Titanium blades and titanium plates

Abstract

To provide a titanium-made cutter excellent in sharpness and persistence and a titanium plate used for the same.SOLUTION: This invention relates to a titanium-made cutter, which is a cutter 10 made of titanium alloy with a Young's modulus of 110 GPa or more in an L direction and a T direction when a direction from the handle 2 of the cutter 10 to the cutting tip 1c of the blade 1 is the L direction, and when, in a direction orthogonal to the L direction, from the ridge 1a of the blade 1 to the tip 1b is the T direction, and with the ratio of 1.15 or more of the value of the higher Young's modulus to the value of the lower Young's modulus, in Young's moduli in the L direction and T direction, and an average value of the Vickers hardness at a center position in the thickness direction of the blade 1 of 300-450 HV1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] ,

[0001] The present invention relates to a titanium blade and a titanium plate.

Background Art

[0002] As a material for blades such as kitchen knives or knives, steel or stainless steel is often used. In addition, titanium, which is lightweight, does not rust, and has extremely little elution of metal ions, is also often used as a material for blades (see, for example, Patent Document 1). A blade cuts an object by concentrating force on a thin blade edge. Therefore, hardness is required for the blade, and most blades made of titanium are made of titanium alloys.

[0003] Well-known titanium alloy is Ti-6Al-4V. However, since Ti-6Al-4V does not have sufficient hardness, even if it is simply applied to a blade, the sharpness and its durability are not sufficient. Therefore, for example, in Patent Document 2, a β-type titanium alloy hardened by aging heat treatment is used as a material for a blade. According to Patent Document 2, by performing cold working of 20% or more and a predetermined aging treatment, it is possible to manufacture a titanium alloy blade having a blade edge with a hardness of HCR45 or more.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Because titanium's Young's modulus is about half that of steel, the cutting edge tends to warp in the elastic range, impairing its straightness and resulting in insufficient sharpness. Conventionally, to improve sharpness, the focus has been on hardening the cutting edge, as disclosed in the aforementioned Patent Document 2, etc.

[0006] However, to improve cutting performance, not only hardening but also rigidity is required, that is, an increase in Young's modulus is necessary. The β-type titanium alloy disclosed in Patent Document 2 has a low Young's modulus, so although aging treatment increases the Young's modulus, it may not be sufficient, making it difficult to maintain the straightness of the cutting edge and thus failing to adequately improve cutting performance. Furthermore, while aging treatment causes the precipitation of fine α-phase, and this precipitation strengthening increases hardness, it also reduces toughness and ductility, making the blade prone to chipping, as described later. In particular, if aging treatment is performed after cold working, more α-phase precipitates in areas where the strain from cold working is localized, making the decrease in toughness and ductility more apparent and leading to more significant chipping.

[0007] Furthermore, with titanium alloys, the harder the alloy, the more significantly its toughness and ductility decrease. In particular, if the material being cut contains minute hard particles, a large localized load is placed on the cutting edge, resulting in chipping if the cutting edge is hard. Chipping during use causes a significant decrease in cutting performance, making it impossible to guarantee the long-term sharpness.

[0008] The present invention aims to solve the above problems and provide titanium blades and titanium plates used therein that have excellent sharpness and sharpness retention. [Means for solving the problem]

[0009] This invention was made to solve the above problems, and its essence is the titanium blade and titanium plate described below.

[0010] (1) A blade made of titanium alloy, When the direction from the handle of the blade toward the tip of the blade is defined as direction L, and the direction perpendicular to direction L toward the blade's spine toward the cutting edge is defined as direction T, The Young's modulus in the L direction and the T direction is 110 GPa or more. In the Young's modulus in the L direction and the T direction, the ratio of the higher Young's modulus to the lower Young's modulus is 1.15 or greater, and The average Vickers hardness at the center of the blade in the thickness direction is 300-450 HV1. Titanium blades.

[0011] (2) The chemical composition of the titanium alloy is, in mass%, Al: 4.0-8.7% C: 0.100% or less, N: 0.050% or less, H: 0.016% or less, O: 0.30% or less, and It contains Si: 0~0.50%, and It contains a total of 0.3-5.0% of one or more elements selected from Fe, Cr, Ni, V, Cu, Mo, Mn, Nb, and Co. The remainder is Ti and impurities. The titanium blade described in (1) above.

[0012] (3) The chemical composition of the titanium alloy is such that a portion of the Ti is replaced by, in mass%, It contains one or more elements selected from Sn and Zr in total amount of 3.0% or less. The titanium blade described in (2) above.

[0013] (4) The chemical composition of the titanium alloy is such that a portion of the Ti is replaced by, in mass%, It contains one or more elements selected from Pd, Pt, Rh, and Ru in total amount of 0.25% or less. The titanium blade described in (2) or (3) above.

[0014] (5) A titanium plate used as a material for a titanium blade as described in any of (1) to (4) above, The Young's modulus in the first direction perpendicular to the thickness direction of the titanium plate, and in the second direction perpendicular to the thickness direction and the first direction is 110 GPa or more, in the Young's modulus in the first direction and the second direction, the ratio of the value of the higher Young's modulus to the value of the lower Young's modulus is 1.15 or more, and the average value of the Vickers hardness at the central position in the thickness direction of the titanium plate is 300 to 450 HV1, Titanium plate.

[0015] (6) The thickness is 2.0 to 7.0 mm, The titanium plate according to (5) above.

Effect of the Invention

[0016] According to the present invention, a titanium cutting tool excellent in sharpness and its durability, and a titanium plate used therefor can be obtained.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a diagram schematically showing an example of the shape of a titanium cutting tool of the present embodiment. [Figure 2] FIG. 2 is a diagram for explaining the measurement position of Vickers hardness. [Figure 3] FIG. 3 is a diagram for explaining the direction of the blade when cutting out the portion that becomes the blade from the titanium plate. [Figure 4] FIG. 4 is a diagram for explaining the shape of the cutting tool used in the present example.

Mode for Carrying Out the Invention

[0018] The inventors of the present invention studied the sharpness and durability of titanium cutting tools and obtained the following findings.

[0019] (a) In order to maintain the straightness of the cutting edge and improve the sharpness, it is necessary to increase the hardness and rigidity of the titanium plate used as the material to a certain extent.

[0020] (b) On the other hand, if the hardness and rigidity are excessive, chipping may occur in the material being cut if microscopic hard material is present, and the durability of the cutting performance will deteriorate.

[0021] (c) By creating a difference in rigidity between the direction from the handle of the blade to the tip of the blade and the direction from the spine of the blade to the cutting edge, when the cutting edge comes into contact with a minute hard object in the object being cut, the cutting edge will avoid the direction of the lower rigidity, thereby suppressing chipping of the blade, while maintaining the straightness of the cutting edge in the direction of the higher rigidity.

[0022] A titanium cutting tool and a titanium plate used therein according to one embodiment of the present invention are based on the above-mentioned findings. The requirements of the titanium cutting tool and titanium plate of this embodiment will be described in detail below.

[0023] 1. Titanium blades The titanium blade according to this embodiment is a blade made of a titanium alloy. Figure 1 is a schematic diagram showing an example of the shape of the titanium blade according to this embodiment. As illustrated in Figure 1, the blade 10 includes a blade 1 and a handle 2. The blade 1 also includes a spine 1a, a cutting edge 1b, and a tip 1c. In this specification, the direction from the handle 2 of the blade 10 toward the tip 1c of the blade 1 is called the L direction, and the direction perpendicular to the L direction, from the spine 1a of the blade 1 toward the cutting edge 1b, is called the T direction.

[0024] In the titanium blade according to this embodiment, in order to maintain the straightness of the cutting edge and improve sharpness, the Young's modulus of the blade 1 in the L and T directions is set to 110 GPa or more, and the average value of the Vickers hardness at the center of the thickness direction of the blade 1 is set to 300 to 450 HV1.

[0025] By setting the Young's modulus of blade 1 in the L and T directions to 110 GPa or higher, it is possible to suppress the deflection of the cutting edge during cutting and maintain the straightness of the cutting edge. In addition, by setting the average Vickers hardness at the center of the thickness direction of blade 1 to 300 HV1 or higher, the cutting performance can be improved and chipping of the blade can be suppressed. On the other hand, if the average Vickers hardness at the center of the thickness direction of blade 1 exceeds 450 HV1, it becomes excessively hard, which impairs the toughness and ductility of the titanium alloy, making chipping more likely.

[0026] It is preferable that the Young's modulus of blade 1 in both the L and T directions be 114 GPa or higher. Furthermore, it is preferable that the average Vickers hardness at the center of blade 1 in the thickness direction be 330 to 420 HV1.

[0027] An example of a method for measuring the Young's modulus of a cutting tool is as follows: Tensile test specimens with a parallel section length of 12 mm, a parallel section width of 6.25 mm, a gauge length of 10 mm, and a shoulder radius of 6 mm are taken from the L and T directions of the blade. Before processing into the test specimen shape, the parallel section is made flat by grinding to a plate thickness of approximately 0.5 to 1.5 mm. A strain gauge with a gauge length of 3 mm is attached to the center of the parallel section of the tensile test specimen, and a stress load of 100 to 400 MPa is applied five times at a stroke speed of 0.25 mm / min, and the average value is taken. If the blade is small and the above test specimen cannot be taken, a tensile test specimen with a proportionally reduced parallel section may be used.

[0028] Furthermore, an example of a method for measuring the Young's modulus of the material plate is as follows: Prepare a 13B tensile test specimen according to JIS Z 2241:2011 (parallel section width 12.5 mm, parallel section length 60 mm, gauge length 50 m). Attach a strain gauge with a gauge length of 3 mm to the center of the parallel section of the tensile test specimen, and apply a stress load of 100 to 400 MPa five times at a stroke speed of 0.25 mm / min, and take the average value.

[0029] The method for measuring the average Vickers hardness at the center of the thickness direction of blade 1 will be explained with reference to Figure 2. At an arbitrary position, a thickness cross section parallel to the L direction (referred to as the L section) and a thickness cross section parallel to the T direction (referred to as the T section) are cut out, and measurements are taken at five points each at the center of the thickness direction in the L section and the T section.

[0030] Then, by averaging the Vickers hardness measurements obtained at the 10 points, the average Vickers hardness at the center position in the thickness direction of blade 1 is determined. Note that "HV1" refers to the "hardness symbol" when the Vickers hardness test is performed with a test force of 9.8 N (1 kgf) (see JIS Z 2244-1:2020).

[0031] In the titanium blade according to this embodiment, the ratio of the higher Young's modulus to the lower Young's modulus in the L and T directions of the blade 1 is set to 1.15 or higher. As described above, by creating a difference in rigidity between the L and T directions, when the cutting edge comes into contact with a minute hard object in the object to be cut, the cutting edge avoids chipping by moving in the direction of lower rigidity, while maintaining the straightness of the cutting edge in the direction of higher rigidity.

[0032] It is acceptable for the Young's modulus to be higher in either the L direction or the T direction. The ratio of the Young's moduli in the L and T directions is preferably 1.20 or higher. While there is no specific upper limit, the industrially feasible upper limit is 1.30.

[0033] 2. Titanium plate The titanium plate according to this embodiment is used as the material for the titanium blade described above. Therefore, the titanium plate used as the material has the same mechanical properties as the titanium blade described above. Specifically, when the direction perpendicular to the thickness direction of the titanium plate is taken as the first direction, and the direction perpendicular to both the thickness direction and the first direction is taken as the second direction, the Young's modulus in the first and second directions is 110 GPa or more, the ratio of the higher Young's modulus value to the lower Young's modulus value in the first and second directions is 1.15 or more, and the average Vickers hardness value at the center of the thickness direction of the titanium plate is 300 to 450 HV1.

[0034] The Young's modulus in the first and second directions is preferably 114 GPa or higher, the ratio of the Young's moduli in the first and second directions is preferably 1.20 or higher, and the average Vickers hardness at the center of the thickness direction of the titanium plate is preferably 330 to 420 HV1.

[0035] There are no particular restrictions on the thickness of the titanium plate according to this embodiment, but it is preferable that it be in the range of 2.0 to 7.0 mm since it is used as a material for cutting tools.

[0036] 3.Chemical composition The titanium alloy and the type of titanium plate used to make up the titanium blade according to this embodiment are not particularly limited as long as they have the mechanical properties described above. However, as mentioned above, since β-type titanium alloys generally have a low Young's modulus, it is preferable to use an α-type titanium alloy or an α+β-type titanium alloy.

[0037] Furthermore, there are no particular restrictions on the chemical composition of titanium alloys and titanium plates, however, a titanium alloy generally refers to an alloy containing 70% or more by mass of Ti. Examples of α-type titanium alloys include high corrosion-resistant alloys (titanium alloys specified in JIS standards 11-13, 17, 19-22, and ASTM standards Grade 7, 11, 13, 14, 17, 30, 31, or titanium alloys containing small amounts of various other elements), Ti-5Al-2.5Sn (ASTM standard Grade 6), Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb, etc.

[0038] Examples of α+β type titanium alloys include Ti-3Al-2.5V, Ti-5Al-1Fe, and Ti-6Al-4V. Examples of β type titanium alloys include Ti-3Al-8V-6Cr-4Mo-4Zr, Ti-13V-11Cr-3Al, Ti-15V-3Al-3Cr-3Sn, Ti-20V-4Al-1Sn, and Ti-22V-4Al.

[0039] The following describes in more detail the preferred chemical compositions of the titanium alloy and titanium plate according to this embodiment. In the following description, "%" for content refers to "mass%".

[0040] Al: 4.0~8.7% Al is an α-phase stabilizing element that enhances the strength of titanium alloys through solid solution strengthening. This effect is sufficiently obtained when the Al content is 4.0% or more. For this reason, the Al content is preferably 4.0% or more, more preferably 4.5% or more, and even more preferably 5.0% or more. On the other hand, if the Al content exceeds 8.7%, the ductility and cold workability at high temperatures and room temperature may decrease. Therefore, the Al content is preferably 8.7% or less, more preferably 8.0% or less, and even more preferably 7.5% or less.

[0041] C: 0.100% or less C is an impurity, and if included in large quantities, it may reduce ductility, cold workability, and hot workability. Therefore, the C content is preferably 0.100% or less, more preferably 0.090% or less, and even more preferably 0.080% or less.

[0042] N: 0.050% or less N is an impurity, and its content is preferably 0.050% or less. Furthermore, to improve ductility and cold workability, it is even more preferable that the N content be 0.020% or less.

[0043] H:0.016% or less H is an impurity, and its content is preferably 0.016% or less. Furthermore, to improve ductility and cold workability, it is even more preferable that the H content be 0.010% or less.

[0044] O: 0.30% or less Oxygen (O) may be added to increase hardness. However, to avoid impairing ductility and cold workability, the O content is preferably 0.30% or less. Furthermore, to further enhance ductility and cold workability, the O content is more preferably 0.25% or less, and even more preferably 0.20% or less.

[0045] Si: 0~0.50% Although silicon (Si) is an impurity, its inclusion in trace amounts has the effect of improving oxidation resistance and strength. For this reason, it may be included as needed. However, if a large amount of Si is included, it may reduce ductility, cold workability, and hot workability. Therefore, the Si content is preferably 0.50% or less, more preferably 0.40% or less, and even more preferably 0.30% or less. If the above effects are to be obtained, the Si content is preferably 0.001% or more, more preferably 0.01% or more, and even more preferably 0.10% or more.

[0046] One or more elements selected from Fe, Cr, Ni, V, Cu, Mo, Mn, Nb, and Co: 0.3-5.0% in total Fe, Cr, Ni, V, Cu, Mo, Mn, Nb, and Co, as β-phase stabilizing elements, not only increase the strength of titanium alloys through solid solution strengthening but also contribute to improved hot and cold workability. Therefore, the total content of one or more elements selected from these is preferably 0.3% or more, more preferably 0.5% or more, and even more preferably 0.7% or more. On the other hand, if the total content of these elements is excessive, problems of solidification segregation may occur. Therefore, the above total content is preferably 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less.

[0047] In particular, Fe, Cr, and V exhibit a more significant effect in improving strength, hot workability, and cold workability. Therefore, it is preferable to contain at least 0.3% in total of one or more elements selected from Fe, Cr, and V.

[0048] The titanium alloy and titanium plate according to this embodiment may further contain one or more elements selected from Sn, Zr, Pd, Pt, Rh, and Ru, in addition to the elements mentioned above.

[0049] One or more elements selected from Sn and Zr: Total of 3.0% or less Sn and Zr have the effect of improving the hardness of titanium alloys. For this reason, they may be included as needed. However, excessive amounts of Sn and Zr may make the alloy more prone to cracking. Therefore, the total content of one or more elements selected from Sn and Zr is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2.0% or less. If the above effect is to be obtained, the total content is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more.

[0050] One or more elements selected from Pd, Pt, Rh, and Ru: total amount less than 0.25% Pd, Pt, and Ru have the effect of improving corrosion resistance. For this reason, they may be included as needed. However, including these elements in excess increases manufacturing costs. For this reason, it is preferable that the total content of one or more elements selected from Pd, Pt, Rh, and Ru be 0.25% or less. It is more preferable that the total content of one or more elements selected from Pd, Pt, Rh, and Ru be 0.20% or less. On the other hand, in order to obtain the above effect, it is preferable that the content be 0.04% or more.

[0051] In the chemical composition of this embodiment, the remainder consists of Ti and impurities. Here, "impurities" refers to components that are mixed in during the industrial production of titanium alloy due to various factors in the raw materials such as ore and scrap, and in the manufacturing process, and which are acceptable as long as they do not adversely affect this embodiment. Specifically, examples include Cl, Na, Mg, Ca, B, and Zr, Sn, and Ta mixed in during the refining process, etc., and Zr, Sn, and Ta mixed in from scrap, etc., but are not limited to these. It is acceptable if the content of each element is 0.1% or less and the total amount of impurities is 0.5% or less.

[0052] The above chemical composition is the average chemical composition from 0.1 mm or more in the depth direction from the surface. The content of each element can be measured by inert gas fusion infrared absorption spectroscopy, inert gas fusion thermal conductivity spectroscopy, high-frequency combustion infrared absorption spectroscopy, or inductively coupled plasma (ICP) emission spectroscopy.

[0053] 4. Manufacturing method The titanium blades of this embodiment can be reliably manufactured, for example, by the following manufacturing method.

[0054] A titanium alloy slab having the chemical composition described above is subjected to hot rolling into a plate shape. Specifically, the titanium alloy slab is heated to a temperature range of β transformation point + 30°C to β transformation point + 150°C, and then hot-rolled under conditions that result in a rolling ratio of 85% or more, with the finishing temperature set to a temperature range of β transformation point - 50°C to β transformation point - 170°C. A rolling ratio of 90% or more is preferable, and 95% or more is more preferable. By performing hot rolling in one direction under the above conditions, the Young's modulus in the direction perpendicular to the hot-rolling direction is increased, making it possible to control the ratio of the Young's modulus in the hot-rolling direction to that perpendicular to it to 1.15 or more.

[0055] The β transformation point can be obtained not only from the chemical composition of the titanium alloy itself, but also from the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) method. For example, it can be confirmed using Thermo-Calc, an integrated thermodynamic calculation system from Thermo-Calc Software AB, and a designated database (TI3).

[0056] After hot rolling and finish rolling, the material is cooled by air cooling or water injection. After hot rolling, annealing and cold rolling may be performed as needed. However, if cold rolling is performed with an excessive degree of processing, the ratio of Young's modulus in the hot rolling direction to that in the direction perpendicular to the hot rolling direction may decrease. Therefore, when cold rolling is performed, it is preferable to keep the cold rolling ratio to 30% or less.

[0057] The portion that will become the blade is cut out from the titanium plate obtained as described above. Figure 3 is a diagram illustrating the direction of the blade when cutting out the portion that will become the blade from the titanium plate. As shown in Figure 3, the blade may be cut so that the Young's modulus is higher in the L direction than in the T direction, or it may be cut so that the Young's modulus is higher in the T direction than in the L direction.

[0058] Furthermore, in order to determine the Young's modulus of the titanium plate in each direction beforehand, test pieces may be cut from the titanium plate at various angles and their Young's modulus may be measured. In this case, it is preferable to use a predetermined direction, such as the hot-rolling direction, as the reference direction and measure the Young's modulus in directions from 0 to 90° at 15° intervals from that reference direction. Then, based on the obtained directional distribution of Young's modulus, the direction in which the blade portion will be cut can be determined.

[0059] Next, the cutting edge is shaped by polishing or other methods to obtain the cutting tool. Additionally, surface treatments such as nitriding, carbide, physical vapor deposition (PVD), and chemical vapor deposition (CVD) may be applied as needed.

[0060] The titanium blades according to the present invention will be described in more detail below with reference to examples, but the embodiments are not limited to these examples. [Examples]

[0061] Titanium alloy slabs having the chemical composition shown in Table 1 were prepared and hot-rolled under the conditions shown in Table 2 to produce titanium sheets. Some of these were further cold-rolled.

[0062] [Table 1]

[0063] [Table 2]

[0064] Next, the type of titanium alloy used was identified using the following method, particularly to determine whether or not it was a β-type titanium alloy. A test piece measuring 10 mm x 10 mm thickness was cut out and heated at 1100°C for 1 hour, a temperature exceeding the β-phase transformation point where the β-phase becomes a single phase, and then water-cooled. This heat treatment causes the β-type titanium alloy to consist mainly of a β-phase with a body-centered cubic (bcc) crystal structure. X-ray diffraction at θ-2θ was measured using a Cu tube on the heat-treated test piece. A SmartLab X-ray diffractometer manufactured by Rigaku Corporation was used for the measurement.

[0065] The X-ray diffraction measurement surface was finished by polishing with colloidal silica. X-ray diffraction intensity was measured in the range of 2θ from 10 to 100 degrees. From the angles of the peaks detected in the obtained X-ray diffraction, the peaks from the β phase (bcc) and the peaks from the α phase (hcp) were identified, and the peak intensities of each were compared. A β-type titanium alloy was identified if the diffraction peak with the highest intensity was attributable to the β phase, and the peak intensity attributable to other phases was 1 / 10 or less of that peak. Similarly, an α+β-type titanium alloy was identified if the diffraction peak with the highest intensity was attributable to the α phase, and the peak intensity attributable to other phases was 1 / 10 or less of that peak.

[0066] Figure 4 is a diagram illustrating the shape of the cutting tool used in this embodiment. The titanium plate was ground and polished to a thickness of 1 mm in order to produce the cutting tool. As shown in Figure 4(a), the angle of the tip 1c is 45°, and a cutting tool was produced having a cutting edge 1b with the cross-sectional shape shown in Figure 4(b).

[0067] Next, using the above-mentioned cutting tool, the Young's modulus in the L and T directions, as well as the Vickers hardness, were measured using the method described above. In addition, the following evaluation tests were conducted to assess the durability of the cutting edge and its straightness.

[0068] First, a cutting test stand was prepared by solidifying a transparent resin to which silica powder with an average particle size of approximately 0.2 μm was added at a volume ratio of 30%. The corners of the cutting test stand had a radius of approximately 12.5 mm, and a cutting tool prepared as described later was used to cut into these corners. This test stand was designed to accelerate the load on the cutting edge.

[0069] Next, three sheets of 0.09 mm (approximately 90 μm) thick copy paper were stacked, folded in half so that the mountain fold was 100 mm long, and cut using the aforementioned blade to check the initial cutting performance. Subsequently, the blade was used to cut the corner of the cutting test stand with an amplitude of approximately 20 mm, making 10 back-and-forth cuts. Then, the durability of the cutting performance was evaluated by cutting three more sheets of 0.09 mm thick copy paper. The evaluation criteria for cutting performance and its durability are as follows.

[0070] ○: The cutting performance remained unchanged from the initial state, and observation of the cut surface of copy paper using a 50x magnifying glass revealed that the torn appearance (frayed appearance) was about the same as in the initial state. △: Visual inspection of the cut edges of the copy paper revealed that the torn appearance was similar to that of the initial sample. However, observation with a 50x magnifying glass revealed that the torn appearance was more pronounced than in the initial sample. ×: The resistance when cutting the copy paper has clearly increased, and visual inspection of the cut area of ​​the copy paper reveals that it appears more torn than before.

[0071] Furthermore, the cutting edge of the blade (1c in Figure 4(a)) was used to cut the cutting test stand using the same procedure as above. Then, the straightness of the blade tip was evaluated by cutting through 10 layers of cloth adhesive tape, also known as gummed tape (TANOSEE cloth tape TGK-KKT50). The cloth adhesive tape used was approximately 0.21 mm thick and 50 mm wide, cut to a length of 50 mm, and 10 layers were attached to a rubber mat, alternating their orientations by 90 degrees. The 50 mm x 50 mm diagonal of the 10 layers of cloth adhesive tape was then cut with the blade under evaluation, using a plastic ruler as a guide. The cloth adhesive tape contains cloth fibers, which play a role in inhibiting straightness, and was therefore used as an evaluation index for the straightness of the blade tip. The evaluation criteria for straightness are as follows. ○: Number of pieces of cloth adhesive tape cut: 10 △: Number of pieces cut from the cloth adhesive tape is 8-9. ×: The number of pieces of cloth adhesive tape cut is 7 or less.

[0072] The results of the metal structure observation, mechanical property measurement, and sharpness evaluation are summarized in Tables 3 and 4. Note that the blades for Tests No. 39-56 in Table 4 were each taken from the same titanium plate as Tests No. 1-18, but with the cutting direction changed by 90°.

[0073] [Table 3]

[0074] [Table 4]

[0075] As shown in Tables 3 and 4, the examples of the present invention that fully satisfy the provisions of the present invention showed excellent initial sharpness, sharpness retention, and straightness of the cutting edge. In contrast, the comparative examples that did not satisfy the provisions of the present invention showed deterioration in at least one of these aspects.

[0076] Specifically, in test No. 19, sufficient hardness could not be obtained due to the low content of alloying elements. In tests Nos. 20-23, since they were β-type titanium alloys, the Young's modulus was low, and it was not possible to create a difference in rigidity between the L-direction and T-direction of the cutting tool.

[0077] In tests No. 24 and 25, the cold rolling rate was excessive, which reduced the ratio of Young's modulus in the L-direction to the T-direction of the cutting edge, which had been increased by hot rolling. In tests No. 26 and 27, the heating temperature during hot rolling was excessive, and in test No. 27, in addition, the hot rolling rate was low, resulting in a high finishing temperature. Similarly, in test No. 30, the hot rolling rate was low and the finishing temperature was high. In test No. 38, a common manufacturing method, so-called cross-rolling, was performed. Therefore, in these examples, it was not possible to increase the ratio of Young's modulus in the L-direction to the T-direction of the cutting edge.

[0078] If the Young's modulus is low, or if there is no direction with a high Young's modulus in the L and T directions as in the present invention, the linearity of the blade is poor. As a result, when cutting onto the cutting test stand, the deflection of the blade tip becomes large, the load on the blade tip becomes large locally, and minute chipping is likely to occur. Consequently, the cutting performance on copy paper after cutting decreases, and the durability evaluation is negative. Also, the cutting performance on cloth adhesive tape after cutting is poor, and the straightness evaluation is negative. [Explanation of Symbols]

[0079] 1. Blade 1a.mine 1b. Cutting edge 1c. Tip 2. Pattern 10. Blades

Claims

1. It is a blade made of titanium alloy, When the direction from the handle of the blade towards the tip of the blade is defined as direction L, and the direction perpendicular to direction L, from the spine of the blade towards the cutting edge, is defined as direction T, The Young's modulus in the L direction and the T direction is 110 GPa or more. In the Young's modulus in the L direction and the T direction, the ratio of the higher Young's modulus to the lower Young's modulus is 1.15 or greater, and The average Vickers hardness at the center of the blade in the thickness direction is 300 to 450 HV1. Titanium blades.

2. The chemical composition of the aforementioned titanium alloy is, in mass%, Al: 4.0-8.7%, C: 0.100% or less, N: 0.050% or less, H: 0.016% or less, O: 0.30% or less, It contains Si: 0 to 0.50%, and One or more elements selected from Fe, Cr, Ni, V, Cu, Mo, Mn, Nb, and Co, in a total concentration of 0.3 to 5.0%. One or more elements selected from Sn and Zr, totaling 0-3.0%, and It contains one or more elements selected from Pd, Pt, Rh, and Ru in total amount of 0 to 0.25%, The remainder is Ti and impurities. The titanium blade according to claim 1.

3. A titanium plate used as a material for a titanium blade according to claim 1 or claim 2, The Young's modulus in a first direction perpendicular to the thickness direction of the titanium plate, and in a second direction perpendicular to the thickness direction and the first direction, is 110 GPa or more. In the Young's modulus in the first and second directions, the ratio of the higher Young's modulus to the lower Young's modulus is 1.15 or greater, and The average Vickers hardness at the center of the thickness direction of the titanium plate is 300 to 450 HV1. Titanium plate.

4. The thickness is 2.0 to 7.0 mm. The titanium plate according to claim 3.

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