Apparatus for the detection and measurement of particulates in molten metal

In a probe for insertion into molten metal to detect and measure particulates suspended therein using the electric sensing zone method, the probe comprising:

• a sealed inner tube of an electrically insulative material forming a molten metal receiving chamber, the tube including at least one orifice proximate an insertion end of the probe to permit molten metal to flow into the chamber;
• a gas passageway extending out of the inner tube for connection to a vacuum source to create a pressure differential between the inside and outside of the inner tube for facilitating the flow of molten metal through the at least one orifice;
• a first electrode extending into the chamber for engaging metal within the chamber, the first electrode including the gas passageway and at least one first elongate member having a first length and electrically connected to the gas passageway;
• a second electrode surrounding at least a portion of the inner tube for engaging molten metal outside of the chamber, the first and second electrodes being connectable to a measurement device for establishing a current path through the electrodes and passing through the at least one orifice and for measuring changes in the electrical potential between the electrodes produced by the passage of particulates entrained in the molten metal passing through the orifice;
• an outer sheath of heat resistant material surrounding at least a portion of the second electrode to provide thermal insulation therefor;
• a liquidus depressing material within the chamber for alloying with molten metal entering the chamber to lower the liquidus temperature of the molten metal in the chamber and permit a longer time period for detecting and measuring particulates in the molten metal,
• an improvement comprising:
• at least one second elongate member electrically connected to the gas passageway at a first end of the at least one second member and extending into the chamber for engaging metal within the chamber;
• and
• a chill block attached to a second end of the at least one second member, the at least one second member having a second length such that the chill block is spaced from the liquidus depressing material.