Patent Application
20110297138
1. Field
The disclosed and claimed concept relates generally to heating operations performed with a furnace, and more particularly, to an improved cover for a workpiece that is used during such a heating operation.
2. Background Information
Numerous types of heat treatment operations are known for use in conjunction with metals that have been worked such as through rolling, extrusion, and the like. Heat treatment operations are employed in operations including annealing, normalizing, and tempering, among others. Such heating operations desirably occur within a non-oxidizing environment, which can be one in which oxygen has been consumed or removed or can be an otherwise inert or non-reactive environment. In order to maintain such a non-reactive environment, a cover is typically employed within the interior of a furnace, with the object that is undergoing the heat treatment operation being disposed within the interior of the cover.
Such a heat treatment operation involves heating the furnace which heats the cover which, in turn, heats the workpiece. The cover typically will be disposed on a layer of refractory materials that are situated on the ground or on a floor of a factory. The workpiece undergoing the heat treatment operation is likewise disposed on the layer of refractory material but is enclosed within the cover.
While such covers have been generally effective for their intended purposes, such covers have not, however, been without limitation. Due to the high temperatures involved in such heat treatment operations, as well as the duration of such heat treatment operations, such covers typically are formed out of costly materials that are suited to withstand such high heat for extended lengths of time. For example, such covers may be formed from Inconel or other stainless steel formulations having a relatively high proportion of nickel. Such covers typically may be of a cylindrical configuration six to ten feet in diameter and ten to twenty feet in height, or of a polyhedron configuration six to ten feet wide, twelve to thirty-five feet long, and ten to twenty feet high. Thus, due to their large size and the costly nature of the material out of which such covers are formed, the cost to manufacture such covers is extremely high.
Moreover, the lifespan of such covers often is relatively limited due to the destructive environment in which many such covers are used. Many furnaces are fired with fossil fuels such as natural gas, oil, etc., which require oxygen for combustion, and with the result that the surface of the cover that is exposed to such combustion will become oxidized or otherwise affected and will fail mechanically due to breaching of the material due to corrosion alone or due to corrosion in conjunction with slumping of the material due to its weight.
It thus would be desirable to provide an improved cover that addresses these and other concerns associated with other covers known in the art.
A further understanding of the disclosed and claimed concept can be gained from the following Description of the Preferred Embodiments when read in conjunction with the accompanying drawings in which:
Similar numerals refer to similar parts throughout the specification.
An improved cover 4 in accordance with a first embodiment of the disclosed and claimed concept is indicated generally in
As can be understood from
As can be understood from
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As can be understood from
In the first embodiment of the cover 4, the emission apparatus 20 is in the form of an emission layer 48 disposed on the first surface 32 of the support 16. By way of example, the emission layer 48 may be a coating of a product known as ITC 213 manufactured by International Technical Ceramics, Inc., of Jacksonville, Fla., USA, or other appropriate material. The first surface 32 of the support 16 has an emissivity value that is dependent upon a number of factors such as the material from which the support 16 is formed, the degree of polishing or oxidation on the first surface 32, the geometry of the support 16, and other factor. Advantageously, however, the emission layer 48 has an emissivity value that is relatively greater than the emissivity value of the first surface 32.
As is generally understood, the emissivity of a surface of a material can be characterized as the proportion of radiation that occurs from the surface at a given temperature compared with what would be radiated from an ideal black body at the same temperature. At a given temperature, a surface having a relatively higher emissivity will radiate more heat than another surface having a relatively lower emissivity. As such, since the emission layer 48 has an emissivity value greater than the emissivity value of the first surface 32, the cover 4 with its emission apparatus 20 will radiate more heat into the workpiece 12 at a given temperature of the furnace 8 than could be radiated into the workpiece 12 by the support 16 by itself, i.e., in the absence of the emission apparatus 20.
Accordingly, the furnace 8 can advantageously be operated at a relatively lower temperature when using the cover 4 with its emission layer 48 since the emission layer 48 radiates into the workpiece 12 a desired amount of heat at a relatively lower temperature of the furnace 8 than would be required in the absence of the emission layer 48. This advantageously saves money due to the reduced heating requirement of the furnace 8. Moreover, and further advantageously, since the furnace 8 can be operated at a relatively lower temperature, the support 16 can itself be formed of a relatively less costly material than would otherwise be required in the absence of the emission layer 48. For example, whereas the support 16 might otherwise have been required to be formed from Inconel, the support 16 when used in conjunction with the emission layer 48 can instead be formed of 309 stainless steel, which is relatively less costly. Thus, the addition of the emission apparatus 20 to the support 16 provides great cost savings.
In a second embodiment of the disclosed and claimed concept, a cover 104 is depicted generally in
While the cover 4 and the cover 104 can be employed with any type of furnace 8, they are most desirably used with a furnace 8 that does not employ fossil fuels for heating and rather employs electricity or another heat source that does not cause oxidation, corrosion, or other destruction of the second surface 36. While the cover 4 certainly can be employed in fossil fuel fired furnaces 8, and would still provide improvements in cost due to improved heating and reduced material costs, its lifespan may be similar to that of other covers that employ only a support without an emission apparatus.
Advantageously, therefore, a third embodiment of a cover 204 in accordance with the disclosed and claimed concept is depicted generally in
It is noted, however, that the another emission layer 256 on the second surface 236 that faces generally toward the furnace 8 will resist heating of the cover 204 because of its emissivity value being relatively higher than that of the first surface 232. As such, the furnace that heats the cover 204 will need to be heated to a temperature relatively greater than the temperature used in conjunction with either the cover 4 or the cover 104. However, since the radiation from the emission layer 248 on the first surface 232 is greater than that of the first surface 232 itself, such greater radiation from the emission layer 248 will compensate for the resistance to heating that is caused by the another emission layer 256. That is, while the another emission layer 256 will resist heating by the furnace 8, thus requiring the furnace 8 to be operated at a relatively higher temperature than would be required in the absence of the another emission layer 256, the presence of the emission layer 248 correspondingly increases the radiation from the cover 204 into the workpiece 12, with the result that the furnace 8 typically will at most need to be heated to the same temperature as would be required if the cover were devoid of the emission apparatus 220.
However, the result of heating such a furnace 8 to the same temperature as would be required if the cover 204 were devoid of the emission apparatus 220 nevertheless results in the support 216 itself being at a relatively lower temperature than would be the case if the cover 216 were employed in the same furnace without the emission apparatus 220. That is, in a given furnace 8 at a given temperature, the support 216 by itself would reach a steady state of a given temperature and would radiate into the workpiece a given amount of heat. However, with the addition of the emission apparatus 220 that includes the emission layer 248 and the another emission layer 256 on the second and first surfaces 236 and 232, respectively, the same amount of heat can be radiated into the workpiece, but the support 216 in such a scenario is at a relatively lower steady state temperature than it would be in the absence of the emission apparatus 220.
As such, the support 216 of the cover 204 can be formed of a relatively less expensive material than would be required in the absence of the emission apparatus 220. For example, the cover 216 could be formed of 309 stainless steel rather than Inconel, with significant cost savings. Moreover, the another emission layer 256 on the second surface 236 of the cover 204 shields the support 216 from oxidation, corrosion, etc. in the fossil fueled environment of a furnace. Since the cover 204 is not subject to such degradation, the service life of such a cover 204 is far greater than what would be possible in the absence of the emission apparatus 220. Thus cost savings are possible with the cover 204 due to the usability of a relatively less expensive material for the support 216 as well as the extended service life of the cover 204.
A fourth embodiment of the cover 304 is indicated generally in
It should be apparent from the cover 304 and the other embodiments herein that additional configurations of a cover in accordance with the disclosed and claimed concept other than those expressly set forth herein can be developed. For instance, a secondary emission layer can be added to the another emission layer 356 of the cover 304. Other combinations will be apparent to those skilled in the art.
While specific embodiments of the disclosed and claimed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed and claimed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
