JPS5920727B2 - Method for adjusting composition of molten steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adjusting the composition of molten steel.
The present invention relates to an improved method of blending alloy components in a mixing container and adjusting the components so that the yield of alloy components can be increased and the components can be adjusted accurately.

As a method of adjusting the composition of molten steel melted and refined in a converter, electric furnace, open hearth, etc., after transferring the molten steel to a ladle, Mnt and C are added to it.
There is a method of adding alloy components such as r5Ws Vt Nbt At and TL Si.

At this time, in order to melt and disperse the alloy components evenly in the molten steel, it is natural that the molten steel should be sufficiently stirred in the alloy addition process, and the current amount generally practiced is shown in Figure 1. As shown, this is a method in which components are adjusted simultaneously during the vacuum degassing step.

That is, FIG. 1 is a schematic cross-sectional view illustrating the case where component adjustment is performed in the implementation step of the vacuum degassing method known as the RH method.
In the figure, 1 is a ladle, 2 is a mixing container, 3 is a molten steel rising pipe, 4 is a molten steel down pipe, 5 is an inert gas (generally Ar) feed pipe,
6 is a vacuum suction port, 7 is an alloy component container, A is molten steel, and B is an alloy component.

When carrying out the illustrated method, a mixing vessel 2 is placed above the ladle 1.
are placed, the rising pipe 3 and the descending pipe 4 are immersed in the molten steel A in the ladle 1, and the inside of the mixing container 2 is brought into a vacuum state by suction from the vacuum suction port 6.

Then, the difference between the pressure in the mixing container 2 and the pressure in the ladle 1 is approximately 1
A pressure difference is created, and the molten steel A is sucked up into the mixing vessel 2 (the suction height h at this time is about 1.48 m when the pressure difference is 1 atmosphere).

When an inert gas such as argon gas is fed into the riser pipe 3 from the inert gas feed pipe 5, the molten steel A is pushed up into the mixing vessel 2 by the principle of an air lift pump, while the above-mentioned suction height h When the amount exceeds 1, the liquid gradually flows down from the downcomer pipe 4 into the ladle 1.

That is, the molten steel A circulates between the ladle 1 and the mixing container 2,
Since the inside of the mixing container 2 is always maintained in a reduced pressure state, the molten steel A is melted in this portion.

02. Degassing with N2°N2, etc. is performed.

When alloying component B is added from the alloying component container 7 in this step, it is added to the molten steel A in the ladle 1 along with the molten steel A in the mixing container 2.
Alloy component B
is uniformly dispersed in molten steel A.

That is, in this method, by circulating the molten steel A and the alloy component B, both can be mixed uniformly, and it can be said to be an excellent method for adjusting the components.

However, in the above method, the following difficulties arise due to the supply of inert gas, which poses a major problem in practical application.

That is, the inert gas blown from the feed pipe 5 through the riser pipe 3 escapes from the surface of the molten steel A in the mixing container 2 and is then suctioned and discharged in the direction of the suction chamber 6, but is not discharged from the container 7. A part of the alloy component B in the form of fine powder may be flowed toward the suction port 6 by this inert gas flow and may adhere to the wall surface, or may be washed away along with the inert gas toward the suction line.

If this happens, the actual amount of alloy added will decrease and the specified composition adjustment will not be carried out, or the alloy powder that was sucked and discharged together with the inert gas will accumulate on the suction line, or even have a negative effect on the vacuum pump. Various difficulties arise from the viewpoint of equipment maintenance as well.

In addition, in both the RH method and the DH method, the temperature of the molten steel gradually decreases during the circulation treatment process, and the dissolution rate of the alloy components drops accordingly, so try shortening the circulation cycle. However, it is not possible to shorten the component adjustment time (the time required to uniformly dissolve the alloy components).

In addition, as shown in Japanese Patent Publication No. Sho 47-15561, a method has also been proposed in which an electromagnetic pump is used as a means to suck up molten steel from a ladle into a vacuum vessel, and alloy components are dropped from the top of the vacuum vessel to adjust the composition. has been done.

However, even if you directly implement the method listed in the above publication,
Satisfactory results are not always obtained.

However, in the method described in the above-mentioned publication, an electromagnetic pump is simply used to circulate the molten steel between the ladle and the vacuum vessel, and the effect of shortening the component adjustment time is hardly exhibited.

In particular, in the method described in the above publication, a low frequency of 0.9 to 16 cycles is used as the power source for the electromagnetic pump to avoid heating the molten steel as much as possible, so a drop in molten steel temperature due to circulation is unavoidable. Complete melting of the alloy components takes a considerable amount of time.

Moreover, since the above-mentioned special frequency must be used, there is a disadvantage in that the power supply cost is two to three times higher than that of equipment that can use the commercial frequency as is, and overall, it is difficult to put it into practical use on an industrial scale. It is difficult to

The inventors of the present invention focused on the above-mentioned circumstances, and thought that it would be advantageous to use a linear motor in order to overcome the above-mentioned difficulties associated with the use of inert gas. We have been conducting intensive research in hopes of improving the ingredient adjustment method used.

As a result, the frequency was increased to 50% as the operating source for the C linear motor.
By doing ~60 cycles, the molten steel can be heated simultaneously and the dissolution rate of the alloy components can be greatly accelerated.The alloy components are added to the molten steel that is sucked up into the vacuum vessel while being heated by the C linear motor. If you adopt a method of holding this in a vacuum container for a while, the alloy components can be melted more efficiently.■ If the frequency is 50 to 60 cycles, you can use commercial electricity as is, so there is less burden on equipment. I knew that I was going to live.

The present invention was made based on these findings, and has a structure in which a part of the molten steel in the ladle is passed through at least one molten steel passage pipe to a mixing pipe located at a higher position than the ladle. In a method for adjusting the composition of molten steel that is sucked up into a container, mixed with alloy components in the mixing container, and then flowed back into the ladle container through at least one molten steel passage pipe, the outer periphery of the said passage pipe that sucks up the molten steel is Arrange a linear motor and drive the motor to 50~60
A predetermined amount or more of molten steel is sucked up and held in the mixing vessel while heating the molten steel by operating at a cycle frequency, and alloy components are added to the molten steel and mixed into the molten steel, and then the mixture is passed through the molten steel passage pipe. The gist lies in the fact that it is then poured back into the ladle.

In other words, one feature of the present invention is that the linear motor is operated at a frequency of 50 to 60 cycles to heat and suck up the molten steel, thereby preventing the temperature of the molten steel from dropping due to circulation and significantly reducing the melting of alloy components. It can be promoted.

For example, when adding alloying components to molten steel at a temperature of 1670 to 1680°C, increasing the molten steel temperature by 10°C according to the present invention can approximately double the dissolution rate of the alloying components, and the composition adjustment time is inversely proportional to this. can be shortened to about 1/2.

Another feature of the present invention is that the molten steel after addition of alloying components is held for a while in a vacuum vessel, thereby making it possible to adjust the components more efficiently.

That is, when alloy components are added to molten steel heated by a linear motor and held in a vacuum container for a predetermined period of time (usually about 10 to 30 minutes), the alloy components are almost completely dissolved in the molten steel during this time, so it is relatively Uniform component adjustment can be performed in a short time.

On the other hand, in the method of adding alloy components through a simple circulation process, the alloy components are poured back into the ladle without being fully dissolved in the vacuum container, resulting in a considerable dissolution rate of the alloy components as a whole in the processing system. This would make it too late to achieve the purpose of the present invention.

The configuration and effects of the present invention will be explained below based on the drawings which are examples, but the following are only representative examples, and it is possible to carry out the invention with appropriate changes in accordance with the spirit of the preceding and following. Also included in the scope of the technology of the present invention.

2 and 3 are schematic cross-sectional views illustrating the component adjustment method of the present invention, and the overall structure of the apparatus is substantially the same as the example shown in FIG. 1.

However, in this example, a linear motor 8 is disposed at a suitable position on the outer circumference of the molten steel passing pipes 3' and 4', and by operating this at a frequency of 50 to 60 cycles, the molten steel A in the ladle 1 is is heated and lifted into the mixing container 2.

Then, while lifting a predetermined amount of melt @A into the mixing container 2,
Alternatively, after lifting the alloy component B from the alloy component container 7 (Fig. 2), hold it for a predetermined time to mix the alloy component B into the molten steel, and then stop driving the linear motor 8 or The propulsive force of the motor 8 is switched downward to flow the mixture back into the ladle 1 (Fig. 3) and mix it with the molten steel A in the ladle 1.

After repeating this operation to add a predetermined amount of alloy component, alloy component B can be uniformly mixed into molten steel A by repeating lifting and pouring back the molten steel an appropriate number of times.

At this time, in the present invention, the propulsive force of the linear motor 8 is used to lift the molten steel A without using an inert gas.
There is no fear that the loose alloy powder in the example of FIG. 1 will adhere to the vicinity of the vacuum suction port 6 or be discharged into the suction line, etc., and all of the dropped alloy component B is mixed into the molten steel A.

Therefore, the components can be adjusted extremely accurately, and furthermore, there is no possibility that the alloy component B will enter the suction line, vacuum pump, etc. and cause an unexpected accident.

If the inside of the mixing container 2 is maintained in a reduced pressure state during this step, the molten steel A can be degassed at the same time, but in the present invention, the propulsive force of the linear motor 8 is used to lift the molten steel A. Since lifting is possible even without a vacuum suction force, it is also possible to adjust the components while maintaining the inside of the mixing container 2 at normal pressure depending on the case.

However, in this case, it is desirable to replace the space inside the mixing vessel 2 with an inert gas such as argon to prevent oxidative deterioration of the molten steel A and the alloy component B.

Figures 4 and 5 show another embodiment of the present invention, in which a single molten steel passage pipe 3' is used, and when molten steel A is lifted into the mixing container 2, a near motor 8 applies an upward driving force to the molten steel A. After adding alloy components in the container 2 and holding for a predetermined time, the passage pipe 3' is used as a descending pipe, and the linear motor 8 is stopped (or the same or a different linear motor is used to move downward). The mixture is poured back into the ladle 1 (Fig. 5), and this process is repeated to adjust the ingredients.

In this way, in the present invention, the linear motor 8 is used to lift the mixing container 2-\ of the molten steel A, and the molten steel A is lifted at the same time as the molten steel A.
The biggest feature is that the alloy components are melted and dispersed in the molten steel A as quickly as possible by heating the molten steel A and holding the molten steel A in the mixing vessel 2 for a predetermined period of time after adding the alloy components. There is.

Therefore, as long as such characteristics can be effectively exhibited, various modifications can be made in addition to the illustrated example. For example, the mixing container 2
The shape, structure, size, etc., or the size, shape, number, etc. of the molten steel passing pipes constituting the molten steel rising pipe and the descending pipe can be changed as appropriate depending on the situation at the work site.

The present invention is roughly constructed as described above, and its effects can be summarized as follows, and various effects suitable for practical use can be enjoyed as a method for adjusting the composition of molten steel in a ladle.

■ By setting the frequency used by the linear motor to 50 to 60 cycles, molten steel can be heated at the same time.
The dissolution rate of alloy components can be maintained at a high level at all times,
Component adjustment time can be significantly reduced.

(2) Since this method involves holding the molten steel in a mixing vessel for a predetermined period of time after adding the alloying components and pouring it back into the ladle after the alloying components have been completely dissolved, extremely uniform composition adjustment can be achieved.

■ Even when degassing is performed at the same time as component adjustment, a high degree of vacuum can be maintained at all times because the inert gas used to lift the molten steel into the mixing container is less than a year old.

Furthermore, there is no risk of alloy powder entering the suction line, vacuum pump, etc. (there is no loss of alloy components), so the components can be adjusted accurately.

■ Since the commercial frequency of 50 to 60 cycles can be used as the operating source for the linear motor, electricity costs can be reduced to 1/2 to 1/3 compared to conventional methods that use frequencies of 0.9 to 16 cycles. You can

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional explanatory diagram showing the conventional component adjustment method;
5 are schematic cross-sectional explanatory diagrams illustrating the component adjustment method of the present invention. DESCRIPTION OF SYMBOLS 1... Ladle, 2... Mixing container, 3, 4... Molten steel passage pipe, 5... Inert gas feed pipe, 6... Vacuum suction port, 7... Alloy component container , 8... linear motor, A.
... Molten steel, B... Alloy component.

Claims (1)

[Claims] 1 A portion of the molten steel in the ladle is sucked up through at least one molten steel passage pipe into a mixing container located at a higher position than the ladle, and after blending alloy components in the mixing container, at least 1
In this method of adjusting the composition of molten steel flowing back into a ladle container through a molten steel passage pipe, a linear motor is placed on the outer circumferential side of the passage pipe that sucks up molten steel, and the motor is operated at a frequency of 50 to 60 cycles. By heating the molten steel, a predetermined amount or more is held in the mixing container by suction, and after adding alloying components to this and mixing it into the molten steel, the mixture is poured back into the ladle through the molten steel passage pipe. A method for adjusting the composition of molten steel.