JP2008231553A - Method for producing low elastic titanium alloy sheet and titanium alloy sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a low elastic titanium alloy sheet in which only an elastic modulus is reduced while maintaining its strength, and to provide a titanium alloy sheet. <P>SOLUTION: A low elastic titanium alloy sheet having a martensitic structure is produced through: a solution treatment step at a β transformation temperature or above; a first cold rolling step succeeding to the solution treatment step; and a second cold rolling step using a cross system with respect to the first cold rolling. When the reduction rates (%) of the first cold rolling step and the second cold rolling step are expressed as RD1 and RD2, respectively, RD2/RD1 is 1.1 to 2.5, and also satisfies RD1×RD2>400. The titanium alloy is obtained by the above production method, and contains 6 to 18% vanadium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a low-elasticity titanium alloy plate and a titanium alloy plate, and more particularly to a method for producing a low-elasticity titanium alloy plate having high strength and low elastic modulus and high elastic deformability, and a titanium alloy plate.

  Titanium alloys are excellent in specific strength and corrosion resistance, and are widely used in fields such as aviation, military, space, deep sea exploration, and chemical plants. This general-purpose titanium alloy is classified into α type, α + β type, and β type according to its structure. Among them, Ti-6% Al-4% V of α + β type titanium alloy has been frequently used because of its high strength.

Further, as conventional β-type alloys, for example, there are Ti-15V-3Cr-3Sn-3Al, Ti-22V-4Al, etc., which are used for spectacle frames and golf clubs because of their supple characteristics. Furthermore, in addition to the general-purpose β-type alloys, β-type titanium-based alloys whose Young's modulus is less than 80 GPa have been proposed. For example, biocompatible products (for example, artificial bones), jewelry (for example, glasses frames) ), Application to sports equipment (for example, golf clubs), springs, and the like is expected (see, for example, Patent Documents 1 to 4).
JP 2005-113227 A Japanese Patent Laid-Open No. 2002-180168 JP 2004-353039 A Japanese Patent No. 3375083

On the other hand, titanium alloys having a martensitic structure can be cited as titanium alloys other than the α-type, α + β-type, and β-type titanium alloys. In this titanium alloy, when a β-stabilizing element material such as V, Mo, Nb is appropriately controlled and a solution treatment is performed in a β-phase stable temperature range, a martensitic structure of α ′ or α ″ may appear. It is a feature.
As specific alloys, Ti—V—Al, Ti—V—Al—Fe, Ti—Nb—Sn, Ti—Nb—Al, Ti—Mo—Sn, and the like are known. Since these titanium alloys have a martensite structure, they exhibit a shape memory effect. Also, the elastic modulus is lower than that of pure titanium.
Therefore, it is expected to be applied not only as a shape memory alloy but also to biocompatible products, accessories, sports equipment, springs and the like for which low elasticity is desired. For example, Ti—Nb—Sn and Ti—Mo—Sn alloys having good compatibility with the human body are expected to be applied to medical applications (see, for example, Patent Documents 5 and 6).
Ti-V alloys are easy to melt because V has a low melting point relative to Nb and Mo, and are manufactured at a low cost, just like general-purpose alloys such as Ti-15V-3Cr-3Sn-3Al. Since it can be applied, it is expected to be applied to other types of uses other than medical uses.
Japanese Patent No. 3512253 Japanese Examined Patent Publication No.59-35978

These titanium alloys having a martensite structure are generally processed into a plate shape by hot and cold rolling when manufactured as a plate material, and in that case, the martensite structure is oriented in the plate surface. As a result, the elastic modulus tends to cause in-plane anisotropy (anisotropy).
For this reason, when the difference in the direction of the elastic modulus in the plate surface affects the performance of the product, the performance deteriorates or varies. For example, when punching a part from a plate manufactured by rolling, if it is not unified in a specific direction, the spring back will not be stable when manufacturing the part in the subsequent press molding process, and the dimensional system of the part will deteriorate There was a problem.
In addition, there is a problem that the performance varies greatly depending on the product. As a specific example, when used for the face of a golf club, if the anisotropy of the elastic modulus is large, the flight distance deteriorates and the direction of the hit ball is damaged.
Furthermore, when the titanium alloy plate material is processed and used for a rotating body part such as an automobile, the difference in elastic modulus depending on the rotating position causes vibration and noise, and the fatigue characteristics of the part deteriorate due to stress concentration. There was a drawback.

On the other hand, the present inventors have made various studies on the construction method of a titanium alloy plate having a martensite structure in order to achieve such a problem, and as a result, have obtained the following knowledge.
That is, by performing a solution treatment at a temperature higher than the beta transus temperature, a martensite structure of α ′ or α ″ phase is formed, and then cold-rolled, the martensite structure forms a processed texture. Anisotropy occurs in the elastic modulus depending on the tissue.
However, it has been clarified that when the second cold rolling process is performed in the cross direction with respect to the previous cold rolling direction, the texture changes, and as a result, the anisotropy of the elastic modulus is greatly reduced.

  The present invention has been made in view of the problems and new knowledge of the prior art, and the object of the present invention is to produce a low-elasticity titanium alloy plate having only a reduced elastic modulus while maintaining strength. It is to provide a method and a titanium alloy plate.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by performing cross rolling after the solution treatment at the β transformation temperature or higher, and to complete the present invention. It came.

That is, the manufacturing method of the titanium alloy plate of the present invention, in manufacturing a low-elasticity titanium alloy plate having a martensite structure,
solution treatment process above the β transformation temperature,
A first cold rolling step following the solution treatment step,
A second cold rolling step in which a cross method is used for the first cold rolling;
It is characterized by performing.

Moreover, when the suitable form of the manufacturing method of the titanium alloy plate of this invention sets the reduction | decrease rate (%) of a 1st cold rolling process and a 2nd cold rolling process to RD1, RD2, respectively,
RD2 / RD1 is 1.1 or more and 2.5 or less, and the following inequality:
RD1 × RD2> 400
It is characterized by satisfying.

Furthermore, the titanium alloy plate of the present invention is a titanium alloy plate obtained by the above production method,
It contains 6 to 18% of vanadium.

  According to the present invention, since the cross rolling is performed after the solution treatment at the β transformation temperature or higher, a low elastic titanium alloy plate manufacturing method and a titanium alloy plate having a reduced Young's modulus compared to conventional products are provided. be able to.

  Hereafter, the manufacturing method of the low elastic titanium alloy plate of this invention is demonstrated in detail. In the present specification and claims, “%” for concentration, content, filling amount and the like represents a mass percentage unless otherwise specified.

As described above, the present invention can produce a low-elasticity titanium alloy plate having a martensite structure by the following 1 to 3 steps. solution treatment process above the β transformation temperature,
2. A first cold rolling step following the solution treatment step,
3. A second cold rolling step in which a cross method is used for the first cold rolling;
It is characterized by performing.

In the manufacturing method of the present invention, by performing the above steps, the manufactured titanium alloy sheet not only has an elastic modulus, but also has improved strength due to work hardening by cold rolling. In other words, the present inventors have found that strength characteristics such as tensile strength and elongation of the titanium alloy plate are improved when the anisotropy is small in the plate surface.
The elastic modulus and strength values of the titanium alloy plate obtained by the production method of the present invention vary depending on the alloy components and processing conditions. Specifically, the elastic modulus has a low value of less than 80 GPa and strength. As a result, a material that simultaneously satisfies a high tensile strength exceeding 1 GPa can be obtained.
Therefore, since the titanium alloy plate has little difference depending on the direction of the elastic modulus in the plate surface, for example, when punching a component, any direction in the plate surface does not hinder product performance. In addition, since the spring back is constant when the parts are manufactured in the press molding process, the dimensional system of the parts is good and the yield is improved. Furthermore, when such a titanium alloy plate is used for the face of a golf club, for example, the direction of the hit ball and the flight distance are stabilized. When the titanium alloy plate is processed and used for rotating parts such as automobiles, there is little difference in elastic modulus depending on the rotating position, so vibration and noise do not occur, and stress concentration caused by elastic modulus anisotropy This also improves the fatigue characteristics of the parts.

The cross direction means that the second cold rolling is performed by changing the angle with respect to the first rolling, and the angle is not particularly limited, but with respect to the first rolling direction. Although the direction is preferably approximately 90 degrees, there is no particular problem as long as the effect of the present invention can be exhibited even when the angle is set to 45 degrees, for example.
In the present invention, 1. Solution treatment step → 2. First cold rolling process → 3. Although the cross-type second cold rolling process is performed, the process before the solution treatment process is not particularly limited. That is, because the martensite structure is recrystallized in the solution treatment step, the martensite structure is not greatly influenced by the previous structure in controlling the martensite structure in the present manufacturing method. Therefore, there is no problem even if a general titanium alloy manufacturing method such as hot rolling is adopted as a pre-process of the solution treatment process.
Further, there is no problem even if various steps are interposed between these three steps without departing from the gist of the present invention. For example, a pickling process may be inserted after the solution treatment process, a polishing process for adjusting the surface properties may be inserted after the second cold rolling process, and martensite is added after the second cold rolling process. A short annealing process may be included as long as the site structure is not broken.

Furthermore, in the production method of the present invention, when the reduction ratios (%) of the first cold rolling step and the second cold rolling step are RD1 and RD2, respectively,
RD2 / RD1 is 1.1 or more and 2.5 or less, and the following inequality:
RD1 × RD2> 400
It is preferable to satisfy.
Thereby, a martensite structure | tissue is orientated moderately and the anisotropy of an elasticity modulus can be reduced suitably.

When RD2 / RD1 is less than 1.1 or more than 2.5, the processed texture may develop to promote the anisotropy of elastic modulus within the plate surface. , Sufficient anisotropy may not be obtained. Further, when RD1 × RD2 is less than 400, since the reduction ratio is insufficient, the martensite structure is not sufficiently distorted, and the processed texture is difficult to be formed.
Here, the rolling reduction is a value determined by the relationship between the plate thickness before rolling and the plate thickness after rolling, and the number of rolling passes in each of the first cold rolling and the second cold rolling is particularly limited. Although it is not performed, the rotation of the crystal proceeds to the inside of the material with a smaller number of passes than the method of rolling down with a large number of passes (since distortion occurs only near the surface in one pass, the crystal is difficult to rotate). It is preferable to have such conditions.

The titanium alloy plate obtained by the manufacturing method described above is made of a titanium alloy having a martensite structure and contains 6 to 18% of vanadium (V).
By including 6% or more of V as a component element and forming a single martensite phase at room temperature by solution treatment, deformation at room temperature, that is, cold working becomes easy. On the other hand, when V exceeds 18%, the β phase is stabilized and it becomes difficult to form a martensite structure after the solution treatment, and the density is increased, and the weight reduction, which is a characteristic characteristic of the titanium alloy, cannot be achieved.
In addition, the titanium alloy plate may contain molybdenum (Mo), niobium (Nb), tantalum (Ta), etc. as a β-stabilizing element, and further aluminum (Al), tin (Sn). Etc. may be added to improve processability.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

(Examples 1-12)
Titanium alloys (Ti-7.68V-4Sn, Ti-11) having two kinds of compositions shown in Table 1 were obtained by arc melting in an argon atmosphere using pure metals of Ti, V, Al, and Sn with a purity of 99.9%. .76V-2Al) to obtain about 90 g of ingot.

  The ingot was homogenized at 1150 ° C. for 24 hours in a vacuum and then hot-rolled at 800 ° C. to obtain a plate having a predetermined thickness. Further, a solution treatment was carried out at 950 ° C. above the beta transus temperature for 1 hour, and then quenched in ice water. The results of observing the structure of the alloy after solution treatment with an optical microscope are shown in the photographs of FIGS. As can be seen from these photographs, it was confirmed that the structure had a needle-like martensite structure.

About the sample which completed the solution treatment as mentioned above, after grinding and removing the surface oxide scale, the first cold rolling is performed at the rolling reduction shown in Table 1, and further in the cross direction with respect to the first cold rolling. The second cold rolling was performed to obtain a titanium alloy plate of this example.
Here, the second cold rolling was performed in the direction of 90 degrees with respect to the first cold rolling. The plate thickness of the sample after the second cold rolling was all 1 mm (the thickness of the sample before the first cold rolling was adjusted so as to be 1 mm after the second cold rolling).

(Comparative Examples 1 and 2)
A titanium alloy sheet of this example was obtained by repeating the same process as in Example 1 except that the cold rolling was performed in only one direction and the first cold rolling was not performed.

<Evaluation method>
The following evaluation was performed about the titanium alloy plate of each said example.

1. Young's Modulus According to JIS Z 2280, Young's modulus in the 0 degree direction and the 90 degree direction was measured at room temperature using the resonance method with the RD2 direction as a reference. The results are shown in Table 1.

2. Tensile test Tensile strength of the titanium alloy plates shown in Examples 7 and 8 and Comparative Example 2 was measured by a tensile test according to the JIS Z 2241 test. The results are shown in Table 2.

  From Table 1, the titanium alloy plates of Examples 1 to 12, which are examples of the present invention, have an anisotropy of Young's modulus of 15 GPa or less, and the titanium alloy plates of Comparative Examples 1 and 2 that are the results of unidirectional rolling. In comparison, the anisotropy could be reduced sufficiently.

  FIG. 3 shows a graph in which the results of Table 1 are plotted with the horizontal axis representing RD2 / RD1 and the vertical axis representing the difference in size depending on the direction of the elastic modulus. RD2 / RD1 is 1.1 or more 2 It was confirmed that the anisotropy of the elastic modulus was particularly small in the range of .5 or less.

  Further, from Table 2, the difference in the tensile strength angle of the titanium alloy plates of Examples 6 and 7 is less than half compared to the tensile test result of the unidirectional rolling of the titanium alloy plate of Comparative Example 2. I also understood that.

  Furthermore, from Tables 1 and 2, the titanium alloy plate of Example 6 has a low modulus of elasticity and strength anisotropy within the plate surface, a strength of 1100 MPa or more, and a modulus of elasticity of about 70 GPa. It was confirmed that this was a titanium alloy plate having both elasticity and small in-plane anisotropy. Compared with the Ti-6Al-4V alloy which is most frequently used at present, this means that the elastic modulus can be lowered by about 40 GPa while having the same strength.

The titanium alloy plate of the present invention described above can be widely used for various products, imparts high strength and low elasticity, and can improve productivity and reduce costs.
Typically, it can be used for automobiles, industrial machines, motorcycles, bicycles, precision equipment, home appliances, aerospace equipment, ships, accessories, sports / leisure products, biological products, medical equipment, toys, and the like.

  It can also be used for products that require anti-vibration characteristics. That is, the titanium alloy sheet of the present invention has a lower Young's modulus than conventional titanium alloys and can use a martensite phase or a martensite transformation. The martensite phase is represented by Ti-Ni or Mn-Cu. As with twin-type damping alloys, twin deformation occurs, so that products having excellent vibration absorption characteristics can be obtained in the same manner as these twin-type damping alloys.

  Specifically, the titanium alloy plate of the present invention is used, for example, as an anti-vibration cushioning material that prevents the occurrence of a booming noise in an automobile interior, and to eliminate chattering noise when used for mounting a car audio. It can be preferably used.

  Furthermore, it can be suitably used for golf clubs and bats, which are a kind of sports and recreation goods, and particularly for the face portion. The flight distance can be extended considerably.

  Furthermore, the titanium alloy plate of the present invention includes, for example, various metal seals for automobiles, chassis, bolts, springs, power transmission belts (CVT hoops, etc.), gears, gears, tire linings, tire reinforcements, fuel tanks. It can be used for various products in various fields such as various containers.

It is an optical micrograph after the solution treatment of Ti-7.68V-4Sn alloy. It is an optical micrograph after the solution treatment of Ti-11.76V-2Al alloy. It is a graph showing the influence of the ratio of RD1 and RD2 on the anisotropy of elastic modulus.

Claims (3)

In producing a low elastic titanium alloy plate having a martensite structure,
solution treatment process above the β transformation temperature,
A first cold rolling step following the solution treatment step,
A second cold rolling step in which a cross method is used for the first cold rolling;
A method for producing a low-elasticity titanium alloy plate, characterized in that: When the reduction ratio (%) of the first cold rolling process and the second cold rolling process is RD1 and RD2, respectively,
RD2 / RD1 is 1.1 or more and 2.5 or less, and the following inequality:
RD1 × RD2> 400
The method for producing a low-elasticity titanium alloy plate according to claim 1, wherein: A titanium alloy plate obtained by the method for producing a low-elasticity titanium alloy plate according to claim 1 or 2,
A titanium alloy plate containing 6 to 18% of vanadium.

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