JPH05293511A - Method for welding sheet bar in completely continuous hot rolling - Google Patents

Abstract

PURPOSE:To secure the roll-welding of sheet bar in the early stage of a finishing mill by heating the butted part between the sheet bars on the inlet side of the finishing mill in a completely continuous hot rolling. CONSTITUTION:The sheet bar rolled by a rough mill 6 to a prescribed dimension is cut by a shear 2 at the tip and the rear end, the cut parts at the tip and the rear end are hearted by a mobile heating device 8, the tip part of the following sheet bar 6 is clamped by a mobile guide 3, pressed to the rear end of the finishing-rolled sheet bar 7 to positioned and the sheet bar is roll-welded by rolling the abutling part in the early stage of the finishing mill.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling joining of a sheet bar in a front stage of a finishing rolling mill by heating a butt portion of the sheet bar at an entrance side of the finishing rolling mill when performing a completely continuous hot rolling. And a joining method for ensuring the above.

[0002]

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

However, in the finish rolling, since the sheet bar has a finite length, it is inevitable that the front end of the sheet bar is caught and the rear end of the sheet bar is unsteady rolling. From the viewpoint of preventing the occurrence of plate defects, it has been necessary to slow the plate passing speed when 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. 3 is disclosed in Japanese Patent Laid-Open No. 57-109504.
As shown in FIG. 1, a process including a rough rolling mill 1, a coil box 16, a heat retaining device, an unwinding device, a movable joining machine (swing roller table) 10, and a finish rolling mill 4 is disclosed. This method requires a large joining area because the joining strength must be secured only by welding, and therefore the traveling distance of the mobile joining machine becomes long in order to obtain a sufficient joining time. That is, since the swing roller type table is installed, many mill suspension periods and remodeling costs are required when remodeling an existing mill, which is practically unusable.

In Japanese Patent Laid-Open No. 58-112601 and Japanese Patent Laid-Open No. 59-209405, as shown in FIG. 4, a rough rolling mill, a coil box, a shear, a fixed welding machine 13,
A process comprising a seat bar storage device or spiral looper, finish rolling mill is disclosed.

As an example of a fixed welding machine, Japanese Patent Laid-Open No. 61-15
8285 and Japanese Patent 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 m.
Considering that the size of the equipment is large, it is inevitable that the equipment such as the looper becomes large in size, which causes a problem of high cost. That is,
It cannot be practically used to modify 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, it is possible to adopt a pressure welding method without welding. However, in continuous rolling, the plate temperature, plate size, steel type, rolling reduction, etc. frequently change with the improvement of the continuation rate, so the welding method changes the joining force of the sheet bar and stabilizes the plate rupture. There was a problem that it could not be threaded.

[0008]

Conventionally, in order to carry out completely continuous hot rolling by modifying an existing mill, a new process of solid-phase joining a sheet bar before a finishing rolling mill is advantageous. However, in the solid phase joining process, there has been a problem in that the joining strength of the sheet bar pressed in the preceding stage of the finish rolling mill varies due to changes in rolling conditions during continuous rolling.

Activation of the bonding interface is important for increasing the bonding strength. Therefore, in order to ensure the pressure welding in the front stage of the finish rolling mill, the inventors have paid attention to the temperature of the sheet bar as a factor affecting the pressure welding by an experiment using rolling theory and hot steel, and at that time, The present invention has been completed based on the obtained knowledge.

[0010]

A feature of the present invention is that a movable heating device for heating a butt portion of a sheet bar at an entrance side of a finish rolling mill is used in performing a complete continuous hot rolling. It is in. Hereinafter, the present invention will be described in detail with reference to the drawings showing exemplary embodiments 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 finish rolling mill, 5 is a work roll in the preceding stage of the finish rolling mill, 6 is a succeeding sheet bar, 7 is a preceding sheet bar, and 8 is a movable heating device. Rough rolling machine 1
The sheet bar rolled into a predetermined size by means of the shear 2 cuts the leading end and the trailing end, and the movable heating device 8 heats the cut portion of the leading end and the trailing end, so that the leading end of the trailing sheet bar 6 is cut. The movable guide 3 clamps and positions the sheet bar 7 by pressing it against the rear end of the sheet bar 7 during finish rolling, and the butted portion is rolled in the front stage of the finish rolling mill to press-contact the sheet bar.

Next, the operation of the present invention will be described. Figure 2
Shows the sheet bar temperature on the horizontal axis and the bonding strength of the sheet bar on the vertical axis. Generally, as the temperature changes from the lower side to the higher side, it is divided into the following regions due to the change in the bonding strength. There are unbonded regions where bonding does not occur below the bonding limit temperature, unstable regions where the bonding strength changes above the bonding limit temperature, stable regions where the bonding strength is large, and unstable regions where the bonding strength near the melting temperature of the material decreases. ..

In order to achieve reliable joining, it is necessary to carry out the rolling joining in the former stage of the finishing rolling mill at a temperature in the stable region, and for that purpose, the temperature of the seat bar abutting portion is set to a target temperature at the entrance of the finishing rolling mill. Must be set. The heating temperature of the sheet bar is a region considerably below the melting point, and the unstable region on the high temperature side does not matter.

Generally, the heating temperature of the sheet bar is equal to or higher than the joining limit temperature, but it may be in an unstable region on the low temperature side. In this case, heating is indispensable for reliable joining at the stable region temperature. is there.

In the case where the temperature of the rear end portion of the leading seat bar 7 in FIG. 1 is in an unstable range, or the trailing seat bar 6
If the temperature of the leading end is in the unstable range, the movable heating device 8 is heated to the temperature in the stable range while traveling along the rear end or the leading end. By performing such heating, rolling pressure welding is performed at a temperature in the stable region, so that reliable sheet bar joining is possible.

Since the movable heating device 8 moves in synchronization with the movement of the plate, it is possible to heat only the vicinity of the plate abutting portion and the heat affected zone is small.

[0017]

Embodiments of the present invention will be described with reference to FIG. 1 and Table 1. As a result of conducting the continuous hot rolling test under the conditions of Table 1, joining was performed under the condition without heating, and the sheet bar of the sheet bar did not break during finish rolling, but the joint of the sheet after rolling was considerably large. Some defective joints were found.

When the heating temperature is set to 1120 ° C., the joining is performed, the sheet bar of the sheet bar does not break during finish rolling, and the poorly joined portion of the joined portion of the sheet after rolling is significantly larger than that in the condition without heating. The effect of heating was remarkable.

[0019]

[Table 1]

[0020]

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

[Brief description of drawings]

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

FIG. 2 is a chart showing the relationship between the seat bar temperature and the bonding strength of the seat bar, showing the operation of the present invention.

FIG. 3 is an explanatory diagram of a conventional process using a mobile joining machine and a swing table.

FIG. 4 is an explanatory view of a conventional process using a stationary welding machine and a storage device for a sheet bar or a spiral looper.

[Explanation of symbols]

 1 Rough Rolling Mill 2 Shear 3 Movable Guide 4 Finishing Rolling Mill 5 Finishing Rolling Machine Work Roll in Previous Stage 6 Subsequent Seat Bar 7 Preceding Sheet Bar 8 Movable Heating Device 9 Coil 10 Movable Joiner 11 Rail 12 Swing Roller Table 13 Fixed welder 14 Pinch roll 15 Sheet bar storage device or spiral looper 16 Coil box

Claims (1)

[Claims] 1. A method for joining sheet bars after rough rolling to a preceding sheet bar during finish rolling and continuously rolling the sheet bar in a completely continuous hot rolling method, comprising a rough rolling machine and a finish rolling machine. Between the leading end of the trailing sheet bar and the trailing end of the preceding sheet bar, which is located between them, is heated from the upper surface of the sheet bar by a moving type heating device. Joining method.