CLADDINGS FOR ALUMINUM PUSHER FURNACES

                                                                             

  The use of pusher type furnaces for the reheating and homogenization of aluminum ingots is widely recognized for providing excellent quality with good thermal and production efficiency. It is also widely known that the hardware inside the furnace, which transports the ingots at temperatures approaching 1100 deg F., faces a daunting task. A furnace configuration consists of a pair of full length stationary rails, with or without rail pad inserts, which contact  a series of paired moving shoes, and each pair of shoes slides into the furnace supporting  one ingot. A fully loaded furnace could contain 30 or more ingots and the total load could be well over one million pounds. The hot, dry friction coefficient between the shoes and the rails is usually over .7, meaning that it takes a pushing force of over three quarter million pounds to slide the shoes when the furnace is fully loaded. Every furnace push is a stick-slip event, a conflict between static and dynamic friction. The resulting “stiction”, the cycling of strain-causing forces within the furnace, is evidenced by a loud “chatter” which has become a trademark of this equipment.  All of the manufacturers of these furnaces, both foreign and domestic, have recognized the severity of this problem, and a range of solutions from compositional changes in rail/shoe chemistry, to PM rail pad inserts, to grease injection systems, has all been tried and found to be less than satisfactory from both a performance and cost standpoint.

  In 1997 SEA began using their claddings to solve this problem. By lowering the hot friction coefficient, high pushing forces and chatter were reduced by about half, shoe/rail wear was reduced, and airborne scale was reduced by 80%. A series of innovations in metallurgy and manufacturing practice, and repeated successes in the marketplace since then, has allowed SEA to make the following claims today;

 

1. We have the only technology in the industry which allows us to reclaim worn shoes to their original dimensions and give them better than new sliding performance at a lower cost than new equipment.

2. We are the only supplier of new “composite construction” castings, which means that we provide low friction material on the slideways while maintaining the necessary structural properties in the body of the casting.

3. We can repair rails or supply new rails with a low friction clad surfacing.

4. We can supply rail pad inserts, where necessary, consisting of a cladding on high alloy steel  which gives lower friction and wear than ductile iron, and without the risk of brittle failure associated with pads made by powder metallurgy processes.

5. We have empirical data that supports the reasonable expectation of a ten year shoe life and a five year rail life, running dry, with lower friction and stiction than any other system on the market.

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