CS208709B2 - Method of decarburization of the ferromangan or ferrochrome with high contents of the carbon - Google Patents

Abstract

1499049 Decarbonizing ferro chrome and ferro manganese GFE GES FUR ELEKTROMETALLURGIE mbH 7 July 1976 [11 July 1975 10 Sept 1975] 28172/76 Heading C7D High carbon ferro manganese or ferro chromium are decarbonized by blowing a superheated melt of the alloy with oxygen using jacketted nozzles. The alloy is heated to more than 100‹C above its melting range and blown, without the addition of cooling materials, to 1650-1900‹C for FeMn and 1750-2000‹C for FeCr to form high melting point Mn or Cr oxides which are reduced by lime and additions of reducing agents i.e. Si or Al and/or their alloys. The lime and reducing agents are added simultaneously, the lime being blown into the melt through the jacketted nozzles with an inert gas (Ar or Ar/H) and the reductants being added in solid or liquid form from above. Examples of reductants are FeSi, FeAl, SiCr and SiMn. The rate and amount of oxygen blown in is adjusted so that the decarburization reaction takes place in an area just above the gas nozzles, so that intensive mixing of the melt, oxygen and possibly, the jacket gas will occur there. The amount of oxygen required is 10-3 0Nm<SP>3</SP> for each 1%C to be removed per tonne of alloy, and it should be blown into the melt in 1-12.5 minutes. The protective jacket gas may be natural gas, propane &c., and up to 20% of the charge may be added in the form of solid material, provided the addition of the solid charge does not interfere with the decarbonization reaction above the nozzles.

Description

(54) A method for decarburizing ferro-manganese or high carbon ferro-chromium __. and

The present invention relates to a method for decarburizing ferro-manganese or high carbon ferro-chromium by refining using jacketed gas nozzles, wherein the alloy melt is superheated prior to blowing oxygen, for example to a temperature above 100 ° C above the melting point.

This method is based on the application of known measures for decarburizing conventional molten steel by blowing oxygen through sheathed gas nozzles and applying it to the decarburization of high-carbon ferrochromium or ferro-manganese, wherein the alloy melt is heated above 100 ° C prior to blowing oxygen. above about the melting point and, on the other hand, about 15 oxygen, measured under normal conditions, is blown into the ferro-alloy for 1 to 5 minutes per 1% of the carbon to be removed and per ton of alloy. In this context, the term alloy melt means a melt of a ferro-alloy during processing.

The known measures can largely suppress the formation of slag rich in chromium oxide, respectively. of manganese. The slag that eventually arises is dry slag and contains essentially only physically bound amounts of ferro-alloys that can be easily melted.

Using known measures, a special carbon-consuming reaction, which was otherwise believed to occur in the slag, is said to take place in the alloy melt.

While all of these assumptions have been confirmed, they necessitate the maintenance of defined reaction rates, which in practice means that within 1 to 5 minutes, 1% carbon must be removed from the entire alloy melt charge using about 15 m of oxygen (measured in normal conditions) per ton of alloy melt (the dimension of reciprocal decarburization rate thus defined is min. ° C ¹ ). This requires appropriate control and regulation measures and limits to a certain limit the amount of charge that can be processed in the manner described per batch.

It is an object of the present invention to improve the process so that the decarburization process can be controlled at a temperature of the alloy melt at a substantially increased charge size.

The essence of the invention consists in that the temperature slitnoové melt with an oxygen blowing without addition of refrigerant increases in ferro temperature 1650 ° C I 900 ° C and ferochiromu temperature 1 ⁷ 5 ° ^C to ²⁰⁰⁰ ° C ^No IMZ manganese, res ^p . the chromium oxide phase, and this oxide phase is then reduced by the addition of lime and by the addition of reducing agents such as silicon and aluminum and / or their alloys.

Preferably, solid reducing agents are used. The addition of lime is effected by blowing it with an inert carrier gas, for example argon, in the treatment of ferrochromium and argon and / or nitrogen in the treatment of ferro-manganese, by jacket gas nozzles into the alloy melt.

According to the process of the invention, the high carbon content of ferromanganese and ferrochromium can be burned without the formation of excessive amounts of oxygen phase, which would not have to be post-treated outside the tank. The resulting oxygen phase from manganese or chromium oxides, which is formed in the process according to the invention, although it contains only a small amount of oxides, can easily be avoided by supplying lime and adding solid reducing agents.

As reducing agents, for example, silicon, phenyl, silicon, aluminum, silico-chromium or silicon-comganate can be used. These reducing agents are, for example, introduced in lump form from above into the container or poured into it when in liquid form. In the process of the invention, lime can be blown with the oxygen to provide faster and quieter gas release from the melt.

In this process, it is advantageous to work so that the metal oxide phase is as small as possible. In order to keep the metal oxide as low as possible, it is necessary to ensure that the reaction does not take place in the slag on the surface of the bath. This can be achieved by selecting the oxygen supply and the rate of oxygen supply in each jacket gas nozzle so that the quenching reaction takes place in the focus above the jacket gas nozzles.

The invention is based on the original, yet unknown knowledge, that in the process according to the invention, the quenching reaction to secoki does not take place in the alloys melt and in particular not over the string but in the foci above the sheathed gas nozzles.

The term "thniskt" means that area above the mantle gas nozzle in which the melt is intensively mixed with the oxygen and possibly the mantle gas. In a molten melt, spherical or more or less elongated gas bubbles or chains of bubbles are formed above the casing gas nozzle, the gas-facing inner wall of which consists of chromium oxide or manganese in a very thin or monoecuary layer which readily reacts .

OOdhhičovénk then performed so that the carbon reacts with the kyslččnkeem chromium or manganese according to the equation ZCC ^ o ^ / l ⁴ 2C - · 4Cr / 3 + 2C0. This is an endothermic reaction that consumes oxygen and which has hitherto been realized only in the slag above the melt.

However, there are quite different thermodynamic ratios at the focus than at other locations in the lithium melt or slag. On the one hand, temperatures in the core are different and higher; On the one hand, there are very high pressures in the large bubbles, depending on their diameter, which do not add only from the atmospheric spherical pressure and the hydrostatic pressure of the melt, but are also determined by the surface tension of the drums.

Thus, under all conditions, the reaction proceeds which results in virtually no slagging of chromium or manganese, and possibly a string which floats on the surface of the melt and participates in the reaction.

According to the invention, the amount and velocity of the oxygen supply can be voltaged within relatively wide limits so that the dehumidification reaction takes place above the jacket gas nozzles in the focus. The overheating must be such that the dehumidification reaction begins when the oxygen is recovered. К this end the ^e be the superheat ^sl i ^ ⁱ ^ 0o L7E tevein e.g. ^ d ^ Aa I v'ce not ^{with 00} ° C above the melting point, but may be lower.

Since the decarburization reaction of the process according to the invention starts to take place in the furnace above the jacket gas nozzle, according to another aspect of the invention, the melt may have different temperatures at other locations.

Especially it is possible to carry out the method according to the invention to increase the size of the charge so as to slítlo polyaminocarboxylic melt in the converter adds the solid alloying metal up in such _ιnno0sSví) to n ^ i ^ i ^ uitl outbreaks and beginning oduuhičovací responses in these OH ^ ítcích.

Temperature control or regulation can also be performed. According to the invention, up to 20% of the solid alloying metal, preferably about 12% of the solid alloying metal, based on the alloying metal, may be added to the melting melt. a total amount of alloy melts and solid alloying metals of 100%.

In the process according to the invention may proceed so that 1 ton taveoioy fed 10 ^and 3 ⁰ m ^3, preferably about 15 m ³ Tysl ^ u, (measured NORM ^ i ^ conditions ^ and b ^y of the total charge was removed within 5 to 12.5 mn of 1% oxygen.

Thus to comprehend ^and REC ^ ro ^ ^ cheers odulh suddenness has dimension mn. fc “ ¹ . ° C ~ ¹ ° C. When the silicon content of the tilapic rock is very high, the man-shifts in the water. of added oxygen to the upper edge. The ferro-chromium or ferro-manganese containing silicon, optionally in two stages, can be processed without difficulty in the process according to the invention, whereby the slag is removed after the first stage and then dehumidification is carried out according to the process of the invention.

In the described process, the decarburization reaction is stable in the furnace. The sputtering oxide phases from manganese or chromium oxide, which is formed, although it contains only small quantities of oxides, can be easily reduced by supplying lime and adding solid reducing agents such as silicon or aluminum and / or their alloys.

The invention will be elucidated on the basis of examples in which all the above percentages are indicated. the composition of it and the volume of the blown gases is the volume measured under aormic conditions.

Example 1-feoGmangan

It is the production of manganese with a maximum content of 1% carbon.

- ^{1840 kg for} te ut ^{f eh} of molten eoomнogaou -Temperature about ¹³⁷⁰ ° ^C, and ^76.8% verbal Мщ

6.3% C, 0.61% S, 0.18% P and 0.04% 3, and 5,000 kg of a solid ferro-manganese of the same composition were fed to a magnesia-laden converter (melting point of ferro-manganese s; (060 to 110 ° C). '

K J / l / torrtor had 6 double jets in the bottom that were inclined to the sky at an angle of 15 °.

As a shielding gas there was gas in the outer shell. During the decarburization phase, a period of time is maintained

Blowing oxygen for 24.78 min at 18 m ^J / min. At the end of the phase the temperature of the lithium melt rose to 1840 ° C. Then into taveni.ny hal VDIM over 3.75 min and argon at ¹⁴ during interval t ^ rotatably together with a stream of argon put in a melt ^y

240 kg of powdered lime.

At the same time, 482 kg of silico-manganese were poured into the converter from above. After the reduction phase, the ferro-manganese alloy melt was discharged from the converter through a tundish into the ladle.

A total of 5,030 kg of a ferro-manganese of 81.0% Mn, 0.61% Si, 0.96% C, 0.18% P and 0.02 S was obtained. The manganese yield was 91.8% Mn.

Example 2 - Ferrochromium

This involved the production of ferro-chromium with a maximum carbon content of 1%.

540 kg of molten ferochrome with a temperature of 1 520 ° C and a composition of 66,4% Cr, 5,1% C, 0,71% Si, 0,10% S and 0,04% P, and 1 100 kg of solid ferochrome of the same composition was fed to a magnesite-lined converter (melting point of the ferrochrome alloy 1360 to 1400 ° C, lining temperature of 1000 ° C). The converter had 6 jacket nozzles in the bottom. Propane was used as a protective medium in the outer sheath.

During the decarburization phase, oxygen was blown for 25.44 min at a rate of 25 m ^ / min.

At the end of the oxygen blowing phase, i.e. at the end of the decarburization phase, the temperature of the alloy melt rose to 1920 ° C. Then argon was blown for 3 min at a rate of 15 m m / min. During this time, 627 kg of lime powder were fed into the converter at a flow of argon, and 386 kg of silicochrome was introduced from above into the converter at the same time. After the reduction phase the melt from the converter was poured through a tundish into a ladle.

A total of 9,050 kg of refined ferochrome with 69.7% Cr, 0.40% Si, 0.91% C, 0.03% S and 0.02% P were produced. The chromium yield was 96.1%.

Claims (3)

SUBJECT OF THE INVENTION 1. A process for decarburizing high carbon ferro-manganese or ferrochrome by refining in a jacketed gas nozzle reaction vessel in which the alloy melt is heated to above 100 ° C above the melting point, wherein the temperature of the alloy melt is increased by oxygen blowing without adding refrigerants. for ferro-manganese to a temperature of over 1 650 ° C to 1 900 ° C and for ferro-chromium to a temperature of over 1 750 ° C to 2 000 ° C, a high-melting oxide phase is formed from manganese oxide and chromium respectively. It is reduced by blowing lime through sheath gas nozzles using an inert carrier gas and the addition of solid reducing agents such as silicon and aluminum and / or their alloys. 2. A method according to claim 1, characterized in that up to 20%, preferably 12%, of solid alloyed metal, based on the total weight of the charge of the alloyed melt and solid alloyed metal, is added to the alloy melt. The process according to claim 1, wherein the decarburization reaction takes place in foci above the jacket gas nozzles. 3. Process according to claim 1, characterized in that 10 to 30, preferably 15 m &lt; 3 &gt; of oxygen (measured under normal conditions) are supplied per 1000 kg of alloy melt so that 1% of carbon in the total charge is removed. time from 5 to 12.5 min.