BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an exemplary coil handling system in accordance with the present invention;
FIGS. 2 and 3 are sectional views on an enlarged scale taken respectively along lines 2-2 and 3-3 of FIG. 1; and
FIG. 4 is a graph depicting cooling rates and transport and dwell times.
DETAILED DESCRIPTION
FIG. 1 depicts an exemplary layout of the delivery end of a rolling mill producing hot rolled steel bars. The hot rolled product is delivered from the rolling mill (not shown) along a path 10 leading to shears 12 which serve to crop and subdivide the product into customer lengths. The subdivided lengths are then subjected to cooling in a water box 14 before being alternately directed by a switch 16 to one or the other of two pouring reels 18 which form the product lengths into upstanding coils at a coil forming station A. A rotary table 20 then transfers the coils to the first leg 22a of a conveyor system 22 defining a transport path.
The conveyor system comprises a series of individually driven conveyor sections indicated typically at 24 which preferably will comprise short roller tables. Because the conveyor sections are individually driven, their transport speeds can be adjusted to accommodate a wide range of thermal treatments for the product coils.
A rotary roller table 26 serves to transfer the coils from the conveyor leg 22a to a second perpendicular leg 22b leading through a heat treating station B. With additional reference to FIG. 2, it will be seen that station B includes a tunnel enclosure 28 internally provided with a series of forced air cooling installations 30. At each installation 30, a motor driven fan 32 serves to drive ambient air through a duct 34 upwardly into the interior of a coil 36. At station A, each coil is formed around a central stem 36 projecting upwardly from a pallet 40 on which the coil is supported. The stem 36 provides a central support which lends stability to the coil as it progresses along the transport path. A vertically adjustable louvered cap 42 serves to redirect the air flow radially outwardly through the coil, and external louvers 44 in the tunnel walls and roof serve to further control air flow. An external drive 46 serves to manipulate the louvers over a range of adjustments between fully open and fully closed positions. With the louvers 44 fully open and the fans 32 in operation, the coils 36 are subjected to cooling at an accelerated maximum rate. Conversely with the fans 32 shut down and the louvers 44 closed, the coils undergo retarded cooling at a greatly reduced minimum rate. A myriad of cooling rates are possible between these two extremes.
With reference again to FIG. 1, side shift transfer cars 48 receive the coils from station B and serve either to transfer them to any one of several processing lines 50a, 50b, 50c, and 50d at a second heat treating station C, or to bypass station C and transfer the coils to a conveyor leg 22c which leads to remote hook carriers and packaging equipment (not shown). Side shift transfer cars 49 receive coils from the process lines 50a, 50b, 50c, and 50d and also serve to convey them to the conveyor leg 22c.
It will be seen from FIG. 3 that the processing lines 50a, 50b, 50c, and 50d each comprise louvered tunnel enclosures of the type provided at station B, but without associated cooling stations fed by forced air fans. For illustrative purposes, the louvers of processing line 50a are shown fully open, those of processing line 50b are shown partially open, and those of processing lines 50c and 50d are shown fully closed. These different adjustments respectively achieve progressively slower cooling rates.
By subdividing the conveyor system into individually driven segments, transport times between heat treating stations can be different from and beneficially faster than the transport times through the stations, the latter times being selected to coact with the rate of cooling at each station in order to achieve desired metallurgical properties in the coiled products.
Thus, as shown in FIG. 4, the transport time t1 between heat treating stations A and B can be relatively brief in order to limit uncontrolled cooling during that interval. The transport time t2 through station B can be selected to achieve the desired metallurgical objective, and transport time t3 between stations B and C can again be beneficially brief. Transport time t4 at station C can be prolonged to again achieve the desired metallurgical objectives, and transport time t5 can be selected to dovetail with prior process steps and to insure that the coils are delivered in a timely and coordinated sequence to the downstream hook carriers and packaging equipment.
In a typical mill environment, and by way of example only, hot rolled steel bar products are received along path 10 at temperatures on the order of 1000° C. The products are formed into coils at station A at temperatures ranging from 800°-1000° C., and are cooled to temperatures of about 600°-700° C. at station B. Retarded cooling at rates of between 0.2° to 0.5° C./sec. may then take place at station C for extended periods of up to twenty four hours.
In light of the foregoing, it will be understood by those skilled in the art that the layout shown in FIG. 1 is merely exemplary and is not intended to be limiting in the number and type of equipment components, the manner in which they are arranged, or their method of employment. Although the conveyor system has been shown as a series of individually driven roller tables, other individually driven segments such as short chain conveyor sections and short carryover beam sections could serve as equivalents. Similarly, although the tunnel enclosures have been shown with louvered openings, other mechanisms for adjusting the openings could serve as equivalents, non limiting examples being slidable doors, mutually slidable foraminous plates, etc. Also, for certain metallurgical treatments, heat may be added to the tunnel enclosures, either to further retard cooling rates or to maintain a desired soaking temperature for prolonged periods.
Patent Application
20080019805
