US2006231173A1PendingUtilityA1

Magnesium alloy sheet and its production

32
Individually held — no corporate assignee on recordPriority: Feb 28, 2003Filed: Sep 22, 2003Published: Oct 19, 2006
Est. expiryFeb 28, 2023(expired)· nominal 20-yr term from priority
Inventors:Daniel LiangWendy BorbidgeDaniel EastRoss AlienDavid Eugene RenshawColleen Joyce BettlesMark Antony Gibson
B22D 11/16B22D 11/06B22D 21/04B22D 27/20B22D 11/001C22F 1/06B22D 11/0622
32
PatentIndex Score
0
Cited by
0
References
0
Claims

Abstract

A method of producing magnesium alloy strip, suitable for use in the production of magnesium alloy sheet by rolling reduction and heat treatment, involves casting magnesium alloy as strip, using a twin roll casting installation. In the casting, the thickness and temperature of the strip exiting from between rolls of the installation are controlled whereby the strip has a microstructure characterised by a primary phase having a form selected from deformed dendritic, equiaxed dendritic and a mixture of deformed and equiaxed dendritic forms. The resultant strip is amenable to production of sheet material by application of a homogenizing heat treatment followed by rolling and annealing.

Claims

exact text as granted — not AI-modified
1 . A method of producing magnesium alloy strip, suitable for use in the production of magnesium alloy sheet by rolling reduction and heat treatment, wherein the method includes the steps of: 
 (a) casting magnesium alloy as strip, using a twin roll casting installation; and    (b) controlling the thickness and temperature of the strip exiting from between rolls of the installation whereby the strip has a microstructure characterised by a primary phase having a form selected from deformed dendritic, equiaxed dendritic and a mixture of deformed and equiaxed dendritic forms.    
   
   
       2 . The method of  claim 1 , wherein the controlling of step (b) includes adjusting the spacing between the rolls to provide strip having a thickness of less than 10 mm.  
   
   
       3 . The method of  claim 2 , wherein the adjusting provides strip having a thickness of not more than about 7 mm.  
   
   
       4 . The method of  claim 2 , wherein the adjusting provides strip having a thickness of less than about 5 mm down to about 2.5 mm.  
   
   
       5 . The method of  claim 1 , wherein the controlling of step (b) results in the strip exiting from between the rolls at a temperature of about 200° C. to about 350° C.  
   
   
       6 . The method of  claim 1 , wherein the controlling of step (b) results in the strip exiting from between the rolls at a temperature of about 200° C. to about 260° C.  
   
   
       7 . The method of  claim 1 , wherein the controlling of step (b) is conducted to provide strip exiting from between the rolls at a temperature of from about 200° C. to 220° C. and a thickness of from about 4 mm to about 5 mm, whereby the strip has a microstructure characterised by deformed dendritic primary phase substantially free of equiaxed dendritic primary phase.  
   
   
       8 . The method of  claim 1 , wherein the controlling of step (b) is conducted to provide strip exiting from between the rolls at a temperature of from about 200° C. to 245° C. and a thickness less than about 4 mm, whereby the strip has a microstructure characterised by deformed dendritic primary phase substantially free of equiaxed dendritic primary phase.  
   
   
       9 . The method of  claim 1 , wherein the controlling of step (b) is conducted to provide strip exiting from between the rolls at a temperature of at least 230° C. and a thickness of from about 4 mm to about 5 mm, whereby the strip has a microstructure substantially characterised by equiaxed dendritic primary phase.  
   
   
       10 . The method of  claim 9 , wherein the temperature is from about 230° C. to about 240° C.  
   
   
       11 . The method of  claim 1 , wherein the controlling of step (b) is conducted to provide strip exiting from between the rolls at a temperature of at least 245° C. and with a thickness of less than about 4 mm, whereby the strip has a microstructure substantially characterised by equiaxed dendritic primary phase.  
   
   
       12 . The method of  claim 9 , wherein the equiaxed dendritic primary phase is characterised by grains which are of spheroidal form.  
   
   
       13 . The method of  claim 7 , wherein the deformed dendritic primary phase is characterised by grains which, while reflecting dendritic growth, are of an elongate flattened form extending in the rolling direction, substantially parallel to major surfaces of the strip.  
   
   
       14 . The method of  claim 1 , wherein the strip is subjected to a homogenizing heat treatment to achieve recrystallization to a required grain size.  
   
   
       15 . The method of  claim 14 , wherein the homogenizing heat treatment is conducted at a temperature of from about 330° C. to 500° C.  
   
   
       16 . The method of  claim 14 , wherein the homogenizing heat treatment is conducted at a temperature of from about 400° C. to 500° C.  
   
   
       17 . The method of  claim 14 , wherein the strip passes from the twin roll casting installation to a furnace in which the homogenizing heat treatment is conducted, whereby loss of heat energy from the strip prior to the heat treatment is minimised.  
   
   
       18 . The method of  claim 14 , wherein the strip is held at an intermediate temperature, which is suitable for reducing segregation by secondary phase being taken into solid solution, before the strip is heated to the homogenizing temperature.  
   
   
       19 . The method of  claim 18 , wherein the intermediate temperature is from about 340° C. to 360° C.  
   
   
       20 . A method of producing magnesium alloy sheet, wherein the method includes the steps of: 
 (a) casting magnesium alloy as strip, using a twin roll casting installation;    (b) controlling the thickness and temperature of the strip exiting from between rolls of the installation whereby the strip has a microstructure characterised by a primary phase having a form selected from deformed dendritic, equiaxed dendritic and a mixture of deformed and equiaxed dendritic forms;    (c) subjecting the strip to a homogenizing heat treatment to achieve full or partial recrystallization of the microstructure to a required grain size;    (d) rolling the homogenized strip to produce magnesium alloy sheet of a required gauge; and    (e) annealing the sheet produced by step (d).    
   
   
       21 . The method of producing magnesium alloy sheet, wherein the method includes the steps of: 
 (i) producing magnesium alloy strip by the method of  claim 2;     (ii) subjecting the strip to a homogenizing heat treatment to achieve full or partial recrystallization of the microstructure to a required grain size;    (iii) rolling the homogenized strip to produce magnesium alloy sheet of a required gauge; and    (iv) annealing the sheet produced by step (iii).    
   
   
       22 . The method of producing magnesium alloy sheet, wherein the method includes the steps of: 
 (i) producing magnesium alloy strip by the method of  claim 15;     (ii) subjecting the strip to a homogenizing heat treatment to achieve full or partial recrystallization of the microstructure to a required grain size;    (iii) rolling the homogenized strip to produce magnesium alloy sheet of a required gauge; and    (iv) annealing the sheet produced by step (iii).    
   
   
       23 . The method of  claim 20 , wherein the homogenizing heat treatment is conducted at a temperature and for a period sufficient to substantially eliminate segregation of deformed dendritic primary phase.  
   
   
       24 . The method of  claim 23 , wherein the strip on completion of the homogenizing heat treatment is characterized by a microstructure consisting substantially of fine grains of from about 10 μm to about 15 μm in size resulting from recrystallization of deformed dendritic microstructure.  
   
   
       25 . The method of  claim 20 , wherein the strip on completion of the homogenizing heat treatment is characterized by a microstructure consisting of grains of from 50 μm to about 200 μm in size resulting from recrystallization of deformed dendritic microstructure.  
   
   
       26 . The method of  claim 20 , wherein the step of rolling the homogenized strip includes stages of finish cold rolling, followed by an anneal heat treatment.  
   
   
       27 . The method of  claim 26 , wherein the step of rolling includes, before the finish cold rolling, a stage of finish hot rolling.  
   
   
       28 . The method of  claim 27 , wherein the finish hot rolling is conducted at a temperature at which hot rolling causes recrystallization of the microstructure.  
   
   
       29 . The method of  claim 28 , wherein the finish hot rolling is conducted at a temperature of from 200° C. to 500° C.  
   
   
       30 . The method of  claim 28 , wherein the finish hot rolling is conducted at a temperature of from 350° C. to 500° C.  
   
   
       31 . The method of  claim 28 , wherein the finish hot rolling is conducted at a temperature of from 400° C. to 500° C.  
   
   
       32 . The method of  claim 27 , wherein the finish hot rolling achieves from 20% to 25% thickness reduction per pass of hot rolling.  
   
   
       33 . The method of  claim 26 , wherein the finish cold rolling achieves from 15% to 25% thickness reduction per pass of cold rolling.  
   
   
       34 . The method of  claim 26 , wherein the anneal heat treatment involves an inverse temperature/time relationship of the order of about 350° C. for less than about 60 minutes or 420° C. for less than about 30 minutes, suitable for achieving recrystallization of the microstructure.  
   
   
       35 . Magnesium alloy strip produced by the method of  claim 1 .  
   
   
       36 . Magnesium alloy sheet produced by the method of  claim 20.

Join the waitlist — get patent alerts

Track US2006231173A1 — get alerts on status changes and closely related new filings.

We store only your email — no account needed. See our privacy policy.