TRANISH RESISTANT SILVER ALLOY, IN PARTICULAR TO THE SULFIDATION AND PRODUCING METHOD THEREOF

Tarnish resistant silver alloys, in particular to the sulfidation, and producing method thereof, contain except pure metals silver Ag, zinc Zn and copper Cu, and pre-alloys: aluminum-silicon, Si content from 7 to 20%, and Al up to 100%, aluminum-zinc, Zn content 75 to 80%, and Al up to 100% , copper-silicon, Si content from 5 to 10%, and Cu up to 100%, and copper-zinc, Zn content from 25 to 30%, and Cu to 100%, which by melting and washing processes give silver alloy more resistant to tanning, in particular to the sulfidation of similar alloys from the state of the art, and also have a significantly lower degree of surface tanning. The novelty of the invention is particularly reflected in the use of aluminum, silicon and zinc as the alloying elements and they always appear together as pre-alloys in silver alloy. The optimum content of silicon in the alloys of the present invention ranges from 0,2 to 0,5%. The results of the study show that the degree of tarnish of the main alloy surface AgCu1,9Zn3,7Al1,6Si0,3 has approximately 30 times lower value of this parameter than the reference alloy of sterling silver in a sodium sulfide solution of 0,01 mol/dm3 concentration and approximately 40 times the lower value of the jkor coefficient in a sodium sulfide solution of 0,1 mol/dm3 concentration from the reference alloy of sterling silver. Legure srebra otporne na tamnjenje, naročito na sulfidizaciju i postupak za njihovo dobijanje, sadrži osim čistih metala srebra Ag, cinka Zn i bakra Cu i predlegure: aluminijum-silicijum, sadržajSi od 7 do 20%, i Al do 100%, aluminijum-cink, sadržaj Zn od 75 do 80%, i Al do 100%, bakar-silicijum, sadržajSi od 5 do 10%, i Cu do 100%,i bakar-cink, sadržaj Zn od 25 do 30%, i Cu do 100%, koji postupkom topljenja i livenja daju leguru srebra otporniju na tamnjenje, naročito na sulfidizaciju od sličnih legura iz stanja tehnike, a takođe imaju i znatno manji stepena tamnjenja površina. Novost pronalaska, naročito se ogleda u korišćenju aluminijuma, silicijuma i cinka kao legirajućih elemenata i što se oni uvek pojavljuju zajedno kao predlegure u leguri srebra. Optimalni sadržaj silicijuma u legurama predmetnog pronalaska se kreće u granicama 0,2-0,5%. Rezultati ispitivanja pokazuju da stepen tamnjenja površine glavne legure AgCu1,9Zn3,7Al1,6Si0,3 ima približno 30 puta manju vrednost ovog parametra od referentne legure sterling srebra u rastvoru natrijum sulfida koncentracije 0,01 mol/dm3 i približno 40 puta manju vrednost koeficijenta