JPS6232251B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing metal alloys such as metal chromium or aluminum-vanadium alloys by the thermite method. More specifically, the present invention relates to a method for producing metal alloys such as metal chromium or aluminum vanadium alloys by the thermite method. This paper proposes a method for producing metal alloys that can produce ingots with low segregation at a high yield. There are two methods for producing metallic chromium (hereinafter abbreviated as metallic Cr): thermite method (pyrometallurgical refining method) and electrolytic method (hydro-refining method). The Thermite method involves mixing chromium oxide (Cr ₂ O ₃ ) with aluminum (Al) as a reducing agent, and adding an oxidizing agent such as sodium chlorate and a slag-forming agent such as quicklime, and then igniting the raw material to cause a reaction. , is a method to obtain metal Cr by reducing an oxide with Al. Therefore, the raw material chromium oxide or
Al contains impurities such as silicon (Si), iron (Fe), or sulfur (S), and impurities such as Al, oxygen (O), or nitrogen (N) are incorporated during the reaction, so the metal In Cr products, Al, O, and N are present in fairly high concentrations of 0.1 to 0.3% by weight, 0.08% by weight, and 0.06% by weight, respectively, 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 Fe, 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 separate particles, which are then processed in vacuum or in hydrogen gas. 1000~1500℃
It is necessary to perform a degassing treatment by heating the metal to a temperature of 100.degree. C. or to remelt the electroslag under an argon gas atmosphere using this crude metal as a consumable electrode. Electricity is consumed for reheating in this post-purification treatment,
There is a drawback that the equipment cost is high, and furthermore, this post-processing process causes handling loss, resulting in poor product yield and high manufacturing cost. On the other hand, in the production of titanium alloys such as Ti-6Al-4V, an Al-V master alloy containing 50% or 60% Al is used as an additive for Al and vanadium (V). This Al--V master alloy is usually produced by the thermite method. That is, a raw material mixture of V oxide, Al, and quicklime is ignited and reacted, and is melted by the heat of the reaction. After the reaction is complete, the metal and slag are separated by specific gravity in a furnace, then cooled and solidified to obtain an ingot, and after the slag is ground and removed, it is sized and made into a product, or after the molten slag is separated and removed. , casting molten metal to produce products. By the way, because the difference between the melting point of Al and the melting point of V is large, component segregation and blowholes are likely to occur in Al-V alloy ingots. It is easily oxidized and nitrided, forming a thick oxide film on the entire surface of the ingot. Therefore, in order to commercialize the Al--V master alloy, it is necessary to mechanically or chemically remove the porosity and oxide film of the ingot to improve its 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, O and N still each contain 0.05% by weight or more, which poses a quality problem. This invention was made in view of the above circumstances, and it provides degassing treatment, electroslag remelting,
A method for producing metal alloys using the thermite method, which allows obtaining ingots with low impurity concentration, less segregation and oxide film, and excellent cleanliness at a high yield without post-processing such as machining or chemical processing. The purpose is to provide A 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 with aluminum, in which the oxide and aluminum are charged into a reactor,
It is characterized by igniting these to melt at least a portion of them, and then blowing gas into this melt to stir it. 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 may be immediately before the end of the reaction, immediately after the end of the reaction, or a period spanning before and after the end of the reaction. By blowing gas into the mixed melt of molten metal and molten slag containing unreacted substances and unmelted substances and stirring it strongly, the oxide that remains partially unreacted is brought into contact with the aluminum,
In addition to promoting the reaction and quickly bringing it to a close, by introducing gas into the molten material after the reaction is complete, bubbles of the injected gas float through the molten metal, causing them to remain in the molten metal. Non-metallic inclusions and gas generated during the cooling process of the metal are caught up in the bubbles of the blown gas, promoting levitation.
It is quickly discharged into 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 a reactor 1. FIG. A plurality of nozzles 2 are installed in the lower part of the side wall of the reactor 1 with their longitudinal direction substantially horizontal, and these nozzles 2 are connected to a gas supply source such as Ar gas or O ₂ gas. First, a method for producing 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 powder, a small amount of inert gas such as Ar gas is passed through the nozzle 2 during charging to prevent nozzle clogging, and even after charging, Ar gas is passed through the nozzle 2 into the charged material. air purge in the charge. Next, the raw material is ignited to start a reaction, and at the same time the flow rate of Ar gas introduced into the furnace from the nozzle 2 is increased. This is because the raw material melts due to ignition, which tends to cause nozzle clogging. Therefore, the amount of Ar gas blown at this time may be set to a flow rate that does not cause nozzle clogging due to backflow of the molten metal. By igniting the raw materials, a reaction (mainly
The reaction between Cr ₂ O ₃ and Al begins, and is reduced by Al to produce metal Cr. Further, the charge is melted into molten metal 3 and molten slag 4 by the reaction heat generated at this time. In this way, after at least a part of the charge is melted, the flow rate of the inert gas such as Ar gas blown into the charge from 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 unreacted and remaining chromium oxide and the reducing agent aluminum, promoting the reaction and causing the unreacted chromium oxide to transfer to slag.
is reduced, the chromium yield is improved, and the reaction is quickly completed. In addition, the floating of non-metallic inclusions such as Cr ₂ O ₃ or Al ₂ O ₃ dissolved in the molten metal is promoted by the bubbles of the inert gas, and the concentration of O and Al in the molten metal increases. decreases. Further, by blowing inert gas, the molten metal 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 performed for 1 to 2 minutes immediately before or after the completion of the reaction. In this invention, inert gas is discharged from the nozzle 2 into the charge at high speed, and the charge is strongly stirred by the powerful discharge energy, thereby promoting the reaction and floating non-metallic inclusions. Because it aims to promote
The amount of inert gas blown is an important factor in achieving the object of the present invention. As a result of various experiments and research conducted by the inventors of the present application, the amount of inert gas blown was determined at a flow rate V converted to the standard state.
200Nm/sec or more or flow rate L converted to standard condition
per kg of molten material (molten metal and molten slag)
It has been found that extremely excellent effects can be achieved by setting the flow rate to 0.15 Nl/min or more. By vigorously stirring in this manner, the O and N concentrations of the metal Cr product are 0.05% by weight and 0.04% by weight, respectively, which are approximately 30 to 40% lower than conventional products. Also,
The concentration of Al is 0.07 to 0.10% by weight, which is 0.03 to 0.2% by weight lower than that of conventional products, and the variation in Al concentration in the ingot is extremely low, being 1/2 to 1/3 of the variation in conventional products. low. After strong stirring, the flow rate of the blowing gas is reduced and the gas blowing is continued for about 1 hour. This gas flow rate 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 rate is further reduced to the flow rate at the time of 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 during cooling of the ingot is to prevent oxidation and nitridation of the ingot surface by coating the high temperature ingot surface with inert gas. . Note that in order to obtain a metal Cr product with a further reduced Al impurity concentration, inert gas and oxygen gas or oxygen-containing gas are used instead of inert gas as the gas blown through the nozzle 2 as described above. You can use a mixed gas with In particular, by using this mixed gas in the stirring process of the molten metal, unreacted Al in the molten metal reacts with the oxygen gas in the blown gas to become Al ₂ O ₃ , which floats up in the molten metal and forms slag. Move inside. By this,
It is possible to produce metallic Cr with an Al concentration of 0.07% by weight or less. Further, by performing the above-mentioned treatments in an inert gas atmosphere as described below, a metal Cr product with a further reduced impurity N concentration can be obtained. Figure 2 shows a reactor 1 housed in a housing 5.
A vertical cross-sectional view is shown. The housing 5 consists of a main body 6 and a lid 7. After the reactor 1 is installed in the main body 6, the main body 6 and the lid 7 are sealed together with a rubber gasket 8, and both are fixed with a presser fitting 9. A gas supply port 13 and a gas discharge port 14 are provided on the side wall of the main body 6.
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 1 is connected via a supply pipe 15 to a gas supply source such as Ar gas or O ₂ 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 10 is fixed to this gas outlet with a presser fitting 12 through a rubber packing 11. 5 is now sealed.
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, such as Ar gas, is introduced into the housing 5 through the gas supply port 13 and air inside the housing 5 is exhausted through the gas exhaust port 14, thereby replacing the inside of the housing 5 with Ar gas. At the same time as this replacement work, Ar is applied to the raw material in the reactor 1 through the nozzle 2.
Blow gas and air purge the raw material. The replacement work is performed while detecting the oxygen concentration in the exhaust gas discharged from the gas outlet 14.
The replacement work is terminated when the value falls below the capacity%. After the replacement work is completed, open the lid plate 10 and close the reactor 1.
The raw material inside is ignited to start the reaction, and the melt is stirred by inert gas blown through the nozzle 2 in the same manner as described above. Note that during this time, the introduction of Ar gas into the housing 5 continues.
During the reaction and stirring period, the charge in the reactor 1 is kept under an inert gas atmosphere. 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 lid plate 10 of the gas outlet is closed. From the gas supply port 13,
The ingot is cooled while supplying Ar gas in an amount that can maintain a pressure of about 10 mmH ₂ O inside the housing 5. In this way, metal Cr can be prepared under an inert gas atmosphere.
By producing this, a metal Cr product with an extremely low N concentration of 0.010% by weight or less can be obtained, and an ingot with excellent uniformity without segregation of Al can be obtained. According to the experiments of the present inventors,
When the O concentration in the exhaust gas discharged from the gas outlet 14 exceeds 3% by volume, the N concentration increases to 0.010% by weight.
Since it will be difficult to obtain the following metal Cr, the interior of the housing 5 must be sufficiently argonized before igniting the raw materials.
It is preferable to replace with gas. Next, a method for manufacturing the Al--V master alloy will be explained. A vanadium compound (vanadium pentoxide or sodium hexavanadate, etc.) containing V in the amount necessary to obtain the desired composition of the mother alloy, Al in the amount necessary to reduce this vanadium compound, and the desired composition of the mother alloy. The amount of Al necessary to obtain the composition and an appropriate amount of a slag-forming agent such as quicklime are blended, and the raw materials are mixed. Then, in the same manner as in the production of metal Cr, the steps of charging, air purge, ignition, reaction, stirring, and cooling are performed to produce an Al-V master alloy. When stirring the charge, the inert gas injection rate should be 200 Nm/sec or more and/or the melt 1
It is preferable to set it to 0.15 Nl/min or more per kg. As a result, the O and N concentrations of the Al-V master alloy product are both approximately 0.03% by weight, approximately 40% lower than the Al-V master alloy product produced using the conventional thermite method. Al with
A V master alloy is obtained. In addition, Al segregation within the ingot is reduced compared to conventional products, the generation of cavities inside the ingot is suppressed, and the formation of an oxide film on the ingot surface is extremely small. Furthermore, since the post-treatment of the product is extremely light, the clean section ingot yield [(clean section ingot weight)/(produced ingot weight)] is improved by 15 to 20% compared to the conventional method. The reason why 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 the remaining unreacted vanadium compound into sufficient contact with the aluminum, promoting the reaction, and transferring it unreacted to the molten slag. By reducing V, the yield of V in 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 concentration of the product is reduced and the occurrence of cavities in the ingot is suppressed. Furthermore, by blowing 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 conventional method.
Although the N concentration is lower than that of the mother alloy product, O and N
In order to obtain a product with a lower concentration, each step may be carried out under an inert gas atmosphere in the same manner as described above. As a result, both O and N concentrations are
A high purity master alloy of 0.010% by weight or less can be produced. In this case as well, the product's O and N
In order to reduce the concentration to 0.010% by weight or less, the residual O concentration in the housing (O concentration in exhaust gas) must be reduced to 3.
It is preferable to make it less than % by volume. 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 amount was:
Chromium oxide, Al, sodium chlorate and quicklime weigh 3130Kg, 1242Kg, 276Kg and 76Kg, respectively. The inner surface of the reactor 1 is lined with magnesia clinker, and the inner diameter and height are 1500 mmφ and 2300 mm, respectively. Furthermore, ten gas blowing nozzles 2 made of stainless steel and having an inner diameter of 3 mmφ are attached to the side wall of the reactor 1 at positions 2 cm apart from the lower end.

【table】

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[Table] Table 1 shows the gas injection conditions into the reactor for each step of charging/air purge, ignition, reaction, stirring, cooling, and cooling. Note that the flow rate is the total flow rate, and therefore, when the flow rate during stirring of 1200 Nl/min is converted to 0.254 Nl/min per 1 kg of melt. Further, in all Examples, stirring by high-speed gas injection was started immediately after the reaction was thought to have ended. In Example 1, Ar gas was used in all steps, and in Example 2, a mixed gas in which Ar gas and O ₂ gas were mixed at 50% by volume up to the stirring step was used. In Example 3, Ar gas was introduced through five nozzles and O ₂ gas was introduced through the other five nozzles until the stirring step. That is, for example, during stirring, Ar gas was blown at 600 Nl/min from five nozzles, and O ₂ gas was blown at 600 Nl/min from 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 Nl/min. At this time, the O concentration in the exhaust gas decreased to 2.9% by volume or less. Dispersion (variation) of composition, chromium yield, and Al concentration of metal Cr products manufactured as described above
are shown in Table 2. The impurity concentrations of Al, O, and N are extremely low. In particular, in the case of Example 4 manufactured under an inert gas atmosphere, the N concentration was 0.009%.
extremely low. In addition, the Cr yield is 90% or more in all cases, and the variation in Al concentration is also extremely small.
In Example 1, Al concentration in the ingot (wt%)
Table 3 shows the results of investigating the variation in . The Al concentration was analyzed for a total of 15 samples, which were divided into 5 equal parts in the diameter direction of the ingot and 3 equal parts in the height direction: upper, middle, and lower. As a result, as is clear from Table 3,
It can be seen that the variation in Al concentration is extremely small. Next, Example 5 regarding the production of Al-V master alloy
and 6, and a comparative example thereof using a conventional method will be explained. In both Examples 5 and 6 and the comparative example, the raw material blending amounts were 900 kg of V ₂ O ₅ , 945 kg of Al, and 945 kg of CaO.
It weighed 150Kg. In addition, the gas blowing nozzle 2 is 6
I used this book. Charge. The gas injection conditions into the reactor in each step of air purge, ignition, reaction, stirring, cooling, and cooling are as shown in Table 4. Note that the blowing gas flow rate of 700 Nl/min during stirring is converted to 0.351 Nl/min per 1 kg of melt. In Example 6, each treatment was performed in an inert gas atmosphere inside the housing, and Ar gas was supplied into the housing at a flow rate of 50 Nl/min. In the comparative example, the above-mentioned treatments were performed in the atmosphere without blowing gas into the melt. The composition, properties, and yield of the Al--V master alloy products in Examples 5 and 6 and Comparative Examples are shown in Table 5. The O and N concentrations of the comparative example are both
0.05% by weight or more, whereas Examples 5 and 6
The O and N concentrations of both are as low as 0.05% by weight or less. 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 were generated when the ingot was cooled.
For this reason, it could not be used as an Al--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 part is extremely low at 73%. On the other hand, in the case of the method of the present invention (Examples 5 and 6), almost no cavities were generated and the oxide film was extremely small. For this reason, the ingot yield was high at over 90% in all cases. Furthermore, Fig. 3 is a graph showing the segregation of Al, with the distance from the bottom surface of the ingot being plotted on the horizontal axis and the Al concentration on the vertical axis. It can be seen that there is little segregation. As explained in detail above, according to the present invention,
Metals and alloys with low impurity concentration, high quality, and excellent cleanliness can be produced at high yields. Note that this invention uses metal Cr as in the above embodiment.
Or not limited to the production of Al-V alloys, but also Al-Mo alloys,
Fe-V alloy, Fe-Mo alloy, Fe-Nb alloy or Fe
-Applicable to the production of various metal alloys such as B alloy.

[Brief explanation of the drawing]

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. 1... Reactor, 2... Nozzle, 3... Molten metal, 4
...Melted slag, 5...Housing.

Claims (1)

[Claims] 1. In a method for producing a metal alloy by the thermite method in which an oxide is reduced with aluminum, the oxide and aluminum are charged into a reactor, ignited to melt at least a portion of the oxide, and A method for producing a metal alloy by the thermite method, which is characterized by blowing gas into a molten material and stirring it. 2. The method for producing a metal alloy by the thermite method according to claim 1, characterized in that the gas is blown into the melt at a rate of 200 Nm/sec or more and/or 0.15 Nl/min/kg of molten material 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. The 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.