Ultra-high strength weathering steel and method for making same

Abstract

An air-cast ultra-high strength weathering steel prepared by combining C, Si, Cr, Cu, Mo, Ni, Co, and Fe, wherein the steel has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent. In a preferred embodiment, the air-cast ultra-high strength weathering steel includes at least one ingredient selected from the group consisting of V, W, N and mixtures thereof In another preferred embodiment C is present in the range of from about 0.16 to 0.23 percent by weight, Si is present in the range of from about 0.2 to 1.5 percent by weight, Cr is present in the range of from about 2 to 5 percent by weight, Cu is present in the range of from about 0.2 to 2 percent by weight, Mo is present in the range of from about 0.8 to 3 percent by weight, Ni is present in the range of from about 7 to 12 percent by weight, Co is present in the range of from about 13 to 17 percent by weight; and Fe is present in a remaining amount.

1 . An air-cast ultra-high strength weathering steel prepared by combining C, Si, Cr, Cu, Mo, Ni, Co, and Fe; 
 wherein C is present in the range of from about 0.16 to 0.23 percent by weight, Si is present in the range of from about 0.5 to 1.5 percent by weight, Cr is present in the range of from about 2 to 5 percent by weight, Cu is present in the range of from about 0.2 to 2 percent by weight, Mo is present in the range of from about 0.8 to 3 percent by weight, Ni is present in the range of from about 7 to 12 percent by weight, Co is present in the range of from about 13 to 17 percent by weight; and Fe is present in a remaining amount;    wherein the steel is essentially free of Al and Ti; and    wherein the steel has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.    
   
   
       2 . The air-cast ultra-high strength weathering steel as recited in  claim 1  wherein the steel has a yield strength in the range of from about 255,000 to 300,000 psi, a tensile strength in the range of from between 255,000 and 320,000 psi, and an elongation of between about 10 to 14 percent.  
   
   
       3 . The air-cast ultra-high strength weathering steel as recited in  claim 1  further comprising at least one ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       4 . The air-cast ultra-high strength weathering steel as recited in  claim 1  wherein C is present in the range of from about 0.16 to 0.23 percent by weight, Si is present in the range of from about 0.2 to 1.5 percent by weight, Cr is present in the range of from about 2 to 5 percent by weight, Cu is present in the range of from about 0.2 to 2 percent by weight, Mo is present in the range of from about 0.8 to 3 percent by weight, Ni is present in the range of from about 7 to 12 percent by weight, Co is present in the range of from about 13 to 17 percent by weight; and Fe is present in a remaining amount.  
   
   
       5 . The air-cast ultra-high strength weathering steel as recited in  claim 1  wherein the steel is essentially free of Al and Ti.  
   
   
       6 . The air-cast ultra-high strength weathering steel as recited in  claim 1  wherein the steel comprises: 
 in the range of from about 0.17 to 0.22 percent by weight C;    in the range of from about 0.5 to 1.2 percent by weight Si;    in the range of from about 2.5 to 4 percent by weight Cr;    in the range of from about 0.5 to 1.5 percent by weight Cu;    in the range of from about 1 to 2 percent by weight Mo;    in the range of from about 8 to 10.5 percent by weight Ni; and    in the range of from about 14 to 16 percent by weight Co.    
   
   
       7 . The air-cast ultra-high strength weathering steel as recited in  claim 6  further comprising at least one ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       8 . The air-cast ultra-high strength weathering steel as recited in  claim 1  wherein the steel comprises: 
 in the range of from about 0.18 to 0.21 percent by weight C;    in the range of from about 0.5 to 0.9 percent by weight Si;    in the range of from about 3 to 4 percent by weight Cr;    in the range of from about 0.7 to 1.5 percent by weight Cu;    in the range of from about 1.3 to 1.7 percent by weight Mo;    in the range of from about 9 to 10.5 percent by weight Ni; and    in the range of from about 14 to 15.5 percent by weight Co.    
   
   
       9 . The air-cast ultra-high strength weathering steel as recited in  claim 8  further comprising at least one ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       10 . An ultra-high strength weathering steel consisting essentially of: 
 in the range of from about 0.16 to 0.23 percent by weight C;    in the range of from about 0.5 to 1.5 percent by weight Si;    in the range of from about 2 to 5 percent by weight Cr;    in the range of from about 0.2 to 2 percent by weight Cu;    in the range of from about 0.8 to 3 percent by weight Mo;    in the range of from about 7 to 12 percent by weight Ni;    in the range of from about 13 to 17 percent by weight Co; and    a remaining amount Fe.    
   
   
       11 . The ultra-high strength weathering steel as recited in  claim 10  further comprising at least one ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       12 . The ultra-high strength weathering steel a recited in  claim 10  wherein the steel has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.  
   
   
       13 . An ultra-high strength weathering steel comprising: 
 in the range of from about 0.16 to 0.23 percent by weight C;    in the range of from about 0.5 to 1.5 percent by weight Si;    in the range of from about 2 to 5 percent by weight Cr;    in the range of from about 0.2 to 2 percent by weight Cu;    in the range of from about 0.8 to 3 percent by weight Mo;    in the range of from about 7 to 12 percent by weight Ni;    in the range of from about 13 to 17 percent by weight Co;    up to about 2 percent by weight V;    up to about 2 percent by weight W;    up to about 0.4 percent by weight N; and    a remaining amount Fe.    
   
   
       14 . The ultra-high strength weathering steel a recited in  claim 13  wherein the steel has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.  
   
   
       15 . A casting made from a weathering steel that is prepared according to the steps of: 
 hot isostatic pressing a cast part made from weathering steel at a temperature of above about 1,900° F. for about 3 to 5 hours at a pressure of greater than about 14,000 psi;    homogenating the cast part at a temperature of above about 2,000° F. for a period of from about 1 to 6 hours;    solution heat treating the cast part at a temperature in the range of from about 1,600° to about 2,100° F. for about 1 to 4 hours, followed by cooling to room temperature;    cooling the cast part by refrigeration for about 1 to 8 hours at a temperature below about −50° F.; and    aging the cast part at a temperature of between about 800° F. and about 1,000° F. for about 4 to about 5 hours.    
   
   
       16 . The casting as recited in  claim 15  wherein, prior to the step of pressing, the casting is formed by: 
 combining in the range of from about 0.16 to 0.23 percent by weight C, with in the range of from about 0.2 to 1.5 percent by weight Si, in the range of from about 2 to 5 percent by weight Cr, in the range of from about 0.2 to 2 percent by weight Cu, in the range of from about 0.8 to 3 percent by weight Mo, in the range of from about 7 to 12 percent by weight Ni, in the range of from about 13 to 17 percent by weight Co, and a remaining amount Fe;    melting the combined ingredients to form a weathering steel mixture; and    pouring the weathering steel mixture to form the cast part.    
   
   
       17 . The casting as recited in  claim 16  further comprising, during the step of combining, adding one or more ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       18 . The casting as recited in  claim 16  wherein the steps of melting and pouring are conducted in an air environment.  
   
   
       19 . The casting as recited in  claim 15  wherein the cast part after the step of aging has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.  
   
   
       20 . The casting as recited in  claim 15  wherein the hipping step is conducted in the range of from about 2,000° F. to 2,240° F., the homogenating step is conducted in the range of from about 2,150° F. to 2,220° F., the solution heat treating step is conducted in the range of from about 1,800° F. to 1,950° F., the cooling step is conducted in the range of from about −110° F. to −75° F., and the aging steps is conducted in the range of from about 900° F. to 1,000° F.  
   
   
       21 . The casting as recited in  claim 15  wherein, prior to the step of pressing, the casting is formed by: 
 combining in the range of from about 0.17 to 0.22 percent by weight C, with in the range of from about 0.3 to 1.2 percent by weight Si, in the range of from about 2.5 to 4 percent by weight Cr, in the range of from about 0.5 to 1.5 percent by weight Cu, in the range of from about 1 to 2 percent by weight Mo, in the range of from about 8 to 10.5 percent by weight Ni, in the range of from about 14 to 16 percent by weight Co, and a remaining amount Fe;    melting the combined ingredients to form a weathering steel mixture; and    pouring the weathering steel mixture to form the cast part.    
   
   
       22 . The casting as recited in  claim 21  further comprising, during the step of combining, adding one or more ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       23 . The casting as recited in  claim 21  wherein the steps of melting and pouring are conducted in an air environment.  
   
   
       24 . The casting as recited in  claim 23  wherein the cast part after the step of aging has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.  
   
   
       25 . A method for making a cast part from a weathering steel comprising the steps of: 
 combining in the range of from about 0.16 to 0.23 percent by weight C, with in the range of from about 0.5 to 1.5 percent by weight Si, in the range of from about 2 to 5 percent by weight Cr, in the range of from about 0.2 to 2 percent by weight Cu, in the range of from about 0.8 to 3 percent by weight Mo, in the range of from about 7 to 12 percent by weight Ni, in the range of from about 13 to 17 percent by weight Co, and a remaining amount Fe;    melting the combined ingredients to form a weathering steel mixture; and    pouring the weathering steel mixture to form the cast part.    
   
   
       26 . The method as recited in  claim 25  further comprising, during the step of combining, adding one or more ingredient selected from the group consisting of V, W, N and mixtures thereof.  
   
   
       27 . The method as recited in  claim 25  wherein the steps of melting and pouring are conducted in an air environment.  
   
   
       28 . The method as recited in  claim 25  further comprising the steps of 
 hot isostatic pressing the cast part at a temperature of above about 1,900° F. for about 3 to 5 hours at a pressure of greater than about 14,000 psi;    homogenating the cast part at a temperature of above about 2,100° F. for a period of from about 1 to 6 hours;    solution heat treating the cast part at a temperature in the range of from about 1,600° to about 2,100° F. for about 1 to 4 hours, followed by cooling to room temperature;    cooling the cast part by refrigeration for about 1 to 4 hours at a temperature below about −50° F.; and    aging the cast part at a temperature of between about 800° F. and about 1,000° F. for about 4 to about 5 hours.    
   
   
       29 . The method as recited in  claim 28 , wherein after the step of aging, the cast part has a yield strength of greater than about 230,000 psi, a tensile strength of greater than about 250,000 psi, and an elongation of greater than about 6 percent.