A method for producing a double-layered alloy composite seamless pipe

Abstract

The present application relates to a kind of production methods of double-layer alloy composite seamless pipe.The outer layer material of double-layer alloy composite seamless pipe is low-carbon steel, the inner layer material is nickel-based alloy, outer layer alloy bar material is continuous casting billet or rolling blank, and inner layer alloy bar material is forging blank.The production steps are: (1) blank preparation; (2) upsetting; (3) blank machining; (4) hot expansion; (5) hot extrusion; (6) heat treatment; (7) surface treatment; (8) cold rolling; (9) finishing treatment.The blank preparation process includes: (1) theoretical calculation; (2) blanking; (3) electroplating; (4) blank assembly; (5) head and tail pad welding.The double-layer alloy composite seamless pipe produced by the present application has firm combination of the inner and outer layers of alloy, reduces the defects of extrusion delamination, the outer layer alloy has high strength, the inner layer alloy has good corrosion resistance, improves the yield rate of processing defects, and reduces material cost.

Description

Technical Field

[0001] This invention belongs to the field of industrial equipment manufacturing technology and relates to a method for producing a double-layer alloy composite seamless tube. Background Technology

[0002] With the development of industries such as petroleum, natural gas, and chemicals, the demand for pipelines is increasing, placing higher requirements on the mechanical and corrosion resistance properties of pipe materials. This necessitates that the pipe manufacturing industry adopt a market-oriented approach, developing and utilizing reasonably priced, high-performance pipe materials to meet the ever-growing market needs, while simultaneously establishing its own brands within the industry. Nickel-based alloy pipes have been widely used in corrosion-resistant applications, but their high price deters many users. To reduce pipe costs, double-layer alloy composite pipes have emerged.

[0003] Existing manufacturing technologies include: There are many manufacturing processes for composite seamless tubes, such as explosive forming composite, weld overlay forming composite, centrifugal casting extrusion forming, etc. Generally, the process involves using two alloys as raw materials for composite.

[0004] From the perspective of composite processes and deformation characteristics, all processes can manufacture double-layer alloy composite seamless tubes. The centrifugal casting composite round tube blank + extrusion process is very suitable for manufacturing high-end composite tube products such as those with nickel-based alloys as the inner metal. However, due to the poor plasticity of the as-cast structure and the tendency to delamination and cracking after extrusion, other composite processes are only used in low-end fields due to defects such as low bonding strength. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing a double-layer alloy composite seamless tube, which facilitates the bonding of the alloy during the extrusion process, reduces extrusion delamination defects, improves the strength and corrosion resistance of the seamless tube, saves precious metals, and reduces material costs.

[0006] The technical solution of this invention is: a method for producing a double-layer alloy composite seamless tube, wherein the outer layer of the double-layer alloy composite seamless tube is made of low-carbon steel and the inner layer is made of nickel-based alloy. The production method includes the following steps:

[0007] (1) Blank preparation: Select suitable outer alloy bar and inner alloy bar of appropriate material for double-layer alloy composite seamless tube, calculate the size, and carry out electroplating, assembly and welding.

[0008] (2) Upsetting: Coat the double-layer alloy billet with an anti-oxidation coating, heat to 100℃~150℃, and hold for 1 hour to dry. Preheat in a resistance furnace to 700℃~800℃, hold for 3~5 hours, and then heat in an electromagnetic induction heating furnace to 1170℃~1220℃. After removing from the furnace, evenly coat the outer surface with glass powder lubricant, and place it in an upsetting barrel with an inner diameter 6mm~12mm larger than the outer diameter of the double-layer alloy billet for upsetting to eliminate the gap between the inner and outer layers. After upsetting, air cool to room temperature.

[0009] (3) Blank machining: After upsetting, 3mm to 5mm is machined off one side of the outer diameter of the double-layer alloy blank, and a through hole with a diameter of 35mm to 100mm is machined in the center. A flared mouth is machined at the inner hole of the head pad, and an R30mm radius is machined at the outer diameter. The inner and outer surfaces are ground and polished to remove defects such as dents and tool marks, and the surface roughness Ra≤3.2μm.

[0010] (4) Hot expansion: After machining, the blank is placed in the expansion barrel of a vertical expansion machine for hot expansion.

[0011] (5) Hot extrusion: After hot expansion, the billet is placed in the extrusion barrel of a horizontal extruder for hot extrusion.

[0012] (6) Heat treatment: Heat the extruded double-layer alloy composite seamless tube to 950℃~1050℃; hold for 0.5h~1h, and then air cool to room temperature after removing from the furnace.

[0013] (7) Surface treatment: pickling and grinding to remove surface glass powder, oxide scale and defects.

[0014] (8) Cold rolling: One or more cold rolling passes are performed using a two-roll cold rolling mill. The feed rate is 2.5 to 3.5 mm / pass, the rolling speed is 30 to 50 passes / minute, and the deformation per pass is 30% to 50%. After each pass of cold rolling, degreasing and annealing are performed. Annealing is carried out in a vacuum furnace or an atmosphere-protected furnace.

[0015] (9) Finishing process: Inspection - Marking - Bundling.

[0016] The outer layer of the double-layer alloy composite seamless tube is made of 16Mn, 12MnV, 15MnV, or 20MnV, while the inner layer is made of N06022, N10276, GH4169, N08825, N06625, N09925, N08028, N06200, or N08800. The outer alloy bar is a continuously cast billet or a rolled billet, while the inner alloy bar is a forged billet.

[0017] The billet preparation process includes:

[0018] (1) Theoretical calculation: Based on the finished dimensions of the double-layer alloy composite seamless tube, the deformation distribution process of the finished product and the dimensions of the inner and outer alloy bars are calculated.

[0019] (2) Blanking: Cut and process the inner alloy bar and the outer alloy bar into lengths of 400mm to 1200mm. The outer diameter of the inner alloy billet is 0.6mm to 1.5mm smaller than the inner diameter of the outer alloy billet. Welding bevels are machined at both ends.

[0020] (3) Electroplating: A layer of nickel metal with a thickness of 0.1mm to 0.3mm is electroplated on the bonding surfaces of the inner alloy blank and the outer alloy blank.

[0021] (4) Billet assembly: The inner and outer alloy bars processed in step (3) are assembled together in a vacuum chamber and the two ends are sealed and welded to form a double-layer alloy billet.

[0022] (5) Head and tail pad welding: Weld a head pad to the head of the double-layer alloy billet processed in step (4) and a tail pad to the tail. The head pad is 120mm to 150mm long and the tail pad is 60mm to 100mm long. The head pad and tail pad are made of low carbon steel.

[0023] The hot expansion process includes: ① The outer diameter of the billet is 10mm to 12mm smaller than the inner diameter of the expansion barrel, and the expansion barrel is preheated to 100℃ to 200℃; ② The billet is coated with an anti-oxidation coating, heated to 100℃ to 150℃ and held for 1 hour, heated to 800℃ to 900℃ in a resistance furnace and held for 3 to 5 hours, and heated to 1150℃ to 1170℃ in an electromagnetic induction heating furnace; ③ Before expansion, the inner and outer surfaces of the billet are coated with glass powder lubricant, placed in the expansion barrel with the flared end facing upwards, and a pre-prepared lubricating glass bowl is placed at the flared end. After standing for 1.5min to 2.5min, the expansion head is placed above the lubricating glass bowl to expand the hole. The expansion speed is 150mm / s to 250mm / s, and the expansion ratio is 1.02 to 1.38.

[0024] The hot extrusion process includes: ① Preheating the extrusion barrel to 250℃~350℃, preheating the conical extrusion die and mandrel to 300℃~350℃, and lubricating the inner wall of the extrusion barrel and the surface of the mandrel with graphite emulsion; ② Before extrusion, the billet is rapidly heated to 1170℃~1220℃ using electromagnetic induction; ③ After heating and exiting the furnace, the inner and outer surfaces of the billet are evenly coated with glass powder lubricant and placed in the extrusion barrel, with a glass lubricating pad placed at the entrance of the extrusion die. The inner diameter of the extrusion barrel is 5mm~10mm larger than the outer diameter of the billet after reaming; the extrusion speed is 80mm / s~200mm / s; the extrusion ratio is 4.0~25.0; after extrusion, the double-layer alloy composite seamless tube is air-cooled to room temperature.

[0025] Glass powder lubricant is used for lubrication during the upsetting, hot expansion, and hot extrusion stages. This lubricant consists of SiO2, Al2O3, CaO, MgO, TiO2, K2O, Na2O, and B2O3. The mass percentage composition of the glass powder lubricant is 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%. Based on the characteristics of the extrusion process, a suitable ratio of glass powder composition is selected. The shape of the glass pad used for extrusion is determined by the working surface of the extrusion die and the shape of the front end of the billet. The inner diameter of the glass pad is 15mm–40mm larger than the diameter of the tube, and the thickness of the glass pad is 15mm–25mm.

[0026] This invention discloses a method for producing a double-layer alloy composite seamless tube. A transition layer of nickel is pre-plated at the bonding surface using electroplating, ensuring a strong bond between the inner and outer alloy layers. This facilitates alloy bonding during extrusion and reduces delamination defects. The outer alloy is low-carbon steel with high strength, while the inner alloy is a nickel-based alloy with excellent corrosion resistance, saving precious metals and reducing material costs. The presence of head and tail pads reduces extrusion pressure, promoting uniform metal flow during composite tube forming, reducing processing defects, and improving yield. The seamless tube produced by this invention exhibits high dimensional accuracy, good surface quality, dense internal structure, fine grains, and stable mechanical properties. It possesses comprehensive performance characteristics of high strength, high toughness, and good corrosion resistance, surpassing the performance of single-alloy steel tubes. Attached Figure Description

[0027] Figure 1 A schematic diagram of the structure of a double-layer alloy composite billet after upsetting and machining;

[0028] Figure 2 This is a schematic diagram of the process flow for the production method of the double-layer alloy composite seamless tube of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of a vertical reamer;

[0030] Figure 4 This is a schematic diagram of a horizontal extrusion press.

[0031] Figure 5 This is a schematic diagram of the cold rolling process;

[0032] Figure 6 for Figure 5 The A-direction graph.

[0033] Wherein: 1—head pad, 2—outer layer of billet, 3—inner layer of billet, 4—tail pad, 5—flared mouth, 6—composite billet, 7—composite seamless tube, 8—core rod, 9—pre-rolled tube, 10—post-rolled tube, 11—upper roll, 12—lower roll, 17—ejection mechanism, 18—expansion barrel base, 19—shear ring support, 20—shear ring, 21—expansion barrel, 22—expansion rod, 23—expansion head, 24—die base, 25—extrusion die, 26—die support, 27—extrusion cylinder liner, 28—extrusion cylinder intermediate layer, 29—extrusion cylinder outer sleeve, 30—core rod, 31—extrusion pad, 32—extrusion rod. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the embodiments and accompanying drawings. The scope of protection of the present invention is not limited to the embodiments, and any modifications made by those skilled in the art within the scope defined by the claims also fall within the scope of protection of the present invention.

[0035] like Figure 3 The diagram shows a vertical reaming machine, equipped with an ejector mechanism 17, a reaming barrel base 18, a shearing ring support 19, a shearing ring 20, a reaming barrel 21, a reaming pin 22, and a reaming head 23. 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 shearing ring is 1mm to 2mm larger than the working section diameter of the reaming head. The reaming pin must not deviate more than 1mm from the centerline of the reaming barrel. The reaming barrel has a taper of 0.4mm to 1mm along its inner length. The reaming barrel base and the reaming barrel are fixedly connected by high-strength bolts. The reaming pin is connected to a force transmission rod via a threaded connector. The reaming barrel base supports the shearing ring support, which in turn supports both the shearing ring and the billet. The shearing ring supports the billet and removes excess material. The force transmission rod applies reaming force to the reaming head via the reaming pin. With the flared end of the billet facing upwards, the reaming head is placed at the flared end of the billet for reaming.

[0036] like Figure 4The image shows a horizontal extrusion press, equipped with a die holder 24, an extrusion die 25, a die support 26, an extrusion barrel liner 27, an extrusion barrel intermediate layer 28, an extrusion barrel outer layer 29, a mandrel 30, an extrusion pad 31, and an extrusion rod 32. The die holder and die support are fixed by bottom slots. The front end structure of the extrusion barrel is designed to correspond to the die holder structure. The extrusion barrel has a taper of 0.3mm to 1mm along its inner length. The cavity of the die support is 15mm to 30mm larger than the cavity of the extrusion die. The extrusion rod's deviation from the centerline of the extrusion barrel must not exceed 0.5mm. The gap between the outer circle of the extrusion pad and the inner hole of the extrusion barrel is 1.0mm to 1.5mm. The gap between the inner hole of the extrusion pad and the mandrel is 1.5mm to 2.5mm. The extrusion pad is 200mm to 210mm long. The front end of the extrusion pad is the billet, and the rear end is the extrusion rod. The extrusion pad transmits the thrust of the extrusion rod. The extrusion die consists of an inlet transition zone, an intermediate sizing zone, and an outlet reverse cone. During operation, the extrusion rod, mandrel, and extrusion barrel are powered by hydraulic cylinders, and the extrusion barrel moves back and forth via the bottom slide.

[0037] like Figure 5 The diagram shows a two-roll cold rolling mill, comprising an upper roll 11 and a lower roll 12. The cold rolling process includes composite billet 6, composite seamless tube 7, mandrel 8, pre-rolled tube 9, and post-rolled tube 10. One or more cold rolling passes are performed, with a feed rate of 2.5–3.5 mm / pass, a rolling speed of 30–50 passes / minute, and a deformation of 30%–50% per pass. After each cold rolling pass, annealing and degreasing are performed in a vacuum furnace or an atmosphere-protected furnace.

[0038] Example 1

[0039] The double-layer alloy composite seamless tube is made of 15MnV / N08825, with an outer layer of 15MnV and an inner layer of N08825. The nominal dimensions are φ178mm (outer diameter) × 11mm (outer layer thickness 7.5mm + inner layer thickness 3.5mm), with a length greater than 3m. The actual inner layer wall thickness is required to be between 2.5mm and 4.5mm. The production steps are as follows:

[0040] (1) Blank preparation: including calculating dimensions, electroplating, assembly and welding.

[0041] ① Theoretical calculation: Based on the finished dimensions of the double-layer alloy composite seamless tube, the deformation distribution process is calculated by reverse deduction: Double-layer alloy billet assembly φ357mm (outer diameter) / φ200.6mm (middle diameter) → upset billet φ363mm (outer diameter) / φ206.6mm (middle diameter) → machined billet φ357mm (outer diameter) / φ206.6mm (middle diameter) / φ75mm (inner diameter) → extruded tube φ219mm (outer diameter)×16mm (outer layer thickness 10.86mm + inner layer thickness 5.14mm) → cold-rolled tube φ178mm (outer diameter)×11mm (outer layer thickness 7.5mm + inner layer thickness 3.5mm), that is, the inner alloy bar diameter is φ200.6mm and the outer alloy bar diameter is φ357mm.

[0042] ② Blanking: Cut the inner alloy bar and the outer alloy bar into equal lengths of 500mm, and machine welding bevels at both ends. The outer diameter of the inner alloy billet is 1mm smaller than the inner diameter of the outer alloy billet. After processing, the outer diameter of the inner alloy billet is φ200.1mm and the inner diameter of the outer alloy billet is φ201.1mm.

[0043] ③ Electroplating: A layer of nickel metal with a thickness of 0.15mm is electroplated onto the joint surface of the inner alloy blank and the outer alloy blank.

[0044] ④ Billet assembly: The inner and outer alloy bars are assembled together in a vacuum chamber and the two ends are sealed and welded to form a double-layer alloy billet. The nominal specifications of the double-layer alloy billet are φ357mm (outer diameter) / φ200.6mm (middle diameter).

[0045] ⑤ Head and tail pad welding: Weld a head pad to the head of the double-layer alloy billet and a tail pad to the tail. The head pad is 120mm to 150mm long and the tail pad is 60mm to 100mm long. The head pad and tail pad are made of low carbon steel.

[0046] (2) Upsetting: First, coat the double-layer alloy billet with an anti-oxidation coating, heat it to 100℃~150℃ and hold it at that temperature for 1 hour to dry. Then, heat it in a resistance furnace to 700℃~800℃ and hold it at that temperature for 3 to 5 hours for preheating. Finally, heat it in an electromagnetic induction heating furnace to 1170℃~1220℃. After removing it from the furnace, evenly roll-coat the outer surface with glass powder lubricant. Finally, place it in an upsetting barrel with an inner diameter 6mm larger than the outer diameter of the double-layer alloy billet for upsetting to eliminate the gap between the inner and outer layers of the double-layer alloy billet. After upsetting, air-cool it to room temperature. The specifications of the upset billet are φ363mm (outer diameter) / φ206.6mm (middle diameter).

[0047] (3) Blank Machining: After upsetting, remove 3mm from one side of the outer diameter of the double-layer alloy blank and machine a 75mm diameter through hole in the center. Machin a flared mouth at the inner hole of the head pad and a 30mm radius corner at the outer diameter. Grind and polish the inner and outer surfaces to remove defects such as dents and tool marks. The surface roughness Ra≤3.2μm. The machining blank specifications are φ357mm (outer diameter) / φ206.6mm (middle diameter) / φ75mm (inner diameter).

[0048] (4) Hot expansion; The billet is placed in the expansion barrel of a vertical expansion machine for expansion. The steps include: ① Preheating the expansion barrel to 100℃~200℃. ② Coating the billet with an anti-oxidation coating, heating it to 100℃~150℃, holding it at that temperature for 1 hour, heating it in a resistance furnace to 800℃~900℃, holding it at that temperature for 3 hours~5 hours, and then heating it in an electromagnetic induction heating furnace to 1150℃~1170℃. ③ Before expansion, coating the inner and outer surfaces of the billet with glass powder lubricant, placing it in the expansion barrel with the flared end facing upwards, placing the pre-prepared lubricating glass bowl at the flared end, and letting it stand for 1.5min~2.5min. Then placing the expansion head above the lubricating glass bowl and expanding the hole at a speed of 150mm / s~250mm / s, with an expansion head diameter of 200mm and an inner diameter of 369mm for the expansion barrel.

[0049] (5) Hot Extrusion: The hot-expanded billet is placed in the extrusion barrel of a horizontal extruder for extrusion. The steps include: ① Preheating the extrusion barrel to 250℃~350℃, preheating the conical extrusion die and mandrel to 300℃~350℃, and lubricating the inner wall of the extrusion barrel and the surface of the mandrel with graphite emulsion. ② Before extrusion, the billet is rapidly heated to 1170℃~1220℃ using electromagnetic induction. ③ After heating and exiting the furnace, the inner and outer surfaces of the billet are evenly coated with glass powder lubricant, placed in the extrusion barrel, and a glass lubricating pad is placed at the entrance of the extrusion die. The inner diameter of the extrusion barrel is 5mm to 10mm larger than the outer diameter of the billet after expansion. The extrusion speed is 80mm / s to 200mm / s. The inner diameter of the extrusion barrel is 375mm, the mandrel diameter is 189.2mm, and the inner diameter of the extrusion die is 223.4mm. After extrusion, the double-layer alloy composite seamless tube is air-cooled to room temperature. The specifications of the extruded tube after cooling are φ219mm (outer diameter) × 16mm (outer layer thickness 10.86mm + inner layer thickness 5.14mm).

[0050] (6) Heat treatment: Heat the extruded double-layer alloy composite seamless tube to 980℃ and hold for 0.5h to 1h, then air cool to room temperature after removing it from the furnace.

[0051] (7) Surface treatment: pickling and grinding to remove surface glass powder, oxide scale and defects.

[0052] (8) Cold rolling: using Figure 5The two-roll cold rolling mill shown performs one-pass cold rolling with a feed rate of 2.5-3.5 mm / pass and a rolling speed of 45 passes / minute. The cold-rolled tube has a specification of φ178 mm (outer diameter) × 11 mm (outer layer thickness 7.5 mm + inner layer thickness 3.5 mm). After cold rolling, it is degreased and annealed.

[0053] (9) Finishing process: Inspection - Marking - Bundling.

[0054] Ultrasonic testing was performed on the produced 15MnV / N08825 double-layer alloy composite seamless tubes, and no delamination defects were found. The sampling inspection data are shown in Table 1.

[0055] Table 1.15 MnV / N08825 Double-Layer Alloy Composite Seamless Tubes - Sampling and Testing Results

[0056] project Bonding force / MPa bending Flatten flaring Sample 1#-1 325 qualified qualified qualified Sample 1#-2 308 qualified qualified qualified Technical indicators ≥250 No delamination or cracks No delamination or cracks No delamination or cracks

[0057] Example 2

[0058] The double-layer alloy composite seamless tube is made of 16Mn / N08800, with the outer layer being 16Mn and the inner layer being N08800. The nominal specifications are φ114mm (outer diameter) × 10mm (outer layer thickness 7mm + inner layer thickness 3mm), with a length greater than 2.5mm. The actual wall thickness of the inner layer is required to be 2mm to 4mm.

[0059] The specific production steps are as follows:

[0060] (1) Blank preparation: including calculating dimensions, electroplating, assembly and welding.

[0061] ① Theoretical calculation: Based on the finished dimensions of the double-layer alloy composite seamless tube, the deformation distribution process is calculated by reverse deduction: Double-layer alloy billet assembly φ242mm (outer diameter) / φ133.3mm (middle diameter) → upset billet φ248mm (outer diameter) / φ139.3mm (middle diameter) → machined billet φ242mm (outer diameter) / φ139.3mm (middle diameter) / φ65mm (inner diameter) → extruded tube φ161mm (outer diameter)×18mm (outer layer thickness 12.49mm + inner layer thickness 5.51mm) → cold-rolled tube φ133mm (outer diameter)×13mm (outer layer thickness 9.07mm + inner layer thickness 3.93mm) → cold-rolled tube φ114mm (outer diameter)×10mm (outer layer thickness 7mm + inner layer thickness 3mm), that is, the inner alloy bar diameter is φ133.3mm and the outer alloy bar diameter is φ242mm.

[0062] ② Blanking: Cut the inner alloy bar and the outer alloy bar into equal lengths of 650mm, and machine welding bevels at both ends. The outer diameter of the inner alloy billet is 1.4mm smaller than the inner diameter of the outer alloy billet. After processing, the outer diameter of the inner alloy billet is φ132.6mm and the inner diameter of the outer alloy billet is φ134.0mm.

[0063] ③ Electroplating: A layer of nickel metal with a thickness of 0.25mm is electroplated on the bonding surfaces of the inner alloy blank and the outer alloy blank.

[0064] ④ Billet assembly: The processed inner and outer alloy bars are assembled together in a vacuum chamber and the two ends are sealed to form a double-layer alloy billet. The nominal specifications of the double-layer alloy billet are φ242mm (outer diameter) / φ133.3mm (middle diameter).

[0065] ⑤ Head and tail pad welding: Weld a head pad to the head of the processed double-layer alloy billet and a tail pad to the tail. The head pad is 120mm to 150mm long and the tail pad is 60mm to 100mm long. The head pad and tail pad are made of low carbon steel.

[0066] (2) Upsetting: First, coat the double-layer alloy billet with an anti-oxidation coating, heat it to 100℃~150℃ and keep it at that temperature for 1 hour to dry it, then heat it in a resistance furnace to 700℃~800℃ and keep it at that temperature for 3 hours~3.5 hours for preheating, then heat it in an electromagnetic induction heating furnace to 1170℃~1200℃. After taking it out of the furnace, evenly roll a glass powder lubricant onto the outer surface, and finally put it into an upsetting barrel with an inner diameter 6mm larger than the outer diameter of the double-layer alloy billet for upsetting to eliminate the gap between the inner and outer layers of the double-layer alloy billet. After upsetting, air cool it to room temperature. The specifications of the upset billet are φ248mm (outer diameter) / φ139.3mm (middle diameter).

[0067] (3) Blank machining: After upsetting, the outer edge of the double-layer alloy blank is machined off by 3mm, and a through hole with a diameter of 65mm is machined in the center. A flared mouth is machined at the inner hole of the head pad, and an R30mm radius is machined at the outer circle; the inner and outer surfaces are ground and polished to remove defects such as dents and tool marks. The surface roughness Ra≤3.2μm. The specifications of the machined blank are φ242mm (outer diameter) / φ139.3mm (middle diameter) / φ65mm (inner diameter).

[0068] (4) Hot Reaming: The processed billet is placed in the reaming barrel of a vertical reaming machine for reaming. The steps include: ① Preheating the reaming barrel to 100℃~200℃. ② Coating the billet with an anti-oxidation coating, heating it to 100℃~150℃ and holding it for 1 hour, heating it to 800℃~900℃ in a resistance furnace and holding it for 3 hours~5 hours, and then heating it to 1150℃~1170℃ in an electromagnetic induction heating furnace. ③ Before reaming, coating the inner and outer surfaces of the billet with glass powder lubricant, placing it in the reaming barrel with the flared end facing upwards, placing the pre-prepared lubricating glass bowl at the flared end, and letting it stand for 1.5min~2.0min. Then placing the reaming head above the lubricating glass bowl and reaming at a speed of 150mm / s~250mm / s, with a reaming head diameter of 135mm and an inner diameter of reaming barrel of 250mm.

[0069] (5) Hot Extrusion: The hot-expanded billet is placed in the extrusion barrel of a horizontal extruder for extrusion. The steps include: ① Preheating the extrusion barrel to 250℃~350℃, preheating the conical extrusion die and mandrel to 300℃~350℃, and lubricating the inner wall of the extrusion barrel and the surface of the mandrel with graphite emulsion. ② Before extrusion, the billet is rapidly heated to 1170℃~1210℃ using electromagnetic induction. ③ After heating and exiting the furnace, the inner and outer surfaces of the billet are evenly coated with glass powder lubricant and placed in the extrusion barrel. A glass lubricating pad is placed at the entrance of the extrusion die. The inner diameter of the extrusion barrel is 5mm~10mm larger than the outer diameter of the expanded billet, the extrusion speed is 100mm / s~200mm / s, the inner diameter of the extrusion barrel is 255mm, the diameter of the mandrel is 126mm, and the inner diameter of the extrusion die is 164mm. After extrusion, the double-layer alloy composite seamless tube is air-cooled to room temperature. The dimensions of the extruded tube after cooling are φ161mm (outer diameter) × 18mm (outer layer thickness 12.49mm + inner layer thickness 5.51mm).

[0070] (6) Heat treatment: Heat the extruded double-layer alloy composite seamless tube to 1150℃ and hold for 0.5h to 1h, then air cool to room temperature after removing it from the furnace.

[0071] (7) Surface treatment: pickling and grinding to remove surface glass powder, oxide scale and defects.

[0072] (8) Cold rolling: using Figure 5 The two-roll cold rolling mill shown performs two-pass cold rolling with a feed rate of 2.5–3.5 mm / pass and a rolling speed of 45 passes / minute. The first pass cold rolling specification is φ133 mm (outer diameter) × 13 mm (outer layer thickness 9.07 mm + inner layer thickness 3.93 mm). The second pass cold rolling specification is φ114 mm (outer diameter) × 10 mm (outer layer thickness 7 mm + inner layer thickness 3 mm). After each cold rolling pass, degreasing and annealing are performed.

[0073] (9) Finishing process: Inspection - Marking - Bundling.

[0074] Ultrasonic testing was performed on the produced 16Mn / N08800 double-layer alloy composite seamless tubes, and no delamination defects were found. The sampling inspection data are shown in Table 2.

[0075] Table 2.16 Sampling and testing results of Mn / N08800 double-layer alloy composite seamless tubes

[0076] project Bonding force / MPa bending Flatten flaring Sample 2#-1 265 qualified qualified qualified Sample 2#-2 278 qualified qualified qualified Technical indicators ≥210 No delamination or cracks No delamination or cracks No delamination or cracks

Claims

1. A method of producing a double-alloyed composite seamless pipe, characterized by: The production method comprises the following steps: (Ⅰ) blank preparation: selecting suitable outer layer alloy bar and inner layer alloy bar of double-layer alloy composite seamless pipe; the outer layer material of the double-layer alloy composite seamless pipe is 16Mn, 12MnV, 15MnV or 20MnV, and the inner layer material is N06022, N10276, GH4169, N08825, N06625, N09925, N08028, N06200 or N08800; the blank preparation process comprises: (1) theoretical calculation: according to the size of the finished product of the double-layer alloy composite seamless pipe, the size of the inner layer alloy bar and the outer layer alloy bar is reversely calculated; (2) blanking: the inner layer alloy bar and the outer layer alloy bar are blanked and processed in equal lengths of 400mm-1200mm, the outer diameter of the inner layer alloy blank is smaller than the inner diameter of the outer layer alloy blank by 0.6mm-1.5mm, and welding bevels are processed at both ends; (3) electroplating: a layer of nickel metal with a thickness of 0.1mm-0.3mm is respectively electroplated on the bonding surface of the inner layer alloy blank and the outer layer alloy blank; (4) blank assembly: the inner and outer layer alloy bars treated in step (3) are assembled together in a vacuum chamber, both ends are sealed, and a double-layer alloy blank is formed; (5) head and tail pad welding: the head pad of the double-layer alloy blank treated in step (4) is welded, and the tail pad is welded, wherein the length of the head pad is 120mm-150mm, the length of the tail pad is 60mm-100mm, and the material of the head pad and the tail pad is low-carbon steel; (Ⅱ) upsetting; the double-layer alloy blank is coated with an anti-oxidation coating, heated to 100℃-150℃, and dried for 1h; heated to 700℃-800℃ in a resistance furnace, and preheated for 3h-5h; heated to 1170℃-1220℃ in an electromagnetic induction heating furnace; the outer surface is uniformly rolled and coated with glass powder lubricant, and placed in an upsetting barrel with an inner diameter larger than the outer diameter of the double-layer alloy blank by 6mm-12mm for upsetting, and then air-cooled to room temperature; (Ⅲ) blank machining: the outer circle of the double-layer alloy blank after upsetting treatment is machined by 3mm-5mm on one side, a through hole with a diameter of 35mm-100mm is machined at the center, a horn mouth is machined at the inner hole of the head pad, and an R30mm round corner is machined at the outer circle; the inner and outer surfaces are ground and polished to remove scratches and tool marks, and the surface roughness Ra≤3.2μm; (Ⅳ) hot expanding; the blank after machining is placed in an expanding barrel of a vertical expanding machine for hot expanding; (Ⅴ) hot extrusion; the blank after hot expanding is placed in an extrusion barrel of a horizontal extrusion machine for hot extrusion; (Ⅵ) heat treatment; the double-layer alloy composite seamless pipe after extrusion is heated to 950℃-1050℃, and held for 0.5h-1h, and then air-cooled to room temperature; (Ⅶ) surface treatment: pickling and grinding to remove surface glass powder, oxide skin and defects; (Ⅷ) cold rolling: one pass or multiple passes of cold rolling are performed by using a two-roll cold rolling mill, the feed amount is 2.5-3.5mm / pass, the rolling speed is 30-50 times / minute, the deformation amount of each pass is 30%-50%, and oil removal and annealing are performed after each pass of cold rolling, and the annealing is performed in a vacuum furnace or an atmosphere protection furnace; (Ⅸ) finishing treatment: inspection, marking and bundling.

2. The method of producing a double alloyed composite seamless pipe according to claim 1, characterized by: The outer layer alloy bar is a continuous casting billet or a rolled billet, and the inner layer alloy bar is a forged billet.

3. The method of producing a double alloyed composite seamless pipe according to claim 1, characterized by: The hot expanding step comprises: ① the outer diameter of the billet is 10mm-12mm smaller than the inner diameter of the expanding barrel, and the expanding barrel is preheated to a temperature of 100℃-200℃; ② the billet is coated with an anti-oxidation coating, heated to 100℃-150℃ for 1h, heated to 800℃-900℃ in an electric resistance furnace for 3h-5h, and heated to 1150℃-1170℃ in an electromagnetic induction heating furnace; ③ the inner and outer surfaces of the billet are coated with a glass powder lubricant before expanding, and the billet is placed in the expanding barrel with the trumpet end facing upwards, a lubricating glass bowl prepared in advance is placed at the trumpet end, and the billet is left to stand for 1.5min-2.5min, and then the expanding head is placed above the lubricating glass bowl to expand the billet, the expanding speed is 150mm / s-250mm / s, and the expanding ratio is 1.02-1.

38.

4. The method of producing a double alloyed composite seamless pipe according to claim 1, characterized by: The hot extrusion step comprises: ① the extrusion barrel is preheated to a temperature of 250℃-350℃, the conical extrusion die and the mandrel are preheated to a temperature of 300℃-350℃, and the inner wall of the extrusion barrel and the surface of the mandrel are coated with graphite milk for lubrication; ② the billet is rapidly heated to 1170℃-1220℃ by electromagnetic induction before extrusion; ③ after heating and leaving the furnace, the billet is uniformly coated with a glass powder lubricant, and the billet is placed in the extrusion barrel, and a glass lubricating pad is placed at the entrance of the extrusion die; the inner diameter of the extrusion barrel is 5mm-10mm larger than the outer diameter of the billet after expanding, the extrusion speed is 80mm / s-200mm / s, the extrusion ratio is 4.0-25.0, and the double-layer alloy composite seamless pipe is air-cooled to room temperature after extrusion.

5. The method of producing a double alloyed composite seamless pipe according to claim 1, characterized by: The upsetting, hot expanding and hot extruding stages are lubricated with a glass powder lubricant, and the glass powder lubricant is composed of SiO2, Al2O3, CaO, MgO, TiO2, K2O, Na2O and B2O3; the glass powder lubricant comprises, 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%.

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