Production method of rectangular flat steel

Abstract

The invention relates to a production method of rectangular flat steel, and belongs to the field of flat steel rolling. The method comprises the steps of blooming and cogging and continuous rolling, wherein blooming and cogging are that a future billet is rolled into a middle fillet square billet, a box-shaped hole with inclination is adopted, the upper fillet and the lower fillet are the same, rolling passes are arranged for odd number times, and steel is turned up and down for the odd number of passes during rolling; roll hole patterns for continuous rolling are designed in an up-down symmetry mode, continuous rolling is divided into intermediate rolling and finish rolling, the intermediate rolling is divided into 1-6 passes, a first-pass double-ellipse and circle and ellipse alternating hole pattern is adopted, and a square billet with the middle rounded corner is rolled into round steel; the finish rolling is performed for four passes, round steel is rolled into rounded rectangular flat steel by adopting a flat and vertical alternate box square hole pattern, a finished box hole and a front box hole of the finished box hole adopt an up-and-down R angle design, the R angle is consistent with the up-and-down R angle of the flat steel, a finished product is produced by erecting a rack, and the width is greater than the height.

Description

Technical Field

[0001] The invention relates to the technical field of alloy rolling, in particular to rolling forming of rectangular flat steel. Background Art

[0002] The traditional rectangular flat steel production process requires complex hole configuration and multiple rolling passes to roll the billet into a finished product, which has low production efficiency and high energy consumption. Moreover, the billet is prone to twisting and being scrapped after multiple rolling passes, resulting in a low yield rate and high production costs.

[0003] There are few domestic enterprises that can produce round steel and can flexibly convert rectangular flat steel and carry out mass production. In order to ensure seamless production of round steel and flat steel, it is necessary to reasonably design the rolling hole system to reduce the gauge change time. If the gauge change time is too long, the billet will be detained in the heating furnace for a long time, causing a series of quality problems, such as excessive decarburization, microscopic pores, etc.

[0004] Flat steel has a simple cross-sectional shape, and currently the square hole type with concave edges and the flat-vertical hole type system are widely used. However, due to the instability of the rolled piece when the vertical hole is used for small-sized flat steel, the roller may sometimes be entangled. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a production method of rectangular flat steel in response to the above-mentioned prior art. The method uses square billets as the incoming material specifications. The rectangular flat steel rolled by this method not only meets the size requirements in terms of height and width, but also can meet the production requirements of different upper and lower R angles. It is compatible with the existing round steel hole type system and can be seamlessly connected with the round steel hole type system, which facilitates the change of specifications between round steel and flat steel, ensures the internal quality of the flat steel, and ensures production efficiency.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problem is: a production method of rounded rectangular flat steel, including initial rolling and continuous rolling, wherein the initial rolling is to roll the future billet into an intermediate rounded square billet, adopt a box-shaped hole with an inclination, the upper and lower rounded corners are the same, an odd number of rolling passes are set, and the steel is turned up and down in the odd number of passes during rolling; the continuous rolling roller hole type adopts an upper and lower symmetrical design, and the continuous rolling is divided into intermediate rolling and finishing rolling. The intermediate rolling is 1 to 6 passes, and the first pass double ellipse and circle and ellipse alternate hole types are adopted to roll the intermediate rounded square billet into round steel; the finishing rolling has a total of 4 passes, and the box-shaped hole type that alternates horizontally and vertically is adopted to roll the round steel into a rounded rectangular flat steel, the finished product box-shaped hole and the box-shaped hole before the finished product box-shaped hole adopt an upper and lower R angle design, the R angle is consistent with the upper and lower R angles of the flat steel to ensure that the final finished product R angle meets the delivery requirements, and the finished product is output by a vertical rack, and the width is greater than the height.

[0007] As a preferred solution: in the blooming stage, the blooming rolling passes are 11 - 13, the upper and lower fillet radii R are 30 mm, the deformation per pass is ≥15%, the total deformation is ≥80.8%, and the width - thickness ratio of the cross - section of the intermediate billet is 0.93 - 1.

[0008] As a preferred solution: the deformation per pass of the intermediate rolling is ≥20%, and the total deformation of the intermediate rolling is ≥78%.

[0009] As a preferred solution: in the finishing stage, the side - wall slopes of the finishing pass and the pass before the finishing pass are 4.5° - 11°, the reduction of the four finishing passes gradually decreases, and the spread coefficient is controlled at 0.2±0.02, so as to ensure the flatness of the finished product surface and no convex belly appears.

[0010] As a preferred solution: the reduction coefficient of the cube pass in the finishing stage is 1.1 - 1.8, the total deformation is ≥36%, and the finishing temperature is 930 - 970°C, higher than Ar3.

[0011] As a preferred solution: the elongation coefficient of the continuous rolling passes is 1.02 - 1.4.

[0012] As a preferred solution: after obtaining the intermediate billet by blooming, the head of the intermediate billet is cut to remove the head defects.

[0013] As a preferred solution: after intermediate rolling, the cutting lengths of the head and tail of the round steel are 30 - 60 cm.

[0014] Compared with the prior art, the advantages of the present invention are as follows: in rough rolling and the intermediate rolling of continuous rolling, the original round - steel pass system is adopted, and in finishing, the No. 7 - 10 passes adopt the horizontal - vertical box square - pass design. At the same time, it is supplemented with a rolling guide system to ensure the stability of steel running. The upper inner fillet radius R of the finished box pass and the box pass before the finished box pass (i.e., the box passes of the last pass and the second - last pass) is specially designed. The finished product is discharged from the vertical stand, the width is greater than the height, and the steel discharging is stable without torsion, so as to achieve a perfect fit of the size and R - angle to the customer requirements.

[0015] Through the control of the three rolling processes of blooming, intermediate rolling, and finishing, a rectangular flat steel with an R - angle is obtained. Not only the dimensional tolerance meets the customer requirements, but also the steel - discharging rhythm is controlled to ensure that the decarburization meets the customer requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the blooming pass - type structure diagram in the embodiment of the present invention; Figure 2 It is the intermediate - rolling pass - type structure diagram in the embodiment of the present invention; Figure 3 It is the finishing pass - type structure diagram in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings. The embodiments are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention. The text description in this embodiment corresponds to the accompanying drawings, and the description of the orientation is also based on the description of the accompanying drawings, which should not be understood as limiting the scope of protection of the present invention.

[0018] The incoming material specifications are 300mm×340mm, and the cross-section width-to-thickness ratio is 0.88; the blank is heated according to Figure 1 In the hole pattern diagram, No. 1 to No. 5 holes are reciprocatingly opened in turn, and the reciprocating rolling mill is used to roll the intermediate square billet 135mm×145mm through 11-13 passes. The deformation amount of each pass is ≥15%, and the total deformation amount from the continuous casting billet to the intermediate billet is ≥80.8%. The whole process is controlled to be completed within 2 minutes. The specific reduction amount and related parameters of each pass are shown in Table 1.

[0019] Table 1

[0020] Head cutting: After the billet is opened, the defects on the head need to be cut off. During the billet opening process, the head and tail of the billet have irregular defects due to the large amount of pressure reduction. The bad materials at the head and tail must be cut off.

[0021] Intermediate rolling; continuous rolling, the intermediate billet is cut and then directly sent to the continuous rolling mill for 1~6 passes to be rolled into round steel bars. The deformation of each pass is ≥20%, and the total deformation of intermediate rolling is ≥78%. For details, see the schematic diagram of 1~6 pass type Figure 2 .

[0022] Flying shear head: After medium rolling, the head is slightly irregular, and the length of the head and tail cut is 30~60cm.

[0023] Finish rolling: according to Figure 3 , after 7~10 boxes of square hole rolling, the rectangular flat steel has a total deformation of ≥36% and a round steel final rolling temperature of 930~970℃, which is higher than Ar3. The whole process is completed within 1.5 minutes. The specific size, reduction and elongation coefficient distribution of each pass are shown in Table 2.

[0024] Table 2

[0025] After the finished product is rolled, the irregular part of the head needs to be cut off, and then the finished flat steel is sawed to the length required by the customer.

[0026] The time for opening the slab needs to be strictly controlled, and the rolling should be rapid to minimize the residence time in the high temperature stage. As long as the heating time is controlled well and the three rolling production links are strictly controlled at the same time, the comprehensive performance quality of the flat steel can be guaranteed.

[0027] After rolling through the above steps, the rolling of the second bar is carried out repeatedly. While ensuring the rolling rhythm, the internal quality is also guaranteed. To roll round steel of other specifications, only the last four stands need to be replaced, which is convenient and fast.

Claims

1. A production method of a flat steel with rounded corners, characterized in that: It includes blooming and continuous rolling. In the blooming process, the incoming billet is rolled into an intermediate square billet with rounded corners. A box pass with a slope is used, and the upper and lower rounded corners are the same. An odd number of rolling passes are set, and the steel is reversed up and down during the odd-numbered passes. In the continuous rolling process, the roll pass is designed symmetrically up and down. The continuous rolling is divided into medium rolling and finishing rolling. The medium rolling has 1 to 6 passes, and the pass shapes of the first pass are double ellipse, and the ellipse and circle alternate, rolling the intermediate square billet with rounded corners into round steel. The finishing rolling has a total of 4 passes, and a flat-stand alternate box-square pass is used to roll the round steel into a flat steel with rounded corners and a rectangular shape. The finished box pass and the box pass before the finished box pass adopt an upper and lower R corner design, and the R corner is consistent with the upper and lower R corners of the flat steel. The finished product is produced by a vertical stand, and the width is greater than the height.

2. The production method of the filleted rectangular flat steel according to claim 1, characterized in that: In the blooming stage, the blooming rolling passes are 11 to 13, the upper and lower rounded corner R is 30 mm, the deformation per pass is ≥15%, the total deformation is ≥80.8%, and the width-thickness ratio of the intermediate billet cross-section is 0.93 to 1.

3. The production method of the flat steel with rounded corners according to claim 1, characterized in that: The deformation per pass in the medium rolling is ≥20%, and the total deformation in the medium rolling is ≥78%.

4. The production method of the fillet rectangle flat steel according to claim 1, characterized in that: In the finishing rolling stage, the sidewall slopes of the finished pass and the pass before the finished pass are 4.5° to 11°. The reduction in the four finishing rolling passes gradually decreases, and the spread coefficient is controlled at 0.2 ± 0.

02.

5. The production method of the filleted rectangular flat steel according to claim 1, characterized in that: In the finishing rolling stage, the reduction coefficient of the cubic pass is 1.1 to 1.8, the total deformation is ≥36%, and the final rolling temperature is 930 to 970 °C, which is higher than Ar3.

6. The production method of the filleted rectangular flat steel according to claim 1, characterized in that: The elongation coefficient of the continuous rolling passes is 1.02 to 1.

4.

7. The production method of the flat steel with rounded corners and rectangular shape according to claim 1, characterized in that: After obtaining the intermediate billet in the blooming process, the head of the intermediate billet is cut off to remove the head defects.

8. The production method of the fillet rectangle flat steel according to claim 1, characterized in that: After medium rolling, the cutting lengths of the head and tail of the round steel are 30 to 60 cm.

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