JPS62224452A - Ladle refining method - Google Patents

Abstract

PURPOSE:To prevent the local over-heating of molten steel at the upper part of a ladle, to decrease the melting loss of the ladle refractory, and to reduce the heat segregation at the upper part of the ladle and to strengthen the reducing refining, by controlling automatically as relating an input electric power control mechanism into the electrodes, to a gas supplying rate control mechanism into the ladle. CONSTITUTION:At the time of the refining, the inert gas is supplied a little too much from a porous plug 4 at first under condition as ascending the electrodes 6 to stir the molten steel 2, and slag making materials are charged from a charging hole 7. Next, the electrodes 6 are descended and a gas supplying rate is decreased by turning down a flow rate control value 13 through the gas supplying rate control device 16 and the arc heating is executed by supplying much electric power to the electrodes 6 from the input electric power control device 25. Then, during stopping arc by ascending the electrodes 6, the flow rate control valve 13 is opened by the gas supplying rate control device 16 to increase the gas supplying rate. Such a control is automatically executed by a command from a microcomputer 17.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a ladle refining method used for refining molten steel in a ladle to clean it and adjust its composition. It is something.

(Conventional technology) In recent years, the ladle refining method (LF method) has been used as an out-of-furnace refining method for mass-produced steel.
are increasingly being adopted. In this ladle refining method, the molten steel in the ladle is stirred by gas bubbling, but this agitation of the molten steel by gas bubbling has the following effects: (2) Mixing between slag and molten steel to prevent melting of large ladle-resistant materials and to reduce heat dissipation by preventing overheating by gas stirring and by uniformizing molten steel heating. The objective is to promote desulfurization by gas agitation to improve desulfurization efficiency and homogenize the components.

(Problem to be solved by the invention) Conventionally, in order to perform such gas bubbling, A
An inert gas such as R, N2, etc. is used, but if the gas supply m% is small in this case, the gas consumption cost is low and the vertical movement of the electrode during arc heating is small.
Although it is effective for stable operation, the slag and molten steel at the top of the ladle are locally overheated, resulting in greater erosion of large ladle-resistant parts.
This results in an increase in operating costs, and since the gas agitation is slow, the desulfurization efficiency is low and there is a risk that the components may not be homogenized in one minute. On the other hand, if the gas supply amount is large, the slag and molten steel in the Mk part will not be locally overheated, there will be less erosion of large ladle-resistant materials, and the gas will be stirred rapidly, resulting in higher desulfurization efficiency. However, the cost is high due to high gas consumption, and the vertical movement of the electrode is large during arc heating, which increases electrode wear and reduces the amount of carbon picked up. It will increase.

Therefore, it is necessary to adjust the flow rate of the stirring gas supplied for gas bubbling to an appropriate value.

However, in the conventional case, a slag-forming agent is added.

Because workers manually controlled the gas supply amount by operating valves at each stage of alloy injection and desulfurization, it was difficult to respond quickly and the timing of the gas supply meter's increase and decrease operations varied. There is a problem in that gas consumption tends to be excessive.

(Purpose of the Invention) This invention has been made by focusing on the conventional problems mentioned in E. In ladle operation, the invention prevents local overheating of slag and molten steel in the ladle part, and makes the ladle resistant to large parts. In addition to reducing melting loss in the ladle refining process, this technology aims to reduce aging segregation at the ladle tip, which is important in ladle refining, and strengthen reduction refining. It also reduces vertical fluctuations of the electrode during arc heating, stabilizes operations, and improves carbon pickup. The purpose is to reduce the amount of sulfur, improve the desulfurization efficiency, make the components more uniform, and avoid variations caused by manual operations.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a mechanism for controlling the amount of electric power input to the electrodes and a mechanism for controlling the amount of electric power input into the ladle when stirring molten steel in the ladle by gas bubbling in ladle refining. Automatic control is performed in conjunction with a gas supply amount control mechanism to reduce the gas supply amount during arc heating by the electrode and to increase the gas supply amount during arc interruption. It is said that

FIG. 1 is a diagram showing one embodiment of the present invention, in which 1 is a ladle main body, 2 is molten steel placed in the ladle main body 1, and 3 is a molten steel 2.
4 is a porous plug provided at the bottom of the ladle body 1, 5 is a water-cooled furnace lid installed on the top of the ladle body 1, 6 is a Miki electrode that penetrates the water-cooled furnace lid 5, Reference numeral 7 denotes a slag forming agent and alloy inlet provided in the water-cooled furnace cover 5.

Further, 10 is a gas supply pipe, and this gas supply pipe 1
0 has a flow control valve 11°, a pressure control valve 12°, a flow control valve 13. Orifice plate 14. Couplers 15 and the like are provided sequentially.

Among these, the flow control valve 13 controls the flow fftF
A gas flow rate control device 16 that constitutes a gas supply amount control mechanism together with the IJ control pulp 13 is provided, and a control signal from a microcomputer (CPU) 17 can be supplied to this gas flow rate control device 16 through a wiring 16a. It is.

Further, between the orifice plates 14, each valve 2
A differential pressure oscillator 24 is connected via wires 1, 22, and 23, and the gas supply amount detected by the differential pressure oscillator 24 is sent to the microcomputer (CPU) 1 through a wire 24a.
7 so that feedback can be provided.

Further, the electrodes 6 are provided with a cable 6 for each electrode 6.
An input power amount control device 25 as an input power amount control mechanism that adjusts the amount of power input through a is connected to the input power amount control device 25. This is so that a control signal can be provided.

To explain how to perform ladle refining using a ladle and its control mechanism having the configuration shown in L, first, molten steel 2 is transferred into the ladle body 1, and then the water-cooled furnace lid 5 is
Set up.

Next, in a state where the electrode 6 is raised L.

More inert gas than the porous plug 4 (for example, A
r, N2) is supplied to stir the molten steel 2, and the molten tJI
While stirring J2, a slag-forming agent (for example, quicklime, gravel, carbonaceous material, aluminum ash, etc.) is introduced from the input lower.

Next, the electrode 6 is lowered in response to a command from the microcomputer 17, and prior to igniting the arc, the gas supply amount control device 16 is driven in response to a command from the microcomputer 17 to throttle the flow rate control valve 13, thereby controlling the gas flow rate. The supply amount is reduced, and after a few seconds, the input power amount control device 25 supplies large power to each electrode 6 according to a command from the microcomputer 17 to start arc heating. At this time, the gas supply amount is detected by the differential pressure oscillator 24,
is input to the microcomputer 17 through the wiring 24a, and when the gas supply amount is less than or greater than a predetermined value, the gas supply amount control device 16 is driven to move the flow rate control valve 13 in the opening direction or the closing direction, respectively. Ensure that the gas supply amount is constant.

Next, after arc heating the molten steel 2 by supplying large electric power, the electrode 6 is heated by a command from the microcomputer 17.
is increased to cut off the arc and reduce the input power amount, and after a slight delay, the gas supply amount control device 16 is driven by a command from the microcomputer 17 and the flow rate control valve 13 is opened to increase the gas supply amount. . and.

While the molten steel 2 is rapidly stirred by increasing the amount of gas supplied, alloys for composition adjustment (ferroalloy, non-ferrous alloy 9) are added from the input lower.
(including single alloying elements, etc.) is added. At this time as well, the gas supply amount is detected by the differential pressure oscillator 24 and fed back to the microcomputer 17 to operate the gas supply amount control device 16 and the flow rate control valve 13, so that the gas supply amount is kept constant in a large state. Do what you want.

After charging the alloy, the microcomputer 17 commands drive the gas supply amount control device 16 to throttle the flow rate control valve 13 to reduce the gas supply amount, and the microcomputer 17 also commands the electrode 6
After a few seconds have elapsed after lowering the gas supply amount and reducing the amount of gas supplied, a large amount of power is applied from the input power amount control device 25 according to a command from the microcomputer 17 to ignite the arc.
Molten steel 2 is heated by arc heating.

In this way, the microcomputer controls the control to reduce the gas supply amount during arc heating when the electrode 6 is lowered, and to increase the gas supply amount during arc interruption when the electrode 6 is raised.
Cleaning and composition adjustment of molten steel 2 are carried out automatically according to commands from 7, and after the second and subsequent alloy injections as necessary, the arc is blocked and desulfurized by reducing the amount of power input. After that, the process is completed using the usual method.

According to such an operation, since the amount of gas supplied is reduced during arc heating, the vertical movement of the electrode 6 is reduced and stable operation is possible, and the wear of the electrode 6 is small, so that carbon pickup is reduced. In addition, since the amount of gas supplied is increased when adding slag and alloys and during desulfurization, it is possible to uniformize the components and quickly desulfurize, and the amount of gas supplied can be reduced by arc heating. Since it is controlled according to the presence or absence of gas, gas usage efficiency is increased, gas consumption is reduced, and operating costs can be reduced.

According to an example of implementation, compared to the conventional case, gasification was improved by 5 points, molten steel temperature by 8 points, and refractory corrosion by 15 points. If the cost index of ladle refining operation is 100, Lもgo/Volume 7-InnL#? I was able to reduce the ^soya 72 of the illusion Gito Hayanai 2.

[Effects of the Invention] As described above, according to the present invention, when stirring the grooved steel in the ladle by gas bubbling in ladle refining, a mechanism for controlling the amount of electric power input to the electrodes and a mechanism for controlling the amount of electric power input into the ladle are provided. The gas supply amount control mechanism is automatically controlled to reduce the gas supply amount during arc heating by the electrode and increase the gas supply amount during arc interruption. During out-of-furnace refining of molten steel in a ladle, by preventing local overheating of the slag and molten steel in the ladle hill and reducing melting damage to large ladle-resistant materials, the number of ladle repairs can be reduced. It is possible to reduce thermal segregation in the ladle hill, which is important in ladle refining, and to strengthen reduction refining.It also reduces the vertical fluctuation of the electrode during arc heating, which stabilizes operations and prevents carbon pickup due to electrode wear. It is possible to achieve a reduction in the amount of sulfur, and in addition, it is possible to improve desulfurization efficiency and make the composition uniform, and it also has the extremely excellent effect of making it possible to avoid variations caused by manual operation. It will be done.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a ladle refining apparatus according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between input power amount and gas supply amount over time during ladle refining. . 1... Ladle body, 2... Molten steel. 3... Slag, 4... Porous plug, 5... Water-cooled furnace lid, 6... Electrode, 7... Slag forming agent and alloy inlet, 13... Flow rate control valve (gas supply amount control mechanism), 14... orifice, 16... gas supply amount control device (gas supply amount control mechanism)
, 17...Microcomputer (CPU), 24...
・Differential pressure oscillator. 25...Input power amount control device (input power amount control mechanism)
.

Claims (3)

[Claims] (1) When stirring the molten steel in the ladle by gas bubbling in ladle refining, a mechanism for controlling the amount of electric power input to the electrode,
Performing automatic control in conjunction with a gas supply amount control mechanism into the ladle, reducing the gas supply amount during arc heating by the electrode and increasing the gas supply amount during arc interruption. A ladle refining method characterized by (2) The ladle refining method according to claim (1), wherein the amount of gas supplied is reduced prior to ignition of the arc when arc heating by the electrode is started. (3) An arrangement according to claim (1) or (2), in which the amount of gas supplied is increased with a slight delay after the arc is interrupted when increasing the amount of gas supplied while the electrode arc is interrupted. Pot smelting method.