Roll Manufacture: static and spun cast
East Anglian branch event
Alan Robertson, Director of Technology at Davy Roll Co. Ltd. Gateshead, made a round trip of some 550 miles to speak to the East Anglian section of the London Branch of ICME.
He first spoke about the historical side of the company, the original foundry starting in 1840 by James Coulthard and the company is now the producer of cast steel rolls of which 82% of production is sold overseas.
Alan explained the method of die preparation, the use of chemically bonded sand to preform the bottom end of the roll as well as for to form the head metal. Between the base core and head metal a gap is formed which equates to the thickness of the hard steel shell. The die is spun at around 650rpm whilst using a long probe the hard steel is poured into the mould, within the preformed gap, up to the required thickness. The metal must be poured at a specific rate.
The speed is controllled from the control room and signalled to the pourer through a system of lights, amber being the correct pouring rate. After a waiting period, another thin layer is applied to prevent oxidation of the inner surface and then the final mould fill, duplexing, is carried using a softer metal.
The steel roll surface is rough ground to remove adhered sand after which it is heat treated and water quenched. This necessitates a high degree of temperature control.
All rolls are fully machined before being dispatched to the customer.
Some rolls are produced by static casting when only one metal is poured into the mould through a tangential bottom pour system.
The evening ended with a buffet giving members time to socialise.