JP2006326651A - Method for manufacturing very thin wall seamless metal pipe by cold-rolling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a very thin wall seamless metal pipe by a cold-rolling process, which method can remarkably extend the manufacturable range of the seamless metal pipe to the thin wall side. <P>SOLUTION: The method for manufacturing the very thin wall seamless metal pipe employs a cold pilger mill. In the method, remarkable thickness reduction can be achieved by carrying out the cold-rolling operation, while extending the diameter of the pipe, using a roll having a tapered bore, in which its diameter increases from the entrance side of the engagement of rolls toward the exit side of the finish of the engagement, and a tapered mandrel, in which its diameter increases from the entrance side of the engagement of rolls toward the exit side of the finish of the engagement. Especially, the very thin wall seamless metal pipe having a wall thickness of about 0.6 mm can be relatively easily obtained by reheating the small diameter thin wall seamless metal pipe manufactured by a hot-rolling process, and by hot-rolling the thin wall seamless metal pipe using an inclined rolling mill so as to extend its diameter, and further by carrying out the cold-rolling operation for the thin wall seamless metal pipe as a mother pipe so as to extend its diameter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for cold rolling a seamless metal pipe, and particularly greatly expands the production range of the seamless metal pipe on the thin wall side, and also manufactures an ultra-thin seamless metal pipe by the cold rolling method. Is to provide a method.

  The seamless metal pipe is sent to the cold working process when it does not satisfy quality, strength or dimensional accuracy requirements in the hot finished state. As the cold working process, a cold drawing method using a die and a plug or a mandrel and a cold rolling method using a cold pilga mill are generally used.

  In the cold rolling method using a cold pilga mill, a blank tube is formed between a pair of rolls having a tapered hole shape whose diameter gradually decreases in the circumferential direction and a tapered mandrel whose diameter gradually decreases in the length direction. Is subjected to reduction rolling. That is, a hole type is cut on the circumference of the pair of rolls, and the shape is such that the hole type becomes narrow as the roll rotates. The roll repeats advancing and retreating along the taper of the mandrel while rotating, and the raw tube is rolled between the roll and the mandrel (Non-Patent Document 1, Non-Patent Document 2, etc.).

  FIG. 1 is a diagram showing the principle of rolling by a cold pilga mill, in which FIG. 1 (a) is an explanatory diagram of a forward stroke start point, and FIG. 1 (b) is an explanatory diagram of a backward stroke start point. As shown in FIG. 1, in the cold pilgamill, the outer diameter and wall thickness dimension (do and to in the figure, respectively) of the raw tube 1 and the outer diameter and wall thickness dimension (respectively, FIG. Depending on d and t), the roll 2 having the tapered hole mold 3 whose diameter gradually decreases from the biting inlet side to the finishing outlet side of the pair of rolls, and also finishing from the biting inlet side The taper-shaped mandrel 4 that gradually decreases in diameter toward the outlet side is employed, and the reciprocating rolling process of reducing the wall thickness while reducing the diameter of the raw tube 1 is repeated.

  At the starting point of the reciprocating forward stroke and the starting point of the reverse stroke, the tube material (element tube 1) is intermittently given a rotation angle of approximately 60 ° and a feed of approximately 5 to 15 mm. The rolling of the part is repeated.

  Cold rolling with cold pilga mill has a very high degree of processing of the tube material, can be stretched approximately 10 times, has a great effect of correcting the uneven thickness of the tube, and does not require a drawing process, resulting in a high yield. There is an advantage. On the other hand, however, the production efficiency is extremely low compared to the cold drawing method. Therefore, the cost of high-grade pipes such as stainless steel pipes and high alloy steel pipes, which are mainly high in material costs and require intermediate processing, is low. Suitable for hot working. In addition, in the copper drawing industry, high-efficiency production is realized by three-strand rolling, and cold pilga mill is the most core manufacturing process in the copper drawing business.

  The present invention aims at technical development for further enhancing the above-described high workability characteristics of cold pilgamil.

Edited by Japan Iron and Steel Institute: Third Edition Steel Handbook, Volume 3 (2) Steel, Steel Pipe and Rolling Equipment (November 20, 1980) 996-1009 Chihiro Hayashi: Manufacturing method of steel pipe (October 10, 2000) 231-264

  The present invention has been made in view of the above-mentioned problems, and the problem is that an ultra-thin seamless metal tube by a cold rolling method that can dramatically expand the manufacturable range on the thin-wall side of a seamless metal tube. It is to provide a manufacturing method.

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

  Generally, the wall thickness processing in plastic processing of a pipe material is achieved by drawing and rolling a pipe material in the longitudinal direction of the pipe. That is, in the cold rolling of the tube material, when the wall thickness processing is performed between the perforated roll and the tapered mandrel, the tube material is rolled while being reduced in diameter and stretched in the longitudinal direction.

  On the other hand, the present inventor tries to stretch only in the longitudinal direction when plastically processing the pipe material to reduce the wall thickness, so that the amount of wall thickness reduction is limited and further thinning becomes difficult. It was considered that the above problem could be avoided if the pipe was reduced in thickness by cold pilga mill by extending in the longitudinal direction and also in the pipe circumferential direction. Incidentally, as an extreme case, when considering the rolling of an annular product by a ring mill, the annular material is not stretched in the longitudinal direction (axial direction) but is stretched only in the circumferential direction. It becomes possible without limit.

  In the cold pilgam mill, in order to extend in the longitudinal direction while extending in the pipe circumferential direction, the taper roll hole type whose diameter gradually increases from the biting inlet side to the finishing outlet side, A tapered mandrel that gradually increases in diameter from the biting inlet side toward the finishing outlet side may be employed to reduce the wall thickness while expanding the pipe material, and to perform rolling. In this case, if a tapered mandrel having a finishing maximum diameter larger than at least the outer diameter of the raw pipe is used, the diameter of the raw pipe can be reliably expanded.

  The present invention has been completed based on the above findings, and the gist thereof resides in a method for manufacturing an ultrathin metal tube by the cold rolling method shown in the following (1) to (4).

  (1) An ultra-thin seamless metal pipe manufacturing method using a cold pilga mill, in accordance with the outer diameter and wall thickness of the base pipe and the product rolling pipe, the finish outlet from the biting inlet side of the pair of rolls Using a roll having a tapered hole mold whose diameter gradually increases toward the side, and a tapered mandrel whose diameter gradually increases from the biting inlet side toward the finishing outlet side, the thickness is increased while increasing the diameter. A method for producing an ultra-thin seamless metal tube by a cold rolling method, characterized in that it is reduced and stretch-rolled.

  (2) The method for producing an ultra-thin seamless metal pipe by the cold rolling method according to (1), wherein a maximum finishing diameter of 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 manufacturing method of the ultra-thin wall seamless metal pipe as described in 1) or (2).

  (4) The method for producing an ultra-thin seamless metal pipe according to (3), wherein the hot stretch rolling is rolling that reduces the wall thickness while expanding the diameter using a tilt rolling mill.

  In the present invention, the “ultra-thin seamless metal tube” means a seamless metal tube having a wall thickness of 1.3 mm or less.

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

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

  According to the method of the present invention, in the cold rolling method using a cold pilga mill, a roll having a tapered hole shape whose diameter increases from the biting inlet side of the pair of rolls toward the finishing outlet side, and the biting inlet side By using a tapered mandrel whose diameter increases from the end toward the finish exit side, the ultrathin seamless metal pipe can be manufactured by extending and rolling while reducing the wall thickness while expanding the diameter. 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 metal pipe by the cold working method can be dramatically expanded.

  As described above, the present invention is a method for manufacturing an ultra-thin seamless metal pipe using a cold pilga mill, and has a tapered shape in which the diameter gradually increases from the biting inlet side to the finishing outlet side of a pair of rolls. Cold roll characterized by using a roll having a hole shape and a tapered mandrel whose diameter gradually increases from the biting inlet side to the finishing outlet side, and extending and rolling while reducing the wall thickness while expanding the diameter. It is a manufacturing method of an ultra-thin seamless metal pipe by a rolling method.

  An embodiment of the invention is shown in FIG. FIG. 4A shows the starting point of the forward stroke, and FIG. 5B shows the starting point of the backward stroke. As shown in FIG. 5A, a pair of upper and lower rolls 12 each having a tapered hole mold 13 with a diameter that smoothly increases from the biting inlet side toward the finishing outlet side is provided at the biting inlet. Advancing in the direction indicated by arrow A in the figure along the taper of the tapered mandrel 14 whose outer diameter smoothly increases from the side toward the finish outlet side, and the surface of the tapered hole mold 13 of the roll 12 The raw tube 1 is drawn and rolled between the surface of the tapered mandrel 14. Next, as shown in FIG. 4B, the pair of upper and lower rolls 12 are reversed and retracted in the direction indicated by the arrow B in the figure, and the tapered hole mold 13 of the roll 12 and the like. The raw tube 1 is stretched and rolled between the tapered mandrel 14.

  By repeating the reciprocating rolling process as described above, the base tube 1 having the outer diameter do and the wall thickness to is expanded and rolled into the product rolling tube 5 having the outer diameter d and the wall thickness t. The method of feeding and turning the pipe (element tube 1) performed at the starting point of the reciprocating stroke and the starting point of the return stroke is the same as the conventional method described above.

  In order to confirm the effect of the manufacturing method of the ultra-thin seamless metal pipe by the cold 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 with 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 element pipe, and an outer diameter of 50.8 mm was obtained with a cold pilga mill. Diameter expansion rolling was performed to a thickness of 1.3 mm.

  The test conditions and results are summarized below.

Tapered mandrel diameter: dm: 26.0-47.2 mm
Feed: f = 10.0mm
Turn angle: θ = 60 °
Raw tube outer diameter: do = 34.0 mm
Tube thickness: to = 3.5mm
Tube outer diameter after rolling: d ₁ = 50.8 mm
Tube thickness after rolling: t ₁ = 1.3 mm
Expansion ratio: d ₁ /do=1.49
Drawing ratio: to (do-to) / {t ₁ (d ₁ -t ₁ )} = 1.66
(Thickness / outer diameter) ratio: t ₁ / d ₁ = 2.56%
The inner and outer skins of the steel pipe obtained by the above test were beautiful, and there was no particular problem in quality. In addition, when cold-rolling by a conventional reduced diameter rolling method, the minimum wall thickness that can be produced for 18% Cr-8% Ni stainless steel pipe is about 2.0 mm when the outer diameter is 50.8 mm, It is clear that the effect of the diameter expansion rolling method of the present invention is remarkable.

(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 is expanded and rolled to an outer diameter of 38.2 mm and a wall thickness of 1.2 mm using a two-roll type inclined rolling mill, and then in the cold rolling step, an outer diameter of 50 is used using a cold pilga mill. The diameter was expanded to 0.8 mm and the wall thickness was 0.6 mm.

The test conditions and results are summarized below.
(1) Hot gradient rolling process Roll crossing angle: γ = 20 °
Roll tilt angle: β = 12 °
Plug diameter: dp = 34.0 mm
Base tube outer diameter: do = 25.4 mm
Tube thickness: to = 3.3mm
Pipe outer diameter after tilt rolling: d ₁ = 38.2 mm
Tube wall thickness after tilt 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 Tapered mandrel diameter: dm: 34.8-48.6 mm
Feed: f = 10.0mm
Turn angle: θ = 60 °
Base tube outer diameter: d ₁ = 38.2 mm
Tube thickness: t ₁ = 1.2 mm
Pipe outer diameter after cold rolling: d ₂ = 50.8 mm
Tube thickness after cold rolling: t ₂ = 0.6 mm
Diameter expansion ratio: d ₂ / d ₁ = 1.33
Drawing ratio: t ₁ (d ₁ -t ₁ ) / {t ₂ (d ₂ -t ₂ )} = 1.47
(Wall thickness / outer diameter) ratio: t ₂ / d ₂ = 1.18%
In the above test, the spiral mark generated in the inclined rolling process disappeared completely by cold rolling, and the inner and outer surface skins of the tube were beautiful.

  If the manufacturing method of the ultra-thin seamless metal pipe by the cold rolling method of the present invention is used, the manufacturable range on the thin wall side of the seamless metal pipe by the cold working method can be greatly expanded. If a seamless metal pipe having a thickness of about 2/3 or less of a conventional cold-finished seamless metal pipe can be produced economically and stably by the method of the present invention, a TIG welded pipe, a laser welded pipe Such a thin welded metal pipe can be replaced by a highly reliable ultrathin seamless metal pipe manufactured by the method of the present invention. Furthermore, if ultra-thin seamless metal pipes with a wall thickness of 0.6 mm or less can be produced stably, they can be applied to high-tech fields such as heating sleeves for color laser printers, pressure rolls, and cell cases for fuel cells. It becomes possible.

It is explanatory drawing of the conventional diameter reduction rolling method, The figure (a) shows a forward stroke start point, The figure (b) shows a backward stroke start point, respectively. It is explanatory drawing of the diameter-expansion rolling method which concerns on this invention, The figure (a) shows the forward stroke start time, and the figure (b) shows the backward stroke start time, respectively.

Explanation of symbols

1: Raw tube, 2: Roll, 3: Hole type, 4: Mandrel, 5: Product rolling tube, 12: Tapered hole type roll, 13: Tapered hole type, 14: Tapered mandrel, 15: Product rolling tube

Claims (4)

  A method for producing ultra-thin seamless metal pipes using cold pilgamil, from the bite inlet side to the finish outlet side of a pair of rolls, depending on the outer diameter and wall thickness of the base pipe and product rolled pipe. Using a roll with a tapered hole mold whose diameter gradually increases and a tapered mandrel whose diameter gradually increases from the biting inlet side to the finishing outlet side, the diameter is reduced while extending the diameter and stretched. A method for producing an ultra-thin seamless metal tube by cold rolling characterized by rolling.   The method for producing an ultra-thin seamless metal pipe according to the cold rolling method according to claim 1, wherein the maximum finished diameter of the tapered mandrel is larger than the 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. The manufacturing method of the ultra-thin wall seamless metal pipe as described in 2. The method for producing an ultra-thin seamless metal pipe according to claim 3, wherein the hot drawing rolling is rolling that reduces the wall thickness while expanding the diameter using an inclined rolling mill.

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