Method for Producing Ti or Ti Alloy, and Pulling Electrolysis Method Applicable Thereto

Abstract

In producing Ti or a Ti alloy through reduction by Ca, an electrolytic-bath salt taken out from a reduction process is electrolyzed to recover Ca and the electrolytic-bath salt as a solid substance, and the recovered Ca and electrolytic-bath salt are delivered to the reduction process. Therefore, heat generation is suppressed in the reduction process by utilizing latent heat of fusion possessed by the solid substance, thereby largely improving production efficiency and thermal efficiency. Additionally, a reaction temperature is easily controlled, and a raw-material loading rate can be enhanced to efficiently produce Ti or the Ti alloy. At this point, using a pulling electrolysis method of the invention, the solid-state Ca and electrolytic-bath salt can be obtained at a low voltage and high current efficiency, i.e., with the relatively small power consumption. When the solid-state Ca and electrolytic-bath salt is used as a Ca source in producing Ti or the Ti alloy through reduction by Ca, the Ti or Ti alloy can efficiently be produced.

1 . A method of producing Ti or a Ti alloy going through a reduction process in which a metallic chloride containing TiCl 4  is caused to react with Ca in a Ca-containing electrolytic-bath salt to generate Ti or the Ti alloy in the electrolytic-bath salt,
 the method comprising feeding the solid-state Ca and electrolytic-bath salt to the reduction process.   
     
     
         2 . The Ti or Ti alloy production method according to  claim 1 , wherein a Ca-containing electrolytic-bath salt containing CaCl 2  is used as the Ca-containing electrolytic-bath salt. 
     
     
         3 . A Ti or Ti alloy production method including a reduction process in which a metallic chloride containing TiCl 4  is caused to react with Ca in a Ca-containing electrolytic-bath salt to generate Ti or the Ti alloy in the electrolytic-bath salt and an electrolysis process in which Ca is generated by electrolyzing the electrolytic-bath salt taken out from the reduction process,
 the method comprising:   recovering a solid substance containing Ca and the electrolytic-bath salt in the electrolysis process; and   delivering the solid substance to the reduction process.   
     
     
         4 . The Ti or Ti alloy production method according to  claim 3 , wherein the recovery of the solid substance containing Ca and the electrolytic-bath salt is performed by pulling a cathode while the solid substance is caused to adhere to and solidified in a cathode surface. 
     
     
         5 . The Ti or Ti alloy production method according to  claim 3 , wherein a Ca-containing electrolytic-bath salt containing CaCl 2  is used as the Ca-containing electrolytic-bath salt. 
     
     
         6 . The Ti or Ti alloy production method according to  claim 4 , wherein a Ca-containing electrolytic-bath salt containing CaCl 2  is used as the Ca-containing electrolytic-bath salt. 
     
     
         7 . A pulling electrolysis method of recovering a solid-state Ca using a Ca-containing electrolytic-bath salt,
 the method comprising:   electrolyzing an electrolytic-bath salt at a bath temperature of 680 to 900° C., a cathode current density of 0.1 to 200 A/cm 2 , and a voltage of 10V or less; and   recovering Ca and the electrolytic-bath salt in a solid state by pulling a cathode at a pulling rate of 0.05 cm/min or more while a solid substance is caused to adhere to and solidified in a cathode surface.   
     
     
         8 . The pulling electrolysis method according to  claim 7 , wherein the pulling rate satisfies a following equation (1):
     V≧ 0.0035 ×t− 2.4  (1)   where V: cathode pulling rate (cm/min), and   t: bath temperature (° C.).   
     
     
         9 . The pulling electrolysis method according to  claim 7 , wherein a Ca-containing electrolytic-bath salt containing CaCl 2  is used as the Ca-containing electrolytic-bath salt. 
     
     
         10 . A pulling electrolysis method including a reduction process in which a metallic chloride containing TiCl 4  is caused to react with Ca in a Ca-containing electrolytic-bath salt to generate Ti or the Ti alloy in the electrolytic-bath salt and an electrolysis process in which Ca is generated by electrolyzing the electrolytic-bath salt taken out from the reduction process, the Ca being recovered from the Ca-containing electrolytic-bath salt in the electrolysis process,
 the method comprising:   electrolyzing an electrolytic-bath salt at a bath temperature of 680 to 900° C., a cathode current density of 0.1 to 200 A/cm 2 , and a voltage of 10V or less; and   recovering Ca and the electrolytic-bath salt in a solid state by pulling a cathode at a pulling rate of 0.05 cm/min or more while a solid substance is caused to adhere to and solidified in a cathode surface.   
     
     
         11 . The pulling electrolysis method according to  claim 10 , wherein the pulling rate satisfies a following equation (1):
     V≧ 0.0035 ×t− 2.4  (1)   where V: cathode pulling rate (cm/min), and   t: bath temperature (° C.).   
     
     
         12 . The pulling electrolysis method according to  claim 10 , wherein a Ca-containing electrolytic-bath salt containing CaCl 2  is used as the Ca-containing electrolytic-bath salt.