JPH0211247A - Twin directional drawing type horizontal continuous casting method - Google Patents

Abstract

PURPOSE:To separate solidified shell at stable position and to reduce the development of oscillation mark by impressing ultrasonic vibration to a mold near a feed nozzle. CONSTITUTION:In twin directional drawing type horizontal continuous casting method, the ultrasonic vibration is impressed to outer circumference of the mold 8 in cross sectional plane passing center line of the feed nozzle 6. By this method, air layer is developed at between water cooled steel plate 12 and the solidified shell 18 and as there is slowly cooled and becomes separating point 22, break position exists at stable position. In this result, drawing speed to right and left cast billets can be equalized and the surface characteristic of the cast billet and internal quality can be drastically improved. Further, friction between the mold 8 and the solidified shell 18 can be reduced and wear of the mold 8 is reduced and the service life thereof can be extended.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a bidirectional drawing type horizontal continuous casting method, and particularly to a casting method that can stabilize the separation point position of left and right solidified shells and improve casting stability. , widely used in steel continuous casting field.

[Conventional technology]

In the field of continuous casting, instead of the conventional vertical or curved continuous casting method, a horizontal continuous casting method has been proposed in which a horizontally arranged continuous casting mold is used to pull out and cast slabs horizontally. Casting of slabs is carried out. This type of horizontal continuous casting method also evolved from the initial method in which slabs were pulled out from the right end of the mold, to the method developed in JP-A-58
As disclosed in Japanese Patent No. 138,544, a method of pulling out molds from both ends in opposite directions has been proposed, and an improvement in production capacity has been achieved.

This method will be explained with reference to FIG. That is, the molten steel 4 stored in the tundish 2 is injected into the mold 8 through the feed nozzle 6. A break ring 10 is set in the part of the feed nozzle 6 that connects to the mold 8.
A water-cooled copper plate 12 is provided inside. The mold 8 is vibrated from side to side in the horizontal direction by an oscillation device 14, while pinch rolls 16 pull out the solidified shell, that is, the slab 18, in two opposite horizontal directions.

In horizontal continuous casting, in which a slab is pulled out horizontally from both ends of a mold, it is necessary to satisfy the contradictory demands of forming a strong solidified shell and stably breaking the solidified shell at a fixed position.

The formation of a solidified shell in a mold in horizontal continuous casting will be explained with reference to FIG. As shown in FIG. 3, the formation start position of the solidified shell 18 is at the center of the mold 8, directly below the feed nozzle 6, and ideally the solidified shell 18 is broken at this point. However, in actual operation, as shown in Fig. 4, for some reason an unhealthy thin solidified shell 18 is formed in the off-center part and breaks, and if this is repeated, it becomes off-center and large as shown in Fig. 5. A thin part of the solidified shell 18 of width is formed;
From there, it breaks, and eventually the break position moves away from the mold 8, causing a breakout and a major accident. In addition, when the left and right solidified shells are separated in the thick part of the solidified shell, traces of the separation point remain as oscillation marks, and the thicker the solidified shell, the deeper the oscillation marks. There is a problem that flaws remain on the steel plate after rolling, degrading the quality of the steel plate.

In order to prevent the above-mentioned movement of the fracture position and to stably fracture the solidified shell at a fixed position, various studies have been made. There is.

(a) A method of controlling the starting position of solidified shell formation using a highly insulating refractory.

(b) A method in which localized slow cooling is performed in the mold using a heater, a refractory, or a combination thereof to control the starting position of solidified shell formation.

However, these methods have the following problems.

(A) When using refractories, it is difficult to match the surfaces of the refractories and the copper plate mold, and the refractories and copper plate molds are not only eroded during use, but also become uneven, causing breakouts. Additionally, the need to replace refractories increases running costs.

(B) When using a heater, the temperature of the copper plate increases, resulting in accelerated deformation and wear of the mold.

Other conventional techniques include the following.

(c) A method of controlling the drawing speed of the left and right slabs so that the fracture position is directly below the feed nozzle 6.

(d) A method of plating or spraying a material with low thermal conductivity on the water-cooled copper plate 12 in order to slowly cool the mold 8 near the feed nozzle 6.

However, these methods also have the following problems.

(C) In method (c), the internal quality of the slab is unstable because the drawing speed of the left and right slabs is not constant.

(D) The method (d) has a small slow cooling effect and is expensive.

[Problem that the invention seeks to solve]

The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to separate the solidified shell in a stable position without using special refractories or heaters for the mold, thereby reducing the occurrence of oscillation marks. The object of the present invention is to provide a horizontal continuous casting method using horizontal drawing.

[Means for solving problems]

The gist of the present invention is as follows.

In other words, it is a two-way horizontal continuous drawing type in which molten steel is injected from a container such as a tundish into a horizontally placed vibrating mold through a feed nozzle, and the solidified slab is pulled out from both ends of the mold by pinch rolls in opposite directions. The casting method is a bidirectional drawing type horizontal continuous casting method characterized by applying ultrasonic vibration to the mold near the feed nozzle.

Therefore, the frequency of the ultrasonic vibration is 1 to 50 kHz,
The strength should be limited to 1 to 50 kW/aJ per horn.

The details of the present invention will be explained by referring to the embodiment shown in FIG. FIG. 1 shows four ultrasonic application horns 20A, 20B, 20 at two locations A and H on the outer periphery side of the mold 8 passing through the center of the feed nozzle 6 and at two locations C and D on the top surface.
This is an example in which a C120D is provided and ultrasonic vibration is applied near the feed nozzle 6.

The direction in which the ultrasonic vibrations are applied is perpendicular to each surface of the mold 8, the frequency is in the range of 1 to 50 kHz, and the intensity is required to be in the range of 1 to 60 kw/aJ per application horn. The reason is that the frequency is 1kHz or the strength is lk.
If w/aJ does not drop, the purpose of the present invention of slow cooling by reducing the contact between the mold 8 and the solidified shell 18 will not be achieved, and on the contrary, if the frequency of the ultrasonic wave exceeds 50 kHz or the intensity If it exceeds 50 kw/aJ, the effect of slow cooling becomes excessive, forcing the casting speed to be reduced, and the equipment cost of the ultrasonic vibration device becomes excessive, resulting in high costs. In the present invention, the frequency is limited to 1 to 50 kl (z), and the intensity is limited to 1 to 50 kw/aJ per horn. By applying a voltage to the mold 8, the area 10 near the application position is
01 square, the amount of heat removed from the solidified shell 18 is reduced by more than 20%, and the purpose of slow cooling can be achieved.

[Effect]

As mentioned above, a plurality of ultrasonic application horns are attached to the outer periphery of the mold 8 within the cross section passing through the center line of the feed nozzle 6.
By applying ultrasonic vibration in a limited range according to the present invention, an air layer is formed between the mold 8 and the solidified shell 18, and the amount of heat removed from the solidified shell 18 by the water-cooled copper plate 12 is reduced. Growth is inhibited in this area. As previously explained with reference to FIG. 3, in bidirectional drawing type continuous casting, the molten steel 4 in contact with the water-cooled copper plate 12 of the mold 6 directly below the feed nozzle 6 is slowly cooled, so that the cast material drawn in both directions is cooled. Ideally, the break point of the piece is the separation point 22, but in the present invention, by applying ultrasonic vibration to the outer periphery of the mold 8 in a cross section passing through the center line of the feed nozzle 6, Since an air layer is generated between the water-cooled copper plate 12 and the solidified shell 18, and the plate is slowly cooled, this portion becomes the separation point 22, so that the fracture position exists stably. As a result, the defects as explained in FIGS. 4 and 5 are eliminated, and the left and right slabs 18 can be pulled out at approximately the same speed, so that the internal quality of the slabs can be significantly improved.

It should be noted that if the frequency and intensity of the ultrasonic vibrations are increased within the limited range of the present invention, the thickness of the air layer will increase accordingly, and the gradual cooling effect will increase. Therefore, the most appropriate vibration frequency and strength can be selected depending on the molten steel temperature, casting speed, etc.

〔Example〕

As shown in FIG. 1, ultrasonic application horns are attached at two locations A and B on the side surface of the outer periphery of the mold 8 in a cross section passing through the center line of the feed nozzle 6, and at two locations C and D on the top surface to vibrate. A billet measuring 150 m x 150 m was horizontally continuously cast at a frequency of 20 kHz and an intensity of 10 kv/a# for each horn.

As a result, the amount of heat extracted from the solidified shell 18 at the application positions A, B, C, and D is reduced by 25%, and the separation point 22 of the left and right drawn slabs is stabilized near the top of the A, B, C, and D surfaces. I confirmed that it was generated. As a result, it is possible to make the drawing speed of the left and right slabs 18 almost the same, and there are no accidents such as breakouts during drawing, and the surface and internal quality of the manufactured slabs are both excellent. It was confirmed.

〔Effect of the invention〕

Conventionally, in vertical or curved continuous casting, an ultrasonic transducer was attached to the outer periphery of the mold at right angles to the outer wall of the mold.
Preventing molten steel from seizing on the inside of the mold by vibrating the entire mold is a conventional technology, but ultrasonic waves are applied to a local part of the mold near the phyto nozzle 6 of a horizontal continuous casting machine. Conventionally, there has been no technology for stabilizing the separation point 22, which is the fracture position of the left and right drawn slabs, by applying pressure to locally cool the mold.

In the present invention, by uniformly applying ultrasonic waves with a limited frequency and a limited intensity to the outer periphery of the mold near the feed nozzle 6, the following effects can be achieved.

(a) Since it has become possible to always stably form the separation point of the left and right slabs in a local area directly below the feed nozzle, it has become possible to keep the drawing speed of the left and right slabs at the same constant. It was possible to significantly improve the surface quality and internal quality of the slab.

(b) (b) It became possible to reduce the friction between the mold and the solidified shell, reducing wear and tear on the mold and extending its life.

(c) As a result of (b), there have been no accidents such as breakouts during operation, and it has become possible to significantly improve productivity and reduce costs.

(d) The apparatus according to the present invention is relatively inexpensive and extremely simple to operate.

[Brief explanation of the drawing]

Fig. 1 is a partial perspective view showing the horizontal continuous casting method according to the present invention, Fig. 2 is a schematic sectional view showing a conventional bidirectional drawing type horizontal continuous casting machine, and Fig. 3 is a partial perspective view showing the horizontal continuous casting method according to the present invention. 4 and 5 are cross-sectional views showing the formation situation of a solidified shell in abnormal horizontal continuous casting. 2... Tanditshu 4... Molten steel 6...
Feed nozzle 8... Mold 10... Break ring 12... Water-cooled copper plate 14... Oscillation device 16... Pinch roll 18... Solidified shell (slab) 20... Ultrasonic application horn 22... Slab separation point

Claims (2)

[Claims] (1) Bidirectional drawing in which molten steel is injected from a container such as a tundish into a horizontally placed vibrating mold through a feed nozzle, and the solidified slab is pulled out from both ends of the mold in opposite directions using pinch rolls. A bidirectional drawing horizontal continuous casting method, characterized in that ultrasonic vibrations are applied to the mold near the feed nozzle. (2) The bidirectional pultrusion horizontal continuous casting method according to claim 1, wherein the ultrasonic frequency is 1 to 50 kHz and the strength is 1 to 50 kW/cm^2 per horn.