Thick products made of 7XXX alloy and manufacturing process
View Patent ↗The present invention relates to an aluminum alloy for the manufacture of thick blocks comprising (as a percentage by weight), Zn: 5.3-5.9%, Mg: 0.8-1.8%, Cu: <0.2%, Zr: 0.05 to 0.12%, Ti<0.15%, Mn<0.1%, Cr<0.1%, Si<0.15%, Fe<0.20%, impurities having an individual content of <0.05% each and <0.15% in total, the rest aluminum, The alloy may be used in a process comprising the steps of: (a) casting a thick block of an alloy according to the invention (b) solution heat treating said cast block at a temperature of 500 to 560° C. for 10 minutes to 20 hours, (c) cooling said solution heat treated block to a temperature below 100° C., (d) tempering said solution heat treated and cooled block by heating to 120 to 170° C. for 4 to 48 hours, In this process, said block is not subjected to any significant deformation by working between the casting and the tempering. The alloy and the method according to the invention are particularly useful for the manufacture of molds for injection-molding plastics.
1. A method of manufacturing a thick block of aluminum comprising:
(a) casting a rough alloy shape comprising an aluminum alloy comprising (as a percentage by weight)
Zn: 5.7-5.8%,
Mg: 0.8-1.8%,
Cu: <0.05%,
Zr: 0.08-0.12%,
Ti: <0.15%,
Mn: <0.1%,
Cr: <0.1%,
Si: <0.15%,
Fe: <0.20%,
impurities with individual content <0.05% each and <0.15% of the total, rest aluminum,
(c) solution heat treating said cast block at a temperature of from 500 to 560° C. for 10 minutes to 20 hours,
(d) cooling said solution heat treated block to a temperature of not more than 100° C. in still air or with a fan, the cooling rate being less than 200° C/h,
(e) tempering said solution heat treated and cooled block by heating to from 120 to 170° C. for 4 to 48 hours,
wherein said block is not subjected to any significant deformation by working between the casting and the tempering, and wherein said block has a thickness greater than 350 mm, and
wherein the manufactured thick block of aluminum exhibits at ¼ thickness in direction TL, yield strength RP0.2 and a ratio called NSR between the mechanical strength on a notched bar and the yield strength RP0.2 measured according to ASTM E602-03, the following properties:
NSR>−0.017*Rp0.2+6.4 and
Rp0.2>330 MPa.
2. The method according to claim 1 , wherein the aluminum ahoy comprises (as a percentage by weight):
Mg: 1.0-1.4%.
3. The method according to claim 1 , wherein the aluminum alloy comprises a Zr: 0.08-0.10% by weight.
4. The method according to claim 1 , wherein the aluminum alloy comprises one or more of (as a percentage by weight):
Ti: 0.01-0.05%,
Mn: <0.05%,
Cr: <0.05%,
Si: <0.10%, and
Fe: <0.15%.
5. The method according to claim 1 , wherein the manufactured thick aluminium block exhibits an NSR>0.8.
6. The method according to claim 1 , wherein the manufactured thick aluminum block is capable of being used for manufacturing molds for injection-molding plastics.
7. The method according to claim 1 , further comprising:
(b) homogenizing at a temperature of from 450 to 550° C. for a period of from 10 minutes to 30 hours and/or stress-relieving at a temperature of from 300 to 400° C. for a period of from 10 minutes to 30 hours followed by cooling to a temperature of not more than 100° C.
8. The method according to claim 1 , wherein the tempering of (e) is carried out by heating said solution heat treated and cooled block to from 130 to 160° C. for 8 to 24 hours.
9. The method according to claim 1 , wherein the tempering of (e) is performed to reach temper T6 or T652, corresponding to a peak of static mechanical properties (R m and R p0.2 ).
10. The method according to claim 1 , wherein the aluminum alloy comprises (as a percentage by weight) about 5.7% Zn.
11. The method according to claim 1 , wherein said block has a thickness greater than 450 mm.
12. The method according to claim 1 , wherein said block has a thickness greater than 550 mm.