Quiescent transfer of melts

Abstract

A quiescent melt handling system includes a holding furnace ( 2, 120, 320 - 720 ) for a molten metal melt. The holding furnace has a relatively large surface area and a relatively shallow depth, having a width to depth ratio in the range of 4-100 to 1. Also provided is structure ( 650 - 680 ) in the holding furnace for separating inclusions from the melt in the holding furnace. A quiescent transfer casting method includes melting a metal to form a melt and transferring the melt into a holding furnace. A hydrogen content in the melt is passively equilibrated with a dry atmosphere maintained in the holding furnace. Subsequently, the melt is withdrawn from the holding furnace.

1 . A quiescent melt handling system comprising:
 a holding furnace for a molten metal melt, wherein said holding furnace comprises a relatively large surface area and a relatively shallow depth having a width to depth ratio in the range of 4-100 to 1; and   a means for separating inclusions from the melt in said holding furnace.   
     
     
         2 . The system of  claim 1  further comprising:
 a melting furnace; and,   a conduit communicating said melting furnace with said holding furnace such that a level of the molten metal melt in said melting furnace and said holding furnace is substantially equal.   
     
     
         3 . The system of  claim 2  wherein said melting furnace comprises a dry hearth furnace, including a sloping hearth. 
     
     
         4 . The system of  claim 1  further comprising a means for replenishing a dry atmosphere in said holding furnace, wherein said holding furnace allows hydrogen in the melt to equilibrate with the dry atmosphere being replenished into said holding furnace. 
     
     
         5 . The system of  claim 4  wherein the means for replenishing comprises a gas inlet located adjacent an outlet of said holding furnace so that a counter current flow of the dry atmosphere takes place. 
     
     
         6 . The system of  claim 3  wherein said holding furnace further comprises a dry heating means. 
     
     
         7 . The system of  claim 3  wherein said holding furnace has a length in the range of 1 to 200 meters and wherein a length to width ratio is in the range of 1-100 to 1. 
     
     
         8 . The system of  claim 1  wherein said means for separating inclusions comprises at least one of a filter and a flow obstructing device. 
     
     
         9 . The system of  claim 1  further comprising a pump furnace positioned downstream from said holding furnace and communicating therewith at the same melt level wherein said pump furnace comprises:
 a well; and,   a pump mounted in said well.   
     
     
         10 . The system of  claim 1  further comprising a snorkel ladle which selectively withdraws melt from said holding furnace and transfers it to an associated casting station. 
     
     
         11 . A quiescent transfer casting method comprising:
 melting a metal to form a melt;   transferring the melt into a holding furnace;   passively equilibrating a hydrogen content in the melt with a dry atmosphere maintained in the holding furnace; and,   subsequently withdrawing the melt from the holding furnace.   
     
     
         12 . The method of  claim 11  further comprising maintaining a substantially fixed horizontal level of a melt surface in the holding furnace. 
     
     
         13 . The method of  claim 12  further comprising avoiding a disturbance of the melt surface and of melt below the surface in the holding furnace. 
     
     
         14 . The method of  claim 11  further comprising separating inclusions from the melt in the holding furnace. 
     
     
         15 . The method of  claim 11  further comprising filtering the melt during its stay in the holding furnace. 
     
     
         16 . The method of  claim 11  further comprising flowing the dry atmosphere in a counter current manner in the holding furnace. 
     
     
         17 . The method of  claim 11  further comprising passively allowing the melt to flow in the holding furnace. 
     
     
         18 . The method of  claim 11  wherein said step of withdrawing the melt from the holding furnace includes pressurizing the melt in a pump well furnace, communicating with the holding furnace, with a pump. 
     
     
         19 . The method of  claim 11  wherein said step of withdrawing the melt from the holding furnace includes employing a snorkel ladle to transfer melt from the holding furnace to a casting station. 
     
     
         20 . A quiescent melt handling system comprising:
 a melting furnace which transforms solid metal into a melt;   a holding furnace for the melt, wherein said holding furnace comprises a relatively shallow bath having a relatively large surface area and a heater located above a surface of the melt, wherein said holding furnace has a width to depth ratio on the order of at least approximately 4-100 to 1 and a length to width ratio on the order of at least approximately 1-100 to 1;   a first channel communicating said holding furnace with said melting furnace such that a level of the melt in both furnaces is substantially equal; and,   a means for withdrawing the melt from said holding furnace.   
     
     
         21 . The system of  claim 20  further comprising a filter located in or adjacent to said holding furnace for filtering the melt flowing into said holding furnace. 
     
     
         22 . The system of  claim 20  further comprising a means for replenishing a dry atmosphere in said holding furnace, wherein said holding furnace allows hydrogen in the melt to equilibrate with the dry atmosphere being replenished into said holding furnace. 
     
     
         23 . The system of  claim 22  wherein said holding furnace further comprises a dry-heating means. 
     
     
         24 . The system of  claim 20  wherein said means for withdrawing the melt comprises a pump furnace including:
 a well; and,   a pump mounted in said well.   
     
     
         25 . The system of  claim 24  wherein said pump furnace further comprises a crucible mounted in said well, in which crucible said pump and said second filter are located. 
     
     
         26 . The system of  claim 20  wherein said means for withdrawing the melt comprises a snorkel ladle which selectively withdraws melt from said holding furnace and transfers it to a casting station. 
     
     
         27 . The system of  claim 20  further comprising a means for separating inclusions from said holding furnace, said means comprising at least one of a filter and a flow obstructing block of material. 
     
     
         28 . The system of  claim 20  further comprising a gas inlet located adjacent an outlet of said holding furnace so that a counter current flow of a gas takes place in said holding furnace.