WO2017047795A1 - Titanium pipe-forming roll, titanium pipe-forming apparatus, and titanium pipe-manufacturing method - Google Patents

Abstract

A titanium pipe-forming roll provided with a base material having, in mass%, C:1.00-2.30%, Si: 0.10-0.60%, Mn: 0.20-0.80%, P: 0.030 or less, S: 0.030% or less, Cr: 4.80-13.00% with the balance being iron and unavoidable impurities, a nitride layer (800-1200 Hv) on said base material (600-700 Hv), a CrN film (800-2000 Hv), and a DLC film, wherein: in said DLC film, Vickers hardness is 3000-3500 in the region from the film surface to 0.20t (wherein t is the film thickness), and is 1500-3000 in the region from the interface with said CrN film to 0.20t; the ratio I₁₃₈₀/I₁₅₄₀ of absorption intensities at wave number 1380 cm^-1 and 1540 cm^-1 measured by Raman spectroscopy is 0.5-0.7 in the region from the film surface to 0.20t and is 0.3-0.5 in the region from the interface between the DLC film and the CrN film to 0.20t. Said titanium pipe-forming roll has excellent adhesion resistance, abrasion resistance, peeling resistance and roll surface friction coefficient.

Description

Titanium tube forming roll, titanium tube forming apparatus, and titanium tube manufacturing method

The present invention relates to a titanium tube forming roll, a titanium tube forming apparatus, and a method for manufacturing a titanium tube.

Usually, when manufacturing steel pipes and other metal pipes, a forming process using a forming roll is performed after welding for the purpose of ensuring a highly accurate outer diameter and roundness and correcting the bending of the pipe.

¡If the forming roll is heavily worn, it will not be possible to form with high precision, and it will not be possible to ensure high accuracy roundness in the steel pipe to be formed. For this reason, the forming roll is required to have excellent wear resistance capable of maintaining the state of the roll surface over a long period of time.

In recent years, in order to improve the productivity of steel pipes, molding is often performed under harsh conditions with increased transport speed in the molding process. When operating under such conditions, adhesion (seizure) is likely to occur in the portion due to the difference in peripheral speed between the steel pipe surface and the forming roll surface, and seizure flaws may occur. As described above, if adhesion occurs between the forming roll and the steel pipe, soot remains on the surface of the steel pipe, reducing the commercial value. Therefore, the forming roll must be replaced before wear or adhesion occurs.

Therefore, a roll for forming a steel pipe is required to have a long-life roll that has both wear resistance and adhesion resistance that can reduce seizure flaws and can reduce the frequency of roll replacement.

Conventionally, various techniques have been studied for the demands of wear resistance and adhesion resistance for such forming rolls.

For example, a method of securing a hardness by forming a ceramic film on the roll surface (Patent Document 1), and forming a surface hardened layer selected from a sulfur nitrided layer, a nitrided layer and TiC on the roll surface to improve the hardness and In a roll having a hard coating on the surface (Patent Document 2), the carbide dispersed in the roll surface layer is refined to ensure adhesion between the roll and the hard coating, and to prevent peeling of the hard coating. A method for securing wear resistance and adhesion resistance (Patent Document 3) and the like have been studied.

In general, tool steel such as die steel is often used as the material of the forming roll, but measures to use cemented carbide instead of tool steel are also available to improve wear resistance and adhesion resistance. Has been taken.

Here, titanium has been developed as a constituent material for various chemical reaction towers, containers, pipes, and the like because it has significantly superior corrosion resistance in various environments compared to other metal materials. In recent years, titanium pipes are often used as heat transfer pipes for steam turbine condensers and evaporative seawater desalination equipment for thermal power and nuclear power plants.

JP-A-8-174014 JP-A-1-201443 International Publication No. 00/51756

As described above, various studies have been made on the wear resistance and adhesion resistance of a forming roll when forming a steel pipe. However, little mention has been made of the characteristics of the forming roll for forming the titanium tube. Furthermore, even when the above-described conventional technology is adopted for the forming roll at the time of forming the titanium tube, the wear resistance and adhesion resistance may be insufficient.

In recent years, a copper alloy is often used as the material of the titanium tube forming roll because the surface properties of the roll can be maintained well. However, since the hardness of the copper alloy is insufficient, sufficient wear resistance cannot be ensured. There was a case.

Generally, when a titanium tube is formed, roundness and residual stress are controlled by forming with a plurality of forming rolls arranged in a plurality in the conveying direction.

¡A plurality of forming rolls are roughly divided into drive rolls and non-drive rolls. The drive roll consists of a pair of rolls arranged opposite to each other in the vertical direction. The rolls are driven by applying a driving rotational force to the upper and lower rolls to pull the titanium tube in the conveying direction. It consists of a pair of made rolls, and no driving torque is applied.

Here, the present inventors investigated in detail the characteristics required for the drive roll and the non-drive roll. As a result, the driving roll has a larger peripheral speed difference than the non-driving roll, and thus it has been found that the roll surface is particularly peeled off at the flange portion, and the titanium tube which is a molding object is easily wrinkled. Furthermore, it was found that even when a hard film was applied for the purpose of hardening the roll surface, the drive roll was easier to peel off than the non-drive roll, and the roll life was shortened.

In other words, the driving roll is used in a harsher environment than the non-driving roll, so it has not only wear resistance and adhesion resistance, but also peeling resistance, and excellent sliding properties of the roll surface, that is, low friction. Was found to be required.

The present invention has been made in view of the above problems, and is excellent in wear resistance, adhesion resistance, peel resistance, and friction coefficient of the roll surface in a roll used when forming and forming a titanium tube. It is another object of the present invention to provide an inexpensive titanium tube forming roll, a titanium tube forming apparatus capable of extending the life of the roll, and a titanium tube manufacturing method.

The present inventors have studied titanium tube forming rolls that are inexpensive and have excellent wear resistance, adhesion resistance, peeling resistance, and friction coefficient of the roll surface, and have a long roll life. By using the alloy tool steel used as a base material, forming a nitride layer and a CrN film having low affinity with titanium on the base material, and further forming a diamond-like carbon film thereon, It has been found that it is possible to provide a long-life roll that can achieve both wear resistance, adhesion resistance, peel resistance, and low friction on the roll surface, and can reduce the frequency of roll replacement.

The gist of the present invention is as follows.

(1) In mass%,
C: 1.00-2.30%,
Si: 0.10 to 0.60%,
Mn: 0.20 to 0.80%,
P: 0.030% or less,
S: 0.030% or less,
Cr: 4.80 to 13.00%,
Mo: 0 to 1.20%,
V: 0 to 1.00%,
W: 0 to 0.80%,
A substrate having a chemical composition with the balance being iron and inevitable impurities;
A nitride layer formed on at least the rolled surface on the substrate;
A CrN film formed on the nitride layer;
A diamond-like carbon film formed on the CrN film,
The substrate has a Vickers hardness of 600 to 700,
The nitride layer has a Vickers hardness of 800 to 1200;
The CrN film has a Vickers hardness of 800 to 2000,
The diamond-like carbon film has a Vickers hardness of 3000 to 3500 in the region from the film surface to 0.20 t (where t is the film thickness), and 1500 to 3000 in the region from the interface with the CrN film to 0.20 t. And
In the diamond-like carbon film, the ratio I ₁₃₈₀ / I ₁₅₄₀ of the absorption intensity I ₁₃₈₀ at a wave number of ₁₃₈₀ cm ^{−1 and} the absorption intensity I ₁₅₄₀ at a wave number of 1540 cm ⁻¹ measured by Raman spectroscopy is 0.20 t from the film surface. 0.5 to 0.7 in the region up to 0.3, and 0.3 to 0.5 in the region up to 0.20 t from the interface between the diamond-like carbon film and the CrN film.
Titanium tube forming roll.

The thickness of the diamond-like carbon film is preferably 0.5 μm to 2.0 μm.

The thickness of the CrN film is preferably 0.5 μm to 5.0 μm.

The thickness of the nitride layer is preferably 0.5 μm to 50.0 μm.

The average nitrogen concentration of the nitrided layer is preferably 10.0 to 25.0% by mass.

It is preferable that the nitrogen concentration distribution in the nitride layer has a concentration gradient that decreases in the depth direction from the surface layer of the nitride layer.

The base material contains one or more selected from Mo: 0.70 to 1.20%, V: 0.15 to 1.00% and W: 0.60 to 0.80% by mass. Is preferred.

The titanium tube forming roll of (1) is a perforated roll provided with a semi-circular roll recess in cross-section over the entire circumference of the roll body, and the rolling surface is the surface of the roll recess. preferable. The roll main body includes a roll center portion and a pair of rotating flange portions that are arranged on both sides of the roll center portion and are rotatable with respect to the roll center portion, and the roll recess portion includes the roll It is preferable that the center portion and the rotating flange portion are divided.

It is preferable that the roll center portion is fixed to a rotating shaft that drives the roll body, and the rotating flange portion is rotatable with respect to the rotating shaft and the roll center portion.

When the outer diameter of the titanium tube serving as a workpiece is D, the width of the roll recess at the center of the roll is preferably in the range of 0.7D to 0.87D.

The roll center part includes a base part and a protrusion part protruding from the center part in the roll width direction of the base part toward the outer periphery of the roll, and the rotating flange part is on the base part and protrudes from the base part. It is preferable that a first bearing portion is provided between the base portion of the central portion of the roll and the rotating flange portion.

The opposing surfaces that face each other between the base portion and the rotating flange portion at the center of the roll are the raceway surfaces of the rolling elements of the first bearing portion, and the opposing surfaces are the nitride layer The CrN film and the diamond-like carbon film are preferably provided.

A fixed flange portion disposed on both sides of the pair of rotating flange portions in the roll width direction and fixed to the center portion of the roll, and a second bearing portion disposed between the fixed flange portion and the rotating flange portion Are preferably provided.

The opposing surfaces facing each other between the fixed flange portion and the rotating flange portion are raceway surfaces of the rolling elements of the second bearing portion, and the opposing surfaces are the nitride layer and the CrN. It is preferable to provide a film and the diamond-like carbon film.

It is preferable that a pulling screw portion for pulling and fixing the rotating flange portion is provided on the fixing flange portion.

(2) A titanium tube forming apparatus including the titanium tube forming roll according to (1), wherein the titanium tube has a lubrication nozzle for supplying a lubricant to the part of the titanium tube forming roll during the titanium tube forming. Molding equipment.

In the above titanium tube forming apparatus (2), it is preferable that the position of the lubrication nozzle can be varied in accordance with the forming size of the titanium tube.

In the titanium tube forming apparatus of (2), it is preferable that the position of the lubrication nozzle can be varied according to the diameter of the titanium tube forming roll.

In the titanium tube forming apparatus (2), it is preferable that the position and orientation of the lubricating nozzle can be arbitrarily adjusted.

The lubrication nozzle is preferably a tube having an inner diameter of 0.5 to 3.0 mm.

In the titanium tube forming apparatus of (2) above, it is preferable to use a soluble oil lubricant as the lubricant, and supply the lubricant dropwise in a small amount at 1.0 to 20.0 ml / hr or less.

A method for manufacturing a titanium tube, which is formed using the titanium tube forming roll of (1) above.

A method for manufacturing a titanium tube, which is formed using the titanium tube forming apparatus of (2) above.

According to the present invention, in a roll used for forming and forming a titanium tube, a titanium tube forming roll excellent in wear resistance, adhesion resistance, peeling resistance, and friction coefficient of the roll surface, and inexpensive. It is possible to provide a titanium tube forming apparatus capable of extending the life of a roll and a method for manufacturing a titanium tube.

FIG. 1 is a schematic side view illustrating a titanium tube manufacturing method using a titanium tube forming roll as a first example of an embodiment of the present invention. FIG. 2 is a schematic front view showing a titanium tube forming roll according to an embodiment of the present invention. FIG. 3 is a schematic front sectional view showing a titanium tube forming roll which is a second example of the embodiment of the present invention. FIG. 4 is a front sectional exploded schematic view showing a titanium tube forming roll as a second example of the embodiment of the present invention. FIG. 5 is a schematic front sectional view showing a roll center portion and a rotating flange portion of a titanium tube forming roll which is a second example of the embodiment of the present invention. FIG. 6 is a diagram for explaining the slip ratio in the titanium tube forming roll, (a) is a schematic diagram for explaining the slip ratio in the drive roll, and (b) is a schematic diagram for explaining the slip ratio in the non-drive roll. It is a figure, (c) is a schematic diagram explaining the slip ratio in the titanium tube forming roll of this embodiment. FIG. 7 is a schematic front sectional view showing another example of the titanium tube forming roll of the present embodiment. FIG. 8 is a schematic front sectional view showing still another example of the titanium tube forming roll of this embodiment. FIG. 9 is a schematic front sectional view showing a titanium tube forming roll which is a third example of the embodiment of the present invention. FIG. 10 is a schematic front view for explaining a lubrication method and apparatus using a titanium tube forming apparatus. FIG. 11 is a schematic front view for explaining an arrangement example of the lubricating nozzle 1 shown in FIG. 10. 12 is a schematic top view and schematic side view for explaining the width direction adjusting mechanism and the vertical direction adjusting mechanism of the lubricating nozzle 1 shown in FIG. FIG. 13 is a view showing a structure of a roller pump (lubricant supply device) for dripping a small amount of lubricant using the lubrication nozzle 1. 14 is a graph showing the result of component analysis in the forming roll of Example 1. FIG. FIG. 15 is a graph showing the result of component analysis in the forming roll of Example 1. FIG. 16 is a graph showing the result of component analysis in the forming roll of Example 1. 17 (a) is a micrograph of the surface layer of the forming roll of Example 1, FIG. 17 (b) is a Raman spectrum of the surface layer of the forming roll of Example 1, and FIG. 17 (c) is the forming roll of Example 1. Raman spectrum inside the DLC film. 18A is a micrograph of the surface layer of the forming roll of Comparative Example 1, FIG. 18B is a Raman spectrum of the surface layer of the forming roll of Comparative Example 1, and FIG. 18C is the forming roll of Comparative Example 1. Raman spectrum inside the DLC film. FIG. 19A is a view showing a measurement result of roundness of a titanium tube formed using the forming roll of Example 2, and FIG. 19B is formed using the forming roll of Example 3. It is a figure which shows the measurement result of the roundness of the made titanium tube. In each case, the deviation from the perfect circle is enlarged.

Hereinafter, a titanium tube forming roll, a titanium tube forming apparatus, and a titanium tube manufacturing method according to embodiments of the present invention will be described.

In addition, since this embodiment is described in detail for better understanding of the purpose of the titanium tube forming roll of the present invention, the present invention is not limited unless otherwise specified.

[First example of titanium tube roll and titanium tube manufacturing method]
FIG. 1 is a schematic side view of a titanium tube forming roll and a titanium tube manufacturing method using the titanium tube forming roll, which is a first example of the present embodiment. Moreover, in FIG. 2, the front schematic diagram of a titanium pipe forming roll is shown. As shown in FIGS. 1 and 2, the titanium tube forming roll 1 of the present embodiment is a so-called hole-type roll (caliber roll), and a roll body 2 made of a steel material and a rotating shaft 3 inserted through the roll body 2. And are provided. On the roll surface 2 a of the roll body 2, a roll recess 4 formed in a semicircular shape in cross section is provided over the entire circumference of the roll body 2. In addition, a nitride layer, a CrN film, and a diamond-like carbon film are formed in this order on the base material on the surface of the roll recess 4 that is a rolled surface.

As shown in FIG. 1, when the titanium tube 10 that is a cylindrical tube is formed into a perfect circle, the rotation shafts 3 of the pair of titanium tube forming rolls 1 are arranged horizontally, and the rotation shafts 3 are parallel to each other. Arrange so that In this way, the respective titanium tube forming rolls 1 are arranged to face each other in the vertical direction. And the titanium pipe | tube 10 before shaping | molding is passed between a pair of titanium pipe shaping | molding roll 1 arrange | positioned up and down. Between the pair of titanium tube forming rolls 1, a hole having a perfect circle shape when viewed from the front side is provided by the roll recess 4 of each titanium tube roll 1. When the tube passes, the titanium tube 10 is formed into a perfect circle. In addition, arrangement | positioning of the titanium tube forming roll 1 is not restricted to an up-down direction, A horizontal direction or the diagonal direction may be sufficient.

The rotating shaft 3 of the titanium tube forming roll 1 may be a driving shaft driven by driving means or a non-driving shaft. Even if the titanium tube forming roll 1 of this embodiment is connected to the drive shaft, the titanium tube forming roll 1 is provided with a diamond-like carbon film formed on the CrN film, so that it has wear resistance, adhesion resistance, and peeling resistance. And excellent friction coefficient on the roll surface.

The base material of the roll body 2 of the titanium tube forming roll 1 according to the present embodiment is C: 1.00-2.30%, Si: 0.10-0.60%, Mn: 0.00% by mass. A chemical composition containing 20 to 0.80%, P: 0.030% or less, S: 0.030% or less, Cr: 4.80 to 13.00%, the balance being iron and inevitable impurities It consists of steel material. A CrN film and a diamond-like carbon film are provided on the surface of the roll recess 4 of the titanium tube forming roll 1 made of this base material. In the diamond-like carbon film, the ratio I ₁₃₈₀ / I ₁₅₄₀ between the absorption intensity I ₁₃₈₀ at a wave number of ₁₃₈₀ cm ^{−1 and} the absorption intensity I ₁₅₄₀ at a wave number of 1540 cm ⁻¹ measured by Raman spectroscopy is 0.20 t from the film surface. In the region up to 0.5 to 0.7, and 0.3 to 0.5 in the region from the interface between the diamond-like carbon film and the CrN film to 0.20 t.

Hereinafter, the reasons for limitation of the titanium tube forming roll in this embodiment will be described in detail.

[Chemical composition of substrate]
First, the reason for limitation of each element is explained in full detail regarding the chemical composition of the base material in the titanium tube forming roll 1 of this embodiment.

In the following description, “%” represents mass% unless otherwise specified.

(C: carbon) 1.00-2.30%
C is an element necessary for forming carbide and ensuring hardness. Moreover, since it combines with Cr, Mo, V, etc. to form a hard carbide, it is important as an element that increases the quenching and tempering hardness and constitutes the wear resistance. Therefore, in this embodiment, C is contained by 1.00% or more. From the viewpoint of ensuring hardness, it is preferable to contain 1.4% or more.

On the other hand, if the C content exceeds 2.30%, the toughness is remarkably deteriorated. Therefore, in this embodiment, the C content is limited to 2.30% or less. From the viewpoint of ensuring toughness, the upper limit of the C content is preferably 2.20%, and more preferably 2.00% or less.

(Si: silicon) 0.10 to 0.60%
Si is contained as a deoxidizer. Further, Si is contained because it has an effect of increasing softening resistance during high-temperature tempering. From these viewpoints, Si is contained by 0.10% or more. On the other hand, if the Si content exceeds 0.60%, hot workability and toughness are reduced, and nonmetallic inclusions may increase. Therefore, the Si content is set to 0.60% or less. From the viewpoint of securing toughness, the upper limit of Si content is preferably 0.50%.

(Mn: Manganese) 0.20 to 0.80%
Mn is an element having a deoxidizing effect like Si, and is an element that improves hardenability and at the same time increases retained austenite. From this viewpoint, Mn is contained by 0.20% or more. In addition, it is preferable to contain 0.30 or more from a viewpoint of ensuring hardness. In consideration of the balance with toughness, the upper limit of the amount of Mn is set to 0.8% in the present embodiment. Preferably, it is 0.6% or less.

(P: Phosphorus) 0.030% or less (S: Sulfur) 0.030% or less Both P and S are preferable impurity elements that do not exist in steel. For this reason, the content of both P and S is limited to 0.030% or less. Preferably, it is limited to 0.020% or less.

(Cr: Chromium) 4.80-13.00%
Cr is an element that is in demand to improve wear resistance by combining with C to form carbides. Moreover, in this embodiment, since a CrN film (hard film) is formed on the base material of the titanium tube forming roll 1, it is very important also in ensuring adhesion with the CrN film. From these viewpoints, the Cr content is 4.80% or more, preferably 8.00% or more, and more preferably 11.00% or more.

On the other hand, if Cr is added excessively, toughness may be deteriorated due to the formation of coarse carbides, so the upper limit of Cr content is 13.00%. In addition, Preferably it is 12.50% or less.

(Mo: Molybdenum) 0 to 1.20%
Mo improves resistance to temper softening and also has an effect of imparting wear resistance by the formation of carbides, so it may be contained. From these viewpoints, Mo is preferably contained in an amount of 0.70% or more, and more preferably 0.80% or more.

On the other hand, if Mo is added excessively, the toughness may be deteriorated. Therefore, Mo is preferably contained in an amount of 1.20% or less, and more preferably 1.10% or less.

(V: Vanadium) 0-1.00%
V is effective for improving the hardenability of the base material, suppressing temper softening, and further miniaturizing the carbide. V is preferably contained in an amount of 0.15% or more, more preferably 0.20% or more.

On the other hand, when V is added excessively, cold workability may be hindered. Therefore, V is preferably contained in an amount of 1.00% or less, and more preferably 0.50% or less.

(W: Tungsten) 0 ~ 0.80%
W, like V, is effective for improving the hardenability of the base material, suppressing temper softening, and further miniaturizing the carbide, and therefore may be contained. W is preferably contained in an amount of 0.6% or more. On the other hand, if W is added excessively, cold workability may be impaired, so W is preferably contained in an amount of 0.80% or less.

In the present embodiment, the balance other than the above-described elements is substantially made of Fe, and trace amounts of elements that do not impair the effects of the present invention, such as inevitable impurities, can be added.

In addition, in the titanium tube forming roll 1 of this embodiment, what has the said chemical composition is used as a material of a base material, However, Among these, it is cheaper and a viewpoint which ensures abrasion resistance and adhesion resistance in good balance. Therefore, it is preferable to use SKD1, SKD2, SKD10, SKD11 or SKD12 (all within the above chemical composition range) defined in JIS G 4404, and among these, it is more preferable to use SKD11.

The hardness of the base material having the above chemical composition is 600 to 700 in terms of Vickers hardness. That is, when the titanium tube 10 is formed in the state of the base material without forming a film or the like on the base material, the hardness of the base material itself can be secured, so that the wear resistance is relatively good. However, with respect to adhesion resistance, titanium is baked on the base material, and a large number of wrinkles are generated in the titanium tube forming roll 1.

Therefore, in this embodiment, since affinity with Ti is very low and continuity (raw material continuity) with Cr in the base material can be maintained, a CrN film is formed on the base material surface (rolled surface). This is very important. By forming a CrN film on the surface of the base material, adhesion between the titanium tube 10 and the titanium tube forming roll 1 can be secured, and adhesion resistance can be improved. However, a hardness disparity (strength discontinuity) occurs between a CrN layer having a high hardness (800 to 2000 in Vickers hardness) and a relatively soft substrate (interface). As a result, stress tends to concentrate at the interface between the CrN layer and the base material, and depending on the thickness of the CrN film, sufficient adhesion between the CrN film and the base material may not be ensured.

Therefore, as a result of investigations by the present inventors, the hardness disparity is reduced by providing a nitride layer capable of connecting the CrN film and the base material between the high hardness CrN film and the relatively soft base material. It was found that the adhesion between the CrN film and the base material and the strength of the titanium tube forming roll 1 can be made compatible.

From the above, it is preferable to provide a nitride layer obtained by plasma nitriding the substrate surface layer between the substrate and the CrN layer. Thus, by forming the nitride layer on the surface layer of the base material, the hardness difference between the CrN film and the base material can be relaxed, and the concentration of stress can be suppressed. As a result, adhesion and strength between the CrN layer and the base material can be improved, peeling of the CrN layer can be reduced, and adhesion resistance can be improved.

[Nitride layer]
The titanium tube forming roll 1 according to the present embodiment forms a nitride layer on a base material and forms a CrN film and a high-hardness diamond carbon film on the nitride layer. Ensures adhesion resistance and low friction.

The Vickers hardness of the nitrided layer is 800-1200. If the Vickers hardness is less than 800, the hardness difference from the CrN film becomes too large, and if it exceeds 1200, the hardness difference from the base material becomes large.

The thickness of the nitride layer is not particularly limited, but is preferably 0.5 μm to 50.0 μm in the present embodiment. In order to reduce the difference in strength between the high hardness CrN layer and the relatively soft base material, it is preferable to secure a thickness of the nitride layer of 0.5 μm or more. More preferably, it is 1.0 μm or more. On the other hand, when the thickness of the nitrided layer is excessively increased, the time required for the plasma nitriding treatment becomes longer and the productivity is lowered, and the manufacturing cost is increased. Moreover, if the thickness of the nitride layer is excessively increased, the surface roughness of the base material increases, and it is necessary to polish the base material surface before forming the CrN film. From these viewpoints, the thickness of the nitride layer is preferably 50.0 μm or less.

The average nitrogen concentration in the nitrided layer is preferably 10.0-25.0% by mass.

If the nitrogen concentration in the nitrided layer is too low, the effect of improving the strength is small, and sufficient abrasion resistance may not be obtained. Therefore, the average nitrogen concentration in the nitrided layer may be 10.0% by mass or more. preferable. More preferably, it is 12.0% or more.

On the other hand, if the nitrogen concentration in the nitrided layer is too high, the surface of the nitrided layer tends to become brittle and cracks may occur. Therefore, the average nitrogen concentration in the nitride layer is preferably 25.0% by mass or less. More preferably, it is 23.0% or less.

Further, it is preferable that the nitrogen concentration distribution in the nitride layer has a concentration gradient that decreases from the surface layer of the nitride layer in the depth direction.

As described above, it is not preferable from the viewpoint of the adhesion between the CrN layer and the base material and the strength that the strength difference occurs inside the roll. Therefore, it is preferable that the difference in strength between the CrN layer, the substrate surface layer, and the inside of the substrate, that is, the strength gradient along the depth direction inside the roll is made gentle. For this purpose, it is preferable to control the concentration distribution of nitrogen in the nitride layer formed between the CrN layer and the base material so as to have a concentration gradient that decreases from the surface layer of the nitride layer toward the base material side.

In order to control the nitrogen concentration distribution so as to have a gradient that decreases in the depth direction from the surface layer of the nitride layer, the plasma nitridation treatment for the substrate surface layer for forming the nitride layer is divided into a plurality of times, In addition, the concentration distribution of nitrogen in the nitride layer may be adjusted by performing each process under different conditions.

Note that the determination of the “nitride layer” (determination of the boundary between the base material and the “nitride layer”) can be performed by a glow discharge emission spectrometer (GDS). Specifically, first, in the base material surface layer nitrided by the plasma nitriding treatment, the analysis region is set to a diameter of 1 mm, and normal glow discharge emission analysis is performed. Subsequently, the analysis proceeds in the depth direction, and a region where the nitrogen amount in the analysis region exceeds the average nitrogen concentration of the base material (base material) is defined as a “nitriding layer”. That is, the glow discharge emission analysis is performed in the depth direction, and the point where the nitrogen amount has decreased to the average nitrogen concentration of the substrate is determined as the boundary between the substrate and the “nitriding layer”.

The average nitrogen concentration in the nitride layer can also be measured using GDS. In this embodiment, the analysis region is 1 mm in diameter, analysis is performed in the depth direction using GDS, and the QDP (Quantitative Depth Profile) method defined in JIS K 0150 is applied to each depth of 50 nm. Measure the nitrogen concentration. Thereby, the nitrogen concentration distribution in the nitride layer can be obtained. Moreover, the average nitrogen concentration of the whole nitride layer can be calculated | required by calculating the average of each nitrogen concentration for every 50 nm depth.

Before forming the nitrided layer, it is desirable that the surface of the roll (base material) be mirror-polished. It is also desirable to perform shot blasting. As a result, the roll surface properties can be improved, the adhesion between the CrN film and the substrate can be improved, and as a result, excellent adhesion resistance can be obtained.

[CrN coating (hard coating)]
The Vickers hardness of the CrN film is 800 to 2000. The hardness of the CrN film is preferably high from the viewpoint of improving the wear resistance of the titanium tube forming roll 1. Therefore, in the present embodiment, the Vickers hardness of the CrN film is preferably 800 or more, more preferably 1200 or more, and even more preferably 1500 or more.

On the other hand, since an excessive increase in the hardness of the CrN film may cause cracks, the Vickers hardness of the CrN film is preferably 2000 or less.

The thickness of the CrN film is not particularly limited, but is preferably 0.5 μm to 5.0 μm. If the CrN film is too thin, unevenness may occur during film formation, and adhesion resistance may be insufficient. On the other hand, if the CrN film is excessively thick, the hardness is improved, but the film is liable to be cracked and may become brittle, and the production cost is increased from an economical viewpoint, which is not preferable. For these reasons, the thickness of the CrN film is preferably 0.5 μm to 5.0 μm.

The film forming method of the CrN film is not particularly limited, but it is preferable to use a PVD method (physical vapor deposition method) because adhesion to the substrate can be secured and the hardness of the formed film can be improved. Although the CrN film according to the present embodiment can be formed by other vapor deposition methods (for example, CVD method), there is a risk that the hardness may be insufficient or the film thickness of the CrN film may be excessively increased. As the film forming method, the PVD method is preferably used.

The CrN film may have a single layer structure or a multilayer structure in which two or more layers are laminated. However, as described above, if the film thickness of the CrN film becomes too thick, cracks may occur, and a multi-layer structure causes a decrease in productivity and an increase in manufacturing cost. A single layer structure is preferable.

[Diamond-like carbon film (DLC film)]
Of the titanium tube forming roll 1, the driving roll for pulling the titanium tube 10 in the conveying direction is more severe in use environment and usage conditions than the non-driving roll, so that it has not only wear resistance and adhesion resistance. That is, the anti-peeling property and the excellent low friction property of the surface of the roll recess 4 are required.

In this embodiment, a high-hardness DLC film made of carbon with sp ² hybrid orbitals (sp ² structure) and carbon with sp ³ hybrid orbitals (sp ³ structure) is formed on the CrN film.

However, just forming a high-hardness DLC film on the CrN layer causes a hardness disparity (strength discontinuity) between the CrN layer and the DLC film (interface), and the interface between the CrN layer and the DLC film. As a result, stress is easily concentrated in the steel layer, and as a result, sufficient adhesion between the CrN layer and the DLC film cannot be secured, and the DLC film may be peeled off during the formation of the titanium tube 10.

Therefore, it is important to control the hardness distribution (hardness gradient) in the film thickness direction of the DLC film so as to reduce the hardness difference between the CrN layer and the DLC film.

Specifically, in the DLC film, the ratio I ₁₃₈₀ / I ₁₅₄₀ between the absorption intensity I ₁₃₈₀ at a wave number of ₁₃₈₀ cm ^{−1 and} the absorption intensity I ₁₅₄₀ at a wave number of 1540 cm ⁻¹ measured by Raman spectroscopy is measured from the film surface. Control to be 0.5 to 0.7 in the region up to 0.20 t (upper layer region) and 0.3 to 0.5 in the region (lower layer region) from the interface between the DLC film and the CrN film to 0.20 t. Then, a hardness gradient is applied such that the proportion of the sp ³ structure decreases (hardness decreases) from the film surface toward the CrN film side.

As described above, I ₁₃₈₀ is an absorption intensity at a wave number of 1380 cm ⁻¹ measured in Raman spectroscopy, a so-called “D band”, and the other I ₁₅₄₀ is a wave number of 1540 cm measured in Raman spectroscopy. The absorption intensity at ⁻¹ , the so-called “G band”, can be used as a measure of the sp ³ structure by calculating I ₁₃₈₀ / I ₁₅₄₀ (D / G).

DLC is a mixture of carbon having a relatively high carbon ratio in sp ³ hybrid orbitals (diamond structure) and carbon having a relatively high carbon ratio in sp ² hybrid orbitals (graphite structure). That is, when the sp ³ structure is increased, the properties are closer to diamond (high hardness), and when the sp ² structures are increased, the properties are closer to graphite (soft).

Therefore, the film thickness direction of the DLC film is controlled by controlling the ratio of the sp ³ structure and the sp ² structure in the DLC film so that the lower layer area on the CrN film side is soft and the upper layer area on the film surface side is hard. The hardness difference between the CrN layer and the DLC film can be reduced.

As described above, since the Vickers hardness of the CrN layer is 800 to 2000, it is desirable that the lower layer region of the DLC film has a Vickers hardness of 1500 to 3000 and the upper layer region of 3000 to 3500.

Thus, by making the upper layer region of the DLC film hard with an increased proportion of the sp ³ structure, it is possible to exhibit excellent wear resistance with respect to the titanium tube 10, and the upper layer region has an sp ² hybrid orbital ( Low friction is also ensured because it contains some carbon (graphite structure). On the other hand, by making the lower layer region of the DLC film soft with the ratio of the sp ³ structure being suppressed, the hardness difference with the CrN layer can be alleviated and peeling resistance can be ensured.

Furthermore, since the DLC film has a low affinity with titanium, it can also have good adhesion resistance.

It should be noted that I ₁₃₈₀ / I ₁₅₄₀ can be measured by Raman spectroscopy. In Raman spectroscopy, the sample surface is irradiated with laser light, etc., and the Raman scattered light emitted by the sample is dispersed, and the molecular structure and bonding state of the sample surface are revealed from the difference in wavelength between the incident light and the Raman scattered light. It is a technique to make.

The thickness of the DLC film is not particularly limited and is preferably in the range of 0.5 to 2.0 μm, but may be appropriately determined depending on the production method, its conditions, the usage environment of the titanium tube forming roll 1, and the like.

The DLC film according to this embodiment can be formed by, for example, a plasma CVD method.

In order to control the ratio of the sp ³ structure and the sp ² structure in the DLC film as described above, each condition (film formation condition) of the plasma CVD method may be adjusted. Specifically, the ratio of the sp ³ structure and the sp ² structure in the DLC film can be adjusted by appropriately adjusting the type and ratio of the reaction gas, the substrate temperature, the cathode voltage, the degree of vacuum, and the like. In other words, as long as the above-described hardness gradient is provided in the film thickness direction of the DLC film, the film formation may be performed while appropriately adjusting the film formation conditions. May be.

The reaction gas can be a mixed gas of CH ₄ and H ₂ or only CH ₄ gas. When a mixed gas is used as the reaction gas, the ratio of the sp ³ structure and the sp ² structure can be adjusted by adjusting the flow rate of each gas, and when only the CH ₄ gas is used, other conditions may be adjusted.
In the DLC film according to the present embodiment, it is important that the sp ³ structure and the sp ² structure have a desired ratio, and therefore it is not preferable that a large amount of H (hydrogen) is mixed in the film. Therefore, it is better to suppress H ₂ to an appropriate amount as a reaction gas.

Since the film formation conditions described above are affected by the type and specifications of the plasma CVD apparatus used, the ratio of the sp ³ structure and the sp ² structure may be adjusted while examining the Raman peak of the generated DLC film.

In addition to the above, the DLC film according to the present embodiment can be formed by an unbalanced magnetron sputtering (UBMS) method. At this time, it is possible to gradually increase the hardness of the film from the interface with the CrN film toward the surface by changing the flow ratio of methane gas to Ar gas.

In addition, until the CrN film is formed on the substrate and the DLC film is formed, the surface of the CrN film is exposed to the atmosphere and is easily contaminated. Therefore, in this embodiment, it is desirable to perform plasma cleaning on the surface of the CrN film before forming the DLC film, and to decompose and remove the dirt on the surface before forming the DLC film. Thereby, the adhesiveness between the CrN film and the DLC film can be further improved.

[Second example of titanium tube roll and titanium tube manufacturing method]
Next, a second example of a titanium tube roll and a titanium tube manufacturing method according to an embodiment of the present invention will be described with reference to FIGS.

3 and 4 show a titanium tube forming roll 11 which is a second example of the present embodiment. The titanium tube forming roll 11 shown in FIGS. 3 and 4 is a so-called perforated roll (caliber roll), and includes a roll body 12 made of a steel material and a rotating shaft 3 inserted through the roll body 12. On the roll surface 12 a of the roll body 12, a roll recess 14 formed in a semicircular shape in cross section is provided over the entire circumference of the roll body 12. Moreover, a nitride layer, a CrN film, and a DLC film are formed in this order on the base material on the surface of the roll recess 14 that is a rolled surface.

The roll body 12 includes a roll center portion 21, a pair of rotating flange portions 22 that are disposed on both sides of the roll center portion 21 and are rotatable with respect to the roll center portion 21, and a pair of fixed flange portions 23. Is provided. The roll recess 14 is divided by a roll center portion 21 and a rotating flange portion 22. A first bearing portion 24 is provided between the roll center portion 21 and the rotating flange portion 22, and a second bearing portion 25 is provided between the fixed flange portion 23 and the rotating flange portion 22. Yes. Further, the roll center portion 21 and the fixing flange portion 23 are fixed to each other by a fixing bolt 26.

The roll center portion 21 is fixed to the rotary shaft 3 that drives the roll body 12. On the other hand, the rotating flange portion 22 is rotatable with respect to the rotating shaft 3 and the roll center portion 21. The fixing flange portion 23 is fixed to the roll center portion 21 by fixing bolts 26. That is, the fixed flange portion 23 is fixed to the rotating shaft 3 integrally with the roll center portion 21. As the rotating shaft 3 rotates, the roll center portion 21 and the fixed flange portion 23 rotate. On the other hand, since the rotation flange portion 22 is rotatable with respect to the roll center portion 21 and the fixed flange portion 23 by the first and second bearing portions 24 and 25, the roll center portion 21 and the fixed flange portion 23. Does not work with. Hereinafter, each part will be described in detail.

The roll center portion 21 includes a cylindrical base portion 21a through which the rotary shaft 3 is inserted, and a protruding portion 21b protruding from the center of the base portion 21a in the roll width direction. The base portion 21a is provided with an insertion hole 21c for allowing the rotary shaft 3 to pass therethrough. The upper surface 21d of the protruding portion 21b is formed in a round groove shape that is recessed toward the rotating shaft 3 and is continuous over the entire circumference of the roll body 12, and this upper surface 21d constitutes a part of the roll concave portion 14. Yes. The roll center portion 21 is composed of a base material having the chemical composition described in the first example. The upper surface 21d of the roll central portion 21 is provided with the CrN film and the DLC film described in the first example.

The rotating flange portion 22 is a substantially ring-shaped member, and is fitted on the outer peripheral side of the base portion 21a of the roll center portion 21 and on both sides of the protruding portion 21b in the roll width direction. In this manner, the rotating flange portion 22 is disposed on both sides of the protruding portion 21b in the roll width direction on the base portion 21a. A first bearing 24 is disposed between the base portion 21 a of the roll center portion 21 and the rotating flange portion 22. Further, a gap of about 0.1 mm is provided between the side wall surface 21 b ₁ of the protruding portion 21 b of the roll center portion 21 and the rotating flange portion 22. By this gap and the first bearing portion 24, the rotating flange portion 22 is rotatable without sliding with respect to the roll center portion 21. Further, the outer peripheral inclined surface 22 a of the rotating flange portion 22 is formed into a concave arc surface when viewed in cross section, and is an arc surface continuous with the upper surface 21 d of the roll center portion 21. Thereby, the roll concave portion 14 is constituted by the outer peripheral inclined surface 22 a of the rotating flange portion 22 and the upper surface 21 d of the roll center portion 21.

Further, as can be seen from a cross-sectional view of the rotating flange portion 22, the tip end portion 22d including the outer peripheral inclined surface 22a of the rotating flange portion 22 is bent so as to cover the tip of the protruding portion 21b. Thereby, when the rotation flange part 22 receives the load from the titanium pipe | tube 10, it becomes possible to fully receive a load.

Rotating flange portion 22 is composed of a base material having the chemical composition described in the first example. Further, the outer peripheral inclined surface 22a of the rotating flange portion 22 is provided with the CrN film and the DLC film described in the first example. Further, a CrN film and a DLC film may be provided on the entire surface of the rotating flange portion 22.

Next, the 1st bearing part 24 is provided with the rolling element which consists of needle rollers which are not shown in figure, and the holder | retainer which is not shown in figure which hold | maintains several rolling elements. Then, a face adjacent to the first bearing portion 24, and the outer peripheral surface 21a ₁ of the base portion 21a of the roll central portion 21, and the inner peripheral surface 22b of the rotating flange 22, the trajectory of the rolling elements of the first bearing portion 24 It is a surface. In other words, the base 21a of the roll center portion 21 and the rotating flange portion 22 are an inner race and an outer race of the first bearing portion 24, respectively. In this embodiment, also on the inner peripheral surface 22b and these outer peripheral surfaces 21a _1, as in the first example, on a substrate, a nitride layer, CrN coatings and DLC film are formed in this order.

Next, the fixed flange portion 23 is a substantially disk-like member, and is a member provided with an insertion hole 23a through which the rotary shaft 3 can be inserted at the center. The fixed flange portions 23 are disposed on both sides of the roll body 12 in the roll width direction. A portion of the fixed flange portion 23 near the rotation axis is fixed to the base portion 21 a of the roll center portion 21 by a fixing bolt 26. Further, the portions near the outer periphery of the fixed flange portion 23 are located on both sides of the rotating flange portion 22 in the roll width direction and face the rotating flange portion 22. A second bearing portion 25 is disposed between the fixed flange portion 23 and the rotating flange portion 22.

The fixed flange portion 23 is composed of a base material having the chemical composition described in the first example. Moreover, the nitrided layer, CrN film | membrane, and DLC film which were demonstrated in the 1st example may be provided in the opposing surface 23b facing the rotation flange part 22 among the fixed flange parts 23. FIG.

The second bearing portion 25 includes a rolling element made of needle rollers (not shown) and a cage (not shown) that holds a plurality of rolling elements. On the other hand, the opposing surface 23b of the fixed flange portion 23 and the side surface 22c of the rotating flange portion 22, which are surfaces adjacent to the second bearing portion 25, are raceway surfaces of the rolling elements of the second bearing portion 25. . In other words, the facing surface 23b of the fixed flange portion 23 and the side surface 22c of the rotating flange portion 22 are races of the second bearing portion 25, respectively. In the present embodiment, a nitride layer, a CrN film, and a DLC film are formed in this order on the base material on the facing surface 23b and the side surface 22c as in the first example.

As shown in FIG. 4, the titanium tube forming roll 1 of this example removes the fixing bolt 26, thereby removing the roll main body 12 from the roll center portion 21, the rotating flange portion 22, the fixing flange portion 23, and the first. The bearing part 24 and the second bearing part 25 can be disassembled.

With the above configuration, when the titanium tube 10 is formed, the roll center portion 21 and the fixed flange portion 23 are rotated by the rotational drive of the rotary shaft 3. When the titanium tube 10 is inserted between the pair of titanium tube rolls 1 in this state, the upper surface 21 d of the roll center portion 21 contacts the titanium tube 10 and transmits the rotational torque of the rotating shaft 3 to the titanium tube 10. On the other hand, the titanium tube 10 also contacts the outer peripheral inclined surface 22 a of the rotating flange portion 22, but the rotating flange portion 22 is rotated by the titanium tube 10 in accordance with the movement of the titanium tube 10. At this time, since the peripheral speed of the outer peripheral inclined surface 22 a is smaller than the peripheral speed of the upper surface 21 d of the roll center portion, the rotational speed of the rotating flange portion 22 is smaller than the rotational speed of the roll center portion 21. The rotating flange portion 22 is rotatable with respect to the roll center portion 21 and the fixed flange portion 23 by the first and second bearing portions 24 and 25, respectively. Since there is a gap of about 0.1 mm between the protruding portion 21 b of the portion 21, the rotating flange portion 22 rotates at a rotation speed smaller than the rotation speed of the roll center portion 21. Thereby, the slip rate of the roll with respect to the titanium tube 10 is reduced as a whole, and the generation of wrinkles in the titanium tube 10 is suppressed.

Further, when the titanium tube 10 is inserted between the pair of titanium tube forming rolls 1 and the titanium tube 10 enters the roll recess 14, the rotating flange portion 22 is slightly pushed outward in the roll width direction and the fixed flange portion 23. On the other hand, a gap of about 0.1 mm is secured between the rotating flange portion 22 and the protruding portion 21b of the roll center portion 21. Thereby, the rotation flange part 22 rotates smoothly, without the rotation flange part 22 and the protrusion part 21b rubbing.

Next, the preferred range of the width of the protruding portion 21b of the roll center portion 21 and the slip rate of the roll will be described with reference to FIGS.

As shown in FIG. 5, the width W of the upper surface 21d of the protruding portion 21b of the roll central portion 21 is in the range of 0.7D to 0.87D, where D is the outer diameter of the titanium tube serving as the workpiece. preferable. Here, as shown in FIG. 5, the boundary position between the upper surface 21 d of the roll center portion 21 and the outer peripheral inclined surface 22 a of the rotating flange portion 22 is A, and the direction from the central axis O of the titanium tube 10 toward the boundary position A And the horizontal direction is θ, the boundary position A when the width W is 0.7D is θ = 45 °, and the boundary position A when the width W is 0.87D is θ = 30 ° position. That is, in the present embodiment, the boundary position A may be set so that the angle θ is in the range of 30 to 45 °. The reason for this will be described below.

FIG. 6A is a schematic diagram for explaining the slip ratio in the non-dividing type driving roll. In the case of a driving roll, the pinch position where the rotational torque can be most efficiently transmitted to the titanium tube 10 is the bottom of the roll recess 4. Therefore, the roll diameter at the lowermost portion of the roll recess 14 and R _d, the roll diameter at the pinch position and R _p, when the roll diameter of the flange portion upper surface of the roll and R _f, slip ratio to titanium pipe in the flange portion near the top surface Is as follows.

(Flange portion) Slip rate = (R _f −R _p ) / R _p (1)

For example the outer diameter D of the titanium tube and _25mm, R _d = _50mm, when the R f = 62.25mm, because _{R p} is substantially equal to _{R d (R p = R d} = 50mm), the slip in the drive roll The rate is 0.245.

Next, FIG. 6B is a schematic diagram for explaining the slip ratio in the non-dividing type non-driving roll. The pinch position in the case of a non-driving roll is in the middle between the bottom of the roll recess 4 and the upper surface of the flange. In this case, the slip ratio with respect to the titanium tube in the vicinity of the upper surface of the flange portion is, for example, that the outer diameter D of the titanium tube is 25 mm, R _d = 50 mm, R _f = 62.25 mm, R _p = 56.125 mm. Is introduced into the above equation (1), the slip ratio of the non-driving roll becomes 0.109.

As is clear from the comparison between FIG. 6A and FIG. 6B, the driving roll has a higher slip rate than the non-driving roll, and the titanium tube 10 is easily wrinkled, and the roll itself is easily worn. .

Next, as shown in FIG. 6C, the split type driving roll of this embodiment will be examined. In the titanium tube forming roll 11 of this embodiment, the roll center part 21 functions as a driving roll, and the rotating flange part 22 functions as a non-driving roll. Then, R _f , R _p and R _d are as shown in FIG.

Here, as shown in FIG. 5, when the boundary position A is at the position of θ = 30 °, the slip rate at the roll center portion 21 is 0.1225, the slip rate at the rotating flange portion 22 is 0.0517, Both are smaller than the slip ratio (0.125) of the non-split type non-driving roll in FIG. However, when the angle θ is less than 30 °, the slip ratio becomes larger than the slip ratio (0.125) of the non-split type non-driving roll.

Further, as shown in FIG. 5, when the boundary position A is at a position of θ = 45 °, the slip ratio at the roll center portion 21 is 0.073, and the slip ratio at the rotating flange portion 22 is 0.076. In either case, the slip ratio (0.125) of the non-split type non-driving roll in FIG. However, when the angle θ exceeds 45 °, the width of the outer peripheral inclined surface 22a of the rotating flange portion 22 becomes too small to fully receive the load of the titanium tube 10, and the rotating flange portion 22 may be damaged. .

From the above, the angle θ shown in FIG. 5 is preferably in the range of 30 to 45 °. When this is represented by the width W of the upper surface 21d of the protruding portion 21b of the roll central portion 21, the width W is in the range of 0.7D to 0.87D, where D is the outer diameter of the titanium tube 10 serving as a workpiece. . Within this range, the titanium tube 10 can be molded without causing wrinkles, and damage to the rotating flange portion 22 can be prevented.

As described above, according to the titanium tube forming roll 11 of the second example of the present embodiment, the roll main body 12 is disposed on both sides of the roll central portion 21 and the roll central portion 21 so as to be in the roll central portion 21. Since the roll recess 14 is divided by the roll center portion 21 and the rotation flange portion 22, the rotation flange portion 22 and the titanium tube are formed. Accordingly, the titanium tube 10 is less likely to be wrinkled, and the CrN film and the DLC film formed on the rotating flange portion 22 are not easily peeled off. Thus, according to the titanium tube forming roll 1 of this example, wear resistance, adhesion resistance, and peel resistance are improved, and the friction coefficient of the roll surface can be reduced.

Further, the roll center portion 21 is fixed to the rotating shaft 3 that drives the roll body 12, while the rotating flange portion 22 is rotatable with respect to the rotating shaft 3 and the roll center portion 21. When the shaft 3 is a drive shaft, the roll central portion 21 is a drive roll, the rotation flange portion 22 is a non-drive roll, and the slip rate in the rotation flange portion 22 that is a non-drive roll is reduced. 10 can be prevented, and peeling of the CrN film and the DLC film formed on the rotating flange portion 22 can be suppressed. Thereby, the durability of the titanium tube forming roll 1 can be improved, and the frequency of maintenance can be reduced.

Further, when the outer diameter of the titanium tube 10 serving as a workpiece is D, the slip ratio with respect to the titanium tube 10 is reduced by setting the width of the roll concave portion 14 in the roll central portion 21 in the range of 0.7D to 0.87D. In addition, the rotating flange portion 22 can be prevented from being damaged.

Further, the roll central portion 21 is provided with a base portion 21a and a protruding portion 21b. The rotating flange portions 22 are disposed on both sides of the protruding portion 21b in the roll width direction on the base portion 21a. Since the first bearing portion 24 is provided between the rotation flange portion 22 and the roll center portion 21, the rotation flange portion 22 can be smoothly rotated.

Further, when the titanium tube 10 enters the roll recess 14, the rotating flange portion 22 is slightly pushed outward in the roll width direction, and a gap of about 0.1 mm is secured between the rotating flange portion 22 and the protruding portion 21 b. Thus, the rotating flange portion 22 can be smoothly rotated without the rotating flange portion 22 and the protruding portion 21b rubbing against each other.

Moreover, the opposing surface which mutually opposes between the base 21a of the roll center part 21 and the rotation flange part 22 is made into the track surface of the rolling element of the 1st bearing part 24, and CrN membrane | film | coat and DLC film | membrane are formed in these opposing surfaces. Therefore, the life of the first bearing portion 24 can be extended. In addition, since the first bearing portion 24 itself can be reduced in size, the roll body 12 can be made smaller and the equipment can be made compact.

Further, the roll main body 12 is provided with a fixed flange portion 23 and a second bearing portion 25, and the second flange portion 23 prevents the turning flange portion 22 from falling off from the roll center portion 21 by the fixed flange portion 23. The rotating flange portion 22 can be smoothly rotated by the bearing portion 25.

Further, the opposing surfaces that face each other between the fixed flange portion 23 and the rotating flange portion 22 are the raceway surfaces of the rolling elements of the second bearing portion 25, and on these opposing surfaces, the nitride layer, the CrN coating, and the DLC Since the film is provided, the life of the second bearing portion 25 can be extended. In addition, since the second bearing portion 25 itself can be reduced in size, the roll body 12 can be reduced in size and the equipment can be made compact.

Further, as shown in FIG. 4, the titanium tube forming roll 1 of the present example removes the fixing bolt 26, so that the roll main body 12 is moved to the roll center portion 21, the rotating flange portion 22, the fixing flange portion 23, Since the first bearing portion 24 and the second bearing portion 25 can be disassembled, maintenance work can be easily performed. For example, when only the rotating flange portion 22 is worn and the CrN film and the DLC film are peeled off, it can be immediately used by replacing the spare rotating flange portion 22 with the titanium tube. Can continue. Further, the removed rotating flange portion 22 can be made into a reusable state only by forming a nitride layer, a CrN film, and a DLC film at a place where repair is necessary.

Moreover, the CrN film and the DLC film according to the present embodiment can extend the life of the titanium tube forming roll 1 by forming the film on not only the surface of the roll recess 14 but also every part. For example, as described above, a nitride layer, a CrN film, and a DLC film are originally formed on the portions that serve as the raceway surfaces of the rolling elements of the first and second bearing portions 24 and 25, so that the wear resistance and fatigue resistance are inherently achieved. Even if it is a place where the material for bearings excellent in is applied, it becomes possible to make a raceway surface of the rolling element by forming a nitride layer, a CrN film and a DLC film on the base material of the roll body 14. . In addition, by forming a nitride layer, a CrN film, and a DLC film on the surface of the roll center portion 21 where the protruding portion 21b and the rotating flange portion 22 face each other, wear of the protruding portion 21b and the rotating flange portion 22 is prevented. Can be prevented.

The titanium tube forming roll of the second example has been described above, but in this example, the modification shown in FIG. 7 or FIG. 8 may be adopted.

7, when the roll body 12 is viewed in cross section, the boundary surface between the rotating flange portion 22 and the protruding portion 21b extends straight toward the outer peripheral direction of the roll body 12. According to the example of FIG. 7, the shapes of the rotating flange portion 22 and the protruding portion 21 b can be made relatively simple as compared with the case of FIG. Accuracy can be increased. The example of FIG. 7 can be applied when the load received from the titanium tube 10 is relatively small.

Further, in the modification shown in FIG. 8, when the roll main body 12 is viewed in cross section, the distal end portion 22d of the rotating flange portion 22 is bent almost right side. Also in the example of FIG. 8, the shapes of the rotating flange portion 22 and the protruding portion 21 b can be made relatively simple compared to the case of FIG. Can be increased. The example of FIG. 8 can also be applied when the load received from the titanium tube 10 is relatively small.

[Third example of titanium tube roll and titanium tube manufacturing method]
Next, a third example of a titanium tube roll and a titanium tube manufacturing method according to an embodiment of the present invention will be described with reference to FIG. The difference between the titanium tube forming roll 31 shown in FIG. 9 and the titanium tube forming roll 11 of the second example shown in FIGS. 3 to 4 is that the mechanism for fixing the rotating flange portion 22 to the fixed flange portion 23 is different. There are no differences in other points. In the following description, a mechanism for fixing the rotating flange portion 22 to the fixed flange portion 23 will be described.

FIG. 9 shows a titanium tube forming roll 31 which is a third example of the present embodiment. The titanium tube forming roll 31 is provided with a pulling screw portion 32 that pulls and fixes the rotating flange portion 22 to the fixing flange portion 23. For example, the pulling screw portion 32 is provided at three locations of the fixing flange portion 23. The pulling screw portion 32 includes a detachable bolt 32a and a screw hole 32b into which the detachable bolt 32a is inserted. The screw holes 32b are provided in the fixed flange portion 23 and the rotating flange portion 22, respectively.

When forming the titanium tube 10, the detachable bolt 32 a is removed so that the rotating flange portion 22 is rotatable with respect to the fixed flange portion 23 and the roll center portion 21.

On the other hand, when repairing the roll recess 14 of the titanium tube forming roll 31, the detachable bolt 32a is inserted into the screw hole 32b and tightened. As a result, the rotating flange portion 22 is drawn toward the fixed flange portion 23 and is in close contact with the fixed flange portion 23, while 0.1 mm is provided between the rotating flange portion 22 and the protruding portion 21 b of the roll center portion 21. A gap of a degree is generated. This state is substantially the same as the state in which the rotating flange portion 32 is pushed toward the fixed flange portion 23 while the titanium tube 10 is being formed. And the roll recessed part 14 is repaired in the state which the rotation flange part 22 and the fixed flange part 23 contact | adhered. Specifically, the inner surface of the roll recess 14 is polished so as to restore the roundness when the roll recess 14 is partially worn and the roundness is lowered. That is, repair is performed in the same state as when the rotating tube 22 is pulled toward the fixed flange 23 and the titanium tube 10 is molded.

As described above, the titanium tube forming roll 31 of this example is provided with the pulling screw portion 32 that fixes the rotating flange portion 22 and the fixing flange portion 23 in close contact with each other, and repairs the roll recess 14. In doing so, the rotating flange portion 22 can be in the same state as when the titanium tube 10 is molded, so that the roundness of the roll recess after repair can be increased.

[Method and apparatus for manufacturing titanium tube]
The titanium tube forming apparatus according to the present embodiment includes any of the titanium tube forming rolls 1, 21, and 31 described above, and lubricates a part of the titanium tube forming rolls 1, 21, and 31 during titanium tube forming. A lubrication nozzle for supplying the agent is provided. Although it is preferable to use a lubricant, the supply of the lubricant is not essential because the production is possible without using the lubricant. In addition, it is preferable to use a lubrication nozzle for supplying the lubricant, but other methods may be used.

In general, when a titanium pipe is actually formed, a water-soluble lubricant is often used for prevention of pipe flaws and cooling in a standard process after welding the titanium pipe.

Therefore, in order to further improve the life of the titanium tube forming roll according to the present embodiment and prevent roll marks and wrinkles on the roll surface, the titanium tube forming apparatus according to the present embodiment has a It is preferable to provide a lubricating nozzle for supplying a lubricant.

Hereinafter, an example of a titanium tube forming apparatus having a lubrication nozzle will be described with reference to the drawings. However, the drawings shown below are for explaining the configuration of the titanium tube forming apparatus, The size, thickness, dimensions, and the like may differ from the actual dimensional relationship of the heating furnace.
Various methods can be applied to the welding of the titanium tube, but TIG welding is preferable.

10A and 10B are diagrams showing a titanium tube forming apparatus according to the present embodiment, in which FIG. 10A is a schematic front view, FIG. 10B is a side view showing a configuration in the vicinity of the lubricating nozzle 101, and FIG. ) Is a cross-sectional view showing a configuration in the vicinity of the lubricating nozzle 101. 11A and 11B are diagrams for explaining an arrangement example of the lubricating nozzle 101, where FIG. 11A is a schematic front view, and FIG. 11B is a schematic side view. 12A and 12B are diagrams for explaining in detail the width direction adjusting mechanism and the vertical direction adjusting mechanism of the lubricating nozzle 101, wherein FIG. 12A is a schematic top view of the titanium tube forming apparatus, and FIG. 12B is a schematic side view. FIG.

The titanium tube 10 is conveyed while being formed by titanium tube forming rolls 1, 21, 31 arranged so as to face each other in the vertical direction.

At this time, in the vicinity of the roll flange part (roll parallel part at the end of the hole mold) where the forming rolls 1, 21, 31 and the titanium tube 10 are in contact, wear due to friction and generation of wrinkles are more likely to occur than other parts. . Therefore, when forming the titanium tube 10, the lubricant needs to be dropped in the vicinity of the roll flange portion.

However, the position of the roll flange portion changes each time due to a change in the diameter of the titanium tube forming rolls 1, 21, 31 or the like. Therefore, the position of the lubricating nozzle 101 for dropping the lubricant must be adjusted each time. Therefore, in this embodiment, when the lubricating nozzle 101 for dropping the lubricant is disposed, it is preferable to provide an expansion / contraction mechanism that can adjust the dropping position of the lubricant in the width direction and the vertical direction.

A mechanism for expanding and contracting the lubricating nozzle 101 according to the present embodiment in the width direction will be described.

As shown in FIG. 10, a pipe-like horizontal movement guide 103 provided with a width movement groove (long groove) 118 is disposed in front of the forming rolls 1, 21, 31, and on the horizontal movement guide 103, The lubrication nozzle fixing base 102 and the lubrication nozzle 101 placed on the lubrication nozzle fixing base 102 are provided via a width movement guide 119 fitted in the width movement groove 118. The width moving guide part 115 connected to the lubrication nozzle angle adjusting jig 109 provided so as to be slidable is a width adjusting screw (left and right from the center are forward and reverse screws, respectively, and when the adjusting screw is rotated, The right guide portion 115 is symmetrically moved in the opposite direction) (see FIG. 12) and has a mechanism that expands and contracts in the width direction.

Further, as a mechanism for expanding and contracting the lubricating nozzle 101 in the vertical direction, a dovetail base 107 fixed to the forming stand column 117 and a center position adjusting jig 106 provided so as to be slidable in the vertical direction with respect to the dovetail base 107 are provided. And the vertical position of the lubricating nozzle 101 is adjusted by the vertical movement screw 116 inserted into the center position adjusting jig 106. Since the center position adjustment jig 106 is also connected to the horizontal movement guide 103, when the center position adjustment jig 106 moves in the vertical direction on the dovetail pedestal 107, the horizontal movement guide 103, that is, the lubrication nozzle 101 is similarly moved up and down. Will move in the direction.

The vertical movement screw 116 is connected to the vertical position adjustment handle 104. By turning the vertical position adjustment handle 104, the vertical movement of the center position adjustment jig 106 can be controlled, and lubrication according to the roll flange portion is performed. The nozzle 101 can be adjusted in the vertical direction.

Further, the angle adjustment for positioning the lubricating nozzle 101 in consideration of the contact with the titanium tube 10 due to the variation of the diameters of the titanium tube forming rolls 1, 21, 31 is performed by a lubricating nozzle sandwiching jig (lubricating nozzle front-rear adjusting jig) 113. The lubrication nozzle angle adjustment jig 109 can be adjusted by rotating it with the lubrication nozzle angle fixing screw 112.

The mechanism in which the lubrication nozzle 101 moves back and forth can be adjusted by the lubrication nozzle angle fixing screw 112 in an apparatus having a lubrication nozzle sandwiching jig (lubricating nozzle longitudinal adjustment jig) 113.

By these mechanisms, the lubricant can be dropped in the vicinity of the roll flange portion where the titanium tube forming rolls 1, 21, 31 and the titanium tube 10 are in contact.

Here, as the lubricant, water or an emulsion or a soluble oil-based lubricant that is usually used for forming a metal tube can be used as the lubricant. However, the lubrication performance and the ease of removing the lubricant adhering to the product are eliminated. From this point of view, a soluble oil lubricant which is a water-soluble cutting fluid is most suitable.

The lubrication nozzle 101 needs to be adjusted in position so as to correspond to the roll flange portion according to the titanium tube size (roll flange width). In addition, depending on the state of roll lubrication, it is necessary to drop the upper part of the titanium tube forming rolls 1, 21, and 31 from the top of the roll.

FIG. 11 is a schematic front view for explaining an arrangement example of the lubrication nozzle 101. The titanium pipe forming apparatus as described above is provided with front / rear / up / down and left / right adjustment mechanisms of the lubrication nozzle 101. FIG. Therefore, the position of the lubrication nozzle 101 can be appropriately changed to a desired position in accordance with the flange width of the titanium tube forming rolls 1, 21, 31.

The width direction adjusting mechanism and the vertical direction adjusting mechanism of the lubricating nozzle 101 will be described in detail with reference to FIG.
In addition, in order to make it easy to explain each direction adjustment mechanism of the lubrication nozzle 101, description is omitted about some members in FIG.

At the substantially central portion in the pipe-shaped horizontal movement guide 103, two width adjusting screws 114 (left and right screws) that are reversed in the forward and reverse directions are arranged. The width adjusting screw 114 is connected to a left / right position adjusting handle 105 installed in the horizontal moving guide 103, and the horizontal moving guide 103 can be moved in the horizontal direction by turning the left / right position adjusting handle 105. As a result, the expansion / contraction of the lubricating nozzle 101 in the width direction in accordance with the roll flange portion can be adjusted.

Further, the center positions of the titanium tube forming rolls 1, 21, and 31 can be adjusted by moving around the width adjusting screw 114 and adjusting the center position adjusting jig 106 provided on the dovetail pedestal 107. it can.

Further, as shown in the side view of FIG. 12, the dripping position of the lubricant can be freely changed by adjusting the front and rear of the lubrication nozzle 101 and adjusting the expansion / contraction movement position, and the titanium tube 10 and the titanium tube forming rolls 1, 21, Adjustment of the dropping position of the lubricant to the contact portion with 31 is possible.

The dovetail pedestal 107 is fixed to the molding stand column 117 via the stand column mounting jig 108, but when the stand column mounting jig 108 is fixed to the molding stand column 117, it is easily attached by the stand fixing screw 120. It is a cantilever format that you can.

FIG. 13 is a view showing the structure of a roller pump (lubricant supply device) for dripping a small amount of lubricant using the lubrication nozzle 101.

Lubricant is transported while crushing a tube 132 called a tube pump by a roller 130 that rotates and revolves around a central axis 131 in order to attach a small amount of a thick lubricant equivalent to the stock solution to the roll.

As a lubrication method, a tube 132 having an inner diameter of 3 mm or less is used, and a minute amount is dropped using a contamination-free tube (roller) pump having a dropping speed of 20.0 ml / hr or less.

Here, it is appropriate to use a tube having an inner diameter of 0.5 mm or more and 3.0 mm or less as the lubrication nozzle 101 in order to supply an appropriate amount of lubricant.

Furthermore, it is suitable to supply the lubricant by dripping a small amount of the lubricant at a dropping speed of 1 ml / hr or more and 20 ml / hr or less.

When the supply rate of the lubricant is less than 1.0 ml / hr, the function as a lubricant cannot be sufficiently exhibited. On the other hand, when the supply rate exceeds 20.0 ml / hr, the function as a lubricant is saturated, Rather, the titanium tube forming rolls 1, 21, and 31 are idled, which may interfere with titanium tube forming and increase the amount of lubricant to be removed from the final product, increasing the manufacturing cost.

As described above, according to the titanium tube forming roll according to the present invention, a CrN coating that is hard and has low affinity with titanium and excellent affinity with Cr in the substrate, and Since the DLC film is formed, wear resistance and adhesion resistance can be improved. In addition, in the DLC film, the hardness difference between the CrN layer and the DLC film can be reduced by providing an inclination of the hardness in the film thickness direction of the DLC film. As a result, the upper layer region of the DLC film is made hard so that it can exhibit excellent wear resistance against the titanium tube, and it also contains some sp ² hybrid orbital (graphite structure) carbon and has low friction. Can be secured. By making one lower layer region soft, the hardness disparity with the CrN layer can be relaxed and peeling resistance can be secured.

Also, when the titanium tube is formed, the friction coefficient of the forming roll, particularly the driving roll, can be reduced by forming the lubricant while dropping a small amount of lubricant on a part of the forming roll. By preventing the adhesion of the roll flange portion due to the large peripheral speed difference (large slip) due to the effect, wrinkles on the roll flange portion and roll marks generated on the drive roll can be suppressed. .

That is, according to the titanium tube forming roll, the titanium tube forming apparatus, and the titanium tube manufacturing method according to the present invention, the life of the forming roll can be remarkably improved, the replacement frequency of the forming roll can be reduced, and the manufacturing cost can be greatly reduced. . In addition, by reducing the frequency of replacement of the forming rolls by improving the life of the forming rolls, it is possible to prevent the yield from being lowered due to roll adjustment (position adjustment, etc.) at the time of roll replacement, and to improve the yield (high accuracy) by improving the forming dimensional accuracy. Can be achieved.

Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the conditions used in the following examples.

<Forming roll>
Example 1
First, the tool steel SKD11 prescribed | regulated by JISG4404 was employ | adopted as a base material of a forming roll, and quenching and tempering processing were performed.

Next, the obtained substrate surface was subjected to nitriding treatment to form a nitride layer having a thickness of 25 μm and an average nitrogen concentration of 0.20% by mass on the substrate surface layer.

The nitriding treatment used was a radical nitriding treatment in which nitriding was performed using active species having high reactivity generated by direct current glow discharge in a mixed gas atmosphere of ammonia and hydrogen (NH ₃ , H ₂ , Ar). The treatment temperature was 500 ° C. and the treatment was performed for 3 hours.

Next, a 1.5 μm μm CrN film (single layer) was formed on the surface layer (nitrided layer) subjected to nitriding treatment by PVD vapor deposition.

Next, the base material on which the CrN film was formed was processed into a roll with dimensions of a hole type R: 12.6 mm, a roll bottom diameter Dr: 100 mm, a roll outer diameter Do: 124 mm, and a roll width W: 60.0 mm. The forming roll shown in 2 was manufactured.

For the forming roll, component analysis was performed in the depth direction from the CrN coating surface using a glow discharge emission spectrometer (GDS). The analysis results are shown in FIGS. 14 to 16, the horizontal axis represents the depth (μm) from the CrN layer surface, and the vertical axis represents the concentration (mass%) of each component.

14 and 15, it can be seen that a CrN layer having a thickness of 1.5 μm is formed on the surface layer of the base material. FIG. 16 is a graph in which the vertical axis range of the graph of FIG. 14 is changed in order to confirm the concentration behavior of the element contained in a trace amount in the depth direction. From the graph of FIG. 16, it can be seen that a nitride layer is formed between the CrN film and the substrate. Further, as is apparent from the graph, it shows a gradient in which the nitrogen concentration gradually decreases from the CrN film side to the base material side, and the hardness fluctuation in the depth direction in the nitride layer is also gentle. I understand.

Next, plasma cleaning was performed on the surface of the molding roll in advance to remove dirt on the CrN film, and a DLC film was formed on the CrN film. The film thickness was 1.0 μm.

The DLC film was formed by a plasma CVD method. The apparatus used was a capacitively coupled high-frequency plasma CVD apparatus, and the temperature was 500 ° C. A high frequency power supply of 13.56 MHz was used as the plasma generation power supply. As the reaction gas, a mixed gas of CH ₄ and H ₂ was used. At this time, the hardness of the film gradually increased from the interface with the CrN film toward the surface by changing the mixing ratio of the mixed gas of CH ₄ and H ₂ .

(Comparative Example 1)
Using the tool steel SKD11 employed in Example 1 as a base material, a forming roll was produced by processing into a nitrided layer and a CrN film (single layer) roll in the same manner as in Example 1.

Next, a DLC film having a thickness of 1.0 μm was formed on the CrN film by ion plating. At this time, as usual, the mixing ratio of the mixed gas of CH ₄ and H ₂ was constant.

<Raman spectroscopy>
The ratio of sp ² hybrid orbital carbon to sp ³ hybrid orbital carbon (sp ³ / sp ² ) in the surface layer of the molding roll obtained in Example 1 and Comparative Example 1 was measured by Raman spectroscopy.

Results are shown in FIGS. 17A to 17C and FIGS. 18A to 18C and Tables 1 and 2.

17A is a micrograph of the surface layer of the forming roll of Example 1, FIG. 17B is the Raman spectrum of the surface layer of the DLC film of the forming roll of Example 1, and FIG. The Raman spectrum inside the DLC film of a forming roll is shown. 18A is a micrograph of the surface layer of the forming roll of Comparative Example 1, FIG. 18B is the Raman spectrum of the surface layer of the DLC film of the forming roll of Comparative Example 1, and FIG. 18C is the forming of Comparative Example 1. The Raman spectrum inside the DLC film of the roll is shown. In the figure, “near the surface” is a surface layer of the DLC film, “inside the DLC film”, inside the DLC film, and “near the interface” is a Raman spectrum near the interface between the DLC film and the CrN film.

Table 1 shows the Raman band parameters of Example 1, and Table 2 shows the Raman band parameters of Comparative Example 1.

As is apparent from FIGS. 17A to 17C and Table 1, in the DLC film obtained in Example 1, I ₁₃₈₀ / I ₁₅₄₀ increases as it goes from the CrN film to the DLC film.
That is, it can be seen that the hardness gradient increases as the hardness increases from the CrN film toward the DLC film.

Next, the Vickers hardness of the nitride layer, CrN film, and DLC film obtained in Example 1 and Comparative Example 1 were measured. The substrate and the nitride layer were measured with a micro Vickers hardness meter. Moreover, about the CrN film | membrane and the DLC film | membrane, the indentation test of the very low load was performed by the nanoindentation (indentation) method, and it converted into Vickers hardness. Specifically, when a load of 0.005 to 0.1 mN is applied for 20 seconds using a triangular pyramid indenter (Berkovic indenter) according to the nanoindentation (indentation) method (load 20 s, holding 5 s, unloading) The indentation hardness of 20 s) was determined as nanoindentation hardness. At this time, it measured on the conditions which become 10 times or more of indentation depth. In addition, measurement by surface grinding and side (cross-sectional) indentation by embedded polishing were used in combination. From the obtained nanoindentation hardness, Vickers hardness was calculated | required by the following conversion formula.
H _v = 0.0945 × H _IT
However, H _v in the above formula the Vickers hardness, H _IT means respectively nanoindentation hardness.

In any layer or film, three points were measured in the cross section, and the average was defined as “Vickers hardness”. The nitrided layer was measured in the vicinity of the interface with the base material (region up to 2 μm depth: inner region) and in the vicinity of the interface with the CrN coating (region up to 2 μm depth: outer region). The DLC film includes a region from the film surface to 0.20 t (near the surface), a region from the interface between the DLC film and the CrN film to 0.20 t (near the interface), and a central portion in the film thickness direction of the DLC film (DLC film). Measurements were made at a total of three locations.

The results are shown in Table 3. As shown in Table 3, in Example 1, the average Vickers hardness of each layer / film is 1000 for the nitride layer, 2000 for the CrN film, 2500 for “near the interface” of the DLC film, and “inside the DLC film” 3000, “near the surface” of the DLC film was 3500, and a hardness gradient was given in the film thickness direction.

On the other hand, as is clear from FIGS. 18A to 18C and Table 2, the DLC film obtained in Comparative Example 1 has large I ₁₃₈₀ / I _{1540 in} both “near the surface” and “inside the DLC film”. It can be seen that no hardness gradient is given in the film thickness direction.

Further, as shown in Table 3, when the Vickers hardness was measured in the same manner as in Example 1 in “near the surface”, “inside the DLC film”, and “near the interface” of the DLC film obtained in Comparative Example 1, The “near the interface” was 2000, the “inside the DLC film” was 2000, and the “near the interface” was 2000, and the hardness distribution was uniform in the film thickness direction.

<Mechanical property evaluation>
In each forming roll of Example 1 and Comparative Example 1, mechanical properties were evaluated. As the evaluation conditions, an industrial titanium pipe having a diameter of 25.0 mm and a thickness of 0.5 mm was used, and the pipe making speed was 6 m / min, and molding was performed using the molding apparatus shown in FIG. At this time, a soluble oil-based lubricant was used as the lubricant, and molding was performed while dripping this lubricant in a small amount at 10 ml / hr.

As a result, in Example 1, even when the molding time was 24 hours, roll wrinkles did not occur, adhesion resistance and wear resistance were good, and generation of wrinkles and roll marks on the roll flange portion was suppressed. did it.

On the other hand, when the titanium tube was formed using the roll of Comparative Example 1, roll wrinkles and film peeling occurred without standing for 30 minutes, and the CrN film was exposed.

(Example 2, Example 3)
As Example 2, the forming roll shown in FIG. In that case, the clearance gap between the rotation flange part 22 and the protrusion part 21b of the roll center part 21 was adjusted to 50 micrometers.

Further, as Example 3, the forming roll shown in FIG. 3 was manufactured, and the gap between the rotating flange portion 22 and the protruding portion 21b of the roll central portion 21 was adjusted to 10 μm or less. The quality of the CrN film and the DLC film in each forming roll was the same as in Example 1.

JIS type 3 titanium tubes having a diameter of 25.0 mm and a thickness of 0.5 mm were formed using the forming rolls of Examples 2 and 3. Molding conditions are TIG welding using JIS type 3 titanium, pipe forming speed is 6 m / min, and after TIG welding, the roll of FIG. 3 is used in the molding apparatus shown in FIG. Using this agent, molding was performed while dripping this lubricant in a small amount at 10 ml / hr. The evaluation result of the roundness of the titanium tube after forming is shown in FIG. In FIG. 19, the measurement result of the roundness of the titanium tube after 300 hours of continuous pipe production is shown by a solid line, and the allowable roundness of the product is shown by a triple circle (dotted line). The inner and outer circles of the triple circle indicate the allowable range, and the remaining circles indicate the forming target.

As shown in FIG. 19, the roundness is good in both Example 2 (see FIG. 19 (a)) and Example 3 (see FIG. 19 (b)), and is within the allowable range of roundness as a product. However, Example 3 showed higher roundness. Moreover, in Example 2, the clearance gap between the rotation flange part 22 and the protrusion part 21b of the roll center part 21 produced the wrinkle of the grade which is accept | permitted as a product on the surface of a titanium pipe | tube.

Further, in both Example 2 and Example 3, seizure with the roll on the titanium pipe and seizure between the roll center part or the fixed flange part and the rotating flange part occurred even after 300 hours of continuous pipe making. In this state, the continuous pipe making could be continued.

Therefore, as in Example 3, adjusting the gap between the rotating flange portion 22 and the protruding portion 21b of the roll center portion 21 to 10 μm or less means that even if they slide relative to each other during pipe making, The friction coefficient is reduced by the CrN film and the DLC film, so that they are not worn out and can be continuously produced without problems, and it is desirable from the viewpoint of maintaining the roundness of the titanium tube product and preventing wrinkles.

1, 21, 31 ... Titanium tube forming roll, 3 ... Rotating shaft, 10 ... Titanium tube, 12 ... Roll main body, 4,14 ... Roll recess, 21 ... Roll center, 21a1 ... Outer peripheral surface (opposing surface), 21a ... Base part, 21b ... Projection part, 22 ... Turning flange part, 22b ... Inner peripheral surface (opposing surface), 22c ... Side surface (opposing surface), 23 ... Fixed flange part, 23b ... Opposing surface, 24 ... First bearing part, 25: Second bearing portion, 32: Pull screw portion, 101: Lubrication nozzle, 102: Lubrication nozzle fixing base, 103: Horizontal movement guide, 104: Vertical position adjustment handle, 105: Left / right position adjustment handle, 106: Center position adjustment Jig 107, Dovetail type pedestal 108, Stand post mounting jig 109, Lubrication nozzle angle adjustment jig 112, Lubrication nozzle angle fixing screw 113, Lubrication nozzle front / rear adjustment jig 114, Width adjustment Screws (positive and screw used), 115 ... Guide parts for width movement, 116 ... Vertical movement screws, 117 ... Molding stand column, 118 ... Width movement groove, 119 ... Width movement guide, 120 ... Stand fixing screw, 130 ... Roller 131 ... Center axis 132 ... Silicon tube

Claims (24)

1. % By mass
   C: 1.00-2.30%,
   Si: 0.10 to 0.60%,
   Mn: 0.20 to 0.80%,
   P: 0.030% or less,
   S: 0.030% or less,
   Cr: 4.80 to 13.00%,
   Mo: 0 to 1.20%,
   V: 0 to 1.00%,
   W: 0 to 0.80%,
   A substrate having a chemical composition with the balance being iron and inevitable impurities;
   A nitride layer formed on at least the rolled surface on the substrate;
   A CrN film formed on the nitride layer;
   A diamond-like carbon film formed on the CrN film,
   The substrate has a Vickers hardness of 600 to 700,
   The nitride layer has a Vickers hardness of 800 to 1200;
   The CrN film has a Vickers hardness of 800 to 2000,
   The diamond-like carbon film has a Vickers hardness of 3000 to 3500 in the region from the film surface to 0.20 t (where t is the film thickness), and 1500 to 3000 in the region from the interface with the CrN film to 0.20 t. And
   In the diamond-like carbon film, the ratio I ₁₃₈₀ / I ₁₅₄₀ of the absorption intensity I ₁₃₈₀ at a wave number of ₁₃₈₀ cm ^{−1 and} the absorption intensity I ₁₅₄₀ at a wave number of 1540 cm ⁻¹ measured by Raman spectroscopy is 0.20 t from the film surface. 0.5 to 0.7 in the region up to 0.3, and 0.3 to 0.5 in the region up to 0.20 t from the interface between the diamond-like carbon film and the CrN film.
   Titanium tube forming roll.
2. The diamond-like carbon film has a thickness of 0.5 to 2.0 μm.
   The titanium tube forming roll according to claim 1.
3. The CrN film has a thickness of 0.5 to 5.0 μm.
   The titanium tube forming roll according to claim 1 or 2.
4. The nitride layer has a thickness of 0.5 μm to 50.0 μm.
   The titanium tube forming roll according to any one of claims 1 to 3.
5. The titanium tube forming roll according to any one of claims 1 to 4, wherein the nitride layer has an average nitrogen concentration of 10.0 to 25.0 mass%.
6. The concentration distribution of nitrogen in the nitride layer has a concentration gradient that decreases in the depth direction from the surface of the nitride layer.
   The titanium tube forming roll according to any one of claims 1 to 5.
7. The base material is in mass%,
   Mo: 0.70 to 1.20%,
   The titanium tube forming roll according to any one of claims 1 to 6, comprising at least one selected from V: 0.15 to 1.00% and W: 0.60 to 0.80%.
8. A hole-type roll provided with a semicircular roll recess in cross-sectional view over the entire circumference of the roll body,
   The rolling surface is the surface of the roll recess.
   The titanium tube forming roll according to any one of claims 1 to 7.
9. The roll body includes a roll center portion and a pair of rotating flange portions disposed on both sides of the roll center portion and rotatable with respect to the roll center portion,
   The roll recess is divided by the roll center and the rotating flange.
   The titanium tube forming roll according to claim 8.
10. The roll center portion is fixed to a rotating shaft that drives the roll body, and the rotating flange portion is rotatable with respect to the rotating shaft and the roll center portion.
    The titanium tube forming roll according to claim 9.
11. When the outer diameter of the titanium tube used as a workpiece is D, the width of the roll recess at the roll center is in the range of 0.7D to 0.87D.
    The titanium tube forming roll according to any one of claims 8 to 10.
12. The roll center part is provided with a base part and a protruding part that protrudes from the center part in the roll width direction of the base part toward the outer periphery of the roll,
    The rotating flange portion is disposed on both sides in the roll width direction of the protruding portion on the base portion,
    A first bearing portion is provided between the base portion of the roll central portion and the rotating flange portion.
    The titanium tube forming roll according to any one of claims 9 to 11.
13. The opposing surfaces that face each other between the base portion and the rotating flange portion at the center of the roll are the raceway surfaces of the rolling elements of the first bearing portion, and the opposing surfaces are the nitride layer , Comprising the CrN film and the diamond-like carbon film,
    The titanium tube forming roll according to claim 12.
14. A fixed flange portion disposed on both sides of the pair of rotating flange portions in the roll width direction and fixed to the center portion of the roll, and a second bearing portion disposed between the fixed flange portion and the rotating flange portion And comprising
    The titanium tube forming roll according to any one of claims 8 to 13.
15. The opposing surfaces facing each other between the fixed flange portion and the rotating flange portion are raceway surfaces of the rolling elements of the second bearing portion, and the opposing surfaces are the nitride layer and the CrN. A coating and the diamond-like carbon film;
    The titanium tube forming roll according to claim 14.
16. The fixing flange portion is provided with a pulling screw portion that pulls and fixes the rotating flange portion.
    The titanium tube forming roll according to claim 14 or 15.
17. A titanium tube forming apparatus comprising the titanium tube forming roll according to claim 1, comprising a lubricating nozzle for supplying a lubricant during titanium tube forming to a part of the titanium tube forming roll.
    Titanium tube forming equipment.
18. The position of the lubrication nozzle can be varied according to the forming size of the titanium tube.
    The titanium tube forming apparatus according to claim 17.
19. The position of the lubricating nozzle can be varied according to the diameter of the titanium tube forming roll.
    The titanium tube forming apparatus according to claim 17 or 18.
20. The position and orientation of the lubricating nozzle can be adjusted arbitrarily,
    The titanium tube forming apparatus according to any one of claims 17 to 19.
21. The lubricating nozzle is a tube having an inner diameter of 0.5 to 3.0 mm;
    The titanium tube forming apparatus according to any one of claims 17 to 20.
22. A soluble oil-based lubricant is used as the lubricant, and the lubricant is supplied in a small amount at 1.0 to 20.0 ml / hr or less.
    The titanium tube forming apparatus according to any one of claims 17 to 21.
23. Forming using the titanium tube forming roll according to any one of claims 1 to 16,
    A method for manufacturing a titanium tube.
24. Forming using the titanium tube forming apparatus according to any one of claims 17 to 22,
    A method for manufacturing a titanium tube.

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