NS3306 corrosion-resistant alloy pipe and production process thereof

Abstract

The NS3306 corrosion-resistant alloy pipe is a seamless pipe with the outer circle diameter being 30-168 mm and the wall thickness being 1.9-20 mm, the tensile strength Rm of the NS3306 corrosion-resistant alloy pipe is larger than or equal to 690 MPa, the Rp0.2 yield strength of the NS3306 corrosion-resistant alloy pipe is larger than or equal to 276 MPa, the elongation of the NS3306 corrosion-resistant alloy pipe is larger than or equal to 30%, and the grain size of the NS3306 corrosion-resistant alloy pipe is larger than or equal to 3.0 grades. The production process of the NS3306 corrosion-resistant alloy pipe comprises the steps of blank preparation (theoretical calculation, alloy smelting and centrifugal casting), blank processing, blank heating, pierced billet extrusion, cold rolling, solution treatment of a finished pipe, finishing treatment and the like. The NS3306 corrosion-resistant alloy pipe is produced by adopting a process route combining centrifugal casting, hot extrusion and cold rolling, so that a blank forging procedure and a hot reaming procedure in a traditional process are omitted, a large-diameter inner hole is prevented from being machined in a blank, material waste is reduced, and meanwhile, energy consumption is also reduced. According to the method, the material utilization rate is increased, the process flow is short, the cost is low, and the produced pipe is high in size precision, good in surface quality and uniform in grain and has good mechanical and corrosion-resistant performance.

Description

Technical Field

[0001] The invention relates to the processing of corrosion-resistant alloy materials that are difficult to deform, in particular to a NS3306 corrosion-resistant alloy pipe and its production process. Background Art

[0002] NS3306 is a solid solution strengthened nickel-based alloy with Mo and Nb as the main strengthening elements. It has excellent corrosion resistance, oxidation resistance, mechanical properties and high temperature durability. It is mostly used to manufacture key parts in aerospace, petrochemical and other fields.

[0003] Seamless pipe is one of the common products of NS3306 alloy. NS3306 alloy seamless pipe has high deformation resistance and narrow deformation temperature range during hot working. Conventional forging process is slow and has poor precision; hot perforation process is prone to cracking; hot extrusion process puts the billet in a three-dimensional compressive stress state and is more conducive to improving the plastic deformation ability of the material, which is suitable for hot working of low plastic alloys. Therefore, the current mainstream production process of NS3306 alloy seamless pipe is: vacuum induction smelting + electroslag remelting + forging + outer rounding and inner boring + hole expansion + rough pipe extrusion + cold rolling, but this process has the following problems: First, multiple firings are required during the forging stage, which results in high energy consumption and high material loss; Second, the inner hole needs to be processed before expanding (i.e., the outer hole is rounded and the inner hole is bored). When extruding large-diameter pipes, the deformation of the hole is relatively large, and the problem of cracking often occurs. In order to reduce the deformation of the hole, drilling a large-diameter inner hole will lead to excessive material waste. Third, when the extrusion temperature is too high, it is easy to produce coarse grains or cracks; when the extrusion temperature is too low, it is easy to cause the car to be stuck due to excessive extrusion pressure. In addition, when using conventional flat dies for extrusion, the metal deformation is unstable, and the rough pipe is prone to extrusion defects such as cracks and delamination in the wall thickness direction; Fourthly, after the extrusion of the rough pipe is completed, the billet of about 25mm to 50mm at the tail cannot be extruded, resulting in material waste. Summary of the invention

[0004] In order to solve the above deficiencies in the prior art, the present invention aims to provide a NS3306 corrosion-resistant alloy pipe and a production process thereof, so as to achieve the purpose of reducing material waste, reducing extrusion defects and improving the yield rate.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present invention is as follows: a NS3306 corrosion-resistant alloy pipe, whose components by mass percentage are: C: ≤0.06, Si: ≤0.50, Nb: 3.50-4.00, Mo: 8.5-9.0, Cr: 20-23, Fe: ≤5, Ni: 57-64.5, Cu: ≤0.30, Al: ≤0.25, Ti: ≤0.35, Co: ≤1.0, Mn: ≤0.45, S: ≤0.010, P: ≤0.015, B: ≤0.006, Mg: ≤0.10, W: ≤0.10, V: ≤0.10, and the rest are unavoidable impurities.

[0006] As a limitation of the present invention, the NS3306 corrosion-resistant alloy pipe is a seamless pipe with an outer diameter of 30 to 168 mm and a wall thickness of 1.9 to 20 mm.

[0007] As a further limitation of the present invention, the properties of the NS3306 corrosion-resistant alloy pipe are: tensile strength Rm ≥ 690 MPa, Rp0.2 yield strength ≥ 276 MPa, elongation ≥ 30%, and grain size ≥ grade 3.0.

[0008] The present invention also discloses a production process of NS3306 corrosion-resistant alloy pipe, comprising the following steps performed in sequence: S1. Billet preparation: NS3306 corrosion-resistant alloy hollow tube billet is produced by centrifugal casting process; S2. Billet processing: Process the outer wall and inner wall of the hollow tube billet to remove defects on the inner and outer surfaces; S3, billet heating: After the hollow tube billet is preheated in the resistance furnace, it is transferred to the electromagnetic induction heating furnace for two consecutive heatings; S4, rough tube extrusion: the heated hollow tube blank is extruded into a rough tube by a horizontal extruder; S5, cold rolling: use a two-roll cold rolling mill for two to seven passes of cold rolling, with a deformation of 30% to 55% per pass, a feed of 2.6 to 5.6 mm / time, a rolling speed of 30 to 60 times / minute, and control the deformation of the last pass to be between 30% and 50%; S6, solution treatment of finished pipe: when the furnace temperature is 1000-1025°C, the pipe formed by cold rolling in step S5 is placed in the furnace, heated for 5-10 min / mm, and transferred to a water pool within 60 seconds after heating to be rapidly cooled using water as a cooling medium, and finally subjected to finishing treatment to obtain the NS3306 corrosion-resistant alloy pipe as described above.

[0009] As a limitation of the present invention, step S1 includes the following steps performed in sequence: S1.1. Theoretical calculation: Based on the size and weight of the finished tube, combined with the production process, the size and weight of the hollow tube blank to be prepared can be inferred; S1.2, Alloy smelting: pure metal is used to melt the ingredients. After the alloy is baked at 200-500℃, it is melted in a medium frequency furnace. During this period, argon blowing is used to protect the furnace mouth to prevent excessive gas content in the liquid metal; S1.3, centrifugal casting: pouring the liquid alloy into a centrifugal casting machine, and preparing a hollow tube blank according to the calculation result of step S1.1.

[0010] As a further limitation of the present invention, in the centrifugal casting stage of step S1.3, The thickness of the tube mold coating is 0.9 to 2.2 mm; The pouring temperature is 1500~1550℃; The temperature of the tube mold is 240-300℃ during coating baking, and the temperature of the tube mold is reduced to 160-200℃ before pouring; The tube die starts at 800 rpm and then gradually increases to 1130 rpm without changing speed until the tube is pulled out; Argon protection is used during the centrifugal pouring stage. The pressure is maintained at 0.5MPa before and during pouring. After pouring, it is adjusted to 0.2MPa and maintained until the tube mold slows down. Pouring rhythm: The amount of liquid alloy in the first batch should be 60-300kg / 5s, and the subsequent pouring can be slow, and the total pouring time is controlled within 60-90s; Cooling method: After pouring, spray water to cool the tube mold until the inner surface of the hollow tube is 1300-1360℃, then push the tube and quench it with water. The temperature of the hollow tube is 1050-1160℃ when entering the water.

[0011] As another limitation of the present invention, in step S2, the head of the hollow tube blank is also processed, specifically: a chamfer with an angle of 30° is processed on the outer circle of the head of the hollow tube blank, and a fillet with a radius of 20 mm is processed at the connection between the chamfer and the hollow tube blank body.

[0012] As a further limitation of the present invention, in step S3, the hollow tube blank is preheated to 950°C in a resistance furnace and kept warm for 3 to 5 hours; after being transferred to the electromagnetic induction heating furnace, the hollow tube blank is heated to 1140 to 1160°C for the first time at a power of 500 to 600 kW and a frequency of 40 to 65 Hz for a holding time of 1 to 3 minutes, and the hollow tube blank is heated to 1180 to 1215°C for a second time at a power of 650 to 900 kW and a frequency of 70 to 100 Hz, and then taken out of the furnace.

[0013] As a further limitation of the present invention, step S4 includes the following steps performed in sequence: S4.1. Heat the inner wall of the extrusion barrel of the horizontal extruder to 310-500°C, and heat the surface of the extrusion die and the core rod to 250-450°C; S4.2. Apply glass powder on the inner and outer surfaces of the high-temperature hollow tube blank, and then transfer it to the extrusion cylinder. The inner diameter of the extrusion cylinder is 5 to 11 mm larger than the outer diameter of the hollow tube blank, and a glass pad is placed at the entrance of the extrusion die; S4.3, heat the carbon steel tail pad to 900-1050℃, place it at the tail of the high-temperature hollow tube billet, and extrude the carbon steel tail pad together with the hollow tube billet; S4.4. The power system of the horizontal extruder enables the extrusion rod to push the hollow tube billet to move in the extrusion direction. The forward speed of the hollow tube billet is 30 to 150 mm / s. The hollow tube billet passes through the cavity composed of the core rod and the extrusion die to become a rough tube. The extrusion ratio of the rough tube is 2.5 to 15. The extruded rough tube is cooled to room temperature in water at above 900°C.

[0014] As a further limitation of the present invention, in step S5, the intermediate tube before each cold rolling needs to be pickled and degreased, solution annealed, and pickled and descaled in sequence; the solution annealing process is: when the furnace temperature rises to 1160°C, the intermediate tube is placed in the furnace for a heating time of 5 to 10 min / mm, and after heating, it is transferred to a water pool within 70S to achieve rapid cooling using water as a cooling medium.

[0015] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art: The present invention adopts a process route combining centrifugal casting + hot extrusion + cold rolling to produce NS3306 corrosion-resistant alloy pipes, eliminating the billet forging process and hot hole expansion process in the traditional process, avoiding the processing of large-diameter inner holes on the billet, reducing material waste, and also reducing energy consumption.

[0016] The present invention adopts a double cone die as an extrusion die in the rough pipe extrusion stage, which reduces the extrusion force, facilitates the smooth flow of metal, reduces the degree of deformation, and thus avoids extrusion defects such as cracks and delamination. In addition, a carbon steel tail pad is added behind the billet to solve the problem that the billet of about 25mm to 50mm at the tail cannot be extruded after the rough pipe extrusion is completed, thereby improving the yield rate.

[0017] The present invention adopts a two-roller cold rolling mill to perform two to seven passes of cold rolling treatment in the cold rolling stage, and controls the deformation amount of each pass to 30 to 50%, which is beneficial to improving the size uniformity and surface quality of the pipe, and further improving the performance quality of the pipe.

[0018] In summary, the present invention improves material utilization, shortens the process flow, and reduces costs. The produced pipes have high dimensional accuracy, good surface quality, uniform grains, and good mechanical and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a production process flow chart of NS3306 corrosion-resistant alloy pipe in an embodiment of the present invention; Figure 2 It is a schematic diagram of the longitudinal structure of a horizontal extruder in an embodiment of the present invention; Figure 3 Schematic diagram of the longitudinal section structure of the hollow tube blank in the embodiment of the present invention; Figure 4 Schematic diagram of the structure of the double cone mold in the embodiment of the present invention; wherein, Figure 4 a is the main view of the structural relationship of the double cone mold, Figure 4 b is a cross-sectional view of the structural relationship of the double cone mold; Figure 5 It is a schematic diagram of the structure of the mold base in the embodiment of the present invention; wherein, Figure 5 a is the structural relationship sectional view of the mold base, Figure 5 b is a schematic diagram of the three-dimensional structure of the mold base; In the figure: 1. hollow tube blank; 2. double-cone die; 3. die base; 4. die support; 5. extrusion cylinder; 6. mandrel; 7. extrusion pad; 8. extrusion rod; 9. mandrel force transmission rod; 10. tail pad; 11. first inlet die angle; 12. second inlet die angle; 13. sizing belt; 14. outlet anti-cone area; 15. circular platform. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and understand the present invention, and are not used to limit the present invention.

[0022] This embodiment discloses a NS3306 corrosion-resistant alloy pipe, which is a seamless pipe with an outer diameter of 30 to 168 mm and a wall thickness of 1.9 to 20 mm. Except for unavoidable impurities, its composition is as shown in Table 1: Table 1 Composition of NS3306 corrosion-resistant alloy pipe

[0023] The properties of the NS3306 corrosion-resistant alloy pipe disclosed in this embodiment are: tensile strength Rm ≥ 690 MPa, Rp0.2 yield strength ≥ 276 MPa, elongation ≥ 30%, and grain size ≥ grade 3.0.

[0024] This embodiment also discloses a production process of NS3306 corrosion-resistant alloy pipe. Figure 1As shown, taking the NS3306 corrosion-resistant alloy pipe with an outer diameter of 30 mm and a wall thickness of 1.95 mm as an example, the production process includes the following steps performed in sequence: S1. Billet preparation: NS3306 corrosion-resistant alloy hollow tube billet is produced by centrifugal casting process 1 S1.1, Theoretical calculation: Based on the size and weight of the finished tube, combined with the production process, the size and weight of the hollow tube blank 1 to be prepared are inferred. In this embodiment, the size of the hollow tube blank 1 is 230 mm outer diameter×100 mm inner diameter×1250 mm length.

[0025] S1.2 Alloy smelting: Pure metal is used to melt the ingredients. After the alloy is baked at 200-500℃, it is melted in a medium frequency furnace. During this period, argon blowing is used at the furnace mouth to prevent the gas content in the liquid metal from being too high.

[0026] In this stage, raw materials need to be added according to Table 1, specifically: first place the Ni plate densely in the medium frequency furnace, and then supply power at high power. After the Ni plate is melted, add electrolytic manganese and Si-Fe. Electrolytic manganese is added according to the middle limit of the component requirements, and Si-Fe is added according to the lower limit. Then add lime and fluorite to make reducing slag. The ratio of lime to fluorite is 5 to 8:1. The total slag making amount ensures that the slag layer thickness is 20 to 30 mm; The reducing agent mainly uses aluminum wire, and the amount of aluminum wire added is 0.2% of the amount of molten steel. The aluminum wire is only added to the slag layer and must not be added to the molten steel in large quantities. After the reducing slag turns white, other alloys are gradually added. The order of addition is generally: metallic chromium - molybdenum bar - Nb-Fe. Among them, metallic chromium needs to be added in small batches. Each time metallic chromium is added, a small amount of aluminum wire needs to be inserted into the slag layer. When adding metallic chromium to molten steel, it should be added to the molten steel and must not be added to the slag. For broken pieces of metallic chromium, the slag layer should be pulled apart and added to the molten steel to prevent the generation of chromium slag in the reducing slag, which causes the reducing slag to become viscous. All molybdenum bars must be added to the molten steel and must not be exposed on the slag surface; The temperature of the entire melting process shall not exceed 1600°C; After all the alloys are melted, samples are taken, the composition is tested, and the composition is fine-tuned based on the test results; Before leaving the furnace, easily oxidized alloys such as Ti-Fe and V-Fe are added. Since the Fe content in Ti-Fe is relatively high, accounting for about 70%, the effect of Ti-Fe on the Fe addition of the alloy should be considered during batching and spectral analysis.

[0027] S1.3, centrifugal casting: pouring the liquid alloy into a centrifugal casting machine, and preparing a hollow tube blank 1 according to the calculation result of step S1.1.

[0028] In this stage, before pouring the liquid alloy, it is necessary to scrape off the solid reduction slag on the surface, add 1-2 kg of fluorite, and melt the steel (using fluorite as a flux can lower the melting point and generate low-melting point compounds, thereby improving the fluidity of the reduction slag. In addition, fluorite can also desulfurize and dephosphorize during the smelting process, enhancing the forgeability and tensile strength of the metal); In this stage, the thickness of the tube mold coating is 0.9-2.2 mm; the pouring temperature is 1500-1550°C; the tube mold temperature is 240-300°C during coating baking, and the tube mold temperature is reduced to 160-200°C before pouring; In this stage, the tube mold starts with a speed of 800 rpm, then gradually increases to 1130 rpm, and does not change speed until the tube is pulled out (tube pulling refers to taking the hollow tube out of the tube mold); In this stage, argon gas protection is used, and 0.5MPa is maintained before and during pouring. After pouring, it is adjusted to 0.2MPa and maintained until the tube mold slows down. In this stage, the pouring rhythm adopted is: the first batch of liquid alloy should be guaranteed to be 60-300kg / 5s, and the subsequent pouring can be slow, and the total pouring time for all batches of liquid alloy pouring is controlled within 60-90s; In this stage, the cooling method adopted is: spray water to cool the tube mold after pouring is completed, until the inner surface of the hollow tube blank 1 is 1300-1360°C, the tube is pulled out, quenched with water, and the temperature of the hollow tube blank 1 is 1050-1160°C when entering the water.

[0029] S2. Billet processing: Process the outer wall and inner wall of the hollow tube billet 1 to remove defects on the inner and outer surfaces. The outer wall of the water-cooled hollow tube 1 is machined to be no less than 4mm on one side, and the inner wall is machined to be no less than 4.5mm on one side to remove defects on the inner and outer surfaces. After processing, the size of the hollow tube 1 is 217mm outer diameter × 110mm inner diameter × 600mm length. In addition, the inner hole deviation of the hollow tube 1 is ±0.5mm; the outer diameter deviation is ±1mm; the two ends are flat-headed, and the end face verticality is ≤1mm; the surface roughness Ra≤1.6μm, the length deviation is ±5mm, and the concentricity of the inner and outer circles is ≤1mm. In addition, it is necessary to machine a chamfer with an angle of 30° on the outer circle of the head of the hollow tube 1, and a fillet with a radius of 20mm is machined at the connection between the chamfer and the body of the hollow tube 1. The final shape of the hollow tube 1 is as follows Figure 3 It should be noted that the "head of the hollow tube 1" referred to in this embodiment is the end of the hollow tube 1 close to the extrusion die.

[0030] S3, billet heating: After the hollow tube billet 1 is preheated in the resistance furnace, it is transferred to the electromagnetic induction heating furnace for two consecutive heatings. The hollow tube blank 1 is preheated to 950°C in a resistance furnace for 3 to 5 hours; then it is transferred to an electromagnetic induction heating furnace and heated twice. The first heating power is 500 to 600 kW and the frequency is 40 to 65 Hz. The hollow tube blank 1 is heated to 1140 to 1160°C for 1 to 3 minutes. The second heating power is 650 to 900 kW and the frequency is 70 to 100 Hz. The hollow tube blank 1 is heated to 1180 to 1215°C and then taken out of the furnace.

[0031] S4, rough tube extrusion: the heated hollow tube blank 1 is extruded into a rough tube by a horizontal extruder S4.1. The inner wall of the extrusion barrel 5 of the horizontal extruder is heated to 310-500°C, and the surface of the extrusion die and the core rod 6 is heated to 250-450°C; S4.2, the inner and outer surfaces of the high-temperature hollow tube 1 are coated with glass powder, and then transferred to the extrusion cylinder 5. The inner diameter of the extrusion cylinder 5 is 5 to 11 mm larger than the outer diameter of the hollow tube 1, and a glass mat is placed at the entrance of the extrusion die; S4.3. Heat the carbon steel tail pad 10 to 900-1050°C, place it at the tail of the high-temperature hollow tube blank 1, and extrude the carbon steel tail pad 1 together with the hollow tube blank 1. The outer diameter of the carbon steel tail pad 10 is the same as the outer diameter of the hollow tube blank 1, the inner diameter of the carbon steel tail pad 10 is 5-6mm larger than the inner diameter of the hollow tube blank 1, and the length of the carbon steel tail pad 10 is 90mm. The specific dimensions of the carbon steel tail pad 10 in this embodiment are outer diameter 217mm×inner diameter 116mm×length 90mm. Adding the carbon steel tail pad 10 can extrude the entire hollow tube blank 1 into a rough tube, which can improve material utilization and facilitate the separation of the residual and rough tube; S4.4, the power system of the horizontal extruder makes the extrusion rod 8 push the hollow tube 1 to move in the extrusion direction, the forward speed of the hollow tube 1 is 30-150 mm / s, the hollow tube 1 passes through the cavity formed by the core rod 6 and the extrusion die to become a rough tube, the extrusion ratio of the rough tube is 2.5-15, and the extruded rough tube is cooled to room temperature by water at above 900°C. In this embodiment, the extrusion ratio of the rough tube is 5.2. The size of the extruded rough tube at room temperature is 131.5 mm in outer diameter × 15.5 mm in wall thickness.

[0032] It should be noted that the horizontal extruder used in this embodiment is improved on the basis of the existing structure. The specific improvements are: 1. A double cone die 2 is used as the extrusion die; 2. A tail pad 10 is added to the tail of the hollow tube 1. Figure 1As shown, the horizontal extruder includes a double cone die 2, a die base 3, a die support 4, an extrusion barrel 5, a core rod 6, a tail pad 10, an extrusion pad 7, an extrusion rod 8 and a core rod force transmission rod 9. Among them, the double cone die 2 (i.e., the extrusion die), the die base 3, the die support 4, the extrusion barrel 5, the core rod 6, the extrusion pad 7, the extrusion rod 8 and the core rod force transmission rod 9, the positional relationship and connection relationship between the above components are all prior art, and will not be repeated here. The tail pad 10 is arranged between the tail of the hollow tube 1 and the extrusion pad 7, as shown in FIG. Figure 1 Under the action of the oil pressure system, the extrusion rod 8 provides extrusion force to the hollow tube 1 through the extrusion pad 7 and the tail pad 10, and the hollow tube 1 passes through the cavity formed by the core rod 6 and the double cone die 2 to become a rough tube.

[0033] In this embodiment, the dimensions of the extrusion cylinder 5 are 800 mm in outer diameter×225 mm in inner diameter×1500 mm in length; the inner diameter of the extrusion die is 134.5 mm, and the diameter of the core rod 6 is 101 mm.

[0034] Further, the structure of the double cone mold 2 is as follows Figure 4 a and Figure 4 As shown in b, its external contour is the same as the shape of the positioning groove of the die base 3 for placing the double cone die 2, and has a conical surface with an angle γ' of 24°; its internal cavity is composed of the first inlet die angle 11, the second inlet die angle 12, the sizing belt 13 and the outlet anti-cone area 14, wherein the first inlet die angle 11β is 126°, the second inlet die angle 12β' is 35°, and the sizing belt 13 is 12mm long. In this embodiment, the first inlet die angle 11 and the second inlet die angle 12 are connected by a rounded transition, and the rounded radius is 8mm; the second inlet die angle 12 and the sizing belt 13 are also connected by a rounded transition, and the rounded radius is 12mm.

[0035] In this embodiment, a circular platform 15 is provided at the entrance of the mold base 3. Figure 5 a and Figure 5 As shown in FIG. 2 b, the width L of the circular platform 15 is 20-60 mm and is used to fix the glass pad. The cone angle γ at the position where the double cone mold 2 is installed inside the mold base 3 is 24°.

[0036] S5, cold rolling: two to seven passes of cold rolling are carried out using a two-roll cold rolling mill This embodiment has carried out six cold rolling processes, and the deformation process is as follows: the outer diameter of the rough pipe is 131.5mm×the wall thickness is 15.5mm-the outer diameter of the cold-rolled intermediate pipe is 114mm×the wall thickness is 12mm-the outer diameter of the cold-rolled intermediate pipe is 89mm×the wall thickness is 8.5mm-the outer diameter of the cold-rolled intermediate pipe is 76mm×the wall thickness is 5.2mm-the outer diameter of the cold-rolled intermediate pipe is 57mm×the wall thickness is 3.5mm-the outer diameter of the cold-rolled intermediate pipe is 44mm×the wall thickness is 2.45mm-the outer diameter of the cold-rolled intermediate pipe is 30mm×the wall thickness is 1.95mm. The deformation amount of each pass is 30% to 55%, the feed amount is 2.6 to 5.6mm / time, the rolling speed is 30 to 60 times / minute, and the cold rolling deformation amount of the last pass is controlled to be 30% to 50%.

[0037] In this embodiment, the intermediate tube before each cold rolling is first pickled to remove foreign matter such as oil, then subjected to solution annealing treatment, and then pickled to remove oxide scale. The solution annealing process is as follows: when the furnace temperature rises to 1160°C, the intermediate tube is placed in the furnace for a heating time of 5 to 10 min / mm, and after heating, it is transferred to a water pool within 70 seconds to achieve rapid cooling using water as a cooling medium. During cold rolling, the intermediate tube needs to be cut according to the length of the finished tube.

[0038] S6. Solution treatment and finishing treatment of finished tubes Solution treatment of finished pipes: When the furnace temperature is 1000-1025°C, the pipe formed by cold rolling in step S5 is placed in the furnace, heated for 5-10 min / mm, and transferred to a water pool within 60 seconds after heating to be quickly cooled using water as a cooling medium; Finishing treatment: After a series of treatments such as straightening, testing, surface treatment, flattening, and packaging, the target product - NS3306 corrosion-resistant alloy seamless pipe is obtained.

[0039] The product was tested and the results are shown in Table 2 and Table 3.

[0040] Table 2 Composition of the final product

[0041] Note: The rest are unavoidable impurities.

[0042] Table 3 Properties of the final product

[0043] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A NS3306 corrosion-resistant alloy pipe, characterized in that: Its components in mass percentage are: C: ≤0.06, Si: ≤0.50, Nb: 3.50~4.00, Mo: 8.5~9.0, Cr: 20~23, Fe: ≤5, Ni: 57~64.5, Cu: ≤0.30, Al: ≤0.25, Ti: ≤0.35, Co: ≤1.0, Mn: ≤0.45, S: ≤0.010, P: ≤0.015, B: ≤0.006, Mg: ≤0.10, W: ≤0.10, V: ≤0.10, and the rest are unavoidable impurities.

2. The NS3306 corrosion-resistant alloy pipe according to claim 1, characterized in that: The NS3306 corrosion-resistant alloy pipe is a seamless pipe with an outer diameter of 30 to 168 mm and a wall thickness of 1.9 to 20 mm.

3. The NS3306 corrosion-resistant alloy pipe according to claim 2, characterized in that: The properties of the NS3306 corrosion-resistant alloy pipe are as follows: tensile strength Rm ≥ 690 MPa, Rp0.2 yield strength ≥ 276 MPa, elongation ≥ 30%, and grain size ≥ grade 3.

0.

4. A production process for NS3306 corrosion-resistant alloy pipe, characterized in that: It includes the following steps, performed in order: S1. Billet preparation: NS3306 corrosion-resistant alloy hollow tube billet is produced by centrifugal casting process; S2. Billet processing: Process the outer wall and inner wall of the hollow tube billet to remove defects on the inner and outer surfaces; S3, billet heating: After the hollow tube billet is preheated in the resistance furnace, it is transferred to the electromagnetic induction heating furnace for two consecutive heatings; S4, rough tube extrusion: the heated hollow tube blank is extruded into a rough tube by a horizontal extruder; S5, cold rolling: use a two-roll cold rolling mill for two to seven passes of cold rolling, with a deformation of 30% to 55% per pass, a feed of 2.6 to 5.6 mm / time, a rolling speed of 30 to 60 times / minute, and control the deformation of the last pass to be between 30% and 50%; S6. Solution treatment of finished pipes: When the furnace temperature is 1000-1025°C, the pipe formed by cold rolling in step S5 is placed in the furnace, heated for 5-10 min / mm, and transferred to a water pool within 60 seconds after heating to be rapidly cooled using water as a cooling medium, and finally subjected to finishing treatment to obtain the NS3306 corrosion-resistant alloy pipe as claimed in claim 1.

5. The production process of NS3306 corrosion-resistant alloy pipe according to claim 4, characterized in that: The step S1 comprises the following steps which are performed in sequence: S1.

1. Theoretical calculation: Based on the size and weight of the finished tube, combined with the production process, the size and weight of the hollow tube blank to be prepared can be inferred; S1.2, Alloy smelting: pure metal is used to melt the ingredients. After the alloy is baked at 200-500℃, it is melted in a medium frequency furnace. During this period, argon blowing is used to protect the furnace mouth to prevent excessive gas content in the liquid metal; S1.3, centrifugal casting: pouring the liquid alloy into a centrifugal casting machine, and preparing a hollow tube blank according to the calculation result of step S1.

1.

6. The production process of NS3306 corrosion-resistant alloy pipe according to claim 5, characterized in that: In the centrifugal casting stage of step S1.3, The thickness of the tube mold coating is 0.9 to 2.2 mm; The pouring temperature is 1500~1550℃; The temperature of the tube mold is 240-300℃ during coating baking, and the temperature of the tube mold is reduced to 160-200℃ before pouring; The tube die starts at 800 rpm and then gradually increases to 1130 rpm without changing speed until the tube is pulled out; Argon protection is used during the centrifugal pouring stage. The pressure is maintained at 0.5MPa before and during pouring. After pouring, it is adjusted to 0.2MPa and maintained until the tube mold slows down. Pouring rhythm: The amount of liquid alloy in the first batch should be 60-300kg / 5s, and the subsequent pouring can be slow, and the total pouring time is controlled within 60-90s; Cooling method: After pouring, spray water to cool the tube mold until the inner surface of the hollow tube is 1300-1360℃, then push the tube and quench it with water. The temperature of the hollow tube is 1050-1160℃ when entering the water.

7. The production process of NS3306 corrosion-resistant alloy pipe according to any one of claims 4 to 6, characterized in that: In step S2, the head of the hollow tube blank is also processed, specifically: a chamfer with an angle of 30° is processed on the outer circle of the head of the hollow tube blank, and a fillet with a radius of 20 mm is processed at the connection between the chamfer and the body of the hollow tube blank.

8. The production process of NS3306 corrosion-resistant alloy pipe according to claim 7, characterized in that: In step S3, the hollow tube blank is preheated to 950°C in a resistance furnace for 3 to 5 hours; after being transferred to the electromagnetic induction heating furnace, the first heating power is 500 to 600 kW, the frequency is 40 to 65 Hz, the hollow tube blank is heated to 1140 to 1160°C, the holding time is 1 to 3 minutes, the second heating power is 650 to 900 kW, the frequency is 70 to 100 Hz, the hollow tube blank is heated to 1180 to 1215°C, and then taken out of the furnace.

9. The production process of NS3306 corrosion-resistant alloy pipe according to claim 8, characterized in that: Step S4 includes the following steps which are performed in sequence: S4.

1. Heat the inner wall of the extrusion barrel of the horizontal extruder to 310-500°C, and heat the surface of the extrusion die and the core rod to 250-450°C; S4.

2. Apply glass powder on the inner and outer surfaces of the high-temperature hollow tube blank, and then transfer it to the extrusion cylinder. The inner diameter of the extrusion cylinder is 5 to 11 mm larger than the outer diameter of the hollow tube blank, and a glass pad is placed at the entrance of the extrusion die; S4.3, heat the carbon steel tail pad to 900-1050℃, place it at the tail of the high-temperature hollow tube billet, and extrude the carbon steel tail pad together with the hollow tube billet; S4.

4. The power system of the horizontal extruder enables the extrusion rod to push the hollow tube billet to move in the extrusion direction. The forward speed of the hollow tube billet is 30 to 150 mm / s. The hollow tube billet passes through the cavity composed of the core rod and the extrusion die to become a rough tube. The extrusion ratio of the rough tube is 2.5 to 15. The extruded rough tube is cooled to room temperature in water at above 900°C.

10. The production process of NS3306 corrosion-resistant alloy pipe according to claim 9, characterized in that: In step S5, the intermediate tube before each cold rolling needs to be pickled and degreased, solution annealed, and pickled to remove oxide scale in sequence; the solution annealing process is: when the furnace temperature rises to 1160°C, the intermediate tube is placed in the furnace for a heating time of 5 to 10 min / mm, and after heating, it is transferred to a water pool within 70S to achieve rapid cooling using water as a cooling medium.

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