Ultrasonic roll bite measurements in cold rolling – Roll stress and deformation

Abstract

In cold rolling of thin metal strip, contact conditions between the work rolls and the strip are of great importance: roll deformations and their effect on strip thickness variation may lead to strip flatness defects and thickness inhomogeneity. To control the process, several online measurements are usually carried out such as the rolling load, forward slip and strip tensions at each stand. Shape defects of the strip are usually evaluated after the last stand of a rolling mill thanks to a flatness measuring roll. However, none of these measurements is made within the roll bite itself due to the harsh conditions taking place in that area. This paper presents a sensor capable of monitoring roll deformations as well as roll radial stresses in situ and in real time. The sensor emits ultrasonic pulses that reflect from the roll surface. The time-offlight (ToF) of the pulses is recorded during the testing. Ultrasonic roll bite measurements in cold rolling roll stress and deformation 2 The sensor system was incorporated into a work roll and tested on a pilot rolling mill. Measurements were taken as steel strips were rolled under different strip elongation. Roll deformation and radial stresses obtained from the experimental data are in good agreement with numerical results computed with a cold rolling model developed in non-linear Finite Element software.

Measurement of metal–roll interface during metal rolling using normal and oblique ultrasonic reflection

“…At points A and B (before the entry and after the exit of the roll bite, respectively), the reflection coefficient is great than 1. These high values of reflection coefficient might be due to interference at these points, and this was also observed by Carreta et al [5]. The value of reflection coefficient decrease within the roll bite, and this can be attributed to the decrease in reflected ultrasonic signal as sensor beam now focused on the roll bite (metal-strip interface).…”

“…Ultrasound is an attractive tool for non-invasive evaluation of the metal-roll interface conditions during metal rolling due to its high penetration power and sensitivity. Ultrasound pulse-echo technique has been previously used to investigate metal-roll interface conditions during the cold metal rolling process but with clear limitations [4][5][6]. In these studies, ultrasonic longitudinal and shear wave sensors were oppositely mounted on a plug pressurised in radial holes drilled in the roll and facing outwards from the roll.…”

A method to determine acoustic properties of solids and its application to measuring oil film thickness in bearing shells of unknown composition

“…An air reference signal was also obtained, for which the test medium was removed, and the delay line cleaned to remove any remaining oil. The acoustic impedance of air is orders of magnitude smaller than the steel delay line, thus it may be assumed that this solid-air interface is perfectly reflective [20].…”

Ultrasonic technique for measurement of oil-film thickness in metal cold rolling

“…An ultrasonic technique (pulse-echo method) has previously been used to study conditions at metalroll interface within roll-bite during cold metal rolling process [13][14][15]. Carretta et al [15] engaged piezoelectric transducers (sensors) internally installed in steel roll to measure contact length and metal strip thickness at the metal-roll interface during the cold rolling operation.…”