Method of manufacturing door frame for wind tower

Abstract

Disclosed herein is a method of manufacturing a door frame for a wind tower. The method includes a first step of forging a circular planar substance, thereby forming a through hole in a central portion of the substance, a second step of heating the substance that was processed in the first step, a third step of ring-rolling the heated substance around the through hole in an annular shape such that a circumstance of a center hole of the substance is equal to a length of a center line of the door frame, a fourth step of upset-forging the annular substance so that opposite sides of the substance are pressed to form linear sections, and a fifth step of fine-finishing the substance that was processed by the fourth step, thus completing the door frame.

What is claimed is: 
     
         1 . A method of manufacturing a door frame for a wind tower, comprising:
 forging a circular planar substance, thereby forming a through hole in a central portion of the substance;   heating the substance processed by the forging;   ring-rolling the heated substance around the through hole in an annular shape such that a circumstance of a center hole of the substance is equal to a length of a center line of the door frame;   upset-forging the annular substance so that opposite sides of the substance are pressed to form linear sections; and   fine-finishing the substance processed by the upset-forging, thus completing the door frame.   
     
     
         2 . The method as set forth in  claim 1 , wherein a ratio (t/w) of a thickness (t) to a width (w) of the substance processed by the fine-finishing ranges from 0.5 to 1. 
     
     
         3 . The method as set forth in  claim 1 , wherein in the fine-finishing the substance, a length ratio (a/b) of the linear section (a) formed in each of the opposite sides of the substance to a curved section (b) is 0.7 or more. 
     
     
         4 . The method as set forth in  claim 1 , wherein a ratio (w/L) of a width (w) to a height (L) of the substance processed by the fine-finishing is 0.1 or more.