JPS61186153A - Continuous casting method of thin strip by solidifying it below molten metal surface - Google Patents

Abstract

PURPOSE:To obtain a thin strip having a surface quality uniform in its width direction without oxidizing it by air and to perform repairless rolling, by bringing the bottom of an intermediate vessel into tight contact with a quenching device and heating the neighborhood of a feeding nozzle, in a continuous casting of a thin strip between cooling rolls and/or water-cooling belts. CONSTITUTION:A molten metal charged into an intermediate vessel 3 from a tundish through an immersed nozzle 4, is poured from a nozzle part provided with a heating element 5 in-between cooling rolls 1 and/or water-cooling belts under a fixed head and in a stationary flowing state, to quench the metal into a thin strip. The molten metal flows uniformly in-between the cooling devices 1 under the proper head and at the proper temperature without contacting air to be oxidized, and is formed into a thin strip, having an excellent surface free from surface flaws and raggedness to make repairless rolling possible.

Description

[Detailed description of the invention] CIyfi industry application field) This invention combines water-cooled rolls and/or water-cooled belts (either a water-cooled roll and a water-cooled roll, a water-cooled roll and a water-cooled belt, or a water-cooled belt and a water-cooled belt). combination)
The present invention relates to a method of improving the surface properties of a thin plate in a method of casting a thin plate using a mold.

(Conventional technology and its problems) In the past, thin plates were manufactured using a steel ingot--branch rolling--hot rolling process, but now they are mainly manufactured using a continuous casting--plate down--hot rolling process. .

Many attempts have been made to manufacture slabs having the same thickness as hot-rolled steel sheets by continuous casting with the aim of further simplifying the process compared to these manufacturing methods.

JP-A-58-163554 discloses that molten steel is continuously supplied between water-cooled rolls to produce a thin plate,
In Japanese Patent No. 179550, an attempt is made to manufacture a thin plate by supplying molten steel between water-cooled belts. However, the reality is that neither method has been put into practice.

The biggest problem with these manufacturing methods is ensuring the surface quality of the thin plate. In the production of thin sheets, the surface roughness per unit weight is extremely large compared to conventional steel ingots and continuously cast slabs, so that no or only very light treatments are allowed on the surfaces of the thin sheets. This is because the reduction in yield outweighs the benefit of omitting the process.

Surface flaws on thin plates are defects such as surface irregularities, surface cracks, and encrustations caused by air oxidation that occurs when molten steel is fed between water-cooled rolls and/or water-cooled belts, drifting of molten steel, and uneven heat. Air oxidation occurs when molten steel is injected directly between water-cooled rolls or between water-cooled belts in an air atmosphere, or when molten steel comes into contact with air when injected using a sludge, etc., and scum or scum produced by air oxidation occurs. Inclusions are incorporated into the surface of the thin plate and remain as defects.

In order to prevent air oxidation, the molten steel is collected in the upper recess formed by the water-cooled roll and/or the water-cooled belt, and the molten steel is supplied using a submerged nozzle, or the atmosphere is adjusted with Ar, etc. in the grate. water-cooled roll and/or
Alternatively, a method of supplying molten steel between water-cooled belts has not been tried yet. However, with these methods of supplying molten steel using immersed nozzles or gages, it is extremely difficult to completely prevent uneven flow and uneven heat. That is, when molten steel is supplied using a submerged nozzle or a grate, it is almost impossible to create a uniform flow in the direction of a wide plate, and some non-uniform flow occurs, and this non-uniform flow also causes uneven heat. These uneven currents and uneven heat make the formation start position and formation speed of solidified shells uneven on the water-cooled roll and/or water-cooled belt wall, and cause surface irregularities and surface cracks called hot water wrinkles to occur on the surface of the thin plate. becomes. In order to ensure the surface quality of the i-plate, it is essential to completely prevent uneven flow and uneven heat at the position where solidification begins.

(Means for Solving the Problems) The present invention provides continuous flow of molten steel between water-cooled rolls and/or water-cooled belts, that is, between water-cooled rolls and water-cooled rolls, between water-cooled rolls and water-cooled belts, or between water-cooled belts and water-cooled belts. In this method, an intermediate container is placed above the water-cooled roll and/or the water-cooled belt, and the dome structure of the intermediate container is shaped to be in close contact with the water-cooled roll and/or the water-cooled belt. The molten steel held in the container is supplied in a static flow according to the casting speed and is solidified below the surface of the molten steel under the intermediate container, thereby eliminating surface flaws, i.e., air oxidation, drifting, surface irregularities due to uneven heat, surface cracks, and b
This is an attempt to prevent crowding. It is more effective if the lower structure of the intermediate container has a heating element near the lower nozzle that supplies molten steel to the water-cooled roll and/or the water-cooled belt.

(Operation) FIGS. 1 to 3 show examples of devices for carrying out the present invention.

The water-cooled rolls 1 and/or the water-cooled belts 2 are arranged at intervals that provide the required plate thickness. This water-cooled roll 1 and/or water-cooled belt 2 is a rotating mechanism.

An intermediate container 3 is placed above these. The intermediate container 3 should be structured so that it is connected to the water-cooled roll 1 and/or the water-cooled belt 2 as much as possible, so that molten steel does not leak from between the water-cooled roll 1 and/or the water-cooled belt 2 and the intermediate container 3. is important. Molten steel is supplied from the ladle through a long nozzle into the dandy cup, and is further injected into the intermediate vessel 3 through a submerged nozzle 4.

The molten steel maintained at a constant level in the intermediate container 3 is naturally supplied and cast according to the casting speed caused by the rotation of the water-cooled rolls 1 and/or the water-cooled belt 2.

A feature of the present invention is that air oxidation between the intermediate container and the water-cooled roll and/or water-cooled belt is completely prevented by arranging the intermediate container. By calming the flow of molten steel and supplying molten steel in a static state according to the production speed by static pressure, uneven heat and uneven flow can be prevented.

Furthermore, by installing the heating element 5 at the nozzle portion of the intermediate container 3 that is in contact with the water-cooled belt and/or the water-cooled roll, it is possible to equalize the temperature of the supplied molten steel and eliminate uneven heat. That is, by installing the heating element in the intermediate container and its nozzle part, drifting of current and uneven heat can be prevented, and a thin plate without defects and having a smooth surface can be manufactured.

(Effects of the Invention) By implementing the present invention, problems such as the occurrence of surface defects and low yield, which were the biggest drawbacks of conventional thin plate casting, can be solved, there is no air oxidation, and uniformity in 111 directions is achieved. A good surface quality is obtained, and there are no surface irregularities, surface cracks, or inclusions, and no-touch rolling is possible.

[Brief explanation of the drawing]

fjS1 is a water-cooled roll and a water-cooled roll, FIG. 2 is a water-cooled roll and a water-cooled belt, and FIG. 3 is a water-cooled belt and a water-cooled belt. It is.

Claims (2)

[Claims] (1) In a method of casting thin plates while continuously supplying molten steel between water-cooled rolls and/or water-cooled belts, an intermediate container is placed above the water-cooled rolls and/or water-cooled belts, and the lower structure of the intermediate container is water-cooled. A below-the-molten steel system is characterized by having a shape that makes close contact with a roll and/or a water-cooled belt, supplying molten steel held in an intermediate container in a static flow state according to the casting speed, and solidifying it below the surface of the molten steel under the intermediate container. Solidified thin plate continuous casting method. (2) The continuous casting method for submerged thin plate solidification under the hot water surface according to claim 1, wherein the lower structure of the intermediate container has a heating element near the lower nozzle for supplying molten steel to the water-cooled rolls and/or the water-cooled belt. .