Hot forming and in-situ cooling of metallic articles

Abstract

Disclosed herein is a hot forming method and apparatus that can improve strength of a product via die operation. The hot forming apparatus includes a lower die on which a workpiece is placed, an upper die coupled to the lower die to press the workpiece, a holder disposed between the upper and lower dies to form an inner space of the workpiece, and a cooling unit to cool the workpiece. The hot forming method includes coupling an upper die, a lower die and a holder with a workpiece placed on the lower die, followed by pressing the workpiece to perform a hot forming operation, determining whether or not a preset time has elapsed after pressing the workpiece, and cooling the workpiece by supplying a cooling fluid around the workpiece, if the preset time has elapsed.

1 . A hot forming apparatus comprising:
 a lower die;   an upper die movable relative to the lower die, wherein the lower and upper dies are configured to press a workpiece placed between the lower and upper dies;   a holder configured to hold the workpiece while placed between the lower and upper dies; and   a cooler configured to cool the pressed workpiece while placed between the lower and upper dies.   
   
   
       2 . The apparatus according to  claim 1 , wherein the cooler is configured to cool at least one of the lower die, the upper die, and the holder. 
   
   
       3 . The apparatus of  claim 1 , wherein the cooler is configured to quench the workpiece so as to transform at least part of the workpiece from austenite to martensite. 
   
   
       4 . The apparatus according to  claim 1 , wherein the cooler comprises:
 a cooling path provided in at least one of the lower die, the upper die and the holder so as to flow a cooling fluid therethrough; and   a pump configured to pump the cooling fluid to the cooling path.   
   
   
       5 . The apparatus according to  claim 4 , wherein the cooling path comprises a die path defined in the lower or upper die, and a holder path defined in the holder. 
   
   
       6 . The apparatus according to  claim 5 , wherein the holder path comprises a suction path and an exhaust path surrounding the suction path. 
   
   
       7 . The apparatus according to  claim 1 , further comprising a guide member provided between the lower and upper dies and configured to guide movement of the upper die relative to the lower die. 
   
   
       8 . The apparatus according to  claim 1 , wherein a space is defined between the holder, the lower die and the upper die. 
   
   
       9 . The apparatus according to  claim 8 , wherein the cooler comprises a direct cooling path having an outlet configured to discharge cooling fluid toward the space. 
   
   
       10 . The apparatus according to  claim 9 , wherein the direct cooling path is formed in at least one of the lower die, the upper die and the holder. 
   
   
       11 . The apparatus of  claim 1 , wherein the holder comprises an insert configured to be inserted in the interior space of the workpiece. 
   
   
       12 . The apparatus of  claim 1 , wherein the holder comprises a cam. 
   
   
       13 . A hot forming method comprising:
 providing an apparatus comprising an upper die, a lower die and a holder;   holding a workpiece with the holder between the upper die and the lower die;   moving the upper die relative to the lower die and pressing the workpiece so as to perform a hot forming operation;   maintaining pressing of the workpiece for a predetermined time; and   cooling in-situ the pressed workpiece with a cooling fluid.   
   
   
       14 . The method according to  claim 13 , wherein cooling comprises quenching the workpiece to transform at least part of the workpiece from austenite to martensite. 
   
   
       15 . The method according to  claim 13 , wherein cooling comprises circulating a cooling fluid through a cooling path formed in at least one of the upper die, the lower die and the holder. 
   
   
       16 . The method of  claim 13 , wherein the holder comprises an insert which is inserted in the interior space of the workpiece. 
   
   
       17 . The method according to  claim 13 , wherein cooling comprises contacting the workpiece with a cooling fluid. 
   
   
       18 . The method according to  claim 13 , further comprising determining that the pressed workpiece reached a predetermined temperature.