JPS58173064A - Continuous casting device - Google Patents

Abstract

PURPOSE:To decrease the cracking of an ingot and to obtain the ingot having good quality by providing rolling rolls at the point from the bending part of the ingot up to the linear part or near said point and exerting rolling-down force on the ingot. CONSTITUTION:An ingot 3 conducted to rolling rolls 7 by pinch rolls 5 on the inlet side of the rolling roll is exerted with the rolling down determined by screw-down devices 8, 9 and is thereby rolled. If a crack is generated, the crack is crushed positively by this rolling by which the crack is decreased. Not only the crack but also the cavity can be annihilated. The speed of a motor 10 is so controlled that the tension between the rolls 5 and the rolls 7 attains a prescribed value.

Description

[Detailed description of the invention] The present invention relates to improvements in continuous casting equipment.

The generally known and most widely used continuous casting apparatus is as shown in FIG. l is tandish, 2
is the mold, and 3 is the section. 4 is Kaitrol and 5 is Pinchroll. 6 is the point from the curved part to the straight part (
Also called the μ lower tangential point. ) is a straight line pinch roll near . The molten steel poured into the tundish is poured into the mold 3. The molten steel poured into the mold 3 is completely cooled in the mold to form a shell, and while being further cooled by a spray provided below the mold 3, it becomes a slab 3 and is pulled out by a kite roll 4 and a pinch roll 5. . R is the half 11 of the curved part, D is the slab 3
It shows the thickness. A problem with this device is that when the slab 3 passes through the tangential point, cracks occur inside the slab. The main reason for this is that in the process of the slab transitioning from the curved section to the straight section, the slab
This is because distortion occurs above and below. That is, as shown in FIG. 2, a tensile strain pt is applied to the upper part of the slab 3 in the vicinity of the tangential point, and a compressive force F is applied to the lower part, and cracks occur due to αFt + Ep.

Several methods are known to prevent these cracks (for example, the magazine "Steel Research" No. 294)
. A typical example of this is a method called "compression casting". In this method, the speeds of guide rolls and pinch rolls are controlled so that compressive force is applied to the slab near the mendential point.

However, in reality, it is difficult to always maintain the compressive force at the required value due to slippage between the slab 3 and the rolls, and cracks remain.

An object of the present invention is to provide a continuous casting equipment that can reduce cracking of slabs and obtain slabs of good quality.

According to one feature of the present invention, at least one pair of rolling rolls is provided at or near a point extending from the curved part to the straight part of the section, and a rolling device that applies a rolling blade to the rolling roll; A drive device is provided to drive the vehicle.

The present invention will be explained in more detail below. FIG. 3 is an embodiment drawing for explaining the present invention. In this diagram,
5 is a pinch roll, 7 is a roll for rolling, 8 is a screw for rolling, and 9 is a rolling motor. 8 and 9 constitute a rolling device 89.

lO is a drive motor. Most of the internal cracks in the slab 3 occur near the pinch roller in the straight section and on the curved section side of the roller. As mentioned above, this is caused by the difference in stress between the upper and lower sides of the slab. The rolling roll 7 has tangential voids which are prone to internal cracking.
or nearby. The slab 3 guided to the rolling rolls 7 by the pinch rolls 5 on the entry side of the rolling rolls is subjected there to a predetermined reduction by a rolling device 89 and rolled δ. By this rolling, even if cracks occur, they can be actively crushed, reducing the number of cracks. Moreover, not only cracks but also cavities can be eliminated.

The motor lO that drives the rolling rolls has a larger capacity than the motor (not shown) that drives the pinch rolls 5. This is because the motor lO requires each sound to satisfy one rolling load. Therefore, since the speed of this motor greatly affects the tension applied to the slab and the speed of the slab, this should be controlled to an appropriate value. This speed is controlled so that the tension between the pinch roll 5 and the rolling roll 7 becomes a predetermined value. This does not mean that the tension on the input side of the rolling mill always matches the tension on the output side; rather, the tension on the input side and the output side are the set value of the input side tension and the set value of the output side tension. Control so that The set value of each tension will be different depending on the temperature of the slab, the nine types of cross-sectional area of the slab, etc.

This setting value is lf determined in advance through experiments etc.
t shall be fully used. Also, the speed of motor lO is
The tension between the pinch rolls and rolling rolls (the tension on the slab) should be controlled to a predetermined value, and the slab drawing speed (or slab speed) should be matched to the target value. This slab withdrawal speed is set to prevent the melt level in the mold from fluctuating and to prevent breakout (the surface of the slab that has left the mold breaks and the unsolidified molten copper inside spouts out). It is set to a value that does not exist.

Next, other embodiments of the present invention will be explained with reference to FIG. In this figure, 10 and 10' are rolling roll drive motors, and 11 and 11' are well-known speed control devices such as Leonard. Reference numeral 12 denotes a speed command distributor for setting the peripheral speeds of the upper roll and lower roll of the rolling rolls to a constant value. 13 is a speed command device. 1
4 indicates a roller table. DI is the plate thickness at the entrance of the rolling mill,
DD is the plate thickness at the exit side of the rolling machine, and DzDn is the rolling reduction amount. As is clear from the figure, rolling mills 7 to 9 are installed in the continuous casting apparatus, specifically, in the vicinity of the slab from the curved part to the straight part. In the rolling roll 7, the lower roll is larger than the upper roll in this example. It does not necessarily have to be this way.

The hot water poured into the mold from the tandish is cooled by the slab and drawn downward while forming the slab.

The drawn slab passes through pinch rolls 5 while being further cooled and is led to a rolling mill. The roll opening degree 8 of the rolling rolls is set to be narrower than the entrance side thickness Dx. Therefore, the piece leaving the rolling roll is Dg
The sides are also small and thick.

becomes. The rolling rolls 7 are each independently driven by drive motors to and to'. The speed setter 13 outputs a rolling speed command signal VL that provides a predetermined drawing speed. This VL is between the speed control device 11 and the speed command distributor 1.
given to 2. In this case, the distributor 12 outputs a speed command Vuk that is somewhat smaller than VL. For example, Vu can be found using the following relationship.

Vu = K・V, where K; constant a; constant R; bending radius of slab Vn obtained in this way is determined by speed control device 11'
is given as a speed command signal. Each speed control device 11.11' controls the motor 10,
10'. In this way, operating with a speed difference between the upper roll and the lower roll can reduce the stress difference between the upper and lower surfaces of the slab, which helps prevent internal cracking.

In addition, if you change the rolling position (roll opening degree) of the rolling mill,
Although it is well known that the thickness can be controlled, the speed of the slab on the inlet and outlet sides fluctuates as a result of this thickness control, making it impossible to maintain the tension at the planned value at 1\.

In this case, the motor speed may be controlled so that the volume is constant according to the law of constant volume, or feedback control may be performed to keep the speed constant.

As explained in detail above, according to the present invention, it is possible to provide a rolling cutter to a slab during the process of continuous casting, and to actively reduce cracks and cavities occurring inside the slab. In addition, since the slab is rolled down at a high temperature, less power is needed to reduce friction, which can be expected to be an advantage.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a general continuous casting apparatus, and FIG. 2 is a diagram for explaining the occurrence of cracks in a slab during continuous casting. Figure m3 and Figure 4 are diagrams showing one embodiment of the present invention. 3... Slab, 5... Pinch roll, 7... Rolling roll, Fig. 1) Fig. 2 6

Claims (1)

[Claims] 1. In a curved continuous casting device, at least 1'
A continuous casting apparatus characterized in that a pair of rolling rolls is provided, a rolling device for applying a rolling blade to the rolling rolls, and a driving device for driving the rolling rolls.