Kutentha kotentha smelting of silver and its alloys

Characteristics of silver and its alloys

Silver is a precious metal with a melting point of 960.8Y and a density of 10.49g/cm3. It does not oxidize at room temperature. Pure silver is silvery white. It can form an alloy with any proportion of gold or copper. When the alloy contains gold or copper proportions As it increases, the color turns yellow. When silver is eutectic with aluminum and zinc, it is also very easy to alloy. Among all metals, silver has the best conductivity.

When silver is smelted in a general metallurgical furnace, it will oxidize and become volatile. But when there is splashed metal (splashed metal refers to the low-priced metals that coexist and exist as impurities in the ore, concentrate and intermediate products of metallurgical plants of gold, silver and tong group metals, mainly including copper, lead, zinc The silver oxide is quickly reduced. Under normal smelting (furnace temperature 1100-1300^), the volatilization loss of silver is about 1% or less, but when the oxidation is strong, there is no covering agent on the molten silver, and the charge contains more lead, zinc, monuments, fetters, etc. When the metal is volatilized, the loss of silver will increase.

When silver melts in the air, it can absorb approximately 21 times its own volume of oxygen, which is released when silver is condensed to form a boiling state, commonly known as “silver rain”, which will cause the splash loss of fine silver beads.

Silver casting process

The final step of silver purification and refining is to melt the high-purity silver powder or silver plate refined by electrolytic or chemical methods, and then cast into ingots or pellets that meet national standards or other specifications.

The induction melting furnace used for the noble casting of gold and silver. The capacity can be selected according to the daily processing capacity of gold and silver, usually about 50~200kg. If there are special needs, a larger induction melting furnace can also be used for induction melting. The main points of the technical operation of furnace smelting silver are as follows.

AAdd proper amount of flux and oxidant

Generally, saltpeter and sodium carbonate or saltpeter and borax are added. The amount of flux and oxidant added varies with the purity of the metal. Such as smelting electrolytic silver powder containing more than 99.88% silver, generally only add 0.1% -0.3% sodium carbonate to oxidize impurities and dilute the slag; while smelting silver with higher impurities, you can add appropriate amount of saltpeter and borax to strengthen Oxidize a part of the impurities to make slagging and remove. At the same time, the amount of sodium carbonate should be appropriately increased. The amount of oxidant should not be too much, otherwise the crucible will be strongly oxidized and damaged.

After the smelting process of oxidation and slagging, the silver grade of the cast ingot is higher than that of the raw material silver, so it is necessary to add an appropriate amount of protective flux and oxidant.

B Strengthen the protection and deoxidation of silver

When silver melts in the air, it can dissolve a large amount of gas, which is released when it is condensed, which brings difficulties to the production operation and causes the loss of metal.

When silver melts in the air, it can dissolve approximately 21 times the volume of oxygen. This oxygen is released when the metal is cold, forming a “silver rain”, causing the splash loss of fine-grained silver. If the oxygen is too late to release, defects such as shrinkage holes, pores, and pitted surfaces are formed in the silver ingot.

Mu ntchito yeniyeni, pamene kutentha kwa siliva wosungunuka kumawonjezeka, kusungunuka kwa okosijeni mu siliva kumachepa. Pofuna kuchepetsa vuto la kuponyera, kutentha kwa madzi a siliva kuyenera kuwonjezereka musanayambe kuponyera, ndipo gawo lochepetsera (monga makala, phulusa la zomera, etc.) liyenera kuphimbidwa pamwamba pa madzi asiliva kuti achotsedwe. mpweya. Palinso mtengo wa pine womwe umawonjezeredwa pamtengowo, womwe umatenthedwa makamaka ndi kusungunuka kwa siliva kuchotsa mbali ya mpweya. Palinso kugwiritsa ntchito ndodo zamatabwa kusokoneza madzi osungunuka asanaponyedwe kuti akwaniritse cholinga cha deoxygenation.

C kudziwa kutentha kuthira

Pamene zitsulo zasiliva zimaponyedwa, kuwonjezeka kwa kutentha kwachitsulo kumathandiza kuchepetsa kuchuluka kwa mpweya wosungunuka, ndipo zitsulo zotentha zimatsanuliridwa mu nkhungu, ndipo kuchuluka kwa condensation kumachedwa, zomwe zimapindulitsa kutulutsa mpweya ndikuchepetsa kuwonongeka kwa ingot. Kawirikawiri kutentha kwa siliva kuyenera kukhala 1100-1200T; o

D nkhungu khoma ayenera kugwiritsa ntchito utoto, kuthira ntchito ayenera kukhala wololera

Pamene ingot ya siliva imaponyedwa, gwiritsani ntchito ethane kapena petroleum (mafuta olemera kapena dizilo) lawi kuti muzisuta utsi wochepa kwambiri pa khoma lamkati la nkhungu, ndipo zotsatira zake zimakhala zabwino.

Kuonjezera apo, khalidwe la ntchito yoponya limagwirizana kwambiri ndi khalidwe la ingot. Pakupanga nkhungu yowongoka, kutuluka kwamadzimadzi kuyenera kukhala kokhazikika, kutuluka kuyenera kukhala pakati, ndipo zinthuzo zisabalalike ndipo khoma lamkati siliyenera kutsukidwa. Yambani pang’onopang’ono, ndiyeno muwonjezere kuthamanga kwamadzimadzi mpaka pamwamba pazitsulo zidzadzazidwa ndi pafupifupi magawo atatu pa asanu a nkhungu kutalika, ndipo pang’onopang’ono muchepetse kuti mpweya utuluke. Mukathira pachipata, tcherani khutu ndikubwezeretsanso madziwo mpaka yankho silinapopedwe. Pakuti chotseguka chophatikizika chathyathyathya nkhungu, ntchitoyo ndi yosavuta, bola ngati nkhungu imayikidwa pamtunda wopingasa, mpukutu wapansi ndi perpendicular. mpaka kumtunda wautali wa nkhungu, ndipo chitsulo chosungunuka chimatsanuliridwa mofanana pakati pa nkhungu. Pofuna kuteteza khoma lamkati la nkhungu, malo omwe zitsulo zosungunuka zimatsanuliridwa ziyenera kusinthidwa nthawi zonse poponyera kuti pakatikati pa nkhungu zisawonongeke mu dzenje.