Improved method for manufacturing a structure component for a motor vehicle body

Abstract

A method for manufacturing a rolled product for automobile bodywork or body structure with an alloy containing Si: 0.75-1.10, Fe: max 0.4, Cu: 0.5-0.8, Mn: 0.1-0.4, Mg: 0.75-1, Ti: max 0.15, Cr: max 0.1 and V: max 0.1 is disclosed with several process steps from casting the ingot to forming and painting a car body part. The various possibilities of pre aging of the sheet as well as of the heat treatment of the part offer advantageous material properties in forming, material strength and low sensitivity to the bake hardening process which can vary depending in the part location in the car body.

1 . A method for manufacturing a rolled product for automobile bodywork or body structure, and/or a “body in white”, from an aluminium alloy, comprising:
 a. casting of an ingot with the following composition (% by weight):
 Si: 0.75-1.10; 
 Fe: max 0.4; 
 Cu: 0.5-0.8; 
 Mn: 0.1-0.4; 
 Mg: 0.75-1; 
 Ti: max 0.15; 
 Cr: max 0.1; 
 V: max 0.1; 
 
 
       inevitable elements and impurities at maximum 0.05% each, and total 0.15% maximum; remainder aluminium,
 b. homogenization of the ingot, 
 c. hot rolling of the ingot, 
 d. cold rolling into a sheet, 
 e. solution heat treatment, quenching of the sheet, 
 f. pre aging of the sheet, 
 g. natural aging of the sheet. 
 
     
     
         2 . The method according to  claim 1 , wherein the Cu maximum content of the ingot is 0.70% and/or the Cu minimum content is 0.55%. 
     
     
         3 . The method according to  claim 1 , wherein the Mn maximum content of the ingot is 0.35% and/or the Mn minimum content is 0.15%, optionally 0.24% and optionally 0.25%. 
     
     
         4 . The method according to any  claim 1 , wherein the Ti maximum content of the ingot is 0.05% and/or the Ti minimum content is 0.01%. 
     
     
         5 . The method according to  claim 1 , wherein V is among the inevitable elements or impurities. 
     
     
         6 . The method according to  claim 1  wherein:
 b. homogenization of the ingot is at a temperature from 520 to 560° C. optionally during from 2 to 8 hours, 
 and/or 
 c. hot rolling of the ingot is to a thickness from 3 to 10 mm, 
 and/or 
 d. cold rolling into a sheet is to a thickness from 1 to 4 mm, 
 and/or 
 e. solution heat treatment temperature is from 540 to 580° C. optionally from 1 s to 5 minutes, 
 and/or 
 f. pre aging is during at least 8 hours at a temperature optionally from 50° C. to 120° C., optionally by coiling the sheet at a coiling temperature from 50° C. to 120° C., 
 and/or 
 g. natural aging is at ambient temperature, optionally from 72 hours to 6 months. 
 
     
     
         7 . The method according to  claim 1 , wherein the casting a is a vertical semi continuous casting. 
     
     
         8 . The method according to  claim 6  wherein the pre aging is obtained by coiling the sheet at a coiling temperature from 70° C. to 95° C., 95° C. being excluded. 
     
     
         9 . The method according to  claim 6  wherein the pre aging is obtained by coiling the sheet at a coiling temperature between 50° C. and 70° C. 
     
     
         10 . The method according to  claim 6  wherein the pre aging is obtained by coiling the sheet at a coiling temperature above 95° C., and optionally preferably from 95° C. to 105° C. 
     
     
         11 . A rolled product obtainable according to the method of clam  1 . 
     
     
         12 . A rolled product obtainable with the method of  claim 8  wherein the tensile yield strength of the rolled product in a T4 temper is below 165 MPa and wherein the tensile yield strength of the rolled product in a T6B temper is at least 345 MPa. 
     
     
         13 . The rolled product obtainable with the method of  claim 9  wherein the tensile yield strength of the rolled product in T8A temper is at least 275 MPa. 
     
     
         14 . The rolled product obtainable with the method of  claim 10  wherein the tensile yield strength of the rolled product in T8C and T8D tempers and made from the same rolled product in T4 temper, differ by less than 5 MPa, and wherein the tensile yield strength of the rolled product in T6C and T6D temper and made from the same rolled product in T4 temper differ of less than 5 MPa and/or wherein T4 temper rolled product has a maximum tensile yield strength of 190 MPa and/or wherein the T6B temper rolled product has a minimum tensile yield strength of 340 MPa and/or wherein T8A temper rolled product has a minimum tensile yield strength of 280 MPa, optionally of 290 MPa. 
     
     
         15 . The method according to  claim 1  further comprising the following:
 g. Forming the rolled product, optionally by press stamping, into a shape, 
 h. optionally artificial aging of the shape, 
 i. painting and “bake hardening” of the shape into a part at a temperature from 150° to 190° C. and optionally from 170° to 190° C., during from 5 to 30 minutes, optionally from 15 to 30 minutes. 
 
     
     
         16 . Part obtainable with the method according to  claim 15 . 
     
     
         17 . A product comprising the part according  claim 16  in a car as bodywork skin parts (or external bodywork panels) optionally front wings, roofs, bonnet, boot or door skins, and/or lining parts or bodywork structure components optionally door, bonnet, tailgate or roof linings or reinforcements, or, optionally, spars, bulkheads, load-bearing floors, tunnels and front, middle and rear pillars, and/or impact absorbers or “crashboxes”.