JPH0763816B2 - Continuous casting method for thin metal strips and thin slabs - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a running metal belt, and a molten metal in a pool formed on the surface of the metal belt by a side weir and a rear weir provided on the metal belt. Is poured, and the molten metal is solidified by removing heat through the metal belt to produce a thin metal strip.A single belt type continuous casting device is used to oscillate the rear weir located behind the pool. The present invention relates to a method for manufacturing a ribbon / thin slab.

2. Description of the Related Art In recent years, attention has been paid to a continuous casting method for directly producing a thin strip / slab having a thickness of several mm to several tens of mm, which is close to the final shape, from molten metal such as molten steel. When this method is used, the hot rolling step can be simplified or omitted, and the rolling to obtain the final shape can be light, so that the steps and equipment can be simplified.

The belt method is one of the continuous casting methods for such metal ribbons / thin slabs. In this method, for example, a molten metal pool formed on an endless running belt is cooled and solidified by removing heat from the molten metal poured through the belt, and the generated shell is accompanied by the running of the belt. It is sent from the hot water pool to manufacture thin metal strips and thin slabs. At this time, the molten metal is cooled from one direction, and the surface opposite to the belt is open. Therefore, there is less restriction on the arrangement of the nozzles that supply the molten metal from the container such as a tundish to the pool on the belt.

The present inventors have developed a casting device in which a weir that partitions the side surface of the molten metal pool can be moved in this belt system, and filed as Japanese Patent Application No. 60-155247.

FIG. 3 shows the device proposed in this earlier application. In this device, a metal belt 1 is stretched over a pair of pulleys 2a and 2b so as to travel on an endless track. Then, by holding one pulley 2a high, the endless track of the belt 1 rises toward the pulley 2a. A plurality of heat resistant blocks 3 connected by a chain or the like are arranged around the belt 1, and the heat resistant blocks 3 move in synchronization with the running of the belt 1.

The heat-resistant block 3 serves as a side weir 5 that partitions the side of the pool 4 at the upper portion where the belt 1 travels in a straight line. On the other hand, a rear weir 6 is provided behind the hot water pool 4. As a result, the basin 4 is formed in which only the traveling direction of the belt 1 is open. Molten metal 8 is poured into the pool 4 from a pouring device 7.

The molten metal 8 poured is removed from heat by a cooling device 9 arranged on the back surface of the belt 1, cooled and solidified into a solidified shell 10. The solidified shell 10 is conveyed rightward in FIG. 3 as the belt 1 moves. Since the heat removal is continued in the course of this transportation, the solidified shell 10 grows into a thin strip 11 having a predetermined thickness and is sent out from the molten metal pool 4.

This thin strip 11 is then rolled by a pressure roll 12 to a target plate thickness, and is wound up as a thin plate coil 14 by a winding device 13. The pressure roll 12 can also be operated as a process for adjusting the surface texture of the ribbon 11 without essentially changing the plate thickness.

Problems to be Solved by the Invention When the molten metal 8 is solidified on the belt 1 as described above, heat is dissipated around the molten metal pool 4, that is, at a portion in contact with the rear weir 6 and / or the side weir 5.

Therefore, the molten metal at the portion in contact with the rear weir 6 solidifies to form a solidified shell. The solidified shell 10 is peeled off from the rear weir 6 by the traveling of the belt 1 and is carried out from the molten metal pool 4. Molten metal newly flows into the inner wall of the rear weir 6 after being peeled off and solidifies. In this way, the solidified shell is intermittently formed on the inner wall of the fixed weir 6,
This is peeled off as the belt 1 runs. A so-called cold shut occurs and is a thin strip that is carried out of the hot water pool 4.
It appears as a surface defect on 11.

In order to prevent the occurrence of cold shut, a method of vibrating the rear weir can be considered. When vibration is applied to the rear weir, the molten metal in the vicinity of the rear weir is agitated, and by its action, the dendrite tip of the solidified shell on the rear weir is broken or redissolved. For this reason, the rear weir upper shell and the belt upper shell are not connected, and cold shut can be prevented.

However, even if vibration is applied to the rear weir, cold shut may occur, or the flow of molten metal due to vibration may not be appropriate and the surface quality may be deteriorated. Therefore, it is an object of the present invention to clarify the proper vibration for obtaining a good cast slab surface property without cold shut when vibration is applied to the rear weir.

Means for Solving the Problems In order to achieve the object, the continuous casting method of the present invention, when cooling and solidifying the molten metal poured into the molten metal pool formed on the traveling belt, the molten metal pool part In the method of manufacturing a metal ribbon / thin slab by vibrating a rear weir located at the rear, a vibration of 5 ≦ f · a ≦ 200 mm / sec (f is the frequency, a is the amplitude on both sides) is parallel to the belt running. It is characterized in that it is applied in different directions.

According to the method of the present invention, when vibration of 5 ≦ f · a ≦ 200 mm / sec is applied to the rear weir in a direction parallel to the belt running, the molten metal near the rear weir is agitated and the dendrite tip of the rear weir upper shell is broken or Since it is redissolved, the rear weir upper shell and the belt upper shell are not connected, and cold shut can be prevented.

However, when f · a <5 mm / sec, the flow velocity of the molten metal caused by the rear weir vibration is small, so the dendrite tip of the shell on the rear weir is not destroyed or redissolved, and the cold shut prevention effect cannot be obtained. . Also,
If f ・ a> 200 mm / sec, the flow velocity of the molten metal becomes too high, and the pseudo oscillation mark is greatly disturbed such as bending and uneven depth. The surface quality deteriorates.

The above is related to the initial stage of solidification in casting, and is determined only by the flow velocity of the molten metal due to the rear dam vibration, so it is applied when the cast plate thickness is in the range of several mm to several tens of mm. .

Examples Hereinafter, the present invention will be specifically described with reference to the drawings with reference to the examples. FIG. 1 shows an embodiment of the present invention in which the rear weir is vibrated. In FIG. 1, the rotation of the motor 15 is converted into a translational motion through the eccentric cam 16, so that the rear weir 10 is vibrated in a direction parallel to the casting direction (belt running direction) as shown by an arrow in the figure.

Next, the effect of the present invention will be specifically shown by the operation data.

The side weir 5 and the rear weir 6 were arranged on the steel belt 1 having a width of 500 mm to form the basin 4 having a width of 285 mm, a length of 800 mm and a maximum depth of 50 mm. Molten steel having a normal steel composition and a temperature of 1590 ° C. is poured into the pool 4 at a flow rate of 180 kg / min, and the wall thickness is 7 mm.
Ribbon 11 was produced at a speed of 12 m / min.

As a first embodiment, the rear weir was applied with a vibration frequency f of 10 ¹ / sec and bilateral vibration a of 0.5 mm. Therefore f · a
= 5.0 mm / sec. As a second embodiment, the rear weir was applied with a vibration frequency f of 50 ¹ / sec and bilateral vibration a of 1 mm. Therefore, f · a = 50.0 mm / sec. As a third embodiment, the rear weir has a frequency f of 50 ¹ / sec and a bilateral vibration a of 3.0 mm.
Vibration was applied. Therefore, f · a = 150.0 mm / sec.

As a first comparative example, the rear weir has a frequency f of 10 ¹ / sec,
Vibration of 0.4 mm was applied to both-side vibration a. Therefore f ·
a = 4.0 mm / sec. Further, as a second comparative example, the rear dam was given a vibration of frequency f of 50 ¹ / sec and both-side vibration a of 5.0 mm. Therefore, f · a = 250.0 mm / sec. The surface texture of the product obtained by rolling 57% of the thin ribbon thus cast was measured, and the implementation status is shown in Table 1 together with the example of the present invention and the comparative example.

As shown in Table 1, in the examples according to the present invention, thin rolls having good surface properties were obtained, whereas in the comparative examples, the surface was very poor.

Next, the side weir 5 and the rear weir 6 are placed on the steel belt 1 having a width of 500 mm, and the width is 285 mm, the length is 2000 mm, and the maximum depth is 100 mm.
The basin 4 was formed. Molten steel having a normal steel composition and a temperature of 1590 ° C. was poured into the pool 4 at a flow rate of 54 kg / min to manufacture a thin slab having a thickness of 50 mm at a rate of 0.5 m / min.

FIG. 2 shows the results obtained by performing various combinations of the frequency f and the amplitude a on both sides. FIG. 2 shows the surface property of the slab for each vibration. The degree of surface texture is ◎
(No cold shut, good), ○ (no cold shut, however, pseudo oscillation mark was disturbed, good after rolling), △ (surface texture worse than ○, many scratches after rolling), × (cold shut) Occurrence)
It is shown in four stages. From FIG. 2, the vibration applied to the rear weir needs to be 5 ≦ f · a ≦ 200 mm / sec.

From the above, the method of the present invention can obtain the cold shut prevention effect.

Furthermore, the method of applying vibration to the rear weir is not limited to the method using the eccentric cam shown in FIG. 1, but elastic vibration, electric vibration, ultrasonic vibration, or the like may be used.

EFFECTS OF THE INVENTION As described above, in the present invention, 5 ≦ f is applied to the rear weir.
・ The cold shut generated when the shell generated on the rear weir is intermittently taken into the belt upper shell by applying vibration of a ≦ 200 mm / sec is connected to the rear weir upper shell and the belt upper shell. Preventing and suppressing the occurrence.

Therefore, the obtained ribbon / thin slab has a good surface property without cold shut. Therefore, when rolling the thin strip / thin slab, breakage and surface scratches did not occur.

[Brief description of drawings]

FIG. 1 is a side view of an apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the frequency applied to the rear weir, the amplitude on both sides, and the surface property of the slab. FIG. 3 is a side view of the continuous casting apparatus previously proposed by the present inventors. 1 ... Belt, 2a, 2b ... Pulley, 3 ... Heat resistant block, 4 ... Hot water pool, 5 ... Side weir, 6 ... Rear weir,
7: pouring device, 8: molten metal, 9: cooling device, 10
...... Coagulation shell, 11 ...... Thin band, 12 ...... Pressurized call, 13 ...
… Winding device, 14… Thin coil, 15… Motor, 16…
… Eccentric cam.

Claims (1)

[Claims] 1. A molten metal is poured into a molten metal pool formed on the surface of the metal belt by a running metal belt and side and rear weirs provided on the metal belt, and the molten metal is drained through the metal belt. In a method for producing a metal ribbon / thin slab by vibrating a rear weir located behind a molten metal pool, using a single belt type continuous casting device, which solidifies a molten metal by heat to produce a metal ribbon, A continuous casting method for metal thin strips / thin slabs, characterized in that vibration of 5 ≦ f · a ≦ 200 mm / sec (f is frequency, a is amplitude on both sides) is applied in a direction parallel to belt running.