JPS5942562B2 - Slab hot rough rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot rough rolling method for steel sheets.

Slabs supplied to the hot rough rolling mill of a hot strip mill as a material to be rolled have been manufactured by blooming a steel ingot.

In the blooming process, the width of the slab was determined by taking into account the finished width of the steel strip. The difference between the width of the slab fed to the machine and the finished width of the steel strip was relatively small, about 10 to about 20 mm.

However, in recent years, the continuous casting method, which has various advantages over the blooming method, has become industrially popular and has become widely used, making it difficult to supply many types of slabs with different widths to the hot rough rolling mill. It became difficult.

The reason for this is that in the continuous casting method, the width of the slab cannot be changed without replacing the mold, and replacing the mold can greatly reduce the improvement in slab productivity achieved by the continuous casting method. Because it will be.

As a result, the width reduction of the slab by the hot rough rolling mill increased significantly from about 50 to about 75 r/Lrft.

However, as the width reduction of the slab increases, conventional width rolling using vertical rolls (edgers)
As shown in Fig. 1, the amount of loss at the fishtail-shaped deformed part that occurs at the front and rear ends of the slab 1, that is, the head knob (the shaded part in the figure) increases significantly, and the yield decreases significantly. .

Conventionally, hot rough rolling methods for reducing the amount of crop loss include the following methods.

■ A method of optimizing the rolling pass schedule, that is, as shown in Fig. 2 atb, the fishtail-like deformation caused by the width rolling by the vertical rolls 2 and the convex deformation caused by the horizontal rolling by the horizontal rolls 3 are appropriately controlled. A method of constructing a rolling pass schedule that minimizes the amount of crop loss by combining.

- A method of optimizing the shape of the slab before rolling, that is, minimizing the amount of crop loss by chamfering the corners of the slab 1 before rolling, as shown in FIG.

■ As shown in Figure 4a, using a rolling roll 4 with a large convex crown, the front and rear ends of the slab are rolled into a convex shape as shown in Figure 4a before width rolling with vertical rolls. This method minimizes the fishtail-like deformation that occurs during subsequent width rolling.

However, the above method (1) inevitably has limitations due to various rolling conditions such as slab dimensions, finished strip dimensions, mill capacity, and number of rolling passes.

In addition, in method (2) above, if the corners of the slab are chamfered by gas cutting, etc., the yield will decrease by the amount of cut-off, and
If chamfering is performed by press working or the like, the above-mentioned problem does not occur, but special equipment for chamfering is required, which increases equipment costs.

Furthermore, in the method (2) above, by controlling the rolling amount of the rolling roll 4 having a convex crown, the size of the convex shape at the leading and trailing ends of the slab can be controlled according to the width reduction amount of the slab, so that the amount of crop loss can be reduced. This is an effective method for reducing the size of

However, a rolling mill incorporating a rolling roll having a convex crown has a scale comparable to that of a hot rough rolling mill, and therefore requires equipment costs. When performing hot rough rolling, the hot rough rolling mill comprises a pair of vertical rolls and a pair of horizontal rolls installed between the vertical rolls, at least on the upstream side of the final roll stand; At least one universal rolling mill is installed in which the roll axes of the vertical roll and the horizontal roll are arranged on the same plane perpendicular to the slab, and the universal rolling mill applies compressive stress to the slab in its thickness direction and width direction. It is characterized in that the amount of crop loss occurring at the front and rear ends of the slab is reduced by simultaneously applying it.

This invention will be explained in more detail.

FIG. 5 is a schematic diagram showing one embodiment of the method of the present invention.

In the drawing, 5 is a heating furnace, 6 is a slab heated to a predetermined temperature in the heating furnace 5, 7 is a known hot rough rolling mill consisting of a plurality of roll stands, and 8 is a hot rough rolling mill. 9 is a known hot finishing rolling mill that is installed on the exit side of the crop shear 8 and is composed of a plurality of roll stands; and 10 is a hot finishing rolling mill. This is a coiler installed on the exit side of 9.

Each roll stand except the 10th stand of the hot rough rolling mill 7 consists of a pair of vertical rolls 11 and a pair of horizontal rolls 12. Located downstream, some horizontal rolls 12 are provided with backup rolls 13.

The slab 6 heated to a predetermined temperature in the heating furnace 5 is rough-rolled by a hot rough rolling mill 7, and then a crop produced at the front and rear ends of the slab is cut off by a crop shear 8, and then subjected to hot finishing rolling. After being rolled into a final product, the steel strip, by the machine 9, it is wound up by the roller 10.

In FIG. 5, 14 is a universal rolling mill installed in a row of hot rough rolling mills γ.

As shown in FIGS. 6a and 6b, the universal rolling mill 14 includes a pair of vertical rolls 15 and
Consisting of a pair of horizontal rolls 16 installed between,
Moreover, the roll axes of the vertical roll 15 and the horizontal roll 16 are arranged on the same plane that is orthogonal to the slab 6, respectively.

In order to effectively reduce the amount of crop loss of the slab 6 in the universal rolling mill 14, it is necessary to satisfy the following relational expression.

W1≧wHnW.

/2 However, Wo: Slab width before rolling, Wl: Slab width after rolling, WH: During rolling by the horizontal rolls 12.

As shown in FIGS. 6a and 6b, the vertical rolls 15 in the universal rolling mill 14 may have a caliber or may have a tapered surface or a flat surface (not shown). As such, the universal rolling mill 14 is arranged in a row of hot roughing mills 7, and the irregular deformation of the front and rear ends of the slabs, which results in strain crop loss, is located upstream of the hot roughing mill I. Since most of the rolling is determined by rolling with a roll stand, it is desirable to install the universal rolling mill 14 as close to the upstream side of the hot rolling mill 7 as possible.

Moreover, the number of universal rolling mills 14 to be installed is not limited to one.

FIG. 5 shows a case where one universal rolling mill 14 is installed upstream of the tenth stand of the hot rough rolling mill 7.

In addition to this, the universal rolling mill 14 may be installed between the continuous casting machine (not shown) and the heating furnace 5, and the slab width may be changed using the sensible heat of the slab after casting. good.

The slab 6 heated to a predetermined temperature by the heating furnace 5 is transferred to the vertical roll 15 and the horizontal roll 1 of the universal rolling mill 14.
6, the slab is simultaneously rolled down in the thickness direction and width direction.

As a result, unlike the case where the slab thickness direction and the width direction are rolled down independently, compressive stress acts simultaneously in the slab thickness direction and width direction, so the unsteady deformation region at the front and rear ends of the slab is reduced.

Therefore, the amount of crop loss at the leading and trailing ends of the slab is reduced.

Furthermore, as the amount of width reduction of the slab increases, the amount of lowering per pass inevitably increases, and in normal vertical rolls, the slab buckles between the rolls.

However, in the method of the present invention, the horizontal rolls 16 in the universal rolling mill 14 prevent buckling of the slab 6 caused by the heavy rolling by the vertical rolls 15.

Next, an example of the method of this invention will be described.

In order to confirm the effects of the method of the present invention, slabs were rolled by the conventional hot rough rolling method and the hot rough rolling method of the present invention, and the amount of crop loss was compared.

The configuration of the hot rough rolling mill in the conventional hot rough rolling method was as follows.

V, -V2H1-V3H2-V, H3-V5H, -V,
H5-Force, the configuration of the hot rough rolling mill in the method of this invention was as follows.

UH, -V, H2-V2H3-V3H, -V4H5-V
5H6 However, ■1-6: Ordinary vertical rolls, H1-6: Ordinary horizontal rolling mill, U: Universal rolling mill according to the method of this invention.

Moreover, the rolling conditions at this time are as follows.

Slab dimensions: thickness 220mm, width 1500mm, slab steel type: low carbon steel (C: 0.10%), slab heating furnace extraction temperature: 1250°C, slab thickness on rough rolling exit side: 36mm.

Slab width reduction: 50-300wLTIL.

Table 1 shows the results of the amount of crop loss (sum of crop lengths at the leading and trailing ends of the slab) when slabs were rolled by both methods.

As is clear from the results in Table 1, according to the method of the present invention, the amount of crop loss is 30 to 50% lower than that of the conventional method.
% reduction.

As explained above, according to the present invention, a row of a hot rough rolling mill is comprised of a pair of vertical rolls and a pair of horizontal rolls provided between the vertical rolls, and the rolls of both rolls are A universal rolling mill whose axis is perpendicular to the slab and arranged on the same plane is installed, and this universal rolling mill simultaneously rolls the slab in the thickness direction and width direction, thereby eliminating the scuffing knobs that occur at the front and rear ends of the slab. An entirely useful effect is that the amount of losses can be significantly reduced.

[Brief explanation of drawings]

Figure 1 is a plan view of the crop that occurs at the tip and rear end of the slab;
Figures 2a and b are plan and side views showing the deformation of the front and rear ends of the slab due to vertical rolls and horizontal rolls, and Figure 3 is a
The plan view of the chamfered slab, Figures 4a and b, are as follows:
A front view showing the state of rolling of the slab by a rolling roll having a convex crown and a plan view of the slab after rolling, No. 5
The figure is a block diagram showing one embodiment of the method of the present invention, FIG.
and b are a front view and a plan view of a universal rolling mill according to the method of the present invention. In the drawing, 1...slab, 2...
Vertical roll, total...Horizontal roll, 4...
Rolling roll having a convex crown, 5... Heating furnace, 6... Slab, I... Hot rough rolling mill, 8... Crop shear, 9 ...Hot finishing rolling mill, 10... Coiler 1, '11...
... Vertical roll, 12 ... Horizontal roll, 1
3... Backup roll, '%4...
・Universal BE! , 15... Vertical roll,
16...Horizontal roll.

Claims (1)

[Claims] 1. When hot rough rolling a slab, the hot rough rolling mill comprises a pair of vertical rolls and a pair of horizontal rolls installed between the vertical rolls, at least on the upstream side of the final roll stand, and , at least one universal rolling mill is installed in which the roll axes of the vertical roll and the horizontal roll are arranged on the same plane perpendicular to the slab, and in the universal rolling mill, the slab is rolled in the thickness direction and the width direction. By simultaneously applying compressive stress,
A method for hot rough rolling of slabs, characterized by reducing the amount of crop loss occurring at the leading and trailing ends of the slab.