Mold with a function ring

Abstract

The invention relates to a hot-top mold for a strand casting apparatus, consisting of a hot-top, which lies on the upper side of a parting agent distributor and presses it with its underside against the surface of a mold, an overhang being formed on the radially inner surface of the hot-top, which protrudes beyond the parting agent distributor in the direction of take off of the strand, the hot-top being centered and held by an outer ring, which is releasably fastened to the mold. The mold surrounds a function ring toward the bearing surface of the mold which, together with the parting agent distributor, forms function surfaces with adjustable roughness on the surfaces. In the parting agent distributor, radial channels are formed at the upper side and the underside, the channel cross sections at the upper side and the underside being in a ratio of 1:3 to 1:5 to one another.

We claim:  
     
         1 . A hot-top mold for a strand casting apparatus comprising a mold ( 3 ), a parting agent distributor ( 2 ), a hot-top ring ( 1   a ,  1   b ) lying on the top ( 2   a ) of the parting agent distributor ( 2 ) and pressing its bottom ( 2   b ) against the top surface ( 3   a ) of the mold ( 3 ), an overhang being formed at the radially interior surface of the hot-top ring ( 1   a ,  1   b ) protruding beyond the parting agent distributor ( 2 ) in the withdrawal direction of the strand and forming an annular gap ( 11 ) with the mold surface, an outer ring ( 4 ) releasably fastened to the mold ( 3 ), for centering and holding the hot-top ring, a function ring ( 5 ) surrounded by the mold positioned toward the inner surface of the mold, the function ring and parting agent distributor ( 2 ) forming function surfaces with adjustable roughnesses on the surfaces, and radial passages formed on the top and bottom surfaces ( 2   a ,  2   b ) of the parting agent distributor, the passage cross sections between the upper and bottom surfaces being in a ratio of 1:3 to 1:5.  
     
     
         2 . The hot-top mold of  claim 1 , wherein the function ring ( 5 ) includes copper or copper alloys.  
     
     
         3 . The hot-top mold of  claim 1 , wherein the function ring ( 5 ) includes ceramic or composite materials.  
     
     
         4 . The hot-top mold of  claim 1 , wherein the function ring ( 5 ) includes graphite material.  
     
     
         5 . The hot-top mold of  claim 1 , wherein a clamping ring ( 6 ) is disposed above the hot-top ( 1   a ,  1   b ), by which the hot-top ( 1   a ,  1   b ), the parting agent distributor ( 3 ), the function ring ( 5 ) and the mold ( 3 ) are clamped.  
     
     
         6 . The hot-top mold of  claim 5 , wherein the function ring ( 5 ) has a closed porosity of 0-20% and a density of 1.5-10 g/cc.  
     
     
         7 . The hot-top mold of  claim 6 , wherein the radial channels, incorporated into the upper side  2   a  of the parting agent distributor ( 2 ), are connected to a pressurized gaseous medium and that radial passages are formed at the underside ( 2   b ) of the parting agent distributor ( 2 ) and are connected to a pressurized liquid reservoir.  
     
     
         8 . The hot-top mold of  claim 7 , wherein the lower radial passages of the parting agent distributor are configured in the manner of a diffuser, an approximately square cross section being given to the radially outward lying passage carrying the parting agent distributor ( 2 ) and a rectangular cross section with a surface ratio of at least 1:2 being formed on the radially inward-lying exit side.  
     
     
         9 . The hot-top mold of  claim 8 , wherein cooling passages ( 15 ) are disposed in the mold ( 3 ), which reach into the area underneath the parting agent distributor ( 2 ) and the function ring ( 5 ), heat removal being performed in the annular gap ( 14 ) through a foam layer ( 16 ) produced by the gas and liquid medium and issuing in the descending direction of the strand.  
     
     
         10 . The hot-top mold of  claim 9 , wherein the bottom part of the thermal conductivity of the hot-top ( 1   b ) is  1 . 5  to 2.0 times greater than that of the upper part of the hot-top ( 1   a ).  
     
     
         11 . The hot-top mold of  claim 10 , wherein the upper part ( 2   a ) of the parting agent distributor ( 2 ) is covered by an activator ring ( 7 ).