Method for producing seamless tube/pipe

Patent metadata

Field	Value
Publication number	US-9254511-B2
Application number	US-201113991635-A
Country	US
Kind code	B2
Filing date	Dec 6, 2011
Priority date	Dec 8, 2010
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

By using a piercing mill that includes a pusher on the entrance side, a plug on the exit side along a pass line, and a plurality of angled rolls as being provided around the plug so as face to each other, in the case where the maximum diameter of an unsound region consisting of center segregation and porosity in a cross section of a billet is d [mm], piercing-rolling is performed under the condition that the plug nose rolling reduction ratio (TDF) expressed by Formula (1) satisfies Formula (2).

TDF =(Bd− D 1)/Bd  (1)

TDF ≦−0.50×( d /Bd)+0.06  (2)

In Formulae (1) and (2), Bd is the billet diameter [mm], and D 1 is the opening [mm] between the angled rolls at the plug nose position. Thereby, when piercing-rolling is performed, the occurrence of an inner surface flaw attributable to the center segregation and porosity in the billet can be prevented reliably.

First claim

What is claimed is:

1. A method for producing a seamless tube/pipe by using a piercing mill including a pusher on the entrance side, a plug on the exit side along a pass line, and a plurality of angled rolls as being provided around the plug, the method comprising the steps of:
supplying a billet on the pass line, the billet including an unsound region consisting of center segregation and porosity in a cross section of the billet;
pushing the billet to convey the billet toward the angled rolls; and piercing-rolling the billet by the piercing mill so that a plug nose rolling ratio (TDF) expressed by Formula (1) satisfies Formula (2):
TDF =(Bd− D 1)/Bd  (1)

TDF ≦−0.50×( d /Bd)+0.06  (2)

where, in Formulae (1) and (2),
Bd: billet diameter [mm],
D 1 : opening [mm] between angled rolls at plug nose position, and
d: maximum diameter [mm] of the unsound region in the cross section of the billet.

2. The method for producing a seamless tube/pipe according to claim 1 , wherein
in the step of pushing the billet, after the billet has been pushed by the pusher and has been engaged into the angled rolls, the pushing of the billet by the pusher is continued until the piercing-rolling reaches a steady state.

3. The method for producing a seamless tube/pipe according to claim 2 ,
further comprising performing the piercing-rolling under a condition that a roll gorge draft (GDF) expressed by Formula (3) is in a range of 12% or more to 15% or less:
GDF=(Bd− D 2)/Bd×100  (3)

where, in Formula (3),
Bd: billet diameter [mm], and
D 2 : opening [mm] between gorge portions of angled rolls.

4. The method for producing a seamless tube/pipe according to claim 3 ,
further comprising using the plug having a geometry that satisfies Formula (4):
1.8≦Pl/Pd  (4)

where, in Formula (4),
Pl: length [mm] from plug nose to plug maximum diameter position, and
Pd: maximum plug diameter [mm].

5. The method for producing a seamless tube/pipe according to claim 2 ,
further comprising using the plug having a geometry that satisfies Formula (4):
1.8≦Pl/Pd  (4)

where, in Formula (4),
Pl: length [mm] from plug nose to plug maximum diameter position, and
Pd: maximum plug diameter [mm].

6. The method for producing a seamless tube/pipe according to claim 1 ,
further comprising performing the piercing-rolling under a condition that a roll gorge draft (GDF) expressed by Formula (3) is in a range of 12% or more to 15% or less:
GDF=(Bd− D 2)/Bd×100 . . .   (3)

where, in Formula (3),
Bd: billet diameter [mm], and
D 2 : opening [mm] between gorge portions of angled rolls.

7. The method for producing a seamless tube/pipe according to claim 6 ,
further comprising using the plug having a geometry that satisfies Formula (4):
1.8≦Pl/Pd  (4)

where, in Formula (4),
Pl: length [mm] from plug nose to plug maximum diameter position, and
Pd: maximum plug diameter [mm].

8. The method for producing a seamless tube/pipe according to claim 1 ,
further comprising using the plug having a geometry that satisfies Formula (4):
1.8≦Pl/Pd  (4)

where, in Formula (4),
Pl: length [mm] from plug nose to plug maximum diameter position, and
Pd: maximum plug diameter [mm].

Assignees

• Saitou Kenichi
• Shimoda Kazuhiro
• Yamakawa Tomio
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Saitou Kenichi
• Shimoda Kazuhiro
• Yamakawa Tomio

Classifications

• B21B19/04 Primary

  Rolling basic material of solid, i.e. non-hollow, structure; Piercing {, e.g. rotary piercing mills} · CPC title

• B21B25/00

  Mandrels for metal tube rolling mills, e.g. mandrels of the types used in the methods covered by group B21B17/00; Accessories or auxiliary means therefor {; Construction of, or alloys for, mandrels or plugs} · CPC title

• B21B2261/08

  Diameter · CPC title

• B21B21/02 Primary

  Rollers therefor · CPC title

• B21B2261/10

  Cross-sectional area · CPC title