JPS63220959A - Method for pouring molten metal by ladle - Google Patents

Abstract

PURPOSE:To pour molten metal into a mold at the fixed flow velocity and to eliminate the need of a tundish by detecting molten metal weight in a ladle to grasp the static hydraulic pressure, detecting the pressure in the ladle after tightening the ladle and supplying gas in the ladle so that the sum of the static hydraulic pressure and the pressure in the ladle becomes constant. CONSTITUTION:In accordance with pouring the molten metal 12, the gross weight of the ladle 10 is reduced, and then, electric resistant value of a load cell 14 is changed and voltage value is an arithmetic unit 16 is reduced. Next, based on the detected voltage, the static hydraulic pressure of the molten metal 12 is calculated and the calculated value is transmitted to a control device 18. On the other hand, the pressure in the ladle 10 is detected by a detector 24 and the detected value is inputted to the control device 18. The control unit 18 outputs the voltage signal corresponding to the total pressure value of the static hydraulic pressure and the pressure in the ladle. And, a voltage difference is found by comparing the voltage signal with the pressure setting value. next, at the time of transmitting the voltage difference from the control unit 18 to flow rate adjusting valve 28, the suitable quantity of gas is supplied in the ladle 10 through piping 26 and the pressure in the ladle, which is gradually decreased from starting of pouring, is gradually increased, and the whole molten metal 12 in the ladle is poured into the mold at a constant flowing speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention applies to continuous casting of molten metal in a ladle! This invention relates to a method for pouring molten metal into mold 8 using a ladle.

U Prior Art] In continuous casting, when the height of the molten metal in the mold fluctuates, surface flaws occur in the slab. For this reason, it is necessary to keep the flow rate of the molten metal injected into the mold approximately constant.Normally, the molten metal in the ladle is once poured into the tundish, and the molten metal level in the tundish is maintained at a predetermined height. Pour the molten metal into the mold.

[Problems to be Solved by the Invention] However, in the conventional method of pouring molten metal in continuous & 8-build construction, a tundish with a large contact area with the molten metal is used, so there is a problem that the cost of refractories increases.

Therefore, there is a strong demand in continuous casting for the practical application of a molten metal injection method that directly injects the molten metal in the ladle into the mold, thereby omitting the tundish and reducing the cost of refractories. In this case, molten steel is injected into the mold via a sliding nozzle provided at the bottom of the ladle.

FIG. 3 is a sectional view showing a ladle when molten steel in the ladle is directly injected into a mold via a sliding nozzle.

When the sliding nozzle 4 at the bottom of the ladle 1 is opened, the molten steel 2 is injected into the mold 6 through the immersion nozzle 5. At this time, since the molten steel pressure is high in the initial stage of casting, nozzle 4
Reduce the opening amount (opening degree: $) and adjust the melt rj4in. That is, molten steel is injected with the nozzle 4 being slightly displaced from the outlet 3. For this reason, as shown by the arrow 7 in the figure, non-uniformity (@ flow) occurs in the flow of the injected molten steel, and the molten metal is not evenly distributed from the pair of discharge ports at the bottom of the nozzle 5. There is a problem in that it disturbs the surface.

Figure 4 is a graph showing the relationship between molten steel depth and discharge flow rate, with the horizontal axis representing the molten steel depth in the ladle and the vertical axis representing the molten steel discharge flow rate. The depth of the molten steel in the pot is taken, and the opening ratio of the sliding nozzle is taken on the vertical axis.
Injected into the mold with a nozzle with a diameter of 50+n and a thickness of 25
It is a graph diagram showing the relationship between the molten steel depth and the nozzle opening rate when a slab with a width of 0 mm and a width of 1000 an+ is handled at a speed of 1 m/min. As is clear from FIG. 4, the molten steel discharge flow rate rapidly decreases in the final stage of casting. Furthermore, as is clear from Fig. 5, the depth of the molten steel in the ladle at the end of casting is approximately 2
If the diameter is less than 00 mm, there is a problem that casting cannot be continued because the molten steel discharge flow rate decreases rapidly even when the nozzle opening rate is set to 100%. Furthermore, as is clear from FIG. 5, if the nozzle opening ratio is set to about 18% or less in the early stage of casting, there is a problem that the nozzle will become clogged.

In FIG. 6, the horizontal axis represents the horizontal movement distance of the sliding nozzle, and the vertical axis represents the opening ratio of the sliding nozzle and the cross-sectional area of the molten steel, and the diameter is 50 mm.

It is a graph diagram showing the relationship between the nozzle opening rate and the molten steel passage cross-sectional area for each of 6011111 and 70 mm nozzles. In the figure, black circles and white circles indicate the nozzle opening rate and molten steel passage cross-sectional area when the nozzle diameter is 701, and black triangles and white triangles indicate the nozzle opening rate and molten steel passage cross-sectional area when the nozzle diameter is 60Ill1m. , Also, the nozzle diameter of the black square and white square is 501! The nozzle opening ratio and molten steel passage cross-sectional area in the case of lIm are shown. As is clear from FIG. 6, there is a problem in that during casting, it is necessary to sequentially adjust the sliding nozzle according to the drop in the metal level.

This invention was made in view of such circumstances, and
To provide a method for pouring molten metal using a ladle, which can directly inject molten metal in a ladle into a mold at a constant flow rate without using a sliding nozzle, and can eliminate the need for a tundish.

[Means for Solving the Problems] The method for pouring molten metal using a ladle according to the present invention is a method for pouring molten metal using a ladle in which molten metal stored in the ladle is poured into a mold from a sliding nozzle at the bottom of the ladle. The weight of the molten metal in the ladle is detected to determine the hydrostatic pressure of the molten metal applied to the sliding nozzle, while the inside of the ladle is sealed and the pressure inside the ladle is detected to determine the hydrostatic pressure of the molten metal and the pressure inside the ladle. It is characterized in that the gas is supplied into the ladle so that the sum with the pressure remains substantially constant.

[Function] In the method for pouring molten metal using a ladle according to the present invention, the hydrostatic pressure of the molten metal is determined from the weight of the molten metal in the ladle, and the pressure in the sealed ladle is detected.

Then, when the molten metal level in the ladle gradually decreases and the hydrostatic pressure of the molten metal decreases, gas is supplied into the ladle to increase the pressure in the ladle, thereby increasing the molten metal hydrostatic pressure and the hydrostatic pressure in the ladle. The sum of the pressure and pressure is kept approximately constant. Therefore, the flow rate of 1 m flowing out from the sliding nozzle at the bottom of the ladle is approximately constant.

[Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a ladle to which a method for pouring molten metal using a ladle according to an embodiment of the present invention is applied. Weight is about 2
Molten tA 12 is stored in a 50-ton chamber 110 to a depth of approximately 3 m (the depth indicated by symbol H in the figure). A sliding nozzle (not shown) is provided at a suitable location at the bottom of the ladle 10, and molten steel is injected into the mold (not shown) through a submerged nozzle (not shown) attached to the sliding nozzle. It looks like this. Further, a load cell 14 is disposed at the bottom of the ladle 10 to detect the total amount m of the ladle 10. Load cell 14 is connected to calculation device 16 .

The calculation device 16 includes a detection section connected to the strain gauge of the load cell 14 and a calculation section that calculates the hydrostatic pressure of molten steel from the detected weight. The calculation unit of the calculation unit @16 is the control device 1
It is connected to the input side of 8.

On the other hand, the ladle 10 is covered with a lid 20.

A flexible refractory material (for example, copper wool) is interposed at the contact surface between M2O and the tray 110 to prevent gas in the tray 1110 from leaking from the contact surface.

Further, 120 is fixed to the mounting plate by appropriate means. Piping 22 and piping 26 penetrate f120, and
Each tip opens into 1410 . The base end of the pipe 22 is connected to a pressure detector 24, and the pressure detector 24 is connected to the input side of the Wv control device 18. This pressure detector 24 has a conversion function of converting the detected ladle internal pressure into voltage. The output side of the control device 18 is the outflow regulating valve 2
It is connected to a drive unit that opens and closes the valve body No. 8.

Further, a predetermined pressure setting value is given as a voltage signal to the control device 18, and this pressure setting value, the hydrostatic pressure of the molten steel calculated by the calculation device 16, and the hydrostatic pressure in the ladle detected by the pressure detector 24 are used. The total value of the pressure is compared, the difference between the two is determined, and this is used as a differential pressure command to send a signal to the flow m regulating valve 28. The flow m adjustment valve 28 is provided at a suitable position in the pipe line of the pipe 26. The base end of this pipe 26 is connected to a nitrogen gas supply source (not shown), and when the flow rate adjustment valve 28 opens, nitrogen gas is taken up via the pipe 26.
It is designed to be supplied internally.

Next, the operation of the embodiment of this invention will be explained. At the start of casting, the pressure inside the chamber 110 is approximately the same as atmospheric pressure (approximately 1 atmosphere). This ladle internal pressure is detected by the pressure detector 24 and a detection signal is sent to the control device 18. On the other hand, the total weight of the ladle 10 is detected by the load cell 14, and this detected N
Based on the amount, the calculation device 16 calculates the weight of only the molten steel 12. Furthermore, the calculation device 16 calculates the hydrostatic pressure from the weight of the molten steel 12, and uses this as a voltage signal to control the tA device 1.
Send to 8. The control fl device 18 combines the ladle internal pressure voltage signal from the pressure detector 24 and the hydrostatic pressure voltage signal from the calculation device 16, and combines this combined voltage signal with a predetermined pressure setting. Compare the value with the voltage signal.

At this time, since the total value before the start of casting matches the pressure setting value, the flow II\14 regulating valve 28 is closed. When preparations for casting are completed, the sliding nozzle at the bottom of the ladle 10 is opened to start casting. Then, the molten steel 12 is discharged into the mold through the immersion nozzle, and the molten steel 1ii in the ladle 10 is
12 decreases, and the hot water level gradually decreases. For example, when the molten metal level falls to the depth indicated by @h in the figure, the hydrostatic pressure of the molten steel 12 decreases and the flow rate of the molten steel discharged from the immersed nozzle into the mold tends to decrease, but at this time the flow ffi Regulating valve 2
8 opens and nitrogen gas is supplied into the ladle 110, and the pressure inside the ladle increases by ΔP, so the decrease in the hydrostatic pressure of the molten steel 12 ((H-h) multiplied by the unit weight of the molten steel) is This is compensated for by the increase in the pressure inside the ladle (ΔP), and the situation where the discharge flow rate of the molten steel 12 decreases is avoided.In other words, when the total weight of the ladle 10 decreases due to the injection of the molten steel 12, the strain gauge of the load cell 14 The electrical resistance value changes, and the voltage value detected by the detection unit of the arithmetic device 16 decreases accordingly.
Calculate the hydrostatic pressure of the molten rA12 based on this detected voltage,
This calculated value is sent to the control device 18 as a voltage signal. On the other hand, the pressure inside the ladle 10 is detected by the pressure detector 24, and which detected value is inputted to the control device 18 as a voltage signal. The control device 18 synthesizes a voltage signal corresponding to the total pressure value of the molten steel hydrostatic pressure and the ladle internal pressure based on the respective voltage signals. Then, by comparing the voltage signal corresponding to this total pressure value and the voltage signal of a predetermined pressure setting value using the control device @18, a voltage difference is determined. When this voltage difference is sent as a differential pressure command from the control device 18 to the valve body drive part of the flow m regulating valve 28, the opening amount of the regulating valve 28 is adjusted and an appropriate amount of gas is supplied into the intake valve A10 via the piping 26. be done. The amount of gas supplied at this time is, for example, about 100 ni/hour.

FIG. 2 is a graph showing the relationship between the molten steel depth and the ladle pressure in the above example, with the horizontal axis representing the molten steel depth and the vertical axis representing the pressure within the ladle. . As is clear from Figure 2, as the molten steel depth gradually decreases from about 3 m at the start of casting, the pressure inside the ladle increases gradually due to gas supply, and just before the completion of casting, the pressure inside the ladle reaches a maximum of 3 m. ．．
The pressure rises to 35 atmospheres. This increase in pressure inside the ladle causes melting inside the ladle 10! The entire amount of g12 is injected into the mold at a constant flow rate.

As described above, in the above embodiment, molten steel can be injected from the ladle into the mold at a constant flow rate from the initial stage of casting to the final stage of casting. Therefore, it is possible to avoid nozzle clogging and drifting that occur when the opening ratio of the sliding nozzle is reduced in the early stage of casting, and there is no need for adjustment operations to sequentially change the opening ratio of the sliding nozzle during casting. can do. Further, since it is possible to prevent the molten steel discharge flow rate from decreasing at the final stage of casting, the molten steel in the ladle can be poured into the mold without any molten steel remaining in the ladle.

[Effects of the Invention] According to this invention, the molten metal in the ladle can be flowed out at a constant flow rate without using a sliding nozzle. Therefore, the molten metal in the ladle can be directly injected into the mold during manufacturing, making it possible to eliminate the need for a tundish and significantly reducing the cost of refractories.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a ladle to which the method of pouring molten metal using a ladle according to an embodiment of the present invention is applied, FIG. 2 is a graph diagram explaining the effects of the embodiment, and FIG. Cross-sectional view showing the ladle when pouring, No. 4
Figures 6 through 6 are graphs showing problems with sliding nozzles. 10; ladle, 12: molten steel, 14; load cell, 16; calculation device, 18: control device, 20: lid, 24; pressure detector, 28: flow adjustment valve applicant's agent, patent attorney Takehiko Suzue Muke

Claims (1)

[Claims] In a ladle injection method in which the molten metal stored in the ladle is injected into the mold from a sliding nozzle at the bottom of the ladle, the weight of the molten metal in the ladle is detected and the hydrostatic pressure of the molten metal applied to the sliding nozzle is calculated. At the same time, sealing the inside of the ladle, detecting the pressure inside the ladle, and supplying gas into the ladle so that the sum of the hydrostatic pressure of the molten metal and the pressure inside the ladle becomes substantially constant. A method of pouring molten metal using a ladle, which is characterized by: