Device for hot expanding a steel pipe with a large reduction in diameter

Abstract

The utility model relates to steel pipe plastic deformation processing technical field discloses a big variable diameter rate steel pipe heat expansion device, including core rod, induction heating coil, support roller and heat expansion unit, the core rod is used for wearing into the steel pipe of waiting for processing to complete the expansion, the core rod includes the introduction section, deformation section, sizing section and straightening section that link up in proper order, and deformation section, sizing section and straightening section are all hollow structure, the induction heating coil is around the steel pipe outside, and covers introduction section, deformation section and sizing section, the support roller sets up in the below of steel pipe, and the support roller is in rolling contact with the steel pipe, and heat expansion unit is connected with introduction section through connecting rod, the above -mentioned big variable diameter rate steel pipe heat expansion device passes through hollow core rod cooperation even covering induction heating coil, realizes the heat expansion processing of big variable diameter rate to steel pipe, can effectively reduce the core rod weight, makes the core rod have enough strength and rigidity simultaneously, need not multiple heat expansion, and the steel pipe forming quality is high.

Description

Technical Field

[0001] This utility model relates to the field of steel pipe plastic deformation processing technology, and in particular to a thermal expansion device for steel pipes with large diameter ratio. Background Technology

[0002] As the transport capacity of heating networks and fluid transportation pipelines increases, the diameter of seamless steel pipes used is also increasing. Medium-frequency hot expansion steel pipe technology is the mainstream process for producing large-diameter seamless steel pipes.

[0003] In existing technologies, the primary diameter change rate of low-alloy steel pipes does not exceed 1.4, and that of carbon steel pipes does not exceed 1.6. As the diameter change rate increases, the size and weight of the mandrel also increase. Since the curvature of the steel pipe support roller remains constant, it is usually only in line contact with steel pipes of different diameters. The weight of the larger mandrel is entirely borne by the smaller support surface. Furthermore, the steel pipe is still at a high temperature after thermal expansion deformation, resulting in lower yield strength at high temperatures. This leads to wall thinning at the contact area with the rollers.

[0004] Therefore, steel pipes with large diameter changes often require multiple hot expansion processes, which is time-consuming, labor-intensive, and results in significant energy consumption. Utility Model Content

[0005] To address the aforementioned problems, the purpose of this utility model is to provide a thermal expansion device for steel pipes with large diameter ratios, enabling the processing of steel pipes with even larger diameter ratios, ensuring forming quality, and reducing energy consumption.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A hot expansion device for steel pipes with large diameter changes includes a mandrel, an induction heating coil, support rollers, and a hot expansion unit, wherein:

[0008] The mandrel is used to insert into the steel pipe to be processed to complete the diameter expansion. The mandrel includes an inlet section, a deformation section, a sizing section and a straightening section connected in sequence. The deformation section, the sizing section and the straightening section are all hollow structures.

[0009] The induction heating coil is wound around the outside of the steel pipe and covers the inlet section, deformation section and sizing section;

[0010] The support rollers are located below the steel pipe, and the support rollers make rolling contact with the steel pipe;

[0011] The thermal expansion unit is connected to the inlet section via a connecting rod.

[0012] As an alternative, the inner cavities of the deformation section, the sizing section, and the straightening section are sequentially connected to form a hollow cavity, which is formed by centrifugal casting of a mandrel.

[0013] As an alternative, the outer diameter of the inlet section is set to d, the outer diameter of the sizing section is set to D, and the semi-cone angle of the deformed section is set to α. Then the length of the deformed section is L = (Dd) / (2*tgα), where the value of α is 8° to 10°.

[0014] As an alternative, the winding length of the induction heating coil is 100mm to 200mm longer than the sum of the axial lengths of the induction section, the deformation section and the sizing section, and the winding diameter of the induction heating coil is 80mm to 150mm longer than the outer diameter of the steel pipe.

[0015] As an alternative, the taper of the induction heating coil at the deformation section is the same as the taper of the deformation section.

[0016] As an alternative, the central angle of the arc supporting the roller is β, and the value of β is 100° to 160°.

[0017] As an alternative, the contact surface between the support roller and the steel pipe is covered with a nylon pad.

[0018] The beneficial effects of this utility model are:

[0019] This large-diameter-ratio steel pipe hot expansion device uses a hollow mandrel in conjunction with a uniformly covered induction heating coil to achieve large-diameter-ratio hot expansion processing of steel pipes. It can effectively reduce the weight of the mandrel while giving the mandrel sufficient strength and rigidity, eliminating the need for multiple hot expansions and resulting in high-quality steel pipe forming. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the large diameter ratio steel pipe thermal expansion device provided in this embodiment of the utility model;

[0021] Figure 2 This is a schematic diagram of the structure of the mandrel involved in an embodiment of the present utility model;

[0022] Figure 3 This is a schematic diagram of the supporting roller involved in an embodiment of the present utility model.

[0023] In the attached image:

[0024] 1. Steel pipe; 2. Mandrel; 21. Inlet section; 22. Deformation section; 23. Sizing section; 24. Straightening section; 25. Hollow cavity; 3. Induction heating coil; 4. Support roller; 41. Nylon pad; 5. Connecting rod. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0026] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0027] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0028] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0029] Furthermore, the terms "first" and "second" are merely used to distinguish between different terms in description and do not have any special meaning.

[0030] Please see Figures 1 to 3 As shown, this embodiment provides a hot expansion device for steel pipes with large diameter changes, including a mandrel 2, an induction heating coil 3, a support roller 4, and a hot expansion unit, wherein:

[0031] The mandrel 2 is used to insert into the steel pipe 1 to be processed to complete the diameter expansion. The mandrel 2 includes an inlet section 21, a deformation section 22, a sizing section 23 and a straightening section 24 connected in sequence. The deformation section 22, the sizing section 23 and the straightening section 24 are all hollow structures.

[0032] The induction heating coil 3 is wound around the outside of the steel pipe 1 and covers the inlet section 21, the deformation section 22 and the sizing section 23;

[0033] The support roller 4 is located below the steel pipe 1, and the support roller 4 makes rolling contact with the steel pipe 1;

[0034] The thermal expansion unit is connected to the inlet section 21 via connecting rod 5.

[0035] Therefore, by using the hollow mandrel 2 in conjunction with the uniformly covered induction heating coil 3, the steel pipe 1 can be thermally expanded with a large diameter change rate. This can effectively reduce the weight of the mandrel 2 while ensuring that the mandrel 2 has sufficient strength and rigidity. Multiple thermal expansions are not required, resulting in high forming quality of the steel pipe 1.

[0036] Optionally, the inner cavity of the deformation section 22, the inner cavity of the sizing section 23, and the inner cavity of the straightening section 24 are connected in sequence to form a hollow cavity 25, which is formed by centrifugal casting of the mandrel 2.

[0037] Therefore, the design of the hollow cavity 25 reduces the structural weight of the core rod 2, allowing the core rod 2 to be made larger, thereby increasing the diameter ratio and improving the thermal expansion efficiency. In addition, the hollow cavity 25 also helps to distribute heat evenly and reduce thermal stress.

[0038] Optionally, the outer diameter of the inlet segment 21 is set to d, the outer diameter of the sizing segment 23 is set to D, and the semi-cone angle of the deformed segment 22 is set to α. Then the length of the deformed segment 22 is L = (Dd) / (2*tgα), where the value of α is 8° to 10°.

[0039] Therefore, by optimizing the length of the deformation section 22, the primary diameter change rate of the steel pipe 1 can be reasonably increased to 1.7 to 2.5, avoiding local overheating or uneven deformation, and further improving the forming quality of the steel pipe 1.

[0040] For example, for a carbon steel pipe 1 with an outer diameter of 1168 mm and a wall thickness of 26.45 mm, using an original pipe with an outer diameter of 508 mm and a wall thickness of 30 mm for hot expansion results in a diameter change rate of λ = 1168 / 508 = 2.30. Existing technology requires at least two hot expansion operations. However, this embodiment uses a mandrel 2 with a large diameter change rate and a hollow cavity 25. The mandrel 2 is made of 1Cr18Ni9Ti (SUS321), and the hot expansion temperature is 725℃. The coefficient of linear expansion of carbon steel between 20℃ and 725℃ is 15.2 × 10⁻⁶. -6 The coefficient of linear expansion of 1Cr18Ni9Ti at temperatures ranging from 20℃ to 725℃ is 19.3 × 10⁻⁶ °C. -6At a temperature of / ℃, the inner diameter of the finished steel pipe 1 is 1115.1 mm. The difference in expansion between the steel pipe 1 material and the mandrel 2 material at the thermal expansion temperature is ΔD = -3.3 mm. Therefore, the outer diameter of the sizing section 23 of the mandrel 2 is D = 1115.1 - 3.3 = 1111.8 mm. Taking the outer diameter of the inlet section 21 as d = 508 - 2 * 30 - 20 = 428 mm, and α = 9°, the length of the deformation section 22 is L = (1111.8 - 428) / (2 * tg9°) = 2177.6 mm.

[0041] Optionally, the winding length of the induction heating coil 3 is 100mm to 200mm longer than the sum of the axial lengths of the inlet section 21, the deformation section 22 and the sizing section 23, and the winding diameter of the induction heating coil 3 is 80mm to 150mm longer than the outer diameter of the steel pipe 1.

[0042] Therefore, by precisely controlling the coverage area and winding parameters of the induction heating coil 3, the steel pipe 1 at the corresponding positions of the inlet section 21, the deformation section 22 and the sizing section 23 is heated evenly, reducing heat loss and improving thermal expansion efficiency.

[0043] Furthermore, the taper of the induction heating coil 3 at the deformation section 22 is the same as the taper of the deformation section 22, which further ensures that the steel pipe 1 is heated evenly and avoids excessive local temperature difference, which would affect the heat expansion effect.

[0044] Optionally, the central angle of the arc supporting the roller 4 is β, and the value of β is 100° to 160°.

[0045] Therefore, by reasonably setting the arc angle of the support roller 4, the steel pipe 1 is stably supported during the hot expansion process, the support area is increased, and the wall thickness of the steel pipe 1 is avoided from being reduced at the contact point.

[0046] Furthermore, the contact surface between the support roller 4 and the steel pipe 1 is covered with a nylon pad 41, and the inner diameter of the nylon pad 41 is equal to the outer diameter of the hot-expanded steel pipe 1, thereby increasing the contact area.

[0047] Therefore, nylon material is resistant to high temperature and wear, has good wrapping properties for steel pipe 1, can evenly bear the weight of steel pipe 1, and will not damage the outer surface of steel pipe 1.

[0048] In summary, the above-mentioned large-diameter steel pipe thermal expansion device has the following advantages:

[0049] 1) Using a mandrel 2 with a large diameter change ratio, the diameter change ratio of the steel pipe 1 can reach 1.7 to 2.5; the deformation section 22, sizing section 23 and straightening section 24 of the mandrel 2 have hollow cavities 25, which can effectively reduce the weight of the mandrel 2, while giving the mandrel 2 sufficient strength and rigidity.

[0050] 2) The length of the induction heating coil 3 covers the inlet section 21, deformation section 22 and sizing section 23 of the core rod 2. At the same time, the radial distance between the induction heating coil 3 and the outer surface of the steel pipe 1 is basically the same, which can improve the efficiency of induction heating and reduce energy consumption.

[0051] 3) The use of large-arc support rollers 4 increases the contact area with the steel pipe 1, and the support force is evenly distributed on the outer surface of the steel pipe 1, which can effectively avoid uneven wall thickness of the steel pipe 1 and ensure the forming quality.

[0052] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A thermal expansion device for steel pipes with large diameter changes, characterized in that, It includes a mandrel (2), an induction heating coil (3), a support roller (4), and a thermal expansion unit, wherein: The mandrel (2) is used to insert into the steel pipe (1) to be processed to complete the diameter expansion. The mandrel (2) includes an inlet section (21), a deformation section (22), a sizing section (23) and a straightening section (24) connected in sequence. The deformation section (22), the sizing section (23) and the straightening section (24) are all hollow structures. The induction heating coil (3) is wound around the outside of the steel pipe (1) and covers the inlet section (21), the deformation section (22) and the sizing section (23); The support roller (4) is disposed below the steel pipe (1), and the support roller (4) makes rolling contact with the steel pipe (1); The thermal expansion unit is connected to the inlet section (21) via a connecting rod (5); The inner cavity of the deformation section (22), the inner cavity of the sizing section (23) and the inner cavity of the straightening section (24) are connected in sequence to form a hollow cavity (25), which is formed by centrifugal casting of the mandrel (2). Let the outer diameter of the inlet segment (21) be d, the outer diameter of the sizing segment (23) be D, and the semi-cone angle of the deformable segment (22) be α. Then the length of the deformable segment (22) is... , where α takes values ​​from 8° to 10°.

2. The thermal expansion device for large diameter steel pipes according to claim 1, characterized in that, The winding length of the induction heating coil (3) is 100mm to 200mm longer than the sum of the axial lengths of the inlet section (21), the deformation section (22), and the sizing section (23), and the winding diameter of the induction heating coil (3) is 80mm to 150mm longer than the outer diameter of the steel pipe (1).

3. The thermal expansion device for large diameter variable steel pipes according to claim 2, characterized in that, The taper of the induction heating coil (3) at the deformed section (22) is the same as the taper of the deformed section (22).

4. The thermal expansion device for large diameter steel pipes according to claim 1, characterized in that, The central angle of the arc of the supporting roller (4) is β, and the value of β is 100° to 160°.

5. The large diameter ratio steel pipe thermal expansion device according to claim 4, characterized in that, The contact surface between the support roller (4) and the steel pipe (1) is covered with a nylon pad (41).

Images