Wettable injectors for degassing of molten metal

Abstract

Various illustrative embodiments of an apparatus and method for reducing the dissolved hydrogen content of a molten metal alloy are provided. The disclosed embodiments can be utilized for the processing of molten metal alloys such as aluminum, and more particularly, for the removal of dissolved hydrogen from molten metal alloys such as aluminum. Gas permeable diffusers can be employed that are wettable by molten metal. When used as gas injectors, either in combination with ultrasonic oscillation or without, the gas permeable wettable diffusers can provide a high density of ultrafine inert gas bubbles that can be used to rapidly and efficiently reduce the level of dissolved hydrogen within the molten metal.

1 . An apparatus for degassing a molten metal, the apparatus comprising:
 a container for holding the molten metal;   a dispenser capable of dispensing purge gas; and   a diffuser in fluid communication with the molten metal from the container, the diffuser being wettable by the molten metal and capable of receiving the purge gas from the dispenser, forming purge gas bubbles from the purge gas, and emitting the purge gas bubbles into the molten metal.   
     
     
         2 . The apparatus of  claim 1 , wherein the diffuser has a face with a plurality of pores formed thereon, the pores being in fluid communication with the molten metal and capable of forming purge gas bubbles from the purge gas and emitting the purge gas bubbles into the molten metal. 
     
     
         3 . The apparatus of  claim 2 , wherein the average diameter of the pores is not greater than 200 microns. 
     
     
         4 . The apparatus of  claim 1 , wherein the molten metal is aluminum. 
     
     
         5 . The apparatus of  claim 1 , wherein the molten metal contains dissolved hydrogen gas and the purge gas bubbles are capable of removing the dissolved hydrogen gas from the molten metal. 
     
     
         6 . The apparatus of  claim 1 , further comprising an ultrasonic oscillator disposed adjacent to the diffuser such that the diffuser lies within a sonicated field of the oscillator. 
     
     
         7 . The apparatus of  claim 6 , wherein the ultrasonic oscillator is in direct mechanical communication with the diffuser. 
     
     
         8 . The apparatus of  claim 6 , wherein the ultrasonic oscillator is operable below or above the cavitation power required for the molten metal. 
     
     
         9 . The apparatus of  claim 6 , wherein the diffuser oscillates below the cavitation power required for the molten metal. 
     
     
         10 . The apparatus of  claim 6 , wherein the diffuser oscillates above the cavitation power required for the molten metal. 
     
     
         11 . The apparatus of  claim 1 , wherein the composition of the diffuser includes a wettable material comprising titanium diboride. 
     
     
         12 . The apparatus of  claim 1 , wherein the composition of the diffuser includes a wettable material comprising silicon carbide. 
     
     
         13 . A method of degassing a molten metal, the method comprising:
 providing a molten metal alloy with hydrogen gas dissolved therein;   introducing a purge gas into a diffuser, the diffuser being in fluid communication with the molten metal at a diffuser-molten metal interface and wettable with respect to the molten metal;   forming purge gas bubbles at the diffuser-molten metal interface;   injecting the purge gas bubbles from the diffuser into the molten metal;   transferring the dissolved hydrogen gas from the molten metal to the purge gas bubbles; and   reducing the concentration of dissolved hydrogen gas in the molten metal.   
     
     
         14 . A method of degassing a molten metal containing dissolved hydrogen gas, the method comprising:
 contacting a face of a diffuser with the molten metal;   wetting the face of the diffuser with the molten metal;   flowing a purge gas through a plurality of pores in the face, the pores having a pore size in the range from 2-200 microns;   producing purge gas bubbles at the pores;   emitting the purge gas bubbles from the pores and into the molten metal;   transferring the dissolved hydrogen gas from the molten metal to the purge gas bubbles; and   reducing the concentration of the dissolved hydrogen gas in the molten metal.   
     
     
         15 . The method of  claim 14 , further comprising oscillating the diffuser below or above the cavitation power of the molten metal. 
     
     
         16 . The method of  claim 14 , further comprising disposing the diffuser within the sonicated field of an oscillator. 
     
     
         17 . The method of  claim 14 , further comprising attaching the diffuser to the sonotrode of an oscillator.