JPH05318043A - Method of continuously casting metal strip and apparatus therefor - Google Patents

Abstract

PURPOSE:To stably cast a metal strip having good shape for a long period without developing breakage of the cast strip, in a twin roll type continuous casting method. CONSTITUTION:At the time of producing the metal strip by solidifying A molten metal supplied into a basin part 6 constituted of one pair of cooling drums 2, 3 and side weirs 4, the cast strip is produced while keeping the temp. Ty ( deg.C) of the molten metal in the pouring basin part and the temp. Ts ( deg.C) of a side weir in the temp. range satisfying the following two expressions, Tm+10<=Ty<=Tm+70...(I), 2xTm-Ty-140<=Ts<=2xTm-Ty+10...(II). Wherein, Tm: liquidus temp. ( deg.C) of the molten metal in the pouring basin part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous casting of metal ribbon, and more particularly to twin drum continuous casting method and apparatus.

[0002]

2. Description of the Related Art In the twin-drum type continuous casting method, a molten metal pool is formed between a pair of rotary cooling drums whose axes are parallel to each other and a pair of side dams, and molten metal ( (For example, molten steel) is injected and the molten steel is cooled and solidified at the portion in contact with the peripheral surface of the cooling drum to form a solidified shell. Casting slab (metal ribbon). Therefore, stable growth of this solidified shell is extremely important for obtaining a thin cast piece having good surface properties.

In order to carry out stable casting as described above, it is necessary to maintain the molten steel temperature in the molten metal pool appropriately. As a technique focusing on such molten steel temperature, for example, Japanese Patent Laid-Open No. 1-91
No. 941 discloses that the superheat temperature when pouring molten metal is 15 ° C.
The manufacturing method of suppressing the contraction force at the time of solidification to prevent the generation of vertical cracks is disclosed below.

[0004]

However, the adjustment of the temperature of the molten steel in the molten metal pool required for stable casting is not sufficient merely by adjusting the overheating temperature of the molten steel. The present inventor has confirmed that it is extremely important to adjust the temperature of the side weir in contact with the molten steel in addition to the superheat temperature of the molten steel. That is, during casting, if the molten steel temperature is too low, the bare metal will stretch on the surface of the molten metal, causing the formation of hot bands. Conversely, if it is too high, the shell development will be insufficient and breakout will occur. If the weir temperature is too low, the side weir stretches the metal and causes the generation of hot bands. On the other hand, if the weir temperature is too high, the solidification of the end of the slab is insufficient and the edge is missing.

Here, the hot band means that a foreign material such as a piece of metal or refractory is caught in the solidified shell during casting, and the thickness of the cast piece temporarily increases at that portion. As a result of a momentary reduction of the pressing force on the slab, the contact surface pressure between the cooling drum and the slab decreases, so that the amount of heat removed decreases and a high temperature or unsolidified portion appears as a strip on the slab. When the slab comes out of the gap of the drum and is guided toward the coiler, tension acts on the slab, so that the slab easily breaks at a weak point such as a hot band formed on the slab, If it breaks, not only the continuous casting operation will be interrupted, but also the restoration work will waste a lot of time and materials.

The present invention has been made on the basis of such recognition, and an object thereof is to carry out stable continuous casting without causing breakage and defective shape of a cast piece.

[0007]

In order to achieve the above object, the present invention provides the following casting method and casting apparatus. That is, according to the present invention, the temperature T _Y of the molten metal in the molten metal pool in the molten metal pool is produced when the molten metal supplied to the molten metal pool composed of the pair of cooling drums and the side dam is cooled and solidified to produce the metal ribbon. (M) and the temperature T _S (° C.) of the surface of the side weir in a temperature range satisfying the following formulas (1) and (2): a continuous casting method for a thin metal strip, wherein T _m + 10 ≦ T _Y ≦ _{T m + 70 ..................... (1)} 2 × T m -T Y -140 ≦ T S ≦ 2 × T m -T Y + 10 ...... (2) where T _m: the molten metal in the basin section Liquidus temperature (° C.) Further, in a device for manufacturing a thin metal strip by cooling and solidifying a molten metal supplied to a molten metal pool portion composed of a pair of cooling drums and a side weir, the side weir heating device And a temperature measuring device for detecting the temperature of the molten metal in the basin, and the temperature of the surface surface of the side dam. A temperature measuring device for output, a casting apparatus provided with a control device for outputting a temperature control signal to the heating device temperature and the side weir surface temperature signals to inputs compared side weirs of the molten metal.

[0008]

As a result of various studies to obtain stable casting conditions, the present inventor has found that a stable casting region exists in the relationship between the molten steel temperature in the pool and the side dam temperature. The occurrence of hot band, that is, the ease of tensioning the metal in the pool is determined by the overheating temperature of molten steel ( _TY −
T _m ) and the solidification property of the slab edge is considered to be related to the difference between the liquidus temperature and the side weir preheating temperature (T _m −T _s ), so the results of the examples shown in Table 1 are _Y- T _m and T
which was organized in the context of _m -T _S is shown in FIG 1. In the figure, the horizontal axis is an overheat temperature of the hot water reservoir portion of molten steel in (° C.) (molten steel temperature inside the hot water reservoir portion T _Y - liquidus temperature T _m) (℃)
Required by. The vertical axis represents (liquidus temperature T _m −side weir surface layer temperature T _S ) (° C.), and the higher the side weir surface layer temperature, the lower the temperature.

In the stable casting area in the figure, the molten steel temperature (T _Y ) is T
_{A range of m} + 10 ° C. or higher and T _m + 70 ° C. or lower, side dam temperature (T _S ) of −T _Y + (2T _m −140) (° C.) or lower, −T _Y + (2T _m +10) (° C.) or higher. It is the area surrounded by and the range. This stable casting area (hatched area)
However, the amount of hot bands generated can be suppressed to less than 0.05 per drum rotation (Rev), the slabs are not broken, and the slab edges are not unsolidified. This region is defined by the equations (3) and (4) below.
It is represented by.

10 ≦ T _Y −T _m ≦ 70 (3) T _Y −T _m −10 ≦ T _m −T _S ≦ T _Y −T _m +140 …… (4 ) When the formulas (3) and (4) are modified, T _m + 10 ≦ T _Y ≦ T _m +70 (1) 2 × T _m −T _Y −140 ≦ T _S ≦ 2 × T _m −T _Y +10 (2) is obtained.

That is, the molten steel temperature T _Y and the side weir preheating temperature T in the pool are satisfied so as to satisfy the equations (1) and (2).
By controlling _S , the generation of hot bands can be suppressed to prevent breakage of the slab, and it is possible to prevent unsolidification of the slab and prevent breakout and chip edge loss for a long time. This enables stable casting of. 2 and 3 exemplify a twin-drum type continuous casting apparatus 1 for a thin metal strip embodying the present invention. A pair of cooling drums 2 and 3 forming the main part of the apparatus are used to cool water like circulating water. While being cooled by the medium, they are rotationally driven in opposite directions (directions of arrows) at the same rotational speed by a drive mechanism (not shown).

At the upper part of the gap between the cooling drums 2 and 3, there is formed a hot water pool portion 6 whose side surfaces are partitioned by side dams 4 and 5 (only one of which is shown). The molten steel (generally, molten metal) is supplied into the pool 6 by the nozzle. The molten steel supplied into the basin 6 is stored in the drums 2 and 3
Where it cools and solidifies to form shells 8 and 9, which drums 2 and 3 are driven to rotate in the direction of the arrow to pass through the narrowest gap between the drums 2 and 3, Upon receiving the pressing force, a strip-shaped slab S is continuously sent out downward. The cast slab S sent out is further cooled while being guided by a pinch roller or the like (not shown), and finally wound up on a coiler.

FIG. 3 is a schematic diagram for explaining the temperature control of the side weir.
It is a figure. Add to side weirs 4 and 5 (only 4 is shown) in the figure.
An electric heater is embedded as the heating device 10,
The temperature of the molten steel in the ridge 6 is detected by the temperature measuring device 11.
In addition, the surface temperature of the side weirs 4 and 5 is also measured by the temperature measuring device 12.
Is detected. Detected temperature of molten steel M (T_Y) And
And surface temperature of side weir (T_S) Signal is sent to the controller 13
Is input to the control device 13, and both signals are expressed by the above equation 2
The side weir temperature (T_S) Satisfies Equation 2
Heating device for side weirs 4 and 5 so that the temperature control signal is added
It is output to 10. For example, SUS304 (liquidus temperature T
_m= 1455 ° C), the temperature of molten steel (T _Y) Is 150
0 ℃, temperature of side weir (T_S) Is 1450 ° C,
Side weir temperature (T_S) Is too high, so electric heater 1
1 is stopped and the temperature of molten steel (T_Y)But
1500 ℃, side weir temperature (T_S) Is 1200 ℃
The temperature of the side weir (T_S) Is too low,
The signal that increases the power supplied to the target 11 is output.

The temperature of the side weir decreases if the side weir is not heated because heat radiation is dominant. Therefore, the cooling control of the side weir temperature is omitted in the above.

[0015]

EXAMPLES SUS304 (liquidus temperature T _m : 1455)
As shown in Table 1, the molten steel temperature T _Y and the side weir temperature T _S after preheating are changed variously as shown in Table 1, and are poured into the pool 6 of the continuous casting apparatus 1 shown in FIG. 130m / mi
A slab with a n of 1.6 to 5.0 mm was cast.

The cooling drums 2 and 3 have a diameter of 1200 mm and a width of 8
As shown in FIG. 3, the temperature of the molten steel continuously injected from the pouring nozzle 7 into the molten metal pool is measured by the temperature measuring device 10 as shown in FIG.
The temperature of the side weir 3 was controlled by the controller 13 based on the temperature data.

[0017]

[Table 1]

As shown in Table 1, the cast pieces cast under the conditions other than the stable casting area shown in FIG. 1 are defective in edge shape due to missing edges (Sample No. 1-1, 4-1) or cast by hot band. One piece (Sample No. 1-5, 2-3, 3, 4-4)
In addition, the casting was interrupted due to the occurrence of breakout (Sample No. 5). On the other hand, in each test piece satisfying the conditions of the present invention, the amount of hot band generated can be suppressed to less than 0.05 per drum rotation (Rev) (no cutting of the slab), and the unsolidification of the slab is also possible. Did not occur.

An experiment similar to the above was conducted with steel types other than SUS304 (SUS308, 310, 430),
Similar results were obtained.

[0020]

As described above, according to the present invention, by suppressing the generation amount of hot bands to a low level, it is possible to prevent the slab from breaking and to prevent the slab shape defect due to the non-solidification of the slab. It enables stable casting for a long time and has an extremely large industrial effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a molten steel temperature and a side dam temperature in continuous casting of a thin metal strip.

FIG. 2 is a schematic view showing a state of twin drum type continuous casting.

FIG. 3 is a schematic partial cross-sectional view showing a temperature control system for a side weir of the present invention.

[Explanation of symbols]

 1: Twin-drum type continuous casting device 2, 3: Cooling drum 4,5: Side weir 6: Hot water pool portion 7: Pouring nozzle 8, 9: Solidification shell 10: Heating device 11: Molten steel temperature measuring device 12: Side Weir surface temperature measuring device 13: control device 14: tundish S: cast slab M: molten steel

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshimori Fukuda 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (2)

[Claims] 1. A method for producing a metal ribbon by cooling and solidifying a molten metal supplied to a molten metal pool portion comprising a pair of cooling drums and side dams, wherein a temperature T of the molten metal in the molten metal pool portion _Y (° C) and temperature T of the surface of the side dam
A continuous casting method for a metal ribbon, characterized in that _S (° C) is maintained in a temperature range that satisfies the following formulas (1) and (2). T _m + 10 ≦ T _Y ≦ T _m +70 (1) 2 × T _m −T _Y −140 ≦ T _S ≦ 2 × T _m −T _Y +10 (2) where T _m : Liquidus temperature (℃) of molten metal in the pool 2. An apparatus for producing a metal strip by cooling and solidifying a molten metal supplied to a molten metal pool portion comprising a pair of cooling drums and side weirs, wherein a side weir heating device (1
0), a temperature measuring device (11) for detecting the temperature of the molten metal in the basin, a temperature measuring device (12) for detecting the surface temperature of the side weir, the temperature of the molten metal and the temperature of the side weir surface layer. And a control device (13) for outputting a temperature control signal to the side weir heating device (10), the continuous casting device for metal strips.