JP2000096165A - Titanium alloy excellent in antibacterial property and organism sticking resistance and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart excellent antibacterial properties and organism sticking resistance to an alloy by allowing it to contain a specified ratio of Cu and forming its structure into the equiaxed crystal one of the specified average crystal grain size. SOLUTION: It is preferable that the ratio of Cu to be contained is controlled to, by weight, 0.01 to <2%, and the average crystal grain size is controlled to <=100 μm. In the case Cu is contained in the range of 0.01 to <2%, a cocentrated region of Cu is formed on the grain boundaries of the crystal grains of the α phases. It is because Cu is a β phase forming element for titanium, and they are concentrated on the grain boundaries. The stock for producing the Ti alloy uses sponge titanium as the raw material, is melted in a vacuum or in an argon atmosphere to control the elements to be added and is thereafter cast into an ingot. Its metallic structure is formed into the equiaxial one, and the crystal grains of <=100 μm average crystal grain size are worked at the temp. below βtransus and at a working degree of >=20% to sufficiently destroy the needle crystals and is held at 60 deg.C to the temp. below βtransus. The working degree denotes the reduction of cross section in the stock generated by forging, rolling or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to medical equipment such as building interior materials, kitchenware, watch side materials, eyeglass frames, scalpels, etc., food production equipment, etc., which are required to have antibacterial properties, and bioadhesion resistance. Offshore structures, fishing nets for aquaculture,
The present invention relates to a Ti alloy suitable as a material for heat exchanger piping and seawater desalination equipment by seawater cooling, and a method for producing the same.

[0002]

2. Description of the Related Art Ti is used as a material for various members because of its excellent corrosion resistance and light weight. Ti
Has excellent corrosion resistance especially against seawater,
It is widely used for piping of condensers for seawater cooling, seawater desalination equipment and the like.

[0003] Further, Ti is a metal that does not cause an allergic reaction to a living body, and is therefore used as a material for a watch side member or a frame of eyeglasses used in direct contact with a human body. Furthermore, since it has excellent biocompatibility, it is also used as a material for artificial bones and the like.

[0004] As mentioned above, Ti has a wide variety of uses. However, Ti has some problems due to its high affinity for living things. For example, when Ti is used in a heat exchanger pipe by seawater cooling, organisms such as shellfish enter the pipe and adhere to the inner surface, so that there is a problem that the circulation of the cooling water is hindered and the cooling effect is deteriorated. In order to avoid this problem, it is necessary to periodically perform a process of cleaning the inside of the pipe with a sponge or the like.

[0005] Ti is also expected to be used as a material for fish nets for aquaculture, but in this case also, there is a problem that the flow of seawater is restricted because organisms adhere to the fishing nets.
For this reason, surface treatment with zinc or the like has been considered, but this surface treatment has the disadvantages of increasing the product cost and causing environmental pollution problems due to zinc, and thus has not been put to practical use.

[0006] In order to solve the above problems, it is necessary to improve the bio-adhesion resistance of Ti, that is, the performance of preventing the adhesion of organisms.

Japanese Patent Application Laid-Open No. Hei 8-9836 discloses a float made of a Ti alloy to which marine organisms are unlikely to adhere.
However, the phrase "the marine organisms are hard to adhere" referred to in this publication merely means that the material of the float is changed from a conventional resin to a Ti alloy to which organisms are less likely to adhere than the resin. It is not what improved the character.

[0008] On the other hand, Ti has a drawback that bacteria easily propagate because of high affinity with living things. As described above, Ti is also used as a raw material for daily necessities that comes into direct contact with the human body. With the increasing interest in fungi in recent years, Ti is required to have antibacterial properties.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Ti alloy excellent in antibacterial properties and bio-adhesion resistance and a method for producing the same.

[0010]

The gist of the present invention resides in the following Ti alloy having excellent antibacterial and bioadhesive properties and a method for producing the same.

(1) Cu is 0.01% or more by weight%,
A Ti alloy excellent in antibacterial properties and bio-adhesion resistance, characterized by containing less than 2%.

(2) The Ti alloy according to claim 1, having an equiaxed crystal structure having an average crystal grain size of 100 μm or less.

(3) The titanium alloy as described in (1) above,
After performing processing with a working ratio of 20% or more at a temperature equal to or lower than Transus, heat-treating the alloy at a temperature of 600 ° C. or higher and lower than β Transas for 1 minute or more. Production method.

Here, the average crystal grain size is defined by JIS H5
The crystal grain size is determined by the cutting method specified in 01.

The present inventor conducted various experiments and studies in order to impart antibacterial properties and bio-adhesion resistance to Ti, ie, the ability to prevent the adhesion of organisms, and as a result, obtained the following findings and completed the present invention. I let it.

A) When Cu is contained in an amount in the range of 0.01 to less than 2%, α phase crystal grains (hereinafter referred to as α grains)
Cu-rich regions are formed at the grain boundaries. The formation of the Cu-enriched region exerts antibacterial properties or biological adhesion.

B) The formation of a Cu-enriched region at the grain boundaries of α grains is because Cu is a β-phase forming element for titanium, so that Cu is discharged from the α phase and they are collected at the grain boundaries. It is.

C) The metal structure is preferably an equiaxed structure, and the average grain size of the equiaxed crystals is preferably 100 μm or less. If the average particle size exceeds 100 μm, the distance between grain boundaries increases,
This is because bacteria may exist without crossing the grain boundaries where Cu is concentrated, and the antibacterial action may be reduced.

D) Equiaxed crystal grains having an average crystal grain size of 100 μm or less are processed at a temperature of not more than β transus at a processing degree of 20% or more, and the needle-like crystals are sufficiently destroyed to obtain a temperature of from 600 ° C. to less than β transas. Obtained by holding at temperature.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The Ti alloy of the present invention and a method for producing the same will be specifically described.

(1) Chemical Composition of Ti Alloy Hereinafter, the percentages used in the description of the chemical composition represent weight percentages.

Cu: 0.01 to less than 2% In order to exhibit antibacterial properties and bioadhesion resistance, it is necessary to contain Cu in an amount of 0.01% or more. 0.01 for Cu
% Or more, a Cu-enriched region is formed in the α grain and the grain boundary of the α grain in the final stage of the manufacturing process. That is, the solid solubility limit of Cu in α grains is low,
Since Cu is a β-phase forming element for titanium, Cu tends to be discharged from the α-phase. As a result, it is presumed that Cu is concentrated at and around the grain boundaries of α grains and becomes β phase. However, if the Cu content is too large, the workability is reduced, and cracks and the like occur when forming into a product shape.
In order to prevent this adverse effect, the Cu content needs to be less than 2%. Desirably, it is 1.5% or less.

The following tests were conducted on the effect of the Cu content on the workability of the Ti alloy.

A 15 mm thick titanium alloy ingot having various Cu contents of 0 to 2.5% was cast by a button arc melting method, heated to 850 ° C., and then hot rolled to a thickness of 5 mm. Was manufactured. This plate was annealed at 800 ° C. for 30 minutes, and was then cut to remove oxide scale formed on the plate surface and finished to a thickness of 4 mm. Next, the 4 mm-thick plate was cold-rolled to a thickness of 1 mm and kept at 700 ° C. for 1 hour in an argon atmosphere. A JIS13B tensile test piece was created from this plate,
Tensile strength and elongation at break were determined. Table 1 shows the results.

[0025]

[Table 1]

As is clear from the table, the Cu content is 2
%, The elongation is significantly reduced, and the workability is deteriorated.

In addition to Cu, if necessary, Fe and O (oxygen) can be contained.

Fe Fe is usually contained at about 0.03%. Further, Fe may be positively contained to adjust the strength. However, when the content is large, the corrosion resistance tends to deteriorate, and the workability also deteriorates.
% Or less.

Oxygen (O): 0.3% or less Oxygen usually contains about 0.05%. Oxygen has the effect of increasing the strength similarly to Fe, and may be positively contained. However, when the content is large, the workability particularly in the cold state is reduced, so that the content is preferably set to 0.3% or less.

The following elements are included as impurities.

Ni: an element inevitably mixed in the raw titanium sponge. If the Ni content exceeds 0.05%, a problem of deterioration in workability occurs. Therefore, the content is preferably set to 0.05% or less.

Cr: Cr is also an element inevitably mixed in the raw material titanium sponge. Cr content is 0.0
If it exceeds 5%, a problem of deterioration in workability occurs. Therefore, the content is preferably set to 0.05% or less.

Nitrogen (N): N is sponge titanium or an element mixed in the melting step. When the content of nitrogen (N) is 0.
If it exceeds 02%, a problem of deterioration in workability occurs. Therefore, the content is preferably set to 0.02% or less.

Hydrogen (H): H is an element mixed in the dissolution step or the heat treatment step described later. H content is 0.
If it exceeds 015%, the problem of hydrogen embrittlement occurs. Therefore, the content is preferably set to 0.015% or less.

Carbon (C): C is an element inevitably mixed in the raw material sponge titanium. When the content of C exceeds 0.01%, a problem of deterioration in workability occurs. Therefore, the content is preferably set to 0.01% or less.

(2) Metal Structure, Average Crystal Grain Size The metal structure is not particularly limited, but the equiaxial structure is superior to the acicular structure in antibacterial properties and workability. It is preferred that

In the course of its formation, the needle-like tissue forms
The needle-like α phase forms a colony and grows toward the center of the β grain starting from the grain boundary. At this time, Cu
And the amount of enrichment is small at the boundaries of colonies. On the other hand, titanium has a very high growth rate of crystal grains in the β phase temperature range, and thus the old β grains are coarse. That is,
In the needle-like structure, the interval between the Cu enriched regions is wide. In such a state, since the probability that the bacteria touch the Cu-enriched region on the titanium surface is low, the degree of antibacterial activity is lower than that of the equiaxed crystal described later.

In the case of the equiaxed structure, since there is no concentrated portion of Cu in the α grains, it is preferable that the crystal grains are small. If the grain size exceeds 100 μm, the distance between the crystal grain boundaries becomes long. Cu-concentrated portions having an antibacterial action will be reduced. From this viewpoint, the crystal grain size is preferably set to 100 μm or less.

The equiaxed structure is α grains in which the aspect ratio of the α phase is close to 1, and the aspect ratio is preferably set to about 1 to 4. However, when the aspect ratio is set to close to 1, the antibacterial property is improved. Preferably it is 1-3. (3) Production Method The material for producing a Ti alloy of the present invention was prepared, for example, by using titanium sponge as a raw material and dissolving it in a vacuum or an argon atmosphere, and adjusting the additive elements so as to have the chemical composition specified in the present invention. Thereafter, it can be manufactured by casting into an ingot. Ingots may be used as a material,
Furthermore, this ingot can be processed into a plate, a rod, a pipe, or the like as a material by subjecting the ingot to plastic working such as normal forging and rolling according to the purpose.

In the case of producing a Ti alloy having higher antibacterial and bioadhesive properties, the chemical composition is set within the range specified above, and processing under the following specific conditions is performed in the final step of material production. And heat treatment is effective.

First, the above-described Ti alloy material is processed at a temperature of not more than β transus and a working degree of 20% or more. Next, it is kept at a temperature of 600 ° C. or more and less than β transus for 1 minute or more. The working degree referred to in the present invention refers to a cross-sectional reduction rate of a material caused by forging, rolling, or the like, and is a value obtained by the following equation.

Degree of processing (%) = ｛(Material cross-sectional area before processing−
Material cross-sectional area after processing) x 100 mm / material cross-sectional area before processing If the degree of processing below β transus is lower than 20%, it was formed by heating to a temperature higher than β transus at the stage of ingot or rough processing. The needle-like tissue remains without being sufficiently destroyed. If the needle-like structure remains in the material, the workability is reduced, so that press cracking or the like occurs. In addition, since the Cu-enriched region remains along the coarse old β grain boundary, and the distance between the enriched portions becomes large, the antibacterial property cannot be expected to exhibit much. The lower limit of the processing temperature is not particularly defined because cold processing is also possible. The upper limit of the working ratio is not limited and is not particularly limited. Subsequent to the above-described processing, heat treatment is performed at a temperature of 600 ° C. or more and less than β transus for 1 minute or more. When this heat treatment is combined with the above-mentioned processing, an equiaxed α phase is formed. If the temperature of the heat treatment is lower than 600 ° C., no equiaxed α phase is formed. At a temperature equal to or higher than β transus, the phase becomes a β single phase, the crystal grains become coarse, a needle-like structure is formed, and the workability is reduced.

If the processing time is less than 1 minute, the processed structure remains and no equiaxed α phase is formed. Although the maximum time of the treatment is not particularly specified, the particle size is preferably set to 100 μm or less.

The excellent antibacterial property and the anti-bioadhesive property are exhibited by the equiaxed structure because Cu-enriched regions are formed at the crystal grain boundaries of the equiaxed crystal grains formed by the heat treatment.
That is, a region having a high Cu concentration, that is, a region having excellent antibacterial properties is scattered on the surface.

[0045]

EXAMPLES Example 1 Using a button arc melting furnace in an argon atmosphere, a width of 100 mm and a length of 300 m were used.
m and ingots of various chemical compositions having a thickness of 25 mm were cast. The chemical composition of the ingot is shown in Table 2.

[0046]

[Table 2]

The ingot was heated to 1000 ° C. (β transus or more) and subjected to hot rolling by a usual method to have a thickness of 12 m.
m and rolled slowly.

Thereafter, the temperature is equal to or lower than β transus 8
The sheet was heated to 00 ° C., hot-rolled, processed to a degree of working of 38%, and formed into a 7.5 mm hot-rolled sheet. Machined to remove scale formed on the surface of hot rolled sheet
mm.

The hot-rolled sheet having a thickness of 7 mm obtained as described above was subjected to cold rolling by a conventional method to obtain a cold-rolled sheet having a thickness of 3 mm. This cold-rolled sheet was subjected to an annealing heat treatment at 700 ° C., which is a temperature of 600 ° C. or higher and lower than β transus, for 1 hour, to produce a Ti alloy sheet.

The antibacterial properties (bioadhesion resistance) and microstructure of the plate of the manufactured Ti alloy were examined. The antibacterial test is
It carried out as follows. Escherichia coli
acoli strain W3110) was dispersed in a 1 / 500-diluted bouillon medium to prepare a bacterial solution for inoculation. The bouillon medium was prepared by dissolving 5 g of meat extract, 10.0 g of peptone, and 5 g of sodium chloride in 1 liter of purified water.

Next, a test piece (a Ti alloy plate cut into a 50 mm square) which had been sterilized by previously wiping with ethanol was placed in a sterile petri dish, and the surface of the test piece was inoculated with a bacterial solution (0.5 ml). 2.0 × 10 ⁵ bacteria). 50mm plastic bag sterilization Kensa pack for stomacher
After covering the test piece with the coated film cut into corners, it was stored under the conditions of a temperature of 35 ± 1 ° C. and a relative humidity of 95%.

After 24 hours, the bacteria adhered to the surface of the test piece and the film were washed out with 9.5 ml of physiological saline, and sprayed on a standard agar medium. Furthermore, after culturing at a temperature of 35 ± 1 ° C. for 48 hours, the number of grown colonies was counted, and the viable cell ratio was calculated.
It was used as an index for evaluating antibacterial properties. The bioadhesion resistance is T
Since it is an index indicating the susceptibility of organisms to adhere to the surface of the i-alloy plate, it is considered to be proportional to the antibacterial property, and those having excellent antibacterial properties were judged to be excellent in bioadhesion resistance. That is,
Those having excellent antibacterial properties were evaluated as having excellent bioadhesion resistance.

For the microstructure, a sample was taken from a longitudinal cross section of the roll, polished and corroded, observed with an optical microscope of 100 times, and the crystal grain size was measured.

Table 2 also shows the results of investigations on antibacterial properties and tissues.

In the column of antibacterial activity, ○ indicates that the survival rate of the bacteria is less than 30%, and X indicates that the survival rate of the bacteria is 70% or more. As is clear from Table 1, the Ti alloy of the present invention was excellent in antibacterial properties, but Test No. 1 in which the Cu content was lower than the lower limit specified in the present invention did not have antibacterial properties.

(Example 2) In the same manner as in Example 1, a button arc melting furnace in an argon atmosphere was used to have a width of 100 m.
m, a length of 300 mm, and a thickness of 25 mm were cast. The chemical composition of the ingot is 0.5% by weight of Cu.
%, Fe was 0.1%, and oxygen (O) was 0.05%. Using these ingots, the working degree, the heating temperature during working, and the temperature and time of the annealing heat treatment were variously changed to produce a Ti alloy for a test, and the antibacterial properties and the microstructure were examined. The β transus of the sample used was
About 840 ° C.

In the example of the present invention, each ingot was first heated to 1000 ° C. in the same manner as in Example 1 and subjected to hot rolling and machining to form a hot-rolled sheet having a thickness of 7.5 mm.
Using this hot-rolled sheet as a raw material, hot-rolled sheets having various thicknesses were formed at various temperatures and working degrees shown in Table 3, and then subjected to annealing heat treatment.

[0058]

[Table 3]

After the annealing heat treatment, test pieces were cut out by machining to examine the antibacterial properties and the structure. The test method was the same as in Example 1, and the evaluation criteria for the antibacterial property was that the survival rate of the bacteria was 30%.
Less than is indicated by ○ for excellent antibacterial properties, and の も の for those with a survival rate of 30 to 70% of bacteria is slightly inferior in antibacterial properties.

Table 2 also shows the results of the investigation on the antibacterial properties and the microstructure.

It can be seen that the test specimen produced by the production method specified in the present invention has good antibacterial properties and workability. In particular, the test No. 1.3.6 in which the needle-like structure remained,
Antibacterial properties are slightly inferior. The reason for this is that in the needle-shaped structure, the crystal grain size is coarse, the distance between the Cu-enriched regions present at the crystal grain boundaries increases, and the probability that bacteria will encounter this Cu-enriched region is reduced, so that the antibacterial property is reduced. Seems not to be exhibited. For the same reason, a test with a large grain size even in an equiaxed structure
No. 8 failed to exhibit antibacterial properties.

[0062]

The Ti alloy of the present invention has excellent antibacterial properties and bio-adhesion resistance, and can be used in a wide range of applications requiring anti-bacterial properties and bio-adhesion resistance. Further, according to the production method of the present invention, a Ti alloy excellent in antibacterial properties and bio-adhesion resistance can be easily produced.

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Claims (3)

[Claims] 1. A Ti alloy excellent in antibacterial properties and bio-adhesion resistance, characterized by containing Cu in an amount of 0.01% or more and less than 2% by weight. 2. The Ti alloy according to claim 1, having an equiaxed crystal structure having an average crystal grain size of 100 μm or less. 3. After subjecting the titanium alloy according to claim 1 to processing at a temperature of not more than β transus and a working degree of not less than 20%,
A method for producing a Ti alloy having excellent antibacterial properties and bioadhesion resistance, which comprises performing a heat treatment for maintaining the temperature within a temperature range of 00 ° C. or more and less than β transus for 1 minute or more.