JPH044388B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing medium- and low-carbon ferromanganese, and particularly the present invention relates to a method for producing medium- and low-carbon ferromanganese using a top-blown and bottom-blown converter using molten high-carbon ferromanganese as a raw material. Conventionally, medium and low carbon ferromanganese are generally as follows:
Manufactured through steps (a) and (b). (a) Using manganese ore and silica stone as main raw materials, reduction smelting is performed in an electric smelting furnace using carbonaceous material as a reducing agent to produce 60-70% Mn, 14-23% Si, 0.5-2% C,
Silicomanganese is produced, the balance being iron and unavoidable impurities. (b) By charging and melting the silicomanganese together with high-grade manganese ore and lime in a separate electric smelting furnace, the Si in the silicomanganese is dissolved.
By oxidizing to form SiO ₂ , that is, by causing a desiliconization reaction, Mn75-85%, Si0.2%
~2%, C0.5~2%, the remainder is essentially
Manufacture medium/low carbon ferromanganese made of Fe. According to the above-mentioned conventional method for producing medium-low carbon ferromanganese by desiliconizing silicomanganese, the electrical energy consumed in producing silicomanganese in step (a) is 3500 to 500 KWh per ton, and (b) Since 800 to 1200 KWh is consumed per ton of product in the desiliconization reaction process, the cost of electrical energy is high, and as a result, especially in Japan, where electricity costs are high, product costs have become too high to meet international competitiveness. Furthermore, the process (b) also requires an electric furnace, which increases costs in terms of equipment and personnel. On the other hand, Japanese Patent Publication Nos. 55-4238 and 57-27166 disclose a method for producing medium- and low-carbon ferromanganese by blowing oxygen into molten high-carbon ferromanganese without using the silicomanganese method.
According to the former method, oxygen is blown in through a jacket-type nozzle provided on the side wall of the reaction vessel, and in the latter method, oxygen and natural gas are blown in through a double-pipe structure nozzle provided on the bottom of the reaction vessel. In addition, US Patent No. 3305352 and People's Republic of China Steel Magazine Vol. A manufacturing method using a converter is disclosed. By the way, manganese is more easily oxidized than iron or chromium, and its vapor pressure is quite high. Even if decarburization is carried out according to this method, it cannot be an economical refining process in terms of Mn yield, and therefore, medium- to low-oxygen smelting methods, in which oxygen is blown by top blowing, side blowing, or bottom blowing, are used. The method for producing ferromanganese has not been carried out on an industrial scale. The present invention eliminates the drawbacks of the conventional method for producing medium- and low-carbon ferromanganese by blowing oxygen,
It is an object to provide an improved method, and this object can be achieved by providing the method according to the claims. Next, the present invention will be explained in detail. In refining molten high-carbon ferromanganese into medium- to low-carbon ferromanganese by oxygen blowing, it is important to increase the decarbonization rate by the blown oxygen, to prevent manganese oxidation as much as possible, and to reduce the amount of manganese generated during the decarburization reaction. It is necessary to suppress the evaporation loss of manganese and to efficiently recover the manganese that has migrated into the slag during refining. It is known that the equilibrium of formula (2) is thermodynamically established in the following reaction formula (1) involving manganese, carbon, and oxygen. MnO+C=Mn+CO ……(1) logK=−12853/T+7.91 ……(2) As can be seen from equation (2), in the low temperature range, the oxidation of Mn has priority over the oxidation of C, and in the high temperature range, the opposite is true. oxidation of C takes precedence over oxidation of Mn. Therefore, for the purpose of decarburization, it is desirable to cause the reaction to occur at as high a temperature as possible, but on the other hand, the evaporation of manganese becomes more active, and wear and tear of the lining of the reaction vessel becomes a problem. Therefore, appropriately controlling the temperature of the container is an important operational factor. The reaction vessel used in the present invention has one or more gas blowing means at the bottom or a side wall near the bottom, and this means consists of a double or triple pipe, and from the outer pipe of these pipes, gas blowing means is provided. At least one type of gas selected from argon, nitrogen, carbon dioxide, and propane is injected as a cooling gas to prevent melting and damage at the tip of the tube, and oxygen gas or waste gas such as argon, nitrogen, etc. is injected from the inner tube. The active gas can be switched and injected during the refining process. In the present invention, the molten high-oxygen ferromanganese used as the main raw material is generally produced in an electric smelting furnace or shaft furnace, and its composition is Si2%.
Hereinafter, high carbon ferromanganese containing 6 to 7% of C and 75 to 85% of Mn, with the remainder substantially composed of Fe, can be advantageously used, and such molten metal can be extracted directly from a smelting furnace or by using this molten metal. Once charged into a holding furnace, it is charged into a reaction vessel and refined whenever necessary. The temperature of the molten metal charged into the reaction vessel is preferably as high as possible in consideration of the decarburization reaction, but there is no problem as long as it is above the melting temperature. When charging the molten metal into the reaction vessel, the molten metal is charged while blowing oxygen through the inner tube of the bottom blowing means provided at the bottom of the vessel or the side wall near the bottom, and blowing inert gas through the outer tube. Enter. At this time, the amount of oxygen blown from the inner pipe of the bottom blowing means is 3 of the total oxygen capacity blown by the top blowing means and the bottom blowing means.
20%, and it is advantageous that the amount of inert gas blown from the outer pipe of the bottom blowing means is approximately the same as the oxygen capacity from the inner pipe. After completing the injection of the molten metal into the reaction vessel as described above, the top blowing means starts blowing oxygen.
The oxygen capacity at that time is 80-97% of the total oxygen capacity used. It is advantageous to introduce quicklime, dolomite, ferromanganese slag, etc. into the container at the same time as the ejaculation starts to generate slag early and prevent loss of manganese. At the beginning of oxygen blowing, silicon and manganese in the molten metal are oxidized, and the molten metal temperature rises rapidly.Subsequently, carbon oxidation begins and the molten metal temperature continues to rise, but the molten metal temperature remains at 1650~1850.
℃ to control the carbon content of the final product.
In other words, to reduce the C content in the final product to 2% or less, the final temperature of the molten metal must be 1750 to 1780°C, and the C content must be 1%.
To achieve the following, adjust the temperature to 1820-1850°C. If the molten metal temperature is lower than 1650℃, manganese oxidation takes precedence over carbon oxidation, while if it is higher than 1850℃, manganese evaporation becomes active and loss of manganese increases, so the molten metal temperature should be in the range of 1650 to 1850℃. It is preferable to smelt in-house. The temperature of the molten metal can be controlled not only by charging a coolant such as high, medium or low carbon ferromanganese or flux, but also by adjusting the amount of oxygen absorbed. When the carbon content in the molten metal is lowered to a predetermined value in this way, manga is oxidized in the slag that is generated, and the manganese content is reduced as manganese oxide.
Contains 30-50%. To recover the manganese in this slag, the oxygen blowing from the top blowing means is stopped, and the oxygen blowing from the inner pipe of the bottom blowing means is switched to inert gas blowing. One or more selected from metal silicon and aluminum are charged into a container along with flux if necessary, and
The molten metal and slag are stirred by blowing inert gas from the bottom for a minute to reduce the manganese oxide in the slag and recover the reduced manganese into the molten metal to complete the refining. The features of the method of the present invention described above will be explained below while comparing with the conventional method. (1) In order to oxidize and decarburize the carbon in the molten high-oxygen ferromanganese, it is necessary to increase the chances of the oxygen blown in from the top blowing means always coming into contact with fresh molten metal.According to the present invention, Compared to conventional oxygen blowing using only top blowing, the blowing of inert gas and oxygen gas from the bottom blowing means not only effectively stirs the molten metal, but also eliminates carbon in the molten metal by bottom blowing oxygen gas. Oxidation is promoted and produced by the oxidation of carbon
CO or CO ₂ further increases the stirring of the molten metal. When slag is generated as the molten metal is refined and a slag layer is formed on the surface of the molten metal, it is necessary to locally remove the slag layer and allow the oxygen blown from the top blowing means to reach the surface of the molten metal. For this reason,
When blowing oxygen using the conventional single top blowing method, it is necessary to increase the oxygen pressure to eliminate the slag layer, but this method causes phenomena such as spitting and forming in the container, making it difficult to proceed smoothly. As a result, not only the operating time was inevitably extended, but also the efficiency of oxygen used was low. On the other hand, according to the present invention, since the gas is blown from the bottom blowing means, the slag layer on the surface of the molten metal can be locally removed, and the top blowing oxygen pressure can be lowered, that is, soft blowing can be performed. It is efficient, reduces operating time, and improves operational stability. (2) According to single top blowing, oxidized manganese quickly migrates into the slag. On the other hand, according to the present invention, manganese oxide oxidized by oxygen blown from the inner tube of the bottom blowing means floats in the molten metal and while reaching the surface, it contacts and reacts with carbon in the molten metal, and the manganese oxide is reduced. It becomes manganese and melts into the molten metal. In this way, not only does the oxygen efficiency increase, but the manganese content in the slag at the end of the oxygen blowing process is lower than that in the conventional method due to the bottom blowing process, so it can be used to reduce manganese oxide in the slag. The amount of reducing agent, ie, silicomanganese, ferrosilicon, metallic silicon, or aluminum, used can be reduced, and the yield of manganese can be improved by 4 to 5%. (3) According to the conventional top-blowing single ejaculation method, if the temperature of the molten high carbon ferromanganese in the reaction vessel is low, it is not only difficult to ignite it during oxygen ejaculation, but even if it is ignited, it will be difficult to ignite it in the initial stage. The oxidation loss of manganese is large due to low temperatures. For this reason, it is necessary to raise the temperature of the molten high carbon ferromanganese to a predetermined temperature in a separate heating furnace before charging it into the reaction vessel. On the other hand, according to the method of the present invention, the problem of ignition is resolved by the bottom blowing semen, so
Since the initial temperature of the molten metal has little influence, the need to raise the molten metal temperature using a heating furnace is reduced, and the molten metal from, for example, an electric smelting furnace can be directly charged into the reaction vessel. As described above, according to the present invention, the oxygen consumption rate used in refining is reduced by about 20% compared to the conventional method, and the manganese yield is increased by 4 to 5% as described above. Next, the present invention will be explained with reference to examples. Example 1 A brick with an inner diameter of 1100 mm was lined with magnesia brick using raw materials having the composition shown in Table 1 below.
When molten high carbon ferromanganese is blown with oxygen in a reaction vessel of mmφ according to the present invention, 450 ml of oxygen is blown from the inner tube of the bottom blowing means provided at the center of the bottom of the vessel.
3 tons of the molten metal was charged into the container while blowing argon at 450/min from the outer tube. The temperature of the molten metal at that time was 1280°C, but when oxygen was blown in from the top blower, it was easily ignited and the decarburization reaction started. For the first 10 minutes, the top-blown oxygen delivery rate is
9.6Nm ³ /min, and 7.2Nm ^{3 /} min for the next 15 minutes and 45 seconds.
min, and the amount of oxygen used is the total of top blowing and bottom blowing.
It was ^221Nm3 . During that time, 120 kg of quicklime, 30 kg of dolomite, and 45 kg of manganese slag were charged as flux. Changes in the oxygen supply rate were made while monitoring the molten metal temperature. In other words, oxygen was blown at 9.6 Nm ³ /min until the temperature reached 1650°C, at which the oxidation of manganese proceeded with priority over that of carbon. The time up until now was 10 minutes after ignition. After the temperature reached 1650°C, the oxygen flow rate was reduced to 7.2Nm ³ /min and the oxygen was continued until the temperature reached 1770°C. The time taken so far was 25 minutes and 45 seconds after ignition. At this point, the top blowing was stopped, the oxygen in the inner tube of the bottom blowing means was changed to the same amount of nitrogen, and 250 kg of silicomanganese, 150 kg of medium carbon ferromanganese, and 40 kg of quicklime were added.
Stirring and refining was performed for 10 minutes, and after removing the slag, the molten metal was cast.
The weight of the obtained product was 3030 kg, and the metal and slag were well separated, with almost no metal mixed into the slag. The ingredient composition of the product is shown in Table 2.

【table】

[Table] Example 2 3000 kg of molten high carbon ferromanganese was placed in the same reaction vessel as in Example 1, and oxygen was introduced from the inner tube of the bottom blowing means.
The reactor was charged while blowing argon at a rate of 450/min from the outer tube. The temperature of the high carbon ferromanganese was 1250℃, and it was easily ignited when oxygen was blown into it from a top blowing lance. The oxygen delivery rate is
11 until the melting temperature reaches 1650℃ at 9.6Nm ³ /min.
After that, ejaculation was performed for 20 minutes and 15 seconds at 7.2 Nm ³ /min until the temperature reached 1830°C. The amount of oxygen used is 265N
It was ^m3 . Meanwhile, quicklime is used as flux.
120Kg, dolomite 3Kg, and manganese slag 45Kg were charged. After stopping the top blowing oxygen, change the bottom blowing oxygen to the same amount of nitrogen, add 325 kg of silicomanganese, 150 kg of low carbon ferromanganese size, and 50 kg of quicklime, and perform bottom blowing stirring for 10 minutes to remove the sludge, and then remove the sludge. was cast. The weight of the obtained product was 2940 kg, and the metal and slag were separated well. The component composition of the product is shown in Table 3.

[Table] Comparative Example Medium carbon ferromanganese was produced by top blowing alone with oxygen blowing. In order to assess the effects of the top and bottom blowing methods, the nozzle at the bottom of the reaction vessel shown in Example 1 was removed and magnesia bricks were constructed. Blowing was carried out in the same manner as in Example 1, but it was extremely difficult to ignite the poured high carbon ferromanganese, even though the temperature was 1270°C. Although it ignited again, there were many misfires during the blowing process. After the temperature exceeded 1650℃, where the decarburization reaction becomes active, slopping became severe, forcing the oxygen delivery rate to be reduced by about 20% compared to top and bottom blowing. During this period, a considerable amount of manganese loss occurs. As a result, the oxygen consumption rate of the obtained product increased by 50% compared to the method of the present invention, and the manganese yield was 5 to 7%.
There was a decline in From the above results, when looking at the manufacturing cost of medium- and low-carbon products, the present invention has a cost of 91% compared to the conventional silicomanganese method and the conventional oxygen blowing method when producing medium-carbon ferromanganese at a total cost. %, 92% when producing low carbon ferromanganese,
According to the present invention, medium to low carbon ferromanganese can be produced most economically on an industrial scale.

Claims (1)

[Claims] 1. A reaction vessel equipped with top blowing means and bottom blowing means is charged with molten high carbon ferromanganese containing 6 to 7% C and 75 to 85% Mn, and the top blowing means is Refining oxygen gas is blown into the molten metal from the bottom blowing means and the C content in the molten metal is 2%.
After that, the blowing of oxygen gas from the top blowing means is stopped, while inert gas is blown from the bottom blowing means, and silicomanganese, ferrosilicon, metal silicon, A medium/low oxygen ferromanganese which is characterized in that the manganese oxide transferred to the slag during the decarburization refining is reduced and recovered into the molten metal by charging at least one selected from aluminum. Production method. 2. When the total volume of oxygen gas blown from the top blowing means and the bottom blowing means is converted to 100 parts by volume in a standard state, the patent claim that the oxygen gas blown from the top blowing means is 80 to 97 parts by volume. The method described in item 1.