JPH0245688B2 - FUNRYUSHIKITORIBESEIRENSOCHI - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is an apparatus for the purpose of secondary refining of molten steel, in which a hollow tube covered with a refractory is immersed in the molten steel in a ladle. This invention relates to a refining device that stirs molten steel using pressure fluctuations inside a hollow tube.

(Prior art) Conventionally, molten steel that has undergone primary refining in a converter or electric furnace is tapped from the furnace into a ladle, where alloys and deoxidizing agents are added to remove impurities such as oxygen. So-called secondary refining of molten steel is carried out for the purpose of removal and component adjustment to obtain the desired steel composition.

As this secondary refining device, a hollow tube covered with a refractory is immersed in molten steel in a ladle, and the molten steel is sucked up and discharged into the hollow tube by means of varying the gas pressure inside the hollow tube. There is a refining device that stirs molten steel using a so-called pulsating or mixing device (hereinafter referred to as a PM device).

FIG. 2 is an explanatory diagram of a pressure control means of a conventional PM device. As shown in Figure 2, the PM device includes a ladle 1 that receives molten steel 2 from the primary refining furnace, and a ladle 1
A hollow tube 3 immersed in the molten steel 2 for stirring the molten steel 2 inside, a pressurizing piping system for pressurizing the gas pressure inside the hollow tube 3, and a pressure reduction system for reducing the gas pressure inside the hollow tube 3. A pressure reducing piping system is provided. The pressurization piping system includes a pressurization gas source 6, a pressure reducing valve 6a that reduces the pressure of the gas source 6 to the working pressure, a gas tank 6b that temporarily stores gas, and a gas flow rate adjustment valve 4.
a, an electromagnetic on-off valve 4, etc. are provided, and the pressure reduction piping system is provided with a pressure reduction pump 7, an electromagnetic on-off valve 5, etc., and further detects the pressure inside the hollow pipe 3 and sends a signal. A transmitter 8 and a control means 9 that receives a signal from the transmitter 8 and controls the electromagnetic on-off valves 4 and 5 are provided.

According to this device, in order to stir the molten steel 2 in the ladle 1, the pressure in the hollow tube 3 is varied at approximately 5 second intervals by switching the pressurizing solenoid valve 4 and the pressure reducing solenoid valve 5. , the molten steel 2 inside the hollow tube 3 is discharged to the outside of the hollow tube 3 or sucked up into the hollow tube 3.
At this time, in order to efficiently apply stirring energy to the molten steel, it is important to control the maximum value of the internal pressure of the hollow tube 3 during pressurization to a specified value. Special Public Service 1986
As disclosed in No.-5834, the conventional hollow tube 3
The gas pressure value in the hollow tube 3 at the end of the suction period is sent by the transmitter 8 to the control means 9, and the gas pressure value in the hollow tube 3 at the end of the suction period created in advance is determined. For pressurizing the inside of the hollow tube 3 so that the maximum value of the gas pressure inside the hollow tube 3 becomes a constant value based on the relation between The pressure inside the hollow tube 3 was controlled by opening and closing the gas solenoid valve 4 and the pressure reducing gas solenoid valve 5. According to this device, the factor that controls the pressure inside the hollow tube 3 is the time that the solenoid valve 4 is in the open state, and the control means 9 calculates the time that the solenoid valve 4 is kept in the open state. There is.

(Problem to be Solved by the Invention) However, even in the above-mentioned device, measures are not taken to reduce the influence of the opening/closing speed of the solenoid valve 4 and the gas tank 6b to reduce pressure fluctuations, which are sources of error in pressure control. However, it is not possible to completely avoid the effects of fluctuations in the source pressure of the nitrogen gas source 6 in the factory.
It was not possible to accurately maintain the maximum pressure within the hollow tube 3 constant during pressurization. Further, if the control means 9 fails, excessive pressure will be applied in the hollow tube 3 for several seconds or more, which may lead to an accident in which the molten steel 2 is spouted out from the ladle 1. For the reasons mentioned above, in order to take into account the accuracy of the control means 9 and ensure safe operation, it was necessary to reduce the maximum pressure setting value during pressurization, so that sufficient stirring energy could be applied to the molten steel. However, there was a drawback that the system had to operate with the possibility of an accident occurring due to failure of the control means 9.

An object of the present invention is to provide a jet ladle refining device that can eliminate and improve the conventional drawbacks and problems, and provides the jet ladle refining device as described in the claims. By this, the above object can be achieved.

That is, the present invention provides a pressure buffer buffer tank provided in the middle of a conduit for transporting gas from a pressurized gas source into the hollow tube in a refining device that stirs the molten steel by varying the pressure inside the hollow tube immersed in the molten steel. , a pressure reducing valve used to supply gas at a constant pressure from a pressurized gas source to the buffer tank, an electromagnetic on-off valve provided on the inlet side piping of the buffer tank, an electromagnetic on-off valve provided on the outlet side piping of the buffer tank, and attached to the buffer tank. An electromagnetic opening/closing valve is provided to dissipate the pressurized gas in the tank into the atmosphere, a pressure gauge is provided to monitor the pressure inside the buffer tank, and the electromagnetic opening/closing is controlled by a hollow pipe internal pressure signal and a signal from the pressure gauge. The present invention relates to a jet ladle refining apparatus provided with a control means for controlling a valve to maintain the pressure inside the buffer tank at a predetermined value.

(Means for Solving the Problems) The jet ladle refining apparatus of the present invention will be described in detail below.

FIG. 1 is an explanatory diagram of the pressure control means of the present invention. In the figure, a ladle 1 receives molten steel 2 from a primary refining furnace, a hollow tube 3 immersed in the molten steel 2 to stir the molten steel 2 in the ladle 1, and a gas pressure inside the hollow tube 3. Pressurizing piping system and hollow pipe 3
It has a pressure reduction piping system that reduces the gas pressure in the
The pressurizing piping system is provided with a pressurizing gas source 6, a pressure reducing valve 6a that reduces the pressure of the gas source 6 to the working pressure, and the depressurizing piping system is provided with a depressurizing pump 7 and an electromagnetic on-off valve 5. The second feature is that a transmitter 8 that detects the pressure inside the hollow tube 3 and transmits a signal, and a control means 9 that controls the solenoid valves 4 and 5 in response to the signal from the transmitter 8 are provided. It is no different from the conventional device explained in the figure.

According to the apparatus of the present invention, the pressure piping system further includes a pressure buffer buffer tank 11 and a buffer tank 11.
An electromagnetic on-off valve 12 provided on the inlet side piping, an electromagnetic on-off valve 4 provided on the outlet side piping, an electromagnetic on-off valve 13 that releases the pressure in the buffer tank 11 to the atmosphere, and the electromagnetic on-off valve 4, The only difference from the conventional device is that in addition to 5, arithmetic control means 9 is further provided to control the electromagnetic on-off valves 12 and 13 based on a signal from a pressure gauge that monitors the pressure inside the buffer tank. However, as described below, it is possible to achieve remarkable effects not found in conventional devices.

Next, the basic valve operation of the device of this invention will be explained. In FIG. 3, the operation of each on-off valve 4, 5, 12 shown in FIG. 1 and the hollow pipe 3 are explained.
The internal pressure and the pressure of the buffer tank 11 are shown. As shown in the figure, the valve 12 is opened while the valve 4 is closed, the valve 5 is opened and the inside of the hollow tube 3 is being exhausted (referred to as during depressurization), and the buffer calculated by the calculation control means 9 is Tank charge pressure set value P ₁
Nitrogen gas is charged from the pressurizing gas source 6 in the buffer tank until the pressure in the buffer tank 11 matches the pressure in the buffer tank 11. After charging is completed (time t ₁ ) valve 12
, then after confirming that the valve 12 is closed, open the valve 4, close the valve 5 (time t ₂ ), send nitrogen gas to the hollow tube 3, and give downward energy to the molten steel 2 ( (called pressurization). After a certain period of time, the valve 4 is closed, and the valve 5 is opened to switch to reduced pressure (time t ₃ ) and then proceed to nitrogen charging into the buffer tank 11. By adopting such a method, in the pressurized piping system, either the valve 4 or the valve 12 is closed, and the pressure of the pressurizing gas source 6 is not directly transmitted into the immersion pipe, and the pressure is not transmitted directly into the hollow pipe 3. Molten steel 2 due to excessive pressure
can prevent blowout accidents.

Next, set the pressure inside the buffer tank 11 to the set value P ₁
Explain the operation to make it equal to . As described above, valve 4 is closed and valve 12 is opened to increase the pressure in buffer tank 11. At this time, the pressure is reduced in order to stabilize the pressure of the gas supplied through the valve 12 and to prevent the high pressure of the pressurized gas source 6 from being transmitted directly to the hollow pipe 3 due to leakage or malfunction of the valves 4 and 12. A valve 6a is provided, and the gas from the pressurized gas source 6 is reduced in pressure by the pressure reducing valve 6a and flows into the buffer tank 11. The calculation control means 9 is a buffer tank 1
The output of the pressure gauge 10 of No. 1 is monitored, and a command is issued to close the valve 12 at a pressure slightly lower than the set pressure _P1 . Furthermore, if the pressure inside the buffer tank exceeds _P1 , the valve 13 is opened until the pressure becomes lower than _P1 ,
Reduce the pressure inside the buffer tank 11.

The set pressure P ₁ in the buffer tank 11
Explain how to calculate.

FIG. 4 is a diagram showing a control pattern for the pressure in the hollow tube 3, and shows the charge pressure in the buffer tank 11.
The correlation with P ₁ is also shown. In the same figure,
From the control start time _t4 , the initial control period (time _t4 to _t5 )
calculates the buffer tank charge pressure P ₁ according to the following equation (1).

P ₁ = P _1S + n×△P ₁ …(1) Here, P _1S : Initial buffer tank setting value n: Number of times of pressurization △P ₁ : Incremental value of P ₁ In other words, the pressure inside the hollow tube 3 is gradually increased. In order to achieve this, the buffer tank charge pressure _P1 is also gradually increased linearly.

During the initial control period, the arithmetic control means 9 monitors the maximum value P _H of the output signal of the transmitter 8 that transmits the pressure signal in the hollow tube 3 during pressurization, and determines the end of the initial control set in advance by P _H. The point in time when the standard value P ₃ is exceeded (point in time
_t5 ), change the calculation method of buffer tank charge pressure _P1 , and use the following formula to calculate buffer tank charge pressure.
Calculate P ₁ .

P ₁ = P ₁ (previous buffer tank charge pressure) + (P ₂ − P _H ) × k … (2) where, P ₂ : Upper limit pressure setting value when pressurizing inside the hollow pipe P _H : Inside the hollow pipe Maximum value k during pressurization: Proportionality coefficient By this calculation method, the maximum pressure P _H during pressurization can be converged to the target pressure P ₂ as quickly as possible. However, if control using equation (2) is performed immediately after the start of control, |P ₂ −P _H | will increase, making control unstable and potentially leading to a blowout accident. It is necessary to set a control period.

Next, embodiments will be described with reference to the drawings.

FIG. 5 shows the difference in pressure changes within the hollow tube 3 when using the conventional device and when using the device of the present invention. As shown in the figure, the conventional apparatus employs a method in which an operator monitors the actual value of the maximum pressure P _H in the hollow tube 3 and adjusts the time period during which the valve 4 is open. Therefore, hollow tube 3
Although the maximum value P _H of the internal pressure has reached close to the set pressure P ₂ , there is still a variation of about ±0.2 Kg/cm ² .

In the device of the present invention, all pressure control is performed automatically, so the operator does not have to change the set value at intervals of about 5 seconds as in conventional devices, and it is possible to control the pressure in just 2 seconds after starting the control. The maximum pressure P _H in the hollow tube has converged to the set pressure P ₂ . In this case, the error from the set pressure P ₂ is approximately 0.01 Kg/cm ² and cannot be discerned on the recording paper.

(Effects of the Invention) According to the device of the present invention, the on-off valve 12 is provided on the inlet side piping of the buffer tank 11, and it can be made independent of the pressurizing gas source 6, so there is no risk of excessive pressure being applied inside the hollow tube 3. Therefore, the safety is very superior compared to conventional equipment, and the set value P ₂ in the hollow tube 3
can be set to 0.1-0.2Kg/ ^cm2 higher than conventional equipment. Therefore, a larger stirring force than the conventional device was obtained, and the quality of the steel material was also improved.In the conventional device, there could be small-scale molten steel spouting, but with this device, there was none.

As explained above, when the jet ladle refining apparatus of the present invention is used, the pressurizing means includes a buffer tank for pressure buffering, a regulating valve for supplying gas at a constant pressure to the buffer tank, and piping on the inlet side of the buffer tank. and a solenoid valve provided in the outlet side pipe and controlled by a signal based on the pressure inside the hollow pipe;
Furthermore, by installing an on-off valve that can control the pressure inside the buffer tank by dissipating the pressurized gas in the buffer tank into the atmosphere, a jet-type ladle refining device with significantly increased stirring power and extremely high safety can be obtained. Ta.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the jet ladle device of the present invention, Fig. 2 is an explanatory diagram of the conventional device, and Fig. 3 is an operating time chart of the valve of the present invention and pressure changes in the hollow pipe and buffer tank. FIG. 4 is an explanatory diagram showing a control pattern for the pressure inside the hollow tube and the pressure in the buffer tank, and FIG. 5 is a diagram showing a comparison of the pressure inside the hollow tube between the device of the present invention and the conventional device. 1... Ladle, 2... Molten steel, 3... Hollow tube, 4...
... Pressure piping on-off valve, 5... Pressure reduction piping on-off valve, 6...
... Pressurization gas source, 7 ... Decompression pump, 8 ... Hollow tube pressure transmitter, 9 ... Control device, 10 ... Buffer tank pressure gauge, 11 ... Buffer tank, 12
...Battle tank inlet side piping on/off valve, 13...
Vacuum tank atmosphere release valve.

Claims (1)

[Claims] 1. A jet stream comprising a hollow tube immersed in molten steel and a pressure means for making the pressure inside the tube positive and a pressure reducing means for making the pressure negative. A jet-type ladle refining apparatus, characterized in that the pressurizing means is provided with the following devices (a) to (f). (a) A buffer tank for pressure buffering provided in the middle of the pipe line that sends gas from a pressurized gas source into the hollow pipe; (b) A buffer tank used for supplying gas at a constant pressure from a pressurized gas source to the buffer tank. a pressure reducing valve, (c) an electromagnetic on-off valve provided on the inlet pipe of the buffer tank, (d) an electromagnetic on-off valve provided on the outlet pipe of the buffer tank, and (e) a pressurized gas in the tank provided incidentally on the buffer tank. An electromagnetic on-off valve for dissipating into the atmosphere, a pressure gauge for monitoring the pressure inside the buffer tank, and (f) the pressure signal inside the hollow tube and the signal from the pressure gauge in (e) above, allow the above (c) and (ho) A control means that operates to control each electromagnetic on-off valve of (a) to maintain the internal pressure of the buffer tank at a predetermined value.