KR20180076355A - Manufacturing method for mold for casting titanium alloy and mold for casting titanium alloy thereof - Google Patents

Abstract

The present invention relates to a mold manufacturing method for casting a titanium alloy and a mold for casting a titanium alloy manufactured by the same, which can reduce manufacturing costs and increase productivity. The mold manufacturing method for casting a titanium alloy according to an embodiment of the present invention comprises the steps of: dipping a wax molded article defining a cavity shape in a first slurry, applying first sand for casting, and drying the wax molded article to form a first chemically resistant coating layer; repeating a process of dipping the wax molded article, on which the first chemically resistant coating layer is formed, in a second slurry, applying second sand for casting, and drying the wax molded article several times so as to form a plurality of second chemically resistant coating layers; manufacturing a backup mold by dipping the surface of the second chemically resistant coating layer in the second slurry and drying the wax molded article to form a backup coating layer; and heating the backup mold to dewax and burning the backup mold.

Description

TECHNICAL FIELD [0001] The present invention relates to a casting mold for casting a titanium alloy, and a casting mold for casting a titanium alloy,

The present invention relates to a process for producing a mold for casting a titanium alloy and a mold for casting the same. More particularly, the present invention relates to a method for producing a mold for casting a titanium alloy used in centrifugal pressure precision casting of a titanium-based alloy, and a mold for casting a titanium alloy produced thereby.

Recently, regulations such as fuel consumption and exhaust gas emission of vehicles have been strengthened. Therefore, not only the weight of the vehicle body but also the weight of the engine parts in the vehicle are required to be reduced.

The powertrain of the vehicle collectively refers to all the engines between the engine and the driving wheels of the vehicle and occupies about 25% of the weight of the vehicle body. The light weight of the vehicle powertrain is 10 times or more higher than the weight of the vehicle Effect can be obtained.

In order to reduce the weight of the engine, it is not necessary to reduce the size of the engine. It is essential to improve the fuel efficiency by reducing the size of the engine and increasing the output. Aluminum (Al) and magnesium (Mg) materials, which are mainly used as lightweight materials, are difficult to achieve by weight reduction by simply changing the engine design while using the existing materials as they are. Due to problems such as heat resistance, oxidation resistance, There was a problem that was not suitable as material. For this purpose, titanium (Ti) alloy material has been proven to be more effective in achieving light weight of the engine. However, in the production of engine materials using such a titanium alloy, since the manufacturing cost is too high in the current manufacturing method, it is necessary to reduce the manufacturing cost in order to be applied to a general type of vehicle.

Titanium (Ti), on the other hand, is used extensively in aerospace, automotive, energy, chemical, marine, power generation, sports leisure and biomedical applications. The titanium has a high specific strength at room temperature, and is excellent in acid resistance and corrosion resistance. However, titanium has a very high affinity with oxygen, hydrogen and nitrogen in a molten state, and it is difficult to obtain a pure melt when a conventional casting technique is applied. In addition, there is a problem in that the manufacturing process is complicated due to difficulty in processing at room temperature, and the processing cost is very high if it is manufactured only by simple cutting.

The titanium alloy body can be manufactured by a method such as constant temperature forging, powder metallurgy and casting. The above-mentioned constant-temperature forging is manufactured through a multi-step forging process by melting and casting an ingot. When manufacturing complex parts such as aircraft parts, the final product must be used through a multi-step forging process, , There is a problem that the recovery rate of the raw material is very low and the economical efficiency is low. For example, when a Ti-6Al-4V alloy, which is a titanium (Ti) alloy, is subjected to a constant temperature forging process, a large amount of scrap is produced in a yield of 20% or less from a billet.

Powder metallurgy is a method of shaping using powders, which makes it possible to produce products with complex shapes, but it is difficult to produce high-purity titanium rod and titanium powder used as raw materials, and it is difficult to mass-produce titanium powder having a uniform distribution. In addition, the parts made of powder metallurgy are not completely densified, and hot isostatic pressing (HIP) treatment is absolutely necessary after sintering to remove defects.

Castings include casting, mold casting and precision casting using roast wax. Investment casting is a method of producing a mold by using a ceramic having a low coefficient of thermal expansion, and injecting molten metal into the mold for casting.

In the precision casting, first, a wax injection step of injecting a wax pattern, a spur, a runner, and the like of a product to be made by casting wax with wax is performed. Then, a wax tree making step is performed in which the wax pattern, spruce, runner and the like are connected by a suitable casting method to make a wax tree. Then, a mold coating process is performed in which the refractory slurry and the sand are coated on the wax tree in a stepwise manner, and the coating layer forms a coating layer having an appropriate thickness according to the required product. Next, the coated mold is subjected to a dewaxing process in which the wax therein is removed by heating, thereby forming a hollow mold having the same shape as the product to be produced therein. Then, the mold is fired at a predetermined temperature for removal of moisture and imparting appropriate strength to the mold, thereby completing the mold for precise casting. Then, the product is produced through a casting step of injecting molten metal into the mold thus formed, a degreasing step of removing the remaining mold after casting, and a processing step of cutting the product from the gate and processing it into a desired shape and dimensions .

Titanium-based alloys are known to be more suited to precision casting as a molding method capable of producing a near net shape because the mechanical properties of the casting material are similar or superior to those of the whole product (processed product). have.

However, even in such a precise casting process, a reaction occurs between the mold and the melt, and oxygen decomposed in the mold is solved as an intercalation-type atom to form a reaction layer called an alpha-case. The alpha case of the titanium alloy is light and brittle, and can easily crack to form cracks on the surface, and such cracks can reduce the mechanical properties of the product by acting as a notch. In order to remove the alpha case, a chemical polishing process such as mechanical machining and pickling with strong acid is additionally required, and the cost of these processes is about 27% of the price of the titanium casting product, which causes a rise in the unit price.

Further, since the flowability of the titanium alloy melt is low, casting defects such as shrinkage voids and bubbles are likely to occur in the casting during casting. In order to remove such casting defects, HIP treatment to remove internal defects by applying high temperature and high pressure in an inert atmosphere And there is a problem in that additional cost is incurred.

Since the alpha case removal and the HIP process account for about 63% of the production cost of the casting, there is a need for a casting process that does not require the alpha case removal process and HIP process in order to minimize the increase in the unit price. Therefore, the research direction of the casting mold for titanium alloy is mostly to control the alpha case, which is the surface reaction layer, and research using various materials is being carried out.

Prior art relating to the present invention is disclosed in Korean Patent Registration No. 10-1364563 (published on Apr. 21, 2014, entitled " Mold and Method of Manufacturing the Invention ").

It is an object of the present invention to provide a method for producing a casting mold for a titanium alloy casting which can suppress formation of an alpha-case reaction layer at a casting interface at the time of casting a titanium alloy.

Another object of the present invention is to provide a method of manufacturing a mold for a titanium alloy casting which can minimize unfilled, shrinkage defects, bubble defects and other casting defects.

It is still another object of the present invention to provide a method for producing a mold for casting a titanium alloy, which is excellent in product precision and can be manufactured in a complicated shape.

Another object of the present invention is to provide a method of manufacturing a casting mold for casting a titanium alloy, which can reduce costs and increase productivity.

It is still another object of the present invention to provide a mold for casting a titanium alloy produced by the above-described method for producing a mold for casting a titanium alloy.

One aspect of the invention relates to a method of making a mold for casting a titanium alloy. In one embodiment, the method for casting a titanium alloy casting includes dipping a wax-formed body defining a cavity shape into a first slurry, applying a first casting sand, and drying to form a first refractory coating layer; Forming a plurality of second refractory coating layers by repeating a process of dipping the wax-formed body formed with the first refractory coating layer into a second slurry, applying the second mold sand, and drying the same; Dipping the surface of the second refractory coating layer in a second slurry and drying the refractory coating layer to form a preliminary mold; And dewaxing and firing the preliminary mold, wherein the first slurry is a graphite powder having an average particle size of 20 탆 or less, Wherein the first slurry contains zircon powder and colloidal silica, and the first and second sand have at least one of zircon and chamois; and at least one of zircon and zircon powder, zircon powder, and zircon powder. .

In another embodiment, the method for casting a titanium alloy casting includes coating a first slurry on a cavity formed in a metal base material and drying to form an inner coating layer, wherein the first slurry has an average size of 20 mu m or less Graphite powder, solvent, zircon powder and binder.

In another embodiment, the casting method for casting the titanium alloy casting includes processing the graphite base material into a predetermined shape.

In one embodiment, the first slurry may comprise zircon powder and graphite powder in a volume ratio of 1: 1 to 3: 1.

In one embodiment, the solvent may include one or more of alcohol-based, ketone-based, and ester-based solvents.

In one embodiment, the first slurry may comprise from 15 to 60 vol% of graphite powder, from 30 to 85 vol% of solvent, from 4 to 25 vol% of zircon powder, and from 0.001 to 5 vol% of binder.

In one embodiment, the second slurry may comprise 50-90 vol% colloidal silica and 10-50 vol% zircon powder.

In one embodiment, the sand for the first casting mold may further include at least one of graphite powder, carbon powder, and activated carbon powder.

In one embodiment, the second slurry may further comprise at least one of a surfactant and a defoamer.

In one embodiment, the viscosity of the first slurry and the second slurry using the cup viscometer # 4 may be 18 to 25 seconds and 15 to 20 seconds, respectively.

Another aspect of the present invention relates to a mold for a titanium alloy produced by the above-described method for manufacturing a mold for a titanium alloy casting.

The mold for casting a titanium alloy of the present invention suppresses formation of an alpha-case reaction layer at the casting interface at the time of centrifugal pressure precision casting, minimizes uncharged, shrinkage defects, bubble defects and other casting defects, It is possible to manufacture a complicated shape product, and a near net shape similar to that of the final product can be manufactured, so that the post-processing such as additional chemical polishing and mechanical processing can be minimized and productivity and economy can be excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a method of manufacturing a mold for casting a titanium alloy according to one embodiment of the present invention.
Fig. 2 shows a titanium alloy casting manufactured using a mold for casting a titanium alloy according to an embodiment according to the present invention and a comparative example according to the present invention.
FIG. 3 (a) shows a titanium alloy mold manufactured by the embodiment of the present invention, FIG. 3 (b) shows a titanium alloy casting manufactured through the titanium alloy mold of the above embodiment, ) Is a photograph of the titanium alloy casting manufactured through the above embodiment.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Titanium alloy casting mold manufacturing method

One aspect of the invention relates to a method of making a mold for casting a titanium alloy. In the present invention, the "titanium alloy" is defined to include all alloys including titanium and titanium.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a method of manufacturing a mold for casting a titanium alloy according to one embodiment of the present invention. Referring to FIG. 1, the titanium alloy casting mold manufacturing method includes the steps of: (S10) forming a first refractory coating layer; (S20) forming a second refractory coating layer; (S30) forming a backup coating layer; And (S40) a dewaxing and firing step. More specifically, the method for producing a casting mold for titanium alloy casting comprises the steps of (S10) dipping a wax-formed body defining a cavity shape into a first slurry, coating the first casting sand, and drying to form a first refractory coating layer ; (S20) forming a plurality of second refractory coating layers by repeating a process of dipping the wax-formed body having the first refractory coating layer in a second slurry, applying and drying the second mold sand; (S30) dipping the surface of the second refractory coating layer in a second slurry and drying the refractory coating layer to form a preliminary mold; And (S40) heating the preliminary mold to dewax and firing the preform.

Wherein the first slurry comprises at least one of a graphite powder having an average size of 20 탆 or less, a solvent, a zircon powder and a binder, the second slurry comprising zircon powder and colloidal silica, The second sand for molding includes at least one of zircon yarn and chamois yarn.

Hereinafter, a method of manufacturing a casting mold for casting a titanium alloy according to one embodiment of the present invention will be described step by step.

(S10) forming a first refractory coating layer

In this step, the wax-formed body defining the cavity shape is dipped in the first slurry, and then the first casting sand is coated and dried to form the first refractory coating layer.

The first slurry

In one embodiment, the first slurry comprises at least one of graphite powder, solvent, zircon powder and binder, having an average size of 20 탆 or less. In one embodiment, the first slurry may comprise 15-60 vol% graphite powder having an average size of 20 microns or less, 30-85 vol% solvent, 4- 25 vol% zircon powder, and 0.001-5 vol% rhodium. In the above composition, the reactivity with the molten metal is minimized, and the effect of preventing casting defects is excellent.

The graphite powder may have a high crystalline graphite structure. In one embodiment, the graphite powder may use at least one of pyrolytic graphite, spherical graphite, scaly graphite, massive graphite, earthy graphite, artificial graphite and expanded graphite. When the graphite powder is applied, the reaction of the titanium alloy melt and the first refractory coating layer can be minimized, and alpha-case reaction layer formation on the surface of the titanium alloy casting can be suppressed, and casting defects can be prevented.

In one embodiment, the mean size (D50) of the graphite powder is 20 mu m or less. The "size" is defined as being the "maximum length" of the graphite powder. When the graphite powder having an average size out of the above range is applied, the durability of the first refractory coating layer may be lowered to cause casting defects. For example, 3 to 10 mu m.

In one embodiment, the graphite powder may comprise 15 to 60% by volume of the total volume of the first slurry. Within the above-mentioned range, the reactivity between the first refractory coating layer and the titanium alloy melt can be minimized, and the economical efficiency can be improved.

The solvent improves the homogeneity and dispersibility of the first slurry component. The solvent includes at least one of an alcohol-based solvent, a ketone-based solvent, and an ester-based solvent. The alcohol-based solvent may include at least one of methanol, ethanol, propanol, and butanol. The ketone-based solvent may include at least one of dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. Examples of the ester solvents include acetates, ethyl acetate, n-propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone, decanolide and valerolactone ≪ / RTI > For example, an alcohol-based solvent. When the solvent is applied, the reactivity with the titanium alloy melt can be minimized, and the dispersibility and homogeneity can be excellent.

In one embodiment, the solvent may comprise from 15 to 60% by volume of the total volume of the first slurry. When contained in the above volume, the dispersibility and the mixing property can be excellent.

The zircon powder contains zirconium silicate (ZrSiO ₄ ) as a main component and has excellent chemical stability. Therefore, the reactivity with the titanium alloy melt is minimized to suppress formation of alpha-case reaction layer on the surface of the casting and prevention of casting defects May be included for further purposes.

In one embodiment, the average size of the zircon powder may be less than or equal to 45 탆. The mixing and chemical stability may be excellent in the above range. For example, 3 to 7 mu m.

In one embodiment, the zircon powder may comprise from 4 to 25% by volume of the total volume of the first slurry. When included in the above range, chemical stability may be excellent.

In one embodiment, the first slurry may comprise zircon powder and graphite powder in a volume ratio of 1: 1 to 3: 1. Within the above range, the reactivity with the titanium alloy melt is minimized, the chemical stability is excellent, the casting defect prevention effect is excellent, and the economical efficiency can be excellent.

In one embodiment, the dot-payment may include at least one of an organic-based payment and an inorganic-based payment. For example, organic based binders may include polymeric resins. The inorganic binder may include at least one of colloidal zirconia and colloidal graphite. For example, the above-mentioned viscous solution may contain a phenolic resin. In one embodiment, the phenolic resin includes phenol, cresol, resorcin, bisphenol A, bisphenol C, bisphenol E, and bisphenol F, and may include at least one of the above. When the above-mentioned viscous solution is applied, the moldability of the first refractory coating layer is excellent, and durability and crack resistance can be excellent.

In one embodiment, the tackifier may comprise from 0.001% to 5% by volume of the total volume of the first slurry. When it is included in the above range, the first refractory coating layer is excellent in moldability and durability and crack resistance.

In one embodiment, the first slurry may have a viscosity of 18-25 seconds using zahn cup viscometer # 4. The mixing and flowability of the first slurry and the moldability and durability of the first refractory coating layer can be excellent under the above conditions.

Sand for first molding

The first sand for molding includes at least one of zircon yarn and chamotte yarn. For example, zircon yarns.

In one embodiment, the zircon sand may include 50-80 wt% zirconia (ZrO ₂ ), 20-45 wt% silica (SiO ₂ ), and the balance impurities. In one embodiment, the average size of the zircon sand may be 10 to 500 탆 or less. For example, 120 to 200 mu m.

In one embodiment, the chamois is obtained by calcining and pulverizing clay, which comprises silica (SiO ₂ ), 40-60 wt%, alumina (Al ₂ O ₃ ) 30-50 wt%, iron oxide (Fe ₂ O ₃ ) By weight, and the balance of impurities. In one embodiment, the average size of the chamois yarns may range from 10 to 500 microns or less.

In one embodiment, the first refractory coating layer may be formed by dipping the wax-formed body into the first slurry, applying the first casting sand, and drying the first casting mold for 1 to 5 hours. In one embodiment, the first refractory coating layer can be formed by drying at a temperature of 15 to 35 ° C for 2 to 4 hours.

In one embodiment, the sand for the first casting mold may further include at least one of graphite powder, carbon powder, and activated carbon powder. When the graphite powder, the carbon powder, and the activated carbon powder are further included, the reactivity with the titanium alloy melt is minimized, the chemical stability is excellent, and the effect of preventing casting defects is excellent.

In one embodiment, the graphite powder may include those having an average size (D50) greater than 20 microns. In this range, the first refractory coating layer is excellent in durability and reactivity with the titanium alloy melt is minimized, so that the effect of preventing casting defects can be excellent. For example, 120 to 200 mu m.

The carbon powder may include carbon black. The carbon black may exist as a structure (agglomerate) in which primary particles having an average particle diameter of several tens of nanometers are fused to each other to form a structure, and the structures are bonded by van der Waals force.

In one embodiment, the carbon black may be at least one of furnace black, channel black, acetylene black, lamp black, and thermal black.

In one embodiment, the active carbon powder is prepared by treating wood, lignite and peat with chemicals such as zinc chloride or phosphoric acid, which is an activator, by drying, or by activating charcoal with water vapor, It can be used in powder form.

In one embodiment, the carbon powder and activated carbon powder having an average size of 0.5 to 500 mu m can be used. Under the above conditions, the first refractory coating layer is excellent in durability, and reactivity with the titanium alloy melt is minimized, so that the effect of preventing casting defects can be excellent.

In one embodiment, the thickness of the first refractory coating layer may be 150 to 500 탆. In this range, the durability and the chemical resistance can be excellent while minimizing the reactivity with the titanium alloy melt. For example, 200 to 300 mu m.

(S20) Second refractory coating layer forming step

The step of dipping the wax-formed body having the first refractory coating layer in the second slurry, applying the second casting sand, and drying the wax-formed body is repeated a plurality of times to form a plurality of second refractory coating layers.

The second slurry

The second slurry includes zircon powder and colloidal silica. For example, the second slurry may comprise 10-50 vol% zircon powder and 50-90 vol% colloidal silica.

The zircon powder contains zirconium silicate (ZrSiO ₄ ) as a main component and has excellent chemical stability. Therefore, the reactivity with the titanium alloy melt is minimized to suppress formation of alpha-case reaction layer on the surface of the casting and prevention of casting defects May be included for further purposes.

In one embodiment, the average size of the zircon powder may be less than or equal to 45 탆. The mixing and chemical stability may be excellent in the above range. For example, 3 to 7 mu m.

In one embodiment, the zircon powder may comprise 10 to 50% by volume of the total volume of the second slurry. When included in the above range, chemical stability may be excellent.

The colloidal silica is a liquid in which silica particles of negative Si-O-Si structure are dispersed in water to form a colloidal state, and the size of the silica particles may be 0.01 to 10 탆.

In one embodiment, the colloidal silica may comprise from 50 to 90% by volume of the total volume of the second slurry. When it is in the above range, the stability and durability of the second refractory coating layer can be excellent.

In one embodiment, the second slurry may further comprise at least one of a surfactant and a defoamer.

In one embodiment, the surfactant may comprise at least one of an anionic surfactant, an anionic surfactant, and an amphoteric surfactant.

Examples of the anionic surfactant include sodium fatty acid, monoalkylsulfate, sodium alkylbenzenesulfonate, sodium laurylsulfate, and sodium ether sulfate. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, fatty acid sorbitan ester, and alkyl polyglucoside. Examples of the amphoteric surfactant include cocamidopropyl betaine, cocamidopropyl hydroxysultaine and lauryldimethylaminoacetic acid betaine.

In one embodiment, the surfactant may be present in an amount of 0.01 to 5% by volume based on the total volume of the second slurry. For example, 0.01 to 0.3% by volume.

The defoamer may be included in order to suppress bubble formation at the time of forming the second refractory coating layer using the second slurry. When bubbles are formed, the thickness of the second refractory coating layer may be non-uniform and holes may be generated. The defoaming agent may be an alcohol defoaming agent, a silicone defoaming agent, a fatty acid defoaming agent, an oil defoaming agent, an ester defoaming agent, and an oxyalkylene defoaming agent. Examples of the silicone defoaming agent include dimethyl silicone oil, polyorganosiloxane, and fluorosilicone oil. Examples of the fatty acid defoaming agent include stearic acid and oleic acid. Examples of the oil-based antifoaming agent include kerosene, animal and plant oil, castor oil, and the ester-based antifoaming agents include solitol trioleate and glycerol monoricinolate. Examples of the oxyalkylene antifoaming agents include polyoxyalkylene, acetylene ethers, polyoxyalkylene diazoxide esters, polyoxyalkylene alkylamines, and the like. Examples of the antifoaming agent include glycol. The antifoaming agent may be contained in an amount of 0.01 to 5% by volume based on the total volume of the second slurry. The bubble formation inhibiting effect of the second refractory coating layer can be excellent in the above range. For example, 0.01 to 0.3% by volume.

In one embodiment, the second slurry may have a viscosity of 15-20 seconds using zahn cup viscometer # 4. The mixing and fluidity of the second slurry and the moldability and durability of the second refractory coating layer can be excellent under the above conditions.

Secondary sand

The second sand for molding includes at least one of zircon yarn and chamotte yarn. For example, it may include Chamoth Company. The sand for the second casting mold is the same as the sand for the first casting mold described above, so a detailed description thereof will be omitted.

In one embodiment, a plurality of second refractory coating layers may be formed by repeating the process of dipping the wax-formed body formed with the first refractory coating layer into the second slurry, applying the second casting sand and drying the same plural times . For example, the second refractory coating layer may be formed of 5 to 10 layers.

In one embodiment, the second refractory coating layer may be formed by drying at a temperature of 15 to 35 ° C. for 3 to 5 hours.

In one embodiment, the thickness of the second refractory coating layer may be 50 to 500 탆. In this range, the durability and the chemical resistance can be excellent while minimizing the reactivity with the titanium alloy melt. For example, 100 to 300 mu m.

(S30) Backup coating layer forming step

In this step, the surface of the second refractory coating layer is dipped in a second slurry and dried to form a backup coating layer, thereby preparing a preliminary mold.

Since the second slurry can use the same components and contents as those described above, a detailed description thereof will be omitted. In one embodiment, the back coating layer can be formed by drying at a temperature of 15 to 35 DEG C for 5 to 20 hours.

In one embodiment, the thickness of the backup coating layer may be 50 to 500 mu m. In this range, the durability and the chemical resistance can be excellent while minimizing the reactivity with the titanium alloy melt. For example, 100 to 300 mu m.

(S40) Tallow wax  And firing step

The above step is a step of heating the preliminary mold, dewaxing and firing. For example, the dewaxing may be performed at a temperature of 150 to 250 ° C. Under these conditions, the wax component can be easily removed. For example, at 150 to 200 ° C.

In one embodiment, the calcination may be performed at 600-1000 < 0 > C. The mechanical strength of the mold for casting the titanium alloy of the present invention under the above conditions can be excellent.

According to another embodiment of the present invention, there is provided a method of manufacturing a mold for casting a titanium alloy, comprising the steps of: (S11) applying a first slurry to a cavity formed in a metal base material and drying to form an inner coating layer. The first slurry includes at least one of graphite powder, solvent, zircon powder, and binder having an average size of 20 mu m or less. In one embodiment, the inner coating layer can be formed by drying at a temperature of 15 to 35 DEG C for 3 to 5 hours.

The method for manufacturing a mold for casting a titanium alloy according to another embodiment of the present invention includes: (S12) machining a graphite base material into a predetermined shape. The reactivity with the molten titanium alloy is minimized during the production of the mold using the graphite base material, and the effect of suppressing the formation of the alpha-case reaction layer at the casting interface can be excellent.

A titanium alloy casting mold manufactured by a casting mold for casting a titanium alloy

Another aspect of the present invention relates to a mold for casting a titanium alloy by the above-described method for producing a casting mold for casting a titanium alloy.

The mold for casting a titanium alloy of the present invention suppresses formation of an alpha-case reaction layer at the casting interface at the time of centrifugal pressure precision casting, minimizes uncharged, shrinkage defects, bubble defects and other casting defects, It is possible to manufacture a complicated shape product, and a near net shape similar to that of the final product can be manufactured, so that the post-processing such as additional chemical polishing and mechanical processing can be minimized and productivity and economy can be excellent.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Example  And Comparative Example

The ingredients used in the following Examples and Comparative Examples are as follows.

The first slurry

(A) Graphite powder: A spherical graphite powder having an average size of 4 to 6 占 퐉 (product name: MG 5, manufactured by Samjong C & G Co., Ltd.) was used.

(B) Solvent

(B1) ethanol was used. (B2) water was used.

(C) Zircon powder: Zircon powder having an average size of 5 탆 was used.

(D) Dispersion: phenol resin (product name: TD-850, manufactured by Kangnam Hwaseong Co.).

(E) Antifoaming agent: A silicone antifoaming agent was used.

(F) Surfactant

Sand for first casting: Zircon yarn having an average size of 100 탆 was used.

The second slurry

Zircon powder: Zircon powder having an average size of 5 탆 was used.

Colloidal silica was used.

Secondary sand: Chamot yarn having an average size of 100 mu m was used.

Example  One

Formation of first refractory coating layer: A wax-formed article defining a predetermined cavity shape was produced by a conventional method.

A first slurry was prepared, which contained 79 vol% of ethanol, 6 vol% of graphite powder, 14 vol% of zircon powder and 1 vol% of phenol resin, and having a viscosity of 18 to 25 seconds based on Cup No. 4. Then, the wax-formed body was dipped in the first slurry, and then the first casting sand was coated and dried at 23 ° C for 2 to 4 hours to form a first refractory coating layer having a thickness of 150 μm.

Second refractory coating layer formation: A second slurry containing 41.65% by volume of zircon powder, 58.2% by volume of colloidal silica, 0.08% by volume of surfactant and 0.07% by volume of defoamer and having a viscosity of 16-20 seconds Respectively. Next, the wax-formed body having the first refractory coating layer formed thereon was dipped in a second slurry, and then the second casting sand was coated and dried at 23 ° C for 2 to 4 hours to form a second fireproof coating layer having a thickness of 150 μm . The above procedure was repeated five times to prepare a second refractory coating layer including five refractory coating layers.

Then, the surface of the second refractory coating layer was dipped in a second slurry and dried at 23 DEG C for 12 hours to form a backup coating layer having a thickness of 200 mu m to form a preliminary mold. Then, the preliminary mold was heated and dewaxed, and then fired at 700 to 1000 ° C to prepare a mold.

Example  2

Except that the first refractory coating layer was formed by using the first slurry having the contents as shown in Table 1 below, a mold for casting a titanium alloy was prepared.

Example  3

Formation of an inner coating layer: A first slurry having the components and contents shown in Table 1 below was applied to a cavity formed in a metal base material, and the inner coating layer was formed by drying to form a mold for casting the titanium alloy.

Comparative Example  1 to 7

Except that the first refractory coating layer was formed by using the first slurry having the contents as shown in Table 1 below, a mold for casting a titanium alloy was prepared.

Manufacture of titanium alloy castings

Titanium alloy castings were cast by injecting a titanium alloy melt into the cavities in the molds of Examples 1 to 3 and Comparative Examples 1 to 7.

The properties of Examples 1 to 3 and Comparative Examples 1 to 7 were evaluated as follows.

(1) Flowability of first slurry: Viscosity was measured using a cup viscometer # 4. When the viscosity is 18 to 25 seconds:?, When the viscosity is less than 18 seconds or more than 25 seconds: X is determined.

(2) Adhesiveness of the first refractory coating layer: The adhesiveness between the first refractory coating layer and the second refractory coating layer was evaluated and evaluated as good: good and poor: X.

(3) Dewaxing workability: Evaluation was made as to whether or not the first refractory coating layer was easily dewaxed upon dewaxing.

Referring to the results of Table 2, it was found that when the first slurry according to Examples 1 to 3 of the present invention was applied, the fluidity was excellent, and the adhesion of the first refractory coating layer and the dewaxing workability were excellent. On the other hand, in the case of Comparative Examples 1 to 7 in which a solvent different from that of the present invention is applied or in which the first slurry component of the present invention is not included, the first refractory coating layer is not easily formed, It was found that the adhesion between the coating layers was deteriorated and the dewaxing was not easily performed.

Example  4

The graphite base material was processed into a predetermined shape to prepare a mold for casting a titanium alloy.

Fig. 2 shows a titanium alloy casting manufactured using the casting mold for titanium alloy according to Example 1 of the present invention and Comparative Examples 1 to 3. Fig. 3 (a) shows the titanium alloy casting produced through Example 4, FIG. 3 (b) shows a titanium alloy casting manufactured through the titanium alloy mold of Example 4, FIG. 3 (b) is a photograph of the titanium alloy casting manufactured through Example 4 to be.

2 and 3, when the casting mold for casting a titanium alloy according to the present invention is applied, the reaction between the casting mold and the titanium molten metal is minimized to obtain a cast product with a clean surface state, It was found that the reduction effect was excellent. On the other hand, in the case of the comparative example deviating from the condition of the present invention, it was found that casting defects occurred and the surface quality of the cast article was remarkably lowered.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (11)

Forming a first refractory coating layer by dipping a wax-formed body defining a cavity shape into a first slurry, applying a first casting sand, and drying the first refractory coating layer;
Forming a plurality of second refractory coating layers by repeating a process of dipping the wax-formed body having the first refractory coating layer on the second slurry, applying the second mold sand, and drying the same;
Dipping the surface of the second refractory coating layer in a second slurry and drying the refractory coating layer to form a preliminary mold; And
Heating the preliminary mold, dewaxing and firing the preliminary mold,
The first slurry may be a graphite powder having an average particle size of 20 탆 or less, A solvent, a zircon powder, and a binder,
Wherein the second slurry comprises zircon powder and colloidal silica,
Wherein the first and second casting sands comprise at least one of zircon yarn and chamois yarn.
Applying a first slurry to a cavity formed in the metal base material and drying to form an inner coating layer,
Wherein the first slurry contains at least one of graphite powder, solvent, zircon powder, and tackifier having an average size of 20 mu m or less.
And processing the graphite base material into a predetermined shape. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to any one of claims 1 and 2, wherein the first slurry comprises zircon powder and graphite powder in a volume ratio of 1: 1 to 3: 1.
The process for producing a casting mold for a titanium alloy casting according to any one of claims 1 and 2, wherein the solvent comprises at least one of alcohol, ketone and ester solvents.
The method of any one of claims 1 and 2, wherein the first slurry comprises 15-60 vol% graphite powder, 30-85 vol% solvent, 4- 25 vol% zircon powder, and 0.001-5 vol% Wherein the casting mold is made of a titanium alloy.
The method of claim 1, wherein the second slurry comprises 50 to 90 vol% colloidal silica and 10 to 50 vol% zircon powder.
The method according to claim 1, wherein the first casting sand further comprises at least one of graphite powder, carbon powder, and activated carbon powder.
The method of claim 1, wherein the second slurry further comprises at least one of a surfactant and a defoaming agent.
The method of claim 1, wherein the first slurry and the second slurry have viscosities of 18 to 25 seconds and 15 to 20 seconds, respectively, using a cup viscometer # 4.
A mold for a titanium alloy produced by a method for manufacturing a mold for casting a titanium alloy according to any one of claims 1 to 3.

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