JPS60187449A - Method and device for continuous casting - Google Patents

Abstract

PURPOSE:To obtain a billet free from segregation, surface crack, etc. in horizontal and continuous casting by cooling the base of a mold to grow a solidified shell in an early period and accelerating the upward solidification in one direction while drawing the solidified shell in the horizontal direction. CONSTITUTION:A molten steel is cooled from the base of a mold 6 curved to increase the thickness of a cast billet in the drawing direction to form a solidified shell and to grow the shell in an early period. The mold 6 has an inside mold plate 19 manufactured of a material having good heat conductivity such as a copper plate or the like for the above-mentioned purpose. Said inside plate 19 is cooled by the cooling water for the mold and is so formed as to have the acute angle between the surface of the molten steel and the base of the plate 19. The base and side face of the solidified shell are subjected to heat extraction by a force cooler 9 and while the solidified shell is grown in the direction of the top surface, the solidification is completed at the point P. The rate of pouring and the drawing speed by pinch rolls 11 are controlled by a control device 17 with the measured value of a device 16 for measuring the thickness of the billet 5 as a reference.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a horizontal continuous casting method for molten steel, and relates to a novel horizontal continuous casting method and apparatus for obtaining high quality slabs with less segregation within the slab. .

BACKGROUND TECHNOLOGY Conventionally, as a continuous casting method for thin-walled slabs, there has been an open belt horizontal continuous casting method (Japanese Unexamined Patent Publication Nos. 54-152928 and 1983-139834), or an open mold horizontal continuous casting method (see Kaisho 55-2
No. 4710) has been proposed.

FIG. 1 is a schematic diagram of open belt type horizontal continuous casting. (1) is a tongue pusher, (2) is a metal belt, (
3) is a cooling device, and (4) and (4) are cooling rolls.

The molten metal supplied from the tongue pusher (1) onto the metal belt (2) is cooled by the cooling device (3), and further cooled down by the cooling rolls (4) and (4) to form the slab (5). It's something you get.

FIG. 2 is a schematic diagram of open mold horizontal continuous casting. (6) is a mold, (7), (7) is a reduction opening, and (8) is a leak prevention wall. Tongue push (
The molten metal supplied into the mold (6) from 1) is cooled by the mold (6) and the cooling device (3), and rolled down by the rolling rolls (7) and (7) to obtain a slab (5). It is something.

However, these conventional horizontal continuous casting methods have various problems.

First, in the open-belt horizontal continuous casting shown in Figure 1, a solidified shell is generated from above by the upper cooling roll (4), and a nonmetallic inclusion segregation area is generated between the solidified shell and the solidified shell from below. . In addition, if the solidified shell is not sufficiently developed, cooling rolls (
4) After (4), molten metal enters and bulging occurs, the thickness of the slab changes and cracks occur in the solidified shell. Hence the cooling roll (4).

It is difficult to cast thick slabs because it is necessary to completely solidify the part (4), and solidification takes time.

In addition, non-uniform thermal expansion of the metal belt (2) occurs, and especially since the elongation of the belt in the width direction cannot be absorbed, hot water wrinkles occur, which deteriorates the quality after rolling and causes a decrease in yield due to maintenance.

Furthermore, the life of the metal belt (2) is short, deterioration of the quality of the slab due to belt deformation and melting damage, or breakout, and especially when the molten steel temperature is 160
If the temperature exceeds 0''C, it is necessary to replace the belt at an early stage.Therefore, there are problems such as restrictions on so-called multiple casting, in which casting is performed continuously by changing pots.

In addition, in horizontal continuous casting using the open mold method shown in Fig. 2, solidified shells are also generated on the side of the mold on the opposite side of the direction in which the slab is pulled out. Cracks occur in the slab, which impairs the quality of the slab. In addition, the development of the solidified shell on the sides is insufficient relative to the depth of the molten steel, and there are many problems such as leakage from the sides due to fluctuations in the molten metal surface.

Purpose of the Invention This invention addresses the above-mentioned problems and aims to obtain a high-quality slab without segregation of non-metallic inclusions in the slab and without surface cracks. - Provides a flat continuous casting method and apparatus.

Structure of invention The gist of this invention is as follows.

(1) In horizontal continuous casting, a solidified shell is formed by cooling from the curved bottom of the mold so that the manufactured slab thickness increases in the drawing direction, and unidirectional solidification is performed upward while the solidified shell is pulled out in the horizontal direction. A horizontal continuous casting method characterized by accelerated solidification so that the upper surface solidifies last.

(2) A mold equipped with a molten steel water heater, a bottom surface curved to increase the thickness of manufactured cast slabs in the drawing direction, and a mechanism for cooling the bottom surface, and the solidified shell formed inside the mold is pulled out in the horizontal direction. A pinch roll, a forced cooling device that supports and cools the solidified shell, a thickness measuring device that measures the thickness of the slab between the mold and the pinch roll, and a quantity of hot water and a drawing speed based on the measured value. A horizontal continuous casting device comprising a control device for controlling the device.

FIG. 3 is a side view showing one example of the horizontal continuous casting apparatus of the present invention, and FIG. 4 is a plan view thereof. The mold (6) of the device of this invention has a bottom surface curved in the drawing direction. (9) is a forced cooling device that supports and cools the solidified shell, (1G is a low chevron, θ◇ is a pinch roll that pulls out the slab, and Q is a cutting machine that cuts the slab into a predetermined size. The mold (6) is provided with an oil-laying device 01, a powder material supply device a4, and a heat insulating material supply device 06.Furthermore, a thickness measurement device is used to measure the thickness of the slab between the pinch roll α force and the mold (6). Device α→
A control device α force is provided which controls the hot water supply amount of the tongue push (1) and the pulling speed of the pinch roll zero force based on this measured value.

FIG. 5 is a side sectional view at the time of starting casting by the apparatus of this invention, and FIG. 6 is a sectional view taken along the line AA in FIG. (to)
00 is the mold inner plate, (E) is the mold frame, (C) is the dummy bar head, 翺 is the mold cooling water supply port, 2) is the drain port, (C) is the powder material supply port be.

In preparation for casting, the dummy par head 12D is positioned at the end of the mold, and the gap between it and the inner plate of the mold is filled with a known sealing material to prevent water from leaking. Since the tummy bar head a is exposed to molten steel for a long time, a cooling water channel is provided inside for the purpose of preventing erosion and accelerating the solidification of the molten steel that comes into contact with it.

The inner plate rm of the mold is made of a material with good thermal conductivity, such as a copper plate, to promote heat removal. Furthermore, in order to prevent melting and deformation of the inner plate, mold cooling water is supplied from the water supply port and drained from the drain port for cooling.

The feature of the mold (6) of the present invention is that the solidified shell, which forms the lower surface of the slab, is grown at an early stage to prevent the solidified shell from being broken by the pulling force of the pinch rolls. Therefore, the angle between the surface of the molten steel and the bottom of the mold inner plate was made to be an acute angle to reduce the amount of heat supplied from the unsolidified molten steel to the solidified shell from which heat was removed. Furthermore, the bottom surface of the mold is a curved surface that is curved in the drawing direction of the solidified shell so that the solidified shell on the bottom surface of the mold can be smoothly formed as the lower surface of the slab.

The cross-sectional curve of this curved surface may be a combination of a circular arc and a circular arc, a circular arc and a straight line, or a bidirectional line.

FIG. 7 is a side sectional view during casting using the apparatus of the present invention, and FIG. 8 is a sectional view taken along line BB in FIG. (Foundation) is a weir, (
7) is a heat insulating material supply port. After supplying molten steel until the molten steel surface reaches a height corresponding to a predetermined slab thickness, the dummy bar is pulled out at a controlled speed according to the molten steel supply rate so that the molten steel surface does not change. The drawing speed of the dummy bar is controlled so that the surface of the molten steel does not change depending on the amount of expansion of the molten steel in the pool and the amount of molten steel injected until the solidified shell reaches a predetermined slab thickness, that is, until it is completely solidified. .

In order to produce a non-segregating slab by solidification in only one direction from the bottom, heat insulating material such as rice husk or bellum buit is used on the surface of the molten steel, which is separated from the powder material (lubricant) that is introduced into the mold by a weir (c). The material is supplied, kept warm, and finally allowed to solidify on the top surface.

The structure of the forced cooling device (9) consists of a support plate (b) provided with an opening large enough to prevent bulging or breakage of the solidified shell, and a spray nozzle (c) or a mist spray nozzle. That is, water spray, air, or mist spray is ejected onto the bottom and side surfaces of the slab to remove heat and grow a solidified shell toward the top surface. After the solidified shell has grown to a thickness that provides sufficient strength, it can be supported with a laurel pron OQ. The solidified shell grows further and the third
Solidification is completed at point P shown in the figure to form a slab. Since low melting point inclusions accumulate in the final solidified part, depending on the purpose, by scraping off about 15% of the surface layer after finishing casting,
It is possible to remove inclusions that are segregated in the center of the slab and cannot be removed using normal continuous casting methods.

When the mold (6) is subjected to a known oscillation motion, it is effective in forming a solidification point and in preventing seizure between the inner plate of the mold and the solidified shell.

Further, after the forced cooling device, it is easy to use a walking bar, belt support, etc. instead of the roller apron.

EXAMPLE An example of the method of this invention will be described. Figures 3 to 8
Continuous casting of slabs was carried out using the apparatus of the invention illustrated in the figure. Table 1 shows the ladle composition of cast molten steel.

1st Table casting temperature 1550'C, pinch roller withdrawal speed 0.4
m/min, Menpush nozzle supply tray 1.3 T/min The powder material used is granular neutral powder, the heat insulating material is Bermphyto, thickness 2505 tts X medium 1800
Manufactured fighting slabs. The analysis results of the top and bottom surfaces of the obtained slab are shown in Table 2.

As is clear from Table 2, the component segregation within the slab before and after the upper surface has almost disappeared. The condition of the lower surface was also investigated and no surface defects such as cracks were found.

Effects of the Invention As described above, in this invention, since the upper surface of the slab is solidified last, a homogeneous slab without segregation within the slab can be obtained. Also,
Solidified shell formation is smooth and bending stress is low, which improves the quality of continuously cast slabs such as obtaining slabs with excellent surface quality without surface cracks, and reduces operational troubles, improving manufacturing efficiency. It has many effects such as

[Brief explanation of drawings]

Figure 1 is a schematic diagram of horizontal continuous casting using the open belt method.
Fig. 2 is a schematic diagram of horizontal continuous casting using an open mold method, Fig. 3 is a side view showing an example of the horizontal continuous casting apparatus of the present invention, Fig. 4 is a plan view thereof, and Fig. 5 is a diagram showing an example of the horizontal continuous casting apparatus of the present invention. 6 is a sectional view taken along the line A-A shown in FIG. 5, FIG. 7 is a side sectional view taken during pouring by the device of the present invention, and FIG. 8 is a sectional view taken from B in FIG. 7. -B sectional view. In the figure, 1...tongue push, 2...metal belt, 3
... Cooling device, 4... Cooling row A/, 5... Slab, 6... Mold, 7... Reduction roll, 8...
Hot water leak prevention wall, 9... Forced cooling device, lo... Robe apron, 11... Pinch roller, 12... Cutting machine, 11... Onlay V-yon device, 14... Powder material Supply device, 15... Insulating material supply device, 16...
・Thickness measuring device, 17... Control device, 18... Button push nozzle, 19... Mold inner plate, 20...
・Mold frame, 21...Dummy par head, 2
2...Water supply port, 23.Second drain port, 24...Powder material supply port, 25...Weir, 26...Heat insulation material supply port, 2
7... Support plate, 28... Spray nozzle. Applicant: Sumitomo Metal Industries, Ltd. Special Opening aGO-187449 (5)

Claims (1)

[Claims] 1. In order to perform horizontal continuous casting, a solidified shell is formed by cooling from the curved bottom of the mold so that the thickness of the produced slab increases in the drawing direction, and the solidified shell is drawn upward while being drawn horizontally. A horizontal continuous casting method characterized by promoting unidirectional solidification toward the top surface so that the top surface solidifies last. 2. A molten steel hot water supply device, a mold having a curved bottom surface so that the thickness of manufactured cast slab increases in the drawing direction and a mechanism for cooling the bottom surface, and a pinch roll that horizontally pulls out the solidified shell generated in the mold. , a forced cooling device that supports and cools the solidified shell, a thickness measuring device that measures the thickness of the slab between the mold and the pinch rolls, and controls the amount of hot water supplied and the drawing speed based on the measured value. A horizontal continuous casting device characterized by comprising a control device.