First, the preparation of the charge After all the gold mud smelting is finished, the gold nuggets are collected for ingot casting. 5. Ingot: After the slag is basically cleared, the metal can be poured into the mold. The number of molds depends on the amount of metal. It is better to keep a little slag when ingot casting. On the one hand, it can preheat the mold, on the other hand, it can be used as an ingot covering, so that the ingot has a better surface. After the slag and the ingot are all solidified, the mold is turned over and released, and the slag on the surface of the gold ingot is removed. These slags often have some gold beads that should be incorporated into the charge of the next furnace. [next] The mold should be preheated to 100 ~ 200 ° C each time, and the inner surface is evenly smoked with a layer of black smoke 1 to 2 mm thick.
The formation of fluoride crystal mica is a sub-grade, and does not adsorb impurities. It was selected by the Chinese Academy of Sciences Environmental Biology Research Center Peking University, Tsinghua University, Shanghai Fudan University, Nanjing University, and more than 100 national research institutions and universities for AFM substrate After (microscopy carrier wave), the relevant person said: Compared to natural mica, fluorite mica has better flatness and less adsorption impurities. The images observed in the analysis of the DNA structure, especially in the 1 nm to 100 nm scale, have observed surface interference fringes not found in the natural mica experiment, which are clearly dozens of times better than the natural mica substrate. Experts involved in the experiment believe that the use of fluoride mica instead of natural mica as a substrate material is expected to catch up with the international level.
The main performance in the field of atomic force microscopy:
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The preparation of the charge mainly refers to the gold mud. Wet gold mud generally contains 25-40 % water. When smelting with smelting, the gold mud must be dried beforehand, because the wet gold mud will cause the mash to break. When smelting in a converter, it may be determined by the circumstances. Pre-drying is advantageous for making full use of the oxidizing flux.
The flux must be broken, then mix well with the gold mud in the large iron plate, and turn it many times. This allows the flux to fully contact the gold mud, ensuring complete oxidation and slagging reactions. The dried golden mud should be sprayed with a small amount of water during the mixing to prevent the loss of flying.
The ingredients of sponge gold and heavy sand are relatively simple. Heavy sand can be mixed well with the charge. The smelting of sponge gold is as long as it is placed in the crucible, and a certain amount of flux is added to the lower part and the upper part.
Second, the operation of smelting
The smelting operation of sputum can be divided into four steps of heating, feeding, melting and ingot casting.
Heating: When the furnace is warmed up, it is directly ignited with wood, and then the burner is directly started to introduce fuel and air into the furnace. You must choose carefully. Since cockroaches may be damp, they must be baked strictly before use. Severely dampened cockroaches are slow to roast and avoid sudden bursts of heat. There are two kinds of lining refractory materials for graphite crucible. One is to place the refractory crucible in the graphite crucible, the gap between the two crucibles is filled with graphite powder, and the other is to place a mechanical mold and crucible in the graphite crucible. A layer of refractory material is placed between the inner walls, baked and sintered to form an inner lining. When the liner is damaged and the graphite crucible is intact, the liner can be removed and a refractory crucible or liner lined.
Feeding: the furnace heats up to
Melting: After the charge is fully added, it enters the melting stage. Due to the removal of the gas generated by the slagging reaction, especially when aqueous borax is used, the water evaporates in a large amount, causing the melt to boil. After the reaction is completed, the melt is completely calm, and the length of the melting time depends mainly on the amount of charge in the crucible. Usually, a 20 #å©åŸš can smelt 10 to 15 kg of gold mud at a time, which takes about 1.5 hours. Due to the boiling of the melt during melting, some slags often flow into the furnace with some charge overflowing. When the slag in the furnace accumulates a lot, the slabs of the slabs will float up. At this time, it is necessary to use an iron scoop to smash the slag from the furnace. This is a very difficult job.
After the melting is completed, the oil supply and air supply are stopped, and the concrete is removed from the furnace with a dedicated clamp. Pour the melt quickly into a tapered cast iron tank (as shown below). The slag and the metal are separated by specific gravity. After the cans are moved into the sink and cooled, the solidified melt is poured out and the gold nuggets at the bottom are laid. [next] 
The used cockroaches should be carefully inspected and the severely corroded cockroaches should be removed. Used crucibles are generally not used for ingot casting.
Third, the operation of converter smelting
The converter smelting operation can be roughly divided into six unit operations of heating, feeding, melting, pouring slag, ingot casting, and furnace shutdown. [next]
1. Heating: The heating system is mainly determined by the lining material. Aluminum siliceous lining heating takes about 16 to 24 hours. The cold stove is first baked with wood for 4 to 8 hours, then a small amount of wind is sent to the furnace to make the firewood burn more and the furnace temperature gradually rises to
2. Feeding : the furnace temperature must be reached before feeding
Practice has proved that when using converter smelting, it is best to use a feeding method. Therefore, multiple feedings often cause the furnace to be excessively cooled, and the furnace charge is too much, and the molten pool is too deep, so that the temperature difference between the upper and lower melts is too large, which is unfavorable for the smelting process. Therefore, the second feeding can only be considered if the remaining charge is not sufficiently smelted once. Be careful when feeding the second time because there is already a melt in the furnace. It is possible that the water in the charge from the second addition will cause the material to spray outside, so when the second material is added, the human body should be prevented from facing the mouth of the furnace to avoid injury.
Feed as fast as possible to avoid excessive cooling of the furnace. Add a thin layer of borax to the surface of the material.
One inner diameter is
3. Melting: Fire immediately after adding the material, and the furnace temperature should be maximized in the shortest time as possible to allow the charge to melt rapidly.
The melting of the charge begins at the surface. The metal droplets in the molten charge are infiltrated, and during the infiltration process, the impurities in the droplets are sufficiently reacted with the flux to form a slag. Shake the furnace often so that the unmelted material is exposed to the flame as much as possible, and if necessary, stir the molten pool with iron shovel to accelerate the melting.
As the melting progresses, the molten pool gradually expands and violently boils due to the evolution of the gas. The large amount of volatilization of zinc and lead makes the smoke appear thick white.
It is worth noting that the flame must be kept bright during the melting process and no black smoke can be emitted. A flame containing a large amount of unburned fuel will take oxygen from the charge and be harmful to the slagging reaction, and the supply of a large amount of fuel does not increase the temperature of the furnace, and the color of the flame is preferably bright orange.
Every smelting operator must have good observation ability. He can determine the furnace temperature from the color of the furnace, and can also judge the condition of the burner supply and supply of air from the sound of the furnace, and adjust it in time.
After the charge is completely melted, the molten pool gradually calms down and the flame appears more incandescent and bright. Generally, the lining cannot be seen without using sunglasses.
4. Pour the slag: The furnace material is completely melted, and after the molten pool is no longer tumbling, the slag can be poured after being left for half an hour. The slag is divided into two parts, and the slag poured for the first time accounts for about 80% of the total slag. The furnace was slowly tilted to allow the slag to flow into the cone-shaped slag bag (as shown below). After the first slag is poured, it is necessary to observe the condition inside the furnace. If the slag is relatively sticky, some borax should be added, and the slag should be poured after being melted. Slow down the second slag and try to prevent the gold mud from falling out. But this situation is hard to avoid. In order to ensure a relatively high direct recovery rate, in the actual operation, the second slag and the bottom of the first slag are often returned to the furnace along with the charge of the next furnace. Under normal circumstances, the viscosity of the first slag is small, and the gold content does not exceed
6. Shutdown: After the smelting is completed, the fuel and wind supply should be stopped immediately, and the burner and the furnace mouth should be sealed with refractory material or yellow mud to gradually lower the furnace temperature, which can protect the furnace lining.
Fourth, gold ingots
The gold ingot obtained by smelting is relatively rough, and its surface may have many defects such as shrinkage cavities, pores, and flash. There may also be some inclusions. In order to obtain gold ingots with better physical specifications, it is often necessary to recast the ingots.
The secondary ingot is usually carried out in a crucible furnace or a high frequency (intermediate frequency) electric furnace. The latter is easy to operate, easy to control, and easy to control. The size of the standard mold is 237×57 at the bottom and 265×87 at the top.
The crucibles used for ingot casting, especially the crucibles for casting red gold, must be clean and selected and heated to bake until
In practice, the melting temperature is from 1250 to 1350 ° C , the residence time of gold in the furnace is 25 to 30 minutes, and the casting temperature is 1200 to 1250 ° C. Borax is applied to remove the scum from the surface of the melt before the priming gold is cast.
There must be no wind in the operating room of the ingot. The mold should be flat. The cast standard ingot should also be marked with a boundary line in the mold. The ingoting time is 7 to 14 seconds, and the flow rate is from small to large and then small, and the flow should be clean and clean. At the moment of pouring, press the heat to
Ingot casting operations require a wealth of experience and operational skills, and any negligence is impossible to obtain ingots of good quality.
After solidification of the ingot, sequentially unloading asbestos board, into nitric acid or aqueous hydrochloric acid, immersing a moment, an acid wash with water, dry Serve. Cast standard ingots and prevent the tool from scratching the surface of the ingot after unloading.
A standard ingot should be a fine work with no scratches on the surface, pores, burrs, protruding points, complete corners, dimples on the surface, the size is satisfactory, and the weight does not exceed the specified range. The number on the ingot should be numbered.