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Method for manufacturing seamless pipe

A manufacturing method, technology of seamless pipes, applied in the direction of metal rolling, etc., capable of solving problems such as rolling failure, poor bite, and insufficient prevention of inner surface defects, etc.

Active Publication Date: 2011-04-06
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although the method disclosed in Japanese Patent Application Laid-Open No. 61-3605 can prevent the occurrence of inner surface defects on the material to be rolled, it may cause rolling failure (hereinafter also referred to as "misroll") caused by bad bite or the like.
Also, the method disclosed in JP-A-2000-140911, like JP-A-03-13222, cannot sufficiently prevent the occurrence of inner surface defects at the top of the slab.

Method used

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  • Method for manufacturing seamless pipe
  • Method for manufacturing seamless pipe
  • Method for manufacturing seamless pipe

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0179] In Example 1, a slab with an outer diameter of 70 mm including the center was cut out from the round cast slab produced by Test No. A1 of the first invention, and then pierced and rolled to confirm the fifth invention The effect of the manufacturing method of the seamless pipe. As a plug to use, prepare the above image 3 A two zone plug of the shape shown and the above Figure 4 The shape of the head shown, Image 6 Dimensions of the various parts of these plugs are shown. Here, plug number C8 is a 2-zone type plug. All plugs are made of 0.5%Cr-1.5Mo-3.0%W alloy steel.

[0180] Table 6

[0181]

[0182] (Note) The unit of D, d, L1 to r and R is (mm), and the unit of θ is (°).

[0183] * Symbols indicate departure from the scope specified in the fifth invention.

[0184] The skewed rolls (main rolls) of the piercing and rolling mill were all set so that the outer diameter of the roll gouges was 410 mm, the skewed angle β was 0°, and the crossing angle γ was s...

Embodiment 2

[0204] In Example 2, a piercing and rolling test was carried out on a steel slab made of a round cast slab produced by the continuous casting method of the first invention using an actual piercing and rolling machine, and the advantages and disadvantages of the fifth to seventh inventions were examined. The effect of the manufacturing method of the seam tube.

[0205] Consisting of a circular cast slab manufactured by Test No. A1 of the first invention, with an outer diameter of 310 mm and a length of 5600 mm, C: 0.05% to 0.07%, Si: 0.05 to 0.3%, and Mn: 1.2 to 1.5% After heating the billet of the steel composition to 1250°C, a piercing and rolling test was carried out to produce a hollow tube with an outer diameter of 325 mm, a wall thickness of 48 mm, and a length of 10,000 mm.

[0206] As a plug for use, prepare the above Figure 4 3 types of plugs in the shape shown and image 3 2 zone type head shown. Table 9 shows the dimensions of the various parts of these plugs.

...

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Abstract

A process for producing a seamless pipe characterized by including a continuous casting step in which a round billet is cast in which the whole region in a central part having a diameter of at least 60 mm in the cross section is constituted of an isometric crystal structure and which has a carbon content of 0.1 mass% or lower and a diameter in terms of cross-section diameter beyond 300 mm. In theprocess for seamless-pipe production, the round billet produced in the continuous casting step may be pierced / rolled with a piercer under conditions in which the ratio of the billet rotation speed tothe billet outer-diameter draft is a value in a range suitable for the ratio of the gorge part diameter to the inlet diameter in the tilting rolls, thereby giving a seamless pipe reduced in defects in the inner surface. As a piercing plug may be used a plug of a suitable shape which is approximately cylindrical and has a spherical rolling part at the plug tip. Thus, Mannesmann fracture and circumferential-direction shear strain are significantly inhibited and no billet nipping failure occurs at all. This process for seamless-pipe production enables a seamless pipe having even higher inner-surface quality to be produced with exceedingly high productivity.

Description

technical field [0001] The present invention relates to a method of manufacturing seamless pipes. Specifically, it relates to a method for producing a seamless pipe that can produce a seamless pipe with few inner surface defects including a continuous casting process of a round billet and a piercing and rolling process, and the continuous casting process of the round billet can In order to reduce cracks in the axial center that tend to occur in the center of the slab, which is one of the causes of inner surface defects of the product, this piercing and rolling process uses the circular slab cast by the above-mentioned casting process to prevent the hollow tube ( hollow shell) internal surface defects without causing rolling failure. Background technique [0002] In the process of manufacturing seamless pipes from continuously cast slabs without rolling or forging processes by the Manesmann method, etc., the central part of the continuously cast slabs tends to have a unique ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B21B19/04B22D11/124B22D11/00B22D27/04
CPCB22D11/124B21B19/04
Inventor 山中章裕足立学山川富夫中池纮嗣下田一宗安乐敏朗
Owner NIPPON STEEL CORP