]

[0139] Table 4 above shows the main control requirements for the degreasing process of UNS S32750 seamless tube intermediates (wall thickness S < 3) and finished tubes for umbilical cables. After degreasing, heat treatment can only be carried out after the technicians confirm the degreasing quality of the inner and outer surfaces. The outer surface should not turn black when wiped with a white cloth strip. The inner wall should be inspected by endoscopy to confirm that there is no oil stain, oil spot or oil film.

[0140] In this embodiment, the heat treatment of the intermediate seamless tubes (wall thickness S≥3) for UNS S32750 umbilical cables was carried out in a roller hearth furnace with a slightly oxidizing atmosphere; the heat treatment of the intermediate tubes (wall thickness S<3) and the finished tubes was carried out in a bright furnace with a pure hydrogen atmosphere. The heat treatment regime is shown in Table 5 below.

[0141] Table 5 Heat Treatment Regime for UNS S32750

[0142]

[0143] As shown in Table 5, the solution heat treatment of intermediate products (wall thickness S≥3) was carried out in a roller hearth furnace with a slightly oxidizing atmosphere. The furnace had six temperature zones: zones T01-T03 were heating zones, and zones T04-T06 were holding zones. The heat treatment temperature was 1090℃, the holding time was 10 min, and the cooling method was water cooling. The heat treatment of intermediate products (wall thickness S<3) and finished products was a bright heat treatment, with a pure hydrogen atmosphere. The furnace had five temperature zones: zones T01-T02 were heating zones, and zones T03-T05 were holding zones. The heat treatment temperature of intermediate products (wall thickness S<3) was 1090℃, and the holding times were 8 min, 6 min, and 5 min, respectively. The cooling method was water jacket cooling. The heat treatment temperature of finished products was 1070℃, the holding time was 5 min, and the cooling method was water jacket cooling.

[0144] Table 6 shows the straightening parameters for intermediate and finished products of the UNS S32750 seamless tube for umbilical cables in this embodiment. By specifying the straightening machine model, straightening speed, straightness, and the range of outer diameter deviation after straightening, especially for finished product straightening, a plastic roller straightening machine is specified. The specified straightening speed ensures the correct curvature while avoiding the risks of straightening damage and marks caused by iron rollers, thus guaranteeing the quality of the straightened product. Strictly specifying the straightening process, especially the range of outer diameter deviation after finished product straightening, effectively avoids the risk of outer diameter deviation caused by straightening, thereby improving dimensional accuracy.

[0145] Table 6 UNS S32750 Straightening Parameters

[0146]

[0147] The requirements for cutting intermediate and finished seamless tubes for UNS S32750 umbilical cables in this embodiment are shown in Table 7. By strictly controlling the end-cutting amount (end-cutting amount of grinding wheel ≤10mm, end-cutting amount of tube cutting machine ≤5mm; if tube opening is encountered during cutting, the technician shall be notified) and strictly adhering to the center-cutting method, the center position must be manually measured and marked before cutting, and visual inspection is not allowed. This can reduce the risk of the intermediate and finished tubes being under-length, and improve the final product inspection pass rate and final yield.

[0148] Table 7 UNS S32750 Pipe Cutting Requirements

[0149]

[0150] The main control requirements for pickling the seamless tube intermediates for UNS S32750 umbilical cables in this embodiment are shown in Table 8 below. These include strict control of the acid tank ratio, temperature, and time to ensure pickling quality. Using this method, the S32750 intermediate tubes produced have no oxide scale residue on either the inner or outer walls, and there is no tendency for over-acidification. This significantly improves the inspection efficiency of endoscopes, reduces the polishing cost of internal oxide scale removal, and only requires internal bore repair for defective endoscopes, thus improving production efficiency and shortening the overall production cycle of the intermediate products.

[0151] Table 8 Main Control Requirements for the Pickling Process of UNS S32750 Intermediate Product

[0152]

[0153] The inspection and grinding requirements for seamless tube piercing blanks and intermediate tubes for UNS S32750 umbilical cables in this embodiment are shown in Table 9 below. The PT (Pre-Test) re-inspection of hot-pierced blanks is to ensure the absence of residual cracks on the outer surface. The endoscopy of each hot-pierced blank is for more precise and efficient treatment of internal wall defects, preventing defects from flowing to the next cold rolling process and causing defect extension. The endoscopy of each intermediate tube during grinding ensures the quality of the inner wall of the finished cold-rolled product, reducing the risk of ultrasonic internal damage and internal wall defects leading to endoscopic failure, thereby improving the final ultrasonic pass rate, surface inspection pass rate, and final yield. The addition of an ultrasonic process to the intermediate product inspection before cold drawing ensures the quality of the finished cold-drawn product and prevents defects missed by manual visual inspection and endoscopic inspection from flowing to the finished product stage.

[0154] Table 9 UNS S32750 Grinding Operation Requirements

[0155]

[0156] In Table 9 above, during the grinding and inspection of intermediate products, the grinding method is a combination of local spot grinding and overall external polishing. External polishing is performed using a flap wheel, while local spot grinding is performed using a polishing machine equipped with a flower-shaped flap wheel. Inspection is performed by visual inspection and individual endoscopes. Endoscopes that fail to meet the standards are internally polished. The internal polishing is performed by an automatic internal polishing machine with a cross-shaped polishing head made of sandpaper. Before the finished product is cold-drawn, the intermediate product inspection is performed by visual inspection, individual endoscopes, and ultrasonic testing of the intermediate product.

[0157] Table 10 shows the ultrasonic, eddy current, hydrostatic, visual, and dimensional inspection results of the finished seamless tube for umbilical cables (UNS S32750) in this embodiment. Ultrasonic testing: depth 0.10±0.02mm, length 12.5mm, U-groove; two circumferential tests in opposite directions according to ASME SE213; ultrasonic water quality requirement: Class B water. Eddy current testing: penetration hole 0.5mm; according to ASME SE-309 standard. Hydrostatic requirements: according to GB / T 241, each seamless tube should undergo a hydrostatic test; hydrostatic water quality requirement: Class B water; hydrostatic test pressure 46~58MPa, holding time ≥10s. Surface visual requirements: The outer surface of the seamless tube shall be free from defects that affect its use, such as cracks, folds, delamination, and scars. The inner surface shall be inspected indirectly with an endoscope, and the outer surface shall be inspected directly with a visual inspection. The roughness of the inner and outer surfaces shall be ≤1.6μm. The outer diameter requirement is 14.7±0.13mm, and the wall thickness requirement is 1±0.1mm. The out-of-roundness shall be ≤0.16mm, and the straightness shall be ≤1mm / m.

[0158] Table 10. Ultrasonic, eddy current, hydrostatic, visual, and dimensional inspection results of UNS S32750 finished pipes.

[0159]

[0160] As shown in Table 10, the seamless tubes for S32750 umbilical cables produced by this production method have an ultrasonic qualification rate of 94.64%, an eddy current qualification rate of 97.36%, a hydrostatic qualification rate, and a dimensional inspection qualification rate of 100.00%. The dimensional accuracy is far higher than the dimensional accuracy specified in ISO-13628-5:2009 standard. The visual inspection qualification rate is as high as 96.90%, and the first-pass inspection qualification rate is as high as 89.29%. The inner and outer surface roughness Ra is measured to be 0.88-1.08μm, meeting the requirement of roughness Ra≤1.6μm.

[0161] Table 11 shows the yield statistics for seamless tubes for umbilical cables using UNS S32750 in this embodiment. A total of 1.485 tons of φ75mm material were issued, and 250 pieces of φ14.7×1×12500mm finished products were put into storage, weighing 1.105 tons, with a yield rate as high as 74.41%.

[0162] Table 11. UNS S32750 Yield

[0163]

[0164] Chemical composition analysis was performed on samples of finished straight pipes in the delivery condition in accordance with the requirements of ASME SA751. The results are shown in Table 12, which shows that the chemical composition meets the technical requirements.

[0165] Table 12 Chemical Composition Analysis of UNS S32750 Finished Pipe

[0166]

[0167] Metallographic structure of the finished seamless tube for umbilical cables in this embodiment:

[0168] (a) α phase

[0169] The α phase was evaluated according to ASTM E45 requirements, and the metallographic structure was as follows: Figure 1 As shown, the α phase area content is 45%~60%.

[0170] (b) Non-metallic inclusions

[0171] Non-metallic inclusions in round tube blanks should be rated according to ASTM E45. Photos of non-metallic inclusions are shown below. Figure 2 As shown, the levels of various non-metallic inclusions should conform to the provisions of Table 13.

[0172] Table 13 UNS S32750 Requirements for Non-metallic Inclusions in Finished Pipes

[0173]

[0174] (c) Low-magnification tissue

[0175] The acid-etched test piece of the steel pipe cross-section must be free of visible white spots, inclusions, subcutaneous bubbles, peeling, and delamination. Inspection result: Qualified.

[0176] Mechanical properties of the finished seamless tube for umbilical cables (UNS S32750) in this embodiment:

[0177] The room temperature tensile test of the steel pipe was carried out in accordance with the specifications of ASTM A1016 / A1016M, ASTM E8 / E8M and ASTM A370. The properties are shown in Table 14 (one batch number is selected). It can be seen that its mechanical properties meet the technical requirements.

[0178] Table 14 Mechanical Properties of UNS S32750 Finished Pipe

[0179]

[0180] The following are the process performance characteristics of the finished seamless tube for umbilical cables in this embodiment:

[0181] (a) Flattening test

[0182] Flattening was performed according to ASME SA-999 / SA-999M. A 65mm long section of pipe was used for the flattening test. After the flattening test, the steel pipe should not show any cracks or fissures. Test results: Pass, no cracks. Macroscopic photograph of the flattened test specimen is shown below. Figure 3 and 4 As shown.

[0183] (b) Flaring test

[0184] The flaring test shall be conducted according to ASME SA-370. A conical mandrel with a 60° apex angle shall be used for the flaring test, and the flaring ratio of the outer diameter of the steel pipe shall be 15% of the outer diameter. After the test, no cracks or fissures shall appear on the surface of the specimen. Test result: Pass. Macroscopic photograph of the flared test specimen is shown below. Figure 5 and 6 As shown.

[0185] Mechanical properties of the finished seamless tube for umbilical cables (UNS S32750) in this embodiment:

[0186] Finished pipes should be tested according to ASTM G48-03, Method A, at 50°C for 24 hours, using high-precision detection instruments, with a maximum weight loss of 1.0 g / m2, and no visible pitting corrosion at 20x magnification.

[0187] The test results are shown in Table 15. The test result is: qualified.

[0188] Table 15 Results of pitting corrosion test on finished UNS S32750 pipe

[0189]

[0190] This invention solves the problems of low first-pass yield, low yield, low dimensional accuracy, and poor internal and external surface quality by strictly optimizing the seamless tube process for UNS S32750 umbilical cables. As shown in Tables 10-13, the products produced by this method have a high first-pass yield, high yield, high dimensional accuracy, good internal and external surface quality, stable physical and chemical properties, and strong practicality, which is conducive to mass production.

[0191] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method of manufacturing a seamless pipe for small-bore UNS S32750 umbilical characterized by, Specifically comprising the following steps: (1) The UNS S32750 round steel is peeled, cut, centered, and surface ground after hot piercing, the piercing temperature is 1170℃, the holding time is 20 min, the pierced pipe blank is water cooled, and the cooled pipe blank is subjected to size and inner and outer surface inspection; (2) The UNS S32750 hot piercing blank is pickled, the acid pickling solution contains HF: 1.5-2.5%, HNO3: 8-12%, and the balance is tap water, the total of the above components is 100%, the acid tank temperature is 45-55℃, the pickling time is 5-6h, and the pickling is stopped when the inner and outer surfaces are free of oxide skin; (3) The pipe blank after pickling in step (2) is subjected to incoming inspection and inner and outer surface grinding, specifically: the pipe blank is subjected to initial inspection + grinding + reinspection, the reinspection is performed by endoscope, and PT is performed for the sampled pipe; (4) The pipe blank obtained in step (3) is subjected to multi-pass intermediate product cold rolling, and after each pass, the intermediate product is subjected to intermediate product oil removal, intermediate product heat treatment, intermediate product straightening, intermediate product pipe cutting, intermediate product grinding, and intermediate product inspection, wherein: During the intermediate product cold rolling, the rolling mill type, cold rolling deformation, rolling speed, and feed amount are controlled as follows: The rolling mill type is LG60, the cold rolling deformation is controlled to be 55%-65%, the rolling speed is ≤60 times / min, and the feed amount is ≤3mm / turn; The rolling mill type is LG40, the cold rolling deformation is controlled to be 55%-65%, the rolling speed is ≤100 times / min, and the feed amount is ≤2.5mm / turn; The rolling mill type is LG30, the cold rolling deformation is controlled to be 50%-60%, the rolling speed is ≤100 times / min, and the feed amount is ≤2mm / turn; The rolling mill type is LD30, the cold rolling deformation is controlled to be 35%-50%, the rolling speed is ≤60 times / min, and the feed amount is ≤2mm / turn; The Q value of the intermediate product cold rolling is controlled to be ≥1, and the outer diameter deviation and wall thickness deviation after rolling are controlled as follows: The rolling mill type is LG60, the outer diameter deviation is controlled to be ±0.5%Dmm, and the wall thickness deviation is controlled to be ±5%Smm; The rolling mill type is LG40, the outer diameter deviation is controlled to be ±0.4%Dmm, and the wall thickness deviation is controlled to be ±4%Smm; The rolling mill type is LG30, the outer diameter deviation is controlled to be ±0.3%Dmm, and the wall thickness deviation is controlled to be ±3%Smm; The rolling mill type is LD30, the cold rolling outer diameter deviation is controlled to be ±0.05mm, and the wall thickness deviation is controlled to be ±0.05mm; The intermediate product oil removal process is as follows: If the intermediate product wall thickness is ≥3mm, the intermediate product oil removal process adopts oil scraping by an oil scraper → alkali tank oil removal → rinsing → hot water tank soaking → acid tank oil removal → rinsing → inspection; If the intermediate product wall thickness is <3mm, the intermediate product oil removal process adopts oil scraping by an oil scraper → alkali tank soaking → hot water tank soaking → outer surface wiping → inner wall wool ball beating → inspection; The intermediate product heat treatment is as follows: If the intermediate product wall thickness is ≥3mm, it is placed in a roller hearth furnace, the furnace atmosphere is slightly oxidizing gas, the heat treatment temperature is 1090±10℃, and the holding time is as follows: If 6mm≥steel pipe intermediate product wall thickness≥3mm, the holding time is ≥wall thickness×2.5min, If 13 mm ≥ the wall thickness of the steel pipe intermediate product > 6 mm, the holding time ≥ the wall thickness × 2 min, If the wall thickness of the intermediate product < 3 mm, the heat treatment is carried out in a bright furnace, the furnace atmosphere is pure hydrogen, the heat treatment temperature is 1090 ± 10 ℃, and the holding time is as follows: If 3 mm > the wall thickness of the steel pipe intermediate product ≥ 2.5 mm, the holding time ≥ the wall thickness × 3 min, If 2.5 mm > the wall thickness of the steel pipe intermediate product ≥ 2 mm, the holding time ≥ the wall thickness × 3.5 min, If 2 mm > the wall thickness of the steel pipe intermediate product ≥ 1.5 mm, the holding time ≥ the wall thickness × 4 min, If 1.5 mm > the wall thickness of the steel pipe intermediate product ≥ 1 mm, the holding time ≥ the wall thickness × 5 min, If 1 mm > the wall thickness of the steel pipe intermediate product, the holding time is 6 min; When the intermediate product is straightened, the straightening parameter control is as follows: If the outer diameter of the steel pipe intermediate product > 57 mm, the straightening control speed ≤ 10 m / min, the bending degree after straightening ≤ 2 mm / m, and the outer diameter deviation after straightening ± 0.05 %D mm; If the outer diameter of the steel pipe 32 mm ≤ the intermediate product outer diameter ≤ 57 mm, the straightening control speed ≤ 8 m / min, the bending degree after straightening ≤ 1.5 mm / m, and the outer diameter deviation after straightening ± 0.05 %D mm; If the outer diameter of the steel pipe intermediate product < 32 mm, the straightening control speed ≤ 10 m / min, the bending degree after straightening ≤ 1.0 mm / m, and the outer diameter deviation after straightening ± 0.05 %D mm; (Five) The steel pipe obtained in step (four) is subjected to head rolling, finished product cold drawing, and head cutting; When the finished product is cold drawn, the cold drawing die is selected to be a polycrystal outer die, the die specification is the finished product outer diameter specification, the outer diameter increment and the wall thickness increment during the finished product cold drawing are both 0.02-0.03 mm, so the finished product cold drawing outer diameter deviation is -0.02~+0.08 mm, and the wall thickness deviation is -0.02~+0.08 mm; (Six) The steel pipe obtained in step (five) is subjected to finished product oil removal; The finished product pipe oil removal step is specifically: oil scraping by using an oil scraping machine → alkali tank soaking → hot water tank soaking → outer surface wiping → inner wall wool felt ball beating → inspection; (Seven) The steel pipe obtained in step (six) is subjected to finished product heat treatment; The finished product heat treatment is carried out in a bright furnace, and the furnace atmosphere is pure hydrogen; The finished product heat treatment control heat treatment temperature is 1070 ± 10 ℃, and the holding time is as follows: If 3 mm > the wall thickness of the finished product pipe ≥ 2.5 mm, the holding time ≥ the wall thickness × 3 min, If 2.5 mm > the wall thickness of the finished product pipe ≥ 2 mm, the holding time ≥ the wall thickness × 3.5 min, If 2 mm > the wall thickness of the finished product pipe ≥ 1.5 mm, the holding time ≥ the wall thickness × 4 min, If 1.5 mm > the wall thickness of the finished product pipe ≥ 1 mm, the holding time ≥ the wall thickness × 5 min, If 1 mm > the wall thickness of the finished product pipe, the holding time is 6 min; (Eight) The steel pipe obtained in step (seven) is subjected to finished product straightening; (Nine) The steel pipe obtained in step (eight) is subjected to finished product ultrasonic eddy current, water pressure, back straightening, fixed cutting, cleaning, end branch-by-branch PT, and outer throwing, and sampling is carried out for physical and chemical tests during pipe cutting; (Ten) The steel pipe obtained in step (nine) is subjected to finished product surface inspection, size inspection, cleaning, mark spraying, and finishing processes, and finally is packaged and stored; The finished pipe obtained by the manufacturing has the following properties: yield strength ≥ 710 MPa, tensile strength ≥ 950 MPa, and elongation after fracture ≥ 35%; the finished pipe obtained by the manufacturing has the following properties: hardness 270-290 HV.

2. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1, characterized by: In the step (four), the intermediate product oil removal process comprises the following steps: oil scraping by an oil scraper, alkali tank oil removal, rinsing, hot water tank soaking, acid tank oil removal, rinsing, and inspection; the solution composition in the alkali tank is controlled as follows: degreasing agent: water = 1:20, alkali tank temperature: 50-60℃, and alkali tank soaking time: 30-40 min; the solution composition in the acid tank is controlled as follows: HF: 1%, HNO3: 10-15%, and the balance is tap water, the sum of the above components is 100%, acid tank temperature: 55-60℃, and pickling time: 40-60 min. In the step (four), the intermediate product oil removal process comprises the following steps: oil scraping by an oil scraper, alkali tank soaking, hot water tank soaking, outer surface wiping, inner wall wool ball beating, and inspection; the solution composition in the alkali tank is controlled as follows: degreasing agent: water = 1:8, alkali tank temperature: 40-60℃, alkali tank soaking time: 15-25 min, hot water tank temperature: 70-80℃, and hot water tank soaking time: 10-20 min; after the hot water tank, the outer surface is wiped with acetone-soaked cotton cloth, and the inner wall is cleaned with wool until the number of times is 2-4.

3. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1 characterized in that: If the intermediate product wall thickness ≥ 3mm in the intermediate product heat treatment, the intermediate product is placed in a roller hearth furnace; after the intermediate product is cut, the intermediate product is pickled before grinding; the solution composition in the acid tank is controlled as follows: HF: 5-8%, HNO3: 10-15%, and the balance is tap water, the sum of the above components is 100%, acid tank temperature is controlled as: 50-55℃, and pickling time is 6-8h; after pickling for 6h, the inner and outer surfaces of the steel pipe are observed every 20 min; when there is no oxide skin on the inner and outer surfaces, the pickling is stopped.

4. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1 characterized in that: In the step (four), the intermediate product grinding and the intermediate product inspection are performed by local point grinding and overall outer polishing; the outer polishing is performed by a thousand-leaf wheel outer polishing, and the local point grinding is performed by a grinding machine with a flower wheel; In the step (four), the intermediate product inspection is performed by visual inspection and endoscope; the unqualified endoscope is polished by an automatic inner polishing machine with a cross polishing head made of sandpaper; before the cold drawing of the finished product, the intermediate product is inspected by visual inspection, endoscope and intermediate product ultrasonic inspection.

5. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1 characterized in that: In the step (six), the solution composition in the alkali tank is controlled as follows: degreasing agent: water = 1:8, alkali tank temperature: 40-60℃, alkali tank soaking time: 25-35 min, hot water tank temperature: 70-80℃, and hot water tank soaking time: 20-30 min; after the hot water tank, the outer surface is wiped with acetone-soaked cotton cloth, and the inner wall is cleaned with wool until the number of times is 3-5.

6. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1, characterized by: In the step (eight), the straightening machine control speed is ≤ 10 m / min, the bending degree after straightening is ≤ 1.0 mm / m, and the outer diameter deviation after straightening is ± 0.01 mm.

7. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1, characterized by: In the step (nine), the one-time ultrasonic qualified rate is ≥ 92%, the one-time eddy current qualified rate is 95%, and the end PT qualified rate is 100%.

8. The method of manufacturing a small bore, seamless pipe for an UNS S32750 umbilical as claimed in claim 1, characterized by: The surface inspection in the step (ten) has the inner wall and outer wall roughness Ra≤1.6μm.

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