Heat treatment and tube forming process for high strength aluminum tube body structure reinforcements
A first method is disclosed for forming a tubular reinforcement that comprises the steps of: providing a 7xxx aluminum tube, heating tube to at least 450° C. and water quenching the tube in less than or equal to 20 seconds after heating. All of the forming processes on the tube are then completed from within 1 to 8 hours of quenching. A second method for forming a tubular reinforcement is disclosed that comprises the steps of providing a 7xxx-O temper aluminum tube and forming the tube into a predetermined shape. The tube in then heated the tube to at least 450° C. and quenched the tube with water or air in a hydroforming die just prior to or while hydroforming the tube.
1. A method of forming a tubular reinforcement, comprising:
providing a 7xxx aluminum tube;
heating tube to at least 450° C.;
quenching the tube to less than 300° C. at a minimum rate of 300° C./s with no more than a 20 second delay between heating and quenching; and
pre-bending, preforming, or hydroforming the tube within 8 hours after quenching.
2. The method of claim 1 further comprising:
heating the tube to a predetermined temperature and holding the tube at the predetermined temperature for a predetermined period of time to artificially age the tube and provide a yield strength of more than 470 MPa.
3. The method of claim 2 wherein the predetermined temperature is between 110-130° C. and the predetermined time is 24 hours.
4. The method of claim 1 wherein the tube is a round straight tube having an outer diameter of less than 5 inches.
5. The method of claim 1 further comprising:
applying axial tension to the tube during the quenching steps to reduce distortion of the tube.
6. A method of thrilling a tubular reinforcement, comprising:
providing a 7xxx-O temper aluminum tube;
forming the tube into a predetermined shape;
heating the tube to at least 450° C.;
contact quenching the tube in a hydroforming die to less than 300° C. at a minimum rate of 300° C./s with no more than a 20 second delay between heating and quenching; and
hydroforming the tube in the hydroforming die.
7. The method of claim 6 wherein the quenching step is performed in a cooled hydroforming die to provide a tubular reinforcement having yield strength of more than 470 MPa.
8. The method of claim 6 wherein the quenching step is performed daring the hydroforming step in a hydroforming die having high contact pressure of more than 0.1 MPa between the tube and the die.
9. The method of claim 6 wherein the quenching step is performed during the hydroforming step in a hydroforming die that is maintained at a temperature of less than 50° C. to cool the tube.
10. The method of claim 6 further comprising:
trimming, the tube after hydroforming the tube.
11. The method of claim 10 further comprising:
heating the tube to between 1.00 and 150° C. for 0.2 to 4 hours and then heating the tube to between 150 and 185° C. for 0.5 to 5 hours to artificially age the tube after trimming the tube.