JPH0219415A - Converter blowing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a blowing method for adjusting molten metal components in converter blowing, and particularly to a converter blowing method for adjusting the phosphorus concentration of molten metal to an appropriate value. Regarding.

[Prior Art] Recently, dynamic control has been adopted in which blowing conditions are computer-controlled based on various measurement information during blowing. In a so-called belly blowing furnace, an oxygen jet is blown onto the furnace and the molten metal is stirred by bottom blowing gas to promote the reaction between slag and metal, and bring the molten metal composition closer to the target value at the time of tapping.

In adjusting the molten metal components, decarburization and dephosphorization reactions are particularly important.

The dephosphorization reaction during blowing proceeds as shown in equation (1) below.

2 [P] +5 (F eo) -P20s +5F
e...(1) That is, phosphorus [P] in the molten metal is equivalent to (F e O
) and becomes p2o, which combines with calcium oxide (Cab) in the slag and is incorporated into the slag to become stable.

The conventional converter blowing method indirectly adjusts [P] while appropriately controlling the decarburization reaction, which is a dynamic model, based on the molten metal temperature and EC obtained by sublance measurement.

[Problem to be solved by the invention] However, in the conventional converter blowing method, the molten metal As a result, the dephosphorization rate in low-grade steel becomes too low than necessary, resulting in overspecification, which is not rational.

In addition, since there are a wide variety of factors that govern the dephosphorization reaction, such as molten metal composition, temperature, slag composition, and slag slag conversion rate, the amount of dephosphorizing agent (lime) required to obtain an appropriate dephosphorization rate must be determined. It is difficult to calculate accurately and quickly.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a converter blowing method that allows the dephosphorization rate to be adjusted to a reasonable value depending on the type of steel.

[Means for Solving the Problems] The converter blowing method according to the present invention detects the components and amounts of furnace gas generated during converter blowing at any time, and adjusts the detected values and preset blowing conditions to Based on this, a predetermined mathematical model is used to find the optimal conditions, and after adding a dephosphorizing agent based on this, the blowing conditions are controlled so that the molten metal temperature and the phosphorescence in the slag (FeO) reach the target values, and the phosphorus in the molten metal is It is characterized by adjusting [P].

[Operation] In the converter blowing method according to the present invention, the components and amounts of the furnace gas are measured at any time, and the blowing conditions (
(Hot metal composition, target temperature, molten metal phosphorus concentration, total iron content of slag)
into the computer.

Then, based on these input data, the amount of slag (FeO) and the molten metal temperature T such that [P] becomes a predetermined target value are determined using equations (1) to (3) below. That is, by solving the following simultaneous equations (1) to (3), the respective input amounts of CaO and MgO are determined before the start of blowing.

l o g (P20s) / [P] 2-λ f
ll, 2X log ((Cab) +0.3 (
MgO) −0,05(F e O) ) +29600
/ (T +273)+5 log (FeO)l
・” (1) The above equation (1) represents the dephosphorization equilibrium equation, where the symbol λ represents the dephosphorization equilibrium coefficient and the symbol T represents the molten metal temperature, respectively.

Input P = Output P-WM X [P] /1
00 +WSX (P20s)/100X
82/ 142 ... (2) Above (
The formula 2) represents a phosphorus balance formula, in which the symbol WM represents the amount of molten metal, and the symbol Ws represents the slag weight.

100(%) −(Cab)+ (FeO)+ (S fo2)+ (
MnO)+ (P20s)+ (MgO)+C...
(3) Equation (3) above represents a slug balance equation, and the symbol C in the equation represents a constant.

CaO and MgO are added to the molten metal in amounts determined by computer calculation. On the other hand, during blowing, the flow rate and components of the exhaust gas are measured online, and based on this measurement information, the blowing conditions are adjusted as needed so that the temperature of the slag (FeO) and the molten metal approach the target values. [P] Control the value to an appropriate value.

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

The converter 10 is a composite blowing furnace configured to blow stirring gas into the molten metal 12 through a bottom blowing nozzle 14 and to blow an oxygen jet from a main lance 20 onto the surface of the molten metal. Piping 16 and main lance 2 communicating with bottom blowing nozzle 14
Flowmeters 18 and 24 are installed in the piping 22 communicating with the
are provided, each connected to the input side of the process computer 40. The computer 40 has a memory that stores input data, an arithmetic unit that executes various operations, and a CPU (central processing unit) that sequentially retrieves and processes data stored in the memory, and collects various process data. Optimum control conditions for blowing are determined based on mathematical models corresponding to predetermined static and dynamic models, and optimal control commands are issued to various devices.

A hood 26 of a duct 28 is provided to cover the charging port of the converter 10, and gas generated within the converter is guided through the duct 28 to an exhaust gas treatment device (not shown). A chute 30 is attached to the duct 28 near the converter charging inlet, and the auxiliary raw material weighed by the weigher 32 is transferred to the chute 30.
It is cut out into the duct 28 through the duct 28, and further falls into the converter. On the other hand, a gas analyzer 34 and a mass spectrometer 35 are installed at the top of the duct 28,
The components and mass of exhaust gas are detected.

Further, an exhaust gas flow meter 36 is provided at the throttle at the bottom of the duct to detect the flow rate of exhaust gas.

In addition, the weighing device 32. Gas analyzer 34. Each of the mass spectrometer 35 and the flow meter 36 is connected to an input end of the computer 40.

Additionally, a sublance device (not shown) is installed above the converter 10.
is provided, and when the sub-lance is lowered, the tip of the sub-lance is inserted into the converter from the charging port and immersed in the molten metal 12. Incidentally, a probe is attached to the tip of the sublance so that the molten metal temperature and carbon concentration [C] can be immediately detected.

Next, a case will be described in which the end point temperature is estimated in this embodiment.

Before starting blowing, various conditions such as hot metal composition, target temperature, target (FeO) amount, and target dephosphorization rate are input into the computer 40 in advance. These conditions were determined empirically depending on the steel type based on previous operational results. Then, based on these input data, the simultaneous equations consisting of equations (1) to (3) described above are solved to calculate the amounts of CaO and MgO required for blowing, respectively. Next, amounts of CaO and MgO according to the calculated amounts are put into the converter and blowing is started.

On the other hand, during blowing, the exhaust gas components, the mass of each component,
and the exhaust gas flow rate, respectively, and input these detected values into the computer 40. When various exhaust gas information data is input into the computer, the target molten metal temperature and (F
eO) Control the blowing conditions so that the actual value approaches ffi.

That is, depending on the ever-changing blowing conditions, the input amount of auxiliary raw materials is adjusted to keep the molten metal temperature T within the target range of 1600 to 1750°C, and the total iron t (T-FeO) in the slag to the target range of 10 to 1750°C.
The blowing is finished when the content reaches 20% by weight.

In Figure 2, the difference in [P] between the target and actual results is plotted on the horizontal axis.
It is a graph diagram in which the accuracy of [P] in a 250-ton composite blowing furnace was investigated, with the occurrence frequency plotted on the vertical axis.

As is clear from the figure, the average difference between the two is -2.1
X10' weight%, deviation value σ1.95X10-3 weight%
We were able to significantly reduce the variation.

As a result, the average level of phosphorus contained in the product can be adjusted to an appropriate level according to the standard value of steel, and the consumption of CaO and MgO as solvents can be reduced per ton of molten metal compared to conventional methods. We were able to reduce the weight by approximately 4 kg per unit.

[Effects of the Invention] According to the present invention, blowing conditions can be controlled so that the dephosphorization rate is appropriate depending on the steel type, so blowing can be performed economically. In particular, in the case of low-grade steel, it is possible to avoid excessive dephosphorization of the molten metal, so the amount of auxiliary raw materials used can be significantly reduced, and operating costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a converter blowing method according to an embodiment of the present invention, and FIG. 2 is a graph diagram showing the effects of the present invention. 10; converter, 12; molten metal, 14; bottom blowing nozzle, 16.
22; pipe, 18, 24, 36; flow meter, 20: lance,
26; Hood, 28; Duct, 30; Shooter, 32;
Weighing instrument, 34.35; Analyzer, 40; Process computer Patent attorney Takehiko Suzue

Claims (1)

[Claims] Detects the components and amount of furnace gas generated during converter blowing at any time,
Based on this detected value and preset blowing conditions, a predetermined mathematical model is used to find the optimal conditions, and after adding a dephosphorizing agent based on this, the molten metal temperature and the amount of (FeO) in the slag reach the target values. The blowing conditions are controlled to reduce phosphorus [P] in the molten metal.
A converter blowing method characterized by adjusting.