Tribological Behavior of Hot Rolling Mills Under High Temperature Conditions

W. R. TUCKART; MONTESI, GUSTAVO; ESTEBAN UBICI; ANDRES ESTEBAN; H. FERNANDEZ; DANIELA CAVALERI; W. CHIAPPAROLI

Rosario

Conferencia; 20º Conferencia de Laminación de Acero; 2014

Instituto Argentino de Tribología

The objective of this work is to evaluate the tribological behavior of two working rolls materials of hot rolling mills. This development is very important because involves economically having good control of hot rolling rolls. For this purpose two groups of samples were obtained from rolls taken out of service. One of the materials was high speed steel (also called HSS), and the other was indefinite chill double pour type (called ICDP). The compositional and microstructural characteristics were evaluated by optical emission spectroscopy and metallographic studies using optical and scanning electron microscopy with precise chemical composition microanalysis.While the mechanical properties were determined by measurement of Rockwell hardness. Friction behavior was determined on a block type tribometer (fixed test piece taken from the roll) on a movil ring (SAE 1045). Both ring and block were heated up to 600 °C using an electric furnace. Test were performed with 3.5 N normal load, 0.1 m/ s of relative speed during 60 seconds with a non-lubricated condition. Like wise the comparative performance between the tested materials was determined using a specially home- made built tribometer to provide sliding and thermal fatigue conditions (applying quenching cycles between 600 °C and 90 °C) during 250 cycles. Comparative wear level was weighted by weight difference of the samples (before and after the test) and topographic roughness, thermal fatigue damage was evaluated through metallographic studies. The obtained results shown that the friction coefficient of the high speed steel HSS material, both static and dynamic, was 0.20-0.23, about 30% lower than that obtained with ICDP specimens. Also, the microstructure with graphite nodules in the ICDP material, was more favorable for nucleation and growth of thermal fatigue cracks, which resulted ina higher level of surface damage comparing with the high speed steel HSS material.