6xxx series aluminium alloy sheets or blanks with improved formability

Abstract

The invention concerns a process for producing a sheet or a plate or a blank, comprising the following successive steps: (a) casting a 6xxx alloy comprising, in wt. %: Si: 1.25-1.45; Fe: ≤0.30; Cu: ≤0.15; Mn: 0.01-0.15; Mg: 0.25-0.40; Cr: 0.03; Ni: ≤0.04; Zn: <0.15; Ti: 0.01-0.10; other elements: <0.05 each and <0.15 in total; rest aluminium; (b) heat treating; (c) hot rolling; (d) cold rolling; (e) optionally inter-annealing between hot rolling and cold rolling and/or during cold rolling and/or after cold rolling; (f) solution heat treating; (g) quenching; (h) optionally pre-aging; (i) shearing without any milling step.

1 .- 27 . (canceled) 
     
     
         28 . Process for producing a sheet or a blank, comprising the following in succession:
 (a) casting a 6xxx alloy comprising, in wt. %:   Si: 1.25-1.45   Fe: <0.30   Cu: <0.15   Mn: 0.01-0.18   Mg: 0.25-0.40   Cr: <0.03   Ni: <0.04   Zn: <0.15   Ti: 0.01-0.10   other elements: <0.05 each and <0.15 in total   rest aluminium;   (b) heat treating;   (c) hot rolling;   (d) cold rolling;   (e) optionally inter-annealing between hot rolling and cold rolling and/or during cold rolling and/or after cold rolling;   (f) solution heat treating;   (g) quenching;   (h) optionally pre-aging;   (i) shearing without any milling   wherein a sheet temperature at a beginning of the quenching is from 480 to 570° C. and optionally, the sheet temperature at an end of the quenching is from 50 to 160° C.   
     
     
         29 . A process according to  claim 28 , wherein (g) quenching is a water quenching. 
     
     
         30 . A process according to  claim 28 , wherein an ingot is heat treated and hot rolled without any reheating and without forced cooling before start of hot rolling and further comprising cooling from a first hot hot rolling exit temperature to a second hot rolling start temperature between the first hot rolling and the second hot rolling, the cooling being obtained with a cooling rate of the temperature of V=C/e, where V is in ° C./s, e is a thickness after the first hot rolling in mm, and C is a constant which equals between 400and 1000° C./s*mm, optionally between 60° and 900° C./s*mm, optionally between 70° and 800° C./s*mm. 
     
     
         31 . A 6xxx alloy comprising, in wt. %:
 Si: 1.25-1.45   Fe: ≤0.30   Cu: ≤0.15   Mn: 0.01-0.15   Mg: 0.25-0.40   Cr: ≤0.03   Ni: ≤0.04   Zn: ≤0.15   Ti: 0.01-0.10   
     
     
         32 . A 6xxx alloy according to  claim 31  wherein the Si content of the 6xxx alloy is 1.30-1.40 wt. %. 
     
     
         33 . A 6xxx alloy according to  claim 31 , wherein the Mg content of the 6xxx alloy is 0.30-0.35 wt. %. 
     
     
         34 . A 6xxx alloy according to  claim 31 , wherein the Mn content of the 6xxx alloy is <=0.15 wt. %. 
     
     
         35 . A 6xxx alloy according to  claim 31 , comprises, in wt. %:
 Si: 1.30-1.40   Fe: 0.10-0.20   Cu: ≤0.09   Mn: 0.05-0.10   Mg: 0.30-0.35   Cr: ≤0.02   Ni: ≤0.03   Zn: ≤0.10   Ti: 0.01-0.04   other elements: <0.05 each and <0.15 in total   rest aluminium.   
     
     
         36 . A 6xxx alloy according to  claim 31 , wherein the Cu content of the 6xxx alloy from 0.01 wt % to 0.14 wt %. 
     
     
         37 . A 6xxx alloy according to  claim 31 , wherein the Mg content of the 6xxx alloy is at least 0.32 wt %. 
     
     
         38 . A 6xxx alloy according to  claim 31 , wherein the Cr content of the 6xxx alloy is at least 0.01 wt %. 
     
     
         39 . A 6xxx alloy according to  claim 31 , wherein the Zn content of the 6xxx alloy is at least 0.01 wt %. 
     
     
         40 . A 6xxx alloy according to  claim 31 , wherein the Ti content of the 6xxx alloy is from 0.03%, optionally 0.04 wt % to 0.10 wt %. 
     
     
         41 . A Sheet or blank obtained according to  claim 28 , comprising an improved sheared edge stretchability compared to non-milled previous sheets or plates or blanks. 
     
     
         42 . A sheet or blank according to the  claim 41  adapted to be capable of producing a vehicle part.