JPS62263854A - Prevention method for molten steel spout-out from end part of continuous casting slab - Google Patents

Abstract

PURPOSE:To stabilize the end part shape of casting slab and to prevent the end part from molten steel spout-out by changing rolling reduction rate of roll in accordance with fluctuation of static iron pressure in the inner part of a casting slab at the end period of continuous casting. CONSTITUTION:The molten phase 8 in the casting slab 5, in which the solidification progresses at the end period of the casting, in the continuous casting of molten steel to reduce the static iron pressure. The rolling reduction force F of the roll 4 supporting the casting slab 5 is gradually changed through the hydraulic pressure P2 of a cylinder 6 corresponding to this static iron pressure and the detection of the casting slab position in the continuous caster. In this way, the casting is finished as keeping to stabilize the end part shape of the casting slab 5, and the break-down of the roll, caused by bleed, etc., of the molten steel is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for preventing molten steel from blowing out from the end of a continuously cast slab.
In continuous casting, in which a molten material with a relatively large specific gravity, such as molten steel, is continuously solidified, the shape of a slab in which a molten state and a solidified state are mixed is always kept constant.19.

[Conventional technology]

In continuous casting, in which slabs are continuously cast from molten steel, the technology for keeping the shape of slabs constant during casting is unique in the following respects.

During casting, the outer shell of the slab is solidified, but the inside of the slab is in a molten state. An example of this state is shown in FIG. 1(a). As solidification progresses, the thickness of the solidified phase increases and the thickness of the molten phase decreases. In this solid-liquid mixed state, the slab is subjected to static iron pressure on the molten phase side until it is completely solidified, and a force (bulging) is applied to spread the slab surface. To offset this force, the continuous casting machine supports the casting with rolls until it is completely solidified.

The force with which this roll supports the slab is determined from the static iron pressure.
i! I! When casting slabs with a P# machine, there are two cases: when there is a slab throughout the continuous casting machine (hereinafter referred to as a steady state), and when casting is finished and the end of the slab passes (hereinafter referred to as an unsteady state). The static iron pressure is different between. In the song title, the static iron pressure applied to each roll of the continuous casting machine is a constant value if the moving speed of the slab (referred to as the 'jlu speed or casting speed) is constant. In the later name, it changes continuously depending on the solidification thickness when the end of the slab passes through it. Therefore +
If you hold the slab with a roll pressure that takes into account the static iron pressure of only the third person, the excessive pressure will move against the unsteady slab, and in some cases the shape of the MJS may change or the As shown in Figure 2, molten steel may be pushed out from the end of the slab in the final solidification section (referred to as bleed), which may damage the continuous pI machine.

Conventional techniques for preventing bleeding include (1) After stopping the injection of molten metal into the mold E, the molten steel in the mold is stirred and the slag is scraped out to solidify the end of the slab. (2) After the injection of molten metal into the mold has stopped m, There was a method of hardening the end of the slab by hanging wood on it.

However, method 1) has the problem that slag enters the molten steel in order to stir the molten steel in the mold, resulting in poor quality. In addition, (2), υ, poses a problem as there is a risk of steam explosion.

[Problem that the invention seeks to solve]

The purpose of the present invention is to prevent the bleeding described in L, that is, the blowing of molten steel from the end of a continuously cast slab, which may cause poor quality of the slab or steam explosion as described in L. There is no way to do that.

[Means for solving problems]

In other words, the present invention prevents excessive stress on the end portion by varying the rolling reduction t of the rolls as the static iron pressure fluctuates (reduces) in the process of sequentially passing the end portion of a slab that has been cast through each roll in a continuous casting machine. Prevents the reduction blade from getting stuck. As a result, the slab cast in an unsteady state could have the same shape as the slab cast in a steady state, and furthermore, the molten steel could not bleed from the end of the slab.
19 accidents can be prevented from occurring.

In order to make the shape of a slab cast in an unsteady state the same as that of a slab cast in a steady state, it is necessary to have equipment that can accurately detect the position of the slab in an unsteady state, as well as the movement of the slab. Equipment with a roll structure that allows the reduction blade to be changed arbitrarily is required. Further, a logic circuit is required that can calculate or actually measure the fluctuation of the static iron pressure and output an appropriate pressure F force instruction to the roll based on the result.

[Effect]

An overall view of the present invention is shown in FIG. 1, which shows the movement of the end slab in the order of (a), (b), and (c). Figure 1 (a
) is the boundary between the steady state and the steady state, and the static iron pressure applied between each roll is at its maximum value. This situation! When the M structure is bonded with a ram, the end of the slab will be as shown in Fig. 1(b).
1(c). During this time, solidification progresses, the molten phase 8 decreases, and the static iron pressure decreases. The value of this static iron pressure can be easily estimated from a prediction calculation of solidification thickness. Alternatively, it can be easily measured by measuring the stress applied to the roll.

This static iron pressure value corresponds to the detection of the slab position in the continuous casting machine measured by the measure roll 11 shown in FIG. 4, and the rolling force of the roll 4 shown in FIG. 1(d) is sequentially varied. This allows the shape of the slab to be kept constant.For example, bleeding is likely to occur at the reduction roll position within 10 m from the meniscus. Therefore, in order to keep the shape of the slab constant, it is not necessary to equip all the rolls with equipment fc to vary the pressure, and the rolls that vary the downstream edge only need to maintain a constant value at regular intervals. Rolls are used only to prevent bulging of the slab.

When the end of the slab begins to pass, the static iron pressure decreases, so it is necessary to lower the roll pressure. On the other hand, in order to pull out the cast slab, it is necessary to apply a reduction blade to the slab and pull it out. Of course, the roll having the pull-out machine and the roll whose rolling blade can be varied may be the same, and they may be arranged at regular intervals.

The spacing and number of rolls are such that the slab can be pulled out.
It is necessary to satisfy a certain condition of f IFs, and the value differs depending on the continuous casting machine.

The method of setting the roll pressure F will be explained using the symbols shown in FIG.

Static iron pressure P1 on the roll to which force is applied is determined by equation (1).

P1=yXHXiXb ・= (1) However, Pl: Iron static pressure kg Cross: Distance from the center between rolls to the center between the next rolls! t
m b: [Ro of the slab m H: Distance from the center of the roll on which the reduction blade is applied to the meniscus m γ: Ratio kg / m' The pressure force F of the roll is determined by the following equation (2).

F = π (d/2) 2 ...Relationship (3) needs to be achieved. - At the final stage of casting, always use (1) and (2) to prevent molten steel from bleeding from the end of the slab.
) It is necessary to balance the equation, and it is necessary to take the inequality sign from equation (3) and control it so that F=P...(4). Add equations (1) and (2) to equation (4) as 1'(
In the right side of equation (5), γ is a constant, the value of d and love are constants that can be determined by the equipment, and b is a value that can be set for casting riT.

Therefore, formula (5) is Pl = Kf (H cross) K is a constant... (6)
It is expressed as (
The right side of equation 6) varies, and by varying Pl (hydraulic pressure) accordingly, it is possible to balance the roll reduction blade F of the roll and the static iron pressure P1 of the slab. This (6
) The bleeding shown in FIG. 2 can be prevented by performing control corresponding to the equation (2) during casting and after completion of casting as the slab passes from the end.

〔Example〕

In the continuous casting machine shown in Fig. 1, the distance between the rolls is # vertical = 0.33 m in the slab = 1.50 m The position of the rolls with indenter force (distance gl from the meniscus)
H = 6.2 m Specific gravity γ near 0 Hydraulic cylinder diameter Xn 1.4 cm x 2 wooden equipment, operated under casting conditions. A1 of P,,F is Pl = 3-4
65XH(h7) :H(m)F=308X10
-3 XP2 (tons): Pl (k
g/crn'), and the value of Pl is as shown in equation (7).

P2=11.25XH...(7) Since the value of H is constant at 6.2 m during casting, Pl = 11
．． 25X6.2=69.8 (kg/cm')...(
8) The hydraulic pressure was set as follows. After completion of casting (9) formula % formula %
According to (9), Pl was varied along with the variation of H as shown in Fig. 3, and the casting was completed. It was possible to complete the VF construction without causing any bleeding from the end of the slab.

〔Effect of the invention〕

When casting slabs using a continuous caster, unlike ordinary slabs, the slabs at the final stage of casting tend to have poor shapes, and molten steel tends to bleed from the ends of the slabs, making them unstable. According to the present invention, this unstable state can be maintained in a stable state by varying the pressure F of the rolls, and the casting of the end slab can be completed.

As a result, roll damage due to molten steel bleeding, etc. can be prevented.

[Brief explanation of drawings]

Figure 1 is a side sectional view showing the relationship between the drawing of the slab and the rolls, Figure 2 is an explanatory diagram showing the state where the end of the slab bleeds, Figure 3 is a graph showing an example, and Figure 4 is the rolling reduction. It is a flow sheet showing a force control mechanism system diagram. l... Mold for continuous casting 2... Meniscus 3... Roll (does not have a reduction blade) 4... Roll (has pressure force) 5... Slab 6... Cylinder 7... ... Solidification phase 8 ... Molten phase 9 ... Bleeded molten steel 11 ... Measure roll 12 ... Arithmetic unit 13 ... Pressure control H ... Height Pl that affects static iron pressure ... Static iron pressure 2 ... Distance between rolls b ... Slab 111

Claims (1)

[Claims] 1. A continuously cast slab characterized in that, in continuous casting of molten steel, the rolling blade of the roll supporting the slab is adjusted in accordance with the static iron pressure inside the slab at the final stage of casting when the continuous casting ends. A method for preventing molten steel from blowing out from the end of a steel.