JPH0280160A - Twin roll type continuous casting method and apparatus thereof - Google Patents

Abstract

PURPOSE:To prevent the development of defect such as penetration of molten steel, edge break and crack in a cast strip, caused by developing gap between a roll and a short side weir by suitably controlling rolling reduction force of the rolls at the time of starting continuous casting when the strip is continuously and directly cast from the molten steel with twin roll type continuous casting apparatus. CONSTITUTION:The molten steel 5 is cast into pouring basin part constituted with two rolls 1, 2 and the short side weirs 7 between the rolls from a nozzle 3, and both rolls 1, 2 are mutually and reversely rotated to continuously cast the strip 10 with the solidified shell C formed at the narrow gap. In this case, preceded the start of casting, the gap between both rolls 1, 2 is set to the prescribed value with an energization device 15 by using a motor 26 and continuous casting is started. The rolling reduction force developed with the development of the solidified shell in the molten steel 5 at the gap between both rolls is detected with a load detector 16, and by adjusting the gap between both rolls, which the detected value is apt to widen, to the suitable value with drive of the energization device 15, it is prevented that the yield of the continuous cast strip 10 is lowered dy developing the defect of the penetration of the molten steel 5 from the gap and the other edge break, crack in the cast strip 10, etc., caused by developing the gap between both rolls 1, 2 and the short side weirs 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a twin-roll continuous casting method and apparatus for manufacturing a thin plate material by rotating a pair of rolls arranged in parallel in directions facing each other.

[Conventional technology]

A twin-roll continuous casting machine forms solidified shells on the surfaces of both rolls while injecting molten metal between the rolls, and rotates the rolls in directions facing each other to form the two solidified shells into the narrowest part of the twin rolls. This is a continuous thin plate casting machine that manufactures thin plates by crimping them in the gaps.

Here, a schematic diagram of a typical example of a twin-roll continuous casting machine is shown in Fig. 6.
As shown in the figure. Molten metal is supplied between the two rolls 1 and 2 from a jet hole 4 of a nozzle 3, and a molten metal pool 5 is formed. This PIj hot water pool 5 is pooled in a space formed by combining a long side weir 6 and a short side weir 7 with two rolls 1 and 2 without a gap. The long side weir 6 and the short side weir 7 are made of a heat-retaining refractory, and prevent the temperature of the molten metal in the molten metal pool 5 from decreasing. The molten metal cools over time on the surface of the roll 1゜2, forming a solidified shell 8.
．． 9 is shaped, and by rotating the rolls 1 and 2 in the direction of the arrow, the twin rolls are pressed together at the narrowest gap, and a thin plate 10 is manufactured.

Now, as shown in Japanese Utility Model Application Publication No. 58-157249 (hereinafter referred to as Conventional Example 1), a method of continuously manufacturing thin plates using twin rolls is a method of manufacturing slabs using a conventional continuous slab casting machine. Compared to the case where a thin plate is obtained by rolling this, it is an extremely economical method because a thin plate can be produced in one step from the molten metal.

In such a twin roll type continuous casting machine, the present technology is capable of sealing the molten metal between the weir for pooling the molten metal between the two rolls, that is, the long side weir or the short side weir described in Conventional Example 1 above, and the rolls. This has become the most important issue for achieving the goal.

In Conventional Example 1, a method is adopted in which a fluid such as inert gas or oil is supplied to the roll and the molten metal in order to ensure the molten metal seal.

However, when the solidified shell that has been cooled and shaped by two rolls is pressed together at the narrowest gap between the twin rolls, a separating force acts to separate the two rolls.

Due to this separation force, in the conventional example 1, the set gap between the two rolls changes. Therefore, a gap is created between the roll surface and the yield, especially between the short side weir and the joint between the rolls. If this gap becomes large, molten metal will infiltrate and solidify into the area, damaging the short side weir and making it impossible to continue normal operation. This problem occurs not only in the conventional example 1 in which the entire short side weir is installed inside both end faces of the roll, but also in cases in which a part of the short side weir is installed inside both ends of the roll. Research is also being conducted into practical use of a type of continuous casting machine that presses the short side weir against the end face of the roll, but in this type of continuous casting machine, the material of the short side weir is metal, and the part that contacts both sides of the roll is metal. The parts that come into contact with the molten metal are made of refractory material, so when the set gap between the two rolls increases, the molten metal comes into contact with the metal part of the short side weir and solidifies, creating a large resistance force when it is sent downward and crimped. Occur. This force not only increases the gap between the rolls but also pushes the short side weir wider in the roll axis direction.

A gap is created between the short side weir and the roll end face.

Even in this type of continuous casting machine, an increase in the roll gap must be avoided.

A typical method for supporting the rolling force acting between the rolls is disclosed in Japanese Unexamined Patent Publication No. 60-83747 (hereinafter referred to as Conventional Example 2).
The method shown in ) is used.

That is, one roll is fixedly attached to a stand, and the other roll is brought close to or separated from this roll using a screw or the like, and a gap between the rolls is set. The rolling force is detected by a load detector, and the rotation speed of the roll is controlled based on the detected value so that the rolling force reaches a target value.

In the apparatuses of Conventional Examples 1 and 2, it is not specified how to start casting.

In Japanese Utility Model Application Publication No. 58-170149 (hereinafter referred to as conventional example 3) and Japanese Utility Model Application Publication No. 58-189060 (hereinafter referred to as conventional example 4), a dummy bar is inserted into the gap at the closest portion of a stopped roll. It has been proposed to start pouring molten metal into the space formed by the dummy bar, rolls, and short side weir, and after forming a certain amount of molten metal pool, start rotating the rolls and start casting. .

[Problem to be solved by the invention]

After forming a molten metal pool in the roll as in the conventional method,
In the method of starting the rotation of the rolls and performing T4 construction, it is very difficult to determine the timing to start pouring and to form a suitable solidified shell and then to start drawing. has become a fatal flaw. That is, if drawing is started too early, the poured molten metal will still be in an unsolidified state at the upper end of the dummy bar, and if the dummy bar is started in that state, the slab will break and the molten metal will leak, resulting in a breakout. Furthermore, if the timing is too late, the shell solidified between the rolls becomes thicker than the target thickness of the slab, that is, the value of the set gap between the rolls, resulting in the following problems.

(1) A solidified shell larger than the closest point between the rolls is rolled between the rolls, and an excessive load acts between the rolls, which places a load on the casting equipment, exceeding the capacity of the roll rotation motor and causing it to trip. Casting may be stopped. In addition, in order to prevent this, it is necessary to increase the capacity of the motor and increase the rigidity of a device similar to a rolling mill, resulting in very large and expensive equipment.

(2) When an excessive load is generated and the gap between the rolls is expanded, molten metal is inserted between the short side weir and the rolls, damaging the short side weir and making it impossible to continue normal operation.

(3) The oversized solidified shell is rolled between the rolls to the closest point between the two rolls, and the rolled slab expands in the axial direction of the rolls. The short side weir in contact with the end face of the roll is
As the roll expands in the axial direction, a gap is created between the roll end face and the short side weir, and molten metal may enter this area, damaging the roll or short side weir, or the end of the slab may be restrained by the hot water pouring part. My ears are cut off and my ears are cut off.

Experimental results show that when making 12 thin plates with a thickness of 3rrrn, the optimum timing for starting is 2 to 3 seconds, and it is impossible to ensure reliable starting manually.

The reality is that the above-mentioned problem has not been fundamentally solved even if the shape and structure of the dummy bar are modified as shown in Conventional Examples 3 and 4.

An object of the present invention is to provide a twin-roll continuous casting method and an apparatus therefor, which enable stable continuous casting of thin plates by appropriately controlling the roll rolling force at the start of casting.

[Means to solve the problem]

In order to achieve the above object, the method of the present invention injects molten metal between a pair of rolls arranged in parallel, generates a solidified shell of the molten metal on the surface of the rolls, and moves the rolls in directions facing each other. A large series of twin rolls for continuously manufacturing thin plates by rotating the solidified shell at the narrowest gap between the rolls and keeping the rolling force of the rolls constant.
In the I-forming method, the rolls are rotated in advance before casting is started, and a rolling force smaller than the target rolling force in a steady state is maintained between the start of casting and the time when the rolling force of the rolls is kept constant. The feature is that the vf construction conditions have been selected.

Further, the casting conditions include starting casting while rotating the roll at an initial roll speed calculated by the following formula, and applying a rolling reduction force of the roll when the cooling length of the molten metal by the roll reaches a target value. is to hold constant.

V, = (0.05-0.30) ・(Vmax-Vm
in) +Vmin. = Qmax - (0,05 ~
0.30) ・(Qroax −Qmin) Here, v
o: Initial roll speed (m/m1n) Ω: Cooling length of molten metal by roll (mIl) A, B: Coefficient of solidification rate equation D: 172 value of initial roll gap (Oll) D'
:Thickness of the light solid shell at the point closest to the roll when the rolling force reaches the target value (■) Furthermore, the casting conditions are such that while the roll is rotated at a speed that achieves the target rolling force at the target cooling length, When casting is started and the cooling length of the molten metal by the rolls reaches an initial cooling length calculated by the following formula, the rolling force of the rolls may be held constant.

Here, the initial cooling length of the molten metal by Qo two rolls (mm
) vo: Target roll circumferential speed (m/m1n) A, B: Coefficient of solidification rate formula D = 1/2 value of initial roll gap (tomo) D': Roll closest point when rolling force reaches target value Thickness of solidified shell at (m+n) Furthermore, the apparatus of the present invention includes a pair of rolls arranged in parallel and rotating in directions facing each other, and a short side weir and a roll provided in contact with the outer peripheral surface of the rolls. a nozzle for supplying molten metal into a puddle formed by a nozzle, a rolling part for rolling down the rolls in a direction toward each other, a detection part for detecting the rolling force, and a rotation of the rolls at a predetermined time from the start of casting. a first setting section that sets the initial roll speed calculated by the following formula; and a second setting section that sets the rotation of the roll based on a signal from the detection section after a predetermined time has elapsed. This is what I did.

V, = (0.05-0.30) ・(Vmax-Vm
in) a first setter that sets the cooling length to be rejected by +Vmin to an initial cooling length calculated by the following formula, and a first setting device that sets the cooling length based on a signal from the detection section after a predetermined time has elapsed. and a second setting device.

Qo=Qmax-(0.05~0.30)・(Q
max -Qn+in) Here, Vo: Initial roll speed (m/ff1in) Q = Cooling length of molten metal by roll (mm) A, B: Coefficient of solidification rate formula D: 172 value of initial roll gap (mm) D':
The thickness of the solidified shell at the closest point of the rolls when the rolling force reaches the target value (Inm) Furthermore, the apparatus of the present invention includes a pair of rolls arranged in parallel and rotating in directions facing each other;
a nozzle that supplies molten metal to a pool formed by the roll and a short side weir provided in contact with the outer peripheral surface of the roll;
a rolling part that rolls down the rolls in a direction toward each other;
A detection part detects the rolling force, and a detection part that detects the rolling force is used for cooling the molten metal by the rolls at a predetermined time from the start of casting.
m1n) A, B: Coefficient of solidification rate formula D: 172 value of initial roll gap (nun) D'
: Thickness of the solidified shell at the point closest to the rolls when the rolling force reaches the target value (mm) [Function] The casting speed, that is, the number of revolutions of the rolls, depends on the steel type, the thickness of the slab, and the height of the /8 molten metal between the rolls. An appropriate value can be obtained by substituting the cooling length of the molten metal by the rolls determined from above into the solidification rate equation obtained by measurement in advance.

A specific calculation method will be shown. The casting speed V is determined by the cooling length Q of the molten metal by the rolls and the cooling time, where v;
It is calculated as follows: casting speed (m/min) Q; cooling length (mm) t; cooling time (sec). Here, the cooling time is defined as the time the roll is in contact with the molten metal. In order for a slab to be formed, solidification must be completed by the closest point of the rolls, and the solidification rate formula obtained by pre-measurement % formula % Here, D: Solidified shell thickness = initial roll 1/2 of the gap
Values (mm) A, B: Calculate the cooling time t using the constants. ■From the formula, it becomes,■′
By substituting the formula into formula (2), the casting speed Vmax at which the rolling force becomes O can be obtained as follows. When the speed is lower than this, the thickness D' of the solidified shell at the closest point of the rolls is 1/2 of the roll gap.
It will become larger and rolled. At this time, there is a certain relationship between the rolling force generated between the rolls and (D'-D), and if the target rolling force is determined, D' will be determined. Substituting D' into equations ``■'' and ``2'' yields.

As is clear from the above explanation, as the target reduction force increases, +D' increases, and Vwin has the property of decreasing according to the equation (2). This relationship is shown in FIG.

The basic casting condition is to perform casting at this casting speed V win.

When starting casting, this calculated casting speed Vmax
Below, the rolls are rotated in advance at a speed of V+++in or more, and the injection of molten metal between the rolls is started. From the experimental results, the rotational speed v0 of this pre-rotated roll is (0.05~0.30)・(V wax
-V m1n) + V win is found to be appropriate. If the roll rotation speed is 0.05・(V wax −V m1n) + V m
If it is set to less than in, the target rolling force may be exceeded when pouring starts due to variations in the hot water temperature, hot water surface height, etc., and the rolling force applied to the slab increases as described above. It is not possible to completely eliminate the problems caused by
) When set larger than +Vmin, it takes a long time to reach a predetermined casting speed (=Vmin) and rolling force after the start of constant rolling force control. Furthermore, 0,8・
If the speed is higher than (Vmax - Vmin) + Vain, in addition to the above problems, when pouring starts, the initial molten metal will not solidify sufficiently, and a Pa molten metal pool will be formed.
Problems such as inability to form slabs may occur. For the above reasons, the initial casting speed is V.

(0.05~0.30)・(Vmax−Vmin)+
It is appropriate to set it to Vmin. This range is indicated by diagonal lines in FIG.

From the moment pouring starts, the entire amount of the molten metal cannot pass through the gap at the point closest to the rolls, and at the same time the surface of the molten metal rises, a solidified shell begins to form on the roll surface. When a solidified shell is formed across the gap between the closest points of the rolls, the initial pouring amount is selected to be larger than the casting amount, so the molten metal level rises between the rolls at a speed determined by the difference between the two. When a molten metal pool is formed and the thickness of the solidified shell becomes larger than the gap between the rolls, the separation force applied between the rolls, that is, the rolling force applied to the slab increases.

The amount of poured molten metal is adjusted so that it becomes equal to the amount of casting when the level of the molten metal pool reaches a target value.

When the level height reaches the target value, the rolling force will be smaller than the target rolling force, so if you start controlling the roll speed so that the rolling force reaches the target value, the casting speed will decrease and the rolling force will reach the target value. Approach the target value from a value lower than the target value.

The above is an explanation of the method of controlling the casting speed so that the rolling force is constant, but a method of controlling the cooling length Q in order to keep the rolling force constant can also be adopted. In this case, casting can be started as follows.

When the cooling length Q is increased while the roll is rotating at the target casting speed V, the thickness of the solidified shell at the point closest to the roll becomes D', which is the length Q ll1in,
Q Wax exists. These transform the 0107 formula to 1000°7・(D+B)・・・・・・・
00m1°=60 A,,ax=1000"V (D' +B) 2
, , , , ■t60 A is given. When Q≦Q min, the rolling force is 0, and when Ω=f2wax, the rolling force is equal to the target value. Therefore, when starting casting, the rolls are rotated at the target casting speed and the injection of molten metal between the rolls is started. Q = Q0 = Qm before starting cooling length control
ax −(0,05~0.30)N(Qrnax−Ll
If we create a state of
ax and the rolling force is smaller than the target value.

After the start of the control, Q increases, and the rolling force approaches the target value from a value lower than the target value.

In order to form a good slab, if the rolling force per unit length of the slab in the l11iT direction exceeds 50 kgf/mta, cracks may occur due to the slab being rolled down between rolls. Therefore, it is necessary to suppress the rolling force applied to this slab to 50 kgf/mm or less.

This makes it possible to suppress the excessive load between the rolls that occurs in the initial stage of casting, and to carry out # production without causing the operational problems described above.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the two rolls 1, 2 are housed in a stand 14, each supported by a bearing box 11, 12 supporting its roll shaft 17,18.

This stand 14 has a cover member 19 on the upper side, and by removing this cover member 19, the roll 1,
It is now possible to perform two rearrangements. Two bearing boxes 11 and 12 are built into the stand 14, and between the stand 14 and the bearing box 11 is a biasing device 15 consisting of a worm jack driven by an electric motor 26.
A load detector 16 is provided between the stand 14 and the bearing box 12, respectively. Note that the urging device 15 constitutes a rolling section, and the load detector 16 constitutes a detecting section.

The molten metal 5 is delivered to two rolls 1 and 2 by the jet hole 4 of the nozzle 3.
It is injected between the short side weir 7 and pooled.

Melt? ! 5 is cooled by rolls 1 and 2, and solidified shells 8 and 9 as shown in FIG. Ru.

Prior to the start of casting, the urging device 15 is operated to set the roll gap to a desired value.

In this state, when a rolling force is generated to press the solidified shell at the narrowest gap C between the twin rolls 1 and 2 and the detected value of the load detector 16 becomes P, the electric motor 26 is activated as follows. By driving and controlling the roll gap, changes in the gap between the twin rolls 1 and 2 are reduced.

That is, the amount of change in the roll gap when the rolling force P is δ,
Assuming that P and δ are proportional, let the coefficient be K. If P is known, then the gap change δ between the twin rolls 1°2 can be calculated using the formula δ = P/, and the control gain α is added to this. is applied to obtain the necessary stroke of the biasing device 15.

The magnitude of the control gain α is selected within the range of 0 to 1 so that the control characteristics do not become unstable. α and δ are compared with the current stroke, and if there is a difference, the rotation speed of the electric motor 26 is controlled so as to eliminate the difference.

In other words, when the rolling force P is generated, the roll gap is reduced to α・P/
The rolling force P is controlled to be reduced relative to the roll gap before it is generated.

By controlling in this manner, the apparent spring constant Kc of the roll gap increases to /(1-α).

Next, a method of controlling the rotational speed of the rolls 1 and 2 so that the rolling force P is constant according to changes in the signal P from the load detector 16 will be explained.

Rolls 1 and 2 are moved to a pinion stand 32 by a motor 36.
, 33, and shafts 34, 35, the setting value P of the setting device 37 is set so that the reduction force P becomes constant. It becomes possible to adjust and control the speed of the motor 36 by the arithmetic and control unit 38 by comparing the speed of the motor 36 with the speed of the motor 36.

At the start of casting, the aforementioned casting speed■. The rolls 1 and 2 are rotated by a signal from the speed setting device 39 so that the melt pouring starts. In advance, the time required from the start of pouring until the height of the molten metal pool reaches the target value. Understand the
The time from the start of pouring is τ. Until t4, the manufacturing speed is kept constant and τ becomes τ. When this happens, the signal to the drive device 36 is switched to the signal from the arithmetic and control device 38 to control the roll rotation speed. The timing τ0 for starting this control is (1) manually by visually detecting the scene height, (2) automatically by detecting the scene height by a sensor, and (3) measuring the elapsed time from the start of pouring by the timer hand. It may be appropriate to adopt means such as automatic determination based on the following information.

The setting device 37 for the initial rolling force P0 and the initial fJI manufacturing speed v
The setting section of the 0 setting device 39 is installed on the operation panel surface,
The optimum value can be easily set according to the type of molten metal, plate width, initial roll gap, etc.

Note that the setting device 39 constitutes a first setting section, and the setting device 37 and the arithmetic and control device 38 constitute a second setting section.

The casting results according to the above embodiment will be shown in comparison with a conventional method in which the rolls are stopped and pouring is started.

(1) Conventional method [twin roll continuous casting machine] Roll diameter: 800mm, width: 600n+m [Casting conditions] 5US304. Roll gap: 2.1mm Casting temperature:
1500°C Target rolling force: 25 tons Target casting speed: 30 m/min Two seconds after starting pouring, the rolls begin to rotate and increase the speed to the target speed. FIG. 2 shows a chart of the rolling force between the rolls at the initial stage of casting conducted under these conditions. As shown in Figure 2, an abnormally large rolling force between the rolls is generated as soon as the rolls start rotating, and the rolling force cannot be stabilized by controlling the casting speed, and the rolling force is larger than the set roll gap. A slab of 4 mm~2, 81n01 thickness was cast. In addition, it was observed that molten metal was inserted between the roll and the side dam, and the ends of the slab were cut.

Further, the current value of the motor that rotates the rolls became excessive and tripped, causing casting to stop at a casting length of 10 m.

(2) Method of the present invention [twin roll continuous casting machine] Roll diameter: 800 mm + width: 60011 m [Casting conditions] 5US304. Roll gap: 2.1mm Casting temperature:
1500'C Target rolling force: 25 m on Target casting speed: 30 n/min Roll peripheral speed before starting casting: 31 m/minVma
x=”40m/min, Vmin=30m/min
For n, V, = 0.1 ・(Vmax-Vmin)
Select +Vmin= 31m/min and 1 water speed■.

Rotate the roll in advance and start pouring. FIG. 3 shows the rolling force Char 1 between the rolls at the initial stage of casting performed under these conditions. As shown in Figure 3, the rolling force between the rolls rises smoothly from 0 to 22 tons, and there is no abnormal increase in load, making it possible to perform stable casting. was able to complete. Also, almost the same as the roll gap 2.
It was possible to obtain a slab with a thickness of 2+ nm, and no abnormality at the end of the slab was observed as in the conventional method. In the above embodiment, the rotational speeds of the rolls 1 and 2 were controlled in order to keep the rolling force P constant; however, the rotational speed of the rolls 1 and 2 was not limited to this. Controlling the height of the surface of the hot water pooled between them (2) An arc-shaped plate for suppressing the start of solidification is placed along the surface of the rolls 1 and 2, including the portions that contact the hot water surface, and the position thereof is controlled.

Even if appropriate means such as the above are adopted, the same effects as in the above embodiment can be obtained.

FIG. 5 shows an embodiment of the above (1). This example will be described below. However, description of the same parts as in FIG. 1 will be omitted.

The molten metal 5 in the tundish 40 is injected into the roll t1 through the gap between the stopper 41 and the nozzle 4. The stopper 41 is fixed to an arm 42 which is attached to the tundish 40 so as to be movable up and down, and the stopper 41 is moved up and down by rotating a screw that engages with a nut 43 of a part of the arm 42 using a drive device 44. It has become.

Next, a method for controlling the height of the molten metal pool in accordance with changes in the signal P from the load detector 16 so that the rolling force P is constant will be described.

The signal P from the load detector 16 is output to an arithmetic device 38', and the set value P of the setting device 37 is determined in the arithmetic device 38'.

Which comparison is made to calculate the change ΔQ in the cooling length Q so that the reduction force P is constant, and the signal ΔQ is sent to the calculation control device 45.
Output to. The arithmetic and control device 45 uses ΔQ to send a signal to the drive device 44 so that the opening degree of the stopper 41 corresponds to the change in the amount of molten metal poured from the tundish 40.

In this way, the rolling force P becomes the set value P. If it is larger, the stopper 41 is lowered to reduce the amount of molten metal poured from the tundish 40 to lower the scene height in the molten metal pool, and if the reduction force P is the set value P, if it is smaller, the opposite operation is performed to reduce the reduction force. Control is performed so that P is constant.

At the start of casting, rolls 1 and 2 are adjusted to reach the target casting speed.
Rotate and drive to start pouring. In advance, the time required from the start of pouring for the cooling length Q to reach the above value. , the opening degree pattern of the stopper 41 is grasped, and this pattern signal is output from the signal generator 46 to the hospital motion device 44 to control the opening degree of the stopper 410. The time τ from the start of pouring is τ
. When this happens, the signal to the active device 44 is switched to the signal from the arithmetic and control device 45 to control the cooling length ρ.

The above initial pressure reduction force P. Setting f! The setting section of the It37 and opening pattern signal generator 46 is installed on the operation panel surface, so that optimum values can be easily set according to the type of molten metal, plate width, initial roll gap, etc.

In this embodiment, the signal generating device 46 uses the first setting section as the setting device 37, the arithmetic device 38' and the arithmetic control device 4.
5 is an oval second setting portion.

〔Effect of the invention〕

According to the present invention, it is possible to prevent the generation of excessive rolling force at the initial stage of VT casting, and to prevent problems with casting equipment, melting due to gaps between the rolls and side dams, and defects such as edge cuts and cracks in the slab. It becomes possible to prevent this, and the following effects can be expected.

(1) Excessive load does not act between the rolls.

There is no excessive load on the casting equipment, and troubles such as tripping of the motor that rotates the rolls do not occur in the V4 manufacturing equipment.
Enables stable operation for long periods of time.

(2) No need for equipment as rigid as a rolling mill, resulting in lower equipment costs.

(3) The gap between the rolls does not expand due to an increase in load, and the molten metal does not get inserted between the short side weir and the rolls, thereby preventing damage to the short side weir.

(4) Hot water does not leak between the end face of the roll and the short side weir, so damage to the roll or the short side weir, and end abnormalities and cracks of the cast slab do not occur.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing an embodiment of the present invention, Fig. 2 is a chart for measuring the rolling force of a slab at the start of g velocity using a conventional method, and Fig. 3 is a casting start method according to the present invention. Fig. 4 is a graph showing the relationship between initial casting speed and target reduction force, Fig. 5 is an overall configuration diagram showing another embodiment of the present invention, and Fig. 6 is a chart for measuring the rolling force of the slab at the start. FIG. 2 is an explanatory diagram showing the principle of manufacturing a thin plate material using a twin-roll continuous caster. 1.2... Roll, 3... Nozzle, 4... Spout, 5... Molten metal, 7... Short side weir, 8.9... Solidified shell, 10... Thin plate, 11.12...Bearing box, 14...
·stand. 15... energizing device, 16...'RM detector, 17.
18... Roll axis, 2G... Electric motor, 36... Motor, 37.39... Setting device, 38.45... Arithmetic control unit, 41... Stopper. 44... Active device, 46... Signal generator.

Claims (1)

[Claims] 1. Injecting the molten metal between a pair of rolls arranged in parallel,
While producing a solidified shell of the molten metal on the surface of the roll,
A twin-roll continuous method in which the rolls are rotated in directions facing each other to press the solidified shell at the narrowest gap between the rolls, and the rolling force of the rolls is maintained constant to continuously produce a thin plate material. In a casting method, casting is started after the rolls are rotated in advance, and a rolling force smaller than a target rolling force in a steady state is maintained between the start of casting and the time when the rolling force of the rolls is kept constant. A twin roll continuous casting method characterized by the selection of casting conditions. 2. In the method according to claim 1, the casting conditions include starting casting while rotating the roll at an initial roll speed calculated by the following formula, and setting the cooling length of the molten metal by the roll to a target value. A twin-roll continuous casting method in which the rolling force of the rolls is held constant when . V_0=(0.05~0.30)・(V_m_a_x-
V_m_i_n)+V_m_i_nV_m_a_x=(
60l/1000)・(A/[D+B])^2V_m_
i_n=(60l/1000)・(A/[D'+B])
^2 Here, V_0: Initial roll speed (m/min) l: Cooling length of molten metal by roll (mm) A, B: Coefficient of solidification rate formula D: 1/2 value of initial roll gap (mm) D': Thickness (mm) of the solidified shell at the point closest to the roll when the rolling force reaches the target value. 3. In the method according to claim 1, the casting conditions are such that the rolling force reaches the target rolling force when the target cooling length is reached. Casting is started while rotating the roll at a speed that is constant, and when the cooling length of the molten metal by the roll reaches the initial cooling length calculated by the following formula, the rolling force of the roll is held constant. Twin roll continuous casting method. l_0=l_m_a_x-(0.05~0.30)・(
l_m_a_x−l_m_i_n)l_m_a_x=(
1000・V_0/60)・([D′+B]/A)^2
l_m_i_n=(1000・V_0/60)・([D
'+B]/A)^2 Here, l_0: Initial cooling length of molten metal by roll (m
m) V_0: Target roll circumferential speed (m/min) A, B: Coefficient of solidification rate formula D: 1/2 value of initial roll gap (mm) D': Roll latest when rolling force reaches target value Thickness of solidified shell at contact point (mm) 4. Molten metal formed by a pair of rolls arranged in parallel and rotating in directions facing each other, and a short side weir provided in contact with the outer peripheral surface of the rolls and the rolls. A nozzle that supplies molten metal to a pool, a rolling part that rolls down the rolls in a direction toward each other, a detection part that detects the rolling force, and a rotation of the rolls at a predetermined time from the start of casting using the following formula. A twin-roll type continuous comprising: a first setting section that sets the calculated initial roll speed; and a second setting section that sets the rotation of the roll based on a signal from the detection section after a predetermined period of time has elapsed. Casting equipment. V_0=(0.05~0.30)・(V_m_a_x-
V_m_i_n)+V_m_i_nV_m_a_x=(
60l/1000)・(A/[D+B])^2V_m_
i_n=(60l/1000)・(A/[D'+B])
^2 Here, V_0: Initial roll speed (m/min) l: Cooling length of molten metal by roll (mm) A, B: Coefficient of solidification rate formula D: 1/2 value of initial roll gap (mm) D': Thickness of the solidified shell at the point closest to the rolls when the rolling force reaches the target value (mm) 5. A pair of rolls arranged in parallel and rotating in directions facing each other, and a A nozzle for supplying molten metal to a pool formed by a short side weir and a roll, a rolling part for rolling down the rolls in a direction toward each other, a detection part for detecting the rolling force, and a casting start. A first step that sets the cooling length to be cooled by the roll in a predetermined time from
and a second setting device that sets the cooling length based on a signal from the detection section after a predetermined time has elapsed. l_0=l_m_a_
x-(0.05~0.30)・(l_m_a_x-l_
m_i_n)l_m_a_x=(1000・V_0/6
0)・([D'+B]/A)^2l_m_i_n=(1
000・V_0/60)・([D+B]/A)^2 Here, l_0: Initial cooling length of molten metal by roll (m
m) V_0: Target roll circumferential speed (m/min) A, B: Coefficient of solidification rate formula D: 1/2 value of initial roll gap (mm) D': Roll latest when rolling force reaches target value Thickness of solidified shell at contact point (mm)