A method and apparatus for forming a thick-walled corrosion-resistant alloy pipe having a yield strength of zero steel grade

Abstract

The application discloses a forming method and device for thick-wall corrosion-resistant alloy pipe with yield strength of 100 steel grade, which comprises the following steps: smelting an electroslag ingot by an electric arc furnace and electroslag remelting; taking scrap steel and alloy as raw materials, smelting an electrode billet by EAF+AOD+LF+VD, and then smelting the electroslag ingot by electroslag remelting. The forming method and device for thick-wall corrosion-resistant alloy pipe with yield strength of 100 steel grade adopts the process route of combining optimized components, electroslag ingot, hot expanding, hot extrusion and cold working to produce thick-wall corrosion-resistant alloy seamless pipe, so that the purity of the alloy is improved, the grain is refined, the solid solution treatment of the strong cold process optimizes the organization and straightness, and the hot expanding and hot extrusion improve the surface quality and the qualified rate of the hollow pipe. The thick-wall corrosion-resistant alloy seamless pipe with yield strength of 100 steel grade produced by the application has high size precision, good surface quality, small internal grain, stable mechanical properties, high strength and high toughness and good corrosion resistance.

Description

Technical Field

[0001] This invention relates to the technical field of industrial equipment manufacturing, specifically to a method and apparatus for forming thick-walled corrosion-resistant alloy tubes with a yield strength of 110 steel grade. Background Technology

[0002] With continuous extraction, the readily exploitable oil and gas resources on the Earth's surface are dwindling, leading to a shift in extraction from the mainland to deep-sea, desert, and mountainous regions. Some oil and gas wells operate in complex environments, characterized by high temperature and pressure, high mineralization, and the presence of CO2, H2S, and Cl-. - Various corrosive media, such as carbon steel, martensitic stainless steel, and duplex stainless steel, can easily cause corrosion, leading to pipe leaks and ruptures. Therefore, it is necessary to improve the corrosion resistance and mechanical properties of materials. Consequently, the demand for materials with high mechanical properties and good corrosion resistance is gradually increasing in oil and gas fields. Ordinary carbon steel, martensitic stainless steel, and duplex stainless steel can no longer meet the requirements for high strength, high toughness, and high corrosion resistance. Nickel-based alloys contain higher levels of alloying elements such as Cr, Ni, and Mo, and have an austenitic matrix. After cold working, they exhibit high strength and impact toughness, as well as good corrosion resistance, making them the preferred material for complex environmental conditions and widely used in the oil and gas extraction field.

[0003] Extrusion deformation is primarily triaxial compressive stress deformation. Under this optimal state, the metal exhibits good density and uniform structure, resulting in superior internal and external surface quality, metallographic structure, and properties. Cold deformation can increase the strength of metals, achieving the required strength within specified cold deformation parameters, making it suitable for nickel-based high-alloy tube production. The traditional production process for high-alloy corrosion-resistant tubes involves piercing followed by cold rolling. Piercing is prone to defects such as cracks and folds, resulting in low material yield. Cold rolling employs a single-stage deformation process with a deformation amount of 20%–40%, primarily used for products with wall thicknesses below 25mm. For high-alloy corrosion-resistant tubes with wall thicknesses above 30mm, requiring a cold deformation amount of 50%–60% to achieve grade I-110 steel, the cold working force is relatively high. Traditional dies such as rolls and mandrels cannot meet the strength requirements, making the production of high-grade steel extremely difficult.

[0004] Therefore, we propose a method and apparatus for forming thick-walled corrosion-resistant alloy tubes with a yield strength of 1-0 steel grade, in order to solve the problems mentioned above. Summary of the Invention

[0005] The purpose of this invention is to provide a thick-walled corrosion-resistant alloy pipe with a yield strength of 110 steel grade, giving the pipe high strength and good toughness, good surface quality, high dimensional accuracy, and good corrosion resistance, suitable for use in industries such as petroleum, natural gas, and chemicals. Another purpose of this invention is to provide a forming method and apparatus for a thick-walled corrosion-resistant alloy pipe with a yield strength of 110 steel grade, which improves the purity of the alloy, refines the grain size, optimizes the microstructure and straightness, improves production efficiency, decomposes the cold working deformation into multiple forming passes, reduces cold working force, and improves the uniformity of pipe deformation.

[0006] The technical solution of this invention is:

[0007] The alloy tube comprises, by mass percentage: C: ≤0.03, Si: 0.15~0.50, Mn: 0.40~2.5, P: ≤0.020, S: ≤0.010, Cr: 22~29, Ni: 29.5~45.5, Mo: 2.8~4.0, Cu: 0.6~3.0, Ti: 0.02~1.0, Al: 0.005~0.16, Co: 0.20~0.55, N: 0.07~0.13, O: ≤0.0050, H: ≤0.0008, with the remainder being Fe and unavoidable impurities. The alloy tube forming method includes the following steps:

[0008] (1) Alloy smelting: Electroslag ingots are produced by electro-slag remelting in an electric arc furnace; Electrode billets are produced by smelting scrap steel and alloys through EAF+AOD+LF+VD, and then electroslag ingots are produced by electroslag remelting.

[0009] (2) Electroslag ingot forging: Heat the electroslag ingot to 1150℃~1180℃, the final forging temperature is not lower than 900℃, the forging ratio is greater than 3.0, and cool it in water after forging.

[0010] (3) Blank processing: The inner hole of the head is machined into a flared mouth, and the outer circle of the tail is machined with an oblique angle and a rounded corner; after processing, the α angle of the flared mouth of the head is 46°, the M value is 10mm to 20mm larger than the diameter of the working section of the reaming head, and the L value is calculated based on the α angle using trigonometric function relationships. The outer circle of the tail is machined with an oblique angle of β of 35°, and a rounded corner with a radius of R30mm is machined at the connection between the oblique angle and the ingot body. The inner and outer surfaces are ground and polished to remove scratches and tool marks. The surface roughness RA≤3.2μm, the diameter deviation is ±1.0mm, the length deviation is ±5mm, and the end face perpendicularity is ≤1mm.

[0011] (4) Preheating of billet: The billet is put into the furnace at a temperature below 600℃, and the heating rate is 80℃~120℃ / h. The processed billet is heated to 850℃~900℃ in the resistance furnace and held for 2h~4h.

[0012] (5) Hot expansion stage: The billet is first heated to 1120℃~1160℃ by electromagnetic induction, and then expanded by a 2500-ton vertical expansion machine after lubrication. This includes: ① The outer diameter of the preheated billet is 7mm~15mm smaller than the inner diameter of the expansion barrel body, and the expansion barrel body is preheated to 100℃~350℃; ② The preheated billet is first heated by electromagnetic induction to 1120℃~1160℃ before expansion; ③ After the billet is first heated by electromagnetic induction, glass powder lubricant is evenly applied to the inner and outer surfaces, and then it is placed in the expansion barrel body with the flared end facing upward. The pre-prepared ball wrapped with glass powder lubricant is placed in the flared end, and then the expansion head is placed above the flared end of the billet. The expansion speed is 150mm / s~250mm / s, and the ratio of the cross-sectional area of ​​the billet before expansion to the cross-sectional area after expansion is 1.02~1.45.

[0013] (6) Hot extrusion stage: The expanded billet is heated to 1170℃~1210℃ using secondary electromagnetic induction heating, and after lubrication, it is extruded into a rough tube using a 6300-ton horizontal extruder. This includes: ① Preheating the extrusion barrel to 260℃~360℃, preheating the extrusion die and mandrel to 280℃~380℃, and coating the inner wall of the extrusion barrel and the surface of the mandrel with graphite emulsion; ② Placing the expanded billet on the conveyor rollers, and then turning the expanded billet so that the flared end faces backward; ③ Performing secondary electromagnetic induction heating at a temperature of 1170℃~1210℃; ④ After secondary induction heating, the inner and outer surfaces of the billet are coated with glass powder lubricant, and then placed in the extrusion barrel, with the extrusion die inlet placed... Glass lubricating pad, then extruded into a rough tube; ⑤ Before extrusion, prepare a tail pad. The tail pad is made of ordinary carbon steel. The outer diameter of the tail pad is 3mm to 7mm smaller than the inner diameter of the extrusion barrel, and the inner diameter is 3mm to 5mm larger than the reaming head. The length is 60mm to 100mm. The heating temperature of the tail pad is 950℃ to 1030℃. It is attached to the back of the billet and extruded together before extrusion. After extrusion, it automatically separates from the tube body, saving the hot sawing process and improving the yield. The inner diameter of the extrusion barrel is 4mm to 10mm larger than the inner diameter of the reaming barrel body. The extrusion speed is 100mm / s to 300mm / s. The ratio of the cross-sectional area before extrusion to the cross-sectional area after extrusion is 2.0 to 10.0. The rough tube is water-cooled after extrusion.

[0014] (7) Solution treatment of raw tubes: Heat to 1050℃~1160℃ using a bogie hearth furnace or walking beam furnace, then water-cool to below 40℃ using a forced cooling process; the steps are as follows: load into the furnace at <500℃, heat to the target temperature at a rate of 100~300℃ / h, hold for 1.5h, then remove from the furnace; treat with a dedicated heat treatment cooling system: quickly transfer the raw tubes to rotating rollers in a water tank filled with cooling water, with the rollers rotating at 30rpm~50rpm and the spacing between each pair of rotating rollers being 1.05m. ~1.55m, the rough tube rotates under the drive of the rotating support roller, and the inner nozzle switch arranged at one end of the rough tube is opened. The inner diameter of the inner nozzle is 20mm~40mm smaller than the inner diameter of the rough tube. The inner water is sprayed into the inner hole of the rough tube along the axis. The time from exiting the furnace to the start of water cooling is ≤120s. After the inner water cooling is 10s~12s, the rotating support roller device sinks as a whole, so that the diameter of the rough tube is immersed in the water surface less than 400mm. Under the simultaneous action of the inner spray and the immersed water, it is cooled to below 40℃, and the processing ends.

[0015] (8) Straightening and head cutting: Straightening is performed using a pressure straightening machine, and the head is cut using a band saw;

[0016] (9) Pickling: After straightening and cutting, use a mixed acid solution to remove oxide scale and oil stains from the rough pipes. The concentration of nitric acid is 18% to 20%, the concentration of hydrofluoric acid is 2% to 4%, and the remainder is water. The temperature of the mixed acid solution is 30℃ to 50℃.

[0017] (10) Grinding; Measure the wall thickness of the rough tube, check the surface quality, grind the uneven wall, and remove cracks, pits and defects on the inner and outer surfaces;

[0018] 11. Cold working: Perform two to four cold working deformations, with a deformation amount of 14% to 35% per pass, a feed rate of 2.5 to 4.5 mm / pass, a rolling speed of 25 to 40 passes / minute, and a total deformation amount of 50% to 60%. It can be processed using a periodic cold rolling mill or a cold forging mill. No heat treatment is performed after each cold working pass. Use degreasing acid solution to remove the cold rolling lubricating oil, wherein the concentration of nitric acid is 13%, the concentration of hydrofluoric acid is 2%, and the remainder is water.

[0019] 12 Finishing process: Inspection - Marking - Bundling.

[0020] The alloy tube has a wall thickness of 30-60 mm, and the alloy tube body material includes UNSN08028 and UNSN08825.

[0021] The alloy tube body has the following properties: tensile strength ≥800MPa, yield strength Rp0.2 758~965MPa, elongation ≥16%, average hardness ≤32HRC, and transverse Charpy V-notch full-size impact energy ≥80J at -10℃.

[0022] During the hot extrusion stage, the billet after expansion and reversal is electromagnetically induction heated twice before extrusion. To achieve uniform material temperature, compensation pads are placed at the head and tail of the billet before heating. The first heating power is 450KW~550KW, the frequency is 40~60HZ, and the temperature reaches 1150℃~1160℃, with uniform heating for 2~4 minutes. The second heating power is 600KW~800KW, the frequency is 50~85HZ, and the temperature reaches 1170℃~1210℃. The heating is uneven, and the billet is descaled by high-pressure water after exiting the furnace.

[0023] During the hot expansion and hot extrusion stages, the glass powder lubricant consists of SiO2, Al2O3, CaO, MgO, TiO2, K2O, Na2O, and B2O3, with the following composition by mass percentage: SiO2: 50%–70%, Al2O3: 1%–8%, CaO: 2%–12%, MgO: 2%–8%, TiO2: 0.1%–3%, K2O: 0.2%–3%, Na2O: 5%–20%, and B2O3: 0.5%–10%. The lubricant is selected based on the characteristics of the extrusion process. The glass powder composition is appropriately proportioned, with a particle size of 0.2mm to 0.3mm for the inner and outer lubricating powders, a viscosity of 20pA•s to 80pA•s, and a coating thickness of 0.1mm to 0.4mm for both inner and outer lubricating powders; the glass lubrication bowl and glass lubrication pad powders have a particle size of 0.2mm to 1.5mm, a viscosity of 70pA•s to 100pA•s, and the shape of the glass pad is determined by the working surface of the extrusion die and the shape of the front end of the blank. The inner hole of the glass pad is 25mm to 35mm larger than the diameter of the rough tube, and the thickness of the glass pad is 22mm to 30mm.

[0024] The 2500-ton vertical reamer used in the hot reaming stage is equipped with an ejection mechanism, a reaming barrel base, a shear ring support, a shear ring, a reaming barrel body, a reaming head, a reaming pin, and a force transmission rod. The diameter of the reaming pin is 5mm to 10mm smaller than the working section diameter of the reaming head, and the inner diameter of the shear ring is 1mm to 2mm larger than the working section diameter of the reaming head. The deviation of the reaming pin from the centerline of the reaming barrel body must not exceed 1mm. The reaming barrel body consists of a reaming barrel liner and a reaming barrel outer shell. The inner diameter has a taper of 0.4mm to 1mm, and the thickness of the inner lining of the reaming barrel is less than the thickness of the outer shell. The reaming barrel base and the reaming barrel body are fixedly connected by high-strength bolts. The reaming pin is connected to the force transmission rod through a threaded connector. The reaming barrel base supports the shear ring support, which in turn supports the shear ring and the billet. The shear ring supports the billet and removes excess material. The force transmission rod applies reaming force to the reaming head through the reaming pin, and the reaming head performs the reaming operation.

[0025] The 6300T horizontal extrusion press for the hot expansion stage is equipped with a die base, extrusion die, die support, extrusion barrel, mandrel, extrusion pad, mandrel connector, and extrusion rod. The extrusion die and die support are located inside the die base. A middle die support and a tail die support are sequentially arranged behind the die support. The die support, middle die support, and tail die support work together to fix and support the extrusion die and withstand the extrusion force. The extrusion barrel consists of an inner liner, an intermediate liner, and an outer shell. The front end of the extrusion barrel is designed to correspond to the shape of the die base. The mandrel is connected to the mandrel support via a threaded mandrel connector. The gap between the extrusion rod and the inner liner of the extrusion barrel is 4mm-5mm, and the gap between the maximum outer diameter of the mandrel support and the inner hole of the extrusion rod is 0.1mm-2mm. The extrusion pad applies force to the billet to deform it. The die base is designed to house the extrusion die in a built-in manner, allowing installation from the pipe extrusion side for easy die fixation.

[0026] The cavity size of the die support is 10mm to 15mm larger than that of the extrusion die cavity, the cavity size of the die middle support is 15mm to 20mm larger than that of the die support cavity, and the cavity size of the die tail support is 20mm to 25mm larger than that of the die middle support cavity. The cavity shapes of the die support, die middle support, and die tail support are all consistent with the shape of the pipe. The upper part is designed with a lifting hole, and the bottom is fixed with a slot.

[0027] The gap between the outer circle of the extrusion pad and the inner hole of the extrusion barrel is 1.0mm to 2.5mm, which is increased appropriately as the outer circle increases. The gap between the inner hole of the extrusion pad and the mandrel is 1.5mm to 2.5mm. The length of the extrusion pad is 200mm to 220mm. The material is hot work die steel H13 with a hardness of HRC48 to HRC52. The front end of the extrusion pad is the blank, and the rear end is the extrusion rod. The extrusion pad plays the role of transmitting the thrust of the extrusion rod.

[0028] The portion of the mandrel connector that connects to the mandrel is machined with an internal thread, while the portion of the mandrel connector that connects to the mandrel support is machined with an external thread; the extrusion die has a thickness of 15mm to 65mm and a length of 30mm to 50mm; the inner cavity of the extrusion die consists of an inlet transition zone, an intermediate sizing zone, and an outlet reverse cone; the length of the parallel section of the extrusion rod is equal to the inner lining length of the extrusion barrel; the extrusion rod, mandrel, and extrusion die are all made of hot work die steel H13 with a hardness of HRC48 to HRC52;

[0029] During the solution treatment stage of the rough tube, the special heat treatment cooling system is equipped with a cooling water tank, an inner nozzle, a rotating support roller, and a stirring device. The rotating support roller is used to place the rough tube horizontally during cooling, and the inner nozzle is used to spray cooling water into the inner hole of the rough tube along the axial direction. The cooling water tank is filled with cooling water and has an outlet. The outlet is connected to the inner nozzle through a water pump. The water volume is large enough to ensure that the water temperature is always below 35°C.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. This method and apparatus for forming thick-walled corrosion-resistant alloy tubes with a yield strength of 110 grade steel employs a process route combining optimized composition, electroslag ingots, hot expansion, hot extrusion, and cold working to produce seamless thick-walled corrosion-resistant alloy tubes. This improves the purity of the alloy, refines the grain size, and optimizes the microstructure and straightness through strong cold solution treatment. Hot expansion and hot extrusion improve the surface quality and yield of the rough tubes, increasing production efficiency. The cold working deformation is decomposed into multiple forming passes, reducing cold working force, lowering equipment load, and improving the uniformity of tube deformation. The thick-walled corrosion-resistant alloy seamless tubes with a yield strength of 110 grade steel produced using this invention exhibit high dimensional accuracy, good surface quality, fine internal grains, stable mechanical properties, high strength, high toughness, and excellent corrosion resistance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process flow for forming thick-walled corrosion-resistant alloy pipes with a yield strength of 110.

[0033] Figure 2 This is a schematic diagram of the structure used for extruding billets;

[0034] Figure 3 This is a structural schematic diagram of a vertical hole reamer;

[0035] Figure 4 This is a structural schematic diagram of a horizontal extrusion press;

[0036] Figure 5 This is a schematic diagram of the cooling system structure for solution treatment;

[0037] Figure 6 This is a schematic diagram of the cold processing machine.

[0038] Figure 7 This is for Figure 6 The A-direction graph.

[0039] In the diagram: 1. Ejection mechanism; 2. Expanding barrel base; 3. Shear ring support; 4. Shear ring; 5. Expanding barrel body; 51. Expanding barrel liner; 52. Expanding barrel shell; 6. Expanding head; 7. Expanding pin; 8. Force transmission rod; 9. Billet; 11. Die tail support; 12. Die center support; 13. Die base; 14. Extrusion die; 15. Die support; 21. Liner; 22. Intermediate liner; 23. Shell; 24. Extrusion barrel; 31. Mandrel; 32. Extrusion pad; 33. Mandrel connector; 34. Mandrel support; 35. Extrusion rod; 36. Cooling water tank; 37. Inner nozzle; 38. Rotating support roller; 39. Stirring device; 40. Cooling water; 41. Raw tube; 42. Mandrel; 43. Upper roll; 44. Lower roll; 45. Pre-roll tube; 46. Post-roll tube. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The forming device for thick-walled corrosion-resistant alloy tubes with a yield strength of 110 in this invention is as follows: Figures 3-6 As shown, it includes a reamer, an extruder, a solution treatment cooling system, and a cold working machine.

[0042] like Figure 3 As shown, the reaming machine is a 2500T vertical reaming machine, equipped with an ejector mechanism 1, a reaming barrel base 2, a shear ring support 3, a shear ring 4, a reaming barrel body 5, a reaming head 6, a reaming pin 7, and a force transmission rod 8. The diameter of the reaming pin 7 is 5mm to 10mm smaller than the working section diameter of the reaming head 6, and the inner diameter of the shear ring 4 is 1mm to 2mm larger than the working section diameter of the reaming head 6. The deviation of the reaming pin 7 from the centerline of the reaming barrel body 5 must not exceed 1mm. The reaming barrel body 5 consists of a reaming barrel liner 51 and a reaming barrel outer shell 52. The reaming barrel liner 51 has a taper of 0.4mm to 1mm in the inner length direction, and the thickness of the reaming barrel liner 51 is less than the thickness of the reaming barrel outer shell 52. The reaming barrel base 2 and the reaming barrel body 5 are fixedly connected by high-strength bolts. The reaming pin 7 is connected to the force transmission rod 8 via a threaded connector; the reaming barrel base 2 supports the shear ring support 3, which in turn supports the shear ring 4 and the blank 9. The shear ring 4 supports the blank 9 and removes excess material from it. The force transmission rod 8 applies reaming force to the reaming head 6 via the reaming pin 7, and the reaming head 6 performs the reaming operation.

[0043] like Figure 4As shown, the extruder is a 6300T horizontal extruder, including a die base 13, an extrusion die 14, a die support 15, an extrusion barrel 24, a mandrel 31, an extrusion pad 32, a mandrel connector 33, and an extrusion rod 35. The extrusion die 14 and the die support 15 are located inside the die base. Behind the die support 15, a die center support 12 and a die tail support 11 are arranged in sequence. The die support 15, the die center support 12, and the die tail support 11 together fix and support the extrusion die 14 and bear the extrusion force. The extrusion barrel 24 is composed of an inner liner 21, an intermediate liner 22, and an outer shell 23. The front end structure of the extrusion barrel 24 is designed to correspond to the structure of the die base 13. The mandrel 31 is connected to the mandrel support 34 by a thread through the mandrel connector 33. The gap between the extrusion rod 35 and the extrusion barrel 24 is 3mm to 5mm. The gap between the maximum outer diameter of the mandrel 31 support and the inner hole of the extrusion rod 35 is 0.1mm to 0.3mm. The extrusion pad 32 applies extrusion force to the high-temperature billet 9 to deform it. The die holder 13 is designed to house the extrusion die 14 in a built-in manner, allowing the extrusion die 14 to be installed from the extrusion side of the rough tube 41, facilitating its fixation. The portion of the mandrel connector 33 that connects to the mandrel 31 is machined with internal threads, while the portion that connects to the mandrel support 34 is machined with external threads. The extrusion die 14 has a thickness of 15mm–65mm and a length of 30mm–50mm. The inner cavity of the extrusion die 14 consists of an inlet transition zone, an intermediate sizing zone, and an outlet reverse cone. The length of the parallel section of the extrusion rod 35 is equal to the length of the extrusion barrel 24. The extrusion rod 35, mandrel 31, and extrusion die 14 are all made of hot-work die steel H13 with a hardness of 48–52 HRC. During operation, the extrusion rod 35, mandrel 31, and extrusion barrel 24 are powered by hydraulic cylinders, and the extrusion barrel 24 moves back and forth via a bottom slide rail.

[0044] like Figure 5 As shown, the solution treatment cooling system includes a cooling water tank 36, an inner nozzle 37, a rotating support roller 38, and a stirring device 39. The rotating support roller 38 is used to horizontally place the steel pipe during cooling, and the inner nozzle 37 is used to spray cooling water 40 into the inner hole of the steel pipe. The cooling water tank 36 is filled with cooling water 40 and has an outlet, which is connected to the inner nozzle 37 via a water pump. The stirring device is used to agitate the cooling water 40, causing it to flow within the cooling water tank 36.

[0045] like Figure 6 As shown, a periodic cold rolling mill is used for processing. It is equipped with an upper roll 43, a lower roll 44, a mandrel 42, a pre-roll tube 45, and a post-roll tube 46. It performs two to four passes of cold working deformation, with a deformation amount of 14% to 30% per pass, a feed rate of 2.5 to 4.5 mm / pass, a rolling speed of 25 to 40 passes / minute, and a total deformation amount of 50% to 60%. After each pass of cold working, degreasing acid is used to remove the cold rolling lubricating oil.

[0046] Example 1

[0047] This invention relates to a thick-walled corrosion-resistant alloy pipe with a yield strength of 110 steel grade, made of UNSN08028 steel. The cold-worked pipe dimensions are an outer diameter of φ219mm and a wall thickness of 35mm. The chemical composition is shown in Table 1.1.

[0048] Table 1.1 Chemical composition of corrosion-resistant alloy UNSN08028 (mass percentage)

[0049]

[0050] Note: Co: 0.21%, the remainder is Fe and unavoidable impurities.

[0051] A method for forming thick-walled alloy tubes of UNSN08028 steel grade with a yield strength of 110 includes the following steps:

[0052] (1) Alloy smelting: Electroslag ingots are smelted by electric arc furnace and electroslag remelting; electrode billets are smelted by EAF+AOD+LF+VD using scrap steel and alloys as raw materials, and then electroslag ingots with a diameter of φ820mm are smelted by electroslag remelting.

[0053] (2) Electroslag ingot forging: Heat the electroslag ingot to 1150℃~1180℃, the final forging temperature is not lower than 900℃, the forging ratio is greater than 3.0, forge a bar with a diameter of φ424mm, and cool it in water after forging.

[0054] (3) Processing of billet 9: After processing, the α angle of the head flare is 46°, and the β angle of the tail outer circle is machined into a bevel of 35°. The bevel is machined into a rounded corner with a radius of R30mm at the connection between the bevel and the ingot body. The surface roughness Ra≤3.2μm, the diameter deviation ±1.0mm, the length deviation ±5mm, and the end face perpendicularity ≤1mm; a billet 9 with an outer diameter of φ415mm / inner diameter of φ80mm × length of 900mm is produced.

[0055] (4) Preheating of billet 9: Put it into the furnace at a temperature below 600℃, with a heating rate of 80℃~120℃ / h. Heat the processed billet 9 in the resistance furnace to 850℃~900℃ and hold for 2h~4h.

[0056] (5) Hot expansion: The blank is first heated to 1120℃~1160℃ by electromagnetic induction, and then expanded by a 2500-ton vertical expansion machine after lubrication. This includes ① preheating the expansion barrel body 5 to 100℃~350℃; ② heating the preheated blank 9 to 1120℃~1160℃ by electromagnetic induction before expansion; ③ after the blank 9 is first heated by electromagnetic induction, glass powder lubricant is evenly applied to the inner and outer surfaces, and then it is placed in the expansion barrel body 5 with the flared end facing upward. The pre-prepared ball wrapped with glass powder lubricant is placed in the flared end, and then the expansion head 6 is placed above the flared end of the blank 9. The expansion speed is 150mm / s~250mm / s, the diameter of the expansion head 6 is 219mm, and the inner diameter of the expansion barrel body 5 is 428mm.

[0057] (6) Hot extrusion: The expanded billet 9 is heated to 1170℃~1210℃ using secondary electromagnetic induction heating. After lubrication, the blank tube 41 is extruded using a 6300-ton horizontal extruder. This includes: ① Preheating the extrusion barrel 24 to 260℃~360℃, and preheating the extrusion die 14 and mandrel 31 to 280℃~380℃. The inner wall of the extrusion barrel 24 and the surface of the mandrel 31 are coated with graphite emulsion. ② The expanded billet 9 is placed on the conveyor rollers, and then the expanded billet 9 is turned around so that the flared end faces backward. ③ Secondary electromagnetic induction heating is performed at a temperature of 1170℃~1210℃. ④ After secondary induction heating, glass powder lubricant is applied to the inner and outer surfaces of the billet 9, and then it is placed in the extrusion barrel 24. A glass lubricating pad is placed at the entrance of the extrusion die 14, and then the blank tube 41 is extruded. ⑤ Before extrusion, prepare a tail pad. The tail pad is made of ordinary carbon steel. The outer diameter of the tail pad is 3mm to 7mm smaller than the inner diameter of the extrusion barrel 24, and the inner diameter is 3mm to 5mm larger than the reamer head 6. The length is 60mm to 100mm. The heating temperature of the tail pad is 950℃ to 1030℃. Before extrusion, it is attached to the back of the billet 9 and extruded together. After extrusion, it automatically separates from the tube body, saving the hot sawing process and improving the yield. The inner diameter of the extrusion barrel 24 is 435mm, the extrusion speed is 100mm / s to 300mm / s, the diameter of the mandrel 31 is 207.0mm, the inner diameter of the extrusion die 14 is 312mm, and the size of the extruded tube after cooling is φ306mm×51mm. The rough tube 41 is water-cooled after extrusion.

[0058] (7) Solution treatment of raw tube 41: Heat to 1150℃~1160℃ using a bogie furnace, and then water-cool to below 40℃ using a forced cooling process: The steps are as follows: Load into the furnace at <500℃, raise the temperature to the target temperature at a rate of 100~300℃ / h, hold for 1.5h, and then remove from the furnace; process with a special heat treatment cooling system: Quickly transfer the raw tube 41 to the rotating rollers 38 in a water tank filled with cooling water 40, with the rollers rotating at a speed of 30rpm~50rpm, and the distance between each pair of rotating rollers 38 being 1.05m~1.55m. Driven by the rotating support roller 38, the rough tube 41 rotates and opens the switch of the inner nozzle 37 arranged at one end of the rough tube 41. The inner diameter of the inner nozzle 37 is 20mm to 40mm smaller than the inner diameter of the rough tube 41. The inner water is sprayed into the inner hole of the rough tube 41 along the axial direction. The time from exiting the furnace to the start of water cooling is ≤120s. After the inner water cooling is 10s to 12s, the rotating support roller 38 device sinks as a whole, so that the rough tube 41 is immersed in the water surface 400mm below the diameter. Under the simultaneous action of the inner spray and the immersion water, it is cooled to below 40℃, and the processing ends.

[0059] (8) Straightening and head cutting: Straightening is performed using a pressure straightening machine, and the head is cut using a band saw;

[0060] (9) Pickling: Use a mixed acid solution to remove oxide scale and oil stains from the rough pipe 41 after step (8). The concentration of nitric acid is 18% to 20%, the concentration of hydrofluoric acid is 2% to 4%, and the remainder is water. The temperature of the mixed acid solution is 30℃ to 50℃.

[0061] (10) Grinding; Measure the wall thickness of the rough tube 41, check the surface quality, grind the uneven wall, and remove cracks and pits on the inner and outer surfaces;

[0062] 11. Cold working: Based on the cold work hardening characteristics of UNSN08028, a cold working deformation process was designed: φ306mm×51mm→φ273mm×43mm→φ245mm×37mm→φ219mm×35mm, with a feed rate of 2.5~4.5mm / pass, a rolling speed of 25~40 passes / minute, and a total deformation of 50.4%. No heat treatment is performed after each cold working pass, and a periodic cold rolling mill is used for processing.

[0063] 12 Finishing process: Inspection - Marking - Bundling.

[0064] The produced thick-walled corrosion-resistant alloy pipes with a yield strength of 110 were inspected, and the inspection data are shown in Table 1.2.

[0065] Table 1.2. Performance of corrosion-resistant alloy pipes with a yield strength of 110 grade steel and a diameter of φ219mm×35mm

[0066]

[0067] Example 2

[0068] This invention relates to a thick-walled corrosion-resistant alloy pipe with a yield strength of 110 steel grade, made of UNSN08825 steel. The cold-worked pipe dimensions are an outer diameter of φ206mm and a wall thickness of 32mm. The chemical composition is shown in Table 2.1.

[0069] Table 2.1 Chemical composition (mass percentage) of corrosion-resistant alloy UNSN08825

[0070]

[0071] Note: Co: 0.26%, the remainder is Fe and unavoidable impurities.

[0072] A method for forming thick-walled alloy tubes of UNSN08825 steel grade with a yield strength of 110 includes the following steps:

[0073] (1) Alloy smelting: Electroslag ingots are smelted by electric arc furnace and electroslag remelting; electrode billets are smelted by EAF+AOD+LF+VD using scrap steel and alloys as raw materials, and then electroslag ingots with a diameter of φ820mm are smelted by electroslag remelting.

[0074] (2) Electroslag ingot forging: Heat the electroslag ingot to 1150℃~1180℃, the final forging temperature is not lower than 900℃, the forging ratio is greater than 3.0, forge a bar with a diameter of φ424mm, and cool it in water after forging.

[0075] (3) Processing of billet 9: After processing, the α angle of the head is 46°, and the β angle of the outer circle of the tail is machined into a bevel of 35°. The bevel is machined into a rounded corner with a radius of R30mm at the connection between the bevel and the ingot body. The surface roughness Ra≤3.2μm, the diameter deviation ±1.0mm, the length deviation ±5mm, and the end face perpendicularity ≤1mm; a billet 9 with an outer diameter of φ415mm / inner diameter of φ80mm × length of 910mm is produced.

[0076] (4) Preheating of billet 9: Put it into the furnace at a temperature below 600℃, with a heating rate of 80℃~120℃ / h. Heat the processed billet 9 in the resistance furnace to 850℃~900℃ and hold for 2h~4h.

[0077] (5) Hot expansion: The blank is first heated to 1120℃~1150℃ by electromagnetic induction, and then expanded by a 2500-ton vertical expansion machine after lubrication. This includes ① preheating the expansion barrel body 5 to 100℃~350℃; ② heating the preheated blank 9 to 1120℃~1150℃ by electromagnetic induction before expansion; ③ after the blank 9 is first heated by electromagnetic induction, glass powder lubricant is evenly applied to the inner and outer surfaces, and then it is placed in the expansion barrel body 5 with the flared end facing upward. The pre-prepared ball wrapped with glass powder lubricant is placed in the flared end, and then the expansion head 6 is placed above the flared end of the blank 9. The expansion speed is 150mm / s~250mm / s, the diameter of the expansion head 6 is 219mm, and the inner diameter of the expansion barrel body 5 is 428mm.

[0078] (6) Hot extrusion: The expanded billet 9 is heated to 1170℃~1210℃ using secondary electromagnetic induction heating. After lubrication, the blank tube 41 is extruded using a 6300-ton horizontal extruder. This includes: ① Preheating the extrusion barrel 24 to 260℃~360℃, and preheating the extrusion die 14 and mandrel 31 to 280℃~380℃. The inner wall of the extrusion barrel 24 and the surface of the mandrel 31 are coated with graphite emulsion. ② The expanded billet 9 is placed on the conveyor rollers, and then the expanded billet 9 is turned around so that the flared end faces backward. ③ Secondary electromagnetic induction heating is performed at a temperature of 1170℃~1210℃. ④ After secondary induction heating, glass powder lubricant is applied to the inner and outer surfaces of the billet 9, and then it is placed in the extrusion barrel 24. A glass lubricating pad is placed at the entrance of the extrusion die 14, and then the blank tube 41 is extruded. ⑤ Before extrusion, prepare a tail pad. The tail pad is made of ordinary carbon steel. The outer diameter of the tail pad is 3mm to 7mm smaller than the inner diameter of the extrusion barrel 24, and the inner diameter is 3mm to 5mm larger than the reamer head 6. The length is 60mm to 100mm. The heating temperature of the tail pad is 950℃ to 1030℃. Before extrusion, it is attached to the back of the billet 9 and extruded together. After extrusion, it automatically separates from the tube body, saving the hot sawing process and improving the yield. The inner diameter of the extrusion barrel 24 is 435mm, the extrusion speed is 100mm / s to 300mm / s, the diameter of the mandrel 31 is 207.8mm, the inner diameter of the extrusion die 14 is 311mm, and the size of the extruded tube after cooling is φ305mm×50mm. The rough tube 41 is water-cooled after extrusion.

[0079] (7) Solution treatment of raw tube 41: Heat to 1050℃~1060℃ in a walking beam furnace, and then water-cool to below 40℃ using a forced cooling process: The steps are as follows: Load the tube into the furnace at <500℃, raise the temperature to the target temperature at a rate of 100~300℃ / h, hold for 1.5h, and then remove it from the furnace; process it with a special heat treatment cooling system: quickly transfer the raw tube 41 to the rotating rollers 38 in a water tank filled with cooling water 40, with the rollers rotating at a speed of 30rpm~50rpm, and the distance between each pair of rotating rollers 38 being 1.05m~1.55m. Driven by the rotating support roller 38, the rough tube 41 rotates and opens the switch of the inner nozzle 37 arranged at one end of the rough tube 41. The inner diameter of the inner nozzle 37 is 20mm to 40mm smaller than the inner diameter of the rough tube 41. The inner water is sprayed into the inner hole of the rough tube 41 along the axial direction. The time from exiting the furnace to the start of water cooling is ≤120s. After the inner water cooling is 10s to 12s, the rotating support roller 38 device sinks as a whole, so that the rough tube 41 is immersed in the water surface 400mm below the diameter. Under the simultaneous action of the inner spray and the immersion water, it is cooled to below 40℃, and the processing ends.

[0080] (8) Straightening and head cutting: Straightening is performed using a pressure straightening machine, and the head is cut using a band saw;

[0081] (9) Pickling: Use a mixed acid solution to remove oxide scale and oil stains from the rough pipe 41 after step (8). The concentration of nitric acid is 18% to 20%, the concentration of hydrofluoric acid is 2% to 4%, and the remainder is water. The temperature of the mixed acid solution is 30℃ to 50℃.

[0082] (10) Grinding; Measure the wall thickness of the rough tube 41, check the surface quality, grind the uneven wall, and remove cracks and pits on the inner and outer surfaces;

[0083] 11. Cold working: Based on the cold work hardening characteristics of UNSN08825, a cold working deformation process was designed: φ305mm×50mm→φ265mm×40mm→φ230mm×35mm→φ206mm×32mm, with a feed rate of 2.5~4.5mm / pass, a rolling speed of 25~40 passes / minute, and a total deformation of 56.3%. No heat treatment is performed after each cold working pass, and a periodic cold rolling mill is used for processing.

[0084] 12 Finishing process: Inspection - Marking - Bundling.

[0085] The produced thick-walled corrosion-resistant alloy pipes with a yield strength of 110 were inspected, and the inspection data are shown in Table 2.2.

[0086] Table 2.2. Performance of corrosion-resistant alloy pipes with a yield strength of 110 grade steel and a diameter of φ206mm×32mm

[0087]

[0088] Contents not described in detail in this specification are prior art known to those skilled in the art. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Terms such as "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," and "tail" indicate orientations or positional relationships based on the accompanying drawings, and are used only for ease of description and simplification, not to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0089] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming a thick-walled corrosion-resistant alloy pipe with a yield strength of zero steel grade, comprising alloy pipe ingredients in mass percentage: C: ≤0.03, Si: 0.15-0.50, Mn: 0.40-2.5, P: ≤0.020, S: ≤0.010, Cr: 22-29, Ni: 29.5-45.5, Mo: 2.8-4.0, Cu: 0.6-3.0, Ti: 0.02-1.0, Al: 0.005-0.16, Co: 0.20-0.55, N: 0.07-0.13, O: ≤0.0050, H: ≤0.0008, and the rest being Fe and inevitable impurities, the method comprising the following steps: (1) alloy smelting: arc furnace plus electroslag remelting to produce electroslag ingot; using scrap steel and alloy as raw materials, EAF+AOD+LF+VD smelting to produce electrode billet, and then electroslag remelting to produce electroslag ingot; (2) electroslag ingot forging: heating the electroslag ingot to 1150-1180℃, final forging temperature not less than 900℃, forging ratio greater than 3.0, and water cooling after forging; (3) blank (9) processing: processing a flared mouth in the head inner hole, and processing a bevel and a round corner in the tail outer circle; after processing, the head flared mouth α angle is 46°, the M value is greater than the working section diameter of the hole expanding head (6) by 10-20mm, and the L value is calculated according to the α angle using a trigonometric function relationship; the tail outer circle is processed to have a β angle of 35°; wherein the α angle is the taper angle of the blank (9) head flared mouth; the M value is the large end diameter of the blank (9) head flared mouth; the L value is the axial length of the blank (9) head flared mouth; the β angle is the bevel angle of the blank (9) tail outer circle, and a round corner with a radius R of 30mm is processed at the connection between the bevel and the ingot body; the inner and outer surfaces are ground and polished to remove scratches and tool marks, the surface roughness Ra is ≤3.2μm, the diameter deviation is ±1.0mm, the length deviation is ±5mm, and the end surface perpendicularity is ≤1mm; (4) blank (9) preheating: entering the furnace below 600℃, and the heating rate is 80-120℃ / h; heating the processed blank (9) to 850-900℃ in a resistance furnace for 2-4h. ⑸ Hot hole expansion stage: once electromagnetic induction heating to 1120℃-1160℃, lubricated with 2500 tons vertical hole expander, including: ① the preheated blank (9) outer diameter is smaller than the inner diameter of the hole expander barrel body (5) by 7mm-15mm, the hole expander barrel body (5) is preheated to a temperature of 100℃-350℃; ② the preheated blank (9) is heated by once electromagnetic induction before hole expansion, the heating temperature is 1120℃-1160℃, ③ after the blank (9) is heated by once electromagnetic induction, the inner and outer surfaces are evenly coated with glass powder lubricant, then placed in the hole expander barrel body (5) with the horn mouth end facing up, the previously prepared glass powder lubricant wrapped pellets are placed in the horn mouth, and then the hole expander head (6) is placed above the blank (9) horn mouth, followed by hole expansion, the hole expansion speed is 150mm / s-250mm / s, the ratio of the cross-sectional area of the blank (9) before hole expansion to the cross-sectional area after hole expansion is 1.02-1.45; ⑹ Hot extrusion stage: the hole-expanded blank (9) is heated to 1170℃-1210℃ by twice electromagnetic induction, and then extruded into a crude pipe (41) by a 6300-ton horizontal extruder, including: ① the extrusion barrel (24) is preheated to a temperature of 260℃-360℃, the extrusion die (14) and the core rod (31) are preheated to a temperature of 280℃-380℃, and the inner wall of the extrusion barrel (24) and the surface of the core rod (31) are coated with graphite milk; ② the hole-expanded blank (9) is placed on the conveying roller, and then the hole-expanded blank (9) is turned around with the horn mouth end facing backward; ③ twice electromagnetic induction heating is performed, and the heating temperature is 1170℃-1210℃; ④ after the twice induction heating, the blank (9) is coated with glass powder lubricant on the inner and outer surfaces, then placed in the extrusion barrel (24), and a glass lubricating pad is placed at the entrance of the extrusion die (14), then the crude pipe (41) is extruded; ⑤ a tail pad is prepared before extrusion, the tail pad is made of plain carbon steel, the outer diameter of the tail pad is smaller than the inner diameter of the extrusion barrel (24) by 3mm-7mm, the inner diameter is larger than the hole expander head (6) by 3mm-5mm, the length is 60mm-100mm, the heating temperature of the tail pad is 950℃-1030℃, and the tail pad is attached to the back of the blank (9) before extrusion and separated from the pipe body after extrusion, saving the hot sawing process and improving the yield, the inner diameter of the extrusion barrel (24) is larger than the inner diameter of the hole expander barrel body (5) by 4mm-10mm, the extrusion speed is 100mm / s-300mm / s, the ratio of the cross-sectional area before extrusion to the cross-sectional area after extrusion is 2.0-10.0, and the crude pipe (41) is water-cooled after extrusion; ⑺Solution treatment of the raw pipe (41): heating to 1050-1160℃ in a trolley furnace or a walking beam furnace, and water cooling to below 40℃ by using a quenching process; the steps are: loading into the furnace at <500℃, heating to the target temperature at a rate of 100-300℃ / h, holding for 1.5h, and then discharging; using a special heat treatment cooling system: rapidly transferring the raw pipe (41) to the rotating support wheel (38) in the water tank (40) filled with cooling water (40), the rotating speed of the support wheel (38) is 30-50rpm, the distance between each pair of rotating support wheels (38) is 1.05-1.55m, the raw pipe (41) rotates under the drive of the rotating support wheel (38), opening the switch of the inner nozzle (37) arranged at one end of the raw pipe (41), the inner diameter of the inner nozzle (37) is 20-40mm smaller than that of the raw pipe (41), the inner nozzle (37) sprays water into the inner hole of the raw pipe (41) along the axial direction, and the time from discharging to starting water cooling is ≤120s; after water cooling for 10-12s, the rotating support wheel (38) device is lowered as a whole, so that the raw pipe (41) is immersed below the water surface by 400mm in the diameter direction, and the raw pipe (41) is cooled to below 40℃ under the simultaneous action of the inner nozzle (37) and the water immersion, and the treatment is completed; ⑻Straightening and cutting: straightening by using a pressure straightening machine, and cutting by using a band saw; ⑼Pickling: using mixed acid liquid to remove the oxide scale and oil stains on the raw pipe (41) after straightening and cutting, wherein the concentration of nitric acid is 18-20%, the concentration of hydrofluoric acid is 2-4%, and the rest is water, and the temperature of the mixed acid liquid is 30-50℃; ⑽Grinding: measuring the wall thickness of the raw pipe (41), checking the surface quality, grinding the wall thickness, and removing the cracks and pit defects on the inner and outer surfaces; ⑾Cold working: setting the core rod (42), the upper roller (43), the lower roller (44), the pipe before rolling (45), and the pipe after rolling (46) to perform two to four times of cold working deformation, the deformation amount of each pass is 14-35%, the feeding amount is 2.5-4.5mm / pass, the rolling speed is 25-40 times / min, the total deformation amount is 50-60%, and the periodical cold rolling pipe machine or the cold forging machine can be used for processing, and no heat treatment is performed after each pass of cold working, and the oil removing acid liquid is used to remove the cold rolling lubricating oil, wherein the concentration of nitric acid is 13%, the concentration of hydrofluoric acid is 2%, and the rest is water; ⑿Finishing treatment: inspection, marking, and bundling.

2. A method of forming a thick wall corrosion resistant alloy pipe of yield strength one-zero steel grade as claimed in claim 1, wherein: The wall thickness of the alloy pipe is 30-60mm, and the material of the alloy pipe includes UNS N08028 and UNS N08825.

3. A method of forming a thick wall corrosion resistant alloy pipe of yield strength one-zero steel grade as claimed in claim 1, wherein: The performance of the alloy pipe is as follows: the tensile strength is ≥800MPa, the Rp0.2 yield strength is 758-965MPa, the elongation is ≥16%, the average hardness is ≤32HRC, and the transverse Charpy V-notch full-size impact energy at -10℃ is ≥80J.

4. A method of forming a thick wall corrosion resistant alloy pipe of yield strength one-zero steel grade as claimed in claim 1, wherein: The hot extrusion stage, the expanded hole after the blank (9) is heated by electromagnetic induction before extrusion for 2 times, in order to realize the uniformity of the whole material temperature, the blank (9) head and tail are placed respectively before heating compensation pad, the first heating power is 450KW-550KW, the frequency is 40-60HZ, the temperature is 1150℃-1160℃, and the temperature is kept for 2-4min; the second heating power is 600KW-800KW, the frequency is 50-85HZ, the temperature is 1170℃-1210℃, and the temperature is not kept, and the high-pressure water descaling is carried out after discharging.

5. A method of forming a thick wall corrosion resistant alloy pipe of yield strength one-zero steel grade as claimed in claim 1, wherein: The hot expansion stage and the hot extrusion stage, the glass powder lubricant is composed of SiO2, Al2O3, CAO, MgO, TiO2, K2O, NA2O and B2O3, and the components are as follows: SiO2: 50%-70%, Al2O3: 1%-8%, CAO: 2%-12%, MgO: 2%-8%, TiO2: 0.1%-3%, K2O: 0.2%-3%, NA2O: 5%-20%, B2O3: 0.5%-10%, according to the characteristics of the extrusion process, the appropriate ratio of glass powder composition is selected, the particle size of the inner and outer lubricating powder is 0.2mm-0.3mm, the viscosity is 20pA·s-80pA·s, the thickness of the inner and outer lubricating powder is 0.1mm-0.4mm; the particle size of the glass lubricating bowl and the glass lubricating pad powder is 0.2mm-1.5mm, the viscosity is 70pA·s-100pA·s, the shape of the glass pad is determined by the working surface of the extrusion die (14) and the front end shape of the blank (9), the inner hole of the glass pad is larger than the diameter of the raw pipe (41) by 25mm-35mm, and the thickness of the glass pad is 22mm-30mm.

6. The forming device for the method of forming a thick walled corrosion resistant alloy pipe of yield strength in the grade of 1-0 as claimed in claim 1, wherein: The hot expansion stage, the 2500-ton vertical expansion machine is provided with an ejection mechanism (1), an expansion barrel base (2), a shear ring support (3), a shear ring (4), an expansion barrel body (5), an expansion head (6), an expansion needle (7) and a force transmission rod (8); the diameter of the expansion needle (7) is smaller than the diameter of the working section of the expansion head (6) by 5mm-10mm, the inner diameter of the shear ring (4) is larger than the diameter of the working section of the expansion head (6) by 1mm-2mm; the expansion needle (7) deviates from the center line of the expansion barrel body (5) by not more than 1mm; the expansion barrel body (5) is composed of an expansion barrel lining (51) and an expansion barrel shell (52), the expansion barrel lining (51) has a taper of 0.4mm-1mm in the length direction of the inner circle, and the thickness of the expansion barrel lining (51) is smaller than that of the expansion barrel shell (52); the expansion barrel base (2) and the expansion barrel body (5) are fixedly connected through high-strength bolts; the expansion needle (7) is connected together through a threaded connecting piece and the force transmission rod (8); the expansion barrel base (2) supports the shear ring support (3), the shear ring support (3) supports the shear ring (4) and the blank (9), the shear ring (4) supports the blank (9) and the excess of the blank (9) cut off; the force transmission rod (8) applies expansion force to the expansion head (6) through the expansion needle (7), and the expansion head (6) performs expansion work.

7. The forming device for the method of forming a thick walled corrosion resistant alloy pipe of yield strength - zero grade as claimed in claim 1 wherein: 6300T horizontal extrusion machine of hot expanding hole stage, be provided with die holder (13), extrusion die (14), die support (15), extrusion barrel (24), core rod (31), extrusion pad (32), core rod connecting piece (33) and extrusion rod (35), extrusion die (14) and die support (15) are set up inside die holder (13), die support (15) back is sequentially set up die middle support (12), die tail support (11), die support (15), die middle support (12) and die tail support (11) jointly to extrusion die (14) play the role of fixed and support, bear extrusion pressure, extrusion barrel (24) is composed of inner lining (21), intermediate lining (22) and outer shell (23), extrusion barrel (24) front end structure shape and die holder (13) structure shape correspond design, core rod (31) is connected to core rod support (34) by core rod connecting piece (33) with threaded mode, extrusion rod (35) and extrusion barrel (24) inner lining (21) clearance is 4mm~5mm, the maximum outer diameter of core rod support (34) and extrusion rod (35) inner hole clearance 0.1mm~2mm, by extrusion pad (32) to blank (9) exert force and make it deform, the position of die holder (13) placing extrusion die (14) is designed into built-in mode, realizes from the pipe extrusion one side installation, reaches the effect that extrusion die (14) is convenient to fix; Die support (15) bore cavity size is greater than extrusion die (14) bore cavity size 10mm~15mm, die middle support (12) bore cavity size is greater than die support (15) bore cavity size 15mm~20mm, die tail support (11) bore cavity size is greater than die middle support (12) bore cavity size 20mm~25mm, the bore cavity shape of die support (15), die middle support (12) and die tail support (11) are consistent with the shape of the pipe, and a lifting hole is designed at the top, and a clamping groove is used for fixing at the bottom. Extrusion pad (32) outer circle and extrusion barrel (24) inner hole clearance is 1.0mm~2.5mm, and the clearance is appropriately increased with the increase of the outer circle, the inner hole of the extrusion pad (32) and the core rod (31) is 1.5mm~2.5mm, the length of the extrusion pad (32) is 200mm~220mm, the material is hot work die steel H13, and the hardness is HRC48~HRC52; the front end of the extrusion pad (32) is the blank (9), and the rear end is the extrusion rod (35), and the extrusion pad (32) plays a role of transmitting the thrust of the extrusion rod (35). The part connected with the core rod (31) on the core rod connecting piece (33) is processed with internal thread, and the part connected with the core rod support (34) on the core rod connecting piece (33) is processed with external thread; the thickness of the extrusion die (14) is 15mm~65mm, and the length is 30mm~50mm; the inner cavity of the extrusion die (14) is composed of an inlet transition zone, an intermediate sizing zone and an outlet reverse cone; the length of the parallel section of the extrusion rod (35) is equal to the length of the inner lining (21) of the extrusion barrel (24); the materials of the extrusion rod (35), the core rod (31) and the extrusion die (14) are hot work die steel H13, and the hardness is HRC48~HRC52.

8. The forming device for the method of forming a thick wall corrosion resistant alloy pipe of yield strength in the grade of 1-0 as claimed in claim 1, wherein: The special heat treatment cooling system is provided with a cooling water tank (36), an inner nozzle (37), a rotating supporting wheel (38) and a stirring device (39). The rotating supporting wheel (38) is used for horizontally placing the blank pipe (41) during cooling, and the inner nozzle (37) is used for spraying the cooling water (40) into the inner hole of the blank pipe (41) along the axial direction. The cooling water tank (36) is filled with the cooling water (40), and the cooling water tank (36) is provided with a water outlet connected to the inner nozzle (37) through a water pump. The water quantity is large enough to ensure that the water temperature is always below 35℃.

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