JPS5845155B2 - Seikouyoua Kurono Seiren Kateiniokeru Youkoon Dojidou Seigiyohouhou - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a method for automatically controlling the temperature of molten steel in the refining process of an arc furnace for steelmaking, and more specifically, it includes ferroalloy input for adjusting the composition after the final treatment of oxidation refining in the refining process. This invention relates to a method for automatically controlling the temperature of molten steel up to the point where it is exposed.

Conventionally, temperature control of molten steel in the refining process of arc furnaces for steelmaking has been done manually by controlling the electrode voltage, setting the tapping temperature as the final target value.
This was done by adjusting the electrode current.

However, in the refining process of arc furnaces for steelmaking, ferroalloy is added after the final oxidation process in order to adjust the composition to obtain the desired steel type, which causes the temperature of the molten steel to fluctuate rapidly, making it difficult to control the temperature manually. However, it took a lot of time to tap the steel after adding the alloy.

This invention was made in view of the above-mentioned situation, and provides a desirable and appropriate temperature automatic control method in the refining process of an arc furnace for steelmaking.

In other words, the period after the end of the oxidation refining period in the refining process of an arc furnace for steelmaking is divided into two temperature control periods: before the ferroalloy is added, and after the ferroalloy is added until the steel is tapped. predicts the change in molten steel temperature caused by adding ferroalloy based on the amount of ferroalloy added using a predetermined calculation formula (described later), and adjusts the electrode voltage (
■, electrode current (■), and electrode vertical response sensitivity (S) are obtained to compensate for temperature changes when ferroalloy is added, and during the temperature control period after ferroalloy is added, a predetermined electrode voltage (■, electrode current (■) A method for automatically controlling the temperature of molten steel in the refining process of an arc furnace for steelmaking is provided, which is characterized in that the target temperature of tapping is maintained by the sensitivity (S) of the response to the rise and fall of the electrodes.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the configuration and control circuit of a steelmaking arc furnace in which the automatic temperature control method of the present invention is implemented.

In the same figure, 1 is an arc furnace for steelmaking, mainly a set of 3
A phase arc furnace is used, and depending on the charging method, any type of arc furnace such as a side charging method (rotating furnace lid type, moving furnace lid type, moving furnace body type) or a top charging type can be used.

Reference numeral 2 denotes an electrode, which consists of three graphite electrodes insulated and inserted into the furnace lid of the arc furnace 1.

3 is the steel tapping gutter.

The furnace body 1 is equipped with a limit switch 6 that detects the tilt angle.

Reference numeral 4 denotes a ferroalloy charging section, in which a predetermined ferroalloy is cut out based on the specified steel type and is charged into the arc furnace 1.

The ferroalloy input section is provided with a loading door, and the loading door is equipped with a limit switch 5 for detecting opening/closing of the door.

A temperature detector 7 detects the temperature of molten steel in the arc furnace.

Reference numeral 8 denotes a temperature setting device, in which a tapping temperature predetermined for each type of steel is set as a heating target temperature for molten steel.

9 is a computer which has the operating process of the arc furnace 1 as a time schedule, and according to this time schedule, the electrode current (■), the electrode voltage (■), and the electrode vertical response sensitivity (S) according to the automatic temperature control of the present invention are calculated. outputs a control signal.

Reference numeral 10 denotes a power control unit, which outputs a current setting value, a voltage switching tap signal, and a sensitivity setting value according to the output control signal of the computer 9, and controls the amount of control power from the power equipment 11.

Reference numeral 12 denotes an electrode lifting device which controls the lifting position of the electrode 2 based on the electrode lifting response sensitivity (S) from the power control unit 10.

Reference numeral 13 denotes a bunker for storing ferroalloy, into which ferroalloy is charged from the alloy charging section 4 via a chute 14.

FIG. 2 is a graph showing changes in molten steel temperature according to the temperature control methods of the present invention and the prior art.

In the same figure, curve A shows the molten steel temperature according to the temperature control method of the present invention, and curve B shown by a broken line shows the molten steel temperature when the temperature change in molten steel temperature due to the addition of ferroalloy is not compensated for before the addition of ferroalloy according to the conventional technology. Show change.

As shown on the horizontal axis, time t1 represents the ferroalloy charging time, time t2 represents the steel tapping time according to the present invention, and time t3 represents the steel tapping time according to the prior art.

Next, the temperature control method of the present invention will be specifically explained using FIGS. 1 and 2.

The computer 7 has the ferroalloy charging time t1 and steel tapping time t2 shown in FIG. 2 in advance as a time schedule.

This time schedule was obtained empirically and experimentally depending on the scale of the equipment, the type of steel, etc.

When the final oxidation process is completed in the operation of the arc furnace, the composition analysis of the molten steel is performed, and the computer has finished determining the amount of ferroalloy input to obtain the target composition value, the computer performs the next calculation process. conduct.

That is, α=×(ΣWi) (1) ■ △T−(Ts+α)−Ti (2) However, α= molten steel fluctuation temperature predicted by inputting ferroalloy QK-temperature correction coefficient (°C/kg) is given as the fluctuating temperature of molten steel per unit weight of ferroalloy input.

Ts = target set temperature CO, and the normal tapping temperature is used.

Ti - molten steel temperature, ferroalloy (FMn, FS
i.

Predict the fluctuating temperature α of molten steel when ferroalloy is added at time t1 from the input weight of SiMn, FCr, etc.),
Next, from equation (2), the temperature control value to be compensated for in the time period ΔT1, which is the change in molten steel temperature at the time of charging the ferroalloy with respect to the molten steel temperature Ti at the current time, up to the time t1 when the ferroalloy is charged is obtained.

Depending on the magnitude of ΔT, the calculator 9 determines the electrode current (2), the electrode voltage (2) to be supplied, and the vertical response sensitivity S of the electrode.

One example of determining these control output signals is to use a computer to determine I, V, and S corresponding to the magnitude of ΔT in advance.
Establish the table information for △T, and immediately refer to this table to find the current value (analog amount), voltage value (rip switching position), and sensitivity S (strong, medium, weak). .

I, V, and S obtained in this way are sent to the power control unit 10.
The electrode power amount is controlled by the output signal of the power control section 10 to obtain the temperature curve A of the molten steel before time t1 in FIG.

At time t1, when the ferroalloy is fed from the ferroalloy feeder 4, the temperature of molten steel drops rapidly and gradually recovers to the tapping target temperature Ts.

The completion of charging the ferroalloy is detected by the limit switch 5 provided on the ferroalloy charging door 4, and is input to the computer 9, and the computer 9 uses the ferroalloy charging completion signal from the limit switch 5 to change the control pattern after charging the ferroalloy. control pattern.

That is, ΔT = T s - T i (
As 3), ΔT is determined and temperature control is performed using the tapping target temperature Ts as the control target.

Current ■ and lightning voltage due to ΔT obtained from equation (3).

The determination of the sensitivity S also uses a method of referring to table information predetermined corresponding to ΔT, similar to the temperature control before alloy injection.

When tapping is completed at time t2, an operation completion signal is input to the computer 9 by the operation of the limit switch 6 for detecting the tilt angle of the furnace body 1, and the computer cancels temperature control.

The broken line B in FIG. 2 shows the case of the prior art,
A sudden drop occurs due to the addition of ferroalloy, and it takes until time t3 to recover to the tapping target temperature Ts.

In the present invention, the required time was 35 minutes, which enabled the operation time to be shortened, compared to the conventional technology which required 40 minutes or more.

As explained in detail above, as an automatic temperature control method in the refining process of an arc furnace for steelmaking, the period from the end of the oxidation stage to the tapping is divided into two temperature control time bands, before and after the addition of ferroalloy; The automatic temperature control method of the present invention, which controls the temperature by predicting the change in molten steel temperature when ferroalloy is added from the amount of iron input, and after adding the alloy, controls the temperature with the tapping temperature as the control target. This reduces the influence of molten steel on the molten steel temperature, making it easier to adjust the tapping temperature and reducing the operating time spent on temperature control. This has brought about uniformity and stability in quality, and has enabled a dramatic improvement in the operational efficiency of steelmaking arc furnaces.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing steelmaking arc furnace equipment and a control block in which the present invention is used, and FIG. 2 is a graph diagram showing molten steel temperature according to the present invention. 1... Steelmaking arc furnace, 2... Electrode,
3... Steel tapping gutter, 4... Ferroalloy input section,
5, 6... Limit switch, 1...
Temperature detector, 8...Temperature setting device, 9...
・Calculator, 10...Power control music loudspeaker 11...
...Power equipment, 12... Electrode lifting device, 13.
...Hopper, 14...Chute, t,...
.... Ferroalloy input time, t2... Steel tapping time, t3... Steel tapping time according to the conventional technology.

Claims (1)

[Scope of Claims] 1. A method for controlling the temperature of molten steel in a refining process in which the temperature of molten steel is adjusted to a target component value by adding a predetermined ferroalloy determined by the steel type specification of an arc furnace for steelmaking, wherein The operational process after the end of the refining period is divided into two temperature control periods: before the ferroalloy is added, and after the ferroalloy is added until the steel is tapped.In the temperature control period before the ferroalloy is added, changes in molten steel temperature due to the ferroalloy are added. (ΔT) is expressed by the formula % formula % () However, α = Fluctuation temperature of molten steel predicted by adding ferroalloy Q K = Temperature correction coefficient (°C/Kg) Ts - Target set temperature CQ Ti = Molten steel temperature Wi - = Alloy The electrode voltage (■), electrode current (I), and electrode vertical response sensitivity (S) of the steelmaking arc furnace are determined from the value of the molten steel temperature change (△T), and the ferroalloy is determined from the input amount for each iron brand. The molten steel temperature is controlled for a certain period of time before the ferroalloy is added to obtain a molten steel temperature of (Ts + ΔT) at the time of ferroalloy injection to compensate for the temperature change in the molten steel due to the ferroalloy injection. A method for automatically controlling molten steel temperature in the refining process of an arc furnace for steelmaking, characterized in that the tapping temperature (Ts) is maintained at a predetermined electrode voltage (■) of the furnace, electrode current (I), and response of rising and falling electrodes.