KR20180021536A - Composition for sintering - Google Patents

Abstract

The present invention relates to a sintering composition for producing a metal sintered body or a method of manufacturing the sintered body, and more particularly, to a method for manufacturing a sintered body by increasing the sintering driving force by reducing the particle size of the raw material powder having the active metal hydride powder as a main component, The present invention relates to a method for producing a compact metal alloy sintered body by sintering the powder compacted body in an atmospheric pressure or a non-pressurized state in vacuum, hydrogen, or an inert gas atmosphere, According to the sintering composition of the present application, a sintered body having a very high relative density can be manufactured at a low sintering temperature of 1000 ° C or less and at a low cost .

Description

COMPOSITION FOR SINTERING [0002]

 The present invention relates to a sintering composition for producing a metal sintered body or a method of manufacturing the sintered body, and more particularly, to a method for manufacturing a sintered body by increasing the sintering driving force by reducing the particle size of the raw material powder having the active metal hydride powder as a main component, The present invention relates to a method of producing a dense metal alloy sintered body by producing a powder compact by molding raw material powder and subjecting it to pressureless sintering or pressureless sintering in vacuum, hydrogen, or an inert gas atmosphere.

Of the active metals, titanium, in particular, has a low specific gravity (4.5 g / cm ³ ), excellent tensile strength, excellent resistance to fatigue, cracking and corrosion. The titanium is a gray metallic luster metal having a low density, ductility and a relatively high melting point of 1650 캜. Commercial 99.2% pure titanium has a tensile strength of about 63,000 Psi and is about 60% more denser and twice as strong as the commercially available 6061-T6 aluminum. Certain titanium alloys, for example, Beta C, have a tensile strength of at least 200,000 Psi. However, when titanium is heated above 430 ℃, its strength is lost. The most notable chemical properties of titanium are their resistance to corrosion, for example, titanium can tolerate corrosion by chlorine gas or most organic fatty acids as well as sulfuric acid and hydrochloric acid, Have.

The titanium and oxygen and immediately react at about 1200 ℃ to form a titanium dioxide (TiO _2). Therefore, titanium can not be melted in the air, and the titanium burns before it reaches the melting point. Therefore, the melting of titanium is possible only in an inert atmosphere or in a vacuum. Further, the titanium easily reacts even in a pure nitrogen gas atmosphere and forms titanium nitride (TiN) when the temperature reaches about 800 ° C.

Titanium and its alloys are widely proven to be technically superior and economically viable throughout the aerospace, general industry, offshore and commercial sectors. In North America, about 70% of titanium demand is being applied to aerospace related fields. In addition, remarkable growth has been achieved in the general industrial, marine and commercial sectors due to the spread of the above application fields and the development of new titanium applications. For example, in the aerospace industry, titanium metal itself or an alloy is used to make various parts such as engines. It is estimated that about 59 tons for the Boeing 777, 45 tons for the Boeing 747, and 32 tons for the Airbus A340 . Also, a large amount of titanium is used for missiles, armored vehicles, and spaceships. Particularly, since titanium is not corroded in seawater, it can be used for ship parts such as propulsion shafts of ships, heat exchangers for seawater desalination devices, heating and cooling devices for aquariums, fishing tackle, diver knives, Can also be used. The titanium is also used to make various devices and facilities used in the chemical industry and the paper industry such as pipes and vessels in which reactors and chemicals move because they do not corrode chemically well. Especially, . Also, since titanium is known to be excellent in biocompatibility, it is also used in artificial joints, dental implants, artificial heart pacemakers, and spectacle frames. In addition, titanium is widely used in sports equipment such as mobile phones, watch cases, jewelry, golf clubs, and automobile parts. Furthermore, as described above, titanium is used as a material for structural parts in a variety of fields such as aerospace, automobile, medical, chemical industry and the like by utilizing the high specific gravity (non-strength) have.

On the other hand, the greatest merit of titanium is that it is non-toxic and non-allergenic to humans, and has a very strong corrosion resistance by forming a strong passive film on its surface. However, since titanium has a high melting point and is highly reactive with oxygen, oxides are formed on the surface even in a high vacuum, so that it is not easy to produce a product having a specific shape by a casting method or the like.

(1) a machining process in which a titanium ingot is cut and machined into parts of desired dimensions and sizes, (2) the titanium is melted in a vacuum, and the titanium is poured into a mold (3) Titanium or titanium hydride (TiH ₂ ) powder is filled in a mold and then press-molded or mixed with a polymer resin to be melted, and then injected into a mold to perform injection molding A method such as powder metallurgy in which a powder compact is densified by heat treatment at a high temperature (hereinafter may be expressed as " sintering ") is used.

The machining method (1) is mainly used for manufacturing a large number of small number of titanium structures, and the vacuum centrifugal casting method (2) is used for manufacturing a medium shape and a medium number of titanium parts having complicated shapes. The final powder metallurgy method (3) is a mass production method that can be applied to mass production of small to medium-sized titanium parts. Therefore, powder metallurgy is very economical when a relatively small-sized component is to be produced in large quantities, and many attempts have been made to manufacture a titanium alloy component since it can produce a large amount in a short period of time.

Meanwhile, in the conventional titanium powder metallurgy technology, a sintered compact is sintered at a high temperature of 1100 to 1400 ° C to densify titanium or titanium hydride (TiH ₂ ) powders. However, in this case, pores are formed in the vacuum heat treatment process Therefore, there has been a problem that residual pores remain in the sintered body. Therefore, in order to completely remove the residual pores, a subsequent heat treatment called hot isostatic pressing (HIP) which compresses with high temperature and high pressure gas has been performed. However, the heat treatment at a high temperature for a long time causes grain growth, which not only lowers the strength of the material but also increases the incorporation of oxygen into the titanium, increases the manufacturing time, increases the manufacturing cost, and increases the cost / There is a problem that it is not economical in terms of cost. Further, when a sintered body is manufactured using a titanium-based powder, it is impossible to realize a high-density dense titanium alloy sintered body because of the low sintering driving force of the conventional powder particles and the oxide formed on the surface of the powder, thereby obstructing the densification of these oxide layers in the sintering heat treatment process.

In order to solve the problems of the above-described conventional techniques, TiH ₂ powder is finely pulverized into fine powder having a size of about 20 nm by ball milling, and then charged into a graphite mold and pressurized at a pressure of 80 MPa in a vacuum atmosphere of 0.04 torr There is an attempt to manufacture a titanium sintered body by high-frequency induction heating at a temperature of about 1080 占 폚 under an applied state (WO2011074741 A1). However, this method has a fatal weakness in spite of various advantages. That is, it is a method of sintering by pressure sintering, that is, sintering in a state where the powder is filled in the graphite mold and pressurized by the upper and lower punches. Such a pressure sintering method can be applied only to a disk or cylinder shaped product by imposing a large restriction on the size and shape of the product to be manufactured and the size thereof is also limited by the size of the device and only one There are many limitations on the mass production and economical efficiency such that the product can be sintered only.

The present invention provides a sintering composition and a method for producing a sintered body which can produce a sintered body having a very high relative density at a low sintering temperature and at a low cost.

The present application provides a composition for sintering. Exemplary compositions for sintering of the present application include active metal hydride powder particles having controlled particle size so as to have an excellent sintering driving force. According to the sintering composition of the present application, at a low sintering temperature of 1000 DEG C or less, It is possible to manufacture a sintered body having a very high relative density at a low cost.

In one embodiment, the composition for sintering of the present application comprises an active metal hydride powder. Hereinafter, the active metal may be represented by a first metal.

The active metal hydride powder is represented by the following formula (1).

[Chemical Formula 1]

MH _x

M represents at least one metal selected from the group consisting of titanium, zirconium, aluminum, hafnium, vanadium, uranium, palladium, yttrium, rubidium, plutonium, thallium, lithium, indium, gallium and beryllium, Hydrogen, and preferably M is titanium, but is not limited thereto. In Formula 1, x may be 1 to 4, preferably 2, but is not limited thereto. In one example, the active metal hydride powder may be a titanium hydride (TiH _x ) powder. In the titanium hydride, the ratio (x) of hydrogen (H) to titanium (Ti) can be variously selected, and titanium hydrogen compounds having various ratios (x) can be mixed and used.

The titanium hydride (TiH ₂ ) powder is cheaper than the titanium (Ti) powder and has excellent oxidation resistance. For example, active metal powders such as titanium have a very strong affinity with oxygen. Therefore, when the active metal powder is used as a raw material to produce a powder compact and then sintered, An oxidation reaction takes place on the surface of the active metal powder, thereby forming an oxide layer on the active metal surface. The oxide layer formed may interfere with the mass transfer between the active metal powder particles in the sintering process, and as a result, prevents formation of a dense sintered body. On the other hand, when a powder compact is produced by using the active metal hydride powder of the above formula (1) such as titanium hydride (TiH ₂ ) as raw material powder and sintered, the titanium hydride is decomposed into titanium and hydrogen during sintering TiH _{2 -} > Ti + H ₂ ). The hydrogen generated at this time reacts with a very small amount of oxygen existing between the particles in the powder compact to further lower the oxygen concentration, thereby preventing the formation of an oxide layer on the surface of the powder particles, thereby forming a dense sintered body can do.

In addition, as the particle size of the powder particles constituting the powder compact becomes finer, the sintering driving force increases, and in this case, a dense powder sintered body can be formed by sintering. Therefore, in order to produce a dense active metal sintered body, it is preferable to make the raw material metal powder finer. However, in various mechanical grinding processes such as ball milling, induction milling and high energy milling for finely atomizing the active metal powder such as titanium, the crushing energy can be absorbed by the plastic deformation of the active metal powder, Crushing of the active metal powder particles may not occur well. This is because the principle of pulverization in the mechanical pulverization process is mainly brittle fracture, since most of the metals have little brittleness and are rather ductile. In other words, the soft titanium powder may be difficult to miniaturize through a mechanical milling process. Therefore, the sintering composition of the present application includes a titanium hydride (TiH ₂ ) powder which is not ductile but rather brittle So that the size of the powder particles can be miniaturized through a mechanical grinding process. Applying this principle, various variations are possible. For example, in order to improve the mechanical and chemical properties of titanium, a titanium alloy powder such as Ti-6Al-4V prepared by adding various alloying elements to titanium is heated in a hydrogen atmosphere, for example, at 700 ° C for several hours When the alloy powder contains hydrogen by heat treatment, the alloy powder becomes a hydrogen embrittlement as an alloy hydride ((Ti-Al-V) H _x ), which is subjected to ball milling or high energy milling , It is possible to easily obtain a fine titanium alloy hydride powder because of the brittleness, and when the shaped body is manufactured and sintered by using the milled body, the dense active metal alloy sintered body can be easily manufactured at a low temperature.

The active metal hydride powder may have an average particle size of 15 탆 or less, for example, 10 탆 or less, 0.01 to 5 탆 or less, preferably 0.1 to 4 탆, but is not limited thereto.

As described above, the size of solid powder particles is an important factor for the production of dense sintered bodies. For example, the solid powder particles in the powder compact are firmly bonded to each other through the heat treatment process, and at the same time, the pores existing between the powder particles are densified. Thus, a solid material sintered body having almost no pores is formed . For example, in the sintering process, a bond between particles in the powder compact is formed, and a large amount of void space existing between the particles, that is, pores, escapes out of the formed body, accompanied by shrinkage of the entire volume , Resulting in a dense sintered body having almost no pores. At this time, the force for bonding the powder particles is called a sintering driving force, and the sintering driving force is proportional to the specific surface area of the particles, that is, the ratio of the surface area per unit mass. Therefore, in order to form a dense active metal sintered body by using an active metal hydride and / or an active metal powder, it is preferable to use a powder having a high sintering driving force, that is, a powder having a large specific surface area value. However, most of the commercially available active metal hydride raw material powders have an average particle diameter of about 40 탆 or more, and the specific surface area is very small. When a compact is produced from these powders, the sintering drive force is low, . Some manufacturers produce active metal hydride powder with a size of several micrometers. In this case, however, the sintering power is not sufficient due to the presence of a large number of coarse particles having a size of 30 μm or more. There was a problem. In order to solve such a problem, in the present application, the average particle diameter of the active metal hydride powder particles is controlled to fall within the above-mentioned range, whereby a more compact sintered body can be formed.

The active metal hydride powder particles having an average particle diameter of 15 mu m or less may be prepared by milling or pulverizing a commercially available active metal hydride powder having an average particle diameter of more than about 5 mu m, for example, more than 15 mu m or not less than 40 mu m In one example, the milling can be performed by ball milling, pronomite milling, vibration milling, high energy milling, jet milling or attrition milling. The active metal hydride fine powder having an average particle size of 15 mu m or less thus produced has a high sintering driving force and can exhibit a very high densification behavior as described above. On the other hand, if the size of the active metal hydride powder particles becomes excessively fine due to excessive pulverization or milling, the sintering driving force may be further improved. However, since impurity inclusion from the crushing ball and the crushing vessel may increase, It is preferable to make it fine. Further, when the size of the active metal hydride powder particles is excessively fine to 0.1 μm or less, the specific surface area of the powder becomes too large, and due to the excessive cohesion between the powder particles, Uniform dispersion becomes difficult during wet mixing. In the present specification, "granule" means aggregate particles of powder particles formed by mutual agglomeration of individual powder particles (hereinafter referred to as "primary particles") with very weak binding force (hereinafter referred to as "secondary particles") do. In the process of producing a sintered body using fine metal powder of several micrometers in size, a metal powder made of fine primary particles is used to make granules without producing a molded body, and this is pressed or cold pressed Cold Isostatic Pressing, CIP). This is because the fine primary powder particles tend to clump together and are liable to be scattered during the molding process, and in particular, excessive friction with the inner wall of the mold may occur during press molding, and further, It causes various molding defects such as molding layer separation (lamination). Therefore, in a general powder metallurgy process, a metal powder made of primary particles having a size of several tens of micrometers or more is used instead of the fine primary powder. For this reason, ultrafine powders of 0.1 탆 or less are rarely used in the conventional sintered body production process, and the fine powders are difficult to produce and expensive, and are generally not suitable for mass production.

On the other hand, the granules are prepared by injecting a mixed powder having a desired composition into a liquid vehicle, adding a dispersant and a plasticizer, which are organic materials for producing a good molded article, and a plasticizer for uniform dispersion and mixing, To prepare a suspension, and drying the vehicle in the suspension by using a spray dryer or a hot plate stirrer. Further, in the press-molding, the granular powder thus produced is charged into a press mold, and after pressurization, the mold is generally manufactured by demolding. However, in this case, if the powder particle size becomes too small, the molding density becomes low even if molded at the same pressure, and the molded article has an uneven molding density due to excessive aggregation of the powder, and friction between the powder particle and the mold inner wall Can occur. In this case, it may cause a big problem in mass production of the actual product. For example, if the density of the shaped body is lowered, even if complete densification is performed during the sintering process, the sintering shrinkage ratio may become too large and the final dimensional accuracy of the produced product may deteriorate. In addition, the nonuniform molding density of the molded article and the friction between the powder particle and the inner wall of the mold may cause deformation and cracking of the sintered body, which may lead to failure of the final product, Do.

As described above, it is difficult to produce a dense sintered body of good quality, which is economical because of the above-described problems even when the compact is made in an unpressurized state, that is, at normal pressure sintering.

The above-mentioned active metal is a metal which can be easily oxidized, and an oxide layer formed on the surface of the active metal hydride powder can inhibit densification of the active metal powder, that is, sintering. Therefore, in order to suppress the formation of the oxide layer, the sintering composition of the present application may contain sintering aids having higher oxidation resistance than the active metal. Hereinafter, the sintering auxiliary agent may be represented by a second metal.

The sintering aid may have a higher oxidation resistance than the active metal. In one example, the sintering auxiliary may satisfy the following general formula (1).

[Formula 1]

Ps - Pa > 0

In the general formula 1,

Ps is the equilibrium oxygen partial pressure of the sintering aid,

Pa is the equilibrium oxygen partial pressure of the active metal of formula (1).

The term "equilibrium oxygen partial pressure" as used herein means an oxygen partial pressure which is obtained when the oxidation reaction of the material reaches equilibrium. For example, the equilibrium oxygen partial pressure can be calculated using the Ellingham diagram . That is, by satisfying the above general formula (1), the sintering auxiliary agent has a higher equilibrium oxygen partial pressure than the active metal, so that the sintering auxiliary agent can prevent the oxidation of the active metal, thereby forming a more dense active metal sintered body have.

In one example, the sintering auxiliary may satisfy the following general formula (2).

[Formula 2]

S ₁ - S ₂ > 0

In the general formula 2,

S ₁ is the solubility of the active metal M in the sintering aid,

S ₂ is the solubility of the sintering aid in the active metal M.

In the above, "solubility" means solubility limit.

The sintering auxiliary which satisfies the above-mentioned general formula 2, that is, the sintering auxiliary agent may include a metal having a low solubility in the active metal but a high solubility of the active metal in the sintering auxiliary agent. The sintering aid having such properties does not dissolve into the active metal powder but is present in the neck region between the powder particles while forming an alloy layer with the active metal which is dissolved in the sintering auxiliary agent itself, It is possible to induce densification of the active metal sintered body by inhibiting the formation of the oxide layer of the active metal in the boundary region between the active metal powder particles due to its high oxidation resistance. For example, palladium (Pd) is a metal having a high oxidation resistance enough to retain the properties of a metal even if the powder is sintered in the air. Even when only a small amount of palladium is added as a sintering aid, an active metal such as titanium The densification of the titanium (Ti) is greatly promoted, and the principle of the densification mechanism according to the addition of the sintering aid can be understood. In addition, the phase diagram of titanium-palladium (Ti-Pd) shows that the solubility of palladium in titanium is as small as about 1%, while the solubility of titanium in palladium is as large as about 20% . When the solubility of the sintering auxiliary agent to the active metal is small and the solubility of the active metal in the sintering auxiliary agent is large, the sintering aid alloy which is formed in the neck region between the active metal powder particles during sintering or heat treatment, The active material sintered body can be more densely moved due to the excellent oxidation resistance of the sintering assisted alloy layer.

For example, the sintering auxiliary may be a transition metal of Group 3 to 12, a metal of Group 13 to Group 15, and a metal of group lanthanum or actinide Rare earth metals, and rare earth metals.

In one example, the transition metals of Groups 3 to 12 are selected from the group consisting of cobalt, nickel, molybdenum, niobium, tantalum, tungsten, zirconium, hafnium, zinc, copper, scandium, yttrium, vanadium, chromium, manganese, , Palladium, iridium, rhodium, gold, silver, and osmium. Preferably, nickel, molybdenum, tungsten, or palladium may be used. More preferably, palladium may be used. But is not limited thereto.

In one example, the metal of Group 13 to Group 15 may include at least one element selected from the group consisting of aluminum, silicon, boron, indium, tin, antimony, gallium and germanium, Boron may be used, but is not limited thereto.

In another example, the rare earth metal may include, but is not limited to, at least one selected from the group consisting of lanthanum, cerium, neodymium, samarium, gadolinium, praseodymium, europium and thorium.

The sintering aid may be contained in an amount of 5 parts by weight or less based on 100 parts by weight of the active metal hydride powder, preferably 2 parts by weight or less, more preferably 0.1 to 1 part by weight.

In yet another embodiment, the composition for sintering of the present application may further comprise additive metals or alloying metal elements. The additive metal may be added to improve the physical properties of the sintered body such as corrosion resistance or strength. For example, when the additive metal is included, the sintered body produced by the sintering composition of the present application may not be a pure active metal sintered body but may be an alloy sintered body having improved mechanical and chemical performance, and in one example, 6% In order to manufacture a Ti-6Al-4V alloy sintered body containing aluminum (Al) and 4% vanadium (V), various elemental metals capable of forming an alloy with titanium in addition to titanium hydride (TiH ₂ ) Their compound powders can be added.

The additive metal may be a different metal than the sintering aid described above, and the additive metal may include one or more metals of the transition metals of Groups 3 to 12. For example, when the sintering aid is palladium, the additive metal may be a transition metal of group 3 to 12 except for palladium. In one example, the transition metals of Groups 3 to 12 are selected from the group consisting of cobalt, nickel, molybdenum, niobium, tantalum, tungsten, zirconium, hafnium, zinc, copper, tin, scandium, yttrium, aluminum, vanadium, And may include at least one selected from the group consisting of aluminum, vanadium, manganese, iron, platinum, palladium, iridium, rhodium, gold, silver and osmium, and preferably aluminum, vanadium, hafnium, niobium, iron, , Tantalum, silicon, cobalt, chromium, ruthenium, tin, zirconium and molybdenum, and more preferably at least one selected from the group consisting of aluminum, vanadium and zirconium But is not limited thereto.

The additive metal may be contained in an amount of 0.1 to 30 parts by weight, preferably 0.2 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, based on 100 parts by weight of the active metal hydride powder. But is not limited to.

The present application also relates to a method for producing a sintered body using the above-described composition for sintering. According to the exemplary method for producing a sintered body of the present application, atmospheric pressure sintering of a composition containing active metal hydride powder particles having controlled particle size to have excellent sintering driving force and a specific metal as a sintering auxiliary agent enables low sintering temperature and low cost A sintered body having a very high relative density can be produced.

The method for producing the sintered body of the present application is performed using the above-described sintering composition, and therefore, the description of the sintering composition will be omitted.

The manufacturing method of the sintered body of the present application includes the steps of preparing the above-described sintering composition, molding the compact for sintering, and heat-treating the compact.

The step of preparing the composition for sintering may include milling an active metal hydride powder having an average particle size of more than 5 mu m, for example, more than 15 mu m and having the average particle size of 15 mu m or less, Powder. ≪ / RTI > In one example, the milling can be carried out by ball milling, plane milling, vibration milling, high energy milling, jet milling or attrition milling, preferably by ball milling or high energy milling But is not limited thereto.

The step of molding the sintering composition to form a molded article is a step for molding the sintering composition into a desired size and shape. The molding may be performed by, for example, pressing, cold isostatic pressing (CIP) Such as injection molding, extrusion, gel-casting and tape-casting, and can be carried out through various molding methods known in the art, But may be performed by press molding or injection molding, but the present invention is not limited thereto.

In the heat-treating step, the powder compact is heat-treated to remove hydrogen from the organic substances and active metal hydrides in the compact, and at the same time, through the chemical reaction, the material exchange and the sintering reaction between the active metal powders in the compact, It is possible to form an active metal sintered body having a dense density of at least%.

In one example, the heat treating step comprises heating the shaped body at a temperature of 1000 DEG C or less, for example, 500 DEG C to 900 DEG C or 600 DEG C to 800 DEG C for 5 minutes to 10 hours, 30 minutes to 4 hours, For a period of time.

The heat treatment step may be performed in a vacuum, hydrogen, or an inert gas atmosphere. In addition, the heat-treating step may be performed at a normal pressure or a pressure-less state. In this case, the desired sintered body having various shapes and dimensions can be heat-treated in a large amount.

In the heat-treating step, the powder compact may be heat-treated in a container made of one or more metal materials selected from the group consisting of titanium, tungsten, molybdenum, carbon steel and stainless steel. In this case, oxidation of the active metal in the formed body during sintering heat treatment can be prevented, and a dense sintered body can be formed. In one example, a chip, scrap, granule or foil, optionally made of one or more materials selected from the group consisting of titanium, calcium, magnesium and aluminum, is charged into the vessel for further reduction of the oxygen partial pressure in the vessel, .

The step of performing the heat treatment is not particularly limited and may be carried out by, for example, heating a resistance heating element using a vacuum electric furnace, electromagnetic induction heating, electron beam heating, laser heating, infrared heating, plasma heating, microwave heating, or rapid heating .

The method of manufacturing the sintered body according to the present application can be performed based on a powder metallurgy method, and various methods known in the field of powder metallurgy can be applied to the manufacturing method of the present application. The powder metallurgy process is a method of manufacturing a dense metal part by molding a metal powder into a desired size and shape and sintering it at a high temperature. According to the powder metallurgy method, a metal part having a complicated shape is not heated to a melting temperature It can be produced quickly and economically at low temperatures.

The present application also provides a sintered metal body formed from the above-described composition for sintering.

The metal sintered body of the present application can be produced by the above-described sintering composition and the method for producing a sintered body, and therefore, the contents overlapping with those described above will be omitted.

The sintered body of the present application includes a first metal and a second metal.

The first metal is an active metal which is sintered as hydrogen is removed during the heat treatment of the above-mentioned active metal hydride. As described above, the first metal is titanium, zirconium, hafnium, vanadium, uranium, palladium, yttrium, rubidium, Thallium, lithium, indium, gallium, and beryllium, preferably titanium, but is not limited thereto.

The second metal is, as one of the sintering auxiliary components described above, in one example, the second metal is a transition metal of Groups 3 to 12; Metals of Groups 13 to 15; And a rare earth metal of the lanthanum or the actinium group.

The second metal may be included in an amount of 5 parts by weight or less based on 100 parts by weight of the first metal.

The sintered body may further include a third metal. The third metal is the above-described additive metal component, the third metal is a different component from the second metal, and may include at least one metal among the transition metals of Groups 3 to 12.

In one example, the transition metals of Groups 3 to 12 are selected from the group consisting of cobalt, nickel, molybdenum, niobium, tantalum, tungsten, zirconium, hafnium, zinc, copper, tin, scandium, yttrium, aluminum, vanadium, And may include at least one selected from the group consisting of aluminum, vanadium, manganese, iron, platinum, palladium, iridium, rhodium, gold, silver and osmium, and preferably aluminum, vanadium, hafnium, niobium, iron, , Tantalum, silicon, cobalt, chromium, ruthenium, tin, zirconium and molybdenum, and more preferably at least one selected from the group consisting of aluminum, vanadium and zirconium But is not limited thereto.

The third metal may be contained in an amount of 0.1 to 30 parts by weight, preferably 0.1 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, based on 100 parts by weight of the first metal. It is not.

In one example, the sintered body may have a relative density of at least 90%, for example, at least 92%, at least 95%, at least 97%, at least 98%, or at least 99% For example, 5% or less, 4% or less, 3% or less, or 2% or less. The relative density is a relative density of the sintered body excluding the porous layer portion of the surface in contact with air on a scanning electron microscope or an optical microscope photograph with respect to the sintered body cross section, Can be measured through a method of measuring the fraction.

The present application relates to the production of titanium products such as medical implants and apparatuses, petroleum / chemical industry equipment, automobile parts, aerospace equipment, leisure goods and accessories by providing a method of economically manufacturing dense sintered bodies of active metals such as titanium at low temperatures Can be widely used in the field. In addition, the titanium is manufactured in the form of a sponge and a powder in a smelting process. Since the present application provides an economical powder metallurgy process capable of hydrogenating the sponge or powder, the present application provides a process for producing The final product can be manufactured by shaping.

The sintering composition of the present application contains active metal hydride powder particles having controlled particle size so as to have an excellent sintering driving force and a specific metal as a sintering auxiliary agent. According to the sintering composition of the present application, A sintered body having a high relative density can be produced.

1 is a flowchart of a method of manufacturing a metal sintered body according to an embodiment of the present application.
2 is an SEM photograph of the commercial TiH ₂ powder used in Example 1. Fig.
FIG. 3 is an SEM photograph of the powder obtained by ball milling the commercial TiH ₂ powder for 72 hours using ethyl alcohol and a zirconia ball.
FIG. 4 is a scanning electron micrograph of powder after high-energy milling for 1 hour after ball milling commercial TiH ₂ powder for 6 hours.
FIG. 5 shows the result of analyzing the particle size of the TiH ₂ powder prepared in Example 1 by using a PSA (Particle Size Analyzer). FIG.
6 is a photograph of the outer appearance of the sintered body manufactured in each of Examples 1 to 12 and Comparative Examples 1 to 4.
7 shows the sintering shrinkage ratios of the sintered bodies produced in Examples 1 to 12 and Comparative Examples 1 to 4, respectively.
Figs. 8 and 9 are photographs of the cross-sectional microstructure of the sintered body manufactured in Example 9 and Comparative Example 1, respectively, taken at 500 times using an optical microscope.
10 and 11 are cross-sectional photographs of the sintered body produced in Example 10 and Example 11, respectively.
FIGS. 12 to 14 are photographs of the cross-sectional microstructure of the sintered bodies manufactured in Examples 13 to 15, respectively, at 500-fold magnification using an optical microscope.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present application is not limited by the following description.

Metal hydride  Comparison of finer effect of powder particles

Preparation of fine titanium hydride powder

Manufacturing example  One

Specifically, commercially available titanium hydride (TiH ₂ ) powder (99.95%, Nanoshel) having an average particle diameter of about 60 탆 was prepared. At this time, wet TiH ₂ powder (Nanoshel) having an average particle diameter of about 60 μm was subjected to wet ball milling or high energy milling (HEM) using ethyl alcohol as an organic solvent in order to make the TiH ₂ powder smaller than 3 μm. A fine titanium hydride powder (BM 72h) having an average particle diameter of about 3.9 탆 was produced by wet ball milling for about 72 hours.

Manufacturing example  2

A commercially available titanium hydride (TiH ₂ ) powder (99.6%, MTIG) having an average particle size of about 35 μm was prepared in place of the commercial TiH ₂ powder (Nanoshel) having an average particle diameter of about 60 μm, and after ball milling for 6 hours, A fine titanium hydride powder (HEM 1h) having an average particle diameter of about 1.0 탆 was prepared through HEM.

Manufacturing example  3

A commercially available titanium hydride (TiH ₂ ) powder (99.6%, MTIG) having an average particle diameter of about 35 μm prepared in Production Example 2 was milled for 6 hours by ball milling for 3 hours through a HEM to obtain a fine titanium powder having an average particle diameter of about 0.8 μm A hydride powder (HEM 3h) was prepared.

2 is a scanning electron micrograph of commercial TiH ₂ powder (Raw TiH ₂ ) having an average particle diameter of about 60 μm prepared in Example 1, and FIG. 3 is a scanning electron micrograph of raw TiH ₂ powder prepared by using ethyl alcohol and zirconia balls for 72 hours FIG. 4 is a scanning electron micrograph of a fine TiH ₂ powder (BM 72h) after wet ball milling, FIG. 4 is a photograph of a TiH ₂ powder after high-energy milling (HEM) for 1 hour after ball milling a commercial TiH ₂ powder for 6 hours ₂ powder (HEM 1h).

FIG. 5 shows the result of analyzing the particle size of the TiH ₂ powder thus prepared by a PSA (Particle Size Analyzer). As can be seen from the above results, it can be confirmed that the commercially available TiH ₂ powder has a very large average particle size of about 60 탆 and coarser particles are present in the powder. When the commercial TiH ₂ powder containing the coarse particles (denoted by Raw TiH ₂ ) was ball milled for 72 hours (denoted as BM 72h), the average size of the particles was reduced to 3.9 μm and the particle size distribution was narrow Can be confirmed. In addition, when the commercial TiH ₂ powder was ball milled for 6 hours and then subjected to high energy milling for 1 hour (denoted by HEM 1h), the mean particle size was about 1.0 μm and the average particle size was 3 hours (denoted by HEM 3h) And the particle size distribution was narrowed to a single peak.

Preparation of titanium sintered body

Example  One

For the preparation of the composition for sintering, fine TiH ₂ powder (BM 72h) having an average particle diameter of 3.9 μm prepared in Preparation Example 1 was added to ethyl alcohol in a volume ratio of about 30 vol% Wet ball milling was carried out for about 3 hours by adding about 0.5 to 1 wt% of a dispersant and 1-3 wt% of binder (PVB) and a plasticizer (DOP) to prepare a slurry.

After the ball milled slurry was dried on a hot plate, the dried powder was sieved to prepare a granulated powder for press forming. The prepared granular powder was filled in a metal mold and then uniaxially press-molded at a pressure of 100 MPa to prepare a powder compact. The prepared powder compact was placed in a tungsten container with a lid and charged into a tungsten vacuum furnace. The temperature was raised to a target temperature of 800 ° C at a rate of 5 ° C per minute at a vacuum of about 2.5 x 10 ^-5 torr, (BM 72h_800 ℃ _In) having a relative density of 92.5% was prepared by sintering the powder particles and inducing a chemical reaction.

Example  2

The slurry was prepared under the same conditions as in Example 1 except that the sintering temperature was set to 600 ° C and the granulated powder prepared from the slurry was molded to prepare a powder compact and then heat treated to obtain a slurry having a relative density of 87.6% Sintered body (BM 72h_600 ° CIn) was prepared.

Example  3

A slurry was prepared under the same conditions as in Example 1 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 92.1% (BM 72h - 800 ° C _Out).

Example  4

A slurry was prepared under the same conditions as in Example 2 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 85.0% (BM 72h_600 ° C _Out).

Example  5

For the preparation of the composition for sintering, fine TiH ₂ powder (HEM 1h) having an average particle diameter of 1.0 탆 prepared in Preparation Example 2 was added to ethyl alcohol in a volume ratio of about 30 vol% Wet ball milling was carried out for about 3 hours by adding about 0.5 to 1 wt% of a dispersant and 1-3 wt% of binder (PVB) and a plasticizer (DOP) to prepare a slurry.

After the ball milled slurry was dried on a hot plate, the dried powder was sieved to prepare a granulated powder for press forming. The prepared granular powder was filled in a metal mold and then uniaxially press-molded at a pressure of 100 MPa to prepare a powder compact. The prepared powder compact was placed in a tungsten container with a lid and charged into a tungsten vacuum furnace. The temperature was raised to a target temperature of 800 ° C at a rate of 5 ° C per minute at a vacuum of about 2.5 x 10 ^-5 torr, (HEM 1h_800 ℃ _In) having a relative density of 97.6% was prepared by sintering the powder particles and inducing a chemical reaction.

Example  6

A slurry was prepared under the same conditions as in Example 5, except that the sintering temperature was changed to 600 ° C. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to have a relative density of 93.7% The sintered body (HEM 1h_600 ° CIn) was prepared.

Example  7

A slurry was prepared under the same conditions as in Example 5 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 95.7% (HEM 1h_800 DEG C_Out).

Example  8

A slurry was prepared under the same conditions as in Example 6 except that the tungsten container was not used, and the granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 92.5% (HEM 1h_600 ° C _Out).

Example  9

For the preparation of the composition for sintering, fine TiH ₂ powder (HEM 3h) having an average particle diameter of 0.8 탆 prepared in Preparation Example 3 was added to ethyl alcohol in a volume ratio of about 30 vol% Wet ball milling was carried out for about 3 hours by adding about 0.5 to 1 wt% of a dispersant and 1-3 wt% of binder (PVB) and a plasticizer (DOP) to prepare a slurry.

After the ball milled slurry was dried on a hot plate, the dried powder was sieved to prepare a granulated powder for press forming. The prepared granular powder was filled in a metal mold and then uniaxially press-molded at a pressure of 100 MPa to prepare a powder compact. The prepared powder compact was placed in a tungsten container with a lid and charged into a tungsten vacuum furnace. The temperature was raised to a target temperature of 800 ° C at a rate of 5 ° C per minute at a vacuum of about 2.5 x 10 ^-5 torr, (HEM 3h_800 ℃ _In) with a relative density of 99.8% was prepared by sintering the powder particles and inducing a chemical reaction.

Example  10

A slurry was prepared under the same conditions as in Example 9, except that the sintering temperature was changed to 600 ° C, and the granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to have a relative density of 97.7% Sintered body (HEM 3h_600 ° CIn) was prepared.

Example  11

A slurry was prepared under the same conditions as in Example 9 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 98.3% (HEM 3h_800 DEG C_Out).

Example  12

A slurry was prepared under the same conditions as in Example 10 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to prepare a powder compact, which was heat-treated to obtain a sintered body having a relative density of 94.0% (HEM 3h_600 ° C _Out).

Comparative Example  One

A commercially available titanium oxide hydride (TiH ₂ ) powder (Raw TiH ₂ ) having an average particle diameter of about 60 탆 was obtained in the same manner as in Example 1, except that the step of finishing the commercially available titanium hydride (TiH ₂ ) TiH ₂ powder was prepared, and the slurry was molded to prepare a powder compact, which was then heat-treated to prepare a sintered body (Raw TiH _{2 -} 800 캜 In) having a relative density of 88.8%.

Comparative Example  2

A slurry was prepared under the same conditions as those of Comparative Example 1 except that the sintering temperature was set to 600 ° C, and the granulated powder prepared from the slurry was molded to prepare a powder compact, which was heat-treated to have a relative density of 86.9% Sintered body (Raw TiH _{2 -} 600 캜 In) was prepared.

Comparative Example  3

A slurry was prepared under the same conditions as in Comparative Example 1 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 86.5% (Raw TiH ₂ _ 800 캜 _ Out).

Comparative Example  4

A slurry was prepared under the same conditions as in Comparative Example 2 except that the tungsten container was not used. The granulated powder prepared from the slurry was molded to produce a powder compact, which was heat-treated to obtain a sintered body having a relative density of 82.7% (Raw TiH _{2 -} 600 ° C _Out).

Experiment result

In order to analyze the characteristics of the sintered bodies produced in Examples 1 to 12 and Comparative Examples 1 to 4, it was confirmed that the sintered bodies of the planar and cross-sectional microstructures of the sintered bodies were observed through an optical microscope, a scanning electron microscope, an x- Phase analysis, and composition analysis.

(Raw TiH ₂ ) having an average particle diameter of about 60 μm and three types of titanium hydride powders (BM 72h, HEM 1h, and HEM 3h) finely divided in Production Examples 1 to 3, respectively, Were sintered in a vacuum atmosphere of 600 ° C and 800 ° C for 4 hours, respectively. The outer shapes of the specimens were photographed, and the relative density, sintering shrinkage and relative density of each sample were measured. In this case, at the time of sintering at each temperature, the powder compact was sintered in a tungsten container (marked In) and sintered without a tungsten container (marked Out).

Fig. 6 is a graph showing the results of a TiH ₂ powder compact consisting of four powders (Raw, BM 72h, HEM 1h and HEM 3h) prepared in Examples 1 to 12 and Comparative Examples 1 to 4, respectively at 600 ° C and 800 ° C for 4 hours And the specimens sintered in a tungsten container. As can be seen from FIG. 6, when a container made of tungsten is used, surface oxidation of the sintered body is inhibited and the surface has a bright metallic color tone. On the other hand, in case of sintering without a tungsten container, The surface was oxidized by oxygen, and the black color was observed. However, in this case as well, it was confirmed that a metal-specific luster appeared when the surface layer was removed. Also, as shown in FIG. 6, it was confirmed that as the powder particles became finer, the sintering shrinkage ratio increased and the outer diameter of the specimen decreased. In addition, as can be seen from Fig. 6, even in the case of the sintered body made from HEM 3h powder having an average particle diameter of 0.8 탆 (Example 9), even the sintered body sintered at 600 캜 (Example 10) had almost the same outer diameter.

7 shows the sintering shrinkage ratios of the sintered bodies produced in Examples 1 to 12 and Comparative Examples 1 to 4. As can be seen from FIG. 7, it was confirmed that the sintered body (HEM 3h) sintered at 800 ° C had almost the same sintering shrinkage value of about 21% regardless of the use of the tungsten container. The sintering shrinkage (HEM 3h) sintered at 600 ° C was about 20%. From these results, it can be seen that the HEM 3h powder is almost completely densified even at 600 ° C. and has a very high density.

The relative density of the sintered bodies of Example 9 and Comparative Example 1 was measured by the Archimedes method. As a result, the relative density of the specimen of Example 9 was 99.8% and the specimen of Comparative Example 1 was 88.8%. That is, Example 9 and Comparative Example 1. As can be seen in cross-section pictures of 8 to 9, taken in the sintered body, TiH ₂ powder finer than commercial TiH ₂ powder (9), sintering at 800 ℃ (FIG. 8), the densification of the sintered body was greatly improved, and the relative density was increased.

10 is a cross-sectional photograph of the sintered body of Example 10 manufactured using HEM 3h powder having an average particle diameter of 0.8 탆. As can be seen from FIG. 10, when the HEM 3h powder is used, almost complete densification occurs even at 600 ° C. The relative density of the sintered body manufactured in Example 10 was measured by the Archimedes method, And the relative density.

11 is a cross-sectional photograph of the sintered body manufactured in Example 11. Fig. As can be seen from FIG. 11, when the HEM 3h powder is used, sufficient densification is achieved without sintering in a closed state in a container made of tungsten. The relative density of the sintered body produced in Example 11 was measured by the Archimedes method, and it was confirmed that the sintered body had a high relative density of 98.3%.

Comparison of effect of addition of sintering additive or additive metal

In order to further lower the sintering temperature or to obtain an almost completely dense titanium sintered body having a relative density of 98% or more, besides the miniaturization of the powder particle size, the sintered body was densified The effect of addition of sintering aids which can accelerate sintering was investigated.

Example  13

A slurry was prepared under the same conditions as in Example 5 except that 0.5 wt% of palladium (Pd) was added to the TiH ₂ powder, and the granulated powder prepared from the slurry was molded to prepare a powder compact , And a sintered body having a relative density of 97.0% was prepared by heat treatment.

Example  14

A slurry was prepared under the same conditions as in Example 5 except that 0.5 wt% of tungsten (W) was added to the TiH ₂ powder by weight, and the granulated powder prepared from the slurry was molded to prepare a powder compact , And a sintered body having a relative density of 97.5% was prepared by heat treatment.

Example  15

A slurry was prepared under the same conditions as in Example 5 except that 0.5 wt% of boron (B) was added to the TiH ₂ powder by weight, and the granulated powder prepared from the slurry was molded to prepare a powder compact , And a sintered body having a relative density of 96.5% was prepared by heat treatment.

Experiment result

In order to analyze the characteristics of the sintered bodies prepared in Examples 13 to 15, the plane and cross-sectional microstructure and phase analysis of the sintered body were carried out through an optical microscope, a scanning electron microscope, an x-ray energy spectroscopy analysis and an X- , Compositional analysis and the like were carried out. The results are shown in Figs. 12 to 14. Fig.

12 is a photograph of the microstructure of the sintered body according to Example 13 prepared by adding 0.5 wt% of palladium. As can be seen from FIG. 12, a dense titanium sintered body having a porosity of about 3% or less can be manufactured at a sintering temperature of 800 ° C.

Also in the case of Example 14 (Fig. 13) in which tungsten was added in an amount of 0.5 wt% (Fig. 13) and in Example 15 (Fig. 14) in which boron was added in an amount of 0.5 wt%, a dense titanium sintered body having a porosity of about 3% Sintering temperature.

Claims (28)

1. A sintering composition comprising an active metal hydride powder having an average particle diameter of 15 mu m or less and represented by the following formula (1)
[Chemical Formula 1]
MH _x
In Formula 1,
M represents at least one metal selected from the group consisting of titanium, zirconium, aluminum, hafnium, vanadium, uranium, palladium, yttrium, rubidium, prtanium, thallium, lithium, indium, gallium,
H is hydrogen,
x is 1 to 4; The composition for sintering according to claim 1, wherein M is titanium and x is 2. The sintering composition according to claim 1, wherein the active metal hydride powder has an average particle diameter of 0.01 to 5 탆. The sintering composition of claim 1, further comprising a sintering aid. 5. The sintering aid composition according to claim 4, wherein the sintering auxiliary agent satisfies the following general formula (1)
[Formula 1]
Ps - Pa > 0
In the general formula 1,
Ps is the equilibrium oxygen partial pressure of the sintering aid,
Pa is the equilibrium oxygen partial pressure of the active metal M of formula (1). The sintering aid composition according to claim 1, wherein the sintering auxiliary agent satisfies the following general formula (2)
[Formula 2]
S ₁ - S ₂ > 0
In the general formula 2,
S ₁ is the solubility of the active metal M in the sintering aid,
S ₂ is the solubility of the sintering aid in the active metal M. The method according to claim 1, wherein the sintering aid is selected from the group consisting of transition metals of Groups 3 to 12; Metals of Groups 13 to 15; And a rare earth metal of lanthanum or an actinide group. The composition for sintering according to claim 1, wherein the sintering aid is contained in an amount of 5 parts by weight or less based on 100 parts by weight of the active metal hydride powder. The composition for sintering according to claim 4, further comprising an additive metal. The composition for sintering according to claim 9, wherein the additive metal is a metal different from the sintering aid and contains at least one metal selected from the transition metals of Groups 3 to 12. The method according to claim 9, wherein the additive metal comprises at least one selected from the group consisting of aluminum, vanadium, hafnium, niobium, iron, nickel, tungsten, tantalum, silicon, cobalt, chromium, ruthenium, tin, zirconium and molybdenum / RTI > The composition for sintering according to claim 9, wherein the additive metal is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the active metal hydride powder. At least one first metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, uranium, palladium, yttrium, rubidium, plutonium, thallium, lithium, indium, gallium and beryllium; And
Transition metals of Groups 3 to 12; Metals of Groups 13 to 15; And at least one second metal selected from the group consisting of lanthanides or actinides rare earth metals,
A metal sintered body having a relative density of 90% or more. 14. The metal sintered compact according to claim 13, wherein the porosity is 5% or less. 14. The metal sintered body according to claim 13, wherein the first metal is titanium. 14. The metal sintered compact according to claim 13, wherein the second metal is contained in an amount of 5 parts by weight or less based on 100 parts by weight of the first metal. 14. The metal sintered body according to claim 13, further comprising a third metal different from the second metal, wherein the third metal comprises at least one metal selected from the transition metals of Groups 3 to 12. The method according to claim 17, wherein the third metal comprises at least one selected from the group consisting of aluminum, vanadium, hafnium, niobium, iron, nickel, tungsten, tantalum, silicon, cobalt, chromium, ruthenium, tin, zirconium and molybdenum Metal sintered body. The metal sintered compact according to claim 17, wherein the third metal is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the first metal. 13. A method for sintering comprising: preparing a composition for sintering according to any one of claims 1 to 12;
Molding the composition for sintering to produce a molded body; And
And heat treating the formed body. 21. The method of manufacturing a metal sintered body according to claim 20, wherein the heat treatment is performed at a temperature of 1000 DEG C or less for 5 minutes to 10 hours. 21. The method of manufacturing a metal sintered body according to claim 20, wherein the heat treatment is performed in a vacuum, hydrogen, or inert gas atmosphere. The method of manufacturing a metal sintered body according to claim 20, wherein the heat treatment is performed in an unpressurized state. 21. The method of manufacturing a metal sintered body according to claim 20, wherein the heat treatment is performed in a vessel made of at least one metal material selected from the group consisting of titanium, tungsten, molybdenum, carbon steel and stainless steel. The method of manufacturing a metal sintered body according to claim 24, wherein a chip, scrap, granule or foil made of at least one material selected from the group consisting of titanium, calcium, magnesium and aluminum is charged in the container. 21. The method of manufacturing a metal sintered body according to claim 20, wherein the heat treatment is performed by a resistance heating body using a vacuum electric furnace, electromagnetic induction heating, electron beam heating, laser heating, infrared heating, plasma heating, microwave heating, or rapid heating . 21. The method of producing a metal sintered body according to claim 20, wherein preparing the composition for sintering comprises milling an active metal hydride powder having an average particle diameter of more than 5 mu m and represented by the following formula (1)
[Chemical Formula 1]
MH _x
In Formula 1,
M represents at least one metal selected from the group consisting of titanium, zirconium, aluminum, hafnium, vanadium, uranium, palladium, yttrium, rubidium, prtonium, thallium, lithium, indium, gallium,
H is hydrogen,
x is 1 to 4; 28. The method of manufacturing a metal sintered body according to claim 27, wherein the milling is performed by ball milling, precisely milling, vibration milling, high energy milling, jet milling or attrition milling.

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