PURPOSE: To manufacture easily a hollow bar material excellent in dimensional accuracy without using a mandrel by elongation-rolling a hollow blank material by a skew rolling mill equipped with plural cone-type rolls forming specific intersection and slant angles.
CONSTITUTION: A hollow blank material, made by boring a hole by a drill in the central part of a round steel billet, is heated in a heating furnace, and is cut into a standard length after elongation-rolling it by a skew mill to manufacture a hollow bar-shaped body having the prescribed wall thickness. In this case, three or four rolls are used for the skew mill, which are arranged so that an intersection angle γ and a slant angle β, formed by the intersection of the central axis Y-Y of the roll with the pass line of a material A2 to be rolled, are γ≥0, 3°≤β≤20° respectively in accordance with the target finished outer diameter and wall thickness of the hollow bar material. Thus a hollow bar material excellent in dimensional accuracy can be manufactured without using a mandrel by inserting it into a hollow hole.
HAYASHI CHIHIRO
JPS57137009A | 1982-08-24 |
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