FLAT BLANK MADE OF Al-Mg ALLOY FOR FLOW FORMING

Abstract

The invention relates to a method of manufacturing a flat blank for flow forming comprising DC Casting a rolling ingot having the composition, in weight % Mg: 2.2-2.6, Cr: 0.16-0.25, Fe: 0.10-0.35, Cu: 0.01-0.09, Ti: 0.005-0.15, Si: up to 0.15, Mn: up to 0.08, Zn: up to 0.10, impurities up to 0.05 each and up to 0.15 total, remainder aluminum; Machining said rolling ingot to a slab with a thickness of at least 10 in; Preheating said slab with minimum 2 hours soak at metal temperature of from 1000° F. to 1100° F.; First hot rolling said slab with a break down mill to an intermediate plate with thickness of at least 1.1 in; Second hot rolling said intermediate plate with a tandem mill, with an exit temperature from 650° F. to 690° F., to a plate with a final thickness from 0.27 to 0.48 in; Cutting said plate to obtain a flat blank for flow forming. The invention also relates to a flat blank obtainable by the method of the invention and to the use of a flat blank according to the invention for flow.

1 . A method of manufacturing a flat blank for flow forming comprising
 (a) DC Casting a rolling ingot having a composition, in weight %
 Mg: 2.2-2.6, optionally 2.3 to 2.5, 
 Cr: 0.16-0.25, optionally 0.19 to 0.22, 
 Fe: 0.10-0.35, optionally 0.20 to 0.30, 
 Cu: 0.01-0.09, optionally 0.02 to 0.07, 
 Ti: 0.005-0.15, optionally 0.01 to 0.05, 
 Si: up to 0.15, optionally 0.05 to 0.13, 
 Mn: up to 0.08, optionally 0.03 to 0.07, 
 Zn: up to 0.10, optionally up to 0.05, 
 impurities up to 0.05 each and up to 0.15 total, remainder aluminum, 
   (b) Machining said rolling ingot to a slab with a thickness of at least 10 in,   (c) Preheating said slab with minimum 2 hours soak at metal temperature of from 1000° F. to 1100° F. optionally from 1025° F. to 1075° F.,   (d) First hot rolling said slab with a break down mill to an intermediate plate with thickness of at least 1.1 in, optionally from 1.2 to 1.4 in,   (e) Second hot rolling said intermediate plate with a tandem mill, with an exit temperature from 650° F. to 690° F., optionally from 660° F. to 680° F. to a plate with a final thickness from 0.27 to 0.48 in, optionally from 0.31 to 0.43 in,   (f) Cutting said plate to obtain a flat blank for flow forming.   
     
     
         2 . A method according to  claim 1  wherein in (d), the entry temperature is at least 850° F. optionally at least 870° F. and/or is at most 950° F. optionally at most 930° F. 
     
     
         3 . A flat blank for flow forming obtainable by the method of  claim 1 . 
     
     
         4 . A flat blank according to  claim 3  wherein the TYS is from 8 to 25 ksi in any direction and wherein the spread of TYS in any direction is at most 12 ksi. 
     
     
         5 . A flat blank according to  claim 3  wherein the UTS is from 25 to 30 ksi in any direction and wherein spread of UTS in any direction is at most 10 ksi. 
     
     
         6 . A flat blank according to  claim 3  wherein the grain size measured at mid-thickness on a L/ST section in the short direction is at least 40 μm, optionally at least 43 μm. 
     
     
         7 . A flat blank according to  claim 3  wherein the difference between hardening texture, quantified by the sum of the bulk volume fraction of “copper”, “brass” and “S” orientations and softening texture, quantified by a sum of a bulk volume fraction of “Cube”, “Goss” and “Rotated cube” orientations is no larger than 7%, optionally no larger 6%, optionally, no larger than 5%. 
     
     
         8 . A flat blank according to  claim 3  for flow forming. 
     
     
         9 . A flat blank according to  claim 8  for manufacturing by flow forming a cylindrical part that has side walls with a thickness of at least 0.08 in optionally at least 0.09 in and/or a cylindrical dimension with a length of at least 8 in optionally at least 9 in. 
     
     
         10 . A flat blank according to  claim 9  wherein the cylindrical part is used to make a transmission housing. 
     
     
         11 . A flat blank with a thickness from 0.27 to 0.48 in, optionally from 0.31 to 0.43 in,
 having a composition, in weight %   Mg: 2.2-2.6, optionally 2.3 to 2.5,   Cr: 0.16-0.25, optionally 0.19 to 0.22,   Fe: 0.10-0.35, optionally 0.20 to 0.30,   Cu: 0.01-0.09, optionally 0.02 to 0.07,   Ti: 0.005-0.15, optionally 0.01 to 0.05,   Si: up to 0.15, optionally 0.05 to 0.13,   Mn: up to 0.08, optionally 0.03 to 0.07,   Zn: up to 0.10, optionally up to 0.05,   impurities up to 0.05 each and up to 0.15 total, remainder aluminum.   
     
     
         12 . A flat blank according to  claim 11  wherein the TYS is from 8 to 25 ksi in any direction and wherein the spread of TYS in any direction is at most 12 ksi. 
     
     
         13 . A flat blank according to  claim 11  wherein the UTS is from 25 to 30 ksi in any direction and wherein spread of UTS in any direction is at most 10 ksi. 
     
     
         14 . A flat blank according to  claim 11  wherein the grain size measured at mid-thickness on a L/ST section in the short direction is at least 40 μm, optionally at least 43 μm. 
     
     
         15 . A flat blank according to  claim 11  wherein the difference between hardening texture, quantified by the sum of the bulk volume fraction of “copper”, “brass” and “S” orientations and softening texture, quantified by a sum of a bulk volume fraction of “Cube”, “Goss” and “Rotated cube” orientations is no larger than 7%, optionally no larger 6%, optionally, no larger than 5%. 
     
     
         16 . A flat blank according to  claim 11  for flow forming. 
     
     
         17 . A flat blank according to  claim 11  for manufacturing by flow forming a cylindrical part that has side walls with a thickness of at least 0.08 in optionally at least 0.09 in and/or a cylindrical dimension with a length of at least 8 in optionally at least 9 in. 
     
     
         18 . A flat blank according to  claim 11  wherein the cylindrical part is used to make a transmission housing.