Temperature Control Method for Extruded Nickel-based Alloy Tubes for Special Pipe Fittings of Pressure Vessels

Abstract

Temperature control method for nickel-based alloy extruded tubes used in special pipe fittings of pressure vessels, including a ring furnace preheating process and an electromagnetic induction heating process. In the ring furnace preheating process, the processed 00Cr30Ni60Fe10 nickel-based high-temperature blank is heated to 950 - 1050 °C at high temperature, and then electromagnetic induction heating is carried out to meet the requirements of subsequent high-temperature extrusion tube manufacturing. The electromagnetic induction heating steps are as follows: feeding into the induction furnace → adjusting the position of the copper sheet tap → first-stage heating → uniform temperature holding in the furnace → blank discharging and air cooling → secondary feeding into the induction furnace → second-stage heating → uniform temperature holding in the furnace → blank discharging (transporting to subsequent extrusion tube manufacturing). The key lies in controlling the secondary heating temperature, heating-up power of the electromagnetic induction furnace, adjusting the tap position to increase the head temperature compensation, etc. Finally, the heating temperature of the blank is controlled within the range of 1070 - 1110 °C.

Description

Technical Field

[0001] The present invention relates to the production field of seamless steel pipes in the metallurgical and mechanical industries, and in particular to a temperature control method for nickel-based alloy extrusion pipe manufacturing during the manufacture of special pipe fittings for pressure vessels, and is particularly applicable to the high-temperature heating process of billets (round steel) in the extrusion pipe production of 00Cr30Ni60Fe10 nickel-chromium-iron-based solid-solution strengthened nickel-based alloy seamless steel pipes with a finished pipe diameter of more than 100 mm and a wall thickness of more than 20 mm. Background Art

[0002] The so-called nickel-based alloy refers to an alloy with higher strength and certain oxidation and corrosion resistance at high temperatures of 650-1000 °C and a metal nickel content > 30%. Nickel-based alloys are classified according to their main properties into: nickel-based heat-resistant alloys, nickel-based corrosion-resistant alloys, nickel-based wear-resistant alloys, nickel-based precision alloys, nickel-based shape memory alloys, etc.

[0003] Among them, 00Cr30Ni60Fe10 is a nickel-chromium-iron-based solid-solution strengthened corrosion-resistant nickel-based alloy. The contents of metal Cr (chromium) and metal Ni (nickel) in this alloy are as high as 30% and 60%. Its main components include C = 0.01-0.04%, Cr = 28-31%, Ni ≥ 58%, Fe = 8-11%, Ti ≤ 0.30%, S ≤ 0.005%, P ≤ 0.01%, etc. This nickel-based alloy has good high-temperature corrosion resistance and oxidation resistance, excellent hot and cold working and welding properties, excellent thermal strength and plasticity below 700 °C, can be strengthened by cold working, and can also be used for resistance welding, fusion welding or brazing connections, especially for the preparation and processing of antioxidant parts with low loads below 1100 °C.

[0004] In addition, it has been found in the application research in related fields at home and abroad that the 00Cr30Ni60Fe10 alloy has excellent corrosion resistance in a variety of corrosive aqueous media and high-temperature atmospheres, and has better stress corrosion cracking resistance than alloys such as 0Cr15Ni75Fe8 and 0Cr20Ni32AlTi in chloride-containing and sodium hydroxide solutions. At the same time, it has high strength, good metallurgical stability and excellent processing characteristics. Therefore, this nickel-based alloy has become the key material for key components of equipment in the energy, nuclear power, petrochemical, mining and other industries with harsh working conditions at home and abroad, especially widely used in the penetrators of special-purpose pressure vessels.

[0005] The special pipe fittings for pressure vessels refer to a kind of penetration piece. This penetration piece of the pressure vessel is an important part of the pressure vessel for special purposes. It is to locally penetrate the outer shell of the pressure vessel with a circular seamless steel pipe and connect the penetration piece with the outer shell of the pressure vessel into one body through processes such as welding to become a tubular component that communicates the inside and outside of the pressure vessel. The so-called penetration means, on the one hand, the penetration of the containment. There are many pipes that need to enter and exit the containment for installing various pipelines. The containment is the third safety barrier of a nuclear power plant, and its integrity is directly related to the radiation safety of the nuclear power plant. Therefore, the penetration piece is required to be strictly sealed with the containment. On the other hand, it is for the penetration of the control rod drive mechanism seat of the reactor pressure vessel. As an important pressure boundary of the primary loop system of the reactor, it bears high temperature and high pressure and is in direct contact with the coolant. Therefore, extremely high requirements are imposed on the strength, plasticity and toughness, corrosion resistance, fatigue resistance and other aspects of the materials used for the penetration piece.

[0006] The seat penetration piece of the first-generation pressure vessel for special purposes was made of 0Cr15Ni75Fe8 alloy material. The stress corrosion resistance of this alloy is relatively poor and has now been replaced by 00Cr30Ni60Fe10 alloy to improve the mechanical properties and corrosion resistance of the pipe fittings used for the penetration piece. Due to various reasons such as material processing technology and technical equipment, the old technology adopted the process of metal smelting → metal forging → mechanical cutting processing (drilling first and then boring). Although this process technology can complete the processing of the penetration pieces of domestic pressure vessels for special purposes, the utilization rate of its alloy materials is low, the loss is large, the cost is high, and the non-uniformity of the metal structure is high, and the quality is unstable. With the improvement of the requirements for product safety and reliability, this process technology can no longer meet the continuous development of the domestic energy (nuclear power) field. As a high-end product in the metallurgical industry, international technical blockade and barriers make international procurement extremely difficult. According to the development of equipment technology in the domestic seamless steel pipe production field, optimizing and improving the production and processing technology of the penetration pieces of pressure vessels for special purposes can not only meet the needs of the energy (nuclear power) field for high-end seamless steel pipes. Therefore, the high-temperature extrusion pipe-making technology can be used to replace the original metal cutting technology as the processing method for preparing the penetration pieces for pressure vessels for special purposes.

[0007] Seamless steel pipes are common metallurgical metal products. The above-mentioned high-temperature extrusion pipe manufacturing process for seamless steel pipes is carried out under a triaxial compressive stress state. Utilizing the good plasticity of metal materials at high temperatures, through the die hole formed by the inner hole of the extrusion die and the outer circle of the mandrel, the metal is extruded when it is above the recrystallization temperature, and the tube blank (hot round steel) is extruded from a die hole to obtain a metal forming method for a pipe with a cross-section shape of the die hole. In addition, due to its large deformation, high production capacity, high precision control of dimensional tolerances, uniform metal structure, easy one-time forming control, and convenient continuous production organization, etc., the high-temperature extrusion pipe manufacturing process for seamless steel pipes is applicable to the forming and pipe manufacturing of various alloy steels, stainless steels, high-strength steels, nickel-based superalloys and other pipes. Therefore, it has gradually replaced the traditional hot rolling piercing process and has currently become the main pipe manufacturing method for high-alloy seamless steel pipes at home and abroad.

[0008] The common production processes for high-temperature extrusion pipe manufacturing of seamless steel pipes under the existing technology mainly include tube blank preparation, tube blank heating in a ring furnace, tube blank piercing / expanding, descaling of the billet, secondary induction heating of the tube blank, extrusion pipe manufacturing, finished product cooling, inspection, etc. Among them, the ring furnace heating and secondary induction heating provide tube blanks at appropriate temperatures for the extrusion pipe manufacturing process. The tube blank heating process is a crucial key production process in the entire high-temperature extrusion pipe manufacturing process. The hot extrusion production process flow of seamless steel pipes is: blank preparation → fixed-length sawing (band sawing machine) → centering hole drilling (centering hole drilling machine) → outer circle cutting (lathe) → deep hole drilling (deep hole drilling machine) → end face machining (lathe) → inspection of the bright blank → grinding → cleaning and degreasing (cleaning machine) → tube blank preheating (ring furnace) → primary induction heating (electromagnetic induction furnace) → piercing / expanding (vertical expanding machine) → secondary induction heating (electromagnetic induction furnace) → high-temperature extrusion (horizontal extrusion machine) → hot sawing (fixed-length hot saw) → cooling on a cooling bed (cooling bed) or quenching (quenching tank) → inspection → finished product leaving the factory or transferred to cold processing production.

[0009] The grain size of the 00Cr30Ni60Fe10 nickel-chromium-iron-based solid-solution strengthened nickel-based corrosion-resistant alloy used for special-purpose pressure vessel penetrations is finer than grade 5. Grain size is a scale representing the size of grains. In industrial production, the grain size grade is used to represent the grain size. The standard grain size is divided into 12 grades in total. Grades 1-4 are coarse grains, grades 5-8 are fine grains, and grades 9-12 are ultra-fine grain sizes. When metal crystallizes, each grain grows from a single crystal nucleus; therefore, the size of the grains depends on the relative magnitudes of the number of crystal nuclei and the grain growth rate. The larger the nucleation rate of the crystal nucleus, the more the number of crystal nuclei in the unit volume, and the finer the grains. The smaller the growth rate, the more batches of crystal nuclei are formed during the growth process, and the more the number of crystal nuclei, so the finer the grains. Conversely, the smaller the nucleation rate and the larger the growth rate, the coarser the grains.

[0010] However, there is no precedent in China for the production of 00Cr30Ni60Fe10 nickel-chromium-iron based solid solution strengthened nickel-based corrosion-resistant alloy seamless steel pipe high-temperature extrusion pipe making method. At present, the only way to carry out trial production is to refer to the process method of high-temperature extrusion pipe making of the same type of nickel-based alloy (similar elemental composition). During the test, the grain size exceeded the standard, resulting in failure to meet the technical requirements of the product and being scrapped.

[0011] Although a variety of test methods have been adopted, such as optimizing the high-temperature pipe making process, the high-temperature extrusion pipe making process flow of billet preparation → cut-to-size sawing (band saw machine) → drilling centering holes (centering hole drilling machine) → external cylindrical cutting (lathe) → drilling deep holes (deep hole drilling machine) → end surface processing (lathe) → smooth billet inspection → grinding → cleaning and degreasing (cleaning machine) → preheating of pipe billet (ring furnace) → secondary induction heating (electromagnetic induction furnace) → high-temperature extrusion (horizontal extruder) → hot sawing (cut-to-size hot billet) → cooling on cooling bed (cooling bed) or quenching (quenching tank) → inspection → finished product delivery is used for production, but the grain size index of hot extruded pipes under the existing technology is still unstable, and the yield rate is low. After research, the reason is still that there are problems in the temperature control of the pipe billet (round steel). That is:

[0012] 1) The heating control temperature is high, the temperature during extrusion deformation is high, the grain growth rate is fast, and the grain size of the extruded tube exceeds the standard: Due to the harsh operating environment of special pipe fittings (through-pieces) of pressure vessels, high requirements for metal structure uniformity require that the grain size of the pipe fitting material must be finer than level 5. At present, the extrusion temperature of the same type of nickel-based alloy products is controlled at 1170±20℃. The deformation temperature of the pipe billet (round steel) at this temperature is high during extrusion pipe making, the grain growth rate is fast, and the grain size is coarse, which cannot meet the requirement of grain size finer than level 5.

[0013] 2) Limited by the extrusion pressure, the low deformation temperature is prone to cause "stuck car" failure: Since the grain size is required to be finer than level 5, under the existing technical equipment conditions, the grain size of the hot extruded tube can only be met by reasonably adjusting (lowering) the heating temperature and deformation temperature of the tube billet to meet the technical requirements of the extrusion tube. However, when the heating temperature is reduced, the deformation resistance of the material increases, and the tube billet requires a greater extrusion force to complete the extrusion. However, the extrusion force of the extrusion equipment (extruder) has an upper limit and cannot be increased endlessly. Under the action of the material deformation resistance, the extrusion rod can neither move forward to extrude nor retreat to withdraw (commonly known as "stuck car" in production practice), which not only causes the scrapping of the billet, but also damages the core rod and extrusion barrel and other devices, directly causing process failure shutdown, and large energy and other shutdown losses.

[0014] 3) Poor temperature uniformity of the tube blank (round steel): The transportation process of the tube blank (round steel) from the induction furnace to the extrusion machine is relatively long. The decrease in the surface temperature of the tube blank, especially the end temperature, is not conducive to extrusion. Due to the skin effect, when an alternating current passes through a conductor, the current will concentrate on the surface of the conductor and flow, rather than being evenly distributed across the entire cross-sectional area of the conductor. Therefore, when the external temperature of the tube blank reaches the set temperature, the core temperature is relatively low, unable to meet the temperature requirements for subsequent tube extrusion.

[0015] 4) The transportation process of the tube blank (round steel) from the induction furnace to the extrusion machine is relatively long. The decrease in the surface temperature of the tube blank, especially the end temperature, is not conducive to extrusion: When the 00Cr30Ni60Fe10 alloy tube blank (round steel) is reheated and transported from the electromagnetic induction furnace to the extrusion machine through a manipulator and roller table for tube extrusion processing, the temperature of the tube blank (round steel) will drop. In particular, the temperature of the head (end) of the tube blank drops significantly, and it is directly related to the seasonal climate. Depending on the ambient temperature, the temperature of the head of the tube blank drops by 20 - 30 °C from the furnace to before extrusion, combined with the heat loss of the molten glass pad. Since the temperature drop will cause the extrusion temperature of the tube blank (round steel) during tube extrusion to drop synchronously and the temperature to be uneven, it not only affects the grain size but also increases the deformation resistance of the material, and the extrusion force also increases accordingly. When the extrusion force exceeds the limit of the extrusion equipment, it may even cause "jamming".

[0016] In summary, in the production practice of high-temperature extrusion of seamless steel tubes using the 00Cr30Ni60Fe10 nickel-chromium-iron-based solid-solution strengthened nickel-based corrosion-resistant alloy under the existing technology, due to the difficulty in controlling the temperature of the tube blank (round steel), on the one hand, it cannot meet the requirement of a grain size finer than grade 5, and on the other hand, it is prone to technological failures such as extrusion "jamming", which has become a difficult point in the high-temperature extrusion production of this type of product. Therefore, there is an urgent need for a temperature control method for nickel-based alloy extrusion for special pipe fittings of pressure vessels to carry out the industrial production of 00Cr30Ni60Fe10 seamless steel tubes for penetrators of special-purpose pressure vessels. Through this method, the key process parameters for high-temperature extrusion of nickel-based corrosion-resistant alloys represented by 00Cr30Ni60Fe10 can be mastered and accumulated, laying a foundation for the industrialization and large-scale production of penetrators for special-purpose pressure vessels in China. Summary of the Invention

[0017] In order to solve the problems of difficulty in temperature control, failure to meet the requirement of grain size finer than level 5, and easy extrusion "stuck car" and other process failures in the production practice of high-temperature extrusion of seamless steel pipes of 00Cr30Ni60Fe10 nickel-chromium-iron based solid solution strengthened nickel-based corrosion-resistant alloy under the prior art, the present invention provides a temperature control method for extrusion pipe making of nickel-based alloy for special pipe fittings of pressure vessels, which can effectively solve the problems, has reasonable process parameters, uniform alloy structure, good dimensional accuracy, high yield rate, is safe, reliable, practical and efficient, and has significant energy-saving, emission-reduction and consumption-reduction effects.

[0018] The temperature control method of nickel-based alloy extrusion pipe making for special pipe fittings for pressure vessels of the present invention is specifically described as follows:

[0019] 1. A temperature control method for extruding a nickel-based alloy pipe for special pipe fittings for pressure vessels, comprising a ring furnace and an electromagnetic furnace, wherein the specific steps are as follows:

[0020] 1) Ring furnace preheating process:

[0021] The processed 00Cr30Ni60Fe10 nickel-based high-temperature billet is heated at high temperature, which is divided into two parts: ring furnace temperature control and billet charging method, as follows:

[0022] 1.1) The temperature control of the annular furnace is divided into controlling the annular furnace charging temperature, heating time, holding time and the control temperature of the billet. Specifically, the annular furnace charging temperature is ≤700°C, the heating time is 120 to 300 minutes, the holding time is 90 to 180 minutes, and the billet temperature control parameters are 950 to 1050°C;

[0023] 1.2) Billet charging method: The billet end faces forward and is charged in a single row with one charging station between them to control the steel-out rhythm, which is conducive to the precise control of the preheating temperature;

[0024] 2) Electromagnetic induction heating process:

[0025] After the ring furnace preheating process in step 1), the 00Cr30Ni60Fe10 nickel-based alloy high-temperature billet that has been heated to a temperature range of 950-1050°C is subjected to a second electromagnetic induction heating to meet the requirements of the subsequent high-temperature extrusion pipe making process, as follows:

[0026] 2.1) The upper end of the internal working chamber of the induction furnace is provided with 22 levels of upper heating copper sheets, and the lower end is provided with 4 levels of lower heating copper sheets. The distance between the copper sheets is 30 mm, and the thickness of the copper sheets is 2 mm. First, adjust the position of the upper heating copper sheet of the induction furnace to be 2 to 4 copper sheet spacings higher than the length of the billet;

[0027] The purpose of this step is to appropriately increase the heating temperature of the head of the tube blank and reduce the temperature drop of the tube blank during transportation after high-temperature heating.

[0028] 2.2) After confirming the adjustment in step 2.1), take the billet out of the rotary hearth furnace in step 1);

[0029] 2.3) The billet is transported by the roller table to the position of the billet inlet and outlet (1b) at the lower part of the induction furnace;

[0030] 2.4) Before the fork loader feeds the billet, measure the temperature of the billet first, and confirm that the temperature of the billet is in the range of 750 - 850 °C;

[0031] 2.5) The lifting oil cylinder sends the billet into the internal working cavity of the induction furnace;

[0032] 2.6) Start the induction furnace, and the induction coil heats the billet;

[0033] 2.7) The heating power of the induction furnace is set to 600 kw / m, and the heating time is 1 - 2 minutes;

[0034] 2.8) Heat the billet temperature to 1000 °C;

[0035] 2.9) Keep the billet in the furnace for 40 - 90 seconds;

[0036] 2.10) The lifting oil cylinder descends, and the billet also descends accordingly;

[0037] 2.11) Take the billet out of the furnace for air cooling;

[0038] 2.12) Wait until the internal temperature and external temperature of the billet reach equilibrium, and measure its surface temperature to be in the range of 900 - 980 °C;

[0039] 2.13) Start the lifting oil cylinder again, and send the billet into the internal working cavity of the induction furnace for reheating;

[0040] 2.14) The heating power is 600 kw / m, and the heating time is 1 - 2 minutes;

[0041] 2.15) The billet temperature reaches the set temperature range of 1070 - 1110 °C after heating;

[0042] 2.16) Keep the billet in the furnace for 30 - 60 seconds;

[0043] 2.17) The lifting oil cylinder descends, and the billet also descends accordingly, and take the billet out of the furnace;

[0044] 2.18) The billet is sent to the subsequent extrusion pipe-making process through the conveying roller table.

[0045] The electromagnetic induction heating process of this step is summarized as follows: feeding into the induction furnace → adjusting the position of the copper sheet tap → first-stage heating → in-furnace uniformity heat preservation → billet discharging and air cooling → secondary feeding into the induction furnace → second-stage heating → in-furnace uniformity heat preservation → billet discharging (conveyed to the subsequent extrusion pipe-making process). The key lies in controlling the secondary heating temperature, heating-up power of the electromagnetic induction furnace, adjusting the tap position to increase the head temperature compensation, etc. Finally, the heating temperature of the billet is controlled within the range of 1070 - 1110 °C.

[0046] It should be noted that since the deformable temperature of the tube blank material is between 1050 - 1200 °C, and in order to ensure that the grain size of the hot-extruded tube meets the technical requirements, the deformation temperature is required to be between 1050 - 1110 °C. Among them, the preheating temperature of the rotary hearth furnace is 950 - 1050 °C, and the secondary heating temperature of the electromagnetic induction furnace is 1070 - 1110 °C, which can meet the production requirements of high-temperature extrusion pipe-making for special pipe fittings with a large thickness-diameter ratio, high strength, large deformation resistance, and slender shape.

[0047] According to the nickel-based alloy extrusion pipe-making temperature control method for special pipe fittings of pressure vessels of the present invention, it is characterized in that the billet temperature control parameter in step 1.1) is preferably 1000 ± 20 °C.

[0048] According to the nickel-based alloy extrusion pipe-making temperature control method for special pipe fittings of pressure vessels of the present invention, it is characterized in that the working position calculation model of the upper heating copper sheet in step 2.1) is H = L + t;

[0049] In the formula:

[0050] H = the vertical height of the upper heating copper sheet when the billet enters the induction furnace;

[0051] L = the billet length, that is, the vertical height of the billet placed in the induction furnace;

[0052] t = the adjustment coefficient of the upper heating copper sheet, with a value of 2 - 4 copper sheet spacings.

[0053] Taking a 750 mm length as an example, the working position of the upper heating copper sheet is between 750 + 2×(30 + 4) - 750 + 4×(30 + 4) = 818 - 886 mm.

[0054] Using the nickel-based alloy extrusion pipe-making temperature control method for special pipe fittings of pressure vessels of the present invention has obtained the following beneficial effects:

[0055] 1. The temperature control method for extruding a nickel-based alloy pipe for special pipe fittings for pressure vessels of the present invention reasonably sets the parameters of the relevant process and the like for heating the pipe blank according to the element composition of the 00Cr30Ni60Fe10 nickel-chromium-iron-based solid solution strengthened nickel-based corrosion-resistant alloy, so as to provide a pipe blank that meets the temperature technical requirements for subsequent high-temperature extrusion pipe production, and realize the industrial-scale production of penetration pieces for special-purpose pressure vessels;

[0056] 2. The temperature control method for extruding nickel-based alloy pipes for special pipes for pressure vessels of the present invention can meet the high-temperature extrusion pipe production requirements of special pipes with large thickness-to-diameter ratio, high strength, large deformation resistance and slender shape;

[0057] 3. The temperature control method for extruding a nickel-based alloy tube for special pipe fittings for pressure vessels of the present invention adjusts the tap position, appropriately increases the head heating temperature, reduces the temperature drop of the tube blank during transportation after high-temperature heating, and achieves precise control of the extrusion temperature by reasonably adjusting the tube blank temperature, thereby meeting the technical performance requirement that the grain size of the hot extruded tube after extrusion tube making is finer than grade 5;

[0058] 4. The temperature control method for extruding nickel-based alloy pipes for special pipe fittings for pressure vessels of the present invention has reasonable process parameters, uniform alloy structure, good dimensional accuracy, high yield rate, safety, reliability, practicality and efficiency, significant energy-saving, emission reduction and consumption reduction effects, strong versatility, breaking international technical barriers, and having certain reference and application value for the research and development and industrial production of high-temperature extrusion pipes of nickel-based corrosion-resistant alloy seamless steel pipes in the industry, and can promote the localization of key materials in the domestic energy (nuclear power) field, with broad market application prospects and considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a specific schematic diagram of a tube blank in an electromagnetic induction furnace in the temperature control method for extruding a nickel-based alloy tube for special pipe fittings for pressure vessels of the present invention;

[0060] In the figure: 1-induction furnace, 1a-internal working chamber, 1b-blank inlet and outlet, 2-upper heating copper sheet, 3-blank, 4-lifting cylinder, 5-induction coil. DETAILED DESCRIPTION

[0061] The temperature control method for extruding a nickel-based alloy pipe for a special pipe fitting for a pressure vessel of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0062] A temperature control method for extruding a nickel-based alloy pipe for a special pipe fitting for a pressure vessel includes a ring furnace and an electromagnetic furnace, and the specific steps are as follows:

[0063] 1) Ring furnace preheating process:

[0064] The 00Cr30Ni60Fe10 nickel-based superalloy billet after processing is heated at high temperature, which is divided into two parts: the temperature control of the ring furnace and the billet charging method into the furnace, as follows:

[0065] 1.1) The temperature control of the ring furnace is divided into controlling the charging temperature of the ring furnace, the heating-up time, the holding time, and the controlled temperature of the billet. Specifically, the charging temperature of the ring furnace ≤ 700 °C, the heating-up time is 120 - 300 minutes, the holding time is 90 - 180 minutes, and the billet temperature control parameter is 950 - 1050 °C;

[0066] 1.2) Billet charging method into the furnace: The end face of the billet faces forward, and single-row charging is adopted, with one charging station interval, to control the tapping rhythm and is conducive to the precise control of the preheating temperature;

[0067] 2) Electromagnetic induction heating process:

[0068] After the ring furnace preheating process in step 1) above, the 00Cr30Ni60Fe10 nickel-based alloy high-temperature billet that has been heated to the temperature range of 950 - 1050 °C is subjected to secondary electromagnetic induction heating to meet the requirements of the subsequent high-temperature extrusion pipe processing, as follows:

[0069] 2.1) As Figure 1 shown, at the upper end of the internal working chamber 1a of the induction furnace 1, there are 22 upper heating copper sheets 2, and at the lower end, there are 4 lower heating copper sheets. The distance between the copper sheets is 30 mm, and the thickness of the copper sheets is 2 mm. First, adjust the position of the upper heating copper sheet of the induction furnace to be 2 - 4 copper sheet spacings higher than the length of the billet 3;

[0070] 2.2) After confirming that the adjustment in step 2.1) is completed, take the billet out of the ring furnace in step 1);

[0071] 2.3) The billet is transported to the billet inlet and outlet 1b position at the lower part of the induction furnace through the roller table;

[0072] 2.4) Before the fork loader feeds the billet, measure the billet temperature first, and confirm that the billet temperature is within the range of 750 - 850 °C;

[0073] 2.5) The lifting oil cylinder 4 sends the billet into the internal working chamber of the induction furnace;

[0074] 2.6) Start the induction furnace, and the induction coil 5 heats the billet;

[0075] 2.7) The heating-up power of the induction furnace is set to 600 kw / m, and the heating time is 1 - 2 minutes;

[0076] 2.8) Heat the billet temperature to 1000 °C;

[0077] 2.9) The blank is heat-insulated in the furnace for 40 to 90 seconds;

[0078] 2.10) The lifting oil cylinder descends, and the blank also descends accordingly;

[0079] 2.11) Take the blank out of the furnace for air cooling;

[0080] 2.12) Wait until the internal temperature and external temperature of the blank reach equilibrium, and measure its surface temperature in the range of 900 - 980 °C;

[0081] 2.13) The lifting oil cylinder starts again, and the blank is sent to the internal working cavity of the induction furnace for reheating;

[0082] 2.14) The heating power is 600 kw / m, and the heating time is 1 - 2 minutes;

[0083] 2.15) The temperature of the blank reaches the set temperature in the range of 1070 - 1110 °C after heating;

[0084] 2.16) The blank is heat-insulated in the furnace for 30 - 60 seconds;

[0085] 2.17) The lifting oil cylinder descends, and the blank also descends accordingly, and the blank is taken out of the furnace;

[0086] 2.18) The blank is sent to the subsequent extrusion machine for pipe making processing through the conveyor roller path.

[0087] The blank temperature control parameters in step 1.1) are preferably 1000 ± 20 °C.

[0088] The station calculation model of the upper heating copper sheet 2 in step 2.1) is H = L + t;

[0089] In the formula:

[0090] H = the vertical height of the upper heating copper sheet 2 where the blank 3 enters the induction furnace 1;

[0091] L = the length of the blank, that is, the vertical height of the blank placed in the induction furnace;

[0092] t = the adjustment coefficient of the upper heating copper sheet, and the value is 2 - 4 copper sheet spacings.

[0093] Example

[0094] Taking the nickel-chromium-iron-based solid solution strengthened nickel-based corrosion-resistant alloy seamless steel pipe of 00Cr30Ni60Fe10 with the blank specification of Φ239×Φ60×750mm and the finished product specification of the hot-extruded pipe of Φ114×35mm as an example, the nickel-based alloy extrusion pipe making temperature control method for special pipe fittings of pressure vessels of the present invention is as follows:

[0095] 1) Ring furnace preheating process:

[0096] The function of this process is to heat the processed 00Cr30Ni60Fe10 nickel-based superalloy billet at high temperature by using the heating method of a ring furnace. The technical characteristics of this process are as follows: First, control the charging temperature, heating-up time, holding time of the ring furnace, and the controlled temperature of the billet. The controlled temperature for preheating the ring furnace is controlled in the range of 950 - 1050 °C, and it is particularly suitable at 1000 ± 20 °C. Second, control the billet charging method into the furnace. The billet end faces forward, and single-row charging is adopted, with one charging station interval, so as to control the tapping rhythm and is conducive to the precise control of the preheating temperature. As shown in Table 1 below:

[0097]

[0098] Table 1 - Preheating Process Parameters of Ring Heating Furnace

[0099] 2) Electromagnetic Induction Heating Process:

[0100] The function of this process is to heat the 00Cr30Ni60Fe10 nickel-based alloy high-temperature billet that has been heated (preheated) to the temperature range of 950 - 1050 °C in the ring furnace for the second time by using the electromagnetic induction heating method to meet the requirements of subsequent high-temperature extrusion pipe processing. The technical key points of this process are as follows: Adopt steps such as induction furnace feeding → copper sheet tap position adjustment → first-stage heating → in-furnace uniformity holding → billet out-of-furnace air cooling → induction furnace second-time feeding → second-stage heating → in-furnace uniformity holding → billet out-of-furnace (transported to the extruder). The key lies in controlling the second heating temperature, heating-up power of the electromagnetic induction furnace, adjusting the tap position to increase the head temperature compensation, etc. The heating temperature of the billet is controlled in the range of 1050 - 1110 °C, and it is particularly suitable at 1090 ± 20 °C. As shown in Table 2 below:

[0101]

[0102] Table 2 - Induction Heating Process Parameters

[0103] Combined with the above examples, it can be seen that the temperature control method for extruding nickel-based alloy pipes for special pipe fittings for pressure vessels of the present invention reasonably sets the relevant process parameters such as pipe blank heating according to the element composition of 00Cr30Ni60Fe10 nickel-chromium-iron-based solid solution strengthened nickel-based corrosion-resistant alloy, so as to provide pipe blanks that meet the temperature technical requirements for subsequent high-temperature extrusion pipe production, and realize the industrial-scale production of penetration parts for special-purpose pressure vessels; the present invention can meet the high-temperature extrusion pipe production requirements of special pipe fittings with large thickness-to-diameter ratio, high strength, large deformation resistance and slender shape; and the present invention appropriately increases the heating temperature of the head by adjusting the tap position, thereby reducing the temperature drop of the pipe blank during transportation after high-temperature heating. , and by reasonably adjusting the temperature of the tube blank, the extrusion temperature can be accurately controlled to meet the technical performance requirements of the hot extruded tube grain size finer than level 5 after extrusion tube making; in addition, the temperature control method for extrusion tube making of nickel-based alloy for special pipe fittings of pressure vessels of the present invention has reasonable process parameters, uniform alloy structure, good dimensional accuracy, high yield rate, safety and reliability, practicality and high efficiency, significant energy-saving, emission reduction and consumption reduction effects, and strong versatility, breaking international technical barriers, and having certain reference and application value for the research and development and industrial production of high-temperature extrusion tube making of nickel-based corrosion-resistant alloy seamless steel tubes in the industry, and can promote the localization of key materials in the domestic energy (nuclear power) field, with broad market application prospects and considerable economic benefits.

[0104] However, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used to limit the present application. As long as they are within the spirit of the present application, any changes or modifications to the above embodiments will fall within the scope of the claims of the present application.

Claims

1. Temperature control method for nickel-based alloy extrusion pipe making for special pipe fittings of pressure vessels, including a ring furnace and an induction furnace, and the specific steps are as follows: 1) Ring furnace preheating process: The processed 00Cr30Ni60Fe10 nickel-based high-temperature blank is heated at high temperature, which is divided into two parts: ring furnace temperature control and blank charging method into the furnace, specifically as follows: 1.1) Ring furnace temperature control includes controlling the furnace charging temperature, heating-up time, holding time of the ring furnace and the control temperature of the blank. Specifically, the furnace charging temperature of the ring furnace ≤ 700 °C, the heating-up time is 120 - 300 minutes, the holding time is 90 - 180 minutes, and the blank temperature control parameter is 950 - 1050 °C; 1.2) Blank charging method into the furnace: The end face of the blank faces forward, and single-row charging is adopted, with one charging station interval, so as to control the tapping rhythm and is conducive to the precise control of the preheating temperature; 2) Electromagnetic induction heating process: After the ring furnace preheating process in step 1) above, the 00Cr30Ni60Fe10 nickel-based alloy high-temperature blank that has been heated to the temperature range of 950 - 1050 °C is subjected to secondary electromagnetic induction heating to meet the requirements of subsequent high-temperature extrusion pipe making processing, specifically as follows: 2.1) At the upper end of the internal working cavity (1a) of the induction furnace (1), 22 upper heating copper sheets (2) are provided, and 4 lower heating copper sheets are provided at the lower end. The distance between the copper sheets is 30 mm, and the thickness of the copper sheets is 2 mm. First, adjust the working position of the upper heating copper sheet of the induction furnace to be 2 - 4 copper sheet intervals higher than the length of the blank (3); 2.2) After confirming that the adjustment in step 2.1) is completed, take the blank out of the ring furnace in step 1); 2.3) The blank is transported to the position of the blank inlet and outlet (1b) at the lower part of the induction furnace through the roller table; 2.4) Before the fork loader feeds the blank, first measure the temperature of the blank and confirm that the temperature of the blank is within the range of 750 - 850 °C; 2.5) The jacking oil cylinder (4) sends the blank into the internal working chamber of the induction furnace; 2.6) Start the induction furnace, and the induction coil (5) heats the blank; 2.7) The heating power of the induction furnace is set to 600 kw / m, and the heating time is 1 - 2 minutes; 2.8) Heat the blank temperature to 1000 °C; 2.9) Keep the blank in the furnace for 40 - 90 seconds; 2.10) The jacking oil cylinder descends, and the blank also descends accordingly; 2.11) Take the blank out of the furnace for air cooling; 2.12) Wait until the internal temperature and external temperature of the blank reach equilibrium, and measure its surface temperature in the range of 900 - 980 °C; 2.13) Start the jacking oil cylinder again, and send the blank into the internal working chamber of the induction furnace for reheating; 2.14) The heating power is 600 kw / m, and the heating time is 1 - 2 minutes; 2.15) The blank temperature reaches the set temperature in the range of 1070 - 1110 °C after heating; 2.16) Keep the blank in the furnace for 30 - 60 seconds; 2.17) The jacking oil cylinder descends, and the blank also descends accordingly, and take the blank out of the furnace; 2.18) Send the blank to the subsequent extrusion machine for pipe making through the conveying roller table.

2. The temperature control method for nickel-based alloy extrusion pipe making of special pipe fittings for pressure vessels according to claim 1, characterized in that, The blank temperature control parameter in step 1.1) is preferably 1000 ± 20 °C.

3. The temperature control method for nickel-based alloy extrusion pipe making of special pipe fittings for pressure vessels according to claim 1, characterized in that, The station calculation model of the upper heating copper sheet (2) in step 2.1) is H = L + t; In the formula: H = the vertical height of the upper heating copper sheet (2) where the blank (3) enters the induction furnace (1); L = the length of the blank, that is, the vertical height of the blank placed in the induction furnace; t = the adjustment coefficient of the upper heating copper sheet, and the value is 2 - 4 copper sheet pitches.

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