Manufacturing method of high strength titanium alloy using ferrochromium and high strength titanium alloy

Abstract

A method for producing a high-strength titanium alloy using ferrochromium and a high-strength titanium alloy are disclosed. The method for producing a high-strength titanium alloy according to the present invention includes the steps of adding ferrochromium containing Cr, Fe, Si, and C to pure Ti, melting and cooling the mixture to form a titanium alloy base material, and then hot forming the titanium alloy base material. At this time, the content of ferrochromium is less than 4 wt%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing high-strength titanium, and more particularly to a method for producing a high-strength titanium alloy using ferrochromium.

[0002] The present invention also relates to titanium alloys that can exhibit high strength along with good elongation. [Background technology]

[0003] Titanium has excellent specific strength, corrosion resistance, and biocompatibility, and is therefore widely used in a wide range of industrial fields, including aerospace, national defense, the energy industry, medicine, and consumer goods.

[0004] Titanium alloys are generally classified into pure titanium, α alloys, α-β alloys, and β alloys based on their stability at room temperature. Of these, α alloys are known to have excellent creep strength and weldability, while β alloys are known to have improved workability.

[0005] Pure titanium is cheaper than other titanium alloys in terms of cost, and has excellent formability, weldability, workability, and corrosion resistance. However, pure titanium has low strength, which limits its application. Most applications of titanium require high strength properties, which require the addition of large amounts of alloying elements, which can increase the cost.

[0006] Therefore, there is a need to develop titanium alloys made from relatively inexpensive elements that can control properties such as excellent strength, formability, weldability, workability, corrosion resistance, and biocompatibility while minimizing cost increases, and methods for manufacturing such alloys. Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a method for producing a high-strength titanium alloy using ferrochromium. In particular, the present invention provides a method for producing a high-strength titanium alloy using ferrochromium as an alloy additive, which not only reduces the production cost of the titanium alloy but also ensures strength and elongation.

[0008] Another problem to be solved by the present invention is to provide a titanium alloy having high strength together with a good elongation ratio.

[0009] The objects of the present invention are not limited to the objects mentioned above, and other objects and advantages of the present invention not mentioned above can be understood from the following description and can be more clearly understood from the examples of the present invention. Furthermore, it can be easily understood that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims. [Means for solving the problem]

[0010] In order to solve the above problems, a method for manufacturing a high-strength titanium alloy according to an embodiment of the present invention includes the steps of: (a) adding ferrochromium containing chromium (Cr), iron (Fe), silicon (Si), and carbon (C) to pure titanium (Ti); (b) melting the resultant of step (a) and cooling it to form a titanium alloy base material; and (c) hot forming the titanium alloy base material, wherein the ferrochromium is added in an amount of less than 4 wt% based on the total weight of the titanium alloy.

[0011] The present invention HighThe method for producing a high-strength titanium alloy includes the steps of: (a) adding ferrochrome containing chromium (Cr), iron (Fe), silicon (Si), and carbon (C) to pure titanium (Ti); (b) melting the result of step (a) and cooling it to form a titanium alloy base material; and (c) hot forming the titanium alloy base material, wherein the ferrochrome contains 20-35 wt% iron (Fe), 1-4 wt% silicon (Si), and 0.15 wt% or less carbon (C), with the remainder being chromium (Cr) and unavoidable impurities, and the ferrochrome is added in an amount of less than 4 wt% of the total weight of the titanium alloy. In this case, the titanium alloy produced contains 0.1 to 3.0 weight percent chromium (Cr), 0.1 to 1.0 weight percent iron (Fe), 0.01 to 0.1 weight percent silicon (Si), 0.4 weight percent or less oxygen (O), the balance being titanium (Ti) and unavoidable impurities, and has a tensile strength of 861 to 1165 MPa. do.

[0012] It is preferable to add 0.5 to 2% by weight of the ferrochromium to the total weight of the titanium alloy.

[0013] The hot forming can be carried out at a temperature of 800 to 850° C. with a forming rate of 90% or less.

[0014] In order to solve the above-mentioned problems, a high-strength titanium alloy according to an embodiment of the present invention is characterized by containing 0.1 to 3.0 wt% chromium (Cr), 0.1 to 1.0 wt% iron (Fe), 0.01 to 0.1 wt% silicon (Si), 0.4 wt% or less oxygen (O), with the remainder being titanium (Ti) and unavoidable impurities.

[0015] A high-strength titanium alloy according to a preferred embodiment of the present invention contains 0.1 to 3.0 wt% chromium (Cr), 0.1 to 1.0 wt% iron (Fe), 0.01 to 0.1 wt% silicon (Si), and 0.4 wt% or less oxygen (O), with the chromium (Cr) content being greater than the iron (Fe) content, and the remainder being titanium (Ti) and unavoidable impurities, and is characterized by having a tensile strength of 861 to 1165 MPa.

[0016] The chromium content may be 1.7 to 4 times the iron content.

[0017] The titanium alloy may have a molybdenum equivalent ([Mo]eq.) of 5 or less, as represented by the following formula 1, and a β transformation point of 840 to 930°C ([] in formula 1 represents the weight % of the component):

[0018] [Formula 1] [Mo]eq.=[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+2.5[Fe]

[0019] The titanium alloy has a yield strength of 460 to 1280 MPa and a Young's modulus of 95 to 105 GPa. do. [Effects of the Invention]

[0020] According to the method for manufacturing a high-strength titanium alloy of the present invention, low-carbon ferrochrome made of elements (Cr, Fe, Si, etc.) that are harmless to the human body is used as an additive alloy material for pure titanium (c). This not only reduces costs in terms of raw material costs and processing compared to adding individual elements such as Cr, Fe, Si, etc., but also provides advantageous effects in terms of ensuring strength and elongation.

[0021] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief explanation of the drawings]

[0022] [Figure 1a] FIG. 1 shows the phase fraction of a pure titanium (Ti-0.05O) specimen. [Figure 1b]This is a diagram showing the phase fraction of a specimen in which 4 wt% of ferrochromium was added to pure titanium (Ti-0.05O). [Figure 1c] This is a diagram showing the phase fraction of a specimen in which 0.5 wt% of ferrochromium was added to pure titanium (Ti-0.05O). [Figure 2a] FIG. 1 shows the phase fraction of a pure titanium (Ti-0.39O) specimen. [Figure 2b] This is a diagram showing the phase fraction of a specimen in which 4 wt% of ferrochromium was added to pure titanium (Ti-0.39O). [Figure 2c] This is a diagram showing the phase fraction of a specimen in which 0.5 wt% of ferrochromium was added to pure titanium (Ti-0.39O). [Figure 3a] FIG. 1 is a diagram showing the mechanical properties of specimens 1 and 3 of comparative examples and specimens 1 to 4 of examples. [Figure 3b] FIG. 1 is a diagram showing the mechanical properties of specimens 2 and 4 of the comparative examples and specimens 5 to 8 of the examples. DETAILED DESCRIPTION OF THE INVENTION

[0023] The above-mentioned objects, features, and advantages will be described in detail below, so that those skilled in the art can easily implement the technical concept of the present invention. In describing the present invention, if it is determined that a detailed description of known techniques according to the present invention would obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0024] Hereinafter, a method for producing a high-strength titanium alloy using ferrochromium according to several embodiments of the present invention and the high-strength titanium alloy will be described.

[0025] Methods for increasing the strength of pure titanium include adding alloying elements to increase strength, and reducing the size of the internal crystal grains through plastic working and heat treatment to increase strength. However, these methods increase costs because they require a separate process for refining the crystal grains after adding alloying elements. Furthermore, the method of refining the crystal grains through plastic working and heat treatment has the disadvantage that the mechanical properties of the titanium alloy produced vary significantly depending on the process, making it difficult to directly apply the process to actual production processes.

[0026] Therefore, adding alloying elements is more advantageous than refining the grain size through plastic processing and heat treatment. In particular, selecting inexpensive alloying elements for alloying is the most preferable method for minimizing cost increases and increasing strength. Furthermore, to ensure biostability, it is preferable to avoid the addition of toxic elements such as Co, Cu, Ni, and V. The titanium alloy of the present invention does not contain these elements, although they may be unavoidably included as impurities in exceptional cases.

[0027] After extensive research, the inventors have developed a method of alloying pure titanium by adding ferrochrome, which contains elements such as Fe, Cr, and Si, which are non-toxic and easily soluble in pure titanium. In particular, Si, an element contained in ferrochrome, is expected to provide nucleation sites during melting and refine the crystal grains of the melted ingot. As a result, they have developed a new Ti-Cr-Fe-Si alloy based on pure titanium.

[0028] The following describes in more detail the method for producing a high-strength titanium alloy using ferrochromium.

[0029] The method for producing a high-strength titanium alloy according to the present invention includes the steps of adding ferrochrome containing chromium (Cr), iron (Fe), silicon (Si), and carbon (C) to pure titanium (Ti), melting the pure titanium and ferrochrome and then cooling the melt to form a titanium alloy base material, and hot forming the titanium alloy base material.

[0030] Pure titanium and ferrochromium can be melted using various known methods, such as vacuum melting, electron beam melting, plasma arc melting, non-consumable electrode arc melting, or induction skull melting. Hot forming can be performed by hot rolling, hot forging, or the like. Hot forming can be performed at 800-850°C with a forming ratio of 90% or less. In the case of rolling, the forming ratio can be expressed as the reduction ratio. In the present invention, as described below, less than 4 wt% of ferrochromium is added, thereby providing the effect of preventing cracks from occurring even when forming at 800-850°C with a forming ratio of 90%.

[0031] After hot forming, various cooling methods can be used, such as water cooling, air cooling, furnace cooling, etc. The cooling method can be determined depending on whether or not there is a further hot process after hot forming. For example, if there is no further hot process, water cooling can be performed after hot forming. After hot forming, further heat treatments such as homogenization treatment, solution treatment, and aging treatment can be performed.

[0032] One feature of ferrochrome melting is that the melting temperature is significantly lower than when melting chromium, iron, silicon, etc. individually, and is similar to the melting point of titanium. This allows ferrochrome to be melted together with pure titanium at a relatively low temperature, thereby reducing the production cost of titanium alloys.

[0033] In the present invention, the amount of ferrochromium added is preferably less than 4 wt.% of the total weight of the titanium alloy. More preferably, it is 3 wt.% or less, and most preferably, it is 0.5 to 2 wt.%. The addition of ferrochromium can increase the strength compared to pure titanium. However, if the amount of ferrochromium added is 4 wt.% or more, the elongation rate will be very low, and cracks may occur.

[0034] Ferrochrome may contain 20 to 35 weight percent iron (Fe), 1 to 4 weight percent silicon (Si), and 0.15 weight percent or less carbon (C), with the remainder being chromium (Cr) and unavoidable impurities. Ferrochrome is characterized in that the Cr content is higher than the Fe content. The Cr content in ferrochrome may be 1.7 to 4 times, for example, 2 to 4 times, the Fe content.

[0035] Chromium (Cr) is a non-toxic element and a beta-phase stabilizer with a higher strength than molybdenum (Mo) in titanium alloys. Adding chromium to pure titanium can increase its strength through solid solution strengthening. However, adding too much chromium increases the likelihood of fracture during the forming process due to the formation of Laves phase (TiCr2). For example, the addition of Cr to titanium alloys such as Ti-33Zr-3Fe-2Cr alloy, Ti-33Zr-5Fe-2Cr alloy, and Ti-33Zr-7Fe-2Cr alloy is known to form Laves phase, resulting in cracking during compression testing.

[0036] Iron (Fe), like chromium (Cr), is non-toxic and a beta-phase stabilizing element with better stabilization than molybdenum. Adding iron to pure titanium can increase its strength through the solid solution strengthening effect. However, when titanium alloys containing more than 2% by weight of iron are melted, macro- or micro-segregation can be induced, and when heat-treated at a certain temperature, a very weak phase, TiFe, can form.

[0037] Silicon (Si) is a non-toxic element that forms many nucleation sites when dissolving titanium alloys, leading to refinement of crystal grains. Silicon also contributes to increasing the static strength of titanium alloys. However, if the silicon content exceeds 0.25 wt%, it can promote cracking due to the formation of brittle silicides.

[0038] When the content of ferrochromium is less than 4 wt%, the preferable ranges of the contents of chromium, iron, and silicon in the titanium alloy can be satisfied as described above.

[0039] The titanium alloy according to the present invention may contain oxygen (O) in an amount of 0.4 wt.% or less based on the total weight of the titanium alloy. Oxygen is an interstitial element that does not significantly affect corrosion resistance and is a solid-solution strengthening alloying element that strengthens the lattice. However, if the oxygen content exceeds 0.4 wt.%, twinning at low temperatures can be suppressed, resulting in a rapid decrease in impact resistance.

[0040] By using the above-described method, the present invention can provide a high-strength titanium alloy containing 0.1 to 3.0 wt% chromium (Cr), 0.1 to 1.0 wt% iron (Fe), 0.01 to 0.1 wt% silicon (Si), and 0.4 wt% or less oxygen (O), with the remainder consisting of titanium (Ti) and unavoidable impurities. The Cr, Fe, and Si contents in the high-strength titanium alloy according to the present invention are determined by the amount of ferrochromium added, and the above-described Cr, Fe, and Si contents can be satisfied by adding ferrochromium in an amount of less than 4 wt%, more preferably 3.0 wt% or less, and most preferably 0.5 to 2.0 wt%.

[0041] The high-strength titanium alloy according to the present invention may have a molybdenum equivalent ([Mo]eq.) represented by the following formula 1 of 5 or less ([ ] in formula 1 represents the weight % of the component):

[0042] [Formula 1] [Mo]eq.=[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0.67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+2.5[Fe]

[0043] The high-strength titanium alloy according to the present invention may have a β transformation point of 840 to 930°C.

[0044] Furthermore, experimental results show that the high-strength titanium alloy of the present invention 、8 Tensile strength of 61 to 1165 MPa, yield strength of 460 to 1280 MPa, and Young's modulus of 95 to 105 GPa do.

[0045] Example Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred examples of the present invention. However, these are merely preferred examples of the present invention and are not to be construed as limiting the present invention in any sense. Contents not described in the following examples can be fully inferred by those skilled in the art, and therefore, explanations thereof will be omitted.

[0046] 1. Analysis of ferrochrome The three ferrochrome specimens were analyzed as follows: EDS analysis was performed three times on three locations (left, center, and right) of each 10 mm x 10 mm specimen, and the results are shown in Table 1.

[0047] [Table 1]

[0048] All three specimens contained about 66 wt% Cr, about 31 wt% Fe, and about 3 wt% Si, and it was found that there was not much difference in the content of the elements.

[0049] The following experiment was conducted on ferrochrome specimen #1.

[0050] After removing the surface oxide layer of ferrochrome specimen #1, O, N were measured by EDS. 、C The results of the analysis of the content are shown in Table 2.

[0051] [Table 2]

[0052] Ferrochrome is classified into low-carbon, medium-carbon, and high-carbon ferrochrome depending on the carbon content, and low-carbon ferrochrome refers to a carbon content of 0.2 wt% or less or 0.15 wt% or less. In the case of ferrochrome specimen #1 analyzed above, the carbon content is about 0.1 wt% and the chromium content is about 67%, which corresponds to low-carbon ferrochrome.

[0053] The melting points of Cr, Fe, and Si are 1907°C, 1538°C, and 1414°C, respectively, but the melting point of low-carbon ferrochromium, which has a carbon content of 0.15% by weight or less, is known to be approximately 1620°C. Also, the melting point of titanium is 1668°C.

[0054] O, N, C, H, and other elements in titanium are the main elements that reduce fracture ductility and require special management. These elements in pure titanium must be controlled to the weight percent or less shown in Table 3 (there are very small differences in the allowable values ​​depending on the country). H, in particular, reduces fracture ductility even when added in small amounts, so it requires special management compared to other elements.

[0055] [Table 3]

[0056] The ferrochrome specimen #1 analyzed above is a low carbon ferrochrome and satisfies the maximum weight percentages of elements such as O, N, C, and H in Table 3.

[0057] Titanium alloy specimen manufacturing Pure titanium (Ti-0.05O and Ti-0.39O) and ferrochromium in the amounts shown in Table 4 were melted in an induction skull melting furnace to form titanium alloys, which were then cooled to produce ingots measuring 10 mm wide, 30 mm long, and 10 mm thick.

[0058] The ingots were rolled at 830°C ± 20°C at a forming ratio of about 90% as shown in Table 4, and then water-cooled to obtain Comparative Examples 1 and 2. 、 Example 1 5 and Reference Examples 1 to 3 Titanium alloy specimens were prepared using the method described above.

[0059] Table 4 shows Comparative Examples 1 and 2 、 Example 1 5 and Reference Examples 1 to 3 In the titanium alloy specimens manufactured according to the above, the Mo equivalent and the β transformation point are shown according to the ferrochromium content. 5 and Reference Examples 1 to 3 Cr, Fe, and Si contents due to the ferrochromium added in the titanium alloy specimens according to the present invention are shown.

[0060] [Table 4]

[0061] [Table 5]

[0062] Figure 1a shows the phase fraction of a pure titanium (Ti-0.05O) specimen according to Comparative Example 1. Figure 1b shows the phase fraction of a titanium alloy specimen manufactured by adding 4 wt% ferrochromium to pure titanium (Ti-0.05O). Figure 1c shows the phase fraction of a titanium alloy specimen manufactured by adding 0.5 wt% ferrochromium to pure titanium (Ti-0.05O).

[0063] The pure titanium (Ti-0.05O) used in FIGS. 1a to 1c corresponds to Grade 1 or Grade 2, which has an oxygen content of about 0.05% by weight.

[0064] Referring to Table 4 and Figure 1a, it can be seen that pure titanium (Ti-0.05O) exists in the β phase at high temperatures above about 890°C, but actually exists only in the α phase at lower temperatures.

[0065] However, referring to Table 4 and Figure 1b, in the case of a titanium alloy specimen manufactured with 4 wt% ferrochromium added, it exists in the β phase at high temperatures above about 850°C, coexists in the β and α phases at temperatures between 600 and 850°C, and exists in the α phase at temperatures below about 600°C. In particular, referring to Figure 1b, it can be seen that TiCr2 precipitates in the 600 to 650°C range during the phase transformation from the high-temperature β phase to the low-temperature α phase. If there is too much TiCr2, it may fracture during the forming process.

[0066] On the other hand, referring to FIG. 1c, in the case of the titanium alloy specimen manufactured by adding 0.5 wt% of ferrochromium, unlike FIG. 1b, almost no precipitates were formed, which can be said to be more advantageous in the forming process.

[0067] Figure 2a shows the phase fraction of a pure titanium (Ti-0.39O) specimen according to Comparative Example 2. Figure 2b shows the phase fraction of a titanium alloy specimen manufactured by adding 4 wt% ferrochromium to pure titanium (Ti-0.39O). Figure 2c shows the phase fraction of a titanium alloy specimen manufactured by adding 0.5 wt% ferrochromium to pure titanium (Ti-0.39O).

[0068] The pure titanium (Ti-0.39O) used in Figures 2a to 2c can be said to correspond to Grade 4, which has an oxygen content of approximately 0.39 wt%.

[0069] Referring to Table 4 and Figure 2a, it can be seen that pure titanium (Ti-0.39O) exists in the β phase at high temperatures above about 930°C, but actually exists only in the α phase at lower temperatures.

[0070] However, referring to Table 4 and Figure 2b, in the case of a titanium alloy specimen manufactured with 4 wt% ferrochromium added, the β phase exists at high temperatures above about 910°C, the β phase and the α phase coexist at temperatures between 600 and 910°C, and the α phase exists below 600°C. In particular, referring to Figure 2b, it can be seen that TiCr2 precipitates at about 600 to 650°C during the phase transformation from the high-temperature β phase to the low-temperature α phase.

[0071] On the other hand, referring to FIG. 2c, in the case of the titanium alloy specimen manufactured by adding 0.5 wt. % of ferrochromium, unlike FIG. 2b, it can be seen that almost no precipitates are formed.

[0072] 3a and 3b show comparative examples of specimens 1 to 4. 、 Example specimen 1 5 and Reference Samples 1-3 The mechanical properties of the specimen are shown.

[0073] The specimen according to Comparative Example 3 is a titanium alloy specimen prepared by adding 4 wt% of ferrochromium to pure titanium (Ti-0.05O), and the specimen according to Comparative Example 4 is a titanium alloy specimen prepared by adding 4 wt% of ferrochromium to pure titanium (Ti-0.39O).

[0074] The mechanical properties were determined by conducting tensile tests on each titanium alloy specimen at room temperature and at a deformation rate of 1.5 mm / min.

[0075] Comparative Example Samples 1-2 and Example Samples 1- 5 and Reference Samples 1-3 The mechanical properties of the specimens are shown in Table 6.

[0076] [Table 6]

[0077] 3a, 3b, and Table 6, it can be seen that the pure titanium specimens according to Comparative Examples 1 and 2, which do not contain ferrochromium, exhibit tensile strengths of 418 to 758 MPa and yield strengths of 352 to 672 MPa. In contrast, the titanium alloy specimens manufactured by adding 3.0 wt% or less of ferrochromium to pure titanium exhibit tensile strengths of 540 to 1370 MPa and yield strengths of 460 to 1280 MPa. In other words, it can be seen that the strength of titanium alloys manufactured by adding ferrochromium is higher than that of pure titanium. In particular, referring to Table 6, it can be seen that the titanium alloys manufactured by adding ferrochromium exhibit higher strengths than pure titanium. 1~5 In this case, it is found that the film has a tensile strength of 861 to 1165 MPa and a good elongation ratio.

[0078] Table 7 shows the results of the specimens according to Comparative Examples 1 to 4 and Examples 1 to 4. Specimens according to 5 and specimens according to reference examples 1 to 3 1 shows the measurement results of the elongation rate and the observation results of crack occurrence.

[0079] [Table 7]

[0080] Referring to Figures 3a and 3b and Table 7, when comparing Comparative Example 1, Examples 1 to 4 and Comparative Example 3, and when comparing Comparative Example 2, Examples 5 to 8 and Comparative Example 4, it is clear that the addition of ferrochromium to the pure titanium specimens tends to decrease the elongation rate.

[0081] However, in the case of Comparative Examples 3 and 4, when 4.0 wt. % of ferrochromium was added to pure titanium containing an oxygen concentration of 0.05 to 0.39 wt. %, the elongation ratio dropped sharply to 1.1 to 1.4, but it was still higher than in Examples 1 to 4. 5 and Reference Examples 1 to 3 In this case, when ferrochromium is added to pure titanium containing an oxygen concentration of 0.05 to 0.39 wt%, less than 4.0 wt%, more specifically, 3.0 wt% or less, the range of elongation is expressed as 2.2 to 16.8% without a sudden decrease in elongation. Reference examples 1~2, Example 1 2 When comparing Comparative Example 3 and Example 4, 3~5, Reference example 3When comparing Comparative Example 1 and Comparative Example 4, it can be seen that the addition of less than 4 wt. % ferrochromium does not result in a drastic decrease in the elongation rate, but the addition of 4 wt. % or more ferrochromium results in a drastic decrease in the elongation rate.

[0082] moreover, Reference Examples 1-2 and Example 1 and examples 2 , Example 3~5 and Reference example 3 When comparing the results, it can be seen that the degree of decrease in elongation is greater when the amount of ferrochromium added is 3.0 wt% than when the amount of ferrochromium added is 0.5 to 2.0 wt%. Therefore, in consideration of strength and elongation, it can be said that the amount of ferrochromium added is most preferably 0.5 to 2.0 wt%.

[0083] Also, referring to Table 7, in the case of the titanium alloy specimen according to Comparative Example 4, cracks were generated. Reference Examples 1 to 3 and Example 1 5 It can be seen that no cracks were generated in the titanium alloy specimens.

[0084] Although the present invention has been described above with reference to illustrative drawings, the present invention is not limited to the embodiments and drawings disclosed in this specification, and it is clear that various modifications can be made by those skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention are not explicitly described and explained while the embodiments of the present invention are described above, it is natural that the effects that can be predicted by the configuration should also be recognized.

Claims

1. (a) adding ferrochromium to pure titanium (Ti); (b) melting the resultant of step (a) and then cooling it to form a titanium alloy base material; (c) hot forming the titanium alloy base material; Including, The ferrochrome contains 20 to 35 wt % of iron (Fe), 1 to 4 wt % of silicon (Si), and 0.15 wt % or less of carbon (C), with the remainder being chromium (Cr) and inevitable impurities; The ferrochromium is added in an amount of less than 4% by weight based on the total weight of the titanium alloy, The titanium alloy produced contains 0.1 to 3.0 wt% of chromium (Cr), 0.1 to 1.0 wt% of iron (Fe), 0.01 to 0.1 wt% of silicon (Si), 0.4 wt% or less of oxygen (O), the balance being titanium (Ti) and unavoidable impurities, and has a tensile strength of 861 to 1165 MPa. A method for manufacturing high-strength titanium alloys.

2. The ferrochromium is added in an amount of 0.5 to 2% by weight based on the total weight of the titanium alloy. The method for producing the high-strength titanium alloy according to claim 1.

3. The hot forming is performed at 800 to 850 ° C. with a forming rate of 90% or less. The method for producing the high-strength titanium alloy according to claim 1.

4. The alloy contains 0.1 to 3.0 wt% of chromium (Cr), 0.1 to 1.0 wt% of iron (Fe), 0.01 to 0.1 wt% of silicon (Si), and 0.4 wt% or less of oxygen (O), but the chromium (Cr) content is greater than the iron (Fe) content, with the remainder being titanium (Ti) and unavoidable impurities, and has a tensile strength of 861 to 1165 MPa; Characterized in that it has a yield strength of 460 to 1280 MPa and a Young's modulus of 95 to 105 GPa; High strength titanium alloy.

5. The chromium content is 1.7 to 4 times the iron content. The high-strength titanium alloy according to claim 4.

6. The titanium alloy is characterized in that it has a molybdenum equivalent ([Mo]eq.) represented by the following formula 1 of 5 or less and a β transformation point of 840 to 930°C. The high-strength titanium alloy according to claim 4. [Formula 1] [Mo]eq. =[Mo]+0.2[Ta]+0.28[Nb]+0.4[W]+0. 67[V]+1.25[Cr]+1.25[Ni]+1.7[Mn]+1.7[Co]+ 2.5 [Fe]

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