Casting and operation of finished gold ingots

Finished gold ingot cast material, mainly electrolytic gold. The gold purified by chemical method and various hydrometallurgical methods is based on whether the grade meets the requirements of gold ingots.

The casting of the finished gold ingot is generally performed by melting the graphite crucible in a diesel furnace to ingot. The use of diesel fuel is to increase the furnace temperature to 1300 ~ 1400 ° C, in order to facilitate the melting and ingot casting of gold.

Factory configured with said diesel fuel to the furnace hearth as coal gas, but Burning diesel fuel. Diesel fuel is usually supplied by a gear oil pump, but some plants use a high fuel tank to increase the oil pressure by the height difference. The height difference from the tank to the nozzle is generally not less than 3 to 4 m. The atomizing air used compressed air of 98.066 to 196.133 kPa (1 to 2 kg ∕cm ² ).

If the No. 60 graphite crucible is used, after baking and checking that there is no damage, 35 to 60 kg of electrolytic gold is added in each step, and the temperature is gradually raised to 1300 to 1400 ° C for melting. All gold to be melted and superheated to the gold solution was red white, chemically pure potassium nitrate and boron added to each of 10 ~ 20g slag sand.

Using an open ingot mold cast iron inverted trapezoidal rectangular flat die, the internal dimensions of the mold was machined: 260mm long (on), 235mm (lower); 80mm wide (a), 55mm (at); high 40mm. The ingot mold is cleaned with diesel cotton yarn, placed on the floor cover and baked to 150-180 ° C. The acetylene is ignited to a uniform layer of smoke, and the mold is placed horizontally (check with a level to avoid uneven thickness of the ingot) To be cast.

After slag formation and cleaning of the slag, the crucible is taken out, and the remaining slag of the net rinsing is cleaned with a stainless steel piece. The liquid liquid is injected along the vertical direction of the long axis of the mold at a liquid temperature of 1200 to 1300 ° C and a mold temperature of 120 to 150 ° C. Mold center. The casting speed should be fast, stable and uniform, avoiding the violent fluctuation of the gold liquid in the mold, causing cracks and wrinkles on the ingot surface. In order to prevent the gold liquid from eroding the mold bottom, the gold liquid injection position should be smoothly moved left and right.

Since gold dissolves in the air, it can dissolve a large amount of gas. In order to ensure that the ingot surface is cooled first, the ingot surface is flattened to avoid the formation of large shrinkage pits. After pouring a piece of ingot, a factory immediately saturates with an aqueous solution of potassium nitrate. The paper cover is covered with bricks that have been preheated to a temperature above 80 °C. Cover paper and brick movements are quick and accurate. After the ingot is condensed, poured asbestos board, then put into a stainless steel forceps cylinder 5% dilute hydrochloric acid soak 10 ~ 15min, washing net extraction with tap water, wipe dry with gauze, and then dried over anhydrous ethanol or gasoline wiping surface. A good quality gold ingot, after being cleaned, is bright and mirror-like.

3 to 5 pieces per ingot, and 3 to 4 test samples. The gold ingots produced are 99.99% gold or higher, and each piece weighs 10.89~13.30kg. After passing the inspection by the factory inspector, the steel code is used to mark the order number of the ingot and the year and month according to the block size (one hundred grams of precision, the current standard stipulates that the weight of the single spindle is 11 to 13 kg, and the weight of the single spindle is revised to 0.1 g). Hand over the library. Waste ingot recast.

Many factories have changed small ingots and do not cover paper and bricks, that is, thin ingots with a thickness of 5 to 25 mm are cast in an open flat die. This small ingot, because of its small thickness, condenses quickly and does not generate large shrinkage pits. However, there are often depressions in the middle of the ingot and ingot bubbles.

Some factories use small crucibles to cast gold ingots, one for each gold ingot, and the weight is added before casting. After the gold liquid is injected into the mold, a little borax is sprinkled on the surface of the gold ingot to oxidize the liquid surface impurities, and then cold water is poured on the surface of the ingot, and the mouth is repeatedly blown, and the surface can be washed and floated, and the surface of the gold ingot can be cooled first than the inside. Avoid generating large shrink pits. The watering action should be light and timely, that is, watering the surface of the ingot after the condensation film has been formed, so as not to punch the surface of the gold ingot into a pit.

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