KR102447313B1 - Commercially pure titanium having high strength and high ductility and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a commercially pure titanium alloy that satisfies both high strength and high ductility at the same time and a method for manufacturing the same, wherein titanium according to an embodiment of the present invention is in weight%, oxygen (O): 0.35% by weight or less, hydrogen ( H): 0.015 wt % or less, iron (Fe): 0.3 wt % or less, carbon (C): 0.1 wt % or less, and the remainder titanium (Ti). (excluding 0); is characterized.

Description

Pure titanium having high strength and high ductility and manufacturing method thereof

The present invention relates to titanium having high strength and high ductility and a method for manufacturing the same, and more particularly, to titanium having high strength and high ductility by introducing a new microstructure into commercially pure titanium to achieve excellent tensile properties and It relates to a manufacturing method thereof.

Titanium alloy has a low density, high strength, excellent specific strength (specific strength) and biocompatibility (biocompatibility) is used in many industrial fields.

Among them, commercially pure titanium (hereinafter, titanium or pure titanium means commercially pure titanium) has excellent corrosion resistance and biocompatibility. However, since pure titanium has a low yield strength due to the characteristics of a hexagonal close packed (HCP) single phase, industrial applications have been limited.

In order to increase the strength of the pure titanium, a grain refinement method has been mainly applied in the prior art.

As one of the grain refining methods, deformation twin by deformation is used as the main mechanism for refining the grain matrix in various metals.

The deformed twin forms a high-angle twin boundary that behaves similarly to a grain boundary, thereby dividing the grain matrix. The above twin structure includes numerous high-angle twin boundaries, leading to significant refinement of the grain matrix.

As a result, in face centered cubic metals, an ultra-fine microstructure with an average grain size of less than 1 μm can be obtained through twin organic grain refinement, which significantly increases the strength of FCC metals. can increase

On the other hand, it is known that the twin microstructure in hexagonal metals such as titanium is not effective for grain refinement because it consists of only a few thick (tens to hundreds of μm) twins in the grains.

Therefore, since the ultrafine grain microstructure is not easily formed in pure titanium, it is known that only a very limited increase in strength occurs in pure titanium.

On the other hand, it is known that the ultrafine grain microstructure in pure titanium is possible only by severe plastic deformation such as ECAP (equi channel angular procedure). Processing methods such as rolling and extrusion, which have been widely used in the metal field, have not been able to introduce ultra-fine grains into commercially pure titanium.

However, the conventional plastic processing method has a problem in that it is not practical because it can make only a small specimen having a limited shape. In particular, a processing method that is difficult to make a shape capable of forming a structure by itself, such as a limited shape of a workpiece or a plate material, has a fundamental problem in that its range of use is very limited.

On the other hand, it is known that in general metals containing titanium or alloys thereof, ductility and/or toughness decrease when strength increases. In other words, it is common for strength and ductility and/or toughness to have a trade-off relationship with each other.

An object of the present invention is to provide a method for manufacturing titanium capable of forming an ultrafine grain microstructure by introducing numerous thin fine twins even in commercially pure titanium grains. Through this, it is intended to provide pure titanium with remarkably improved yield strength without significant reduction in elongation.

It is an object of the present invention to provide a high-strength and high-ductility titanium having a novel microstructure and a method for manufacturing the same.

Specifically, an object of the present invention is to provide a method for manufacturing high-strength and highly ductile titanium capable of introducing an ultra-fine grain microstructure into pure titanium, and by having the microstructure, it can have high strength and high ductility properties that were not previously achieved at the same time. to provide titanium.

More specifically, an object of the present invention is to provide high-strength and high-ductility titanium having an ultra-fine grain microstructure through twin organic grain refinement and at the same time controlling dislocation density.

Another object of the present invention is to provide a method for manufacturing titanium capable of achieving high strength and high ductility only by a general rolling process without performing a separate plasticizing process.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention not mentioned may be understood by the following description, and will be more clearly understood by the examples of the present invention. It will also be readily apparent that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the appended claims.

Titanium according to an embodiment of the present invention for achieving the above object may be commercially pure titanium having an average thickness of twin bands of 1 μm or less (excluding 0).

Titanium according to another embodiment of the present invention in weight %, oxygen (O): 0.35 wt% or less, hydrogen (H): 0.015 wt% or less, iron (Fe): 0.3 wt% or less, carbon (C): 0.1 It may be titanium, characterized in that the component and composition range are weight % or less and the balance is titanium (Ti); and the average thickness of the twin band is 1 μm or less (excluding 0).

Preferably, the average grain size of the titanium may be 5.2㎛ or less (excluding 0).

Preferably, the average number of twin bands per crystal grain may be 19 or more.

Preferably, the dislocation density of the titanium may be 4.5*10 ¹⁵ /m 2 or less.

Preferably, the tensile property value defined by the yield strength * elongation of the titanium may be 10.5 MPa% or more.

More preferably, the tensile property value defined by the yield strength * elongation of the titanium may be 12.5 MPa% or more.

The manufacturing method of titanium according to another embodiment of the present invention comprises the steps of preparing a commercially pure titanium base material; It may include; rolling the alloy base material in the range of 20% to 40% of the rolling reduction and the temperature in the range of -196°C to -10°C.

Preferably, the titanium base material in weight %, in weight %, oxygen (O): 0.35 wt % or less, hydrogen (H): 0.015 wt % or less, iron (Fe): 0.3 wt % or less, carbon (C) : 0.1 wt% or less and the remainder may have a component and composition range of titanium (Ti).

Preferably, the titanium base material may have an annealed microstructure after rolling.

More preferably, the titanium base material may have a texture in which the c-axis is aligned in the thickness direction.

According to the present invention, it is possible to implement a method of manufacturing titanium having high strength and elongation even with a conventional general rolling process.

In addition, according to the present invention, there is an advantage in that it is possible to provide titanium and a method for manufacturing the same, in which grain refinement and dislocation density control are possible due to twin bands.

Furthermore, according to the present invention, titanium having a very high tensile property value that does not exist in the prior art and a method for manufacturing the same can be implemented.

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

1 shows the microstructure (a) and the texture (b) of the grade 2 titanium initial material used in an embodiment of the present invention.
2 is a photograph of observing the microstructure of titanium rolled at room temperature under the conditions of 20% to 60% of the rolling reduction.
3 is a photograph of observing the microstructure of cryogenically rolled titanium under the conditions of 20% to 60% of the rolling reduction.
Figure 4 shows the tensile properties of the titanium rolled at room temperature and the cryogenically rolled titanium under the condition of 30% of the rolling reduction.
5 is a stress-strain curve of titanium (a) and cryogenically rolled titanium (b) rolled at room temperature under various reduction conditions of 10% to 60%.
6 shows the relationship between elongation versus yield strength of conventional titanium, room temperature rolled titanium and cryogenically rolled titanium.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. The present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms.

Only this embodiment is provided so that the disclosure of the present invention is complete, and to fully inform those of ordinary skill in the art to which the present invention belongs, the scope of the invention, the present invention is defined by the scope of the claims it will only be

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification. Further, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

In describing the components of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the nature, order, order, or number of the elements are not limited by the terms. When it is described that a component is “connected”, “coupled” or “connected” to another component, the component may be directly connected or connected to the other component, but other components may be interposed between each component. It should be understood that each component may be “interposed” or “connected,” “coupled,” or “connected” through another component.

In addition, the average grain size in the present invention is determined by a high angle twin boundary using a method or program for measuring grain size as well as grains separated by a traditional high angle grain boundary. It means the average size of all grains including the distinct grains.

In addition, as described above, titanium, pure titanium, or commercially pure titanium in the present invention means commercially pure titanium.

Hereinafter, with reference to the drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them.

Titanium is a polymorphous element having two crystal structures: a high-temperature beta phase with a body centered cubic (BCC) structure and a low-temperature alpha phase with a hexagonal close packed (HCP) structure. .

The temperature at which the isotropic transformation occurs is referred to as a beta transus temperature, and titanium has a hexagonal closed packing (HCP) crystal structure at a temperature lower than the beta transus temperature.

The so-called commercially pure titanium means titanium without artificially adding a separate alloying element to the titanium. However, even pure titanium contains several representative impurities due to thermodynamic reasons and manufacturing fanciful reasons such as refining, and the components and composition ranges of the impurities are determined by standards such as ASTM (American Society for Testing Materials). stipulated

Components and composition ranges of titanium having high strength and high ductility according to embodiments of the present invention are as follows.

Oxygen (O): 0.35% by weight or less,

Hydrogen (H): 0.015% by weight or less,

Iron (Fe): 0.3 wt% or less;

Carbon (C): 0.1% by weight or less and the balance titanium.

The components and composition ranges in the present invention are defined as grade 3 in ASTM. In other words, the components and composition ranges of titanium having high strength and high ductility according to embodiments of the present invention include titanium of grade 3 or less of ASTM, that is, grades 1 to 3 of titanium.

In particular, the content of oxygen has a great influence on the ultrafine grain microstructure of titanium having high strength and high ductility of the present invention. This is because, when the oxygen content is higher than 0.35%, the activation of twin crystals is inhibited, thereby making it difficult to form an ultrafine grain microstructure.

Next, a method for manufacturing titanium having high strength and high ductility used in Examples of the present invention will be described.

In the present invention, the microstructure in pure titanium deformed (workability) at a cryogenic temperature of about -196°C (77K) was controlled.

In the present invention, numerous thin and individual twins are formed within the grains. This enabled very strong twining induced grain refinement.

The pure titanium processed by the production method of the present invention had an ultrafine grain microstructure. The ultrafine grain microstructure significantly increased the strength of pure titanium, and surprisingly did not cause a significant decrease in ductility despite the dramatic increase in strength. The remarkable improvement in mechanical strength is due to the increased resistance to necking instability due to the twin structure and the relatively small number of dislocations in the processed titanium. The present invention provides a new industrial method for obtaining excellent tensile properties from pure titanium.

The present invention confirmed that a twin microstructure was formed in pure titanium by the cryogenic processing, thereby forming an ultrafine grain microstructure. The cryogenically processed titanium has very improved yield strength with excellent elongation, and both yield strength and elongation were superior to cryogenically processed titanium than to processed titanium at room temperature.

In the present invention, a titanium plate having a thickness of 4 mm that has been annealed after hot rolling is used as an initial material and subjected to cryogenic processing. The component and composition range of the titanium plate was measured as weight % (wt. %, hereinafter referred to as %) oxygen 0.21%, carbon 0.01%, nitrogen 0.01%, and the remainder titanium (Ti). The initial material had an equiaxed grain microstructure without twins, the average grain size was 31 μm, and it was measured to have a typical rolled texture structure.

In the manufacturing method of the present invention, the maximum value of the total reduction ratio (thickness reduction rate) after cryogenic processing (specifically, cryogenic rolling) and room temperature processing was set to 40%. This is because, if the thickness reduction rate exceeds 40%, the twin activity rapidly decreases.

The initial material in the present invention was immersed in liquid nitrogen at -196°C (77K) immediately before each pass during rolling for cryogenic rolling. When the initial material is immersed in liquid nitrogen, liquid nitrogen is boiled, and when the temperature of the initial material is cooled to the temperature of liquid nitrogen, the boiling of liquid nitrogen is stopped. The boiling phenomenon of liquid nitrogen as described above can ensure that the temperature of the initial material is cooled to the temperature of liquid nitrogen.

However, it was measured that the temperature of the initial material cooled with liquid nitrogen slightly increased due to the surrounding environment and friction during cryogenic rolling. However, it was confirmed that the temperature of the specimen during cryogenic rolling did not become higher than -10°C in all examples.

The microstructure was investigated using electron backscatter diffraction (EBSD) measurements. X-ray diffraction (XRD) peaks were measured using a θ-2θ diffractometer using monochromatic CuKα radiation. Tensile properties were measured using INSTRON equipment at room temperature and strain rate of 10-3/s. The tensile specimens were machined to a gauge length of 25 mm, a width of 6 mm, and a thickness of 2 mm according to the ASTM-E8 standard. Samples were collected and processed along the rolling direction of the plate-shaped specimen. The necking behavior during the tensile test was quantified using a digital image correction (DIC) with Aramis system.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and cannot be construed as limiting the present invention in any sense.

Content not described herein will be omitted because it can be technically inferred by those skilled in the art.

1 shows the microstructure (a) and the texture (b) of a grade 2 (grade 2) titanium initial material used in an embodiment of the present invention.

As described above, as the initial material of the present invention, titanium in the form of a plate material that was annealed after rolling was used. Accordingly, as shown in (a) of FIG. 1 , the initial material has a microstructure composed of equiaxed grains. Also, as shown in (b) of FIG. 1 , it can be seen that the initial material has a texture in which the c-axis of titanium having a hexagonal tight lattice is aligned in the thickness direction of the plate material.

The c-axis is the direction in which slip is difficult to occur in the hexagonal tight lattice. Therefore, if the c-axis has a microstructure aligned in the thickness direction of the plate as the initial material, the occurrence of slip during subsequent rolling is suppressed and the generation of twins becomes easier. As a result, activation of twin is further promoted, which makes it advantageous to acquire ultrafine grains by twin, and furthermore, it is advantageous in delaying work softening by preventing an increase in dislocation density due to suppression of slip.

2 is a photograph of observing the microstructure of titanium rolled at room temperature under the conditions of 20% to 60% of the rolling reduction.

In titanium rolled at room temperature, {11-22} twins were first formed in most grains, and {10-12} twins were activated in the previously formed {11-22} twins. These two twins are the most common twin systems in titanium.

On the other hand, it can be seen from FIG. 2 that, in the titanium rolled at room temperature, the coarse long crystal grains without twin bands were almost maintained in the section where the rolling reduction was 20 to 60%. In the case of crystal grains including twin bands, the thickness was maintained at a level of several μm regardless of the reduction amount, and as a result, the crystal grains in which twins occurred did not show a high grain segmentation effect.

In addition, in the case of titanium rolled at room temperature, the total amount of twins did not increase even when the rolling reduction was increased from 20% to 60%, and it was found to be substantially the same or similar.

The result of the microstructure of the titanium rolled at room temperature as described above means that the room temperature rolling is not effective in realizing the ultrafine grain microstructure of titanium.

3 is a photograph of observing the microstructure of cryogenically rolled titanium under the conditions of 20% to 60% of the rolling reduction.

First, it was confirmed that the cryogenically rolled titanium has the same twin system as the room temperature rolled titanium.

On the other hand, twin crystals in cryogenically rolled titanium are significantly different from twins in room temperature rolled titanium in many ways.

First, in cryogenically rolled titanium, a narrow and uniform twin crystal was formed in all grains even with a small deformation amount of 20%. In particular, it was confirmed that the twin bandwidth (0.4-1.5 μm) in the cryogenically rolled titanium grains was much smaller than the twin bandwidth (1-5 μm) in the room temperature rolled titanium grains.

In addition, in the cryogenically rolled titanium, as the rolling reduction increased from 20% to 60%, twin crystals continued to be formed uniformly, and the amount of formed twin crystals was also increased.

The microstructure results of the cryogenically rolled titanium as described above intuitively indicate that cryogenic rolling is very effective in realizing the ultrafine grain microstructure of titanium even if the characteristics of twins are not quantitatively measured.

Table 1 below summarizes the results of quantitatively measuring the microstructures of FIGS. 2 and 3 .

<Table 1>

(Since twins cannot be clearly distinguished in the microstructure of the 60% reduction specimen, twin properties cannot be measured)

First, the grade 2 (grade 2) titanium initial material has a relatively large average grain size of several tens of μm because it is in an annealed state after rolling, and further has a microstructure without twin crystals.

Meanwhile, the room temperature rolled titanium shown in FIG. 2 has an average grain size of several to several tens of μm. In addition, the average thickness of the twin crystal bands in the titanium rolled at room temperature was measured to be about 4 to 5 μm, and the average number of twin bands per crystal grain was measured to be 2 to 11 pieces.

More specifically, as a result of considering only the {11-22} twins that mainly determine the twin structure, 95% or more of the crystal grains in cryogenically rolled titanium have 10 or more twins, whereas in the room temperature rolled titanium, 70% or more of the crystal grains have 5 or less. was observed to have tweens of As a result, it was measured that the cryogenically rolled titanium was approximately 2.9 times higher than that of the room temperature rolled titanium under the condition of the reduction ratio of 20%-40% in the average number of twins per grain.

The relatively coarse average grain size and thickness of twin bands, and the number of low density twin bands of the titanium rolled at room temperature as described above mean that room temperature rolling is not effective for grain refinement of titanium.

On the other hand, the dislocation density of the titanium rolled at room temperature clearly shows a tendency to continuously increase up to 40% of the rolling reduction.

When the dislocation density is increased, the strain hardening rate during tension is low, and thus the possibility of work softening even at a small reduction ratio increases. As a result, local deformation such as necking occurs, resulting in lower ductility.

On the other hand, the cryogenically rolled titanium shown in FIG. 3 was measured to have an average grain size of 0.6 to 5.2 μm, particularly under the condition of a reduction of 20 to 40%. In addition, in the cryogenically rolled titanium, the average thickness of twin bands was measured to be several hundred nm, which is less than approximately 1 μm, and the average number of twin bands per one grain was measured to be 19 to 23.

As described above, the fine average grain size of the cryogenically rolled titanium, the thickness of the twin band, and the number of twin bands of high density mean that the cryogenic rolling is very effective in refining the crystal grains of titanium.

On the other hand, the dislocation density of the cryogenically rolled titanium was measured to be 1/3 or less compared to the room temperature rolled titanium in the range of 20 to 40% of the rolling reduction.

When the dislocation density is lowered, the strain hardening rate during tensile is high, so that the possibility of work softening is lowered even at a high reduction rate. As a result, resistance to localized deformations such as necking is increased, resulting in no reduction in ductility.

On the other hand, in the case of cryogenically rolled titanium, it was measured that the grain size reduction was not sufficient in the 10% reduced titanium and the average number of twin bands per grain was not large. The reduction amount of 10% is considered to mean that the amount of deformation required for the formation of twin bands essential for the formation of ultrafine grains is insufficient.

In addition, in the case of cryogenically rolled titanium, when the rolling reduction is 60%, the dislocation density is too high despite the small grain size, and work softening occurs, which is detrimental to ductility.

Figure 4 shows the tensile properties of the titanium rolled at room temperature and the cryogenically rolled titanium under the condition of 30% of the rolling reduction.

First, as shown in Fig. 4 (a), the initial material had a yield strength lower than 200 MPa, while the elongation showed tensile properties close to 60%.

On the other hand, room temperature rolled titanium and cryogenically rolled titanium have higher yield strength and lower elongation than the initial material in common. In particular, it can be seen that cryogenically rolled titanium has a yield strength of 100 MPa or more higher than that of room temperature rolled titanium, and at the same time, ductility is also greatly increased.

The result of FIG. 4(a) agrees very well with the microstructure of FIGS. 2 and 3 . In other words, it is judged that the dense and fine twin band in the cryogenically rolled titanium refines the crystal grains, and as a result, the ultrafine grain microstructure realizes excellent tensile properties again.

On the other hand, Figure 4 (b) is a comparison of the values of strain hardening rate (strain hardening rate) of the titanium rolled at room temperature and the cryogenic rolled titanium.

In general, based on a case where the work hardening rate value is 0, a positive value may be distinguished as work hardening, and a negative value may be distinguished as work hardening.

It can be seen that work softening occurs at a higher strain in cryogenically rolled titanium than in room temperature rolling titanium. In other words, cryogenically rolled titanium occurs in a wider deformation range than room temperature rolled titanium, which means that cryogenically rolled titanium has a higher resistance to work softening than room temperature rolled titanium.

The result of FIG. 4(b) agrees very well with the microstructure of FIGS. 2 and 3 . In other words, the low dislocation density in cryogenically rolled titanium causes dislocations to multiply during deformation (tensile test), resulting in active work hardening and wide deformation range.

As a result, cryogenically rolled titanium weakens work softening during a tensile test and improves resistance to local deformation such as necking compared to room temperature rolled titanium. In addition, the improved strain hardening capacity of cryogenically rolled titanium greatly improves workability in subsequent processing.

4 (c) and (d) show the necking index (necking index) and DIC images according to the elongation of the titanium rolled at room temperature and the cryogenically rolled titanium.

As shown in FIGS. 4 (c) and (d), it was found that necking did not occur in cryogenically rolled titanium until almost fracture occurred, whereas in room temperature rolled titanium, necking occurred from the beginning of deformation. can

5 is a stress-strain curve of titanium (a) and cryogenically rolled titanium (b) rolled at room temperature under various reduction conditions of 10% to 60%.

Table 2 below summarizes the tensile properties obtained from the stress-strain curve in FIG. 5 .

<Table 2>

First, it was investigated that the tensile strength and yield strength of cryogenically rolled titanium were higher than that of room temperature rolled titanium under all reduction ratio conditions. The high strength characteristics of the cryogenically rolled titanium are attributed to the ultrafine grain microstructure formed due to the development of twin bands.

In addition, the low dislocation density along with the ultrafine grain microstructure of cryogenically rolled titanium resulted in improvement of work hardening properties and weakening of work softening properties, resulting in high elongation.

The high strength and ductility properties of cryogenically rolled titanium become clearer when comparing the tensile properties defined as the product of yield strength and elongation (yield strength * elongation).

Table 3 below summarizes the tensile properties of grade 2 titanium specified in ASTM.

<Table 3>

First, it was investigated that the tensile properties of grade 2 titanium specified in ASTM have a value of about 5.5 to 8.2 GPa%. Meanwhile, the initial material of grade 2 titanium used in the present invention was measured to show a tensile property value of about 10.1 GPa%.

Meanwhile, it was investigated that the titanium rolled at room temperature had a tensile property value of up to 10.1 GPa% even under all conditions of 10 to 60% of rolling reduction.

The reason for the low tensile properties of the titanium rolled at room temperature even though it has a higher yield strength than the initial material is because of the low ductility of the titanium rolled at room temperature. The low ductility of the titanium rolled at room temperature is because the microstructure of titanium does not have ultra-fine grains even by room temperature rolling and the dislocation density is too high.

On the other hand, cryogenically rolled titanium has a very good tensile property value of at least 12.6 GPa% or more under the condition of a rolling reduction of 20 to 40%.

The reason why cryogenically rolled titanium has excellent tensile properties is because of its high strength and relatively excellent ductility. The excellent tensile properties of the cryogenically rolled titanium is because the microstructure of the titanium has ultrafine grains and at the same time the dislocation density is low by the cryogenic rolling, so that the work softening resistance is high.

On the other hand, even in cryogenically rolled titanium, when the rolling reduction is 10%, the tensile properties were found to be not very high compared to the initial material or room temperature rolled titanium. The reduction ratio of 10% is because the deformation amount is somewhat insufficient to form a dense twin band in titanium during cryogenic rolling, and as a result, the strength does not increase significantly.

In addition, in the cryogenically processed titanium with a reduction ratio of 60%, an increase in strength and grain refinement were realized due to the formation of twin bands. However, at the same time, the excessively increased dislocation density could not suppress work softening, causing deterioration of ductility. Therefore, the cryogenically processed titanium with a reduction ratio of 60% has a low tensile property value.

FIG. 6 shows the relationship between elongation versus yield strength of general-processed titanium, room temperature rolled titanium, and cryogenically rolled titanium.

It can be seen from FIG. 6 that the tensile properties of both the general-processed (conventional annealed after rolling) and room-temperature rolled titanium do not exceed 10.5 GPa%. Since the general-processed titanium or the room-temperature rolled titanium does not have ultrafine crystal grains due to twin bands, it has no choice but to have a low tensile property value.

On the other hand, it can be seen that the cryogenically rolled titanium in the present invention has a high tensile property value of 10.5 GPa% or more in the reduction ratio of 20% to 40%. The excellent tensile properties of the cryogenically rolled titanium are attributed to the ultrafine grains due to the twin band and the low dislocation density.

As described above, the present invention has been described with reference to the illustrated drawings, but the present invention is not limited by the embodiments and drawings disclosed in the present specification. It is obvious that variations can be made. In addition, although the effects of the configuration of the present invention are not explicitly described and described while describing the embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

Claims (8)

In weight %, oxygen (O): 0.35 wt% or less, hydrogen (H): 0.015 wt% or less, iron (Fe): 0.3 wt% or less, carbon (C): 0.1 wt% or less, and the balance is titanium (Ti) components and composition ranges are satisfied;
The average number of twin bands per grain is 19 or more,
Titanium, characterized in that the average thickness of the twin band is 1㎛ or less (excluding 0).
The method of claim 1,
Titanium, characterized in that the average grain size of the titanium is 5.2㎛ or less (excluding 0).
The method of claim 1,
The dislocation density of the titanium is 4.5 * 10 ¹⁵ /m 2 or less; Titanium, characterized in that.
The method of claim 1,
The tensile property value defined by the yield strength * elongation of the titanium is 10.5 MPa% or more; Titanium, characterized in that.
In weight %, in weight %, oxygen (O): 0.35% by weight or less, hydrogen (H): 0.015% by weight or less, iron (Fe): 0.3% by weight or less, carbon (C): 0.1% by weight or less and the balance titanium Preparing a commercially pure titanium base material having a component and composition range of (Ti);
rolling the titanium base material in the range of a reduction ratio of 20% to 40% and a temperature in the range of -196°C to -10°C;
A method for producing titanium comprising a.
delete 6. The method of claim 5,
The titanium base material in the step of preparing the base material is annealed after rolling, titanium manufacturing method.
8. The method of claim 7,
The titanium base material has a texture in which the c-axis is aligned in the thickness direction, the titanium manufacturing method.

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