Speaker
Description
Back-up rolls (BURs) in cold and temper rolling mills often exhibit very inhomogeneous wear rates over their barrel length. Associated profiles have a large effect on local stress distribution along the BUR-WR (work roll) contact length, which may impact subsequent stages of BUR (sub)surface degradation, which in turn affects strip profile or flatness. A poor prediction of BUR profile loss, which may differ strongly between consecutive mill campaigns of a same BUR, results in mills struggling to define adequate (= safe and economical) practical maximum BUR campaign length limits.
A better understanding of BUR profile loss mechanisms is thus required to help in their prediction by modelling, which is the target of the European funded RFCS Project BURWEAR.
An assessment of BUR wear and rolling contact fatigue phenomena by examination of worn BUR surfaces in association with rolling mill process data and profiles has enabled to determine the degradation mechanism of various rolls in different kinds of cold rolling and temper mills, stand positions and BUR materials. This analysis, based on light optical microscopy, hardness, roughness and profile measurements was performed on-site at Tata Steel in IJmuiden.
Roll material samples from various BUR qualities have been extracted during the manufacturing process at GP and heat- treated to different hardness levels. A series of laboratory trials have been conducted on the cylindrical rolling pairs (WR disk/BUR disk) at University of Twente to investigate and simulate rolling contact fatigue failure in BURs via a twin disk machine. The trials were done reproducing the Hertzian contact pressure between the BUR-WR contact in cold rolling mill stands and under pure rolling and partial slip conditions.
Both on-site and laboratory investigations lead in the frame of the BURWEAR project clearly demonstrated contact fatigue being a major actuator in BUR profile loss on both forged and cast BUR grades.
Summary
Back-up rolls (BURs) in cold and temper rolling mills often exhibit very inhomogeneous wear rates over their barrel length. Associated profiles have a large effect on local stress distribution along the BUR-WR (work roll) contact length, which may impact subsequent stages of BUR (sub)surface degradation, which in turn affects strip profile or flatness. A poor prediction of BUR profile loss, which may differ strongly between consecutive mill campaigns of a same BUR, results in mills struggling to define adequate (= safe and economical) practical maximum BUR campaign length limits.
A better understanding of BUR profile loss mechanisms is thus required to help in their prediction by modelling, which is the target of the European funded RFCS Project BURWEAR.
An assessment of BUR wear and rolling contact fatigue phenomena by examination of worn BUR surfaces in association with rolling mill process data and profiles has enabled to determine the degradation mechanism of various rolls in different kinds of cold rolling and temper mills, stand positions and BUR materials. This analysis, based on light optical microscopy, hardness, roughness and profile measurements was performed on-site at Tata Steel in IJmuiden.
Roll material samples from various BUR qualities have been extracted during the manufacturing process at GP and heat- treated to different hardness levels. A series of laboratory trials have been conducted on the cylindrical rolling pairs (WR disk/BUR disk) at University of Twente to investigate and simulate rolling contact fatigue failure in BURs via a twin disk machine. The trials were done reproducing the Hertzian contact pressure between the BUR-WR contact in cold rolling mill stands and under pure rolling and partial slip conditions.
Both on-site and laboratory investigations lead in the frame of the BURWEAR project clearly demonstrated contact fatigue being a major actuator in BUR profile loss on both forged and cast BUR grades.
| Speaker Country | Belgium |
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