Process for recovery of tungsten values

Claim 1

IN A PROCESS OF RECOVERING TUNGSTEN FROM TUNGSTEN TOOL STEELS THE STEPS COMPRISING, HEATING THE ALLOY AT 11001300* C. UNDER CARBURIZING CONDITIONS TO COMPLETE HARDNESS, QUENCH-COOLING THE CARBURIZED MATERIAL, DIGESTING THE MATERIAL IN A SULPHURIC ACID SOLUTION WITH ADDING OF INCREMENTS OF THE ACID AT A RATE CONTROLLING THE TEMPERATURE TO AROUND 100* C., CONTINUING THE DIGESTION UNTIL A CARBIDE SLUDGE FORMS, SEPARATING THE LIQUID FROM THE CARBIDE SLUDGE, ADDING TO THE LIQUID NITRIC ACID IN AMOUNT ABOUT TEN TO THIRTY PER CENT OF THE WEIGHT BASED ON THE ANHYDROUS HN03 CONTENT, BOILING TO FORMATION OF A PRECIPITATE, SEPARATING THE PRECIPITATE AND COMBINING IT WITH THE CARBIDE SLUDGE, DRYING SUCH MASS AND CALCINING IN OXIDIZED CONDITIONS AT 750-850* C., THEN DIGESTING IN CAUSTIC SODA SOLUTION AT AROUND 100* C., DILUTING, WASHING THE PRECIPITATE FORMED, AND COLLECTING THE TUNGSTEN LIQUID FOR FURTHER PROCESSING.