Casting, vertical casting method and vertical casting apparatus

Abstract

A molten steel of a special steel or the like including a high-alloy steel is poured in a mold whose bottom portion is closed with a dummy head of a lift table. As the lift table is vertically moved down at a given casting speed, a casting whose lower end is supported by the dummy head is continuously pulled out from the bottom portion of the mold. As a pair of movable molds that constitute the mold are relatively moved away from each other in synchronism with the downward movement of the lift table, both widthwise side surfaces of the casting are provided with required tapering.

What is claimed is:  
     
         1 . A casting of a predetermined length cast by pouring a molten special steel including a high-alloy steel and tool steel in a mold open to the top and bottom thereof and vertically pulling out the casting having a required cross-sectional shape and having a shell formed on a surface from a bottom portion of said mold, 
 at least a pair of opposing sides being tapered in such a way that an opposite side size of both sides becomes smaller toward said bottom portion from a top portion.    
     
     
         2 . A vertical casting method for casting a casting of a predetermined length by pouring a molten special steel including a high-alloy steel and tool steel in a mold open to the top and bottom thereof and vertically pulling out the casting having a required cross-sectional shape and having a shell formed on a surface from a bottom portion of said mold; 
 wherein at a time of casting said casting, tapering at least a pair of opposing sides of said casting in such a way that an opposite side size of both sides becomes smaller toward said bottom portion from a top portion by relatively moving at least a pair of opposing movable molds of said mold away from each other while pulling out said casting from said bottom portion of said mold.    
     
     
         3 . The vertical casting method according to  claim 2 , wherein a casting speed of pulling out said casting from said mold is set equal to or less than 0.2 m/min to thereby suppress occurrence of a center porosity and segregation in said casting to be cast.  
     
     
         4 . A vertical casting apparatus for casting a casting of a special steel including a high-alloy steel and tool steel, comprising: 
 a mold which is open to the top and bottom thereof and has at least a pair of movable molds that are relatively moved close to and away from each other by movable means and where a molten special steel including said highalloy steel and tool steel is poured;    a lift table, provided below said mold in a vertically movable manner, for supporting a lower end of the casting having a shell formed on a surface thereof and pulling out said lower end of said casting from a bottom portion of said mold; and    lifting means for moving said lift table up and down.    
     
     
         5 . A vertical casting method for casting a casting of a predetermined length by pouring a molten special steel including a high-alloy steel and tool steel in a mold open to the top and bottom thereof and vertically pulling out the casting having a required cross-sectional shape and having a shell formed on a surface from a bottom portion of said mold; 
 wherein at a time of casting said casting, after completion of pouring, covering a top portion of said mold with a lid member and heating said molten steel in said mold with a plasma or arc with an internally defined heating chamber set in an atmosphere of an inert gas and under such a heating condition as to be able to keep a temperature of a surface of said molten steel at a solidus casting temperature or higher, thereby suppressing occurrence of an internal defect in said casting to be cast.    
     
     
         6 . The vertical casting method according to  claim 5 , wherein said lid member is preheated to a predetermined temperature before covering said top portion of said mold with said lid member.  
     
     
         7 . A vertical casting apparatus for casting a casting of a predetermined length by pouring a molten special steel including a high-alloy steel and tool steel in a mold open to the top and bottom thereof, supporting a lower end of the casting having a shell formed on a surface thereof and pulling out said lower end of said casting from a bottom portion of said mold with a lift table, provided below said mold and movable up and down vertically by lifting means, comprising: 
 a lid member capable of covering a top portion of said mold and set an internally defined heating chamber in an atmosphere of an inert gas; and    heating means for heating said molten steel in said mold covered by said lid member with a plasma or arc.    
     
     
         8 . The vertical casting apparatus according to  claim 7 , further comprising preheating means for preheating said lid member.  
     
     
         9 . The vertical casting apparatus according to  claim 7  or  8 , wherein said lid member is constructed by covering an outer side of an inside lining member of a refractory material with an outside lining member of a heat insulating material.