Induction Heat-Treating Apparatus and Process

Abstract

An apparatus for induction heat treating and quenching a metallic part with rolls to convey, guide and restrain the part during processing. The apparatus includes a heating coil assembly with two sections of coils wound in opposite directions. The apparatus may include a quenching station with individual quenching sections having different pressures and flows of a liquid. A process for induction heat treating and quenching a metallic part in a series of rolls includes induction heating the part in a counter-wound coil assembly; quenching the part with a liquid while under restraint, and induction heating the part again after quenching. Controlling varying speed and the proximity of the metallic part to the coil assembly is ideal.

What is claimed is: 
     
         1 . An apparatus that performs induction heat treatment of a part, the apparatus comprising:
 rolls to convey, guide and restrain the part as it passes through the apparatus;   a first heating station including a first heating coil assembly, the first heating coil assembly including a coil section configured to surround the part, the coil section having a spacing relative to an outer surface of the part that varies along the outer surface of the part in such a way that induction heating of the part is uniform regardless of the cross sectional geometry of the part;   a device that controls varying speed of the part through the apparatus; and   a quenching station with individual quenching sections having different pressures and flows of a liquid.   
     
     
         2 . The apparatus of  claim 1 , wherein
 the part has a C-shaped cross section, and   the coil section includes
 an outer C-shaped portion that surrounds a portion of an outer surface of the part, 
 an inner C-shaped portion that surrounds a portion of an inner surface of the part, and 
 end portions that surround free ends of the part. 
   
     
     
         3 . The apparatus of  claim 2 , wherein at least one of the outer C-shaped portion and the inner C-shaped portion is spaced a distance d 1  from a surface of the part, and the end portions are spaced a distance d 2  from the part, where the distance d 2  is greater than the distance d 1 . 
     
     
         4 . The apparatus of  claim 2 , wherein the end portions of the coil section are concave. 
     
     
         5 . The apparatus of  claim 2 , wherein the end portions of the coil section are rounded. 
     
     
         6 . The apparatus of  claim 2 , wherein the end portions of the coil section have a shape corresponding to a portion of a circle. 
     
     
         7 . The apparatus of  claim 1  further comprising a device that controls proximity of the part to the heating coil assembly. 
     
     
         8 . The apparatus of  claim 1 , wherein the first heating coil assembly includes two coil sections, and the two coil sections are wound in opposite directions. 
     
     
         9 . The apparatus of  claim 8  further comprising a second heating station downstream of said quenching station, wherein the second heating station includes a second heating coil assembly having two coil sections wound in opposite directions. 
     
     
         10 . The apparatus of  claim 1  wherein the first heating coil assembly includes a first coil section and a second coil section that is wound in a direction opposite to that of the first coil section, and induction on the first coil section is performed from one distal end of the coil to the other extreme, and induction on the second coil section is performed in an opposite direction wherein the first heating coil assembly provides substantial magnetic neutralization. 
     
     
         11 . A process for induction heat treating including quenching a metallic part of a vehicle structural frame in an apparatus, the process comprising:
 controlling speed of the part through the apparatus;   induction heating the part in a heating station including a heating coil assembly, the heating coil assembly including a coil section configured to surround the part, the coil section having a spacing relative to an outer surface of the part that varies along the outer surface of the part in such a way that induction heating of the part is uniform regardless of the cross sectional geometry of the part;   quenching the part with a liquid while under restraint, including the step of restraining the part in a series of restraining rolls during quenching; and   induction heating the part again after quenching.