Large elbow formed by cold heading

Abstract

The utility model relates to the technical field of stainless steel pipes, in particular to a cold heading formed large bent pipe which comprises a steel pipe body, the steel pipe body comprises a first steel pipe and a second steel pipe, the first steel pipe and the second steel pipe are formed at a time through a cold heading technology, a hollow groove is fixedly formed in the inner side of the steel pipe body, and the left end and the right end of the hollow groove are fixedly communicated. The hollow grooves comprise the first hollow groove, the second hollow groove and the third hollow groove, the first hollow groove is formed in the first steel pipe, the third hollow groove is formed in the second steel pipe, the third hollow groove and the second hollow groove are concentric and equal in diameter, and chamfers are arranged at the joints of the first steel pipe, the second steel pipe, the first hollow groove and the second hollow groove. According to the cold heading steel pipe, one-time forming is achieved through the cold heading technology, meanwhile, the anti-pressure units are arranged, the service life of the steel pipe is prolonged, and the anti-pressure capacity is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to stainless steel pipe technical field, specifically, relates to a big elbow pipe of cold heading forming. BACKGROUND

[0002] Stainless steel pipe is a kind of material widely used in modern industry and building field, and its excellent corrosion resistance, strength and weldability make it outstanding in various complex environments.Stainless steel pipe production involves alloy design and smelting process, with the development of science and technology, the precision requirement of stainless steel pipe for the industries such as manufacturing automobile parts, high-precision industrial steel pipe and medical equipment is higher and higher, the precision of stainless steel pipe usually involves its diameter, wall thickness, tolerance range and concentricity Key parameters, which have a direct impact on its final application performance, at the same time, the service life of steel pipe is also an important factor to be considered.

[0003] However, the existing steel pipe is prone to leakage after long-term use, or damaged by external or internal pressure impact.

[0004] Therefore, a technology is needed to solve the problem of poor compression resistance of steel pipe. INVENTION CONTENTS

[0005] In view of the above, the utility model provides a big elbow pipe of cold heading forming for solving the problem of poor compression resistance of steel pipe.

[0006] The utility model provides a big elbow pipe of cold heading forming, comprising:

[0007] Steel pipe body, the steel pipe body includes first steel pipe and second steel pipe, the first steel pipe and the second steel pipe are formed by cold heading process once, the inner side of the steel pipe body is fixedly provided with hollow groove, the left and right ends of the hollow groove are fixedly interconnected, the hollow groove includes first hollow groove, second hollow groove and third hollow groove, the first hollow groove is arranged in the first steel pipe, the third hollow groove is arranged in the second steel pipe, the third hollow groove is concentric with the second hollow groove, the first steel pipe, the second steel pipe and the first hollow groove and the second hollow groove connection are all provided with chamfer, the first steel pipe and the second steel pipe are provided with compression unit, the compression unit is installed in the oxidation resistance layer of the first steel pipe and the second steel pipe surface, the oxidation resistance layer is rustproof paint material, the oxidation resistance layer is internally provided with fireproof layer, the fireproof layer is refractory mortar material.

[0008] Further, comprising: the fireproof layer is internally provided with heat insulation layer, the heat insulation layer is rock wool material, the heat insulation layer is internally provided with sound insulation layer, the sound insulation layer is rubber material, the sound insulation layer is internally provided with reinforcing layer.

[0009] Further, comprising: the reinforcing layer comprises a reinforcing rib layer, the reinforcing layer is internally provided with vertical reinforcing ribs and horizontal reinforcing ribs, the vertical reinforcing ribs and the horizontal reinforcing ribs are vertically arranged.

[0010] Further, the reinforcing layer is internally provided with a heat preservation layer, and the heat preservation layer is made of polyurethane foam material.

[0011] Further, comprising: the heat preservation layer is internally provided with a leakage prevention layer, the leakage prevention layer is internally provided with a corrosion resistant layer, and the corrosion resistant layer is made of epoxy resin coating material.

[0012] Further, comprising: the first hollow groove has a diameter of 7.3±0.03 mm, the first hollow groove is provided with a first chamfer at an opening of the first steel pipe, the first chamfer has a length and a width of 0.3 mm, the second hollow groove is provided with a second chamfer at a connection position of the first hollow groove, the second chamfer has an angle of 120°±3° and a radius of 0.3 mm.

[0013] Further, the second steel pipe is provided with a third chamfer at an opening of the third hollow groove, and the third chamfer has a length and a width of 0.3 mm.

[0014] Further, the second hollow groove and the third hollow groove have diameters of 4.2+0.25 mm, and the second hollow groove and the third hollow groove have a concentricity of 0.2 mm.

[0015] Further, the first steel pipe has a diameter of 9.2-0.05 mm, a concentricity of 0.1 mm and a length of 82.5-0.2 mm.

[0016] Further, the second steel pipe has a diameter of 11.5+0.2 mm, a concentricity of 0.1 mm and a length of 15+0.2 mm.

[0017] Compared with the prior art, the utility model has the advantages that (1) the utility model is formed by cold heading process once, improves the utilization rate of raw materials, reduces waste and reduces production cost. Compared with the traditional welded elbow pipe, the utility model reduces the traditional welding interface, reduces the corrosion problem caused by welding, can exert high pressure on the metal material, ensures the consistency of the connection between the first steel pipe and the second steel pipe while maintaining the mechanical properties of the material, avoids the size deviation and geometric error caused by the traditional welding or splicing process, and reduces the rework and waste caused by machining error.

[0018] (2) The utility model discloses a compression -resistant unit is set up, and the contact of oxygen and moisture in air and steel material is effectively blocked to slow down the oxidation process, and the carrying capacity decline and structural failure caused by the corrosion of steel pipe are avoided, and the compression -resistant unit can not only provide excellent chemical medium corrosion resistance, but also realize high temperature resistance, wear resistance and multiple protection. BRIEF DESCRIPTION OF DRAWINGS

[0019] Fig. 1 A large elbow pipe structure schematic diagram of cold heading is provided for the utility model embodiment;

[0020] Fig. 2 A large elbow pipe structure schematic diagram of cold heading is provided for the utility model embodiment;

[0021] Fig. 3 The compression -resistant unit layered structure amplification schematic diagram of the utility model cold heading large elbow pipe.

[0022] Wherein: 1, steel pipe body;2, first steel pipe;3, second steel pipe;4, antioxidant layer;5, fireproof layer;6, heat insulation layer;7, sound insulation layer;8, reinforcing layer;9, vertical reinforcing rib;10, horizontal reinforcing rib;11, heat preservation layer;12, leakage prevention layer;13, corrosion -resistant layer;14, first hollow groove;15, second hollow groove;16, third hollow groove;17, first chamfer;18, second chamfer;19, third chamfer. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0024] In the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation to the present application.

[0025] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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 between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0027] See Figs. 1-3 As shown, this embodiment provides a cold-forged large bent pipe, including: a steel pipe body 1, which includes a first steel pipe 2 and a second steel pipe 3. The first steel pipe 2 and the second steel pipe 3 are formed in one step by a cold-forging process. A hollow groove is fixedly provided on the inner side of the steel pipe body 1, and the left and right ends of the hollow groove are fixedly interconnected. The hollow groove includes a first hollow groove 14, a second hollow groove 15, and a third hollow groove 16. The first hollow groove 14 is provided inside the first steel pipe 2, and the second steel pipe 3 is provided with... The third hollow groove 16 is coaxial with the second hollow groove 15 and has the same diameter. The first steel pipe 2, the second steel pipe 3, and the connection between the first hollow groove 14 and the second hollow groove 15 are all provided with chamfers. The steel pipe body 1 is provided with a pressure-resistant unit for the first steel pipe 2 and the second steel pipe 3. The pressure-resistant unit includes an anti-oxidation layer 4 installed on the surface of the first steel pipe 2 and the second steel pipe 3. The anti-oxidation layer 4 is made of anti-rust paint. A fireproof layer 5 is provided inside the anti-oxidation layer 4. The fireproof layer 5 is made of fire-resistant mortar.

[0028] Specifically, the first steel pipe 2 and the second steel pipe 3 are formed by a cold heading process, the total length of the steel pipe is 97.2-0.2 mm, a hollow groove is arranged in the center of the steel pipe, the hollow groove is respectively a first hollow groove 14, a second hollow groove 15 and a third hollow groove 16, wherein the first hollow groove 14 and the second hollow groove 15 are arranged in the first steel pipe 2, a chamfer is arranged at the connection of the first hollow groove 14 and the second hollow groove 15, the third hollow groove 16 is arranged in the second steel pipe 3, the second hollow groove 15 is connected with the third hollow groove 16, at the same time, the second hollow groove 15 and the third hollow groove 16 are coaxial and have the same diameter, the coaxial degree and the radius are the same, chamfers are arranged at the openings of both sides of the steel pipe body 1, chamfers are arranged at the connection of the first hollow groove 14 and the second hollow groove 15 in the first steel pipe 2, the first steel pipe 2 and the second steel pipe 3 are provided with a compression resisting unit, the compression resisting unit includes an anti-oxidation layer 4, a fireproof layer 5 and the like to reduce the probability of performance failure of the steel pipe due to corrosion and long-term use.

[0029] It can be understood that the length of the steel pipe body 1 is 97.2-0.2mm, which reflects high precision and low error in length control. The cold heading process reduces material defects and structural discontinuity in the traditional welding process, thereby realizing seamless connection and improving the overall strength and durability of the steel pipe. The first hollow groove 14, the second hollow groove 15, and the third hollow groove 16 optimize the performance of the steel pipe in fluid conveying applications. The connection between the first hollow groove 14 and the second hollow groove 15 and the connection between the second hollow groove 15 and the third hollow groove 16 are chamfered, which reduces the turbulence and resistance of the fluid when flowing through the connection, improves the comfort of the fluid flow, and improves the conveying efficiency by reducing the amplitude of the flow rate. The chamfer enhances the mechanical bonding strength and durability of the steel pipe. The same core and equal diameter of the second hollow groove 15 and the third hollow groove 16 improve the symmetry and balance inside the steel pipe, ensuring uniform distribution of the fluid inside the steel pipe and reducing vortex and local pressure loss caused by asymmetric or non-uniform pipe diameter. At the same time, the concentricity and radius consistency also ensure the precision of the steel pipe during manufacturing and assembly, improving the sealing performance and pressure resistance of the steel pipe. In addition, the openings on both sides of the first steel pipe 2 and the second steel pipe 3 are chamfered, which can effectively reduce the edge stress concentration and avoid cracks and damage to the steel pipe under stress or temperature change, thereby enhancing the safety and long-term stability of the steel pipe connection. The cold heading process improves material utilization, reduces waste and defective steel pipes, and the oxidation-resistant layer 4 is an effective barrier to protect the metal surface from oxygen, moisture, and chemical substances. Oxidation is one of the main causes of natural aging and corrosion of metal materials. By coating the steel pipe surface with an oxidation-resistant layer 4, the influence of oxidation on steel can be delayed, reducing the strength and surface degradation of the material caused by oxidation. The oxidation-resistant layer 4 not only prolongs the service life of the steel pipe, but also reduces the risk of accidental damage and leakage of the steel pipe caused by corrosion. Secondly, the main function of the fireproof layer 5 is to delay heat transfer and prevent direct contact of the flame with the steel pipe, thereby preventing rapid degradation of the material caused by high temperature. In the event of a fire, the fireproof layer 5 prevents the degradation of the steel pipe caused by high temperature, reduces the loss caused by the accident, and ensures the safety of personnel.

[0030] In some embodiments of the present application, the fireproof layer 5 is internally provided with a heat insulation layer 6, the heat insulation layer 6 is made of rock wool, the heat insulation layer 6 is internally provided with a sound insulation layer 7, the sound insulation layer 7 is made of rubber, and the sound insulation layer 7 is internally provided with a reinforcing layer 8.

[0031] Specifically, the fireproof layer 5 is internally provided with a heat insulation layer 6, the heat insulation layer 6 is internally provided with a sound insulation layer 7, and the sound insulation layer 7 is internally provided with a reinforcing layer 8, which collectively improves the compression resistance of the steel pipe through a multi-layer structure.

[0032] It can be understood that the heat protection capability is further enhanced when the fireproof layer 5 is provided with the heat insulation layer 6. The heat insulation layer 6 reduces the influence of high-temperature environment on the inside of the steel pipe by insulating and reflecting heat, thereby ensuring the structural integrity of the steel pipe. The heat insulation layer 6 not only reduces temperature conduction, but also inhibits thermal deformation of the steel pipe when exposed to high-temperature environment for a long time. By reducing the transmission of thermal load, the heat insulation layer 6 not only protects the steel pipe, but also ensures the temperature stability of the conveyed fluid, thereby improving the thermal efficiency.

[0033] The sound insulation layer 7 reduces noise pollution by absorbing noise generated during the conveying process. The sound insulation layer 7 material has vibration absorption characteristics, which can reduce vibration conduction caused by mechanical vibration and fluid flow rate changes, thereby protecting the steel pipe structure and surrounding facilities and reducing fatigue damage and maintenance frequency caused by vibration.

[0034] The reinforcing layer 8 enhances the load-bearing capacity and resistance to external physical impact of the steel pipe by using high-strength materials. The reinforcing layer 8 can provide additional structural support to the steel pipe, so that the steel pipe is not prone to deformation or rupture when subjected to internal and external pressure changes. The reinforcing layer 8 ensures the stability of the large bend pipe, prevents accidents, and prolongs the service life of the large bend pipe.

[0035] In some embodiments of the present application, the reinforcing layer 8 includes a reinforcing rib layer, and the reinforcing layer 8 is provided with vertical reinforcing ribs 9 and horizontal reinforcing ribs 10, which are arranged vertically.

[0036] Specifically, the reinforcing rib layer is divided into vertical reinforcing ribs 9 and horizontal reinforcing ribs 10, which are arranged vertically and bear the lateral stress and vertical stress of the steel pipe.

[0037] It can be understood that the vertical reinforcing ribs 9 are mainly used to cope with the lateral stress of the steel pipe. Stress usually comes from external environment and dynamic factors inside the steel pipe, such as lateral force generated by internal fluid pressure fluctuation, pressure of external soil, traffic load, and influence of geological movement. The vertical reinforcing ribs 9 increase the longitudinal buckling strength of the pipe wall, preventing the steel pipe from deforming or rupturing when coping with lateral pressure. The vertical reinforcing ribs 9 not only ensure the structural integrity of the steel pipe and uniform distribution of lateral pressure, but also reduce the risk of structural fatigue and potential damage caused by external impact. Secondly, the horizontal reinforcing ribs 10 are used to bear the vertical stress. The vertical stress comes from the self-weight of the steel pipe, the weight of the internal fluid, and the vertical load applied from outside. By uniformly distributing the horizontal reinforcing ribs 10 around the steel pipe, the steel pipe can effectively cope with these pressures, thereby preventing vertical compression deformation. The vertical and horizontal reinforcing ribs 10 are arranged vertically, forming a grid reinforcing system in structure. Not only can it effectively disperse stress from different directions, but also can improve the overall seismic resistance and the ability to resist sudden stress of the steel pipe.

[0038] In some embodiments of the present application, the reinforcing layer 8 is internally provided with a thermal insulation layer 11, which is made of polyurethane foam material.

[0039] In some embodiments of the present application, the thermal insulation layer 11 is internally provided with a leak-proof layer 12, which is internally provided with a corrosion-resistant layer 13, which is made of epoxy resin coating material. The corrosion-resistant layer can effectively protect the metal material from chemical, acid and alkaline, and moisture corrosion. It can prevent the corrosive medium from contacting the metal surface through the pipe wall, and avoid the weakening of the material and the shortening of the service life caused by chemical reaction.

[0040] It can be understood that the polyurethane foam has low density and extremely small thermal conductivity, which can effectively reduce the heat energy transmission through the steel pipe wall. For the steel pipe conveying cold and hot fluid, the energy utilization efficiency is improved, the interference of environmental temperature change on the fluid temperature in the steel pipe is reduced, and the energy loss is also reduced. In addition, the polyurethane foam material also has the characteristics of light weight, which makes the steel pipe maintain high thermal insulation effect without increasing the weight of the thermal insulation layer 11 and causing excessive burden on the structure. The leak-proof layer 12 prevents the leakage of the contents in the steel pipe, has high barrier property and excellent sealing property, and can prevent liquid and gas leakage accidents.

[0041] In some embodiments of the present application, the first hollow groove 14 has a diameter of 7.3±0.03mm, the first hollow groove 14 is provided with a first chamfer 17 at the opening of the first steel pipe 2, the first chamfer 17 has a length and a width of 0.3mm, the second hollow groove 15 is provided with a second chamfer 18 at the connection with the first hollow groove 14, the second chamfer 18 has an angle of 120°±3°, and the second chamfer 18 has a radius of 0.3mm.

[0042] Specifically, among the three hollow grooves, the first hollow groove 14 has the largest diameter, the first steel pipe 2 is provided with a first chamfer 17 at the opening of the first hollow groove 14, the first chamfer 17 has a length and a width of 0.3mm, the diameter of the first hollow groove 14 is larger than that of the second hollow groove 15, so the first hollow groove 14 is provided with a second chamfer 18 at the connection with the second hollow groove 15, the second chamfer 18 has an angle of 120°±3°, and the second chamfer 18 has a radius of 0.3mm.

[0043] It can be understood that the diameter of the first hollow groove 14 increases the capacity of fluid flow. In application scenarios requiring larger flow rate or flow volume, the first hollow groove reduces flow resistance and energy consumption, thereby improving overall efficiency. The chamfer reduces edge resistance and turbulence generation when fluid enters the hollow groove, prevents excessive edge resistance from causing energy loss and efficiency reduction, achieves more stable and smooth fluid movement, improves fluid dynamics performance, reduces the risk of cracks caused by external stress or thermal cycling, and enhances the structural performance of the large elbow. Improving the fatigue resistance and durability of the steel pipe. The elbow maintains stable quality during long-term high-load operation, avoiding performance failure of the steel pipe due to stress concentration. The cold heading forming process controls the flow of steel pipe material through the chamfer, thereby reducing secondary processing requirements and costs. Hollow grooves with different diameters will produce certain flow interference when connected, resulting in vortex and increased resistance. A 120°±3° chamfer provides a smooth transition. This angle optimizes the flow path of fluid between two grooves of different diameters, reducing turbulence and pressure drop caused by edge effects, thereby improving fluid smoothness and transportation efficiency. Secondly, in terms of structure, chamfering helps to evenly distribute stress concentration at the connection. Stress concentration is a common cause of material failure at the interface and transition area. Smooth transitions reduce the risk of crack formation and propagation, improving the stress resistance of the steel pipe under high pressure and long-term cyclic loading conditions. The chamfer radius is 0.3mm. Compared to sharp corners or abrupt changes, rounded corners reduce secondary processing requirements and provide longer service life and safety performance. In addition, during installation or maintenance, smooth chamfers and rounded corners reduce damage and wear caused by misoperation, simplify the operation process, and reduce the requirement for maintenance tools. Chamfering reduces the likelihood of fine cracks, thereby improving corrosion resistance.

[0044] In some embodiments of the present application, the second steel pipe 3 is provided with a third chamfer 19 at the opening of the third hollow groove 16, and the length and width of the third chamfer 19 are both 0.3mm.

[0045] Specifically, the second steel pipe 3 is also provided with a third chamfer 19 at the opening of the third hollow groove 16, and the third chamfer 19 is the same as the first chamfer 17, and the length and width of the third chamfer 19 are both 0.3mm.

[0046] It can be understood that the chamfer reduces the turbulence and edge resistance of the fluid when entering or leaving the hollow groove, and improves the flow efficiency and smoothness of the fluid in the steel pipe by reducing the interference of the boundary effect on the flow. The reduced flow resistance directly leads to lower pressure drop and energy consumption. The chamfer also provides convenience and safety for operation and maintenance. Reducing sharp edges reduces the risk of component cutting and wear during installation and maintenance of large elbows, improving the safety of construction. In addition, the standardized chamfer not only improves compatibility, but also enhances the fixing and sealing performance of the steel pipe, making the connection more tight, reducing the possibility of leakage when the steel pipe bears internal and external pressure, and increasing the ability to resist external impact and vibration.

[0047] In some embodiments of the present application, the diameters of the second hollow groove 15 and the third hollow groove 16 are 4.2+0.25 mm, and the concentricities of the second hollow groove 15 and the third hollow groove 16 are 0.2 mm.

[0048] It can be understood that the diameters of the second hollow groove 15 and the third hollow groove 16 are 4.2+0.25 mm, and the concentricities of the second hollow groove 15 and the third hollow groove 16 are 0.2 mm, which optimizes the fluid flow path, reduces turbulence and pressure drop. It can meet the flow requirements in the industry standard, while reducing energy consumption by maintaining smooth and continuous fluid delivery. Secondly, the concentricity of 0.2 mm improves the stability and precision of the steel pipe, ensuring that all components remain aligned during operation, reducing the risk of uneven internal stress, thereby reducing deformation or displacement of the steel pipe under pressure and temperature changes, ensuring that each part of the steel pipe body remains in good alignment after long-term use, reducing the risk of mechanical wear and performance degradation, thereby extending the service life of the embodiment.

[0049] In some embodiments of the present application, the diameter of the first steel pipe 2 is 9.2-0.05 mm, the concentricity of the first steel pipe 2 is 0.1 mm, and the length of the first steel pipe 2 is 82.5-0.2 mm.

[0050] In some embodiments of the present application, the diameter of the second steel pipe 3 is 11.5+0.2 mm, and the concentricity of the second steel pipe 3 is 0.1 mm.

[0051] Specifically, the diameter of the first steel pipe 2 is 9.2-0.05 mm, and the diameter of the second steel pipe 3 is 11.5+0.2 mm. The diameter of the first steel pipe 2 is smaller than that of the second steel pipe 3, but the concentricities of the first steel pipe 2 and the second steel pipe 3 are both 0.1 mm.

[0052] It can be understood that, first, the steel pipe diameter is used to control the flow and pressure. The first steel pipe 2 has a smaller diameter of 9.2-0.05 mm, and the second steel pipe 3 has a larger diameter of 11.5+0.2 mm, and the size difference creates a natural fluid regulation mechanism. When the fluid flows from the smaller diameter to the larger diameter, the flow rate after entering the second steel pipe 3 is reduced, thereby reducing the turbulence phenomenon, and second, the concentricity of 0.1 mm ensures that the two steel pipes are in good alignment when connected. High concentricity helps to reduce the mechanical stress and uneven wear caused by eccentricity, thereby enhancing the overall stability and reliability of the steel pipe body. Even under different diameters, the control of concentricity ensures accurate positioning and docking, reducing the risk of vibration, air leakage or liquid leakage during operation. During the installation and maintenance of the steel pipe, the concentricity of 0.1 mm makes the installation process fast and simple, reducing the risk of installation difficulties or failures caused by misalignment. In addition, high concentricity simplifies the maintenance and inspection process, all components are in the expected position and state, and frequent adjustment is not required, improving the overall availability and long-term stability of the steel pipe body.

[0053] In some embodiments of the present application, the length of the second steel pipe 3 is 15+0.2 mm.

[0054] The cold heading forming large elbow pipe in each of the above embodiments is formed by a cold heading process once, the utilization rate of raw materials is reduced, and the production cost is reduced. Compared with traditional welded elbow pipes, the number of traditional welded joints is reduced, the corrosion problem caused by welding is reduced, and a very high pressure can be applied to the metal material, thereby ensuring that the connection between the first steel pipe and the second steel pipe has high consistency while maintaining the mechanical properties of the material. Since the traditional welding or splicing process is not required, the size deviation and geometric error caused by the process are avoided, and the rework and scrap rate caused by processing errors are reduced.

[0055] The cold heading forming large elbow pipe in each of the above embodiments can effectively block the contact of oxygen and moisture in the air with the steel material by setting the pressure-resistant unit, thereby slowing down the oxidation process and avoiding the decrease in carrying capacity and structural failure of the steel pipe due to corrosion. Not only can it provide excellent chemical medium corrosion resistance, but also can realize multiple protection of high temperature resistance and wear resistance. Second, surface treatment and sealing technology can be used to reduce the penetration of moisture into the surface of the steel pipe, especially in humid or underground environments, which can prevent corrosion problems caused by moisture. The pressure-resistant unit design can increase the installation convenience of the steel pipe, reduce the secondary construction and repair caused by adverse site environment, and reduce the waste of steel caused by corrosion.

[0056] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A large bent pipe formed by cold heading, characterized in that, include: The steel pipe body includes a first steel pipe and a second steel pipe, which are formed in one piece by cold heading. A hollow groove is fixedly provided on the inner side of the steel pipe body, and the left and right ends of the hollow groove are fixedly interconnected. The hollow groove includes a first hollow groove, a second hollow groove, and a third hollow groove. The first hollow groove is provided inside the first steel pipe, and the third hollow groove is provided inside the second steel pipe. The third hollow groove is concentric and has the same diameter as the second hollow groove. Chamfers are provided at the connection points of the first steel pipe, the second steel pipe, and the first hollow groove and the second hollow groove. The first steel pipe and the second steel pipe are provided with a pressure-resistant unit, which is installed on the anti-oxidation layer on the surface of the first steel pipe and the second steel pipe. The anti-oxidation layer is made of anti-rust paint, and a fireproof layer is provided inside the anti-oxidation layer. The fireproof layer is made of refractory mortar.

2. The large bent pipe formed by cold heading according to claim 1, characterized in that, include: The fireproof layer has an internal heat insulation layer made of rock wool, and an internal sound insulation layer made of rubber. The internal sound insulation layer also has a reinforcement layer.

3. The large bent pipe formed by cold heading according to claim 2, characterized in that, include: The reinforcement layer includes a reinforcing rib layer, and the reinforcement layer is provided with vertical reinforcing ribs and horizontal reinforcing ribs, which are arranged perpendicularly.

4. The large bent pipe formed by cold heading according to claim 3, characterized in that, The reinforcement layer has an internal insulation layer, which is made of polyurethane foam.

5. The large bent pipe formed by cold heading according to claim 4, characterized in that, include: The insulation layer has a leak-proof layer inside, and the leak-proof layer has a corrosion-resistant layer inside, which is made of epoxy resin coating material.

6. The large bent pipe formed by cold heading according to claim 1, characterized in that, include: The diameter of the first hollow groove is 7.3±0.03mm. A first chamfer is provided at the opening of the first hollow groove and the first steel pipe. The length and width of the first chamfer are both 0.3mm. A second chamfer is provided at the connection between the second hollow groove and the first hollow groove. The angle of the second chamfer is 120°±3° and the radius of the second chamfer is a rounded corner of 0.3mm.

7. The large bent pipe formed by cold heading according to claim 1, characterized in that, The second steel pipe and the opening of the third hollow groove are provided with a third chamfer, the length and width of which are both 0.3mm.

8. The large bent pipe formed by cold heading according to claim 4, characterized in that, The diameter of the second hollow groove and the third hollow groove is 4.2 + 0.25 mm, and the concentricity of the second hollow groove and the third hollow groove is 0.2 mm.

9. The large bent pipe formed by cold heading according to claim 1, characterized in that, The diameter of the first steel pipe is 9.2-0.05mm, the concentricity of the first steel pipe is 0.1mm, and the length of the first steel pipe is 82.5-0.2mm.

10. The large bent pipe formed by cold heading according to claim 1, characterized in that, The diameter of the second steel pipe is 11.5 + 0.2 mm, the concentricity of the second steel pipe is 0.1 mm, and the length of the second steel pipe is 15 + 0.2 mm.

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