JP2006231354A - Method of manufacturing ultra thin-walled seamless metallic tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an ultra thin-walled seamless tube by which a hot manufactured seamless metallic tube is used as a tube stock and the manufacturable range on the thin-wall side of the metallic tube can be radically expanded by cold-working after performing hot elongation rolling of the tube stock. <P>SOLUTION: The method of manufacturing the ultra thin-walled seamless metallic tube is characterized in that the seamless metallic tube manufactured by a hot manufacturing process is used as the tube stock, thickness is reduced by performing the elongation rolling after reheating and the thickness is further reduced by a cold-manufacturing process. When performing the elongation rolling, it is desirable to perform a expansion and elongation rolling by using a two-roll type or a three-roll type skew rolling mill and using a plug the diameter of which is larger than the outside diameter of the tube stock. By this method, the ultra thin-walled seamless tube having a thickness of approximately about 1.0 mm is easily manufactured. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a seamless metal pipe, and more specifically, by using a seamless metal pipe produced by a hot production process as a base pipe, and further undergoing a hot drawing and rolling process, and then a cold production process. The present invention relates to a method for manufacturing an ultra-thin seamless metal pipe that drastically expands the range of manufacture on the thin-walled side of a seamless metal pipe.

  The manufacturing method of the seamless metal pipe includes a Mannesmann mandrel mill process, a Mannesmann plug mill process, a Mannesmann Assel mill process, or a Mannesmann push bench mill process. In these manufacturing methods, a solid billet heated to a predetermined temperature in a heating furnace is pierced by a piercing mill to form a hollow piece, which is drawn by a stretching mill such as a mandrel mill, plug mill, assel mill or push bench mill. The thickness is mainly reduced to form a hollow shell, and then the outer diameter is mainly reduced by a drawing mill such as a sizer or a stretch reducer to finish a metal tube having a predetermined size (Non-patent Document 1, Non-patent Document 2). Such).

  FIG. 1 is a diagram for explaining a Mannesmann mandrel mill process as an example of the above process, in which (a) is a rotary hearth type heating furnace, (b) is a rotary piercer (piercing and rolling mill), (c) ) Shows a mandrel mill (drawing rolling mill), (d) shows a reheating furnace, and (e) shows a stretch reducer (drawing rolling mill).

  In addition to these Mannesmann processes, there is the Eugene extrusion process. In this process, billets with holes prepared by machining are extruded at once using an extrusion press to form metal pipe products.

  A part of the metal tube product manufactured by the above hot manufacturing process is sent to the cold manufacturing process, where it is cold drawn by a draw bench mill, a cold punching process by a push bench mill, or a cold pilger. By a process such as a cold rolling process using a mill, the outer diameter and the wall thickness are reduced to a predetermined size.

  FIG. 2 is an explanatory view showing a typical cold manufacturing process, in which FIGS. (A) to (c) are cold drawing methods using a draw bench mill, (a) is plug drawing, (b) Is a floating plug drawing, (c) is a mandrel drawing, (d) is a cold punching method using a push bench mill, and (e) is a cold rolling method using a cold pilger mill.

  In the cold drawing method using the draw bench mill shown in FIGS. 1A to 1C, the plug 2, the floating plug 5 or the mandrel 6 is inserted into the element tube 1, and the element tube 1 is pulled out through the die 4. Is cold drawn. The cold punching method using a push bench mill shown in (d) is a method in which a mandrel 6 is inserted into the base tube 1 whose one end is closed, and the base tube 1 is punched out through a die 4. In the cold rolling method using a cold pilger mill shown in (e), a mandrel 6 is inserted into a raw pipe having an outer diameter D, and rolling is performed by a roll 7 having a hole shape having a tapered cross-sectional shape in the circumferential direction. This is a method for manufacturing a finished pipe having an outer diameter d.

  The present invention relates to a method of manufacturing a seamless metal tube that is finished through a cold manufacturing process following a hot manufacturing process. In the following description, the Mannesmann mandrel mill process will be described as an example of the hot manufacturing process.

  In a mandrel mill, a mandrel bar is inserted inside a hollow piece drilled by a piercing rolling mill, and the whole bar is continuously rolled. Considering the area where the mandrel bar is in contact with the inner surface of the pipe as the groove bottom side of the perforated roll and the area where the mandrel bar is not in contact with the inner surface of the pipe as the flange side of the perforated roll, The deformation behavior of the pipe material is different between the bottom side and the flange side as follows.

  That is, the material on the groove bottom side is rolled while receiving an external pressure from the perforated roll and an internal pressure from the mandrel bar, and is stretched in the axial direction (longitudinal direction) and expands in the circumferential direction of the tube. . On the other hand, the flange side material is stretched by being stretched by the extension of the material on the groove bottom side without being in contact with the mandrel bar, and narrows in the circumferential direction. That is, in plastic deformation of the pipe in the mandrel mill, the material on the groove bottom side is deformed under external pressure, internal pressure, and axial compression force, and the material on the flange side has zero internal pressure. Deforms under directional tensile force.

  Furthermore, in the mandrel mill, the hole rolls of each stand are driven independently, so that tension or compressive force is generated between the stands depending on the setting of the rotation speed of the hole roll, and this is the internal stress of the shell in each stand. Is superimposed on. As a result, when the tensile stress in the axial direction on the flange side is high, fracture occurs on the flange side, creating a hole in the metal tube, and when the axial compressive stress on the groove bottom side is high, the groove bottom It will buckle on the side and cause undulations on the inner surface of the tube. This phenomenon is more prominent as the tube thickness decreases, which determines the minimum wall thickness that can be rolled in a mandrel mill.

Next, the plastic deformation of the pipe in the stretch reducer is the same as the plastic deformation on the flange side in the mandrel mill, and is deformed under external pressure and axial tensile stress. The tensile stress in the axial direction is maximized in the drawing rolling of the thin-walled tube and easily breaks. In general, when the deformation resistance of the metal material was k _f, a tensile stress sigma _l axial starts thinning pull to reach 0.5 k _f, breaks to reach 1.0k _f. Therefore, the reducing rolling step, interstand tension stress sigma _l it is necessary to control so as not to exceed the 0.9k _f. Considering that the inter-stand tension stress σ _l increases in inverse proportion to the wall thickness of the pipe entering the drawing mill, even if no drilling occurs in the mandrel mill, the thin-walled pipe is stretched by a stretch reducer or sizer. It is extremely dangerous to perform rolling with a continuous rolling machine such as the above.

  Although the wall thickness can be slightly changed by adjusting the stretch pattern with the stretch reducer, the minimum wall thickness that can be produced for seamless metal pipes in the hot manufacturing process is the minimum wall thickness that can be manufactured in a mandrel mill. In addition, this greatly affects the lower wall thickness that can be produced in the cold production process.

  Generally, the minimum manufacturable thickness in the mandrel mill is about 4.0 mm, and the lower limit of the thickness after finishing by the stretch reducer varies depending on the outer diameter of the metal tube, and the outer diameter is 30.0 to 40.0 mmφ. 3.5 mm in the range, 3.7 mm in the range of 40.0 to 70.0 mmφ, 4.0 mm in the range of 70.0 to 80.0 mmφ, 4.2 mm in the range of 80.0 to 90.0 mmφ, and 90.mm. In the range of 0 to 140.0 mmφ, it is about 4.5 mm. The lower limit of the wall thickness of the finished product after reducing the outer diameter and wall thickness by a draw bench mill, push bench mill or cold pilger mill in the cold manufacturing process is approximately the lower wall thickness limit in the hot manufacturing process. It becomes about 1/2.

  As described above, in the conventional pipe making method, there is a limit to reducing the thickness of the finished product even if the thickness reduction in the cold manufacturing process is further added to the thickness reduction in the hot manufacturing process. It has been difficult to drastically expand the manufacturable range on the thin side of the metal tube.

Edited by Japan Iron and Steel Institute: 3rd Edition Steel Handbook Volume 3 (2) Steel, Steel Pipe and Rolling Equipment (November 20, 1980) 903-1054

Chihiro Hayashi: Manufacturing method of steel pipe (October 10, 2000) 17-264

  The present invention has been made in view of the above problems, and the problem is that a seamless metal tube manufactured by a hot manufacturing process is used as a base tube, and after reheating, stretched and rolled, and further a cold manufacturing process Thus, an object of the present invention is to provide a method for producing an ultra-thin seamless metal tube that drastically expands the manufacturable range on the thin-wall side of a seamless metal tube.

  In order to solve the above-mentioned problems, the present inventor has conducted research based on the conventional problems, obtained the following knowledge (a) to (f), and completed the present invention.

  (A) Even if the conventional hot and cold manufacturing processes are strengthened and rolled under high pressure, the thickness of the seamless metal pipe is 3.0 mm in the hot manufacturing process, and in the cold manufacturing process. About 1.5 mm is the limit, and it is not possible to expect a reduction in thickness to reach that limit. However, if a spinning process is employed in the cold manufacturing process, the wall thickness can be reduced to 1.5 mm or less, but the production efficiency is remarkably lowered, and cannot be established economically.

  (B) In order to stably manufacture an ultra-thin metal tube having a wall thickness of approximately 1.2 mm or less in a cold manufacturing process, a thin-wall seamless metal tube manufactured by a conventionally known hot manufacturing process As a raw tube, it is necessary to further stretch and roll hot to make the wall thickness 2.0 mm or less, and to send it to the cold manufacturing process.

  (C) As a further drawing and rolling process in the above (b), the tube circumference is obtained by a two-roll type inclined rolling mill or a three-roll type inclined rolling mill rather than a continuous rolling method in which the rolling is performed in the tube axis direction like a mandrel mill. A tilt rolling method that rolls in the direction is also desirable. This is because, in the continuous rolling method in which rolling is performed only in the tube axis direction, problems such as material perforation and fracture may be repeated as in the conventional stretching and rolling process.

  (D) In the drawing and rolling process using the inclined rolling mill of (c) above, the diameter-expanded reduction rolling in which the plug is inserted rather than the diameter-reduction thickness reduction rolling method in which the mandrel bar is inserted inside the pipe and rolled together with the mandrel bar. The method is much more advantageous. In the reduced diameter reduction rolling method in which a mandrel bar is inserted, not only does the tube wall protrude between the inclined rolls, causing flaring and not only causing a motor stop, that is, an operation stoppage, but also a two-roll type inclined rolling. This is because, in the case of a machine, the flare tube is easily peeled off at the edge of the solid guide shoe or disk roll in the circumferential direction.

  (E) It is desirable to use a plug having a diameter larger than the outer diameter of the raw tube in the pipe expansion and drawing process by the inclined rolling mill of (d). Further, it is desirable to set the inclination angle of the rolling roll (angle β in FIG. 3 described later) as small as possible to reduce the spiral marks on the inner and outer surfaces of the pipe inevitably generated in the inclined rolling process as much as possible.

  (F) The cold production process includes a cold drawing method, a cold punching method, or a cold rolling method, and the spiral of the inner and outer surfaces of the pipe generated when a tilt rolling mill is used in the drawing and rolling process after the reheating. Erase the mark.

  In both the case of piercing and rolling, if a plug is used as the inner surface regulating tool of the inclined rolling mill, it is inevitable that spiral marks are generated on the inner and outer surfaces of the pipe. This spiral mark also appears in the further drawing and rolling in the present invention. In order to erase the spiral mark, a drawing and rolling process in which rolling is performed continuously in the tube axis direction or a drawing and rolling process using an inclined roll using a mandrel bar as an inner surface regulating tool is required. In the Mannesmann mandrel mill process, Mannesmann plug mill process, Mannesmann Assel mill process, Mannesmann push bench mill process, etc., a process for erasing the spiral mark is provided. Of course, if the spiral mark remains, it cannot be shipped to the market as a hot rolled product.

  The present invention is premised on a cold rolled product, and the spiral mark generated in the further hot drawing and rolling process of (b) is a tube in cold drawing, cold punching or cold rolling process. It is completely erased by the axial thinning rolling, and the inner and outer surfaces of the pipe are smooth and beautiful with very few irregularities. Even when tilt rolling is performed, when a mandrel bar is used as the inner surface regulating tool, the occurrence of spiral marks is extremely slight and does not cause a quality problem.

  The present invention has been completed on the basis of the above findings, and the gist thereof resides in a method for manufacturing an ultrathin seamless metal pipe shown in the following (1) to (4).

  (1) Using a seamless metal tube manufactured by a hot manufacturing process as a base tube, after reheating, stretch rolling to reduce the wall thickness, and after pickling, further reduce the wall thickness by a cold manufacturing process. A method for producing a featured ultra-thin seamless metal tube.

  (2) The method for producing an ultrathin seamless metal pipe according to (1) above, wherein an inclined rolling mill equipped with two or three rolling rolls is used when performing the stretching and rolling.

  (3) The method for producing an ultra-thin seamless metal pipe according to (2), wherein in the rolling using the inclined rolling mill, pipe expansion is performed using a plug.

  (4) The method for producing an ultra-thin seamless metal pipe according to (3), wherein a plug having a diameter larger than the outer diameter of the raw pipe is used in the pipe expansion rolling using the plug.

  In the present invention, the “hot manufacturing process” refers to 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. Means.

  The “cold manufacturing process” means a cold drawing process using a draw bench mill, a cold punching process using a solid die type push bench mill, or a cold rolling process using a cold pilger mill.

  “Ultra-thin seamless metal tube” means a seamless metal tube with a thickness of 2.0 mm or less after drawing and rolling after heating, or a seamless metal tube with a thickness of 1.2 mm or less after cold working. Means a metal tube.

  According to the method of the present invention, a seamless metal tube manufactured by a hot manufacturing process is used as a base tube, and after reheating, stretch rolling is performed to further reduce the wall thickness, and after passing through a cold manufacturing process, ultrathinness is achieved. Meat seamless metal tubes can be produced. Therefore, by applying the method for manufacturing a seamless metal pipe according to the present invention, the manufacturable range on the thin wall side of the seamless metal pipe can be drastically expanded.

  As described above, the present invention uses a seamless metal tube manufactured by a hot manufacturing process as a base tube, and after reheating, stretches and rolls to reduce the wall thickness, pickles, and further cools by a cold manufacturing process. An ultra-thin seamless metal pipe manufacturing method characterized in that the thickness is reduced.

  As the best mode of the present invention, it is desirable to employ a tube-stretching and rolling process in which a plug is inserted into a pipe and rolled using an inclined rolling mill in the drawing and rolling process. Although it is as having described in (c)-(e) of the term of the above, it cannot be overemphasized that the effect according to this invention is acquired even if it uses other thinning means.

  FIG. 3 is an explanatory view showing a tube-rolling process by an inclined rolling mill, in which (a) is a side view of the tube-rolling process, (b) is a plan view of (a), and (c) is of (a). Front views are shown respectively.

  The rotation center axis of the roll is inclined at an angle β (hereinafter referred to as “roll inclination angle”) with respect to a horizontal plane (or vertical plane) including the pass line 16, and the rotation center axis includes the pass line 16. Of a pair of rolling rolls (cone-type main rolls) 11 that are arranged to cross each other at an angle γ (hereinafter referred to as “roll crossing angle”) with respect to a vertical plane (or horizontal plane) and rotate in the same direction. The raw tube 14 is supplied to the gap from the direction indicated by the arrow X in the figure. The raw tube 14 is supplied into the gap of the rolling roll 11 while being guided around the pass line 16 by a disk roll 13 that is driven to rotate. The supplied raw pipe 14 is rolled in the pipe circumferential direction and the pipe axis direction while being given a spiral motion by the rolling roll 11, and is expanded by the plug 12 to form a stretched shell 15.

  Further, as described in the above (f), the cold production process includes a cold drawing method, a cold punching method, and a cold rolling method, and the inner and outer surfaces of the pipe generated by drawing rolling using a tilt rolling mill. The spiral mark is erased by thinning rolling in the tube axis direction, and the inner and outer surfaces of the tube are smoothed.

  In order to confirm the effect of the method for producing a seamless metal pipe according to the present invention, the following tests were conducted and the results were evaluated. In the test, as the best embodiment of the present invention, a pipe expansion and drawing process using a tilt rolling mill was adopted for the drawing and rolling process.

(Invention Example 1)
Carbon steel with an outer diameter of 34.0 mm and a wall thickness of 3.5 mm (C: 0.15%, Si: 0.35%, Mn: 1.20%, P: 0.010%, S: 0.010%) The steel pipe was used as a test element pipe. The specimen tube was manufactured by the Mannesmann mandrel mill process. Using the above-mentioned sample tube, tilt rolling with a tube expansion ratio of 1.50 was performed at a temperature of 920 ° C. using a pilot mill of a two-roll type inclined rolling mill, an outer diameter of 50.8 mm, and a thickness of 1. A 4 mm stretched shell was used. Furthermore, after cooling this, it was cold-drawn by an actual draw bench mill to produce a steel pipe having an outer diameter of 40.0 mm and a wall thickness of 1.2 mm.

Test conditions are shown below.
(1) Hot tube rolling conditions Roll crossing angle: γ = 25 °
Roll tilt angle: β = 8 °
Plug diameter: dp = 46mm
Raw tube outer diameter: do = 34.0 mm
Tube thickness: to = 3.5mm
Stretched shell outer diameter after rolling: d = 50.8 mm
Stretched shell wall thickness after rolling: t = 1.4mm
Expansion ratio: d / do = 1.50
Stretch ratio: to (do-to) / {t (dt)} = 1.54
(Wall thickness / outer diameter) ratio: t / d = 2.05%
(2) Cold drawing conditions Plug diameter: dp = 37.0 mm
Base tube outer diameter: do = 50.8mm
Tube thickness: to = 1.4mm
Pipe outer diameter after drawing: d = 40.0 mm
Tube thickness after drawing: t = 1.2mm
Drawing ratio: to (do-to) / {t (dt)} = 1.48
(Wall thickness / outer diameter) ratio: t / d = 3.00%
The spiral marks on the inner and outer surfaces of the drawn shell generated by tilt rolling using a plug completely disappeared by cold drawing, and a beautiful steel pipe with inner and outer surface skin could be obtained.

(Invention Example 2)
Similarly to Example 1 of the present invention, a steel pipe made of carbon steel having an outer diameter of 34.0 mm and a wall thickness of 3.5 mm was used as a test element pipe, and a tube expansion ratio was set at a temperature of 920 ° C. using a two-roll type inclined rolling mill. Is 1.62 and rolled into a stretched shell with an outer diameter of 55.0 mm and a wall thickness of 1.3 mm. After cooling, it is cold-punched with a pilot mill of a push bench mill, and has an outer diameter of 40.0 mm and a wall thickness. A 1.0 mm steel pipe was produced.

Test conditions are shown below.
(1) Hot tube rolling conditions Roll crossing angle: γ = 25 °
Roll tilt angle: β = 8 °
Plug diameter: dp = 50mm
Raw tube outer diameter: do = 34.0 mm
Tube thickness: to = 3.5mm
Stretched shell outer diameter after rolling: d = 55.0 mm
Stretched shell wall thickness after rolling: t = 1.3mm
Tube expansion ratio: d / do = 1.62
Stretch ratio: to (do-to) / {t (dt)} = 1.53
(Wall thickness / outer diameter) ratio: t / d = 2.36%
(2) Cold punching condition Mandrel outer diameter: dm = 37.0 mm
Base tube outer diameter: do = 55.0mm
Tube thickness: to = 1.3mm
Pipe outer diameter after punching: d = 40.0mm
Tube thickness after punching: t = 1.0mm
Punching ratio: to (do-to) / {t (dt)} = 1.79
(Thickness / outer diameter) ratio: t / d = 2.50%
The spiral marks on the inner and outer surfaces of the drawn shell generated by tilt rolling using a plug completely disappeared by the tandem punching process, and a beautiful steel pipe with an inner and outer surface skin was obtained.

(Invention Example 3)
Similarly to Example 1 of the present invention, a steel pipe made of carbon steel having an outer diameter of 34.0 mm and a wall thickness of 3.5 mm was used as a test element pipe, and a tube expansion ratio was set at a temperature of 920 ° C. using a two-roll type inclined rolling mill. Was 1.78 inclined rolling to obtain a stretched shell having an outer diameter of 60.5 mm and a wall thickness of 1.2 mm. Furthermore, after cooling this, it cold-rolled with the actual cold pilger mill (75VMR), and manufactured the steel pipe of outer diameter 40.0mm and thickness 0.8mm.

Test conditions are shown below.
(1) Hot tube rolling conditions Roll crossing angle: γ = 25 °
Roll tilt angle: β = 8 °
Plug diameter: dp = 56mm
Raw tube outer diameter: do = 34.0 mm
Tube thickness: to = 3.5mm
Stretched shell outer diameter after rolling: d = 60.5 mm
Stretched shell wall thickness after rolling: t = 1.2mm
Tube expansion ratio: d / do = 1.78
Stretch ratio: to (do-to) / {t (dt)} = 1.50
(Thickness / outer diameter) ratio: t / d = 1.98%
(2) Cold rolling conditions Mandrel outer diameter: dp = 37.0 mm
Base tube outer diameter: do = 60.5mm
Tube thickness: to = 1.2mm
Tube outer diameter after rolling: d = 40.0 mm
Tube thickness after rolling: t = 0.8mm
Feed amount: f = 8mm
Turn angle: θ = 60 °
Rolling ratio: to (do-to) / {t (dt)} = 2.27
(Thickness / outer diameter) ratio: t / d = 2.00%
The spiral marks on the inner and outer surfaces of the stretched shell generated by tilt rolling disappeared completely by cold rolling, and the inner and outer surfaces of the tube after cold rolling were beautiful.

  According to the method for manufacturing an ultrathin wall seamless metal pipe of the present invention, a seamless metal pipe manufactured by a hot manufacturing process is used as a base pipe, and is drawn and rolled after reheating, and further through a cold manufacturing process. The production range on the thin wall side of the seamless metal pipe can be drastically expanded. Therefore, by applying the method of the present invention, it is possible to expect a broad advance into the field of ultra-thin welded pipes such as TIG welded pipes and laser welded pipes.

It is explanatory drawing which shows a Mannesmann-mandrel mill process, The figure (a) is a rotary hearth type heating furnace, (b) is a rotary piercer (piercing rolling mill), (c) is a mandrel mill (drawing rolling mill), (d ) Shows a reheating furnace, and (e) shows a stretch reducer (drawing mill). It is explanatory drawing which shows a typical cold manufacturing process, The figure (a)-(c) is the cold drawing method by a draw bench mill, (a) is plug drawing, (b) is floating plug drawing. (C) shows mandrel drawing, (d) shows a cold punching method using a solid die type push bench mill, and (e) shows a cold rolling method using a cold pilger mill. It is explanatory drawing which shows the pipe expansion rolling process by an inclination rolling mill, The same figure (a) is a side view of a pipe expansion rolling process, (b) is a top view of (a), (c) shows the front view of (a). .

Explanation of symbols

1: Raw tube, 2: Plug, 3: Plug support rod, 4: Die, 5: Floating plug,
6: mandrel, 7: roll, 11: rolling roll (cone main roll), 12: plug, 13: disc roll, 14: base tube, 15: stretched shell,
16: Pass line of rolling mill,
β: Roll inclination angle, γ: Roll cross angle

Claims (4)

  A seamless metal tube manufactured by a hot manufacturing process is used as a base tube, and after reheating, stretch rolling is performed to reduce the thickness, and after pickling, the thickness is further reduced by a cold manufacturing process. Manufacturing method of ultra-thin seamless metal pipe.   The method for producing an ultra-thin seamless metal pipe according to claim 1, wherein an inclined rolling mill provided with two or three rolling rolls is used when performing the drawing and rolling.   3. The method for producing an ultra-thin seamless metal pipe according to claim 2, wherein in the stretching using the inclined rolling mill, the pipe is expanded using a plug. 4. The method for producing an ultra-thin seamless metal pipe according to claim 3, wherein a plug having a diameter larger than the outer diameter of the raw pipe is used in the pipe expansion rolling using the plug.

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