Abstract:
A cast component having localized areas of improved physical properties is disclosed. The component may initially be produced having a void portion in a predetermined area requiring improved physical properties. A second molten material may be added to the void portion such that it chemically bonds to the void portion. The component may then be finished such to a final shape with a localized area of improved physical properties.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to a cast component, and more particularly a cast component having localized areas of improved physical properties. 
       BACKGROUND 
       [0002]    Cast components are often designed to the limit of their mechanical properties to take advantage of strength to weight ratios. The requirement for more stringent emissions is also a contributing factor due to seeking high combustion pressures and temperatures. Because of the physical characteristics of cast materials, specifically gray cast iron in engine applications, the thermal fatigue limit is often reached causing failure in certain areas of the component. When this happens, it is difficult and time consuming to repair castings and other components often resulting in significant downtime and costs for the component owner. Typically repairs to castings involve removing damaged portions of the casting through machining, and subsequently rebuilding the damaged area by welding. 
         [0003]    An example of a component that is susceptible to damage is the cylinder head of an internal combustion engine. Because of repeated heating and cooling of the engine, the cylinder heads often reach their thermal fatigue limit and develop cracks near openings, such as valve seats, fuel injector bores, and exhaust ports. Another problem associated with cylinder heads is warping. When warped, the bottom surface of the head becomes uneven and does not seal properly. Some warped cylinder heads can be milled until the fireside surface is again flat. However, milling the surface reduces the thickness of the head, making the head more susceptible to future operating damage. Heads that can&#39;t be milled flat are typically scrapped. 
         [0004]    One example of producing a casting having localized areas of improved thermal resistance of the cylinder head is U.S. Pat. No. 4,337,736 (the &#39;736 patent) issued to Raush et al. The &#39;736 patent discloses a cast iron cylinder head having a preformed workpiece of a thermal fatigue-resistant alloy material metallically bonded to the cylinder head around the valve bridge area to provide reinforcement in this area. The preformed workpiece has thin fusible sections, which melt when the hot base material is cast over them. Although the disclosure of the &#39;736 patent may provide for localized areas of improved thermal resistance, it may be costly and have limited applicability. 
         [0005]    The present disclosure is directed to overcoming one more of the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0006]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
         [0007]    One aspect of the present disclosure is directed to a method of producing a component. The method may include form forming the component to include a void portion, heating the component to a first predetermined temperature, and adding a quantity of molten filler material into the void portion. The molten filler material may then further heat the void portion to chemically bond the filler material to the void portion. 
         [0008]    Another aspect of the present disclosure is directed toward the component itself. The component may comprise a first component portion made from a first material and a second component portion made from a molten filler material. The first component portion may be produced with a void portion. The molten filler material may be cast into the void portion such that the second component portion is chemically bonded to the first component portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings, 
           [0010]      FIG. 1  is an elevated view of a bottom surface of a cylinder head according to an embodiment of the present disclosure; 
           [0011]      FIG. 1   a  is a sectional view of the cylinder head of  FIG. 1  taken along line  1   a - 1   a;    
           [0012]      FIG. 2  is an elevated view of the bottom surface of a first component portion of the cylinder head of  FIG. 1  according to an embodiment of the present disclosure; 
           [0013]      FIG. 2   a  is sectional view of the first component portion of  FIG. 2  taken along line  2   a - 2   a;    
           [0014]      FIG. 2   b  is a sectional view of the first component portion of  FIG. 2  taken along line  2   a - 2   a  including a dam and plugs; 
           [0015]      FIG. 2   c  is sectional view of the first component portion of  FIG. 2  taken along line  2   a - 2   a  after the addition of a second component portion; 
           [0016]      FIG. 2   d  is a sectional view of the first component portion of  FIG. 2  taken along line  2   a - 2   a  after adding the second component portion and removing the dam and plugs; and 
           [0017]      FIG. 3  is a flowchart describing a method of producing a component according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  is an elevated view of a bottom (fireside) surface  12  of a component, in this case a cylinder head  10 , according to an embodiment of the present disclosure. The cylinder head  10  may include a first component portion  15  and a second component portion  60  separated by a bond layer  65 . In this instance, the cylinder head  10  may be in a rough state after casting and some machining. The cylinder head  10  may include a plurality of side surfaces  14  in addition to the fireside surface  12  and a top surface (not shown). The fireside surface  12  may be cast with a plurality of valve openings  20  associated with each cylinder (not shown). The fireside surface  12  may be fastened to an engine block (not shown) after final machining the fireside surface  12 , the valve openings  20 , and other necessary openings, such as the fuel injector openings (not shown) associated with each cylinder (not shown). 
         [0019]      FIG. 1   a  is a sectional view of the cylinder head  10  of  FIG. 1  taken along line  1   a - 1   a . The valve openings  20  are more clearly shown extending through the second component portion  60  and into the first component portion  15 . A bond layer  65  is shown representing a metallurgical, or chemical, bond between the first component portion  15  and the second component portion  60 . Although a gray iron cylinder head  10  is shown, it should be noted that the present disclosure is not limited to use with cylinder heads  10  cast from gray iron, but may be applied to other cast and non-cast components made from various other metallics, such as ductile iron, wrought steel, mild steel, stainless steel, aluminum and the like. While the second component portion  60  may also be gray iron, the second component portion  60  may be any one of a number of other materials, such as ductile iron, mild steel, stainless steel, inconel, aluminum and the like depending on compatibility with the first component portion  60 . In the case where the base material of the first component portion  15  and the second component portion  60  is the same, the microstructure of the second component portion  60  may differ significantly from the first component portion  15 , thereby imparting different physical properties. 
         [0020]      FIG. 2  is an elevated view of the bottom surface of a first component portion  15  of the cylinder head  10  according to an embodiment of the present disclosure. A plurality of void portions  30  may be shown produced in the first component portion  15 .  FIG. 2   a  is a sectional view of the first component portion  15  of  FIG. 2  taken along line  2   a - 2   a . The sectional view more clearly shows the void portion  30  and valve openings  20  cast into the cylinder head  10 . The void portion  30  may be structured to receive a quantity of molten filler material to form the second component portion  60 . As the molten filler material forms the second component portion  60 , the terms may be interchanged throughout the disclosure and the figures. 
         [0021]    Referring now to  FIG. 3 , a flowchart is provided describing a method of producing a component  10  according to one embodiment of the present disclosure. In the first control block  200 , the first component portion  15  of the component  10  may be produced with a void portion  30  in a predetermined area. This may be represented as shown in  FIGS. 2 and 2   a . Production of the first component portion  15  having at least one void portion  30  may be by any one of a number of operations, such as casting, forging, machining and the like. The void portion  30  may be created such that void portion  30 , itself, may provide for an area to receive and contain the molten filler material  60  without a mold being necessary to the operation. In control block  202 , the void portion  30  may be cleaned up as necessary to provide a surface suitable for forming a metallurgical bond upon the addition of a molted filler material  60 . This may not always be required, but may include machining and the like to provide an oxide free surface in the void portion  30 . 
         [0022]    In the third control block  204 , the component  10  may be preheated to a predetermined temperature. The preheat temperature will vary depending on the type and thickness of material surrounding the void portion  30  and the type and amount of molten filler material  60  being added to the void portion  30 . For proper determination of preheat temperature, computer simulation or experimentation may be necessary. It may desirable to preheat the first component portion  15  as much as possible without damaging the component  10 . Depending on the component  10 , types of damage may include stress relieving and warping caused by overheating or melting of the original surface. On the other hand, failure to preheat the component  10  to high enough of a temperature may cause cracking of the parent material when the melted filler material is poured or lack of bonding between the two materials. In one embodiment, the preheat temperature for a cast iron cylinder head  10  may be in the range of 950° F. to 2000° F. For certain types of cylinder heads  10 , a preheat temperature of 1100° F. has been found to reduce stress and warping while reducing the risk of cracking. 
         [0023]    In the fourth control block  206 , a quantity of filler material  60 , or second component portion, is melted and poured into the void portion  30  of the first component portion  15 . As the melting point of the first component portion  15  and the second component portion  60  may be the same or may be different, the melting point of the second component portion  60  may be exceeded to cause further heating of the first component portion  15  at the void portion  30 . As the molten filler material  60 , or second component portion, and the first component portions cool, a metallurgical bond may be formed between the filler material  60  and the first component portion  10  at a bond layer  65 . In the final control block  208 , the component  10 , including the solidified filler material  60 , may be machined to a final component shape. 
       Industrial Applicability 
       [0024]    Embodiments of the present disclosure may be applicable to produce a variety of components having localized areas of improved physical properties, such as improved thermal fatigue properties, hardness, and the like. Referring now to  FIG. 2   a ,  2   b ,  2   c  and  2   d , a method for casting a molten filler material  60  onto a solidified parent material prepared with a void portion  30  will be described in detail. 
         [0025]    As shown in  FIG. 2   a , the first component portion  15  may be produced with a void portion  30  in a predetermined location to receive a molten filler material  60 . The void portion  30  may be designed into the component  30  at a predetermined location in place of a portion of the component  30  where experience has shown similar components have failed or needed repair. Critical or crack prone areas identified through experience or finite element analysis may be typical areas to which the present disclosure may be applied. It is envisioned that the void portion  30  may be cleaned up as necessary to provide a surface suitable for forming a metallurgical bond upon the addition of a molted filler material  60 . 
         [0026]      FIG. 2   b  is a sectional view of the first component portion  15  of  FIG. 2  taken along line  2   a - 2   a  including a dam  50  and plugs  40 . Plugs  40  may prevent the molten filler material  60  from entering original features of the cylinder head  10 . The plugs may be manufactured from a heat resistant material, such as machinable graphite and the like. In one embodiment the plugs may be capable of withstanding extreme temperatures without deforming and may be thermally conductive. The plugs  40  may not be necessary, but may also be of a variety of shapes and sizes to fill specific features. For example, a plug  40  to fill and protect a valve opening  20  is machined to a size and shape substantially equal to that of its respective rough valve opening  20 . The plug  40  may be pushed into the valve opening  20 , preventing filler material  60  from running through or otherwise filling the valve opening  20 . Additionally a dam  50  may be positioned around the void portion  30  on the fireside surface  12 . The dam  50  may be positioned on the fireside surface  12  in a manner where pouring the molten filler material  60  into the void portion  30  provides a riser of filler material  60 . The dam  50  may be made of machinable graphite similar to the plug  40 . The dam  50  may allow for a surplus of molten filler material  60  to be added to the void portion  30  to allow for shrinkage during cooling. 
         [0027]    As described in the second control block  204 , the cylinder head  10  may be preheated in an oven to a first temperature. In one embodiment the first temperature range is in the range of 950° F. to 2000° F., more preferably 1050° F. to 1150° F. From the preheat oven, the cylinder head  10 , with the graphite plugs  40  and dams  50  in position, may be moved to a heated and insulated box (not shown) adapted to maintain the first temperature range and allow for addition of the molten filler material  60 . 
         [0028]    A quantity of filler material  60 , such as cast iron, or other material suitable to attain the desired gradient properties in the void portion  30  is prepared by melting. For example, the filler material  60  may be melted in a crucible and held in a furnace at a temperature sufficient to complete a porosity free bond with the parent material. In the case of a cylinder head  10 , the temperature may be approximately 2725° F. The filler material  60  may be of a chemical composition similar to that of the cylinder head  10  or component, or it could be quite different depending on the properties desired. 
         [0029]    It is envisioned in the present disclosure that it may be necessary to locally heat the void portion  30  of the first component portion  15  to a second predetermined temperature. The second predetermined temperature may vary depending upon the type, mass and wall thickness of the parent material and the volume of filler material  60 . The second predetermined temperature range is hot enough to permit bonding of the void portion  30  and filler material  60 , but cool enough to prevent the filler material  60  from melting through the parent material of the void portion  30 . The lower limit of the range may be determined through simulation and/or experimentation and may account for factors such as material shrinkage, bonding strength, microstructure, and stress associated the parent and/or filler material. Factors that impact bonding point may include type and volume of the parent material, the type and volume of the filler material, the chemistry of the parent component. Additionally, the second preheat temperature may prevent rapid cooling of the filler material  60 , in turn maintaining desired mechanical properties. Additionally or alternatively, the molten filler material  60  may be heated beyond its melting point to further increase heating of the first component portion  15 . 
         [0030]    A quantity of welding flux (not shown) may also be applied to the void portion  30 . The flux may act to remove oxidation, other contaminants, and aids in wetability of the filler material  60  onto the void portion  30  after the molten filler material  60  is poured. A typical flux may be manufactured from a borax-based material. With the temperature of the void portion  30  within second temperature range, molten filler material  60  may be removed from the furnace. Slag that may be floating on the surface of the molten filler material  60  may be skimmed from the melted filler material. With the molten filler material  60  substantially free of slag, it is poured into, and fills the void portion  30  as shown in  FIG. 2   c . In one embodiment, filler material may be permitted to overflow from the void portion  30  and rise above the bottom surface  12  along the dam  50 . 
         [0031]    After addition of the molten filler material  60 , the component  10  may then be allowed to cool. In one embodiment, the component  10 , or a portion thereof, may be partially cooled using compressed air. A wand (not shown) having a diffuser attached thereto and being attached to a compressed air source may be moved about, over the filler material  60 . In one embodiment, to achieve desired mechanical properties, such as hardness and microstructure, it is desired to employ a cooling rate sufficient enough, depending on chemistry, to cool the entire volume of the void portion  30  to achieve desired microstructure, or transformation products, of the matrix structure at a newly formed bond layer  65  between the void portion  30  and the filler material  60 . For example using cast iron and dependent on the volume of material affected, it may be desired to bring the temperature of the void portion  30  down to a range of 1100° F. to 1200° F. in a time period of 30 to 180 seconds. After all void portions  30  have been filled, the cylinder head  10  may be cooled, preferably, at a rate slow enough to avoid distortion or cracking of the component. The plugs  40  and dams  50  may then be removed as shown in  FIG. 2   d . The cylinder head  10  may then be machined to original specifications to form necessary valve seats (not shown) and fuel injector openings (not shown) such that the cylinder head  10  may be assembled for use.