JPS5924559A - Curved type continuous casting machine - Google Patents

Abstract

PURPOSE:To decrease the deformation resistance and tensile strain of a solidified shell and to prevent the cracking thereof by disposing heating or heat retaining devices near the setting point for bending of a billet and disposing driving rolls before and after the setting point. CONSTITUTION:A billet 1 from a mold 4 is supported with support rolls 6 while forming a solidified part and is drawn by at least two pairs of driving rolls 5 for drawing billet just before setting rolls 8. The surface of the billet 1 is held at a prescribed temp. with heating devices 7 near the setting point in this stage. Heat insulating devices may be disposed in place of the devices 7. The billet 1 drawn with the rolls 5 is straightened by the rolls 8 and is additionally applied thereon with the braking force by at least two pairs of the rolls 5 for braking billet right after the rolls 8, whereby the tensile strain of the billet 1 generated during the setting is decreased. It is also possible to provide >=3 pairs of the rolls 5, 5a before and behind the setting point and to dispose both heating and heat retaining devices.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a curved continuous casting machine, and more particularly to a continuous casting machine that can prevent cracks occurring at the solidification interface during bend straightening of a slab.

Generally, during bend straightening in a curved continuous casting machine, as shown in Fig. 1, tensile strain A occurs at the interface between the solidified part 1a and the unsolidified part 2 inside the slab 1, and there is almost no ductility in the vicinity of the solidified interface. Cracks are likely to occur because there is no roll (numeral 3 is a roll). To prevent this, two representative measures have been conventionally taken, the first of which is to disperse the correction points and gradually bend the bending to reduce the amount of strain per bend. With this method, the tensile stress is eliminated in a high temperature state until the next straightening.

The second means is to reduce tensile strain by applying compressive force to the straightened slab using pinch rolls.

That is, as shown in FIG. 2, the latter second means is cast by pressing drive rolls 5, 5a against the copper piece 1 and moving it in the direction of the arrow to apply braking. is bent by applying a compressive force. For this reason, if other means are applied as shown in Figure 2, A
The tensile strain represented by (in FIG. 2, reference numeral 6 indicates a support roll) is reduced. On the other hand, the former first method has a certain effect by dispersing the correction points, but it has a problem in that it takes time and effort to maintain and manage the bus line of the roll. Furthermore, the actual situation is that the second means cannot exert a sufficient effect because the compressive strain that can be applied is small against the tensile strain caused by straightening for the following reasons. The reason for this is as follows.

The force F that can be applied by one drive roll is (1 ) is expressed by the formula.

F≦(W-2xS)xLxPxμ... (11) This value is generally about 10 tons, and when divided by the area of the solidified section of the slab cross section, the stress is about 0.03 to 0.06 kg/mn2. Because it is small, the solidification shell is in a high temperature state, and low deformation resistance is an essential condition.

Furthermore, in conventional compression casting methods, the drive rolls are not closely arranged with respect to the straightening points, so generally the support rolls 4
Since there is one drive roll for six rolls, even if compressive force is applied by the drive roll, the load is not accumulated due to stress relaxation and is not effective. Therefore, even if many pairs of drive rolls are provided before and after the correction point in the roll arrangement shown in FIG. 2, the current result is that only one pair of compressive force effects can be seen.

In short, in the conventional example, even if a compressive force is applied by a drive roll, the load is not accumulated and a sufficient effect of reducing the tensile strain at the solidification interface inside the slab cannot be obtained. The inventor of the present invention researched this point and found that one of the causes was that in conventional casting machines, only about one drive roll was arranged for every four to six support rolls.

The present invention was established based on the above findings, and specifically proposes a continuous casting machine that can effectively prevent cracks occurring at the solidification interface during bend straightening of slabs.

That is, in the present invention, one or both of a slab heating device and a heat retaining device are arranged near the bending straightening point of a curved continuous machine, and a driving roll for drawing the slab is arranged, while immediately after the straightening point. It is characterized in that at least two pairs of drive rolls for braking the slab are arranged adjacently.

The present invention will be described in detail below with reference to FIG.

First, FIG. 3 is a layout diagram of a curved continuous casting machine according to one embodiment of the present invention, and as shown in FIG. The side 1 is supported and transported by support rolls 6, and these support rolls 6 are arranged curved at a constant curvature.

Next, in this curved continuous casting machine, a straightening roll 8 is arranged near the straightening point, and the slab 1 is straightened by this straightening roll 8, and immediately before the straightening roll 8 there are at least two
A pair of drive rolls 5 are arranged, and a predetermined pulling force is applied to the casting 1 by these drive rolls 5. On the other hand, immediately after the straightening roll 8, there are at least two pairs of drive rolls 5a.
These drive rolls 5a are pressed against the slab 1 and driven, and in this way a predetermined braking force is applied to the slab 1, and a drive roll 5b is provided behind the drive roll 5a. Can be done. Furthermore, near the correction point, that is, 2
In the vicinity of the seed drive rolls 5, 5a or the straightening roll 8, either or both of a heating device 7 such as a high frequency heating device or a heat retaining device is arranged.

That is, in the casting machine configured as described above, the slab 1 that has exited the mold 4 is supported by the support roll 6 while forming a solidified portion 1a, and is pulled out by the drive roll 5 immediately before the straightening roll 8. Since the heating device 7 is provided in the vicinity of this straightening point, the surface temperature of the slab 1 is maintained at 1000° C. or higher, and the deformation resistance of the solidified portion 1a, that is, the solidified shell, is kept small. It should be noted that a heat retaining device may be provided in place of the heating device 7, and it is preferable that the heat retaining device is, for example, a compartment system that isolates the air on the surface of the slab from the outside air.

In addition, the surface temperature can be increased to 1000 by using a heating device like this.
The slab 1 heated above ℃ is pulled out in this state by a driving roll 5, straightened by a straightening roll 8 immediately after that, and a predetermined braking force is applied thereto by a driving roll 5a immediately after the straightening roll 8. It will be done.

In short, at least two pairs of drive rolls 5 for drawing the slab
A compressive force is applied between the cast slab 1 and at least two pairs of drive rolls 5a for control, thereby efficiently reducing the tensile strain generated in the solidified portion 1a of the slab 1 during straightening by the straightening rolls 8.

In addition, when casting was performed under the following conditions using the continuous casting machine shown in FIG. 3 and the conventional continuous casting machine, the results were as follows.

Casting conditions: Slab cross section 270 mm x 1500 mm Arc radius of continuous casting machine 12 m Number of straightening points 1 In the present invention, two pairs of drive rolls were arranged before and after the straightening point.

Driving force per roll: 10 tons Specific water amount: 0.8 l/kg-steel In the present invention, four high-frequency heating devices are installed, and the slab is heated to 105
Heated to 0°C.

As a result, in the conventional example, straightening cracks occurred at a casting speed of 1.25 m/min, but in the case shown in Figure 3, straightening cracks occurred at a casting speed of 1.4 m/min.
It was found that casting can be performed for up to 1 minute without cracking.

As explained above in detail, the present invention is capable of superimposing compressive force before stress relaxation occurs by arranging at least two pairs of compressive force loading drive rolls closely to the straightening point. By applying compressive force effectively, the surface of the solidifying part of the heating device or heat retaining device is
By raising the temperature above ℃, the deformation resistance is lowered, and tensile strain is relaxed to a greater extent.

Although an example has been shown in which two pairs of drive rolls are provided before and after the straightening point, three or more pairs may be provided, the heating device may be of any type, and a heat retaining device may be provided in addition to this.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of bend correction in continuous casting, FIG. 2 is a layout map of a conventional compression continuous casting machine, and FIG. 3 is a layout map of a continuous casting machine according to an embodiment of the present invention. Code 1... Column piece 1a... Solidified part of slab 2... Unsolidified part of slab: 3... Roll 4...・Mold 5. ．．
．． ．． ．． ．． ．． Drive roll 5a. 5b... Drive roll 6... Support roll 7... Slab heating device 8... Straightening roll

Claims (1)

[Claims] Either one or both of a slab heating device or a heating device is arranged near the bend straightening point of the curved continuous casting machine, and at least two pairs of slab drawing drive rolls are arranged adjacently just before the straightening point. A curved continuous casting machine characterized in that at least two pairs of drive rolls for braking the slab are arranged adjacent to each other immediately after the straightening point.