JPS5938282B2 - Slag coating method on bottom blowing converter furnace wall surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating slag on the wall surface of a bottom-blown converter furnace.

Conventionally, slag coating has been applied to protect the furnace wall bricks of converters and the like.

In a top-blown converter, after the refined molten steel is tapped, a portion of the molten slag is left in the furnace and dolomite is added to the remaining slag. to raise the melting point of the molten slag,
To make it easier for so-called slag to adhere to the furnace wall.

Then, the furnace body is swung within a range of ±90° around the trunnion axis, and the residual slag is deposited mainly on the charging side and the tapping side of the furnace to cover and protect the furnace wall surface. This is the technology that made it possible.

However, in this case, the slag coating on the furnace wall surface on the trunnion side was insufficient compared to other areas such as the tapping port side, and there was a drawback that the bricks were eroded unevenly.

On the other hand, when applying slag coating to a bottom blowing converter,
This is the same as in the case of the above-mentioned top-blown converter in that the molten slag remains after tapping and the furnace body is rocked to cause the molten slag to adhere to the furnace wall surface, and the same drawbacks were observed.

Moreover, in some cases of bottom-blown converters, while molten steel, molten slag, etc. are present in the furnace, high flow rates (approximately 5.0 x 102m
/ see ) inert gas (Ar, N) must be flowed.

However, the conventional piping design for the bottom tuyere system allows the flow to flow at a constant rate in order to simplify operations, so the flow rate is also regulated during slag coating.

As a result, as shown in FIG. 1 of the drawings, the degree of slag scattering is large and constant, so that the slag is concentrated near the furnace mouth and the throat constriction.

Then, the adhesion near the furnace mouth gradually increases, and metal, etc., accumulates, reducing the internal volume of the furnace.

Therefore, when the furnace body is tilted during tapping, the molten slag overflows from the furnace mouth, resulting in insufficient tilting of the furnace, and iron remains in the furnace, resulting in a permanent decline in the steel production rate. i. If a large amount of deposits were formed on the upper part of the furnace, the tilting torque of the furnace body would increase, causing the motor to be overloaded and shortening its life.

This invention is a method developed with the aim of overcoming the drawbacks of the above-mentioned slag removal coating method, and focuses on the gas blown from the bottom tuyere of a bottom blowing converter, and actively utilizes this. This method coats the furnace wall with slag.

That is, during slag coating, the furnace body 1 is oscillated to mainly achieve slag coating on the charging side and tapping side furnace walls, and on the other hand, the trunnion side furnace wall surface, which is insufficient by itself, is coated with slag from the tuyeres at the bottom of the furnace. This is a technique to deposit and coat slag with a predetermined thickness by controlling the gas blowing speed according to the amount of residual slag and its slag viscosity and according to the targeted position.

Naturally, if the flow rate of the blown gas is increased, the slag will adhere to the upper part of the furnace near the throat constriction part 4.
By reducing the flow rate of the blown gas, the coating can be applied to the furnace wall near the bottom constriction part 5, and by changing the flow rate, the coating can be applied to any desired position.

In particular, with this method, slag coating can be applied to both trunnion sides.

When the relationship between the slag scattering height and the flow rate of the gas blown from the tuyere was investigated, the results shown in Figure 2 were obtained.

As can be seen from this figure, the greater the flow rate of the coating gas, the greater the distance of scattering, and it is clear that the distance is completely proportional to the flow rate.

The flow rate of the blown gas is controlled depending on the amount of slag left in the furnace and the viscosity of the slag.

When the amount of slag is large and the slag viscosity is high, the flow velocity described above must be increased in order to make it adhere to the specified location.On the other hand, when the amount of residual slag is small and the slag viscosity is low, even if the flow velocity is low, the flow velocity must be increased. can be attached to.

For example, to show the conditions under which favorable results were obtained in an example conducted by the present inventor, in a 230-ton converter, approximately 5 to 50% of slag was
Remaining 6, put dolomite T-1,5, and reduce the furnace body to ±30
The test was carried out in a state where the test was oscillated within a range of °.

In this invention, the purpose of shaking the furnace body together with gas injection from the bottom of the furnace is mainly to coat the furnace walls on the charging and tapping sides of the converter with slag. When the amount of residual slag is small, gas blow-through occurs,
If the amount of slag scattered decreases, effective coating becomes impossible, so the idea was to compensate by shaking the furnace body.

The swing angle is selected to be an appropriate angle necessary to prevent gas blow-through.

Example 1 1.5 tons of dolomite was charged into a bottom blowing converter, leaving about 61 tons of slag.

At this time, the condition of the furnace wall was that after about 1000 strokes of the furnace mouth, the melting damage at a position of about 1.5 to 3 m from the furnace bottom had progressed significantly.

Air was used as the blowing gas at a blowing gas flow rate of 2.5×102 m/sec.

As a result of this blowing, it was possible to achieve intensive adhesion between 1.0 and 3.5 m.

The swing angle at this time was ±5°. Example 2 Since the hearth bottom was replaced after 2000 times of hearth throttling, 2~
Coating treatment was carried out in a state where there was significant erosion at the 4 m position.

Therefore, we left about 5% of the slag in the furnace and 1.5% of the dolomite.
was introduced.

The flow rate of gas injection from the hearth bottom tuyere is 3.5X1
Nitrogen gas was blown at a rate of 0.2 m/sec.

The swing angle is ±10°.

As a result, it was possible to intensively apply slag coating between 1.5 and 4.5 m from the bottom of the furnace.

As explained above, according to the present invention, by changing the gas blowing speed, it has become possible to apply slag coating to any part of the furnace inner wall.

Moreover, compared to conventional slag coating for bottom-blown converters, the resistance to adhesion on the upper part of the furnace is reduced, eliminating any negative impact on operation, and it also prevents adhesion on the trunnion side, which was not possible in top-blowing converters. is now also possible.

As a result, it is very beneficial for improving the life of the furnace.

Although the present invention has been explained using a bottom-blowing converter, even in a top-blowing and bottom-blowing converter that has recently been developed, the slag can be blown away by changing the gas flow rate blown from the bottom of the furnace.
Slag coating can be applied to any position.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing the state of slag coating in a conventional bottom-blown converter, and Fig. 2 is a view showing the relationship between the slag blow-off height and the slag gas flow rate when the method of the present invention is implemented. It is. 1...Furnace body, 2...Furnace bottom tuyere, 3...
...Furnace wall, 4...Furnace throttle part, 5...
... Hearth bottom throttle part.

Claims (1)

[Claims] 1. A method in which slag left in the furnace after tapping refined molten steel is attached to the wall surface of a converter via gas injection means, in which the furnace body is centered around the trunnion without overturning the converter. The remaining slag can be removed as desired by blowing gas through the tuyere provided at the bottom of the furnace and changing the flow rate of the blown gas according to the amount and viscosity of the slag left in the furnace. A method for coating a slag on a wall of a bottom blowing converter, characterized by coating the slag on the wall of a bottom blowing converter.