ISO 5940:1981

Carbonaceous materials for the production of aluminium — Pitch for electrodes — Determination of softening point by the ring-and-ball method

Specifies a method using a disc-shped test piece to be prepared by moulding a test portion ina ring which is fitted into a heated bath. A steel ball is placed on the upper surface of the test piece. Then the temperature (softening temperature) is determined at which the test piece, on heating at a prescribed rate, softens sufficiently to sag to a specifeid depth under the mass of the ball. Details on the thermometers to be used and information on the melting of pitch samples are included in two annexes.