TW202128301A - Processed titanium material and manufacturing method thereof for pressing a first pressing body into the surface of a titanium blank - Google Patents

Abstract

Disclosed is a manufacturing method of a processed titanium material. The manufacturing method includes a step of pressing a first pressing body into the surface of a titanium blank, wherein the first pressing body is provided with a first pressing surface which has a circular arc shape and extends in a predetermined direction. Moreover, in a cross section orthogonal with the extension direction of the first pressing surface, the radius (mm) of curvature of the first pressing surface is greater than 2.5mm and smaller than 17.5mm, and the following formulae (1) and (2) are met. As a result, surface defects are not easily generated on the surface of the obtained processed titanium material during hot rolling. The formula (1) is expressed as: 0.5<=X1<=R1×(1-cos<theta>1), and the formula (2) is expressed as: 1.0<=Y1<=(-0.16R12 +4.4R1)×(0.25X1+0.037), wherein <theta>1 is 50 DEG, R1 is the radius (mm) of curvature of the first pressing surface in a first cross section, X1 is the pressing-in amount (mm) of the first pressing surface to the titanium blank, and Y1 is a distance (mm) between adjacent pressing-in positions of the first pressing surface in a direction where the extension direction of the first pressing surface is orthogonal with a pressing-in direction of the first pressing body.

Description

Processed titanium material and its manufacturing method

The invention relates to a processed titanium material and a manufacturing method thereof.

Background of the invention The production method of a general titanium hot-rolled titanium material is as follows, for example. First, use the consumable electrode type arc melting method (VAR: Vacuum arc remelting) or the electron beam melting method (EBR: Electron beam remelting) to melt and solidify the titanium, thereby manufacturing an ingot. Then, the ingot is decomposed by hot working such as block division, forging, rolling, etc., to produce titanium materials for hot rolling, such as flat billets or small blocks. In addition, in recent years, a technology has been continuously developed to omit the above-mentioned decomposition step by manufacturing a rectangular ingot that can be directly hot-rolled by the electron beam melting method.

However, large ingots used in industry have coarse crystal grains as large as several tens of mm in the solidification structure. If such an ingot is directly hot-rolled without going through the decomposition step, uneven deformation will occur due to coarse crystal grains, and may grow into larger surface defects. In addition, even in the case of a decomposition step, etc., when the processing rate is low or the temperature is not appropriate, the cast structure may remain, or the structure may become coarse instead, which may cause surface defects during hot rolling.

If the above-mentioned surface flaws occur, the yield in the subsequent descaling step will become very poor, and a hot-rolled titanium material that is not prone to hot-rolled surface flaws is required.

Patent Document 1 proposes the following method: when directly hot working an ingot of titanium material, in order to refine the crystal grains near the surface layer, strain is applied to the surface layer and then heated to a temperature higher than the recrystallization temperature so that the surface rises from the surface. After recrystallization at a depth of 2 mm or more, hot working is performed.

In addition, Patent Documents 2 and 3 describe a titanium material for hot rolling, which uses a steel tool with a radius of curvature of 3 to 30 mm or a steel ball with a radius of 3 to 30 mm to produce plasticity on the surface of the titanium material. Deformation imparts strain to the surface layer part. According to Patent Documents 2 and 3, it is said that by hot rolling such a titanium material for hot rolling, the influence of the coarse solidification structure can be made harmless and surface defects can be reduced.

Prior art literature Patent literature Patent Document 1: Japanese Patent Laid-Open No. 1-156456 Patent Document 2: International Publication No. 2010/090352 Patent Document 3: Japanese Patent Application Publication No. 2018-1249

The problem to be solved by the invention Patent Document 1 lists forging, roll reduction, and shot blast as means for imparting strain. However, the general spray bead is small because the diameter of the bead is 0.5~1mm, so the amount of strain that can be applied is also small. In addition, so-called dead metal is generated during forging or roll reduction, which reduces the amount of strain or causes strain to be introduced into the interior. Therefore, the thickness of the required recrystallized layer may not be ensured, or the granulation may be insufficient.

In Patent Documents 2 and 3, the strain is applied by hammering or pressing with a steel tool. Therefore, it may take a long time to stably apply the strain to the entire surface, and the efficiency is low. In addition, for high-strength materials, there are cases where the impact energy cannot be transmitted to the inside and the thickness of the required fine-grained structure cannot be ensured. Therefore, there is still room for further improvement.

The present invention was made in view of the above-mentioned circumstances, and its subject is to provide a processed titanium material and a manufacturing method thereof that can reduce surface defects caused by hot rolling delay.

Means for Solving the Problems The gist of the present invention for solving the above-mentioned problems is as follows. A manufacturing method of processed titanium material is to form a plurality of first grooves on the surface of the titanium blank; The first pressing body of the surface is pressed into the surface of the titanium blank; in the first section orthogonal to the direction in which the first pressing surface extends, the radius of curvature of the first pressing surface is 2.5mm or more and 17.5mm or less ; And the foregoing first step satisfies the following (1) formula and (2) formula. 0.5≦X ₁ ≦R ₁ ×(1-cosθ ₁ ) (1) 1.0≦Y ₁ ≦(-0.16R ₁ ² +4.4R ₁ )×(0.25X ₁ +0.037) (2) However, in the above formula, θ ₁ is 50°; R ₁ is the radius of curvature of the first pressing surface in the first cross section (mm); X ₁ is the pressing amount of the titanium blank on the _{first pressing surface (mm); Y 1} is The distance (mm) between adjacent pressing positions of the first pressing surface in a direction orthogonal to both the extending direction of the first pressing surface and the pressing direction of the first pressing body.

Invention effect According to the present invention, it is possible to reduce the occurrence of surface defects during the hot rolling delay. Moreover, according to the present invention, even if the titanium blank is still in the post-casting state even if the decomposition step of the ingot is omitted, the surface flaws generated during hot rolling can be stably reduced, and excellent hot rolling and cold rolling can be provided. Rolled products.

The embodiments of the present invention will be described below using drawings. Based on the viewpoint of reducing the surface defects caused by hot rolling, the inventors of the present invention aimed at a method of harmlessly making the coarse solidified structure of an ingot with a crystal grain as large as several tens of mm, and the remaining after decomposition. The method of making the effect of the solidification structure harmless and the processing titanium material suitable for this method have been repeatedly studied incisively. As a result, the following knowledge and insights have been obtained, and the present invention has been completed.

In order to fine-grain the coarse solidified structure or to eliminate the parts affected by the solidified structure, it may be considered to provide grooves (recesses) on the surface to impart strain, and then recrystallize it by a predetermined heat treatment such as heating with a delay in hot rolling. method.

The present invention includes the following steps: pressing the pressing body into the surface of the titanium blank to form a plurality of first grooves on the surface of the titanium blank. In this way, a plurality of grooves are provided on the surface of the titanium blank to impart strain. The processed titanium material obtained by this method can obviously suppress the surface defects of the hot rolling delay. In addition, in the present invention, the pressing surface of the pressing body is actually pressed in to cause physical plastic deformation to form grooves, and it is possible to stably introduce strain regardless of the crystal orientation. In addition, by performing the pressing step of the pressing body multiple times without overlapping the elongation direction of the groove formed by each step, it is possible to introduce efficient and sufficient strain in the groove and its periphery, and then through the subsequent hot rolling time delay The heating causes the surface layer to form fine recrystallization, which can inhibit surface defects.

Hereinafter, the processed titanium material of this embodiment and its manufacturing method will be described. The processed titanium material of this embodiment has a plurality of grooves formed on the surface. In the thickness direction of the processed titanium material, the difference between the Vickers hardness at a position 3mm from the bottom of the groove and the Vickers hardness at 1/2 of the thickness ΔHV Above 20. The processed titanium material with a difference ΔHV of 20 or more is the following: When heat treatment is performed at 800°C for 4 hours, an equivalent circle is formed at least from the bottom of the groove to a depth of 3.0mm. The average particle size is 1.00 The standard deviation of the logarithmic conversion value of the equivalent circle diameter of the crystal grain is less than 1.00. In other words, the processed titanium material of the present embodiment can refine the surface layer structure by heating with a delay in hot rolling, so that it is possible to suppress the occurrence of surface defects during hot working. Therefore, it is suitable as a titanium material for hot rolling.

The processed titanium material of this embodiment preferably has an angle of 50° or less between the inner surface of the groove and the surface of the processed titanium material in a cross section orthogonal to the direction in which the groove extends. The titanium blank used in the manufacturing method of the processed titanium material of this embodiment is preferably made of industrial pure titanium or titanium alloy. In addition, the titanium blank used in the manufacturing method of the processed titanium material of this embodiment can be exemplified: ingot, flat blank, medium block or small block.

Fig. 1 shows an example of the processed titanium material of this embodiment. The processed titanium material of this embodiment can be flat blank 1, as shown in Figure 1(a), or medium block 2, as shown in Figure 1(b), or as shown in Figure 1(c) It is a small block 3 with a rectangular cross section perpendicular to the longitudinal direction. In addition, it can also be a small piece with a circular cross-section as described above. In addition, in the flat embryo 1 in Figure 1 (a), the middle block 2 in Figure 1 (b), and the small block 3 in Figure 1 (c) on the respective surfaces 1a, 2a, and 3a, a plurality of linear grooves are formed 1b, 2b, 3b. The extending direction of the grooves 1b, 2b, 3b is set as the long side direction of each of the flat embryo 1, the middle block 2 and the small block 3 in the figure, but it is not limited to this, for example, the flat embryo 1 The width direction of each of the medium block 2 and the small block 3 may also be formed to extend along a direction having a predetermined inclination from the width direction of each of the flat blank 1, the medium block 2 and the small block 3. In the following description, an example in which grooves 1b, 2b, and 3b are formed along the longitudinal direction of each of the flat embryo 1, the middle block 2 and the small block 3 is used.

In the processed titanium material of this embodiment, the Vickers hardness at a depth of 3 mm from the bottom of the groove (the position of the line of symbol S in Figure 3) and the 1/2 depth position of the thickness (the position of the line of symbol M in Figure 3) The difference ΔHV of the Vickers hardness of the position) is 20 or more. In addition, FIG. 3 is a schematic diagram showing a cross section orthogonal to the direction in which the groove of the processed titanium material is extended.

In addition, for the flat embryo or middle block shown in Fig. 1(a) or Fig. 1(b), the 1/2 depth position of the thickness is the thickness position of the flat embryo thickness t or the 1/2t thickness position of the middle block thickness t, respectively . For small blocks with a rectangular cross-section with an aspect ratio of about 1 shown in Figure 1(c), it is the position of the center of gravity of the cross-section of the small blocks.

In order to suppress the surface defects caused by the hot rolling delay, it is necessary to refine the crystal structure of the processed titanium material. Refining the overall crystal structure of the processed titanium material can of course also suppress surface defects, but for this purpose, a large amount of strain must be applied to the entire blank. In addition, if necessary, when rolling in the width direction before hot rolling, if the rolling shrinkage in the width direction of the titanium blank in the post-casting state becomes large, the coarse cast structure may occur. The resulting wrinkles, resulting in surface flaws after hot rolling.

In order to stably suppress the surface flaws caused by not only the cast structure but also the wrinkles caused by the increased rolling time in the width direction as described above, it is necessary to make at least the surface layer into a recrystallized structure. The surface layer referred to here is the area from the bottom of the groove of the processed titanium material to the position with a depth of 3 mm. In order to make the surface layer into a recrystallized structure during the heating of hot rolling, _{strain must be applied to the region from the bottom of the groove 1b 1} , 2b ₁ , 3b ₁ to a depth of at least 3 mm (the position of the line of symbol S in FIG. 3) . After various analyses, the inventors of the present invention have clarified that as long as _{the equivalent strain from the bottom of the groove 1b 1} , 2b ₁ , 3b ₁ to the depth of 3 mm is 0.2 or more, recrystallization occurs during the heating of hot rolling. And can produce fine structure on the surface. And it is known that the equivalent strain system is related to the Vickers hardness, as long as the Vickers hardness at the _{depth of 3mm from the groove bottom 1b 1} , 2b ₁ , and 3b _{1 is} relative to the Vickers hardness at the 1/2 thickness position of the processed titanium material If the value is greater than 20, it can be achieved that the value should be greater than 0.2. The Vickers hardness at the 1/2 thickness position of the processed titanium material is almost the same as the hardness after casting, so ΔHV corresponds to the increase in surface layer hardness when an equivalent strain of 0.2 or more is introduced into the surface layer. As long as the ΔHV of the processed titanium material is 20 or more, it becomes the one that has introduced sufficient strain in the surface layer, and the subsequent heating (heating of hot rolling) can form fine and uniform recrystallized grains. The thickness of the recrystallized layer obtained in the above manner can reach 3 mm or more, which can suppress the surface defects of the hot rolling delay time. The thickness of the recrystallized layer is sufficient as long as it is 3 mm or more, and the upper limit is not particularly specified. In order to increase the thickness, the pressing load for introducing strain must be increased. Therefore, from the viewpoint of the load-bearing limit of the pressing machine, the substantial upper limit of the thickness of the recrystallized layer is 25 mm.

The method of measuring the Vickers hardness is to cut the surface of the titanium material with grooves formed, and the cut cross section (the cross section perpendicular to the direction of groove extension) is mirror-polished, and then the Vickers is used. Hardness testing machine for measurement. Measure 7 points at a depth of 3mm from the bottom of the groove and 1/2 of the thickness of the processed titanium material with a load of 1kg, and calculate the average of 5 points after removing the maximum and minimum hardness. Then calculate the hardness difference (ΔHV) between the position of 3mm from the bottom of the groove and the position of 1/2 thickness.

In addition, regarding the processed titanium material of this embodiment, the flat blank 1, the middle block 2 in Fig. 1(b), and the small block 3 in Fig. 1(c) are all along their long sides. In this way, a plurality of linear grooves 1b, 2b, and 3b are arranged. In the cross section orthogonal to the direction in which the groove extends, the angle (θ) formed by the inner surface of the groove 1b, 2b, 3b and the surface 1a, 2a, 3a is preferably 50° or less.

Even if strain is applied to the surface layer of the titanium blank in the above manner, if an excessively large groove (the angle of the inner surface of the groove is steep) is generated, surface defects may occur during hot rolling due to the groove shape. Therefore, as shown in Fig. 2, in the cross section orthogonal to the direction in which the grooves 1b, 2b, and 3b extend, the angle θ formed by the inner surfaces of the grooves 1b, 2b, and 3b and the surfaces 1a, 2a, and 3a is set to 50 °below is better. Thereby, the angle of the inner surface of the groove does not become steep, and surface defects caused by the groove shape can be prevented. Preferably, the angle θ is 45° or less. In addition, the smaller the angle θ, the less likely it is to produce surface defects due to the groove shape. Therefore, the lower limit of the angle θ is not particularly specified. However, if the angle θ becomes too small under the premise that the surface layer of the blank is sufficiently strained, it means that the pressing step is repeated multiple times for processing, and the manufacturing efficiency is significantly reduced. Therefore, the angle θ is preferably 10° or more. More preferably, it is above 20°.

The processed titanium material of this embodiment is preferably the following: After simulating hot rolling, for example, heat treatment at a temperature of 800°C for a heating time of 4 hours, at least from the bottom of the groove to the depth of 3.0mm, the equivalent will be formed. Those with a grain structure with an average circle diameter of 1.00 mm or less. In addition, the standard deviation σ of the logarithmic conversion value of the equivalent circle diameter of the crystal grains is preferably 1.00 or less. The crystal grains formed by simulating the heat treatment of hot rolling become crystal grains with relatively uniform grain size.

The larger the crystal grains, the easier it is to produce surface flaws that will occur when the hot-rolled titanium material is hot-rolled. For example, in the case of a mixed-grain structure in which fine-grained parts and coarse-grained parts are mixed, crystal grains with a large particle size become the starting point and hot rolling defects are likely to occur. Therefore, after heating to simulate hot rolling, it is better if a polycrystalline structure with relatively small grain sizes and less variation in grain size can be formed. Therefore, it is preferable that the processed titanium material of this embodiment has a grain structure whose standard deviation σ of the logarithmic conversion value of the equivalent circle diameter becomes 1.00 or less by heating at 800°C for 4 hours. When the crystal grain size of the metal material becomes a distribution close to the logarithmic normal distribution, the narrower the logarithmic normal distribution is, the more uniform the crystal grain size is, and the less likely it is to produce surface defects during hot rolling. That is, as long as the crystal grains are fine to a certain extent and the standard deviation of the logarithmic normal distribution is within a certain range or less, a uniform structure will be formed and surface defects will become less likely to occur.

If the standard deviation σ of the distribution of the converted value obtained by converting the equivalent circle diameter D of each crystal grain into the natural logarithm LnD is less than 1.00, when the equivalent circle average diameter is less than 1.00 mm, surface defects will be suppressed produce. The standard deviation σ is preferably 0.80 or less. The narrower the distribution of the crystal grain size, that is, the smaller the standard deviation σ, the less likely to produce surface flaws, so the lower limit of the standard deviation is not specifically defined.

Regarding the average crystal grain size, it is preferable to make it finer than the cast structure having an average grain size of 10 mm or more. After the processed titanium material of this embodiment is heat-treated at 800°C for 4 hours, the equivalent circle average grain size of the crystal grains from the bottom of the groove to the depth of 3.0mm is preferably 1.00mm or less, preferably 0.80mm or less, preferably 0.70mm or less. If it is larger than this, even within the above-mentioned standard deviation σ, surface flaws during hot rolling may still occur. Since the smaller the equivalent circle average particle size is, the less surface defects will occur, so the lower limit of the equivalent circle average particle size is not specifically defined.

The crystal grain size is coarsened during hot rolling and heating. After investigation, it was found that as long as the crystal grain size after the heat treatment at 800°C for 4 hours is within the above range, the surface flaws can be sufficiently reduced even in the hot rolling temperature range of the actual machine. Therefore, the range of the equivalent circle average particle diameter of the crystal grains and the standard deviation σ is the latter after the strain is applied to the surface layer and the heat treatment at 800° C. for 4 hours.

The method of measuring the crystal grain size is to cut to include the strained surface of the processed titanium material. After the cut cross section is chemically polished, the electron backscatter diffraction method (EBSD (Electron Back Scattering) is used). Diffraction Pattern)), measure in a 5mm×5mm area with a step distance of 5-20μm and measure a field of view of about 2-10. Then, calculate the equivalent circle diameter (area A=π×(diameter D/2) ² ) for the crystal grain size based on the crystal grain area measured by EBSD, and calculate the logarithmic normal distribution standard based on the crystal grain size distribution差σ。 Difference σ.

Titanium blanks are used for hot rolled titanium cast slabs, and examples of such as the following (A) or (B), such as ingots, flat blanks, medium blocks, and small blocks, can be used as titanium blanks. That is, the titanium plate system that has been rolled to a thickness smaller than a predetermined thickness by hot rolling or cold rolling is excluded from the titanium blank. Therefore, if it is a rectangular or cubic titanium blank, the thickness is, for example, 100 mm or more, and if it is a cylindrical titanium blank, the diameter is, for example, 90 mm or more. In addition, the titanium blank (B) is composed of a solidified structure obtained by melting and casting titanium, and has a structure in a state after casting with coarse crystal grains having a crystal grain size of 10 mm or more.

(A) A titanium blank, which uses a consumable electrode type arc melting method (VAR: Vacuum arc remelting) or an electron beam melting method (EBR: Electron beam remelting) to temporarily melt titanium and then solidify it to obtain an ingot, The ingot is further decomposed by thermal processing such as block division, forging, rolling, etc., and formed into titanium blanks in the shape of flat blanks, small blocks, and the like.

(B) A titanium blank, which is formed into a rectangular or cylindrical ingot of a size that can be directly hot-rolled when the titanium is temporarily melted by the electron beam melting method or the plasma arc melting method and then solidified to omit the above (A) Titanium blank obtained by the decomposition step.

In the electron beam melting method, the irradiated electron beam can be concentrated by polarized light, so even if it is a narrow area between the mold and the molten titanium, it is easy to supply heat, so that the surface of the casting can be well controlled. Moreover, the degree of freedom of the cross-sectional shape of the mold is high. Therefore, it is preferable to use an electron beam melting furnace to melt a rectangular or cylindrical ingot of a size that can be directly supplied to hot rolling as described in (B).

The titanium blank is preferably made of industrial pure titanium or titanium alloy. Industrial pure titanium shall include the industrial pure titanium specified in the following specifications: JIS H4600 standard 1~4, and corresponding ASTM 265B standard grade (Grade) 1~4, DIN 17850 standard grade I ( WL3.7025), Class II (WL3.7035), Class III (WL3.7055). That is, the industrial pure titanium targeted in the present invention is C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less, and Fe: 0.5% or less in mass%, and the remainder Partly composed of Ti. Hereinafter, the "%" related to the content of each element means "mass%".

On the other hand, a low-alloy or α-type titanium alloy may be used as long as an appropriate alloy is used for the desired application. Preferably, a low alloy having an alloy composition of 5% or less is preferable. For example, high corrosion resistance alloys, heat resistant alloys, etc. can be exemplified. The high corrosion resistance alloys are added with Pd <0.15%, Ru <0.10% and rare earth elements <0.02%, and the heat resistant alloys are added with Cu, Al, Si, Sn, Nb and Fe are added in a total of less than 5%. More specifically, as low alloys, there are, for example, high corrosion resistance alloys (ASTM grades 7, 11, 16, 26, 13, 30, and 33, or corresponding JIS grades or less containing various elements), Ti- 0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb, Ti-0.5Al-0.45Si, Ti-0.9Al-0.35Si, etc. Also, α-type titanium alloys include, for example, Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2.75Sn-4Zr-0.4Mo-0.45Si, and the like.

α+β titanium alloys include, for example: Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-7V, Ti-3Al-2.5V, Ti-3Al-5V, Ti-5Al-2Sn-2Zr- 4Mo-4Cr, Ti-6Al-2Sn-4Zr-6Mo, Ti-1Fe-0.35O, Ti-1.5Fe-0.5O, Ti-5Al-1Fe, Ti-5Al-1Fe-0.3Si, Ti-5Al-2Fe, Ti-5Al-2Fe-0.3Si, Ti-5Al-2Fe-3Mo, Ti-4.5Al-2Fe-2V-3Mo, etc.

In addition, β-type titanium alloys include, for example: Ti-11.5Mo-6Zr-4.5Sn, Ti-8V-3Al-6Cr-4Mo-4Zr, Ti-10V-2Fe-3Mo, Ti-13V-11Cr-3Al, Ti-15V -3Al-3Cr-3Sn, Ti-6.8Mo-4.5Fe-1.5Al, Ti-20V-4Al-1Sn, Ti-22V-4Al, etc.

The titanium alloy of the present invention, for example, by containing one or more elements selected from the following and containing more than 0%, the target function can be given to the surface of the processed titanium material: O: 0~0.5%, N: 0~0.2%, C : 0~2.0%, Al: 0~8.0%, Sn: 0~10.0%, Zr: 0~20.0%, Mo: 0~25.0%, Ta: 0~5.0%, V: 0~30.0%, Nb: 0~40.0%, Si: 0~2.0%, Fe: 0~5.0%, Cr: 0~10.0%, Cu: 0~3.0%, Co: 0~3.0%, Ni: 0~2.0%, platinum group elements ：0~0.5%, rare earth elements: 0~0.5%, B: 0~5.0% and Mn: 0~10.0%.

Among the elements other than the above, the elements that can be contained in titanium are based on the general common sense of metal materials, and can be expected to be brought about by solid solution strengthening and precipitation strengthening (in solid solution and the formation of precipitates). Elements such as strength enhancement. These elements can be exemplified from hydrogen (1) to marrow (85) in the atomic number (except for the inert gas elements of group 18 elements), and can be tolerated up to about 5% in total.

The remainder other than the above is Ti and impurities. Impurities can be contained within the range that does not hinder the target characteristics. Other impurities mainly include impurity elements mixed from raw materials or waste materials and elements mixed in manufacturing. For example, C, N, O, Fe, and H are representative elements There are also elements such as Mg and Cl mixed in from raw materials, or elements such as Si, Al, and S mixed in manufacturing. If the above element is less than 2%, it can be considered that it does not hinder the scope of the target characteristics of this case.

In addition, the titanium alloy of the present invention may also contain, for example, one or more elements selected from: O: 0.01~0.5%, N: 0.01~0.2%, C: 0.01~2.0%, Al: 0.1~8.0%, Sn: 0.1~10.0%, Zr: 0.5~20.0%, Mo: 0.1~25.0%, Ta: 0.1~5.0%, V: 1.0~30.0%, Nb: 0.1~40.0%, Si: 0.1~2.0%, Fe: 0.01 ~5.0%, Cr: 0.1~10.0%, Cu: 0.3~3.0%, Co: 0.05~3.0%, Ni: 0.05~2.0%, platinum group elements: 0.01~0.5%, rare earth elements: 0.001~0.5%, B: 0.01~5.0% and Mn: 0.1~10.0%.

The titanium alloy of the present invention preferably contains one or more elements selected from: O: 0.02~0.4%, N: 0.01~0.15%, C: 0.01~1.0%, Al: 0.2~6.0%, Sn: 0.15~ 5.0%, Zr: 0.5~10.0%, Mo: 0.2~20.0%, Ta: 0.1~3.0%, V: 2.0~25.0%, Nb: 0.15~5.0%, Si: 0.1~1.0%, Fe: 0.05~2.0 %, Cr: 0.2~5.0%, Cu: 0.3~2.0%, Co: 0.05~2.0%, Ni: 0.1~1.0%, platinum group elements: 0.02~0.4%, rare earth elements: 0.001~0.3%, B: 0.1~5.0% and Mn: 0.2~8.0%; more preferably, it contains more than one element selected from the following: O: 0.03~0.3%, N: 0.01~0.1%, C: 0.01~0.5%, Al: 0.4 ~5.0%, Sn: 0.2~3.0%, Zr: 0.5~5.0%, Mo: 0.5~15.0%, Ta: 0.2~2.0%, V: 5.0~20.0%, Nb: 0.2~2.0%, Si: 0.15~ 0.8%, Fe: 0.1~1.0%, Cr: 0.2~3.0%, Cu: 0.3~1.5%, Co: 0.1~1.0%, Ni: 0.1~0.8%, platinum group elements: 0.03~0.2%, rare earth elements ：0.001~0.1%, B: 0.2~3.0% and Mn: 0.2~5.0%.

Here, the platinum group element specifically includes Ru, Rh, Pd, Os, Ir, and Pt, and one or more of these may be contained. When two or more types of platinum group elements are contained, the content of the aforementioned platinum group elements refers to the total amount of platinum group elements. In addition, the rare earth elements (REM) specifically include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and may contain these One or more of them. When two or more rare earth elements are contained, mixtures or compounds of rare earth elements such as rare earth metal alloys (Mm) and neodymium alloys can also be used. In addition, when two or more kinds of rare earth elements are contained, the content of the above rare earth elements refers to the total amount of rare earth elements.

Next, the manufacturing method of the processed titanium material of this embodiment will be described. The manufacturing method of this embodiment includes the following steps: pressing the pressing body into the surface of the titanium blank to form a plurality of first grooves on the surface of the titanium blank. Generally, when it is desired to apply strain to an ingot or the like by forging or a large-diameter roll, metal flow does not occur in the part contacting the mold, and a so-called stagnant metal part occurs. Since the amount of strain in the stagnant metal portion is reduced, if the strain is applied by forging or large-diameter rolls, the strain will be introduced into the interior rather than into the surface portion, and the surface layer structure cannot be made into fine grains. On the other hand, when the impact energy of hammering using protrusions as described in Patent Document 2 is used to impart strain, the strain can be imparted to the surface layer, so that the surface layer structure can be made into fine grains. However, this method sometimes takes a lot of time to stably impart strain on the entire surface. In addition, for high-strength materials, impact energy may not be transmitted to the inside, and the required fine-grained structure thickness may not be ensured.

Therefore, the inventors of the present invention have studied a method for preventing the generation of coarse-grained parts by uniformly imparting strain to the surface layer of the titanium blank by preventing the generation of retained metal, and found that the following method can be used to treat The surface layer imparts strain efficiently. Hereinafter, the manufacturing method of the processed titanium material of this embodiment is demonstrated in detail.

The manufacturing method of this embodiment is shown in FIG. 4, which is a method of manufacturing a processed titanium material in which a plurality of first grooves are formed on the surface of a titanium blank 10, and the manufacturing method includes pressing the first pressing body 51 into the titanium blank 10 The step (first step) of the surface, wherein the first pressing body 51 has an arc-shaped first pressing surface 51a extending in a predetermined direction. The present embodiment shows an example of using a round rod (the shape of the cross-section perpendicular to the direction in which the first pressing surface 51a extends is a round rod). The pressing surface 51a of the first pressing body 51 has a radius of curvature (mm) of 2.5 mm or more and 17.5 mm or less in a cross section orthogonal to the direction in which the first pressing surface 51a extends. If the radius of curvature is too small, the equivalent strain at the depth of 3mm will become smaller. And the processing time becomes longer. Therefore, the radius of curvature is set to 2.5 mm or more. The lower limit is preferably 5.0 mm. On the other hand, if the radius of curvature is too large, the retained metal portion becomes larger, and sufficient strain cannot be applied to the surface layer of the titanium blank, and the equivalent strain at the depth of 3 mm becomes smaller. Therefore, the radius of curvature is set to 17.5 mm or less. The preferred upper limit is 15 mm.

Here, the pressing body usable as the first pressing body is not limited as long as it has an arc-shaped pressing surface at least at the portion in contact with the titanium blank 10. In addition to the rod-shaped pressing body 51 with a circular cross-sectional shape as shown in FIG. 4(a), for example, as the first pressing body, the pressing body 52 may also be used as shown in FIG. 5(a). The pressing body 52 has a first pressing surface 52a having an arc shape extending in a predetermined direction at the lower part (the part in contact with the titanium blank 10), and a rigid body having a cubic shape (rectangular cross-sectional shape) at the upper part. The pressing body 52 of such a shape is particularly useful in the case of a rod with a small radius of curvature or a long rod. That is, the reason is that by increasing the section modulus of the rectangular rigid body located on the upper part, the rigidity of the rod body can be improved. In addition, as the first pressing body, for example, as shown in FIG. 6(a), a pressing body 53 provided with a plurality of pressing surfaces 53a at the lower portion may be used. According to the pressing body 53 of such a shape, although there is a disadvantage that the pressing load becomes larger, a plurality of grooves can be formed on the surface of the titanium blank 10 at the same time, and the production efficiency can be improved. In addition, by increasing the load resistance of the pressing machine, making the upper rectangular rigid body larger, etc., as shown in FIG. 7, it can also be used as a pressing body 54 with a planar body with more pressing surfaces 54a at the lower part. . If the pressing body 54 is used, the number of times of pressing the pressing body can be reduced and the production efficiency can be improved.

Here, the first step must satisfy the following equations (1) and (2). Hereinafter, description will be mainly given by taking a case where the pressing body shown in FIG. 4 is used as an example. 0.5≦X ₁ ≦R ₁ ×(1-cosθ ₁ ) (1) 1.0≦Y ₁ ≦(-0.16R ₁ ² +4.4R ₁ )×(0.25X ₁ +0.037)(2) However, in the above formula, θ ₁ is 50°; R ₁ is the radius of curvature of the first pressing surface in the first cross section (mm); X ₁ is the pressing amount of the titanium blank on the _{first pressing surface (mm); Y 1} is The distance (mm) between adjacent pressing positions of the first pressing surface in a direction orthogonal to both the extending direction of the first pressing surface and the pressing direction of the first pressing body.

_{The pressing amount X 1} of the first pressing surface 51a into the titanium blank 10 is the distance shown by the symbol X in FIG. If the pressing amount X _{1 is} too small, sufficient strain cannot be applied to the surface, and the processing time will be longer. Therefore, the pressing amount X _{1 is} set to 0.5 mm or more. The preferred lower limit is 1.0 mm. On the other hand, if the pressing amount X _{1 is} too large, in Fig. 2, the angle θ between the inner surfaces of the grooves 1b, 2b, 3b and the surfaces 1a, 2a, 3a will become too large, resulting in overlapping defects (Overlapped defect)d and other bad situations. Therefore, the pushing amount X _{1 is} set to R ₁ ×(1-cosθ ₁ ) or less. The preferred upper limit is 0.29×R ₁ .

The pitch Y ₁ is the distance shown by the symbol Y in FIG. 4(b), which is in the direction orthogonal to both the extending direction of the first pressing surface 51a and the pressing direction of the first pressing body 51, the first pressing surface 51a The distance between adjacent press-in positions. This point is consistent with the following distance: in the cross-section parallel to the first cross-section of the manufactured titanium material 1, the groove bottom of any first groove and the other first groove adjacent to any of the aforementioned first grooves The distance to the bottom of the ditch. If the pitch Y _{1 is} too small, the processing time becomes longer, so it is set to 1.0 mm or more. The lower limit is preferably 5.0 mm. On the other hand, _{if the pitch Y 1 is} too large, it becomes impossible to impart sufficient strain to the surface layer. Therefore, the pitch Y _{1 is} set to (-0.16R ₁ ² +4.4R ₁ )×(0.25X ₁ +0.037) or less.

When the titanium blank is flat blank 1 or medium block 2, as shown in Figure 1, the surface 1a, 2a with the largest area in the titanium blank will become the rolled surface, so it is only necessary to press the pressing body 51 into the surface to form Ditch it. When the titanium blank is a small piece of material, its entire surface extending along the longitudinal direction can become a rolled surface. Therefore, for example, in the case of a small block 3 having a rectangular cross section as shown in FIG. 3, it is desirable to form a groove on the entire surface to introduce strain on the entire surface.

Hereinafter, the processing method of using a round bar as the pressing body will be described in detail. In addition, in the following description, a method of manufacturing the flat embryo 1 of FIG. 1(a) using a round rod as the first pressing body or as the second pressing body is taken as an example. 8 is a diagram illustrating the first pressing step (first step) in the manufacturing method of the processed titanium material of the present embodiment, (a) is a schematic plan view, and (b) is a schematic side view. 9 is a diagram illustrating the second press-fitting step (second step) in the manufacturing method of the processed titanium material of another embodiment, (a) is a schematic plan view, and (b) is a schematic side view. Also, the second step is not a necessary step.

As a method of pressing a round bar to form groove-shaped indentations on the surface of the blank, the following steps are repeated to form groove-shaped indentations 1c on the surface 1a of the flat embryo: 1 is equipped with a pressing body (round bar) 5, the round bar 5 is pressed into the thickness direction from the surface of the flat blank 1 by the force F, and after unloading, the round rod 5 is moved to a fixed direction (the flat blank 1 in Fig. 8 (The first step) of moving the round bar 5 from the surface of the flat blank 1 in the thickness direction by force F, and then unloading it (first step). In addition, in this manual, the above-mentioned work may be referred to as "moving and pressing". By performing the above operations, the desired strain can be applied to the surface of the titanium blank. There is no limit to the number of presses. For example, the pressing bodies 51, 52, and 53 shown in FIGS. 4 to 6 may be used to repeat the steps of pressing in, unloading, moving, and pressing. In addition, although the example shown in FIG. 8 shows that the round bar 5 is moved in a fixed direction, it is not limited to this form. The round bar 5 can be moved in a fixed direction and pressed in, and then moved in the opposite direction and pressed in, etc., as long as As a result, a plurality of grooves are aligned and formed on the surface of the titanium blank 10, and the moving direction is not limited. However, the production efficiency is better when the round bar 5 is moved in a fixed direction. In addition, a planar pressing body 54 may be used, which has more pressing surfaces 54a at the lower portion as shown in FIG. 7. If such a planar pressing body 54 is used, the number of times of pressing the pressing body can be reduced (for example, set to once), and the production efficiency can be improved.

After the first step is performed on the entire surface of the surface 1a, the following steps can be repeated to form a plurality of grooves 1b: As shown in Fig. 9, from the groove formed in the first time, the force F is used to flatten the round rod 5 from the The surface of the blank 1 is pressed in in the thickness direction, and after unloading, the round bar 5 is moved in a fixed direction (the width direction of the flat blank 1 in Fig. 9), and the steps of pressing in and unloading are also performed by the force F (section Two steps). In this embodiment, the case where the number of press-in steps is set to two is described. For example, the press-in steps may be repeated three times or four times, and the press-in steps may be performed multiple times within a range in which the blank itself does not break. The greater the number of press-in, the higher the equivalent strain becomes, and the structure can be made finer, which is preferable.

The second pressing body has an arc-shaped pressing surface at the portion contacting the surface of the titanium blank 10, and in the second cross section orthogonal to the axial direction, the radius of curvature (mm) of the pressing surface is 2.5 mm or more and Below 17.5mm. The reason is the same as the reason for restricting the radius of curvature of the first pressing body. In addition, as long as the pressing body that can be used as the second pressing body has an arc-shaped pressing surface at least at the portion in contact with the titanium blank 10, the cross-sectional shape of the pressing body is not limited. This point is the same as the first pressing body.

Here, the second step must satisfy the following equations (3) and (4). Hereinafter, description will be mainly given by taking a case where the pressing body shown in FIG. 4 is used as an example. 0.5≦X ₂ ≦R ₂ ×(1-cosθ ₂ ) (3) 1.0≦Y ₂ ≦50.0 (4) However, in the above formula, θ ₂ is 50°; R ₂ is the aforementioned second pressing in the aforementioned second section The radius of curvature of the surface (mm); X ₂ is the pressing amount (mm) of the titanium blank of the _{second pressing surface; Y 2} is the second pressing surface in the direction extending from the second pressing surface and the first pressing surface The distance (mm) between adjacent press-in positions in the direction orthogonal to the press-in directions of the two pressing bodies.

Likewise, the second pressing surface 51a of titanium billet with a first intake pressure of the pressing member pressing amount X ₁ X ₂ line 10 of FIG. 4 (b) is shown from the symbols X, in the processing of titanium-based 1 The distance between the surface of the processed titanium material and the bottom of the groove in the thickness direction. X ₂ pressing amount based on the amount of pressure of the first pressing body ₁ of X for the same reason, the pushing amount X ₁ should be set to 0.5mm or more, preferably a lower limit of 1.0mm. On the other hand, for the same reason as the pressing _{amount X 1 of the first pressing body, the pressing amount X 2 is} set to R ₂ ×(1-cosθ ₂ ) or less. The preferred upper limit is 0.29×R ₁ .

The pitch Y ₂ is the distance shown by the symbol Y in FIG. 4(b). Like the pitch Y _{1 of the} first pressing body, the second pressing surface 51a extends in the direction extending from the second pressing surface 51a and the second pressing body 51 The distance between adjacent press-in positions in the direction orthogonal to the two press-in directions. This point is consistent with the following distance: in the cross-section parallel to the second cross-section of the manufactured titanium material 1, the bottom of any second groove and the other second groove adjacent to any of the aforementioned second grooves The distance to the bottom of the ditch. The pitch Y _{2 is} preferably 1.0 mm or more for the same reason as _{the pitch Y 1 of the} first pressing body, and the lower limit is preferably 5.0 mm. The second step is performed on the surface where the first step has been performed, so even if it is set to a _{wider range than the pitch Y 1 of the} first step, it will not be hindered. However, in order to impart sufficient strain to the surface layer, the pitch Y _{2 is} preferably set to 50.0 mm or less. In addition, the pitch Y _{2 is} preferably (-0.16R ₁ ² +4.4R ₁ )×(0.25X ₁ +0.037) or less like the pitch Y _{1 of the first pressing body.}

Here, in the second step, if a plurality of grooves (second grooves) extending in the same direction as the extending direction of the grooves (first grooves) formed through the first step are formed, strain, especially near the surface layer The strain becomes very small, and it may not be possible to form a fine structure during hot rolling and heating. Therefore, when the second step is performed following the first step, it is preferable to perform the press-fitting step so as to form a plurality of second grooves extending in a direction different from the direction in which the first groove extends. That is, in the first step shown in FIG. 8, the round bar (first pressing body) 5 is moved and pressed in the longitudinal direction of the flat blank 1, so that the groove-shaped indentation (groove) 1c is formed along the flat The embryo 1 extends in the width direction, and in the second step shown in FIG. 9, the round bar (second pressing body) 5 is moved in the width direction of the flat embryo 1 in a manner orthogonal to it, and pressed in to form the groove 1b The shape extends along the long side of the flat embryo 1. By forming the groove 1b by the above-mentioned method, it is possible to stably impart strain (equivalent strain) to the surface layer. In addition, by applying strain from different directions, it is possible to suppress the occurrence of surface defects without growing the aggregate structure during hot rolling heating. In addition, the angle formed by the extending direction of the first groove and the extending direction of the plurality of second grooves may be 90° as shown in FIG. 9, and there is no particular limitation as long as it is greater than 0°. However, in order to stably impart sufficient strain to the surface layer, the angle is preferably set to a range of 30° to 90°.

In the above, the method of forming the groove using the linearly elongated pressing surface has been mainly explained, but as long as the strain (equivalent strain) can be stably imparted to the surface layer, it is not limited to the above-mentioned form. That is, as shown in FIG. 10, for example, a pressing body whose pressing surface is bent on the way may be used to form the surface groove 10 b in the titanium blank 10. At this time, observe the cross section perpendicular to the direction in which the pressing surface extends (the cross section shown by the arrow in FIG. 10), and when the first groove satisfies the above formulas (1) and (2) in the observed cross section, and when In the case where the second groove satisfies the above-mentioned equations (3) and (4) when the second step is carried out, the effect of the present invention can be obtained. In addition, although the plurality of grooves formed by the first step or the second step are preferably arranged side by side, they do not need to be parallel. In particular, there may be non-parallel parts. In this case, in any observation section (a section orthogonal to the direction of extension of the pressing surface) of the processed titanium material, the first groove of the observed part satisfies the above formula (1) and (2), or when it is also implemented In the case where the part of the second groove observed in the second step satisfies the above equations (3) and (4), the effects of the present invention can also be obtained. In addition, a pressing body whose pressing surface intersects in an X shape may also be used. In any case, the first groove and the second groove may not be formed on the entire surface of the processed titanium material.

Figure 11 shows the recrystallization of No. 2 (1 press-in, large-diameter round rod), No. 18 (1 press-in, small-diameter round bar) and No. 16 (press-in 2 times) of the examples described later. The logarithmic normal distribution of the crystal grain size of the layer. The horizontal axis of FIG. 11 shows the crystal grain size (natural logarithm ln), and the vertical axis shows the occurrence probability (%). It can also be seen from Figure 11 that when the pressing step is one time, if a large-diameter round rod (radius of curvature: 30mm) is used as the pressing body, the distribution range of the logarithmic normal distribution is wide (the standard deviation σ is large), and the crystal grain size is not Uniform. On the other hand, it can be seen that even if the pressing step is one time, if a small diameter round rod (radius of curvature: 5 mm) is used as the pressing body, the distribution width of the logarithmic normal distribution becomes narrow (the standard deviation σ is small), and the crystal The particle size becomes uniform. In addition, it can be seen that when the pressing step is performed twice, the distribution width of the logarithmic normal distribution becomes narrower (the standard deviation σ is small), and the crystal grain size becomes more uniform. That is, by using a pressing body having a pressing surface with a small radius of curvature to perform the pressing-in step, and performing the pressing-in step two or more times, the strain near the surface layer becomes very small, and the surface layer structure can be refined. And homogenization, the result can fully reduce the occurrence of surface defects.

The pressing step may be performed in a cold state without heating the titanium blank, or may be performed after heating the titanium blank to a temperature zone below 500°C. The above heating temperature can be tolerated up to 650°C depending on the chemical composition.

In the present embodiment, it is assumed that strain is applied to the surface of the processed titanium material to be the rolled surface in a cold state to a warm state. In order to reduce the surface flaws that occur during the hot rolling delay, it is necessary to form a recrystallized structure to a certain depth. Particularly, with a titanium blank with high hardness, it is difficult for strain to enter the inside of the titanium blank. In order to impart strain to a deeper position in the surface layer, a large load must be applied to the process of forming grooves. However, it has recently been learned that the imparted strain causes the ductility near the surface layer to decrease, and cracks occur on the surface. Therefore, in order to stably impart strain to a deep position and increase the ductility of the surface layer, it is also effective to increase the temperature by a certain level to lower the strength of the titanium blank itself. On the other hand, for low-strength titanium blanks, it is better to concentrate strain on the surface layer to make the surface layer structure finer, so it is better to impart strain at room temperature.

On the other hand, if the press-in step is performed at a high temperature higher than 500°C, the strain imparted by processing will disappear on the spot, and it may become impossible to recrystallize during subsequent heating. In addition, at a temperature higher than 500°C, an oxide film may be formed on the surface of the titanium blank, and the oxide film may be pressed in during processing to generate surface defects, which may progress to surface defects during the subsequent hot rolling. Therefore, although it can be tolerated up to 650°C depending on the chemical composition, it is better to set 500°C as the upper limit.

In addition, depending on the type of alloy, the temperature zone where the strength and ductility of the titanium blank become higher is different, and it is not only necessary to perform it at a higher temperature. For example, in the case of industrial pure titanium, the twin deformation of titanium, which is an important deformation mechanism, will be active around room temperature, but it will not occur at a temperature of about 400 to 500°C. The twin crystals are deformed, so the ductility is lower than that at room temperature, and on the contrary, it becomes prone to cracking. On the other hand, in Al-rich alloy systems, this twin-crystal deformation hardly occurs near room temperature, so it is impossible to ensure ductility by heating to 500°C or lower. In addition, if the titanium blank is heated to a high temperature to extremely weaken the strength of the material, the groove-like undulations (the depth of the groove) on the surface will become too large when it is plastically deformed, and the undulations may cause surface defects. Therefore, it is only necessary to select a temperature range that does not cause cracks on the surface after rolling and obtains an appropriate recrystallized structure and surface state. The lower limit of the surface temperature of the titanium blank in the pressing step is preferably set to 0°C.

As explained above, in the manufacturing method of this embodiment, the round rod is actually pressed into the surface of the titanium blank, and it is physically plastically deformed to form a groove. As a result, strain can be stably introduced into the surface layer of the blank regardless of the crystal orientation, so that the fine crystal grains can be uniformly dispersed in the surface layer of the blank. In addition, as long as the step of pressing the round bar is carried out multiple times under the predetermined conditions, an efficient and sufficient strain can be introduced into the bottom of the groove, and then the surface layer can be finely recrystallized by heating through the subsequent hot rolling time delay. , It can suppress surface flaws.

By applying the processed titanium material of the present invention, surface defects after hot rolling are obviously suppressed. By applying the present invention to a rectangular or cylindrical ingot (still a solidified structure after casting), even if it does not undergo decomposition steps such as block rolling, it can be hot rolled into a plate, strip coil or bar wire At the same time, it still exerts the effect of suppressing surface defects to the extent that there are no problems. As described above, the processed titanium material produced according to this embodiment is not only suitable for supply to hot rolling, but also the surface defects of the hot rolled material produced by hot rolling are significantly suppressed, and it can be used even if cold rolling is subsequently performed. Yan can also produce sound effects of products.

As explained above, according to the present embodiment, even if the ingot decomposition step is omitted, the titanium blank is still in the state after casting, the surface flaws generated during hot rolling can be reduced, and excellent hot rolling can be provided. , Cold rolled products.

In addition, if the present embodiment is applied to a titanium blank that has undergone a decomposition step, the surface defects caused by the time delay of hot rolling will be extremely slight. As a result, it is possible to further increase the yield of the rust-removing step of the hot-rolled plate or rod wire and the final product. Example

Hereinafter, the present invention will be explained in more detail through examples. <Example 1> Use electron beam melting (EBR) or plasma arc melting (PAM) to cast flat blanks (titanium blanks). The flat blanks (titanium blanks) have the chemical composition shown in Table 1, and are 1050mm wide and 250mm thick. × 6000mm in length. The press-fitting steps shown in Table 2 were performed on the cast titanium blank. In the examples of No. 6, 9, 13, and 16, the pressing body shown in FIG. 5 was used, while in the other examples, a round rod pressing body was used. In each of the first to fourth steps, repeat the following actions to form multiple grooves on the surface of the titanium blank: press the pressing body into the surface of the titanium blank and then unload it, then move the pressing body and place it on the surface of the titanium blank. The position is pressed into the surface of the titanium blank. In Table 2, the "radius of curvature of the pressing surface" means the radius of curvature (mm) of the pressing surface of the pressing body, and the "indentation amount" means the indentation amount (mm) of the titanium blank by the pressing surface, and the "spacing" means Refers to the distance (mm) between adjacent pressing positions of the pressing surface in the direction orthogonal to both the extending direction of the pressing surface of the pressing body and the pressing direction of the pressing body. The angle formed by the extending direction of the groove formed in one step and the extending direction of the groove formed in each step.

[Table 1]

[Table 2]

Next, the groove angle of the processed titanium material having grooves formed by plastic deformation as described above was measured. Regarding the Vickers hardness of the processed titanium material, the hardness difference ΔHV was determined according to the following procedure. First, cut to include the surface of the processed titanium material with grooves formed. After the cut section is mirror-polished, the depth is 3mm from the bottom of the groove and the 1/2 thickness of the processed titanium material. , Use a Vickers hardness tester to measure 7 points with a load of 1 kg, and find the average of 5 points after removing the maximum and minimum hardness. Then, the difference in hardness (ΔHV) between the position of 3 mm from the bottom of the groove and the position of 1/2 thickness is obtained.

Next, after heating at 800°C for 4 hours, the average equivalent circular diameter and standard deviation of the recrystallized structure (recrystallized layer) from the bottom of the groove to a depth of 3 mm (surface layer) were measured according to the following procedure. First, the processed titanium material before hot rolling was heat-treated under the condition of heating for 4 hours at an reaching temperature of 800°C in an Ar gas atmosphere. Next, it is cut to include the surface of the processed titanium material with grooves formed after the heat treatment, and the cut cross section is chemically polished, and the electron backscattering diffraction method (EBSD (Electron Back Scattering Diffraction Pattern)), measured in a 5mm×5mm area with a step distance of 5-20μm, and measured a field of view of about 2-10. Then, for the crystal grain size, the equivalent circle diameter is calculated based on the grain area A measured by EBSD (area A=π×(grain size D/2) ² ), and the logarithmic normal state is calculated based on the crystal grain size distribution The standard deviation of the distribution σ.

In addition, the "thickness (mm) of the recrystallized layer" in the table was measured in the following manner. First, the thickness of the recrystallized layer was observed by EBSD with respect to the cross section cut so as to include the surface on which grooves were formed in the processed titanium material after the heat treatment. At this time, the area near the surface layer of the processed titanium material that has a crystal grain size smaller than the average crystal grain size at the position of 1/2 thickness of the processed titanium material is defined as the "recrystallized layer", and the thickness of the layer is defined as " The thickness of the recrystallized layer" is measured.

Next, the processed titanium material with grooves formed by the above-mentioned plastic deformation is inserted into a furnace at 820°C, heated for about 240 minutes, and a 5mm thick hot-rolled sheet is manufactured using a continuous slat hot rolling mill. Reel into coils. Next, bead spraying is performed on the hot-rolled sheet, and it passes through a continuous pickling production line composed of nitric-hydrofluoric acid to dissolve about 50 μm per single side. Then, the two rolled surfaces were visually observed to evaluate the occurrence of surface defects. The results are shown in Table 3. In Table 3, "groove angle" means the angle (°) between the inner surface of the groove and the surface of the processed titanium material in a cross-section perpendicular to the direction in which the groove extends, and "difference in hardness" means the angle from the bottom of the groove The difference (ΔHv) between the Vickers hardness at the position of 3 mm and the Vickers hardness at the position 1/2 of the thickness.

Regarding the evaluation of surface flaws, in the rolled surface of the hot-rolled sheet after passing through the continuous pickling line, if the number of surface flaws of 10 mm or ^{more exceeds 0.3 per 1m 2, it} is judged as unacceptable (evaluation D), 0.3 The following are evaluated as qualified (evaluation A~C). When the number of surface flaws is ^{0.05 or less per 1 m 2, it} is rated as evaluation A, more than 0.05 and less than 0.2 is rated as evaluation B, and more than 0.2 and less than 0.3 is rated as evaluation C.

[table 3]

As shown in Tables 1 to 3, No.1 is too small because the radius of curvature of the pressing surface is 1.5mm, so the groove angle between the inner surface of the groove and the surface of the processed titanium material becomes steeper, and the The surface of the hot-rolled sheet after pickling frequently produces coarse surface defects. No. 2 was large because the radius of curvature of the pressing surface was 30 mm, and a sufficient difference in hardness could not be obtained. As a result, the crystal grain size of the recrystallized layer is large, and the distribution width of the logarithmic normal distribution is wide (the standard deviation σ is large), and the crystal grain size is not uniform (see also FIG. 11). Therefore, surface flaws frequently occur. In No. 3, although the radius of curvature and the pressing amount of the pressing surface are appropriate but the spacing is too large, the crystal grain size of the recrystallized layer is large, and the distribution range of the logarithmic normal distribution is wide (the standard deviation σ is large), and the crystal grain size is uneven . Therefore, surface flaws frequently occur. In No. 4, although the radius of curvature and pitch of the pressing surface were appropriate, the pressing amount was too small, and a sufficient difference in hardness could not be obtained. As a result, the crystal grain size of the recrystallized layer is large, and the distribution width of the logarithmic normal distribution is wide (the standard deviation σ is large), and the crystal grain size is not uniform. Therefore, surface flaws frequently occur. On the other hand, in No. 5 to 27, at least any one of the radius of curvature of the pressing surface, the amount of indentation, and the spacing in the first step is appropriate, the hardness difference ΔHV of the processed titanium material is large enough, and it will successfully recrystallize The crystal grain size of the layer is made small enough and uniform. As a result, in these examples, the surface properties of the hot-rolled sheet after hot rolling and pickling were good.

<Example 2> An electron beam melting method (EBR) was used to cast flat blanks (titanium blanks). The flat blanks (titanium blanks) had the chemical composition shown in Table 4 and were 1050 mm wide×250 mm thick×5500 mm long. The press-fitting steps shown in Table 5 were performed on the cast titanium blank. In either case, a round rod pressing body was used. In each step of the first step and the second step, repeat the following actions to form multiple grooves on the surface of the titanium blank: press the pressing body into the surface of the titanium blank and then unload, then move the pressing body and place it on the surface of the titanium blank. The position is pressed into the surface of the titanium blank. The meaning of each term in Table 5 is the same as that in Table 2.

[Table 4]

[table 5]

The evaluation of the hardness difference ΔHV, equivalent circle average diameter of crystal grains, standard deviation, and surface flaws was performed in the same manner as in <Example 1>. The results are shown in Table 6.

[Table 6]

In No. 28~36, at least any one of the radius of curvature of the pressing surface, the amount of indentation, and the spacing in the first step is appropriate, the hardness difference ΔHV of the processed titanium material is large enough, and the crystal grains of the recrystallized layer are successfully removed. The diameter is small enough and uniform. As a result, in these examples, the surface properties of the hot-rolled sheet after hot rolling and pickling were good.

1,2,3: Processing titanium material (flat embryo, medium block, small block) 1a, 2a, 3a: surface 1b, 2b, 3b: groove 1b ₁ , 2b ₁ , 3b ₁ : groove bottom 1c: indentation 5: Pressing body (round bar) 51, 52, 53, 54: Pressing body 51a, 52a, 53a, 54a: Pressing surface 10: Titanium blank 10b: Surface groove F: Force M, S: Line R: Radius of curvature X , Y: distance d: overlap defect t: thickness θ: angle

Fig. 1 is a perspective view showing an example of the shape of a processed titanium material according to an embodiment of the present invention. Fig. 2 is a perspective view for explaining the shape of grooves arranged on the processed titanium material according to the embodiment of the present invention. Fig. 3 is a schematic diagram showing a cross section orthogonal to the direction in which the groove of the processed titanium material according to the embodiment of the present invention is extended. Fig. 4 is a schematic diagram showing the pressing body used in the manufacturing method of the processed titanium material according to the embodiment of the present invention. (a) shows a perspective view, and (b) shows a schematic diagram showing the press-fitting state of a cross section orthogonal to the axial direction of the pressing body. Fig. 5 is a schematic diagram showing a pressing body used in a method of manufacturing a processed titanium material according to another embodiment of the present invention. (a) shows a perspective view, and (b) shows a schematic diagram showing the press-fitting state of a cross section orthogonal to the axial direction of the pressing body. Fig. 6 is a schematic diagram showing a pressing body used in a method of manufacturing a processed titanium material according to another embodiment of the present invention. (a) shows a perspective view, and (b) shows a schematic diagram showing the press-fitting state of a cross section orthogonal to the axial direction of the pressing body. Fig. 7 is a perspective view showing a pressing body used in a method of manufacturing a processed titanium material according to another embodiment of the present invention. 8 is a diagram illustrating a method of manufacturing a processed titanium material according to an embodiment of the present invention, (a) is a schematic plan view, and (b) is a schematic view showing a cross section perpendicular to the axial direction of the pressing body. 9 is a diagram illustrating a method of manufacturing a processed titanium material according to an embodiment of the present invention, (a) is a schematic plan view, and (b) is a schematic view showing a cross section orthogonal to the axial direction of the pressing body. Fig. 10 is a schematic plan view showing a groove of a processed titanium material obtained by a method of manufacturing a processed titanium material according to an embodiment of the present invention. FIG. 11 is a graph showing the logarithmic normal distribution of the crystal grain size of the recrystallized layer of Example Nos. 2, 18, and 16.

10: Titanium blank

51: press body

51a: pressing surface

R: radius of curvature

X, Y: distance

Claims (9)

A manufacturing method of processed titanium material is to form a plurality of first grooves on the surface of the titanium blank; The first pressing body of the surface is pressed into the surface of the titanium blank; in the first section orthogonal to the direction in which the first pressing surface extends, the radius of curvature of the first pressing surface is 2.5mm or more and 17.5mm or less ; And the foregoing first step satisfies the following formulas (1) and (2): 0.5≦X ₁ ≦R ₁ ×(1-cosθ ₁ ) (1) 1.0≦Y ₁ ≦(-0.16R ₁ ² +4.4R ₁ )×(0.25X ₁ +0.037) (2) However, in the above formula, θ ₁ is 50°; R ₁ is the radius of curvature of the first pressing surface in the first section (mm); X ₁ is the first A pressing surface of the pressing amount of the titanium blank (mm); Y ₁ is the direction of the first pressing surface in a direction orthogonal to both the extending direction of the first pressing surface and the pressing direction of the first pressing body Above, the distance between adjacent press-in positions (mm). Such as claim 1, wherein the first step is to repeat the following actions: press the first pressing body into the surface of the titanium blank, and then make the pressing position of the first pressing surface satisfy The first pressing body is moved and pressed in in the manner of the aforementioned (2) formula. For the manufacturing method of processed titanium material of claim 1 or 2, a plurality of second grooves are formed on the surface of the titanium blank on which the plurality of first grooves are formed, and the plurality of second grooves are aligned with the first The grooves extend in different directions; the manufacturing method of the processed titanium material includes a second step of press-fitting a second pressing body having an arc-shaped second pressing surface extending in a predetermined direction to form the plurality of The surface of the titanium blank of the first groove; in a second cross section orthogonal to the direction in which the second pressing surface extends, the radius of curvature of the second pressing surface is 2.5 mm or more and 17.5 mm or less; and the second The steps satisfy the following equations (3) and (4): 0.5≦X ₂ ≦R ₂ ×(1-cosθ ₂ ) (3) 1.0≦Y ₂ ≦50.0 (4) However, in the above equation, θ ₂ is 50 °; R ₂ is the radius of curvature of the second pressing surface in the second section (mm); X ₂ is the pressing amount of the titanium blank _{(mm) on the second pressing surface; Y 2} is the second pressing The distance (mm) between adjacent pressing positions of the surface in a direction orthogonal to both the direction in which the second pressing surface extends and the pressing direction of the second pressing body. The manufacturing method of processed titanium material of claim 3, wherein the second step is to repeat the following actions: press the second pressing body into the surface of the titanium blank, and then make the pressing position of the second pressing surface satisfy The second pressing body is moved and pressed in in the manner of the aforementioned formula (4). The method of manufacturing a titanium material according to claim 3 or 4, wherein the angle formed by the extending direction of the first groove and the extending direction of the second groove is greater than 0° and less than 90°. The method for manufacturing a processed titanium material according to any one of claims 3 to 5, wherein the first pressing body and the second pressing body are the same or different. The manufacturing method of processed titanium material according to any one of claims 1 to 6, wherein the first step and/or the second step are performed at a temperature of 0°C or more and 500°C or less on the surface of the titanium blank . A processed titanium material produced by the manufacturing method as in any one of Claims 1 to 7; and In the thickness direction of the processed titanium material, the difference ΔHV between the Vickers hardness at a depth of 3 mm from the bottom of the groove and the Vickers hardness at a position 1/2 of the thickness is 20 or more. Such as the processed titanium material of claim 8, wherein after heat treatment at 800°C for 4 hours, in the thickness direction of the processed titanium material, an equivalent circle average is formed in the range from the bottom of the groove to the depth of 3.0mm The grain size is a crystal grain of 1.00 mm or less, and the standard deviation of the logarithmic conversion value of the equivalent circle diameter of the aforementioned crystal grain is 1.00 or less.

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