A method of rolling a circular cast billet into a rail

Abstract

The application discloses a method for rolling a rail by using a round billet, and comprises the following steps: ensuring that the compression ratio of rail rolling after the round billet is used is not less than that of a square billet; and optimizing a pass system of rail rolling when the round billet is used, and designing a deformation pass as a BD1 rough rolling pass, wherein the BD1 rough rolling pass of the square rail billet is composed of two box-shaped holes, one ladder-shaped hole and three open-die holes, and a total of seven passes are rolled, and the existing pass is optimized by using the round billet. The application aims to provide a method for rolling a rail by using a round billet, and solves the size defects of a square billet arc angle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material pressure processing, in particular to a method for rolling rails by using round billets. BACKGROUND

[0002] Long profile rolling adopts continuous casting billets, usually special-shaped billets or square billets, among which rail rolling adopts square billet rolling, and according to the specifications of rail products, 280*380mm or 320*415mm billets are commonly selected as the cross-sectional size of the casting billets. The quality of the casting billets affects the quality of the rail finished products and the surface quality, and different billet selection is beneficial to the elimination of internal defects of the rails. The compression ratio during rail rolling is required to be not less than 1:9, and square casting billets are often selected as the billet type during rail rolling, but square casting billets have some defects in heating, for example, the surface decarburization of the billets is uneven during heating, and the decarburization is more serious at the four right angles of the casting billets, resulting in that the surface decarburization layer thickness of the rail rolling piece exceeds the standard. The round corners of the square casting billet mold are small, and cracks are easily formed at the round corners of the casting billets during the cooling and light pressing of the casting billets, and finally line defect is formed on the surface of the rail rolling piece. Therefore, in order to eliminate the defects at the round corners of the square casting billets, many common grinding devices or flame cutting devices are specially used to eliminate the defects at the round corners of the casting billets. SUMMARY

[0003] The purpose of the present application is to provide a method for rolling rails by using round casting billets, which solves the size defects of the round corners of square casting billets.

[0004] To solve the above technical problems, the present application adopts the following technical solutions:

[0005] The method for rolling rails by using round casting billets comprises the following steps:

[0006] Ensure that the compression ratio of rail rolling after using round casting billets is not less than that of square casting billets;

[0007] Optimize the pass system of rail rolling by using round casting billets, and design the deformation pass as a BD1 rough rolling pass, which is composed of two box passes, one ladder pass and three open pass, and a total of 7 passes are rolled, and the existing pass is optimized by using round casting billets;

[0008] The box hole has a hole depth of 77.5mm and a hole width of 390mm, and is rolled in two passes, the first pass is executed with a roll gap width of 100mm, and the second pass is executed with a roll gap width of 50mm; after the two passes of rolling of the box hole, the blank is turned by 90° and enters the ladder hole for rolling in three passes, the ladder hole has a short side depth of 73mm and a long side depth of 76mm; the first pass of the ladder hole is deformed with a roll gap of 15mm, and is executed with a roll gap width of 200mm and a pass reduction of 120mm, the second pass is executed with a roll gap width of 110mm and a pass reduction of 90mm, the third pass is executed with a roll gap width of 15mm and a pass reduction of 95mm; after the five passes of rolling deformation, the blank is well filled in the hole, and provides a suitable cross-sectional size for the first blooming hole, and the other hole rolling can be performed according to the normal rolling of the bloom blooming hole.

[0009] Further, the cross-sectional area of the square billet is 280mm x 380mm = 106400mm 2 Therefore, the diameter of the round billet in the cold state is 368mm.

[0010] Further, one of the purposes of changing the square billet into a cylindrical billet is to improve the decarburization in the heating process of the billet.

[0011] Further, after using the round billet, the influence of the inner arc and the outer arc shapes during the square billet continuous casting is weakened, and the round billet can completely eliminate such defects and will not cause rail surface lines, cracks and other defects due to the round corner crack of the billet.

[0012] Further, the round billet can not only replace the 280x380mm size, but also replace the 320x415mm size of the square billet, and is not limited to the above two cross-sectional sizes of the square billet.

[0013] Compared with the prior art, the beneficial technical effects of the present application are:

[0014] After changing the billet from a square to a cylindrical billet, the decarburization in the heating process of the billet is improved, and since the round billet surface heat dissipation surface is uniform, there is no problem of local uneven decarburization at the round corner of the square billet, which is beneficial to well control the decarburization layer depth of the rail head. After using the round billet, the influence of the inner arc and the outer arc shapes during the square billet continuous casting is weakened, and the round billet can completely eliminate such defects and will not cause rail surface lines, cracks and other defects due to the round corner crack of the billet. BRIEF DESCRIPTION OF DRAWINGS

[0015] The application will be further described below in conjunction with the drawings.

[0016] Figure 1 Circular bloom size;

[0017] Figure 2 DB1 first pass first pass bloom filling situation;

[0018] Figure 3 DB1 first pass second pass bloom filling situation;

[0019] Figure 4 DB1 second pass first pass bloom filling situation;

[0020] Figure 5 DB1 second pass second pass bloom filling situation;

[0021] Figure 6 DB1 second pass third pass bloom filling situation. DETAILED DESCRIPTION

[0022] A method of rolling a rail from a circular bloom, comprising:

[0023] Rail rolling must meet the rolling deformation compression ratio of 1:9. According to the equal area ratio, the diameter of the round billet is determined to be 368mm. The hole shape is optimized on the basis of the existing square billet rolling hole shape. The square hole rough rolling BD1 has a total of 5 hole shapes and 7 rolling passes, consisting of a box hole, a trapezoidal hole and three burr holes. Three rolling passes are required in the first box hole to compress the 380mm long side of the square billet, which is the rail height direction of the final rail. After the present invention adopts the round billet, it will not be affected by the shape, so only two rolling passes are required when rolling in the first box hole. At the same time, the steel needs to be turned 90° before the first pass of the square billet entering the box hole. The present invention adopts the round billet without turning the steel, and can be directly rolled and deformed. Two passes are rolled in the box-type hole, with a designed roll gap size of 15mm, a hole depth of 77.5mm, and a hole width of 390mm. The roll gap width of the first pass is 100mm, and the pass reduction is 115mm. During rolling, the center of the billet enters the hole in the center. The roll gap width of the second pass is 50mm, and the pass reduction is 50mm. After two passes of rolling, the billet changes from a circle to a rectangle with an arc. The hole width must retain sufficient expansion space to prevent ears from appearing during billet rolling. After the box-type hole rolling is completed, it needs to enter the trapezoidal hole for rolling. The steel needs to be turned 90° before entering the rolling. If necessary, a guide should be used to feed the billet into the trapezoidal hole. It undergoes three passes of rolling deformation in the trapezoidal hole. The short side depth of the trapezoidal hole is 73mm, the long side depth is 76mm, the first pass deformation design roll gap is 15mm, the implementation roll gap width is 200mm, the pass reduction is 120mm, the second pass implementation roll gap width is 110mm, the pass reduction is 90mm, the third pass implementation roll gap width is 15mm, the pass reduction is 95mm.

[0024] The present invention only illustrates the deformation of the first two hole types. It should be noted that after the round billet is fully extended after being rolled and deformed by the first two hole types, the cross-sectional shape of the billet has completely met the hole type system for rolling square billets, and the trapezoidal hole completely provides billets of sufficient size for the next burr hole. Therefore, except for the first two hole types of BD1 in the hole type system of the present invention, after the size optimization is carried out, the other hole types can be rolled and deformed according to the hole type system for rolling square billets.

[0025] The beneficial effects of using the billet rolling steel rail of the present application are that the replacement of the square billet with the cylindrical billet is beneficial to improve the decarburization during the heating process of the billet, since the surface heat dissipation of the cylindrical billet is uniform, there is no problem of uneven local decarburization at the rounded corners of the square billet, and it is beneficial to well control the decarburization depth of the rail head of the steel rail. After using the cylindrical billet, the influence of the inner arc and outer arc shapes during the continuous casting process of the square billet is weakened, and at the same time, the square billet is prone to produce cracks at the rounded corners of the square billet during the continuous casting of the square billet, but the cylindrical billet can completely eliminate such defects, and the surface linear marks and cracks of the steel rail caused by the cracks at the rounded corners of the billet can be avoided.

[0026] Meanwhile, it should be understood by those skilled in the art that the cylindrical billet described in the present application can not only replace the 280x380mm size, but also can replace the 320x415mm size and other square billet sizes, and is not limited to the above two cross-sectional sizes of the square billet.

[0027] The above-described embodiments are only to describe the preferred modes of the present application, and are not to limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method of rolling a rail from a round bloom, characterised in that, Comprise: Ensure that the compression ratio of rail rolling after using round billets is not less than that of square billets; Optimize the pass system of rail rolling by using round billets, and design the deformation pass as BD1 rough rolling pass. The BD1 rough rolling pass of square rail billet is composed of two box passes, one ladder pass and three teeming passes, a total of 7 rolling passes. The existing pass is optimized by using round billets; The box pass has a pass depth of 77.5mm and a pass width of 390mm, and is rolled in two passes. The first pass is executed with a roll gap width of 100mm, and the second pass is executed with a roll gap width of 50mm. After two passes of the box pass, the billet is turned 90° and enters the ladder pass for rolling in three passes. The ladder pass has a short side depth of 73mm and a long side depth of 76mm. The first pass of the ladder pass is designed with a deformation roll gap of 15mm, an executed roll gap width of 200mm, a pass reduction of 120mm, a second pass executed roll gap width of 110mm, a pass reduction of 90mm, a third pass executed roll gap width of 15mm, and a pass reduction of 95mm. After five passes of rolling deformation, the billet is well filled in the pass, providing a suitable cross-sectional size for the first teeming pass.

2. A method of round bloom rolling into a rail as claimed in claim 1 characterised in that, The cross-sectional area of the square cast blank is 280 mm x 380 mm = 106,400 mm 2 Therefore, the diameter of the round cast blank in the cold state is 368 mm.

3. A method of round billet rolling of rails according to claim 1, characterized in that, One of the purposes of changing the square billet to a cylindrical billet is to improve the decarburization during the heating process of the billet.

4. A method of round billet rolling of rails according to claim 1, characterized in that, After using round billets, the influence of the inner arc and outer arc shapes during square billet continuous casting is reduced, and the square billet is prone to crack at the round corner of the square billet during square billet continuous casting. However, round billets can completely eliminate such defects and will not cause rail surface line and crack defects due to billet round corner cracks.

5. A method of round billet rolling of rails as claimed in claim 1 wherein, Round billets can not only replace 280×380mm size, but also replace 320×415mm size square billets, and are not limited to replacing the above two cross-section square billet sizes.

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