JPS6152969A - Electromagnetic stirrer for continuous casting molten steel - Google Patents

Abstract

PURPOSE:To accelerate the floating of inclusions and to obtain stably a billet having high quality by adjusting discretely the stirring intensity of an electromagnetic stirring means which creates the flow from one short side toward the center of a casting mold, and an electromagnetic stirring means which creates the flow from the other short side toward the center of the mold. CONSTITUTION:Coil devices 6, 7 for electromagnetic stirring which are two units of the electromagnetic stirring means are juxtaposed along the long side walls of the casting mold 1 in the position spaced downward from the molten metal surface. The devices 6, 7 are connected to a DC power source and the molten steel flows 8, 9 from the short side of the mold 1 toward the center of the mold are respectively formed by the electromagnetic force conducted from said power source. The intensity of the current to be impressed to the devices 6, 7 is discretely adjusted by an adjusting device, by which the flow rate of the flows 8, 9 is discretely adjusted in a 0.3-0.8m/sec range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic stirring device for continuous casting molten steel, which stirs molten steel poured into a mold using electromagnetic force.

[Conventional technology]

In continuous casting, by stirring the unsolidified molten slab of the slab using electromagnetic force, segregation inside the slab can be reduced and high quality slabs can be obtained.

In this electromagnetic stirring technology, near the surface of the molten steel in the mold,
There is a known technique in which two electromagnetic stirring devices are installed along the width direction of a mold to provide a flow of molten steel from both short sides of the mold toward the center of the mold. By this method, the depth at which the molten steel discharge flow from the immersion nozzle penetrates into the mold solid solution steel can be made shallow.

By the way, the immersion nozzle is usually provided with two discharge ports facing the short side of the mold, but as the immersion nozzle is used, the diameter of the discharge ports may erode and enlarge or become clogged. The edition may be shortened. In this case, the flow velocity of the molten steel discharged from the immersion nozzle becomes non-uniform for each discharge port, causing an imbalance in the flow of the molten steel within the mold.

However, with conventional electromagnetic stirring technology, it is not possible to eliminate the unbalance of the molten copper flow, and when an unbalance occurs, the intended purpose of shallowing the penetration depth of the discharge flow from the submerged nozzle cannot be achieved. cannot be achieved. For this reason, the following problems have arisen. As shown in FIG. 2, for example, when the molten steel discharge flow from the discharge port on the left side of the figure becomes faster, the depth L at which the molten steel discharge flow penetrates into the mold self-melting becomes extremely deep. It is difficult for inclusions contained in the discharge flow to float up, and the quality of the slab deteriorates. Further, since the molten steel discharge flow on the right side of the figure becomes relatively small, the temperature of the molten metal surface on the right side becomes low. Due to this decrease in the temperature of the molten steel surface, the powder on the surface of the molten steel does not melt sufficiently.
The amount of molten slag flowing between the mold and the solidified shell is insufficient,
In extreme cases, breakouts occur. Furthermore, as in the case of high-speed casting, when the flow rate becomes even faster, the molten steel discharge flow (on the left side of the figure), which has a higher flow rate, has a slight velocity and reaches the solidified shell, so the solidified shell is remelted. Let me hide.

As a result, a breakout is likely to occur, which is extremely inconvenient for operation.

[Problems to be Solved by the Invention] This invention is capable of creating a uniform flow of molten steel in the #steel in the mold even if the flow velocity of the molten steel when discharged from the immersion nozzle is non-uniform. It is an object of the present invention to provide an electromagnetic stirring device for continuous casting molten steel, which can reduce the penetration depth and solve the above-mentioned problems.

[Means for solving problems]

The electromagnetic stirring device for continuous casting molten steel according to the present invention is an electromagnetic stirring device for continuous casting molten steel that uses electromagnetic force to stir molten steel poured into a mold with a rectangular casting cross section. a first electromagnetic stirring means that is provided and creates a flow of molten steel from one short side toward the center of the mold by electromagnetic force;
A second electromagnetic stirring means for creating a flow of molten steel from the other short side toward the center of the mold by electromagnetic force, and an adjusting means for individually adjusting the flow velocity of the molten steel flow by the first and second electromagnetic stirring means. It is characterized by having.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. The mold 1 has a rectangular casting cross section, and the immersion nozzle 2
Molten steel 3 is injected into the mold 1 from above. The immersion nozzle 2 is provided with two discharge ports 4 at its lower end, and each of the discharge ports 4 faces the mold 5 on the short side of the mold l. In addition,
Powder (not shown) is floated on the surface of the molten metal to keep the molten steel warm and prevent it from oxidizing, as well as to lubricate between the mold and the solidified shell.

In a place spaced 15 Qm or more downward from the molten steel surface,
Two electromagnetic stirring coil devices 6 and 7, which are electromagnetic stirring means, are arranged side by side along the long side of the mold l. The coil devices 6 and 7 are connected to a suitable DC power source (not shown), and are energized by this power source to cause molten steel flows 8 and 9 to flow from the short sides of the mold 1 toward the center of the mold, respectively. form. The intensity of the current applied to the coil devices 6, 7 can be adjusted individually by adjusting devices M (not shown). Therefore, depending on this adjustment device, the flow velocity of the molten steel flows 8 and 9 is usually 0-
3'y'0.8 m,/sec, adjusted individually. In the electromagnetic stirring device configured in this manner, the coil device 6° 7 applies molten steel flows 8 and 9 to the molten steel 3 in the mold from the short sides of the mold toward the center of the mold. These molten steel flows 8 and 9 cause a discharge flow 10 from the immersion nozzle 2.
- 11 is buffered, as a result of which the penetration depth of the discharge flow 10.11 from the submerged nozzle 2 into the mold weld is reduced.

By the way, suppose that the flow velocity of the molten steel discharged from the immersion nozzle 2 becomes non-uniform with respect to each discharge port 4, for example, the flow velocity of the molten steel discharge flow 1o on the left side of the figure becomes abnormally fast. In this case, the temperature of the cooling water cooling the inside of the steel wall of the mold 1 increases on the discharge flow 10 side as well as on the discharge flow 11 side. Or mold 1 for automatic control of molten steel surface, etc.
If a thermocouple is embedded in the mold, the discharge flow lQ
When the heat is placed on the side, the detected temperature increases. At this time, it is detected that the molten steel discharge flow 10 has become faster than the discharge flow 11.

Then, the adjustment device increases the current applied to the coil device 6 higher than the current applied to the coil device 7, thereby increasing the flow velocity of the molten steel flow 8. As a result, the flow velocity of the molten steel flow 8 toward the discharge stream 10 having a high discharge flow rate is increased, and the momentum of the discharge stream 10 is reduced.

Therefore, the discharge flows 10 and 11 have substantially the same speed in the mold self-molten steel, and the unbalance of the molten steel flow is eliminated.

The coil device 6.7 may be installed on one long side of the mold, or a pair of coil devices 6.7 may be installed on both long sides.

〔Effect of the invention〕

According to this invention, an electromagnetic stirring means that creates a flow from one short side toward the center of the mold and an electromagnetic stirring means that creates a flow from the other short side toward the center of the mold are combined, and the strength of the electromagnetic stirring is adjusted individually. can be adjusted to Therefore, even if the flow velocity of molten steel is non-uniform when discharged from the immersion nozzle, a uniform flow can be created within the mold, and the penetration depth L of the discharge flow can be made shallow.

This promotes the floating of inclusions and allows stable production of high quality slabs.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view illustrating a non-uniform state of molten steel flow. 1; Mold, 2; Immersion nozzle, 3; Molten steel flow, 4; Discharge port,
5; Casting wall, 6, 7; Coil device, 8° 9; Molten steel flow, 10
, 11; discharge flow. Applicant's agent Patent attorney Takehiko Suzue et al. Figure 1 Figure 2

Claims (1)

[Claims] In an electromagnetic stirring device for continuous casting molten steel that uses electromagnetic force to stir molten steel poured into a mold with a rectangular casting cross section, it is installed near the molten metal surface on the long side of the mold, and the mold is stirred from one short side by electromagnetic force. A first electromagnetic stirring means that creates a flow of molten steel toward the center, a second electromagnetic stirring means that creates a flow of molten steel from the other short side toward the center of the mold by electromagnetic force, and first and second electromagnetic stirring means. 1. An electromagnetic stirring device for continuous casting molten steel, comprising adjustment means for individually adjusting the flow velocity of the molten steel flow by the means.