Reverse temperature field rolling method for mg alloy sheet

Abstract

A rolling technique for manufacturing magnesium alloy sheets with high plasticity which is characterized in that by heating the rolls during rolling to ensure an unconventional decreasing temperature field from the surface to the center within the rolled material. Due to the poor plasticity and formability of magnesium and magnesium alloys, the use of their sheet products are currently limited, in particular, in high performance applications. To solve this problem, improving on the plasticity and formability of magnesium and magnesium alloy sheets is urgently needed. The present invention presents a rolling technique to manufacture magnesium and magnesium alloy sheets with high plasticity. The said rolling method is featured by heating the rolls during rolling to ensure an unconventional decreasing temperature field from the billet surface to its center, and to make the roll temperature to match with the initial temperature field of the billet material. By the said unconventional decreasing temperature field it is meant that the billet surface temperature is higher than the temperature in its center, and there is heat transfer from the surface to the center, during rolling.

1 . A rolling technique for manufacturing magnesium alloy sheets with high plasticity which is characterized in that by heating rolls during rolling to ensure an unconventional decreasing temperature field from the surface to the center within a rolled material. The said heating makes it a reality for a roll temperature to match with an initial temperature field within a billet material to be rolled. 
   
   
       2 . A rolling technique as claimed in  claim 1 , wherein the said unconventional decreasing temperature field means that before rolling the initial temperature in the surface of the billet material is higher than in its center, and thus upon rolling there is heat transfer from the billet surface to its center. 
   
   
       3 . A rolling technique as claimed in  claims 1 , wherein the billet surface and central temperature upon rolling is in a range of 250-450° C. and 20-150° C., respectively. A thickness reduction for each pass of rolling is between 20-70% and a rolling speed is between 5-10 m/min. 
   
   
       4 . A rolling technique as claimed in  claims 2 , wherein the billet surface and central temperature upon rolling is in a range of 250-450° C. and 20-150° C., respectively. A thickness reduction for each pass of rolling is between 20-70% and a rolling speed is between 5-10 m/min. 
   
   
       5 . A rolling technique as claimed in  claims 1 , wherein the said billet surface temperature during rolling is selected from 450° C., 400° C., or 300° C. while the billet center is still at room temperature. 
   
   
       6 . A rolling technique as claimed in  claims 2 , wherein the said billet surface temperature during rolling is selected from 450° C., 400° C., or 300° C. while the billet center is still at room temperature. 
   
   
       7 . A rolling technique as claimed in  claims 1 , wherein the said billet surface temperature during rolling is 450° C. while the billet central temperature is 100° C. 
   
   
       8 . A rolling technique as claimed in  claims 2 , wherein the said billet surface temperature during rolling is 450° C. while the billet central temperature is 100° C. 
   
   
       9 . A rolling technique as claimed in  claims 3 , wherein for the rolling processes with as-cast magnesium alloys as starting billet materials, a thickness reduction for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 6 th  pass, 40-50% from a 7 th  to a 10 th  pass, and 50-60% for further passes, respectively. 
   
   
       10 . A rolling technique as claimed in  claims 4 , wherein for the rolling processes with as-cast magnesium alloys as starting billet materials, a thickness reduction for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 6 th  pass, 40-50% from a 7 th  to a 10 th  pass, and 50-60% for further passes, respectively. 
   
   
       11 . A rolling technique as claimed in  claims 5 , wherein for the rolling processes with as-cast magnesium alloys as starting billet materials, a thickness reduction for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 6 th  pass, 40-50% from a 7 th  to a 10 th  pass, and 50-60% for further passes, respectively. 
   
   
       12 . A rolling technique as claimed in  claims 3 , wherein for rolling of as-cast magnesium alloys billets, a deformation amount for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 5 th  pass, and 30-60% for further passes depending upon a requirement for a final sheet thickness. 
   
   
       13 . A rolling technique as claimed in  claims 4 , wherein for rolling of as-cast magnesium alloys billets, a deformation amount for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 5 th  pass, and 30-60% for further passes depending upon a requirement for a final sheet thickness. 
   
   
       14 . A rolling technique as claimed in  claims 5 , wherein for rolling of as-cast magnesium alloys billets, a deformation amount for each pass of rolling is 20-30% for a first 2 passes, 30-40% from a 3 rd  to a 5 th  pass, and 30-60% for further passes depending upon a requirement for a final sheet thickness.