JPS58130217A - Ladle refining method - Google Patents

Abstract

PURPOSE:To form rapidly a stable nonoxidizable atmosphere in a ladle by supplying an inert material of liquid state to the surface of molten metal in the course of refining in the ladle and vaporizing it upward. CONSTITUTION:The molten metal 3 is accommodated in the ladle 1 and an upper lid 2 is closed. An agitating gas 6 such as Ar is supplied from a porous plug 4 provided at the bottom of the ladle 1 and the inert material 8 of liquid state such as liquid N and liquid Ar are supplied from a supplying pipe 7 to the part centering on the molten metal position exposed from the slag 9 surface. The liquid N, etc. are vaporized at the surface of the metal 3, generate the ascending air current to the direction of an arrow A and form stably the nonoxidizable atmosphere in the ladle 1 in the short time. By said method, the ladle refining method such as the agitation, addition of alloy and removal of impurities in the nonoxidizable atmosphere can be performed stably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an improved ladle refining method in which alloying, impurity removal, stirring, etc. are performed on molten metal in a ladle.
It is something that I will do.

In recent years, the quality of O111 molten metal such as molten steel has improved, productivity has improved,
For the purpose of stable operation, it has become common to perform ladle refining treatment on molten metal. This hammer refining process includes alloy addition, removal of impurities such as desulfurization during deoxidation, stirring of molten metal by bottom blowing of inert gas with a porous plug, and top blowing of inert gas with an immersion lance. To perform such processing stably and effectively,
It is necessary to maintain a non-oxidizing atmosphere inside the ladle.

Conventional methods for maintaining the inside of the ladle in a non-oxidizing atmosphere include covering the ladle with 1 liter of gas and pumping an inert gas such as N, gas or Ar gas into the ladle, or removing the molten metal in the ladle. There is a method of sealing by injecting inert gas toward the exposed part of the molten iron metal when the covering slag layer is broken by gas agitation for treatment (Kin-Sho No. 56-43373). be.

However, in such conventional methods, the difference in specific gravity between the ladle and the atmosphere is small and the atmosphere is turbulent, so when an inert gas pipe is introduced, the surface of the molten metal becomes non-oxidized ( Not only does it take a long time to reach 0, (1vot rumor), but if the flow rate of inert gas is too low, a good non-oxidizing state cannot be obtained, and if the flow rate is too high, outside air may be entrained. Finally, there are restrictions on the conditions for feeding the inert gas, and in addition, if the four-layer structure of the top cover and ladle is poor, the non-oxidizing atmosphere may be eroded. This invention was made by focusing on the above-mentioned drawbacks of the conventional technology. It is an object of the present invention to provide a ladle refining method in which molten metal can be treated with a] and which does not necessarily require the use of slag in the upper lid as in the conventional method.

In a ladle refining method in which alloy addition to molten metal, removal of impurities such as deoxidation and desulfurization, and stirring are performed on molten metal in a ladle, the surface of the molten metal in the ladle is coated with a liquid inert material. The material was supplied to cause the vaporization of the liquid inert substance and the rising air fIL on the surface of the molten gold I4, so that the rapid formation of a non-oxidizing atmosphere and Km# could be realized. Ii mold.

The ladle refining method to which this invention is applied is a refining method that uses a so-called ladle. Specifically, it includes a ladle equipped with an electrode tube for arc heating the molten metal tube in the ladle, and a ladle refining method that uses a ladle. Ninth device for stirring molten metal, such as an electromagnetic induction stirring device, a stirring gas supply device from the top of the ladle or the bottom of the ladle, a mechanical stirring device, etc. alone or in combination;
There are those equipped with a ninth addition device for adding alloy components or slag components in the form of wire or powder, and those equipped with a vacuum device (tank) for refining under reduced pressure.

Furthermore, as the liquid inert substance, it is convenient and effective to use argon soaked in liquid nitrogen.

In the nine ladle refining method described above, when a liquid inert substance such as liquid nitrogen or liquid argon is supplied to the surface of the molten metal in the ladle, the supplied liquid inert substance is directly applied to the surface of the molten metal due to the difference in specific gravity. fall on top.

This liquid inert substance instantly vaporizes as it falls,
At the same time, an inert gas layer is formed on the surface of the molten metal, and at the same time, an upward air current is formed so that the surface of the molten metal becomes an evaporation source. With this in mind, the inside of the ladle can be quickly replaced with a non-oxidizing atmosphere, and the continuous updraft of subcutaneous active gas can completely prevent atmospheric air from entering the ladle from the outside.
A good non-oxidizing atmosphere within the ladle can be maintained.

Actual example 1 Here, the ladle refining apparatus shown in FIG. 1 is used.

The apparatus shown in FIG.
Attach the porous plug 4 to the bottom of the
The stirring gas 6 can be fed into the molten metal 6 through the stirring gas supply 15, and a liquid inert substance supply pipe 7t is attached to the upper lid 2, so that the liquid inert substance is not applied to the surface of the molten metal 6. This allows the active substance 8 to be delivered. In addition, 9
is a slag.

The molten metal 6 used here is aluminum killed low alloy steel having the chemical composition shown in the table.

Next, argon gas was fed as the stirring gas 6 from the stirring gas supply pipe 5 at a flow rate of 0.3 Nm''/min to the molten metal 6 of the above components placed in the broken pot (capacity 15 ton). The molten metal 6 is exposed from between the slag 9 and the molten metal 6 On the surface, the liquid inert material supply pipe 7 supplies the liquid inert material 8 to the housing nitrogen at a flow rate of 1.ON11 l''/min in terms of gas. As a result, liquid nitrogen vaporizes on the surface of the molten metal 60 and
Rising air 5t't- is generated in the direction of the arrow and escapes from between the ladle body 1 and the upper lid 2 and between the upper lid 2 and the liquid inert substance supply pipe 7.

In such a stirring process, 0.00. When the temperature change and the total oxygen concentration change in the molten metal 3 were investigated from the start of the treatment, the results are shown in FIGS. 3 and 4.

Figure 3 shows the change in astringency of 0□ at point x in Figure 1 in the ladle, and in the case of this example, molten gold s! It is clear that because liquid nitrogen is supplied to the surface of the KJI pot, the atmosphere inside the KJI pot can be replaced very quickly due to the difference in specific gravity. On the other hand, the molten metal lI! The same amount (1,0
When gaseous nitrogen is supplied from the island (wim),
It is clear that the time required to replace the atmosphere is considerably longer when the difference in specific gravity with the atmosphere is small. Mayu,
FIG. 4 shows the total oxygen concentration in the molten steel, and it can be seen that the refining effect of the molten metal 3 is clearly promoted when liquid nitrogen is supplied to the surface of the molten metal 6.

Embodiment 2 In this embodiment, as shown in FIG. 6, a pot refining furnace equipped with three electrodes 11t for arc heating the molten metal 5 is taken as an example. Note that the symbols shown in FIG.
The same functional parts as the reference numerals in the figure are the same.

Therefore, a castle pot tank refining furnace (capacity 15 tons) K shown in Fig. 5 was used.
argon gas 6t30L/m1n (D
At the same time, liquid argon 8 was fed at a flow rate and stirred at a rate of 1.0 Nt in terms of gas from the liquid inert material supply pipe 7.
The atmosphere in the ladle was replaced by supplying at a flow rate of n"/mla.Then, from the start of replacement, the 0.0 concentration WIL in the atmosphere at the position of the X mark in Figure 5 was measured. As shown, it is possible to stably obtain an extremely favorable non-oxidizing atmosphere in a very short period of time.Also, when the same amount of argon gas is supplied instead of liquid argon, the atmosphere at the same position is When 08 concentration ft was investigated in the same manner, as shown in FIG. 6, the atmosphere replacement was slow and took time, and in addition, the 02 concentration in the atmosphere was unstable, which were unfavorable results.

Embodiment 3 In this embodiment, as shown in FIG. 7, a top blow lance 14 is attached to the end of the stirring gas supply pipe 5, and the top blow lance 14t is passed through the top cover 2. The ladle has a structure in which the molten metal 6 is stirred by the stirring gas 6 from the above, and an annular fluid pipe 17 arranged around the top blowing lance 14 is attached to the tip of the liquid inert material supply pipe 7. is taken as an example. Note that the symbols shown in FIG. 7 are the same as those in FIG. 1 for the same functional parts.

The annular fluid pipe 17, as shown in FIGS. 8 and 9,
The liquid inert substance 8 has a gas nozzle 21 on the upper surface side for separating and discharging the vaporized inert gas, and
It has a structure in which a liquid nozzle 22 for supplying liquid inert substance 8 toward the surface of molten metal 60 is provided on the lower surface side.

Therefore, argon gas tioOA/m was added to the molten metal 6 having the components shown in Table I in a ladle (capacity 15 ton) from the top blowing lance 14 through the stirring gas supercharging pipe 5.
At the same time, liquid argon is supplied at a flow rate of 1.5 b/min from the liquid inert material supply pipe 7 to provide a stirring force higher than the effective stirring energy density to the annular fluid pipe 17. A friendly liquid nozzle 21 installed on the upper side causes argon gas to flow toward the side of the top blowing lance 14 in the direction of the arrow in FIG. 22, liquid argon is supplied toward the surface of the molten metal 30, and 7'! ,.

In order to stir the molten metal δ by supplying the stirring gas 6 from the top blowing lance 14 in this way, 8 tons of liquid inert material is added to the surface of the molten metal 60.
It was confirmed that by using the supply trap, all 1118 air in the ladle can be quickly replaced with a non-oxidizing atmosphere, and at the same time, the non-oxidizing atmosphere can be maintained at a good Kf41.

In addition, in each embodiment of the upper arrangement, a porous plug 4 or an upper blowing lance 1 is used as a stirring means for the molten metal 3.
The case is shown in which the inert gas 6 supplied from 4 is used, but other stirring means include mechanical stirring devices such as electromagnetic induction stirring devices and propellers 1* alone or in combination. It can also be applied to ladle refining equipment equipped with a ladle refining equipment, and furthermore, this WAtl can be used not only for stirring the molten metal 6, but also for alloy addition processing, or impurity removal processing such as deoxidation and desulfurization. - Can be applied.

As explained above, according to the present invention, in the ladle method in which molten metal is treated in a ladle, a liquid inert substance is supplied to the surface of the molten metal in the ladle, and the molten metal is Since the liquid inert substance is vaporized and an upward air current is generated on the surface, a non-oxidizing atmosphere can be formed in the ladle in a very short time and in a very stable manner, resulting in a good ladle. It is possible to add alloys, remove impurities, stir, etc. to molten metal in a non-oxidizing atmosphere, and there is no need to use a top lid or slag as in the past, and it is also possible to replace the atmosphere. Ninth, it has many significant effects, such as eliminating the need for long hours of operation preparation operations.

[Brief explanation of the drawing]

No. iml is an explanatory longitudinal cross-sectional view of the nine-ladle refining device used in Example 1 of the present invention. Figure 2 is an example of the relationship between the time required for uniform mixing of molten metal (<1) and energy density (-). The graphs shown in Figures 3 and 4 are respectively
0.0 in the atmosphere inside the ladle at the x-point part of the ladle in the figure. Graphs showing the results of investigating concentration changes and total oxygen concentration changes in molten metal from the start of treatment, respectively. FIG. 5 is a vertical cross-sectional explanatory diagram of the ladle refining apparatus used in Example 2 of the present invention, and FIG. 6 is the O in the atmosphere at the x-marked part in the ladle in Figure 5.
8 Graph showing the results of examining concentration changes from the start of replacement,
Fig. 7 is a longitudinal cross-sectional explanatory view of a nine-ladle refining device conveniently used in Embodiment 3 of the present invention, Fig. 8 is a plan view of the annular fluid pipe of Fig. 7, and Fig. 9 (&) (b) is a FIG. 8 is a cross-sectional view taken along line A and B-B of FIG. 8, respectively. DESCRIPTION OF SYMBOLS 1... Ladle body, 6... Molten metal, 5-- Stirring gas supply pipe, 6-- Stirring gas, 7... Liquid inert substance supply pipe, 8... Liquid inert substance supply pipe. Active substance, A--direction of updraft. Patent Applicant: Daido Steel Co., Ltd. Agent: Yutaka Koshio No. 1 Fig. 42N Engineering x Le ff! l ε (Wrl tt/ Ding@M) 3rd
Shij Processing #l Cod fly hat

Claims (1)

[Claims] (1) In a ladle refining method in which molten metal is processed in a ladle, a liquid inert substance is supplied to the surface of the molten metal in the ladle, and the liquid inert substance is applied to the surface of the molten metal. A ladle refining method in which the vaporization and updraft are created at one time.