JPH0647406A - Method for joining sheet bar completely continuously rolled - Google Patents

Abstract

PURPOSE:To attain an inexpensive process that is suitable to the modification of a mill because welding is almost unnecessary by reducing welding or rolling joining sheet bars in the first stage of finishing mills without welding at all at the time of executing completely continuous hot rolling. CONSTITUTION:The tip and rear end of the sheet bar which is rolled into prescribed dimensions with a roughing mill 1 are cut off by a curve of a polynominal of at least second order or more with a shear 2 to increase the adhesion rate of joining races during pressurizing contact. The tip part of the following sheet bar 6 is clamped with a movable guide 3, positioned by pushing it against the rear end part of the sheet bar 7 in finish rolling and also the butt part is rolled and pressurizing joined in the first stage of the finishing mills. Joining force at the degree to which the sheet is not broken in the succeeding finishing stands is attained by solid state welding method and continuous rolling is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for roll-bonding a sheet bar in a front stage of a finish rolling mill with little or no welding at the time of completely continuous hot rolling.

[0002]

2. Description of the Related Art Conventionally, in hot tandem rolling of thin plates, a slab of a finite length sent from the steelmaking process is roughly rolled into a sheet bar, which is then rolled by a multi-stand hot finishing mill. Then, it is wound into a coil to form a thin plate coil having a predetermined size.

However, in finish rolling, unsteady rolling at the leading edge of the sheet bar and unsteady rolling at the trailing edge of the sheet bar due to the finite length of the sheet bar is unavoidable. From the viewpoint of preventing the occurrence of plate defects, it has been necessary to slow down the plate passing speed at the time of passing the front and rear ends of the sheet bar, which has been a factor that impedes productivity.
As a countermeasure, it is considered to join a sheet bar having a finite length between a rough rolling mill and a finish rolling mill to perform endless finish rolling.

FIG. 5 is disclosed in Japanese Patent Laid-Open No. 57-109504.
As shown in FIG. 1, a process including a rough rolling mill, a coil box, a shear, a movable joining machine (swing roller type table), and a finish rolling mill is disclosed. The disadvantage of this method is that it requires a wide joining area because the joining strength must be secured only by welding, and therefore the traveling distance of the mobile joining machine becomes long for the purpose of obtaining sufficient joining time. .

That is, since the swing roller type table is installed, a lot of mill downtime and remodeling cost are required when remodeling an existing mill, and this method cannot be practically adopted. JP-A-58-112601 and JP-A-59
No. 209405 discloses a rough rolling mill as shown in FIG.
A process consisting of a coil box, a shear, a fixed welder, a sheet bar storage or spiral looper and a finishing mill is disclosed.

As an example of a fixed welding machine, Japanese Patent Laid-Open No. 61-15
Japanese Patent No. 8285 and Japanese Patent Application Laid-Open No. 61-242768 disclose processes using electric heating and upset. This method uses a fixed welding machine, so no swing roller table is required. However, a seat bar storage device such as a looper is newly required, and the minimum bending radius of the seat bar that does not cause plastic deformation is 25.
Considering that the length is about m, it is unavoidable that equipment such as a looper is increased in size, which causes a problem of high cost. That is, it cannot be practically used for modifying an existing mill.

In the above-mentioned prior art, since it takes a long time to weld the seat bar, there is a problem that equipment cost increases. In order to solve this problem, it is important to develop a method for joining in a short time. As an effective method, a method of pressing all or most of the joining area of the sheet bar is considered.

However, in continuous rolling, the plate temperature, the plate size, the steel type, the reduction ratio, etc. frequently change with the improvement of the continuation rate. Because of the change, the joining force of the sheet bar changes, and there is a problem that stable passing of the sheet cannot be performed, such as plate breaking.

[0009]

Conventionally, in order to carry out completely continuous hot rolling by modifying an existing mill, all or most of the abutting surfaces of the sheet bars are solid-phase joined at the front stage of the finish rolling mill. The new process is advantageous. For the problem of obtaining a strong joining strength, which is a prerequisite for this, it is important to maintain sufficient adhesion of the mating surfaces over the entire surface during rolling pressure welding in the preceding stage of the rolling mill. On the other hand, the butt portion is hardly welded or not welded before rolling,
The abutting part becomes the same as the leading end of the plate, causing unsteady deformation represented by fish tail.

That is, during the finish rolling, a part of the abutting portion near the both side edges of the plate is separated due to the unsteady deformation, so that the joining strength of the sheet bar pressed at the front stage of the finish rolling mill varies. There was a problem.

Therefore, since the abutting surfaces are not separated during finish rolling, the inventors investigated the mechanism of rolling pressure welding by the theory of rolling and experiments using hot steel, and based on the findings obtained at that time, It is an invention.

[0012]

The feature of the present invention resides in that the front and rear end portions of the roughly rolled sheet bar are cut with a curve of at least a quadratic polynomial and a butt surface due to unsteady deformation during rolling. By offsetting the relative deformation of the above, the separation of the abutting surfaces of the sheet bars during rolling is prevented, the adhesion ratio of the bonding surfaces during pressure welding is increased, and the bonding strength is improved.

The present invention will be described in detail below with reference to the drawings showing an embodiment of the present invention. In FIG. 1, 1 is a rough rolling mill, 2 is a shear, 3 is a movable guide, 4
Is a finishing rolling mill, 5 is a work roll in the front stage of the finishing rolling mill, 6 is a succeeding sheet bar, and 7 is a preceding sheet bar.

The sheet bar rolled to a predetermined size by the rough rolling mill 1 is cut at its leading end and trailing end by at least a quadratic curve with the shear 2 and the trailing end of the following sheet bar 6 is moved by the movable guide 3. The sheet bar 7 is clamped by and is pressed against the rear end of the sheet bar 7 during finish rolling to be positioned, and the butted portion is rolled at the front stage of the finish rolling mill to press-contact the sheet bar. A joining force that does not cause plate breakage in the subsequent finishing stand is obtained by solid-state joining that does not require welding, and continuous rolling is possible.

The operation of the present invention will be described below. Figure 2
Represents the position in the roll bite on the horizontal axis and the vertical pressure p acting on the sheet bar on the vertical axis. According to the theory of rolling, the vertical pressure p in the rolling direction is generated by the friction hills generated by the relative sliding between the roll and the sheet bar, and at the abutting surface of the preceding sheet bar and the following sheet bar,
It acts to press both sides.

Since the sheet bar is hot rolled, 1000
Since it is heated to about ℃, this vertical pressure p
Is sufficiently large, the abutting surface of the seat bar is easily pressed. Further, even if there is a contact failure on the abutting surfaces due to this pressure contact force, if the extent of contact failure is small, a metal flow occurs so as to fill the gap, and pressure contact is possible.

However, in the continuous rolling, there is a possibility that a large amount of butt face separation cannot be filled even by the metal flow. The factors include meandering of the sheet bar and unsteady deformation of the abutting surfaces due to rolling, and strong joining force cannot be obtained unless separation of the abutting surfaces due to this is prevented.

With respect to the factor (1), that is, the meandering of the seat bar, the leading end of the trailing sheet bar is clamped by the movable guide 3 shown in FIG. By pressing it against the rear end of the bar, the abutting portion is guided to the work roll 5 in the front stage of the finishing rolling mill while maintaining a good contact state of the abutting surface of the sheet bar, so that the pressure contact of the sheet bar is ensured.

With respect to the factor (1), that is, the unsteady deformation of the abutting surface due to rolling, the shape of the abutting surface of the sheet bar should be formed in advance so as to cancel the relative displacement of the abutting surface that occurs during rolling pressure contact. Is effective. As one method, a method of cutting into an optimum shape by the shear 2 in FIG. 1 is adopted.

FIG. 3A shows a plan view of the abutting surface of the sheet bar before rolling. The solid line in FIG. 3B shows the shape of the abutting surface after rolling, and the broken line shows the shape before rolling. It can be seen that the shape of the abutting surface changes from the broken line to the solid line by rolling. That is, the relative displacement of the abutting surfaces becomes a separation phenomenon.

FIG. 4A is an example in which the shape of the seat bar of FIG. 3A is selected in advance so as to cancel the deformation shown in FIG. 3B. That is, a shape obtained by subtracting the displacement amount of FIG. 3B from the shape of FIG. 3A is shown.

The solid line in FIG. 4B shows the shape of the abutting surface after rolling the sheet bar of FIG. 4A, and the broken line shows the shape of the abutting surface before rolling. It can be seen that the shape of the abutting surface changes from the broken line to the solid line by rolling. Figure 4B
It can be seen that the relative displacement of the abutting surface is smaller than that in FIG. 3B.

However, the optimum shape selection method of FIG.
It is for the purpose of explanation, and it is not always necessary to adopt it. Rather, as a method of selecting the shape of the abutting surface, it is convenient to use a result obtained from a prediction formula of deformation by experiment or theoretical analysis, that is, an optimum shape is approximated by a curve of at least a quadratic polynomial.

Here, the linear equation is not adopted because it cannot express a curve other than a straight line, that is, an optimum shape. However, it is not necessary to unnecessarily use a large-order equation, and it is sufficient to use the lowest-order equation that satisfies the required accuracy. By the method based on the above prediction, separation of the abutting surfaces during rolling can be considerably prevented.

Further, it is effective to apply learning control to ensure the joining. That is, since rolling pressure welding is repeated in continuous rolling, the learning control device 1 using a computer uses the result of rolling obtained by the joining inspection device 9 in FIG.
The optimum shape of the abutting surface is determined by using the result and the above-mentioned prediction formula, and cutting is performed by the shear 2 based on this. Since the control is adopted, it is possible to perform reliable joining that is hardly affected by various disturbances that occur during operation.

As another method for ensuring the joining,
It is effective to heat and activate the abutting surfaces with the movable heating device 8 of FIG. It is generally known that in pressure welding, the higher the temperature of the material, the easier the joining and the better the joining force. Since the moving type heating device can locally heat the abutting surfaces, which are important for joining, it is advantageous in that the material change portion is small and the heating efficiency is high.

[0027]

Embodiments of the present invention will be described with reference to FIG. 1 and Tables 1 and 2. A continuous hot rolling test was conducted under the conditions shown in Table 1 and Table 2.

As a result, it was proved that the present invention is effective in that the joining is performed in any case, and the plate of the sheet bar is not broken during the finish rolling.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

EFFECTS OF THE INVENTION The present invention is constructed and operated as described above, and has a remarkable effect in rolling and joining a sheet bar in the front stage of a finish rolling mill when performing complete continuous hot rolling. There is.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a chart showing a relationship between a roll bite position and a vertical pressure p in a rolling direction.

FIG. 3 is an explanatory view showing a shape of a butt surface before rolling and a shape of a butt surface after rolling when A is continuously rolled on the butt surface having a normal shape.

FIG. 4 is an explanatory view showing a shape of a butt surface before rolling and a shape of a butt surface after rolling, in the case where continuous rolling is performed on the butt surface having an optimized shape.

FIG. 5 is an explanatory diagram of a process using a movable joining machine and a swing roller table.

FIG. 6 is an explanatory view of a process using a stationary welder and a sheet bar storage device or a spiral looper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rough rolling mill 2 Shear 3 Moving guide 4 Finishing rolling mill 5 Finishing rolling mill Work rolls in front stage 6 Subsequent sheet bar 7 Leading sheet bar 8 Movable welding machine and heating device 9 Joining inspection device 10 Learning control device 11 Coil box 12 Coil 13 Mobile joining machine 14 Rail 15 Swing roller table 16 Fixed welding machine 17 Pinch roll 18 Sheet bar storage device or spiral looper

Claims (5)

[Claims] 1. A joining method of a sheet bar of complete continuous hot rolling, in which a sheet bar after rough rolling is joined to a sheet bar during preceding finish rolling and continuously rolled, in a joining method of a sheet bar after rough rolling. Of the sheet bar of complete continuous hot rolling, characterized in that the rear end of the sheet bar and the sheet bar is cut by a cutting machine arranged in front of the finishing rolling machine with a curve of at least a quadratic polynomial or more. Method. 2. The sheet for completely continuous hot rolling according to claim 1, wherein the sheet is cut along a curve having a shape that cancels out the relative deformation of the butted surfaces due to rolling, which is obtained from a prediction formula based on experiments or rolling theory. How to join bars. 3. The method for joining sheet bars in complete continuous hot rolling according to claim 1 or 2, wherein the sheet bar is cut with a curve having a shape that cancels the relative deformation of the abutting surfaces obtained by learning control. . 4. A movable guide that clamps the leading end of the roughly rolled sheet bar and presses and positions the clamped leading end of the sheet bar on the rear end of the sheet bar during finish rolling. The method for joining sheet bars for completely continuous hot rolling according to claim 1, 2, or 3. 5. A movable heating device, which is located between the rough rolling mill and the finish rolling mill and heats the leading end portion of the trailing sheet bar and the trailing end portion of the preceding sheet bar, is used. Item 5. A method for joining sheet bars in complete continuous hot rolling according to item 1, 2, 3 or 4.