Most steel plants have rolling mill divisions, where cast slabs, blooms and billets are converted into a variety of products such as sheet metal, structural steel, bar stock and rails. The process involves passing metal stock through pairs of rolls to reduce its thickness and make it uniform.
Hot rolling is done at temperatures of up to 900oC, after which cooling beds, some as large as football fields, move and cool the steel. There are two basic types of cooling beds, grate and roller. In grate types the hot-rolled steel moves over steel grates, which can damage the surface of the plates. As a result, much of the industry has gone to roller beds.
A major Scandinavian steel producer with global operations recently installed the first section of a new roller cooling bed, for which it turned to GGB for a bearing solution.
“Designing components for primary metals processing systems demands careful attention to durability, longevity and maintenance,” said GGB Product Manager Ümüt Elitok. “Cooling beds, conveyors, shears and other equipment expose bearings to temperatures, pressures, debris and other factors that can cause conventional roller and needle bearings to fail.”
The application involved bearings to be installed in housings on either side of the cooling bed to support the shafts on which the rollers rotated. At approximately 2 N x mm2, the loads on the bearings would be negligible, as would operating speeds of just 0.01– 0.02 m/sec. under intermittent motion. GGB recommended its GGB-CSM® 118 self-lubricating, ferrous-nickel-copper alloy bearings for the application.
“Formulated using advanced materials and production techniques, these bearings provide maintenance-free operation and superior mechanical characteristics to withstand the extreme conditions encountered in metal processing facilities,” said Elitok. “Their service life of over 10 years can reduce downtime, improve system performance and reduce maintenance costs.”
In addition GGB produced a special high-temperature grease for use in the application and provided on-site technical support and training for the company’s installers. The project was undertaken during the first of three maintenance stops to be conducted over a two-year period.
The bearings have performed well since the cooling bed became operational, and GGB engineers continue to meet regularly with the company, which will use the bearings in subsequent installations as well.