1996 Volume 36 Issue 5 Pages 572-578
Extra-thick-walled tubes, hollow rods, in which wall thickness to outside diameter ratio is 25% or more, are produced at steel rod rolling mills at large, as they cannot be manufactured into seamless tubes at any existing mill plant. They are currently produced by a process in which a square billet with an inserted mandrel of manganese steel is passed through a bar mill. Then, the hollow billet is finished to the desired diameter and wall thickness. After that, the mandrel is removed from the hollow billet. The unit tool requirement of this process is costly and uneconomical, and the dimensionally accuracy is low.
In this paper, the reduce rolling characteristics of hollow piece by rotary rolling mill have been studied in detail. This process, in which a rotary rolling mill with three rolls has been used for reducing the outside diameter of hollow piece, makes it possible both to obtain hollow rods with high dimensional accuracy and to produce hollow rods efficiently. This rotary rolling makes it possible to reduce the outside diameter of hollow pieces and to control the wall thickness of hollow pieces with no internal sizing tool by only setting rotary rolling mill conditions. Hollow pieces having the desired dimensions can be produced with high accuracy.