DEPENDENCE OF ULTRASONIC VELOCITY IN MOLTEN COPPER ON TEMPERATURE ANDIMPURITY CONTENT OF THE MELT

The ultrasonic velocity in molten copper has been studied in a laborat ory furnace using a graphite crucible. The velocity was measured as a function of temperature between 1,150-1,250-degrees-C (2,102-2,282-deg rees-F) both in pure molten copper and in melts with different dissolv ed contents of Sn, Zr, and Cr impurities. Tungsten rods were used as w aveguides and the accumulation of air bubbles at the solid-molten inte rface was prevented by using an on-off pulsing of ultrasound. Ultrason ic velocity values can be used for the detection of temperature change s of the melt with a resolution better than 10-degrees-C (50-degrees-F ). Minor impurity contents had only a relatively small effect on the u ltrasonic velocity values, whereas higher concentrations of Sn and Zr restricted the temperature resolution in a serious way.