Flatness Measurement of Hot Strip by Laser Scanning Method

Abstract

A new type of hot strip shape meter is developed to measure the flatness shape of hot strip at the exit of hot finishing mill with high accuracy and fast response time. This shape meter detects the strip vertical displacement distribution along transversal direction using laser beam, and measures the flatness shape from the variance of displacement. Laser beam from Ar laser is parallel scanned by high speed polygonal mirror and parabolic mirror, and irradiates the strip surface aslant. The strip displacement is measured by detecting the reflected light timing, with photo sensor arranged upper part of the strip. By sample test, it was confirmed that the accuracy of displacement sensing is within ±1mm. This shape meter was installed on the hot strip mill of Yawata Works in 1982 for practical use, and has been playing an important part in mill operation and in automatic shape control system.