JP2018043286A - Metal tube molding roll, metal tube molding device, and metal tube molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding roll excellent in agglutination resistance, abrasion resistance, peeling resistance and a coefficient of friction of a roll surface.SOLUTION: A metal tube molding roll has a base material having a steel composition constituted by, by 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, and Cr:4.80-13.00%, the balance iron with inevitable impurities, a CrN film formed on the base material and a diamond like carbon film (DLC film) formed on the CrN film, where in the DLC film, a ratio I/Iof absorption intensity Iat a wavenumber of 1380 cmmeasured by a Raman spectroscopic method to absorption intensity Iat a wavenumber of 1540 cmis 0.5 to 0.7 in a range of 20% depth of film thickness from a film surface, and is 0.3 to 0.5 in a range of 20% depth from an interface between the DLC film and the CrN film.SELECTED DRAWING: Figure 1

Description

The present invention relates to a metal tube forming roll, a metal tube forming apparatus, and a metal tube forming method, and more particularly to a metal tube forming roll, a metal tube forming apparatus, and a metal tube forming method having excellent adhesion resistance and wear resistance. .

  Normally, when manufacturing metal pipes such as steel pipes, stainless steel pipes, titanium pipes, aluminum alloy pipes, copper alloy pipes, etc., steel pipes and stainless steels are used for the purpose of ensuring high-precision outer diameter and roundness, and correcting the bending of pipes. For steel pipes, titanium pipes, and copper alloy pipes, a molding process is performed by a molding roll after TIG or laser welding, and for aluminum alloy pipes, after MIG welding.

If the forming roll is heavily worn, it is impossible to form with high accuracy, and it is impossible to ensure high-precision roundness in the metal 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.
Furthermore, in recent years, in order to improve the productivity of metal pipes, the molding is often performed under severe conditions in which the transport speed in the molding process is increased. When operating under such conditions, particularly when forming a metal tube with a forming roll that is a semicircular groove roll in cross section, the peripheral speed (circumferential speed) is increased on the bottom side of the semicircular groove in cross section and the end side of the groove. Since the speed is different, adhesion (seizure) is likely to occur in a part of the surface of the metal tube due to the peripheral speed difference from the surface of the forming roll, and seizure flaws may occur. In this way, if adhesion occurs between the forming roll and the metal tube, wrinkles remain on the surface of the metal tube, resulting in a decrease in the commercial value and a decrease in the roundness of the metal tube product. The forming roll must be replaced before this occurs.
As described above, a roll for forming a metal tube is required to have a long-life roll that can achieve both wear resistance and adhesion resistance capable of reducing seizure flaws and can reduce the frequency of roll replacement.

Conventionally, various techniques have been studied in response to the requirements for wear resistance and adhesion resistance for such forming rolls.
For example, in a steel pipe forming roll, a method of forming a ceramic film on the roll surface to ensure hardness (Patent Document 1), and a surface hardening selected from a sulfur nitrided layer, a nitrided layer, and TiC on the roll surface. In a roll having a hard film formed on the surface (Patent Document 2) and a method of improving hardness and hardness, the carbide dispersed in the roll surface layer is refined to ensure adhesion between the roll and the hard film. A method of ensuring abrasion resistance and adhesion resistance by preventing peeling (Patent Document 3) and the like has 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, in particular, 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 as compared with 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.

However, until now, various studies have been made on the wear resistance and adhesion resistance of the forming roll when forming a steel pipe as described above, but most of the characteristics of the forming roll forming a titanium pipe have been mentioned. Not. 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.

Further, titanium has a high yield strength (yield stress), but has a lower elastic modulus (Young's modulus) than other metals, so that molding defects due to so-called springback (elastic recovery) are likely to occur. (Aluminum alloys also have a lower elastic modulus than other metals, but their yield strength is lower, so springback is not a problem as much as titanium.)
In addition to titanium pipes, steel pipes, stainless steel pipes, aluminum alloy pipes, copper alloy pipes, as described above, various studies have been made on the wear resistance and adhesion resistance of the forming rolls. When high roundness is required, further improvement in product yield and improvement in production efficiency by extending the life of forming rolls are required.

In general, when a metal 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.
The plurality of forming rolls are roughly classified into a driving roll and a non-driving roll. The drive roll consists of a pair of rolls arranged opposite to each other in the vertical direction. The rolls are driven by applying drive rotational force to the upper and lower rolls to pull the metal tube in the transport direction. It consists of a pair of made rolls, and no driving torque is applied.

Here, as a more detailed investigation, the drive roll has a larger peripheral speed difference than the non-drive roll, so the roll surface peels off particularly at the flange, and the metal tube that is the object to be formed is wrinkled. I found it easy. 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.

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

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

  The inventors of the present invention have studied metal pipe forming rolls that are inexpensive and have excellent wear resistance, adhesion resistance, peel resistance, and friction coefficient of the roll surface and have a long roll life. The base material is an alloy tool steel used as a base material, further, the forming roll is divided, the divided rolls are adjacent to each other, a CrN film is formed on the base material, and a diamond-like carbon film is further formed thereon. It has been found that the formation of the metal tube can be improved by improving the wear resistance, adhesion resistance, peel resistance and low friction of the roll surface.

  Further, in order to reduce the above-mentioned “circumferential speed difference”, in the forming roll which is a semicircular groove roll in cross section, it is formed on the bottom side of the semicircular groove in cross section and the end sides of the grooves on both sides By dividing the rolls and placing them next to each other so that they are not constrained by the rotation of the other, the difference in rotational speed between the divided rolls on the bottom side and the end sides of the grooves on both sides thereof As a result, it was decided to adopt means for reducing the difference in peripheral speed between the roll surfaces. However, if a so-called “play”, that is, a gap that is unacceptable between the rolls, occurs during operation, the roundness of the metal tube product may be lowered. On the other hand, if each of the forming rolls divided so as to minimize the gap (play), that is, the gap is in contact with each other, the divided forming rolls slide on each other on the contacting surface. Wear, and the roll life is shortened. In addition, if a bearing is interposed between the divided molding rolls in order to prevent the wear, this time, “play”, that is, a gap occurs, and further vibrations occur and the roundness cannot be maintained. There is a problem that causes defects.

  Therefore, the above-mentioned CrN film is formed on the surface of the base material constituting the split roll, at least on the surface where the sliding surfaces of the split roll are in contact with each other, and the above diamond-like carbon film is further formed thereon. Thus, even when “play” between divided rolls, that is, when the gap is minimized, it is possible to prevent mutual wear due to sliding, and to provide a long-life roll that can reduce the frequency of roll replacement. It was. The division of the forming roll and the reduction of wear by the Cr film and the diamond-like carbon film are effective not only for the driving roll but also for the non-driving roll.

In the present invention, when the forming roll is divided at the bottom side of the semicircular groove in cross-sectional view and the end side of the groove on both sides thereof, the bottom side of the semicircular groove in cross-sectional view is referred to as the “roll center portion”. The ends of the grooves on both sides are referred to as “rotating flange portions”.
The gist of the present invention is as follows.

[1] A metal tube forming roll having a roll body provided with a roll recess having a semicircular cross-sectional view over its entire circumference,
The roll body includes at least 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 , Divided by the roll center portion and the rotating flange portion,
The roll center part and the rotating flange part are 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%, the balance is made of steel having a composition consisting of iron and impurities,
A CrN film and a diamond-like carbon film are sequentially laminated on the entire surface of the roll recess and the entire surface of the rotating flange portion,
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 A metal characterized in that it is 0.5 to 0.7 in the range of 20% depth and 0.3 to 0.5 in the range of 20% depth from the interface between the diamond-like carbon film and the CrN film. Tube forming roll.
[2] 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 metal tube forming roll according to [1].
[3] The roll body further includes a fixed flange portion disposed on both sides in the roll width direction of the pair of rotating flange portions and fixed to the roll center portion,
The metal pipe forming roll according to [1] or [2], wherein a pulling screw portion for pulling and fixing the rotating flange portion is provided on the fixing flange portion.
[4] When the outer diameter of the metal tube to be the workpiece is D, the width of the roll recess in the roll center is in the range of 0.7D to 0.87D [1] to [3] ] The metal tube forming roll as described in any one of.
[5] The diamond-like carbon film has a Vickers hardness of 3000 to 3500 in the range of 20% depth from the film surface, and a range of 20% depth from the interface between the diamond-like carbon film and the CrN film. The metal tube forming roll according to any one of [1] to [4], wherein the Vickers hardness is 2500 to 3000.
[6] The metal tube forming roll according to any one of [1] to [5], wherein the diamond-like carbon film has a thickness of 0.5 μm to 2 μm.
[7] The metal tube forming roll according to any one of [1] to [6], wherein the CrN film has a thickness of 0.5 μm to 5 μm.
[8] The metal tube forming roll according to any one of [1] to [7], wherein the CrN film has a Vickers hardness of 800 to 2000.
[9] Any one of [1] to [8], wherein a nitrided layer nitrided by plasma nitriding is formed on the surface of the roll central portion and the rotating flange portion. Metal tube forming roll.
[10] The metal tube forming roll according to [9], wherein the nitride layer has a thickness of 0.5 μm to 5 μm.
[11] The metal tube forming roll according to [9] or [10], wherein the nitride layer has an average nitrogen concentration of 10.0 to 25.0 mass%.
[12] 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, according to any one of [9] to [11] Metal tube forming roll.
[13] One or both of the roll center part and the rotating flange part is further in mass%,
Mo: 0.70 to 1.20%,
V: 0.15-1.00%,
The metal tube forming roll according to any one of [1] to [12], characterized by comprising:
[14] One or both of the roll center part and the rotating flange part may further be in mass%,
W: 0.60 to 0.80%,
The metal tube forming roll according to any one of [1] to [13], characterized by comprising:
[15] A metal tube forming apparatus including the metal tube forming roll according to any one of [1] to [14].
[16] A metal tube forming method, characterized by forming using the metal tube forming roll according to any one of [1] to [14].

  According to the present invention, in a roll used when forming and forming a metal tube, the metal tube forming roll is excellent in wear resistance, adhesion resistance, peel resistance, and friction coefficient of the roll surface, and inexpensive. In addition, a metal tube forming apparatus and a metal tube forming method capable of extending the life of the roll can be provided.

FIG. 1 is a schematic side view showing a metal tube forming method using a metal tube forming roll which is a first example of an embodiment of the present invention. FIG. 2 is a schematic front view showing a metal tube forming roll according to an embodiment of the present invention. FIG. 3 is a schematic front sectional view showing a metal 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 metal 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 metal 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 metal 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 metal tube forming roll of this embodiment. FIG. 7 is a schematic front sectional view showing another example of the metal tube forming roll of the present embodiment. FIG. 8 is a schematic front sectional view showing still another example of the metal tube forming roll of the present embodiment. FIG. 9 is a schematic front sectional view showing a metal 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 metal 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 Reference Example 1, and FIG. 19B is formed using the forming roll of Example 2. 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 metal tube forming roll, a metal tube forming apparatus, and a metal tube forming method according to embodiments of the present invention will be described.
In addition, since this embodiment is described in detail in order to make the purpose of the metal tube forming roll of the present invention better understood, the present invention is not limited unless otherwise specified.

  In addition, the metal pipe which can be applied in the metal pipe forming roll, the metal pipe forming apparatus, and the metal pipe forming method of each embodiment to be described below is a steel pipe, a stainless steel pipe, an aluminum pipe, an aluminum alloy pipe, a titanium pipe, a titanium alloy pipe, Either a copper tube or a copper alloy tube may be used, and a metal tube of a material other than this may be used.

[First example of metal tube roll, metal tube forming apparatus and metal tube forming method]
FIG. 1 shows a schematic side view of a metal tube forming method using a metal tube forming roll, a metal tube forming apparatus, and a metal tube forming roll, which is a first example of the present embodiment. FIG. 2 shows a schematic front view of the metal tube forming roll. As shown in FIGS. 1 and 2, the metal tube forming roll 1 of the present embodiment is a so-called caliber roll, and includes a roll body 2 made of steel and a rotating shaft 3 inserted through the roll body 2. Yes. 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. The surface of the roll recess 4 is provided with a CrN film and a diamond-like carbon film formed on the CrN film.

  As shown in FIG. 1, when the metal tube 10, which is a hollow cylindrical tube, is formed into a perfect circle, the rotation shafts 3 of the pair of metal tube forming rolls 1 are horizontally arranged, and each rotation shaft 3 is arranged. Place them so that they are parallel. In this way, the metal tube forming rolls 1 are arranged so as to face each other in the vertical direction. And the metal tube 10 before shaping | molding is passed between a pair of metal tube shaping | molding roll 1 arrange | positioned up and down. Between the pair of metal 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 metal tube roll 1. The metal tube 10 is formed into a perfect circle when passing through. In addition, arrangement | positioning of the metal tube forming roll 1 is not restricted to an up-down direction, A horizontal direction or the diagonal direction may be sufficient. Further, as shown in FIG. 1, the rotation shafts 3 of the pair of metal tube forming rolls 1 are arranged horizontally, and are arranged so that the rotation shafts 3 are parallel to each other. The part is composed.

  The rotating shaft 3 of the metal tube forming roll 1 may be a driving shaft driven by driving means or a non-driving shaft. Even if the metal tube forming roll 1 of this embodiment is connected to the drive shaft, it 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 metal tube forming roll 1 according to the present embodiment is mass%, C: 1.00-2.30%, Si: 0.10-0.60%, Mn: 0.00. Steel material having a steel composition containing 20 to 0.80%, P: 0.030% or less, S: 0.030% or less, Cr: 4.80 to 13.00%, the balance consisting of iron and impurities Consists of. A CrN film and a diamond-like carbon film are provided on at least the surface of the roll recess 4 of the metal tube forming roll 1 made of the 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 The ratio I ₁₃₈₀ / I ₁₅₄₀ becomes 0.3 to 0.5 in the range of 20% depth from the interface between the diamond-like carbon film and the CrN film in the range of 20% depth. ing.
Below, the metal tube forming roll in this embodiment is demonstrated in detail.

[Composition of base material]
First, the reason for limitation of each element is explained in full detail regarding the base-material component composition in the metal tube forming roll 1 of this embodiment.
In the following description, “%” represents mass% unless otherwise specified. Moreover, the remainder of the basic components and selective elements shown below consists of iron and inevitable impurities.

(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, when 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) 0.10-0.60%
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: chrome) 4.80 to 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 metal 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, the 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.

  In the present embodiment, Mo: 0.70 to 1.20% and V: 0.15 to 1.00% may be further included in the above component composition.

(Mo: Molybdenum) 0.70 to 1.20%
Mo improves the temper softening resistance and also has the effect of imparting wear resistance by forming carbides. 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) 0.15-1.00%
V is effective for improving the hardenability of the base material, suppressing temper softening, and further miniaturizing the carbide. Therefore, 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.

  In the present embodiment, W: 0.60 to 0.80% may be further included in the above component composition.

(W: Tungsten) 0.60 to 0.80%
W, like V, is effective for improving the hardenability of the base material, suppressing temper softening, and further miniaturizing the carbide. Therefore, it is preferable to contain W by 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 impurities and other elements that do not impair the effects of the present invention can be added.

  In addition, in the metal tube forming roll 1 of this embodiment, what has the said component composition is used as a material of a base material, 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 component composition range) defined in JIS G 4404, and among these, it is more preferable to use SKD11.

[CrN coating (hard coating)]
The substrate having such a component composition has a Vickers hardness of about 500 to 600. In other words, when the metal tube 10 is molded 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, the material of the metal tube may be baked on the base material, and a large number of wrinkles may occur on the metal tube forming roll 1.

  Therefore, in this embodiment, it discovered that it was important to form a CrN film | membrane on the base-material surface. By forming a CrN film on the surface of the base material, adhesion between the metal tube 10 and the metal tube forming roll 1 can be ensured, and adhesion resistance can be improved.

  The thickness of the CrN film is not particularly limited, but can be 0.5 μm to 5 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 μm.

  The film forming method of the CrN film is not particularly limited, but it is preferable to use the 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.

Further, the Vickers hardness of the CrN film is preferably in the range of 800 to 2000.
The hardness of the CrN coating is preferably high from the viewpoint of improving the wear resistance of the metal tube forming roll 1. Therefore, in the present embodiment, the Vickers hardness of the CrN film is preferably 800 or more, and 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 CrN film may have a single layer structure or a multilayer structure in which two or more layers are stacked. 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 metal tube forming roll 1, the driving roll for pulling the metal tube 10 in the conveying direction has a severer 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 the present embodiment, a high-hardness diamond-like carbon film (DLC film) made of sp ² hybrid orbital carbon (sp ² structure) and sp ³ hybrid orbital carbon (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 likely to concentrate in this case, so that 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 metal tube 10.
For this reason, 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 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 obtained. 0.5 to 0.7 in the region 20% deep from the surface (upper layer region), 0.3 to 0. 0 in the region 20% deep (lower layer region) from the interface between the DLC film and the CrN film. The hardness gradient is imparted so that the ratio 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, 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).

Diamond-like carbon 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 about 800 to 2000, it is preferable that the lower layer region of the DLC film has a Vickers hardness of about 2500 to 3000 and the upper layer region of about 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 against the metal 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, the adhesion resistance can be improved.

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 μm to 2.0 μm, but may be appropriately determined depending on the manufacturing method, its conditions, the use environment of the metal tube forming roll 1, and the like.

The DLC film according to this embodiment can be formed by 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, 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.

[Nitride layer]
The metal tube forming roll 1 according to the present embodiment forms a CrN film on a base material, and further forms a high-hardness diamond carbon film thereon, so that the wear resistance of the metal tube forming roll 1 is increased. Ensures adhesion resistance and low friction. However, a hardness disparity (strength discontinuity) occurs between the high hardness CrN layer and the relatively soft base material (interface), and stress tends to concentrate at the interface between the CrN layer and the base material. Depending on the thickness of the CrN film, sufficient adhesion between the CrN film and the substrate may not be ensured.
Therefore, as a result of the study by the present inventors, a hardness difference is provided by providing another layer capable of connecting the CrN film and the base material between the high hardness CrN film and the relatively soft base material. It has been found that the adhesion between the CrN film and the substrate and the strength of the metal tube forming roll 1 can be made compatible.
Further, generally, from the viewpoint of “Hertz contact stress” in which the maximum shear stress is maximum not directly on the outermost surface but directly on the surface (surface layer), immediately below the surface of the metal tube forming roll 1, that is, the CrN layer and the base material It is preferable to further provide a high hardness layer between them to ensure wear resistance of the metal tube forming roll 1.

  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.

The thickness of the nitride layer is not particularly limited, but can be 0.5 μm to 5 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 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 5 μm or less.

The average nitrogen concentration in the nitride layer is preferably 10.0 to 25.0 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 nitride layer is too high, the surface of the nitride 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 of the nitride layer in the depth direction.
As described above, it is not preferable that the strength difference occurs inside the roll from the viewpoints of adhesion between the CrN layer and the base material and strength. 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.

  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 the present embodiment, the analysis region has a diameter of 1 mm, the analysis is performed in the depth direction using GDS, and the QDP (Quantitative Depth Profile) method defined in JIS K 0150 is applied, and the depth of each 50 nm is applied. 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.

As described above, the metal tube forming roll 1 according to the present embodiment has been described. However, before the CrN film is formed (before plasma nitriding treatment), the roll surface properties are good and the CrN film is formed. In order to ensure film properties, it is desirable to mirror-polish the roll (base material) surface. Thereby, the adhesiveness of a CrN membrane | film | coat and a base material can be improved, and it becomes possible to obtain the outstanding adhesion resistance as a result.
In addition, it is preferable to use water or an emulsion or a soluble oil-based lubricant that is usually used for forming a metal tube as a lubricant because the friction between the metal tube 10 and the metal tube forming roll 1 is further reduced. From the viewpoint of lubrication performance and ease of removal of the lubricant adhered to the product, a soluble oil lubricant which is a water-soluble cutting fluid is most suitable.

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

  3 and 4 show a metal tube forming roll 11 which is a second example of the present embodiment. The metal tube forming roll 11 shown in FIGS. 3 and 4 is a so-called caliber roll, and includes a roll main body 12 made of a steel material and a rotating shaft 3 inserted through the roll main 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. Further, the surface of the roll recess 14 is provided with a CrN film and a diamond-like carbon film formed on the CrN film.

  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. Further, the roll center portion 21 and the fixing flange portion 25 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 25 is fixed to the roll center portion 21 by fixing bolts 26. That is, the fixed flange portion 25 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 part 22 is rotatable with respect to the roll center part 21 and the fixed flange part 23, it does not interlock with the roll center part 21 and the fixed flange part 23. Hereinafter, each part will be described in detail.

The roll center portion 21 includes a cylindrical base portion 21a through which the rotation 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 projecting 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. doing. The roll center part 21 is comprised from the base material which has the steel component demonstrated in the 1st example. Further, the upper surface 21d of the roll central portion 21 is provided with the CrN film and the diamond-like carbon film described in the first example. Further, the CrN film and the diamond-like carbon film described in the first example are also provided on the side wall surface 21 b ₁ of the protruding portion 21 b of the roll center portion 21. Further, on the outer circumferential surface 21a ₁ of the base portion 21a of the roll central portion 21, which may be the the CrN film and the diamond-like carbon film described in the first embodiment are laminated, it may not be stacked.

  Next, 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. 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 central 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 distal end portion 22d including the outer peripheral inclined surface 22a of the rotating flange portion 22 is bent so as to cover the distal end of the protruding portion 21b. Thereby, when the rotation flange part 22 receives the load from the metal tube 10, it becomes possible to fully receive a load.

Further, the side wall surface 21b ₁ of the projecting portion 21b of the roll central portion 21 and the inner surface 22e of the rotating flange 22, which face each other with a gap of less than 30 [mu] m. Due to the presence of this gap, the rotating flange portion 22 is rotatable without rubbing against the roll center portion 21. On the other hand, 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 are mutually slidably contact.

  Furthermore, the rotation flange part 22 is comprised from the base material which has the steel component demonstrated in the 1st example. In addition, the outer peripheral inclined surface 22a of the rotating flange portion 22 is provided with the CrN film and the diamond-like carbon film described in the first example. Furthermore, the CrN film and the diamond-like carbon film of the first example are provided not only on the outer peripheral inclined surface 22 a but also on the entire surface of the rotating flange portion 22.

Here, when attention is focused on a roll central portion 21 and the rotating flange 22, as described above, it is less than 30μm and the inner surface 22e of the roll central portion side wall surface 21b ₁ of the protrusion 21b of 21 and rotating the flange portion 22 It is opposed through a gap. Further, the entire surface of the rotating flange 22, respectively on the side wall surfaces 21b ₁ of the roll central portion 21, and a CrN film and the diamond-like carbon film described in the first embodiment are laminated. Thus, since the inner surface 22e of the side wall surfaces 21b ₁ and the pivot flange portion 22 of the roll central portion 21 is opposed via the CrN coating and diamond-like carbon film, a roll central portion 21 and the rotating flange Friction with the portion 22 is reduced, and the roll central portion 21 and the rotating flange portion 22 can slide smoothly with each other.

Further, as described above, the CrN film and the diamond-like carbon film described in the first example may be laminated on the outer peripheral surface 21 a ₁ of the roll center portion 21. In this case, so the inner peripheral surface 22b of the outer circumferential surface 21a ₁ and the pivot flange portion 22 of the base portion 21a of the roll central portion 21 are opposed to each other via the CrN film and the diamond-like carbon film. Thereby, although both surfaces 21a ₁ and 22b are in contact with each other, the friction between the roll center portion 21 and the rotating flange portion 22 is reduced and the sliding can be performed more smoothly.

  Next, the fixed flange portion 23 is a substantially disc-shaped member, and is a member provided with an insertion hole 23a through which the rotation 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 in the roll width direction of the rotating flange portion 22 and face the rotating flange portion 22.

  The fixed flange portion 23 is composed of a base material having the steel component described in the first example. In addition, the CrN film and the diamond-like carbon film described in the first example are provided on the facing surface 23 b of the fixed flange portion 23 that faces the rotating flange portion 22.

  Here, paying attention to the rotating flange portion 22 and the fixed flange portion 23, the outer surface 22c of the rotating flange portion 22 and the facing surface 23b of the fixed flange portion 23 are opposed to and in contact with each other. Further, the CrN film and the diamond-like carbon film described in the first example are laminated on the entire surface of the rotating flange portion 22, and the opposing surface 23b of the fixed flange portion 23 is also described in the first example. A CrN film and a diamond-like carbon film are laminated. Thus, since the CrN film and the diamond-like carbon film described in the first example are disposed on the outer surface 22c of the rotating flange portion 22 and the facing surface 23b of the fixed flange portion 23, both surfaces 22c. , 23b are in contact with each other, the friction between them is reduced, and the rotating flange portion 22 and the fixed flange portion 23 slide smoothly with each other.

  As shown in FIG. 4, in the metal tube forming roll 1 of this example, the roll body 12 can be disassembled into the roll center portion 21, the rotating flange portion 22, and the fixed flange portion 23 by removing the fixing bolt 26. It has become.

  With the above configuration, when the metal tube 10 is formed, the roll central portion 21 and the fixed flange portion 23 are rotated by the rotational drive of the rotary shaft 3. When the metal tube 10 is inserted between the pair of metal tube rolls 1 in this state, the upper surface 21 d of the roll center portion 21 contacts the metal tube 10 and transmits the rotational torque of the rotating shaft 3 to the metal tube 10. On the other hand, the metal 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 metal tube 10 in accordance with the movement of the metal 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 rotation flange portion 22 is rotatable with respect to the roll center portion 21 and the fixed flange portion 23, and is less than 30 μm between the rotation flange portion 22 and the protruding portion 21b of the roll center portion 21. Therefore, the rotation flange portion 22 rotates at a rotation speed smaller than the rotation speed of the roll center portion 21. Thereby, the slip ratio of the roll with respect to the metal pipe 10 becomes small as a whole, and the generation of wrinkles in the metal pipe 10 is suppressed.

Further, when the metal tube 10 is inserted between the pair of metal tube forming rolls 1 and the metal tube 10 enters the roll recess 14, the rotating flange portion 22 is slightly pushed outward in the roll width direction to fix the fixed flange portion. On the other hand, a gap of less than 30 μm is ensured between the rotating flange portion 22 and the protruding portion 21 b 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.
Furthermore, although a gap is generated between the rotating flange portion 22 and the protruding portion 21b of the roll center portion 21, the width of the gap does not exceed 30 μm. Shaking is extremely small. Thereby, the semicircular roll concave portion 14 formed by the rotating flange portion 22 and the roll central portion 21 is maintained while its roundness is high while the metal tube 10 is formed.

Further, since the CrN film and the diamond-like carbon film are disposed on the inner peripheral surface 22 b of the rotating flange portion 22, the inner peripheral surface 22 b of the rotating flange portion 22 and the outer peripheral surface 21 a ₁ of the roll center portion 21. Friction is reduced, and the rotating flange portion 22 can be rotated more smoothly. Furthermore, when a CrN film and a diamond-like carbon film are disposed on the outer peripheral surface 21a ₁ of the roll center portion 21, the friction reduction effect can be further improved.

  Further, since the CrN film and the diamond-like carbon film are disposed on the outer surface 22c of the rotating flange portion 22, the friction between the outer surface 22c of the rotating flange portion 22 and the facing surface 23 of the fixed flange portion 23 is small. Thus, the rotating flange portion 22 and the fixed flange portion 23 slide smoothly with each other, and the rotating flange portion 22 can be smoothly rotated. Furthermore, when a CrN film and a diamond-like carbon film are disposed on the facing surface 23 of the fixed flange portion 23, the friction reduction effect can be further improved.

  The locations where the CrN film and the DLC film are formed are not limited to the above-described locations, and at least the CrN film and the DLC film are formed on the entire surface of the roll recess 14 and the entire surface of the rotating flange portion 22. For example, the friction between the roll center portion 21 and the fixed flange portion 23 is reduced, and the rotating flange portion 22 can be smoothly rotated. Burn-in is prevented.

Next, a 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 metal 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 metal 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 metal tube 10 is at the bottom of the roll recess 4. Therefore, assuming that the roll diameter at the bottom of the roll recess 14 is Rd, the roll diameter at the pinch position is Rp, and the roll diameter at the upper surface of the flange portion of the roll is Rf, the slip ratio with respect to the metal tube near the upper surface of the flange portion is as follows: It becomes street.

  (Flange part) Sliding rate = (Rf−Rp) / Rp (1)

  For example, when the outer diameter D of the metal tube is 25 mm, Rd = 50 mm, and Rf = 62.25 mm, Rp is almost equal to Rd (Rp = Rd = 50 mm), so the slip rate in the drive roll is 0.245. Become.

  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 metal tube in the vicinity of the upper surface of the flange portion is, for example, that the outer diameter D of the metal tube is 25 mm, Rd = 50 mm, Rf = 62.25 mm, Rp = 56.125 mm. When introduced in (1), the slip ratio in the non-driving roll is 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, the metal 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 metal tube forming roll 11 of this embodiment, the roll center part 21 functions as a drive roll, and the rotation flange part 22 functions as a non-drive roll. Then, Rf, Rp, and Rd are as illustrated 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, if 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 metal tube 10, and the rotating flange portion 22 may be damaged. is there.

  From the above, the angle θ shown in FIG. 5 is preferably in the range of 30 to 45 °. When this is expressed 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 metal tube 10 serving as a workpiece. . If it is this range, it will become possible to shape | mold without producing a wrinkle in the metal pipe 10, and damage to the rotation flange part 22 will also be prevented.

  As explained above, according to the metal 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 metal tube are formed. Thus, the metal 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. As described above, according to the metal tube forming roll 1 of this example, the 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 the peeling of the CrN film and the DLC film formed on the rotating flange portion 22 can be suppressed. Thereby, the durability of the metal tube forming roll 1 can be improved and the frequency of maintenance can be reduced.

  Moreover, when the outer diameter of the metal tube 10 used as a workpiece | work is set to D, the slip ratio with respect to the metal tube 10 is reduced by making the width | variety of the roll recessed part 14 in the roll center part 21 into the range of 0.7D-0.87D. In addition, the rotating flange portion 22 can be prevented from being damaged.

Further, a CrN film and a DLC film are laminated on the entire surface of the rotating flange portion 22, and a CrN film and a DLC film are also laminated on the surfaces of the roll center portion 21 and the fixed flange portion 23 corresponding to the rotating flange portion 22. Therefore, there is no possibility that seizure occurs between the roll center portion 21 and the fixed flange portion 23 and the rotating flange portion 22, and the rotating flange portion 22 can be smoothly rotated.
Further, even when the metal flange 10 enters the roll recess 14 and the rotating flange portion 22 is slightly pushed outward in the roll width direction, a gap is generated between the rotating flange portion 22 and the protruding portion 21b. Since the size of the gap is less than 30 μm, the roundness of the roll recess 14 is maintained while the metal tube is being formed, and the metal tube having a high roundness can be formed.

  Further, since a bearing or the like for smoothly rotating the rotating flange portion 22 is not required, the roll body 12 can be made small and the equipment can be made compact.

  Further, the roll body 12 is provided with a fixed flange portion 23, and the rotating flange portion 22 is smoothly rotated while preventing the rotating flange portion 22 from falling off the roll central portion 21 by the fixed flange portion 23. Can be moved.

  Furthermore, as shown in FIG. 4, the metal tube forming roll 1 of this example disassembles the roll body 12 into a roll center part 21, a rotating flange part 22 and a fixed flange part 23 by removing the fixing bolt 26. Therefore, 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, and the metal tube can be molded. Can continue. Moreover, about the removed rotation flange part 22, it can be made into a reusable state only by forming a CrN film | membrane and a DLC film | membrane in the location which needs repair.

  In addition, it is preferable to use water or an emulsion or a soluble oil-based lubricant that is usually used for forming a metal tube as a lubricant because the friction between the metal tube 10 and the metal tube forming roll 11 is further reduced. Further, by using an emulsion or a soluble oil-based lubricant as a lubricant, the roll central portion 21 and a pair of rotations that are arranged on both sides of the roll central portion 21 and are rotatable with respect to the roll central portion 21. Friction with the flange portion 22 is further reduced, which is preferable. When a lubricant is used, a soluble oil-based lubricant that is a water-soluble cutting fluid is most suitable from the viewpoint of lubrication performance and ease of removing the lubricant attached to the product.

The metal tube forming roll 11 of the second example has been described above. However, in this example, the modification shown in FIG. 7 or FIG. 8 may be adopted.
In the modification shown in FIG. 7, when the roll body 12 is viewed in cross section, the boundary surface between the rotating flange portion 22 and the protruding portion 21 b 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 metal tube 10 is relatively small.

  Moreover, 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. In the example of FIG. 8 as well, the shapes of the rotating flange portion 22 and the protruding portion 21b 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 metal tube 10 is relatively small.

[Third example of metal tube roll and metal tube forming method]
Next, a third example of the metal tube roll and the metal tube forming method according to the embodiment of the present invention will be described with reference to FIG. The difference between the metal tube forming roll 31 shown in FIG. 9 and the metal tube forming roll 11 of the second example shown in FIGS. 3 to 4 is that a mechanism for fixing the rotating flange portion 22 to the fixed flange portion 23 is used. 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.

  In FIG. 9, the metal tube forming roll 31 which is the 3rd example of this embodiment is shown. The metal 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 metal 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 metal 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 attracted to the fixed flange portion 23 side and is in close contact with the fixed flange portion 23, and is less than 30 μm between the rotating flange portion 22 and the protruding portion 21 b of the roll center portion 21. A gap is created. This state is substantially the same as the state in which the rotating flange portion 32 is pushed toward the fixed flange portion 23 during the forming process of the metal tube 10. 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 metal tube 10 is formed by pulling the rotating flange portion 22 toward the fixed flange portion 23 side.

  As described above, the metal tube forming roll 31 of the present example includes 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 metal tube 10 is formed, so that the roundness of the roll recess after repair can be increased.

[Metal tube forming method and apparatus]
The metal tube forming apparatus according to the present embodiment includes any one of the metal tube forming rolls 1, 11, and 31 shown in FIG. 1, FIG. 3, or 9, and a part of the metal tube forming rolls 1, 11, and 31. And a lubrication nozzle for supplying a lubricant during metal tube forming. Although the use of a lubricant and the use of the lubrication nozzle shown here are desirable, whether or not to use a lubricant and whether or not to use a lubrication nozzle may be appropriately selected as necessary. When using a lubricant, other methods such as applying the lubricant by immersing it in a cloth or spraying the lubricant with a spray may be used.

In general, when a metal pipe is actually formed, a water-soluble lubricant is often used for prevention of pipe flaws and cooling in a regular process after metal pipe welding.
Therefore, in order to further improve the life of the metal tube forming roll according to the present embodiment and prevent roll marks and wrinkles on the roll surface, the metal 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 metal tube forming apparatus provided with a lubrication nozzle will be described with reference to the drawings. However, the drawings shown below are for explaining the configuration of the metal tube forming apparatus, The size, thickness, dimensions, and the like may differ from the actual dimensional relationship of the heating furnace.

  10A and 10B are diagrams showing a metal tube forming apparatus according to the present embodiment, where 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 metal tube forming apparatus, and FIG. 12B is a schematic side view. FIG.

The metal tube 10 is conveyed while being formed by the metal tube forming rolls 1, 11, 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, 11, 31 and the metal 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 metal 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 metal tube forming rolls 1, 11, and 31. 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 this 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, 11, and 31. 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.

The angle adjustment for positioning the lubrication nozzle 101 in consideration of the contact with the metal tube 10 due to the variation of the diameters of the metal tube forming rolls 1, 21, 31 is performed by a lubrication nozzle sandwiching jig (lubrication nozzle front-rear adjustment 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 clamping 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 metal tube forming rolls 1, 21, 31 and the metal tube 10 are in contact.

  Here, as a lubricant, a soluble oil lubricant which is a water-soluble cutting fluid is most suitable from the viewpoint of lubrication performance and ease of removing the lubricant attached to the product.

It is necessary to adjust the arrangement position of the lubrication nozzle 101 so as to correspond to the roll flange portion according to the metal tube size (roll flange width). Further, depending on the state of roll lubrication, it is necessary to drop the metal tube forming rolls 1, 21, 31 onto the upper roll from above the roll.
FIG. 11 is a schematic front view for explaining an arrangement example of the lubrication nozzle 101. However, the metal 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 according to the flange width of the metal 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.
Two width adjusting screws 114 (left and right screws) that are reversed in the forward and reverse directions are disposed at a substantially central portion in the pipe-shaped horizontal movement guide 103. 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 position of the metal tube forming rolls 1, 21, 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 metal tube 10 and the metal 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 lubricating nozzle 101.
The lubricant is transported while being crushed by a roller 130 that rotates and revolves around a central axis 131, because a thick lubricant equivalent to the stock solution is attached to the roll in a small amount.
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 tube (roller) pump having a contamination rate of 20 ml / hr or less and without contamination.

  Here, as the lubrication nozzle 101, it is appropriate to use a tube having an inner diameter of 0.5 mm or more and 3 mm or less 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 rate of 1 ml / hr to 20 ml / hr.
When the supply rate of the lubricant is less than 1 ml / hr, the function as a lubricant cannot be sufficiently exerted. On the other hand, when the supply rate exceeds 20 ml / hr, the function as a lubricant is saturated, rather, metal tube forming is performed. Rolls 1, 21, and 31 are caused to slip, which hinders metal tube forming, increases the amount of lubricant to be removed from the final product, and increases manufacturing costs.

As described above, according to the metal tube forming roll according to the present invention, the CrN film and the diamond-like carbon film (DLC film) are formed on the base material, so that the wear resistance and the adhesion resistance are improved. be able to. 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, by making the upper layer region of the DLC film hard, it can exhibit excellent wear resistance against metal pipes, and also contains some sp ² hybrid orbital (graphite structure) carbon and low friction properties 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.

  Further, when forming the metal tube, the friction coefficient of the forming roll, particularly the drive roll, can be reduced by forming the metal pipe while dripping a small amount of lubricant onto 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 metal tube forming roll, the metal tube forming apparatus, and the metal tube forming 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.
The metal tube forming apparatus and the metal tube forming method shown in FIGS. 10 to 13 can exhibit particularly excellent effects when forming a titanium tube as a metal tube.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this 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 base material 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 base material 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.

With respect to the forming roll, component analysis was performed using a glow discharge emission spectrometer (GDS) in the depth direction from the CrN coating surface. The analysis results are shown in FIGS. 14 to 16, the horizontal axis indicates the depth (μm) from the CrN layer surface, and the vertical axis indicates the concentration (mass%) of each component.
As shown in FIGS. 14 and 15, it can be seen that a CrN layer having a thickness of 1.5 μm is formed on the substrate surface layer. 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, the surface of the molding roll (CrN film) was previously subjected to plasma cleaning to remove dirt, and then a diamond-like carbon film (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 diamond-like carbon film (DLC film) with a thickness of 1.0 μm was formed on the CrN film by ion plating.

<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 the comparative example was measured by Raman spectroscopy.
The 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 clear 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 was measured. Since the thickness of each of these layers and films was extremely thin, the Vickers hardness was measured by performing an indentation test with an extremely low load by a nanoindentation (indentation) method. In each layer and film, three points were measured in the cross section, and the average was taken as “Vickers hardness”. The nitride layer was measured in the vicinity of the surface layer with the highest nitrogen concentration (region up to a depth of 2 μm). The DLC film has a region 20% deep from the film surface (near the surface), a region 20% deep from the interface between the DLC film and the CrN film (near the interface), and the center of the DLC film in the film thickness direction. Measurements were made at a total of three locations (inside the DLC film).
As a result, 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, 3000 for “inside the DLC film”, and “near the surface” of the DLC film. Was 3500, and a hardness gradient was imparted 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, 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 z, “DLC film inside” was 2000, “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, mechanical properties were evaluated. The evaluation conditions were as follows: a JIS type 3 titanium metal pipe having a diameter of 25.0 mm and a thickness of 0.5 mm was used, the pipe making speed by TIG welding was set to 6 / min, and the 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 a JIS type 3 titanium tube was formed using the roll of the comparative example, roll wrinkles and film peeling occurred without standing for 30 minutes, and the CrN film was exposed.

(Example 2, Reference Example 1)
The forming roll shown in FIG. 3 was manufactured. 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. This forming roll was used as the forming roll of Reference Example 1.
Moreover, 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. This forming roll was used as the forming roll of Example 2. The quality of the CrN film and the DLC film in each forming roll was the same as in Example 1.

  Using these forming rolls of Example 2 and Reference Example 1, a 25.0 mm diameter, 0.5 mm thick ordinary steel pipe, a SUS304 stainless steel pipe, and an industrial weld metal pipe of JIS type 3 titanium pipe were formed. The forming conditions were as follows: ordinary steel pipe, SUS304 stainless steel pipe, and JIS class 3 titanium pipe were each TIG welded, and the pipe making speed was 6 / min. After the welding, the roll shown in FIG. 3 was used in the forming apparatus shown in FIG. 10, and a soluble oil lubricant was used as the lubricant only during the production of the titanium tube, and molding was performed while dripping this lubricant in a small amount at 10 ml / hr. . No lubricant was used in forming ordinary steel pipe or SUS304 stainless steel pipe. 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 forming for 300 hours continuous production is shown by a solid line, and the allowable range of roundness as a 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.

In ordinary steel pipes, SUS304 stainless steel pipes, and titanium pipes that have been continuously manufactured for 300 hours using rolls adjusted to have a gap of 10 μm or less, the roundness measurement results show that all roundness tolerances ( It was within ± 10 μm of the radius of the target circle), and it was possible to stably perform pipe making with high roundness.
Further, as shown in FIG. 19, the roundness of the titanium tube in both Example 2 and Reference Example 1 was good and was within the allowable range of roundness as a titanium tube product. Showed higher roundness. Moreover, in the reference example 1, 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.
Further, in Example 2 and Reference Example 1, 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 do not occur, and the continuous pipe making It was possible to continue.
Furthermore, in a normal steel pipe and a SUS304 stainless steel pipe formed using a roll whose gap is adjusted to 10 μm and without using a lubricant, the center part of the roll or the fixed flange part and the rotating flange part after 300 hours continuous pipe production. There was no seizure between the two and continuous pipe production was possible.
Therefore, even if the gap between the rotating flange portion 22 and the protruding portion 21b of the roll central portion 21 is adjusted to 10 μm or less as in Example 2, and they slide with each other during pipe making, the CrN film It can be seen that the reduction of the coefficient of friction by the DLC film and the DLC film is desirable from the viewpoint that they can be continuously produced without any problems, can maintain the roundness of the metal tube product, and prevent wrinkling.

  DESCRIPTION OF SYMBOLS 1, 21, 31 ... Metal tube forming roll, 3 ... Rotating shaft, 10 ... Metal tube, 12 ... Roll main body, 4, 14 ... Roll recessed part, 21 ... Roll center part, 21a1 ... Outer peripheral surface (opposite surface), 21a ... Base part, 21b ... Projection part, 22 ... Rotating flange part, 22b ... Inner peripheral surface (opposing surface), 22c ... Outer surface (opposing surface), 23 ... Fixed flange part, 23b ... Opposing surface, 32 ... Pulling screw part, DESCRIPTION OF SYMBOLS 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 ... Type base, 108 ... Stand column attachment Jig, 109 ... Lubrication nozzle angle adjustment jig, 112 ... Lubrication nozzle angle fixing screw, 113 ... Lubrication nozzle front / rear adjustment jig, 114 ... Width adjustment screw (positive / screw use), 115 ... Width movement Guide parts, 116 ... vertical movement screw, 117 ... molding stand support, 118 ... wide moving groove, 119 ... wide moving guide, 120 ... stand fixing screw, 130 ... roller, 131 ... central axis, 132 ... silicon tube.

Claims (16)

A metal tube forming roll having a roll body provided with a roll recess having a semicircular cross-sectional view over the entire circumference,
The roll body includes at least 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 , Divided by the roll center portion and the rotating flange portion,
The roll center part and the rotating flange part are 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%, the balance is made of steel having a composition consisting of iron and impurities,
A CrN film and a diamond-like carbon film are sequentially laminated on the entire surface of the roll recess and the entire surface of the rotating flange portion,
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 A metal characterized in that it is 0.5 to 0.7 in the range of 20% depth and 0.3 to 0.5 in the range of 20% depth from the interface between the diamond-like carbon film and the CrN film. Tube forming roll.   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. Item 2. A metal tube forming roll according to Item 1. The roll body further includes a fixed flange portion disposed on both sides in the roll width direction of the pair of rotating flange portions and fixed to the roll center portion,
The metal pipe forming roll according to claim 1 or 2, wherein a pulling screw portion that pulls and fixes the rotating flange portion is provided on the fixing flange portion.   The width of the said roll recessed part in the said roll center part is the range of 0.7D-0.87D, when the outer diameter of the metal tube used as a workpiece | work is set to D, Any of Claim 1 thru | or 3 characterized by the above-mentioned. A metal tube forming roll according to claim 1.   The diamond-like carbon film has a Vickers hardness of 3000 to 3500 in the range of 20% depth from the film surface, and a Vickers hardness in the range of 20% depth from the interface between the diamond-like carbon film and the CrN film. The metal tube forming roll according to any one of claims 1 to 4, wherein the length is 2500 to 3000.   The metal tube forming roll according to any one of claims 1 to 5, wherein the diamond-like carbon film has a thickness of 0.5 µm to 2 µm.   The metal tube forming roll according to any one of claims 1 to 6, wherein the CrN film has a thickness of 0.5 µm to 5 µm.   The metal tube forming roll according to any one of claims 1 to 7, wherein the CrN film has a Vickers hardness of 800 to 2,000.   9. The metal tube according to claim 1, wherein a nitrided layer nitrided by plasma nitriding is formed on a surface of the roll center portion and the rotating flange portion. Forming roll.   The metal tube forming roll according to claim 9, wherein the nitride layer has a thickness of 0.5 μm to 5 μm.   The average nitrogen concentration of the said nitrided layer is 10.0-25.0 mass%, The metal tube forming roll of Claim 9 or 10 characterized by the above-mentioned.   12. The metal tube forming according to claim 9, wherein a concentration distribution of nitrogen in the nitride layer has a concentration gradient that decreases in a depth direction from the surface layer of the nitride layer. roll. One or both of the roll center part or the rotating flange part is further in mass%,
Mo: 0.70 to 1.20%,
V: 0.15-1.00%,
The metal tube forming roll according to any one of claims 1 to 12, characterized by comprising: One or both of the roll center part or the rotating flange part is further in mass%,
W: 0.60 to 0.80%,
The metal tube forming roll according to any one of claims 1 to 13, characterized by comprising:   A metal tube forming apparatus comprising the metal tube forming roll according to claim 1.   It forms using the metal tube forming roll as described in any one of Claims 1-14, The metal tube forming method characterized by the above-mentioned.