JPS628258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In horizontal continuous casting of steel, this invention prevents segregation of the chemical composition and metallurgical structure of the slab and deformation of the slab due to the imbalance of heat flux during cooling and solidification of molten steel in the mold. This invention relates to a horizontal continuous casting method that can prevent the above problems and produce slabs of excellent quality.

Horizontal continuous casting of steel is produced by continuously drawing a slab from a mold horizontally installed at the lower part of the side wall of a tundish through a feed nozzle, and cooling it in a secondary cooling zone connected to the mold.

FIG. 1 shows a sectional view of a mold part provided in a tundish in a horizontal continuous casting machine, and FIG. 2 shows a sectional view taken along the line A--A in FIG. In the drawings, reference numeral 1 denotes a side wall of the tundish, which is made up of a steel shell 1a and a refractory 1b placed inside the steel shell 1a. 2 is a molten steel outlet provided at the bottom of the side wall 1, and a seating ring 3
and a front nozzle 4 having a recess provided on the inner surface of the seating ring 3 for fitting a feed nozzle.

A feed nozzle 5 is fitted into the recess of the front nozzle 4, and a mold 7 is provided at the end of the feed nozzle through a break ring 6. Therefore, the molten steel in the tundish is supplied to the mold 7 through the front nozzle 4, the feed nozzle 5, and the break ring 6. 8 is a cooling chamber for the mold 7 provided around the outer periphery of the mold 7, and 9 is a cooling channel.

The molten steel supplied to the mold 7 is immediately cooled in the mold 7 and solidified from the part that comes into contact with the mold 7, and is pulled out from the mold 7 to the right in FIG. 1 while a shell 10 is generated, and a solidified layer develops. Slab 11
becomes.

By the way, the problem when pulling a slab out of the above-mentioned mold is that the molten steel that has flowed into the mold solidifies and shrinks while being pressed against the lower surface of the mold due to its own weight and the static pressure of the molten steel. It is to be. As a result, the degree of adhesion between the inner circumferential surface of the mold and the solidified shell is large on the bottom side of the mold, but on the other hand, the degree of adhesion is small on the top and side surfaces of the mold due to the effect of gaps caused by shrinkage. Become.

Heat transfer from the molten steel and solidified shell to the mold is mainly done by radiation (approximately 10 ⁵ Kcal/m ²・h) and heat transfer (approximately 10 ⁶ Kcal/m ²・h), but the above-mentioned gap Due to the occurrence of
is large on the bottom side of the mold, and small on the top and side sides of the mold, resulting in an imbalance. At these locally large heat transfer points (hot spots), the heat flux reaches approximately 10 ⁷ Kcal/m ² h, resulting in a difference in the solidification rate and temperature distribution of the molten steel between the upper and lower parts of the mold. In this case, segregation occurs in the chemical composition and metallurgical structure of the slab, and the cooling of the lower part of the slab is greater than that of the upper part, resulting in the lower part of the slab contracting and bending downward in the longitudinal direction of the slab. There were problems such as curvature and poor shape.

Recently, as shown in FIG. 3 in a side view and in FIG. 4 as a cross-sectional view taken along the line A-A in FIG. The drum-shaped mold 1 is placed on the lower peripheral surface of the mold 12 while in contact with the lower peripheral surface of the mold 12 so as to cover the recess 13.
A recess 13 formed on the circumferential surface of the drum-shaped mold 12 is used.
A casting method using a rotary mold is also known, in which molten steel is injected from one end of the endless belt 14, solidified in the recess 13, and extracted as slabs 11 from the other end.

According to this method, since the slab is pulled out as the mold rotates, friction between the mold and the slab can be eliminated, but on the other hand, the following problems occur.

(1) When pouring molten steel into a rotary mold, it is difficult to seal the molten steel from air, making the structure of the feed nozzle complicated. If even a small amount of air gets mixed into the molten steel, the static pressure of the molten steel will no longer build up.
Surface oxidation occurs. Also, if the seal is incomplete, molten steel may leak out.

(2) It requires a movable mechanism that operates at high temperatures, is prone to breakdowns during operation, and requires a great deal of effort to maintain.

(3) Once the solidified shell has developed, it is necessary to remove the slab from the rotary mold, so the bending of the slab at that time may cause the shell to break, or the metal structure of the slab may become unnecessary or the straightness of the slab may be reduced. There is a risk that it may have an adverse effect on

(4) There are many restrictions on the shape of the agglomerate, especially those with a complex shape, especially those whose surface in contact with the endless belt is not flat,
For example, it is difficult to cast round billets.

From the above-mentioned point of view, this invention aims to reduce the chemical composition of the slab due to the imbalance of heat flux during the cooling and solidification of molten steel in the mold when pulling the slab whose surface layer is solidifying from the mold in horizontal continuous casting. to prevent metallurgical structure segregation and slab deformation,
High-quality slabs with no breakout,
This method provides a horizontal continuous casting method that allows for highly efficient production, and involves continuously drawing slabs from a mold installed horizontally at the bottom of the side wall of the tundish through a front nozzle, feed nozzle, and break ring. In the horizontal continuous casting method, an electrode is attached to a feed nozzle made of a non-magnetic material, a magnetic pole is attached near an initial surface solidification generation part made of a non-magnetic material of the mold, and a magnetic pole is installed near an open end of the mold from the mold. A collector electrode is attached so as to be in contact with the surface of the drawn slab, the electrode and the collector electrode are connected to a power source through a conductive wire, and molten steel is poured from the tundish into the mold to form the initial surface solidification generation area. By passing a current between the electrode and the collecting electrode from the moment the molten steel arrives until the required surface thickness has developed, the molten steel in the mold is directed upward by the action of the magnetic poles. This method is characterized in that casting is carried out while applying an electromagnetic body force of 100 mL to reduce the gravitational force applied to the initial solidification generation area of molten steel.

Next, the present invention will be explained with reference to examples and drawings. FIG. 5 shows a cross-sectional view of the upper half of an example of the apparatus used in the method of the present invention, and FIG. 6 shows an explanatory diagram showing the relationship between magnetic poles and electromagnetic force. In the drawing, 15 is a feed nozzle whose one end is connected to the front nozzle 4 provided at the molten steel outlet 2 of the tundish side wall 1, and whose other end is connected to the mold 18 via the break ring 6. The upper surface 15a of the feed nozzle 15 is made of a ceramic-based refractory.
_ZrO2 - _CeO2 , La1 _{~ 2CaXCrO3} , Fe, Fe alloy,
An electrode 16 made of graphite or the like is provided vertically with its lower surface facing the upper inner peripheral surface of the feed nozzle 15. Note that the electrode 16 may be inserted in any direction, up, down, left, or right. 17 is an electrode rod holder.

The mold 18 is made of a non-magnetic material having electrical insulation properties at least in the portion that contacts the initial surface solidification generation portion of molten steel and in the vicinity thereof. 19 is a gasket interposed between the end surfaces where the feed nozzle 15 and the mold 18 are in contact with each other; and 20 is a jacket provided along the outer periphery of the mold 18 through which cooling fluid flows.

A pair of magnetic poles 21 and 22 are disposed facing each other on both sides of the outer periphery of the mold 18 in a portion close to the initial surface solidification generation portion. 24 is a coil. In addition, the extracted slab 11 is located near the open end of the mold 18, where the slab is extracted from the mold 18.
A collector electrode 23 is provided so as to be in contact with the upper surface of the electrode. Note that the direction in which the collector electrode 23 is arranged may be any direction, up, down, left, or right. The electrode 16 and the collector electrode 23 are connected to a power source by a conductor (not shown), and the current flows from the electrode 16 through the molten steel in the feed nozzle 15, through the slab 11 extracted from the mold 18, and as shown in FIG. It flows to the collector electrode 23 as shown by the dotted line.

The length of the magnetic poles 21 and 22 in the slab drawing direction is 20 to 40% longer than the length of the initial surface solidification generation part in the mold 18, and their central axes are aligned. The length of the initial surface solidification generation part is (1) 1 when the sliding movement of the slab is intermittent.
(2) If the sliding motion of the slab is continuous, the distance from when the molten steel flows into the mold to when a solidified shell is formed that can withstand the tensile stress caused by the sliding motion, etc. , determined by .

The above-mentioned electrode 16, collector electrode 23, and magnetic pole 2
1 and 22, the current flows in the direction of arrow 25 as shown in FIG. An electromagnetic body force is generated in the upward direction shown, that is, in the anti-gravity direction.

The method of passing the current and applying the magnetic field as described above is as follows.
It may be in a continuous state or in an intermittent state in terms of time, and the power source may be either direct current, alternating current, or a combination of direct current and alternating current. Note that when alternating current is used, the current and magnetic field are configured to be synchronized. In the case of alternating current, the direction of electromagnetic force does not change even if the directions of both forces are reversed at the same time.

Since the method of the present invention is constructed as described above, molten steel is poured into the mold 18, and from the moment the molten steel reaches the initial surface solidification generation area until the necessary surface layer thickness has developed, the molten steel is poured into the mold 18, and the electrodes 16 and 23 are When a current is passed and a magnetic field is applied in the direction shown in Figure 6, the electromagnetic body force generated upward reduces the gravity applied to the initial surface solidification generation area, and the imbalance in heat flux due to downward adhesion is reduced. . As a result, segregation of the chemical components and metallurgical structure of the slab and deformation of the slab are appropriately prevented.

From the above, in order to generate an upward electromagnetic body force that counteracts the molten steel static pressure of 200 mm and its own weight, approximately
All you need is a current of 4000 amperes and a magnetic flux density of 3430 Gauss = 0.343 Tesla, and a power supply capacity of about 4KW is required. Note that the voltage between the electrodes in this case is V
= 0.5 volt, and the electrical resistance of the molten steel was R = 75 x 10 ^-6 ohm.

7 and 8 show other embodiments of the apparatus to which the method of the present invention is applied, FIG. 7 is a sectional view of the upper half, and FIG. 8 is a cross-sectional view taken along the line A-A in FIG. FIG.

In this embodiment, linear electromagnetic coils 28, 28 are provided vertically facing each other on both sides of the mold 18 in the vicinity of the initial surface solidification generation area. In the linear electromagnetic coil 28, a large number of grooves 28b running horizontally are provided in the magnetic pole 28a at regular intervals in the length direction of the magnetic pole 28a, and the electric wire 28 is provided in the grooves 28b.
c, and wire the wires so that the ridges are alternately magnetized vertically into north and south poles at one or more arbitrary pitches. Although FIG. 8 shows the case where the north and south poles are arranged at a single peak pitch, a traveling magnetic field in which NS changes sinusoidally at multiple peak pitches is generally used.

In addition, the opposing linear electromagnetic coil has its N
The pole and the S pole are provided so as to face each other at the same height. Note that the linear electromagnetic coil may not be provided on both sides of the mold, but may be provided on one side thereof.

Such linear electromagnetic coils are driven by alternating current so that the magnetic field moves from the bottom to the top, that is, in the opposite direction to gravity, at a predetermined synchronous speed. If provided, they are made to run at equal synchronous speeds.

The mold 18 has at least a linear electromagnetic coil 2
The portion where 8 is provided needs to be a non-magnetic material and an electrical insulator.

Since this embodiment is constructed as described above, the molten steel is poured into the mold 18, and from the moment the molten steel reaches the initial surface solidification generation area until the required surface layer thickness has developed, the linear electromagnetic coil 28 is When a traveling magnetic field with an upward synchronous velocity is generated, the gravitational force applied to the initial surface solidification generation part is reduced by the electromagnetic body force generated upward as shown by the arrow, and the same effect as described above is obtained.

From the above, in order to generate an upward electromagnetic body force that counteracts the static pressure of molten steel of 200 mm, approximately 3.5 m/S is required.
All you need is a traveling magnetic field of 2900 Gauss = 0.29 Tesla with a synchronous speed of .

In this invention, the electromagnetic body force is applied to the molten steel in the mold at a portion of the mold where the molten steel has not yet solidified, or where the solidified surface layer is, for example, 1 mm.
The following areas are not thick and other areas are unnecessary.

As described above, according to the present invention, in horizontal continuous casting, upward electromagnetic body force is generated in the molten steel in the mold. Segregation of components and metallurgical structure, deformation of slabs, etc. are reliably prevented, and excellent industrial effects such as production of slabs of excellent quality are brought about.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the mold part installed in the tundish in a horizontal continuous casting machine, and Figure 2 is a cross-sectional view of the mold part installed in the tundish in a horizontal continuous casting machine.
3 is a schematic side view of a rotary mold type horizontal continuous casting machine, FIG. 4 is a sectional view taken along line AA in FIG. 6 is an explanatory diagram showing the relationship between magnetic poles and electromagnetic force. FIG. 7 is an upper half sectional view showing another embodiment of the device to which the method of the invention is applied.
FIG. 8 is a sectional view taken along the line A--A in FIG. 7. In the drawings, 1... Tundish side wall, 2... Molten steel outlet,
3... Seating nozzle, 4... Front nozzle, 5... Feed nozzle, 6... Break ring, 7... Mold, 8... Cooling chamber, 9...
... Cooling channel, 10 ... Shell, 11 ... Slab, 12 ... Drum-shaped mold, 13 ... Recess, 14
... Endless belt, 15 ... Feed nozzle, 16
... Electrode, 17 ... Electrode rod holder, 18 ... Mold,
19...patsukin, 20...jacket, 21,
22... Magnetic pole, 23... Collector electrode, 24... Coil, 28... Linear electromagnetic coil.

Claims (1)

[Scope of Claims] 1. A horizontal continuous casting method in which slabs are continuously drawn from a mold horizontally installed at the lower part of the side wall of a tundish through a front nozzle, a feed nozzle, and a break ring. An electrode is attached to the feed nozzle of the mold, a magnetic pole is attached near the initial surface solidification generation part made of a non-magnetic material of the mold, and a magnetic pole is installed near the open end of the mold so as to be in contact with the surface of the slab pulled out from the mold. Attach a collector electrode, connect the electrode and the collector electrode to a power source via a conductive wire, pour molten steel from the tundish into the mold, and obtain the necessary surface layer thickness from the moment the molten steel reaches the initial surface solidification generation area. By passing a current between the electrode and the collecting electrode until the molten steel develops, an upward electromagnetic body force is applied to the molten steel in the mold by the action of the magnetic pole, and the initial solidification of the molten steel is caused. A horizontal continuous casting method characterized by performing casting while reducing the gravity applied to the generating section.