Process for low-cost tempering of aluminum casting

Abstract

A thermally stable component formed of a tempered aluminum alloy casting which reduced costs is provided. The aluminum alloy typically has an elongation of at least 8% after casting, which is preferred for self-piercing rivet processes. The aluminum alloy leaves a casting facility in the as-cast (F temper) condition. The cast aluminum alloy is then shipped to another entity, such as an OEM, and is subjected to an artificial aging process, such as on the OEM's existing paint line, rather than at the casting facility. The artificial aging process typically includes electrodeposition coating and curing. The components that can be formed by the reduced cost method include lightweight automotive vehicle components, including structural, body-in-white, suspension, or chassis components, such as front shock towers, front body hinge pillars, tunnels, and rear rails.

What is claimed is: 
     
         1 . An aluminum alloy, comprising: silicon in an amount of 4.0 to 9.0 weight percent (wt. %), copper in an amount up to 0.10 wt. %, iron in an amount up to 0.25 wt. %, manganese in an amount of 0.3 to 0.60 wt. %, magnesium in an amount of 0.10 to 0.60 wt. %, titanium in an amount up to 0.15 wt. %, strontium in an amount of 0.01 to 0.6 wt. %, and a balance of aluminum, except for possible incidental elements and/or impurities, based on the total weight of the aluminum alloy; the aluminum alloy being cast; and a coating applied to the aluminum alloy. 
     
     
         2 . The aluminum alloy according to  claim 1 , wherein the cast aluminum alloy includes at least one rivet. 
     
     
         3 . The aluminum alloy according to  claim 1 , wherein the cast aluminum alloy has an elongation of at least 8% before any heat treatment of the cast aluminum alloy. 
     
     
         4 . The aluminum alloy according to  claim 1 , wherein the coating includes an epoxy. 
     
     
         5 . The aluminum alloy according to  claim 1 , wherein the aluminum alloy forms at least a portion of a component for an automotive vehicle. 
     
     
         6 . The aluminum alloy according to  claim 5 , wherein the component is a front shock tower, front body hinge pillar, tunnel, rear rail, door inner panel, door mirror bracket, cross car beam, inner torque box, outer torque box, or rear shock mount. 
     
     
         7 . A method of manufacturing a cast aluminum alloy, comprising the steps of:
 casting an aluminum alloy, the aluminum alloy including silicon in an amount of 4.0 to 9.0 weight percent (wt. %), copper in an amount up to 0.10 wt. %, iron in an amount up to 0.25 wt. %, manganese in an amount of 0.3 to 0.60 wt. %, magnesium in an amount of 0.10 to 0.60 wt. %, titanium in an amount up to 0.15 wt. %, strontium in an amount of 0.01 to 0.6 wt. %, and a balance of aluminum, except for possible incidental elements and/or impurities, based on the total weight of the aluminum alloy;   applying a coating to the cast aluminum alloy; and   heating the coated cast aluminum alloy.   
     
     
         8 . A method according to  claim 7  including piercing the cast aluminum alloy without forming a hole in the aluminum alloy prior to the piercing step. 
     
     
         9 . A method according to  claim 8 , wherein the piercing step is conducted prior to the coating step and prior to the heating of the cast aluminum alloy. 
     
     
         10 . A method according to  claim 7 , wherein the heating step includes curing the coating. 
     
     
         11 . A method according to  claim 7 , wherein the cast aluminum alloy has an elongation of at least 8% prior to the heating of the cast aluminum alloy. 
     
     
         12 . A method according to  claim 7  including melting the aluminum alloy prior to the casting step;
 trimming, piercing, deburring, grinding, cutting, and/or machining the aluminum alloy after the casting step; and 
 the heating step includes curing the coating on the cast aluminum alloy after the trimming, piercing, deburring, grinding, cutting, and/or machining step. 
 
     
     
         13 . A method according to  claim 7 , wherein the coating is applied by electrodeposition. 
     
     
         14 . A method according to  claim 7  including transferring the aluminum alloy from a first location to a second location after casting the aluminum alloy and prior to coating the cast aluminum alloy, and wherein the heating of the coated cast aluminum alloy is conducted at the second location. 
     
     
         15 . A method according to  claim 7 , wherein the cast aluminum alloy has a yield strength (YS) ranging from 90 to 200 MPa, an ultimately tensile strength (UTS) ranging from 220 to 300 MPa; and an elongation percentage (%) of 7.0% to 19% prior to the heating of the cast aluminum alloy when tested according to the ASTM E8 specification; and the cast aluminum alloy has a yield strength (YS) ranging from 100 to 220 MPa, an ultimately tensile strength (UTS) ranging from 230 to 320; and an elongation percentage (%) of 6.0% to 15% after the coating and heating of the cast aluminum alloy, wherein the heating step includes curing the coating on the cast aluminum alloy. 
     
     
         16 . The aluminum alloy according to  claim 1 , wherein the coating is cured, and the cast and coated aluminum alloy has a yield strength (YS) ranging from 100 to 220 MPa, an ultimately tensile strength (UTS) ranging from 230 to 320, and an elongation percentage (%) of 6.0% to 15%. 
     
     
         17 . The aluminum alloy according to  claim 1 , wherein the cast aluminum alloy has no change in mechanical properties after exposure to heat for 1 hour at 400° F. (205° C.). 
     
     
         18 . The aluminum alloy according to  claim 1 , wherein the cast aluminum alloy has no change in mechanical properties after exposure to heat for 1000 hours at 300° F. (150° C.). 
     
     
         19 . The aluminum alloy according to  claim 1 , wherein the cast aluminum alloy has an elongation of at least 10% before any heat treatment of the cast aluminum alloy. 
     
     
         20 . The method according to  claim 7  including piercing the cast aluminum alloy with a self-piercing rivet.