Perfect Shape for Hot-Rolled Strip

Akira Sako ...

... is a Senior Key Expert at Primetals Technologies, where he did pioneering work on the 3rd-generation pair-cross mill.


Controlling the crown shape and flatness of hot-rolled strip used to be a notoriously difficult. The 1980s witnessed a great leap forward in this context: the introduction of first pair-cross mill at the Hirohata works of Nippon Steel in Japan. The idea was simple, though hard to pull off: The upper and lower roll pairs are put in a slightly crossed position in order to counter the effect of roll bending on strip geometry. 

As rolling speeds were gradually stepped up for higher productivity, and mills were increasingly required to be able to produce high-strength steels that demand high reduction, the central challenge in pair-cross mills shifted to preventing mill vibration. This is where Akira Sako of Primetals Technologies left a permanent mark. A native of Hiroshima prefecture in Japan, he joined Mitsubishi Heavy Industries in 1987 and later moved on to work at Mitsubishi-Hitachi Metals Machinery, advancing to leader of the 3D CAD Group in 2003, and to general manager of the Rolling Mill Design Department in 2010. The mill stabilizing device that was developed under Sako's leadership made it possible to run 3rd generation pair-cross mills with high reduction, avoiding harmful vibration and retaining excellent crown-control accuracy. At the same, the elegant simplicity of Sako's design required fewer mechanical components and thus saved costs. Today, Akira Sako continues to improve hot-rolling mill technology as a Senior Key Expert at Primetals Technologies Japan.