JPS58163559A - Continuous casting method of steel - Google Patents

Abstract

PURPOSE:To suppress the decrease in the temp. of an ingot and to enable hot direct rolling in a method of moving a cast and unsolidified ingot horizontally and cutting the same while curving the ingot along a secondary cooling zone, by making the secondary cooling zone short and providing a heat insulating zone. CONSTITUTION:An unsolidified ingot 6 which is formed with a solidified shell by charging molten metal 3 into a casting mold 4 is guided while the ingot is curved along a secondary cooling zone 8 which is made shorter in length than in the prior art. Only the central part of the ingot 6 in the transverse direction thereof is cooled in this zone 8 without cooling both end parts in the transvers direction of the ingot 6. The decrease in the temp. of the ingot 6 is prevented by a heat insulating device 9 to maintain the temp. until the ingot is cut to a prescribed length with a cutter 7. Thus, the temp. decrease of the ingot 6 is suppressed and hot direct rolling is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuous casting of steel, and particularly to a method for continuous casting of steel capable of obtaining high-temperature slabs.

An overview of the method of casting slabs in curved continuous casting will be explained with reference to FIG.

The molten steel 3 injected from the ladle l into the tundish 2 is injected from the tundish 2 into the mold 4.

The molten steel 3 injected into the mold 4 is guided from the lower part of the mold 4 through a secondary cooling zone 8 while being curved by a large number of slab guide rolls 5 . After this, the slab 6 is gradually straightened horizontally,
The completely solidified slab 6 is cut into a predetermined length by a cutting device 7 and transported to a primary process.

By the way, the slab cut into a predetermined length by the conventional cutting machine 7 is once cooled down to room temperature, and then subjected to flaw removal, etc. After that, it is reheated in a heating furnace and transported to the rolling line for the first process. It was common to do so.

However, the above method requires cooling equipment to cool the hot slab of 900°C or higher to room temperature immediately after cutting, and a heating furnace to reheat the slab after eaves removal, etc. In addition to requiring equipment costs, it also resulted in a large amount of energy loss.

In recent years, various improvements in casting methods have made it unnecessary to protect slabs.

For the purpose of reducing the above equipment costs and saving energy, etc.
Some attempts have been made to use the newly developed hot direct rolling (HDR) method, in which hot slabs immediately after cutting are directly transported to a rolling line without being cooled to room temperature.

The present invention provides a continuous casting method capable of obtaining high-temperature slabs necessary for carrying out the above-mentioned hot direct rolling, in which steel is cast using a mold,
The unsolidified slab in which the solidified shell has been formed is guided while being curved along the secondary cooling zone.Then, the curved unsolidified slab is straightened in the horizontal direction to complete solidification. In a continuous steel casting method in which a slab is cut to a predetermined length in a horizontal state and transported, the length of the secondary cooling zone is shortened, and in the secondary cooling zone, both widthwise ends of the unsolidified slab are Only the central part of the unsolidified slab in the width direction is cooled without cooling the unsolidified slab, and then the temperature of the unsolidified slab is maintained while preventing the temperature of the unsolidified slab from decreasing until solidification of the unsolidified slab is completed. Then, after solidification of the unsolidified slab is completed, the temperature of the solidified slab is prevented from decreasing until cutting of the slab is completed.

This invention will be explained with reference to the drawings.

FIG. 2 is an explanatory diagram showing the method of this invention.

As shown in FIG. 2, the method of the present invention.

The length of the secondary cooling zone 8 is made shorter than the conventional one.

In the secondary cooling zone 8, both ends of the unsolidified slab 6 in the width direction are not cooled, but only the central portion in the width direction is cooled.

This method cools only the center part in the width direction of the slab.

There is a method of closing the nozzles at both ends of a plurality of cooling spray nozzles provided at intervals in the width direction of the slab in the secondary cooling zone. Unsolidified slab 6 passed through secondary cooling zone 8
After the secondary cooling zone 8, solidification is completed while a temperature drop is prevented by a heat insulating device 9 installed in the slab movement path until the slab is completely cut, and then the slab is cut into a predetermined length by the cutting device 7. However, in order to recover heat, the unsolidified molten steel 6 immediately after leaving the secondary cooling zone 8 is moved so as to ensure at least 4 minutes or more until solidification is completed.

The heat insulating device 9 may simply cover the entire slab with a heat insulating plate or the like together with the slab support roll 5, but for the purpose of efficiently preventing the temperature of the slab 6 from decreasing, etc. It is preferable to use a heat insulating device 9 divided into a plurality of pieces as shown in FIGS. 3, 4 and 5. Each of the heat insulating devices 9 includes a U-shaped end heat retaining member 10 for protecting the ends in the width direction of the slab, and a central heat retaining member 10 provided horizontally on the upper and lower surfaces of the end heat retaining member lO. A plate 11, a cylinder l for moving the end heat retaining member 10 in the casting width direction, and a plurality of heat insulating devices 9 are provided at intervals along the longitudinal direction of the slab. . The tip of the center heat insulating plate 11 is configured to sandwich the slab 6 and slide over another center heat insulating plate facing therebetween. , the slab guide roll 5 is provided between the heat insulating devices 9. By using this heat insulating device 9, the heat insulating device 9 can be installed close to both sides of the slab at all times even if the width of the slab changes, so that a drop in the temperature of the slab 6 can be prevented to the maximum. Furthermore, since the heat insulating device 9 is divided into a plurality of pieces, when the cutting device 7 moves with the movement of the slab 6, it is possible to move only the heat insulating device directly below the cutting device 7 away from both ends of the slab. can. This can prevent damage to the heat insulating device due to scattering of nolls that occurs when cutting the cast slab.

Although the above-mentioned heat insulation device 9 is intended only for heat insulation,
Heat retaining member at the end of the insulation device 9 to maintain the temperature of the slab ↓・
A heating member made of porous bricks or the like may be connected inside the slab, and combustion gas may be supplied from the outside to the porous bricks to combust the gas, thereby heating both ends of the slab.

Since the temperature of the piece 6 naturally decreases during cutting and deburring which is performed after cutting the slab, it is preferable to install the above-mentioned heat insulating device also in the movement path of the deburring device (not shown).

Next, an example will be described.

Length 4 (1m, long side 1600m, short side 220m)
A secondary cooling zone is installed at the bottom of the mold to prevent cooling water from splashing onto the end of the slab (150 m), and the remaining 30 m is equipped with a heat insulating device as shown in Figures 3 to 5. Mild steel slabs were cast at a casting speed of 2.0 m/min using a curved continuous casting equipment equipped with the following. When the temperature at the center of the long side surface of the slab obtained as a result and the temperature at a part of both corners of the slab were measured, the temperature at the center of the slab was 13.
At 50℃, the temperature of part of the corner is 1000℃ and 69. 350℃ at the center of the slab compared to when cast using the conventional method
A temperature rise of 200°C was observed in some corners of the slab.

As explained above, according to the method of the present invention.

Useful effects such as being able to obtain high-temperature slabs with no problems during hot direct rolling are brought about.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional continuous casting method. FIG. 2 is an explanatory diagram showing the method of the present invention, FIG. 3 is a plan view showing the installation mode of the heat insulating device, and FIG. 4 is a diagram illustrating the method of the present invention. FIG. 5 is a sectional view taken along the line A--A in FIG. 3. In the drawing. l...Ladle 2...Tandish 3
... Molten steel 4 ... Mold 5 ... Slab guide roll 6 ... Slab 7 ... Cutting device
8...Secondary cooling zone 9...Insulation device lO・
... End heat retention member 11... Center heat retention plate 12.
...Cylinder applicant Nippon Kokan Co., Ltd. Agent Keitabe Tsutsumi (and one other person) 3 Figure 2

Claims (1)

[Scope of Claims] Steel is cast using a mold, the unsolidified slab with a solidified shell formed thereon is guided without being curved along a secondary cooling zone, and then the curved unsolidified slab is horizontally guided. The solidified slab is completed while being straightened in the direction, and the solidified slab is cut into a predetermined length in a horizontal state and transported. In the continuous casting method for steel, the length of the secondary cooling zone is shortened, and the secondary cooling zone does not cool both widthwise ends of the unsolidified slab,
Only the widthwise central portion of the unsolidified slab is cooled, and then. Until the solidification of the unsolidified slab 9 is completed, the temperature of the unsolidified slab is reheated without decreasing the temperature of the unsolidified slab.
- It is characterized in that the temperature of the solidified slab is not lowered until the slab cutting is completed. Continuous casting method for steel.