JP3063808B2 - Twin roll continuous casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-roll continuous casting apparatus for continuously casting a metal sheet directly from a molten metal.

[0002]

2. Description of the Related Art In recent years, a casting method for continuously producing a thin plate from a molten metal such as molten steel has attracted attention, and a twin-roll continuous casting method is one of the methods. In this method, a pair of rolls rotating in opposite directions are opposed to each other in parallel with an appropriate gap therebetween, and two side dams (side dams) are pressed against both end faces of the rolls. An outer peripheral surface and side dams define a pool of molten metal, and the outer periphery of a roll that rotates the molten metal in the pool by continuously supplying molten metal from a tundish provided above the pool. This is a method in which a solidified shell is formed while cooling on a surface, and a metal sheet is continuously cast.

[0003] In the continuous casting method, it is generally unavoidable that a large undulation occurs in the molten metal surface as the molten metal is poured into the pool, and this undulation phenomenon occurs when the molten metal and the outer peripheral surface of the roll are first formed. Disturbance occurs in the contact portion (this is called a meniscus portion), and the solidification start point in the roll width direction tends to be non-uniform. Such a variation in the solidification starting point causes defects such as hot lines and cracks on the surface of the thin slab to be cast, and when the solidified shells generated by both rolls are pressed together. In addition, there is a problem that a phenomenon (called a breakout phenomenon) in which an unsolidified shell inside leaks easily occurs.

[0004] To solve the above-mentioned problem of the twin-roll continuous casting method, for example, as shown in FIG. 6, a pouring nozzle 60 having a molten metal discharge portion 60a provided with a molten metal 8 retaining portion is used. It is connected to a dish 61, and the tip is immersed in a pool 9 so that molten metal 8 overflowing from the stagnation section 9 during casting is supplied to the pool 9 to reduce the undulation of the metal surface. There has been proposed a casting apparatus which attempts to suppress it (JP-A-2-299746).

[0005]

However, in this casting apparatus, the supply of the molten metal to the pool 9 is performed by the molten metal 8 overflowing from the weir 60b forming the stagnation portion and dropping freely. At this time, the surface of the basin is wavy due to hitting of the liquid surface by the falling flow, and the conditions for forming the solidified shell are still unstable.

[0006] In addition, in this casting apparatus, most of the molten metal falling flow from the weir 60b falls into the pool 9 while touching the atmosphere on the pool 9 with a large area. Many oxides will be produced,
This metal oxide floats in the pool 9 and is caught in the solidified shell, which has the problem of significantly deteriorating the surface properties of the slab.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a continuous casting apparatus which suppresses the formation of oxides during pouring, suppresses the ripples on the surface of the pool, and enables stable formation of a solidified shell. It is intended to do so.

[0008]

According to a first aspect of the present invention, a pair of rolls rotating in opposite directions are arranged in parallel and opposed to each other, and side weirs are pressed against both end surfaces of the pair of rolls. A pool of molten metal is defined by the outer peripheral surface of the pool and side dams, and molten metal is poured into the pool through a pouring nozzle from a tundish provided above the pool, In a twin-roll continuous casting apparatus for continuously casting a metal sheet through a gap between rolls, a tip of the pouring nozzle is formed of a hollow columnar porous refractory extending parallel to a longitudinal direction of the twin roll. A twin-roll continuous casting apparatus, wherein the filter is immersed and disposed in the molten metal in the basin, and the molten metal is circulated through the filter into the basin from the hollow portion of the filter to the outside. Is the gist.

[0009]

The molten metal from the pouring nozzle passes through the filter and is supplied to the pool, so that the kinetic energy of the molten metal itself is consumed by the flow resistance when passing through the porous material. The directional component is made uniform, so that the ripples on the surface of the basin are kept low.

Further, since this filter is provided at the tip of the pouring nozzle and supplies the molten metal while being immersed in the pool, the degree of contact with the atmosphere after passing through the filter is low, and the generation of oxides is suppressed.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic appearance of a twin-roll type continuous casting apparatus 1 (hereinafter abbreviated as casting apparatus 1) according to the present invention, in which both ends of a pair of rolls 2 and 3 which are opposed to each other with a gap of a predetermined width therebetween. Fan-shaped side dams 4 and 5 are pressed against the surface.

At the time of casting, the rolls 2 and 3 are driven to rotate in directions opposite to each other as shown by arrows a and b in the figure by a drive mechanism (not shown), so that the outer peripheral surfaces 2a and 3a of the rolls 2 and 3 are on both sides. In the space defined by the weirs 4 and 5,
From the tundish 6 located above it to the pouring nozzle 7
, Molten metal (molten metal) 8 typified by stainless steel (for example, SUS304) or the like is supplied, and here a so-called pool portion 9 is formed.

The pouring nozzle 7 has a tubular refractory conduit 1 connected to a tundish 6 as shown in detail in FIG.
0, and a filter 11 fixed to the tip thereof.
Is immersed in the molten metal 8 in the pool 9. According to the present embodiment, the filter 11 has an upper wall portion 11a made of a porous (also called porous) refractory material and a roll outer peripheral surface 2a, as is apparent from the single unit appearance of FIGS.
It is assembled by a porous side wall portion 11b facing 3a and end wall portions 11c and 11d facing each side weir 4 and 5, and is formed as a housing forming a space 12 therein.

The space 12 of the filter 11 is shown in FIG.
As shown in the figure, the molten metal 8 which is in communication with the inside of the refractory conduit 10 through a hole 13 formed in the upper wall portion 11a and which is supplied from the tundish 6 at the time of casting,
The filter 11 falls inside the refractory conduit 10 to fill the space 12 inside the filter 11. In the present embodiment, the end wall portions 11c and 11d further have a closed wall 11c ', 1 part of which does not have a porous portion (micropore) for a reason to be described later.
1d '.

At the tip of the pouring nozzle 7, the filter 1
1 will be described below with reference to FIGS. During casting, tundish 6
Of molten metal 8 is supplied to the filter 11 through the inside of the refractory conduit 10 and is filled therein.
The molten metal 8 filling the inside of the filter 11
During the primary stagnation in the space 12, those that are in a state of agitation calm down in this space 12 while consuming their own kinetic energy (flow energy), and then each wall portion 11a
Then, the water flows through the porosity of １１11d and flows into the basin 9.

However, the above-mentioned porous material of the filter 11 acts as a flow resistance when the molten metal 8 is allowed to pass therethrough.
The flow energy of the molten metal 8 itself is largely consumed for the passage, and as a result, the molten metal 8 after the porous passage has a small flow velocity and a gentle flow, and flows out to the molten metal 8 in the pool 9. I will be.

The molten metal flowing out flows toward the outer peripheral surfaces 2a and 3a of the roll at a relatively slow speed, and there is no sharp waving on the surface of the pool 9 so that the surface of the pool is flush with the surface of the pool. The contact line with the outer peripheral surface of the roll is not disturbed, and a stable solidified shell generation start line can be formed in the meniscus portion. As described above, in the present embodiment, the molten metal 8
Does not come into contact with the atmosphere above the basin, because it takes the form of being directly supplied into the molten metal of the basin 9,
Therefore, metal oxides are not easily generated.

By the way, regarding the size of the filter 11 described above, considering the balance between the amount of molten metal supplied to the internal space 12 of the filter 11 and the amount of molten metal leaking out of the space 12 to the outside, The refractory wall surface area on the side is preferably at least twice as large as the hole cross-sectional area of the refractory conduit 10. This is because, if the filter 11 is formed too small, the amount of the leaked molten metal tends to catch up with the amount of the molten metal supplied to the filter 11, and as a result, the flow velocity of the molten metal flowing out to the outside becomes large, and the protruding flow Or if the pressure in the space 12 rises excessively,
This is because 1 itself may be damaged. In addition, regarding the setting of the fire-resistant wall surface area, the roll outer peripheral surface 2a,
From the viewpoint of making the flow of the molten metal approaching 3a more quiet and uniform, it is preferable that the size of the filter 11 be increased as far as the pool space allows.

Further, as for the thickness of the refractory wall forming the filter 11, at least the wall thickness of the refractory conduit 10 must be ensured so as not to be damaged by the pressure or heat of the molten metal 8 itself. preferable. by the way,
The shape of the filter 11 in this embodiment is formed so as to have a cross section similar to the cross-sectional shape of the well 9 as shown in FIG. This is intended to make the molten metal 8 leak evenly in a relatively large area in the basin section 9 so as to prevent the uneven molten metal flow in the basin section. The shape of the filter is not limited to this. For example, as shown in FIG. 5, the cross section may be substantially a football shape or another shape.

In addition, the molten metal 8
It has been confirmed by experiments and the like that the flow of the molten metal below the side weirs 4 and 5 promotes the solidification delay at the end of the slab. Closed walls 11c ', 11d' having no porosity are arranged below the end wall portions 11c, 11d, and the flow of molten metal from these portions is suppressed so that the molten metal does not flow downward to the side weirs 4, 5. Is desirable.

Although the preferred embodiment of the present invention has been described above, the pore diameter of the porous material constituting the filter 11 can be easily adjusted by a non-molten precipitate such as a molten oxide contained in the molten metal 8. It is preferable that the size be as small as possible without causing clogging.

[0022]

As described above, according to the present invention, the molten metal from the pouring nozzle is supplied to the molten metal in the pool by passing through the filter, thereby preventing oxidation of the molten metal. A solidified shell can be formed with a stable meniscus portion without disturbance, and a thin plate slab without defects such as hot lines and surface cracks can be cast. In addition, breakout during solidified shell compression bonding can be prevented by the stable meniscus.

[Brief description of the drawings]

FIG. 1 is a schematic external perspective view of a twin-roll continuous casting apparatus according to the present invention.

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3 is an external perspective view of a pouring nozzle alone according to the present invention.

FIG. 4 is a sectional view of a pouring nozzle taken along line AA of FIG. 3;

FIG. 5 is an external view of a pouring nozzle as another embodiment different from FIG. 3;

FIG. 6 is a schematic sectional view of a conventional casting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Twin roll type continuous casting apparatus 2,3 ... Roll 4,5 ... Side weir 6 ... Tundish 7 ... Pouring nozzle 8 ... Molten metal (molten metal) 9 ... Puddle part 10 ... Refractory conduit 11 ... Filter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-183752 (JP, A) JP-A-6-600 (JP, A) JP-A-1-228649 (JP, A) JP-A-62-1988 282753 (JP, A) JP-A-4-322845 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/06 330 B22D 11/10 330

Claims (1)

(57) [Claims] 1. A pair of rolls rotating in opposite directions are arranged in parallel and opposed to each other, and side weirs are pressed against both end surfaces of the pair of rolls, and a pool portion of a molten metal is formed by an outer peripheral surface of the rolls and the side weir. And pouring the molten metal from the tundish provided above the basin portion into the basin portion via a pouring nozzle, whereby the metal sheet is continuously passed through the gap between the rolls. In the twin-roll continuous casting apparatus for casting, at the tip of the pouring nozzle, a filter made of a hollow columnar porous refractory extending in parallel to the longitudinal direction of the twin roll is immersed in the molten metal in the pool. A twin-roll continuous casting apparatus, comprising: disposing a molten metal in the pool through the filter from the hollow portion of the filter to the outside.