Zinc pot bearing material wear rate as a function of contact pressure and velocity

There are currently over 50 galvanizing lines in operation in the United States producing approximately 50 million tons per year of galvanized sheet. Frequently zinc-pot hardware fails which causes production delay, resulting in an economic loss. It takes approximately 3 hours to change the zinc-pot bearings at a downtime cost of {dollar}400/h.;To predict the performance of the submerged bearings, a large number of variables must be considered. These variables include pot chemistry, temperature, line speed and line tension. With these variables it is possible to develop a design guide for sheet mill operators to determine the most cost-effective selection of zinc pot bearing materials/coatings, which will not be the same for all galvanizing lines.;The objective of this project is to measure wear rate of submerged zinc-pot bearing materials as a function of contact pressure and velocity. A small laboratory size-testing machine was developed for this purpose. This machine measures the wear of bearing material samples, submerged in a cup of zinc, in the form of a 1-inch diameter ball rotating against a matched ball seat. The seat and ball can be cast or machined using bearing materials from a test matrix. The seat is placed in a temperature controlled molten zinc bath where load, torque and RPM of the test samples are measured and recorded. From the measured torque the sliding friction coefficient of the bearing materials tested can be calculated. By measurement of the seat radius before and after testing, the wear rate of the material as a function of contact pressure and velocity was determined