US 4,178,789 AGranted

Simultaneous plug-mill rolling for increased production and enhanced tube quality

AssigneeUnited States Steel Corporation

InventorJames W. Ruff

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Abstract

A pierced billet is fed through a plug rolling mill, equipped with a plurality of grooves. Initial rolling is effected in conventional manner, i.e. the shell is (i) rammed over a forming plug mounted on the front end of a mandrel, (ii) drawn over the plug by the work rolls, (iii) removed from the mandrel and (iv) returned to the entering side of the mill. Rather than effecting a second pass on the shell in the same roll groove, the shell is transferred to an adjacent receiving trough, aligned with a second groove of the same work roll. A second shell is then placed on the trough aligned with the first roll groove, thereafter the first shell is given a second pass in conjunction with the first pass of the next shell. Because of the use of more than one groove for subsequent passes, each roll pass can be contoured to suit the reduction desired. Thus, use of a second groove for the second pass permits a reduction in the roll flare employed, such that a significantly rounder tube can be delivered in the finish pass.

Claims6

Dependent claims

In the production of seamless tubing, wherein shells are transferred to a plug rolling mill to receive a rolling operation consisting of at least two plug-rollng passes, each of said rolling passes consisting of pushing the shell over a plug attached to a supported mandrel bar, said plug lying within a first roll groove of the work rolls of said rolling mill, drawing said shell over the plug by the rolling friction of the roll groove, removing the plug and reversing the travel of the shell so as to strip it from the plug, thereafter repeating the rolling procedure for at least one additional pass in the same roll groove,

the improvement for significantly increasing the production rate of said plug rolling operation, which comprises,
(a) after completion of the first pass, and without removal of the mandrel bar from its support, laterally transferring the first shell to position for effecting the second pass in a second roll groove of the same roll,
(b) moving a second shell into position for effecting a first pass thereon in said first roll groove, and
(c) simultaneously pushing said second shell and said first shell through said first and second roll grooves, respectively.

1 more element

Dependencies are inferred from the claim text.