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Gold smelting ingot processing
Finished gold ingot cast material, mainly electrolytic gold. Gold purified by chemical methods 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 ingot in the oil furnace by melting the graphite crucible. 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.
Diesel furnaces can be fed with diesel oil by means of gear oil pumps. However, most plants use high-position fuel tanks to increase oil pressure by height difference. The height difference from tank to nozzle is generally more than 3~4m. The atomizing air used compressed air of 98.066 to 196.133 kPa (1 to 2 kg/cm 2 ).
If the No. 60 stone å©åŸš is used, after baking and checking that there is no damage, 35-60 kg of electrolytic gold is added in each step, and the temperature is raised to 1300-1400 ° C to melt. All gold to be melted and superheated to the white gold was red, chemically pure potassium nitrate and boron was added each 10 ~ 20g slag sand.
Ingot mold using a trapezoidal rectangular opening spacious flat die cast iron, the internal foot after the rain was machined die: 260mm (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 the level to avoid uneven thickness of the ingot). To be cast.
After slag formation and cleaning of the slag, the slag is removed, and the remaining slag of the sputum is cleaned with a stainless steel piece. The liquid liquid is injected along the vertical direction of the mold and the shaft at a liquid temperature of 1200 to 1300 ° C and a mold temperature of 120 to 150 ° C. Molding center. The casting speed should be fast, stable and uniform, avoiding the violent fluctuation of the gold liquid in the mold, so that the ingot surface forms cracks or wrinkles. 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 allow the ingot to be cooled earlier than the inside, to ensure that the ingot surface is flat and avoid the formation of large shrinkage pits, it can be soaked with potassium nitrate solution immediately after pouring an ingot. 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 ingots pliers cylinder 5% dilute hydrochloric acid soak 10 ~ 15min, washed clean with tap water after taken out, the wipe dry with gauze, and then dried over anhydrous ethanol Or gasoline to rub the surface. A good quality gold ingot, after being cleaned, shows a bright light like a mirror.
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 the qualification of the inspector has passed the inspection, the order number and production time of the ingot are marked with the steel code, and the invoice is delivered in the block size (one hundred grams of precision). Waste ingot recast.
Many factories have now converted small ingots and do not cover paper and brick. That is, a thin ingot having a thickness of 5 to 25 mm is cast in an open flat die. This kind of non-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 removed from 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 dross can be washed away, and the surface of the gold ingot can be cooled without internal. 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.