Patent Publication Number: US-2021177195-A1

Title: &#34;Cookware Having a Graphite Core&#34;

Description:
BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure relates generally to multi-ply, bonded cookware, and in particular to multi-ply, bonded cookware having a core layer of perforated graphite between at least two metal layers metallurgically bonded together. A method for making the cookware using a solid state bonding technique is also disclosed. 
     Description of Related Art 
     It has long been known to manufacture multi-layer bonded composite cookware in which various materials are joined together to combine the desired physical properties of each of the materials into a composite. For example, the corrosion resistance of stainless steel is desirable for the cooking surface as well as for the exterior surface of cookware; however, the thermal conductivity of stainless steel is relatively low. On the other hand, aluminum and/or copper offer comparably higher thermal conductivities and have been bonded to stainless steel to provide well-known composite cookware items such as pots, pans, and the like. Multi-layer bonded cookware is known in the art, as shown in a number of patents, such as, for example: U.S. Pat. Nos. 4,246,045 and 4,167,606 to Ulam; and U.S. Pat. Nos. 8,133,596 and 6,267,830 to Groll. These references demonstrate the manufacture of multi-layer bonded cookware having stainless steel outer layers bonded to central layer(s) of a higher conductivity aluminum and/or copper. The bonding between layers of these different materials is commonly achieved by conventional roll-bonding techniques using strips of aluminum and/or copper, roll-bonded to outer strips of stainless steel. 
     A solid state bonding technique using high static pressure and heat applied over time to make a plurality of composite blanks of, for example, a combination of stainless steel—aluminum—stainless steel in manufactured cookware, is disclosed in U.S. Pat. No. 9,078,539 to Groll et al. There is a continued need in the art for producing cookware made using solid state bonding techniques for reducing the weight and improving thermal characteristics of the cookware. 
     SUMMARY OF THE DISCLOSURE 
     In view of the existing need in the art, it is desirable to develop new methods of producing cookware using solid state bonding techniques. It is further desirable to provide cookware made by such methods, wherein the cookware has reduced weight and improved thermal characteristics over existing cookware made by solid state bonding techniques. 
     In accordance with some embodiments or aspects of the present disclosure, cookware made from a bonded multi-layer blank assembly may have a first metal layer; a second metal layer having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; and a perforated graphite layer having a thickness of at least 0.010 in. (0.254 mm) and a plurality of spaced-apart holes formed therethrough. The perforated graphite layer may be positioned within the cavity of the second metal layer such that the plurality of spaced-apart posts extends through the plurality of spaced-apart holes. The second metal layer may be metallurgically bonded to the first metal layer at least via the plurality of spaced-apart posts. 
     In accordance with some embodiments or aspects of the present disclosure, a surface of the second metal layer surrounding the cavity may be metallurgically bonded to the first metal layer. Preferably said surface would be planar. A depth of the cavity may be smaller, the same, or larger than the thickness of the perforated graphite layer. The plurality of spaced-apart posts may have a circular cross-section or a polygonal cross-section. 
     In accordance with some embodiments or aspects of the present disclosure, the perforated graphite layer may be made from anisotropic graphite. The first metal layer may be made of aluminum, stainless steel, or titanium. The second metal layer may be made of aluminum. 
     In accordance with some embodiments or aspects of the present disclosure, a third metal layer may be metallurgically bonded to a planar side of the second metal layer opposite the cavity. The third metal layer may be made of stainless steel. 
     In accordance with some embodiments or aspects of the present disclosure, the second metal layer may have an outer metal layer and a central metal layer received within a central opening of the outer metal layer. The cavity may be provided on the central metal layer. The outer metal layer may be thinner than the central metal layer. 
     In accordance with some embodiments or aspects of the present disclosure, the first metal layer may have a first sub-layer made of aluminum bonded to the spaced-apart posts and a second sub-layer made of stainless steel. The second metal layer may be metallurgically bonded to the first sub-layer of the first metal layer. A surface of the second metal layer surrounding the cavity may be metallurgically bonded to the first sub-layer of the first metal layer. Preferably said surface would be planar. 
     In accordance with some embodiments or aspects of the present disclosure, a method of making cookware may include (a) providing a first metal layer; (b) providing a perforated graphite layer having a thickness of at least 0.010 in. (0.254 mm) and a plurality of spaced-apart holes formed therethrough, (c) providing a second metal layer having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; (d) stacking the layers provided in (a)-(c) in a blank assembly such that the perforated graphite layer is received within the cavity of the second metal layer whereby the plurality of spaced-apart posts of the second metal layer are aligned with and pass through the plurality of spaced-apart holes in the perforated graphite layer such that a lower surface of the first metal layer contacts at least an upper surface of upper end portions of the plurality of spaced-apart posts; and (e) pressing the blank assembly by applying a force in a direction perpendicular to a plane of the layers in the blank assembly and concurrently heating the blank assembly to achieve a metallurgical bond between the first metal layer and the second metal layer at least via the plurality of spaced-apart posts to provide a bonded blank assembly. 
     In accordance with some embodiments or aspects of the present disclosure, the method may further include (f) cooling the bonded blank assembly; and (g) forming the bonded blank assembly into the cookware. The first metal layer may be made of aluminum, stainless steel, or titanium, and the second metal layer may be made of aluminum. 
     In accordance with some embodiments or aspects of the present disclosure, the method may further include (h) providing a third metal layer and stacking the third metal layer with the layers of the blank assembly prior to pressing the blank assembly such that the third metal layer faces a planar side of the second metal layer opposite the cavity. 
     In accordance with some embodiments or aspects of the present disclosure, the method may further include (i) providing a fourth metal layer and stacking the fourth metal layer on top of the first metal layer of the blank assembly prior to pressing the blank assembly. The third metal layer and the fourth metal layer may be made of stainless steel. 
     These and other features and characteristics of the cookware described herein, as well as methods of making such cookware, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting. Further, it is to be understood that the disclosure may assume various alternative variations and step sequences, except where expressly specified to the contrary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded side cross-sectional view of a blank assembly for making cookware in accordance with some embodiments or aspects of the present disclosure; 
         FIG. 2  is an assembled side cross-sectional view of the blank assembly of  FIG. 1 ; 
         FIG. 3  is an enlarged view of Detail A shown in  FIG. 2 ; 
         FIG. 4  is a top view of an intermediate layer shown in  FIG. 1   
         FIG. 5  is a cross-sectional view of a formed fry pan shape made from the bonded blank assembly of  FIG. 1 ; 
         FIG. 6  is an enlarged view of Detail B shown in  FIG. 5 ; 
         FIG. 7  is an enlarged view of Detail C shown in  FIG. 5 ; 
         FIG. 8  is an exploded side cross-sectional view of a blank assembly for making cookware in accordance with some embodiments or aspects of the present disclosure; 
         FIG. 9  is an assembled side cross-sectional view of the blank assembly of  FIG. 8 ; 
         FIG. 10  is an enlarged view of Detail D shown in  FIG. 9 ; 
         FIG. 11  is a cross-sectional view of a formed fry pan shape made from the bonded blank assembly of  FIG. 8 ; 
         FIG. 12  is an enlarged view of Detail E shown in  FIG. 11 ; 
         FIG. 13  is an enlarged view of Detail F shown in  FIG. 11 ; 
         FIG. 14  is an exploded side cross-sectional view of a blank assembly for making cookware in accordance with some embodiments or aspects of the present disclosure; 
         FIG. 15  is an assembled side cross-sectional view of the blank assembly of  FIG. 14 ; 
         FIG. 16  is an enlarged view of Detail G shown in  FIG. 15 ; 
         FIG. 17  is a cross-sectional view of a formed fry pan shape made from the bonded blank assembly of  FIG. 14 ; 
         FIG. 18  is an enlarged view of Detail H shown in  FIG. 17 ; 
         FIG. 19  is an enlarged view of Detail I shown in  FIG. 17 ; 
         FIG. 20  is an exploded side cross-sectional view of a blank assembly for making cookware in accordance with some embodiments or aspects of the present disclosure; 
         FIG. 21  is an assembled side cross-sectional view of the blank assembly of  FIG. 20 ; and 
         FIG. 22  is an enlarged view of Detail J shown in  FIG. 21 . 
     
    
    
     In  FIGS. 1-22 , the same characters represent the same components unless otherwise indicated. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     As used in the specification and the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
     For purposes of the description hereinafter, the terms “end”, “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal” and derivatives thereof shall relate to the disclosure as it is oriented in the drawing figures. However, it is to be understood that the disclosure may assume various alternative variations and step sequences, except where expressly specified to the contrary. 
     All numbers and ranges used in the specification and claims are to be understood as being modified in all instances by the term “about”. By “about” is meant plus or minus twenty-five percent of the stated value, such as plus or minus ten percent of the stated value. However, this should not be considered as limiting to any analysis of the values under the doctrine of equivalents. 
     Unless otherwise indicated, all ranges or ratios disclosed herein are to be understood to encompass the beginning and ending values and any and all subranges or subratios subsumed therein. For example, a stated range or ratio of “1 to 10” should be considered to include any and all subranges or subratios between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges or subratios beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less. The ranges and/or ratios disclosed herein represent the average values over the specified range and/or ratio. 
     All documents, such as but not limited to issued patents and patent applications, referred to herein, and unless otherwise indicated, are to be considered to be “incorporated by reference” in their entirety. 
     The terms “first”, “second”, and the like are not intended to refer to any particular order or chronology, but refer to different conditions, properties, or elements. 
     The term “at least” is synonymous with “greater than or equal to”. 
     As used herein, “at least one of” is synonymous with “one or more of”. For example, the phrase “at least one of A, B, and C” means any one of A, B, or C, or any combination of any two or more of A, B, or C. For example, “at least one of A, B, and C” includes one or more of A alone; or one or more of B alone; or one or more of C alone; or one or more of A and one or more of B; or one or more of A and one or more of C; or one or more of B and one or more of C; or one or more of all of A, B, and C. 
     The term “includes” is synonymous with “comprises”. 
     As used herein, the terms “parallel” or “substantially parallel” mean a relative angle as between two objects (if extended to theoretical intersection), such as elongated objects and including reference lines, that is from 0° to 5°, or from 0° to 3°, or from 0° to 2°, or from 0° to 1°, or from 0° to 0.5°, or from 0° to 0.25°, or from 0° to 0.1°, inclusive of the recited values. 
     As used herein, the terms “perpendicular” or “substantially perpendicular” mean a relative angle as between two objects at their real or theoretical intersection is from 85° to 90°, or from 87° to 90°, or from 88° to 90°, or from 89° to 90°, or from 89.5° to 90°, or from 89.75° to 90°, or from 89.9° to 90°, inclusive of the recited values. 
     As used herein, the term “solid state bonding” means a method of bonding two or more stacked layers of metals or metal alloys together using high pressure (typically over 5,000 psi (34.5 MPa)) and high temperature (typically over 600° F. (315° C.)), wherein the high pressure is applied in a normal or perpendicular direction, i.e., 90° relative to the plane of the stacked layers. 
     As used herein, the term “metallurgical bonding” or “metallurgically bonded” refers to a bond formed between similar or dissimilar metal materials that is free of voids or discontinuities at a bonding interface. 
     With reference to the drawings,  FIGS. 1-3  depict various views of a blank assembly  100  used in making some embodiments of cookware described in the present disclosure. In some embodiments or aspects, each blank assembly  100  may be used to form a piece of cookware, such as a pot or a frying pan depicted in  FIGS. 5-7 . As discussed herein, the blank assembly  100  is formed from a plurality of stacked discs or layers that are metallurgically bonded together to form an integral blank assembly  100 . In some embodiments or aspects, the plurality of stacked discs or layers may be stacked such that the individual discs are substantially parallel to each other. The stacked assembly of discs or layers may then be bonded together using a solid state bonding technique, wherein the stacked discs or layers are bonded using high pressure (typically over 5,000 psi (34.5 MPa)) and high temperature (typically over 600° F. (315° C.)). Desirably, the high pressure is applied in a perpendicular direction, i.e., 90° relative to the plane of the stacked discs or layers. The bonded discs or layers constitute a bonded multi-layer blank assembly  100 . Bonded multi-layer blank assembly  100  is shown on  FIGS. 2-3 . 
     With continued reference to  FIGS. 1-3 , the blank assembly  100  has at least one upper (first) metal disc or layer  102  (hereinafter referred to as “first metal layer  102 ”) and at least one lower (third) metal disc or layer  104  (hereinafter referred to as “third metal layer  104 ”). A second disc or layer  106  (hereinafter referred to as “second layer  106 ”) is disposed between the first metal layer  102  and the third metal layer  104 . An upper or top surface of the first metal layer  102  forms an inner surface of the cookware while a lower or bottom surface of the third metal layer  104  forms an outer surface of the cookware. In some embodiments or aspects, the arrangement of layers in the blank assembly  100  can be flipped 180° such that a lower or bottom surface of the first metal layer  102  forms the outer surface of the cookware and an upper or top surface of the third metal layer  104  forms the inner surface of the cookware. 
     With continued reference to  FIGS. 1-3 , the material from which the first metal layer  102  is selected to have desirable scratch resistance, wear, and thermal properties required for a cooking surface of the cookware. In some embodiments or aspects, the first metal layer  102  may be formed from a food-grade stainless steel. The stainless steel of the first metal layer  102  may be, for example, a 400 series stainless steel, such as a 436 stainless steel, or 300 series stainless steel, such as a 304 stainless steel. In some embodiments or aspects, the stainless steel of the first metal layer  102  may be any corrosion-resistant stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the first metal layer  102  may be made from a titanium alloy suitable for use as a food preparation surface. The material of the first metal layer  102  may be aluminum. In some embodiments or aspects, the material of the first metal layer  102  may be, for example, a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on one or both sides to accommodate metallurgical bonding. In some embodiments or aspects, the material of the first metal layer  102  may be a 1000 series aluminum alloy, such as an 1100 aluminum alloy. 
     In some embodiments or aspects, the first metal layer  102  may be a disc having a diameter of about 14 inches (355.6 mm) to form a near-net size blank for making a fry pan of 10 inches (254 mm) in diameter. In other embodiments or aspects, the first metal layer  102  may be a disc having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) to form cookware of various sizes. The diameter of the first metal layer  102  is selected to be large enough to form the bottom, sidewalls, and rim of the finished cookware. The diameter of the first metal layer  102  is selected such that it matches the diameter of at least one of the second layer  106  and the third metal layer  104 . In some embodiments or aspects, a thickness of the first metal layer  102  may be about 0.010 inches (0.25 mm) to about 0.025 inches (0.65 mm), such as about 0.015 inches (0.40 mm). One of ordinary skill in the art would readily appreciate that the diameter and thickness of the first metal layer  102  can be increased or decreased to make fry pans of larger or smaller diameter and thickness, respectively. 
     In some embodiments or aspects, such as shown in  FIGS. 20-22 , the blank assembly  100  may include a fourth metal layer  140  stacked on the first metal layer  102 . The first metal layer  102  may be made from a material that has a bonding affinity to the metal materials of the fourth metal layer  140  and of the second layer  106 , as discussed herein. In further embodiments or aspects, the blank assembly  200 ,  300  (shown in  FIGS. 8-10 and 14-16 ) may also include a fourth metal layer (not shown) stacked on the first metal layer  202 ,  302 . The material of the first metal layer  102 ,  202 ,  302  may be aluminum. In some embodiments or aspects, the material of the first metal layer  102 ,  202 ,  302  may be, for example, a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the material of the first metal layer  102 ,  202 ,  302  may be a 1000 series aluminum alloy, such as an 1100 aluminum alloy. In some embodiments or aspects, a thickness of the first metal layer  102 ,  202 ,  302  may be about 0.020 inches (0.5 mm) to about 0.100 inches (2.5 mm), such as about 0.040 inches (1.0 mm). 
     With continued reference to  FIGS. 20-22 , the material of the fourth metal layer  140  is selected to have desirable scratch resistance, wear, and thermal properties required for a cooking surface of the cookware. In some embodiments or aspects, the material of the fourth metal layer  140  may be a food-grade stainless steel. The stainless steel of the fourth metal layer  140  may be, for example, a 400 series stainless steel, such as a 436 stainless steel, or 300 series stainless steel, such as a 304 stainless steel. In some embodiments or aspects, the stainless steel of the fourth metal layer  140  may be any corrosion-resistant stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the fourth metal layer  140  may be made from a titanium alloy suitable for use as a food preparation surface. In some embodiments or aspects, a thickness of the fourth metal layer  140  may be about 0.010 inches (0.25 mm) to about 0.025 inches (0.65 mm), such as about 0.015 inches (0.4 mm). 
     In some embodiments or aspects, the third metal layer  104  may be made from a material that has desirable scratch resistance, wear, and thermal properties required for an outside surface of the cookware. The material of the third metal layer  104  is selected such that it has a bonding affinity to the metal material of at least a portion of the second layer  106 , as discussed herein. In some embodiments or aspects, the third metal layer  104  may be made of a ferro-magnetic stainless steel, such as a 400 grade, in order to make the finished cookware suitable for use on an induction cooking apparatus. The stainless steel of the third metal layer  104  may be, for example, a magnetic grade of stainless steel, such as a 430 stainless steel. In some embodiments or aspects, the stainless steel of the third metal layer  104  may be any stainless steel alloy suitable for use as a food preparation surface. In further embodiments or aspects, the third metal layer  104  may be made from a titanium alloy suitable for use as a food preparation surface. The material of the third metal layer  104  may be selected to have similar or identical material properties to that of the first metal layer  102 . 
     In some embodiments or aspects, the third metal layer  104  may be a disc having a diameter of about 14 inches (355.6 mm) to form a near-net size blank for making a fry pan of 10 inches (254 mm) in diameter. In other embodiments or aspects, the third metal layer  104  may be a disc having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) to form cookware of various sizes. The diameter of the third metal layer  104  is selected to be large enough to form the bottom, sidewalls, and rim of the finished cookware. In some embodiments or aspects, a thickness of the third metal layer  104  may be about 0.010 inches (0.25 mm) to about 0.025 inches (0.6 mm), such as about 0.015 inches (0.4 mm). One of ordinary skill in the art would readily appreciate that the diameter and thickness of the third metal layer  104  can be increased or decreased to make fry pans of larger or smaller diameter and thickness, respectively. A bottom surface  124  of the third metal layer  104  may be substantially planar and without any protrusions or recesses. 
     With continued reference to  FIGS. 1-3 , the second layer  106  is disposed between the first metal layer  102  and the third metal layer  104 . The second layer  106  has a perforated graphite disc or layer  108  (hereinafter referred to as “perforated graphite layer  108 ”) having a plurality of spaced-apart holes  114  formed therethrough. The second layer  106  further has a second metal disc or layer  110  (hereinafter referred to as “second metal layer  110 ”) having a cavity  112  configured to receive the perforated graphite layer  108 . 
     In some embodiments or aspects, the second metal layer  110  may be made from a material that has a bonding affinity to the metal materials of the first metal layer  102  and the third metal layer  104 , as discussed herein. The material of the second metal layer  110  may be aluminum. In some examples or aspects, the second metal layer  110  may be made from a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the second metal layer  110  may be made of, for example, a 1000 series aluminum alloy, such as an 1100 aluminum alloy. 
     In some embodiments or aspects, the second metal layer  110  may be a disc having a diameter of about 14 inches (355.6 mm) to form a near-net size blank for making a fry pan of 10 inches (254 mm) in diameter. In other embodiments or aspects, the second metal layer  110  may be a disc having a diameter of about 5 inches to about 20 inches (127 mm to 508 mm) to form cookware of various sizes. The diameter of the second metal layer  110  is selected to be large enough to form the bottom, sidewalls, and rim of the finished cookware. In some embodiments or aspects, a thickness of the second metal layer  110  may be about 0.020 inches (0.5 mm) to about 0.200 inches (5.0 mm), such as about 0.040 inches (1.0 mm). One of ordinary skill in the art would readily appreciate that the diameter and thickness of the second metal layer  110  can be increased or decreased to make fry pans of larger or smaller diameter and thickness, respectively. A bottom surface  126  of the second metal layer  110  may be substantially planar and without any protrusions or recesses. 
     In some embodiments or aspects, the cavity  112  may have a circular shape having a diameter that is the same or slightly larger than a diameter of a circularly-shaped perforated graphite layer  108 . For example, the cavity  112  may have a diameter of about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). The perforated graphite layer  108  may have a corresponding diameter of about 90-99.9% of the diameter of the cavity  112 . In other embodiments or aspects, the cavity  112  may have any desired geometric shape that corresponds to any desired geometric shape of the perforated graphite layer  108 . The cavity  112  may have depth (i.e. distance at which the cavity  112  is recessed relative to an upper surface  120  of the second metal layer  110 ) of about 0.010 inches (0.25 mm) to about 0.100 inches (2.5 mm), such as about 0.020 inches (0.5 mm). The cavity may have a uniform depth or a non-uniform depth, wherein the depth varies over at least a portion of the cavity  112 . In some embodiments or aspects, the cavity  112  may be centered on the second metal layer  110  such that the cavity  112  and the second metal layer  110  share a common axis. One of ordinary skill in the art would readily appreciate that the diameter and depth of the cavity  112  can be increased or decreased to accommodate a larger and thicker perforated graphite layer  108 , respectively. 
     The second metal layer  110  has a plurality of upwardly protruding, spaced-apart posts  116  (hereinafter referred to as “posts  116 ”) within the cavity  112 . The posts  116  extend upwardly from a bottom surface  118  of the cavity  112  which is recessed relative to an upper surface  120  of the second metal layer  110 . As shown in  FIG. 4 , the posts  116  may be arranged in an ordered array or distributed randomly within the cavity  112 . For example, the posts  116  may be arranged in a circular array with an equal or unequal spacing between adjacent posts  116 . In various embodiments or aspects, the density of the posts  116  (i.e., number of posts  116  per unit area) may be uniform across the cavity  112 , or it may vary between different portions of the cavity. For example, the density of the posts  116  may increase or decrease in a radial direction of the cavity  112 . In some embodiments or aspects, the posts  116  may be provided in one or more groupings of posts  116 . The posts  116  may have the same size (i.e., diameter) or a different size relative to each other. 
     With reference to  FIG. 4 , the cavity  112  and the posts  116  may be formed by removing the material from the upper surface  120  of the second metal layer  110 , such as by milling. In some embodiments or aspects, the cavity  112  and the posts  116  may be cast using a mold. The posts  116  may have a circular cross-sectional shape, a polygonal shape (such as a hexagonal shape), or any other geometric shape. 
     In some embodiments or aspects, the posts  116  may have a height of about 0.010 inches (0.254 mm) to about 0.100 inches (2.54 mm), such as about 0.020 inches (0.508 mm) above the bottom surface  118  of the cavity  112 . In some embodiments or aspects, the height of the posts  116  is selected to be slightly higher than a thickness of the perforated graphite layer  108  such that peaks of the posts  116  protrude through the holes in the perforated graphite layer  108 , as described herein. In embodiments or aspects where the posts  116  have a circular shape, the posts  116  may have a diameter of about 0.050 inches (1.27 mm) to about 0.250 inches (6.35 mm), such as about 0.125 inches (3.175 mm). In other embodiments or aspects where the posts  116  have a non-circular shape, the posts  116  may have a surface area of about 0.002 in 2  (1.3 mm 2 ) to about 0.050 in 2  (32 mm 2 ), such as about 0.12 in 2  (7.9 mm 2 ). In some embodiments or aspects, the posts  116  may have a uniform width or diameter along their longitudinal length measured in a direction from the bottom surface  118  of the cavity  112  toward the upper surface  120 . In other embodiments or aspects, the width or diameter of the posts may narrow or widen in a direction from the bottom surface  118  of the cavity  112  toward the upper surface  120 . 
     In some embodiments or aspects, the perforated graphite layer  108  may be made of anisotropic graphite that is configured to transmit thermal energy primarily in a radial (rather than axial) direction. In this manner, the cooking surface can be heated uniformly, while avoiding hot spots. Graphite is preferably selected due to its high coefficient of thermal conductivity (approximately 500-1500 W/mK versus approximately 220 W/mK for aluminum and 340 W/mK for copper). Anisotropic graphite can have approximately 2-6 times the thermal conductivity compared to copper in a direction of the XY plane defining the cooking surface. The anisotropic graphite is also approximately ⅙ the weight of copper and acts as an insulator in the Z direction (i.e., substantially perpendicular to the cooking surface) compared to copper. The low conductivity in the Z direction (approximately 100 times less than in the XY plane) acts as a thermal dam that momentarily impedes the direct flowthrough of heat from the heat source to the food preparation surface, thus giving the heat energy additional time to evenly spread along the cooking surface. The perforated graphite layer  108  is effective in spreading heat evenly across the cooking surface while impeding heat flow in a direction perpendicular to the cooking surface. Without intending to be bound by theory, it has been found that the presence of the perforated graphite layer  108  increases the resistance to current flow, thereby increasing the induction heating effectiveness compared to cookware without the perforated graphite layer  108 . 
     In some embodiments or aspects, the perforated graphite layer  108  may have a circular shape with a diameter of about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). As noted herein, the perforated graphite layer  108  may have a corresponding diameter of about 90-99.9% of the diameter of the cavity  112 . In other embodiments or aspects, the perforated graphite layer  108  may have any desired geometric shape that corresponds to any desired geometric shape of the cavity  112 . The perforated graphite layer  108  may have a thickness of about 0.010 inches (0.25 mm) to about 0.100 inches (2.5 mm), such as about 0.020 inches (0.5 mm). The perforated graphite layer  108  may have a minimum thickness of about 0.010 inches (0.25 mm). Without intending to be bound by theory, it has been found that the perforated graphite layer  108  with a thickness below the minimum thickness may be damaged during the solid state bonding process, thereby compromising its ability to evenly distribute heat along the cooking surface of the cookware. Furthermore, the perforated graphite layer  108  having at least the minimum thickness is easier to handle and cheaper to manufacture than perforated graphite layers with a smaller thickness than the minimum thickness, thereby reducing the overall cost of the cookware. In addition, the perforated graphite layer  108  having at least the minimum thickness is configured to move more energy in the plane defining the cooking surface than perforated graphite layer having a smaller thickness than the minimum thickness. In some embodiments or aspects, the thickness of the perforated graphite layer  108  is selected to be smaller than a height of the posts  116  of the second metal layer  110 . In this manner, upper surface of the perforated graphite layer  108  may be recessed within the cavity  112  relative to the upper surface  120  of the second metal layer  110  and the peaks of the posts  116 . 
     In some embodiments or aspects, the thickness of the perforated graphite layer  108  is selected to be smaller than a height of the posts  116 /depth of the cavity  112  of the second metal layer  110 . In this manner, upper surface of the perforated graphite layer  108  may be recessed within the cavity  112  relative to the upper surface  120  of the second metal layer  110  and the peaks of the posts  116 . In other embodiments or aspects, the thickness of the perforated graphite layer  108  is selected to be the same as the height of the posts  116 /depth of the cavity  112 . In further embodiments or aspects, the thickness of the perforated graphite layer  108  may be selected to be slightly larger than a height of the posts  116 /depth of the cavity  112  of the second metal layer  110 . In this manner, upper surface of the perforated graphite layer  108  may protrude slightly from the cavity  112  relative to the upper surface  120  of the second metal layer  110  and the peaks of the posts  116 . Due to the perforated graphite layer  108  being more compressible than the first and second metal layers  102 ,  110 , the perforated graphite layer  108  is compressed into the cavity  112  during the solid state bonding process. 
     With continued reference to  FIGS. 1-3 , each of the holes  114  extends through the material of the perforated graphite layer  108  between its upper surface and its lower surface. The size and arrangement of the holes  114  in the perforated graphite layer  108  is selected to correspond to the size and arrangement of the posts  116  on the second metal layer  110 . In this manner, the posts  116  can be arranged such that all of the posts  116  are registered (i.e., in alignment) with all of the holes  114 , with each post  116  being received within the respective hole  114 . For example, in embodiments where the posts  116  are arranged in a circular array with a uniform spacing of posts  116  across the cavity  112  of the second metal layer  110 , the holes  114  have a corresponding circular array arrangement such that the posts  116  can be received within the holes  114 . The holes  114  are shaped such that a single post  116  may be received within a single hole  114 . In some embodiments or aspects, a plurality of posts  116  may be received within a single hole  114 . In further embodiments or aspects, the number of holes  114  may be larger than the number of posts  116 , such that some holes  114  do not have posts  116  therein. 
     The holes  114  may have the same or different shape as the posts  116 . For example, the holes  114  may have a circular shape to receive a circular or a non-circular post  116 . In embodiments or aspects where the holes  114  have a circular shape, the holes  114  may have a diameter of about 0.050 inches (1.27 mm) to about 0.250 inches (6.35 mm), such as about 0.125 inches (3.175 mm). The holes  114  may have the same or different size and shape. 
     With reference to  FIGS. 8-10 , a blank assembly  200  is shown in accordance with another embodiment or aspect of the present disclosure. The components of the blank assembly  200  shown in  FIGS. 8-10  are substantially similar to the components of the blank assembly  100  described herein with reference to  FIGS. 1-3 . Reference numerals in  FIGS. 8-10  are used to illustrate identical components of the corresponding reference numerals in  FIGS. 1-3 , with the exception that the first digit of each reference number is replaced with a number  2 . For example, whereas the first metal layer shown in  FIGS. 1-3  is identified by a reference number  102 , the same first metal layer shown in  FIGS. 8-10  is identified by reference number  202 . As the previous discussion regarding the components of the blank assembly  100  generally shown in  FIGS. 1-3  is applicable to the blank assembly  200  shown in  FIGS. 8-10 , only the relative differences between the two blank assemblies are discussed hereinafter. Bonded multi-layer blank assembly  200  is shown on  FIGS. 9-10 . 
     With reference to  FIGS. 8-10 , the blank assembly  200  has at least one upper (first) metal disc or layer  202  (hereinafter referred to as “first metal layer  202 ”) and at least one lower (second) metal disc or layer  210  (hereinafter referred to as “second metal layer  210 ”). A core disc or layer  206  (hereinafter referred to as “core layer  206 ”) is disposed between the first metal layer  202  and the second metal layer  210 . An upper or top surface of the first metal layer  202  forms an inner surface of the cookware while a lower or bottom surface of the second metal layer  210  forms an outer surface of the cookware. 
     The first metal layer  202  may be formed from a food-grade stainless steel, such as a 400 series stainless steel, such as 436 stainless steel, or a 300 series stainless steel, such as a 304 stainless steel, or from a titanium alloy suitable for use as a food preparation surface. The material of the first metal layer  202  may be aluminum. In some embodiments or aspects, the first metal layer  202  may be formed from a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the first metal layer  202  may be made of, for example, a 1000 series aluminum alloy, such as an 1100 aluminum alloy. The material of the second metal layer  210  is selected such that it has a bonding affinity to the metal material of the first metal layer  202 . The material of the second metal layer  210  may be aluminum. In some embodiments or aspects, the second metal layer  210  may be made of, for example, a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the second metal layer  210  may be made of, for example, a 1000 series aluminum alloy, such as an 1100 aluminum alloy. A bottom surface  224  of the second metal layer  210  may be substantially planar and without any protrusions or recesses. 
     With continued reference to  FIGS. 8-10 , the core layer  206  is disposed between the first metal layer  202  and the second metal layer  210 . The core layer  206  is a perforated graphite disc or layer  208  (hereinafter referred to as “perforated graphite layer  208 ”) having a plurality of spaced-apart holes  214  formed therethrough. Whereas the second layer  106  in  FIGS. 1-3  has a second metal layer  110  and a perforated graphite layer  108  received within a cavity  112  on the second metal layer  110 , the core layer  206  in  FIGS. 8-10  only has the perforated graphite layer  208 . The perforated graphite layer  208  is configured for being received within a cavity  212  that is recessed relative to an upper surface  220  of the second metal layer  210 . 
     In some embodiments or aspects, the cavity  212  may have a circular shape having a diameter that is the same or slightly larger than a diameter of a circularly-shaped perforated graphite layer  208 . In other embodiments or aspects, the cavity  212  may have any desired geometric shape that corresponds to any desired geometric shape of the perforated graphite layer  208 . In some embodiments or aspects, the cavity  212  may be centered on the second metal layer  210  such that the cavity  212  and the second metal layer  210  share a common axis. 
     With continued reference to  FIGS. 8-10 , a plurality of spaced-apart posts  216  (hereinafter referred to as “posts  216 ”) protrude upwardly from a bottom surface  218  of the cavity  212 . Similar to the posts  116  shown in  FIG. 4 , the posts  216  may be arranged in an ordered array or distributed randomly within the cavity  212 . The posts  216  may have a circular cross-sectional shape, a polygonal shape (such as a hexagonal shape), or any other geometric shape. 
     In some embodiments or aspects, the perforated graphite layer  208  may be made of anisotropic graphite that is configured to transmit thermal energy primarily in a radial (rather than axial) direction. In this manner, the cooking surface can be heated uniformly, while avoiding hot spots. As described herein with the embodiment shown in  FIGS. 1-4 , the perforated graphite layer  208  may have a minimum thickness of about 0.010 inches (0.25 mm). Without intending to be bound by theory, it has been found that the perforated graphite layer  208  with a thickness below the minimum thickness may be damaged during the solid state bonding process, thereby compromising its ability to evenly distribute heat along the cooking surface of the cookware. Furthermore, the perforated graphite layer  208  having at least the minimum thickness is easier to handle and cheaper to manufacture than perforated graphite layers with a smaller thickness than the minimum thickness, thereby reducing the overall cost of the cookware. In addition, the perforated graphite layer  208  having at least the minimum thickness is configured to move more energy in the plane defining the cooking surface than perforated graphite layer having a smaller thickness than the minimum thickness. In some embodiments or aspects, the thickness of the perforated graphite layer  208  is selected to be smaller than a height of the posts  216 /depth of the cavity  212  of the second metal layer  210 . In this manner, upper surface of the perforated graphite layer  208  may be recessed within the cavity  212  relative to the upper surface  220  of the second metal layer  210  and the peaks of the posts  216 . In other embodiments or aspects, the thickness of the perforated graphite layer  208  is selected to be the same as the height of the posts  216 /depth of the cavity  212 . In further embodiments or aspects, the thickness of the perforated graphite layer  208  may be selected to be slightly larger than a height of the posts  216 /depth of the cavity  212  of the second metal layer  210 . In this manner, upper surface of the perforated graphite layer  208  may protrude slightly from the cavity  212  relative to the upper surface  220  of the second metal layer  210  and the peaks of the posts  216 . Due to the perforated graphite layer  208  being more compressible than the first and second metal layers  202 ,  210 , the perforated graphite layer  208  is compressed into the cavity  212  during the solid state bonding process. 
     With continued reference to  FIGS. 8-10 , each of the holes  214  extends through the material of the perforated graphite layer  208  between its upper surface and its lower surface. The size and arrangement of the holes  214  in the perforated graphite layer  208  is selected to correspond to the size and arrangement of the posts  216  on the second metal layer  210 . In this manner, the posts  216  can be arranged such that all of the posts  216  are registered (i.e., in alignment) with all of the holes  214 , with each post  216  being received within the respective hole  214 . In some embodiments or aspects, a plurality of posts  216  may be received within a single hole  214 . In further embodiments or aspects, the number of holes  214  may be larger than the number of posts  216 , such that some holes  214  do not have posts  216  therein. The holes  214  may have the same or different shape as the posts  216 . 
     With reference to  FIGS. 14-16 , a blank assembly  300  is shown in accordance with another embodiment or aspect of the present disclosure. The components of the blank assembly  300  shown in  FIGS. 14-16  are substantially similar to the components of the blank assembly  100  described herein with reference to  FIGS. 1-3 . Reference numerals in  FIGS. 14-16  are used to illustrate identical components of the corresponding reference numerals in  FIGS. 1-3 , with the exception that the first digit of each reference number is replaced with a number  3 . For example, whereas the first metal layer shown in  FIGS. 1-3  is identified by a reference number  102 , the same first metal layer shown in  FIGS. 14-16  is identified by reference number  302 . As the previous discussion regarding the components of the blank assembly  100  generally shown in  FIGS. 1-3  is applicable to the blank assembly  300  shown in  FIGS. 14-16 , only the relative differences between the two blank assemblies are discussed hereinafter. Bonded multi-layer blank assembly  300  is shown on  FIGS. 15-16 . 
     With reference to  FIGS. 14-16 , the blank assembly  300  has at least one upper (first) metal disc or layer  302  (hereinafter referred to as “first metal layer  302 ”) and at least one lower (third) metal disc or layer  304  (hereinafter referred to as “third metal layer  304 ”). A second disc or layer  306  (hereinafter referred to as “second layer  306 ”) is disposed between the first metal layer  302  and the third metal layer  304 . An upper or top surface of the first metal layer  302  forms an inner surface of the cookware while a lower or bottom surface of the third metal layer  304  forms an outer surface of the cookware. 
     The first metal layer  302  may be formed from a food-grade stainless steel, such as a 400 or 436 series stainless steel, or from a titanium alloy suitable for use as a food preparation surface. The material of the third metal layer  304  is selected such that it has a bonding affinity to the metal material of at least a portion of the second layer  306 , as discussed herein. In some embodiments or aspects, the third metal layer  304  may be made from a food-grade stainless steel, such as a 400 or 436 series stainless steel, or from a titanium alloy. The material of the third metal layer  304  may be aluminum. In some embodiments or aspects, the material of the third metal layer  304  may be, for example, a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the material of the third metal layer  304  may be a 1000 series aluminum alloy, such as an 1100 aluminum alloy. A bottom surface  324  of the third metal layer  304  may be substantially planar and without any protrusions or recesses. 
     With continued reference to  FIGS. 14-16 , the second layer  306  is disposed between the first metal layer  302  and the third metal layer  304 . Whereas the second layer  106  in  FIGS. 1-3  has a second metal layer  110  and a perforated graphite layer  108  received within a cavity  112  of the second metal layer  110 , the second layer  306  in  FIGS. 14-16  comprises a second metal layer  310  and a perforated graphite disc or layer  308  (hereinafter referred to as “perforated graphite layer  308 ”). The second metal layer  310  has a central metal core disc or layer  310   a  (hereinafter referred to as “central metal layer  310   a ”), a ring-shaped outer core metal disc or layer  310   b  (hereinafter referred to as “outer metal layer  310   b ”) surrounding the central metal layer  310   a . Perforated graphite layer  308  is received within a cavity  312  of the second metal layer  310 . Cavity  312  is formed on the central metal layer  310   a . The material of the outer metal layer  310   a  and/or the central metal layer  310   b  may be aluminum. In some embodiments or aspects, the material of the outer metal layer  310   a  and/or the central metal layer  310   b  may be, for example, a high purity aluminum, or an alloyed aluminum material clad with thin pure layers of aluminum on either side to accommodate metallurgical bonding. In some embodiments or aspects, the material of the outer metal layer  310   a  and/or the central metal layer  310   b  may be a 1000 series aluminum alloy, such as an 1100 aluminum alloy. Thus, the material of the second metal layer  310  may be aluminum. 
     The outer metal layer  310   b  has a central opening  322  shaped to receive the central metal layer  310   a  therein. In some embodiments or aspects, the central opening  322  may have a circular shape with a diameter that is the same or slightly larger than a diameter of a circularly-shaped central metal layer  310   a . For example, the central opening  322  may have a diameter of about 3 inches (76.2 mm) to about 12 inches (305 mm), such as about 7 inches (178 mm). A thickness of the central metal layer  310   a  may the same or different than the thickness of the outer metal layer  310   b . For example, the central metal layer  310   a  may be thinner or thicker than the outer metal layer  310   b . In some embodiments or aspects, the central metal layer  310   a  is thicker (such as by 0.004 in (0.1 mm)) than the outer metal layer  310   b . In this manner, the additional material of the central metal layer  310   a  may be compressed during solid state bonding such that the upper and lower surfaces of the central metal layer  310   a  and the outer metal layer  310   b  are substantially planar. The compression of the additional material of the central metal layer  310   a  contributes to a stronger bond with the perforated graphite layer  308  during solid state bonding. Bottom surfaces  326   a ,  326   b  of the central metal layer  310   a  and the outer metal layer  310   b  may be substantially planar and without any protrusions or recesses. 
     With continued reference to  FIGS. 14-16 , the cavity  312  may have a circular shape having a diameter that is the same or slightly larger than a diameter of a circularly-shaped perforated graphite layer  308 . In other embodiments or aspects, the cavity  312  may have any desired geometric shape that corresponds to any desired geometric shape of the perforated graphite layer  308 . In some embodiments or aspects, the cavity  312  may be centered on the central metal layer  310   a  such that the cavity  312  and the central metal layer  310   a  share a common axis. 
     With continued reference to  FIGS. 14-16 , a plurality of spaced-apart posts  316  (hereinafter referred to as “posts  316 ”) protrude upwardly from a bottom surface  318  of the cavity  312 . Similar to the posts  116  shown in  FIG. 4 , the posts  316  may be arranged in an ordered array or distributed randomly within the cavity  312 . The posts  316  may have a circular cross-sectional shape, a polygonal shape (such as a hexagonal shape), or any other geometric shape. 
     In some embodiments or aspects, perforated graphite layer  308  has a plurality of spaced-apart holes  314  formed therethrough. Each of the holes  314  extends through the material of the perforated graphite layer  308  between its upper surface and its lower surface. The size and arrangement of the holes  314  in the perforated graphite layer  308  is selected to correspond to the size and arrangement of the posts  316  on the central metal layer  310   a . In this manner, the posts  316  can be arranged such that all of the posts  316  are registered (i.e., in alignment) with all of the holes  314 , with each post  316  being received within the respective hole  314 . In some embodiments or aspects, a plurality of posts  316  may be received within a single hole  314 . In further embodiments or aspects, the number of holes  314  may be larger than the number of posts  316 , such that some holes  314  do not have posts  316  therein. The holes  314  may have the same or different shape as the posts  316 . 
     The perforated graphite layer  308  may be made of anisotropic graphite that is configured to transmit thermal energy primarily in a radial (rather than axial) direction. In this manner, the cooking surface can be heated uniformly, while avoiding hot spots. As described herein, the perforated graphite layer  308  may have a minimum thickness of about 0.010 inches (0.25 mm). Without intending to be bound by theory, it has been found that the perforated graphite layer  308  with a thickness below the minimum thickness may be damaged during the solid state bonding process, thereby compromising its ability to evenly distribute heat along the cooking surface of the cookware. Furthermore, the perforated graphite layer  308  having the at least minimum thickness is easier to handle and cheaper to manufacture than perforated graphite layers with a smaller thickness, thereby reducing the overall cost of the cookware. In addition, the perforated graphite layer  308  having the minimum thickness is configured to move more energy in the plane defining the cooking surface than perforated graphite layer having a smaller thickness. In some embodiments or aspects, the thickness of the perforated graphite layer  308  is selected to be smaller than a height of the posts  316  of the central metal layer  310   a . In this manner, upper surface of the perforated graphite layer  308  may be recessed within the cavity  312  relative to the upper surface  320  of the central metal layer  310   a  and the peaks of the posts  316 . In other embodiments or aspects, the thickness of the perforated graphite layer  308  is selected to be the same as the height of the posts  316 /depth of the cavity  312 . In further embodiments or aspects, the thickness of the perforated graphite layer  308  may be selected to be slightly larger than a height of the posts  316 /depth of the cavity  312  of the second metal layer  310 . In this manner, upper surface of the perforated graphite layer  308  may protrude slightly from the cavity  312  relative to the upper surface  320  of the second metal layer  310  and the peaks of the posts  316 . Due to the perforated graphite layer  308  being more compressible than the first and second metal layers  302 ,  310 , the perforated graphite layer  308  is compressed into the cavity  312  during the solid state bonding process. 
     Having described the structure of the blank assembly  100 ,  200 ,  300  in accordance with various embodiments or aspects of the present disclosure, a method of making cookware using the bonded multi-layer blank assembly  100 ,  200 ,  300  will now be described. Prior to bonding, the layers of the blank assembly  100 ,  200 ,  300  undergo appropriate surface preparation steps, such as degreasing, surface abrasion by chemical or mechanical methods, and the like. After appropriate surface preparation, an unbonded blank assembly  100 ,  200 ,  300  is formed by stacking the various layers on top of each other. Desirably, the layers are aligned such that centers of each layer share a common axis. In some embodiments or aspects, the layers may be stacked such that their centers are offset from one another. For efficiency of manufacture, a plurality of unbonded blank assemblies  100 ,  200 ,  300  may be stacked on top of each other, with or without spacer layers between adjacent blank assemblies  100 ,  200 ,  300 . 
     In the case of the blank assembly  100  shown in  FIGS. 1-3 , the second layer  106  is stacked on the upper surface of the third metal layer  104 . The perforated graphite layer  108  of the second layer  106  is arranged within the cavity  112  of the second metal layer  110  such that the holes  114  in the perforated graphite layer  108  are aligned with the posts  116  in the cavity  112 . Peaks of the posts  116  are configured to be at a same height or extend above an upper surface of the perforated graphite layer  108  when the posts  116  are received within the holes  114  of the perforated graphite layer  108 . The first metal layer  102  is stacked on top of the second layer  106  such that a lower surface of the first metal layer  102  is positioned opposite an upper surface of the second metal layer  110  and the perforated graphite layer  108 . When stacked, the first metal layer  102 , the second layer  106 , and the third metal layer  104  are substantially parallel to each other. For efficiency of manufacture, a plurality of unbonded blank assemblies  100  may be stacked on top of each other, with or without spacer layers between adjacent blank assemblies  100 . 
     In the case of the blank assembly  200  shown in  FIGS. 8-10 , the core layer  206  (i.e., the perforated graphite layer  208 ) is arranged within the cavity  212  of the second metal layer  210  such that the holes  214  in the perforated graphite layer  208  are aligned with the posts  216  in the cavity  212 . Peaks of the posts  216  are configured to be at a same height or extend above an upper surface of the perforated graphite layer  208  when the posts  216  are received within the holes  214  of the perforated graphite layer  208 . The first metal layer  202  is stacked on top of the core layer  206  and the second metal layer  210  such that a lower surface of the first metal layer  202  is positioned opposite an upper surface  220  of the second metal layer  210  and the perforated graphite layer  208 . When stacked, the upper metal layer  22 , the perforated graphite layer  208 , and the second metal layer  210  are substantially parallel to each other. 
     In the case of the blank assembly  300  shown in  FIGS. 14-16 , the central metal layer  310   a  and the outer metal layer  310   b  are positioned on the upper surface of the third metal layer  304  such that the central metal layer  310   a  is received within the central opening  322  of the outer metal layer  310   b . The perforated graphite layer  308  is arranged within the cavity  312  of the central metal layer  310   a  such that the holes  314  in the perforated graphite layer  308  are aligned with the posts  316  in the cavity  312 . Peaks of the posts  316  are configured to be at a same height or extend above an upper surface of the perforated graphite layer  308  when the posts  316  are received within the holes  314  of the graphite layer  308 . The first metal layer  302  is stacked on top of the second layer  306  (i.e., the central metal layer  310   a , the outer metal layer  310   b , and the perforated graphite layer  308 ) such that a lower surface of the first metal layer  302  is positioned opposite an upper surface of the central metal layer  310   a , the outer metal layer  310   b , and the perforated graphite layer  108 . When stacked, the first metal layer  302 , the second layer  306 , and the third metal layer  304  are substantially parallel to each other. 
     The blank assembly  100 ,  200 ,  300  or a plurality of stacked blank assemblies  100 ,  200 ,  300  are then placed in a press apparatus (not shown) for application of a load or pressure in the normal or perpendicular direction relative to the planes of the layers in the blank assemblies  100 ,  200 ,  300  via a solid state bonding technique. The solid state bonding technique of bonding pre-cut near net shape plate blanks not only reduces scrap losses heretofore encountered in the conventional roll bonding manufacture of composite cookware but also permits the use of other materials in making multiple composites which have proven difficult, impossible and/or expensive to roll-bond. For example, solid state bonding permits the use of different grades of stainless steel than otherwise possible in conventional roll bonding so as to lower costs of materials. Furthermore, solid state bonding further allows encapsulating of materials, such as graphite, that cannot otherwise be bonded to stainless steel. 
     While under a pressure of between 5,000 and 20,000 psi (34.5-137.9 MPa), heat is applied to the blank assembly or assemblies  100 ,  200 ,  300  between about 500° F. and 1,000° F. (260-538° C.) for a sufficient time (about 1-4 hours) to achieve solid state bonding (i.e., metallurgical bonding) between the metal layers in the blank assembly or assemblies  100 ,  200 ,  300 . During the solid state bonding process, air that may be present between the posts of the core metal layer and the perforated graphite layer due to dimensional differences between the core metal layer and the perforated graphite layer is pressed out from the blank assembly  100 ,  200 ,  300 . 
     In the case of the blank assembly  100  shown in  FIGS. 1-3 , during the solid state bonding process, the lower surface of the second metal layer  110  is metallurgically bonded with the upper surface of the third metal layer  104 . The upper surface of the second metal layer  110  and the posts  116  are metallurgically bonded with the lower surface of the first metal layer  102 . The perforated graphite layer  108  is completely encapsulated between the second metal layer  110  and the first metal layer  102 , with the cavity  112  of the second metal layer  110  completely surrounding the perforated graphite layer  108  on its lower and lateral sides and the first metal layer  102  enclosing its upper side. 
     Each blank assembly  100 ,  200 ,  300  is then removed from the press apparatus and allowed to cool. In some embodiments or aspects, cooling may be accomplished by exposure to ambient air or by using a cooling agent, such as forced air or liquid. 
     After solid state bonding, the bonded blank assembly  100 ,  200 ,  300  is formed in a drawing press, a spin form, or a hydroform machine (not shown) into a desired shape of cookware  400 , such as a fry pan shape depicted in  FIGS. 5-7, 11-13, and 17-19 . While the bonded blank assemblies  100 ,  200 ,  300  may be oriented such that the first metal layers  102 ,  202 ,  302  form the inner surface of the cookware  400  and the second metal layer  210  or the third metal layers  104 ,  304  form the outer surface of the cookware  400 , the bonded blank assemblies  100 ,  200 ,  300  can be flipped 180° such that the first metal layers  102 ,  202 ,  302  form the outer surface of the cookware  400  and the second metal layer  210  or the third metal layers  104 ,  304  form the inner surface of the cookware  400 . The cookware  400  has a substantially planar cooking surface  402  and a raised sidewall  404  surrounding the cooking surface  402  and protruding vertically above the cooking surface  402 . The sidewall  404  has a radiused portion  406  connected to the cooking surface  402  and a rim  408  at a free end thereof. A handle or handles (not shown) may be attached to the cookware in a known manner. In further embodiments or aspects, a non-stick coating may be applied to the cooking surface  402  of the cookware  400 . The cookware  400  formed using the blank assembly  100 ,  200 ,  300  described herein has reduced weight, such as around 30% less weight, compared to conventional cookware due to the use of lightweight graphite and aluminum materials. Furthermore, the cookware  400  has increased performance compared to conventional cookware due to increased speed to heat and an even heat distribution across the cooking surface facilitated by the perforated graphite layer. 
     In various examples, the present disclosure may be further characterized by one or more of the following clauses: 
     Clause 1. Cookware  400  made from a bonded multi-layer blank assembly  100 ;  200 ;  300 , the cookware  400  comprising: a first metal layer  102 ;  202 ;  302 ; a second metal layer  110 ;  210 ;  310  having a cavity  112 ;  212 ;  312  with a plurality of spaced-apart posts  116 ;  216 ;  316  protruding from a bottom surface  118 ;  218 ;  318  of the cavity  112 ;  212 ;  312 ; and a perforated graphite layer  108 ;  208 ;  308  having a thickness of at least 0.010 in. (0.254 mm) and a plurality of spaced-apart holes  114 ;  214 ;  314  formed therethrough, wherein the perforated graphite layer  108 ;  208 ;  308  is positioned within the cavity  112 ;  212 ;  312  of the second metal layer such that the plurality of spaced-apart posts  116 ;  216 ;  316  extend through the plurality of spaced-apart holes  114 ;  214 ;  314 , and wherein the second metal layer  110 ;  210 ;  310  is metallurgically bonded to the first metal layer  102 ;  202 ;  302  at least via the plurality of spaced-apart posts  116 ;  216 ;  316 . 
     Clause 2. The cookware  400  of clause 1, wherein a surface of the second metal layer  110 ;  210 ;  310  surrounding the cavity  112 ;  212 ;  312  is metallurgically bonded to the first metal layer  102 ;  202 ;  302 , said surface being preferably planar. 
     Clause 3. The cookware  400  of clause 1 or 2, wherein a depth of the cavity  112 ;  212 ;  312  is the same or larger than the thickness of the perforated graphite layer  108 ;  208 ;  308 . 
     Clause 4. The cookware  400  of any of clauses 1-3, wherein the plurality of spaced-apart posts  116 ;  216 ;  316  have a circular cross-section or a polygonal cross-section. 
     Clause 5. The cookware  400  of any of clauses 1-4, wherein the perforated graphite layer  108 ;  208 ;  308  is made from anisotropic graphite. 
     Clause 6. The cookware  400  of any of clauses 1-5, wherein the perforated graphite layer  108 ;  208 ;  308  has a thickness between 0.010 in. (0.25 mm) to 0.100 (2.5 mm) in 
     Clause 7. The cookware  400  of any of clauses 1-6, wherein the first metal layer  102 ;  202 ;  302  is made of aluminum. 
     Clause 8. The cookware  400  of clause 7, wherein the aluminum is an 1100 alloy. 
     Clause 9. The cookware  400  of any of clauses 1-6, wherein the first metal layer  102 ;  202 ;  302  is made of stainless steel. 
     Clause 10. The cookware  400  of any of clauses 1-6, wherein the first metal layer  102 ;  202 ;  302  is made of titanium. 
     Clause 11. The cookware  400  of any of clauses 1-10, wherein the second metal layer  110 ;  210 ;  310  is made of aluminum. 
     Clause 12. The cookware  400  of any of clauses 1-11, further comprising a third metal layer  104 ;  304  metallurgically bonded to a planar side of the second metal layer  110 ;  310  opposite the cavity  112 ;  312 . 
     Clause 13. The cookware  400  of clause 12, wherein the third metal layer  104 ;  304  is made of aluminum. 
     Clause 14. The cookware  400  of clause 13, wherein the aluminum is an 1100 alloy. 
     Clause 15. The cookware  400  of clause 12, wherein the third metal layer  104 ;  304  is made of stainless steel. 
     Clause 16. The cookware  400  of clause 15, wherein the stainless steel is a ferro-magnetic grade of stainless steel. 
     Clause 17. The cookware  400  of clause 12, wherein the third metal layer  104 ;  304  is made of titanium. 
     Clause 18. The cookware  400  of any of clauses 9-17, wherein the second metal layer  310  comprises an outer metal layer  310   a  and a central metal layer  310   b  received within a central opening  322  of the outer metal layer  310   a , and wherein the cavity  312  is provided on the central metal layer  310   b.    
     Clause 19. The cookware  400  of clause 18, wherein the outer metal layer  310   a  is thinner than the central metal layer  310   b.    
     Clause 20. The cookware  400  of any of clauses 1-19, wherein the first metal layer  102  comprises a first sub-layer  102   a  made of aluminum and a second sub-layer  102   b  made of stainless steel, first sub-layer  102   a  being metallurgically bonded to the spaced-apart posts  116 . 
     Clause 21. The cookware of claim  20 , wherein the second metal layer  110  is metallurgically bonded to the first sub-layer  102   a  of the first metal layer  102 . 
     Clause 22. The cookware  400  of clause 20, wherein a surface of the second metal layer  110  surrounding the cavity  112  is metallurgically bonded to the first sub-layer  102   a  of the first metal layer  102 , said surface being preferably planar. 
     Clause 23. The cookware  400  of any of clauses 1-22, wherein the second metal layer  112 ;  212 ;  312  is metallurgically bonded to a planar lower surface of the first metal layer  102 ;  202 ;  302 . 
     Clause 24. The cookware  400  of any of clauses 1-23, wherein a bottom surface of the second metal layer  110 ;  210 ;  310  is planar. 
     Clause 25. A method of making cookware  400 , the method comprising: (a) providing a first metal layer  102 ;  202 ;  302 ; (b) providing a perforated graphite layer  108 ;  208 ;  308  having a thickness of at least 0.010 in. (0.254 mm) and a plurality of spaced-apart holes  114 ;  214 ;  314  formed therethrough, (c) providing a second metal layer  110 ;  210 ;  310  having a cavity  112 ;  212 ;  312  with a plurality of spaced-apart posts protruding from a bottom surface  118 ;  218 ;  318  of the cavity  112 ;  212 ;  312 ; (d) stacking the layers provided in (a)-(c) in a blank assembly  100 ;  200 ;  300  such that the perforated graphite layer  108 ;  208 ;  308  is received within the cavity  112 ;  212 ;  312  of the second metal layer  110 ;  210 ;  310  whereby the plurality of spaced-apart posts  116 ;  216 ;  316  of the second metal layer  110 ;  210 ;  310  are aligned with and pass through the plurality of spaced-apart holes  114 ;  214 ;  314  in the perforated graphite layer  108 ;  208 ;  308  such that a lower surface of the first metal layer  102 ;  202 ;  302  contacts at least an upper surface of upper end portions of the plurality of spaced-apart posts  116 ;  216 ;  316 ; and (e) pressing the blank assembly  100 ;  200 ;  300  by applying a force in a direction perpendicular to a plane of the layers in the blank assembly  100 ;  200 ;  300  and concurrently heating the blank assembly  100 ;  200 ;  300  to achieve a metallurgical bond between the first metal layer  102 ;  202 ;  302  and the second metal layer  110 ;  210 ;  310  at least via the plurality of spaced-apart posts  116 ;  216 ;  316  to provide a bonded multi-layer blank assembly  100 ;  200 ;  300 . 
     Clause 26. The method of clause 25, further comprising: (f) cooling the bonded multi-layer blank assembly  100 ;  200 ;  300 ; and (g) forming the bonded multi-layer blank  100 ;  200 ;  300  assembly into the cookware  400 . 
     Clause 27. The method of clause 25 or 26, wherein the first metal layer  102 ;  202 ;  302  is made of aluminum or stainless steel or titanium, and wherein the second metal layer  110 ;  210 ;  310  is made of aluminum. 
     Clause 28. The method of any of clauses 25-27, further comprising: (h) providing a third metal layer  104 ;  304  and stacking the third metal layer  104 ;  304  with the other layers of the blank assembly  100 ;  300  prior to pressing the blank assembly  100 ;  300  such that the third metal layer  104 ;  304  faces a planar side of the second metal layer  110 ;  310  opposite the cavity  114 ;  314 . 
     Clause 29. The method of clause 28, further comprising: (i) providing a fourth metal layer and stacking the fourth metal layer on top of the first metal layer of the blank assembly prior to pressing the blank assembly. 
     Clause 30. The method of clause 29, wherein the third metal layer and the fourth metal layer are made of stainless steel. 
     Clause 31. Cookware made from a bonded multi-layer blank assembly, the cookware comprising: a first metal layer; a lower metal layer; and a core disposed between the first metal layer and the lower metal layer, the core comprising: a core metal layer made of aluminum and having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; and a perforated graphite layer having a plurality of spaced-apart holes formed therethrough, wherein the graphite layer is positioned in the cavity of the core metal layer such that the plurality of posts extend through the plurality of holes, and wherein the core metal layer is metallurgically bonded to the first metal layer at least via the plurality of posts and to the second metal layer via a bottom surface of the core metal layer. 
     Clause 32. The cookware of clause 31, wherein an upper surface of the core metal layer surrounding the cavity is metallurgically bonded to the first metal layer. 
     Clause 33. The cookware of clause 31 or 32, wherein a depth of the cavity is smaller, the same, or larger than a thickness of the graphite layer. 
     Clause 34. The cookware of any of clauses 31-33, wherein the core metal layer is metallurgically bonded to a planar lower surface of the first metal layer. 
     Clause 35. The cookware of any of clauses 31-34, wherein the plurality of posts have a circular cross-section. 
     Clause 36. The cookware of any of clauses 31-35, wherein the plurality of posts have a polygonal cross-section. 
     Clause 37. The cookware of any of clauses 31-36, wherein a bottom surface of the core metal layer is planar. 
     Clause 38. The cookware of any of clauses 31-37, wherein the core metal layer comprises an outer core metal layer and a central core metal layer received within a central opening of the outer core metal layer. 
     Clause 39. The cookware of clause 38, wherein the outer core metal layer has a same thickness as the central core metal layer. 
     Clause 40. The cookware of clause 39, wherein the outer core metal layer has a smaller thickness than the central core metal layer. 
     Clause 41. The cookware of any of clauses 31-40, wherein the first metal layer is made of stainless steel or titanium. 
     Clause 42. The cookware of clause 41, wherein the stainless steel is a ferro-magnetic grade of stainless steel. 
     Clause 43. The cookware of any of clauses 31-42, wherein the lower metal layer is made of stainless steel or titanium. 
     Clause 44. The cookware of clause 43, wherein the stainless steel is a ferro-magnetic grade of stainless steel. 
     Clause 45. The cookware of any of clauses 31-44, wherein the core metal layer is made of aluminum. 
     Clause 46. The cookware of clause 45, wherein the aluminum is an 1100 alloy. 
     Clause 47. The cookware of any of clauses 31-46, wherein the graphite layer is made from anisotropic graphite. 
     Clause 48. The cookware of any of clauses 31-47, wherein the first metal layer comprises a first sub-layer made of aluminum and a second sub-layer made of stainless steel. 
     Clause 49. The cookware of clause 48, wherein the core metal layer is metallurgically bonded to the first sub-layer of the first metal layer. 
     Clause 50. The cookware of any of clauses 31-51, wherein the graphite layer has a thickness between 0.010 in. (0.25 mm) to 0.100 in. (2.5 mm). 
     Clause 51. A method of making cookware, the method comprising: (a) providing an upper metal disc of stainless steel; (b) providing a perforated graphite disc having a plurality of spaced-apart holes formed therethrough, (c) providing a core metal disc of aluminum having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; (d) providing a lower metal disc of stainless steel; (e) stacking the discs provided in (a)-(d) in a blank assembly such that the graphite disc is received within the cavity of the core metal disc whereby the plurality of posts in the core metal disc are aligned with and pass through the plurality of holes in the graphite disc, with the plurality of posts having upper end portions extending above an upper surface of the graphite disc such that a lower surface of the upper metal disc contacts an upper surface of an outer portion of the core metal disc and the upper end portions of the plurality of posts; and (f) pressing the blank assembly by applying a force in a direction perpendicular to a plane of the discs in the blank assembly and concurrently heating the blank assembly to achieve a metallurgical bond between metal materials of the discs in the blank assembly to provide a bonded blank assembly. 
     Clause 52. The method of clause 51, further comprising: (g) cooling the bonded blank assembly; and (h) forming the bonded blank assembly into the cookware. 
     Clause 53. Cookware made from a bonded multi-layer blank assembly, the cookware comprising: a first metal layer; a lower metal layer having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; and a perforated graphite layer having a plurality of spaced-apart holes formed therethrough, wherein the graphite layer is positioned within the cavity of the core metal layer such that the plurality of posts extend through the plurality of holes, and wherein the lower metal layer is metallurgically bonded to the first metal layer at least via the plurality of posts. 
     Clause 54. The cookware of clause 53, wherein an upper surface of the lower metal layer surrounding the cavity is metallurgically bonded to the first metal layer. 
     Clause 55. The cookware of clause 53 or 54, wherein a depth of the cavity is smaller, the same, or larger than a thickness of the graphite layer. 
     Clause 56. The cookware of any of clauses 53-55, wherein the second metal layer is metallurgically bonded to a planar lower surface of the first metal layer. 
     Clause 57. The cookware of any of clauses 53-56, wherein the plurality of posts have a circular cross-section. 
     Clause 58. The cookware of any of clauses 53-57, wherein the plurality of posts have a polygonal cross-section. 
     Clause 59. The cookware of any of clauses 53-58, wherein a bottom surface of the core metal layer is planar. 
     Clause 60. The cookware of any of clauses 53-59, wherein the first metal layer is made of stainless steel or titanium. 
     Clause 61. The cookware of clause 60, wherein the stainless steel is a ferro-magnetic grade of stainless steel. 
     Clause 62. The cookware of any of clauses 51-61, wherein the lower metal layer is made of aluminum. 
     Clause 63. The cookware of clause 62, wherein the aluminum is an 1100 alloy. 
     Clause 64. The cookware of any of clauses 53-63, wherein the graphite layer is made from anisotropic graphite. 
     Clause 65. A method of making cookware, the method comprising: (a) providing an upper metal disc of stainless steel; (b) providing a perforated graphite disc having a plurality of spaced-apart holes formed therethrough, (c) providing a lower metal disc of aluminum having a cavity with a plurality of spaced-apart posts protruding from a bottom surface of the cavity; (d) stacking the discs provided in (a)-(c) in a blank assembly such that the graphite disc is received within the cavity of the lower metal disc whereby the plurality of posts in the lower metal disc are aligned with and pass through the plurality of holes in the graphite disc, with the plurality of posts having upper end portions extending above an upper surface of the graphite disc such that a lower surface of the upper metal disc contacts an upper surface of an outer portion of the lower metal disc and the upper end portions of the plurality of posts; and (e) pressing the blank assembly by applying a force in a direction perpendicular to a plane of the discs in the blank assembly and concurrently heating the blank assembly to achieve a metallurgical bond between metal materials of the discs in the blank assembly to provide a bonded blank assembly. 
     Clause 66. The method of clause 65, further comprising: (f) cooling the bonded blank assembly; and (g) forming the bonded blank assembly into the cookware. 
     The present disclosure has been described with reference to specific details of particular examples thereof. It is not intended that such details be regarded as limitations upon the scope of the disclosure except insofar as and to the extent that they are included in the accompanying claims.