JPH0242576B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for guiding a melt by electromagnetic paths during melt solidification in order to improve the quality of continuous casting products.

According to the method of stirring the melt in the secondary cooling zone of the slab installation known from U.S. Pat. No. 3,693,697,
The vertically oriented moving magnetic field causes the flow to flow down the shell and up the center of the slab, and to reach just below the bath surface. The melt supply flow from the casting tube heads diagonally upward above the equilibrium flow that runs diagonally below the bath liquid surface.

In the flow method described above, it is important to check how far the stirring flow reaches upwards in the mold, or whether the stirring flow returns sufficiently from below the bath surface without disturbing the bath surface. Whether or not it depends entirely on chance. Therefore, in normal cases, the bath liquid level is disturbed, and as a result, casting powder or slag is drawn into the sump, or the agitation flow does not reach the upper part of the mold sufficiently.

US Pat. No. 4,200,137 discloses a method of stirring within a mold, in which two different stirring zones are distinguished. In the lower region, a flow is created as in US Pat. No. 3,693,697, but
However, this flow is restricted to the lower mold area. on the other hand,
The pouring tube is immersed very deeply and the pouring tube acts to create a concave bath level, but in the upper region creates a downward counterflow between the mold and the pouring tube. However, in this case, there is a risk of casting powder and slag being involved.

In order to avoid so-called white bands, which occur where the stirring flow is strongest, it has been proposed to carry out the stirring asymmetrically, with the main flow direction transverse to the casting direction. Template flows of this type are described, for example, in "Stahl und Eisen" 1978, No. 22, S. 1183 or 1980, No. 18, S. 1063. This mold system creates a plate-shaped agitated flow whose diameter corresponds to the width of the pool in the slab. Incidentally, since the growth of the shell thickness on the short side of the slab is negligible with respect to the total width of the slab, the width of the pool is constant. However, even with this stirring method in which the bath surface is moved to one side, there is a risk of entrainment of contaminants.

According to JP-A-49-126523, a continuous casting method is known in which the melt is heated by electromagnetic stirring in a region defined in the upper part of the mold to avoid the formation of blowholes in semi-killed and redominated steels. Superheated and newly injected melt is quickly distributed by overlapping the injection flow with the stirring flow, and in this method, the solution surface is stabilized by refractory stabilizing blades installed around the casting tube. This has been achieved.

All known casting methods involving stirring aim to extend the stirring action as far as possible to the bath surface in order to have a favorable influence on the initial stage of solidification.
This either causes the bath liquid level to move, and has the disadvantage that contaminants suspended on the melt are drawn into the pool by the movement of the bath liquid level, or requires additional use of the device. Since the bath liquid level must be stabilized, the disadvantage is that the expense increases both in terms of cost and maintenance.

This is where the present invention becomes relevant, and its purpose is to ensure that the stirring flow extends far within the mold.
The purpose is to offset the molten liquid level in the moving flow region as much as possible by the stirring flow itself, thereby keeping the bath liquid level quiet without adding expense.

According to the present invention, this purpose is to improve the quality of products produced by continuous casting in a method in which the melt is guided by an electromagnetic path during solidification of the melt, in which the stirring flow created by stirring changes from an upward flow to a horizontal flow. directing the melt feed stream downwardly out of at least two outlets of the casting tube such that the feed stream impinges on the agitator stream at substantially the same location as the feed stream transitions into the agitator stream; This is accomplished by a method that achieves improved product quality by offsetting the split flow that agitates the bath surface and superimposing a correspondingly oriented melt feed stream onto said agitated melt stream.

For example, the melt feed stream can impinge on the stirred flow at the exact location where the stirred flow component flowing upwardly against the slab shell flows in a reverse direction away from the slab shell and transitions into a lateral flow. When the stirring flow is asymmetrical with respect to the mold axis, and when the stirring flow consists of upper and lower primary cylinders (annular flow) and upper and lower secondary cylinders, the upper secondary cylinder is offset by the melt supply flow. be able to.

The asymmetric stirred flow generally consists of upper and lower primary cylinders and also includes upper and lower secondary cylinders depending on the spacing of the stirring device from the bath surface. In this case, the melt feed stream isolates the upper lateral component of the uppermost cylinder from the area of the bath surface, ie displaces it downwards.

The strength or energy of the melt feed stream required to offset the agitation flow is matched to the agitation flow by the static iron pressure of the incoming steel, i.e. by the length of the dip tube and the bath height in the tundish. It will be done. This has the potential to influence the melt flow rate.

Since the upward flow in contact with the slab shell transitions into a lateral flow in an arc rather than abruptly, the melt feed flow is guided downwardly and outwardly from at least two outlets of the pouring pipe;
Thus, it is made to hit the stirring flow in the opposite direction to the flow of the stirring flow.

When dividing the melt feed stream into a number of sub-streams, the sub-streams can have different directions and/or different strengths.

The outflow hole can have a tubular connection for flux formation reinforcement.

In the steel slab manufactured by the method according to the present invention, there is less entrainment of casting powder and residual slag.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Molten material is injected into a continuous casting mold 1 for casting a steel slab through a casting pipe 4 from a tundish (not shown), and a partially solidified slab 2 in an amount commensurate with the injection is pulled out of the mold.

An electromagnetic stirrer 7, used on known metallurgical grounds, creates a main flow in the slab sump, indicated by arrow 22, which main flow 22
is the upward direction 1 in contact with the slab shell 11 on the short side of the slab 2.
It is divided into 8 and 23 downward flowing regions. In the regions of the slab shells facing each other, the melt flows later, so that in the upper part 8 and the lower part 9 the formation of a primary cylindrical flow takes place in a known manner. A secondary cylinder rotating in the same direction at the contact with the primary cylinder of the upper and lower parts 10 can then be connected to the respective primary cylinder. However, in the illustrated embodiment, the position of the upper primary cylinder 8 is already quite high, so that its lateral upper flow, indicated by dotted arrows 15, 16 and 17, is not influenced by the melt feed flows 13, 14. Then, it touches the slag layer 3 and changes its motion, so
Contaminants can become entrained within the melt. As shown in the figure, when the stirrer 7 is at a high position, no upper secondary cylinder is formed.

To prevent the entrainment of contaminants, the orientation and energy adjustment of at least a portion of the melt feed stream, indicated by 13, is adjusted as follows, i.e., so that the flow region 15 is offset and transferred as a forced flow 19. to be done. In this case, the direction of the flow 13 is such that the flow substantially contacts a region 12 of the slab shell, and in this region 12 the upward flow 18 changes direction while contacting the slab shell. Flow 13 whose direction changed when contacting the slab shell
By superimposing the flow component 18 on the flow component 18, a flow 19 is generated according to the vector addition law.

Therefore, the lateral upper flow 1 of the upper primary cylinder 8
The energy of streams 5, 16, and 17 is reduced by this measure, such that these streams no longer disturb the bath level. Incoming steel flow 1
The strength of step 3 is adjusted by the height of the bath in the tundish.

The outlet hole 5 is provided with a tubular connection 6 in order to provide a flux of the stream 13 .

To better cancel the various flow components, the cross-section of the outlet hole can be further varied, so that melt feed streams are created in different directions and energies.

[Brief explanation of the drawing]

The drawing schematically shows the casting pipe and the flow inside it. 2... Slab, 7... Stirrer, 8... Upper primary cylinder, 1
1... Slab shell, 13, 14... Melt supply flow, 15, 1
6, 17... Lateral upper flow, 18... Upward flow, 19
...Forced flow, 22...Main flow (due to stirring), 2
3...Downward flow.

Claims (1)

[Scope of Claims] 1. A method for guiding a melt by an electromagnetic path during solidification of the melt in order to improve the quality of a product obtained by continuous casting,
The melt feed stream is directed to at least two outlets of the casting tube such that the feed stream impinges on the agitated stream at substantially the same location where the agitated stream created by the agitation transitions from upward flow to horizontal flow. The quality of the product is improved by overlaying the agitated melt stream with a correspondingly oriented melt feed stream that is guided downwardly and outwardly from the agitated stream, offsetting a substream of the agitated stream that agitates the bath surface. How to achieve improvement. 2. A patent in which the stirring flow, which is asymmetrical with respect to the mold axis, is composed of upper and lower primary cylinders and upper and lower secondary cylinders, and the lateral upper flow of the upper secondary cylinder is offset by the melt supply flow. The method according to claim 1. 3. The method according to claim 1, wherein the agitation flow that is asymmetrical with respect to the mold axis consists of upper and lower primary cylinders and lower secondary cylinders, and the upper secondary cylinder is offset by the melt supply flow. . 4. Any of claims 1 to 3 in which the strength or energy of the melt feed stream necessary to offset the stirring flow is adapted to the stirring flow by the static iron pressure of the incoming steel. Method described in Crab. 5. The method according to claim 1, in which the melt feed stream is divided into a number of branch streams, and the branch streams have different directions and/or strengths.