The principle of gold and silver ingot casting-melting furnace and crucible

  The furnace that melts gold and silver generally adopts a round hearth furnace. The fuel is mostly gas and diesel. Or use the usual coke stove, gas or diesel stove, mostly made of magnesium brick or refractory clay brick, the size of the furnace is mainly determined by the size of the crucible. Under normal conditions, the diameter of the clearance section of the furnace is 1.6 to 1.8 times the outer diameter of the crucible, and the depth is 1.8 to 2.0 times the height of the crucible.

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  However, in actual production, several crucibles are often used for melting and casting in the same furnace. The low-pressure nozzle holes for burning gas or diesel are mostly located on the wall close to the bottom of the furnace, and the furnace cover is provided with a furnace cover. The flue gas is discharged from the central hole of the furnace cover or the underground flue near 100mm below the furnace opening. There are also underground flues installed on the wall near the bottom of the furnace, and the combustion nozzle hole is left 100mm below the furnace mouth. After the furnace is built, put two refractory bricks in the center of the furnace bottom. Place the crucible on the refractory bricks with coke powder during melting to prevent sticking to the bottom.

    Most crucibles use graphite crucibles, which can withstand the maximum temperature of about 1600 , usually use 50-100 graphite graphite crucibles. In view of the hygroscopicity of the graphite crucible, it must be slowly heated and baked for a long time before use to remove moisture, and then slowly heated to red heat (dark red). Otherwise, the damp crucible will burst and break when exposed to high temperature and sudden heat.

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  In modern times, gold or silver ingots are also cast by resistance furnace or induction furnace. The resistance furnace is composed of carbon or uhren replica graphite crucible (or refractory clay crucible lined with smelting metal), usually single-phase AC power supply. After the low-voltage current is turned on, the crucible acts as a resistor and heats the metal to the desired temperature. Based on 20kg of metal per furnace, the power consumption per kilogram of gold is 0.5kW·h, and the power consumption of silver is slightly less.

In the selection of crucibles, in addition to graphite crucibles that use graphite crucibles or lining (or outer lining) refractory clay crucibles alone, there are also those that use refractory clay crucibles alone for smelting.


  When melting pure gold and silver in a crucible furnace, the loss of gold (including recoverable smoke) is generally 0.01% to 0.02%, and silver is 0.1% to 0.25%. When smelting gold-silver alloys or gold-copper alloys, the losses are even greater. When melting in an electric furnace, the loss rate of gold and silver can be reduced by about 70% to 90%.



Post time: Jul-03-2020

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