JPH04266405A - Method and device for manufacturing inside grooved seamless steel tube and plug - Google Patents

Abstract

PURPOSE:To enable manufacture of an inside grooved steel tube provided with a reasonable shape though the thickness is large. CONSTITUTION:The manufacturing device of an inside grooved seamless steel tube having a pair of rolling rolls 21 obliquely arranged with a fixed lead angle and a plug 22 which is arranged in the center of a rolled zone formed by each rolling roll 21 and provided with an annular projection 23 on the outer periphery.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for manufacturing seamless steel pipes with internal grooves, and a plug.

0002

2. Description of the Related Art As a type of steel pipe pile, there is a steel pipe concrete structure in which the inside of a steel pipe is filled with concrete in order to improve the earthquake resistance of the structure. Steel pipe concrete structures have excellent structural performance that can prevent buckling of steel pipes or brittle fracture of concrete, which would otherwise occur if steel pipes and concrete were used alone.

Conventionally, some of the above-mentioned steel pipe piles use steel pipes having grooves on the inner surface in order to increase the adhesion strength to concrete.

[0004] However, as for the conventional internally grooved steel pipe,
Projections are formed in advance on the surface of a hot-rolled steel strip, and these are (1) spirally wound and submerged arc welded (spiral steel pipe), or (2) both edges of a roll-formed steel strip are heated using high-frequency waves. Some are welded using resistance welding (ERW steel pipes).

[0005]

However, the prior art has the following problems (1) to (4).

(2) Since the protrusions are formed during the hot rolling process of the steel strip, special rolling rolls are required, which increases costs, and there is a risk that the protrusions may be damaged during hot winding.

[0007] During pipe manufacturing, the roll forming load acts intensively on the protrusions, damaging the protrusions here as well.

[0008] (1) Since pipe manufacturing requires cold working, thick-walled steel pipes cannot be manufactured.

[0009] An object of the present invention is to make it possible to manufacture a steel pipe having an internal groove of an appropriate shape, even if it is thick.

0010

[Means for Solving the Problems] The present invention as set forth in claim 1 provides that each of the rolling rolls forming a set is arranged inclined at a constant advance angle, and at the center of the rolling area formed by each rolling roll. A plug with ring-shaped protrusions on the outer periphery is placed, and while giving a spiral forward motion to the material to be rolled that is fed between the rolling rolls, the inner and outer surfaces are rolled to form a spiral inner groove on the inner surface of the tube. This is how it was done.

[0011] The present invention according to claim 2 includes a set of rolling rolls arranged at an angle with a constant advance angle, and a ring-shaped protrusion arranged at the center of the rolling area formed by each rolling roll. The plug is configured to include a plug.

[0012] According to a third aspect of the present invention, a ring-shaped protrusion is provided on the outer periphery of the reeling portion that enables the material to be rolled to be rolled between the rolling roll and the rolling roll.

[0013]

[Action] According to the present invention, there are the following effects (1) to (2).

(2) The material to be rolled is rolled between a rolling roll and a plug while being given a spiral forward motion. At this time, the ring-shaped protrusion provided on the plug forms a groove on the inner surface of the material to be rolled, and this groove is connected in a spiral shape on the inner surface of the tube and does not break.

(2) The shape of the inner groove can be controlled by the shape of the ring-shaped protrusion provided on the plug, and the pitch of the groove can be controlled by the advance angle of the rolling rolls.

(2) Complete the formation of the inner groove at the same time as the pipe making. Therefore, after the inner groove is formed, although there is a possibility of adjusting the outer diameter using a sizer or the like, there is no need to process the inner surface, and the shape of the groove will not be damaged.

[0017] A steel pipe with internal grooves is produced by hot working, and thick-walled steel pipes can also be produced.

[0018]

[Embodiment] Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2
is a plan view of FIG. 1, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1, FIG. 4 is a schematic diagram showing the protrusion shape of the plug, FIG. 5 is a schematic diagram showing the inner groove shape, and FIG. It is a schematic diagram showing a process.

In the Mannesmann plug mill tube manufacturing process shown in FIG. 6, the billet 1 is heated in a rotary hearth type heating furnace 2.
Its entire length is heated and then extracted. The billet 1 extracted from the heating furnace 2 is pierced by a piercer 3 to form a shell 4.
becomes. The shell 4 is enlarged in outer diameter and reduced in wall thickness by an elongator 5, reduced in wall thickness and stretched by a plug mill 6, and polished by a reeler 7 and grooved on the inner surface (described later). It becomes a seamless steel pipe 8. Thereafter, it is reheated in a reheating furnace 9, its outer diameter is reduced by a sizer 10, its dimensional accuracy is adjusted, and it passes through a cooling bed 11, a straightening machine 12, etc., and becomes a product tube.

However, in the present invention, in the reeler 7, which is the final inclined rolling mill in the Mannesmann plug mill tube manufacturing process, the inner groove is formed in the shell 4 as described above, and the seamless steel tube with the inner groove is formed. 8 is manufactured.

That is, as shown in FIGS. 1 to 3, the reeler 7 is arranged at the center of a rolling area formed by a pair of upper and lower rolling rolls 21 that are arranged at an angle at a constant advance angle θ. , and a plug 22 having a ring-shaped protrusion 23 on its outer periphery.

The reeler 7 rolls the inner and outer surfaces of the shell 4 fed between the rolling rolls 21 while giving it a spiral forward movement, thereby forming a spiral inner groove 8A on the inner surface of the tube.

In FIG. 2, V0 is the roll circumferential speed,
Vf is a forward velocity component, and Vt is a circumferential velocity component.

Here, the plug 22 is provided with a ring-shaped protrusion 23 on the outer periphery of the rear end of the reeling portion L that allows the shell 4 to be rolled between the plug 22 and the rolling roll 21 .

[0025] When a set of rolling rolls 21 constituting the reeler 7 is made up of two upper and lower rolls, two rolls are formed on the inner surface of the tube.
A striped inner groove 8A is formed (see FIGS. 3 and 5).

According to the above embodiment, the following effects (1) to (4) are obtained.

(2) The material to be rolled is rolled between the rolling rolls 21 and the plugs 22 while being given a spiral forward movement. At this time, the ring-shaped protrusion 23 provided on the plug 22 forms a groove 8A on the inner surface of the material to be rolled, and this groove 8A is connected in a spiral shape on the inner surface of the tube and is not cut.

■The shape of the inner groove 8A can be controlled by the shape of the ring-shaped protrusion 23 provided on the plug 22.
The pitch can be controlled by the advance angle of the rolling rolls 21.

(2) Forming of the inner groove 8A is completed at the same time as the pipe making. Therefore, after the inner groove 8A is formed, although there is a possibility of adjusting the outer diameter using a sizer 10 or the like, there is no need to process the inner surface, and the groove shape will not be damaged.

(2) The internally grooved steel pipe 8 is manufactured by hot working, and thick-walled steel pipes can also be manufactured.

[0031] Hereinafter, concrete implementation results of the present invention will be explained.

In the pipe manufacturing process of the above embodiment, the outer diameter was 30
A seamless steel pipe with an internal groove and a wall thickness of 20.0 mm was manufactured. The advance angle θ of the rolling rolls was 10 degrees, the ring-shaped protrusion provided on the plug was shaped as shown in FIG. 4, and the inner groove as shown in FIG. 5 could be formed. In the inner groove shown in FIG. 5, the groove width W=40 mm and the groove pitch S=83 mm. However, S
=(πD×tan θ)/2 (D is the diameter of the rolled material).

In the pipe manufacturing process of the above embodiment, two rolling rolls are used as a set, so there are two inner grooves, and a spiral groove with a groove width of 40 mm and a groove pitch of 166 mm is formed on the inner surface of the tube. This means that two pieces are formed.

[0034]

As described above, according to the present invention, it is possible to manufacture a steel pipe having an internal groove of an appropriate shape, even if it is thick.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is a plan view of FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is a schematic diagram showing the shape of a protrusion of a plug.

FIG. 5 is a schematic diagram showing the shape of the inner groove.

FIG. 6 is a schematic diagram showing a tube manufacturing process.

[Explanation of symbols]

7 Reeler (inclined rolling mill) 8 Seamless steel pipe with inner groove 8A Inner groove 21 Roll roll 22 Plug 23 Ring-shaped projection

Claims (3)

[Claims] 1. Each of the rolling rolls forming a set is arranged at an angle with a constant advance angle, and a plug having a ring-shaped protrusion on the outer periphery is arranged in the center of the rolling area formed by each rolling roll, A method for manufacturing a seamless steel pipe with internal grooves, characterized in that the inner and outer surfaces are rolled while giving a spiral forward motion to the material to be rolled that is fed between rolling rolls, thereby forming spiral inner grooves on the inner surface of the tube. . 2. A plug comprising: a set of rolling rolls tilted at a constant advance angle; and a plug disposed at the center of the rolling area formed by each rolling roll and having a ring-shaped protrusion on its outer periphery. A manufacturing device for seamless steel pipes with internal grooves. 3. A plug characterized in that a ring-shaped protrusion is provided on the outer periphery of a reeling portion that enables rolling of a material to be rolled between the plug and the rolling rolls.