GRAPHALLOY^® Bearings

For Steel Mill Applications

Steel mills are environments where traditional lubricants can cause problems. The lubrication breaks down due to the high temperatures, causing shaft seizures and equipment failure. The grease or oil can also cause safety hazards in the plant. Furthermore, maintenance on some machines is difficult, so replenishing lubricants is a challenge.

Advantages of Graphalloy Bearings for Steel Temperatures:

• Self-Lubricating: Require No Grease or oil, maintenance-free
• Temperature range: Operate from -450°F to +1000°F (-265°C to +535°C)
• Dimensionally Stable
• Low Coefficient of Thermal Expansion
• Non-galling
• Standard and Custom Sizes

Applications for Graphalloy in Steel Mills:

• Guide Roll Bearings
• Tap Gate Bearings
• Furnace Door Bearings
• Pinch Roll Bearings
• Cooling Bed Rollers
• Steel Bleeder Valve Bearings
• And more-

Successful Graphalloy Applications for Steel Mill Applications

Bleeder Valve Bearings

At a large steel mill in the United States, a blast furnace utilized bronze bushings at each pivot point on the bleeder valves. Depending on the wind direction and activity in the furnace, temperatures average around 250 to 300°F but can sometimes reach as high as 400°F. The original design had grease-lubricated bushings fed by automatic lubrication lines. Over time, the old grease would build up on the valve and, when there was an upset, embers could ignite the grease. The resulting fire often burned off the lubrication lines and the attached electrical instrumentation. Graphite Metallizing Corporation presented the mill with a self-lubricating bushing solution. Bushings made of Graphalloy, a graphite-metal alloy, were installed into all the pivot locations. The steel mill wanted something that would last at least three years, the time interval at which they reline and rebuild the furnaces. They bought enough Graphalloy bushings to upgrade two of the furnaces. These two furnaces worked effectively during the three-year threshold, with no issues. The Graphalloy self-lubricating bushings worked so well that a nearby machine shop decided to use the same solution for bleeder valves at another steel mill.

Pinch Roll Bearings in Annealing Furnace

The annealing furnace at a Pennsylvania metal manufacturer had an interior temperature in the range of 1200°F (650°C). Bearings supporting the pinch rolls were located outside the furnace walls and reached temperatures up to 750°F (400°C) due to heat transmitted through the furnace wall by the shaft.The heat transmitted by the shaft through the oven wall to the bearing was causing lubrication failure. In addition, the movement (linear expansion) of the shaft caused problems well beyond the capability of any standard ball or roller bearing arrangement. GRAPHALLOY high temperature bearings were installed in a metal adapter designed to fit the original bearing housings and solved the problem without a major redesign. With minimal investment, bearings failures and associated maintenance costs were reduced.

Guide Roll Bearings

A steel mill that produces rolled steel products from 100% recycled materials was experiencing bearing failures. The mill used guide rolls to keep the metal bars centered on the conveyor. The bearings for the guide rolls were grease lubricated and the temperature range of 170-180°C was baking out the grease and causing the bearings to seize. The steel mill's plant engineer worked with Graphalloy's engineering team to discuss technical considerations in designing a GRAPHALLOY, graphite/metal alloy, self-lubricating bushing to replace the greased roller bearing. After several engineering discussions, the plant engineer purchased and installed 4 pieces of a Graphalloy bronze-grade bushing, with a stainless steel housing, in the guide roll assembly. Graphalloy bushings require no external lubricating and work in temperatures up to 400°C (750°F). After six months in service, the plant manager said that the Graphalloy bushings "are performing very well" and that they would replace all the roller bearings in these assemblies with the Graphalloy bushings.

Read a case history on Graphalloy bearings in a wastewater application

October 18, 2024