Process for avoiding cracking in welding

Abstract

The new welding process avoids cracking in welding, in repair welding or in cladding of parts of metallic alloys which are sensitive to hot cracking. The process is using a first heat source ( 15 ), directed to the parts ( 11, 12 ) of the metallic alloy forming a melt pool ( 14 ) on the parts ( 11, 12 ) of metal or metallic alloy. The heat source ( 15 ) and the parts ( 11, 12 ) are moved relative to each other. The process is characterized in that there is one ( 13 ) or more additional heat sources directed to the parts ( 11, 12 ) of metal or metallic alloy and following the first heat source ( 15 ) in a distance and with substantially the same speed and in the same direction as the first heat source ( 15 ). The additional heat source ( 13 ) or heat sources are directed to the solidification region (mushy zone) ( 144 ) of the melt pool ( 14 ) generated by the first heat source ( 15 ). The power of the additional heat source ( 13 ) is set such as to reduce the local cooling rate of the solidification region ( 144 ) of the melt pool ( 14 ), or to even shortly reheat this region without substantial remelting or with no remelting it at all and thereby reducing the tensile stresses or even inducing compressive stresses. During this process a central equiaxed zone might also be enhanced. By this new process the formation of hot cracks is avoided.

1 . Process for avoiding cracking in welding, in repair welding or in cladding of parts of metallic alloys ( 11 ,  12 ) which are sensitive to hot cracking, the process using a first heat source, directed to the parts of the metallic alloy and forming a melt pool ( 14 ) on the parts of metallic alloy, the heat source ( 15 ) and the parts being moved relative to each other, the process being characterized in that there is 
 one or more second additional heat sources ( 13 ) directed to the parts ( 11 ,  12 ) of metallic alloy and following the first heat source ( 15 ) in a distance and with substantially the same speed and in the same direction as the first heat source,    the second heat source(s) ( 13 ) being directed to the solidification region of the melt pool ( 14 ) generated by the first heat source ( 15 ),    the power of the additional heat source being set such as to reduce the local cooling rate of the solidification region ( 144 ) of the melt pool ( 14 ) or to even shortly reheat this region ( 144 ) without substantial remelting, thereby reducing the tensile stresses or even inducing compressive stresses, thus avoiding formation of hot cracks.    
     
     
         2 . Process as claimed in  claim 1 , one or more additional heat source ( 13 ) directed to the solidification region/the mushy zone ( 144 ) of the melt pool ( 14 ), the power of the additional heat source ( 13 ) being set such as to reduce the local cooling rate or to even shortly reheat this region of the melt pool ( 14 ), without remelting at all or without substantial remelting, thereby reducing the tensile stresses or even inducing compressive stresses, thus avoiding formation of hot cracks.  
     
     
         3 . Process as claimed in  claim 1 , the first ( 15 ) and/or the additional heat source(s) ( 13 ) being beams of high energy sources such as, laser sources, electron beam sources, electric arc sources, plasma sources, or a combination of those.  
     
     
         4 . Process as claimed in  claim 1 , the first ( 15 ) and/or the second ( 13 ) heat source being beams of one single or of multiple heat sources.  
     
     
         5 . Process as claimed in  claim 1 , using wire, powder or ribbons powder of an alloy of the same or of different composition as the parts to be welded, for filling and cladding purposes.  
     
     
         6 . Process as claimed in  claim 1 , using wire, powder, ribbons or preapplied powder material of an alloy of the same or of different composition as the parts to be cladded.  
     
     
         7 . Use of a process as claimed in  claim 1 , for avoiding cracking in welding, repair welding or cladding of parts of super alloys and/or steels.  
     
     
         8 . Use of a process as claimed in  claim 1 , for avoiding cracking in welding, repair welding or cladding of parts of aluminum alloys.