JPH07100509A - Manufacture of seamless steel tube - Google Patents

Abstract

PURPOSE:To uniformize rolling distribution and to decrease ununiform thickness by piercing and rolling a seamless steel tube with piercing rolls where the majority of the roll is parallel with a pass center when a seamless steel tube is set to a piercer in a manufacture of the seamless steel tube using a Mannessman piercer. CONSTITUTION:A draft becomes maximum in a gorge part but its distribution becomes uniform in the case of a barrel type roll since the majority of the roll is pierced and rolled with a piercing roll 1 parallel with the pass center when it is set to the piercer. Consequently, unnecessary swell of the element tube to the direction of a guide shoe is relieved, a gap between a plug and a shell in the direction of the guide shoe becomes small, the plug is stabilized in the shell, ununiform thickness is restrained, local damages to the plug and the guide shoe can be restrained and the lives of the plug and the guide shoe can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a seamless steel pipe which can extend the life of plugs and guide shoes and reduce the product thickness deviation in a Mannesmann punching machine.

[0002]

2. Description of the Related Art There are two-roll type and three-roll type punching machines of the inclined rolling type in the production of seamless steel pipe. In addition, according to the roll type classification of punching machines, the barrel type is generally used in the two-roll type, but historically, disk type or cone type mills have been used, and especially cone type mills are still used today. It is used in a small diameter size, and the barrel type is used in the 3-roll type. In the barrel-type Mannesmann puncher, a rolled material advances spirally, is rolled down by two rolls inclined in opposite directions, and then rolled by a plug and a roll.

For example, in a two-roll type punching machine, as shown in FIG. 6, the roll axes of the punching rolls 31 and 32 are inclined in opposite directions in a vertical plane by a predetermined angle θ.
Normally set parallel to each other in the horizontal plane. A guide shoe is provided in the vertical direction at the position of the piercing roll to guide the material being pierced and prevent the blank tube from bulging more than necessary.
The piercing roll of the above-mentioned inclined rolling type piercing machine is called a gorge at the maximum diameter part of the roll, and is generally parallel with a width of about 25 to 50 mm in order to smooth the change in wall thickness between the roll and the plug. . The face angle on the inlet side of the roll is 1 to 4
, Empirically, 2.5 to 3.5 ° is often used.
The smaller the inlet face angle, the smaller the bite resistance and the more stable the work, but on the contrary, the distance until the material reaches the plug becomes longer, the number of times of rotary forging increases, and internal collapse of material called tip cracking occurs. It is easy to cause internal flaws. The roll-out side angle of the roll is 2 to 4 °, and around 2.5 to 3.0 ° is used, and it is usually slightly looser than the inlet side. If the flank angle is too large, uneven thickness is likely to occur.

In the piercing and rolling by the Mannesmann piercing machine, the rolled material makes a spiral forward motion,
A roll and a plug apply a reduction every half rotation. The rolling reduction per half rotation is determined by the tool shape and these settings. In the piercing / rolling with the barrel-shaped piercing roll, as shown in FIG. 7, the rolling material 43 is subjected to the reduction at the maximum reduction rate by the gorge 42 of the piercing roll 41, so that the raw pipe swells more than necessary in the guide shoe direction. There is a problem that the gap between the plug 44 and the shell 45 becomes large in the guide shoe direction, and the plug 44 swings in the shell 45 to cause uneven thickness. As a method of solving the above problems, it has been proposed that the gorge 52 of the barrel-shaped piercing roll 51 is arcuate, as shown in FIG.

[0005]

The method of making the gorge of the above barrel type perforating roll into an arc shape is as shown in FIG.
Only local relaxation of the rolling of the gorge portion 52 is not achieved and the rolling distribution is not optimized, and the rolling material 53 is subjected to the rolling reduction at the maximum rolling reduction at the gorge portion 52. It bulges and the gap between the plug 54 and the shell 55 becomes larger in the guide shoe direction, and the plug 5
It is unavoidable that 4 is swung in the direction of the guide shoe to cause uneven thickness.

An object of the present invention is to reduce the uneven bulge by unnecessarily swelling the raw pipe in the guide shoe direction by making the reduction ratio distribution uniform in the piercing and rolling by the barrel type piercing roll. Another object of the present invention is to provide a method for manufacturing a seamless steel pipe capable of suppressing local wear of the plug and the guide shoe.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted various tests and examinations in order to achieve the above object. As a result, by using a piercing roll in which the main rolling part of the piercing roll is parallel to the pass center, the reduction ratio distribution in piercing and rolling becomes uniform, and excessive bulging of the raw pipe in the guide shoe direction is mitigated. It was found that the local wear of the plug and the guide shoe can be suppressed, and the present invention was reached.

That is, the present invention is characterized in that, in a method for producing a seamless steel pipe using a Mannesmann piercing machine, piercing and rolling is carried out by using a piercing roll in which most of the rolls are set parallel to the pass center when set in the piercing machine. It is a method for producing a seamless steel pipe.

[0009]

In the present invention, as shown in FIG. 3, most of the rolls are pierced and rolled by using the piercing roll 1 which is parallel to the pass center when set in the piercing machine. As shown in FIG. 1, the rolling reduction becomes maximum at the gorge portion, while as shown in FIG. 2, the rolling reduction distribution becomes uniform. Therefore, excessive bulging of the raw pipe in the guide shoe direction is mitigated, the gap between the plug and the shell in the guide shoe direction is reduced, the plug is stabilized in the shell, uneven thickness is suppressed, and the plug is Also, local wear of the guide shoe can be suppressed, and the life of the plug and the guide shoe can be extended.

The perforated roll shape according to the present invention is such that the entrance side and the exit side are small, the gorge portion occupies the majority, and the gorge portion which accounts for most of the roll when set on the perforator is parallel to the pass center. The flank angle and the flank angle are the same as the conventional barrel-shaped roll.

[0011]

[Example] An outer diameter of 225 mm and a length of 377 equivalent to carbon steel pipe STK540 for general structure specified in JIS G3444.
Using a Mannesmann punch, a 0 mm billet heated to 1260 ° C was used with a shell outer diameter of 228 mm and a wall thickness of 22.0 m.
m, length 10400 mm by piercing and rolling, product dimensions, outer diameter 177.8 mm, wall thickness 11.51 mm, length 10-12
When setting m, the barrel-shaped roll 11 shown in FIG.
And a roll 12 having a shape shown in FIG. 5A.
In the case of the method of the present invention using, the perforated rolls shown in Table 1 were perforated and rolled under the settings shown in Table 2, and the uneven thickness ratio was measured. The results are shown in FIGS. 4 (b) and 5 (b). The gorge length of the method of the present invention in Table 1 indicates the length of the portion parallel to the path center. In addition, 13 is a rolled material, 1
4 is a plug, 15 is a mandrel bar, and 16 is a shell.

[0012]

[Table 1]

[0013]

[Table 2]

As shown in FIG. 4 (b) and FIG. 5 (b), the uneven thickness ratio of the method of the present invention using a roll occupying most of the portion parallel to the path center is 8.16% on average in the conventional example. The comparison shows a reduction of 7.60%, and the deviation is significantly reduced to 1.19% compared to the conventional example of 1.48%. This is because by using a roll that occupies most of the part parallel to the path center, the strong reduction at the gorge part of the conventional example becomes small, the distribution of the reduction ratio becomes uniform, and the shell in the guide shoe direction is more than necessary. The bulging is alleviated, the gap between the shell and the plug in the guide shoe direction is reduced, and the plug is stabilized in the shell, whereby uneven thickness is improved.

[0015]

As described above, according to the method of the present invention, the rolling distribution in the Mannesmann puncher becomes uniform, uneven thickness is reduced, and local wear of the plug and the guide shoe is mitigated to prolong the life. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a distance from a gorge and a rolling reduction in a Mannesmann puncher for a conventional barrel type roll, together with roll and plug positions.

FIG. 2 is a graph showing the relationship between the distance from the gorge and the rolling reduction in the Mannesmann puncher for rolls of the present invention, together with roll and plug positions.

FIG. 3 is a schematic diagram showing the basic idea of the present invention.

4A and 4B show comparative examples in Examples, in which FIG. 4A is a schematic view of a rolling condition with a barrel-shaped roll, and FIG. 4B is a graph showing the relationship between the uneven thickness ratio and the occurrence frequency.

FIG. 5 shows the method of the present invention in Examples, (a)
The figure is a schematic view of the rolling condition of the roll of the present invention, and the figure (b) is a graph showing the relationship between the uneven thickness rate and the occurrence frequency.

FIG. 6 is a plan view of a barrel roll of a conventional Mannesmann puncher.

7A and 7B show reduction rates of a conventional barrel-type roll in a Mannesmann punching machine. FIG. 7A is an explanatory view of a roll beige position, and FIG. 7B is a relationship between a distance from a gorge and a reduction rate. It is a graph shown with and a plug position.

8A and 8B show a reduction ratio of a conventional Mannesmann punching machine for an improved barrel type roll. FIG. 8A is an explanatory diagram of a roll gorge portion, and FIG. 8B is a relationship between the distance from the gorge and the reduction ratio. It is a graph shown with a roll and a plug position.

[Explanation of reference numerals] 1, 31, 32, 41, 51 Perforated rolls 11 Barrel-shaped rolls 12 Rolls 42, 52 Gorges 13, 43, 53 Rolled materials 14, 44, 54 Plugs 16, 45, 55 Shells

Claims (1)

[Claims] 1. A method for producing a seamless steel pipe using a Mannesmann piercing machine, characterized in that piercing and rolling is performed by using a piercing roll in which most of the rolls are parallel to the path center when set in the piercing machine. Manufacturing method.