Piercing machine, mandrel bar, and method for producing seamless metal pipe using the same

Patent metadata

Field	Value
Publication number	US-11344935-B2
Application number	US-201816762241-A
Country	US
Kind code	B2
Filing date	Nov 28, 2018
Priority date	Nov 29, 2017
Publication date	May 31, 2022
Grant date	May 31, 2022

Abstract

A mandrel bar of a piercing machine includes: a bar body; a coolant channel formed inside the bar body and through which a coolant flows; an inner surface cooling mechanism which is disposed in a cooling zone and is connected to the coolant channel and which, during piercing-rolling or during elongating rolling, ejects the coolant to outside of the bar body to cool an inner surface portion of a hollow shell inside the cooling zone; and an inner surface damming mechanism which is disposed adjacent to the cooling zone on a rearward side of the cooling zone and which, during piercing-rolling or during elongating rolling, suppresses the coolant that is ejected to outside of the bar body from contacting the inner surface portion of the hollow shell that is positioned rearward of the cooling zone.

First claim

The invention claimed is:

1. A piercing machine that performs piercing-rolling or elongating rolling of a material to produce a hollow shell, comprising:
a plurality of skewed rolls disposed around a pass line along which the material passes;
a plug disposed on the pass line between a plurality of the skewed rolls; and
a mandrel bar body extending rearward of the plug along the pass line from a rear end of the plug, the mandrel bar body comprising:
an inner surface cooling mechanism providing a cooling zone at a fore end portion of the mandrel bar body, the inner surface cooling mechanism comprising:
a coolant channel formed inside the mandrel bar body allowing a coolant to pass therein; and
a plurality of coolant ejection holes connected to the coolant channel and arrayed circumferentially about and axially rearwardly along the mandrel bar body,
wherein, during piercing-rolling or during elongating rolling, the inner surface cooling mechanism ejects the coolant that is supplied from the coolant channel to outside of the bar body to cool an inner surface of the hollow shell that is advancing within the cooling zone; and

an inner surface damming mechanism disposed adjacent to the cooling zone on a rearward side of the cooling zone providing a contact suppression zone rearwardly adjacent the cooling zone, the inner surface damming mechanism comprising:
a compressed gas channel formed inside the mandrel bar body through which compressed gas passes; and
a plurality of compressed gas ejection holes connected to the compressed gas channel and arrayed circumferentially about and axially rearwardly along the mandrel bar body,
wherein, during piercing-rolling or during elongating rolling, the inner surface damming mechanism ejects compressed gas supplied from the compressed gas channel to outside of the mandrel bar body to suppress contact of the coolant ejected to outside of the bar body with the inner surface of the hollow shell after the hollow shell leaves from the cooling zone.

2. The piercing machine according to claim 1 , wherein:
the inner surface damming mechanism dams the coolant ejected to outside of the bar body, and accumulates the coolant between the bar body and the inner surface of the hollow shell within the cooling zone.

3. The piercing machine according to claim 1 wherein: the inner surface damming mechanism dams the coolant ejected to outside of the bar body, by means of the compressed gas ejected to outside of the bar body, and accumulates the coolant between the bar body and the inner surface of the hollow shell within the cooling zone.

4. The piercing machine according to claim 1 , wherein:
the mandrel bar body further includes:
a drainage channel that is formed within the mandrel bar body and in which the coolant ejected to outside of the mandrel bar body flows, and one or more drainage holes that is disposed within the cooling zone in the mandrel bar body, and is connected to the drainage channel and recovers the coolant ejected to outside of the bar body.

5. The piercing machine according to claim 1 , wherein:
the inner surface cooling mechanism causes the coolant in the cooling zone to swirl around the mandrel bar body by ejecting the coolant from the coolant ejection holes.

6. The piercing machine according to claim 1 , wherein:
the inner surface damming mechanism causes the compressed gas in the contact suppression zone to swirl around the mandrel bar body by ejecting the compressed gas from the compressed gas ejection holes.

7. The piercing machine according to claim 6 , wherein:
as seen from an advancing direction of the hollow shell, a swirling direction of the coolant ejected from a plurality of the coolant ejection holes is clockwise or counterclockwise,
as seen from an advancing direction of the hollow shell, a swirling direction of the compressed gas ejected from a plurality of the compressed gas ejection holes is clockwise or counterclockwise, and
the inner surface damming mechanism ejects the compressed gas so that the swirling direction of the compressed gas becomes the same as the swirling direction of the coolant.

8. The piercing machine according to claim 6 , wherein:
the inner surface cooling mechanism includes a plurality of annularly arranged coolant-ejection-hole groups that are arrayed in the axial direction of the bar body in the cooling zone of the bar body,
the annularly arranged coolant-ejection-hole group includes a plurality of the coolant ejection holes that are arrayed in the circumferential direction at a same position in the axial direction of the bar body, and
in the inner surface cooling mechanism:
when a distance in the axial direction of the bar body that the swirl flow of the coolant advances until completing one rotation around the bar body is defined as “one swirl period distance”, in the axial direction of the bar body, a distance between the annularly arranged coolant-ejection-hole groups that are adjacent is the same as the one swirl period distance.

9. The piercing machine according to claim 1 , further comprising:
an outer surface cooling mechanism disposed around the mandrel bar, at a position that is rearward of the plug,
wherein, with respect to the outer surface of the hollow shell that is advancing through the cooling zone, as seen from an advancing direction of the hollow shell, the outer surface cooling mechanism ejects a cooling fluid toward an upper part of the outer surface, a lower part of the outer surface, a left part of the outer surface and a right part of the outer surface to cool the hollow shell inside the cooling zone.

10. The piercing machine according to claim 9 , wherein:
the outer surface cooling mechanism includes:
an outer surface cooling upper member disposed above the mandrel bar as seen from an advancing direction of the hollow shell, the outer surface cooling upper member including a plurality of cooling fluid upper-part ejection holes which eject the cooling fluid toward the upper part of the outer surface of the hollow shell in the cooling zone;
an outer surface cooling lower member disposed below the mandrel bar as seen from the advancing direction of the hollow shell, the outer surface cooling lower member including a plurality of cooling fluid lower-part ejection holes which eject the cooling fluid toward the lower part of the outer surface of the hollow shell in the cooling zone;
an outer surface cooling left member disposed leftward of the mandrel bar as seen from the advancing direction of the hollow shell, the outer surface cooling left member including a plurality of cooling fluid left-part ejection holes which eject the cooling fluid toward the left part of the outer surface of the hollow shell in the cooling zone; and
an outer surface cooling right member disposed rightward of the mandrel bar as seen from the advancing direction of the hollow shell, the outer surface cooling right member including a plurality of cooling fluid right-part ejection holes which eject the cooling fluid toward the right part of the outer surface of the hollow shell in the cooling zone.

11. The piercing machine according to claim 9 , further comprising:
a frontward damming mechanism that is disposed around the mandrel bar at a position that is rearward of the plug and is frontward of the outer surface cooling mechanism, wherein:
the frontward damming mechanism comprises a mechanism that, when the outer surface cooling mechanism is cooling the hollow shell in the cooling zone by ejecting the cooling fluid toward the upper part of the outer surface, the lower part of the outer surface, the left part of the outer surface and the right part of the outer surface of the hollow shell, d

Assignees

• Nippon Steel Corp

Inventors

• Obe Haruka
• Sakamoto Akihiro
• Daimon Yasuhiko

Classifications

• B21B25/04 Primary

  Cooling or lubricating mandrels during operation · CPC title

• B21B19/04 Primary

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