Patent Publication Number: US-2015075679-A1

Title: Induction Heat-Treating Apparatus and Process

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application asserts priority from provisional application 61/870,738, filed on Aug. 27, 2013, which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates to an induction heat-treating apparatus and a related process. 
     More specifically, the disclosure relates to heat treating a part, such as a side rail, with controlled speed of the part and the part proximity to heating coil assembly with coils that are preferably counter-wound. 
     BACKGROUND 
     Apparatus have been devised for heat treating structural members, such as vehicle side rails. Parts, such as side rails, are presently heat treated in relatively large furnaces with a high volume capacity. The investment and scale of such furnaces are both large. 
     U.S. Pat. No. 4,394,194 discloses a method and apparatus for induction heat treating and restraint quenching structural members of carbon steel, to a uniform martensitic structure, such that distortion of the member due to rapid quenching is controlled to a minimum. More specifically, the member is generally heated by induction in two stages generally to an austenitizing temperature in the range of 1450 degrees to 1750 degrees F. Then the member is liquid quenched under restraint to below 1000 degrees F. to minimize distortion and finally tempered under restraint at a temperature in the range of 750 degrees to 1250 degrees F. Such structural members attain minimum physical properties after heat treating in the range of 110,000 psi yield strength and 125,000 psi tensile strength. 
     Prior art  FIG. 1  is sourced from the “194 patent and as disclosed therein,  FIG. 1  shows a heat treat line for the treatment of carbon steel channel-shaped structural members  20 . An entry table  22  stacks and presents the structural members  20  in a sequential and singular fashion to the conveyor rolls  24  found at the lower edge of entry table  22 . As the structural members  20  are fed from the entry table  22  onto the conveyor rolls  24 , the conveyor rolls  24  will convey the structural members  20  to the point of entry into the vertical side guide and restraint rolls  26  and  54 . 
     The combination of the vertical side guide and restraint rolls  26  and  54  and the last succeeding or first leaving conveyor rolls  24  are used on each end of the heat treat line so as to formulate a combination system of rolls. The configuration of the vertical side guide and restraint rolls  26  is particularly suited to the containment of the structural member  20  in both horizontal and vertical alignment for entry and leaving from the heat treat line as seen in  FIG. 1 . 
     It can also be noted from  FIG. 1  that the direction of travel is indicated by the directional arrows seen from the entry table onto the line and in line from left to right as shown in  FIG. 1  to the exit point onto the cooling table  23 . 
     At such time as the structural member  20  enters the vertical side guide and restraint rolls  26 , the structural member  20  then commences its entry into the first of the heating stations which contains a preheating coil  28 . As the structural member  20  exits the preheat coil  28 , it encounters a first set of pinch rolls  30 . It is this set of pinch rolls  30  that drives the structural member  20  to the next set of heat induction coils  32  while maintaining vertical restraint on structural member  20 . Between the two heat induction coils  32  there is a supporting roll assembly  34  which supports the structural member  20  in correct vertical alignment for entry into the second set of heat induction coils  32 . 
     As the structural member  20  exits the second set of heat induction coils  32 , it enters a second set of pinch-restraint rolls  36 . The pinch-restraint rolls  36  drive the structural member  20  into the quench zone  40 . In this quench zone  40 , the structural member  20  is surrounded on all sides by the multiplicity of liquid supplies  44  which through a series of apertures will supply an ample amount of liquid to quickly reduce the temperature of the structural member. Additionally at the exit end of the quench zone  40 , sets of guide rolls  48  assures that the member  20  progresses evenly and steadily to the pinch rolls  30  which next drive the structural member  20  to the next set of pinch rolls  30  to prepare the material for the next stage of processing. 
     Next follows the tempering section with an induction coil  50  in which the temperature of the structural member  20  is again raised. Immediately following the tempering section with induction coil  50  is another set of drive pinch rolls  36 . Following the drive pinch rolls  36  are further sets of vertical restraint rolls  54  and  26  restraining the flange members of the structural member  20  so as to assure the true configuration of the structural member  20  through the final stage of processing. The final set of rolls utilized in the processing stage are the exact mirror image of the very first set of rolls used in the processing stage. Finally, the structural member is conveyed to the ends of the conveyor rolls  24  and then moved laterally onto the cooling tables  23 . 
     Each of the induction heating coils  28 ,  32  and  50  are fitted with an alternating current through a generation system which will produce varying frequencies. These heat stations  56  are individualized so as to feed each one of the heating induction coils  28 ,  32  and  50  with the required power of alternating current to produce the most energy efficient means of heating the structural member  20  to the desired temperature ranges. 
     That method and apparatus for induction heat treating are specifically disclosed for use with a truck side rail as the heat-treated part. 
     Adaptions are needed from the current methods and apparatus to make them work better, including more practical frequencies and temperatures with a properly scaled project. A higher efficiency apparatus and method are desirable with better control and less distortion of the heat-treated part. 
     SUMMARY 
     The present disclosure provides induction heat-treating apparatus and process for heat-treating parts. This system is well suited for side rails of a vehicle as the heat-treated part. 
     The induction heat-treating apparatus and processes include improvements over the apparatus and method disclosed in U.S. Pat. No. 4,394,194. No preheating is required with the presently disclosed induction heat-treating apparatus and process. The relationship between speed in which a part passes through the process and the heating coil size assists with avoiding a preheating requirement. Previously preheating at different temperatures required two frequencies and power sources. 
     The present counter-wound design with a space separating the heating coils allows the temperature to be leveled. The coils can use the same frequency and power source with the present design. 
     A relatively slow speed of less than 100 inches per minute avoids a large hot area on a treated part and the resulting problematic distortion of such part. Varying the exit speed of the part from the process and the entrance speed of the part into the process can be a factor for this apparatus and process. While the speed of advance of a part through the heat treat system is known to influence operating conditions, the change in speed via acceleration or deceleration at entry, through specific sections and at exit can now be controlled via computer for enhanced performance and characteristics of the part. 
     Also, a defined distance between the part and the heating coil assembly (part proximity) affects the heat-treating performance. The part proximity can be set to maximize the heat treating benefits for the part. While sometimes set at a predetermined distance, the part proximity be controlled for enhanced performance and characteristics of the part. 
     Next, two coil sections of the heating coil assembly preferably wind in opposite directions. The induction on some heating coils is done from one distal end of the coil section to the other extreme, and a second coil section is wound the other way around. The opposing winding helps avoid the part being pushed by the “electricity force” or in other words, the electromagnetic forces generated by the induction coils, and therefore being distorted by such pushing force or electromagnetic force. 
     The counter-winding also provides magnetic neutralization, which resists material from ionization. This results in less rusting of the material and better durability of the part. 
     Also, the apparatus preferably has individual quenching sections (with different pressures and flows) to maximize physical properties of the part. Quenching with liquid is done longitudinally, but also perpendicularly to minimize distortion of the part. Partitioning in each quench plane (up, down, right, and left) is controlled in the quenching process, which can avoid part distortion, such as camber, twisting and bowing. This solves some of the distortion concerns with parts produced in continuous production. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features of this disclosure and the manner of obtaining them will become more apparent, and the disclosure itself will be best understood by reference to the following descriptions of systems and processes taken in conjunction with the accompanying figures, which are given as non-limiting examples only, in which: 
         FIG. 1  shows a prior art schematic of a heat-treating production line from U.S. Pat. No. 4,394,194; 
         FIG. 2  shows a view of a portion of an induction heat-treating apparatus having a heating coil assembly with sections wound in opposite directions; and 
         FIG. 3  shows a view of a quenching section. 
     
    
    
     The exemplifications set out herein illustrate embodiments of the disclosure that are not to be construed as limiting the scope of the disclosure in any manner. Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
     DETAILED DESCRIPTION 
     While the present disclosure may be susceptible to embodiments in different forms, the figures show, and herein described in detail, embodiments with the understanding that the present descriptions are to be considered exemplifications of the principles of the disclosure and are not intended to be exhaustive or to limit the disclosure to the details of construction and the arrangements of components set forth in the following description or shown in the figures. 
     The disclosed process and apparatus are well suited for side rails of a vehicle, and particularly C-channels having a C-shaped cross-section. Both can heat-treat the part  58 , but also minimize distortion of the part  58 . 
     An apparatus  60  for induction heat treating and quenching a metallic part  58  may have rolls to convey, guide and restrain the part  58  along a treatment line. An entry table can load the part  58  onto the treatment line with initial conveyor rolls and subsequent guide rolls and pinch and restraint rolls as needed. The rolls may be computer controlled. 
     The line includes a heating station  62 , a quenching station  64  and a second heating station  66  before or preferably after the quenching station  64 , wherein the second heating station  66  after the quenching station  64  tempers the part  58 . However, the second heating station  66  need not be located after the quenching station  64 . With an improved heating coil assembly  68  at the initial heating station  62 , preheating may no longer be required. 
     Each heating station may include a heating coil assembly  68  with two sections of coils  70  and  71  wound in opposite directions as shown in  FIG. 2 . The counter-wound coil assembly  68  may have a section of coil  70  and  71  with initiation from one side, and another coil with initiation on the other side of the coil. The induction on one section of coil  70  or  71  is preferably done from one distal end of the coil to the other extreme, and a second section of coil is wound the other way around with induction in an opposite direction wherein the coil assembly  68  provides substantial magnetic neutralization and minimal pushing force. 
     The apparatus  60  includes a space  74  between and separating the heating coils to allow the temperature of the part  58  to be leveled. The coil sections  70  and  71  can use the same frequency and power source for the heating coil assembly  68 , wherein the power (kW) and frequency (kHz) are controlled by a computer. 
     The coil size for the initial heating station  62  may be in a preferred range relative to the part  58 . Its shape may be substantially circular or in a specific shape corresponding to the part  58 . 
     The apparatus  60  preferably has a means  78  for controlling speed and deceleration/acceleration of the part  58  through the apparatus  60 . A computer may control the rolls so that the part  58  can vary speed, acceleration and deceleration through entrance into the apparatus  60 , each station  62 ,  64  and  66 , and the exit of the apparatus  60 . The exit speed of the part  58  from the apparatus  60  may differ from an entrance speed of the part  58  into the apparatus  60 , although this speed difference is not required. Controlling an exit speed of the part  58  from the apparatus  60  and an entrance speed of the part  58  into the apparatus  60  may help control the quality of the part  58 . 
     The preferred speed of the part  58  through the initial heating station  62  may be slower than  100  inches per minute. The speed may be varied through the heating station  62 , the quenching station  64  and the second heating station  66 . 
     The relationship between the speed and coil size of the initial heating station  62  may be varied, and the distance and separation between heating stations  62  and  66  can level temperature to ensure homogeneous heating of the part  58  and its particular shape. This may avoid the need for a separate preheating coil. Further, the first heating station  62  may heat the part at a faster rate since the objective is to heat the part as much as possible to the desired temperature and less temperature control is required. The second heating station  66  preferably provides a more controlled increase in temperature to avoid distortion of the part  58 . This is particularly true where the part  58  is a C-channel which can have side edges and a central web which can heat differently from each other and be more prone to distortion. Preferably, the speed and coil size of each heating station  62  or  66  heat the whole part  58  at the same time so as to heat the part  58  most uniformly or homogeneously, particularly when tempering the part  58  in the second heating station  66 . 
       FIG. 3  shows a quenching station  64  with a horizontal block  80  having sprayers  82  and a vertical block  84  having sprayers  86 . The quenching is preferably done with liquid sprayed both longitudinally and perpendicularly. The sprayers  82  and  86  may be angled, such as toward the direction of movement of the part  58 , to preferably direct the quenching liquid in a desired direction and to avoid the liquid from spraying into the wrong area of the apparatus  60 . As an example, water may be supplied from tubes  88  into block  80  to spray liquid via numerous closely aligned sprayers  82 . 
     The quenching station  64  preferably has individual quenching sections (such as  80  and  84 ) having different pressures and flows of liquid. Other arrangements of quenching stations are contemplated. Each quenching section may use a liquid, such as water, for quenching the part  58 . A computer may control the individual quenching sections with different pressures and flows and the direction of flow of the liquid. 
     The improved and variable control of the quenching station  64  uses less liquid than the prior art. A flow of 50-150 gallons per minute for quenching is less than an estimated flow of 500-1,000 gallons per minute for prior art quenching. 
     The apparatus  60  preferably includes a means  90  for controlling proximity of the part  58  to the heating coil assembly  68 . A computer may control the rolls so that the part  58  is passed by each heating coil assembly  68  at a desired distance, although computer control may not be required. The part proximity may be set in a preferred range. 
     A process for induction heat treating and quenching a metallic part  58  using an apparatus  60  includes induction heating the part  58  in a counter-wound coil assembly  68 ; quenching the part  58  with a liquid while under restraint, preferably in individual quenching sections  80  and  84  using different pressures and flows; restraining the part  58  in a series of restraining rolls during quenching; and induction heating the part  58  again after quenching. 
     The process preferably includes controlling speed of the part  58  through the apparatus  60  including entry, each station, and exit. A computer can control the speed and deceleration/acceleration of the part  58  through the apparatus  60  although is not required for such control. Similarly, the proximity of the part  58  to the heating coil assembly  68  can be set or controlled by a computer. 
     This disclosure has been described as having exemplary embodiments and is intended to cover any variations, uses, or adaptations using its general principles. It is envisioned that those skilled in the art may devise various modifications and equivalents without departing from the spirit and scope of the disclosure as recited in the following claims. Further, this disclosure is intended to cover such variations from the present disclosure as come within the known or customary practice within the art to which it pertains.