WO2023128355A1 - High-strength, high-formability titanium alloy using molybdenum and ferrochrome and method for manufacturing same - Google Patents

Abstract

Disclosed are a high-strength, high-formability titanium alloy using molybdenum and ferrochrome and a manufacturing method therefor. In the titanium alloy manufacturing method according to the present invention, a titanium alloy base material is formed by adding ferrochrome including Cr, Fe, Si and C to an alloy or mixture of Ti and Mo, dissolving and cooling same to form a titanium alloy base material, and then hot molding the formed titanium alloy base material. At this time, addition is made of Mo in an amount of 1 to 15wt% and ferrochrome in an amount of less than 4wt%.

Description

High-strength, high-formability titanium alloy using molybdenum and ferrochrome and method for manufacturing the same

The present invention relates to titanium and methods for its production. More specifically, the present invention relates to a titanium alloy having high strength and high formability using molybdenum and ferrochrome and a manufacturing method thereof.

Due to its high strength, high corrosion resistance and high biocompatibility, titanium and its alloys are widely used in a wide range of industries such as aerospace, national defense, energy industry, medical care and consumer goods.

In general, titanium alloys are classified into pure titanium, alpha (α) alloys, alpha-beta (α-β) alloys, and beta (β) alloys based on their stable phase at room temperature. Among them, alpha alloys are known to have excellent creep strength and weldability, and beta alloys are known to increase workability.

Until now, in the case of titanium alloys, pure titanium for general industrial use and Ti-6Al-4V alloy, an alpha-beta alloy for aviation and defense, have been mainly used, and some Ti-Zr alloys that can obtain low elastic modulus and high strength in medical and consumer goods. , Ti-Nb alloy, and Ti-Mo alloy are used, and research to improve low elastic modulus and high strength is continuously conducted. However, due to limitations in the properties of these alloys, their use has not been expanded.

Pure titanium is cheaper than other titanium alloys in terms of price, and has excellent formability, weldability, workability, and corrosion resistance, but has low strength, which limits its application. Ti-6Al-4V, an alpha-beta titanium alloy, has high strength On the other hand, the price is high and all characteristics except strength tend to be inferior to pure titanium. In addition, the beta alloy can implement desired properties through the control of alloying elements, but has a disadvantage in that the price is significantly higher than that of pure titanium as well as the Ti-6Al-4V alloy. In particular, medical implants and eyeglass frames require excellent biocompatibility, low modulus of elasticity and high strength. is causing

Therefore, there is a need to develop a titanium alloy composed of relatively inexpensive elements that can control properties such as excellent strength, formability, weldability, processability, corrosion resistance, biocompatibility, and low modulus of elasticity while minimizing price increase, and a manufacturing method thereof. do.

The problem to be solved by the present invention is to provide a high-strength, high-formability titanium alloy using molybdenum and ferrochrome.

In addition, the problem to be solved by the present invention is to provide a method for manufacturing a high-strength, high-formability titanium alloy that is advantageous in terms of securing strength and elongation as well as lowering the manufacturing cost of the titanium alloy by using ferrochrome as an alloy additive.

The tasks of the present invention are not limited to the tasks mentioned above, and other tasks and advantages of the present invention that are not mentioned can be understood by the following description and will be more clearly understood by the embodiments of the present invention. will be. It will also be readily apparent that the objects and advantages of the present invention may be realized by means of the instrumentalities and combinations thereof set forth in the claims.

Titanium alloy according to an embodiment of the present invention for solving the above problems is molybdenum (Mo): 1.0 to 15.0% by weight, chromium (Cr): 0.1 to 3.0% by weight, iron (Fe): 0.1 to 1.0% by weight, silicon (Si): 0.01 to 0.1% by weight, oxygen (O): 0.4% by weight or less, characterized in that it consists of the remaining titanium (Ti) and unavoidable impurities.

A titanium alloy according to a preferred embodiment of the present invention contains molybdenum (Mo): 1.0 to 15.0% by weight, chromium (Cr): 0.1 to 1.98% by weight, iron (Fe): 0.1 to 0.93% by weight, silicon (Si): 0.01 ~0.09% by weight, oxygen (O): 0.4% by weight or less, but the content of chromium (Cr) is greater than the content of iron (Fe), and the rest is made of titanium (Ti) and unavoidable impurities, 1109 to 1510 MPa It is characterized by having a tensile strength of.

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

The titanium alloy may have a molybdenum equivalent ([Mo]eq.) of 5.5 to 20 and a beta transformation point of 670 to 815 ° C. (in Equation 1, [ ] is the weight% of the corresponding component) .

[Equation 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]

The titanium alloy may have a tensile strength of 750 to 1510 MPa, a yield strength of 545 to 1420 MPa, and a Young's modulus of 80 to 110 GPa.

A titanium alloy manufacturing method according to an embodiment of the present invention for solving the above problems is (a) an alloy or mixture of titanium (Ti) and molybdenum, chromium (Cr), iron (Fe), silicon (Si) and carbon ( C) adding a ferrochrome comprising; (b) forming a titanium alloy base material by dissolving and then cooling the product of step (a); and (c) hot-forming the titanium alloy base material, wherein 1 to 15% by weight of the molybdenum and less than 4% by weight of the ferrochrome are added based on the total weight of the titanium alloy.

A method for producing a titanium alloy according to a preferred embodiment of the present invention includes (a) an alloy or mixture of titanium (Ti) and molybdenum, including chromium (Cr), iron (Fe), silicon (Si) and carbon (C) Adding ferrochrome; (b) forming a titanium alloy base material by dissolving and then cooling the product of step (a); and (c) hot-forming the titanium alloy base material, wherein the ferrochrome is iron (Fe): 20 to 35 wt%, silicon (Si): 1 to 4 wt%, carbon (C): 0.15 wt% % or less, and is composed of the remaining chromium (Cr) and unavoidable impurities, and is characterized in that 1 to 15% by weight of the molybdenum and less than 4% by weight of the ferrochrome are added with respect to the total weight of the titanium alloy. In this case, the titanium alloy produced is molybdenum (Mo): 1.0 to 15.0 wt%, chromium (Cr): 0.1 to 1.98 wt%, iron (Fe): 0.1 to 0.93 wt%, silicon (Si): 0.01 to 0.09 wt% %, oxygen (O): contains 0.4% by weight or less, the remainder is composed of titanium (Ti) and unavoidable impurities, and may have a tensile strength of 1109 to 1510 MPa.

It is more preferable to add 0.5 to 2% by weight of the ferrochrome based on the total weight of the titanium alloy.

Oxygen (O) may be included in an amount of 0.4% by weight or less based on the total weight of the titanium alloy.

The ferrochrome may include iron (Fe): 20 to 35% by weight, silicon (Si): 1 to 4% by weight, carbon (C): 0.15% by weight or less, and may be composed of the remaining chromium (Cr) and unavoidable impurities. there is.

The hot forming may be performed at a molding rate of up to 90% at 800 to 850 °C.

According to the high-strength, high-formability titanium alloy manufacturing method according to the present invention, low-carbon ferrochrome composed of elements harmless to the human body (Cr, Fe, Si, etc.) Compared to adding individual elements such as , Si, etc., costs can be lowered in terms of raw material prices and processes.

In addition, the high-strength, high-formability titanium alloy according to the present invention can provide excellent formability as well as excellent strength through control of ferrochrome content.

In addition to the effects described above, specific effects of the present invention will be described together while explaining specific details for carrying out the present invention.

Figure 1a shows the phase fraction of a specimen in which 5% by weight of molybdenum was added to titanium.

Figure 1b shows the phase fraction of a specimen in which 5% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium.

Figure 1c shows the phase fraction of a specimen in which 5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

Figure 2a shows the phase fraction of the specimen in which 9.5% by weight of molybdenum was added to titanium.

Figure 2b shows the phase fraction of the specimen in which 9.5% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium.

Figure 2c shows the phase fraction of the specimen in which 9.5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

Figure 3a shows the phase fraction of the specimen in which 15% by weight of molybdenum was added to titanium.

Figure 3b shows the phase fraction of the specimen in which 15% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium.

Figure 3c shows the phase fraction of the specimen in which 15% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

Figure 4a shows the mechanical properties of Comparative Example specimens 1 and 4 and Example specimens 1 to 4.

Figure 4b shows the mechanical properties of Comparative Example specimens 2 and 5 and Example specimens 5 to 8.

Figure 4c shows the mechanical properties of Comparative Example specimens 3 and 6 and Example specimens 9 to 12.

The above objects, features and advantages will be described in detail below, and accordingly, those skilled in the art will be able to easily implement the technical spirit of the present invention. In describing the present invention, if it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a high-strength, high-formability titanium alloy using molybdenum and ferrochrome according to some embodiments of the present invention and a manufacturing method thereof will be described.

As a method of increasing the strength of pure titanium, there are a method of increasing the strength by adding alloying elements and a method of increasing the strength by reducing the internal crystal grains through plastic working and heat treatment. However, this method causes an increase in price because an alloying element is added and a separate crystal grain refinement process is added. In addition, in the case of the method of miniaturizing crystal grains through plastic working and heat treatment, the mechanical properties of the titanium alloy produced according to the process change greatly, and the process is difficult to apply directly to the actual production process. there is.

Therefore, it can be seen that the method of adding an alloying element is more advantageous than the method of miniaturizing crystal grains through plastic working and heat treatment. In particular, alloying by selecting inexpensive alloying elements can be seen as the most desirable method for minimizing price increase and increasing strength. Furthermore, in order to ensure biostability, it is preferable not to add toxic elements such as Co, Cu, Ni, V, etc., and the titanium alloy according to the present invention does not contain these elements, and as an exception, they are inevitably included as impurities. can be

As a result of long-term research, the present inventors selected inexpensive and non-toxic Mo among the elements (Mo, V, Nb, etc.) Mo alloy was selected as the base, and Fe and Cr were selected as non-toxic alloy elements that have a greater effect on Mo equivalent (Mo equivalent greater than 1) and are relatively inexpensive and non-toxic. In addition, alloying method by adding ferrochrome containing Fe, Cr, Si, etc. has been developed. In particular, in the case of Si, which is an element included in ferrochrome, it is possible to additionally expect a feature of refining the crystal grains of the melted ingot by providing a nucleation site during melting. Through this, the present inventors developed a new Ti-Mo-Cr-Fe-Si alloy based on a titanium-moly (Ti-Mo) alloy.

Hereinafter, a method for manufacturing a high-strength titanium alloy using molybdenum and ferrochrome will be described in more detail.

In the method for manufacturing a high-strength titanium alloy according to the present invention, ferrochrome containing chromium (Cr), iron (Fe), silicon (Si), and carbon (C) is added to an alloy or mixture of titanium (Ti) and molybdenum (Mo). and forming a titanium alloy base material by dissolving titanium and ferrochrome and then cooling them, and hot forming the titanium alloy base material.

For the melting of titanium, molybdenum, and ferrochrome, various known methods such as vacuum melting, electron beam melting, plasma arc melting, non-consumable electrode arc melting, or induction skull melting may be used. Hot forming may be performed by hot rolling, hot forging, or the like. Hot forming may be performed at a forming ratio of 90% or less at 800 to 850 °C. The forming rate can be expressed as a reduction rate in the case of rolling. In the case of the present invention, as described below, 1 to 15% by weight of molybdenum and less than 4% by weight of ferrochrome are added, and as a result, no cracks occur even when molding is performed at a molding rate of 90% at 800 to 850 ° C. can provide.

For cooling after hot forming, various methods such as water cooling, air cooling, and furnace cooling may be used. The cooling method may be determined according to the presence or absence of an additional hot process after hot forming. For example, if there is no additional hot process, water cooling may be performed after hot forming. After hot forming, heat treatment such as homogenization treatment, solution treatment, and aging treatment may be additionally performed.

One characteristic of the dissolution of ferrochrome is that the temperature when dissolving ferrochrome is significantly lower than when chromium, iron, silicon, etc. are individually dissolved, and is similar to the melting point of titanium. Through this, ferrochrome can be melted together with titanium at a relatively low temperature, and accordingly, the cost of manufacturing a titanium alloy can be reduced.

In the present invention, it is preferable that the addition amount of ferrochrome is less than 4% by weight based on the total weight of the titanium alloy. More preferably, it is 3% by weight or less, and most preferably 0.5 to 2% by weight. When ferrochrome is added, strength can be increased compared to titanium alloys without ferrochrome. However, when the addition amount of ferrochrome is 4% by weight or more, the elongation is very low and there is a risk of cracking.

Ferrochrome includes iron (Fe): 20 to 35% by weight, silicon (Si): 1 to 4% by weight, carbon (C): 0.15% by weight or less, and may be composed of the remaining chromium (Cr) and unavoidable impurities. . A characteristic of ferrochrome is that the Cr content is much greater than the Fe content. In ferrochrome, the Cr content can be 1.7-4 times the Fe content, for example 2-4 times.

When the content of ferrochrome is less than 4% by weight, the titanium alloy may satisfy the preferred content ranges of chromium, iron, and silicon as described above.

Through the above method, the present invention molybdenum (Mo): 1.0 to 15.0% by weight, chromium (Cr): 0.1 to 3.0% by weight, iron (Fe): 0.1 to 1.0% by weight, silicon (Si): 0.01 to 0.01% by weight 0.1% by weight, oxygen (O): 0.4% by weight or less, and the titanium alloy characterized by consisting of the remaining titanium (Ti) and unavoidable impurities can be provided. More preferably, the present invention contains molybdenum (Mo): 1.0 to 15.0% by weight, chromium (Cr): 0.1 to 1.98% by weight, iron (Fe): 0.1 to 0.93% by weight, silicon (Si): 0.01 to 0.09% by weight, Oxygen (O): It is possible to provide a titanium alloy comprising 0.4% by weight or less, but the content of chromium (Cr) is greater than the content of iron (Fe), and the remainder is composed of titanium (Ti) and unavoidable impurities. .

Molybdenum (Mo) is a non-toxic beta-phase stabilizing element. Molybdenum serves to increase the strength due to the solid solution strengthening effect. However, when molybdenum is excessively added in excess of 15% by weight, there is a problem in greatly increasing the modulus of elasticity of the alloy.

Chromium (Cr) is a non-toxic element and is a higher beta phase stabilizing element than molybdenum (Mo) in titanium alloys. When chromium is added to titanium, its strength can be increased due to the solid solution strengthening effect. For this effect, chromium needs to be added in an amount of 0.1% by weight or more. However, if chromium is added in excess of 3.0% by weight, there is a high possibility of breakage in the molding process due to the formation of the Laves Phase (TiCr ₂ ) phase. Therefore, the content of chromium is preferably 3.0% by weight or less, more preferably 1.98% by weight or less.

Iron (Fe) is non-toxic like chromium (Cr) and is a beta-phase stabilizing element higher than molybdenum. When iron is added to titanium, its strength can be increased due to the solid solution strengthening effect. For this effect iron needs to be added at least 0.1% by weight. However, when dissolving a titanium alloy in which iron is added in an amount exceeding 1.0% by weight, macro or micro segregation may be induced, and when heat treated at a certain temperature, a TiFe phase, which is a very fragile phase, may be formed. Therefore, the content of iron is preferably 1.0% by weight or less, more preferably 0.9% by weight or less.

Silicon (Si) is a non-toxic element, and forms many nucleation sites when titanium alloy is melted to induce crystal grain refinement. Silicon also contributes to increasing the static strength of titanium alloys. For this effect, silicon needs to be added at least 0.01% by weight. However, when the content of silicon exceeds 0.1% by weight, crack generation may be promoted due to formation of brittle silicide. Therefore, the content of silicon is preferably 0.1% by weight or less, more preferably 0.09% by weight or less.

In the titanium alloy according to the present invention, the content of Cr, Fe and Si is determined according to the addition amount of ferrochrome, and the addition amount of ferrochrome is less than 4% by weight, more preferably 3.0% by weight or less, and most preferably 0.5 to 2.0% by weight. Optionally, the above Cr, Fe and Si contents may be satisfied.

In the titanium alloy according to the present invention, oxygen (O) may be included in an amount of 0.4% by weight or less based on the total weight of the titanium alloy. Oxygen is an interstitial element and is a solid solution strengthening alloying element that strengthens the lattice without significantly affecting corrosion resistance. However, when oxygen is excessively included in excess of 0.4% by weight, impact resistance can be rapidly reduced by suppressing twin deformation at low temperatures.

As can be seen in the examples to be described later, the titanium alloy according to the present invention may have a molybdenum equivalent ([Mo]eq.) of 5.5 to 20 represented by Equation 1 below ([ ] in Equation 1 is the corresponding component % by weight of).

[Equation 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]

In addition, the high-strength titanium alloy according to the present invention may have a beta transformation point of 670 to 815 °C.

Furthermore, as a result of the experiment, the high-strength titanium alloy according to the present invention has a tensile strength of 750 to 1510 MPa, and more preferably a tensile strength of 1109 to 1510 MPa, a yield strength of 545 to 1420 MPa, and It may have a Young's modulus of 80 to 110 GPa.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention by this in any sense. Details not described in the following embodiments can be sufficiently technically inferred by those skilled in the art, so description thereof will be omitted.

1. Ferrochrome Assay

Component analysis was performed on the three ferrochrome specimens as follows. EDS analysis was performed three times for each of the three positions (Left, Center, Right) of each specimen of 10 mm × 10 mm size, and the results are shown in Table 1.

[Table 1] (Unit: % by weight)

All three specimens contained about 66% by weight of Cr, about 31% of Fe, and about 3% by weight of Si, and it can be seen that the difference in content of the components is not large.

Hereinafter, experiments were conducted on ferrochrome specimen #1.

After removing the surface oxide layer of ferrochrome specimen #1, the results of analyzing the contents of O, N, H, and C by EDS are shown in Table 2.

[Table 2]

Ferrochrome is classified into low-carbon ferrochrome, medium-carbon ferrochrome, and high-carbon ferrochrome according to the carbon content. Among them, low-carbon ferrochrome means that the carbon content is 0.2% by weight or less or 0.15% by weight or less. In the case of the previously analyzed ferrochrome specimen #1, the carbon content was about 0.1% by weight and the chromium content was about 67%, corresponding to low-carbon ferrochrome.

The melting points of Cr, Fe, and Si are 1907°C, 1538°C, and 1414°C, respectively, but the melting point of low-carbon ferrochrome having a carbon content of 0.15% by weight or less is known to be about 1620°C. Also, the melting point of titanium is 1668°C.

In titanium, O, N, C, H, etc. are major elements that reduce fracture ductility and require special management. In titanium alloys, these elements must be controlled at less than the weight % shown in Table 3 (there is a very small difference in the permissible limit by country). In particular, since H deteriorates fracture ductility even when a small amount is added, special management is required compared to other elements.

[Table 3]

In the case of the previously analyzed ferrochrome specimen #1, it is a low-carbon ferrochrome and satisfies the maximum weight % or less for elements such as O, N, C, and H in Table 3.

Preparation of titanium alloy specimens

Titanium (Ti-0.02 O) and molybdenum and ferrochrome of the contents shown in Table 4 were melted in an induction skull melting furnace to form a titanium alloy, and then cooled to prepare ingots having a width of 10 mm × a length of 30 mm × a thickness of 10 mm.

Ingots were molded at 830° C.±20° C. at a forming ratio of about 90% shown in Table 4 and then cooled with water to prepare titanium alloy specimens according to Comparative Examples 1 to 3 and Examples 1 to 12.

Table 4 shows the Mo equivalent and beta transformation point according to the ferrochrome content in the titanium alloy specimens prepared according to Comparative Examples 1 to 3 and Examples 1 to 12. And, Table 5 shows the contents of Cr, Fe, and Si according to the ferrochrome added in the titanium alloy specimens according to Examples 1 to 12.

[Table 4]

[Table 5]

Figure 1a shows the phase fraction of a specimen in which 5% by weight of molybdenum was added to titanium. Figure 1b shows the phase fraction of a specimen in which 5% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium. Figure 1c shows the phase fraction of a specimen in which 5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

1a to 1c, in the case of specimens in which 5% by weight of molybdenum was added to titanium and specimens in which 5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium, the TiCr ₂ precipitation phase was hardly shown. On the other hand, in the case of the specimen in which 5 wt% of molybdenum and 4.0 wt% of ferrochrome were added to titanium, it can be seen that about 5.63 wt% of TiCr ₂ precipitated phase was exhibited. As described above, if the TiCr ₂ is excessive, there is a possibility of breakage in the molding process. Therefore, ferrochrome needs to be added in an amount of less than 4.0% by weight, more preferably 3.0% by weight or less, and still more preferably 0.5 to 2.0% by weight. .

Figure 2a shows the phase fraction of the specimen in which 9.5% by weight of molybdenum was added to titanium. Figure 2b shows the phase fraction of the specimen in which 9.5% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium. Figure 2c shows the phase fraction of the specimen in which 9.5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

Referring to FIGS. 2a to 2c, in the case of specimens in which 9.5% by weight of molybdenum was added to titanium and specimens in which 9.5% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium, the TiCr2 precipitation phase was hardly shown. , in the case of the specimen in which 9.5 wt% of molybdenum and 4.0 wt% of ferrochrome were added to titanium, it can be seen that about 5.63 wt% of TiCr ₂ precipitated phase was exhibited.

Figure 3a shows the phase fraction of the specimen in which 15% by weight of molybdenum was added to titanium. Figure 3b shows the phase fraction of the specimen in which 15% by weight of molybdenum and 4.0% by weight of ferrochrome were added to titanium. Figure 3c shows the phase fraction of the specimen in which 15% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium.

3a to 3c, in the case of specimens in which 15% by weight of molybdenum was added to titanium and specimens in which 15% by weight of molybdenum and 0.5% by weight of ferrochrome were added to titanium, the TiCr ₂ precipitation phase was hardly shown. On the other hand, in the case of the specimen in which 15 wt% of molybdenum and 4.0 wt% of ferrochrome were added to titanium, it can be seen that about 5.63 wt% of TiCr ₂ precipitated phase was exhibited.

4a to 4c show the mechanical properties of Comparative Samples 1 to 6 and Example Samples 1 to 12. Specifically, FIG. 4a shows the mechanical properties of Comparative Samples 1 and 4 and Example Samples 1 to 4 having a molybdenum content of 5.0% by weight, and FIG. 4B shows Comparative Samples 2 and 5 having a molybdenum content of 9.5% by weight. and Example specimens 5 to 8, and FIG. 4c shows the mechanical properties of Comparative Example specimens 3 and 6 and Example specimens 9 to 12 having a molybdenum content of 15% by weight.

The specimen according to Comparative Example 4 is a titanium alloy specimen prepared by adding 5.0% by weight of molybdenum and 4% by weight of ferrochrome, and the specimen according to Comparative Example 5 is a titanium alloy specimen prepared by adding 9.5% by weight of molybdenum and 4% by weight of ferrochrome. It is an alloy specimen and is a titanium alloy specimen prepared by adding 15% by weight of molybdenum and 4% by weight of ferrochrome.

The mechanical properties were obtained by performing a tensile test on each titanium alloy specimen at a strain rate of 1.5 mm/min at room temperature.

Table 6 shows the mechanical properties of Comparative Samples 1 to 3 and Example Samples 1 to 12.

[Table 6]

Referring to Table 6, it can be seen that the titanium-molybdenum alloy specimens according to Comparative Examples 1 to 3 to which ferrochrome was not added exhibited tensile strength of 786 to 1064 MPa and yield strength of 712 to 855 MPa. In contrast, in the case of titanium alloy specimens prepared by adding 3.0% by weight or less of ferrochrome to the titanium-molybdenum alloy, it can be seen that the tensile strength increased to a maximum of 1510 MPa and the yield strength to a maximum of 1420 MPa. That is, in the case of the titanium alloy prepared by adding ferrochrome, it can be seen that the strength is increased compared to the titanium alloy without it.

In particular, referring to Table 6, in the case of Examples 2-4, it can be seen that it has a good elongation while having a tensile strength of 1109 to 1510 MPa.

Table 7 shows the elongation measurement results and crack observation results of the specimens according to Comparative Examples 4 to 6 and the specimens according to Examples 1 to 12.

[Table 7]

Referring to Figures 4a to 4c and Table 7, in the case of Comparative Examples 4 to 6, when ferrochrome was added at 4.0% by weight in the titanium alloy in which 5 to 15% by weight of molybdenum was added to titanium, the elongation was 1.4 to 2.3%. It can be seen that the elongation rate decreased rapidly. On the other hand, in the case of Examples 1 to 12, when less than 4.0% by weight of ferrochrome was added to a titanium alloy in which 5 to 15% by weight of molybdenum was added to titanium, the elongation range was 2.4 to 49% without a rapid decrease in elongation. can see. Furthermore, when the amount of ferrochrome added is 0.5 to 2.0% by weight, higher elongation is exhibited. Considering both strength and elongation, it is most preferable that the amount of ferrochrome added is 0.5 to 2.0% by weight.

In addition, referring to Table 7, it can be seen that cracks occurred in the titanium alloy specimens according to Comparative Examples 4 and 6, but no cracks occurred in the titanium alloy specimens according to Examples 1 to 12.

As described above, the present invention has been described with reference to the drawings illustrated, but the present invention is not limited by the embodiments and drawings disclosed in this specification, and various modifications are made by those skilled in the art within the scope of the technical idea of the present invention. It is obvious that variations can be made. In addition, although the operational effects according to the configuration of the present invention have not been explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be recognized.

Claims (8)

1. Molybdenum (Mo): 1.0 to 15.0% by weight, Chromium (Cr): 0.1 to 1.98% by weight, Iron (Fe): 0.1 to 0.93% by weight, Silicon (Si): 0.01 to 0.09% by weight, Oxygen (O): 0.4 Including the weight percent or less, but the content of chromium (Cr) is greater than the content of iron (Fe), consisting of the remaining titanium (Ti) and unavoidable impurities,

   A titanium alloy characterized by having a tensile strength of 1109 to 1510 MPa.
2. According to claim 1,

   Titanium alloy, characterized in that the content of the chromium is 1.7-4 times the content of iron.
3. According to claim 1,

   The titanium alloy has a molybdenum equivalent ([Mo]eq.) represented by Equation 1 below of 5.5 to 20 and a beta transformation point of 670 to 815 ° C.

   [Equation 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]
4. According to claim 1,

   The titanium alloy has a yield strength of 545 to 1420 MPa and a Young's modulus of 80 to 110 GPa.
5. (a) adding ferrochrome containing chromium (Cr), iron (Fe), silicon (Si) and carbon (C) to an alloy or mixture of titanium (Ti) and molybdenum;

   (b) forming a titanium alloy base material by dissolving and then cooling the product of step (a); and

   (c) hot forming the titanium alloy base material; including,

   The ferrochrome includes iron (Fe): 20 to 35% by weight, silicon (Si): 1 to 4% by weight, carbon (C): 0.15% by weight or less, and is composed of the remaining chromium (Cr) and unavoidable impurities, ,

   1 to 15% by weight of the molybdenum and less than 4% by weight of the ferrochrome, based on the total weight of the titanium alloy.
6. According to claim 5,

   Titanium alloy manufacturing method, characterized in that the addition of 0.5 to 2% by weight of the ferrochrome relative to the total weight of the titanium alloy.
7. According to claim 5,

   The hot forming is a titanium alloy manufacturing method, characterized in that carried out at a forming rate of 90% or less at 800 ~ 850 ℃.
8. According to claim 5,

   The titanium alloy produced contains molybdenum (Mo): 1.0 to 15.0 wt%, chromium (Cr): 0.1 to 1.98 wt%, iron (Fe): 0.1 to 0.93 wt%, silicon (Si): 0.01 to 0.09 wt%, oxygen (O): A method for producing a titanium alloy, characterized in that it contains 0.4% by weight or less, the remainder is made of titanium (Ti) and unavoidable impurities, and has a tensile strength of 1109 to 1510 MPa.

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