Alloys And Methods To Develop Yield Strength Distributions During Formation Of Metal Parts

Abstract

This invention is related to a method to increase the strength of a metal stamping by supplying a metal blank which has the ability to strengthen in-situ during stamping to achieve sets of properties not expected and much higher based on the starting properties of the blank.

What is claimed is: 
     
         1 . A method to develop yield strength distributions in a formed metal part comprising:
 (a) supplying a metal alloy comprising at least 70 atomic % iron and at least four or more elements selected from Cr, Ni, Mn, Si, Cu, Al, or C, melting said alloy, cooling at a rate of <250 K/s, and solidifying to a thickness of 25.0 mm up to 500 mm;   (b) processing said alloy into sheet form with thickness from 0.5 to 10 mm wherein said sheet exhibits a yield strength of A1 (MPa), an ultimate tensile strength of B1 (MPa), a true ultimate tensile strength C1 (MPa), and a total elongation D1;   (c) straining said sheet one or a plurality of times above said yield strength A1 at an ambient temperature of 1° C. to 50° C. and at a strain rate of 10 0 /s to 10 2 /sec and forming a metal part having a distribution of yield strengths A2, A3, and A4, wherein:
     A 2= A 1±100;  (i)
 
     A 3> A 1+100 and  A 3< A 1+600; and  (ii)
 
     A 4≥ A 1+600.  (iii)
 
   
     
     
         2 . The method of  claim 1  wherein the said alloy in (a) contains at least 70 atomic percent iron is combined with four or more elements that are selected from Cr, Ni, Mn, Al, Si, Cu, or C. 
     
     
         3 . The method of  claim 1  wherein the said alloy in (a) contains at least 70 atomic percent iron is combined with five or more elements that are selected from Cr, Ni, Mn, Al, Si, Cu, or C. 
     
     
         4 . The method of  claim 1  wherein the said alloy in (a) contains at least 70 atomic percent iron is combined with six or more elements that are selected from Cr, Ni, Mn, Al, Si, Cu, or C. 
     
     
         5 . The method of  claim 1  wherein the said alloy in (a) contains at least 70 atomic percent iron up to and including a maximum of 85 atomic percent iron. 
     
     
         6 . The method of  claim 1  wherein;
 Cr when selected is present at 0.2 atomic percent to 8.7 atomic percent; 
 Ni when selected is present at 0.3 atomic percent to 12.5 atomic percent; 
 Mn when selected is present at 0.6 atomic percent to 16.9 atomic percent; 
 Al when selected is present at 0.4 atomic percent to 5.2 atomic percent; 
 Si when selected is present at 0.7 atomic percent to 6.3 atomic percent; 
 Cu when selected is present at 0.2 atomic percent to 2.7 atomic percent; and 
 C when selected is present at 0.3 atomic percent to 3.7 atomic percent. 
 
     
     
         7 . The method of  claim 1  wherein said alloy formed in step (b) indicates
 a yield strength A1 of 250 MPa to 750 MPa; 
 an ultimate tensile strength of B1 of 700 MPa to 1750 MPa; 
 a true ultimate tensile strength C1 of 1100 MPa to 2300 MPa; and 
 a total elongation D1 of 10% to 80%. 
 
     
     
         8 . The method of  claim 1  wherein said alloy formed in step (b) exhibits a magnetic phase volume percent of 0.2 Fe % to 45.0 Fe %. 
     
     
         9 . The method of  claim 1  wherein said metal part in step (c) exhibits a magnetic phase volume percent that is greater than the magnetic phase volume percent present in said sheet in step (b). 
     
     
         10 . The method of  claim 9  wherein said metal part in step (c) exhibits a magnetic phase volume of 0.5 Fe % to 85.0 Fe %. 
     
     
         11 . The method of  claim 1  wherein said alloy formed in step (c) exhibits a yield strength A4 of 850 to 2300 MPa. 
     
     
         12 . The method of  claim 1  wherein said metal part formed in step (c) contains 0.5 volume percent to 85 volume % of ferrite having a particle size of 20 nm to 750 nm. 
     
     
         13 . The method of  claim 12  wherein said metal part formed in step (c) contains nanoprecipitates having a size of 2 to 100 nm. 
     
     
         14 . The method of  claim 1  wherein A4 is further characterized as follows: A4≤C1. 
     
     
         15 . The method of  claim 1  wherein said straining in step (c) is achieved by the process of roll forming, metal stamping, metal drawing, or hydroforming. 
     
     
         16 . The method of  claim 1  wherein said metal part formed in step (c) is positioned in a vehicular frame, vehicular chassis, or vehicular panel. 
     
     
         17 . The method of  claim 1  wherein said metal part formed in step (c) is positioned in a storage tank, freight car, or railway tank car. 
     
     
         18 . A method to develop yield strength distributions in a formed metal part comprising:
 (a) supplying a metal alloy comprising at least 70 atomic % iron and at least four or more elements selected from Cr, Ni, Mn, Si, Cu, Al, or C, melting said alloy, cooling at a rate of <250 K/s, and solidifying to a thickness of 25.0 mm up to 500 mm;   (b) processing said alloy into sheet form with thickness from 0.5 to 10 mm wherein said sheet exhibits a yield strength of A1 (MPa), an ultimate tensile strength of B1 (MPa), a true ultimate tensile strength C1 (MPa), and a total elongation D1 and a magnetic phase volume of 0.2 Fe % to 45.0 Fe %;   (c) straining said sheet one or a plurality of times above said yield strength A1 at a strain rate of 10 0 /s to 10 2 /sec at an ambient temperature of 1° C. to 50° C. and forming a metal part having a distribution of yield strengths A2, A3, and A4, wherein:
     A 2= A 1±100;  (i)
 
     A 3> A 1+100 and  A 3< A 1+600; and  (ii)
 
     A 4≥ A 1+600.  (iii)
 
   wherein said metal part has a magnetic phase volume that is greater than the magnetic phase volume percent present in said sheet in step (b), said greater magnetic phase volume having a value of 0.5 Fe % to 85.0 Fe %.