Continous casting mould

Abstract

An open-ended mold for casting metal strands with a thin slab cross section, the mold having broad-side walls which form a central widening region which extends from the mold inlet edge to the mold outlet edge and at the outlet edge opens out in a rectangular outlet cross section. To prevent to a great extent the strand from coming away from the broad-side walls, the contour of the mold cavity in the widening region is formed, as seen in sectional planes taken at right angles to the longitudinal axis of the mold, by curves which at least in partial regions form clothoids or clothoidal curves, within which sudden changes in curvature (Δk) are minimized or reduced to zero. The curvature reduces to flat at the mold outlet edge. Other cavity surface features are disclosed.

1 . An open-ended casting mold for a continuous casting installation for casting a metal strand with a thin slab cross section the mold comprising: a mold cavity formed by mutually opposing, spaced apart, cooled broad-side walls and of mutually opposing, spaced apart, narrow-side walls between the broad-side walls, the mold having a mold inlet edge and a mold outlet edge; the mutually opposing broad-side walls forming a central widening region between the broad-side walls, and which extends from the mold inlet edge to the mold outlet edge and the widening region ending at the mold outlet edge in a rectangular outlet cross section of the open-ended mold; the widening region extending in the directions toward and narrowing toward the mutually opposing narrow-side walls and merging into laterally adjoining narrow-side adjusting regions where the broad-side walls are closer together than in the widening region; the contour of the mold cavity in the widening region is formed, as seen in sectional planes taken at right angles to the longitudinal axis of the mold, by curves which at least in first partial regions form clothoids or clothoidal curves such that within the clothoids or clothoidal curves, the sudden changes in curvature are minimized or reduced to zero.  
     
     
         2 . The open-ended mold as claimed in  claim 1 , wherein the curves include second partial regions between successive first partial regions, and the second partial regions are either formed approximately or exactly by arcs of a circle or straight lines and are joined by the first partial regions of the curves, whereby sudden changes in curvature (Δk) of these curve portions at their transitional points are minimized or reduced to zero.  
     
     
         3 . The open-ended mold as claimed in  claim 1 , wherein the contour of the mold cavity in the widening region is formed in sectional planes, taken at right angles to the longitudinal axis of the mold, and the curves run symmetrically in relation to the narrow-side walls with a convex-concave profile, the profile starting from the center of the mold cavity contour with only a small curvature or no curvature, and going over into a region with constantly increasing curvature.  
     
     
         4 . The open-ended mold as claimed in  claim 3 , wherein the curvature (k) in the center of the mold cavity contour meets the condition 
         k ≦0.3*(4 H )/( H   2   +L   2 ), 
       where k=curvature (mm) 
 H=half the mold cavity widening (mm)  
 L=half the width of the widening region B 1  (mm).  
 
     
     
         5 . The open-ended mold as claimed in  claim 1 , further comprising transitions between the central region and the narrow-side adjusting regions, wherein sudden changes in curvature at the transitions from the central widening region to the narrow-side adjusting regions and at locations of inflectional tangents in the curve profile are minimized to tend toward zero.  
     
     
         6 . The open-ended mold as claimed in  claim 5 , wherein the sudden changes in curvature (Δk) at the transition from the central widening region to the narrow-side adjusting regions meet the condition 
       Δ k ≦0.5*(4 H )/( H   2   +L   2 ) 
       where k=curvature (mm) 
 H=half the mold cavity widening (mm)  
 L=half the width of the widening region B 1  (mm).  
 
     
     
         7 . The open-ended mold as claimed in  claim 5 , wherein the sudden changes in curvature (Δk) at the locations of the inflectional tangents meet the condition 
       Δ k ≦0.4*(8 H )( H   2   +L   2 ) 
       where k=curvature (mm) 
 H=half the mold cavity widening (mm)  
 L=half the width of the widening region B 1  (mm).  
 
     
     
         8 . The open-ended mold as claimed in  claim 1 , wherein the mold cavity in the widening region has the contour thereof, as seen formed in sectional planes taken parallel to the longitudinal axis of the mold and the contour of the narrow-side walls, by straight lines between the mold inlet edge and the mold outlet edge.  
     
     
         9 . The open-ended mold as claimed in  claim 1 , further comprising transitions from the central widening region to the laterally adjoining narrow-side adjusting region regions, the transitions are formed by a straight line which, in a sectional plane, taken parallel to the longitudinal axis of the mold and the narrow-side walls, joins the mold inlet edge and the mold outlet edge.  
     
     
         10 . The open-ended mold as claimed in  claim 5 , wherein in the contour of the mold cavity, in sectional planes taken at right angles to the longitudinal axis of the mold, the locations of the inflectional tangents form straight lines between the mold inlet edge and the mold outlet edge and the straight lines lie in a sectional plane taken parallel to the longitudinal axis of the mold.  
     
     
         11 . The open-ended mold as claimed in  claim 8 , wherein the straight lines are arranged inclined by the extent of strand shrinkage of the strand being molded.  
     
     
         12 . The open-ended mold as claimed in  claim 1 , wherein in sectional planes taken parallel to the longitudinal axis of the mold and the narrow-side walls, the contour of the mold cavity in the widening region has a curved profile between the mold inlet edge and the mold outlet edge which is dependent on the solidifying conditions of the metal to be cast.  
     
     
         13 . The open-ended mold as claimed in  claim 12 , further comprising transitions between the central widening region and the laterally adjoining narrow-side adjusting region are formed by a curve with an essentially parabolic profile and, in a sectional plane parallel to the longitudinal axis of the mold and the narrow-side walls, that curve joins the mold inlet edge and the mold outlet edge.  
     
     
         14 . The open-ended mold as claimed in  claim 12 , wherein in sectional planes taken at right angles to the longitudinal axis of the mold, the mold has inflectional tangents at locations in the contour of the mold cavity which form curves having an essentially parabolic profile between the mold inlet edge and the mold outlet edge, and the curves lie in a sectional plane parallel to the longitudinal axis of the mold.  
     
     
         15 . The open-ended mold as claimed in  claim 14 , wherein the curves with the essentially parabolic profile are arranged inclined by the extent of strand shrinkage.  
     
     
         16 . The open-ended mold as claimed in  claim 1 , wherein in the widening region, in sectional planes taken at right angles to the longitudinal axis of the mold, the radii of curvature of the contour of the mold cavity become greater between the mold inlet edge and the mold outlet edge in the direction of the mold outlet edge until they are infinite at the outlet edge.  
     
     
         17 . The open-ended mold as claimed  claim 1 , wherein the broad-side walls are essentially parallel to one another in the narrow-side adjusting regions laterally of the central regions.  
     
     
         18 . The open-ended mold as claimed in  claim 1 , wherein the narrow-side walls are convexly formed with respect to the cavity in dependence on the shrinking behavior of a respective metal to be cast.  
     
     
         19 . The open-ended mold as claimed in  claim 1 , wherein the mold is shaped for casting a metal strand with a maximum thickness of 150 mm.  
     
     
         20 . The open-ended mold as claimed in  claim 12 , wherein the contour of the mold cavity in the widening region has a curved parabolic profile.