JPS6036632A - Production of metallic alloy by thermit method - Google Patents

Abstract

PURPOSE:To produce at a high yield, a casting ingot contg. less impurities and having no segregation in the stage of producing a metal by a thermit reaction by blowing an inert gas into the molten metal and molten slag to be formed. CONSTITUTION:A mixture composed of oxide powder of metallic Cr and V alloy, Al powder which is a reducing agent and quicklime, etc. which are a slag forming agent is packed into a reaction furnace 1 then the thermit compounded material is ignited by a sodium chlorate to cause reaction to reduce the oxide, etc. of Cr and V and to form a molten metal 3 and molten slag 4 in the furnace in the stage of producing the metallic Cr and V alloy by a thermit method. An inert gas such as Ar is blown from plural nozzles 2 provided in the bottom of the furnace at 0.15N/min rate for each 1kg in total of the melts 3, 4. The molten metal 4 and the molten slag 4 are stirred and the unreacted raw materials react thoroughly to improve the yield of product. The nonmetallic inclusions (Al2O3, etc.) in the molten metal 3 and gaseous O2, etc. incorporated therein are migrated into the molten slag 4 according to the rise of the inert gas, by which the metal and alloy having high purity and having no segregation in the case of the alloy are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal alloys such as wire mesh chromium or aluminum-vanadium alloys using the thermite method. The present invention proposes a method for producing a metal alloy that can produce ingots with a high yield and a low content of aluminum and low segregation of aluminum and the like.

Thermite method (pyrometallurgy) and electrolytic method (hydrometallurgy) are methods for producing metallic chromium (hereinafter abbreviated as metallic Cr).
There is. In the thermite method, chromium oxide (Cr2O3) is mixed with aluminum (At) as a reducing agent, and an oxidizing agent such as sodium chlorate and a slag-forming agent such as quicklime are added to the raw material, which is then ignited to react. In this method, metal Cr is obtained by reducing Cr with At. Therefore, the raw material chromium oxide or At contains silicon (Sl), iron (Fa) or sulfur (
In addition, impurities such as At, oxygen (0), or nitrogen (N) are incorporated during the reaction, so that At, O, and N are contained in metal Cr products at 0.0. 1
It is present in fairly high concentrations of 0.3% to 0.008% by weight and 0.06% by weight, which poses a quality problem.

On the other hand, the electrolytic method is a method in which high carbon ferrochrome or chromium ore is dissolved in sulfuric acid to extract Cr and Fs, and after further refining only Cr as alum, it is electrolyzed to obtain metal Cr. This method also has the disadvantage that O is present in the product at an extremely high concentration of 0.4 to 0.5%.

Therefore, in order to obtain high-quality metal Cr with a low impurity concentration, conventionally the crude metal obtained by the thermite method or electrolytic method is pulverized into particles or fine particles, and then the particles are pulverized in pure water, air, or hydrogen gas. It is necessary to perform a degassing treatment by heating to 1,000 to 1,500° C., or to remelt the electroslag under an argon gas atmosphere using this crude metal as a consumable electrode. Reheating in this post-refining process consumes electricity and has the disadvantage of high equipment costs.Moreover, this post-processing process causes loss, resulting in poor product yield and high manufacturing costs. There is a drawback.

On the other hand, in the production of titanium alloys such as TI-6At-4V, an At-V master alloy containing 50 or 60 parts of At is used as an additive for At and vanadium (V). This At-V master alloy is usually manufactured by the thermite method.

2) A mixture of oxide, At, and quicklime is ignited and reacted, and the heat of the reaction causes it to melt. After the reaction is complete, the metal and slag are separated by specific gravity in the furnace.
Either the ingot is cooled and solidified to obtain an ingot, the slag is removed by grinding, and then nized to produce a product, or the molten slag is separated and removed, and the molten metal is cast to produce a product.

By the way, since there is a large difference between the melting points of At and V,
KL-V alloy ingots are prone to component segregation and blowholes, and are also easily oxidized and nitrided by oxygen and nitrogen gas in the atmosphere, forming a thick oxide film on the entire surface of the ingot. do.

Therefore, in order to commercialize the At-V master alloy,
It is necessary to mechanically or chemically remove portions of cavities and oxide coatings in the ingot to improve cleanliness and uniformity. This post-processing step has the disadvantage of increasing manufacturing costs and reducing product yield. Moreover, even after removing the cavities and oxide film, both O and N are still 0.0.
It contains more than 5% by weight, which poses a quality problem.

5- This invention was made in view of such circumstances, and
It is possible to obtain ingots with low impurity concentration, less segregation and oxide film, and excellent cleanliness at a high yield without performing post-treatments such as degassing treatment, electroslag remelting, machining, or chemical treatment. The purpose of this invention is to provide a method for producing metal alloys using the thermite method.

The method for producing a metal alloy by the thermite method according to the present invention is a method for producing a metal alloy by the thermite method in which an oxide is reduced to aluminum, in which the oxide and aluminum are charged into a reactor and ignited. It is characterized by melting at least a portion of the melt, blowing gas into the melt, and stirring. That is, the present invention is characterized in that an oxide and aluminum are reacted and melted by the thermite method, and then gas is blown into the melt and stirred. As this stirring gas, an inert gas such as Ar gas is usually used, and is blown into the melt from a nozzle provided near the bottom of the reactor, for example. The stirring period 6 may be any one of immediately before the end of the reaction, immediately after the end of the reaction, or a short period before and after the end of the reaction. By blowing gas into the mixed melt of molten metal and molten slag containing unreacted and undissolved materials and stirring strongly, some of the unreacted and remaining oxides are brought into contact with the aluminum, In addition to promoting the reaction and quickly bringing it to a conclusion, by introducing gas into the molten material after the reaction is complete, when the bubbles of the gas blown into the molten metal float up in the molten metal, The remaining nonmetallic inclusions and the gas generated during the cooling process of the metal are caught up in the bubbles of the blown gas, their floating is promoted, and they are quickly discharged into the slag.

Hereinafter, the method of the present invention will be specifically explained with reference to the drawings showing an example of the apparatus used for carrying out the method. FIG. 1 shows a longitudinal sectional view of the reactor.

A plurality of nozzles 2 are installed at the lower part of the side wall of the reactor J with their longitudinal direction being approximately horizontal, and these nozzles 2
is connected to a gas supply source such as Ar gas or 02 gas.

First, a method for manufacturing metal Cr will be explained.

Similar to the conventional manufacturing method using the thermite method, a predetermined amount of oxides such as chromium oxide, aluminum, and optionally an oxidizing agent such as sodium chlorate and a slag-forming agent such as quicklime are mixed in a mixer. , charged into the reactor 1. Since this raw material is usually a powder, a small amount of inert gas such as Ar gas is passed through the nozzle 2 during charging to prevent nozzle clogging.
Even after charging, Ar gas is introduced into the charged material from the nozzle 2 to purge the charged material with air.

Next, the raw materials are ignited to start a reaction, and at the same time the flow rate of Ar introduced into the furnace from the nozzle 2 is increased.

This is because the raw material melts when ignited, which tends to cause nozzle clogging. Therefore, the amount of Ar gas blown at this time should be set to a flow rate that will not cause nozzle clogging due to backflow of the molten metal. .

By igniting the raw material, a reaction (mainly Cr 20
3 and At starts, and is reduced by At to produce metal Cr. Further, the charge is melted into molten metal 3 and molten slag 4 due to the reaction heat generated at this time. After at least a portion of the charge is melted, the flow rate of the inert gas such as Ar gas blown into the charge through the nozzle 2 is increased to melt the molten metal 3 and the molten slag 4. Stir vigorously. This strong stirring ensures sufficient and uniform contact between the remaining unreacted chromium oxide and the reducing agent aluminum, promoting the reaction and reducing the amount of unreacted Cr that would otherwise transfer to the slag. As a result, the chromium yield is improved and the reaction is completed quickly. Also,
Cr203 or At2o dissolved in molten metal
The floating of nonmetallic inclusions such as No. 3 is promoted by the bubbles of the inert gas blown into the molten metal, and the concentration of O and At in the molten metal decreases. Also, by blowing inert gas) the melt is placed in an inert gas atmosphere and is protected from contamination by nitrogen gas in the atmosphere, thereby reducing the concentration of N in the molten metal.

Stirring with an inert gas is carried out for 1 to 2 minutes immediately before the completion of the reaction or immediately after the completion of the reaction. In this invention, inert gas is discharged from the nozzle 2 into the charge at high speed,
By strongly stirring the charge using the powerful discharge energy, the reaction is promoted and the floating of non-metallic inclusions is promoted. Therefore, this amount of inert gas blown achieves the purpose of the present invention. This is an important element in the process.

As a result of various experiments and research conducted by the inventors of the present application, the amount of inert gas blown was 20O at a flow rate V with exchange and exhaust to standard conditions.
Nm/sec or more or the flow rate converted to the standard state per 1 kg of molten material (molten metal and molten slag) h O,t 5
It has been found that extremely excellent effects can be achieved by setting the Nt to 7 minutes or more. By vigorously stirring in this way, the O and N concentrations of the metal Cr product are each 0.0.
5% by weight and 0.04% by weight, which is 8 degrees lower by 30 to 40% compared to conventional products. Also, the concentration of At is 0.0
7 to 0.10 weight i%, which is 0.03 to 0.2 weight i% lower than conventional products, and the variation in At concentration in the ingot is 1/2 of the variation in conventional products, 10- ~1/3 and 4 more and lower.

After strong stirring, the flow rate of the blown gas is reduced and the blown gas is continued for 1 hour. This gas flow is to prevent nozzle clogging, and during this time solidification of the molten material progresses. After a solidified shell is formed on the surface of the ingot, the gas flow M is further reduced to the level used when charging the raw material, and while gas is continued to be blown, the ingot is cooled and completely solidified. This blown gas flows between the ingot and the inner surface of the reactor and is dispersed. The reason for blowing inert gas through the nozzle even when the ingot is being discarded is to prevent oxidation and nitridation of the ingot surface by coating the high temperature ingot surface with inert gas. be.

In addition, in order to obtain a metal C product in which the impurity At concentration is further reduced, as the gas blown through the nozzle 2 as described above, inert gas and oxygen gas or It is sufficient to use a mixed gas with the containing gas.In particular, by using this mixed gas in the stirring process of the molten metal, unreacted A2 in the molten metal reacts with the oxygen gas in the blown gas and becomes At206. , floats through the molten metal and migrates into the slab.

As a result, metal C with an At concentration of 0.07 weight cycles or less
r can be produced.

Further, by performing the above-mentioned treatments in an inert gas atmosphere as described below, a metal CrfJ product with a further reduced impurity N concentration can be obtained.

FIG. 2 shows a longitudinal sectional view of the reactor 1 housed in the housing 5. As shown in FIG. The housing 5 consists of a main body 6 and a lid 7, and after the reactor 1 is installed inside the main body 6, the main body 6 and the lid 7 are separated.
are sealed via a rubber jack 8, and both are fixed with a presser fitting 9. There is a gas supply port 1.9 on the side wall of the main body 6.
A gas discharge port 14 is provided so that an inert gas such as Ar gas can be introduced into the housing 5 to fill the inside of the housing 5 with the inert gas. The nozzle 2 installed in the reactor is a supply valve 15.
is connected to a gas supply source such as Ar gas or 0□ gas. On the other hand, a gas outlet is bored in the center of the upper surface of the lid body 7, and a lid plate 1o is fixed to this gas outlet with a presser metal fitting 12 via a rubber gasket 11. The housing 5 is hermetically sealed by the housing 10. Note that this housing 5 preferably has a water-cooled jacket structure in order to increase the cooling rate of the ingot.

First, after blending and mixing raw materials and charging them into the reactor 1, the reactor 1 is installed on the main body 6, and after connecting the nozzle 2 and the supply pipe 15, the lid body 7 is placed on the main body 6. and fix it tightly. Inert gas, e.g. A
By introducing r gas into the housing 5 and discharging the air inside the housing 5 through the gas outlet 14, the inside of the housing 5 is replaced with Ar gas. In parallel with this replacement operation, Ar gas is blown into the raw material in the reactor J through the nozzle 2 to perform air purging of the raw material. The replacement work is performed while detecting the oxygen concentration in the exhaust gas discharged from the gas outlet 14, and the replacement work is completed when the oxygen concentration drops to, for example, 3 volumes or less.

13- After the replacement work is completed, open the cover plate 10, ignite the raw materials in the reactor J, start the reaction, and melt by the inert gas blown through the nozzle 2 in the same manner as described above. Stir things. During this period, Ar gas is continuously introduced into the housing 5, and the charge in the reactor 1 is maintained under an inert gas atmosphere during the reaction and stirring period.

After the stirring is completed, as described above, the amount of gas blown into the melt is reduced to begin the cooling process, and at the same time the cover plate 10 of the gas outlet is closed. From the gas supply port J3, the inside of the housing 5 is
The ingot is cooled while supplying mild Ar gas that can maintain the pressure at about ran H20.

By producing metallic Cr under an inert gas atmosphere in this way, a metallic Cr product with an extremely low N concentration of 0.010 gravitons can be obtained, and it is uniform with no segregation of At. An ingot with excellent properties can be obtained. According to experiments conducted by the inventors of the present application, when the O concentration in the exhaust gas discharged from the gas outlet 14 exceeds 3 valleys, the N concentration increases to 14
- Since it is difficult to obtain metal Cr having a weight ratio of 0010 or less, the inside of the housing 5 is thoroughly heated with A before igniting the raw material.
It is preferable to substitute with r gas.

Next, a method for manufacturing the At-V master alloy will be explained. A vanadium compound (modified vanadium oxide or sodium hexyvanadate, etc.) containing V in the amount necessary to obtain the desired composition of the mother alloy, At in the amount necessary to reduce this vanadium compound, and the desired composition of the mother alloy. A of the information necessary to obtain the composition
t and an appropriate amount of a slag-forming agent such as quicklime, and the raw materials are mixed. Then, the At-V master alloy is manufactured by carrying out the steps of charging, air purging, ignition, reaction, stirring, and cooling in the same manner as in the case of manufacturing Cr metal. In addition, when stirring the charge, blow inert gas at 200 N.
m7 seconds or more and/or p O, 15N1 per 1 kg of melted material
It is preferable to set the time to 7 minutes or more. As a result, At
-The O consistency and N concentration of the V master alloy product are both 0.03.
At-V by the conventional thermite method
An At-V 79 alloy is obtained having O and N concentrations approximately 40 orders of magnitude lower than the master alloy product. In addition, At segregation within the ingot is reduced compared to conventional products, and furthermore, the occurrence of cavities inside the ingot is suppressed, and the oxidation grade DC (clean area ingot weight) / (produced ingot weight) on the ingot surface is reduced. heavy firewood)] compared to conventional ones.
Improve by 5 to 20 points.

The reason why the product quality and yield are improved by strongly stirring the melt in this way is the same as in the case of manufacturing Cr metal. In other words, strong stirring by blowing inert gas brings sufficient contact between the remaining unreacted vanadium compound and aluminum, promoting the reaction.
By reducing the unreacted V that migrates into the molten slag, the V yield υ of the ingot is improved.

In addition, nonmetallic inclusions that do not transfer to slag but are dissolved in the molten metal as oxides and gas generated from the metal during the cooling process are caught up in the bubbles of the inert gas that is blown in, promoting floating. Therefore, the O# degree of the product is reduced and the occurrence of cavities in the ingot is suppressed. Furthermore, by injecting the inert gas, the surface of the melt is protected by the inert gas, reducing contamination by nitrogen gas in the atmosphere, and the N concentration of the product is lower than that of the At-V master alloy product produced by the conventional method. However, in order to obtain products with even lower 0 and Nfa degrees, such as At-V master alloys for high-purity titanium alloy addition, each step is carried out under an inert gas atmosphere in the same manner as described above. All you have to do is carry out the following.

As a result, it is possible to produce a high-purity master alloy in which both the 0 and Nl # degrees are equal to or less than the o and oio weight ratios. In this case as well, the O and N concentration of the product should be 0.010% by weight.
In order to achieve the following, it is preferable that the residual O concentration in the housing (zero concentration in the exhaust gas) be 3 volumes or less.

Next, embodiments of the present invention will be described along with their effects. Examples 1 to 4 are about the production of metal Cr, and in each case the raw material blending amounts are chromium oxide, At1
3130 kg each of sodium chlorate and quicklime, 124
2kg, 276kg and 76, 9. The inner surface of the reactor 1 is lined with magnesia clinker.
0mmφ and 2300n++n. In addition, reactor 1
Ten gas blowing nozzles 2 made of stainless steel and having an inner diameter of 3 mm are attached to the side wall of the tank at positions 2α apart from the lower end.

18- -21- The gas injection conditions into the reactor for each step of charging/air injection, ignition/reaction, (W stirring, cooling!, and cooling ■) are as shown in Table 1. , the flow rate is the full flow rate, and therefore the flow rate during stirring of 120ONtZ is converted to 0254Nt1min per 1kg of melt.In addition, stirring by high-speed gas blowing was performed until the reaction was completed in any of the examples. It started immediately after the point in time.

In Example 1, Ar gas was used in all steps, and in Example 2, Ar gas and 02 gas were used at 50% up to the stirring step.
A mixed gas mixed by volume was used. In Example 3, Ar gas was introduced through five nozzles and 0° gas was introduced through the other five nozzles until the stirring step. That is, for example, during stirring, Ar gas was blown in at 60 Nt/min through five nozzles, and 02 gas was blown in at 600 Nt/min through the other five nozzles. In Example 4, each treatment was performed under an argon gas atmosphere. Ar gas was supplied into the housing through the gas supply port at a flow rate of 50 Nt/%. At this time, the 022- concentration in the exhaust gas decreased to below 2.9%.

Table 2 shows the composition, chromium yield, and At1 degree dispersion (variation) of the metal Cr products produced in two series. The impurity concentrations of At, O, and N are extremely low.

In particular, in the case of Example 4, which was manufactured under an inert gas atmosphere, the N concentration was extremely low at over 0.009. Further, the Cr yields are all 90 coefficients or higher, and the variation in At concentration is also extremely small.

Table 3 shows the results of investigating the variation in At concentration (weight ratio) in the ingot in Example 1. Divide the ingot into 5 equal parts in the diameter direction, and divide it into 5 equal parts in the height direction.

The At concentration was analyzed for a total of 15 nannors divided into three equal parts. As a result, as is clear from Table 3, htf
! It can be seen that the variation in #degree is extremely small.

Next, Examples 5 and 6 regarding At-V FJ gold alloy production and a comparative example thereof using a conventional method will be described. In both Example 5.6 and Comparative Example, the blended amount of raw materials was ■20
5 is 900 kg, At is 945 kg and Cll0 is 15
0kl? Met. Note that six gas injection nozzles 2 are used, and the conditions for gas injection into the reactor in each step of charging/air injection, ignition/reaction, stirring, cooling I, and cooling H are as follows.
As shown in the table. In addition, the blowing gas flow rate during stirring 7
00 N11 minutes is equivalent to 1 kli of melted material,
0.35 IN 11 minutes.

In Example 6, each treatment was performed under an inert gas atmosphere inside the housing, and 50% of Ar gas was applied inside the housing.
N was supplied at a flow rate of 11 minutes. In comparative examples, the above-mentioned treatments were carried out in the atmosphere without blowing gas into the melt.

The composition, properties, and yield of the kl-V master alloy products in each Example 5.6 and Comparative Example are as shown in Table 5.

The O and N concentrations of Comparative Example are both 0.05 weight factor or higher, whereas the O and Nl concentration of Examples 5 and 6 are both as low as 0.05 weight factor or lower. In particular, the impurity concentration in Example 6 is extremely low, about 1/10 of that in Comparative Example. In addition, in the comparative example, a large number of cavities were formed from the center to the upper part of the ingot, and a black-purple oxide film was formed on the surface of the ingot and cracks that occurred when the ingot was cooled. For this reason, it could not be used as an At-V master alloy for titanium alloys, so the cavities and oxide film portions were removed by crushing or grinding.

Therefore, the yield of the clean ingot portion is extremely low at 73%. On the other hand, in the case of the method of the present invention (Examples 5 and 6),
There are almost no cavities, and there is very little oxide film. Therefore, the ingot yield was high at 90% or more in all cases.

Furthermore, Fig. 3 shows the distance from the bottom surface of the ingot on the horizontal axis.
The graph shows the segregation of At with the At concentration plotted on the vertical axis, and it can be seen that Examples 5 and 6 have less segregation than the Comparative Example.

It is possible to produce metals and alloys with high yield.

25- Note that, as in the above embodiments, this invention uses metal Cr or A,
Not limited to the production of l-V alloys, At-MO alloys, Fe
It can be applied to the production of various metal alloys such as -V alloy, Fe-Mo alloy, Fe-Nb alloy, and Fe-B alloy.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the reactor, FIG. 2 is a longitudinal sectional view of the reactor installed in the housing, and FIG. 3 is a graph showing the effects of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction furnace, 2... Nozzle, 3... Molten metal, 4... Molten slag, 5... Housing. Applicant's agent Patent attorney Takehiko Suzue 261 Figure 1 Figure 2 0112 ■---Feathers, Figure 3 44 Lower surface height (mm)

Claims (7)

[Claims] (1) In a method for manufacturing a metal alloy by the thermite method in which a # oxide is returned to light by aluminum, the oxide and aluminum are charged into a reactor, ignited to melt at least a part of them, and the molten material is A method for producing metal alloys by the thermite method, which is characterized by stirring by blowing in gas. (2) Is the gas at 200 Nrrt/sec or more and/or a melt? , per o, ls Nz/min or more. (3) The method for producing a metal alloy by the thermite method according to claim 1 or 2, wherein the oxide contains chromium oxide. (4) The method for producing a metal alloy by the thermite method according to claim 1 or 2, wherein the oxide includes vanadium oxide. (5) The method for producing a metal alloy by the thermite method according to claim 3 or 4, wherein the gas is an inert gas. (6) The method for producing a metal alloy by the thermite method according to claim 3, wherein the gas is a mixed gas of an inert gas and oxygen gas. (7) A method for producing a metal alloy by the thermite method according to claim 1, which comprises charging the oxide and aluminum into a reactor and then placing them under an inert gas atmosphere. .