Titanium material, titanium material applications, method for imparting antibacterial property, and method for producing titanium material

Abstract

Aspects of the present disclosure relate to a titanium material, a titanium material application, a method for imparting an antibacterial property, and a method for producing a titanium material, the titanium material having higher strength and antibacterial properties. A titanium material having a titanium content of 98,955 mass% or more, and having at tensile strength in a range of 1000 MPa or more and 1500 MPa or less.

Description

DESCRIPTION TITLE OF THE INVENTION: TITANIUM MATERIAL, TITANIUM MATERIAL APPLICATIONS, METHOD FOR IMPARTING ANTIBACTERIAL PROPERTY, AND METHOD FOR PRODUCING TITANIUM MATERIAL Technical Field

[0001] Aspects of the present disclosure relate to a titanium material, titanium material applications, a method for imparting an antibacterial property, and a method for producing a titanium material. BACKGROUND ART

[0002] Titanium possesses advantageous characteristics such as low specific gravity, excellent corrosion resistance, high strength, low elastic modulus, and superior biocompatibility. Owing to these properties, titanium materials are increasingly utilized in medical applications and aerospace engineering. When high-purity titanium is used, its mechanical strength is often enhanced by alloying with other metallic elements to form titanium alloys. One commonly used example in both medical and aerospace fields is the Ti-6Al-4V alloy, which is known for its high strength and reliable performance.

[0003] Although titanium alloys exhibit improved mechanical strength, they may also pose risks of biological side effects, such as tissue rejection, due to the presence of alloying elements like vanadium and aluminum. To address this issue, and to retain high biocompatibility, techniques have been proposed to enhance the strength of high-purity titanium materials without alloying. One such approach involves mechanically deforming the titanium material from a predetermined direction to induce work hardening and thereby increase its strength. (JP-B2-6737686). PRIOR ART DOCUMENTS PATENT DOCUMENT

[0004] Patent Document 1: JP-B2-6737686 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] Titanium materials are commonly used in the manufacture of orthopedic and dental implants, where high mechanical strength is essential to ensure safety and long- term durability. In addition to mechanical performance, there is a growing need to address implant-relatedinfections, which continue to occur at a significant rate. Accordingly, it is desirable for titanium materials to possess antibacterial properties to help prevent such infections and improve overall clinical outcomes.

[0006] Aspects of the present disclosure relate to a titanium material, titanium material applications, a method for imparting antibacterial property, and a method for producing a titanium material, the titanium material having higher strength and antibacterial properties. MEANS FOR SOLVING THE PROBLEMS

[0007] Aspects of the present disclosure relate to a titanium material having a titanium content of 98.955 mass% or more, and having a tensile strength in a range of 1000 MPa or more and 1500 MPa or less, preferably 1100 MPa or more.

[0008] In some embodiments, the titanium material has an elongation percentage in a range of 3% or more and 15% or less, preferably 4% or more.

[0009] In some embodiments, the titanium material has a fatigue strength or a durability limit each of which isimproved in a range of 10% or more and 30% or less, preferably 20% or more, as compared with a Ti-6Al-4V alloy in a fatigue test in accordance with ASTM F1717.

[0010] In some embodiments, the titanium material has a Vickers hardness in a range of 280 HV or more and 380 HV or less, preferably 300 HV or more.

[0011] In some embodiments, the titanium material has crystal grains whose average crystal grain size is 0.5 nm

[0012] In some embodiments, at least some of crystal grains of the titanium material have an anisotropic expanded structure.

[0013] In some embodiments, at least some of crystal grains of the titanium material have a uniform anisotropic expanded structure.

[0014] In some embodiments, the titanium material may have a rod shape.

[0015] In some embodiments, the titanium material has a polygonal cross-sectional shape.

[0016] In some embodiments, the titanium material has a circular cross-sectional shape.

[0017] In some embodiments, the titanium material has a square bar shape or a sheet shape.

[0018] In some embodiments, the titanium material may have an antibacterial property.

[0019] In some embodiments, the antibacterial property is inhibition of adsorption or growth of at least one microorganism selected from the group consisting of Staphylococcus aureus, Staphylococcus epidermidis, Methicillin-resistant Staphylococcus aureus (MRSA), E. coli, and Pseudomonas aeruginosa.

[0020] Aspects of the present disclosure relate to an implant comprising a titanium material, suitable for use in a variety of medical applications, including orthopedic implants (e.g., bone plates, screws), cardiovascular devices (e.g., vascular stents, heart valve frames), dental implants (e.g., screws, abutments, fixtures), and general surgical components (e.g., surgical fasteners, prosthetic devices) and surgical instruments.

[0021] Aspects of the present disclosure relate to an instrument including the titanium material, which is suitable for orthopaedics or general or micro surgery.

[0022] Aspects of the present disclosure relate to an aerospace industrial component including the titanium material.

[0023] In some embodiments, the aerospace industrial component is a jetliner component, a rocket component, or a satellite component.

[0024] Aspects of the present disclosure relate to a decorative article including the titanium material.

[0025] In some embodiments, the decorative article is an eyeglass frame, a piercing, a tie pin, a lighter, a wristwatch, or a necklace.

[0026] Aspects of the present disclosure relate to a method for imparting an antibacterial property, the method including applying the titanium material to a site requiring an antibacterial property.

[0027] Aspects of the present disclosure relate to a method for producing a titanium material, the method including: preparing a titanium base material having a titanium content of 99 mass% or more; and rolling the titanium base material at a cross- sectional reduction rate of 15% or less per one time (pass).

[0028] In some embodiments, the rolling step is performed a plurality of times.In some embodiments, rolling is performed in sequential mode, with a reduction of approximately 15% at each rolling pass.

[0029] In some embodiments, the titanium base material has a final cross-sectional reduction rate of 90% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Fig. 1 is a logarithmic plot of load vs. cycles in a fatigue test of a 5.5 mm rod bent in advance in a partial vertebrectomy test in accordance with ASTM F1717. Fig. 2A is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 1. Fig. 2B is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 2.Fig. 2C is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 3. Fig. 2D is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 4. Fig. 3A is an EBSD image of the cross section of the titanium material of Example 1 along the longitudinal direction near the centroid of the cross section. Fig. 3B is an EBSD image of the cross section of the titanium material of Example 2 along the longitudinal direction near the centroid of the cross section. Fig. 3C is an EBSD image of the cross section of the titanium material of Example 3 along the longitudinal direction near the centroid of the cross section. Fig. 3D is an EBSD image of the cross section of the titanium material of Example 4 along the longitudinal direction near the centroid of the cross section. Fig. 4 is a graph showing the time-dependent change in the number of viable bacteria attached to each test piece. MODE FOR CARRYING OUT THE INVENTION

[0031] The titanium material, the titanium material applications, the method for imparting an antibacterial property, and the method for producing a titanium materialaccording to an embodiment of the present disclosure willbe described below. The present disclosure is not limitedto these embodiments. A combination of embodiments that isnot explicitly described is also suitably employed. Anumerical range includes any two numerical values described and any numerical value between the two numerical values. Typically, a numerical range includes any lower limit, any upper limit, and any numerical value between the lower limit and the upper limit.

[0032] <<Titanium material>> The titanium material has a titanium content of98.955 mass% or more. The lower limit of the titaniumcontent may be 98.985 mass%, 99.000 mass%, 99.020 mass%, 99.050 mass%, 99.080 mass%, 99.100 mass%, 99.120 mass%, 99.140 mass%, 99.160 mass%, 99.180 mass%, or 99.200 mass%. The upper limit of the titanium content may be 100.000 mass%, 99.980 mass%, 99.960 mass%, 99.940 mass%, 99.920 mass%, 99.900 mass%, 99.880 mass%, 99.860 mass%, 99.840 mass%, 99.820 mass%, or 99.800 mass%.

[0033] The titanium material may contain oxygen, nitrogen, iron, carbon, hydrogen, and the like as an element otherthan titanium. The oxygen content may be 0.30 mass% orless, 0.25 mass% or less, 0.20 mass% or less, or 0.15 mass%or less. The nitrogen content may be 0.05 mass% or less,0.04 mass% or less, 0.03 mass% or less, or 0.02 mass% orless. The iron content may be 0.30 mass% or less, 0.25mass% or less, 0.20 mass% or less, or 0.15 mass% or less. The carbon content may be 0.08 mass% or less, 0.07 mass% orless, 0.06 mass% or less, or 0.05 mass% or less. Thehydrogen content may be 0.018 mass% or less, 0.16 mass% or less, 0.14 mass% or less, or 0.12 mass% or less. Alternatively, the composition of the titanium material may be values according to JIS type 1 to type 4 or ASTM Grade 1 to Grade 4.

[0034] The titanium material may have a tensile strength ina range of 1000 MPa or more and 1500 MPa or less. Thelower limit of the tensile strength may be 1050 MPa, 1080 MPa, 1100 MPa, 1120 MPa, 1140 MPa, 1160 MPa, 1180 MPa, or1200 MPa. The upper limit of the tensile strength may be1460 MPa, 1440 MPa, 1420 MPa, 1400 MPa, 1380 MPa, 1360 MPa, or 1340 MPa.

[0035] The titanium material preferably has a tensile strength of 1100 MPa or more, 1120 MPa or more, 1140 MPa or more, 1160 MPa or more, 1180 MPa or more, 1200 MPa or more, 1220 MPa or more, 1240 MPa or more, 1260 MPa or more, or 1280 MPa or more, within the above range.

[0036] The titanium material may have an elongationpercentage in a range of 3% or more and 15% or less. Thelower limit of the elongation percentage may be 3.5%, 4%,4.5%, or 5%. The upper limit of the elongation percentagemay be 14%, 13%, 12%, 11%, 10%, 9%, 8%, or 7%.

[0037] The titanium material preferably has an elongation percentage of 4% or more, 4.5% or more, 5% or more, or 5.5% or more, within the above range.

[0038] In a fatigue test in accordance with the guidance of ASTM F1717 in which a 5.5 mm rod is bent at 30 degrees, the titanium material has a fatigue strength or a durability limit (hereinafter, also referred to as “fatigue strength or the like”) each of which is improved in a range of 10% or more and 30% or less, preferably 20% or more, ascompared with a Ti-6Al-4V alloy. The fatigue strength orthe like is preferably improved by 11% or more, 12% or more, 14% or more, 14% or more, 15% or more,16% or more, 17% or more, 18% or more, 19% or more, 20% or more, 21% or more, 22% or more, 23% or more, 24% or more, or 25% ormore. The fatigue strength or the like may be improved by29% or less, 28% or less, 27% or less, or 26% or less.

[0039] The fatigue strength or the like is more preferably improved by 21% or more, 22% or more, 23% or more, 24% or more, or 25% or more.

[0040] In a fatigue test in accordance with the guidance of ASTM F1717, a 5.5 mm rod that is bent at 30 degrees in advance is used, and the rod causes no break and withstands up to 5,000,000 cycles even when a load of Le (durableload / shake load) is applied thereto. The rolled rod has adurable load increased by 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 20% or more, or 25% or more.

[0041] The titanium material may have a Vickers hardness ina range of 280 HV or more and 380 HV or less. The lowerlimit of the Vickers hardness may be 285 HV, 290 HV, 295HV, 300 HV, 305 HV, 310 HV, 315 HV, or 320 HV. The upperlimit of the Vickers hardness may be 375 HV, 370 HV, 365 HV, 360 HV, 355 HV, 350 HV, 345 HV, or 340 HV.

[0042] The titanium material preferably has a Vickers hardness of 300 HV or more, 305 HV or more, 310 HV or more, 315 HV or more, or 320 HV or more, within the above range.

[0043] The titanium material may have crystal grains whoseless. The lower limit of the average crystal grain sizemay be 1 nm, 3 nm, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, . The upper limit of the average crystal grain size may be

[0044] In the titanium material, at least some of crystalgrains may have an anisotropic expanded structure. In thetitanium material, at least some of crystal grains preferably have a uniform anisotropic expanded structure. The anisotropic expanded structure refers to a structure in which at least some crystal grains are extended in aspecific direction. The specific direction typicallyrefers to a direction in which the titanium base material is extruded during rolling (hereinafter, also referred toas “rolling direction”). When the titanium material has arod shape or a plate shape, the specific direction corresponds to the longitudinal direction.

[0045] In the anisotropic expanded structure, the lowerlimit of the standard deviation of the average crystal .The upper limit of the standard deviation of the

[0046] The percentage of the crystal grains having an anisotropic expanded structure may be 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 85% or more, 90% or more, 92% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, or 100%, in terms of area ratio in a SEM image, with respect to the total crystal grains included in the titanium material.

[0047] When the titanium material has a rod shape, the average crystal grain size of the crystal grains (DRD1) is determined in the centroid area of a longitudinal cross section along the longitudinal direction passing through the centroid of the cross section of the titanium material; and the average crystal grain size of the crystal grains (DTD1) is determined in the centroid area of a cross section orthogonal to the longitudinal cross section. In this case, the ratio of DRD1to DTD1(DRD1 / DTD1) may be within arange of 1.10 or more and 2.50 or less, and preferably 1.20or more. The lower limit of the ratio (DRD1 / DTD1) may be1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, or 1.50. Theupper limit of the ratio (DRD1 / DTD1) may be 2.40, 2.30, 2.20, 2.15, 2.10, 2.05, or 2.00.

[0048] The ratio (DRD1 / DTD1) is preferably 1.25 or more, 1.30 or more, 1.35 or more, 1.40 or more, 1.45 or more, or 1.50 or more.

[0049] When the titanium material has a rod shape, the average crystal grain size of the crystal grains (DRD1) may or less in the centroid area of a longitudinal cross section along the longitudinal direction passing through the centroid of thecross section of the titanium material. The lower limit ofthe average crystal grain size (DRD1 .The upper limit of the average crystalgrain size (DRD1

[0050] When the titanium material has a rod shape, the average crystal grain size of the crystal grains (DRD1) is determined in the centroid area of a longitudinal crosssection along the longitudinal direction passing through the centroid of the cross section of the titanium material; and the average crystal grain size of the crystal grains along the longitudinal direction (DRD2) is determined in the 0.1 mm-inside area toward the centroid from the outer peripheral surface at which a cross section orthogonal to the longitudinal cross section intersects. In this case, the ratio of DRD1 to DRD2 (DRD1 / DRD2) may be within a range of 1.10 or more and 2.50 or less, and preferably 1.20 or more. The lower limit of the ratio (DRD1 / DRD2) may be 1.15, 1.20,1.25, 1.30, 1.35, 1.40, 1.45, or 1.50. The upper limit ofthe ratio (DRD1 / DRD2) may be 2.40, 2.30, 2.20, 2.15, 2.10, 2.05, or 2.00.

[0051] The shape of the titanium material is not particularly limited, and any shape such as a rod shape, a plate shape, a sheet shape, a spherical shape, a polyhedral shape, a wire shape, a conical shape, a spindle shape, and an irregular shape can be adopted.

[0052] The titanium material preferably has a rod shape. When the titanium material has a rod-like shape, and its cross-sectional shape is not particularly limited. It may include, but is not limited to, regular or irregular polygons, shapes with rounded vertices, circles, ellipses,oval shapes, racetrack (track) shapes, and complex or composite shapes such as T-shapes, H-shapes, I-shapes, L- shapes, U-shapes, or other functional profiles. The cross- sectional shape of the titanium material is preferably a polygon (which may be regular or irregular), a polygon with rounded vertex portions, or a circular shape. The polygon may be a triangle, quadrilateral (e.g., square, rectangle, rhombus), pentagon, hexagon, star shape, or any other suitable polygonal configuration.

[0053] The titanium material preferably has an antibacterialproperty. The term “antibacterial property” as used hereinrefers to a property of preventing or reducing the growth, reproduction, or adsorption of a microorganism (for example, bacterial and fungal organisms), or of killing a microorganism.

[0054] The term “bacterial and fungal organisms” as used in the present disclosure means all genus and species of bacteria and fungi, including, but not limited to, allspherical, rod-shaped, and spiral bacteria. Non-limitingexamples of bacteria include staphylococci (e.g., Staphylococcus epidermidis, Staphylococcus aureus), Enterrococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, Clostridioides difficile among other gram-positivebacteria and gram-negative bacilli. Non-limiting examplesof fungal organisms include Candida albicans, Candida krusei, Candida parapsilosis, Candida spp, Candida pseudotropicalis, Candida glabrata, Candida lusitaniae, and Candida tropicalis.

[0055] In some embodiments, the bacteria are gram positive bacteria including, but not limited to, Staphylococcus aureus, Staphylococcus epidermidis, Methicillin-resistantStaphylococcus aureus (MRSA), or the like. In someembodiments, the bacteria are gram negative bacteria including, but not limited to, Pseudomonas aeruginosa, E. Coli, Klebsiella pneumoniae, Legionella pneumophila, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens, Helicobacter pylori, Salmonella enteritidis, and Salmonella typhi.

[0056] The antibacterial property is preferably exhibited as the inhibition of either the adsorption or the growth, or both, of one or more microorganisms. These microorganisms may include, but are not limited to, those selected from the group consisting of Staphylococcus aureus, Staphylococcus epidermidis, Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli (E. coli), Pseudomonas aeruginosa, or other bacteria known to causeinfection or contamination.

[0057] In some embodiments, the titanium material inhibits the microorganism from adsorption or growth on the titanium material by 100%, 95%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10%, by at least 5%, or by a range between any two values therefrom.

[0058] In some embodiments, when the titanium material has a rod shape, the microorganism can be more inhibited from adsorption or growth on the outer peripheral surface than on the cross section perpendicular to the longitudinaldirection. In some embodiments, when the titanium materialhas a rod shape, the microorganism is preferably more inhibited from adsorption or growth on the outer peripheral surface than on the cross section perpendicular to the longitudinal direction, by at least 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10%, or by a range between any two values from these values.

[0059] Without being bound by any theory, it is presumed that the tensile properties, fatigue strength, antibacterial properties, toughness, and the like of the titanium material are affected by the specific anisotropicexpanded structure. The titanium material excellent intensile properties, fatigue strength, antibacterial properties, and toughness can be widely used in various industrial applications such as medical devices, surgical implants and instruments, aerospace or food industries.

[0060] <<Titanium material application>> Aspects of the present invention provide a titaniummaterial having an antibacterial property. In someembodiments, the titanium material may be used in a medical device, such as, for example, an implant (implant for orthopaedics, implant for general surgery, or implant fordentistry, but not limited thereto). In some embodiments,the titanium material may be used in a surgical instrument, a vascular stent, an endoscopic instrument, a catheter part, a guide wire, a kirschner wire (K-wire), a plate, a pin, a screw, a needle, a pacemaker lead, a dental appliance, or the like, or in an implantable medicaldevice. In some embodiments, the titanium material can beused in surgical instruments. In some embodiments, thetitanium material can be used in biosensors. In someembodiments, the titanium material can be used inkitchenware. In some embodiments, the titanium materialcan be used in experimental tools. In some embodiments,the titanium material can be used in a kirschner wire.

[0061] Non-limiting examples of medical devices include vascular catheters, such as peripherally insertable central venous catheters, dialysis catheters, long term tunneled central venous catheters, peripheral venous catheters, single-lumen and multiple-lumen short-term central venous catheters, arterial catheters, pulmonary artery Swan-Ganz catheters, and the like, urinary catheters, other long term urinary devices, tissue bonding urinary devices, renal stents, penile prostheses, vascular grafts, vascular access ports, wound drain tubes, hydrocephalus shunts, ventricular drainage catheters, neurologic and epidural catheters, neurostimulators, peritoneal dialysis catheters, pacemaker capsules, artificial urinary sphincters, small or temporary joint replacements, dilators, heart valves, orthopedic prosthesis, spinal hardware, surgical site repair mesh (e.g., hernia mesh), endotracheal tubes, biliary stents, gastrointestinal tubes, colorectal tract implants, male and female reproductive implants, cosmetic or reconstructive implants, stethoscope drums, orthopedic implants (e.g., joint (knee, hip, elbow, shoulder, ankle), prostheses, external fixation pins, intramedullary rods and nails, spine implants), cardiac pacemakers, defibrillators, electronic device leads, adaptors, lead extensions, implantable infusion devices, implantable pulse generators, implantable physiological monitoring devices, devices forlocating an implantable pulse generator or implantable infusion device under the skin, and devices (e.g. refill needles and port access cannulae) for refilling an implantable infusion device or other medical and indwelling devices that may be subject to microbial infestation.

[0062] In some embodiments, the device can be used for, but not limited to, high speed surgical drill, vertebroplasty and kyphoplasty devices, minimally invasive surgical instruments, microsurgical instruments and endoscopy devices, orthopedic implants, and surgical instruments.

[0063] In some embodiments, the device is a titanium device and can be used for, but not limited to, orthopedic implants, dental implants, spinal implants, minimally invasive surgical instruments and endoscopy devices, and surgical instruments.

[0064] In some embodiments, the antibacterial property of the titanium material is achieved without adding an antibacterial agent into the titanium material or onto the titanium material.

[0065] Aspects of the present disclosure relate to an aerospace industrial component including the titaniummaterial.

[0066] In some embodiments, the aerospace industrial component is a jetliner component, a rocket component, or asatellite component. In some embodiments, the aerospaceindustrial component may be a fuselage (body), a wing (aerofoil), a stabilizer (stabilizing plate), a control surface (control wing surface), a landing gear (landing equipment), an engine, a propeller, a skin (outer plate), a stringer (longitudinal member), a frame (molding material, circumferential frame, or assistant), a spar (beam), a rib (ossicle), a bulkhead (partition), a longeron (strong longitudinal member), a rivet, a bolt, a screw, a welding member, an antenna, a tank, a nozzle, a nosecone, a turbine, a pump, a gas generator, a wheel, a panel, an arm, a honeycomb, and the like.

[0067] Aspects of the present disclosure relate to adecorative article including the titanium material. Insome embodiments, the decorative article may be an eyeglass frame, a piercing, a tie pin, a lighter, a wristwatch, a pocket watch, a necklace, an earphone, a headphone, a brooch, a finger ring, a bracelet, an anklet, a cuff, a cane, a stick, a key holder, a wallet, a belt, a hair ornament, a badge, a brooch, a fastener, or the like.

[0068] Non-limiting uses of the titanium material according to aspects of the present disclosure are listed below.

[0069] <Application for antibacterial property> Medical device: Medical devices such as an implant for orthopaedics, dentistry, and spinal, a catheter, and a surgical instrument. Water purification: A water purification system that can sterilize bacteria to safely consume water. Equipment for packaging and processing food: The titanium material is used as an antimicrobial metal in a food packaging material to inhibit growth of bacteria causing spoilage, thereby extending the shelf life of fresh food. HVAC system: The titanium material may be incorporated into heating, ventilating, and air- conditioning (HVAC) systems to prevent growth of bacteria and mold in an air duct or a filter. Consumer product: The titanium material can be used as an antimicrobial titanium material in a variety of consumer products, such as kitchenware and a cutting knife to maintain hygiene and reduce bacterial contamination. Veterinary medicine: The titanium material is used as an antimicrobial metal for a veterinary surgical implantand an instrument to prevent bacterial infection in animals.

[0070] <Application for high strength> Aerospace: The titanium with enhanced fatigue strength can be utilized in an aerospace component such as an aircraft frame, a landing gear, and an engine component. The combination of excellent fatigue resistance and lightweight properties is ideal for reducing weight while maintaining structural integrity and improving fuel efficiency and performance. Biomedical implant: The titanium material having improved fatigue strength can be used for a biomedical implant such as an orthopedic implant, a dental implant,and a cardiovascular implant (stent and the like). Due toits biocompatibility and corrosion resistance, the titanium material is suitable for long-term implantation in the human body. Motor vehicle: In the automotive industry, the titanium material with higher fatigue strength is used for a key component such as an engine component, a suspension system, and an exhaust system. Sporting goods: The titanium material with enhanced fatigue strength can be used in sporting goods such as a bicycle frame, a golf club head, a tennis racket, and otherequipment requiring lightweight and highly durable materials.

[0071] Marine application: The titanium material having improved fatigue strength can be used for marine applications such as a hull, a propeller, and a marinestructure. Due to its corrosion resistance in seawater,the titanium material is an attractive material for use in marine environments. Power generation: The titanium material having high fatigue strength can be used for a power generation facility such as a gas turbine, a steam turbine, and anuclear reactor. Due to its resistance to corrosion andhigh temperature environments, the titanium material is suitable for such demanding applications. Chemical treatment: In the chemical treatment industry, the titanium material having enhanced fatigue strength can be used for equipment such as a pressurevessel, a heat exchanger, and a piping system. Due to itsexcellent corrosion resistance, the titanium material is suitable for handling corrosive chemicals and environments.

[0072] Electronics: The titanium material having improved fatigue strength can be used for an electronic device requiring lightweight and durable materials such as amobile phone, a laptop, and a wearable technology. Military and defense: The titanium material with higher fatigue strength can be used in military and defense applications such as an aircraft, a vehicle, a naval vessel, and a ballistic protection system, where strength, durability, and lightweight properties are essential. Industrial equipment: The titanium material with enhanced fatigue strength is applied in various industrial equipment such as a machine part, a tool, and a structure. A material that has high fatigue resistance and is lightweight is beneficial for improving performance and life.

[0073] <<Method for imparting antibacterial property>> Aspects of the present disclosure relate to a method for imparting an antibacterial property, the method including a step of applying the titanium material to a site requiring an antibacterial property.

[0074] Due to the antibacterial property of the titanium material, an antibacterial property can be imparted to a site requiring an antibacterial property only by applying the titanium material to the site requiring an antibacterial property.

[0075] In some embodiments, the site requiring an antibacterial property is not particularly limited and may be a human body (body, body surface (skin, hair, eyeball, etc.)), daily necessities, medical equipment, an automobile, public transportation (railway, aircraft, bus, ship), office supplies, building supplies, school supplies, social infrastructure (water supply facility, gas facility, electric facility, road), industrial supplies, and thelike. The form of the titanium material may beappropriately designed according to these application sites.

[0076] In some embodiments, aspects of the titanium material application may be implantation in the body, contact with a body surface, incorporation into an article, attachment to an article, processing of the titanium material into a component, or the like.

[0077] <<Method for producing titanium material>> Aspects of the present disclosure relate to a method for producing a titanium material, the method including: preparing a titanium base material having a titanium content of 99 mass% or more; and rolling the titanium base material at a cross- sectional reduction rate of 15% or less per one time.

[0078] (Titanium base material preparation step) In this step, a titanium base material having atitanium content of 99 mass% or more is prepared. Sincethe elemental composition does not change between the titanium base material and the titanium material, a titanium base material having the elemental composition described in the titanium material may be prepared.

[0079] The shape of the titanium base material is not particularly limited as long as it can be subjected to thenext step, the rolling step. In some embodiments, theshape of the titanium base material is preferably a rod ora plate shape. A titanium base material having a rod shapemay be obtained to be subjected to the rolling step as itis. In some embodiments, a titanium ingot or a titaniumblock may be subjected to pressing or blooming into a slab, a bloom, or a billet, thereby obtaining a titanium base material.

[0080] (Rolling step) In this step, the titanium base material is rolled at a cross-sectional reduction rate of 15% or less per onetime. When the cross-sectional reduction rate is 15% orless per one time, a titanium material having ananisotropic expanded structure can be suitably produced.

[0081] In some embodiments, the rolling process may be rollrolling, universal rolling, or groove roll rolling. Insome embodiments, the rolling step may be preferably groove roll rolling.

[0082] In some embodiments, the cross-sectional reduction rate per one time in the rolling may be 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, or 4% or less.

[0083] In some embodiments, the cross-sectional reduction rate per one time in the rolling may be 0.5% or more, 1% or more, 1.5% or more, 2% or more, 2.5% or more, 3% or more, or 3.5% or more.

[0084] In some embodiments, the rolling step is preferablyperformed a plurality of times. When rolling is performeda plurality of times at a low cross-sectional reduction rate, a large strain can be introduced into the titanium base material to form fine crystal grains and have ananisotropic expanded structure. The number of rollingsteps may be appropriately set according to the intended use and shape of the titanium material, the structure ofcrystal grains, and the like. In some embodiments, thenumber of rolling steps may be 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, 14 times, 15 times, 16 times, 17 times, 18 times, 19 times, 20 times, 21 times, 22 times, 23 times, 24 times, 25 times, 26 times, 27 times, 28 times, 29 times, 30 times, 31 times, 32 times, 33 times, 34 times, 35 times, 36 times, 37 times, 38 times, 39 times, 40 times, 41 times, 42 times, 43 times, 44 times, 45 times, 46 times, 47 times, 48 times, 49 times, or 50 times, or may be in a range between any two values from these values.

[0085] In some embodiments, the material is rotated between successive rolling steps by an angle ranging from 10 to 350 degrees, inclusive. A preferred rotation angle between steps is approximately 90 degrees or 270 degrees, which facilitates uniform deformation and improved material properties.

[0086] In some embodiments, rolling is performed in a sequential manner, with each rolling pass achieving a cross-sectional area reduction of approximately 15%, and the rolling speed being maintained in the range of 0.6 to 130 m / min, depending on the required material characteristics and processing conditions. Additionally, insome embodiments, rolling of rod material is carried out ata temperature in the range of R.T. to 900 °C, with apreferred temperature range of R.T. to 650 °C, to ensureoptimal workability while preventing undesirable microstructural changes.

[0087] In some embodiments, the final cross-sectional reduction rate of the titanium base material may be 70% or more, 75% or more, 80% or more, 82% or more, 84% or more,86% or more, 88% or more, or 90% or more. Thus, a titaniummaterial excellent in tensile strength, fatigue strength,and antibacterial property can be produced. The finalcross-sectional reduction rate of the titanium base material may be 98% or less, 97% or less, 96% or less, or95% or less. The number of the rolling steps can beappropriately set so that such a final cross-sectional reduction rate is obtained.

[0088] When the rolling step is performed a plurality of times, the rolling step may be performed by passing through a rolling mill a plurality of times so that the cross-sectional area is reduced step by step. Alternatively, twoor more rolling mills different from each other in the setting range of the cross-sectional area are prepared, rolling is performed through the first rolling mill withwhich a titanium material having a larger cross-sectional area is rolled, and then rolling is continuously performed through the second rolling mill with which a titanium material having a smaller cross-sectional area than the cross-sectional area for the first rolling mill is rolled. Thereafter, as necessary, the third rolling mill or the like with which a titanium material having a still smaller cross-sectional area is rolled may be provided tocontinuously perform rolling. The two or more rollingmills may be provided in series, in parallel, or in any arrangement with a combination thereof. The rolling process may be configured for full automation, including the incorporation of an additional step of rotating the rods between rolling mills. This automated rotation facilitates controlled deformation and enhances process efficiency and consistency.

[0089] (Post-step) After the rolling step, a post-step such as bend correction, cutting-off, cutting, or a combination thereofmay be performed. The bend correction is a step ofcorrecting the bend of a titanium material into a linear shape when the titanium material after the rolling step isin a bend state. The cutting-off is a step of cutting-offa titanium material into a length suitable for the nextstep or the final product. The cutting is a step ofcutting the outer periphery of a titanium material to form an intended cross-sectional shape (typically, a circularshape). A swaging process may be performed instead of thebend correction and the cutting. The swaging process is astep of correcting the bend of a titanium material by rotary forging and forming the outer periphery shape (cross-sectional shape) thereof into a predetermined shape(typically, a circular shape). The bend correction,cutting-off, cutting, and swaging processes can be carried out using conventional or known apparatuses. In the method for producing a titanium material according to the present embodiment, any stage of the rolling step, as well as any subsequent processing step provided as needed, may be performed at a temperature that does not promote crystal grain growth in the titanium material. Conducting the process under such conditions contributes to the formation of refined (smaller) crystal grains and an anisotropically expanded grain structure in the titanium material. EXAMPLES

[0090] Hereinafter, the present disclosure will be described in detail with reference to examples, but the present disclosure is not limited to the following examples as long as the gist thereof is not exceeded.

[0091] <<Production of titanium material>> (Example 1) As the titanium base material, a titanium billet (a rod having a circular cross section, a diameter of 1.250 inches mm, a length of 13.1 inches, “Titanium Bar Grade 4” manufactured by Carpenter Titanium by Dynamet) wasprepared, and rolled to produce a titanium material. Therolling was performed according to the following procedure. That is, the titanium base material was passed through a groove roll rolling mill (“10 type groove rolling mill” manufactured by Oono-roll Corporation) a plurality of times to be rolled without heating until the final cross- sectional reduction rate became about 94% (a cross- sectional reduction rate of about 1.7% to about 12.6% per one time), thereby obtaining a titanium precursor having asubstantially square cross section. The titanium precursorwas subjected to bend correction, cutting, and cutting-off to obtain a titanium material having a circular cross section (diameter: 6 mm) and a length of 200 mm.

[0092] (Example 2) A titanium material was produced in the same manner as in Example 1 except that the titanium base material was rolled at 300°C in the rolling step.

[0093] (Example 3) A titanium material was produced in the same manner as in Example 1 except that the titanium base material was rolled at 500°C in the rolling step.

[0094] (Example 4) A titanium material was produced in the same manner as in Example 1 except that the titanium base material was rolled at 700°C in the rolling step.

[0095] (Reference example 1) A commercially available Ti-6Al-4V titanium rod for spinal implant was prepared and used as a reference sample as it was.

[0096] <<Measurement of tensile strength and elongation percentage>> Tensile strength (MPa) and elongation percentage (%) were measured in accordance with ASTM F67.

[0097] <<Measurement of fatigue strength>> A fatigue test was performed in accordance with ASTM F1717, and the number of cycles was recorded until each load (N) decreased and breakage occurred after the start ofthe test. The load was continuously reduced until the testpiece withstood 5,000,000 cycles, which is defined as thedurability limit. The durability limit indicates a loadfor which the test piece causes no break and can withstand infinite load cycles.

[0098] Fig. 1 is a logarithmic plot of load vs. cycles in a fatigue test of a 5.5 mm rod bent in advance in a partialvertebrectomy test in accordance with ASTM F1717. Fig. 1clearly shows that the titanium material of the examples had a fatigue durability limit equal to or higher than that of Ti-6Al-4V.

[0099] <<Measurement of vickers hardness>> A Vickers hardness test was performed in accordancewith JIS Z 2244. Using a micro Vickers hardness tester(“HM-220” manufactured by Mitutoyo Corporation), measurement was performed at 17 points or more per one cross section to calculate the average value.

[0100] <<Measurement of average crystal grain size>> Using a scanning electron microscope (“SU-70” manufactured by Hitachi High-Tech Corporation), an EBSD detector (“DigiViewIV” manufactured by EDAX), and EBSD data analysis software (“OIM Analysis Ver. 6.0” created by TSL Solutions), crystal structure analysis was performed in a. Theallowable orientation difference, at which measurement points were deemed to be included in the same crystal grain, was defined as 5°, and a region surrounded by parts where adjacent measurement points had an orientation difference of 5° or more was regarded as a crystal grain. The crystal grain size was calculated as the diameter of the area of a circle having an area equal to the area ofthe crystal grain. The average crystal grain size wascalculated in terms of weight average from all the crystalgrain sizes within the analysis range. In addition, thedetermined at this time.

[0101] Determined according to the above procedure were: the average crystal grain size (DTD1) in the centroid area of a cross section orthogonal to the longitudinal direction of the titanium material; the average crystal grain size in the 0.1 mm-inside area toward the centroid from the outer peripheral surface at which a cross section orthogonal to the longitudinal direction of the titanium material intersects; the average crystal grain size of the crystal grains (DRD1) in the centroid area of a longitudinal cross section along the longitudinal direction passing through the centroid of the cross section of the titanium material;the average crystal grain size (DRD2) of the crystal grains along the longitudinal direction in the 0.1 mm-inside area toward the centroid from the outer peripheral surface of the titanium material at which a cross section orthogonal to the longitudinal cross section intersects; and the (DRD2).

[0102] <<Confirmation of anisotropic expanded structure>> From the same analysis results as in the measurement of the average crystal grain size, each crystal grain wascolored. Therefore, white indicates that there was nocrystal grain recognized.

[0103] The results are shown in Figs. 2A to 2D and 3A to 3D. Fig. 2A is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 1. Fig. 2B is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 2. Fig. 2C is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 3. Fig. 2D is an EBSD image of the vicinity of the outer peripheral surface of the titanium material of Example 4. Fig. 3A is an EBSD image of the cross section of the titanium material of Example 1 along the longitudinaldirection near the centroid of the cross section. Fig. 3B is an EBSD image of the cross section of the titanium material of Example 2 along the longitudinal direction near the centroid of the cross section. Fig. 3C is an EBSD image of the cross section of the titanium material of Example 3 along the longitudinal direction near the centroid of the cross section. Fig. 3D is an EBSD image of the cross section of the titanium material of Example 4 along the longitudinal direction near the centroid of thecross section. From these results, it is found that thetitanium material of the examples has a crystal grain structure expanded along the longitudinal direction.

[0104] <<Evaluation of antibacterial property>> The test piece was cut to a length of 10 mm with a laser, washed by blasting and passivation in accordancewith ASTM B600, and sterilized with an autoclave. Xen36, amutant species of Staphylococcus aureus, was cultured so asto be 1.0 × 108 CFU / mL and prepared. The Xen36 culturesolution was transferred to a 24 well plate and the testpiece was incubated while being shaken at 37 °C. Thenumber of viable bacteria of Xen36 attached after 1 day, 3days, and 7 days was checked by a CFU test. The resultsare shown in Fig. 4. Fig. 4 shows the time-dependentchange in the number of viable bacteria attached to eachtest piece. In the titanium material of the examples, itwas confirmed that the attached amount of bacteria was suppressed after one day, the bacteria became old and died so that the number of viable bacteria was reduced (after three days), and then a biofilm was moderately formed (after seven days).

Claims

CLAIMS

1. A titanium material, wherein a titanium content is 98.955 mass% or more, and a tensile strength is in a range of 1000 MPa or more and 1500 MPa or less.

2. The titanium material according to claim 1, wherein the tensile strength is in a range of 1100 MPa or more and 1500 MPa or less.

3. The titanium material according to claim 1, wherein the titanium material has an elongation percentage in a range of 3% or more and 15% or less.

4. The titanium material according to claim 1, wherein the titanium material has an elongation percentage in a range of 4% or more and 15% or less.

5. The titanium material according to claim 1, wherein the titanium material has a fatigue strength or a durability limit each of which is improved in a range of 15% or more and 30% or less as compared with a Ti-6Al-4V alloy in a fatigue test in accordance with ASTM F1717.

6. The titanium material according to claim 1, wherein the titanium material has a fatigue strength or a durability limit each of which is improved in a range of 20% or more and 30% or less as compared with a Ti-6Al-4V alloy in a fatigue test in accordance with ASTM F1717.

7. The titanium material according to claim 1, wherein the titanium material has a Vickers hardness in a range of 280 HV or more and 380 HV or less.

8. The titanium material according to claim 1, wherein the titanium material has a Vickers hardness in a range of 300 HV or more and 380 HV or less.

9. The titanium material according to claim 1, wherein the titanium material has crystal grains whose less.

10. The titanium material according to claim 1, wherein at least some of crystal grains of the titanium material have an anisotropic expanded structure.

11. The titanium material according to claim 1,wherein at least some of crystal grains of the titanium material have a uniform anisotropic expanded structure.

12. The titanium material according to claim 1, wherein the titanium material has a rod shape.

13. The titanium material according to claim 12, wherein the titanium material has a polygonal cross- sectional shape.

14. The titanium material according to claim 12, wherein the titanium material has a circular cross- sectional shape.

15. The titanium material according to claim 1, wherein the titanium material has a square bar shape or a sheet shape.

16. The titanium material according to claim 1, wherein the titanium material has an antibacterial property.

17. The titanium material according to claim 16, wherein the antibacterial property is inhibition of adsorption or growth of at least one microorganism selectedfrom the group consisting of Staphylococcus aureus, Staphylococcus epidermidis, Methicillin-resistant Staphylococcus aureus (MRSA), E. coli, and Pseudomonas aeruginosa.

18. An implant comprising the titanium material according to claim 1, which is suitable for orthopaedics, circulatory system, dentistry, or general surgery.

19. An instrument comprising the titanium material according to claim 1, which is suitable for orthopaedics or general surgery.

20. An aerospace industrial component comprising the titanium material according to claim 1.

21. The aerospace industrial component according to claim 20, wherein the aerospace industrial component is a jetliner component, a rocket component, or a satellite component.

22. A decorative article comprising the titanium material according to claim 1.

23. The decorative article according to claim 22,wherein the decorative article is an eyeglass frame, a piercing, a tie pin, a lighter, a wristwatch, or a necklace.

24. A method for imparting an antibacterial property, comprising applying the titanium material according to claim 1 to a site requiring an antibacterial property.

25. A method for producing a titanium material, comprising: preparing a titanium base material having a titanium content of 99 mass% or more; and rolling the titanium base material at a cross- sectional reduction rate of 15% or less per one time.

26. The method for producing a titanium material according to claim 25, wherein rolling the titanium base material is performed a plurality of times.

27. The method for producing a titanium material according to claim 25, wherein the titanium base material after rolling has a final cross-sectional reduction rate of 90% or more.

28. The method for producing a titanium materialaccording to claim 25, wherein rolling the titanium base material is configured for full automation, including incorporation of an additional step of rotating the titanium base material between rolling mills.

29. The method for producing a titanium material according to claim 25, wherein rolling the titanium base material is carried out at a temperatures that promotes crystal grain growth in the titanium material.

Images