A hot rolling method for full continuous rolling of a train brake beam based on small square billets

Abstract

The application discloses a kind of hot rolling methods of train brake beam full continuous rolling based on small square billet, comprising the following steps: (1) the billet after being heated to preset temperature is pushed out from heating furnace, and 6-9 passes of blooming rolling is carried out to small square billet by using cross-column type rolling mill;(2) the small square billet material after preliminary rolling by cross-column type rolling mill is further continuously rolled by 6-7 passes using flat-stand alternation type continuous rolling mill set.The hot rolling mode of cross-column type plus flat-stand alternation type full continuous rolling and the redesigned pass structure are used to produce train brake beam, and the rolling efficiency and yield of the product are greatly improved through continuous and rapid rolling by continuous rolling mill set, which greatly improves the rolling efficiency, and also greatly improves the stability and uniformity of the finished product, reduces the rolling cost and increases the economic benefit.

Description

Technical Field

[0001] This invention relates to a continuous hot rolling method for special-shaped steel for train brake beams, and particularly to a hot rolling method for train brake beams based on small square billets in a fully continuous rolling process, belonging to the field of metallurgical technology. Background Technology

[0002] With rapid economic development, China's transportation industry has also enjoyed tremendous growth opportunities. However, the rapidly increasing freight volume is not proportional to the transport capacity of the freight trains currently in operation. This is mainly because the existing brake beams made of channel steel and round steel are no longer suitable for the requirements of trains with increased speeds and cannot withstand the loads of new trains with large tonnage and high speeds. Therefore, an integrated train brake beam has been developed. This train brake beam uses low-alloy high-strength structural steel and has the characteristics of low alloy content, high strength, and high toughness. However, traditional train brake beams are only rolled on transverse rolling mills, and the finished products have disadvantages such as low rolling efficiency, poor precision, and low steel stability, which cannot meet the production needs of the new train brake beams. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a hot rolling method for train brake beams based on small square billets in continuous rolling. This method has the characteristics of reasonable design, high rolling efficiency, and good stability and uniformity of finished products, thereby overcoming the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: A hot rolling method for train brake beams based on small square billets in continuous rolling includes the following steps: (1) The steel billet heated to the preset temperature is pushed out of the heating furnace and rolled into a small square billet by a horizontal rolling mill in 6-9 passes. (2) For the small square billets that have been pre-rolled by the horizontal rolling mill, the horizontal and vertical alternating continuous rolling mills are used for 6-7 stands of continuous rolling. Among them: the No. 1 rolling mill is a pre-opening type, which pre-rolls the small square billets into the prototype of the train brake beam steel. The upper and lower rolls are designed as asymmetrical shapes. The No. 2 rolling mill further pre-opens the specific shape required for the train brake beam steel rolls, creating conditions for the next pass to continue deformation. The No. 3 rolling mill is a closed roll type, which further distributes the metal flow direction of the head, tail and leg of the train brake beam steel rolls during the roughing process. The No. 4 rolling mill is symmetrically arranged and its shape is similar to a cap-shaped roll. The No. 5 rolling mill is a closed roll type, which is shaped like two wedges cutting into the workpiece at the same time, and simultaneously cutting the head and tail. The No. 6 and No. 7 rolling mills are vertical rolling mills with open roll types.

[0005] As a preferred option, in step (1), the cooling water of the rolls should be avoided from being poured onto the billet to reduce the temperature of the rolled piece and ensure the entry temperature when entering the continuous rolling mill.

[0006] As a preferred option, in step (2), the No. 2 rolling mill adopts vertical pressing and side pressing to increase the deformation of the rolled piece; the No. 3 rolling mill adopts vertical pressing and side pressing to increase the deformation of the rolled piece; the No. 4 rolling mill controls the metal required at the head and tail through side pressing and vertical pressing.

[0007] As a preferred option, in step (2), the elongation coefficient and reduction amount on both sides of each pass of each stand on the continuous rolling mill are kept equal.

[0008] As a preferred option, in step (2), the width and extension of the left and right sides of the No. 6 and No. 7 rolling mills are equal.

[0009] Beneficial Effects: Compared with existing technologies, this invention utilizes a novel continuous hot rolling mode with alternating horizontal and vertical rolling mills and a redesigned die structure to roll train brake beams. Through continuous and rapid rolling on the continuous rolling mill, the rolling efficiency and yield are significantly improved, greatly enhancing rolling efficiency. Simultaneously, the stability and uniformity of the finished product are significantly improved, resulting in products with good stability, uniformity, and high dimensional accuracy. This reduces rolling costs and increases economic benefits. The rolled train brake beam has an irregular cross-section, possessing advantages such as high purity, dense structure, good machinability, and excellent comprehensive performance. It also exhibits good corrosion resistance, heat resistance, and cold resistance, meeting the operating conditions of freight cars accelerating to 120 km / h. The new freight car combined brake beam uses 15Mn2CrVNbE steel, with performance equivalent to GB / T1591-1994 medium-low alloy high-strength steel Q460E, possessing excellent comprehensive mechanical properties (yield strength Rel≥460 N / mm). 2 It has a low-temperature impact toughness of -40℃ (Akv≥27 J) and a fatigue life of more than 1 million cycles, and has the advantages of strong weather resistance and long service life. Attached Figure Description

[0010] Figure 1 This is the design drawing of the train brake beam of the present invention, showing the pass profile from the transverse rolling mill to the continuous rolling mill. Figure 2 This is the finished hole pattern design drawing of the train brake beam of the present invention. Detailed Implementation

[0011] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments.

[0012] Example 1: Hot rolling method for train brake beams based on small billets in continuous rolling. The finished train beams are irregular shapes, and it is necessary to ensure that the flow rate per second is equal on each stand of the continuous rolling mill to reduce or eliminate the phenomenon of steel piling. At the same time, the elongation coefficient and reduction amount on the left and right sides of each pass of each stand of the continuous rolling mill should be kept equal to prevent the rolled piece from twisting.

[0013] Includes the following steps: The 160 cubic meter steel billet, heated to the preset temperature, is pushed out of the heating furnace and enters a horizontal rolling mill for 6-9 passes of initial rolling to form a small square billet (e.g., ...). Figure 1 (as shown in (a)) At the same time, cooling water from the rolls should be avoided from being poured onto the billet to reduce the temperature of the rolled piece and ensure the entry temperature when entering the continuous rolling mill.

[0014] For small square billets that have been initially rolled by a horizontal rolling mill, a horizontal-vertical alternating continuous rolling mill is used for 6-7 consecutive stands: First sortie: such as Figure 1 As shown in (b), the No. 1 rolling mill is a pre-cut section for train brake beam steel (hereinafter referred to as cross beam steel). It pre-rolls the small square billet into the prototype of cross beam steel, creating conditions for continued deformation in the next pass. At this time, the temperature of the rolled piece is high, the deformation is small, the resistance is small, and a large amount of uneven deformation can be achieved. The reduction is large, and the upper and lower rolls are designed with asymmetrical roll patterns.

[0015] Second sortie: Figure 1 As shown in (c), the No. 2 rolling mill further pre-cuts the crossbeam steel pass to the required specific shape, creating conditions for continued deformation in the next pass. This pass has a large cross-section, and the head and legs are in the early stage of shaping. Vertical pressing and side pressing are used to increase the deformation of the rolled piece to achieve the target shape.

[0016] Third sortie: such as Figure 1 As shown in (d), the No. 3 rolling mill has a closed pass, which further distributes the metal flow direction of the head, tail, and legs of the crossbeam steel pass during roughing. At this time, the workpiece temperature is high, the cross section is relatively large, the deformation resistance is small, and the relatively uneven deformation can be guaranteed. At the same time, the cross section of this pass is large, and the head and legs are not yet formed. Vertical pressing and lateral pressing are used to increase the deformation of the workpiece.

[0017] Fourth sortie: Figure 1 As shown in (e), the No. 4 rolling mill has a symmetrically arranged pass, similar in shape to a cap-shaped pass. The required metal at the head and tail is controlled by lateral and vertical pressing. In addition, it ensures that the legs can achieve a relatively wide height dimension.

[0018] Fifth sortie: Figure 1As shown in (f), the No. 5 rolling mill has a closed pass, which is shaped like two wedges cutting into the workpiece at the same time, cutting the head and tail at the same time. At this time, the workpiece is reduced by a large amount, and there is forced widening. The pass has a large widening amount, so that the workpiece can obtain a prototype shape close to the finished product shape by passing through the wedge-shaped pass.

[0019] The sixth and seventh sorties: such as Figure 1 As shown in (g) and (h), the last two stands, #6 and #7, are vertical mills. To ensure the shape and dimensions of the head, tail, and legs, as well as the straightness of the rolled piece, the extension of the head and tail must be adjusted to be equal. Their reduction and widening should not be too large, and the reduction of the cutting depth wedge should be kept uniform. Simultaneously, to ensure that the leg insertion of the rolled piece does not cause jamming, and to facilitate better processing and forming, the leg dimensions and the waist reduction of the tail should be appropriately increased. The finished product dimensions are designed based on the product standard dimensions. The tail and legs, with the smallest thickness, are the fastest cooling parts, and the shrinkage rate of the rolled piece should be considered during the design.

[0020] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A hot rolling method for train brake beams based on small square billets in continuous rolling, characterized in that, Includes the following steps: (1) The steel billet heated to the preset temperature is pushed out of the heating furnace and rolled into small square billets in 6-9 passes using a horizontal rolling mill; (2) For the small square billets that have been pre-rolled by the horizontal rolling mill, the horizontal and vertical alternating continuous rolling mill is used for 6-7 stands of continuous rolling to form a continuous rolling process from billet to finished product. The pass patterns of each rolling mill in the continuous rolling mill unit are configured according to the following functional principles: Mill #1 adopts a pre-opened pass pattern to pre-roll the small square billet into the prototype of the train brake beam steel, and the upper and lower roll pass patterns are designed as asymmetrical patterns; Mill #2 further pre-opens the specific shape required for the train brake beam steel pass pattern, creating conditions for continued deformation in the next pass; Mill #3 adopts a closed pass pattern to further distribute the metal flow direction of the head, tail, and leg of the train brake beam steel pass pattern during rough rolling; Mill #4 adopts a hat-shaped pass pattern arranged symmetrically on top and bottom, controlling the required metal at the head and tail through side pressure and vertical pressure; Mill #5 adopts a closed pass pattern to cut the head and tail depth; Mills #6 and #7 are vertical rolling mills with open pass patterns, ensuring the straightness of the rolled piece by adjusting the extension of the head and tail to be equal.

2. The hot rolling method for train brake beams based on small square billets in continuous rolling according to claim 1, characterized in that: In step (1), cooling water from the rolls should be avoided from being poured onto the billet to reduce the temperature of the rolled piece and ensure the entry temperature when entering the continuous rolling mill.

3. The hot rolling method for train brake beams based on small square billets in continuous rolling according to claim 1, characterized in that: In step (2), the No. 2 rolling mill adopts vertical pressing and side pressing to increase the deformation of the rolled piece; the No. 3 rolling mill adopts vertical pressing and side pressing to increase the deformation of the rolled piece; the No. 4 rolling mill controls the metal required at the head and tail by side pressing and vertical pressing.

4. The hot rolling method for train brake beams based on small square billets in continuous rolling according to claim 1, characterized in that: In step (2), the elongation coefficient and reduction amount on both sides of each pass of each stand on the continuous rolling mill are kept equal.

5. The hot rolling method for train brake beams based on small square billets in continuous rolling according to claim 1, characterized in that: In step (2), the width and elongation of the left and right sides of the No. 6 and No. 7 rolling mills are equal.

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