Production method of Inconel718 super alloy high strength seamless pipe

Abstract

The invention discloses a production method of an Inconel718 superalloy high-strength seamless pipe. The Inconel718 superalloy high-strength seamless pipe is produced by combining upsetting, blind hole expansion, two consecutive expansions, double-cone die hot extrusion, cold rolling, and finished product solution aging treatment. The problem of material waste caused by drilling and then expanding a solid ingot in a traditional process is avoided, and the material utilization rate is improved. The Inconel718 superalloy high-strength seamless pipe produced by the invention has uniform and dense grains and has high toughness and corrosion resistance. The invention adopts a double-cone die during extrusion. Compared with a flat die, the metal flow resistance is reduced, the extrusion force is reduced, the deformation is stable and uniform, and the problems of pipe delamination and cracks are reduced. The invention is suitable for the metal material processing industry.

Description

Technical Field

[0001] The invention belongs to the field of metal material processing, in particular to a production method of an Inconel718 superalloy high-strength seamless pipe. Background Art

[0002] Inconel718 is a nickel-based alloy material, mainly containing Ni and Cr, followed by Nb, Mo, etc. Inconel718 is a precipitation hardening alloy with high deformation resistance and good corrosion resistance in high and low temperature environments; at the same time, the use temperature of Inconel718 material can reach 800 ℃, with good high temperature strength and toughness and good thermal stability. The seamless pipe made of it is delivered in a solution treatment state or precipitation hardened state, which can adapt to the harsh environment of high strength and strong corrosion, and is widely used in aviation, aerospace, nuclear energy and petrochemical industries.

[0003] At present, Inconel718 seamless pipes are usually formed by hot extrusion process. The process route is smelting + solid billet forging + billet drilling + hot hole expansion + flat die extrusion + rough pipe solid solution + cold rolling + finished product heat treatment. It is formed under three-way compressive stress and the product structure is uniform.

[0004] However, the above process route has the following disadvantages: First, drilling a thick-walled hollow tube from the blank will result in a large amount of metal waste, very low material utilization, and high cost; Second, a flat die is used during extrusion, which has large metal flow resistance, high extrusion pressure, and is prone to cracks. Summary of the invention

[0005] In order to solve the above deficiencies in the prior art, the present invention aims to provide a method for producing an Inconel718 superalloy high-strength seamless pipe, so as to achieve the purpose of improving material utilization, reducing production costs and improving the forming quality of seamless pipes.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The invention provides an Inconel718 superalloy high-strength seamless pipe. The components of the steel for the seamless pipe are as follows by mass percentage: Cr: 18-21, Mo: 2.7-3.4, Ni: 50.0-55.0, Nb: 4.95-5.50, Ti: 0.70-1.15, Al: 0.20-0.70, B: 0.002-0.006, C: ≤0.07, S: ≤0.01, Si: ≤0.35, P: ≤0.015, Mn: ≤0.35, Cu: ≤0.30, Co: 0.25-1.0, Mg: ≤0.10, W: ≤0.25, and the rest are Fe and unavoidable impurities.

[0008] As a limitation of the present invention: the outer diameter of the seamless pipe is in the range of 114 to 325 mm, the wall thickness is in the range of 12 to 30 mm, and the inner diameter is greater than 60 mm;

[0009] The properties of the seamless pipe are: tensile strength Rm≥1275MPa, yield strength Rp0.2≥1035MPa, elongation after fracture≥12%, grain finer than grade 4.0, and longitudinal impact energy at room temperature≥30J.

[0010] The present invention also provides a method for producing an Inconel718 superalloy high-strength seamless pipe, the method comprising the following steps:

[0011] S1. Smelting: Use vacuum melting + electroslag remelting + vacuum consumable triple process to cast cylindrical bars;

[0012] S2. High temperature homogenization treatment: heat the cylindrical bar to 1180℃~1195℃, keep warm for 50h~60h, then 1155℃~1165℃, keep warm for 45h~48h;

[0013] S3. Bar rough processing: Cut the cylindrical bar, remove the surface oxide scale, make the two ends flat, and process a blind hole at one end;

[0014] S4. Upsetting the bar; the bar obtained in step S3 is heated to 1100°C to 1120°C, with the blind hole end facing upward, and placed in the reaming tube for upsetting, the upsetting deformation is greater than 30%, and the cross section of the bar after upsetting is filled with the reaming tube;

[0015] S5. Blind hole reaming; the bar after upsetting in step S4 is blind hole reaming in the reaming tube, the inner diameter of the bar after reaming is 30mm to 70mm, and the reaming is water-cooled to room temperature to form a blank;

[0016] S6. Finishing of the blank; the outer circle of the blank obtained in step S5 is turned and polished, the ends are flat, the outer circle of the head is processed with a bevel, the bevel and the ingot body are connected with a fillet, the inner and outer surfaces are ground and polished to remove scratches and tool mark defects;

[0017] S7. Nondestructive testing of the blank; nondestructive testing of the blank obtained in step S6, and grinding defects;

[0018] S8 continuous reaming; heating the blank obtained in step S7, and completing two continuous reamings using a vertical reaming machine;

[0019] S9 double cone die extrusion; the billet obtained in step S8 is heated and extruded into a rough tube using a horizontal extruder;

[0020] S10. Solution treatment of the rough pipe; heating in stages with a continuous roller hearth furnace and then water cooling;

[0021] S11. Cold rolling: Use a two-roller cold rolling mill to perform two to five passes of cold rolling, with a deformation of 30% to 55% for each pass, a feed of 3.0 to 5.0 mm / time, a rolling speed of 35 to 65 times / minute, and a deformation of 30% to 40% for the last pass; the intermediate tubes after each cold rolling pass must first be degreased in a degreasing tank to remove the cold rolling oil, then undergo a solid solution treatment, and finally be transported to a mixed acid pickling tank for pickling to remove the oxide scale to form a finished tube;

[0022] S12. Solution aging treatment of finished pipes; the solution treatment process is to keep the temperature at 960℃~990℃ for 60min~90min, and use water as the cooling medium to achieve rapid cooling; the aging process is to keep the temperature at 720℃ for 8h, then cool to 620℃ at 50℃ / h, keep the temperature for 12h, and then air cool after leaving the furnace.

[0023] As a limitation of the present invention: in step S6, a bevel with an angle α of 35° is machined at the outer circle of the head, and a fillet with a radius of 30 mm is machined at the connection between the bevel and the ingot body. The final surface roughness of the billet is Ra≤1.6μm, the length deviation is ±5mm, and the concentricity of the inner and outer circles is ≤1mm.

[0024] As a further limitation of the present invention, the continuous hole enlarging in step S8 comprises the following steps:

[0025] a. First, put the steel into the electric furnace at 800℃, heat it up to 950℃ at a rate of 150℃ / h, and keep it warm for 2.5h~4.5h; then transfer it to the electromagnetic induction heating furnace and heat it twice. The first time, the heating power is 400KW~500KW, the frequency is 38~58HZ, the temperature reaches 1070℃~1090℃, and the temperature is soaked for 1.5~4.5min; the second time, the heating power is 550KW~750KW, the frequency is 60~100HZ, the temperature reaches 1100℃~1120℃, and then it is taken out of the furnace;

[0026] b. The outer diameter of the blank before expansion is 8mm to 14mm smaller than the inner diameter of the expansion tube, and the inner wall temperature of the expansion tube is preheated to 120℃ to 260℃;

[0027] c. After heating the blank, evenly apply glass powder lubricant on the inner and outer surfaces and then place the blank into the reaming tube. Then place the reaming head on the blank for reaming. The reaming speed is 100mm / s~150mm / s. After the first reaming is completed, add glass powder lubricant to the blank again and reaming for the second time. The reaming ratios of the two times are both 1.02~1.35.

[0028] As a further limitation of the present invention: the double cone die extrusion in step S9 comprises the following steps:

[0029] d. The blank is transferred to a secondary electromagnetic induction heating furnace and heated to 1120°C to 1140°C, and then taken out of the furnace;

[0030] e. The inner wall of the extrusion barrel is heated to 220℃~360℃, and the extrusion die and mandrel are heated to 100℃~300℃;

[0031] f. Apply glass powder lubricant on the inner and outer surfaces of the blank and transfer it to the extrusion cylinder. The inner diameter of the extrusion cylinder is 4mm to 9mm larger than the outer diameter of the blank, and a glass pad is placed at the entrance of the extrusion die;

[0032] g. Heat the tail pad to 900℃~1050℃ and stick it to the tail of the billet. The tail pad is extruded together with the billet. The billet forward speed is 50mm / s~100mm / s, the extrusion ratio of the rough pipe is 3.0~8.0, the temperature of the extruded rough pipe is above 900℃ and water-cooled to below 50℃.

[0033] As a further limitation of the present invention: the outer diameter of the tail pad is equal to the outer diameter of the blank, the inner diameter of the tail pad is 4 mm to 5 mm larger than the inner diameter of the blank, and the length of the tail pad is 100 mm.

[0034] As a further limitation of the present invention: in step S9, the angle γ' of the outer conical surface of the double cone die is 24.5°, and the inner inlet of the double cone die has two die angles, the die angle β is 125°, and the die angle β' is 30°; the length of the sizing belt is 10mm~12mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 20mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 12mm.

[0035] As a further limitation of the present invention: the solution treatment process in step S10 is: heating at 960°C for 1.0min-1.5min / mm, heating at 975°C for 1.5min-2.0min / mm, heating at 1010°C for 2.5min-6.0min / mm, and then using water as a cooling medium to achieve rapid cooling.

[0036] As a further limitation of the present invention: in step S11, the solution treatment is heating at 1000°C for 2.5min to 6.0min / mm, and water is used as a cooling medium to achieve rapid cooling;

[0037] The concentration ratio of the mixed acid in the pickling is HF: 3-6%, HNO3: 15-20%, and the rest is water. The temperature of the mixed acid solution is 40°C-65°C, and the pickling time is 35min-100min.

[0038] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0039] The present invention adopts vacuum melting + electroslag remelting + vacuum consumable technology to smelt ingots, eliminating the blank drilling process of the traditional process, and the ingots obtained in this way have good uniformity of structure composition, few inclusions and high purity;

[0040] The present invention produces Inconel718 superalloy high-strength seamless pipes by combining upsetting, blind hole expansion, two-time continuous expansion, double-cone die hot extrusion, cold rolling, and finished product solid solution aging treatment, thereby avoiding the problem of material waste caused by drilling and then expanding solid ingots in the traditional process, and improving material utilization. In addition, the Inconel718 superalloy high-strength seamless pipes produced by the present invention have uniform and dense grains and have high toughness and corrosion resistance.

[0041] The present invention adopts a double cone die during extrusion, which reduces the metal flow resistance and extrusion force compared with a flat die, and the deformation is stable and uniform, thereby reducing the problems of pipe delamination and cracks.

[0042] In summary, the present invention can improve material utilization, increase circulation efficiency, reduce costs and energy consumption, and can also reduce the problems of pipe delamination and cracks; and is suitable for the metal material processing industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Figure 1 It is a structural schematic diagram of a vertical hole reaming machine;

[0045] Figure 2 It is a structural schematic diagram of a horizontal extruder;

[0046] Figure 3 It is a schematic diagram of the structure of the blank in an embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the structure of a double cone die in a horizontal extruder;

[0048] Figure 5 for Figure 4 Sectional view along AA direction;

[0049] Figure 6 Schematic diagram of the longitudinal section of the die base in the horizontal extruder

[0050] Figure 7 It is a schematic diagram of the three-dimensional structure of the die base in the horizontal extruder;

[0051] Figure 8 It is a structural schematic diagram of the seamless pipe during cold rolling;

[0052] Fig. 9 The figure is a schematic diagram of the production process flow of an embodiment of the present invention.

[0053] In the figure: 1-die tail stock, 2-die middle stock, 3-die stock, 4-double cone die, 5-die support, 6-extrusion cylinder, 7-mandrel, 8-tail pad, 9-extrusion pad, 10-extrusion rod, 11-mandrel force transfer rod, 12-blank, 13-rough pipe, 14-upper roller, 15-lower roller, 16-inner die, 17-finished seamless pipe. DETAILED DESCRIPTION

[0054] The preferred embodiment of the present invention is described below in conjunction with the accompanying drawings. It should be understood that the production method of an Inconel718 superalloy high-strength seamless pipe described herein is a preferred embodiment, which is only used to illustrate and explain the present invention and does not constitute a limitation of the present invention.

[0055] Figure 1 It is an existing vertical reaming machine, and its structure refers to the part disclosed in the invention patent application with publication number CN117086132A, and will not be described in detail in this embodiment.

[0056] Figure 2 It is a horizontal extruder, which includes a die tail seat 1, a die center seat 2, a die base 3, a double cone die 4, a die support 5, an extrusion barrel 6, a core rod 7, a tail pad 8, an extrusion pad 9, an extrusion rod 10 and a core rod force transmission rod 11. The double cone die 4 and the die support 5 are installed inside the die base 3, the die center seat 2 and the die tail seat 1 are arranged on the left side of the die support 5, and the die support 5, the die center seat 2 and the die tail seat 1 jointly support and fix the double cone die 4. The extrusion barrel 6 is located on the right side of the die base 3, the inside of the extrusion barrel 6 is the blank 12, the inside of the blank 12 is the core rod 7, the right side of the blank 12 is sequentially provided with a tail pad 8 and an extrusion pad 9, and the right side of the extrusion pad 9 is the extrusion rod 10, the extrusion rod 10 provides extrusion force under the action of the oil pressure system, and the extrusion pad 9 is used to prevent the extrusion rod 10 from directly contacting the blank 12 and can transmit the extrusion force. A mandrel force transmission rod 11 is arranged inside the extrusion rod 10, and the mandrel force transmission rod 11 is connected to the mandrel 7 through a thread, and the blank 12 is extruded by the mandrel 7 and the double cone die 4 to form a rough pipe 13. This part of the content is the prior art, and this embodiment will not be described in detail. The improvement of this embodiment is that, Figure 4 , 5 As shown, the angle γ' of the outer cone surface of the double cone die 4 is 24.5°, the inner entrance of the double cone die 4 has two die angles, die angle β is 125°, and die angle β' is 30°; the length of the sizing belt is 10mm-12mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 20mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 12mm. Correspondingly, as Figure 6 , 7As shown, a circular platform is arranged in the vertical direction on the outer side of the internal entrance of the mold base 3, and the minimum width L of the platform is 18 mm, which is used to fix the glass pad; the cone angle γ at the position inside the mold base 3 for installing the double cone mold 4 is 24.5°, which is equal to the angle γ' of the external cone surface of the double cone mold 4, so as to facilitate matching installation.

[0057] The finished product specifications of the Inconel718 superalloy high-strength seamless pipe in this embodiment are diameter φ219 mm×wall thickness 12 mm, and the chemical composition is shown in Table 1:

[0058] Table 1 Chemical composition / mass percentage of φ219mm×wall thickness 12mm seamless pipe

[0059]

[0060] Remarks: The rest is Fe and unavoidable impurities.

[0061] The production method of the Inconel718 superalloy high-strength seamless pipe of the present invention is as follows Fig. 9 As shown, the specific steps include:

[0062] S1. Smelting: The cylindrical bar is cast by vacuum melting (VIM) + electroslag remelting (ESR) + vacuum annealing (VAR) triple process. The specification of the cylindrical bar is φ300mm in diameter × 910mm in length.

[0063] It should be noted that the surface of the electrode blank is cleaned of iron oxide scale before electroslag remelting; the electroslag remelting slag system adopts a five-element slag system of CaF2, CaO, MgO, Al2O3 and TiO2, and the content ratio (%) is 70:15:5:5:5; vacuum protection is adopted in the whole process of electroslag remelting.

[0064] S2. High temperature homogenization treatment; the cylindrical rod is heated to 1180°C ~ 1195°C, kept warm for 50h ~ 60h, and then 1155°C ~ 1165°C, kept warm for 45h ~ 48h; in this embodiment, the cylindrical rod is heated to 1190°C, kept warm for 60h, and then 1160°C, kept warm for 48h.

[0065] S3. Bar rough processing: Cut the cylindrical bar, remove the surface oxide scale, make the two ends flat, and process a blind hole at one end; the specification of the obtained bar is outer diameter φ290mm×length 900mm.

[0066] S4. Upsetting of bar stock; the bar stock obtained in step S3 is heated to 1100℃~1120℃, with the blind hole end facing upward, and placed in the reaming tube for upsetting. After upsetting, the cross section of the bar stock is filled with the reaming tube. In this embodiment, the upsetting deformation is about 38.3%, the purpose is to improve the plastic deformation capacity of the material. In this step, the inner diameter of the reaming tube is 369mm and the height is 1600mm. The bar stock specifications after upsetting are an outer diameter of φ369mm and a length of about 555mm. In this embodiment, the forging process and the billet forging process of the traditional process are omitted by replacing the forging billet with a casting billet; the plasticity is improved by the upsetting process and the forging process is reduced.

[0067] S5. Blind hole expansion; the bar material after upsetting in step S4 is subjected to blind hole expansion in the expansion tube. In this embodiment, the inner diameter of the expanded bar material is 55 mm. After expansion, the billet is water-cooled to room temperature to form a blank with a diameter of φ369 mm × inner diameter of φ55 mm.

[0068] S6. Finishing of the blank; the inner hole deviation of the blank obtained in step S5 is ±0.5mm; the outer diameter of the finished product is ±1mm after turning and polishing; the ends are flat, and the end face verticality is ≤1mm; Figure 3 As shown, a bevel with an angle α of 35° is machined on the outer circle of the head, and a fillet with a radius of 30mm is machined at the connection between the bevel and the ingot body. The inner and outer surfaces are ground and polished to remove scratches and tool mark defects. The final surface roughness of the billet is Ra≤1.6μm, the length deviation is ±5mm, the concentricity of the inner and outer circles is ≤1mm, and the specifications are diameter φ357mm×inner diameter φ65mm.

[0069] S7. Nondestructive testing of the blank; performing nondestructive testing on the blank obtained in step S6 and repairing defects.

[0070] S8. Continuous hole expansion: The blank obtained in step S7 is heated and two consecutive hole expansions are completed using a vertical hole expander.

[0071] Specifically, the continuous hole expansion includes the following steps:

[0072] a. First, put the steel into the electric furnace at 800℃, heat it up to 950℃ at a rate of 150℃ / h, and keep it warm for 2.5h~4.5h; then transfer it to the electromagnetic induction heating furnace and heat it twice. The first time, the heating power is 400KW~500KW, the frequency is 38~58HZ, the temperature reaches 1070℃~1090℃, and the soaking is 1.5~4.5min; the second time, the heating power is 550KW~750KW, the frequency is 60~100HZ, the temperature reaches 1100℃~1120℃, and then take it out of the furnace;

[0073] b. The outer diameter of the blank before expansion is 8mm to 14mm smaller than the inner diameter of the expansion tube. The inner diameter of the expansion tube is 369mm and the height is 1600mm. The inner wall temperature of the expansion tube is preheated to 120℃ to 260℃;

[0074] c. After heating the blank, evenly apply glass powder lubricant on the inner and outer surfaces and then place the blank into the reaming tube. Then place the reaming head on the blank for reaming. The reaming speed is 100mm / s~150mm / s. After the first reaming is completed, add glass powder lubricant to the blank while it is hot and carry out the second reaming. The reaming ratios of the two times are both 1.02~1.35.

[0075] The diameter of the reaming head for the first reaming is 173 mm, and the reaming ratio is 1.15. The diameter of the reaming head for the second reaming is 238 mm, and the reaming ratio is 1.33. The reaming ratio is the ratio of the area of ​​the cross section of the blank before reaming to the area of ​​the cross section after reaming.

[0076] The specific calculation of the first hole expansion ratio is:

[0077] Cross-sectional area before expansion: π×(357 / 2) 2 -π×(65 / 2) 2 =96730.84mm 2 ;

[0078] Cross-sectional area after expansion: π×(369 / 2) 2 -π×(173 / 2) 2 =83392.12mm 2 .

[0079] The specific calculation of the second hole expansion ratio is:

[0080] Cross-sectional area before expansion: π×(369 / 2) 2 -π×(173 / 2) 2 =83392.12mm 2 ;

[0081] Cross-sectional area after expansion: π×(369 / 2) 2 -π×(238 / 2) 2 =62420.845mm 2 .

[0082] S9. Double cone die extrusion: heating the billet obtained in step S8, and then using a horizontal extruder to extrude a rough pipe.

[0083] Specifically, the double cone die extrusion comprises the following steps:

[0084] d. The blank is transferred to a secondary electromagnetic induction heating furnace and heated to 1120°C to 1140°C, and then taken out of the furnace;

[0085] e. The inner wall of the extrusion barrel is heated to 220℃~360℃, and the extrusion die and mandrel are heated to 100℃~300℃;

[0086] f. After the inner and outer surfaces of the blank are coated with glass powder lubricant, it is transferred to the extrusion cylinder. The inner diameter of the extrusion cylinder is 4mm to 9mm larger than the outer diameter of the blank. A glass pad is placed at the entrance of the extrusion die. The inner diameter of the glass pad is 20mm larger than the diameter of the rough tube, and the thickness of the glass pad is 18mm.

[0087] g. Heat the prepared tail pad to 900℃~1050℃ and stick it to the tail of the billet. The tail pad is extruded together with the billet. The power system of the extruder makes the extrusion rod push the billet to move in the extrusion direction. The inner diameter of the extrusion barrel is 375mm and the length is 1500mm. The billet forward speed is 80mm / s. The inner diameter of the extrusion die is 279mm, the core rod diameter is 228mm, and the extrusion ratio of the rough pipe is 3.43. The temperature of the extruded rough pipe is above 900℃, water-cooled to below 50℃, and dried out of the water. The cold specifications of the rough pipe are diameter φ273mm×wall thickness 25mm. The extrusion ratio is uniformly calculated according to the hot size during extrusion.

[0088] The specific calculation of extrusion ratio is:

[0089] Cross-sectional area before extrusion: π×(375 / 2) 2 -π×(228 / 2) 2 =69583.185mm 2 ;

[0090] Cross-sectional area after extrusion: π×(279 / 2) 2 -π×(279 / 2-25.5) 2 =20297.745mm 2 .

[0091] It should be noted that in this step, the outer diameter of the tail pad is equal to the outer diameter of the blank, the inner diameter of the tail pad is 4mm to 5mm larger than the inner diameter of the blank, and the length of the tail pad is 100mm. The tail pad can extrude all the Inconel718 blanks into tubes, improving the material utilization rate and yield rate. At the same time, the tail pad is made of carbon steel, which is easy to saw off to reduce saw blade consumption.

[0092] The glass powder lubricant is composed of Al2O3, K2O, Na2O, CaO, MgO, TiO2 and SiO2, wherein the SiO2 content is 45% to 65%, the CaO content is 3% to 10%, the particle size of the glass powder is 0.10mm to 0.30mm, and the coating thickness is 0.1mm to 0.5mm.

[0093] S10. Solution treatment of rough pipe: heating in stages in a continuous roller hearth furnace and then water cooling.

[0094] The solution treatment process is: heating at 960°C for 1.0min-1.5min / mm, and heating at 1.5min / mm in this embodiment; heating at 975°C for 1.5min-2.0min / mm, and heating at 2.0min / mm in this embodiment; heating at 1010°C for 2.5min-6.0min / mm, and heating at 4.0min / mm in this embodiment, and then using water as a cooling medium to achieve rapid cooling.

[0095] S11. Cold rolling; using a two-roller cyclic cold rolling mill for two to five passes of cold rolling, the present embodiment is two passes; the structure of the two-roller cold rolling mill is as follows Figure 8 As shown, it includes an upper roller 14, a lower roller 15 and an inner die 16. The cold rolling process of the seamless pipe is shown in FIG. Figure 8 The deformation of each pass is 30% to 55%, the feed amount is 3.0 to 5.0 mm / time, the rolling speed is 35 to 65 times / minute, and the deformation of the last pass is 30% to 40%.

[0096] Specifically, in this embodiment, the feed rate is 3.5 mm / time, the rolling speed is 45 times / minute, and the deformation process is rough pipe diameter φ273 mm×wall thickness 25 mm-cold-rolled intermediate pipe diameter φ245 mm×wall thickness 17 mm-cold-rolled finished pipe diameter φ219 mm×wall thickness 12 mm. The finished seamless pipe 17 has an outer diameter of 219 mm, a wall thickness range of 12 mm, and an inner diameter of 195 mm. The deformation amount of the first pass is 37.5%, and the deformation amount of the second pass is 35.9%.

[0097] The specific calculation of deformation is:

[0098] The cross-sectional area corresponding to φ273×25mm is: S a =π×(273 / 2) 2 -π×(273 / 2-25) 2 =19468mm 2 ;

[0099] The cross-sectional area corresponding to φ245×17mm is:

[0100] S b =π×(245 / 2) 2 -π×(245 / 2-17) 2 =12170.64mm 2 ;

[0101] The deformation of the first cold rolling is: (S a -S b )×100% / S a =37.5%.

[0102] The corresponding cross-sectional area of ​​φ219×12mm is: Sc =π×(219 / 2) 2 -π×(219 / 2-12) 2 =7799.76mm 2 ;

[0103] The deformation of the second cold rolling is: (S b -S c )×100% / S b =35.9%;

[0104] After each cold rolling, the intermediate quality pipe must first remove the cold rolling oil in the degreasing tank, then undergo solid solution treatment, and finally be transferred to the mixed acid pickling tank for pickling to remove the oxide scale to form a finished seamless pipe 17. Specifically, the solid solution treatment is heating at 1000℃ for 2.5min~6.0min / mm, and using water as a cooling medium to achieve rapid cooling. The concentration ratio of the mixed acid in the pickling is HF: 3~6%, HNO3: 15~20%, and the rest is water. The temperature of the mixed acid solution is 40℃~65℃, and the pickling time is 35min~100min.

[0105] S12. Solution aging treatment of finished pipes; the solution process is to keep the temperature at 960℃~990℃ for 60min~90min. In this embodiment, the temperature is kept at 960℃ for 90min, and water is used as the cooling medium to achieve rapid cooling. The aging process is to keep the temperature at 720℃ for 8h, then cool to 620℃ at 50℃ / h, keep the temperature for 12h, and then air cool after leaving the furnace.

[0106] The finished products of Inconel718 super alloy high-strength seamless pipes were inspected, and the inspection data are shown in Table 2.

[0107] Table 2 Finished product properties of Inconel718 super alloy high strength seamless pipe

[0108]

[0109] It can be seen from Table 2 that the properties of the finished seamless pipe 17 obtained in this embodiment are: tensile strength Rm≥1275MPa, yield strength Rp0.2≥1035MPa, elongation after fracture ≥12%, grain finer than grade 4.0, and longitudinal impact energy at room temperature ≥30J, all of which meet the technical indicators; and it also has good corrosion resistance.

[0110] 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 embodiment, those skilled in the art can still modify the technical solutions described in the above embodiment 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 method for producing Inconel718 super alloy high-strength seamless pipe, characterized in that: The composition of steel for seamless pipes is as follows by mass percentage: Cr: 18-21, Mo: 2.7-3.4, Ni: 50.0-55.0, Nb: 4.95-5.50, Ti: 0.70-1.15, Al: 0.20-0.70, B: 0.002-0.006, C: ≤0.07, S: ≤0.01, Si: ≤0.35, P: ≤0.015, Mn: ≤0.35, Cu: ≤0.30, Co: 0.25-1.0, Mg: ≤0.10, W: ≤0.25, and the rest is Fe and unavoidable impurities; The production method comprises the following steps: S1. Smelting: Use vacuum melting + electroslag remelting + vacuum consumable triple process to cast cylindrical bars; S2. High temperature homogenization treatment: heat the cylindrical bar to 1180℃~1195℃, keep warm for 50h~60h, then 1155℃~1165℃, keep warm for 45h~48h; S3. Bar rough processing: Cut the cylindrical bar, remove the surface oxide scale, make the two ends flat, and process a blind hole at one end; S4. Upsetting the bar; the bar obtained in step S3 is heated to 1100°C to 1120°C, with the blind hole end facing upward, and placed in the reaming tube for upsetting, the upsetting deformation is greater than 30%, and the cross section of the bar after upsetting is filled with the reaming tube; S5. Blind hole reaming; the bar after upsetting in step S4 is blind hole reaming in the reaming tube, the inner diameter of the bar after reaming is 30mm to 70mm, and the reaming is water-cooled to room temperature to form a blank; S6. Finishing of the blank; the outer circle of the blank obtained in step S5 is turned and polished, the ends are flat, the outer circle of the head is processed with a bevel, the bevel and the ingot body are connected with a fillet, the inner and outer surfaces are ground and polished to remove scratches and tool mark defects; S7. Nondestructive testing of the blank; nondestructive testing of the blank obtained in step S6, grinding defects; S8 continuous reaming; heating the blank obtained in step S7, and completing two continuous reamings using a vertical reaming machine; S9 double cone die extrusion; the billet obtained in step S8 is heated and extruded into a rough tube using a horizontal extruder; S10. Solution treatment of the rough pipe; heating in stages with a continuous roller hearth furnace and then water cooling; S11. Cold rolling: Use a two-roller cold rolling mill to perform two to five passes of cold rolling, with a deformation of 30% to 55% for each pass, a feed of 3.0 to 5.0 mm / time, a rolling speed of 35 to 65 times / minute, and a deformation of 30% to 40% for the last pass; the intermediate tubes after each cold rolling pass must first be degreased in a degreasing tank to remove the cold rolling oil, then undergo a solid solution treatment, and finally be transported to a mixed acid pickling tank for pickling to remove the oxide scale to form a finished tube; S12. Solution aging treatment of finished pipes; the solution treatment process is to keep the temperature at 960℃~990℃ for 60min~90min, and use water as cooling medium to achieve rapid cooling; the aging process is to keep the temperature at 720℃ for 8h, then cool to 620℃ at 50℃ / h, keep the temperature for 12h, and then air cool after leaving the furnace; The outer diameter of the final formed seamless pipe ranges from 114 to 325 mm, the wall thickness ranges from 12 to 30 mm, and the inner diameter is greater than 60 mm; the properties of the seamless pipe are: tensile strength Rm ≥ 1275 MPa, yield strength Rp0.2 ≥ 1035 MPa, elongation after fracture ≥ 12%, grain finer than grade 4.0, and longitudinal impact energy at room temperature ≥ 30 J.

2. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 1, characterized in that: In step S6, a bevel with an angle α of 35° is machined at the outer circle of the head, and a fillet with a radius of 30 mm is machined at the connection between the bevel and the ingot body. The final surface roughness of the billet is Ra≤1.6μm, the length deviation is ±5mm, and the concentricity of the inner and outer circles is ≤1mm.

3. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 2, characterized in that: The continuous hole enlarging in step S8 comprises the following steps: a. First, put the steel into the electric furnace at 800℃, heat it up to 950℃ at a rate of 150℃ / h, and keep it warm for 2.5h~4.5h; then transfer it to the electromagnetic induction heating furnace and heat it twice. The first time, the heating power is 400KW~500KW, the frequency is 38~58HZ, the temperature reaches 1070℃~1090℃, and the temperature is soaked for 1.5~4.5min; the second time, the heating power is 550KW~750KW, the frequency is 60~100HZ, the temperature reaches 1100℃~1120℃, and then it is taken out of the furnace; b. The outer diameter of the blank before expansion is 8mm to 14mm smaller than the inner diameter of the expansion tube, and the inner wall temperature of the expansion tube is preheated to 120℃ to 260℃; c. After heating the blank, evenly apply glass powder lubricant on the inner and outer surfaces and then place the blank into the reaming tube. Then place the reaming head on the blank for reaming. The reaming speed is 100mm / s~150mm / s. After the first reaming is completed, add glass powder lubricant to the blank again and reaming for the second time. The reaming ratios of the two times are both 1.02~1.

35.

4. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 3, characterized in that: The double cone die extrusion in step S9 comprises the following steps: d. The blank is transferred to a secondary electromagnetic induction heating furnace and heated to 1120°C to 1140°C, and then taken out of the furnace; e. The inner wall of the extrusion barrel is heated to 220℃~360℃, and the extrusion die and mandrel are heated to 100℃~300℃; f. Apply glass powder lubricant on the inner and outer surfaces of the blank and transfer it to the extrusion cylinder. The inner diameter of the extrusion cylinder is 4mm to 9mm larger than the outer diameter of the blank, and a glass pad is placed at the entrance of the extrusion die; g. Heat the tail pad to 900℃~1050℃ and stick it to the tail of the billet. The tail pad is extruded together with the billet. The billet forward speed is 50mm / s~100mm / s, the extrusion ratio of the rough pipe is 3.0~8.0, the temperature of the extruded rough pipe is above 900℃ and water-cooled to below 50℃.

5. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 4, characterized in that: The outer diameter of the tail pad is equal to the outer diameter of the blank, the inner diameter of the tail pad is 4mm to 5mm larger than the inner diameter of the blank, and the length of the tail pad is 100mm.

6. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 5, characterized in that: In step S9, the angle γ' of the outer conical surface of the double cone die is 24.5°, and the inner inlet of the double cone die has two die angles, the die angle β is 125°, and the die angle β' is 30°; the length of the sizing belt is 10mm~12mm, the fillet radius of the transition area between the die angle β section and the die angle β' section is 20mm, and the fillet radius of the transition area between the die angle β' section and the sizing belt is 12mm.

7. The method for producing the Inconel718 superalloy high-strength seamless pipe according to claim 6, characterized in that: The solution treatment process in step S10 is: heating at 960° C. for 1.0 min to 1.5 min / mm, heating at 975° C. for 1.5 min to 2.0 min / mm, heating at 1010° C. for 2.5 min to 6.0 min / mm, and then using water as a cooling medium to achieve rapid cooling.

8. The method for producing an Inconel 718 superalloy high-strength seamless pipe according to any one of claims 2 to 7, characterized in that: In step S11, the solution treatment is heating at 1000°C for 2.5min-6.0min / mm, and water is used as a cooling medium to achieve rapid cooling; The concentration ratio of the mixed acid in the pickling is HF: 3-6%, HNO3: 15-20%, and the rest is water. The temperature of the mixed acid solution is 40°C-65°C, and the pickling time is 35min-100min.

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