JP4506563B2 - Cold manufacturing method for ultra-thin seamless metal tubes - Google Patents

Description

  The present invention relates to a method for cold rolling a seamless metal tube, and in particular, a new method for dramatically expanding the manufacturable range on the thin wall side of a metal tube, and cold manufacturing of an ultrathin wall seamless metal tube. We are going to propose a method.

  Seamless metal tubes are sent to the cold working process if they cannot satisfy the requirements of quality, strength or dimensional accuracy in the hot finished state. As the cold working process, a cold drawing method using a draw bench mill and a cold rolling method using a cold pilga mill are generally used, but the present invention newly provides a cold rolling method using an inclined rolling mill. It is something to try.

  Inclined rolling mills are common in hot rolling processes, and are adopted as piercing rolling mills, stretch rolling mills or drawing rolling mills, but there are very few examples of adopting inclined rolling mills in cold rolling processes. In Non-Patent Document 1, only an example of a cold inclined rolling mill called a flow finisher is reported. The prior art will be described below by taking a flow finisher as an example.

  1A and 1B are explanatory views of a flow finisher, where FIG. 1B is a front view, FIG. 1A is a cross-sectional view taken along line AA in FIG. 1B, and FIG. Indicates. This rolling mill is a three-roll type inclined rolling mill that uses a plug as an inner surface regulating tool, and reduces the wall thickness while reducing the outer diameter of the tube 1 between the three rolls 3 and the plug 4. The rolled tube 2 is manufactured. In addition, the code | symbol 5 in a figure shows a plug support bar.

  In rolling using a flow finisher, the inner diameter reduction ratio is relatively small, the wall thickness processing ratio can be relatively large, the dimensional accuracy and straightness are excellent, the inner and outer surface skin is beautiful, and the taper tube is also Can be manufactured. This rolling mill can perform size-free rolling simply by replacing the plug, but on the other hand, the rolling speed is extremely slow and the production efficiency is difficult, so it can be used for the production of special tubes such as thin-walled tubes.

Japan Iron and Steel Institute: 23rd and 25th Nishiyama Memorial Technology Course, Hiroshi Kojima (November 1978 and March 1974), pages 111-112 Japanese Patent Application No. 2005-47510 (claims and paragraphs [0028] to [0032])

  The present invention has been made in view of the above problems, and its problem is to dramatically increase the wall thickness processing rate of the cold rolling mill and drastically improve the manufacturable range on the thin wall side of the metal tube. And providing a method for cold production of an ultra-thin seamless metal pipe using an inclined rolling mill.

  In order to solve the above-mentioned problems, the present inventor has advanced research and development based on the conventional problems, obtained the following knowledge, and completed the present invention.

  Generally, in the plastic processing of a pipe material, the wall thickness processing is achieved by extending the pipe material in the longitudinal direction (axial direction). That is, in the cold rolling process of the tube material using the inclined rolling mill, the thickness is reduced while reducing the thickness when the thickness is processed between the inclined roll and the plug, and the tube material is stretched in the longitudinal direction.

  Since the present inventor intends to stretch only in the longitudinal direction as described above when processing the thickness, the thickness reduction rate is limited, and it is difficult to further reduce the thickness. At the time of processing, it was considered that the above-mentioned problems could be avoided by extending in the circumferential direction as well as in the longitudinal direction. By the way, when considering the rolling of an annular product by a ring mill as an extreme case, the annular material is not stretched in the longitudinal direction (axial direction) but is stretched only in the circumferential direction, and the wall thickness can be reduced indefinitely. Is possible.

  Therefore, in the wall thickness processing of the tube material by the inclined rolling mill, regardless of whether it is hot rolling or cold rolling, when reducing the wall thickness between the roll and the plug or the mandrel, the wall thickness is reduced while expanding the diameter. Then, it may be extended in the circumferential direction at the same time as extending in the longitudinal direction. In particular, in the case of cold rolling, the deformation resistance is extremely high compared to the case of hot rolling, and the coefficient of friction between the tube material and the tool is extremely small, so it is easy to slip and the wall thickness processing is more difficult. It is necessary to keep this in mind.

  This invention is completed based on said knowledge, The summary is the cold manufacturing method of the ultra-thin wall seamless metal pipe using the inclination rolling mill shown to the following (1)-(4). is there.

  (1) Adopting a 2-roll or 3-roll type inclined rolling mill in the cold rolling process of seamless metal tubes, and reducing the wall thickness while expanding the raw tube using plugs or taper mandrels as inner surface regulating tools. A method for cold production of an ultra-thin seamless metal tube characterized by

  (2) The method for cold production of an ultra-thin seamless metal pipe according to (1), wherein a maximum finishing diameter of the plug or the tapered mandrel is larger than an outer diameter of the raw pipe.

  (3) The above-mentioned elementary metal pipe is characterized by using a seamless metal pipe whose thickness has been further reduced by re-heating and rolling the seamless metal pipe produced by the hot production process. The cold manufacturing method of the ultra-thin seamless metal pipe as described in 1) or (2).

  (4) The method for cold production of an ultra-thin seamless metal tube according to (3), wherein the hot stretch rolling is rolling that reduces the wall thickness while expanding the diameter using an inclined rolling mill .

  In the present invention, the “tilt rolling mill” means a rolling mill that includes a tilting roll and has a function of stretching the pipe material in the longitudinal direction and at the same time extending in the circumferential direction.

  The “ultra-thin seamless metal tube” means a seamless metal tube having a thickness of 1.2 mm or less.

  The “hot manufacturing process” means a hot pipe manufacturing process such as a Mannesmann mandrel mill process, a Mannesmann plug mill process, a Mannesmann Assel mill process, a Mannesmann push bench mill process, and a Eugene extrusion process.

  And “stretch rolling” means rolling the blank tube between an inner surface regulating tool such as a plug or a mandrel inserted into the blank tube and a roll.

  According to the method of the present invention, a 2-roll or 3-roll type inclined rolling mill is adopted in the cold rolling process of the seamless metal tube, and a plug or a tapered mandrel is used as an inner surface regulating tool. By reducing the wall thickness while expanding the pipe, an ultra-thin seamless metal pipe can be produced. Therefore, by using the method for producing an ultrathin seamless metal pipe according to the present invention, the manufacturable range on the thin wall side of the seamless metal pipe by the cold working method can be dramatically expanded.

  As described above, the present invention employs a 2-roll or 3-roll type inclined rolling mill in the cold rolling process of a seamless metal tube, and expands the raw tube by using a plug or a tapered mandrel as an inner surface regulating tool. A method for cold production of an ultra-thin seamless metal pipe characterized in that the thickness is reduced. Hereinafter, the method of the present invention will be described in more detail.

  An embodiment of the present invention is shown in FIGS. FIG. 2 is an explanatory view of a cold gradient rolling method according to the present invention using a plug as an inner surface regulating tool, wherein FIG. 2 (b) is a front view, FIG. 2 (a) is a cross-sectional view taken along line AA in FIG. c) shows a BB arrow view of (a). FIG. 3 is an explanatory view of a cold gradient rolling method using a taper mandrel as an inner surface regulating tool, and FIGS. 3 (a), (b) and (c) are the same as those in FIG.

  As shown in FIG. 2, an arrow in the figure is attached to a three-roll type inclined rolling mill provided with a plug 4 as an inner surface regulating tool, and the roll 3 is arranged with an inclination angle β and a crossing angle γ with respect to the pass line. The raw tube 1 is supplied from the direction indicated by, and the wall thickness of the raw tube 1 is reduced between the three rolls 3 and the plug 4 supported by the plug support rod 5 while reducing the wall thickness. To manufacture. Further, as shown in FIG. 3, even when the taper mandrel 6 is used as an inner surface regulating tool, the thickness of the raw tube 1 is reduced while the diameter of the raw tube 1 is increased, as in the case of FIG. Tube 2 is manufactured. In FIG. 2 and FIG. 3, for comparison with the conventional method, a three-roll type inclined rolling mill is shown as an inclined rolling mill, but the same applies to the case of using a two-roll type inclined rolling mill. Thus, the rolled tube 2 can be manufactured.

  In the present invention, a 2-roll or 3-roll type inclined rolling mill is employed in the cold rolling process of the seamless metal tube, and a plug or a tapered mandrel is used as an inner surface regulating tool, so that at least the inner diameter is not reduced. Reduce thickness. More preferably, a plug or tapered mandrel having a finished diameter larger than the outer diameter of the raw tube is used to reduce the wall thickness while expanding both the inner diameter and the outer diameter, and in the circumferential direction while extending in the longitudinal direction. It is also good to stretch.

  By using the method of the present invention, the manufacturable range on the thin-walled side of the seamless metal tube is dramatically expanded, but further by combining with the method described in Non-Patent Document 2 previously proposed by the present inventor. This makes it possible to produce a seamless metal pipe that is thinner. That is, the small-diameter thin-walled seamless metal pipe manufactured by the hot manufacturing process is heated again, and the inclined rolling mill according to the present invention is used with the small-diameter thin-walled seamless metal pipe reduced in thickness by adding stretch rolling. By performing the cold rolling used, an ultrathin seamless metal tube can be easily manufactured.

  Above all, in the additional hot drawing rolling process, if the diameter-rolling is performed by the inclined rolling mill, it is possible to produce an epoch-making ultra-thin seamless metal pipe by repeating the diameter-expanding rolling twice. An ultra-thin seamless metal tube having an outer diameter of 1-2 inches and a thickness of about 0.5 mm can be realized.

  In addition, in the cold rolling process, when the rolling is performed by using a plug, not only the spiral mark generated by the inclined rolling in the hot drawing rolling process can be lost, but also a new spiral mark is generated. So be careful. In this case, it is necessary to roll with the roll inclination angle as small as possible. However, if the spiral mark is unacceptable, cold drawing under light pressure must be added.

  In order to confirm the effect of the manufacturing method of the ultra-thin metal tube by the cold gradient rolling method of the present invention, the following tests were conducted and the results were evaluated.

(Invention Example 1)
An 18% Cr-8% Ni stainless steel pipe having an outer diameter of 34.0 mm and a wall thickness of 3.5 mm manufactured by the Mannesmann mandrel mill process was used as a test piece pipe, and a plug was used with a three-roll type inclined rolling mill. And cold rolled to an outer diameter of 50.8 mm and a wall thickness of 1.2 mm.
The test conditions and test results are summarized below.

Roll crossing angle: γ = 8 °
Roll tilt angle: β = 6 °
Plug diameter: dp = 47.4mm
Raw tube outer diameter: do = 34.0 mm
Tube thickness: to = 3.5mm
Pipe outer diameter after cold inclined rolling: d ₁ = 50.8 mm
Tube thickness after cold gradient rolling: t ₁ = 1.2 mm
Expansion ratio: d ₁ /do=1.49
Drawing ratio: to (do-to) / {t ₁ (d ₁ -t ₁ )} = 1.79
(Wall thickness / outer diameter) ratio: t ₁ / d ₁ = 2.36%
In the above test, a plug was used as an inner surface regulating tool, but the roll inclination angle was reduced and roll expansion was performed, so the occurrence of spiral marks was slight, the inner surface of the steel pipe was beautiful, and in terms of quality, There was no particular problem.

(Invention Example 2)
A 25% Cr-35% Ni-3% Mo high alloy steel pipe having an outer diameter of 25.4 mm and a wall thickness of 3.3 mm manufactured by the Mannesmann mandrel mill process was used as a test element pipe, which was reheated to 920 ° C. At a temperature of 5 mm, the film was expanded and stretched to a diameter of 38.2 mm and a wall thickness of 1.2 mm using a plug with a 2-roll type inclined rolling mill. The obtained tube was used as a raw tube, and in the cold rolling step, it was diameter-rolled to a outer diameter of 50.8 mm and a wall thickness of 0.5 mm using a taper mandrel with a three-roll type inclined rolling mill.

The test conditions and test results are summarized below.
(1) Hot inclined rolling process (using a 2-roll type inclined rolling mill and plug)
Roll crossing angle: γ = 20 °
Roll tilt angle: β = 12 °
Rolling temperature: 920 ° C
Plug diameter: dp = 34.0 mm
Base tube outer diameter: do = 25.4 mm
Tube thickness: to = 3.3mm
Tube outer diameter after hot gradient rolling: d ₁ = 38.2 mm
Tube thickness after hot gradient rolling: t ₁ = 1.2 mm
Expansion ratio: d ₁ /do=1.50
Drawing ratio: to (do-to) / {t ₁ (d ₁ -t ₁ )} = 1.64
(Thickness / outer diameter) ratio: t ₁ / d ₁ = 3.14%
(2) Cold rolling process (using a 3-roll type inclined rolling mill and a tapered mandrel)
Roll crossing angle: γ = 8 °
Roll tilt angle: β = 6 °
Tapered mandrel diameter: dm = 48.6 mm
Base tube outer diameter: d ₁ = 38.2 mm
Tube thickness: t ₁ = 1.2 mm
Pipe outer diameter after cold gradient rolling: d ₂ = 50.8 mm
Tube thickness after cold gradient rolling: t ₂ = 0.5 mm
Diameter expansion ratio: d ₂ / d ₁ = 1.33
Drawing ratio: t ₁ (d ₁ -t ₁ ) / {t ₂ (d ₂ -t ₂ )} = 1.77
(Thickness / outer diameter) ratio: t ₂ / d ₂ = 0.98%
In the above test, since a taper mandrel was used in cold inclined rolling, the spiral marks generated in the two inclined rollings were acceptable and the skin inside and outside of the tube was beautiful. There was no problem in quality.

  According to the method of the present invention, an inclined rolling mill is adopted in the cold rolling process of the seamless metal pipe, and a plug or a taper mandrel is used as an inner surface regulating tool while expanding the diameter of the raw pipe by the cold inclined rolling method. By reducing the wall thickness, an ultra-thin seamless metal tube can be produced. Therefore, if a seamless metal pipe having a thickness of about 2/3 or less of a conventional cold-finished seamless metal pipe can be manufactured economically and stably, thin-walled welding such as TIG welded pipes and laser welded pipes. The metal tube can be replaced by a highly reliable ultra-thin seamless metal tube manufactured by the method of the present invention. Furthermore, if an ultra-thin seamless metal tube with an outer diameter of 1 to 2 inches and a wall thickness of 0.6 mm or less can be stably produced, a heating sleeve of a color laser printer, a pressure roll, or a fuel cell It can also be applied to high-tech fields such as cases.

It is explanatory drawing of the conventional cold rolling mill (flow finisher), The figure (b) is a front view, (a) is AA sectional drawing in (b), (c) is B of (a). -A B arrow view is shown. It is explanatory drawing of the cold gradient rolling method regarding this invention which uses a plug as an inner surface control tool, The same figure (b) is a front view, (a) is AA sectional drawing in (b), (c) is ( The BB arrow line view of a) is shown. It is explanatory drawing of the cold gradient rolling method regarding this invention which uses a taper mandrel as an inner surface control tool, The figure (b) is a front view, (a) is AA sectional drawing in (b), (c) is The BB arrow line view of (a) is shown.

Explanation of symbols

1: Raw tube, 2: Rolled tube, 3: Roll, 4: Plug, 5: Plug support rod, 6: Tapered mandrel,
β: Roll inclination angle, γ: Roll cross angle

Claims (4)

  A 2-roll or 3-roll type inclined rolling mill is used in the cold rolling process of seamless metal pipes, and the thickness is reduced while expanding the base pipe using a plug or a tapered mandrel as an inner surface regulating tool. A cold manufacturing method for an ultra-thin seamless metal pipe.   The method for cold production of an ultra-thin seamless metal pipe according to claim 1, wherein a maximum finishing diameter of the plug or taper mandrel is larger than an outer diameter of the raw pipe.   3. The seamless metal pipe having a thickness reduced further by heating and re-rolling the seamless metal pipe manufactured by a hot manufacturing process as the base pipe. 3. A method for cold production of an ultra-thin seamless metal tube according to claim 1. 4. The method for cold production of an ultra-thin seamless metal tube according to claim 3, wherein the hot drawing rolling is rolling that reduces the wall thickness while expanding the diameter using a tilt rolling mill.

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