Rapid cooling device, equipment and method for preparing seamless steel pipe

Abstract

The present invention provides a rapid cooling device, an apparatus and a method for preparing seamless steel pipes. The rapid cooling device includes one or more cooling correction groups, and the cooling correction groups include a rapid cooling device rack and a sizing machine finished product rack arranged in sequence along the pipe transportation direction; the rapid cooling device rack includes a water spray device, and the center line of the water ring of the water spray device is parallel to the center line of the sizing machine finished product rack and is at the same horizontal position. The rapid cooling device includes one or more cooling correction groups, that is, the rapid cooling device rack and the sizing machine finished product rack are arranged in sequence along the pipe transportation direction. This cooling method can allow the steel pipe to enter the sizing machine finished product rack immediately after rapid cooling, and the steel pipe after rapid cooling can be corrected immediately to avoid bending caused by uneven cooling of the steel pipe during the rapid cooling process. The cooling speed of the steel pipe can be greatly improved, thereby obtaining a hot-rolled seamless steel pipe with small straightness and ovality and excellent strength and toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a rapid cooling device, equipment and method for preparing seamless steel pipes. Background Art

[0002] In recent years, with the increasing number of applications in various extreme working conditions such as low temperature, high temperature and high pressure, the requirements for the strength and toughness of seamless steel pipes have become increasingly higher. For example, for the S460NH grade, the yield strength requirement is ≥460MPa, the tensile strength requirement is ≥540MPa, and the low-temperature impact resistance at -20°C is ≥40J. However, hot-rolled seamless steel pipes with a yield strength of 345 and above have problems such as insufficient strength and toughness and poor low-temperature impact toughness. Traditional online normalizing or normalizing processes are difficult to meet the requirements. The existing technology often uses tempering. However, the tempering process not only greatly increases production costs, but also has poor microstructure stability after tempering, and the internal stress of the steel pipe is also large. At the same time, it will greatly increase the yield strength ratio of the steel pipe, which is not conducive to the subsequent welding of the steel pipe and the safety of the components.

[0003] The goal of manufacturing companies is to stably and quickly improve the strength and toughness of steel pipes by controlling the deformation, cooling rate and cooling path of steel pipes. However, although TMCP technology has been maturely applied in the production of hot-rolled strip, medium and thick plates and profiles, the rolling deformation of steel pipes is complex and the controllable range is very small. In addition, compared with other long products, steel pipes have a hollow cross-section, larger cross-sectional dimensions and a larger range of dimensional specifications. Therefore, it is very difficult to implement controlled rolling and online heat treatment.

[0004] To address these issues, Chinese patent application CN109868352A discloses a water-cooled, self-tempering process and apparatus for steel pipes. This process rapidly cools ordinary low-carbon manganese steel to between 550 and 650°C through water spraying on the outer and inner walls of the pipe, producing a fine pearlite structure that improves the pipe's strength and stabilizes its impact toughness. However, the device's design is complex and cannot be utilized with existing production equipment, requiring significant modifications. Furthermore, the entire production process is time-consuming, slowing production pace and hindering production organization. Summary of the Invention

[0005] The main purpose of the present invention is to provide a rapid cooling device, equipment and method for preparing seamless steel pipes, so as to solve the problem of complex structure of the production equipment of high-strength and toughness seamless steel pipes in the prior art.

[0006] To achieve the above-mentioned object, according to one aspect of the present invention, a rapid cooling device is provided, which includes one or more cooling correction groups, the cooling correction groups including a rapid cooling equipment rack and a sizing machine finished product rack arranged in sequence along the pipe transportation direction; the rapid cooling equipment rack includes a water spray device, and the center line of the water ring of the water spray device is parallel to the center line of the sizing machine finished product rack and is at the same horizontal position.

[0007] In some embodiments, the quick cooling equipment rack is an air-through cooling equipment; the water spray device is fixed in the quick cooling equipment rack, the water spray device has a cavity that can accommodate the passage of pipes, and the water spray device is provided with nozzles, which are evenly distributed on the water spray device around one or more circles of the inner wall of the cavity of the water spray device.

[0008] In some embodiments, the direction of the water spraying from the nozzle is along the direction of the pipe transportation, and the angle between the nozzle and the pipe is 30° to 60°.

[0009] In some embodiments, the water flow rate of a single sprinkler device is between 10 and 300 m 3 / h;

[0010] In some embodiments, the cooling rate of the steel pipe in the rapid cooling equipment rack is 1.5-50° C. / s.

[0011] In some embodiments, the water spray device is a cone with an axis parallel to the ground. A small opening and a large opening of the water spray device are respectively provided along the transportation direction of the pipe. The small opening is the opening with a smaller cavity diameter of the water spray device, and the large opening is the opening with a larger cavity diameter of the water spray device. The water spray device has an interlayer for accommodating a cooling medium, and the nozzle is a hole provided on the inner wall of the water spray device; the aperture of the nozzle is 0.5~5mm.

[0012] In some embodiments, the sizing mill finished product frame is a round hole type sizing mill finished product frame; the hole-shaped roller gaps and roller bottoms of the round hole type sizing mill finished product frame are alternately arranged.

[0013] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided an apparatus for preparing seamless steel pipes, which comprises a smelting unit, a perforating unit, a rolling unit, a sizing unit and a cooling unit; wherein the rolling unit comprises a tube stripping machine and a first rapid cooling module arranged in sequence along the pipe transportation direction; the sizing unit comprises a second rapid cooling module and a sizing machine or a sizing machine arranged in sequence along the pipe transportation direction; the cooling unit comprises a third rapid cooling module and an air cooling module arranged in sequence along the pipe transportation direction, and the third rapid cooling module is any one of the above-mentioned rapid cooling devices.

[0014] In some embodiments, the first fast cooling module is a pass-through cooling device.

[0015] In some embodiments, the second fast cooling module is a pass-through cooling device.

[0016] In some embodiments, the perforating unit adopts a tapered diameter expansion perforating method.

[0017] In some embodiments, the rolling unit comprises a tandem tube mill.

[0018] According to another aspect of the present invention, a method for preparing a seamless steel pipe is provided, the method comprising the following steps: step S1, smelting a metallurgical raw material to obtain a billet; step S2, perforating the billet to obtain a rough pipe; step S3, rolling the rough pipe, and subjecting the obtained rough pipe to a first rapid cooling; step S4, subjecting the rough pipe after the first rapid cooling to a second rapid cooling and then to sizing or reducing the rough pipe, and subjecting the obtained steel pipe to a third rapid cooling, the third rapid cooling being performed in any of the above-mentioned rapid cooling devices; step S5, air cooling the steel pipe obtained by the third rapid cooling.

[0019] In some embodiments, the chemical composition of the metallurgical raw material is, by weight percentage, C 0.10%-0.20%, Si 0.15%-0.45%, Mn 1.05%-1.45%, V 0.02%-0.09%, Nb 0.020%-0.06%, Al 0.015%-0.06%, Ti≤0.020%, Cr≤0.30%, Ni≤0.25%, Mo≤0.10%, P≤0.020%, S≤0.010%, N≤0.012%, and the balance is Fe and unavoidable impurities.

[0020] In some embodiments, the temperature of the blank tube decreases by 30-150° C. during the first rapid cooling process.

[0021] In some embodiments, the temperature of the blank tube decreases by 30-150° C. during the second rapid cooling process.

[0022] In some embodiments, the temperature of the steel pipe after the third rapid cooling is 550-650°C.

[0023] In some embodiments, in step S3, the rolling temperature is 950-1150°C.

[0024] In some embodiments, the temperature of the sizing or reducing treatment in step S4 is a non-recrystallized region above Ar3+20°C.

[0025] By applying the technical solution of the present invention, the rapid cooling device includes one or more cooling correction groups, that is, the rapid cooling equipment rack and the sizing machine finished product rack are arranged in sequence along the pipe transportation direction. This cooling method can enable the steel pipe to enter the sizing machine finished product rack immediately after rapid cooling, and the steel pipe after rapid cooling is immediately corrected to avoid bending of the steel pipe caused by uneven cooling during the rapid cooling process. In particular, when the above-mentioned rapid cooling device contains multiple cooling correction groups, multiple rapid cooling equipment racks and sizing machine finished product racks are alternately arranged in sequence along the pipe transportation direction. Multiple racks are alternately cooled and corrected, which can greatly improve the cooling speed of the steel pipe, thereby obtaining a hot-rolled seamless steel pipe with small straightness and ovality and excellent strength and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 A schematic structural diagram of a cooling correction group according to an embodiment of the present invention is shown;

[0028] Figure 2 A schematic structural diagram of a quick cooling equipment rack according to an embodiment of the present invention is shown;

[0029] Figure 3 A schematic diagram showing the relative positions of a water spray device and a steel pipe according to an embodiment of the present invention is shown.

[0030] Among them, the above drawings include the following figure marks: 1. Cooling correction group; 01. Quick cooling equipment rack; 02. Sizing machine finished product rack; 010. Water spray device; 011. Nozzle; 012. Cooling water supply device interface; 013. Finished product rack; 014. Large mouth; 015. Small mouth. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0032] As analyzed in the background of this application, the current requirements for the strength and toughness of seamless steel pipes are becoming increasingly higher. However, the complex structure of the production equipment for high-strength and toughness seamless steel pipes in the technology increases the difficulty of producing high-strength and toughness seamless steel pipes. To address this problem, this application provides a rapid cooling device, equipment, and method for producing seamless steel pipes.

[0033] According to a typical embodiment of the present application, a rapid cooling device is provided, such as Figure 1As shown, the rapid cooling device includes one or more cooling correction groups 1, the cooling correction group 1 includes a rapid cooling equipment rack 01 and a sizing machine finished product rack 02 arranged in sequence along the pipe transportation direction; the rapid cooling equipment rack 01 includes a water spraying device 010 (such as Figure 2 As shown), the center line of the water ring of the water spray device 010 is parallel to the center line of the sizing machine finished product frame 02 and is at the same horizontal position.

[0034] The rapid cooling device of the present application includes one or more cooling correction groups 1, that is, the rapid cooling equipment rack 01 and the sizing machine finished product rack 02 are arranged in sequence along the pipe transportation direction. This cooling method can enable the steel pipe to enter the sizing machine finished product rack 02 immediately after rapid cooling, and the steel pipe after rapid cooling is immediately corrected to avoid bending of the steel pipe caused by uneven cooling during the rapid cooling process. In particular, when the above-mentioned rapid cooling device contains multiple cooling correction groups 1, multiple rapid cooling equipment racks 01 and sizing machine finished product racks 02 are alternately arranged in sequence along the pipe transportation direction. Multiple racks are alternately cooled and corrected, which can greatly improve the cooling speed of the steel pipe, thereby obtaining a hot-rolled seamless steel pipe with small straightness and ovality and excellent strength and toughness.

[0035] In some embodiments of the present application, the aforementioned rapid cooling equipment rack 01 is an air-through cooling device capable of achieving online cooling of the pipe, facilitating precise adjustment of the cooling rate and accurate control of the cooling path based on the pipe's outer diameter, thickness, and length, thereby effectively and accurately controlling the microstructure of the cooled pipe. Preferably, the cooling rate of the steel pipe in the rapid cooling equipment rack is 1.5-50°C / s, specifically 1.5°C / s, 10°C / s, 20°C / s, 30°C / s, 40°C / s, 50°C / s, etc., or other values ​​within the aforementioned range.

[0036] In some embodiments of the present application, Figure 2 As shown, the above-mentioned quick cooling equipment rack 01 includes a water spray device 010, which is fixed in the quick cooling equipment rack 01. The water spray device 010 has a cavity that can accommodate the passage of pipes. The water spray device 010 is provided with a nozzle 011. The nozzle 011 is evenly distributed on the water spray device 010 around the inner wall of the cavity of the water spray device for one or more weeks, so that the temperature of each position of the pipe drops more evenly and quickly, thereby improving the performance of the pipe. Preferably, the direction of water spraying from the nozzle 011 is along the direction of pipe transportation, and the angle with the pipe is 30°~60°, that is, the water flow sprayed by the water spray device 010 is sprayed in the direction of pipe transportation, and the angle with the pipe transportation direction is 30°~60°. Preferably, the water flow of a single water spray device 010 is between 10~300m 3 / h. Figure 1As shown, the above-mentioned fast cooling equipment rack further includes a cooling water supply device interface 012, which is connected to the water spraying device 010 and can continuously supply cooling water to the water spraying device.

[0037] In some embodiments, as Figure 2 As shown, the water spray device 010 is disposed on the finished product rack 013. In some embodiments, the above-mentioned rapid cooling equipment rack can be converted from the finished product rack of the sizing mill. Specifically, the rollers on the finished product rack of the sizing mill are removed to obtain the finished product rack 013, and the water spray device 010 and the cooling water supply device interface 012 are installed on the finished product rack. In other words, the above-mentioned rapid cooling equipment rack can be simply modified based on the original equipment. By cooperating with the finished product rack of the sizing mill, the steel pipe after rapid cooling can be immediately corrected, which not only greatly increases the cooling speed, but also facilitates the production of hot-rolled seamless steel pipes with low straightness and ovality and excellent strength and toughness.

[0038] In some embodiments of the present application, Figure 3 As shown, the water spraying device 010 is a truncated cone with its axis parallel to the ground, along the pipe (the pipe is as shown in FIG. Figure 3 ) in the direction of transport of the cylinder shown in FIG. , a small opening 015 and a large opening 014 of a water spray device 010 are provided. Small opening 015 is the opening with the smaller diameter of the cavity of water spray device 010, and large opening 014 is the opening with the larger diameter of the cavity (also in the shape of a truncated cone) of water spray device 010. Water spray device 010 has an interlayer for accommodating the cooling medium, and nozzle 011 is a hole provided on the inner wall of water spray device 010. The above-mentioned water spray device 010 is formed by opening a hole in the inner wall of the truncated cone-shaped water spray device as nozzle 011, and the angle of the nozzle water spray is controlled by controlling the taper of the cone. Water spray device 010 not only has a good cooling effect, but also has a simple structure, is easy to manufacture, and has a low failure rate. It will be understood by those skilled in the art that for pipes of different thicknesses or specifications, the cooling intensity of water spray device 010 can be adjusted by adjusting the water spray volume of water spray device 010 and the density of nozzle 011 to adapt to pipes of different thicknesses or specifications and achieve the purpose of rapid cooling.

[0039] In some embodiments of the present application, the aperture of the nozzle 011 is 0.5~5 mm, specifically 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, etc., or other values ​​within the above range, which helps to achieve rapid cooling of the pipe and further improve the strength and toughness of the seamless steel pipe.

[0040] In some embodiments of the present application, the sizing mill finished product rack 02 is a round hole type sizing mill finished product rack, which is particularly suitable for correction of seamless steel pipes after cooling.

[0041] In some embodiments of the present application, the groove roll gap and roller bottom of the finished product stand of a round-gap sizing mill are arranged alternately. The groove roll gap refers to the gap between two adjacent groove rolls used to form the steel pipe in the round-gap sizing mill, and the roller bottom refers to the bottom of the groove roll. This alternating arrangement of the groove roll gap and roller bottom means that in the finished product stand of the round-gap sizing mill, the groove roll gap and roller bottom are not continuous but alternate. That is, a certain position of the steel pipe is at the roller bottom (or roll gap) of the groove of one stand, while the same position is at the roller gap (or roller bottom) of the groove of the next stand. This design has the following advantages: the alternating arrangement of the groove roll gap and roller bottom ensures that the deformation of the steel pipe at the same position at the roller bottom (or roll gap) is eliminated as it passes through the sizing mill. This results in more uniform deformation of the entire circular cross-section, which helps eliminate ovality or bending that may occur during rapid cooling or deformation, thereby improving the straightness and out-of-roundness of the product.

[0042] It is understandable that the rapid cooling equipment rack 01 and the sizing machine finished product rack 02 in each cooling and correction group 1 can be provided with a conveying mechanism to convey the pipe from the rapid cooling equipment rack 01 to the sizing machine finished product rack 02. Similarly, when the rapid cooling device contains multiple cooling and correction groups 1, a conveying mechanism can also be provided between adjacent cooling and correction groups 1 to transport the pipe from the sizing machine finished product rack 02 to the next rapid cooling equipment rack 01. It should be pointed out that sometimes, in order to adapt to the production rhythm of seamless steel pipes, for example, when the number of cooling and correction groups is less than the number of sizing machine rack positions, a transport rack is added to transport the steel pipe from the cooling and correction group to the transport roller.

[0043] There is no limit to the specific number of cooling correction groups 1 in the rapid cooling device. For example, the number of cooling correction groups 1 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, or 16. Preferably, the number of cooling correction groups is 2 to 12, which is more effective in improving the strength, toughness, straightness, and ovality of the hot-rolled seamless steel pipe.

[0044] According to another typical embodiment of the present application, an apparatus for preparing seamless steel pipes is provided, which includes a smelting unit, a perforating unit, a rolling unit, a sizing unit and a cooling unit; wherein the rolling unit includes a tube stripper and a first quick cooling module arranged in sequence along the pipe transportation direction; the sizing unit includes a second quick cooling module and a sizing machine or a sizing machine arranged in sequence along the pipe transportation direction; the cooling unit includes a third quick cooling module and an air cooling module arranged in sequence along the pipe transportation direction, and the third quick cooling module is any of the above-mentioned quick cooling devices.

[0045] In the above-mentioned equipment for preparing seamless steel pipes, the steel pipes processed by the sizing and reducing unit are entered into a cooling unit including the above-mentioned rapid cooling device for processing. Since the above-mentioned rapid cooling device includes one or more cooling correction groups, that is, the rapid cooling equipment rack and the sizing machine finished product rack are arranged in sequence along the pipe transportation direction, this cooling method can enable the steel pipe to enter the round hole type finished product sizing rack immediately after rapid cooling, and the steel pipe after rapid cooling is immediately corrected to avoid bending of the steel pipe caused by uneven cooling during the rapid cooling process. In particular, when the above-mentioned rapid cooling device contains multiple cooling correction groups, multiple cooling equipment racks and sizing machine finished product racks are alternately arranged in sequence along the pipe transportation direction. Multiple racks are alternately cooled and corrected, which can greatly improve the cooling speed of the steel pipe, thereby obtaining a hot-rolled seamless steel pipe with small straightness and ovality and excellent strength and toughness. Furthermore, after the seamless steel pipe leaves the sizing mill, it is alternately processed through the rapid cooling equipment rack and the sizing mill finished product rack, so that the steel pipe is rapidly cooled in the medium temperature area, the grains remain in a hardened and deformed state, and refined ferrite and pearlite structures and microalloy precipitates are precipitated during the recovery and phase transformation process. It then passes through the transport rack and transport roller to the air cooling device (such as a large cooling bed), and is slowly cooled in the low-temperature cooling area to avoid the upper bainite transformation area. Finally, a hot-rolled seamless steel pipe with excellent strength, toughness and low-temperature toughness can be produced.

[0046] In some embodiments of the present application, the first rapid cooling module is a through-type cooling device, which is not only beneficial for improving the performance of seamless steel pipes, but also does not affect the normal production rhythm of steel pipes and is easy to implement.

[0047] The second rapid cooling module is connected to the sizing mill or the reducing mill. In some embodiments of the present application, the second rapid cooling module is a through-type cooling device, which does not affect the normal production rhythm of the steel pipe and can significantly improve the strength and toughness of the steel pipe through rapid cooling.

[0048] In some embodiments of the present application, the perforating unit adopts a tapered diameter expansion perforating method. The tapered diameter expansion perforating method can obtain a larger total deformation amount and flexibly adjust the deformation amount of each process such as perforation and rolling.

[0049] In some embodiments of the present application, the rolling unit includes a continuous pipe rolling mill, which is beneficial to improving the dimensional accuracy of the rolled raw pipe.

[0050] According to another typical embodiment of the present application, a method for preparing a seamless steel pipe is provided, which includes the following steps: step S1, smelting metallurgical raw materials to obtain a billet; step S2, perforating the billet to obtain a rough pipe; step S3, rolling the rough pipe, and subjecting the obtained rough pipe to a first rapid cooling; step S4, subjecting the rough pipe after the first rapid cooling to a second rapid cooling and then to sizing or reducing the diameter, and subjecting the obtained steel pipe to a third rapid cooling, and the third rapid cooling is carried out in any of the above-mentioned rapid cooling devices; step S5, air-cooling the steel pipe obtained by the third rapid cooling.

[0051] In the seamless steel pipe preparation method of the present application, the rolled rough pipe is subjected to a second rapid cooling before sizing or reducing treatment. Not only can the final rolling temperature of the steel pipe be reduced by two-stage rapid cooling, but the new phase and carbonitride will surround the strained deformation nucleus, which can greatly refine the grain structure; the rapid cooling of the steel pipe after sizing or reducing treatment can make the steel pipe structure quickly pass through the phase transformation region, and the newly formed phase will not grow and coarsen. At the same time, slow cooling in the low-temperature upper bainite region can avoid the formation of brittle upper bainite, and finally obtain a greatly refined ferrite + pearlite structure. The present application can obtain hot-rolled seamless steel pipes with small straightness and ovality and excellent strength and toughness by reasonably setting the cooling path. Moreover, the preparation method of the present application can make full use of existing seamless steel pipe equipment, and the preparation of high-strength and toughness seamless steel pipes can be completed with a slight modification, without adding any complex rapid cooling equipment, which is convenient for online batch production, can greatly reduce production costs, and improve production efficiency.

[0052] In some embodiments of the present application, the chemical composition of the metallurgical raw material is, by weight percentage, C 0.10%~0.20%, Si 0.15%~0.45%, Mn 1.05%~1.45%, V 0.02%~0.09%, Nb 0.020%~0.06%, Al 0.015%~0.06%, Ti≤0.020%, Cr ≤0.30%, Ni≤0.25%, Mo≤0.10%, P≤0.020%, S≤0.010%, N≤0.012%, and the balance is Fe and unavoidable impurities. By preparing seamless steel pipes using metallurgical raw materials having the above-mentioned composition, the non-recrystallized area of ​​the hot-rolled seamless steel pipe can be expanded, and the hardened austenite can be maintained until the final rolling stage, thereby avoiding the nucleation and growth of deformed tissues in the steel pipe and the formation of coarse tissues, which ultimately leads to deterioration of the strength, toughness and low-temperature toughness of the steel pipe. At the same time, through the synergistic coordination between the components, dispersed carbonitrides are precipitated in the grains during the production process, avoiding the formation of brittle upper bainite, thereby obtaining hot-rolled seamless steel pipes with certain strength, toughness and excellent low-temperature toughness.

[0053] In some embodiments of the present application, in step S2, when the perforation treatment is performed, the temperature of the blank is 1150~1250℃, specifically 1150℃, 1170℃, 1190℃, 1210℃, 1230℃, 1250℃, etc., or other values ​​within this range, which are not limited here. Performing perforation treatment within this temperature range can effectively reduce internal defects and improve the mechanical properties of the steel pipe. Preferably, the perforation treatment is tapered expansion perforation. The use of tapered expansion perforation can obtain a larger total deformation and flexibly adjust the deformation of each process such as perforation and rolling.

[0054] It is understood that the blank may be subjected to a heat treatment before the perforation process. In some embodiments of the present application, step S2 includes: heating the blank in a ring furnace at a temperature of 1200-1290° C. for 3.5-4.5 hours.

[0055] In some embodiments of the present application, the billet is sequentially passed through a heat recovery section, a preheating section I zone, a heating zone I, a heating zone II, a heating zone III, a soaking zone I, and a soaking zone II. Among them, in the heat recovery section, the heat of the exhaust gas discharged from the furnace is mainly used to preheat the billet to reduce energy consumption. In this area, the temperature of the billet will vary according to the temperature of the exhaust gas in the furnace, which serves as a preheating stage. In the preheating section I zone: the billet begins to enter the real heating process. The heating rate at this stage needs to be controlled to avoid excessive temperature gradients on the surface and inside of the billet, which leads to stress concentration; preferably, the temperature of the preheating section I zone is 400°C~650°C. In the heating zone I, the billet begins to experience a more significant temperature rise, and the preferred heating temperature is 650~850°C, which is conducive to promoting uniformity inside the billet. The preferred temperature range of the heating zone II is 850~1120°C, and the billet is heated to close to its deformation temperature, with the aim of enabling the billet to better undergo plastic deformation during the subsequent rolling process. Heating zone III: The preferred heating temperature is 1120~1290℃, which is the stage where the billet reaches the final deformation temperature, so that it can be deformed smoothly during the subsequent piercing and continuous rolling process. Soaking zone I: The preferred heating temperature is 1200~1290℃. The function of this heating area is to ensure that the overall temperature of the billet is uniform and reduce the difference in mechanical properties caused by inconsistent temperature. Soaking zone II: The preferred temperature is 1200~1290℃, which further extends the residence time of the billet at high temperature and ensures that the entire billet reaches the ideal temperature consistency and organizational state before being taken out of the furnace. Preferably, the billet's furnace discharge temperature is 1190~1280℃, and the total heating time is ≥3.8 hours. By precisely controlling the process parameters during the heating process, especially the temperature, uniform heating of the billet can be ensured, the generation of thermal stress and cracks can be avoided, and the comprehensive performance of the finished seamless steel pipe can be improved.

[0056] In step 3, the rough tube is rolled to obtain a rough tube, and the rough tube exiting the tube stripping machine is subjected to a first rapid cooling. In some embodiments of the present application, the rolling temperature is 950-1150°C, specifically 950°C, 970°C, 990°C, 1000°C, 1020°C, 1050°C, 1080°C, 1100°C, 1120°C, 1140°C, 1150°C, etc., and other values ​​within this range are also possible, and are not limited here. Controlling the rolling temperature within the above range is conducive to obtaining rough tubes with superior dimensional accuracy.

[0057] In some embodiments of the present application, the first and / or second rapid cooling processes employ a through-cooling method, which enables more uniform cooling of the rough pipe and a controllable cooling rate, adapting to pipes of varying sizes and shapes. The use of a through-cooling method in seamless steel pipe production, particularly the first rapid cooling process comprising two rapid cooling steps in the present application, can significantly improve the strength and toughness of the steel pipe. By controlling the cooling process, the internal structure of the material is optimized, thereby achieving improved material performance.

[0058] In some embodiments of the present application, the temperature of the rough pipe drops by 30-150°C during the first rapid cooling process. That is, the first rapid cooling cools the rough pipe to a temperature 30-150°C below the rough pipe temperature before entering the first rapid cooling area. Specifically, it can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., or other values ​​within the above range. Preferably, the cooling rate of the first rapid cooling is 1.5-50°C / s, specifically 1.5°C / s, 10°C / s, 20°C / s, 30°C / s, 40°C / s, 50°C / s, etc., or other values ​​within the above range. In some embodiments of the present application, the first rapid cooling is performed after the rough pipe exits the pipe stripping machine. The first rapid cooling can be performed during the transportation of the rough pipe, without affecting the normal production rhythm of the steel pipe, facilitating the improvement of the production efficiency of seamless steel pipes and effectively reducing costs.

[0059] In some embodiments of the present application, the temperature of the rough pipe drops by 30-150°C during the second rapid cooling process. That is, the first rapid cooling cools the rough pipe to a temperature 30-150°C below the temperature of the rough pipe before entering the second rapid cooling area. Specifically, it can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., or other values ​​within the above range. Preferably, the cooling rate of the second rapid cooling is 1.5-50°C / s, specifically 1.5°C / s, 10°C / s, 20°C / s, 30°C / s, 40°C / s, 50°C / s, etc., or other values ​​within the above range. In some embodiments of the present application, the second rapid cooling is carried out before the rough pipe enters the sizing equipment or the reducing equipment, and the two rapid coolings in the first rapid cooling are carried out at different positions during the transportation of the steel pipe, which does not affect the normal production rhythm of the steel pipe, can better utilize the existing equipment for modification, and is relatively simple and easy to implement.

[0060] It should be noted that the first and second rapid cooling processes can be performed at an existing pace. For example, the position of the blank pipe can be rotated in between, allowing the blank pipe to cool naturally to a certain extent. Preferably, the temperature of the blank pipe between the first and second rapid cooling processes drops to 0-200°C.

[0061] In some embodiments of the present application, the rough pipe that has completed the second rapid cooling is subjected to high-pressure water descaling to remove the iron oxide scale generated during the heating or rolling process and improve the surface quality of the steel pipe.

[0062] The rough pipe after the second rapid cooling is sizing or reducing, and the process method of sizing or reducing can refer to the existing technology. In some embodiments of the present application, the temperature of the sizing or reducing treatment in step S5 is the non-recrystallization zone above Ar3+20°C. It can be understood that Ar3 is one of the thermodynamic transition temperatures, specifically the temperature point at which austenite begins to transform into ferrite, and the Ar3 temperature is related to the chemical composition of metallurgical principles; the temperature of the non-recrystallization zone is lower than the recrystallization temperature of the steel pipe structure. When sizing or reducing is performed in the non-recrystallization zone, the grains of the metal material will not recrystallize, but will remain in the hardened state after processing, which helps to form a finer grain structure, thereby improving the strength and toughness of the material. The temperature of the non-recrystallization zone is related to the composition and processing technology of the steel pipe, and those skilled in the art can obtain it through calculation and experimentation based on existing methods.

[0063] In some embodiments of the present application, the temperature of the steel pipe after the third rapid cooling is 550-650°C. Rapid cooling to this temperature range after the steel pipe exits the sizing mill allows the steel pipe structure to quickly pass through the phase transformation region, preventing the newly formed phase from growing and coarsening. Further slow cooling in the low-temperature upper bainite region by air cooling avoids the formation of brittle upper bainite, ultimately obtaining a significantly refined ferrite + pearlite structure. Specifically, the temperature of the steel pipe after the third rapid cooling can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, etc., or other values ​​within the above range, which are not limited here.

[0064] In step S5, the steel pipe having undergone the third rapid cooling and having a temperature of 550-650° C. is air-cooled. The air-cooling method can be selected from the existing technology, such as conveying the steel pipe to a large cooling bed for air cooling.

[0065] After air cooling, the steel pipe can be post-processed according to existing methods to obtain a seamless steel pipe product. The post-processing methods can refer to existing methods. Specifically, the post-processing includes but is not limited to trimming, straightening, physical and chemical testing, non-destructive testing, manual inspection, inkjet printing, and packaging for storage.

[0066] The following examples and comparative examples will further illustrate the beneficial effects that can be achieved by the present application.

[0067] Example 1

[0068] 1) Smelting metallurgical raw materials to obtain billets. The metallurgical raw materials include, by weight, C: 0.15%, Si: 0.30%, Mn: 1.25%, V: 0.05%, Nb: 0.035%, Al: 0.025%, Ti: 0.0070%, Cr: 0.050%, Ni: 0.080%, Mo: 0.053%, P: 0.008%, S: 0.0025%, N: 0.0058%, and the balance being Fe and unavoidable impurities.

[0069] 2) The resulting billet is heated in a ring furnace at 1240°C. It then passes through seven heating zones: heat recovery, preheating zone I, heating zone I, heating zone II, heating zone III, soaking zone I, and soaking zone II. The heating temperatures in these zones are as follows: furnace temperature dependent, 550°C, 750°C, 950°C, 1200°C, 1240°C, and 1240°C. The billet exits the furnace at 1230°C, and the total heating time is controlled within 3.8 hours. The heated billet undergoes conical expansion and perforation at 1200°C to form a capillary tube.

[0070] 3) Continuous rolling is performed at 1100°C using a continuous tube mill to obtain rough tubes of the initially determined dimensions. The rough tubes are immediately rapidly cooled after exiting the mill using a through-cooling method at a cooling rate of 10°C / s until they are 100°C below the rough tube temperature before entering the rapid cooling zone.

[0071] 4) The Ar3 temperature of the rough pipe was tested to be 720°C, and the temperature of the non-recrystallized zone was 720-850°C. The rough pipe was then rapidly cooled again at a cooling rate of 10°C / s to a temperature 100°C below the rough pipe temperature before entering the rapid cooling zone. The rough pipe was first descaled with high-pressure water and then sizing at 800°C.

[0072] 5) The third rapid cooling is carried out immediately after the steel pipe leaves the sizing mill. The equipment for the third rapid cooling includes 5 round hole sizing mill finished product racks and 5 Figure 2 and 3 In the quick cooling equipment rack shown in the figure, the steel pipe immediately enters another round hole sizing mill finished product rack after passing through a quick cooling equipment, and repeats this process until it reaches the last round hole sizing mill finished product rack, rapidly cooling the steel pipe to 560℃. Among them, the angle of the quick cooling equipment nozzle 011 is set to 45°, that is, the angle between the nozzle spray direction and the pipe transportation direction is 45°. The water flow rate of the water spray device of a single quick cooling equipment rack is 50m 3 / h or so.

[0073] 6) The cooled steel pipe is transported to a large cooling bed for air cooling, and finally a seamless steel pipe with a specification of 168×14mm is obtained.

[0074] Example 2

[0075] The difference from Example 1 is that in step 5), the third rapid cooling equipment includes a round hole sizing mill finished product rack and a rapid cooling equipment rack. After passing through one rapid cooling equipment, the steel pipe enters another round hole sizing mill finished product rack to cool the steel pipe to the same temperature.

[0076] Example 3

[0077] The difference from Example 1 is that, in step 1), the metallurgical raw materials include C: 0.21%, Si: 0.46%, Mn: 1.46%, V: 0.10%, Nb: 0.065%, Al: 0.065%, Ti: 0.0065%, Cr: 0.055%, Ni: 0.080%, Mo: 0.053%, P: 0.010%, S: 0.003%, N: 0.006%, and the balance is Fe and unavoidable impurities.

[0078] Example 4

[0079] The difference from Example 1 is that in step 4), the temperature of the sizing treatment is 740°C.

[0080] Example 5

[0081] The difference from Example 1 is that in step 4), the temperature of the sizing treatment is 850°C.

[0082] Example 6

[0083] The difference from Example 1 is that in step 4), the temperature of the sizing treatment is 880°C.

[0084] Example 7

[0085] The difference from Example 1 is that in step 3), the rough pipe is immediately rapidly cooled after exiting the continuous rolling mill using a through-cooling method at a cooling rate of 10°C / s to a temperature 150°C below the temperature of the steel pipe before entering the rapid cooling zone. The rough pipe is rapidly cooled again before entering the sizing mill at a cooling rate of 10°C / s to a temperature 150°C below the temperature of the steel pipe before entering the rapid cooling zone.

[0086] Example 8

[0087] The difference from Example 1 is that in step 3), the rough pipe is immediately rapidly cooled after exiting the continuous rolling mill using a through-cooling method at a cooling rate of 10°C / s to a temperature 50°C below the temperature of the steel pipe before entering the rapid cooling zone. The rough pipe is rapidly cooled again before entering the sizing mill at a cooling rate of 10°C / s to a temperature 50°C below the temperature of the steel pipe before entering the rapid cooling zone.

[0088] Example 9

[0089] The difference from Example 1 is that in step 4), the rough pipe is subjected to a diameter reduction process at a temperature of 800° C. Finally, a finished seamless steel pipe is obtained.

[0090] Comparative Example 1

[0091] The difference from Example 1 is that in step 3), after the rough pipe leaves the continuous rolling mill, it is conveyed to a conveyor roller to be descaled by high-pressure water, and then subjected to a fixed diameter reduction treatment. After the fixed diameter reduction treatment, step 5) is omitted, and the rough pipe is directly conveyed to a large cooling bed for air cooling via a conveyor roller, and finally a hot-rolled seamless steel pipe is obtained.

[0092] Comparative Example 2

[0093] The difference from Example 1 is that in step 3), the rough pipe is only rapidly cooled once after leaving the continuous rolling mill, and the rough pipe is rapidly cooled before entering the sizing mill at a cooling rate of 15°C / s to a temperature 180°C below the steel pipe temperature before entering the rapid cooling zone.

[0094] Comparative Example 3

[0095] The difference from Example 1 is that in step 3), the continuous pipe mill performs continuous rolling at 1150°C to obtain a rough pipe of initially predetermined size. Immediately after exiting the continuous rolling mill, the rough pipe is rapidly cooled using a through-cooling method at a cooling rate of 15°C / s to a temperature below 180°C before entering the rapid cooling zone. Before entering the sizing mill, the rough pipe is rapidly cooled again at a cooling rate of 15°C / s to a temperature below 180°C before entering the rapid cooling zone.

[0096] Comparative Example 4

[0097] The difference from Example 1 is that step 5) is not performed and the steel pipe is directly air-cooled on a large cooling bed after exiting the sizing mill.

[0098] The seamless steel pipes prepared in the above examples and comparative examples were subjected to performance tests according to the following methods. The test results are listed in Table 1 below.

[0099] The outer diameter, straightness and other dimensional accuracy, as well as tensile and impact properties of the seamless steel pipes prepared in Examples 1 to 9 and Comparative Examples 1 to 4 were tested using a vernier caliper, a level and in accordance with GB / T228.1 and GB / T229. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] From the above description, it can be seen that the following technical effects are achieved by adopting the above-mentioned embodiments of the present invention: the rapid cooling device of the present application includes one or more cooling correction groups 1, that is, the rapid cooling equipment rack 01 and the sizing machine finished product rack 02 are arranged in sequence along the pipe transportation direction. This cooling method can enable the steel pipe to enter the sizing machine finished product rack 02 immediately after rapid cooling, and the steel pipe after rapid cooling is immediately corrected to avoid bending of the steel pipe caused by uneven cooling during the rapid cooling process. In particular, when the above-mentioned rapid cooling device contains multiple cooling correction groups 1, multiple rapid cooling equipment racks 01 and sizing machine finished product racks 02 are alternately arranged in sequence along the pipe transportation direction. Multiple racks are alternately cooled and corrected, which can greatly improve the cooling speed of the steel pipe, thereby obtaining a hot-rolled seamless steel pipe with small straightness and ovality and excellent strength and toughness.

[0103] In the seamless steel pipe preparation method of the present application, the rolled rough pipe is subjected to a second rapid cooling before sizing or reducing treatment. This not only reduces the final rolling temperature of the steel pipe through two-stage rapid cooling, and keeps the steel pipe in the non-recrystallized region during the sizing and reducing process, but also maintains the hardened austenite to the phase transformation point. New phases and carbonitrides will surround the strained deformation nucleus, which can effectively refine the grain structure and fully disperse and precipitate the carbonitrides. The rapid cooling of the steel pipe after sizing or reducing treatment can make the steel pipe structure pass through the phase transformation region quickly, and the newly formed phase will not grow and coarsen. At the same time, it is slowly cooled in the low-temperature upper bainite region to avoid the formation of brittle upper bainite, and finally obtain a significantly refined ferrite + pearlite structure. By reasonably setting the cooling path, the present application can obtain a hot-rolled seamless steel pipe with low straightness and ovality and excellent strength and toughness. Moreover, the preparation method of the present application can make full use of existing seamless steel pipe equipment, and with a slight modification, it can complete the preparation of seamless steel pipes with excellent strength and toughness, without adding any complex rapid cooling equipment, which facilitates online batch production and can greatly reduce production costs and improve production efficiency.

[0104] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A device for preparing seamless steel pipes, characterized in that: It includes smelting unit, piercing unit, rolling unit, sizing unit and cooling unit; The rolling unit includes a tube stripper and a first rapid cooling module arranged in sequence along the tube transportation direction; The sizing and reducing unit includes a second rapid cooling module and a sizing mill or a sizing mill arranged in sequence along the pipe transportation direction; The cooling unit includes a third fast cooling module and an air cooling module arranged in sequence along the pipe transportation direction. It comprises one or more cooling correction groups (1), wherein the cooling correction group (1) comprises a quick cooling equipment rack (01) and a sizing machine finished product rack (02) arranged in sequence along the pipe transportation direction; The quick cooling equipment frame (01) includes a water spray device (010), and the center line of the water ring of the water spray device (010) and the center line of the sizing machine finished product frame (02) are parallel and at the same horizontal position; The water spray device (010) is fixed in a quick cooling equipment rack (01), the water spray device (010) has a cavity that can accommodate the passage of pipes, the water spray device (010) is provided with nozzles (011), the nozzles (011) are evenly distributed on the water spray device (010) around one or more circles of the inner wall of the cavity of the water spray device (010), the direction of water spraying of the nozzles (011) is along the direction of pipe transportation, and the angle with the pipe is 30°~60°; the cooling rate of the steel pipe in the quick cooling equipment rack (01) is 1.5~50℃ / s.

2. The equipment for preparing seamless steel pipe according to claim 1, characterized in that: The quick cooling equipment rack (01) is an air-through cooling device.

3. The equipment for preparing seamless steel pipe according to claim 2, characterized in that: The water flow rate of a single water spraying device (010) is between 10 and 300 m 3 / h.

4. The equipment for preparing seamless steel pipe according to claim 2 or 3, characterized in that: The water spray device (010) is a truncated cone with an axis parallel to the ground. A small opening (015) and a large opening (014) of the water spray device (010) are respectively provided along the transportation direction of the pipe. The small opening (015) is the opening with a smaller diameter of the cavity of the water spray device (010), and the large opening (014) is the opening with a larger diameter of the cavity of the water spray device (010). The water spray device (010) has an interlayer for accommodating a cooling medium. The nozzle (011) is a hole provided on the inner wall of the water spray device (010); The aperture of the nozzle (011) is 0.5-5 mm.

5. The equipment for preparing seamless steel pipe according to claim 1, characterized in that: The sizing machine finished product frame (02) is a round hole type sizing machine finished product frame; The hole-type roller gaps and roller bottoms of the finished product frame of the round-hole sizing machine are arranged alternately.

6. The equipment for preparing seamless steel pipe according to claim 1, characterized in that: The first fast cooling module is a through-type cooling device; And / or, the second fast cooling module is a through-type cooling device; And / or, the perforating unit adopts a tapered diameter expansion perforating method; And / or, the rolling unit includes a continuous tube mill.

7. A method for producing a seamless steel pipe using the apparatus for producing a seamless steel pipe according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1, smelting metallurgical raw materials to obtain billets; Step S2, performing a perforation process on the blank to obtain a capillary tube; Step S3, rolling the rough tube and subjecting the obtained rough tube to a first rapid cooling; Step S4, subjecting the rough pipe after the first rapid cooling to a second rapid cooling and then to sizing or reducing, and subjecting the obtained steel pipe to a third rapid cooling, wherein the third rapid cooling is performed in the rapid cooling device according to any one of claims 1 to 6; Step S5, air-cooling the steel pipe obtained by the third rapid cooling.

8. The method for preparing a seamless steel pipe according to claim 7, wherein: The chemical composition of the metallurgical raw material is, by weight percentage, C 0.10%-0.20%, Si 0.15%-0.45%, Mn 1.05%-1.45%, V 0.02%-0.09%, Nb 0.020%-0.06%, Al 0.015%-0.06%, Ti≤0.020%, Cr≤0.30%, Ni≤0.25%, Mo≤0.10%, P≤0.020%, S≤0.010%, N≤0.012%, and the balance is Fe and unavoidable impurities.

9. The method for preparing a seamless steel pipe according to claim 7, wherein: During the first rapid cooling process, the temperature of the blank pipe drops by 30-150°C; and / or, during the second rapid cooling process, the temperature of the blank pipe decreases by 30-150° C.; And / or, the temperature of the steel pipe after the third rapid cooling is 550-650°C.

10. The method for preparing a seamless steel pipe according to claim 7, wherein: In step S3, the rolling temperature is 950-1150°C; And / or, the temperature of the sizing or reducing treatment in step S4 is a non-recrystallized region above Ar3+20°C.

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