JP2020183551A - Titanium plate excellent in lubricity and method for manufacturing the same - Google Patents

Abstract

To provide a titanium plate capable of reducing a dynamic friction coefficient between a die and the titanium plate when press-molded, and a method for manufacturing the same.SOLUTION: The titanium plate includes an oxide film having a thickness of 0.10 μm or more and consisting of a rutile type TiO2 on a surface. The surface properties of the oxide film satisfy that an arithmetic average roughness Ra of a roughness curve obtained by applying the cutoff values of λs=2.5 μm and λc=0.08 mm is 0.20-7.0 μm, a difference (RZJIS-Rc) between the ten-point average roughness RZJIS of the roughness curve and the average height Rc of outline curve elements is 0.5 μm or more, and a root mean square inclination RΔq measured on the conditions of λs=0 μm and λc=0 mm in a region satisfying 0.8 or more times of the maximum mountain height Rp of the roughness curve is 20° or less.SELECTED DRAWING: None

Description

The present invention relates to a titanium plate having excellent lubricity and a method for producing the same.

Titanium is a metal that has a hexagonal close-packed structure at room temperature, is relatively soft, and has excellent workability. On the other hand, since metallic titanium is a very active metal, there is a problem that an increase in the dynamic friction coefficient due to adhesion between titanium and a mold caused by press molding or the like lowers moldability. Therefore, by applying a film-type lubricant to the surface of the titanium plate in advance or attaching a Teflon sheet or the like, adhesion between the titanium and the mold is suppressed during press molding, and the coefficient of dynamic friction is reduced. However, such a lubrication means is troublesome, reduces the efficiency of the press forming process, and increases the cost.

Therefore, as a low-cost means for suppressing the contact between titanium and the mold, an oxide film, a nitride film, a carbonized film, or a carbonized nitride film is formed on the titanium surface by oxidation, nitriding, carbonization, or the like. .. In particular, the formation of an oxide film by atmospheric oxidation does not require special equipment and is useful as an inexpensive method. However, the dynamic friction coefficient when the titanium plate on which the oxide film is formed is press-molded without using the lubricant is higher than the dynamic friction coefficient when the conventional film type lubricant is used. That is, when a conventional film-type lubricant is used, the coefficient of dynamic friction between the titanium plate and the mold is, for example, about 0.17 or less, but the coefficient of dynamic friction of the titanium plate on which the oxide film is formed is non-lubricated. In the state, it becomes larger than 0.17.

In Patent Document 1, as a titanium thin plate having increased strength without lowering formability, the arithmetic average roughness (Ra) in the L direction is 0.2 to 0.8 μm, and the arithmetic average roughness in the T direction is When it is 1.1 times or more and 2 times or less in the L direction and the plate thickness is t, deformed diploids are present in the range of 0.05t to 0.2t on the surface layer, and Vickers at a measured load of 0.25N on the surface. The hardness is 170 or more, the Vickers hardness on the surface at a measured load of 9.8 N is 90 to 180, and the Vickers hardness at a measured load of 0.25 N is higher than the Vickers hardness at a measured load of 9.8 N. A titanium plate that is 1.5 times or more higher is described. In the titanium plate described in Patent Document 1, a surface roughness condition has been found in which a lubricant can be sufficiently applied and the lubricant is sufficiently supplied during molding.

In Patent Document 2, as a titanium plate exhibiting excellent press formability, the arithmetic average roughness (Ra) is 0.15 to 1.5 μm, and the maximum height (Rz) is 1.5 to 9.0 μm. The strain degree (Rsk) is in the range of -3.0 to -0.5, and the Vickers hardness on the surface at a measured load of 0.098 N is higher than the Vickers hardness at a measured load of 4.9 N. , Titanium plates having a difference of 45 or less are described. In the titanium plate described in Patent Document 2, recesses are formed on the surface, and the recesses improve the oil retention property of the lubricating oil.

Japanese Unexamined Patent Publication No. 2016-1560554 Japanese Unexamined Patent Publication No. 2010-255085

The titanium plates described in Patent Documents 1 and 2 focus on improving the coatability and oil retention of the lubricant, and do not relate to the improvement of the oxide film formed by atmospheric oxidation.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a titanium plate capable of reducing the coefficient of dynamic friction with a mold during press molding and a method for producing the same.

In order to solve the above problems, the present invention adopts the following configuration.
[1] The surface has an oxide film made of rutile-type TiO ₂ having a thickness of 0.10 μm or more.
The surface texture of the oxide film is
The arithmetic mean roughness Ra of the roughness curve obtained by applying the cutoff values of λs = 2.5 μm and λc = 0.08 mm is 0.25 to 7.0 μm.
The difference (R _ZJIS- Rc) between the ten-point average roughness R _{ZJIS of the} roughness curve and the average height Rc of the contour curve element is 0.5 μm or more.
The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm is 20 ° or less with respect to the region satisfying 0.8 times or more of the maximum mountain height Rp of the roughness curve.
A titanium plate characterized by satisfying.
[2] High carbon chrome bearing steel specified in Japanese Industrial Standards G4805 under the conditions of a surface pressure of 1 MPa and a speed of 0.1 m / min in a pin-on disk type friction / wear tester without using a lubricant. The titanium plate according to [1], wherein the dynamic friction coefficient when sliding on the surface of the oxide film with a pin made of SUJ2 is 0.17 or less.
[3] The surface of the titanium plate material is polished with an abrasive of P80 or more and P800 or less, or the titanium plate is made of dull roll having an arithmetic mean roughness Ra of the roll surface in the range of 0.20 to 7.0 μm. The first step of rolling the material and
The second step of heating the titanium plate material at 500 ° C. to 900 ° C. in an air atmosphere to form an oxide film on the surface of the titanium plate material, and
A sliding member having a sliding surface having a hardness of 650 HV or more and an arithmetic average roughness Ra of 0.15 μm or less is provided under the conditions of an apparent surface pressure of 1.0 MPa or more and less than 10 MPa and a sliding speed of 0.001 to 1 m / min. The third step of sliding the surface of the oxide film and
The method for producing a titanium plate according to [1] or [2], wherein the above steps are sequentially performed.

According to the present invention, it is possible to provide a titanium plate and a method for manufacturing the same, which can reduce the coefficient of dynamic friction with the mold during press molding.

The schematic diagram explaining the manufacturing method of the titanium plate which is an embodiment of this invention.

The solid surface has minute irregularities. When solids having the same roughness are slid, the convex portion of one solid surface and the convex portion of the other solid surface mainly come into contact with each other, and this contact portion becomes a true contact surface. Therefore, the area of the true contact surface is significantly smaller than the area of the apparent contact surface. Further, on the surface of the oxide film made of rutile-type TiO ₂ formed on the titanium plate, minute irregularities formed with the growth of the oxide film are observed.

When the mold moves during press molding of the titanium plate, the convex portions of both the mold and the titanium plate move relative to each other. At this time, since the oxide film of titanium is relatively soft, digging occurs in the fine irregularities formed during the growth of the oxide film, and digging resistance is generated. It is presumed that the coefficient of dynamic friction of the titanium plate includes the component of this digging resistance.

Therefore, in order to reduce the dynamic friction coefficient of the titanium plate having an oxide film, a method for reducing the digging resistance was examined.

If the fine irregularities of the oxide film are mechanically abraded in advance to smooth them and then press molding is performed, it is expected that the digging resistance will be reduced and the dynamic friction coefficient will be reduced. However, in reality, the coefficient of dynamic friction does not decrease as expected. The present inventors diligently examined the reason.

Since the titanium plate and the die move relative to each other during press molding, the true contact surface naturally changes depending on the uneven shape of the titanium plate and the die. For example, the convex portion of the titanium plate that became the true contact surface at one moment and the convex portion of the mold surface are separated at the next moment, and the other convex portions become the true contact surface. In this way, the true contact surface is determined by the combination of the titanium plate and the uneven shape at the moment of the mold. Normally, since the unevenness of the titanium plate or the mold is random, it is difficult to polish the fine unevenness of the oxide film in advance by aiming at the convex portion of titanium which is the true contact surface with the mold. That is, even if the fine irregularities of the oxide film are mechanically abraded in advance, the convex portion where the fine irregularities of the oxide film are not abraded becomes the true contact surface during press molding, and titanium oxide is dug up at that location. It was speculated that the dynamic friction coefficient would not decrease due to the occurrence of creases.

Therefore, in order to reduce the friction coefficient of the titanium plate, the uneven shape of the titanium plate is improved so that the true contact surface can be specified, and the fine unevenness of the oxide film on the convex portion is ground in advance to reduce the digging resistance. There is a need.

Therefore, as a result of further studies by the present inventors, a relatively high convex portion (mountain) is sparsely formed on titanium, and the fine unevenness of the oxide film at the tip portion including the top of the mountain is used as an wear surface. It was found that the dynamic friction coefficient can be reduced. By sparsely forming relatively high protrusions (peaks) on the surface of the oxide film, even if the mold slides during press molding, the mold always contacts the high peaks to form a true contact surface. It becomes difficult for the true contact surface to be formed in places other than the above. As a result, we succeeded in significantly reducing the coefficient of dynamic friction of the titanium plate.

Hereinafter, the titanium plate of this embodiment will be described.
The titanium plate of the present embodiment 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 texture of the oxide film is cut of λs = 2.5 μm and λc = 0.08 mm. The arithmetic average roughness Ra of the roughness curve obtained by applying the off value is 0.25 to 7.0 μm, and the difference between the ten-point average roughness R _{ZJIS of the} roughness curve and the average height Rc of the contour curve element ( The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm for a region where R _ZJIS −Rc) satisfies 0.5 μm or more and 0.8 times or more of the maximum peak height Rp of the roughness curve. Is a titanium plate satisfying 20 ° or less.
Hereinafter, the titanium plate of the present embodiment will be described in more detail.

The titanium plate of the present embodiment may be a pure titanium plate or a titanium alloy plate. The thickness of the titanium plate is not particularly limited and may be any thickness suitable for press molding. For example, a plate thickness of 0.3 to 1.0 mm can be exemplified.

Pure titanium is specified in JIS H 4600 (2007) 1 to 4 types, and corresponding ASTM standard Grades 1 to 4, DIN standard 3.7025, 3.7035, 3.7055. It shall contain pure industrial titanium. That is, the industrial pure titanium in the present embodiment has C: 0.1% or less, H: 0.015% or less, O: 0.4% or less, N: 0.07% or less, Fe: It consists of 0.5% or less and the balance Ti.

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

Examples of the α-type titanium alloy include highly corrosion-resistant alloys (ASTM Grade 7, 11, 16, 26, 13, 30, 33, or titanium materials containing a small amount of JIS species corresponding to these and 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, Ti-3Al-2.5V, Ti-5Al-2.5Sn, Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-2.75Sn-4Zr-0.4Mo-0. There are 45Si and the like.

Examples of the α + β type titanium alloy include Ti-6Al-4V, Ti-6Al-6V-2Sn, Ti-6Al-7V, 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 There are -2Fe-0.3Si, Ti-5Al-2Fe-3Mo, Ti-4.5Al-2Fe-2V-3Mo and the like.

Further, as the β-type titanium alloy, 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 and the like.

The above-mentioned pure titanium and titanium alloy are examples, and the titanium plate of the present embodiment is not limited to the above-mentioned pure titanium and titanium alloy.

An oxide film is formed on the surface of the titanium plate of the present embodiment. The oxide film is composed of rutile-type TiO ₂ . By forming the oxide film on the surface, the pure titanium or the titanium alloy constituting the titanium plate does not come into direct contact with the mold during press molding, and the adhesion of the titanium plate can be prevented. Further, if the oxide film is an anatase type oxide film, the oxide film becomes too soft, the surface morphology of the oxide film is easily deformed when the press-molding die slides, the digging resistance increases, and the dynamic friction coefficient increases. Since there is a risk, the rutile type TiO ₂ is preferable as the oxide film.

The substance identification of the oxide film is confirmed by the thin film X-ray diffraction method. The X-ray source is Co-Kα ray, and the incident angle is 1 °.

The thickness of the oxide film is preferably 0.10 μm or more. If the thickness is less than 0.10 μm, the oxide film is likely to peel off during press molding, which may cause adhesion to the mold, which is not preferable. The upper limit of the thickness of the oxide film does not need to be specified in particular, but since it may be difficult to form an oxide film of more than 1 μm, the upper limit of the thickness may be set to 1 μm or less.

The thickness of the oxide film can be measured by glow discharge spectroscopy (GDS). In GDS, the distribution of O (oxygen) and Ti in the depth direction is analyzed from the surface of the oxide film toward the depth direction. The thickness of the oxide film is determined by the oxygen concentration. Specifically, the distance in the depth direction from the outermost surface of the oxide film to the depth at which the oxygen concentration becomes 50% of the oxygen concentration on the outermost surface is defined as the thickness of the oxide film.

Next, the surface properties of the oxide film of the present embodiment will be described. The oxide film according to this embodiment preferably has a surface shape represented by the following (1) to (3).

(1) The arithmetic mean roughness Ra of the roughness curve obtained by applying the cutoff values of λs = 2.5 μm and λc = 0.08 mm shall be in the range of 0.20 to 7.0 μm.
(2) The difference (R _ZJIS- Rc) between the ten-point average roughness R _{ZJIS of the} above-mentioned roughness curve and the average height Rc of the contour curve element is 0.5 μm or more.
(3) The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm is 20 ° or less with respect to a region satisfying 0.8 times or more of the maximum mountain height Rp of the above roughness curve. thing.

(1) Arithmetic mean roughness Ra is 0.25 to 7.0 μm
The oxide film of the present embodiment preferably has an arithmetic average roughness Ra in the range of 0.20 to 7.0 μm. If the arithmetic mean roughness Ra is less than 0.20 μm, the difference between R _ZJIS and Rc (R _ZJIS −Rc) cannot be 0.5 μm or more. Further, if the arithmetic average roughness Ra exceeds 7.0 μm, it may become a starting point of cracking due to bending deformation, which is not preferable. The arithmetic mean roughness Ra of the present embodiment is the arithmetic mean roughness Ra defined in JIS B 0601 (2001), and is the average of the absolute values of the total coordinate values Z (x) in the reference length. is there. The arithmetic mean roughness Ra may be 0.25 to 4.0 μm, 0.25 to 3.0 μm, or 0.25 to 1.0 μm.

The roughness curve, which is the basis for calculating the arithmetic average roughness Ra, is obtained by applying a low-frequency filter with a cutoff value of λc = 0.08 mm to the measured cross-sectional curve of the oxide film, and further this step. The roughness curve is obtained by applying a high frequency filter having a cutoff value of λs = 2.5 μm to the surface curve. The reference length of the roughness curve is a length equal to the cutoff value λc, that is, 0.08 mm.

(2) (R _ZJIS- Rc) is 0.5 μm or more The oxide film of the present embodiment has a difference (R _ZJIS- Rc) between the ten-point average roughness R _{ZJIS of the} roughness curve and the average height Rc of the contour curve element. ) Is preferably 0.5 μm or more. The surface of the oxide film has fine irregularities, and there are many convex portions and many concave portions. By sparsely forming relatively high protrusions (peaks) on the surface of the oxide film, the present inventors always contact the high peaks even if the mold slides on the surface of the oxide film during press molding. It was found that the true contact surface is formed by doing so, and the dynamic friction coefficient can be reduced by making it difficult to form the true contact surface in other places. The present inventor has decided to adopt (R _ZJIS- Rc) as an index indicating that relatively high protrusions (mountains) are sparsely formed on the surface of the oxide film.

Ten-point average roughness _{R ZJIS} of the roughness curve of the present embodiment is a JIS B 0601 ten-point average roughness _{R ZJIS} defined in Annex 1 of the (2001). The ten-point average roughness R _ZJIS is the sum of the average of the 5th mountain height from the highest peak to the 5th from the deepest valley bottom to the 5th valley depth in the standard length roughness curve. It is said that. That is, it is the average height of the five large peaks included in the roughness curve.

On the other hand, the average height Rc of the contour curve element of the present embodiment is defined in JIS B 0601 (2001), is the average height of the roughness curve element, and is the contour curve element at the reference length. It is the average value of the height Zt of.

Therefore, as (R _ZJIS −Rc) becomes larger, it means that the height of the convex portion (mountain) included in the roughness curve becomes prominently larger. The oxide film of the present embodiment preferably has (R _ZJIS- Rc) of 0.5 μm or more. As a result, even if the die slides on the surface of the oxide film during press molding, the die is always in contact with the high peak to form a true contact surface. (R _ZJIS- Rc) may be 0.6 μm or more.

If (R _ZJIS- Rc) is less than 0.5 μm, the worn surface and the true contact surface do not match, digging resistance is generated, and the coefficient of dynamic friction increases, which is not preferable.

(3) The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm is 20 ° or less with respect to a region satisfying 0.8 times or more of the maximum mountain height Rp. In this embodiment, the maximum mountain height It is preferable that the root mean square slope RΔq in the region satisfying 0.8 times or more of Rp is 20 ° or less. The present inventors sparsely form relatively high protrusions (mountains) on the surface of the oxide film, and wear the surfaces of these relatively high protrusions (mountains) to make a smooth surface, thereby making true contact. It was found that the digging resistance on the surface can be reduced.

The region that limits the root mean square slope RΔq to 20 ° or less is limited to the region that satisfies 0.8 times or more of the maximum mountain height Rp when the roughness curve is cut by a line 0.8 times Rp. This is because the true contact surface is formed on the portion of the curve sandwiched between the two adjacent intersections above the line of Rp × 0.8.

Further, the reason why the root mean square slope RΔq in the portion above the line of Rp × 0.8 is limited to 20 ° or less is that the dynamic friction coefficient increases when RΔq exceeds 20 °.

The maximum mountain height Rp of the present embodiment is the maximum mountain height Rp of the contour curve defined in JIS B 0601 (2001), and the mountain height of the contour curve (roughness curve in the case of the present embodiment) at the reference length. It is the maximum value of Zp.

Further, the root mean square slope RΔq of the present embodiment is the root mean square slope RΔq defined in JIS B 0601 (2001), and is the root mean square of the local slope dZ / dX at the reference length.

As described above, the dynamic friction coefficient of the titanium plate can be reduced by optimizing the surface shape of the oxide film so as to satisfy the above (1) to (3).

Further, the entire surface of the oxide film may satisfy the above (1) to (3), or a part of the surface of the oxide film may satisfy the above (1) to (3). When the titanium plate is press-molded, the surfaces that the mold can contact are limited, so that the oxide film at the portion that the mold can contact may satisfy the above (1) to (3).

The surface texture of the oxide film is measured, for example, using a laser microscope VK9700 manufactured by KEYENCE CORPORATION in a field of view of 500 times (284.7 × 200 μm). The cutoff values are λs = 2.5 μm and λc = 0.08 mm. The direction of the roughness curve is the direction orthogonal to the polishing grain when there is a polishing grain on the surface of the oxide film. The measurement at one point is measured at N = 2, and the average value is used as the measured value for each measurement point. For RΔq, the measurement at one point is measured at N = 3, and the average value is taken as the measured value for each measurement point.

The measurement position of the roughness curve, which is the basis for calculating the arithmetic average roughness Ra, the ten-point average roughness R _ZJIS , the average height Rc, the maximum mountain height Rp, and the root mean square slope RΔq, is not particularly limited. It may be measured anywhere on the oxide film. It is preferable that the roughness curve is measured at five points per titanium alloy plate. Then, the arithmetic average roughness Ra, (R _ZJIS- Rc) and the maximum mountain height Rp and RΔq are obtained based on the roughness curves measured at the five points, and it is preferable to use these averages.

The coefficient of kinetic friction of the titanium plate of this embodiment is preferably 0.17 or less. By setting the coefficient of kinetic friction to 0.17 or less, when the titanium plate is molded by press molding, there is no risk of sticking to the mold, and press molding can be stably performed.

The dynamic friction coefficient of the titanium plate is high carbon specified in the Japanese Industrial Standard G4805 under the conditions of a surface pressure of 1 MPa and a speed of 0.1 m / min using a pin-on-disk type friction / wear tester without using a lubricant. Chromium bearing steel The dynamic friction coefficient when sliding on the surface of the oxide film of the titanium plate with a pin made of SUJ2. In addition, when sliding the pin on the surface of the oxide film, the pin is not slid to the already slid part, and the non-sliding part is always slid with the pin for measurement. ..

Next, a method for manufacturing the titanium plate of the present embodiment will be described.
The method for producing a titanium plate of the present embodiment includes a first step of polishing the surface of the titanium plate material or rolling the titanium plate material with a dull roll, and the titanium plate material at 550 ° C. to 900 ° C. in an air atmosphere. It is manufactured by sequentially performing a second step of heating with the above step and a third step of sliding the surface of the oxide film by a sliding member.

In the manufacturing method of the present embodiment, the surface of the titanium plate is roughened in the first step, and then an oxide film is formed on the surface of the roughened titanium plate in the second step. As a result, the surface texture of the oxide film is roughened as compared with the case where the first step is not performed. By sliding the sliding member with respect to the surface of the oxide film roughened in this way in the third step, the oxide film is worn out, and particularly the surface of the convex portion having a relatively high height is worn out. As a result, an oxide film satisfying the above (1) to (3) can be obtained.
Hereinafter, each step will be described.

First, the titanium plate material used in the first step is prepared. The titanium plate material may be a pure titanium plate or a titanium alloy plate. As the titanium plate material, for example, a titanium plate that has been cold-rolled and then descaled is preferable.

The surface of the prepared titanium plate material is polished with an abrasive material of P80 or more and P800 or less.
Alternatively, the titanium plate material is rolled by dull roll.

Abrasive materials for polishing titanium plate materials include, for example, the polishing cloth specified in JIS R 6251 (2006), the polishing paper specified in JIS R 6252 (2006), and JIS R 6253 (2006). The specified water-resistant abrasive paper can be used. The type of abrasive used for the abrasive cloth, abrasive paper or water-resistant abrasive paper is not particularly limited, and may be any of an alumina abrasive, a carbide abrasive, a garnet, and a gravel. The particle size of the abrasive may be in the range of P80 to P800.

Polishing is preferably performed by wet polishing. There is no specification for the polishing direction of wet polishing. For example, any polishing method such as parallel polishing, cross polishing, and rotary polishing may be used.

The dull roll for rolling the titanium plate material is preferably a dull roll in which unevenness is imparted by shot blasting of cast iron grit of P25 or less or high carbon cast steel grit grit after ground polishing with an alumina-based or silicon carbide-based grindstone of P600 or more. Such a dull roll has a roughness of the roll surface of about 2 to 7 μm in arithmetic average roughness Ra.

In the first step, it is desirable that the surface texture of the oxide film after polishing or rolling satisfies the following conditions. The polishing conditions and rolling conditions for the titanium plate material in the first step are preferably set so that the surface texture of the oxide film after the first step satisfies the following conditions (A) and (B).

(A) The arithmetic mean roughness Ra is in the range of 0.20 to 7.0 μm.
(B) The difference (R _ZJIS- Rc) between the ten-point average roughness R _ZJIS and the average height Rc of the contour curve element shall be 0.5 μm or more.

For Ra, R _ZJIS and Rc shown in (A) and (B) above, a low-frequency filter having a cutoff value of λc = 0.08 mm is applied to the measurement cross-sectional curve of the oxide film to obtain a cross-sectional curve, and further, this step. It is assumed that the measurement is performed on the roughness curve obtained by applying a high frequency filter having a cutoff value of λs = 2.5 μm to the surface curve.

Next, in the second step, the titanium plate material after the first step is heated at 500 ° C. to 900 ° C. in an air atmosphere to form an oxide film on the surface of the titanium plate material. The heating temperature is preferably 550 to 850 ° C. The heating temperature is preferably a temperature that does not change the mechanical properties of the titanium plate material. If the heating temperature is less than 500 ° C., an oxide film cannot be sufficiently formed, which is not preferable. Further, if the heating temperature exceeds 900 ° C., the titanium plate is heated above the β transformation point, which may deteriorate the mechanical properties of the titanium plate, which is not preferable. The heating time is preferably adjusted so that the thickness of the oxide film exceeds 0.05 μm, preferably 0.1 μm or more. The heating time may be adjusted, for example, between 10 minutes and 24 hours.

Next, in the third step, a sliding member having a sliding surface having a hardness of 650 HV or more and an arithmetic average roughness Ra of 0.15 μm or less has an apparent surface pressure of 1.0 MPa or more and less than 10 MPa, and a sliding speed of 0. The surface of the oxide film is slid under the condition of 001 to 1 m / min. The sliding of the sliding member shall be dry. As a result, the root mean square slope RΔq of the oxide film becomes 20 ° or less in the mountain region satisfying at least 0.8 times or more of the maximum mountain height Rp of the roughness curve.

If the hardness of the sliding surface of the sliding member is less than 650 HV, the oxide film cannot be sufficiently worn, and the root mean square slope RΔq of the oxide film cannot be set to 20 ° or less, which is not preferable. The hardness of rutile-type titanium oxide is about 800 to 1000 HV, but it was confirmed that the root mean square slope RΔq can be 20 ° or less if the hardness of the sliding member is 650 HV or more in the manufacturing method of this embodiment. ing.

The arithmetic average roughness Ra of the sliding member is preferably smaller than the arithmetic average roughness Ra of the titanium plate after the second step. Even if the arithmetic mean roughness Ra exceeds 0.15 μm, the oxide film cannot be sufficiently worn, and the root mean square slope RΔq of the oxide film cannot be set to 20 ° or less, which is not preferable.

Further, the material of the sliding member may be, for example, a steel-based material having a hardness of 650 HV or more, a ceramic material, or the like. If the sliding member is pure titanium or a titanium alloy, adhesion will occur, which is not preferable.

The Vickers hardness of the sliding surface conforms to JIS Z 2244 (2009). The measured load is 500 gf. Further, for the arithmetic mean roughness Ra of the sliding surface, a low frequency filter having a cutoff value of λc = 0.08 mm is applied to the measured cross-sectional curve of the sliding surface to obtain a cross-sectional curve, and further, this stepped surface curve is used. It is assumed that the measurement is performed on the roughness curve obtained by applying a high frequency filter having a cutoff value of λs = 2.5 μm. The measurement length is 2.4 mm.

Further, regarding the size of the sliding surface, by setting the length of the sliding surface along the sliding direction to 2 mm or more, the amount of processing for the oxide film becomes sufficient, and the root mean square inclination RΔq of the oxide film is surely obtained. It will be possible to reduce the temperature to 20 ° or less. FIG. 1 is a schematic side view showing how the oxide film 2 of the titanium plate 1 is slid by the sliding member 3. The direction of the arrow A is the sliding direction of the sliding member. Further, reference numeral 3a indicates a sliding surface. The length L of the sliding surface 3a along the sliding direction A may be 2 mm or more.

Further, if the apparent surface pressure when sliding the sliding member is less than 1.0 MPa, the oxide film cannot be sufficiently worn, and the root mean square slope RΔq of the oxide film can be set to 20 ° or less. It is not preferable because it disappears. Further, if the apparent surface pressure exceeds 10 MPa, the oxide film may be peeled off during the sliding of the sliding member.

Further, if the sliding speed of the sliding member is less than 0.001 m / min, the time required for the third step becomes long and the productivity of the titanium plate is significantly reduced, which is not preferable. Further, when the sliding speed of the sliding member exceeds 1 m / min, the contact state between the sliding member and the oxide film is not stable, the wear of the oxide film becomes insufficient, and the root mean square inclination RΔq of the oxide film is obtained. It is not preferable because the temperature cannot be reduced to 20 ° or less.

The sliding range of the sliding member may be the entire surface of the oxide film or a part of the oxide film. When the titanium plate is press-molded, the surface that the mold can contact is limited, so that the third step may be performed on the oxide film at the portion that the mold can contact.

By going through the above steps, the titanium plate of the present embodiment can be manufactured.

Since the surface texture of the oxide film of the titanium plate of the present embodiment satisfies the conditions described in (1) to (3) above, the dynamic friction coefficient can be set to 0.17 or less. As a result, when the titanium plate is molded by press molding, there is no risk of sticking to the mold, and press molding can be stably performed. Further, since it is not necessary to use a film-type lubricant as in the conventional case, the productivity of press molding can be improved.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the examples described below.

As the titanium plate material, 1 to 4 types of pure titanium plates specified in JIS H 4600 were prepared. As the titanium plate material, a titanium plate having a thickness of 5 mm, which had been hot-rolled and then scale-removed, and a titanium plate which was cold-rolled to a plate thickness of 0.5 mm was used as a test material.

Next, as a first step, the surface of the titanium plate material was wet-polished with abrasive papers of P80 to P1000. Further, some titanium materials (Comparative Example 1) were mirror-polished. Further, for another titanium material (Example 6), the titanium plate material was rolled by dull roll. The dull roll used was a dull roll that was ground-polished with a grindstone of P600 or higher and then uneven by shot blasting of a steel grit of P25 or lower. The arithmetic mean roughness Ra of the roll surface of the dull roll was 3.2 μm. Furthermore, the first step was not carried out for Comparative Example 2 and Comparative Example 3.

Next, as a second step, the titanium plate material after the first step was heated in an air atmosphere at a heating temperature of 450 ° C. to 900 ° C. for 15 minutes to 24 hours. Comparative Example 6 was subjected to anodic electrolysis treatment in which it was held at 30 V for 5 minutes in a phosphoric acid aqueous solution having a temperature of 20 ° C. and a concentration of 20 to 25 g / L.

Next, as a third step, a sliding member having a sliding surface having a hardness of 500 to 1500 HV and an arithmetic average roughness Ra of 0.05 to 0.2 μm was prepared. The shape of the sliding surface has a length along the sliding direction in the range of 2 to 50 mm. The material of the sliding member was SUJ2. Then, the sliding surface of the sliding member was brought into contact with the oxide film, and the surface of the oxide film was slid under the conditions of an apparent surface pressure of 0.5 to 10 MPa and a sliding speed of 0.001 to 10 m / min. For Comparative Example 10, the third step was not carried out.

In this way, the titanium plates of Examples 1 to 22 and Comparative Examples 1 to 12 were produced.

The coefficient of dynamic friction of the obtained titanium plate was measured. The measurement is performed with a pin-on disk type friction / wear tester, without using a lubricant, under the conditions of a surface pressure of 1 MPa and a speed of 0.1 m / min, high carbon chrome bearing steel specified in Japanese Industrial Standards G4805. The measurement was performed by sliding the oxide film surface of the titanium plate with a pin made of SUJ2. When the pin was slid on the surface of the oxide film, the pin was not slid at the already slid part, and the non-sliding part was always slid with the pin for measurement.

The substance identification of the oxide film was confirmed by the thin film X-ray diffraction method. The X-ray source was Co-Kα ray, and the incident angle was 1 °.

The thickness of the oxide film was measured by glow discharge spectroscopy (GDS). The distribution of O (oxygen) and Ti in the depth direction is analyzed by GDS from the surface of the oxide film toward the depth, and the oxygen concentration from the outermost surface of the oxide film is 50% of the oxygen concentration on the outermost surface. The distance in the depth direction to the depth of the oxide film was defined as the thickness of the oxide film.

The surface texture of the oxide film was measured. The surface texture was as shown in (i) to (iii) below.

(I) Arithmetic mean roughness Ra of the roughness curve obtained by applying the cutoff values of λs = 2.5 μm and λc = 0.08 mm.
(Ii) _Difference between the ten-point average roughness R _{ZJIS of the} above-mentioned roughness curve and the average height Rc of the contour curve element (R _ZJIS −Rc).
(Iii) The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm for a region satisfying 0.8 times or more of the maximum mountain height Rp of the above roughness curve.

The surface texture of the oxide film was measured, for example, using a laser microscope VK9700 manufactured by KEYENCE CORPORATION in a field of view of 500 times (284.7 × 200 μm). The cutoff values were λs = 2.5 μm and λc = 0.08 mm. The direction of the roughness curve was the direction orthogonal to the polishing grain when there was a polishing grain on the surface of the oxide film. The measurement at one point was measured at N = 2, and the average value was taken as the measured value for each measurement point. For RΔq, the measurement at one point was measured at N = 3, and the average value was taken as the measured value for each measurement point.

Arithmetic mean roughness Ra, ten-point average roughness R _ZJIS , average height Rc, maximum peak height Rp, and root mean square slope RΔq can be calculated at any of five locations on the oxide film. And said. Then, the arithmetic average roughness Ra, (R _ZJIS- Rc), the maximum mountain height Rp and RΔq were obtained based on the roughness curves measured at the five points, and the averages of these were used.

The Vickers hardness of the sliding surface of the sliding member was measured in accordance with JIS Z 2244 (2009). The measured load was 500 gf. Further, for the arithmetic mean roughness Ra of the sliding surface, a low frequency filter having a cutoff value of λc = 0.08 mm is applied to the measured cross-sectional curve of the sliding surface to obtain a cross-sectional curve, and further, this stepped surface curve is used. The measurement was performed on the roughness curve obtained by applying a high frequency filter having a cutoff value of λs = 2.5 μm. The measurement length was 2.4 mm.
The results are shown in Table 1A and Table 1B.

As shown in Tables 1A and 1B, the titanium plates of Examples 1 to 22 all satisfy the production conditions of the present invention, the surface texture of the oxide film satisfies the range of the present invention, and the friction coefficient is high. It was 0.17 or less and had excellent lubricity.

On the other hand, Comparative Examples 1 to 4 did not satisfy the conditions of the first step, and the surface roughness of the titanium plate after the first step did not become a desired roughness. Therefore, the arithmetic surface roughness Ra of the sliding member is larger than the arithmetic surface roughness Ra of the oxide film after the second step, and the region satisfying the maximum mountain height Rp × 0.8 or more is worn out. I couldn't finish it. Therefore, RΔq exceeds 20 °, and the friction coefficient becomes high.

In Comparative Example 5, since the heating temperature in the second step was low and the thickness of the oxide film was thin, the oxide film was peeled off when measuring the friction coefficient, and the exposed bare metal and the sliding pin were adhered to each other, resulting in a friction coefficient. It got higher.

In Comparative Example 6, an oxide film was formed by the anodizing method, but anatase-type TiO ₂ was formed. Since the anatase-type TiO ₂ is soft, the effect of abrasion on the surface of the oxide film in the third step is small, and the friction coefficient is high.

In Comparative Example 7, the Vickers hardness of the sliding member was low, and the oxide film could not be sufficiently abraded. Therefore, RΔq became large and the friction coefficient became high.

In Comparative Example 8, since the arithmetic average roughness Ra of the sliding member was too large, the region satisfying the maximum mountain height Rp × 0.8 or more could not be completely worn out. Therefore, RΔq became large and the friction coefficient became high.

In Comparative Example 9, since the sliding speed of the sliding member was too fast, the contact between the sliding member and the oxide film was not stable, and the oxide film could not be sufficiently worn away. Therefore, RΔq became large and the friction coefficient became high.

In Comparative Example 10, since the third step was not performed, RΔq became large and the friction coefficient became high.

In Comparative Example 11, the surface pressure of the sliding member was too low, so that the oxide film could not be sufficiently abraded. Therefore, RΔq became large and the friction coefficient became high.

In Comparative Example 12, since the surface pressure of the sliding member was too high, the oxide film was peeled off during sliding and the bare metal was exposed. Then, when the friction coefficient was measured, the exposed metal and the sliding pin adhered to each other, so that the friction coefficient became high.

Claims (3)

It has an oxide film made of rutile-type TiO ₂ with a thickness of 0.10 μm or more on the surface.
The surface texture of the oxide film is
The arithmetic mean roughness Ra of the roughness curve obtained by applying the cutoff values of λs = 2.5 μm and λc = 0.08 mm is 0.25 to 7.0 μm.
The difference (R _ZJIS- Rc) between the ten-point average roughness R _{ZJIS of the} roughness curve and the average height Rc of the contour curve element is 0.5 μm or more.
The root mean square slope RΔq measured under the conditions of λs = 0 μm and λc = 0 mm is 20 ° or less with respect to the region satisfying 0.8 times or more of the maximum mountain height Rp of the roughness curve.
A titanium plate characterized by satisfying. A pin-on disk type friction / wear tester made of high carbon chrome bearing steel SUJ2 specified in Japanese Industrial Standards G4805 under the conditions of surface pressure 1 MPa and speed 0.1 m / min without using lubricant. The titanium plate according to claim 1, wherein the dynamic friction coefficient when sliding on the surface of the oxide film with a pin is 0.17 or less. The surface of the titanium plate material is polished with an abrasive of P80 or more and P800 or less, or the titanium plate material is rolled by a dull roll in which the arithmetic mean roughness Ra of the roll surface is in the range of 0.25 to 7.0 μm. The first step to do and
The second step of heating the titanium plate material at 500 ° C. to 900 ° C. in an air atmosphere to form an oxide film on the surface of the titanium plate material, and
A sliding member having a sliding surface having a hardness of 650 HV or more and an arithmetic average roughness Ra of 0.15 μm or less is provided under the conditions of an apparent surface pressure of 1.0 MPa or more and less than 10 MPa and a sliding speed of 0.001 to 1 m / min. The third step of sliding the surface of the oxide film and
The method for manufacturing a titanium plate according to claim 1 or 2, wherein the above steps are sequentially performed.

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