Concurrent, adjacent heat treatment and cooling in metal annealing

Abstract

The present invention is a system of concurrent, adjacent heat treatment and vigorous cooling in section-annealing of metal workpieces. The invention process is especially advantageous in induction heating for annealing of one section of a workpiece while maintaining relatively non-annealed properties in an adjacent section.

What is claimed is: 
     
         1 . A heating and cooling process for a metal workpiece of substantially the same metal composition comprising simultaneously heating an upper heat treating zone to substantially above ambient temperature and cooling a lower cooling zone to substantially below ambient temperature so that a crystal structure of the metal of the upper heat treating zone is modified and a crystal structure of the lower cooling zone is less modified. 
     
     
         2 . The process of  claim 1  wherein a transition zone is formed between the upper heat treating zone and the lower cooling zone. 
     
     
         3 . The process of  claim 2  wherein the transition zone is relatively narrow compared to a height of the upper heat treating zone. 
     
     
         4 . The process of  claim 2  wherein the transition zone is relatively narrow compared to a height of the lower cooling zone. 
     
     
         5 . The process of  claim 1  wherein the transition zone is less than six inches of the workpiece. 
     
     
         6 . The process of  claim 5  wherein the transition zone is less than four inches of the workpiece. 
     
     
         7 . The process of  claim 6  wherein the transition zone is from one fourth inch to one inch of the workpiece. 
     
     
         8 . The process of  claim 1  wherein the metal workpiece comprises a metal or metals whose line slope of on a plot of thermal conductivity to temperature curve is equal to or less than that of pure aluminum. 
     
     
         9 . The process of  claim 8  wherein the metal workpiece comprises a metal or metals whose line slope of on a plot of thermal conductivity to temperature curve is equal to or greater than 0.004 watts/inch-degree F per degree F. 
     
     
         10 . The process of  claim 9  wherein the metal workpiece comprises aluminum or its alloys. 
     
     
         11 . The process of  claim 1  wherein the upper heat treating zone is heated to above 600 degrees F. 
     
     
         12 . The process of  claim 11  wherein the lower cooling zone is maintained at a temperature no higher than 400 degrees F. 
     
     
         13 . The process of  claim 1  wherein the upper heat treating zone is heated to above 800 degrees F. 
     
     
         14 . The process of  claim 13  wherein the lower cooling zone is maintained at a temperature no higher than 500 degrees F. 
     
     
         15 . The process of  claim 1  wherein after the workpiece is brought to ambient temperature so that the hardness of the lower cooling zone is thirty percent higher than that of the upper heat treating zone. 
     
     
         16 . The process of  claim 15  wherein the workpiece is brought to ambient temperature so that the hardness of the lower cooling zone is thirty percent to twenty-five percent higher than that of the upper heat treating zone. 
     
     
         17 . The process of  claim 15  wherein the workpiece is brought to ambient temperature so that the hardness of the lower cooling zone is twenty-five percent to fifteen percent higher than that of the upper heat treating zone. 
     
     
         18 . The process of  claim 17  wherein the workpiece is brought to ambient temperature so that the hardness of the lower cooling zone is fifteen percent to ten percent higher than that of the upper heat treating zone. 
     
     
         19 . The process of claim wherein the workpiece comprises metals other than aluminum. 
     
     
         20 . The process of  claim 1  wherein after the upper heat treating zone is heated to over 600 degrees F. and the workpiece is brought to ambient temperature that the hardness of the lower cooling zone is thirty percent or less higher than that of the upper heat treating zone.