Controlled magnesium melt process, system and components therefor

Improvements in magnesium die casting in which ingots of magnesium are melted and transferred from a molten bath of magnesium by a siphon tube to the shot hole of a die casting machine comprising providing a computer controlled integrated magnesium melt system in which temperatures of the magnesium are maintained within selected limits of set values, said magnesium melt system including:

• (a) an ingot preheater means having electric resistance heating elements for heating ingots therein and at least one preheater temperature sensing means providing output signals representative of the temperature of the preheated ingots;
• (b) a furnace having a crucible for holding a molten bath of magnesium, electric resistance heating elements in said furnace for heating the crucible to melt the ingots and maintain the magnesium in a molten state, means for controlling power to said furnace heating elements, temperature sensing means providing output signals representative of the temperature of the molten magnesium;
• (c) means for transferring preheated ingots from said preheater into the crucible of said furnace;
• (d) a siphon tube mounted on said furnace for transferring molten magnesium from said crucible to the shot hole of the die casting machine;
• said siphon tube having at least one electric resistance heating element along a selected portion thereof and at least one temperature sensing means providing output signals representative of the temperature of molten magnesium in the tube;
• and
• (e) a programmable logic controller programmed with preset temperature values for preheated ingots, the molten magnesium in the furnace crucible and the molten magnesium in the siphon tube, and including means processing signals outputted by all said heat sensor means with respect to preset values and controlling power supplied to said heating elements to maintain the temperatures within a selected range of the preset values.

A magnesium melt system for use with a die casting machine comprising a computer controlled integrated system including:

• (a) an ingot preheater with conveyor means for moving ingots into and through the preheater to a discharge end thereof, said preheater having resistance heating elements;
• (b) a melt furnace having resistance heating elements and a crucible for molten metal;
• (c) an ingot transfer means including a drop chute having a gate therein selectively to release a preheated ingot for free fall into said crucible in said furnace;
• (d) a siphon tube for transferring molten magnesium from said crucible to a shot hole of a die casting machine, said siphon tube having a resistance heating element on a selected portion thereof;
• and
• (e) programmable logic controller means integrating operations and controlling power requirements to said heating elements to maintain set temperatures for the magnesium at the respective locations, thermocouple temperature sensor means on each of said preheater, furnace and siphon tubes providing signals to said programmable logic controller means representative of actual temperatures, said programmable logic controller means processing said signals with respect to preset values and controlling power requirements to said elements to maintain said set temperatures within a selected range.

A magnesium metal melt system comprising:

• (a) A furnace with a crucible therein for holding a supply of molten metal, electric resistance heating elements in said furnace arranged in a first upper heating zone and a second lower heating zone with each extending around said crucible, metal level and temperature sensors on said furnace that provide output signals representative of the temperature and level of the molten metal in the crucible;
• (b) an ingot preheater chamber having an inlet end and a discharge end and an endless conveyor means for moving metal ingots in sequence into said preheater through said inlet end and through said preheater to said discharge end, electric resistance heating elements arranged in respective first and second heating zones from said inlet end to said discharge end, thermocouple temperature sensor means on the preheater providing output signals representative of the temperature in the preheater respective first and second zones;
• (c) an ingot transfer means for transferring a selected ingot from said discharge end of the preheater into a closed drop chute, gate means in said drop chute, actuators for effecting the transfer and opening and closing said gate and sensors providing output signals representative of the state of operation of said actuators and functions performed;
• (d) siphon tube means on said furnace for withdrawing molten metal from said crucible, said siphon tube including an inlet end heating element, an outlet end heating element and first and second thermocouples providing output signals representative of temperatures at said respective inlet and outlet;
• and
• (e) programmable logic controller means receiving signals from said sensors and in response thereto, in comparison with set values, controlling power to the preheater and furnace to maintain within selected limits temperatures set therefor and controlling feeding of ingots to said furnace as required to maintain the molten metal in the furnace within a selected range of a set level.

A metal melt furnace comprising:

• (a) metal, high temperature insulated, walls extending around a selected area and base means extending across said selected area and including means supporting said walls;
• (b) an insulated top wall supported by said side walls and having an opening therein;
• (c) a crucible suspended from said top wall through said opening and extending downwardly terminating at a bottom end above said base means;
• (d) a lid on said crucible and electric elements on each of said insulated walls comprising a first upper heating zone extending around said crucible and a second lower heating zone independent of said first zone and also extending around said crucible;
• and
• (e) means to proportionally and selectively control power to the respective zones.

Apparatus for use in a magnesium metal melt system comprising:

• (a) an electric furnace having a crucible for melting ingots of metal and holding a supply of such molten metal;
• (b) an electrically heated ingot preheater;
• (c) means for transferring heated ingots from said preheater into the furnace crucible;
• (d) sensor means providing output signals representative of the temperature of the molten metal in the crucible, the level of the molten metal in the crucible, the temperature of metal ingots ready for transfer to the furnace and the state of operation of said ingot transfer means;
• and
• (e) programmable logic controller means receiving signals from said sensors and in response thereto, in comparison with set values, controlling power to the preheater and furnace to maintain within selected limits temperatures set therefor and controlling feeding of ingots to said furnace as required to maintain the molten metal in the furnace within a selected range of a set level and within a selected deviation from a set temperature.

Apparatus for melting ingots of magnesium and provide a source of molten magnesium at a set temperature for delivery to a casting machine, said apparatus comprising:

• (a) an electrically heated furnace having a crucible for holding a selected quantity of molten magnesium, said selected quantity having a free upper surface at a predetermined level, said crucible being closed at the top providing a closed space above said molten metal free upper surface;
• (b) an ingot preheater comprising an electrically heated enclosure having an ingot inlet end and spaced therefrom an ingot outlet end, said ingot outlet end being disposed at an elevation higher than said predetermined level of molten magnesium in said furnace;
• (c) ingot transfer means including an enclosed drop chute having a first ingot inlet end at said preheater discharge end and an outlet end opening into said crucible, a gate in said drop chute and means to open and close the same;
• (d) sensor means providing output signals representative of the temperature of the molten metal in the crucible, the level of the molten metal in the crucible, the temperature of metal ingots ready for transfer to the furnace and the state of operation of said ingot transfer means;
• and
• (e) programmable logic controller means receiving signals from said sensors and in response thereto, in comparison with set values, controlling power to the preheater and furnace to maintain within selected limits temperatures set therefor and controlling feeding of ingots to said furnace as required to maintain the molten metal in the furnace within a selected range of a set level and within a selected deviation from a set temperature.