Patent Publication Number: US-2002005235-A1

Title: Copper-nickel alloy for use in manufacturing containers for holding molten metals

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The invention relates to the use of a copper alloy as a material, in the non-hardened condition, for producing containers for holding metallic melts, such as crucibles for melting and remelting installations. More particularly, the invention is directed towards producing containers made of copper-nickel alloy which can hold melts.  
       [0003] 2. Description of Related Art  
       [0004] Melting and remelting processes are known from practical use. They are applied in order to improve the quality of steels and superalloys based on iron, nickel or cobalt. A further application area is the production of nonferrous metals, such as tantalum, titanium, molybdenum or zirconium.  
       [0005] As materials for making the crucibles, copper and copper alloys are usually considered which have a high thermal conductivity.  
       [0006] Seamless, welded or otherwise assembled crucibles usually have a round tube-shaped or rectangular basic design. However, those of polygonal or square basic design are also applied. Beyond that, occasionally shapes are used which are adapted to the final shape of the component to be produced, for example, for crankshafts and pressure containers.  
       [0007] Containers taking up metallic melts, as for example crucibles, usually have lengths up to as much as 4 m and diameters up to 1.5 m.  
       [0008] In melting and remelting installations, as a rule, the crucibles are surrounded by a cooling jacket used to dissipate the process heat. Here the cooling jacket itself can be constructed of steel. But apart from that, designs are conceivable in which the conduction of the cooling water is integrated directly into the walls of the copper crucible in the form of slots or cooling borings.  
       [0009] From U.S. Pat. No. 2,155,405 a copper alloy is known which contains 0.25 to 3% nickel, 0.05 to 0.6% phosphorus and the balance copper. This alloy, formulated for electrical conductors, has an electrical conductivity of 67% IACS and a relatively high tensile strength.  
       [0010] Also, from European Patent No. A1-0 249 740 a hardenable copper alloy is known, which includes 0.2 to 1.2% nickel and 0.04 to 0.25% phosphorus. This alloy is for use as material for producing continuous casting molds for continuous casting of high melting point metals. After an age-hardening process of several hours, this material reaches a hardness HB 2.5/62.5 of more than 115.  
       SUMMARY OF THE INVENTION  
       [0011] It is an object of the invention to provide a material, preferably for application as a crucible in melting and remelting installations, which has both favorable thermomechanical properties as well as outstanding weldability.  
       [0012] It is another object of the invention to provide a method for producing a container for metallic melts which can possibly be put together from several parts. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0013] These and other objects of the invention are attained by using a copper alloy made of 0.2 to 1.5% nickel, 0.002 to 0.12% of at least one element from the group including phosphorus, aluminum, manganese, lithium, calcium, magnesium, silicon and boron, optionally up to 0.3% zirconium, the balance being copper and impurities resulting from the production process, as the material in the non-hardened condition for producing containers for holding metallic melts, such as crucibles for melting and remelting installations.  
     [0014] Preferably, the alloy to be used according to the invention contains 0.6 to 1.3% nickel and 0.01 to 0.06% of at least one element of the group including boron, magnesium and phosphorus, the balance being copper and impurities resulting from the production process. Most preferably, the copper alloy contains 1.0 to 1.3% nickel and 0.01 to 0.03% phosphorus.  
     [0015] For the targeted increase in strength, it is advantageous to add 0.01 to at most 0.3% zirconium.  
     [0016] In accordance with the method of the invention, there is provided a method for manufacturing containers for metallic melts from the copper alloy of the invention, wherein the alloy, after a hot forming process, is cooled in still environmental air. In a preferred embodiment, the alloy, after the hot forming process, is cold formed by at least 10%. In a most preferred embodiment, the cold forming and a subsequent welding of the alloy at hand in the hot formed condition are adjusted to each other in such a way that the strength and the electrical conductivity in the welding seam do not deviate by more than 15% from the corresponding property values of the basic material.