Patent Application
20220040762
The present invention relates to a method for producing highly pure titanium metal powder or titanium alloy powder that may be used in various fields. Specifically, the present invention relates to a method of producing titanium metal powder or titanium alloy powder, which may achieve mass production and cost reduction by using a multi-step reduction process.
Titanium metal and titanium alloys are light in weight and have excellent mechanical properties, excellent high-temperature properties and excellent corrosion resistance, and thus have been regarded as suitable materials for aerospace applications where it is difficult to use other conventional alloys. However, titanium-based materials have problems that their raw materials are expensive and the production cost thereof is high.
Titanium has excellent properties, but has a problem in that it is expensive. Due to this problem, various production methods for cost reduction have been developed since the 1950s.
Known methods for producing titanium include a method comprising making sponge titanium using the Kroll process, producing an ingot from the sponge titanium by a vacuum arc remelting (VAR) process, and producing a processed material from the ingot through extrusion, rolling, etc.
The Kroll process is currently most often used for the production of titanium metal, and the final product thereof is in the form of sponge, not powder. In the Kroll process, pure titanium ore is converted into a sponge form by applying electric charge thereto in a special electric furnace. This process is performed in a chlorinator where chlorine gas passes through an electric charge to form titanium tetrachloride (TiCl4) in a liquid form. The titanium tetrachloride thus formed is purified through a complex distillation process. After the distillation process, magnesium or sodium is added to and reacted with the purified titanium tetrachloride to produce metal titanium sponge and magnesium or sodium chloride. Then, the titanium sponge is crushed and pressed. The crushed titanium sponge is melted by vacuum arc remelting (VAR). The Kroll process has problems in that the process is complicated and uses a material which is difficult to handle and is unsafe.
Powder metallurgy (PM) technology has attracted attention in that it can provide titanium having a complex shape at low cost without impairing mechanical properties, unlike the ingot technology. The use of the powder metallurgy (PM) technology has great potential in that it can produce titanium at low cost, but the powder metallurgy (PM) technology is not used a lot, because titanium products produced by conventional powder metallurgy processes have unsatisfactory physical properties and the cost reduction effect is less than expected. Thus, in order to produce titanium using the powder metallurgy technology, a method for improving the physical properties of a final product while reducing the production cost is required.
International Patent Publication No. WO2014/187867 discloses a method for producing a wide range of metal powders, metal alloy powders, intermetallic powders and/or their hydride powders, which uses calcium hydride powders or granules to reduce metal powders into a metal or directly uses calcium hydride regardless of the presence of another metal in one or more metal oxides to produce metal alloy powders.
U.S. Pat. No. 6,264,719 discloses a method for producing titanium alumina reinforced with a small amount of aluminum oxide as metal matrix composite powder when reacting a small amount of titanium dioxide with aluminum metal powders.
Various methods for producing titanium metal powder or titanium alloy powder have been attempted, but there is still a need to develop a method which is capable of producing high-quality titanium metal powder or titanium alloy powder at low cost and capable of mass-producing the high-quality titanium metal powder or titanium alloy powder on an industrial scale.
An object of the present invention is to provide a method for producing titanium metal powder or titanium alloy powder, which is capable of producing titanium metal powder or any type of titanium alloy powder with excellent quality at low cost and may be easily performed on an industrial scale.
The above object is accomplished by a method for producing titanium metal powder or titanium alloy powder, the method comprising steps of: a) partially reducing each of at least one metal oxide and a titanium oxide; b) preparing a first mixture by mixing the partially reduced metal oxide and titanium oxide together; c) preparing a second mixture by mixing the first mixture with calcium hydride; and d) producing titanium metal or a titanium alloy by completely reducing the second mixture.
Moreover, the object of the present invention is accomplished by a method for producing titanium metal powder or titanium alloy powder, the method comprising steps of: a) partially reducing one of at least one metal oxide and a titanium oxide; b) preparing a first mixture by mixing the partially reduced one with the other of the metal oxide and the titanium oxide; c) preparing a second mixture by mixing the first mixture with calcium hydride; and d) producing titanium metal or a titanium alloy by completely reducing the second mixture.
Preferably, the method may comprise a step of partially reducing the first mixture, after step b) and before step c).
Preferably, the partial reduction in step a) and the complete reduction in step d) may be performed by heat treatment at a temperature of 1,000° C. to 1,500° C. under a hydrogen atmosphere for 1 to 10 hours.
Preferably, the partial reduction in step a) and the complete reduction in step d) may be performed by heat treatment at a temperature of 1,000° C. to 1,500° C. under a hydrogen atmosphere for 1 to 10 hours.
Preferably, the metal oxide may be selected from the group consisting of CaO, V2O5, Cr2O3, Nb2O5, MoO3, WO3, Y2O3 and ZrO2.
Preferably, the stoichiometric ratio between the first mixture and the calcium hydride may be 1:1.1 to 1.25.
Preferably, the second mixture may further contain aluminum and vanadium oxide (V2O5) powders.
Preferably, the titanium alloy powder may be Ti-6Al-4V powder.
Preferably, the titanium metal powder and the titanium alloy powder may have an oxygen content of less than 0.3 wt % and a particle size distribution of less than 50 μm.
The present invention may provide an inexpensive method capable of producing high-quality titanium powder and titanium alloy powder that may be used in more applications. Through the present invention, it is possible to extend the use of titanium and alloy powder thereof to fields that require high-quality titanium metal powder, such as general industrial application as well as aerospace, medical or military applications.
All technical terms used in the present invention have the following definitions, unless otherwise defined, and have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. In addition, although preferred methods or samples are described in the present specification, those similar or equivalent thereto are also included within the scope of the present invention.
The term “about” refers to an amount, level, value, number, frequency, percentage, dimension, size, weight, or length that varies by as much as 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1% to a reference amount, level, value, number, frequency, percentage, dimension, size, weight, or length.
Throughout this specification, unless the context requires otherwise, the terms “comprise,” “comprises” and “comprising” will be understood to imply the inclusion of a stated step or component or group of steps or components but not the exclusion of any other step or component or group of steps or components.
The method for producing titanium metal powder or titanium alloy powder in any form according to the present invention is characterized by comprising multiple reduction steps. Preferably, the method is characterized by comprising two reduction steps. More preferably, the method comprises the following steps:
a) partially reducing each of at least one metal oxide and a titanium oxide (first reduction step);
b) preparing a first mixture by mixing the partially reduced metal oxide and titanium oxide together (first mixing step);
c) preparing a second mixture by mixing the first mixture with calcium hydride (second mixing step); and
d) producing titanium metal or a titanium alloy by completely reducing the second mixture (second reduction step).
According to one embodiment of the present invention, the method further comprises step e) of crushing and powdering the produced titanium metal or titanium alloy (powdering step).
Hereinafter, each step will be described in detail.
First, each of at least one metal oxide and a titanium oxide is partially reduced (first reduction step).
The first reduction step may be performed by heat-treating each of the metal oxide and the titanium oxide as raw materials at a temperature of 1,000° C. to 1,500° C. under a hydrogen atmosphere for 1 to 10 hours. The heat-treatment temperature may preferably be 1,100° C. to 1,300° C., more preferably 1,100° C. to 1,200° C. The heat-treatment time may preferably be 2 to 4 hours. The hydrogen atmosphere may be provided by a hydrogen gas flow of 1.5 l/min or more, preferably 1.5 l/min to 5 l/min, which may vary depending on the size of a heat-treatment furnace and the amounts of the raw materials.
In the first reduction step, the metal oxide or the titanium oxide is placed in a semicircular cross-sectional crucible made of stainless steel and is heated in the heat treatment zone of a furnace. The heat treatment furnace used may be a tube furnace. The heat treatment furnace that is used in the present invention may have two separate heat treatment zones for the first reduction step and the second reduction step. It is preferable to use any type of heating furnace that is operated under a gas atmosphere capable of promoting the reduction reaction occurring at a temperature of up to 1,500° C. The heat treatment furnace should be suitable for work using a gas such as hydrogen or argon.
Each of the heat treatment zones may individually form a hydrogen gas flow.
In this step, the oxygen contents of the metal oxide and the titanium oxide as raw materials may be decreased by heat treatment, and oxides that may be easily reduced in the second reduction step may be formed.
The metal oxide may be at least one selected from the group consisting of CaO, V2O5, Cr2O3, Nb2O5, MoO3, WO3, Y2O3 and ZrO2, and is preferably CaO. The titanium oxide may be TiO2 or TiO, and is more preferably TiO2.
According to one embodiment of the present invention, in the case in which titanium alloy powder is to be produced, the metal oxide may be CaO and V2O5, and aluminum or aluminum oxide may further be used together with the metal oxide. In this case, the titanium alloy powder may be Ti-6Al-4V.
The metal oxide and the titanium oxide are preferably in a powder form.
According to one embodiment of the present invention, the first reduction step may consist of: a1) a first partial reduction step of partially reducing each of calcium oxide and titanium oxide; and a2) a second partial reduction step of partially reducing a first mixture obtained by mixing the partially reduced calcium oxide and titanium oxide together.
By dividing the first reduction step into two steps as described above, it is possible to obtain a mixture of uniformly reduced calcium oxide and titanium oxide.
According to another embodiment of the present invention, only one of the metal oxide and the titanium oxide may be partially reduced in the first reduction step.
Thereafter, a first mixture is prepared by mixing the partially reduced metal oxide and titanium oxide together (first mixing step), and a second mixture is prepared by mixing the first mixture with calcium hydride (second mixing step).
In this step, the first mixture and calcium hydride are preferably mixed together in a stoichiometric ratio of 1:1.1 to 1.25.
The calcium hydride may be in a powder or granule form, and the particle size thereof may preferably be 0.02 to 2 mm. The calcium hydride that is used in the present invention may be a commercially available product, but it is preferable that the calcium hydride that is used in the present invention be calcium hydride shavings or granules obtained by heating calcium metal shavings or calcium metal granules at a temperature of 550 to 750° C. under a hydrogen gas atmosphere for 1 to 10 hours.
Next, a step (second reduction step) of producing titanium metal or a titanium alloy by completely reducing the second mixture by heat treatment is performed.
The heat treatment may be performed at a temperature of 1,000° C. to 1,500° C. under a hydrogen atmosphere for 1 to 10 hours. The heat-treatment temperature may preferably be 1,100° C. to 1,300° C., more preferably, 1,100° C. to 1,200° C. The heat-treatment time may preferably be 2 to 4 hours. The hydrogen atmosphere may be provided by a hydrogen gas flow of 1.5 l/min or more, preferably 1.5 l/min to 5 l/min, which may vary depending on the size of a heat-treatment furnace and the amount of the mixture. The heat treatment furnace that is used in the second reduction step is as described above with respect to the first reduction step.
In this step, a mixture of the partially reduced metal oxide and titanium oxide may react with calcium hydride as a reducing agent under a hydrogen atmosphere to form titanium metal or a titanium alloy. The titanium metal or titanium alloy thus formed is recovered.
Finally, the powder obtained in recovery step e) may be powdered following a washing and drying step. According to one embodiment of the present invention, the recovered titanium metal or titanium alloy is in a bulk form, and thus may be crushed using a high-energy ball milling device before the washing and drying step.
In the washing and drying step, the crushed powder may be mixed with water to form a slurry which may then be washed with agitation. In order to improve the washing effect, a solvent such as acetic acid may be added to the slurry.
In the drying step after washing, the powder may be dried in an open low-temperature oven at a temperature of 80 to 90° C.
The titanium metal or titanium alloy produced in the present invention is in the form of powder, has a particle size distribution of 50 μm or less, preferably 10 to 50 μm, and an oxygen content of less than 0.3 wt %.
As used herein, the term “powder” refers to one having a particle size of less than 1 mm.
As used herein, “X50” refers to the particle size distribution of the final powder, and indicates the median diameter or the median value of the particle size distribution. Preferably, X50 indicates a particle size distribution of 50 μm or less, or 40 μm or less, more preferably 20 μm or less.
Hereinafter, the present invention will be detail with reference to examples, but the scope of the present invention is not limited by these examples.
The starting materials used in the Examples of the present invention are shown in Table 1 below.
Instruments used to analyze the titanium metal powder and titanium alloy powder finally produced in the present invention are shown in Table 2 below.
Each of 50 g of 99.5% pure CaO powder and 50 g of 99% pure TiO2 powder was placed in a SUS310S crucible and partially reduced in the heat-treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 L/min for 2 hours. 100 g of a first mixture obtained by mixing the partially reduced CaO and TiO2 together was completely mixed with 130 g of calcium hydride powder (particle size: 0.02 to 2 mm), thus preparing a second mixture. The stoichiometric ratio of the calcium hydride to the first mixture was 1.1 to 1.25x. Then, the second mixture was placed in a SUS310S crucible and completely reduced in the heat treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 l/min for 2 hours. The obtained bulk material was placed in a ball milling device, crushed, mixed with water and acetic acid, washed with agitation, and completely dried at 90° C. The physical properties of the metal powder were measured using the instruments shown in Table 2 above. Scanning electron micrographs of the produced powder are shown in
150 g of a mixture of 99.5% pure CaO powder and 99% pure TiO2 powder was placed in a SUS310S crucible and partially reduced in the heat treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 L/min for 2 hours. A first mixture obtained by mixing the partially reduced CaO and TiO2, 7.13 g of 99.6% pure V2O5 powder and 6 g of 99.5% pure aluminum metal powder was completely mixed with 207 g of calcium hydride powder (particle size: 0.02 to 2 mm), thus preparing a second mixture. The stoichiometric ratio of the calcium hydride to the first mixture was 1.1 to 1.25x. Then, the second mixture was placed in a SUS310S crucible and completely reduced in the heat treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 l/min for 2 hours. The obtained bulk material was placed in a ball milling device, crushed, mixed with water and acetic acid, washed with agitation, and completely dried at 90° C. The physical properties of the metal powder were measured using the instruments shown in Table 2 above. Scanning electron micrographs of the produced powder are shown in
150 g of a mixture of 99.5% pure CaO powder and 99% pure TiO2 powder was placed in a SUS310S crucible and partially reduced in the heat treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 L/min for 2 hours. A first mixture obtained by mixing the partially reduced CaO and TiO2, 7.13 g of 99.6% pure V2O5 powder and 7.1 g of 99.5% pure aluminum oxide powder was completely mixed with 207 g of calcium hydride powder (particle size: 0.02 to 2 mm), thus preparing a second mixture. The stoichiometric ratio of the calcium hydride to the first mixture was 1.1 to 1.25x. Then, the second mixture was placed in a SUS310S crucible and completely reduced in the heat treatment zone of a tube furnace at 1,100° C. under a hydrogen gas atmosphere with 2 to 3 l/min for 2 hours. The obtained bulk material was placed in a ball milling device, crushed, mixed with water and acetic acid, washed with agitation, and completely dried at 90° C. to obtain titanium alloy (Ti-6Al-4V) powder.
Although the present invention has been described in detail with reference to the specific features, it will be apparent to those skilled in the art that this detailed description is only of a preferred embodiment thereof, and does not limit the scope of the present invention. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2018-0164365 | Dec 2018 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2019/017801 | 12/16/2019 | WO | 00 |
