JPH06240402A - Method and device for refining carbon containing ferromanganese - Google Patents

Abstract

PURPOSE: To enable better decarbonization with the same amt. of oxygen by executing a second refining step by an oxidative gas and inert gas and executing degassing under a vacuum at this time.

CONSTITUTION: An oxidizing gas is sucked by a blow pipe 18 into a vessel (ladle) 10 housing molten ferromanganese 12 and simultaneously an inert gas is blown from a porous block 14 into the base part of a melt 12. Smoke emitting from the melt 12 is corrected at a hood 22. A first refining step is thus executed. The vessel 10 is sealed by a cap 30, in succession to this step, and the blow pipe 18 is inserted therein and the second refining step by the oxidizing gas and the inert gas is executed. At this time, the degassing is executed under the vacuum by evacuating the inside of the vessel 10. As a result, the temp. of the melt may be lowered.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to blowing an oxidizing gas into a container containing a melt of ferromanganese and at the same time blowing an inert gas into the base of the melt, It relates to a process for refining ferromanganese containing carbon, comprising a first refining stage consisting of collecting the fumes emerging from the hood in a hood located above the melt. The invention also relates to a refining device for carrying out the refining method.

[0002]

Ferromanganese is, in particular, an alloy material for producing special steels or alloys. Ferromanganese is usually present in the oxide form, and its production must first be reduced to the ore, for example in a tank or electric furnace. The product thus obtained, ferromanganese, contains less than 80% manganese, 6% to 8% carbon, and the balance essentially iron and silicon. This ferromanganese cannot be used in steelmaking due to its high carbon content and therefore requires further refining. Conventionally, the most general method for refining ferromanganese is to perform thermal reduction with silicon, but this method has disadvantages that it is very expensive and uses a large amount of energy.

Recently more economical methods have been described in US Pat. No. 3,3.
No. 05,352. The method of this patent is based on the actual case of the steel industry, and is based on the blowing method. The liquid ferromanganese produced in the furnace is transported to the converter using a ladle, in which oxygen is blown into the melt through a blow tube, while the temperature of the melt is 1
It is increased from a casting temperature of around 300 ° C to a temperature of the order of 1750 ° C. The heat used to reheat the melt is essentially obtained from the oxidation of manganese to manganese oxide and carbon to carbon monoxide.

As such, the process temperatures are much higher than in steel refining, which is only on the order of 1600 ° C. at most. Another difference from steel refining is that a large amount of fume is generated due to the easiness of vaporization of manganese.

Since the activity of oxygen varies depending on the carbon content, the decarburization rate in the refining process is not constant.
Even if decarburization is performed relatively quickly in the initial stage of the refining process where the carbon content is about 6%, the decarburization rate gradually decreases from when the carbon content falls below 2.5%. Therefore, it is very difficult to reduce the residual carbon content to 2% or less.

In order to enhance the oxygen activity and decarburization process, attempts have been made to blow an inert gas, such as nitrogen, from the base of the converter into the melt. The results of this attempt are quite valid, as bubbling by gas blowing improves the mixing of the melt with the oxidized slag and brings it closer to metallurgical equilibrium.

Even if an inert gas is blown into the melt, it is practically very difficult to bring the carbon content to close to or below 1.5%. More than 1.5% of the decarburization requires a large amount of oxygen, thus causing excessive oxidation of manganese, leading to temperatures of 1800 ° C or higher. When the temperature becomes high, not only excessive smoke is generated due to the easy vaporization of manganese at the high temperature, but also the loss of manganese due to vaporization is accelerated. It goes without saying that the refractory lining of the converter will be worn more quickly.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the amount of oxidizing gas consumed in refining ferromanganese containing carbon by blowing an oxidizing gas with bubbling with an inert gas. It is an object of the present invention to provide a novel refining method and apparatus capable of reducing the melt temperature and the melt temperature.

[0009]

To achieve the above object, the method of the present invention comprises a first refining step, followed by a second refining step with an oxidizing gas and an inert gas, and the second refining step. It is characterized in that degassing is performed under vacuum during the two refining stages.

The results are good early in the refining process, and are generally not time constrained,
Although it is theoretically possible to carry out the entire refining process under vacuum, in order to reduce the production cost, the refining process under vacuum requires a slower decarburization rate and temperature It is preferable to start from the point when the rise and the rise occur. The starting point of the process under vacuum will depend on the characteristics of the equipment and the desired result. However, it is not the aim of the invention to carry out the entire refining process under vacuum.

According to the method of the present invention, it is possible to reduce the amount of oxygen for performing a certain predetermined amount of decarburization. That is, refining can be performed at a lower temperature. Conversely,
Better decarburization with the same amount of oxygen. However, all this depends on the strength of the vacuum. That is, for a given amount of oxygen, the higher the degree of vacuum, the lower the carbon retention rate.

In refining under atmospheric pressure, the carbon content is 1.5.
%, A temperature on the order of 1850 ° C. is required, but refining under reduced pressure and pressure lower than that can obtain the same carbon content at a much lower temperature, and correspondingly, oxygen consumption The amount is small, and the Mn output is also increased. Furthermore, in low pressure refining it is possible to reduce the carbon content to the order of 0.5%, at temperatures equal to those in conventional processes, or even at lower temperatures.

Refining under vacuum also has the advantage of activating degassing from the melt, which allows gas and smoke (f
ume) is discharged better. In one preferred embodiment, the pressure is progressively reduced during vacuum refining to compensate for the progressive reduction in oxygen activity as the carbon content decreases. can do.

For example, the temperature of the melt depends on the carbon content of 2.
A first atmospheric refining stage is carried out until reaching the order of 1600 ° C. to 1650 ° C., which corresponds approximately to 5%. Once that temperature is reached, a second vacuum decarburization stage is initiated by starting the vacuum pump and reducing the pressure from atmospheric pressure to the order of 3/10 atmospheres. At the same time oxygen blowing is continued to raise the melt temperature to about 1700 ° C. to accelerate the decarburization process and bring the carbon level up to 1%. Of course, it is also possible to further increase the degree of vacuum so that the carbon content can reach the order of 0.5%.

According to another feature of the invention, all refining comprises:
It is usually done in a ladle that is used solely to convey ferromanganese between the reduction furnace and the converter, thus making the converter useless. Of course, the ladle must be designed so that it can be refined by blowing oxygen while bubbling with an inert gas. Connections to inert gas sources are made in accordance with document EP-A2-0,320,84.
It could be done with the device described in 1.

As a further feature of the method according to the invention, the increase in temperature at the end of refining is controlled by blowing in a mixture of gases, for example 60% oxygen and 40% inert gas.

The advantage of this is that by doing so the same kinetic energy of the gas jet is maintained while preventing excessive oxidation of the melt.

The present invention is also an apparatus for refining ferromanganese containing carbon in a movable ladle having a base for injecting an inert gas, the hood for collecting and discharging smoke, An open first lid equipped to elevate and lower the first lid on the ladle, and supporting blow tubes and vertically inserting the blow tubes through the open lid and into the ladle. In a refining apparatus comprising a bracket for the use of at least two openings, one opening allowing the insertion of one blowing tube and the other opening allowing the introduction of additives by a charging chute A closed second lid adapted to be installed in a closed state, said opening having equipment for sealing around said blow tube and charging chute, and a vacuum circuit said closed lid Through the ladle Providing a refining apparatus characterized by being connected to the medium.

[0019]

Other features and advantages of the present invention will become apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings.

FIG. 1 shows a ladle 10 containing ferromanganese 12 containing molten carbon. The ladle 10 is normally used to convey ferromanganese, but is also used in the present invention in the process for refining ferromanganese. To that end, the base of the ladle is provided with one or more porous bricks equipped to connect to a source of an inert gas such as nitrogen. The inert gas is blown into the melt from the base of the ladle, as shown by the arrow in FIG. Ladle 10 is blow tube 1
It is installed below a bracket 16 with a carriage 20 supporting 8. The carriage 20 is vertically movable so that the blow-in tubes can be inserted into the ladle 10 to deposit an oxidizing gas such as oxygen or a mixture of oxygen and a neutral or inert gas. So that it can be blown inside. The smoke emitted from the ladle 10 is collected by the hood 22 and sent to the purification / dust removal post (not shown) through the chimney 24.

A lid 26 is placed on the ladle 10 during the ferromanganese refining process. The lid 26 is open at the top to allow smoke to escape and to insert the blow-in tube 18 and also to introduce additives into the ferromanganese melt.

According to the present invention, a second lid 30 as shown in FIG. 2 is further provided. Second unlike the lid 26
The lid 30 is closed and is designed to be installed in a sealed manner on the ladle 10. The top of the closed lid 30 is provided with a through hole 32 to allow the blow tube 18 to be inserted into the ladle 10 and an opening (not shown) for introducing the additive using a chute. The through hole 32 is
It is equipped with a device for sealing the periphery of the blow-in pipe 18 that is moved downward into the ladle, and also with a device for sealing the additive introduction opening in the same manner. The lid 30 is provided with a connector for connecting the inside of the ladle 10 to a vacuum pump, so that the inside of the ladle 10 is vacuumed and melted while refining using an oxidizing gas and an inert gas is performed. It is possible to discharge the smoke emitted from things.

The two lids 26 and 30 could be supported and moved by any known equipment. For example, supporting both lids 26 and 30 in a single slide, and when lid 26 is lifted from ladle 10 and moved to the right in FIG. It could be equipped with a configuration such that it is moved to the right along and set on the ladle 10.

It goes without saying that the degassing stage under vacuum is started and the closed lid 30 replaces the open lid 26.
When installed, the blow-in tube 18 must be temporarily lifted.

[Brief description of drawings]

1 shows the insufflation stage with a ladle and an open lid.

FIG. 2 shows the degassing under vacuum according to the invention,
Figure 3 shows the insufflation stage with a ladle and a closed lid.

[Explanation of symbols]

 10 Ladle 12 Molten Ferromanganese 14 Porous Brick 16 Bracket 18 Blow Pipe 20 Carriage 22 Hood 24 Chimney 26 Open Lid 30 Closed Lid 32 Through Hole

Claims (6)

[Claims] 1. An oxidizing gas is blown into a container containing a melt of ferromanganese, and at the same time an inert gas is blown into the base of the melt, and smoke emitted from the melt is discharged. A method of refining ferromanganese containing carbon, comprising a first refining step comprising collecting in a hood installed above the melt, wherein the first refining step is followed by an oxidizing gas and an inert gas. A refining method characterized in that a second refining step is carried out, and degassing is carried out under vacuum during the second refining step. 2. The refining process according to claim 1, characterized in that the two refining steps are carried out in a vessel which is also used to carry the ferromanganese. 3. The refining method of claim 1, wherein the vacuum is progressively increased during the second refining stage. 4. The refining process according to claim 1, wherein the oxidizing gas is gradually diluted by an inert gas during refining. 5. A device for refining ferromanganese containing carbon in a movable ladle (10) having an equipment (14) for injecting an inert gas at the base, for collecting and discharging smoke. A hood (22), an open first lid (26) equipped to elevate and lower the first lid (26) on the ladle (10) and a blowing tube (18) supporting and blowing these. Bracket (16) for vertically inserting a bayonet tube through the open lid (26) into the ladle (10)
In a refining apparatus comprising at least two openings (32), one for allowing the insertion of one blowing pipe (18) and one for allowing the introduction of additives by means of a charging chute. Equipment for closing a second lid (30) adapted to be installed in a closed state on a pan (10), the opening being closed around the blow-in pipe (18) and a charging short. And a vacuum circuit is connected through the closed lid and into the ladle. 6. Ferromanganese obtained by the refining process according to any one of claims 1 to 3, containing up to 1.5% carbon.