An induction heating method applied to a pipe blank for high-temperature extrusion of seamless steel pipes

Abstract

The application relates to an induction heating method applied to a seamless steel pipe blank for high-temperature extrusion, which is suitable for two heating process models of an unthreaded / expanded pipe blank and a threaded / expanded pipe blank. The induction heating method of the unthreaded / expanded pipe blank comprises positioning, first-pass manual heating, first-pass cooling, second-pass manual heating, second-pass cooling, third-pass automatic heating and blanking. The induction heating method of the threaded / expanded pipe blank comprises positioning, first-pass manual heating, first-pass cooling, second-pass automatic heating and blanking. The application effectively solves the problem of accurate heating of the pipe blank after heating caused by abnormal working conditions of a production line, eliminates the production cost loss caused by air cooling / water cooling of the pipe blank due to abnormal working conditions of the production line, realizes accurate heating of the pipe blank under abnormal working conditions, is beneficial to subsequent threading / expanding and extrusion production, avoids heating and temperature rising errors, and has strong universality and practical application value for high-temperature extrusion pipe production of seamless steel pipes.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgical processing, and is particularly applicable to the induction heating method for tube blanks in the production of seamless steel pipes under high-temperature hot extrusion, which performs secondary heating on tube blanks when abnormal conditions occur during the high-temperature hot extrusion of seamless steel pipes. Background Technology

[0002] Currently, seamless steel pipes are common products of various steel metallurgical production enterprises. Seamless steel pipes require multiple processes from metal smelting and rolling to finished product delivery. The high-temperature hot extrusion pipe making method (also known as extrusion) used in the production of seamless steel pipes has become the main method for the production of high-end seamless steel pipes at home and abroad because of its large deformation, easy one-time forming, high production precision, easy organization of continuous production, high capacity and suitability for processing high alloy elements.

[0003] In addition to the advantages mentioned above, the high-temperature hot extrusion tube manufacturing method has the advantage that the deformation of metals during high-temperature extrusion is mainly triaxial compressive stress deformation. Under the action of triaxial compressive stress during the extrusion process, the plasticity of the extruded material can be improved, resulting in good metal density, uniform structure, and better internal and external surface quality, metallographic structure and properties.

[0004] In actual production, the main processes of high-temperature hot extrusion tube making for seamless steel pipes include: billet preparation (lathe, saw, etc.), billet heating (ring furnace, induction furnace, etc.), billet piercing / expanding, billet descaling, billet secondary heating, high-temperature extrusion tube making, and finished product cooling (cooling bed). The high-temperature extrusion tube making process involves hydraulically driving heated high-temperature billets (usually round steel) through a circular die (i.e., extrusion cylinder) to form the final product. The detailed process flow for this step is: billet preparation (cutting, end-cutting, length setting, peeling, drilling, cleaning) → ring furnace (preheating) → induction furnace zone one heating → piercing / expanding machine (expanding) → induction furnace zone two heating → extrusion press (high-temperature extrusion) → hot saw (residual pressure separation and cutting) → cooling bed collection, etc.

[0005] As can be seen from the above, the high-temperature extrusion tube-making process is a key process in the entire hot extrusion tube-making production of seamless steel pipes, and it directly determines the output and quality of high-temperature extrusion tubes. The accuracy of the billet heating temperature is the key to ensuring the precision of high-temperature extrusion tube-making.

[0006] However, during production, it was found that precise control of the billet heating temperature is quite difficult. After heating, the billet (round steel) needs to be cooled. This cooling refers to the loss of temperature from the outer surface of the billet, and the penetration of the outer surface temperature into the inner core (core) of the billet. Due to the time difference between the cooling of the outer surface and the inner core of the billet (i.e., the inner core loses temperature more slowly than the outer surface), the temperature of the inner core of the billet will be higher than the temperature of the outer surface. Moreover, in order to prevent the temperature of the billet head from becoming too high after heating, which would affect the microstructure and grain structure of the head, temperature control is a difficult process to control in high-temperature extrusion production.

[0007] Both domestic and international high-temperature extrusion production of seamless steel pipes employs continuous production methods. The billet is produced from heating to extrusion forming in an assembly line manner. Assembly line production avoids ineffective losses after billet heating, resulting in significant energy savings. However, if any step in the assembly line production process malfunctions, the entire line will be unable to operate normally. For example, if the extruder, a critical control piece of the production line, malfunctions, the already heated billet cannot smoothly enter the extruder for processing. It must wait for the equipment or die malfunction to be resolved before extrusion can proceed. Since the waiting time for the high-temperature billet cannot be determined in advance, the billet temperature will drop. Furthermore, due to uneven temperature drop between the outer surface and the inner core of the billet, the waiting high-temperature billet will not meet the requirements for high-temperature extrusion pipe processing and must be reprocessed.

[0008] Under current technology, the method for handling high-temperature tube blanks under the above-mentioned abnormal operating conditions is cooling:

[0009] The high-temperature tube blank is lifted into a special water tank using metal clamps for rapid and complete cooling (air cooling is used if certain steel grades cannot be water-cooled). Then, the glass powder that serves as a high-temperature lubricant on the outer surface of the cooled tube blank is removed manually. (The glass powder adheres to the inner and outer surfaces of the tube blank after high-temperature heating and serves as an online lubricant during high-temperature extrusion tube making, but the glass powder itself cannot be heated at high temperatures.) Then, according to the process requirements, the cooled tube blank that has been cleaned of glass powder is transported back to the annular furnace or induction furnace for heating.

[0010] This existing technology is currently a widely adopted method in the industry for handling billets in the event of sudden abnormal operating conditions. It can meet the technical requirements for secondary handling of billets in the event of sudden abnormalities in the entire production line to a certain extent, but it still has shortcomings, as follows:

[0011] 1) Energy loss:

[0012] The high-temperature tube blank that has been heated is then water-cooled (or air-cooled) and then reheated. This is essentially a secondary heating process, which requires additional electricity (induction furnace) or natural gas (ring furnace). Therefore, it increases the energy consumption of secondary heating, increases the production cost of enterprises, and is not conducive to energy conservation and emission reduction.

[0013] 2) Material loss:

[0014] After the high-temperature tube blank is water-cooled (or air-cooled), operators need to manually remove the glass powder adhering to the inner and outer surfaces of the tube blank. It must be completely removed, otherwise it will affect the effect of subsequent secondary heating and the stability of the heating equipment. After the subsequent secondary heating, glass powder still needs to be reapplied, which increases the consumption of glass powder and the consumption of manpower and tools for removing glass powder.

[0015] 3) Time loss:

[0016] The process of cooling, de-powdering, and then heating high-temperature tube blanks takes a long time. If air cooling is used, it takes even longer. Especially during the pilot production of new steel grades and specifications, since the number of tube blanks in the same batch is small and other specifications cannot be produced, there will be a waiting period for materials, which will affect the normal production organization and the effective production time of the entire production line.

[0017] In summary, the existing billet reheating technology has shortcomings in terms of energy consumption, material consumption, and time consumption. Furthermore, the passive cooling of the billet due to abnormal conditions in the production line is also a common phenomenon. There is an urgent need for a new heating method for billets used in high-temperature extrusion of seamless steel pipes to improve the technology and effectively solve the subsequent losses caused by the reheating of the billet. Summary of the Invention

[0018] To address the aforementioned problems, this invention provides an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes. This invention technically improves upon the shortcomings of traditional secondary heating processes in high-temperature extrusion of seamless steel pipes. The invention consists of seven steps: positioning, first-pass manual heating, first-pass cooling, second-pass manual heating, second-pass cooling, third-pass automatic heating, and blanking. Based on heating process models for un-pierced / expanded and pierced / expanded holes, it achieves precise heating of the tube blank under abnormal operating conditions. The specific details of this induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes are as follows:

[0019] The induction heating method described herein is applicable to two heating process models: un-pierced / expanded tube blanks and pierced / expanded tube blanks.

[0020] The induction heating method for unpierced / re-expanded tube blanks includes the following steps:

[0021] The process consists of seven steps: positioning, first-stage manual heating, first-stage cooling, second-stage manual heating, second-stage cooling, third-stage automatic heating, and unloading.

[0022] The induction heating method for pierced / reamed tube blanks includes the following steps:

[0023] The process consists of five steps: positioning, first-stage manual heating, first-stage cooling, second-stage automatic heating, and unloading.

[0024] The present invention discloses an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes. The method establishes a heating process model based on tube blanks that are not pierced / expanded and tube blanks that have been pierced / expanded, thereby achieving precise heating of tube blanks under abnormal working conditions, which is beneficial to subsequent piercing / expanding and extrusion production.

[0025] According to an induction heating method for seamless steel tube blanks used in high-temperature extrusion, the induction heating method applicable to the heating process model of unpierced / expanded tube blanks, specifically comprises:

[0026] 2.1) Positioning:

[0027] Adjust the tap position of the induction coil according to the billet heating temperature requirements, ensuring that the tap position is adapted to the billet length;

[0028] 2.2) First pass manual heating:

[0029] The billet is transported into the induction coil of the pre-adjusted station in Zone 1 of the induction furnace, and the manual heating system is started. In this step, the power of the induction furnace is 300-400kW, and the temperature is heated to 1050℃, with the error value controlled within ±0-25℃.

[0030] 2.3) First cooling stage:

[0031] The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil, and then it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃.

[0032] 2.4) Second pass manual heating:

[0033] Start the lifting mechanism to raise the tube blank, which has been air-cooled to 850°C, vertically into the induction coil. Manually operate the heating system to heat to 1050°C with a power of 300-400kW, with the error value controlled within ±0-25°C.

[0034] 2.5) Second cooling stage:

[0035] The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil. Then, it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃. In this step, the core temperature of the tube blank is confirmed to be 900~950℃.

[0036] 2.6) Third-stage automatic heating:

[0037] Start the lifting mechanism to raise the tube blank, which has been air-cooled to an external surface temperature of 850°C, vertically lift it into the induction coil, and start the automatic heating system to heat it to the piercing / expanding temperature with a power of 300-400kW.

[0038] 2.7) Material cutting:

[0039] The lifting mechanism is activated to lower the tube blank, which has been heated to the piercing / expanding temperature, away from the induction coil and conveyed to the piercing / expanding machine via roller conveyor for vertical piercing or expanding.

[0040] According to an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes according to the present invention, in step 2.1), the error between the tap position of the induction coil and the height of the tube blank to be heated is controlled within ±0 to 10 mm.

[0041] According to an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes, the heating to the piercing / expansion temperature in the third pass of automatic heating in step 2.6) is specifically 1050~1200℃, depending on the steel grade and specifications, with an error value controlled within ±0~30℃.

[0042] According to an induction heating method for seamless steel tube blanks used in high-temperature extrusion, the induction heating method applicable to the heating process model of pierced / expanded tube blanks is specifically as follows:

[0043] 5.1) Positioning:

[0044] Adjust the tap position of the induction coil according to the billet heating temperature requirements, ensuring that the tap position is adapted to the billet length;

[0045] 5.2) First pass manual heating:

[0046] The billet is transported to the induction coil in the second zone of the induction furnace, and the manual heating system is started. The billet is heated to 1050℃ with a power of 400-600kW, and the error value is controlled within ±0~25℃.

[0047] 5.3) First cooling stage:

[0048] The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil. Then, it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃. In this step, it is confirmed that the core temperature of the tube blank is controlled within 900~950℃.

[0049] 5.4) Second pass automatic heating:

[0050] The lifting mechanism is activated to lift the air-cooled tube blank to an external surface temperature of 850°C vertically into the induction coil. The automatic heating system is then activated, using a power of 400-600kW to heat the tube to the temperature required for high-temperature extrusion.

[0051] 5.5) Material preparation:

[0052] The lifting mechanism is activated to lower the tube blank, which has been heated to the high temperature for tube extrusion, away from the induction coil and is then conveyed to the extruder via roller conveyor for high-temperature tube extrusion processing.

[0053] According to an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes according to the present invention, in step 5.1), the error between the tap position of the induction coil and the height of the tube blank to be heated is controlled within ±0 to 10 mm.

[0054] According to an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes according to the present invention, the temperature of the high-temperature extrusion tube forming in the second automatic heating in step 5.4) is specifically 1050~1200℃, depending on the steel grade and specifications, with an error value controlled within ±0~30℃.

[0055] According to an induction heating method for tube blanks used in high-temperature extrusion of seamless steel tubes, the two heating process models of the tube blanks without piercing / expanding and those with piercing / expanding can be combined to form a continuous processing method of piercing / expanding + high-temperature extrusion tube making.

[0056] The present invention provides an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes. According to the above process model, it can be effectively applied to the high-temperature piercing / expansion and extrusion tube production of seamless steel pipes. In particular, the manual + automatic combined heating method of the present invention meets the technical requirements for continuous and precise heating of leftover tube blanks caused by production line abnormalities, which facilitates on-site production organization and energy saving.

[0057] The overall concept of the induction heating method for tube blanks used in high-temperature extrusion of seamless steel tubes, as described in this invention, is as follows:

[0058] By adjusting the induction furnace tap position in a timely manner to match the actual temperature of the tube blank, heating errors are avoided. The first manual heating ensures the basic heating temperature of the tube blank, and timely cooling achieves a certain temperature difference between the outer surface and the core of the tube blank to optimize the grain size. The second manual heating meets the requirements of piercing / expanding technology, achieving temperature balance between the outer surface and the core, and ensuring the quality of piercing / expanding. The third automatic heating precisely heats the tube blank after piercing / expanding, ensuring temperature uniformity between the outer surface and the core, creating conditions for subsequent extrusion tube production.

[0059] The following beneficial effects were obtained by using the induction heating method of the present invention for tube blanks used in high-temperature extrusion of seamless steel tubes:

[0060] 1. The present invention provides an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes. The method is reasonably designed and has a compact process. It effectively solves the problem of accurate heating of tube blanks after heating caused by abnormal operating conditions of the production line. It eliminates the production cost loss caused by air cooling / water cooling of tube blanks due to abnormal operating conditions of the production line from the source, effectively reduces energy consumption, and has obvious green environmental protection, energy saving and emission reduction effects.

[0061] 2. The present invention provides an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes. Based on heating process models for un-pierced / expanded and pierced / expanded tubes, it achieves precise heating of tube blanks under abnormal working conditions, which is beneficial for subsequent piercing / expanding and extrusion production. Furthermore, by adjusting the position of the induction furnace tap in a timely manner through positioning, it matches the actual temperature of the tube blank and avoids heating and temperature rise errors.

[0062] 3. In an induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes according to the present invention: the first manual heating ensures the basic heating temperature of the tube blank, and through timely cooling, a certain temperature difference is achieved between the outer surface and the core of the tube blank to optimize the grains; the second manual heating meets the requirements of piercing / expanding technology, achieves temperature balance between the outer surface and the core, and ensures the quality of piercing / expanding processing; and the third automatic heating precisely heats the tube blank after piercing / expanding processing to ensure the temperature uniformity between the outer surface and the core, creating conditions for subsequent extrusion tube production.

[0063] 4. The induction heating method of the present invention for tube blanks for high-temperature extrusion of seamless steel pipes does not require additional investment in equipment / facilities, etc. It has low improvement cost, is easy to implement on site, is safe, reliable, practical and efficient, and is convenient to operate on site. It only requires operation according to the process model, reducing the reliance on the skills and experience of operators and realizing standardized operation for handling abnormal working conditions.

[0064] 5. The induction heating method of the present invention for tube blanks used in high-temperature extrusion of seamless steel pipes is highly versatile and has high reference and practical application value for the production of high-temperature extrusion tubes of seamless steel pipes. Attached Figure Description

[0065] Figure 1 This is a process flow diagram of vertical piercing or reaming of a tube blank for high-temperature extrusion of seamless steel tubes, applicable to a heating process model of tube blanks without piercing / reaming according to the present invention.

[0066] Figure 2 This is a process flow diagram of high-temperature extrusion tube manufacturing for a tube blank with pierced / expanded holes, applicable to a heating process model of a tube blank for high-temperature extrusion of seamless steel tubes according to the present invention. Detailed Implementation

[0067] The following description, in conjunction with the accompanying drawings and embodiments, further describes the technical means, creative features, achieved objectives, and effects of an induction heating method for seamless steel pipe billets used in high-temperature extrusion according to the present invention. The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0068] Example 1:

[0069] The batch of tube blanks, grade BG2532, with a finished size of φ114x15 (236 series), is a nickel-based superalloy. Its main metallic elements include nickel (55-60%), chromium (20-25%), cobalt (8-12%), molybdenum (5-7%), aluminum (1-5%), and titanium (1-3%). The tube blank length is 620mm, and the piercing temperature is 1150℃. Due to equipment failure, the entire batch of tube blanks could not be pierced, resulting in excess material. A heating process model for unpierced / expanded tube blanks was used, such as... Figure 1 As shown, the specific steps for performing vertical perforation or hole enlargement using the method provided by this invention are as follows:

[0070] 1) Positioning:

[0071] According to the billet heating temperature requirements, adjust the tap position of the induction coil to 615mm. It is necessary to ensure that the tap position is adapted to the length of the billet. The height error value is 620-615=5mm, which meets the technical requirement of ±0~5mm.

[0072] 2) First pass manual heating:

[0073] The billet is transported to the inductive coil in Zone 1 of the induction furnace, where the position has been adjusted. The manual heating system is started, and the billet is heated to 1040℃ with a power of 300-400kW. The error value is 1050-1040=10℃, which meets the technical requirement of ±0-15℃.

[0074] 3) First cooling stage:

[0075] The lifting mechanism is activated to lower the temperature, which will be heated to 1040℃ and disconnected from the induction coil. Under normal operating conditions, it will be air-cooled to an external temperature of 860℃. The error value is 850-860=-10℃, which meets the technical requirements of ±0~10℃.

[0076] 4) Second stage manual heating:

[0077] Start the lifting mechanism to raise the air-cooled coil to 860℃ and vertically lift it into the induction coil. Manually operate the heating system and use a power of 300~400kW to heat to 1055℃. The error value is 1050-1055=-5℃, which meets the technical requirements of ±0~15℃.

[0078] 5) Second cooling stage:

[0079] The lifting mechanism is activated to lower the tube. The tube is heated to 1055℃ and removed from the induction coil. It is then air-cooled to an external surface temperature of 855℃ under normal operating conditions. The error value is 850-855=-5℃, which meets the technical requirements of ±0~10℃. In this step, the core temperature of the tube blank is 912℃, which is within the range of 900~950℃.

[0080] 6) Automatic heating in the third stage:

[0081] The lifting mechanism is activated to raise the tube blank, which has been air-cooled to an external surface temperature of 855℃ (core temperature of 912℃), vertically into the induction coil. The automatic heating system is then activated, using a power of 300-400kW to heat the tube blank to a piercing / expanding temperature of 1130℃. The error value is 1150-1130=20℃, which meets the technical requirement of ±0-20℃.

[0082] 7) Material feeding:

[0083] The lifting mechanism is activated to lower the tube blank, which has been heated to the piercing / expanding temperature, away from the inductive coil and conveyed via roller conveyor to the piercing / expanding machine for vertical piercing or reaming.

[0084] Example 2:

[0085] The nickel-based superalloy, grade BG2532, with a finished product specification of φ135x25.5 (236 series specification), contains the following main metallic elements: nickel (55-60%), chromium (20-25%), cobalt (8-12%), molybdenum (5-7%), aluminum (1-5%), and titanium (1-3%). The billet length is 650mm, and the extrusion temperature is 1180℃. Due to a mold malfunction, this batch of billets could not be extruded in its entirety, resulting in excess material. Therefore, a heating process model for pre-pierced / expanded billets was used. Figure 2 As shown, the specific steps for high-temperature extrusion tube manufacturing using the method provided by this invention are as follows:

[0086] 1) Positioning:

[0087] According to the billet heating temperature requirements, the tap position of the induction coil is adjusted to 648mm. It is necessary to ensure that the tap position is adapted to the billet length. The height error value is 650-648=2mm, which meets the technical requirement of ±0~5mm.

[0088] 2) First pass manual heating:

[0089] The billet is transported to the inductive coil in the second zone of the induction furnace, where the position has been adjusted. The manual heating system is started, and the billet is heated to 1060℃ with a power of 400-600kW. The error value is 1050-1060=-10℃, which meets the technical requirement of ±0-15℃.

[0090] 3) First cooling stage:

[0091] The lifting mechanism is activated to lower the tube, which is heated to 1060℃ and removed from the induction coil. Under normal operating conditions, it is air-cooled to an external surface temperature of 855℃. The error value is 850-855=-5℃, which meets the technical requirement of ±0~10℃. In this step, the core temperature of the tube blank is 915℃, which is within the range of 900~950℃.

[0092] 4) Second pass automatic heating:

[0093] The lifting mechanism is activated to lift the tube blank, which has been air-cooled to an external surface temperature of 855℃ (core temperature of 915℃), vertically into the induction coil. The automatic heating system is then activated, using a power of 400-600kW to heat the tube to the high-temperature extrusion temperature of 1140℃. The error value is 1150-1140=10℃, which meets the technical requirement of ±0-20℃.

[0094] 5) Material preparation:

[0095] The lifting mechanism is activated to lower the tube blank, which has been heated to the high temperature for tube extrusion, away from the inductive coil and is then conveyed via roller conveyor to the extruder for high-temperature tube extrusion processing.

[0096] Example 3:

[0097] The nickel-based superalloy, grade BG2532, with a finished product specification of φ250x21 (346 series specification), mainly contains nickel (55-60%), chromium (20-25%), cobalt (8-12%), molybdenum (5-7%), aluminum (1-5%), and titanium (1-3%). The billet length is 720mm, the piercing temperature is 1150℃, and the extrusion temperature is 1180℃. Due to equipment failure, this batch of billets could not be pierced in its entirety, resulting in leftover material. This embodiment will use a combination of two methods: a heating process model for billets that have not been pierced / expanded, and a heating process model for billets that have been pierced / expanded. Figure 1 + Figure 2 The process involves continuous heating production, continuously completing the piercing / expansion and high-temperature extrusion tube manufacturing steps, as follows:

[0098] 1) Positioning:

[0099] According to the billet heating temperature requirements, adjust the tap position of the induction coil to 724mm. It is necessary to ensure that the tap position is adapted to the billet length. The height error value is 720-724=-4mm, which meets the technical requirement of ±0~5mm.

[0100] 2) First pass manual heating:

[0101] The billet is transported to the inductive coil in Zone 1 of the induction furnace, where the position has been adjusted. The manual heating system is started, and the billet is heated to 1060℃ with a power of 300-400kW. The error value is 1050-1060=-10℃, which meets the technical requirement of ±0-15℃.

[0102] 3) Cooling:

[0103] The lifting mechanism is activated to lower the temperature, which will be heated to 1060℃ and disconnected from the induction coil. Under normal operating conditions, it will be air-cooled to an external temperature of 860℃. The error value is 850-860=-10℃, which meets the technical requirements of ±0~10℃.

[0104] 4) Second stage manual heating:

[0105] Start the lifting mechanism to raise the air-cooled coil to 860℃ and vertically lift it into the induction coil. Manually operate the heating system and use a power of 300~400kW to heat to 1040℃. The error value is 1050-1040=10℃, which meets the technical requirements of ±0~15℃.

[0106] 5) Second cooling stage:

[0107] The lifting mechanism is activated to lower the tube. The tube is heated to 1040℃ and removed from the induction coil. It is then air-cooled to an external surface temperature of 860℃ under normal operating conditions. The error value is 850-860=-10℃, which meets the technical requirements of ±0~10℃. In this step, the core temperature of the tube blank is 915℃, which is within the range of 900~950℃.

[0108] 6) Automatic heating in the third stage:

[0109] The lifting mechanism is activated to lift the tube blank, which has been air-cooled to an external surface temperature of 860℃ (core temperature of 915℃), vertically into the induction coil. The automatic heating system is then activated, using a power of 300-400kW to heat the tube blank to a piercing / expanding temperature of 1160℃. The error value is 1150-1160=-10℃, which meets the technical requirement of ±0-20℃.

[0110] 7) Material feeding:

[0111] The lifting mechanism is activated to lower the tube blank, which has been heated to the piercing / expanding temperature, away from the inductive coil and conveyed via roller conveyor to the piercing / expanding machine for vertical piercing.

[0112] 8) Positioning:

[0113] The tube blank that has been vertically pierced by the piercing / expanding machine is repositioned. According to the tube blank heating temperature requirements, the tap position of the induction coil is adjusted to 724mm. It is necessary to ensure that the tap position is adapted to the length of the tube blank. The height error value is 720-724=-4mm, which meets the technical requirements of ±0~5mm.

[0114] 9) Fourth stage manual heating:

[0115] The tube blank, which has been vertically pierced by the piercing / expanding machine, is transported to the inductive coil in the second zone of the induction furnace, where the position has been adjusted. The manual heating system is started, and the tube is heated to 1060℃ with a power of 400-600kW. The error value is 1050-1060=-10℃, which meets the technical requirement of ±0-15℃.

[0116] 10) Cooling:

[0117] The lifting mechanism is activated to lower the tube, which is heated to 1060℃ and removed from the induction coil. Under normal operating conditions, it is air-cooled to an external surface temperature of 855℃. The error value is 850-855=-5℃, which meets the technical requirement of ±0~10℃. In this step, the core temperature of the tube blank is 915℃, which is within the range of 900~950℃.

[0118] 11) Automatic heating in the fifth pass:

[0119] The lifting mechanism is activated to lift the tube blank, which has been air-cooled to an external surface temperature of 855℃ (core temperature of 915℃), vertically into the induction coil. The automatic heating system is then activated, using a power of 400-600kW to heat the tube to the high-temperature extrusion temperature of 1170℃. The error value is 1180-1170=10℃, which meets the technical requirement of ±0-20℃.

[0120] 12) Material cutting:

[0121] The lifting mechanism is activated to lower the tube blank, which has been heated to the high temperature for tube extrusion, away from the inductive coil and is then conveyed via roller conveyor to the extruder for high-temperature tube extrusion processing.

[0122] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0123] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0124] Meanwhile, those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any changes or modifications to the above embodiments within the spirit and essence of this application will fall within the scope of the claims of this application.

Claims

1. An induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes, characterized in that: The induction heating method described herein is applicable to two heating process models: un-pierced / expanded tube blanks and pierced / expanded tube blanks. The induction heating method for unpierced / re-expanded tube blanks includes the following steps: The process consists of seven steps: positioning, first-stage manual heating, first-stage cooling, second-stage manual heating, second-stage cooling, third-stage automatic heating, and unloading. The induction heating method for pierced / reamed tube blanks includes the following steps: The process consists of five steps: positioning, first-stage manual heating, first-stage cooling, second-stage automatic heating, and unloading.

2. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes as described in claim 1, characterized in that, The induction heating method applicable to the heating process model of unpierced / expanded tube blanks is specifically as follows: 2.1) Positioning: Adjust the tap position of the induction coil according to the billet heating temperature requirements, ensuring that the tap position is adapted to the billet length; 2.2) First pass manual heating: The billet is transported into the induction coil of the pre-adjusted station in Zone 1 of the induction furnace, and the manual heating system is started. In this step, the power of the induction furnace is 300-400kW, and the temperature is heated to 1050℃, with the error value controlled within ±0-25℃. 2.3) First cooling stage: The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil, and then it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃. 2.4) Second pass manual heating: Start the lifting mechanism to raise the tube blank, which has been air-cooled to 850°C, vertically into the induction coil. Manually operate the heating system to heat to 1050°C with a power of 300-400kW, with the error value controlled within ±0-25°C. 2.5) Second cooling stage: The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil. Then, it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃. In this step, the core temperature of the tube blank is confirmed to be 900~950℃. 2.6) Third-stage automatic heating: Start the lifting mechanism to raise the tube blank, which has been air-cooled to an external surface temperature of 850°C, vertically lift it into the induction coil, and start the automatic heating system to heat it to the piercing / expanding temperature with a power of 300-400kW. 2.7) Material cutting: The lifting mechanism is activated to lower the tube blank, which has been heated to the piercing / expanding temperature, away from the induction coil and conveyed to the piercing / expanding machine via roller conveyor for vertical piercing or expanding.

3. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel tubes as described in claim 2, characterized in that, In step 2.1), the error between the tap position of the induction coil and the height of the tube blank to be heated is controlled within ±0 to 10 mm.

4. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes as described in claim 2, characterized in that, In step 2.6), the heating to the piercing / expanding temperature during the third automatic heating process is specifically 1050-1200℃, depending on the steel grade and specifications, with an error range of ±0-30℃.

5. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes as described in claim 1, characterized in that, The induction heating method applicable to the heating process model of pierced / expanded tube blanks is specifically as follows: 5.1) Positioning: Adjust the tap position of the induction coil according to the billet heating temperature requirements, ensuring that the tap position is adapted to the billet length; 5.2) First pass manual heating: The billet is transported to the induction coil in the second zone of the induction furnace, and the manual heating system is started. The billet is heated to 1050℃ with a power of 400-600kW, and the error value is controlled within ±0~25℃. 5.3) First cooling stage: The lifting mechanism is activated to lower the tube blank heated to 1050℃ away from the induction coil. Then, it is air-cooled to an external surface temperature of 850℃ under normal operating conditions, with the error value controlled within ±0~20℃. In this step, it is confirmed that the core temperature of the tube blank is controlled within 900~950℃. 5.4) Second pass automatic heating: The lifting mechanism is activated to lift the air-cooled tube blank to an external surface temperature of 850°C vertically into the induction coil. The automatic heating system is then activated, using a power of 400-600kW to heat the tube to the temperature required for high-temperature extrusion. 5.5) Material preparation: The lifting mechanism is activated to lower the tube blank, which has been heated to the high temperature for tube extrusion, away from the induction coil and is then conveyed to the extruder via roller conveyor for high-temperature tube extrusion processing.

6. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel tubes as described in claim 5, characterized in that, In step 5.1), the error between the tap position of the induction coil and the height of the tube blank to be heated is controlled within ±0 to 10 mm.

7. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel pipes as described in claim 5, characterized in that, The temperature of the high-temperature extrusion tube in the second automatic heating process of step 5.4) is specifically 1050-1200℃, depending on the steel grade and specifications, with an error value controlled within ±0-30℃.

8. The induction heating method for tube blanks used in high-temperature extrusion of seamless steel tubes as described in claim 1, characterized in that, The two heating process models for un-pierced / expanded tube blanks and pierced / expanded tube blanks can be combined to form a continuous processing method of piercing / expanding + high-temperature extrusion tube making.

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