JPH0794046B2 - How to core a coiled steel pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for continuously drawing a metal pipe such as a long steel pipe or alloy pipe wound in a coil shape.

[Prior Art] As a method of processing a metal tube such as a steel tube into a small diameter tube or a deformed tube, a method of inserting a plug into the tube and cold drawing through a die, a so-called core drawing method, and a plug An empty drawing method is known in which only the dice are used to pull out without inserting. All of these conventional methods have been carried out on straight pipes, such as coiled long steel pipes and superalloys as known from Japanese Patent Application Laid-Open No. 60-137510 filed by the present applicant. The metal tube of No. has not been drawn. In the conventional straight pipe core drawing method, the straight pipe is immersed in a lubricating liquid tank to lubricate the inside of the pipe and then withdrawn, but when this is applied to a long coiled metal pipe, It is extremely difficult to draw over the entire length of the pipe. When a long metal pipe is drawn by a core drawing method, the plug and the inner surface of the pipe are burned due to lack of lubrication, which not only causes a flaw in the pipe but also shortens the life of the plug remarkably.

As a highly efficient method, a drawn tube with no flaws on the inner surface of the tube can be manufactured with high yield, and a required amount of liquid lubricant is inserted into the tube from one end of the coiled metal tube. Japanese Unexamined Patent Publication (Kokai) No. 62-242415 discloses a continuous drawing method for a coiled metal tube which is characterized by drawing through a die. However, even with good lubrication, plug pull-out, chattering, seizure, plug biting failure, etc. may occur, and good withdrawal may not be possible.

[Problems to be Solved by the Invention] The method of introducing the liquid lubricant into the pipe from one end of the coiled pipe is expensive and requires complicated work, resulting in poor workability. The present invention is to insert a small amount of lubricant in advance from one end of a coiled steel pipe, and then continuously draw a long coiled metal pipe without supplying a lubricant. While unwinding a long metal tube that has been cut, it is drawn by the core-drawing method, and the drawn tube has no flaws on the inner surface of the tube with good yield.
In addition, the object is to obtain a long coil metal by a highly efficient method.

[Means and Actions for Solving the Problem] In the present invention, the ratio Y of the outer diameter reduction rate (%) and the wall thickness reduction rate (%) is Y in core processing of a coiled steel pipe using a floating plug.
And the cross-section reduction rate (%) X satisfy the conditions (1) and (2).

Y ≦ 0.0018 (X−15) ² +0.5 (1) 15 ≦ X ≦ 50 (2) The metal tube targeted by the present invention may be any of carbon steel, low alloy steel, alloy steel, and the like. Hot extruded pipes, seamless pipes of various Mannesmann systems, welded pipes such as electric resistance welded pipes and TIG welded pipes, forged pipes are drawn and rolled by a stretch reducer and wound into a coil, and electric resistance welded pipes and TIG welding are performed. It is a long tube such as a metal tube wound into a coil shape without being drawn and rolled by a welded tube such as a tube, or a metal tube wound into a coil shape after cold drawing.

FIG. 2 shows a schematic diagram of a method for core processing of a coiled steel pipe which is the object of the present invention. As shown in the figure, the rewound coiled steel pipe 1 is inserted into the inside of the floating plug 2 and then passed through a die 3 to be cored into a steel pipe 4 having a predetermined diameter.

Next, the reasons for limitation will be described.

FIG. 1 shows the results of conducting a wide range of centering experiments on the centering method for coiled steel pipes and investigating various factors. In the figure, under the conditions marked with X, plug disconnection or tearing occurred, and under the conditions marked with ◯, the above trouble did not occur. If the ratio Y of the outer diameter reduction rate (%) and the wall thickness reduction rate (%) and the cross-section reduction rate (%) X satisfy the equations (1) and (2), the plug will not come off or break. It has become possible to perform good core processing.

Y ≦ 0.0018 (X−15) ² +0.5 (1) 15 ≦ X ≦ 50 (2) That is, if the cross-section reduction rate X is less than 15%, plug omission occurs, and if it exceeds 50%, tearing seizure may occur. Occur.
It is 15 ≦ X ≦ 50 that the floating plug core is stably performed.
The ratio Y of the outer diameter reduction rate A (%) and the wall thickness reduction rate B (%)
As for = A / B, stable centering is impossible in the range of Y> 0.0018 (X-15) ² +0.5 due to chattering or poor plug biting.

[Example] (1) C-0.10%, Si: 0.01%, Mn: 0.30% carbon steel, with an outer diameter of 15.9 mm, a wall thickness of 2.4 mm, and a length of about 900 m. Then, the one whose inner and outer surfaces are coated with zinc phosphate is set in a rewinding machine, straightened, and after inserting a cemented carbide floating plug, it is pre-processed by pressing and the die is removed. Outer diameter: 11.0 mm, wall thickness:
It was cored to 2.0 mm to produce a coiled steel pipe of 1500 m.
The conditions at this time are X = 44.5% and Y = 0.55. Both the inner and outer surfaces of the drawn tube had no flaws and had a beautiful surface texture.

(2) C: 0.02%, Cr: 18%, Ni: 8% stainless steel, outer diameter: 25.4 mm, wall thickness: 3.5 mm, length: about 400 m The outer surface of which is coated with zinc oxalate is set in a rewinding machine, straightened, inserted with a cemented carbide floating plug, and then passed through a die to have an outer diameter of 18.0 mm and a wall thickness. : Core length processed to 3.0 mm, length 6
A 50 mm coiled steel pipe was manufactured. The condition at this time is X = 4
1.7% and Y = 0.48. Both the inner and outer surfaces of the drawn tube had a beautiful surface texture with no defects.

[Effect of the Invention] According to the present invention, it is possible to efficiently manufacture a small-diameter coiled steel pipe having a beautiful surface property without a defect with a small amount of a lubricant and a high yield.

Further, the coiled metal tube pulled out according to the present invention,
If necessary, it can be softened and annealed for direct use in piping work, or can be appropriately subjected to drawing or bending, so that an extremely economical effect can be achieved.

According to the present invention, it becomes possible to manufacture a long steel pipe with high dimensional accuracy from a long coil steel pipe with a small amount of lubricant, and a remarkable economic effect can be exhibited.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the cross-section reduction rate and the wall thickness reduction rate / outer diameter reduction rate in the core drawing method. FIG. 2 is an explanatory diagram of a core-forming method to which the present invention is applied.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kozo Sugiyama, 3434 Shimada, Hikari City, Yamaguchi Prefecture, Nippon Steel Works, Ltd., Hikari Works, Ltd. (72) Yoshihiro Watanabe, 3434 Shimada, Hikari City, Yamaguchi Prefecture, Japan Kotsu Works Ltd. (56) References JP-A-63-242415 (JP, A) JP-A-2-25217 (JP, A) JP-A-2-155511 (JP, A)

Claims (1)

[Claims] 1. In core processing of a coiled steel pipe using a floating plug, the ratio Y of the outer diameter reduction rate (%) to the wall thickness reduction rate (%) and the cross-section reduction rate (%) X are the above (1). Expression and (2)
A method for coring a coiled steel pipe, characterized in that the method is performed under conditions that satisfy the formula. Y ≦ 0.0018 (X−15) ² +0.5 (1) 15 ≦ X ≦ 50 (2)