WO2022138837A1 - Titanium material - Google Patents

Abstract

This titanium material is such that, on at least one surface, the root-mean-square inclination RΔq (rad.) satisfies the following relationship (1) if the average length RSm of a roughness curve element is greater than 8 μm and equal to or less than 300 μm, and the root-mean-square inclination RΔq (rad.) satisfies the following relationship (2) if the average length RSm of the roughness curve element is greater than 300 μm.　Relationship (1): RΔq≥0.060 Relationship (2): RΔq≥2×RSm/10,000

Description

Titanium material

The present invention relates to a titanium material. This application claims priority based on Japanese Patent Application No. 2020-214647 filed in Japan on December 24, 2020, the contents of which are incorporated herein by reference.

Titanium material has high ductility and is processed into products of various shapes by press molding. Press formability, especially deep draw formability, is closely related to the friction coefficient, and reduction of the friction coefficient is extremely effective for improving deep draw formability. This is because in deep drawing molding, the titanium material is strongly rubbed against a part of the mold and processed. On the other hand, titanium is also very active. Therefore, the coefficient of friction becomes high, partly because the titanium material easily adheres to the mold. Therefore, it is important to control the surface texture of the titanium material.

As a technique focusing on the surface texture, for example, Patent Document 1 describes the residual stress concentrated in the shearing direction having a surface roughness in which the value of the center line average inclination (Rθa) of the adhered surface is 0.035 or more. A metal plate for non-oil surface adhesion having excellent adhesiveness to an adhesive, which is characterized by dispersing and releasing the direction, is disclosed.

Patent Document 2 describes a base plate material which is made of a titanium flat plate material having fine irregularities formed on its surface and becomes a heat exchange plate after the flat plate material is pressed as a post-treatment. The original plate material is such that the shape parameter defined by the height of the convex portion (μm) × the width of the concave portion (μm) / the pitch of the adjacent convex portions (μm) is 85 μm or less. The original plate material of the heat exchange plate, which is characterized in that the unevenness of the surface of the above-mentioned plate is set, is disclosed.

Patent Document 3 describes a step of forming an uneven pattern on one or both sides of a titanium plate by rolling using a work roll having an uneven pattern on the surface, a step of baking and / or pickling the titanium plate, and the above. A method for producing a titanium plate having a concavo-convex pattern on one side or both sides is disclosed, which includes a step of straightening a titanium plate with an average elongation rate of 0.1% or more and 1.3% or less by a tension leveler. The titanium plate obtained by the method for manufacturing a titanium plate disclosed in Patent Document 3 has an average convex portion maximum height of 15.0 μm or more in the uneven pattern.

In Patent Document 4, the arithmetic average roughness of the surface in the direction parallel to the rolling direction is 0.25 μm or more and 2.5 μm or less, and the Vickers hardness with a test load of 0.098 N is higher than the Vickers hardness with a test load of 4.9 N on the surface. A titanium plate characterized in that the hardness is 20 or more higher and the Vickers hardness under a test load of 4.9 N is 180 or less is disclosed.

Patent Document 5 has an oxide film made of rutile-type TiO ₂ having a thickness of 0.10 μm or more on the surface, and the surface properties of the oxide film are cutoffs of λs = 2.5 μm and λc = 0.08 mm. The arithmetic mean roughness Ra of the roughness curve obtained by applying the values is 0.20 to 7.0 μm, and the difference between the ten-point average roughness R _ZJIS of the roughness curve and the average height R _c of the contour curve element. The root mean square measured under the conditions of λs = 0 μm and λc = 0 mm for a region where (R _ZJIS −R _c ) satisfies 0.5 μm or more and 0.8 times or more of the maximum mountain height Rp of the roughness curve. A titanium plate characterized in that the square root inclination RΔq is 20 ° or less is disclosed.

Japanese Patent Application Laid-Open No. 2001-198603 Japanese Patent Application Laid-Open No. 2013-76548 Japanese Patent Application Laid-Open No. 2014-589 Japanese Patent Application Laid-Open No. 2002-3968 Japanese Patent Application Laid-Open No. 2020-183551

In the molding of titanium material, a lubrication method that suppresses contact between the titanium material and the mold to reduce the coefficient of friction is selected, and this lubrication method is extremely important for press molding of titanium material. For example, there is a lubrication method in which a lubricant is provided on the surface of a titanium material in order to reduce the coefficient of friction. As the lubricant, for example, a Teflon (registered trademark) sheet or a solid (film type) lubricant is applied. Although the Teflon sheet has excellent lubricity, the man-hours for attaching and removing it to the titanium material are large, and the cost increases. In addition, the Teflon sheet is often torn by one molding, and when the titanium material provided with the Teflon sheet is deep-drawn multiple times, the Teflon sheet needs to be reattached each time, which makes processing complicated. Become. On the other hand, the solid lubricant can be continuously applied, pressed, and washed and removed, but in a severe sliding environment such as deep drawing, a part of the solid lubricant may peel off and the friction coefficient may increase.

In the techniques disclosed in Patent Documents 1 to 4, when the solid lubricant is formed on the surface of the titanium material, the adhesion of the solid lubricant is not sufficient, and the solid lubricant is peeled off when deep drawing is performed. , The coefficient of friction may increase. As a result, the deep drawability is deteriorated, and there is a possibility that the appearance is poor and the titanium material is broken during deep draw molding.

Further, the technique disclosed in Patent Document 5 is a technique that does not use a solid lubricant, and the adhesion between the titanium material and the solid lubricant when the solid lubricant is used is unknown.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a titanium material having excellent deep drawability in deep drawing molding of a titanium material coated with a solid lubricant on the surface. To provide.

The present inventors have studied in detail the relationship between the surface texture of the titanium material and the adhesion of the solid lubricant, and have found that the adhesion of the solid lubricant is improved by controlling the surface texture of the titanium material. .. Furthermore, the present inventors have found that the average length RSm and the root mean square slope RΔq of the surface roughness curve element of the titanium material are extremely important for the adhesion of the solid lubricant of the titanium material. Then, the present inventors have found a method for producing such a titanium material based on the above findings, and have reached the present invention.

The gist of the present invention completed based on the above findings is as follows.
[1] In the titanium material of the present invention, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less on at least one surface, the root mean square slope RΔq (rad.) Has the following formula (1). When the average length RSm of the roughness curve element is more than 300 μm, the root mean square slope RΔq (rad.) Satisfies the following equation (2).
RΔq ≧ 0.060 ・ ・ ・ Equation (1)
RΔq ≧ 2 × RSm / 10000 ・ ・ ・ Equation (2)
[2] In the titanium material according to the above [1], the average length RSm of the roughness curve element is 400 μm or less, and the root mean square slope RΔq is 0.190 rad. It may be as follows.
[3] The titanium material according to the above [1] or [2] may have a Vickers hardness of 30 HV or more when the load is 50 gf, which is larger than the Vickers hardness when the load is 1000 gf.
[4] The titanium material according to any one of the above [1] to [3] may have an oxide film or a nitride film.
[5] The titanium material according to the above [4] may have a thickness of the oxide film or the nitrided film of less than 1.00 μm.

As described above, according to the present invention, it is possible to provide a titanium material having excellent deep drawing formability in deep drawing forming of a titanium material coated with a solid lubricant on the surface.

It is a figure for demonstrating the difference in the adhesion of a solid lubricant depending on the surface texture of a titanium material. It is a figure which shows an example of the roughness curve on the surface of a titanium material which concerns on one Embodiment of this invention. It is a figure for demonstrating the deep drawing test in Example 1 and Example 2. FIG. It is a graph which shows the evaluation result of the deep drawing formability in Example 1. FIG.

A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings below.

<Titanium material>
[Surface texture of titanium material]
In the titanium material according to the present embodiment, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less on at least one surface, the root mean square slope RΔq (rad.) Satisfies the following equation (1). When the average length RSm of the roughness curve element is more than 300 μm, the root mean square slope RΔq (rad.) Satisfies the following equation (2).
RΔq ≧ 0.060 ・ ・ ・ Equation (1)
RΔq ≧ 2 × RSm / 10000 ・ ・ ・ Equation (2)
The titanium material according to this embodiment will be described in detail below.

With reference to FIG. 1, the difference in the adhesion of the solid lubricant depending on the root mean square slope RΔq obtained by the study by the present inventors and the average length RSm of the roughness curve element will be described. FIG. 1 is a diagram for explaining the difference in the adhesion of the solid lubricant depending on the surface texture of the titanium material.

The root mean square slope RΔq represents the degree of inclination of the unevenness of the surface, and the larger the mean square root mean square RΔq is, the steeper the slope of the unevenness is (the unevenness is sharper), and the mean square root mean square RΔq is smaller. It shows that the slope of the unevenness is gentler.

The average length RSm of the roughness curve element represents the interval between the irregularities on the surface, and the larger the average length RSm of the roughness curve element, the larger the interval between the irregularities, and the average length of the roughness curve element. The smaller the RSm, the smaller the spacing between the irregularities.

For example, FIG. 1A schematically shows the surface texture of a titanium material and the solid lubricant formed on the surface of the titanium material when the root mean square slope RΔq is large and the average length RSm of the roughness curve element is small. It is shown in. In this case, as shown in FIG. 1A, the surface of the titanium material has sharp irregularities and the intervals between the irregularities are small, and the solid lubricant is likely to be filled in the concave portions of the irregularities on the surface of the titanium material. When the root mean square slope RΔq is large and the average length RSm of the roughness curve element is small, the solid lubricant adheres due to the anchor effect of fixing the solid lubricant by sharp unevenness and the filling of the recess with the solid lubricant. It is thought that the sex will improve.

FIG. 1B schematically shows the surface texture of the titanium material and the solid lubricant formed on the surface of the titanium material when the root mean square slope RΔq is large and the average length RSm of the roughness curve element is large. Shows. In this case, as shown in FIG. 1 (B), the surface of the titanium material is a surface having sharp irregularities and a large interval between irregularities. When the root mean square slope RΔq is large and the average length RSm of the roughness curve element is large, it is considered that the recesses are not filled with the solid lubricant and the adhesion of the solid lubricant is lowered.

FIG. 1C schematically shows the surface texture of the titanium material and the solid lubricant formed on the surface of the titanium material when the root mean square slope RΔq is small and the average length RSm of the roughness curve element is small. Shows. Further, FIG. 1 (D) schematically shows the surface texture of the titanium material and the solid lubricant formed on the surface of the titanium material when the root mean square slope RΔq is small and the average length RSm of the roughness curve element is large. Is shown. In these cases, as shown in FIGS. 1 (C) and 1 (D), the surface of the titanium material is a surface with gentle irregularities. Since the unevenness is gentle, it is considered that a sufficient anchor effect cannot be obtained and the adhesion of the solid lubricant is lowered.

In the titanium material according to the present embodiment, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, the root mean square slope RΔq (rad.) Satisfies the above equation (1).

As described above, when the average length RSm of the roughness curve element is small, the spacing between the irregularities on the surface is small and the recesses are easily filled with the solid lubricant, but the average length RSm of the roughness curve element is less than 8 μm. Then, the unevenness becomes too fine and it becomes difficult to obtain the anchor effect, and the adhesion of the solid lubricant is lowered. As a result, the coefficient of friction during deep drawing molding becomes large, and the deep drawing formability deteriorates. Therefore, the average length RSm of the roughness curve element is more than 8 μm.

If the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, and the root mean square slope RΔq (rad.) Satisfies the equation (1), the anchor effect and the filling of the recess with the solid lubricant can be used. , Deep draw formability is improved. Even if the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, if the root mean square slope RΔq does not satisfy the above equation (1), the anchor effect due to unevenness cannot be sufficiently obtained, and the solid lubricant Adhesion is reduced and deep drawability is reduced. Therefore, in the titanium material according to the present embodiment, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, the root mean square slope RΔq (rad.) Satisfies the above equation (1).

When the average length RSm of the roughness curve element exceeds 300 μm, if the root mean square slope RΔq satisfies the above equation (2), the deep draw formability is improved by the anchor effect and the filling of the recess with the solid lubricant. .. If the average length RSm of the roughness curve element is more than 300 μm and the root mean square slope RΔq does not satisfy the above equation (2), the anchor effect due to unevenness cannot be sufficiently obtained, and the adhesion of the solid lubricant is poor. It is lowered and the deep drawability is lowered. Therefore, in the titanium material according to the present embodiment, the root mean square slope RΔq (rad.) When the average length RSm of the roughness curve element exceeds 300 μm satisfies the above equation (2).

In addition, if the average length Rsm of the roughness curve element and the root mean square slope RΔq become too large, the convex portion on the surface of the titanium material is crushed by contact with the mold, and the solid cannot follow the deformation of the convex portion. The lubricant may crack and peel off. In this case, the coefficient of friction may increase in the first-stage deep drawing process, and the deep drawing formability may deteriorate. Therefore, the average length Rsm of the roughness curve element is preferably 500 μm or less, and the root mean square slope RΔq is preferably 0.25 rad. It is as follows.

In the titanium material according to the present embodiment, after satisfying the above conditions, the average length RSm of the roughness curve element is 400 μm or less, and the root mean square slope RΔq is 0.190 rad. The following is more preferable. For example, in the case of multi-stage deep drawing, in which the titanium material is deep-drawn with a spherical head punch and then deep-drawn with a cylindrical punch, the first spherical head deep-drawing is strained over the entire spherical portion of the titanium material. Is introduced, strain is concentrated in the partial recess, and the solid lubricant may crack and peel off. If the solid lubricant is cracked and peeled off and the cylinder deep drawing is performed in the next step, the friction coefficient may increase and the deep drawing formability may decrease. The average length RSm of the roughness curve element is 400 μm or less, and the root mean square slope RΔq is 0.190 rad. If it is as follows, peeling of the solid lubricant can be suppressed, and the moldability in the multi-stage deep drawing becomes good.

For the average length RSm of the roughness curve element and the root mean square slope RΔq, the roughness curves at two locations are obtained by a method based on JIS B 0601: 2013, and the average of the values calculated from each roughness curve is obtained. Use the value. When the roughness curve is measured for the titanium material according to the present embodiment by a method according to JIS B 0601: 2013, for example, the roughness curve as shown in FIG. 2 can be obtained. The roughness curve, which is the basis for calculating the average length RSm and the squared average square root slope RΔq of the roughness curve elements, is the surface of the titanium material measured in the rolling width direction, the evaluation length of 15 mm, and the measurement speed of 0.15 mm / s. It is obtained by applying a low frequency filter with a cutoff wavelength λc = 0.8 mm to the measurement cross-sectional curve of the above to obtain a cross-sectional curve, and further applying a high frequency filter with a cutoff wavelength λs = 25 μm to this cross-sectional curve. The roughness curve is used. λc is a filter that defines the boundary between the roughness component and the waviness component. λs is a filter that defines the boundary between the roughness component and the shorter wavelength component.

The average length RSm of the contour curve element is calculated from the following equation (3).

In the above equation (3), m is the number of measurement points, and Xsi is the length of the contour curve element at the reference length.

The root mean square slope RΔq of the roughness curve element is calculated from the following equation (4).

In the above formula (4), N is the number of measurement points. (DZj / dXj) is a local inclination at the jth measurement point in the roughness curve, and is defined by the following equation (5).

In the above equation (5), Z _{j + 3} is the height from the average line of the surface at the j + 3rd measurement point. Similarly, in the formula (5), Z _{j + 2} , Z _{j + 1} , Z _j-1 , Z _j-2 , and Z _j-3 are j + 2, j + 1, j-1, and j-2, respectively. The height from the average plane of the surface at the third and j-3rd measurement points. In equation (5), ΔX is the measurement interval. In the present embodiment, the measurement interval ΔX may be determined as follows. That is, the measurement interval ΔX is a value set by the surface roughness shape measuring machine, and when numerical data is acquired at N points when the measurement length L is measured, ΔX is L / (on average at the measurement interval. It becomes N-1). For example, when a measurement length of 5 mm is measured and 25601 points of numerical data are acquired, ΔX is 5 mm / 25600 points, which is about 0.1905 μm on average.

[The Vickers hardness when the load is 50 gf is 30 HV or more larger than the Vickers hardness when the load is 1000 gf]
The titanium material according to the present embodiment preferably has a Vickers hardness of 30 HV or more when the load is 50 gf and is larger than the Vickers hardness when the load is 1000 gf. If the surface of the titanium material is soft, the surface is deformed during deep drawing and the contact area with the mold becomes large, and the sliding resistance tends to increase. As the sliding resistance increases, the solid lubricant tends to peel off. Therefore, it is preferable that the Vickers hardness with a load of 50 gf, which indicates the hardness closer to the surface of the titanium material, is 30 HV or more larger than the Vickers hardness with a load of 1000 gf. If the inside of the titanium material is too hard to the same extent as the surface, the molding itself becomes difficult even if the slidability is good, and it may crack during deep drawing. On the other hand, if the surface of the titanium material is too hard, deep drawing may be difficult. From the viewpoint of sliding, there is no upper limit to the hardness, but if the Vickers hardness exceeds 800 HV when the load is 50 gf, for example, the hardened layer is too thick and there is a concern that the bending workability may be deteriorated. Therefore, in actual use, the Vickers hardness when the load is 50 gf is preferably 800 HV or less.
The Vickers hardness with a load of 1000 gf is preferably 105 HV or more, and more preferably 110 HV or more, from the viewpoint of the strength after molding. On the other hand, the Vickers hardness with a load of 1000 gf is preferably 300 HV or less, and more preferably 250 HV or less, from the viewpoint of moldability.
For the Vickers hardness, the average value of the values measured at 5 points each by a method according to JIS Z 2244: 2009 is used.

From the above viewpoint, the titanium material according to the present embodiment preferably has an oxide film or a nitrided film. The thickness of the oxide film or the nitrided film is preferably 1.00 μm or less. Since the oxide film and the nitrided film have low ductility, they may be cracked during deep drawing, but if their thickness is less than 1.00 μm, cracking of these films can be prevented. The thickness of the oxide film or the nitrided film may be 0.50 μm or less.
On the other hand, the lower limit of the thickness of the oxide film or the nitrided film is not particularly limited. The thickness of the oxide film or the nitrided film may be, for example, 0.02 μm or more, or may be 0.06 μm or more.

The thickness of the oxide film or the nitrided film can be determined from the distribution of oxygen and nitrogen in the depth direction obtained by glow discharge spectroscopy (GDS: Glow discharge spectroscopy). Specifically, the distance in the depth direction to the position where the O concentration is halved with respect to the O concentration on the outermost surface is defined as the thickness of the oxide film, and the depth to the position where the N concentration is halved with respect to the N concentration on the outermost surface. The distance in the vertical direction is defined as the thickness of the nitrided film.

The titanium material of the present embodiment is not particularly limited and may be pure titanium or a titanium alloy. The titanium material is, for example, pure titanium or a titanium alloy having a Ti content of 70% by mass or more.

Pure titanium includes, for example, 1 to 4 types of JIS standard and industrial pure titanium specified by Grade 1 to 4 of ASTM standard corresponding to these. That is, the target industrial pure titanium in this embodiment is C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less in mass%. , Fe: 0.5% or less, the balance is made of Ti and impurities.

Examples of the titanium alloy include α-type titanium alloy, α + β-type titanium alloy, and β-type titanium alloy.

The α-type titanium alloy is defined by, for example, a highly corrosion-resistant alloy (JIS standard 11 to 13, 17, 19 to 22 and ASTM standard Grade 7, 11, 13, 14, 17, 30, 31). Titanium alloy and titanium alloy containing a small amount of various elements), Ti-0.5Cu, Ti-1.0Cu, Ti-1.0Cu-0.5Nb, Ti-1.0Cu-1.0Sn-0 .3Si-0.25Nb, etc.

Examples of the α + β type titanium alloy include Ti-3Al-2.5V, Ti-5Al-1Fe, Ti-6Al-4V and the like.

Examples of the β-type titanium alloy include Ti-11.5Mo-6Zr-4.5Sn, Ti-8V-3Al-6Cr-4Mo-4Zr, Ti-13V-11Cr-3Al, Ti-15V-3Al-3Cr-3Sn. , Ti-20V-4Al-1Sn, Ti-22V-4Al and the like.

[Plate thickness]
The plate thickness of the titanium material according to this embodiment is, for example, 0.3 mm or more and 4.5 mm or less. The plate thickness of the titanium material may be 0.4 mm or more, or 0.5 mm or more. Further, the plate thickness of the titanium material may be 4.3 mm or less, or 4.0 mm or less.

The titanium material according to the present embodiment has excellent deep drawability when it is applied to at least one surface in a liquid state and then dried to form a solid film by deep drawing using a solid lubricant. Be done.
Up to this point, the titanium material according to the present embodiment has been described.

Next, an example of the titanium material manufacturing method according to the present embodiment will be described. However, the method for producing the titanium material according to the present embodiment is not particularly limited. A titanium material satisfying the above requirements is regarded as a titanium material according to the present embodiment regardless of the manufacturing method thereof. The manufacturing method described below is only a suitable example, and does not limit the titanium material according to the present embodiment.

<Manufacturing method of titanium material>
The method for producing a titanium material according to the present embodiment includes an unevenness forming step of forming irregularities on at least one surface of the titanium material, and a annealing step of annealing in at least one of a vacuum atmosphere, an oxidizing atmosphere, and a nitriding atmosphere. And have. In the unevenness forming step, cold skin pass rolling or blasting using a plurality of dull rolls is performed. The unevenness forming step and the annealing step will be described in detail below.

[Concavo-convex forming process]
In the unevenness forming step, unevenness is formed on at least one surface of the titanium material. In the unevenness forming step, cold skin pass rolling using dull roll is performed at least twice. The surface of the dull roll is dull-processed, but the method of dull-processing the surface of the roll is not particularly limited, and for example, dull processing using a shot or grit may be used. As the shot or grit, for example, one conforming to JIS G 5903: 2018 can be used. Specifically, a steel grit called SG-50, SG-100, SG-140, SG-170, or SG-200, or a steel shot called SS-200 or SS-240 may be used. .. When performing two skin pass rollings, it is preferable to satisfy the following conditions.
(Conditions) Using any of the projection materials SG-50 to SG-240 or SS-50 to SS-240, the surface roughness Ra of the dull roll used for the first skin pass rolling is 7.0 μm or more and less than 8.0 μm. The surface roughness Ra of the dull roll used for the second skin pass rolling is set to 6.0 μm or more and 8.5 μm or less. At this time, it is preferable that the diameter of the projection material when manufacturing the dull roll used for the second skin pass rolling is equal to or larger than the diameter of the projection material when manufacturing the dull roll used for the first skin pass rolling. When dull rolls having different surface roughness Ra manufactured using the same projection material are used, the surface roughness Ra of the dull roll used for the first skin pass rolling is the surface roughness Ra of the dull roll used for the second skin pass rolling. It is preferably smaller than Ra.

Further, under the above conditions, the projection material having the maximum particle size used for dull processing may be SG-200 or SS-200.

When the surface roughness Ra of the dull roll used for the first skin pass rolling is less than 7.0 μm and the surface roughness Ra of the dull roll used for the second skin pass rolling is less than 6.0 μm, the third time under appropriate conditions. Skin path rolling may be carried out.

In order to obtain the titanium material according to this embodiment, it is important that the surface of the dull roll has a steep slope with a fine pitch. The surface texture of dull roll is influenced by, for example, the method of dull processing and the type of projection material used for dull processing. For example, when the particle size of the projecting material is changed and dull processing is performed under the same conditions, a dull roll having a smaller surface roughness Ra is produced when the particle size of the projecting material is smaller. The above formula (1) and the above formula (2) may not be satisfied with the dull roll having a significantly small surface roughness Ra. Therefore, in this step, when the surface roughness Ra of the dull roll used for the first skin pass rolling and the second skin pass rolling is small, it is preferable to perform the third skin pass rolling.

The surface roughness Ra of the dull roll used for the third skin pass rolling may be, for example, 2.9 μm or more and 8.5 μm or less. However, the surface roughness of the dull roll used for the third skin pass rolling is preferably at least one of the surface roughness of the dull roll used for the first or second skin pass rolling. If the surface roughness of the dull roll used for the third skin pass rolling is at least one of the surface roughness of the dull roll used for the first or second skin pass rolling, the surface of the titanium material has finer pitch and sharp unevenness. Is formed.

As described above, when the dull roll surface roughness Ra used for the first skin pass rolling is less than 7.0 μm and the dull roll surface roughness Ra used for the second skin pass rolling is less than 6.0 μm, the third skin pass Rolling is performed using, for example, a dull roll having a surface roughness Ra of 2.9 μm or more and 8.5 μm or less. However, when skin pass rolling is performed three times using the same dull roll, a dull roll having a surface roughness Ra of 4.0 μm or less is used. When the surface roughness Ra of the dull roll in the case of three skin pass rolling using the same dull roll is more than 4.0 μm, the balance between the root mean square slope RΔq and the average length RSm of the roughness curve element is appropriate. It disappears and does not satisfy the above equations (1) and (2). On the other hand, if the surface roughness Ra of the dull roll in the case of three skin pass rollings using the same dull roll is too small, RΔq becomes small and the formulas (1) and (2) are not satisfied. Therefore, the surface roughness Ra of the dull roll in the case of three skin pass rollings using the same dull roll is preferably 2.9 μm or more.

In addition, when skin pass rolling is performed using a plurality of dull rolls of the same type and different surface roughness used for manufacturing dull rolls, it is possible to first skin pass roll the titanium material with dull rolls having a small surface roughness. preferable. By doing so, sharp irregularities are formed on the surface of the titanium material at a finer pitch.

The surface roughness Ra of the bright roll used for normal cold rolling is 0.2 μm or less, which is different from the dull roll used in the skin pass rolling in the unevenness forming step in terms of the surface roughness Ra.

[Annealing process]
In the annealing step, the titanium material is annealed in at least one of a vacuum atmosphere, an oxidizing atmosphere, and a nitrided atmosphere.

The vacuum atmosphere refers to an atmosphere in which the degree of vacuum includes 1 Pa and the pressure is lower than that. The oxidizing atmosphere is an atmosphere containing 5% by volume or more of oxygen, and is, for example, an atmospheric atmosphere. The nitriding atmosphere is an atmosphere containing 99% by volume or more of nitrogen.

When the annealing atmosphere is a vacuum atmosphere, the annealing temperature is preferably 500 ° C. or higher, more preferably 550 ° C. or higher, from the viewpoint of removing distortion of the material and improving cold workability. The annealing temperature is preferably 800 ° C. or lower from the viewpoint of removing the strain of crystals and improving the cold workability. When the annealing atmosphere is a vacuum atmosphere, the annealing time is, for example, 2 minutes or more and 24 hours or less.

When the annealing atmosphere is an oxidizing atmosphere or a nitriding atmosphere, the annealing temperature is 550 in order to remove the distortion of the crystal grains, improve the cold workability, and prevent the film thickness from becoming too thin. The temperature is preferably ℃ or higher, and more preferably 600 ℃ or higher. When the annealing atmosphere is an oxidizing atmosphere, the annealing temperature is 800 ° C. or lower from the viewpoint of removing distortion of crystal grains to improve cold workability and suppressing the formation of an excessively thick film. It is preferably 770 ° C. or lower, and more preferably 770 ° C. or lower. When the annealing atmosphere is an oxidizing atmosphere, the annealing time is, for example, 2 minutes or more and 24 hours or less. When annealed in an oxidizing atmosphere, the surface of the titanium material may be melted.

The annealing atmosphere is preferably an oxidizing atmosphere or a nitriding atmosphere. When the annealing atmosphere is an oxidizing atmosphere or a nitrided atmosphere, an oxide film or a nitrided film is formed, and the Vickers hardness when the load is 50 gf can be increased by 30 HV or more from the Vickers hardness when the load is 1000 gf.

In the method for producing a titanium material according to the present embodiment, the annealing step may be carried out before the unevenness forming step, or the unevenness forming step may be carried out before the annealing step. When the annealing step is performed before the unevenness forming step, a titanium material manufactured by a known method may be used as the titanium material to be subjected to the annealing step. For example, using titanium sponge or a mother alloy for adding an alloy element as a raw material, pure having the above components by various melting methods such as a vacuum arc melting method, an electron beam melting method, or a hearth melting method such as a plasma melting method. Titanium or titanium alloy ingots are made. Next, the obtained ingot is lumped and hot forged as necessary to form a slab. Then, the slab is subjected to hot rolling and cold rolling in order to obtain a cold-rolled coil of pure titanium or a titanium alloy having the above composition. This cold-rolled coil may be annealed. The slab may be subjected to pretreatment such as polishing and cutting, if necessary. Alternatively, when the ingot is formed into a rectangular shape that can be hot-rolled by a melting method, it may be subjected to hot rolling without lumping or hot forging.

Further, the titanium material used for the unevenness forming step when the unevenness forming step is carried out before the annealing step may be manufactured by a known method, and is a hot-rolled coil obtained by hot-rolling the slab or the said slab. A cold-rolled coil obtained by cold-rolling the hot-rolled coil may be subjected to the unevenness forming step.

As described above, the titanium material to be subjected to the annealing step is manufactured by hot rolling and cold rolling, and in the cold rolling, the average reduction rate per pass is preferably 12% or more. .. When the reduction rate is high, a compound of C and Ti (tribo film) is formed on the surface of the titanium material, and the compound is carburized and hardened by the annealing step. As a result, the surface of the titanium material becomes hard. When the average reduction rate per pass is 12% or more, the Vickers hardness of the final product titanium material when the load is 50 gf and the Vickers hardness of the final product titanium material when the load is 1000 gf. On the other hand, it increases by 30 HV or more. On the other hand, the upper limit of the average reduction rate per pass in cold rolling is, for example, 25% from the viewpoint of appearance after cold rolling.

When the unevenness forming step is carried out after the annealing step, the rolling reduction rate of the skin pass rolling in the unevenness forming step may be, for example, 0.3% or more. When the unevenness forming step is carried out after the annealing step, the upper limit of the rolling reduction rate of skin pass rolling in the unevenness forming step is not particularly limited, but if the rolling reduction rate is too large, the strain introduced into the titanium material deteriorates the formability. In some cases. Therefore, when the unevenness forming step is carried out after the annealing step, the rolling reduction rate of the skin pass rolling in the unevenness forming step is preferably 2.0% or less.
On the other hand, when the unevenness forming step is carried out before the annealing step, the rolling reduction rate of the skin pass rolling in the unevenness forming step may be, for example, 0.5% or more. When the unevenness forming step is carried out after the annealing step, the upper limit of the rolling reduction rate of the skin pass rolling in the uneven forming step is not particularly limited. If an attempt is made to increase the rate, the load applied to the rolling mill becomes too large, and it may not be possible to reduce the rolling force at a desired reduction rate. Therefore, when the unevenness forming step is carried out before the annealing step, the rolling reduction rate of the skin pass rolling in the unevenness forming step is, for example, 7.0% or less.

When the unevenness forming step is carried out after the annealing step, in the unevenness forming step, unevenness may be formed on at least one surface of the titanium material by blasting instead of skin pass rolling. When blasting the titanium material after the baking step, the blasting method is as follows: when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less for the titanium material of the final product, the root mean square slope RΔq (rad). When the above equation (1) is satisfied and the average length RSm of the roughness curve element is more than 300 μm, there is no particular limitation as long as the root mean square slope RΔq (rad.) Satisfies the above equation (2). For example, examples of the blasting treatment include bead blasting and wet blasting.

When the unevenness forming step is carried out after the annealing step, it is preferable that the titanium material after the unevenness forming step is further annealed in at least one of a vacuum atmosphere, an oxidizing atmosphere, and a nitrided atmosphere. In the titanium material in which the unevenness is formed by performing the unevenness forming step after the annealing step, a processed layer (a surface layer in which the strain is significantly introduced by the unevenness formation) is formed on the surface layer of the titanium material. This processed layer may have reduced ductility, in which case it may break during deep drawing. In order to suppress this breakage, it is preferable that the titanium material after the unevenness forming step is further annealed in at least one of a vacuum atmosphere, an oxidizing atmosphere, and a nitriding atmosphere. The annealing conditions after the unevenness forming step may be the same as those in the above-mentioned annealing step.

The titanium material that has undergone the unevenness forming step and the annealing step may be subjected to temper rolling for adjusting the mechanical properties or tensile straightening for correcting the shape, if necessary.
The method for producing the titanium material according to the present embodiment has been described above.

Hereinafter, embodiments of the present invention will be specifically described with reference to examples. The examples shown below are merely examples of the present invention, and the present invention is not limited to the following examples.

(Example 1)
In this example, a pure titanium slab corresponding to JIS 1 to JIS 3 types, a titanium alloy slab corresponding to JIS 12 types, JIS 17 types, and JIS 21 types, according to JIS H 4600: 2012 having the components shown in Table 1. , Ti-1.0Cu alloy slab represented by Ti-1.0Cu, Ti-1.0Cu-1.0Sn- represented by Ti-1.0Cu-1.0Sn-0.3Si-0.25Nb. A slab of a 0.3Si-0.25Nb alloy was hot-rolled and then scale-removed to obtain a hot-rolled plate having a plate thickness of 4 mm. "-" In Table 1 indicates that it was not intentionally added.

The hot-rolled plate was cold-rolled at the rolling reduction ratio shown in Table 2 to produce a cold-rolled plate having a plate thickness of 1.5 mm, and the annealing step was performed under the conditions shown in Table 2. When annealing was performed in an air atmosphere, a titanium material from which the oxide film had been removed by melting and a titanium material having an oxide film left were produced. An unevenness forming step was carried out on the titanium material after the annealing step. The dull roll rolling A to W and the dull roll rolling a to c in Table 2 correspond to the dull rolling (skin pass rolling) conditions shown in Table 3. The projection material shown in Table 3 shows the projection material used for dull processing. Ra shown in Table 3 shows the surface roughness Ra of the roll (dull roll) surface after dull processing.
In Comparative Example 1, as the unevenness forming step, one skin pass rolling was performed using a dull roll having a surface roughness Ra of 2.1 μm of the dull roll processed by using a steel grit (SG-50) (dull roll rolling O). ..
In Comparative Example 2, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 8.3 μm of the dull roll processed using a steel grit (SG-200) (dull roll rolling P). ..
In Comparative Example 3, as the unevenness forming step, one skin pass rolling was performed using a dull roll having a surface roughness Ra of 7.3 μm of the dull roll processed by using a steel grit (SG-140) (dull roll rolling Q). ..
In Comparative Example 4, as the unevenness forming step, one skin pass rolling was performed using a dull roll having a surface roughness Ra of 7.4 μm of the dull roll processed by using a steel grit (SG-170) (dull roll rolling R). ..
In Comparative Example 5, as the unevenness forming step, a dull roll having a surface roughness Ra of 8.3 μm processed by a steel shot (SS-200) was used for the first skin pass rolling, and the second skin pass rolling was performed. , A dull roll having a surface roughness Ra of 5.6 μm of the dull roll processed by using a steel shot (SS-200) was used (dull roll rolling S).
In Comparative Example 6, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 8.3 μm of the dull roll processed by using a steel shot (SS-200) (dull roll rolling T). ..
In Comparative Example 7, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 8.1 μm of the dull roll processed by using a steel shot (SS-240) (dull roll rolling U). ..
In Comparative Example 8, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 2.1 μm of the dull roll processed by using a steel grit (SG-50) (dull roll rolling V). ..
In Comparative Example 9, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 2.9 μm of the dull roll processed by using a steel grit (SG-170) (dull roll rolling W). ..
In Comparative Examples 10 and 14, skin pass rolling as a step of forming unevenness was not performed, and the surface of the cold-rolled plate was melted by 100 μm per one side.
In Comparative Example 11, the skin pass rolling as the unevenness forming step was not performed, and the surface of the cold rolled plate was melted by 10 μm per one side. The melting in Comparative Examples 10, 11 and 14 was carried out using niter hydrofluoric acid (HF: 2 mass%, HNO ₃ : 8 mass%).
In Comparative Example 12, the surface of the cold-rolled plate was mirror-polished without performing the unevenness forming step.
In Comparative Example 13, the unevenness forming step was not performed, and the surface state of the cold rolled plate after the annealing step was maintained.
In Comparative Example 15, as the unevenness forming step, skin pass rolling was performed twice using a dull roll having a surface roughness Ra of 3.1 μm of the dull roll processed using a steel grit (SG-100) (dull roll rolling b). ..
In Comparative Example 16, as the unevenness forming step, skin pass rolling was performed three times using a dull roll having a surface roughness Ra of 4.4 μm of the dull roll processed by using a steel grit (SG-170) (dull roll rolling c). ..
Further, the bead blasting shown in the item of the unevenness forming step in Table 2 indicates that the bead blasting was performed using the zirconia beads F40 under the conditions of a pressure of 0.3 MPa, a projection distance of 200 mm, a projection time of 1 min, and wet. The blasting shows that a slurry having a grid volume ratio of 15 vol% using alumina grit F230 was wet-blasted under the conditions of a flow rate of 15 m / s and a line speed of 0.2 m / s.

For Examples 25 to 28 of the present invention, the titanium material after the unevenness forming step was further annealed under the conditions shown in Table 2.

The average length RSm and the root mean square slope RΔq of the roughness curve element of the produced titanium material were measured according to JIS B 0601: 2013 under the following conditions.
Equipment Equipment: Surface roughness shape measuring machine (SURFCOM480B-12 manufactured by Tokyo Seimitsu Co., Ltd., Analysis software: SURFCOM480B Ver.7.06)
Stylus: Tokyo Seimitsu Co., Ltd. Shape stylus (model: DT43801)
Parameter calculation standard: JIS-01 standard Measurement type: Roughness measurement Cutoff type: Gaussian measurement interval Δx: 0.4 μm
Tilt correction: Both ends evaluation length: 15.0 mm
Measurement speed: 0.15 mm / sec
Measurement range: 400 μm
Cutoff wavelength λc: 0.8 mm
λs cutoff wavelength: 25 μm

The average value of the values calculated for the two locations under the above conditions was defined as the average length RSm of the roughness curve element and the root mean square slope RΔq.

The thickness of the oxide film and the nitrided film was measured by glow discharge spectroscopy. O, C, N and Ti were analyzed from the surface of the titanium material by glow discharge spectroscopy, and the thickness of the oxide film was determined by the measured O concentration and the thickness of the nitride film was determined by the N concentration. Specifically, the distance in the depth direction to the position where the O concentration is halved with respect to the O concentration on the outermost surface is defined as the thickness of the oxide film, and the depth to the position where the N concentration is halved with respect to the N concentration on the outermost surface. The distance in the vertical direction was taken as the thickness of the nitrided film.

For the Vickers hardness, 5 points were measured at a load of 50 gf, 1000 gf, and a holding time of 15 s by a method based on JIS Z 2244: 2009, and the average value of the measured values was used. Table 4 shows the average length RSm, the root mean square slope RΔq, the Vickers hardness, and the film thickness of the obtained roughness curve elements of the titanium material.

The obtained titanium material was subjected to a one-step deep drawing test and a multi-step deep drawing test. FIG. 3 is a diagram for explaining a deep drawing test in an example. FIG. 3 shows a deep drawing test using a cylindrical punch.

A circular blank with a diameter of 120 mm was cut out from the obtained titanium material. Mill Bond (registered trademark) manufactured by NOF CORPORATION as a solid lubricant and water were mixed at a volume ratio of 3: 1 and applied to the surface of the cut out blank with a bar coater. The blank coated with the solid lubricant was dried at 60 ° C. for 2 hours. The thickness of the solid lubricant was 3-5 μm.

The blank formed by the solid lubricant was held by the lower die and the upper die. The end of the upper die on the blank side is a curve having a radius of curvature of 5 mm. At this time, the clearance between the lower die and the upper die in the extending direction of the blank was 2 to 4 mm. Then, a load was applied to the held blank from the lower die side.

In the one-step deep drawing test, a spherical head punch with a diameter of 60 mm was used, and a load was applied until the drawing depth reached 40 mm. In the multi-stage deep drawing test, three deep drawings were performed. For the first deep aperture, use a φ60 mm ball head punch to apply a load until the aperture depth becomes 40 mm, and for the second deep aperture, use a φ50 mm ball head punch to make the aperture depth 50 mm. A cylindrical punch with a diameter of 45 mm was used for the third deep drawing, and the load was applied until the drawing depth reached 65 mm. The radius of curvature of the punch shoulder of the cylindrical punch was 5 mm. The deep drawing speed was 100 mm / min.

The specimen after the deep drawing test was visually inspected for appearance.
Defective (C) if the solid lubricant was peeled off and a seizure mark was observed, or if 10 or more linear flaws were observed, some solid lubricant was peeled off and there was no seizure mark, 6 to Those with 9 linear flaws are acceptable (B), those with no solid lubricant peeling, no seizure marks, and 5 or less linear flaws are good (A). I evaluated it.

Further, as an evaluation index of deep drawing formability, the plate thickness reduction rate was calculated by the following formula (6). The plate thickness reduction rate is determined by measuring the thickness of the specimen after deep drawing at a position about 20 mm in height from the deeply drawn bottom surface with a 360 ° point micrometer, and determining the value of the thinnest part after the test. Used as.
Plate thickness reduction rate (%) = {1- (thickness after test / thickness before test)} x 100 ... Equation (6)

In the one-step deep drawing test, the case where the plate thickness reduction rate was less than 20% was passed, and in the multi-step deep drawing test, the case where the plate thickness reduction rate was less than 30% was passed. If the blank was broken, it was also rejected, and it was described as broken in the table. The evaluation results are shown in Table 5. Further, FIG. 4 shows the relationship between the evaluation result of deep drawing formability, the average length RSm of the roughness curve element, and the root mean square slope RΔq. 〇 in FIG. 4 is a condition that the appearance after deep drawing is more than acceptable in both the one-step deep drawing test and the multi-step deep drawing test, and Δ is the deep drawing only in the one-step deep drawing test. It is a condition that the appearance after molding is more than acceptable, and x is a condition that the deep drawing formability is poor or the blank is broken in both the one-step deep drawing test and the multi-step deep drawing test.

As shown in Table 5 and FIG. 4, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, the root mean square slope RΔq (rad.) Satisfies the above equation (1), and the roughness is described. When the average length RSm of the curve element is more than 300 μm, when the root mean square slope RΔq (rad.) Satisfies the above equation (2), as compared with the case where it does not, after the one-step deep drawing test. Was excellent in appearance and deep drawability. Further, the average length RSm of the roughness curve element is 400 μm or less, and the root mean square slope RΔq is 0.190 rad. In the following cases, the appearance after the multi-stage deep drawing test and the deep drawing formability were excellent as compared with the case where it was not.

(Example 2)
In this embodiment, a pure titanium slab having the components shown in Table 1 and corresponding to JIS class 1 conforming to JIS H 4600: 2012 is hot-rolled, scale-removed, and a hot-rolled plate having a plate thickness of 4 mm. And said.

A cold rolled plate having a plate thickness of 1.5 mm was produced by cold rolling with an average rolling reduction of 10%, and skin pass rolling was performed under the conditions shown in Table 6 to form irregularities. The titanium material on which the unevenness was formed was annealed under the conditions shown in Table 6. When annealing was performed in an air atmosphere, a titanium material from which the oxide film had been removed by melting and a titanium material having an oxide film left were produced. An unevenness forming step was carried out on the titanium material after the annealing step. The dull roll rolling A, E, and F of the unevenness forming item shown in Table 6 are the dull roll rolling A, E, and F shown in Table 3, respectively.

For the titanium material produced by the above method, the average length RSm and the root mean square slope RΔq of the roughness curve element were measured, the thicknesses of the oxide film and the nitrided film were measured, and the Vickers hardness was measured in the same manner as in Example 1. The measurement of the hardness, the one-step deep drawing test, the multi-step deep drawing test, the visual inspection and the evaluation of the deep drawing formability were performed. The evaluation results are shown in Table 6.

As shown in Table 6, when the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less, the root mean square slope RΔq (rad.) Satisfies the above equation (1), and the roughness curve element When the average length RSm is more than 300 μm, when the root mean square slope RΔq (rad.) Satisfies the above equation (2), it is compared with the case where both the equation (1) and the equation (2) are not satisfied. Therefore, the appearance after the one-step deep drawing test and the deep drawing formability were excellent.

Although the preferred embodiment of the present invention has been described above in detail, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the field of the art to which the present invention belongs can come up with various modifications or modifications within the scope of the technical idea described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

Claims (5)

1. When the average length RSm of the roughness curve element is more than 8 μm and 300 μm or less on at least one surface, the root mean square slope RΔq (rad.) Satisfies the following equation (1), and the average of the roughness curve elements. A titanium material in which the root mean square slope RΔq (rad.) Satisfies the following formula (2) when the length RSm is more than 300 μm.
   RΔq ≧ 0.060 ・ ・ ・ Equation (1)
   RΔq ≧ 2 × RSm / 10000 ・ ・ ・ Equation (2)
2. The average length RSm of the roughness curve element is 400 μm or less, and the root mean square slope RΔq is 0.190 rad. The titanium material according to claim 1, which is as follows.
3. The titanium material according to claim 1 or 2, wherein the Vickers hardness when the load is 50 gf is 30 HV or more larger than the Vickers hardness when the load is 1000 gf.
4. The titanium material according to any one of claims 1 to 3, which comprises an oxide film or a nitrided film.
5. The titanium material according to claim 4, wherein the thickness of the oxide film or the nitrided film is less than 1.00 μm.

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