Metal founding – Process – With measuring – testing – inspecting – or condition determination
Reexamination Certificate
2000-02-18
2001-04-24
Kastler, Scott (Department: 1742)
Metal founding
Process
With measuring, testing, inspecting, or condition determination
C164S452000, C164S480000, C222S590000
Reexamination Certificate
active
06220336
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to devices for the continuous casting of molten metals and more particularly, to an improved molten metal feed system and method for high productivity continuous casting.
BACKGROUND OF THE INVENTION
The formation and casting of metals and metal alloys of various kinds have been conducted for many years using commercial scale operations. For example, continuous twin roll casters, such as those shown in U.S. Pat. Nos. 2,790,216 and 4,054,173 are commonly used. The casters disclosed therein include an opposing pair of water cooled, counter-rotated and generally horizontally oriented casting rolls. Molten metal is routed through a feed system into the nip of the two rolls just prior to the closest approach of the rolls. Typically, the feed system includes an upstream head box and a feed tip nozzle. The metal is directed from the head box, through the feed tip nozzle and into the nip of the rolls. As the metal comes into contact with the water cooled casting rolls, heat is rapidly extracted and the metal begins to solidify. The solid metal is then compressed into a sheet as it passes through the gap between the caster rolls.
Conventional casting machines of this type are typically capable of producing 6 mm thick strips at productivity rates of approximately 1.7 tons/m width/hour. Recently, however, a new generation of casting machines has been developed for high speed, thin strip casting of molten metal. These new generation casters are capable of casting gauges of less than 1 mm. By developing the technology necessary to cast thinner and faster, it is possible to increase productivity and reduce the number of downstream rolling passes necessary. Specifically, this technology allows for great increases in productivity, greater casting capacity in addition to enhanced quality when compared with conventional casting machines.
In order to satisfy the more demanding requirements of this latest generation of casting machines, a need exits for an improved molten metal feed system. The feed systems currently being used on conventional casting machines have not been able to successfully handle the transition to higher production flow requirements. For example, the feed systems currently being used on conventional casting machines tend to produce uneven, and often turbulent flow through the feed tip nozzle when operated at increased speeds. This turbulence is caused by the presence of baffles, or spacers, within the feed tip nozzle. One or more baffles are typically incorporated along the width of the feed tip to help manipulate and direct the flow of molten metal through the tip. The use of such baffles is described in U.S. Pat. Nos. 4,303,181 and 4,641,767. Although this design has proven sufficient for conventional casting machines operating at nominal production rates, at increased speeds the presence of baffles in the feed tip produces eddy currents in the molten metal as it is being routed through the nozzle which in turn cause the flow to be turbulent.
Additionally, the feed systems currently in use with continuous casters tend to produce a large temperature gradient in the molten metal across the width of the strip. Prior to entering the feed tip nozzle, the molten metal travels through an upstream head box. Since the width of the head box is typically significantly less than the width of the feed tip nozzle, an uneven flow of molten metal may reach the feed tip. Specifically, molten metal may begin to flow through the center section of the feed tip nozzle before a sufficient amount of metal is present to begin flowing through the edges of the feed tip nozzle. Consequently, a temperature gradient is produced in the molten metal along the width of the feed tip nozzle where typically the temperature of the molten metal is greatest at the center of the feed tip nozzle. This temperature gradient affects the profile of the cast sheet.
These and other problems have been experienced when the existing feed system designs are used on machines operating in the high speed, thin gauge range. Many of the casting defects (e.g. buckling, starvation, etc.) experienced on the resulting cast sheet are due to these problems associated with the feed system design. Consequently, a need exists for a molten metal feed system for continuous casters capable of handling the more demanding requirements inherent in high speed, thin gauge casting.
SUMMARY OF THE INVENTION
The present invention, therefore, provides an improved molten metal feed system for continuous casters capable of handling the transition to the higher production requirements associated with high speed, thin gauge casting. Additionally, the molten metal feed system provided for by the present invention may be retrofitted for use with conventional casters, to significantly improve the productivity of conventional casters.
A baffleless feed tip nozzle is provided to eliminate the turbulence problems associated the presence of baffles in the feed tip. By eliminating the baffles it is possible for liquid metal flow to be introduced into the tip in a nonturbulent manner at rates sufficient enough to satisfy the increased production flow requirements. Additionally, the feed tip nozzle is adjustable in opening size to assist in the transition from conventional to thin gauge casting. The fixed tip opening of existing feed systems produces several problems during the transition from conventional to thin gauge casting. By removing the baffles from the nozzle, it is possible to provide the option of an adjustable feed tip opening.
A feed tip control system is provided with the adjustable feed tip to automatically adjust the size of the feed tip opening. In addition, a roll gap control system may also be provided for automatically adjusting the size of a roll gap between a pair of caster rolls downstream from the feed tip. This automatically adjusts the casters according to the feed tip opening size. A feed tip nozzle set-back control system is also provided to automatically adjusting a set-back of the feed tip nozzle from the caster rolls. The feed tip nozzle set-back control system is operatively coupled to either the feed tip control system or the roll gap control system for automatically adjusting the feed tip opening, the roll gap, and the set-back of the feed tip nozzle in relation to one another.
Upstream from the feed tip nozzle, a flow distributor board is provided along the width of the desired casting. The flow distributor board stabilizes and balance the metal flow before it passes into the downstream feed tip. The flow distributor board is housed within a distributor box between an upstream edge and a downstream edge. The flow distributor board generally separates the distributor box into a lower section and an upper section and is oriented generally transverse to the metal flow. The distributor box is insulated to prevent heat loss and may also include an insulated lid when casting larger widths. In addition, the distributor box is advantageously equipped with preheaters which further prevent heat loss.
As is conventionally known, molten metal is introduced into the lower portion of the distributor box from an upstream head box. As the liquid metal flows into the distributor box, it is forced to fill the entire width of the lower portion of the box due to the presence of the flow distributor board. More specifically, the molten metal is restricted to filling the width of the distributor box by a plurality of perforations spaced apart along the width of the flow distributor board. The perforations, including pores or channels of different shapes, sizes, and arrangement, hydrodynamically optimize the flow of the metal into the upper portion of the distributor box and into the feed tip. The metal permeates through the perforations along the flow distributor board at different rates depending on the pore or channel configuration. Therefore, it is possible to regulate the temperature gradient across the width of the cast sheet by stabilizing the flow of molten metal as it enters the feed t
Christie Parker & Hale LLP
Fata Hunter, Inc.
Kastler Scott
LandOfFree
Adjustable molten metal feed system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adjustable molten metal feed system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adjustable molten metal feed system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2531291