JPS61115655A - Method for adding low melting metal to molten steel - Google Patents

Abstract

PURPOSE:To add a low melting metal to a molten steel at a high yield in the stage of adding the metal having a low m.p. and large specific gravity into the molten steel by feeding forcibly the low melting metal in a molten state directly into the molten steel in a vessel from the vessel side part while stirring the molten steel with an inert gas. CONSTITUTION:The molten steel 4 is put into the vessel 1 such as tundish lined with refractories and an inert gas such as Ar is ejected from a porous plug 2 provided to the bottom thereof to stir the molten steel 4. The metal 13 such as Pb or Bi having the low m.p. and large specific gravity is put into a tank 10 and is heated by a heating wire 11 to a molten state. A compressed gas of Ar, etc. is fed into the tank 10 through an inlet 12 thereof to feed forcibly the molten low melting metal 13 through a brick 8, which allows the permeation of the low melting metal and is provided to the side wall of the vessel 1, into the molten steels 4. The low melting metal is stirred by the ascending flow of the gaseous Ar from the plug 2 and is added at the uniform concn. into the molten steel at a high yield of >=90%.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for uniformly adding low-melting point metals such as Pb and Bi to molten steel with good yield during the production of molten steel. It is.

(Prior Art) Conventionally, the method shown in FIGS. 2 and 3 is known as an example of a method for adding a low melting point metal to molten steel.

The system shown in Fig. 2 is called the upward addition method, in which stirring gas 3 is blown into the molten steel 4 through a porous plug 2 provided at the bottom of the container 1, and the molten steel 4 is added from the surface of the molten steel. 5.

The method shown in FIG. 3 is called an injection addition method, and is a method in which an immersion lance 6 is immersed in the molten steel 4, and low melting point metal particles 5 are injected together with a carrier gas 7 such as argon gas to cause decomposition. .

In addition, as a conventional technique, a powder desulfurization agent is injected together with a carrier gas from the bottom of the side wall of a molten steel container.
This is shown in Japanese Patent No. 6722.

(Problems to be Solved by the Invention) However, these conventional techniques have the following difficulties. That is, in the upward addition method shown in FIG. 2, the low melting point metal particles 5 vaporize and emit smoke as soon as they reach the surface of the molten steel, resulting in a poor yield. Moreover, since these vapors are generally harmful to the human body, large-scale dust collection equipment is required. Furthermore, the time that the added low-melting metal particles ride the upward flow of the molten steel 4 is extremely short, and the particles, such as Pb and Bi, which have a higher specific gravity than the molten steel, are quickly caught up in the downward flow. Since the melting point metal reaches the bottom without being dissolved by 10 eM, there is a problem that the rotation at the bottom becomes extremely high.

In addition, in the addition method shown in FIG. 3, the low melting point metal particles 5 discharged into the molten steel 4 together with the carrier gas 7 cannot sufficiently ride the upward flow and are deposited at the bottom as in the upward addition method. It tends to settle easily. Further, since the low melting point metal has a low melting point, the grain surface becomes soft, and clogging is likely to occur near the curved portion 9 of the piping and the discharge hole of the immersion pipe 6. or.

There are problems such as high costs for equipment such as the immersion lance 6 and high operating costs.

Further, JP-A-50-26722 discloses the injection of a desulfurizing agent, and does not mention anything about the injection of molten metal.

(Means and operations for solving the problems) The present invention has been made with the aim of solving the above problems, and its gist is that a molten low melting point metal is press-injected from the lower side wall of the molten steel bath surface of the molten steel container. This is a method of adding a low melting point metal to molten steel.

FIG. 1 shows an example of an apparatus for carrying out the method of adding a low melting point metal to molten steel according to the present invention. A low melting point metal permeable brick 8 is embedded in the side wall of the molten steel container 1, and a conduit 9 is connected to the brick 8.
and connect the other end of the conduit 9 to a storage tank 10 made of low melting point metal.
Attach it to the bottom of the screen.

The storage tank 10 and the conduit 9 are surrounded by an electric heating illumination to heat the low melting point metal inside. Further, a porous plug 2 is provided at the bottom of the container 1 near the side wall in which a permeable brick 8 of low melting point gold 4 is embedded, and a nozzle 3-1 for stirring gas 3 is connected to this. 14 is a molten steel discharge port.

The embedding position of the permeable brick 8 made of low melting point metal is as follows:
It is sufficient if it is below the molten steel bath surface on the (1111) wall of the container, but a more effective position is preferably above 173 and below 2/3 of the molten steel depth from the bottom of the container.

A through pipe or a brick having through holes or slits can be used as the low melting point metal permeable gas 8, but in order to allow only the molten low melting point metal 13 to pass through without penetrating the molten steel, a through hole or a gas can be used. ) The inner diameter of the hole and the slit width of the slit brick are preferably 100μ at maximum.

Next, the method of supplying the low melting point metal will be described. The added low melting point metal is supplied to the low melting point metal permeable brick 8 through a storage tank 10 heated to 350° C. or higher by a heating wire 11 and a conduit 9. There are various ways to control the supply plan, such as adjusting the pressure inside the storage tank 10 using compressed gas 12 or a piston, or adjusting the hot water level in the storage tank. However, in either case, it is necessary to make the static pressure higher than the static pressure of molten steel.

The addition yield can be stabilized at a high level by setting the pumping part of the low melting point metal to the center of the depth of the molten steel in the container l, where an active upward flow is generated by the stirring gas 3 blown from the porous plug 2. preferable.

Further, as the container 1, a tundish, a molten steel ladle, etc. can be used.

(Example) In a tundish with a depth of 2 m and a capacity of 120 tons, bricks having through holes with an inner diameter of 50 to 100 μm were installed on the wall 1.0 m from the bottom of the tundish, and the surrounding area was surrounded by a molten state. A low melting point metal permeable brick 8 surrounded by a metal case was set to prevent the low melting point metal 13 from flowing out. Furthermore, just below that, at the bottom near the wall,
A porous plug 2 was set to supply Ar gas for stirring, and the design was such that an upward flow was generated at the part where the low melting point metal was pumped.

After tapping the steel from the converter, when injecting the molten steel into the tandy rough 2 through the ladle, the molten @ stirring Ar gas is supplied from the porous plug 2.
3 Nm"/Hr. At the same time, the heating wire 11
7' (Pb storage tank 10
By feeding N2 gas at about 4 to 9/ci into
A total of 132 p/T-D additions were made for 11 minutes at a rate of 7 minutes. There was almost no smoke emitted from the surface of the molten steel during addition.

The l'h shoulder content in samples taken from the injection streams at the beginning, middle, and end of injection during continuous casting was all 009 to 0.1.
1%, and an addition yield of about 91% was obtained.

(Effect of the invention) By the method of the present invention, the addition yield of low melting point metal to molten steel is approximately 9.
0%, which can be significantly improved compared to 50% of the conventional method shown in FIG. 2 and 70% of the conventional method shown in FIG. Along with improvement in yield.

The amount of smoke emitted by vaporization from the surface of the molten steel 4 can be reduced, the number of dust collection equipment can be reduced, and the quality of the steel material can be stabilized by uniformly adding it.

Furthermore, in the conventional method, the low melting point metal particles 5 whose particle size is sized to 0.5 to 1011111 are used in the rice hoop, whereas in the method of the present invention, they are added in a molten state, so the weight unit price is lower than that of the sized particles. Approximately 90% of inexpensive bulk products can be used, and it is also effective in reducing running costs.

[Brief explanation of drawings]

FIG. 1 is an explanatory view showing a ninth example of an apparatus for carrying out the method of adding a low melting point metal to molten steel according to the present invention, and FIGS. 2 and 3 are views showing a conventional method. 1... Container, 2... Porous brick,
3... Stirring gas, 3-1... Rizobu,
4... Molten steel, 5... Low melting point metal particles, 6
....Immersion lance, 7..Carrier gas, 8..Low melting point metal permeable brick, 9..
... Conduit, 10 ... Storage tank, 11 ...
・Heating wire. 12... Compressed gas, 13... Low melting point metal in molten state, 14... Molten steel outlet. Agent: Patent attorney Masamitsu Akizawa and 2 others

Claims (1)

[Claims] (1) A method for adding a low melting point metal to molten steel, which comprises press-fitting the molten low melting point metal from the lower side wall of the molten steel bath surface of a molten steel container.