Process Development At Ben Bennett

Excel Heat of Brierley Hill, West Midlands have been awarded a contract by Ben Bennett Jr Ltd to supply an advanced plant which will harden high quality steel strip and flatten it to within 1000th of an inch - per inch.

Ben Bennett Jr is a leading manufacturer of hardened and tempered steel strip and this is the second unit which Excel Heat have supplied to their Rotherham factory. Derry Graham, Technical Manager of Ben Bennett Jr said " the first line which we installed produces strip of exceptionally high quality and we are very pleased that this new unit incorporates additional features to meet our particular requirements, which are based on our operational experience"

The new installation incorporates a temperature controlled bath containing a molten Bismuth lead alloy used as a cooling medium, and pneumatically operated final cooling and flattening dies to continuously treat steel strip at up to a rate of 250 kilograms per hour. The equipment has been designed to fit into an existing hardening and tempering process to improve quality, increase production and provide greater flexibility.

The steel strip to be treated is fed, at approximately 900 degrees centigrade into the bath. This induces uniform and rapid cooling which, when followed by final cooling to ambient, via a set of water cooled dies, results in quench hardened steel. A subsequent set of heated planishing dies complete the flattening process. Final properties of the steel are developed via in-line tempering.

The lead bath is constructed from mild steel plate and is designed to be easily removable for maintenance purposes. The heat source required to melt the alloy is provided by electric heating elements, which are mounted in an insulated chamber beneath the bath. This heating chamber is internally lined with ceramic fibre and mineral wool slabs. Provision has been made to allow access to the elements and all cabling is terminated with a quick release plug and socket arrangement.

To counteract the heating effect of the very hot steel strip entering the bath and to maintain the molten alloy at the required temperature, an automatic water-cooling system is employed. Channels are incorporated into the bath structure itself and cooling is achieved in three stages, regulated by electrically operated valves.

Once the steel strip has been quenched in the lead bath it is fed between cooling dies, which contain a labyrinth of water passages sandwiched between steel plates for final cooling and hardening. The final flattening stage incorporates graphite plates, held between steel plates specially constructed to house electrical heating elements encased in sintered alumina sleeves. Each set of dies is fitted with double acting pneumatic cylinders, which are controlled to aid the flattening process.

As well as carrying out all of the design and manufacture, Excel Heat will supervise the installation and conduct final site testing of the equipment. Mike Kealy, Manager of Excel Heat commented, "Modern technology provides continual improvements in quality, economies and energy saving. We adopt a policy of combining established, reliable engineering with technical innovation wherever possible to meet the individual needs of a particular application".

For further information please contact Mike Kealy.

or Ben Bennett Jr Ltd, Eastwood Rolling Mills, Fitzwilliam Road, Rotherham, S65 1SH. Telephone 01709 382006, Fax 01709 829890.