Methods for recovering machining scrap

Abstract

A method including providing a quantity of metal, the quantity of metal being contaminated by a contaminant including a quantity of carbon; configuring a vacuum induction furnace to operate according to a set of operating parameters, the set of operating parameters being selected based on characteristics of the contaminant, the set of operating parameters including at least one of a pressure, an atmosphere composition, a pour temperature, or a hold time; charging the vacuum induction furnace with the quantity of metal; and operating the vacuum induction furnace to melt the quantity of metal in accordance with the set of operating parameters, whereby at least some of the contaminant is removed from the quantity of metal so as to provide an output metal having a concentration of carbon that is less than or equal to a concentration of carbon in the metal as cast.

We claim: 
     
         1 . A method, comprising:
 charging a furnace with the quantity of metal, the quantity of metal comprising a carbon-containing contaminant;   configuring the furnace to operate according to a set of operating parameters, the set of operating parameters being selected based on characteristics of the carbon-containing contaminant, the set of operating parameters including at least one of a pressure, an atmosphere composition, a pour temperature, and a hold time;   operating the furnace to melt the quantity of metal in accordance with the set of operating parameters, whereby at least some of the carbon-containing contaminant is removed from the quantity of metal;   discharging an output metal, wherein a concentration of carbon in the output metal is less than a concentration of carbon in the quantity of metal.   
     
     
         2 . The method of  claim 1 , wherein the quantity of metal includes a quantity of machining scrap. 
     
     
         3 . The method of  claim 1 , further comprising the step of:
 prior to charging the furnace with the quantity of metal, compacting the quantity of metal into a unitary piece of metal.   
     
     
         4 . The method of  claim 1 , wherein the set of operating parameters includes a hold time, and wherein the hold time is between  0  minutes and  60  minutes. 
     
     
         5 . The method of  claim 1 , wherein the set of operating parameters includes a pressure, and wherein the pressure is between  1  micron and  300  microns, wherein  1  micron of pressure is equal to  1 / 1000 th of a millimeter of mercury. 
     
     
         6 . The method of  claim 1 , wherein the set of operating parameters includes an atmosphere composition. 
     
     
         7 . The method of  claim 6 , wherein the atmosphere composition includes an inert gas atmosphere. 
     
     
         8 . The method of  claim 1 , wherein the set of operating parameters includes a pour temperature, and wherein the pour temperature is between 700° C. and 770° C. 
     
     
         9 . The method of  claim 1 , wherein the quantity of metal comprises sodium. 
     
     
         10 . The method of  claim 9 , wherein the set of operating parameters includes a pressure, a pour temperature, and a hold time, wherein the pressure is between 1 micron and 300 microns, wherein the temperature is between 700° C. and 755° C., and wherein the hold time is between 30 minutes and 90 minutes. 
     
     
         11 . The method of  claim 9 , wherein the operating parameters include a temperature and a hold time, and wherein the temperature and the hold time are selected so as to provide a residual sodium concentration that is less than a target concentration. 
     
     
         12 . The method of  claim 11 , wherein the target concentration is six parts per million. 
     
     
         13 . The method of  claim 1 , wherein the carbon-containing contaminant is an organic compound. 
     
     
         14 . The method of  claim 13 , wherein the operating parameters include a pour temperature of about 700° C. and substantially no hold time. 
     
     
         15 . The method of  claim 14 , wherein the operating parameters include a pressure of about 300 microns. 
     
     
         16 . The method of  claim 15 , wherein the operating parameters include an argon atmosphere and a pressure of about 1 atmosphere. 
     
     
         17 . The method of  claim 1 , wherein the quantity of metal is aluminum alloy scrap. 
     
     
         18 . The method of  claim 17 , wherein the aluminum alloy scrap is scrap of one of a 2000-series aluminum alloy, a 5000-series aluminum alloy, a 6000-series aluminum alloy, a 7000-series aluminum alloy, or an 8000-series aluminum alloy. 
     
     
         19 . The method of  claim 17 , wherein the aluminum alloy scrap is scrap of an aluminum-lithium alloy. 
     
     
         20 . A method comprising:
 charging a furnace with 2000-series aluminum alloy scrap, the 2000-series aluminum alloy scrap comprising lithium and an organic contaminant;   configuring the furnace to operate according to a set of operating parameters, the set of operating parameters being selected based on characteristics of the organic contaminant, the set of operating parameters including at least one of a pressure, an atmosphere composition, a pour temperature, and a hold time;   operating the furnace to melt the 2000-series aluminum alloy scrap in accordance with the set of operating parameters, whereby at least some of the organic contaminant is removed from the quantity of metal;   discharging a purified 2000-series aluminum alloy material, the discharged 2000-series aluminum alloy material comprising the lithium.