JPH09271915A - Production of continuously cast slab - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separately produce a continuously cast slab of different kinds of steel having higher alloy concn. than molten steel in a tundish by electromagnetically-stirring molten steel in a mold while supplying powder for continuous casting mixed with the powdery and granular alloy element into the continuous casting mold during continuous casting. SOLUTION: To the upper molten steel pool 6 surface in the continuous casting mold 1, the powder 4 for continuous casting mixed with the grain or the powder of a prescribed alloy element is added and also, the stirring flow 9 is given in the horizontal cross section in the upper molten steel pool 6 by using an electromagnetic stirring device arranged at the upper part of the continuous casting mold 1. Simultaneously, the spouting holes of an immersion nozzle 2 is held in the electromagnetic stirring flow zone 8, and the alloy element grain or powder 5 mixed and added to the powder 4 for continuous casting is melted in the mold 1 by pouring the molten steel in the tundish and the alloy element is uniformly enriched in the molten steel. By this method, the cast slab of the different kind of steel having alloy element concn. higher than that of the molten steel in the tundish, is obtd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of directly adding an alloying element into a continuous casting mold through a powder for continuous casting so that the concentration of the alloying element in the slab is equal to that in the molten steel in the tundish. The present invention relates to a continuous cast slab production method for producing a relatively high slab.

[0002]

2. Description of the Related Art The inventors of the present invention have disclosed Japanese Unexamined Patent Publication No. 07-28487.
In JP-A-9, a continuous casting powder containing a predetermined alloy element is used, and at a position a certain distance below the molten steel meniscus in the continuous casting mold, the thickness of the slab is almost uniform across the thickness of the slab. While applying a DC magnetic field with a magnetic flux density distribution, inject molten steel of a certain composition and mix alloy elements through the continuous casting powder in the upper molten steel pool of the upper and lower molten steel pools divided by the DC magnetic field zone. Disclosed is a method for producing a multi-layered slab in which the concentration of alloying elements in the surface layer is higher than that in the inner layer by continuously casting while performing the above.

[0003]

Problems to be Solved by the Invention JP-A-07-2848
According to the method disclosed in Japanese Patent Publication No. 79, it has become possible to manufacture a multi-layered slab in which the alloy element concentration of the surface layer is higher than that of the inner layer. However, in this method, although the alloy element added in the powder can be added to the surface layer of the slab,
With this method, the concentration of the inner layer of the cast slab could not be increased. That is, it was not possible to uniformly increase the concentration of the entire slab.

The object of the present invention is to add the alloying element directly into the continuous casting mold via the powder for continuous casting, and further forcibly stir the upper part of the molten steel pool in the mold by using an electromagnetic stirrer. This is to produce a continuous cast slab in which the concentration of alloying elements in the slab is higher than the concentration in the molten steel in the tundish.

[0005]

The present invention uses a powder for continuous casting in which particles or powders of a predetermined alloy element are mixed, and an electromagnetic stirrer is provided in the upper part of the continuous casting mold, While providing a stirring flow in the horizontal cross section in the upper molten steel pool, by providing a discharge hole of the immersion nozzle in the stirring flow, by melting and uniformly mixing the alloy elements in the mold, A method for producing a continuous cast slab, which comprises producing a slab having a higher concentration of alloy elements in the slab than in the molten steel in the tundish.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail with reference to FIG. First, a continuous casting powder 4 in which particles or powders 5 of a predetermined alloy element are mixed is continuously added to the entire molten steel surface in the mold from above the mold 1. Then, in the process in which the powder 4 for continuous casting melts on the surface of the molten steel in the mold, the particles or powders 5 of the predetermined alloy element come into contact with the molten steel and mix from the meniscus into the upper molten steel pool in the mold. Spread.

Next, it is necessary to make the concentration distribution of the alloying elements in the upper molten steel pool 6 in the mold uniform, but in the molten steel pool having a rectangular cross section as in the continuous casting mold 1, a vertical stirring flow is used. A flow pattern that gives a stirring flow over a certain depth in a horizontal cross section is more effective than a mixing process for uniforming the concentration distribution. Therefore, the electromagnetic stirrer 3 is provided in the upper part of the mold, and the stirring flow 9 is applied within the horizontal cross section in the upper molten steel pool 6 in the mold to make the concentration of the alloy element in the stirring flow region 8 uniform. A stirring flow rate of at least 20 cm / sec or more is required for uniform concentration.

Further, the immersion nozzle 2 is placed in the stirring flow area 8.
By arranging the discharge holes of the molten steel, the molten steel discharged from the immersion nozzle 2 becomes more uniform than the alloying element concentration in the molten steel in the tundish by stirring in the upper molten steel pool 6 in the mold having a high alloying element concentration. Can be very high. Further, since the molten steel having a higher alloy element concentration than that in the tundish is supplied to the lower molten steel pool 7 in the mold, the alloy elements in the molten steel in the tundish are uniform throughout the mold. It is possible to produce a slab that is higher than the concentration.

At this time, if the particles or powders sized according to the alloying element are mixed in the continuous casting powder 4 at the concentration of the component to be added into the cast slab, the component having the predetermined concentration in the stirring flow region 8 is obtained. The molten steel composition can be adjusted.

[0010]

[Example] As shown in FIG.
In the continuous casting process in which the center of the electromagnetic stirrer 3 in the height direction is provided 50 mm below so that a swirl flow can be imparted within the horizontal cross section in the upper molten steel pool 6 in the mold, continuous casting is performed under the conditions shown in Table 1. It was The nozzle discharge hole position of the immersion nozzle 2 for supplying molten steel into the mold was 100 mm from the molten metal level to the upper end of the nozzle discharge hole. Also, continuous casting powder 4
A continuous casting powder 4 in which 20% by weight of nickel powder was mixed was continuously supplied during casting from above the mold over the entire molten metal surface. The casting conditions are shown in Table 1 below.

[0011]

[Table 1]

The results of investigating the nickel concentration distribution in the slab after casting are shown in FIGS. 2 (a) and 2 (b). From this, it can be seen that the nickel concentration in the slab is uniform throughout and higher than the nickel concentration in the molten steel in the tundish. In addition, similar experiments were carried out for carbon, silicon, manganese, phosphorus, sulfur, vanadium, boron, copper, niobium, and bismuth. It was possible to obtain a slab having a higher element concentration than that in the tundish.

[0013]

According to the present invention, the concentration of the alloy element in the cast piece is higher than the concentration in the molten steel in the tundish, and the alloy element concentration is uniform over the entire thickness of the cast piece. be able to. Therefore, this method enables different component compositions (different steel types) to be produced in the mold. That is, for a certain molten steel composition in the tundish, the molten steel composition can be adjusted by increasing the concentration of a certain component of the molten steel components in the mold, or by newly adding another alloying element. Since it becomes possible, by adjusting the addition amount of the alloying element in accordance with the type of the added alloying element and the target concentration, it is possible to manufacture the different steel type cast slab as necessary. The present invention is not limited to the size of the slab, and can be applied to the casting of slabs having a small cross section such as bloom and billet.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a continuous casting method of the present invention,
(A) is the figure which looked into the inside of a mold from the top, (b) is the longitudinal cross-sectional view seen from the long side of a mold, (c) is the cross-sectional view of a cast piece.

FIG. 2 is a diagram showing a nickel concentration distribution in a cast piece when added by the method of the present invention, and FIG. 2 (a) shows a nickel concentration distribution in the cast piece thickness direction at the center of the cast piece width direction. Further, (b) shows a distribution of nickel concentration in the width direction of the cast piece at a position 10 mm from the surface of the cast piece.

[Explanation of symbols]

 1 Mold 2 Immersion Nozzle 3 Electromagnetic Stirrer 4 Continuous Casting Powder 5 Alloy Element Grain or Powder 6 Upper Molten Steel Pool in Mold 7 Lower Molten Steel Pool in Mold 8 Stirred Basin 9 Stirred Flow 10 Surface Layer of Cast Piece 11 Inner Layer of Cast Piece Department

Claims (1)

[Claims] 1. In a horizontal cross section in an upper molten steel pool in a mold, a powder for continuous casting in which particles or powders of a predetermined alloy element are mixed is used, and an electromagnetic stirrer is arranged in the upper part of the continuous casting mold. While providing a stirring flow in, by providing the discharge hole of the immersion nozzle in the stirring flow region, by melting and uniformly mixing the alloy element in the mold, the concentration of the alloy element in the slab A method for producing a continuous cast slab, which comprises producing a slab higher than the concentration in the molten steel in the tundish.