KR20230120445A - Forming method for titanium alloy thick plate with low formability - Google Patents

Abstract

A method for forming a hard-to-form titanium alloy plate is provided. Specifically, the method of forming the difficult-to-form titanium alloy thick plate includes the first step of preparing the titanium alloy thick plate and the mold, the second step of pre-treating the surface of the titanium alloy thick plate, and the pre-treated titanium alloy thick plate and the surface of the mold. The third step of forming a protective coating layer, the fourth step of placing the titanium alloy thick plate and the mold on which the surface protective coating layer is formed in a molding machine and performing hot forming at 600 to 620 ° C for 50 to 70 minutes, and the hot-formed titanium It is characterized in that it comprises a fifth step of performing mechanical processing on the alloy thick plate.

Description

Forming method of hard-to-form titanium alloy plate {FORMING METHOD FOR TITANIUM ALLOY THICK PLATE WITH LOW FORMABILITY}

The present invention relates to a method for forming a hard-to-form titanium alloy thick plate, and more particularly, to a method for forming a hard-to-form titanium alloy thick plate by pre-treating the hard-to-form titanium alloy thick plate, forming a surface protective coating layer, and then hot forming under appropriate forming conditions to determine the material utilization rate of a thick plate molded part. (Buy To Fly, BTF) and a method of forming a hard-to-form titanium alloy thick plate capable of improving tensile strength.

In general, thick plate refers to a thick steel plate with a thickness of 6 mm or more, a thick plate with a thickness of 45 mm or more is called a thick material, and a thickness of 100 mm or more is called an ultra-thick plate. Thick plates are standardized for general structures, welded structures, boilers, pressure vessels, and machine structures, depending on the material, and are used in large structures such as ships, boilers, pressure vessels, bridges, and aircraft. The outer plates of such large structures, including ships and aircraft, are formed by joint welding several pieces of curved thick plates. Accordingly, it is common that the thick plate is molded to have a curved surface by placing a flat plate member in a mold and then pressurizing it.

Thick plates are generally known to have higher yield stress and tensile stress than general steel materials. Accordingly, a forming method of performing bending through hot forming is performed on the thick plate in order to improve elongation.

On the other hand, titanium (Ti) material is formed by a smelting method obtained by obtaining titanium tetrachloride (TiCl ₄ ) by chlorination of TiO ₂ ore as a silver-white metal and then reducing it to magnesium (Mg). Titanium is the second lightest material after magnesium and aluminum, easy to process due to high malleability and ductility, and has almost the same strength as carbon steel. In addition, titanium material is strong against heat and has excellent corrosion resistance, so it realizes excellent mechanical properties that do not rust. Due to these characteristics, titanium materials are used as materials in various fields such as aviation, space, power, chemical plants, marine and medical.

In particular, titanium materials can be used in aircraft where high strength, heat resistance and oxidation resistance are required, and as the use of composite parts using titanium materials increases, the importance is increasing.

However, titanium is a representative material that is difficult to form due to its high yield strength, which makes it difficult to process and increases the risk of fire during molding. Prior art 1 (Registered Patent No. 10-1278110) and Prior Art 2 (Registered Patent No. 10-2098271) prior to processing titanium alloy based on the existing aluminum (Al) material forming method In order to increase the material utilization factor (BTF), which means the ratio between the weight and the weight of the final product, additional molding and tooling costs are accompanied. Accordingly, since most parts made of titanium are actually imported, various studies on forming methods of titanium are required.

Republic of Korea Patent No. 10-1278110 Republic of Korea Patent No. 10-2098271

In order to solve the above problems, the present invention is to provide a method for forming a hard-to-form titanium alloy thick plate that can easily form a titanium alloy thick plate.

In addition, the present invention is to provide a method for forming a hard-to-form titanium alloy thick plate capable of improving material utilization rate (BTF).

In addition, the present invention is to provide a method for forming a hard-to-form titanium alloy thick plate that can effectively control the deformation of the formed thick plate during subsequent processes such as mechanical processing or diffusion bonding by minimizing residual stress during hot forming. .

In order to achieve the above object, the present invention is a first step of preparing a titanium alloy thick plate and a mold, a second step of pre-treating the surface of the titanium alloy thick plate, and a first step of forming a surface protective coating layer on the pre-treated titanium alloy thick plate and the mold. Step 3, a fourth step of placing the titanium alloy thick plate and the mold on which the surface protective coating layer is formed in a forming apparatus and performing hot forming at 600 to 620 ° C for 50 to 70 minutes, and performing mechanical processing on the hot-formed titanium alloy thick plate It provides a method for forming a difficult-to-form titanium alloy thick plate, characterized in that it comprises a fifth step of performing.

In one embodiment of the present invention, the second step includes a first pretreatment step of degreasing the titanium alloy thick plate using an alkali solution, and a second pretreatment step of sandblasting the titanium alloy thick plate on which the first pretreatment step has been performed. It is characterized by including a process.

In one embodiment of the present invention, the third step is a first coating step of forming a first surface protective coating layer by applying a lubricant to the pretreated titanium alloy thick plate and the mold, and the first surface protective coating layer is formed It is characterized in that it includes a second coating process of forming a second surface protective coating layer by applying a corrosion inhibitor to the titanium alloy thick plate and the mold.

In one embodiment of the present invention, the first surface protective coating layer is formed to a thickness of 5 to 15 μm, and the second surface protective coating layer is characterized in that it is formed to a thickness of 15 to 45 μm.

In one embodiment of the present invention, the hot forming in the fourth step is characterized in that pressing with a weight of 100 to 110 ton.

The method for forming a difficult-to-form titanium alloy thick plate of the present invention can easily form a titanium alloy thick plate, thereby reducing manufacturing cost.

In addition, the method of forming the difficult-to-form titanium alloy thick plate of the present invention can improve the material utilization rate (BTF) to 30% or more.

In addition, the method of forming a hard-to-form titanium alloy thick plate according to the present invention minimizes residual stress during hot forming, so that deformation of the formed thick plate can be effectively controlled during subsequent processes such as mechanical processing or diffusion bonding.

However, the effects of the invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a flow chart showing a method of forming a difficult-to-form titanium alloy thick plate according to an embodiment of the present invention.
Figure 2 (a) is a model diagram of a T-shaped titanium alloy thick plate according to an embodiment of the present invention, Figure 2 (b) is a real image of the T-shaped titanium alloy thick plate.
Figure 3 (a) is a model diagram of the upper plate of the mold manufactured to form the titanium alloy thick plate of Figure 2 according to an embodiment of the present invention, Figure 3 (b) is a model diagram of the lower plate of the mold, Figure 3 (c ) is the actual image of the mold.
Figure 4 (a) is an actual image after forming a surface protection coating layer on a T-shaped titanium alloy thick plate according to an embodiment of the present invention, Figure 4 (b) is a mold installed in the device to form a surface protection coating layer real image.
5 is a real image showing a state before hot forming by placing a titanium alloy thick plate and a mold in a forming apparatus according to an embodiment of the present invention.
Figure 6 (a) is a model after the T-shaped titanium alloy thick plate according to an embodiment of the present invention is hot formed, Figure 6 (b) is a real image of the titanium alloy thick plate in a bent state by hot forming.
7 is a model diagram showing mechanical processing performed on a hot-formed T-shaped titanium alloy thick plate according to an embodiment of the present invention.
8 is a certified test report of tensile strength of a molded article molded in Example 2 of the present invention.

Hereinafter, a preferred embodiment of a method for forming a difficult-to-form titanium alloy thick plate according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing a method of forming a difficult-to-form titanium alloy thick plate according to an embodiment of the present invention.

Referring to FIG. 1, the method of forming a difficult-to-form titanium alloy thick plate of the present invention includes a first step of preparing a titanium alloy thick plate and a mold (S10), a second step of pre-treating the surface of the titanium alloy thick plate (S20), A third step (S30) of forming a surface protective coating layer on the pretreated titanium alloy thick plate and the mold, placing the titanium alloy thick plate and the mold on which the surface protective coating layer is formed in a molding apparatus at 600 to 620 ° C. for 50 to 70 minutes It may include a fourth step of performing hot forming (S40) and a fifth step of performing mechanical processing on the hot-formed titanium alloy thick plate (S50). That is, the present invention pre-treats a titanium alloy thick plate, forms a surface protective coating layer, and then hot-forms at an appropriate temperature and for an appropriate time to reduce costs and increase molding efficiency by improving the material utilization rate (BTF). It may be to suggest a method of forming the thick plate.

Referring to FIG. 1, the step S10 may be to prepare a titanium alloy thick plate and a mold.

The titanium alloy thick plate is a forming object, and may be an alloy material in which various metals including titanium are mixed. In one embodiment, the titanium alloy thick plate may be composed of titanium (Ti) -6Al (aluminum) -4V (vanadium). The titanium alloy thick plate may be formed in various shapes depending on the purpose.

Figure 2 (a) is a model diagram of a T-shaped titanium alloy thick plate according to an embodiment of the present invention, Figure 2 (b) is a real image of the T-shaped titanium alloy thick plate.

2(a) to 2(b), in one embodiment, the titanium alloy thick plate may be a titanium alloy thick plate having a T-shaped cross section.

The mold may be a mold for forming the titanium alloy thick plate by accommodating the titanium alloy thick plate at one side. The mold may include a thick plate accommodating part capable of accommodating the titanium alloy thick plate according to the shape, material and size of the titanium alloy thick plate. The mold may be made of a material having high strength and toughness at high temperature, excellent resistance to mechanical shock and thermal shock, and particularly excellent abrasion resistance to scale during hot forming, which will be described later. Specifically, for example, chromium (Cr), nickel (Ni), molybdenum (Mc), vanadium (V), or alloys thereof may be used as the material of the mold.

Figure 3 (a) is a model diagram of the upper plate of the mold manufactured to form the titanium alloy thick plate of Figure 2 according to an embodiment of the present invention, Figure 3 (b) is a model diagram of the lower plate of the mold, Figure 3 (c ) is the actual image of the mold.

3(a) to 3(c) , the mold may be composed of an upper plate and a lower plate. Specifically, one end of the titanium alloy thick plate as shown in FIG. 2, which is a molding target, is accommodated on one side of the upper plate, and the other end of the titanium alloy thick plate as shown in FIG. 2 is accommodated on one side of the lower plate. It may be formed in a structure having a portion.

Referring to FIG. 1 , S20 may be to pre-treat the surface of the titanium alloy thick plate. That is, by pre-treating the surface before forming the titanium alloy thick plate, foreign substances attached to the surface of the titanium alloy thick plate that may adversely affect the physical properties of the material or reduce the molding efficiency during hot forming, which will be described later, may be effectively removed. there is.

In one embodiment of the present invention, the S20 is a first pretreatment step (S21) of degreasing the titanium alloy thick plate using an alkali solution, and sand blasting the titanium alloy thick plate on which the first pretreatment step has been performed It may include a second pretreatment step (S22) to do.

Specifically, the first pretreatment step of S21 is to alkali degrease the titanium alloy thick plate, and may be for removing fats and oils such as processing oil that may remain on the surface of the titanium alloy thick plate or impurities attached to the surface. there is. At this time, the alkali solution may be to remove fats and oils through oxidation to make water-soluble soap by combining with fats and oils or impurities.

The S21 may be to use a conventional alkali degreasing agent. Specifically, for example, the alkali degreasing agent used in the alkali degreasing in S21 may be one or more of sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), and sodium silicate (Na ₂ SiO ₃ ). , but is not limited thereto.

In one embodiment, the S21 may be performed for 5 to 10 minutes at a temperature of 60 to 70 ℃.

When the alkali degreasing temperature is less than 60° C. in S21, the above-described saponification process may not be performed smoothly, and degreasing efficiency may decrease. In addition, when the alkali degreasing is performed at a temperature exceeding 70° C., the high temperature reduces the adhesiveness of the alkali degreasing agent, and thus the removal efficiency of oils and fats or foreign substances attached to the surface of the titanium material, that is, degreasing efficiency. this can be lowered

When the alkaline degreasing time in S21 is less than 5 minutes, sufficient time for the alkali degreasing agent to act with the oil and fat on the surface of the titanium material may not be given enough time to lower the degreasing efficiency. In addition, when the alkali degreasing time exceeds 10 minutes, the degree of contamination of the alkali degreasing agent may increase and degreasing efficiency may be lowered.

In addition, the second pretreatment step of S22 may be to sandblast the titanium alloy thick plate on which the first pretreatment step has been performed to smooth or smooth the surface of the titanium alloy thick plate by trimming or cutting.

In general, sandblasting is processed by spraying abrasives from a nozzle. Wet sandblast, which mixes abrasives and water and then sprays them from a nozzle, and dry sand, which processes only abrasives by spraying them from a nozzle using air It is classified as dry sandblast.

In one embodiment of the present invention, the abrasive used during sandblasting is at least one selected from aluminum oxide (Al ₂ O ₃ ), silicon carbide (SiC), glass beads, and plastic powder. may be using

Specifically, in one embodiment, the abrasive in S22 may be aluminum oxide having 140 to 170 mesh. The aluminum oxide generally has high hardness, high purity, and excellent ductility in an angular shape, so that a profile can be quickly formed on the surface of the titanium alloy thick plate, and contaminants on the surface can be effectively removed.

In one embodiment, when the particle size of the abrasive is less than 140 mesh, the cleaning power may be lowered due to the cushion effect, and it may be difficult to achieve good flatness. In addition, when the particle size of the abrasive exceeds 170 mesh, the average surface roughness increases and the formation of the protective surface coating layer described later may not be performed evenly, and the quality and mechanical properties of the final molded product of the titanium alloy thick plate may be affected. can affect,

Referring to FIG. 1 , S30 may be to form a surface protective coating layer on the pretreated titanium alloy thick plate and the mold. That is, in S30, a surface protective coating layer may be formed to minimize deformation of the surface of the titanium alloy thick plate and the mold during hot forming, which will be described later, and to increase molding efficiency.

In one embodiment of the present invention, the S30 is a first coating step (S31) of forming a first surface protective coating layer by applying a lubricant to the pretreated titanium alloy thick plate and the mold, respectively, and the first surface protective coating layer It may include a second coating process (S32) of forming a second surface protective coating layer by applying a corrosion inhibitor to the formed titanium alloy thick plate and the mold, respectively.

Specifically, in S31, a lubricant for forming the first surface protective coating layer may be applied to the titanium alloy thick plate pretreated in S20 and the mold prepared in S10. The lubricant may be applied to the titanium alloy thick plate and the mold to stably secure a friction coefficient of each surface and to uniformly form surface roughness.

Through this, it is possible to maintain the quality of the titanium alloy thick plate even after molding while protecting the surfaces of the titanium alloy thick plate and the mold. In addition, depending on the lubrication characteristics between the titanium alloy thick plate, which is a difficult-to-form material, and the mold, deformation of the material and shape of the part may be affected during hot forming, which will be described later. Accordingly, the present invention may improve lubrication between the titanium alloy thick plate and the mold by forming a first surface protective coating layer by applying the lubricant. Specifically, the lubricant may slow down the cooling rate of the titanium alloy thick plate by blocking heat between molds having a relatively low temperature while the titanium alloy thick plate is heated by hot forming.

In one embodiment, all lubricants used in general metal processing may be used as the lubricant. Specifically, the lubricant is water glass, graphite powder, oil, siloxane, hydrochlorofluorocarbon (HCFC), molybdenum disulfide (MoS ₂ ), acetone, 2-propanone ( 2-propanone), 2-butanone (2-butanone), nitride (nitride), boron nitride (boron nitride), and any one or more selected from mixtures thereof may be used, but is not limited thereto.

In one embodiment, the lubricant is sprayed/sprayed on the surface of the titanium alloy thick plate and the mold, the titanium alloy thick plate and the mold are immersed in heated grease, or the titanium alloy thick plate is used with a roller. And it may be applied by a method of applying to the mold.

In one embodiment of the present invention, in the step S31, the first surface protective coating layer may be formed to a thickness of 5 to 15 μm. When the thickness of the first surface protective coating layer is formed to be less than 5 μm, the first surface protective coating layer is too thin to exhibit the inherent lubricating properties of the lubricant. In addition, when the thickness of the first surface protective coating layer is formed to exceed 15 μm, the first surface protective coating layer can be easily peeled off from the titanium alloy thick plate and the mold during the molding process.

In addition, the step S32 may be to form a second surface protective coating layer by applying a corrosion inhibitor to the titanium alloy thick plate and the mold on which the first surface protective coating layer is formed. That is, in the present invention, after forming the first surface protective coating layer with a lubricant in S31, and then applying a corrosion inhibitor thereon to form a second surface protective coating layer, the titanium alloy thick plate and the mold are heated during hot forming, which will be described later. It can prevent the surface from being oxidized and the formation of an oxide film (oxide scale), and finally improve the corrosion resistance of the titanium alloy thick plate molded product.

As the corrosion inhibitor, all conventional corrosion inhibitors may be used. Specifically, for example, the corrosion inhibitor is a metal salt containing at least one of zinc (Zn), magnesium (Mg), aluminum (Al) and silicon (Si), toluene, talc (Talc (Mg ₃ H ₂ (SiO ₃ ) ₄ )), a naphthol compound (1-(2-Methyl-4-(2-methylphenylazo)phenylazo)-2-naphthol), and quartz (SiO ₂ )). It can be used, but is not limited thereto.

In one embodiment of the present invention, in the step S32, the second surface protective coating layer may be formed to a thickness of 15 to 45 μm. When the thickness of the second surface protective coating layer is less than 15 μm, it may be difficult to effectively suppress oxidation and scale formation on the surface of the titanium alloy thick plate due to heat during hot forming because the second surface protective coating layer is too thin. In addition, when the thickness of the second surface protective coating layer is formed to exceed 45 μm, the thicker coating layer affects the lubricating properties between the titanium alloy thick plate and the mold, causing product deformation and reducing molding efficiency. can

Figure 4 (a) is a real image after forming a surface protection coating layer on a T-shaped titanium alloy thick plate according to an embodiment of the present invention, Figure 4 (b) is a real image of installing the mold on which the surface protection coating layer is formed in the device It is an image.

4(a) to 4(b), the hot forming efficiency can be further increased by forming a surface protective coating layer on the titanium alloy thick plate and the mold.

Referring to FIG. 1 , in S40, hot forming may be performed at 600 to 620° C. for 50 to 70 minutes by placing the titanium alloy thick plate and the mold on which the surface protective coating layer is formed in a molding apparatus. That is, the present invention may appropriately control the forming temperature and time so that the difficult-to-form titanium alloy thick plate can be effectively hot-formed without material deformation or quality loss.

In the present invention, the titanium alloy thick plate can be easily formed to have high strength, excellent tensile strength, and optimal bendability by hot forming the titanium alloy thick plate, so that high strength of large structures such as automobiles, ships, and aviation is required. It can be suitable as a back plate or part. In addition, the titanium alloy thick plate formed with high strength through such hot forming can improve delayed fracture resistance at the machined portion even if mechanical processing described later is performed.

5 is a real image showing a state before hot forming by arranging a titanium alloy thick plate and a mold in a forming apparatus according to an embodiment of the present invention.

As shown in FIG. 5 , the forming apparatus may be a general hot forming apparatus, and depending on an embodiment, a hot press forming apparatus capable of performing press molding may be used.

When the forming temperature during hot forming in S40 is less than 600° C., it is difficult to easily mold a thick plate made of titanium alloy material into a desired shape, which may delay process time and lower product quality. In addition, when the molding temperature exceeds 620 ℃ during hot forming in the above S40, ductility or bendability may be lowered.

If the forming time during hot forming in S40 is less than 50 minutes, it may be difficult to form the titanium alloy thick plate into a desired shape because hot forming is not sufficiently performed. In addition, when the molding time during hot forming in S40 exceeds 70 minutes, the crystal grain size of the titanium alloy increases due to heat, and as a result, the dislocation movement is less hindered, and the vibration energy is easily lost while finally hot forming titanium The tensile strength of the alloy plate may decrease.

In one embodiment of the present invention, the S40 may be to press with a weight of 100 to 110 ton using a press during the hot forming. That is, when hot forming is performed on the titanium alloy thick plate, the titanium alloy thick plate can be more easily formed into a desired shape by pressing with a press in a hot state.

In the case of pressing with a weight of less than 100 ton when using the press, it may be difficult to effectively improve molding efficiency because the titanium alloy thick plate in a hot state is not sufficiently hardened. In addition, when the press is pressed with a weight exceeding 110 ton, deformation may occur after molding due to non-uniform contraction.

Figure 6 (a) is a model after the T-shaped titanium alloy thick plate according to an embodiment of the present invention is hot-formed, Figure 6 (b) is a real image of the hot-formed titanium alloy thick plate.

6 (a) and 6 (b), the present invention can improve the high ratio (BTF) of the raw material by performing hot forming at an appropriate temperature and for an appropriate time suitable for the titanium alloy thick plate, without deforming the product. It can be molded into any desired shape.

Referring to FIG. 1 , S50 may be to perform mechanical processing on the hot-formed titanium alloy thick plate.

7 is a model diagram in which mechanical processing is performed on a hot-formed T-shaped titanium alloy thick plate according to an embodiment of the present invention.

As shown in FIG. 7, the mechanical processing may be to process the size and appearance of the hot-formed titanium alloy thick plate according to the specifications and shapes of parts in a large structure, which is a final product.

Accordingly, the method for forming a difficult-to-form titanium alloy thick plate of the present invention can easily form a titanium alloy thick plate, thereby reducing manufacturing cost.

8 is a certified test report of tensile strength of a molded article molded in Example 2 of the present invention.

As shown in FIG. 8, the titanium alloy thick plate molded product formed by the forming method of the difficult-to-form titanium alloy thick plate of the present invention exhibits excellent tensile strength of 1060 N/mm ² or more, and minimizes residual stress during hot forming, such as mechanical processing or diffusion bonding. It is possible to effectively control the deformation of the molded heavy plate during the subsequent process of

Hereinafter, the contents of the experiment using the method of forming the difficult-to-form titanium alloy thick plate of the present invention will be described in detail.

Experimental Example 1: Evaluation of tensile strength and appearance of titanium alloy thick plate molded products according to the composition of the surface protective coating layer

In the following experiment, a titanium alloy thick plate was hot-formed by changing the configuration of the surface protective coating layer before hot forming in the method of forming a difficult-to-form titanium alloy thick plate according to the present invention. Appearance evaluation was performed based on the measurement of the tensile strength of the molded titanium alloy thick plate molded article and the following evaluation criteria.

1.1 Preparation of materials by process and characteristics by process

1) In the pretreatment process, alkali degreasing was used as an alkali degreasing agent by diluting a blue gold product containing an alkali salt in water.

2) In the pretreatment process, sandblasting was performed using 160 mesh size aluminum oxide (Al Oxide).

3) When forming the surface protective coating layer, Bonderite L-GP 5711 of Iram Chemical Co., Ltd., which contains boron nitride, was used as a lubricant.

4) When forming the surface protective coating layer, Bonderite L-GP 5711 from Iram Chemical Co., Ltd., including toluene, was used as a corrosion inhibitor.

1.2 Tensile strength evaluation

The tensile strength of molded products was measured based on ASTM E8/E8M-16a.

1.3 Appearance evaluation method

After observing the molded product of the titanium alloy thick plate with the naked eye, the surface was touched with a finger.

When a soft texture was formed when touched with a finger and a smooth and uniform appearance was formed when observed with the naked eye, it was marked as ○.

When touched with a finger, a somewhat rough texture was formed, and when observed with the naked eye, if less than 5 irregularities were observed or there were cracks, it was marked as △.

When touched with a finger, a very rough texture was formed, and when observed with the naked eye, if 5 or more irregularities were observed or there were cracks and discoloration and stains were observed, it was marked as X.

[Comparative Example 1]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

A lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a first surface protective coating layer having a thickness of 10 μm.

The titanium alloy thick plate and the mold on which the surface protective coating layer was formed were placed in a forming apparatus, and hot forming was performed for 60 minutes at a temperature of 600° C. and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Comparative Example 2]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

A corrosion inhibitor was applied to the pretreated titanium alloy thick plate and the mold to form a second surface protective coating layer having a thickness of 35 μm.

The titanium alloy thick plate and the mold on which the surface protective coating layer was formed were placed in a forming apparatus, and hot forming was performed for 60 minutes at a temperature of 600° C. and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Comparative Example 3]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

The pretreated titanium alloy thick plate and the mold were placed in a forming apparatus, and hot forming was performed for 60 minutes by applying a temperature of 600° C. and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 1]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 5㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick second layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 2]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 3]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 15㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick second layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 4]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 20㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick second layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 5]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 5㎛ thick second layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 6]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 15㎛ thick second surface layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 7]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 25㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 8]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 45㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 9]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 55㎛ thick second layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

The characteristics of the surface protective coating layer configuration and the thickness of the surface protective coating layer in Comparative Examples 1 to 3 and Examples 1 to 9 are summarized in Table 1 below.

division surface protective coating layer
composition First surface protective coating layer
thickness Second surface protective coating layer
thickness Comparative Example 1 Formation of the first surface protective coating layer 10㎛ _ Comparative Example 2 Formation of the second surface protective coating layer _ 35㎛ Comparative Example 3 No surface protective coating layer _ _ Example 1 Forming a first surface protective coating layer and a second surface protective coating layer 5㎛ 35㎛ Example 2 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 35㎛ Example 3 Forming a first surface protective coating layer and a second surface protective coating layer 15㎛ 35㎛ Example 4 Forming a first surface protective coating layer and a second surface protective coating layer 20㎛ 35㎛ Example 5 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 5㎛ Example 6 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 15㎛ Example 7 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 25㎛ Example 8 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 45㎛ Example 9 Forming a first surface protective coating layer and a second surface protective coating layer 10㎛ 55㎛

Table 2 below shows the physical properties and appearance evaluation results of the titanium alloy thick plate molded articles molded in Comparative Examples 1 to 3 and Examples 1 to 9.

Classification (unit) Tensile strength (N/mm ² ) Appearance evaluation Comparative Example 1 1050 X Comparative Example 2 1048 X Comparative Example 3 1041 X Example 1 1060 ○ Example 2 1068 ○ Example 3 1063 ○ Example 4 1054 △ Example 5 1057 △ Example 6 1062 ○ Example 7 1064 ○ Example 8 1060 ○ Example 9 1056 △

Referring to Tables 1 and 2, as a result of evaluating the physical properties and appearance of the molded articles of Examples 1 to 3 and Examples 6 to 8, the tensile strength was 1060 N/mm ² or more, and the appearance of the molded article was smooth and It can be seen that it is formed uniformly. In particular, it can be seen that the tensile strength and appearance evaluation of the molded article of Example 2 are the most excellent compared to other Examples.

Specifically, in the molded products of Examples 1 to 3 and Examples 6 to 8, a first surface protective coating layer composed of a lubricant and a second surface protective coating layer composed of a corrosion inhibitor are formed to an appropriate thickness during hot molding. By effectively protecting the surface of the Edo titanium alloy thick plate, the tensile strength was maintained high, and it was judged that the surface was uniform in appearance.

In Comparative Examples 1 to 3, cracks due to hot forming were observed even in appearance, and discoloration was observed in some areas. This can be seen as a result of not forming a double surface protective coating layer, like other embodiments of the present invention. In particular, Comparative Example 3 felt a large scale on the surface and showed the lowest tensile strength compared to other Examples and Comparative Examples. This can be seen as the titanium alloy thick plate being deformed in the hot forming process by performing hot forming without a surface protective coating layer.

As described above, in the method of forming a difficult-to-form titanium alloy thick plate of the present invention, the surface protective coating layer is formed by applying a lubricant and a corrosion inhibitor on the first surface protective coating layer. A double layer composed of two surface protective coating layers is preferred, and the first surface protective coating layer is formed to a thickness of 5 to 15 μm, and the second surface protective coating layer may be preferably formed to a thickness of 15 to 50 μm.

Experimental Example 2: Evaluation of tensile strength and appearance of titanium alloy thick plate molded products according to hot forming conditions

In the following experiment, a titanium alloy thick plate was hot-formed by varying the hot forming conditions (temperature, time) in the method of forming a difficult-to-form titanium alloy thick plate according to the present invention. Appearance evaluation was performed based on the measurement of tensile strength of the molded titanium alloy thick plate molded article and the following evaluation criteria.

2.1 Preparation of materials for each process and characteristics for each process

1) In the pretreatment process, alkali degreasing was used as an alkali degreasing agent by diluting a blue gold product containing an alkali salt in water.

2) In the pretreatment process, sandblasting was performed using 160 mesh size aluminum oxide (Al Oxide).

3) When forming the surface protective coating layer, Bonderite L-GP 5711 of Iram Chemical Co., Ltd., which contains boron nitride, was used as a lubricant.

4) When forming the surface protective coating layer, Bonderite L-GP 5711 from Iram Chemical Co., Ltd., including toluene, was used as a corrosion inhibitor.

2.2 Measurement of tensile strength

The tensile strength of molded products was measured based on ASTM E8/E8M-16a.

2.3 Appearance evaluation method

After observing the molded product of the titanium alloy thick plate with the naked eye, the surface was touched with a finger.

When a soft texture was formed when touched with a finger and a smooth and uniform appearance was formed when observed with the naked eye, it was marked as ○.

When touched with a finger, a somewhat rough texture was formed, and when observed with the naked eye, if less than 5 irregularities were observed or there were cracks, it was marked as △.

When touched with a finger, a very rough texture was formed, and when observed with the naked eye, if 5 or more irregularities were observed or there were cracks and discoloration and stains were observed, it was marked as X.

[Example 10]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 590° C. and a pressure of 100 ton for 60 minutes. A molded article was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 11]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed for 60 minutes at a temperature of 610 ° C and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 12]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 620 ° C and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 13]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed at a temperature of 630° C. and a pressure of 100 ton for 60 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 14]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed for 40 minutes at a temperature of 600° C. and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 15]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a forming apparatus, and hot forming was performed at a temperature of 600° C. and a pressure of 100 ton for 50 minutes. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 16]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed for 70 minutes at a temperature of 600 ° C and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

[Example 17]

A T-shaped titanium alloy plate and a mold were prepared.

For the pretreatment of the titanium alloy thick plate, the titanium alloy thick plate was alkali degreased with an alkali degreasing agent at 65° C. for 10 minutes, and then washed with industrial water at room temperature. The washed titanium alloy plate was subjected to sandblasting using an aluminum oxide abrasive having 160 mesh, and then washed with water.

Lubricant was applied to the pretreated titanium alloy thick plate and the prepared mold to form a 10㎛ thick first surface protective coating layer, and then a corrosion inhibitor was applied to the titanium alloy thick plate and the mold on which the first surface protective coating layer was formed to form a 35㎛ thick layer. 2 surface protective coating layers were formed.

The titanium alloy thick plate and the mold on which the first surface protective coating layer and the second surface protective coating layer were formed were placed in a molding apparatus, and hot forming was performed for 80 minutes at a temperature of 600° C. and a pressure of 100 ton. A molded product was manufactured by mechanically processing the hot-formed titanium alloy thick plate into a shape such as an aircraft engine pylon.

The molding temperature and molding time during hot molding in Example 2 and Examples 10 to 17 are summarized in Table 3 below.

division Molding temperature (℃) Molding time (minutes) Example 10 590 60 Example 2 600 60 Example 11 610 60 Example 12 620 60 Example 13 630 60 Example 14 600 40 Example 15 600 50 Example 16 600 70 Example 17 600 80

The physical properties and appearance evaluation results of the titanium alloy thick plate molded articles molded in Example 2 and Examples 10 to 17 are shown in Table 4 below.

Classification (unit) Tensile strength (N/mm ² ) Appearance evaluation Example 10 1057 △ Example 2 1068 ○ Example 11 1063 ○ Example 12 1065 ○ Example 13 1053 △ Example 14 1058 △ Example 15 1061 ○ Example 16 1064 ○ Example 17 1055 △

Referring to Tables 3 and 4, the physical properties and appearance evaluation results of the molded articles of Example 2, Example 11, Example 12, Example 15, and Example 16, tensile strength of 1060 N/mm ² or more, and molded articles in appearance It can be seen that the appearance of was formed smoothly and uniformly.

Specifically, the molded products of Example 2, Example 11, Example 12, Example 15 and Example 16 had improved tensile strength by performing hot forming at an appropriate temperature and for an appropriate time suitable for the titanium alloy material, and It can also be seen that it shows a uniform surface.

Example 10 can be seen that the tensile strength is lower than that of Example 2, which exhibits the best physical properties, since the molding is not effectively performed while the temperature at the time of hot forming is lower than that of Example 2. In addition, the scale caused by the molding process was felt in some areas visually.

In Example 13, the temperature during hot forming was slightly higher than that of the other examples, and many cracks were generated due to the high forming temperature, and the tensile strength was low due to the temperature not suitable for the titanium alloy material. It is judged to be

In Example 14, it can be seen that the overall physical properties or appearance evaluation of the molded product is deteriorated while the molding is not performed well because the molding time is not given sufficiently.

Example 17 is judged to have lower tensile strength and appearance evaluation as the crystal grain size in the titanium alloy thick plate increased as the molding time increased compared to Example 2.

As described above, in the method of forming the hard-to-form titanium alloy thick plate of the present invention, it is determined that it is preferable to perform the hot forming at 600 to 620 ° C. for 50 to 70 minutes.

As such, it will be understood that the technical configuration of the present invention described above can be implemented in other specific forms without changing the technical spirit or essential features of the present invention by those skilled in the art to which the present invention belongs.

Therefore, the embodiments described above should be understood as illustrative and not limiting in all respects, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and All changes or modified forms derived from the equivalent concept should be construed as being included in the scope of the present invention.

Claims (5)

The first step of preparing the titanium alloy plate and mold;
a second step of pre-treating the surface of the titanium alloy thick plate;
a third step of forming a surface protective coating layer on the pretreated titanium alloy thick plate and the mold;
A fourth step of placing the titanium alloy thick plate and the mold on which the surface protective coating layer is formed in a forming apparatus and performing hot forming at 600 to 620 ° C. for 50 to 70 minutes; and
A method for forming a difficult-to-form titanium alloy thick plate, characterized in that it comprises a; fifth step of performing mechanical processing on the hot-formed titanium alloy thick plate. According to claim 1,
In the second step,
A first pretreatment step of degreasing the titanium alloy thick plate using an alkali solution;
A method for forming a difficult-to-form titanium alloy thick plate, characterized in that it comprises a second pre-treatment step of sandblasting the titanium alloy thick plate on which the first pre-treatment step has been performed. According to claim 1,
The third step is
A first coating step of forming a first surface protective coating layer by applying a lubricant to the pretreated titanium alloy thick plate and the mold;
A method for forming a difficult-to-form titanium alloy thick plate, characterized in that it comprises a second coating step of forming a second surface protective coating layer by applying a corrosion inhibitor to the titanium alloy thick plate and the mold on which the first surface protective coating layer is formed. According to claim 3,
The first surface protective coating layer is formed to a thickness of 5 to 15 μm,
The second surface protective coating layer is a method of forming a difficult-to-form titanium alloy thick plate, characterized in that formed to a thickness of 15 to 45㎛. According to claim 1,
In the fourth step,
The hot forming method of forming a difficult-to-form titanium alloy thick plate, characterized in that the pressing with a weight of 100 to 110 ton.