The Third John Player Lecture: Progress in the Manufacture of Large Forgings

Abstract

Difficulties in the production of large steel forgings stem from the metallurgical and physical heterogeneity of large ingots, the extent of which increases with the size of ingot.

The production of large forgings will be discussed with special reference to the manufacture of large mono-bloc rotor forgings for electrical generating plant, the size of which has increased progressively. These rotors are required to meet extremely high standards and must have uniform mechanical and creep properties.

Manufacturing processes are reviewed in relation to steelmaking (the advantages of vacuum treatment of the liquid steel are discussed), forging (involving upsetting operations in a forging press of very large capacity), metallurgical control of properties in components of great metal thickness; and in relation to inspection, involving refined ultrasonic techniques. Recent developments and improved techniques offer the possibility of producing sound unbored rotors with guaranteed creep properties and consequent design advantages to turbine engineers.

Future developments in the production of large forgings are speculated on, and the significance is discussed of the influence of electroslag welding which opens up new possibilities through its ability to join sections of large thickness.