Metal treatment – Process of modifying or maintaining internal physical... – With measuring – testing – or sensing
Reexamination Certificate
1999-09-30
2001-07-24
Ip, Sikyin (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
With measuring, testing, or sensing
C148S508000, C148S574000, C219S608000, C219S645000
Reexamination Certificate
active
06264765
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an improved method and apparatus for casting, hot rolling and annealing non-heat treatable aluminum alloys, and, in particular to a method of inductively heating a cast and hot rolled aluminum alloy sheet directly after hot rolling to continuously produce an annealed aluminum alloy product, thereby eliminating the need for multiple processing lines. This elimination of multiple processing lines results in superior economies of production through both reduced capital expense and the elimination of inventory of coiled products in intermediary stages of processing. This invention is especially suitable for the manufacture of transportation products, such as automotive structural sheet.
BACKGROUND OF THE INVENTION
One of the problems when processing metals, including aluminum, is the accumulation of inventory during processing and the costs associated with maintaining and storing such inventory. These problems are most significant during the production of aluminum sheet through conventional ingot metallurgy. In conventional ingot processing, multiple processing lines are required to take the cast ingot to its final form of annealed coiled product, with inventory capacity required for nearly every intermediary product form. For ingot processing, these processing steps include: casting; homogenizing; hot rolling; intermediate annealing; cold rolling (roughing mill); cold rolling (finish mill); and coil annealing. When the ingot is cast, the ingots are inventoried prior to re-heating to the homogenization treatment. When the ingot is hot rolled, the hot rolled coils are stored prior to further processing. Similarly, cold rolled coils also require storage prior to the cold roll finishing pass and annealing processing steps.
Much of the inventory problem created by ingot casting has been solved through the use of continuous casting followed by in-line hot rolling. This processing method eliminates the re-heating of ingots and the inventory problem associated with storing the ingots prior to homogenization. However, inventory problems still exist in connection with the secondary processing of aluminum. That is, once the cast product is hot rolled, the hot rolled coils must still be stored prior to further processing. As such, a need has developed to provide improved apparatus and processing techniques to overcome the drawbacks associated with present day processing.
The invention solves this problem by combining continuous casting, direct hot rolling and induction heating of non-heat treatable aluminum alloy products into a single production line. With the invention, a final annealed product is produced in coiled form without the production of intermediate product forms. Additionally, this process significantly reduces energy consumption used in the annealing step by exploiting the residual latent heat of the hot rolled product in the annealing process.
The use of induction heating for aluminum alloys alone is known. U.S. Pat. No. 5,739,506 to Hanton et al. discloses an example of an induction heating system which relates to transverse flux heating. These heating systems are desirable when treating a variety of widths of strip or sheet metal.
Induction heating and processing of aluminum is also disclosed in U.S. Pat. No. 5,562,784 to Nishikawa et al. This patent is directed to an aluminum alloy substrate for electrolytically grainable lithographic printing plate. In making this material, the aluminum alloy is continuously cast. The cast material can then be either cold rolled or hot rolled and cold rolled. The substrate is heat treated for recrystallization in the course of cold rolling. The heat treatment is disclosed as either a continuous annealing furnace or a transverse flux induction heating. The induction heating of Nishikawa et al. is associated with recrystallization after cold rolling and is not part of an apparatus or method which continuously casts, hot rolls and inductively heats a non-heat treatable aluminum alloy into a final annealed product.
SUMMARY OF THE INVENTION
Accordingly, it is a first object of the present invention to provide an apparatus and method which produces non-heat treatable aluminum alloys in an economical fashion.
Another object of the present invention is a method of eliminating the need for excessive inventory during processing of cast and hot rolled non-heat treatable aluminum alloys.
Another object of the present invention is a method of reducing the energy required for annealing of non-heat treatable aluminum alloys by using the residual heat latent in the hot rolled sheet product.
One other object of the present invention is an apparatus for processing non-heat treatable aluminum alloys using induction heating and a feedback control system for annealing and control thereof.
A still further object of the present invention is a method and apparatus that use accumulators at the entrance and exit sides of an induction heating apparatus positioned in-line with continuous casting and hot rolling equipment to allow for the production of annealed coils of non-heat treatable aluminum sheet products in a continuous fashion.
One other object of the present invention is a method and apparatus that use quenching devices at the exit side of an induction heating apparatus positioned in-line with continuous casting and hot rolling equipment to allow for the production of annealed coils of non-heat treatable aluminum sheet products in a continuous fashion.
Other objects and advantages of the present invention will become apparent as a description thereof proceeds.
In satisfaction of the foregoing objects and advantages, the present invention comprises an improvement in a method of casting, hot rolling and annealing non-heat treatable aluminum alloys, whereby a cast product is directly hot rolled to form a hot rolled product, and the hot product is annealed to form an annealed product. According to the invention, the hot rolled product is directly inductively heated from an elevated temperature caused by the latent heat in the hot rolled product to a final annealing temperature to form a final annealed product. The inductive heating is controlled using a feedback control based on at least one heating parameter, e.g., the temperature of the hot rolled product entering the induction heating zone. The surface of the final annealed product can be protected prior to coiling. The protection can include oiling or using an interleaving material. Preferably, the elevated temperature exiting the hot rolling step is between 4000 and 600°F. (204 to 316° C.) and the final annealing temperature ranges between 650° and 1000° F. (343 to 538° C.). In addition, belt casting is a preferred mode for the inventive method. The feedback control can use a measure of the elevated temperature of the hot rolled product and/or a measure of the temperature of the final annealed product after heating is completed, the gauge and width of the hot rolled product and the speed of the hot rolled product as it travels through the induction heater.
The present invention also includes an apparatus for practicing the inventive method, the apparatus including a caster, a hot rolling mill and an annealing furnace. The annealing furnace is an inductive heating device positioned directly downstream of the hot rolling mill for annealing the hot rolled product to a final annealing temperature as described above. The apparatus also includes a cooling device which can be a quench device, either air, water or a combination of both, or merely coiling the device for air cooling. An oiler can be interposed downstream of the induction heating device and the final anneal product recovery. Preferably, the induction heating device is a transverse flux induction heating device.
Accumulation can also be utilized in conjunction with the invention, both prior to and downstream of the inductive heating device. The accumulation can be accomplished by using conventional strip accumulators, or coilers, flying shears or the like as a means to recover the hot rolled
Bryant J. Daniel
Platek Stanley
Ip Sikyin
Reynolds Metals Company
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