The silver will absorb a large number of oxygen in molten state. As can be seen, at room temperature Silver hardly absorb oxygen, with the increase of temperature, the solubility of oxygen in the little silver increased, until the temperature reaches the melting point, in the molten state, silver can be dissolved more than 21 times its ownvolume of oxygen, the silver
Nature is a problem for melting and casting. It makes the alloy easily volatile at high temperatures or during cooling from high temperatures caused by splashing and caused a lot of loss. Generally no deoxidizer enough, if the melting without protection,easy accumulation of oxygen, the oxidation of copper, jewelry casting is easy toproduce
Gas hole, inclusion and other defects. Copper oxide in the casting can cause two problems, one is the entire cast will appear copper oxide inclusion, forming a hardpoint when close to the surface, projected on the polished surface, the other is to produce copper oxide inclusions in the shrinkage near, performance for the polishing surface is
Grey cloud point, the point is very deep, it is difficult to discard the clean. Silver meltlong time without protection or serious overheating, copper will seriously oxidized,forming a viscous liquid, reduce the flow of liquid metal, some small parts of filling the casting is incomplete, and often in less water near the surface of a
The red.
In order to prevent the accumulation of silver liquid oxygen, the key is to avoidexposure to the atmosphere or liquid metal smelting casting process. Several methods can be used in the following:
(1) the vacuum melting furnace, or the use of argon or nitrogen and other inert gasprotection. They will be melting indoor oxygen removal, reduce the oxidation of suctionliquid metal;
(2) should be used when the gas flame smelting reduction flame, electric furnacesmelting, sometimes also can be in the crucible opening with the reducing flame covered metal liquid;
(3) and broken charcoal or anhydrous boric acid on metal surface, they float in theliquid silver surface, from the two aspects of protection liquid silver, one is to form a barrier between the metal liquid and air, two is the reduction of copper oxide, is not suitable for this kind of method is adopted in the centrifuge, but in the cable to use theeffect machine manual the
The fruit is very good;
(4) in the method, is also very important to strengthen the protection of the liquid metal casting process, especially the blister machine casting, because it is in thevacuum under manual casting, it is necessary to protect the flow of liquid metal,usually with a reducing flame, plaster into the open flame, the flame will cover casting
Gate, so you can get rid of internal air.
The solubility of oxygen in the silver (pressure: 760mmHg):
Temperature / C: 200400600800973102 10751125
Oxygen content: 0.03 1.4 10.6 38.1305029502770 2640
Weight ratio
(10-4%)