A new high-temperature test rig for optimization of materials for hot-rolling rolls

Abstract Roll consumption and thus roll cost represents an important part of the rolling cost in wire and bar mills. By reduction of roll wear and thus roll consumption, significant cost reductions can be gained. Due to the friction, the velocity and the stress distributions in the roll gap, conventional wear mechanisms are operating on the roll surface, and the extreme shock-heating of the roll surface during the contact with the hot bar causes thermal fatigue at microscopical and macroscopical scale. With the final aim of developing new, more wear-resistant roll grades, a high-temperature test rig has been designed for simulation of the tribological situation at the roll surface. The situations concerning load, velocity, friction, temperature and wear in the roll gap have been analyzed, and a quantitative theory for roll wear rate has been developed. The high-temperature test rig was designed so as to simulate the hot-rolling process as closely as possible, and preliminary tests have been conducted. In spite of its excellent stability and reasonable evaluation of friction, the tribological test method is not yet established. Serious drawbacks of the method have been identified, which must be investigated and evaluated before a reasonable method for the simulation of roll wear can be developed. The most serious problems in the evaluation of the test rig as a tool for roll-wear research concerns the thermal equality between the test method and the simulated rolling process, although the pressure and velocity situations seem to be rather easy to simulate. The evaluated wear-rate figures are of the same order of magnitude as the roll wear rate evaluated from roll consumption figures and the wear patterns are similar. However, long run tests must be carried out on the test rig, to simulate the entire deterioration process in hot-rolling rolls, before any statements can be made concerning the relevancy of the test method, and thus of the use of the test rig in the development of more wear resistant roll grades.