JP7167838B2 - Titanium plate with excellent lubricity and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD 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 in that an increase in dynamic friction coefficient due to adhesion between titanium and a mold during press molding lowers formability. Therefore, by applying a film-type lubricant to the surface of the titanium plate in advance or attaching a Teflon sheet, etc., the adhesion between the titanium and the die during press molding is suppressed and the dynamic friction coefficient is reduced. However, such lubrication means are labor intensive, reduce the efficiency of the press forming process, and increase costs.

Therefore, as a low-cost means for suppressing the contact between titanium and the mold, an oxide film, nitride film, carbide film, or carbonitride film is formed on the titanium surface by oxidation, nitridation, 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 coefficient of dynamic friction when a titanium plate having an oxide film formed thereon is press-formed without using a lubricant is higher than the coefficient of dynamic friction when a 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 lower than that of the titanium plate without lubrication. It becomes larger than 0.17 in the state.

In Patent Document 1, as a titanium thin plate with increased strength without reducing formability, the arithmetic mean roughness (Ra) in the L direction is 0.2 to 0.8 μm, and the arithmetic mean roughness in the T direction is It is 1.1 times or more and 2 times or less in the L direction, and when the plate thickness is t, deformation twins exist in the range of 0.05 t to 0.2 t in the surface layer, and the Vickers at the measurement load of 0.25 N on the surface The hardness is 170 or more, the Vickers hardness at the measured load of 9.8 N on the surface is 90 to 180, and the Vickers hardness at the measured load of 0.25 N is higher than the Vickers hardness at the measured load of 9.8 N. Titanium plates that are more than 1.5 times higher are described. In the titanium plate described in Patent Document 1, a surface roughness condition has been found in which the lubricant can be applied sufficiently and the lubricant can be sufficiently supplied during the forming process.

In Patent Document 2, a titanium plate exhibiting excellent press formability has an arithmetic mean roughness (Ra) of 0.15 to 1.5 μm and a maximum height (Rz) of 1.5 to 9.0 μm. and the strain degree (Rsk) is in the range of -3.0 to -0.5, and the Vickers hardness on the surface at a measurement load of 0.098N is higher than the Vickers hardness at a measurement load of 4.9N. , the difference of which is 45 or less. In the titanium plate disclosed in Patent Document 2, recesses are formed on the surface, and the recesses improve the lubricating oil retaining property.

JP 2016-156054 A JP 2010-255085 A

The titanium plates described in Patent Literatures 1 and 2 focus on improving lubricant applicability and oil retention, and do not relate to improving the oxide film formed by atmospheric oxidation.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a titanium plate and a method of manufacturing the same that can reduce the coefficient of dynamic friction with a die during press molding.

In order to solve the above problems, the present invention employs the following configuration.
[1] Having an oxide film made of rutile-type TiO ₂ with a thickness of 0.10 μm or more on the surface,
The surface properties of the oxide film are
The arithmetic mean roughness Ra of the roughness curve obtained by applying cutoff values of λs = 2.5 µm and λc = 0.08 mm is 0.20 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 profile 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 for a region satisfying 0.8 times or more the maximum peak height Rp of the roughness curve is 20° or less,
A titanium plate characterized by satisfying
[2] High-carbon chromium bearing steel specified in Japanese Industrial Standard G4805 using 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. The titanium plate according to [1], wherein the coefficient of dynamic friction is 0.17 or less when a SUJ2 pin is slid on the surface of the oxide film.
[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 polished with a dull roll having a roll surface with an arithmetic mean roughness Ra in the range of 0.20 to 7.0 μm. A first step of rolling the material;
a 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;
A sliding member having a sliding surface with a hardness of 650 HV or more and an arithmetic mean roughness Ra of 0.15 μm or less is subjected to 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. a third step of sliding the surface of the oxide film;
The method for producing a titanium plate according to [1] or [2], characterized in that the steps are performed sequentially.

ADVANTAGE OF THE INVENTION According to this invention, the titanium plate which can reduce the dynamic friction coefficient with the metal mold|die at the time of press molding, and its manufacturing method can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram explaining the manufacturing method of the titanium plate which is embodiment of this invention.

A solid surface has fine irregularities. When solids having the same degree of roughness are slid, the protrusions on one solid surface mainly come into contact with the protrusions on the other solid surface, and this contact portion becomes the actual contact surface. Therefore, the area of the real contact surface is much smaller than the area of the apparent contact surface. Further, on the surface of the oxide film composed of rutile-type TiO ₂ formed on the titanium plate, fine irregularities formed along with the growth of the oxide film are observed.

When the metal mold moves during press molding of the titanium plate, the convex portions of both the metal 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 fine irregularities formed during the growth of the oxide film, and digging resistance is generated. It is presumed that the dynamic friction coefficient of the titanium plate includes this digging resistance component.

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

If press molding is performed after mechanically abrading the fine unevenness of the oxide film to make it smooth in advance, it is expected that the digging resistance will be reduced and the dynamic friction coefficient will be reduced. However, the dynamic friction coefficient does not actually decrease as expected. The inventors diligently investigated the reason for this.

Since the titanium plate and the die move relative to each other during press molding, naturally the real contact surface always changes depending on the uneven shapes of the titanium plate and the die. For example, at one moment, the convex portion of the titanium plate and the convex portion of the die surface, which are the real contact surfaces, are separated from each other at the next moment, and the other convex portions become the real contact surfaces. In this way, the real contact surface is determined by the combination of the instantaneous concave and convex shapes of the titanium plate and the mold. Normally, the unevenness of the titanium plate and the mold is random, so it is difficult to abrade the fine unevenness of the oxide film in advance by aiming at the convex portions of the titanium that will be the real contact surface with the mold. That is, even if the fine unevenness of the oxide film is mechanically abraded in advance, the protrusions where the fine unevenness of the oxide film is not abraded become the real contact surface during press molding, and titanium oxide is dug up at that place. It was presumed that the coefficient of dynamic friction would not decrease due to the occurrence of cracks.

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

Therefore, as a result of further investigation by the present inventors, by sparsely forming relatively high projections (mountains) on titanium and using the fine unevenness of the oxide film at the tip portion including the top of the mountain as an abrasion 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 die slides during press molding, the die always contacts the high peaks to form a true contact surface. It becomes difficult to form a true contact surface at locations other than the above. As a result, we succeeded in significantly reducing the dynamic friction coefficient of the titanium plate.

The titanium plate of this embodiment will be described below.
The titanium plate of this embodiment has an oxide film made of rutile-type TiO ₂ with a thickness of 0.10 μm or more on the surface, and the surface properties of the oxide film are λs = 2.5 μm and λc = 0.08 mm cut. The arithmetic average roughness Ra of the roughness curve obtained by applying the off value is 0.20 to 7.0 μm, the difference between the ten-point average roughness R _ZJIS of the roughness curve and the average height Rc of the contour curve element ( R _ZJIS -Rc) is 0.5 μm or more, and 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 the maximum peak height Rp of the roughness curve is 20° or less.
The titanium plate of this embodiment will be described in more detail below.

The titanium plate of this embodiment may be a pure titanium plate or a titanium alloy plate. The thickness of the titanium plate is not particularly limited as long as it is suitable for press molding.

Pure titanium is defined by JIS H 4600 (2007) Classes 1 to 4, corresponding ASTM Grades 1 to 4, and DIN Standards 3.7025, 3.7035, and 3.7055. shall include commercially pure titanium. That is, the industrially 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, and Fe: 0.5% or less, the balance is Ti.

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

Examples of α-type titanium alloys include highly corrosion-resistant alloys (ASTM Grade 7, 11, 16, 26, 13, 30, 33, or corresponding JIS types and titanium materials 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, 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. 45Si and the like.

α+β type titanium alloys include, for example, 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 -2Fe-0.3Si, Ti-5Al-2Fe-3Mo and Ti-4.5Al-2Fe-2V-3Mo.

Furthermore, 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, and Ti-22V-4Al.

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

An oxide film is formed on the surface of the titanium plate of this embodiment. The oxide film consists of rutile _TiO2 . By forming an oxide film on the surface, the pure titanium or titanium alloy forming the titanium plate does not come into direct contact with the die during press molding, and adhesion of the titanium plate can be prevented. In addition, if the oxide film is an anatase type oxide film, the oxide film will be too soft, and the surface morphology of the oxide film will be easily deformed when the press molding die slides, increasing the digging resistance and increasing the dynamic friction coefficient. Rutile-type TiO ₂ is preferable for 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 rays, 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, and may adhere to the mold, which is not preferable. Although it is not necessary to specify the upper limit of the thickness of the oxide film, it may be difficult to form an oxide film of more than 1 μm, so the upper limit of the thickness may be 1 μm or less.

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

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

(1) The arithmetic mean roughness Ra of the roughness curve obtained by applying cutoff values of λs=2.5 μm and λc=0.08 mm is 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 roughness curve and the average height Rc of the contour curve elements 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 in the region satisfying 0.8 times or more the maximum peak height Rp of the roughness curve. thing.

(1) Arithmetic mean roughness Ra of 0.20 to 7.0 μm
The oxide film of this embodiment preferably has an arithmetic mean 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. Moreover, if the arithmetic mean roughness Ra exceeds 7.0 μm, it is not preferable because it may become a starting point of cracks due to bending deformation. Note that the arithmetic mean roughness Ra of the present embodiment is the arithmetic mean roughness Ra specified in JIS B 0601 (2001), and is the average of the absolute values of the total coordinate value Z (x) in the reference length. be. The arithmetic mean roughness Ra may be 0.20-4.0 μm, 0.20-3.0 μm, or 0.20-1.0 μm.

In addition, the roughness curve that is the basis for calculating the arithmetic mean roughness Ra is obtained by applying a low-pass filter with a cutoff value λc = 0.08 mm to the measured cross-sectional curve of the oxide film to obtain a cross-sectional curve. Let the surface curve be the roughness curve obtained by applying a high-pass filter with a cut-off value λs=2.5 μm. Also, the reference length of the roughness curve is set to 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} ) 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. The present inventors found that by forming relatively high protrusions (mountains) sparsely on the surface of the oxide film, even if the mold slides on the surface of the oxide film during press molding, the mold is always in contact with the high peaks. By doing so, a true contact surface is formed, and by making it difficult to form a true contact surface at other locations, the dynamic friction coefficient can be reduced. The present inventor decided to adopt (R _ZJIS -Rc) as an index representing that relatively high projections (mountains) are sparsely formed on the surface of the oxide film.

The ten-point average roughness R _ZJIS of the roughness curve of the present embodiment is the ten-point average roughness R _ZJIS specified in Annex 1 of JIS B 0601 (2001). Ten-point average roughness R _ZJIS is the average sum of the average height of the 5th highest peak and the 5th lowest valley depth from the deepest valley in the roughness curve of the reference length. It is said that That is, the average height of the five large peaks included in the roughness curve.

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

Therefore, as (R _ZJIS -Rc) increases, it means that the height of the convex portion (mountain) included in the roughness curve protrudes and increases. The oxide film of the present embodiment preferably has (R _ZJIS -Rc) of 0.5 μm or more. As a result, even if the mold slides on the surface of the oxide film during press molding, the mold is always in contact with the high peaks 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 actual contact surface will not match, and digging resistance will occur, increasing the coefficient of dynamic friction, which is not preferable.

(3) 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 the maximum peak height Rp is 20° or less in the present embodiment. The root-mean-square slope RΔq in the region satisfying 0.8 times or more of Rp is preferably 20° or less. The present inventors sparsely formed relatively high projections (mountains) on the surface of the oxide film, and abraded the surface of these relatively high projections (mountains) to a smooth surface, thereby achieving real contact. It was found that the digging resistance in the surface can be reduced.

The region where the root-mean-square slope RΔq is limited to 20° or less is limited to a region satisfying 0.8 times or more the maximum peak height Rp when the roughness curve is cut by a line 0.8 times Rp. This is because the real contact surface is formed on the upper part of the line of Rp×0.8 among the curves sandwiched between two adjacent intersections of .

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

The maximum peak height Rp of the present embodiment is the maximum peak height Rp of the profile curve defined in JIS B 0601 (2001), and is the peak height of the profile curve (roughness curve in this embodiment) at the reference length. is the maximum value of Zp.

The root-mean-square slope RΔq of this embodiment is the root-mean-square slope RΔq specified in JIS B 0601 (2001), and is the root-mean-square slope of the local slope dZ/dX in 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 a titanium plate is press-molded, the surface with which the mold can come into contact is limited, so the oxide film at the part with which the mold can come into contact may satisfy (1) to (3) above.

The surface properties of the oxide film are measured, for example, using a laser microscope VK9700 manufactured by KEYENCE CORPORATION with a field of view of 500 times (284.7×200 μm). The cutoff values are λs=2.5 μm and λc=0.08 mm. If the surface of the oxide film has polishing marks, the direction of the roughness curve is the direction perpendicular to the polishing marks. The measurement at one point is performed with N=2, and the average value is taken as the measured value for each measurement point. For RΔq, measurements are made at one location with N=3, and the average value is taken as the measured value for each measurement location.

Arithmetic mean roughness Ra, ten-point mean roughness R _ZJIS , average height Rc, maximum peak height Rp and root mean square inclination RΔq are calculated based on the roughness curve measurement position is not particularly limited. Any location on the oxide film may be measured. It is preferable to measure the roughness curve at five points per titanium alloy plate. Then, the arithmetic mean roughness Ra, (R _ZJIS - Rc) and the maximum peak heights Rp and RΔq are obtained based on the roughness curve measured at five points, and these averages are preferably used.

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

The dynamic friction coefficient of the titanium plate was measured using 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. The coefficient of dynamic friction when a pin made of SUJ2 chromium bearing steel is slid on the oxide film surface of a titanium plate. Also, when the pin is slid on the surface of the oxide film, the pin is not slid on the already slid place, and the pin is always slid on the place that has not been slid. .

Next, a method for manufacturing a titanium plate according to this embodiment will be described.
The method for manufacturing a titanium plate according to the present embodiment comprises a first step of polishing the surface of a titanium plate material or rolling the titanium plate material with a dull roll, and and a third step of sliding the surface of the oxide film with 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 roughened surface of the titanium plate in the second step. As a result, the surface texture of the oxide film is roughened compared to when the first step is not performed. In the third step, the sliding member slides against the roughened surface of the oxide film, thereby abrading the oxide film, particularly the relatively high convex surfaces. As a result, an oxide film satisfying the above (1) to (3) can be obtained.
Each step will be described below.

First, a titanium plate material to be used in the first step is prepared. The titanium plate material may be a pure titanium plate or a titanium alloy plate. The titanium plate material is preferably, for example, a titanium plate subjected to descaling treatment after cold rolling.

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

Examples of abrasives for polishing a titanium plate material include abrasive cloth specified in JIS R 6251 (2006), abrasive paper specified in JIS R 6252 (2006), and JIS R 6253 (2006). Specified waterproof abrasive paper can be used. There are no particular restrictions on the type of abrasive used for the abrasive cloth, abrasive paper, or water-resistant abrasive paper, and any of alumina abrasive, silicon carbide abrasive, garnet, and silica may be used. Also, 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, or rotary polishing may be used.

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

In the first step, it is desirable that the surface properties of the oxide film after polishing or rolling satisfy 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 properties of the oxide film after the first step satisfy 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 element is 0.5 μm or more.

Ra, R _ZJIS and Rc shown in (A) and (B) above are obtained by applying a low-pass filter with a cutoff value λc = 0.08 mm to the measured cross-sectional curve of the oxide film to obtain a cross-sectional curve, and shall be measured in the roughness curve obtained by applying a high-pass filter with a cut-off value 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 the atmosphere to form an oxide film on the surface of the titanium plate material. The heating temperature is preferably 550-850°C. The heating temperature is preferably set to a temperature that does not change the mechanical properties of the titanium plate material. If the heating temperature is less than 500° C., a sufficient oxide film cannot be formed, which is not preferable. On the other hand, if the heating temperature exceeds 900° C., the titanium plate is heated to a temperature higher than 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 oxide film has a thickness of more than 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 with a hardness of 650 HV or more and an arithmetic mean roughness Ra of 0.15 μm or less is subjected to an apparent surface pressure of 1.0 MPa or more and less than 10 MPa, and a sliding speed of 0.1 MPa or more. The surface of the oxide film is slid under conditions of 001 to 1 m/min. Sliding members shall be dry. As a result, the root-mean-square slope RΔq of the oxide film becomes 20° or less in the peak region satisfying at least 0.8 times the maximum peak 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 inclination RΔq of the oxide film cannot be reduced to 20° or less, which is not preferable. Although the hardness of rutile-type titanium oxide is about 800 to 1000 HV, it was confirmed that the root-mean-square slope RΔq can be 20° or less in the production method of the present embodiment if the sliding member has a hardness of 650 HV or more. ing.

The arithmetic mean roughness Ra of the sliding member is preferably smaller than the arithmetic mean 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 inclination RΔq of the oxide film cannot be reduced to 20° or less, which is not preferable.

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

The Vickers hardness of the sliding surface complies with JIS Z 2244 (2009). A measurement load is 500 gf. In addition, the arithmetic mean roughness Ra of the sliding surface is obtained by applying a low-pass filter with a cutoff value λc = 0.08 mm to the measured cross-sectional curve of the sliding surface to obtain a cross-sectional curve, and furthermore, to this step surface curve, shall be measured on the roughness curve obtained by applying a high-pass filter with a cut-off value λs=2.5 μm. The measurement length shall be 2.4 mm.

In addition, 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 ensured. 20° or less. FIG. 1 shows a schematic side view of how the oxide film 2 of the titanium plate 1 is slid by the sliding member 3 . The direction of arrow A is the sliding direction of the sliding member. Reference numeral 3a denotes a sliding surface. It is preferable that the length L along the sliding direction A of the sliding surface 3a is 2 mm or more.

Further, if the apparent surface pressure during sliding of the sliding member is less than 1.0 MPa, the oxide film cannot be sufficiently worn away, and the root-mean-square inclination RΔq of the oxide film cannot be 20° or less. I don't like it because it disappears. Further, if the apparent surface pressure exceeds 10 MPa, the oxide film may peel off during sliding of the sliding member.

Furthermore, if the sliding speed of the sliding member is less than 0.001 m/min, the time required for the third step will be long, and the productivity of the titanium plate will be greatly 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 becomes unstable, and the abrasion of the oxide film becomes insufficient. Since it becomes impossible to make it below 20 degrees, it is not preferable.

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

Through the above steps, the titanium plate of the present embodiment can be manufactured.

In the titanium plate of the present embodiment, since the surface properties of the oxide film satisfy the conditions described in (1) to (3) above, the coefficient of dynamic friction can be made 0.17 or less. As a result, when the titanium plate is formed by press forming, there is no risk of adhesion to the mold, and press forming can be stably performed. In addition, since it is not necessary to use a film-type lubricant as in the conventional art, the productivity of press molding can be improved.

EXAMPLES The present invention will be described in more detail below with reference to examples. It should be noted that the present invention is not limited to the examples described below.

Pure titanium plates of types 1 to 4 specified in JIS H 4600 were prepared as titanium plate materials. As a titanium plate material, a titanium plate obtained by cold-rolling a thin titanium plate having a thickness of 5 mm, which was hot-rolled and then descaled to a 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 polishing paper of P80 to P1000. A part of the titanium material (Comparative Example 1) was mirror-polished. Furthermore, for another titanium material (Example 6), a dull roll was used to roll the titanium plate material. The dull roll used was a dull roll obtained by polishing the base with a grindstone of P600 or more and then imparting unevenness by shot blasting of steel grit of P25 or less. The arithmetic mean roughness Ra of the roll surface of the dull roll was 3.2 μm. Furthermore, for Comparative Examples 2 and 3, the first step was not performed.

Next, in the second step, the titanium plate material after the first step was heated at a heating temperature of 450° C. to 900° C. for 15 minutes to 24 hours in an air atmosphere. For Comparative Example 6, anodic electrolytic treatment was performed by holding 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, in the third step, a sliding member having a sliding surface with a hardness of 500 to 1500 HV and an arithmetic mean roughness Ra of 0.05 to 0.2 μm was prepared. As for the shape of the sliding surface, the length along the sliding direction was 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 performed.

Thus, titanium plates of Examples 1-22 and Comparative Examples 1-12 were produced.

The dynamic friction coefficient of the obtained titanium plate was measured. The measurement was performed using 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. It was measured by sliding a SUJ2 pin on the oxide film surface of the titanium plate. When the pin was slid on the surface of the oxide film, the pin was not slid on the already slid portion, and the pin was always slid on the unslidable portion for measurement.

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

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

The surface properties of the oxide film were measured. The surface properties were as described in (i) to (iii) below.

(i) Arithmetic mean roughness Ra of the roughness curve obtained by applying cut-off values of λs=2.5 μm and λc=0.08 mm.
(ii) the difference (R _ZJIS - Rc) between the ten-point average roughness R _ZJIS of the roughness curve and the average height Rc of the profile curve elements;
(iii) The root-mean-square slope RΔq measured under the conditions of λs=0 μm and λc=0 mm for the area satisfying 0.8 times or more the maximum peak height Rp of the roughness curve.

Further, the surface properties of the oxide film were 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. When the surface of the oxide film had polishing marks, the direction of the roughness curve was the direction perpendicular to the polishing marks. The measurement at one point was performed with N=2, and the average value was used as the measured value for each measurement point. For RΔq, measurements were made at one location with N=3, and the average value was taken as the measured value for each measurement location.

Arithmetic mean roughness Ra, ten-point mean roughness R _ZJIS , mean height Rc, maximum peak height Rp and root mean square inclination RΔq are measured at arbitrary five positions of the roughness curve. and Then, based on the roughness curves measured at five points, the arithmetic average roughness Ra, (R _ZJIS - Rc) and the maximum peak heights Rp and RΔq were obtained, and these averages were used.

The Vickers hardness of the sliding surface of the sliding member was measured according to JIS Z 2244 (2009). A measurement load was 500 gf. In addition, the arithmetic mean roughness Ra of the sliding surface is obtained by applying a low-pass filter with a cutoff value λc = 0.08 mm to the measured cross-sectional curve of the sliding surface to obtain a cross-sectional curve, and furthermore, to this step surface curve, It was measured on a roughness curve obtained by applying a high-pass filter with a cut-off value λs=2.5 μm. The measurement length was 2.4 mm.
Results are shown in Tables 1A and 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 properties of the oxide film satisfy the scope of the present invention, and the friction coefficient is It became 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 reach the desired roughness. For this reason, the arithmetic surface roughness Ra of the sliding member becomes larger than the arithmetic surface roughness Ra of the oxide film after the second step, and the area satisfying the maximum peak height Rp×0.8 or more is worn away. I couldn't cut it. As a result, RΔq exceeded 20° and the coefficient of friction increased.

In Comparative Example 5, the heating temperature in the second step was low and the thickness of the oxide film became thin. 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 TiO ₂ is soft, the abrasion effect on the surface of the oxide film in the third step was small, resulting in a high coefficient of friction.

In Comparative Example 7, the Vickers hardness of the sliding member was low, and the oxide film could not be sufficiently worn away. Therefore, RΔq increased and the coefficient of friction increased.

In Comparative Example 8, since the arithmetic mean roughness Ra of the sliding member was too large, the area satisfying the maximum peak height Rp×0.8 or more could not be completely worn away. Therefore, RΔq increased and the coefficient of friction increased.

In Comparative Example 9, since the sliding speed of the sliding member was too high, 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 increased and the coefficient of friction increased.

In Comparative Example 10, since the third step was not performed, RΔq increased and the coefficient of friction increased.

In Comparative Example 11, since the contact pressure of the sliding member was too low, the oxide film could not be sufficiently worn away. Therefore, RΔq increased and the coefficient of friction increased.

In Comparative Example 12, since the surface pressure of the sliding member was too high, the oxide film was peeled off during sliding, exposing the base metal. Then, when the friction coefficient was measured, the exposed base metal and the sliding pin were adhered to each other, resulting in a high friction coefficient.

Claims (3)

The surface has an oxide film made of rutile TiO ₂ with a thickness of 0.10 μm or more,
The surface properties of the oxide film are
The arithmetic mean roughness Ra of the roughness curve obtained by applying cutoff values of λs = 2.5 μm and λc = 0.08 mm is 0.20 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 profile 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 for a region satisfying 0.8 times or more the maximum peak height Rp of the roughness curve is 20° or less,
A titanium plate characterized by satisfying Using 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 chromium bearing steel made of SUJ2 specified in Japanese Industrial Standard G4805. 2. The titanium plate according to claim 1, wherein the coefficient of dynamic friction when the surface of said oxide film is slid 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 with a dull roll having an arithmetic mean roughness Ra of the roll surface in the range of 0.20 to 7.0 μm. a first step of
a 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;
A sliding member having a sliding surface with a hardness of 650 HV or more and an arithmetic mean roughness Ra of 0.15 μm or less is subjected to 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. a third step of sliding the surface of the oxide film;
3. The method for producing a titanium plate according to claim 1 or 2, wherein the steps are performed sequentially.

Images