Method for making structural automotive components and the like

Abstract

A method for making structural automotive components and the like provides a strip of high strength steel having a selected thickness. A predetermined thickness of a metal coating, such as nickel, is applied to the opposite faces of the steel strip. The coated steel strip is cut to form a blank. The blank is heated in a generally open atmosphere to a temperature in the range of 800° C. to 1000° C. within less than ten minutes, thereby diffusing at least a portion of the metal coating a predetermined distance into the faces of the steel strip portion of the blank to alleviate scale formation, and simultaneously raise the temperature of the blank for hot forming the same. The heated blank is hot formed in a pressing tool, and cooled therein to heat treat the formed component through microstructure phase change, without substantial scale formation, such that the component need not be descaled prior to post-form processing and/or assembly in a vehicle.

1 . A method for making contoured structural door beams for vehicles and the like, comprising: 
 providing an elongate strip of high strength steel having a thickness in the range of 0.5-5.0 millimeters;    electroplating the steel strip with a metal comprising primarily nickel to form on at least the opposite faces of the steel strip a nickel coating having a thickness in the range of 1.0-5.0 microns;    cutting a length of the nickel coated steel strip to form a flat, plate-shaped blank;    heating the plate-shaped blank in a generally open atmosphere comprising primarily ambient air to a temperature in the range of 800° C. to 1000° C. within less than ten minutes, thereby diffusing at least a portion of the nickel coating a predetermined distance into the opposite faces of the steel strip portion of the plate-shaped blank to alleviate scale formation, and simultaneously raising the temperature of the plate-shaped blank for hot forming the same;    transporting the heated plate-shaped blank into a pressing tool;    forming the heated plate-shaped blank in the pressing tool into a predetermined contoured shape to define a selected structural door beam;    cooling the formed structural door beam in the pressing tool to heat treat the formed structural door beam through microstructure phase change without substantial scale formation; and    removing the heat treated structural door beam from the pressing tool.    
   
   
       2 . A method as set forth in  claim 1 , wherein: 
 said heating step includes diffusing the nickel coating into the opposite faces of the steel strip a distance in the range of 2 to 8 microns.    
   
   
       3 . A method as set forth in  claim 2 , wherein: 
 said heating step comprises heating the plate-shaped blank to a temperature in the range of 850° C.-950° C. within a range of 20 to 25 seconds to retain a thin undiffused exterior layer of nickel over at least a substantial portion of the opposite faces of the steel strip to alleviate scale formation as the temperature of the plate-shaped blank is raised for hot forming the same, such that the heat treated structural door beam need not be descaled prior to assembly in a vehicle.    
   
   
       4 . A method as set forth in  claim 3 , wherein: 
 said heating step comprises forming a thin oxide layer over the undiffused exterior layer of nickel for enhanced surface protection.    
   
   
       5 . A method as set forth in  claim 3 , wherein: 
 said heating step includes providing an elongate furnace; and including    conveying the plate-shaped blank through the elongate furnace prior to said transporting step; and    performing said heating step within a range of three to seven minutes.    
   
   
       6 . A method as set forth in  claim 3 , wherein: 
 said heating step includes providing an induction heater; and including performing said heating step in less than 45 seconds.    
   
   
       7 . A method as set forth in  claim 6 , wherein: 
 said heating step is performed within a range of 20 to 25 seconds.    
   
   
       8 . A method as set forth in  claim 5 , including: 
 cleaning the steel strip prior to said electroplating step.    
   
   
       9 . A method as set forth in  claim 8 , wherein: 
 said cutting step includes stamping the steel strip at substantially ambient temperature to the final configuration of the plate-shaped blank.    
   
   
       10 . A method as set forth in  claim 9 , wherein: 
 said heating step includes heating the plate-shaped blank to a temperature of about 900° C.    
   
   
       11 . A method as set forth in  claim 10 , wherein: 
 said electroplating step includes selecting a nickel based metal material which has a melting temperature above 1000° C.    
   
   
       12 . A method as set forth in  claim 11 , wherein: 
 said strip providing step comprises selecting the strip from a cold rolled steel alloy.    
   
   
       13 . A method as set forth in  claim 12 , wherein: 
 said strip providing step includes selecting a coil of steel, uncoiling the coil and straightening the coil to define the strip.    
   
   
       14 . A method as set forth in  claim 13 , wherein: 
 said electroplating step comprises dip plating.    
   
   
       15 . A method as set forth in  claim 14 , wherein: 
 said strip providing step comprises selecting the strip from a steel alloy comprising a predetermined percent by weight of carbon (C), manganese (Mn) and boron (B).    
   
   
       16 . A method as set forth in  claim 15 , including: 
 forming at least one aperture in said steel strip prior to said electroplating step.    
   
   
       17 . A method as set forth in  claim 16 , wherein: 
 said strip providing step includes selecting the strip from a steel alloy comprising, in percent by weight,    carbon (C) 0.20% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.0% to 1.40%,    phosphorus (P) 0.0% to 0.03%,    chromium (Cr) 0.0% to 0.35%,    molybdenum (Mo) 0.0% to 0.35%,    sulfur (S) 0.0% to 0.01%,    titanium (Ti) 0.0% to 0.05%,    boron (B) 0.002% to 0.0040%,    aluminum (Al) 0.0% to 0.06%, and    copper (Cu) 0.0% to 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.    
   
   
       18 . A method as set forth in  claim 1 , wherein: 
 said heating step comprises heating the plate-shaped blank to a temperature in the range of 850° C.-950° C. to retain a thin undiffused exterior layer of nickel over at least a substantial portion of the opposite faces of the steel strip to alleviate scale formation as the temperature of the plate-shaped blank is raised for hot forming the same, such that the heat treated structural door beam need not be descaled prior to assembly in a vehicle.    
   
   
       19 . A method as set forth in  claim 1 , wherein: 
 said heating step comprises forming a thin oxide layer over an undiffused exterior layer of the nickel coating for enhanced surface protection.    
   
   
       20 . A method as set forth in  claim 1 , wherein: 
 said heating step includes providing an elongate furnace; and including conveying the plate-shaped blank through the elongate furnace prior to said transporting step; and    performing said heating step within a range of three to seven minutes.    
   
   
       21 . A method as set forth in  claim 1 , wherein: 
 said heating step includes providing an induction heater; and including performing said heating step in less than 45 seconds.    
   
   
       22 . A method as set forth in  claim 21 , wherein: 
 said heating step is performed within a range of 20 to 25 seconds.    
   
   
       23 . A method as set forth in  claim 1 , including: 
 cleaning the steel strip prior to said electroplating step.    
   
   
       24 . A method as set forth in  claim 1 , wherein: 
 said cutting step includes stamping the steel strip at substantially ambient temperature to the final configuration of the plate-shaped blank.    
   
   
       25 . A method as set forth in  claim 1 , wherein: 
 said heating step includes heating the plate-shaped blank to a temperature of around 900° C.    
   
   
       26 . A method as set forth in  claim 1 , wherein: 
 said electroplating step includes selecting a nickel based metal material which has a melting temperature above 1000° C.    
   
   
       27 . A method as set forth in  claim 1 , wherein: 
 said strip providing step comprises selecting the strip from a cold rolled steel alloy.    
   
   
       28 . A method as set forth in  claim 1 , wherein: 
 said strip providing step includes selecting a coil of steel, uncoiling the coil and straightening the coil to define the strip.    
   
   
       29 . A method as set forth in  claim 1 , wherein: 
 said electroplating step comprises dip plating.    
   
   
       30 . A method as set forth in  claim 1 , wherein: 
 said strip providing step comprises selecting the strip from a steel alloy comprising a predetermined percent by weight of carbon (C), manganese (Mn) and boron (B).    
   
   
       31 . A method as set forth in  claim 1 , including: 
 forming at least one aperture in said steel strip prior to said electroplating step.    
   
   
       32 . A method as set forth in  claim 1 , wherein: 
 said strip providing step includes selecting the strip from a steel alloy comprising, in percent by weight,    carbon (C) 0.20% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.0% to 1.40%,    phosphorus (P) 0.0% to 0.03%,    chromium (Cr) 0.0% to 0.35%,    molybdenum (Mo) 0.0% to 0.35%,    sulfur (S) 0.0% to 0.01%,    titanium (Ti) 0.0% to 0.05%,    boron (B) 0.002% to 0.0040%,    aluminum (Al) 0.0% to 0.06%, and    copper (Cu) 0.0% to 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.    
   
   
       33 . A method as set forth in  claim 1 , wherein: 
 said strip providing step includes selecting the strip from a steel alloy comprising, in percent by weight,    carbon (C) 0.23% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.10% to 1.400%,    phosphorus (P) at most 0.025%,    chromium (Cr) 0.15% to 0.35%,    molybdenum (Mo) 0.10% to 0.35%,    sulfur (S) at most 0.01%,    titanium (Ti) 0.03% to 0.05%,    boron (B) 0.002% to 0.004%,    aluminum (Al) 0.02% to 0.06%, and    copper (Cu) at most 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.    
   
   
       34 . In a method for making a vehicle having at least one contoured structural door beam, the improvement, comprising: 
 providing an elongate strip of high strength steel having a thickness in the range of 0.5-5.0 millimeters;    electroplating the steel strip with a metal comprising primarily nickel to form on at least the opposite faces of the steel strip a nickel coating having a thickness in the range of 1.0-5.0 microns;    cutting a length of the nickel coated steel strip to form a flat, plate-shaped blank;    heating the plate-shaped blank in a generally open atmosphere comprising primarily ambient air to a temperature in the range of 800° C. to 1000° C. within less than ten minutes, thereby diffusing at least a portion of the nickel coating a predetermined distance into the opposite faces of the steel strip portion of the plate-shaped blank to alleviate scale formation, and simultaneously raising the temperature of the plate-shaped blank for hot forming the same;    transporting the heated plate-shaped blank into a pressing tool;    forming the heated plate-shaped blank in the pressing tool into a predetermined contoured shape to define a selected structural door beam;    cooling the formed structural door beam in the pressing tool to heat treat the formed structural door beam through microstructure phase change without substantial scale formation;    removing the heat treated structural door beam from the pressing tool; and    welding the heat treated structural door beam in the vehicle without cleaning the same between said removing step and said welding step.    
   
   
       35 . A method as set forth in  claim 34 , wherein: 
 said heating step includes diffusing the nickel coating into the opposite faces of the steel strip a distance in the range of 2 to 8 microns.    
   
   
       36 . A method as set forth in  claim 35 , wherein: 
 said heating step includes providing an elongate furnace; and including    conveying the plate-shaped blank through the elongate furnace prior to said transporting step; and    performing said heating step within a range of three to seven minutes.    
   
   
       37 . A method as set forth in  claim 35 , wherein: 
 said heating step comprises providing an induction heater, and heating the plate-shaped blank to a temperature in the range of 850° C.-950° C. within a range of 20 to 25 seconds to retain a thin undiffused exterior layer of nickel over at least a substantial portion of the opposite faces of the steel strip to alleviate scale formation as the temperature of the plate-shaped blank is raised for hot forming the same, such that the heat treated structural door beam need not be descaled prior to assembly in a vehicle.    
   
   
       38 . A method as set forth in  claim 36 , wherein: 
 said heating step comprises forming a thin oxide layer over the undiffused exterior layer of nickel for enhanced surface protection.    
   
   
       39 . A method as set forth in  claim 38 , including: 
 forming at least one aperture in said steel strip prior to said electroplating step; and    wherein    said strip providing step includes selecting the strip from a steel alloy comprising, in percent by weight,    carbon (C) 0.20% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.0% to 1.40%,    phosphorus (P) 0.0% to 0.03%,    chromium (Cr) 0.0% to 0.35%,    molybdenum (Mo) 0.0% to 0.35%,    sulfur (S) 0.0% to 0.01%,    titanium (Ti) 0.0% to 0.05%,    boron (B) 0.002% to 0.0040%,    aluminum (Al) 0.0% to 0.06%, and    copper (Cu) 0.0% to 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.    
   
   
       40 . A method for making contoured structural parts for vehicles and the like, comprising: 
 providing a strip of steel having a thickness greater than 0.5 millimeters;    coating the steel strip with a metal comprising primarily nickel to form on at least the opposite faces of the steel strip a nickel coating having a thickness in the range of 1.0-5.0 microns;    cutting the nickel coated steel strip to form a flat, plate-shaped blank;    heating the plate-shaped blank to a temperature in the range of 800° C. to 1000° C. within less than ten minutes, thereby diffusing at least a portion of the nickel coating a predetermined distance into the opposite faces of the steel strip portion of the plate-shaped blank, and simultaneously raising the temperature of the plate-shaped blank for hot forming the same;    transporting the heated plate-shaped blank into a pressing tool;    forming the heated plate-shaped blank in the pressing tool into a predetermined contoured shape to define a selected structural vehicle part;    cooling the formed structural vehicle part in the pressing tool to heat treat the formed structural vehicle part; and    removing the heat treated structural vehicle part from the pressing tool.    
   
   
       41 . A method as set forth in  claim 40 , wherein: 
 said heating step includes diffusing the nickel coating into the opposite faces of the steel strip a distance in the range of 2 to 8 microns.    
   
   
       42 . A method as set forth in  claim 41 , wherein: 
 said heating step comprises heating the plate-shaped blank to a temperature in the range of 850° C.-950° C. to retain a thin undiffused exterior layer of nickel over at least a substantial portion of the opposite faces of the steel strip to alleviate scale formation as the temperature of the plate-shaped blank is raised for hot forming the same, such that the heat treated structural vehicle part need not be descaled prior to assembly in a vehicle.    
   
   
       43 . A method as set forth in  claim 42 , wherein: 
 said heating step comprises forming a thin oxide layer over the undiffused exterior layer of nickel for enhanced surface protection.    
   
   
       44 . A method as set forth in  claim 43 , wherein: 
 said heating step includes providing an elongate furnace; and including    conveying the plate-shaped blank through the elongate furnace prior to said transporting step; and    performing said heating step within a range of three to seven minutes.    
   
   
       45 . A method as set forth in  claim 43 , wherein: 
 said heating step includes providing an induction heater; and including    performing said heating step in less than 45 seconds.    
   
   
       46 . A method as set forth in  claim 44 , including: 
 forming at least one aperture in said steel strip prior to said electroplating step.    
   
   
       47 . A method as set forth in  claim 46 , wherein: 
 said strip providing step includes selecting the strip from a steel alloy comprising, in percent by weight,    carbon (C) 0.20% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.0% to 1.40%,    phosphorus (P) 0.0% to 0.03%,    chromium (Cr) 0.0% to 0.35%,    molybdenum (Mo) 0.0% to 0.35%,    sulfur (S) 0.0% to 0.01%,    titanium (Ti) 0.0% to 0.05%,    boron (B) 0.002% to 0.0040%,    aluminum (Al) 0.0% to 0.06%, and    copper (Cu) 0.0% to 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.    
   
   
       48 . A method for making contoured structural parts, comprising: 
 providing a blank made from steel having a thickness greater than 0.5 millimeters;    coating the steel blank on at least the opposite faces thereof with a metal selected from the group consisting essentially of: 
 a) nickel,  
 b) copper, and  
 c) chromium;  
   heating the coated blank to a temperature in the range of 800° C. to 1000° C., thereby diffusing at least a portion of the metal coating a predetermined distance into the opposite faces of the steel strip portion of the coated blank, and simultaneously raising the temperature of the coated blank for hot forming the same;    transporting the heated coated blank into a pressing tool;    forming the heated coated blank in the pressing tool into a predetermined contoured shape to define a selected structural part;    cooling the formed structural part in the pressing tool to heat treat the same; and    removing the heat treated structural part from the pressing tool.    
   
   
       49 . A method as set forth in  claim 48 , wherein: 
 said heating step includes diffusing the metal into the opposite faces of the steel strip a distance in the range of 2 to 8 microns.    
   
   
       50 . A method as set forth in  claim 49 , wherein: 
 said heating step comprises heating the blank to a temperature in the range of 850° C.-950° C. to retain a thin undiffused exterior layer of metal over at least a substantial portion of the opposite faces of the steel to alleviate scale formation as the temperature of the blank is raised for hot forming the same, such that the heat treated structural part need not be descaled prior to assembly.    
   
   
       51 . A method as set forth in  claim 50 , wherein: 
 said heating step comprises forming a thin oxide layer over the undiffused exterior layer of metal for enhanced surface protection.    
   
   
       52 . A method as set forth in  claim 51 , wherein: 
 said coating step comprises electroplating.    
   
   
       53 . A method as set forth in  claim 52 , wherein: 
 said heating step includes providing an elongate furnace; and including conveying the blank through the elongate furnace prior to said transporting step; and    performing said heating step within a range of three to seven minutes.    
   
   
       54 . A method as set forth in  claim 52 , wherein: 
 said heating step includes providing an induction heater; and including    performing said heating step in less than 45 seconds.    
   
   
       55 . A method as set forth in  claim 53 , including: 
 forming at least one aperture in said steel strip prior to said electroplating step.    
   
   
       56 . A method as set forth in  claim 55 , wherein: 
 said blank providing step includes selecting the blank from a steel alloy comprising, in percent by weight,    carbon (C) 0.20% to 0.27%,    silicon (Si) 0.15% to 0.50%,    manganese (Mn) 1.0% to 1.40%,    phosphorus (P) 0.0% to 0.03%,    chromium (Cr) 0.0% to 0.35%,    molybdenum (Mo) 0.0% to 0.35%,    sulfur (S) 0.0% to 0.01%,    titanium (Ti) 0.0% to 0.05%,    boron (B) 0.002% to 0.0040%,    aluminum (Al) 0.0% to 0.06%, and    copper (Cu) 0.0% to 0.10%,    where the remainder is iron, including impurities brought about as a result of smelting.