Preparation method of seamless cold-drawn steel pipe for telescopic beam and telescopic beam

Abstract

The invention discloses a preparation method of a seamless cold-drawn steel pipe for a telescopic beam and the telescopic beam, a seamless round pipe blank, an inner mold and a fixed outer mold with proper sizes are selected and placed on cold-drawing equipment to be fixed, the coaxiality between the round pipe blank and the round inner mold and the coaxiality between the round pipe blank and the fixed outer mold are kept, primary cold-drawing, secondary cold-drawing and forming cold-drawing are carried out, and the seamless cold-drawn steel pipe for the telescopic beam is obtained. Annealing heat treatment is respectively carried out between the primary cold drawing and the secondary cold drawing, and normalizing treatment and post-treatment are sequentially carried out after the forming cold drawing, so that the seamless cold-drawn steel pipe is obtained. According to the telescopic pipe set formed by sleeving the seamless special-shaped steel pipes prepared through the method, the fit clearance of the steel pipe pieces ranges from 0 mm to 0.5 mm, the size fit precision is high, the size stability of the telescopic beam is good, the telescopic friction resistance between the steel pipes is small, and the service life of the telescopic beam can be prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of engineering vehicles, in particular to a method for preparing a seamless cold-drawn steel pipe for a telescopic beam and the telescopic beam. Background Art

[0002] Telescopic beams for excavator undercarriage systems are used to extend and retract the excavator chassis. Currently, most telescopic beams are made from round tubes or welded profiled tubes, which present certain limitations. Round beams lack support from either side, resulting in significant wobbling. Welded profiled tubes suffer from poor dimensional accuracy, unstable clearance control, and the resulting gaps can easily become excessive, leading to misalignment and friction during extension and retraction, making the tube less durable. Furthermore, welded tubes offer low strength, creating the risk of cracking at the weld seams. Summary of the Invention

[0003] The present invention provides a telescopic beam and a preparation method thereof, thereby solving the above-mentioned defects existing in existing telescopic beams when welded pipes are used as telescopic beams.

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a seamless cold-drawn steel tube for a telescopic beam, wherein a seamless round tube billet, an inner die and a fixed outer die of appropriate size are selected to perform primary cold drawing, secondary cold drawing and forming cold drawing to achieve a target deformation size, wherein annealing heat treatment is performed between the primary cold drawing and the secondary cold drawing, and normalizing treatment and post-treatment are performed in sequence after the forming cold drawing to obtain the seamless cold-drawn steel tube.

[0005] In a preferred embodiment of the present invention, the process conditions of the primary cold drawing, the secondary cold drawing and the forming cold drawing are: room temperature, 10-15 m / min.

[0006] In a preferred embodiment of the present invention, the process conditions of the annealing heat treatment are: temperature 700-730°C, time 1-3h, slow cooling to below 200°C in the furnace and then cooling to room temperature outside the furnace.

[0007] In a preferred embodiment of the present invention, the process conditions of the normalizing treatment are: temperature 880-940° C., time 1-3 hours, and high-speed wind cooling to room temperature.

[0008] In a preferred embodiment of the present invention, the cross section of the seamless cold-drawn steel pipe is hexagonal, and any two adjacent sides are connected by arcs.

[0009] In a preferred embodiment of the present invention, the arc angle of the arc is R10-R20.

[0010] To solve the above technical problems, the present invention provides a telescopic beam, comprising two telescopic tube groups and a connecting sleeve. The two telescopic tube groups are linearly arranged, and the opposite ends thereof respectively extend into the connecting sleeve and are connected to the connecting sleeve.

[0011] The telescopic sleeve comprises a first steel pipe and a second steel pipe prepared by any one of the methods of claims 1-6; one end of the first steel pipe extends into the second steel pipe and can telescopically move relative to the second steel pipe; the second steel pipe is disposed at both ends of the connecting sleeve and is fixedly connected to the connecting sleeve.

[0012] In a preferred embodiment of the present invention, the first steel pipe, the second steel pipe and the connecting sleeve all comprise a top edge, a bottom edge, a first side edge connected to both sides of the top edge, and a second side edge connected to both sides of the bottom edge.

[0013] The outer wall surface of the second steel pipe and the inner wall surface of the connecting sleeve are in close fit.

[0014] The outer wall surfaces of the first side edge and the second side edge of the first steel pipe and the inner wall surfaces of the first side edge and the second side edge of the second steel pipe are in close fit.

[0015] In a preferred embodiment of the present invention, the gap at the close fit is 0-0.5 mm.

[0016] In a preferred embodiment of the present invention, the gap is 0.2-0.4 mm.

[0017] The beneficial effects of the present invention are as follows: A preparation method of seamless cold-drawn steel pipes for a telescopic beam of the present invention enables the prepared seamless steel pipes to have good dimensional accuracy through continuous seamless cold-drawing deformation technology; the telescopic tube groups composed of the seamless steel pipes prepared by the method of the present invention have a fitting gap between the steel pipe parts of 0-0.5 mm, with high dimensional fitting accuracy, good dimensional stability of the telescopic beam, and small telescopic friction resistance between the steel pipes, which helps to improve the service life of the telescopic beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a process flow schematic diagram of a preparation method of seamless cold-drawn steel pipes for a telescopic beam of the present invention;

[0019] Figure 2 is a front view structural schematic diagram of the telescopic beam of the present invention;

[0020] Figure 3 is a cross-sectional structural schematic diagram of the telescopic tube group;

[0021] The marks of each component in the drawings are as follows: 10. First steel pipe, 20. Second steel pipe, 30. Connecting sleeve. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following elaborates on the preferred embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0023] Embodiment 1

[0024] The present invention discloses a preparation method for seamless cold-drawn steel pipes for telescopic beams, specifically including the following steps:

[0025] (1) Primary cold drawing: Select a seamless circular tube blank Q355B with an outer diameter of 168 mm and a wall thickness of 7.5 mm, as well as corresponding circular inner die and fixed outer die, place them on the cold drawing equipment for fixation, place the seamless circular tube blank between the circular inner die and the fixed outer die, and maintain the coaxiality between the circular tube blank and the circular inner die and the fixed outer die. At room temperature, at a speed of 10 m / min, the circular inner die and the fixed outer die jointly extrude and draw out the tube at the concentric position of the circular tube blank. After cold drawing, the outer diameter of the circular tube is adjusted to 159 mm and the wall thickness is adjusted to 6.7 mm to complete the primary cold drawing;

[0026] (2) Annealing heat treatment: Send the steel pipe after primary cold drawing into an anaerobic annealing furnace, anneal it at 720 °C for 2 h, slowly cool it in the furnace to below 200 °C and then cool it outside the furnace to room temperature to facilitate subsequent cold drawing and shaping;

[0027] (3) Secondary cold drawing: Select a special-shaped inner die and a special-shaped outer die with a hexagonal cross-section that meet the process dimensions. After heat treatment and pickling and lubrication of the circular tube blank after primary cold drawing, fix it between the special-shaped inner die and the special-shaped outer die, adjust the coaxiality, and then perform secondary cold drawing at a speed of 10 m / min to obtain a special-shaped steel pipe with transitional dimensions and shapes, preparing for the forming cold drawing deformation;

[0028] (4) Annealing heat treatment: Send the steel pipe after primary cold drawing into an anaerobic annealing furnace, anneal it at 720 °C for 2 h, slowly cool it in the furnace to below 200 °C and then cool it outside the furnace to room temperature to facilitate subsequent cold drawing and shaping;

[0029] (5) Forming cold drawing: Select a special-shaped inner die and a special-shaped outer die with a hexagonal cross-section that are suitable for the finished product dimensions. After heat treatment and pickling and lubrication of the special-shaped blank after secondary cold drawing, fix it between the special-shaped inner die and the special-shaped outer die, adjust the coaxiality, and then perform forming cold drawing at a speed of 10 m / min to obtain a special-shaped steel pipe with the target dimensions and shapes;

[0030] Specifically, the cross-section of the obtained special-shaped steel pipe is hexagonal, and the connection between any two adjacent sides is arc-shaped, the arc angle is R10 - R20 mm, and the arc angle is according to the drawing requirements.

[0031] Through the design of the forming and cold drawing process conditions, the plasticity and stability of the steel pipe are improved, ensuring that the dimensional tolerance and shape of the steel pipe after secondary cold drawing meet the set requirements.

[0032] (6) Normalizing treatment: Send the formed and cold-drawn steel pipe to an anaerobic annealing furnace at a temperature of 900 °C for air-cooling normalizing treatment for 2 h to eliminate the internal stress generated during the cold drawing process, adjust the metallographic structure, refine the grains, control the cooling rate at 3 - 5 °C / s, and cool to room temperature.

[0033] Through the normalizing treatment, it is ensured that the finished steel pipe has sufficient toughness and strength, improves the bearing capacity, and has better welding performance when assembled with the walking system of the excavator chassis.

[0034] (7) Post-treatment: Straighten the normalized steel pipe, and then cut it to a fixed length for surface polishing and spraying treatment.

[0035] The seamless cold-drawn first steel pipe B148 is prepared by the above method.

[0036] Example 2

[0037] Select a seamless circular pipe blank with an outer diameter of 146 mm and a wall thickness of 7 mm, and repeat the above steps (1)-(7) to prepare the seamless cold-drawn second steel pipe B123.

[0038] Example 3

[0039] Select a seamless circular pipe blank with an outer diameter of 124 mm and a wall thickness of 7.5 mm, and repeat the above steps (1)-(7) to prepare the seamless cold-drawn third steel pipe B100.

[0040] Example 4

[0041] As Figure 2 and 3 shown, the present invention also provides a telescopic beam, which includes two telescopic pipe groups and a connecting sleeve 30.

[0042] The two telescopic pipe groups are linearly arranged, one end of which is respectively connected to the corresponding main beam on the telescopic walking system of the excavator, and the other end is the opposite end, and the opposite ends respectively extend into the connecting sleeve. That is, the two telescopic pipe groups connected by the connecting sleeve form a telescopic beam for the telescopic walking system of the excavator. The elongation or shortening of the telescopic beam is determined by the main beams at its two ends.

[0043] Specifically, the telescopic pipe group includes a first steel pipe 10 and a second steel pipe 20. The first steel pipe 10 is the inner layer pipe, one end of which is provided with an arc-shaped notch for fixedly connecting with the main beam; the other end extends into the second steel pipe 20 and can telescopically move relative to the second steel pipe 20.

[0044] The second steel pipe 20 is an intermediate layer pipe, which is built into both ends of the connecting sleeve 30 and fixedly connected to the connecting sleeve 30, capable of enhancing the overall strength of the telescopic beam, improving the lateral support force, and thus enhancing the overall load-bearing capacity of the telescopic beam.

[0045] The first steel pipe 10, the second steel pipe 20, and the connecting sleeve 30 are all seamless steel pipes with high dimensional accuracy, which can effectively reduce the friction between the steel pipes during the process of elongation or shortening, reduce the telescopic power, and improve the service life.

[0046] Among them, the length of the second steel pipe 20 is less than or equal to the length of the connecting sleeve 30, and also less than or equal to the length of the first steel pipe 10.

[0047] Specifically, the length of the first steel pipe 10 is 571 mm, the length of the second steel pipe 20 is 56 mm, and the length of the connecting sleeve 30 is 578 mm. Designing the length of the second steel pipe 20 to be less than that of the first steel pipe 10 is conducive to reducing costs and reducing the overall weight of the telescopic beam on the premise of ensuring sufficient support force.

[0048] The cross-sections of the first steel pipe 10, the second steel pipe 20, and the connecting sleeve 30 are all hexagonal pipes, and the connections between the sides are arc-connected, and the arc angle of the arc is R10 - R20, preferably R15, so as to facilitate the telescoping of the steel pipes and reduce the telescopic resistance.

[0049] Specifically, the hexagonal pipe includes a top side, a bottom side, a first side connected to both sides of the top side, and a second side connected to both sides of the bottom side.

[0050] The structures of the second steel pipe 20 and the connecting sleeve 30 are the same, and the outer wall surface of the second steel pipe 20 and the inner wall surface of the connecting sleeve 30 can be closely fitted, and the gap after fitting is 0.2 mm.

[0051] The structure of the first steel pipe 10 is not exactly the same as the structures of the second steel pipe 20 and the connecting sleeve 30. Among them, the lengths of the first side and the second side of the second steel pipe 20 and the connecting sleeve 30 are longer than the lengths of the first side and the second side of the first steel pipe 10. The distance between the top side of the first steel pipe 10 and the top side of the second steel pipe 20 is greater than the distance between the bottom side of the first steel pipe 10 and the top side of the second steel pipe 20. The outer wall surfaces of the first side and the second side of the first steel pipe 10 are closely fitted with the inner wall surfaces of the first side and the second side of the second steel pipe, and the fitting gap is 0.3 - 0.5 mm.

[0052] Specifically, the first steel pipe 10, the second steel pipe 20, and the connecting sleeve 30 are all prepared by using a seamless cold drawing multi-pass deformation technology, and the formed steel pipes are sequentially sleeved and assembled into a telescopic beam.

[0053] After testing the combined telescopic beam, during the telescopic process, the friction coefficient μ between the steel pipes < 0.1.

[0054] Through the above structural and mating designs of each steel pipe, it is convenient for the first steel pipe to extend or retract relative to the second steel pipe, reducing the number of resistance friction surfaces, which is beneficial to improving the flexibility of the telescopic beam during telescoping.

[0055] Perform performance tests on the steel pipes prepared in Example 1, Example 2, and Example 3. The results are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A preparation method of seamless cold-drawn steel pipe for telescopic beam, characterized in that, Select seamless circular tube blanks, inner molds and fixed outer molds of appropriate sizes for primary cold drawing, secondary cold drawing and forming cold drawing to reach the target deformation size. Among them, annealing heat treatment is carried out respectively between the primary cold drawing and the secondary cold drawing, and normalizing treatment and post-treatment are carried out successively after the forming cold drawing to obtain the seamless cold drawn steel pipe.

2. The preparation method of the seamless cold-drawn steel pipe for the telescopic beam according to claim 1, characterized in that, The process conditions for the primary cold drawing, secondary cold drawing and forming cold drawing are: room temperature, 10 - 15 m / min.

3. The preparation method of the seamless cold-drawn steel pipe for the telescopic beam according to claim 1, characterized in that, The process conditions for the annealing heat treatment are: temperature 700 - 730 °C, time 1 - 3 h, slowly cooled in the furnace to below 200 °C and then cooled outside the furnace to room temperature.

4. The preparation method of the seamless cold-drawn steel pipe for telescopic beams according to claim 1, characterized in that, The process conditions for the normalizing treatment are: temperature 880 - 940 °C, time 1 - 3 h, quickly cooled to room temperature by blowing.

5. The preparation method of the seamless cold-drawn steel pipe for the telescopic beam according to claim 1, characterized in that, The cross-section of the seamless cold drawn steel pipe is hexagonal, and the connection between any two adjacent sides is arc-shaped connection.

6. The preparation method of the seamless cold-drawn steel pipe for the telescopic beam according to claim 5, characterized in that, The arc angle of the arc is R10 - R20.

7. A telescopic beam, characterized in that, It includes two telescopic tube groups and a connecting sleeve. The two telescopic tube groups are linearly arranged, and the opposite ends respectively extend into the connecting sleeve and are connected with the connecting sleeve. The telescopic sleeve includes a first steel pipe and a second steel pipe prepared by any method of claims 1 - 6; one end of the first steel pipe extends into the second steel pipe and can telescopically move relative to the second steel pipe; the second steel pipe is built in both ends of the connecting sleeve and is fixedly connected with the connecting sleeve.

8. The telescopic beam according to claim 7, wherein The first steel pipe, the second steel pipe and the connecting sleeve all include a top side, a bottom side, a first side connected to both sides of the top side and a second side connected to both sides of the bottom side. There is a tight fit between the outer wall surface of the second steel pipe and the inner wall surface of the connecting sleeve. There is a tight fit between the outer wall surfaces of the first side and the second side of the first steel pipe and the inner wall surfaces of the first side and the second side of the second steel pipe.

9. The telescopic beam according to claim 8, characterized in that, The gap at the tight fit is 0 - 0.5 mm.

10. The telescopic beam according to claim 8, wherein The gap is 0.2 - 0.4 mm.

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