JPH0636970B2 - Belt type continuous casting method and apparatus for suppressing relative slippage of short side mold - Google Patents

Description

The present invention relates to a belt-type continuous casting method for continuously producing a thin metal strip from a molten metal in a casting space defined by an endless belt and a short-sided mold. And equipment.

[Conventional technology]

Recently, from molten metal such as molten steel, several mm to several tens, which is close to the final shape
A continuous casting method for directly producing a metal ribbon having a thickness of about mm has attracted attention. According to this method, the rolling process in multiple stages as in the prior art can be omitted, so that the process and equipment can be simplified. In addition, since the step of heating the material to the processing temperature between each step is essentially unnecessary, an energy saving effect can be expected.
One of such continuous castings is a twin belt system.

FIG. 6 is a diagram showing an outline of this twin belt type continuous casting machine. In this continuous casting machine, the molten metal in the tundish 1 is supplied from the nozzle 2 to the casting space. This casting space is formed by partitioning opposite sides of a pair of belts 4 made of a heat-resistant material such as steel running around pulleys 3 with short side molds 5 (see FIG. 7). Has been done. The molten metal poured into this casting space is cooled and solidified by the cooling box 6 and is carried out as the metal ribbon 7.

At this time, between the belt 4 and the short side mold 5 and between the short side mold 5
If there is a gap between each of the blocks 5a (see FIG. 7),
Molten metal is inserted there and casting burrs are generated. This cast burr serves as a starting point for limiting the thermal contraction or expansion of the solidified shell, and cracks occur around the cast burr.

Therefore, for example, in JP-A-60-180653,
As shown in FIGS. 7 (a) and 7 (b), the short-side mold 5 is fed into the casting space while tension is applied. The short-side mold 5 has a structure in which individual blocks 5a are connected by links 5b. Each block 5a is connected with a certain clearance before passing through the pulley 8 before coming into contact with the belt 4 and after exiting from the casting space. However, in the casting space, a compression force is generated by the tension pulley 9. Given. As a result, the adjacent blocks 5a are brought into close contact with each other and fed into the casting space to prevent the molten metal from being inserted into the gap between the blocks 5a.

[Problems to be solved by the invention]

In an ideal state, the short-side molds 5 in close contact with each other are conveyed in synchronization with the belt 4, and the molten metal injected in the casting space is between the blocks 5a of the short-side mold 5 and between the belt 4 and the short-side molds 5. It never plugs in between. Also, the belt 4,
Since the three members, the short-side mold 5 and the metal ribbon 7, proceed in synchronization, it is considered that the metal ribbon 7 is not subjected to shearing force from the mold.

However, the belt 4 and the short side mold 5 are used repeatedly and continuously. Therefore, when these are viewed microscopically, due to three-dimensional thermal deformation of the block 5a of the short-side mold 5 and the belt 4 and the trapping of minute foreign matter, the space between the blocks 5a of the short-side mold 5 and the belt A gap may occur between the short side mold 5 and the short side mold 5. On the other hand, when molten steel, for example, is used as the molten metal, it is unavoidable that the gap is inserted even if the gap is about 0.1 to 0.2 mm.

Further, the thermal behaviors of the belt 4, the short-side mold 5 and the metal ribbon 7 are different, including the difference in the physical property values, and the thermal behavior is problematic by simple design means. Is not so simple that it can be solved. FIG. 8 is a diagram for explaining the state at this time.

That is, even if each block 5a of the short-side mold 5 enters the meniscus portion 10 in synchronism with the belt 4, the thermal expansion behavior generated when receiving heat from the molten metal 11 differs between the two.
Therefore, a relative slip 12 occurs between the short side mold 5 and the belt 4. Due to this relative slip 12, the short side mold 5 is
As indicated by the white arrow in (b), the belt 4 slides with respect to the neutral point 13 as a boundary. The neutral point 13 is a point where the following equation is established.

F = P (y) + f (y) + B where F is the pushing force applied to the short-side mold 5 from above, W is the pressing force applied to the short-side mold 5 via the short-side mold holder 5c, and P ( y) is the frictional force between the belt 4 and the short side mold 5, f (y) is the frictional force between the short side mold 5 and the metal ribbon 7,
B is a braking force B applied to the short side mold 5 from below. The relative slip 12 at this time has a vector V ₁ as shown by a white arrow in FIG.

Since the solidified shell contracts during the solidification process, the belt 4
Relative slip occurs between and. Similarly, relative sliding also occurs between the short-side mold 5 and the metal ribbon 7. That is, since the molten metal 11 is pressed against the belt 4 and the short-side mold 5 by its static pressure, a surface pressure is generated, and a frictional force along the surface is generated on the contact surface due to the above relative slip. Has occurred. The neutral points 14 and 15 are determined by the balance between the relative slip and the frictional force.

Now, as shown in FIG. 7C, the vector of relative slip between the short side mold 5 and the belt 4 is V _1, and the vector of relative slip between the solidified shell and the belt 4 is V ₂ . When the vector of relative slip between the short-side mold 5 and the thin metal strip 7 is V ₃ , the following equation holds.

V ₁ + V ₂ = V ₃ This formula shows that the relative slip between the belt 4 and the solidified shell is
Since the area of the wide surface is much larger than that of the narrow surface and the slip is almost constant, V ₂ = C (constant value), and therefore V ₃ is indirectly controlled by controlling V _1. Show. That _{V 3 is} expressed as _V 3 ₌ V 1 + C. And the control at this time is in the opposite direction to V _3.
The vector V _{4 is such} that V ₄ | = | V ₃ |.

If the insertion occurs at the position 16 in the casting space having such a force relationship, the relative displacement between the metal ribbon 7 and the short-side mold 5 is restricted by the vector V ₃ . Therefore, the position where the insertion occurs at or near the meniscus portion 10
When there is 16, the shell strength of the cast flash portion is small and cracks occur in the thin metal strip 7. Therefore, if it is possible to control V ₃ to be small (that is, to reduce V ₁ ), cracking can be minimized. However, the direction and absolute value of V ₃ are different between the entrance and the exit of the casting space.

Therefore, the present invention, by giving a minute velocity difference vector to the short-side mold fed into the casting space, in the vicinity of the mechanical parts or at the site that has the greatest effect on quality, the relative slippage of the short-side mold with respect to the solidified shell is prevented. The purpose is to produce high-quality metal ribbon by controlling it to the minimum.

[Means for solving problems]

In order to achieve the object, the belt-type continuous casting method of the present invention is a metal strip obtained by cooling and solidifying a molten metal injected into a pool of pools partitioned by a pair of endless running belts and a short side mold. When manufacturing the, so as to eliminate the relative slip of the short-side mold to the belt in the vicinity of the meniscus or at the site that most affects the cracking of the solidified shell, running with a minute difference to the running speed of the belt. It is characterized in that the short-side mold is fed into the molten metal pool at a speed.

Here, the setting of the minute speed difference can be standardized on the basis of the relationship between the speed difference and the crack occurrence state of the metal ribbon after casting being analyzed in advance.

In addition, the belt-type continuous casting device for carrying out this method is to manufacture a metal ribbon by cooling and solidifying the molten metal injected into the molten metal pool part where the ends are partitioned by a short side mold between a pair of belts. In the belt type continuous casting machine, a common drive mechanism for driving the belt and the short side mold is provided, and the drive mechanism is directly connected to a drive pulley for driving the belt, and the belt and the short side mold are The drive mechanism is connected to the drive pulley that drives the short-side mold via a differential device so as to generate a minute difference between the traveling speeds.

Further, instead of making a minute difference between the traveling speeds of the belt and the short side mold by the differential device, a mechanism for giving a required torque can be attached to the short side mold.

〔Example〕

Hereinafter, the features of the present invention will be specifically described by way of examples with reference to the drawings.

FIG. 1 is a plan view showing a drive mechanism for a belt and a short side mold in an embodiment of the present invention, and FIG. 2 is a side view. In these figures, parts corresponding to the members shown in FIGS. 6 to 8 are designated by the same reference numerals.

The driving force generated by the main motor 20 is distributed and reduced by the distribution reduction gear 21. Part of the driving force is transmitted to the pulley 3 via the universal joint 22, and the belt 4 is driven so as to have a required casting speed. Distribution reducer
The rest of the driving force from 21 is transmitted to the short side mold drive pulley 25 via the universal joint 24 via the differential device 23, and drives the short side mold 5. The rotational speed of the driving force passing through the universal joint 24 is adjusted by the speed control device 26, the differential motor 46, and the differential device 23.

Here, there is a clearance between the blocks 5a of the short-side mold 5 in order to pass through the pulley 8 on the traveling path. On the other hand, each block 5a is sandwiched between the belts 4 and supports its own weight by the frictional force acting there. When this frictional force decreases, the block 5a slides down and the clearance increases. To prevent this,
A predetermined braking force is applied by the brake generating mechanism 27 to the short side mold 5 sent out from the casting space.

FIG. 3 shows a main part of the distribution reducer 21. That is, the input shaft 31 connected to the main motor 20 is connected via the gear group 32 to the output shafts 33 and 34 connected to the short side mold drive pulley 25 and the belt 4 pulley 3, respectively. And
The gear ratio of the gear group 32 is adjusted so that when the belt 4 and the short side mold 5 are driven without injecting the molten metal between the belts 4, the two run at the same speed.

FIG. 4 shows the main part of the differential device 23. The driving force from the distribution reduction gear 21 is input to the input shaft 4 via the universal joint 24a.
Enter 1 and rotate the bevel gear 42. The rotation of the bevel gear 42 is transmitted to the output shaft 45 via the bevel gears 43 and 44. Bevel gear 43
The shaft is attached to the large gear 48 via the bevel gear shaft 49, and revolves coaxially with the input shaft 41 and the output shaft 45. When the revolution speed is Δn, the rotation speed of the input shaft 41 is n ₁ , and the rotation speed of the output shaft 45 is n ₂ , the following relationships are established.

_{Δn = (n 1 + n 2} ) / 2 Namely, the rotational speed n ₂ rpm n ₁ of the input shaft 41 is output shaft 45
Therefore, the driving force of the distribution reducer 21 is the short side mold drive pulley.
Transmitted to 25.

The large gear 48 is decelerated by the differential motor 46 and the intermediate gear 47 at a reduction ratio i. Now belt 4 and short side mold 5
When and are fed into the casting space at a constant speed, Δn = 0 is controlled, and the rotation speed of the input shaft 41 becomes n ₁ = −n ₂ . Then
To provide a small speed difference between the belt 4 and the short side mold 5, west as the rotational speed n ₁ of the input shaft 41, the rotational speed of the output shaft 45 n ₂ from the _{n 2 '(n 2' ≠} n ₂ ), the rotation speed Δn ′ of the large gear 48 is determined by Δn ′ = (n ₁ + n ₂ ) ′ / 2. Therefore, the differential motor 46 is
The rotation speed is controlled to n'.i. The relationship between the speed of the belt 4 and the speed of the short side mold 5 is that the main motor 20 and the differential motor
Since it is replaced by the relationship of the number of revolutions of 46, the speeds of the both can be detected and the required speed control can be performed by the speed control device 26.

Next, advantages of the drive device of the drive device of the present embodiment will be described while comparing the case where the belt 4 and the short-side mold 5 are run by independent drive devices and the case where they are run by the drive device of the present embodiment. .

As a premise, the effective length of the mold is 3000 mm and the casting speed is
10 m / min, the temperature drop of the solidified shell was 500 ° C, the short side mold 5 was made of copper, and the temperature rise was 200 ° C. At this time, the shrinkage of the solidified shell during passage through the mold is 1.0 × 10 ^-5 × 500 × 30.
00 = 15 mm. Also, the elongation of the short side mold is 1.6 × 10 ^-5
X200 x3000 = 9.6 mm. Therefore, a total of 24.6 mm (= 15 + 9.6) of relative dimensional change occurs between the solidified shell and the short side mold.

On the other hand, the time required for the metal ribbon 7 to pass through the mold is 3000 / 10,000 /
60 = 18 seconds. Therefore, if the neutral point of the relative slip is approximately in the center, the average speed difference is (24.6 / 2) (18 /
2) = 1.4mm / sec, casting speed 167mm / sec (= 10,000 /
60%) is less than 0.8%. However, the order in which the speed can be controlled by a normal DC motor is about 1%, so 0.8
The control for keeping the ratio to 0.0% requires an accuracy of 0.08% or less, and such a minute speed difference cannot be performed by independent speed control of the motor for driving the short side mold 5.

On the other hand, in the case of the present embodiment, the speed difference Δυ
Is given by the following equation and can be adjusted by the control of the differential motor 46. However, k in the following equation is a constant.

Δυ = k (n ₁ −n ₂ ) / n ₁ = 2k Δn / n _1, that is, by adjusting the drive of the differential motor 46 by adjusting the drive speed difference Δn corresponding to the required speed difference Δυ.
It is possible to control the speed of the differential motor 46 within a range of 0 to 100%. Therefore, the speed difference of 0.8% is 1/1
Since it can be controlled with an accuracy of 00, the required speed difference Δυ can be applied to the short-side mold 5 with high accuracy.

FIG. 5 shows the belt 4 and the short side mold 5 using this device.
6 is a graph showing how the metal ribbon 7 and the block 5a of the short-side mold 5 deviate when different traveling speeds are applied. This deviation causes cracks in the metal ribbon and causes it to spread.

In FIG. 6A, the meniscus portion is the origin, the temperature is the X axis, and the casting direction is the Y axis. In the figure, Tb represents the temperature change in y of the short-side mold 5, and Ts represents the temperature change in y of the solidified shell. Further, the point y _n indicates the neutral point of the running speeds of the short-side mold 5 and the solidified shell. The relative deviation amount ΔS (y) at the neutral point y _n is expressed by the following equation.

However, λ _b is the thermal expansion coefficient of the short-side mold 5, and λ _s is the thermal expansion coefficient of the solidified shell. Therefore, when y = 0, ΔS
When (y) = 0, the relative deviation amount ΔS (y) becomes a curve as shown in FIG. 5 (b). A derivative of this curve is the curve indicated by the relative deviation velocity ΔV (y). As is clear from this figure, the relative deviation amount ΔS (y) changes most greatly near the meniscus portion.

In this respect, in this embodiment, a minute speed difference Δυ is given to the short-side mold 5 so as to reduce the relative speed in the vicinity of the meniscus. Therefore, the corrected relative deviation amount ΔS ₁ (y) corresponding to this speed difference Δυ becomes, and the speed of the relative deviation also becomes ΔS _1.
It can be reduced to V ₁ (y). As a result, the molten metal is less likely to be inserted between the blocks 5a of the short-side mold 5 near the meniscus, and the shearing force that causes cracking in the solidified shell having weak strength near the meniscus can be reduced. it can.

In the above description, the belt 4 is used for simplicity of explanation.
And the traveling speeds of the short side molds 5 were assumed to be equal. In reality, relative slippage occurs between the belt 4 and the short-side mold 5, but there is a one-to-one correspondence at a constant speed ratio. Therefore, by giving a slight difference to the speed of the belt 4 to the speed of the short-side mold 5, the shearing force that causes the occurrence of cracks can be similarly reduced.

Further, instead of controlling by the differential device 23 to provide a minute speed difference between the traveling speeds of the belt 4 and the short-side mold 5, a constant torque control is performed on the differential motor 46, so that a constant speed is achieved. By applying a torque of ± ΔT _r to the rotating input shaft 41 from the differential device 23, the torque of the output shaft 45 can be controlled. As a result, the short-side mold 5 can be fed into the casting space while applying a constant pushing force to the short-side mold 5.

〔The invention's effect〕

As described above, in the present invention, in order to absorb the difference between the contraction of the solidified shell caused by the heat received from the molten metal in the casting space and the thermal expansion of the belt and the short side mold,
There is a difference in running speed between the belt and the short side mold. Therefore, in the casting space, a gap is created between adjacent blocks of the short-side mold, and even if molten metal is inserted into the gap, the short-side mold and the metal ribbon do not shift relative to each other, so that a crack initiation point is generated. Is prevented. As a result, it becomes possible to produce a metal ribbon of excellent quality under stable conditions.

[Brief description of drawings]

FIG. 1 is a plan view showing a drive unit used in an embodiment of the present invention, FIG. 2 is a side view of the drive unit, and FIG. 3 is a main part of a distribution reducer in the drive unit.
The figure also shows the main part of the differential device, and FIG. 5 is a graph specifically showing the effect of providing a difference in running speed. On the other hand, FIG. 6 shows a twin-belt type continuous casting device, FIG. 7 shows a conventional short-side mold conveying mechanism, and FIG. 8 shows a force applied to a metal ribbon, a belt and a short-side mold in the conventional device. It is a figure explaining.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuhiro Maeda 1 Nishinosu, Oita-shi, Oita Pref.Nippon Steel Co., Ltd. Oita Works (72) Noriyuki Kanai 1 Nishinosu, Oita-shi, Oita Pref. Oita Steel Works, Steel Works Co., Ltd.

Claims (3)

[Claims] 1. When a metal strip is manufactured by cooling and solidifying a molten metal injected into a pool of water which is partitioned by a pair of endless running belts and a short side mold, a short side mold for the belt is produced. In order to eliminate relative slippage in the vicinity of the meniscus or in the part that most affects the cracking of the solidified shell, the short-side mold is moved to the pool part at a running speed having a minute difference from the running speed of the belt. A belt-type continuous casting method that suppresses relative slippage of a short-side mold characterized by feeding. 2. A belt type continuous casting machine for manufacturing a thin metal strip by cooling and solidifying a molten metal injected into a molten metal pool having a pair of belts partitioned by a short side mold at both ends. Providing a common drive mechanism to drive the short side mold,
A drive pulley that directly connects the drive mechanism to a drive pulley that drives the belt, and drives the short-side mold so as to generate a minute difference between the traveling speeds of the belt and the short-side mold. On the other hand, a belt type continuous casting apparatus in which the relative slip of the short side mold is suppressed, characterized in that the drive mechanism is connected through a differential device. 3. A belt-type continuous casting machine for manufacturing a metal ribbon by cooling and solidifying a molten metal injected into a molten metal pool having both ends partitioned by a short side mold between a pair of belts. Providing a common drive mechanism to drive the short side mold,
The driving mechanism is directly connected to a driving pulley for running the belt, and a pushing force is applied to the short side mold so as to generate a minute difference between the running speeds of the belt and the short side mold. A belt-type continuous casting apparatus which suppresses relative slippage of a short-side mold, which is provided with a torque applying mechanism.