Sponge titanium, method for producing sponge titanium, and method for producing titanium ingot or titanium alloy ingot

Abstract

Provided is sponge titanium produced by the Kroll method, in which the total of a chlorine content and a magnesium content is 350 ppm by mass or lower, and a filling density is 1.65 g/cm3 to 1.95 g/cm3. The present invention can provide sponge titanium for large ingot production that is difficult to cause problems due to chloride inclusion at the time of melting production of the large ingot by a melting method not associated with compression molding and has easy component control and also provide a method for industrially efficiently producing the sponge titanium.

1 - 6 . (canceled) 
     
     
         7 . A method for producing sponge titanium by Kroll method, the method comprising:
 a reduction-separation step of determining an area of a reaction bath surface to be 2.5 m 2  or larger,   (i) determining an average feed rate A of titanium tetrachloride per unit area of the reaction bath surface calculated in accordance with Formula (1):
     A =Average feed rate of titanium tetrachloride per minute (kg/minute)/Area of reaction bath surface (m 2 )  (1)
 
   
       to be 2.8 kg/(minute·m 2 ) to 4.0 kg/(minute·m 2 ) for a period from start of feed of titanium tetrachloride to metal magnesium to generation of sponge titanium to a position corresponding to an upper limit position of a collection target in a crushing step, and
 (ii) determining a total feed amount of titanium tetrachloride to be an amount in which a bottom part load index B of a sponge titanium block calculated in accordance with Formula (2):
     B =Mass of sponge titanium block( t )/Area of disc or seat contacting lower side of sponge titanium block (m 2 )  (2)
 
 
 
       is 3.5 t/m 2  to 5.5 t/m 2 ; and
 the crushing step of determining the upper limit position of the collection target to be a position in a range of 40% to 50% on a mass basis from the bottom of the sponge titanium block and cutting, grinding, and sieving the sponge titanium block lower than the upper limit position of the collection target serving as a collection target to obtain sponge titanium. 
 
     
     
         8 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein the average feed rate A of titanium tetrachloride per unit area of the reaction bath surface is 2.8 kg/(minute·m 2 ) to 3.6 kg/(minute·m 2 ). 
     
     
         9 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein the bottom part load index B of the sponge titanium block is 4.0 t/m 2  to 5.5 t/m 2 . 
     
     
         10 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a lower limit position of the collection target is determined to be a position of 2% to 8% on a mass basis from the bottom of the sponge titanium block. 
     
     
         11 . The method for producing sponge titanium by the Kroll method according to  claim 10 , wherein a lower limit position of the collection target is determined to be a position of 2% to 5% on a mass basis from the bottom of the sponge titanium block. 
     
     
         12 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a temperature of a reduction reaction container in reduction reaction in the reduction-separation step is 700° C. to 950° C. 
     
     
         13 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a vacuum heating temperature in vacuum separation in the reduction-separation step is 900° C. to 1,080° C. 
     
     
         14 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a vacuum heating time in vacuum separation in the reduction-separation step satisfies Formula (3)
   112≤0.26× r−p≤ 125  (3)
   
       where a vacuum heating time is p (hour) and a radius of the disc or seat contacting the lower part of the sponge titanium block is r (mm) (with the proviso that r is 600 mm or longer). 
     
     
         15 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a total of a chlorine content and a magnesium content is 350 ppm by mass or lower and a filling density is 1.65 g/cm 3  to 1.95 g/cm 3  in the sponge titanium obtained by carrying out the crushing step. 
     
     
         16 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein an average particle diameter of the sponge titanium obtained by carrying out the crushing step is 1.7 mm to 19.1 mm. 
     
     
         17 . The method for producing sponge titanium by the Kroll method according to  claim 7 , wherein a ratio of sponge titanium fine particles having a particle diameter of 0.84 mm or smaller in the sponge titanium obtained by carrying out the crushing step is 0.8% by mass or lower.