Intermediate thickness and multiple furnace process line

Abstract

A method and apparatus of making coiled plate, sheet in coiled form or discrete plate. The apparatus includes a continuous strip caster forming a strand of intermediate thickness; a shear for cutting the strand into a slab of desired length; a slab table including a slab takeoff operable transverse of the conveyor table; a slab collection and storage area adjacent to the slab conveyor table adapted to receive slabs from the slab takeoff; one or two reheat furnaces having an entry inline with both the slab conveyor table and the slab collection and storage area for receiving slabs from either; a feed and run back table at the exit of one reheat furnace; a single or twin stand hot reversing mill for reducing the slab to a coiling thickness in a number of flat passes; and a pair of coiler furnaces located on opposite sides of the hot reversing mill.

Description

FIELD OF THE INVENTION

This invention relates to the continuous casting and rolling of slabs and, more particularly, to an integrated intermediate thickness caster and a hot reversing mill with flexibility in slab sourcing and the ability to roll thin gauge products.

BACKGROUND OF THE INVENTION

Since the advent of the continuous casting of slabs in the steel industry, companies have been trying to combine the hot strip mill with the continuous caster through an inline arrangement so as to maximize production capability and minimize the equipment and capital investment required. The initial efforts in this regard consisted of integrating continuous casters producing slabs on the order of 6 to 10 inches with existing continuous or semicontinuous hot strip mills. These existing hot strip mills included a reheat furnace, a roughing train (or a reversing rougher) and a six or seven stand finishing mill with a capacity of 1.5 to 5 million tons per year. This arrangement is the present day design of large steel company hot mills, and it is unlikely that new hot strip mills of this design would ever be built due to the high capital cost. The quest for low cost integrated caster hot strip mills is not solved by current designs. Further, such prior art integrated mills were extremely inflexible as to product mix and thus current market requirements.

These difficulties gave rise to the development of the so-called thin slab continuous hot strip mill which typically produces 1,000,000 tons of steel per year as standard products. These mills have been integrated with thin slab casters on the order of 2 inches or less. Such integrated thin slab casters are enjoying increased popularity but are not without serious drawbacks of their own. Significant drawbacks include the quality and quantity limitations associated with the thin slab casters. Specifically, the trumpet-type mold necessary to provide the metal for the thin slab can cause high frictional forces and stresses along the surface of the thin wall slab which leads to poor surface quality in the finished product. Further, the 2 inch strip casters are limited to a single tundish life of approximately seven heats because of the limited metal capacity of the mold.

Most importantly, the thin casters, by necessity, have to cast at high speeds to prevent the metal from freezing in the current ladle arrangements. This, in turn, requires the tunnel furnace which is just downstream of the slab caster to be extremely long, often on the order of 500 feet, in order to accommodate the speed of the slab and still be able to provide the heat input to a thin slab (2 inches) which loses heat at a very high rate. Since the slab also leaves the furnace at a high speed, one needs the multistand continuous hot strip mill to accommodate the rapidly moving strip and roll it to sheet and strip thicknesses. However, such a system is still unbalanced at normal widths since the caster has a capacity of about 800,000 tons per year and the continuous mill has a capacity as great as 5 million tons per year. The capital cost of such a system then approaches that of the earlier prior art systems which the system was intended to replace.

In addition, the scale loss as a percentage of slab thickness is substantial for the 2 inch thin cast slab. Because of the extremely long furnace, one must provide a long roller hearth which becomes very maintenance intensive because of the exposed rotating rollers.

It has been suggested that light gauge hot band on the order of 0.040 inch be rolled from these 2 inch slabs. However, in the case of low carbon steels, the thermal decay is too great on a multistand continuous mill making it impossible to achieve the necessary finishing temperatures; and in the case of low alloy high-strength steels, it has been reported that the 2 inch thick slab does not produce the reduction required for high-strength low alloy steel which then causes a coarse microstructure which must then be refined through special temperature treatments which are greater than for the cold charging of the same microalloyed steel grade, "Optimisation of hot rolling schedule for direct charging of thin slabs of Nb-V microalloyed steel", N. Zentara and R. Kaspar, Materials Science and Technology, May 1994.

The typical multistand hot strip mill, likewise, requires a substantive amount of work in a short time which must be provided for by larger horsepower rolling stands which, in some cases, can exceed the energy capabilities of a given area, particularly in the case of emerging countries. Thin slab casters, likewise, are limited as to product width because of the difficulty in using vertical edgers on a 2 inch slab. Further problems associated with the thin strip casters include the problems associated with keeping the various inclusions formed during steel-making away from the surface of the thin slab where such inclusions can lead to surface defects if exposed. Furthermore, existing systems are limited in scale removal because thin slabs lose heat rapidly and are thus adversely affected by the high-pressure water normally used to break up the scale.

In addition, this thin strip process can only operate in a continuous manner, which means that a breakdown anywhere in the process stops the entire line, often causing scrapping of the entire product then being processed.

It is an object of our invention to integrate an intermediate thickness slab caster with a hot reversing mill. It is a further object to adopt a system which balances the rate of the caster to the rate of the rolling mill. It is also an object of our invention to adopt a system using less thermal and electrical energy. It is still a further object to adopt an automated system with small capital investment, reasonable floor space requirements, reasonably powered rolling equipment and low operating costs. It is a further object to provide flexibility in slab sourcing and to economically accommodate increased demand for light gauge wide strip.

SUMMARY OF THE INVENTION

Our invention provides for a versatile, integrated caster and minimill capable of producing at least 650,000 and preferably in excess of 1 million finished tons a year with a divergent product mix. Such a facility can produce product 24 to 120 inches wide and can routinely produce a product of 800 PIW with 1,200 PIW being possible. This is accomplished using a casting facility having a fixed and adjustable width mold with a straight, rectangular cross section without the trumpet-type mold. The caster has a mold which contains enough liquid volume to provide sufficient time to make flying tundish changes, thereby not limiting the caster run to a single tundish life. Our invention provides a slab approximately two to three times as thick as the thin cast slab, thereby losing much less heat and requiring a lesser input of Btu's of energy. Our invention provides a slab having a lesser scale loss due to reduced surface area per volume and permits the use of one or two reheat or equalizing furnaces with minimal maintenance required. Further, our invention provides a caster which can operate at conventional caster speeds and conventional descaling techniques. Our invention provides for the selection of the optimum thickness cast slab to be used in conjunction with a twin stand, tandem hot reversing mill providing a balanced production capability. Our invention has the ability to separate the casting from the rolling if there is a delay in either end. Our invention provides for the easy removal of transitional slabs formed when molten metal chemistry changes or width changes are made in the caster. Furthermore, our invention provides for easily bringing cold slabs into the processing line. Such slabs may be outsourced (i.e., slabs not formed by the caster) and may be thicker than those which may be cast by the caster. This versatility will allow the processing line to be operated at the respective capacity of the individual components and allows for various portions of the line to be independently operated. This outsourcing of slabs also permits the product mix to include steel grades beyond the capability of the steel-making facility which forms a part of any given integrated process.

All of the above advantages are realized while maintaining the advantages of a thin caster which include low ferrostatic head, low weight of slab, straight molds, shorter length molds, smaller required mold radii, low cooling requirements, low burning costs or shear capacity and simplified machine constructions.

Our invention provides an intermediate thickness slab caster integrated with a hot strip and plate line which includes a pair of reheat or equalizing furnaces capable of receiving slabs directly from the caster, from a slab collection and storage area positioned adjacent a slab conveyor table exiting the continuous caster or from another area. A feed and run back table is positioned at the exit end of one of the reheat furnaces and inline with a twin stand hot reversing mill having a coiler furnace positioned on either side thereof. The mill can reduce a cast slab to a thickness of about 1 inch or less in about four flat passes. The combination coil, coiled plate, sheet in coil form or discrete plate finishing line extends inline and downstream of the hot reversing mill and the coiler furnaces. The finishing facilities may include a cooling station, a downcoiler, a plate table, a shear, a cooling bed crossover, a plate side and end shear and a piler.

To achieve the necessary balance between the hot reversing mill and the caster, it is preferable to cast slabs having a thickness of 3 to 6 inches and preferably between about 3.5 to about 5.5 inches. As used herein, the term intermediate thickness is intended to define such slabs. The cast slabs are reduced to a thickness capable of being coiled and normally about 1 inch or less in four flat passes on the hot reversing mill before starting the coiling of the intermediate product between the coiler furnaces as it is further reduced to the desired finished product thickness. In order to provide the capability of making coiled plate, discrete plate and sheet in coil form up to 1,000 PIW and higher, slab width may vary from 24 to 120 inches.

A preferred processing line of the present invention includes an intermediate thickness continuous strip caster with an inline shear downstream of the caster for cutting a cast strand into an intermediate thickness slab of the desired length. A slab conveyor table is provided inline with the shear and a slab loading and unloading mechanism positioned adjacent the conveyor for supplying slabs thereto. A slab collection and storage area is adjacent the slab loading and unloading mechanism for receiving and supplying slabs thereto. At least one reheat furnace is provided having an entry end inline with the slab conveyor table for receiving slabs therefrom and supplying reheated slabs to a feed and run back table positioned at the exit end of the reheat furnace. A hot reversing mill is provided inline with the feed and run back table for reducing a slab on the feed and run back table to an intermediate product having a thickness sufficient for coiling in a number of flat passes. Two spaced coiler furnaces are positioned inline with the feed and run back table, with one located upstream of the hot reversing mill and the other located downstream thereof. The coiler furnaces are capable of receiving and paying out the intermediate product as it is passed between the coiler furnaces and through the hot reversing mill so as to be reduced to an end product. A finishing line is provided downstream and inline with the coiler furnaces and the hot reversing mill.

In the preferred apparatus, the hot reversing mill includes a pair of four-high rolling mill stands adapted to be operated in tandem with an adjustable vertical edger positioned between the pair of rolling mill stands. Additionally, the slab loading and unloading means includes a first slab transfer device adjacent the slab conveyor table and operable transverse to the slab conveyor table, wherein the feed and run back table is positioned adjacent an end of the first slab transfer device. A second slab transfer device is adjacent the feed and run back table, wherein the slab collection and storage area is adapted to receive slabs from and supply slabs to the second slab transfer device. Additionally, the preferred embodiment of the present invention includes a second reheat furnace having an entry end inline with a feed and run back table and an exit end inline with the slab conveyor table.

The preferred method of operation of processing coil plate, sheet in coil form or discrete plate according to the present invention includes providing an intermediate thickness continuous caster and inline shear for casting an intermediate thickness strand and shearing the strand into a slab of predetermined length. Additionally, a slab loading and unloading device adjacent the slab collection and storage area for moving slabs between a position inline with the intermediate thickness caster and the slab collection and storage area is provided.

A slab originating from either the intermediate thickness caster or the slab collection and storage area is fed to an inline heating furnace. The slab to be reduced is extracted from the inline heating furnace onto a continuous processing line which includes a hot reversing mill having a coiler furnace on each of the upstream and downstream sides thereof. The slab to be worked is passed back and forth through the reversing mill to form an intermediate product of a thickness capable of being coiled. The intermediate product is coiled in one of the coiler furnaces. The coiled intermediate product is passed back and forth through the mill to reduce the coiled intermediate product to an end product of desired thickness, the intermediate product being collected in and fed out of each of the coiler furnaces on each pass through the hot reversing mill. The end product may be finished into one of either coiled plate, discrete plate or sheet in coil form.

The method according to the present invention also provides that some of the slabs supplied to the heating furnace may be outsourced (i.e., slabs which were not cast in the intermediate thickness caster). These outsourced slabs may have a thickness greater than slabs cast by the intermediate thickness caster and/or a chemistry different from that which can be produced on the melting/refining furnace(s) associated with the caster. The hot reversing mills of the present invention include a pair of rolling mill stands adapted for operation in tandem further including an adjustable vertical edger positioned between the pair of rolling mill stands. The preferred method of the present invention includes a second heating furnace adjacent the inline heating furnace to provide for a wide versatility in slab sourcing, sequencing and processing, as will be described in detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating an intermediate thickness strip caster and inline hot reversing mill and coiler furnace arrangement according to one embodiment of the present invention; and

FIG. 2 is a schematic illustrating an intermediate thickness strip caster and inline hot reversing mill and coiler furnace arrangement with multiple reheat and equalizing furnaces according to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The intermediate thickness slab caster and inline hot strip and plate line of one embodiment of the present invention is illustrated in FIG. 1 and was discussed in greater detail in the aforementioned parent application. One or more electric melting furnaces 26 provide molten metal at the entry end of the combination caster and strip and plate line 25, which is fed into a ladle furnace 28 prior to caster 30 and (curved or straight) mold 32 of rectangular cross section. A torch cutoff or shear 34 at the exit of mold 32 cuts the solidified metal strand into an intermediate thickness slab of the desired length which also has a width of 24 to 120 inches.

The slab then feeds on a conveyor table 36 to a slab takeoff area where it may be directly charged into a furnace 42 or may be removed from the inline processing and stored in a slab collection and storage area 40. The preferred furnace is of the walking beam type, although a walking hearth furnace could also be utilized in certain applications. Full-size slabs 44 and discrete length slabs 46 for certain plate products are shown within walking beam furnace 42. Slabs 38 which are located in the slab collection and storage area 40 may also be fed into the furnace 42 by means of slab pushers 48 or charging arm devices located for indirect charging of walking beam furnace 42 with slabs 38. It is also possible to charge slabs from other slab yards or storage areas. Because the intermediate thickness slabs retain heat to a much greater extent than the 2 inch thin slabs, temperature equalization is all that is required in many modes of operation. Of course, where slabs are introduced from off-line locations, the furnace 42 must have the capacity to add Btu's to bring the slabs up to rolling temperatures.

Slab extractors 50 remove slabs from furnace 42 and position them onto a feed and run back table 52. Descaler 53 and/or a vertical edger 54 may be utilized on the slabs. A vertical edger normally could not be used with a slab of only 2 inches or less.

Downstream of feed and run back table 52 and vertical edger 54 is a hot reversing mill 56 having upstream and downstream coiler furnaces 58 and 60, respectively. Cooling station 62 is downstream of coiler furnace 60. Downstream of cooling station 62 is a coiler 66 operated in conjunction with a coil car 67 followed by a plate table 64 operated in conjunction with a shear 68. The final product is either coiled on coiler 66 and removed by coil car 67 as sheet in strip or coil plate form or is sheared into plate form for further processing inline. A plate product is transferred by transfer table 70, which includes a cooling bed, onto a final processing line 71. The final processing line 71 includes a plate side shear 72, plate end shear 74 and plate piler 76.

The aforementioned parent application contains several specific examples for the processing line of FIG. 1, including the appropriate rolling schedules to illustrate the wide range of products that can be produced.

An intermediate thickness slab caster and inline hot strip and plate line including multiple furnaces and/or a multiple stand hot reversing mill according to a second embodiment of the present invention is illustrated in FIG. 2. The process line in FIG. 2 is similar in many respects to the line illustrated in the embodiment shown in FIG. 1. One or more electrical melting furnaces 126 will provide the molten metal at the entry end of the combination intermediate thickness caster and strip and plate processing line. The molten metal is fed into a ladle furnace 128 prior to being fed into the intermediate thickness caster 130. The caster 130 feeds into a curved or straight mold 132 of rectangular cross section. A torch cutoff or shear 134 is positioned at the exit end of the mold 132 to cut the strand of solidified metal into an intermediate thickness slab of desired length which may also have a width of 24 to 120 inches. The intermediate thickness slab then feeds onto a slab conveyor table 136. A hot scarfer 137 may be positioned above the slab conveyor table 136 for processing the surface of the slabs. The slab may be removed from the inline processing and stored in a slab collection and storage area 140 or it may be directly charged from the slab conveyor table 136 into an entry side of an equalizing or reheat furnace 142. The preferred furnace 142 is of a walking beam type, although a roller hearth furnace could be utilized in certain applications. The various slabs are fed through the furnace 142 and removed in a conventional manner and placed on a feed and run back table 152 positioned at the exit of the furnace 142.

When slabs are transferred to the slab collection and storage area 140, they can be removed from slab conveyor table 136 by a slab transfer table 138 operating transverse to the processing line. The slab transfer table 138 will transfer a slab from the slab conveyor table 136 to the feed and run back table 152. A second slab transfer table 144 is positioned adjacent the feed and run back table 152 to transfer slabs from the feed and run back table 152 to the slab collection and storage area 140. An alternative arrangement would combine the first and second slab transfer tables 138 and 144 into a single transfer table extending from the slab conveyor table to the slab collection and storage area 140 with the feed and run back table 152 extending from and receiving slabs from an intermediate portion of the combined slab transfer table.

A furnace 146 is positioned between the slab conveyor table 136 and the feed and run back table 152 and positioned adjacent the furnace 142. The furnace 146 may have an entrance side on the feed and run back table 152 and an exit end on the slab conveyor table 136. The slab storage area additionally includes a slab conditioning section 148 wherein further surface processing on the slabs can be performed, as needed.

The disclosed dual furnace and slab loading and unloading arrangement provides for great versatility in slab sourcing and processing. As discussed above, a slab cast from the intermediate thickness caster 130 can be fed directly through furnace 142 onto the feed and run back table 152 and into the processing line. Because the intermediate thickness slabs retain heat to a much greater extent than the thin slabs, the temperature equalization is generally all that will be required in many modes of operation.

The present arrangement additionally provides for transferring a slab from a position inline on the slab conveyor table 136 to the slab collection and storage area 140 through slab transfer tables 138 and 144. Such storage may be required to allow continuous casting to continue when a breakdown downstream in the processing line has occurred or, alternatively, allows for removing individual slabs for further processing in the slab conditioning section 148 such as due to any undesirable surface defects. The present arrangement provides for great variety in bringing slabs from the slab collection and storage area 140 back in the processing line.

In short delays, the slab may be passed directly onto the feed and run back table 152 by the slab transfer table 144 for subsequent processing. A second alternative would be to transfer a slab onto the slab conveyor table 136 through both slab transfer tables 138 and 144. The slab can then continue down through furnace 142 and to the feed and run back table 152 for processing. Where cold slabs are being re-introduced into the processing line, the present arrangement allows for the slab to be transferred to the slab conveyor table 136 through the reheat furnace 146 which will have a capacity to add Btu's to bring the slab up to the appropriate temperature for subsequent processing. The present arrangement additionally provides for introducing outsourced slabs into the processing line. Outsourced slabs refer to slabs which were not cast on the intermediate thickness caster 130. Such outsourced slabs may have any thickness, including a thickness greater than that cast on the intermediate thickness caster 130 and/or a chemistry different than what can be produced or achieved in electric melting furnaces 126 and ladle furnace 128. The additional ability of incorporating outsourced slabs into the processing line provides additional options for a more complete matching of the speed of the intermediate thickness caster 130 and the supply of outsourced slabs to the downstream processing.

An alternative embodiment of the present invention is contemplated wherein furnace 146 has an entrance side on the slab conveyor table 136 and an exit side on the feed and run back table 152. In such an arrangement, the slabs from the slab collection and storage area 140 would generally be supplied to the slab conveyor table 136 and then through an appropriate one of the furnaces 142 or 146. In this alternative arrangement, both furnaces would generally be operated in the same manner. In the embodiment disclosed in FIG. 2, furnace 146 can be utilized and operated as a reheat furnace whereas furnace 142 can be generally operated as an equalizing-type furnace.

The present arrangement additionally provides for directly transferring an appropriate slab from the slab conveyor table 136 to the feed and run back table 152 for subsequent processing without going through either of the furnaces 142 or 146. Such procedure would only be possible if the cast slab already contains an appropriate rolling temperature throughout. This alternative is simply intended to illustrate the inherent flexibility of the present design.

The slabs positioned on the feed and run back table 152 for subsequent working are passed through a conventional descaler 153. As discussed above, such a descaler process could be detrimental to 2 inch thin cast slabs.

Downstream of feed and run back table 152 and aligned therewith is a hot reversing mill which includes a pair of four-high rolling mill stands 156 configured to operate in tandem. Positioned between the pair of rolling mill stands 156 is an adjustable vertical edger 154. Vertical edger 154 is intended to be used conventionally or to taper the leading and trailing ends, respectively, of the slab on the first pass through the mill so as to compensate for the flaring out of the extreme ends which occurs during subsequent rolling. Such tapering can be controlled by the AGC, and the vertical edger can be passively driven by the twin stands of the mill. The effectiveness of the tapered ends can be monitored by a width gauge at the exit end of the downstream hot reversing stand wherein a fingerprint of the width is taken and adjustments are made through a feedback loop to the vertical edger, where necessary.

Upstream and downstream coiler furnaces 158 and 160, respectively, are positioned on either side of the pair of rolling mill stands 156 of the hot reversing mill. A run out table 161 extends downstream from the coiler furnace 160. A cooling station 162, such as laminar flow cooling, is downstream of the downstream coiler furnace 160 and extends along the run out table 161. Downstream of the cooling station 162 is an upcoiler 166 which can be operated in conjunction with a coil car 167. A subsequent finishing line may be provided substantially the same as described above in FIG. 1 which includes shear 68, transfer table 70, final processing line 71, plate side shear 72, plate end shear 74 and plate piler 76.

The provision of tandem operated twin reversing stands 156 in the hot reversing mill of the present invention includes increased processing tonnages as well as the ability to achieve lighter gauges such as 0.040 inch, which are of increasing importance in many industries such as the building industry where light gauge hot mill product is formed into studs and the like to replace lumber. The additional expense of incorporating a twin stand reversing mill rather than a single stand reversing mill is justified by the increased productivity and versatility and the incorporation of outsourced slabs from the slab collection and storage area 140, as discussed above. As noted, such outsourced slabs may have a thickness greater than those cast in the caster 130 and can provide for an even greater variety of product mix. The following Examples illustrate such a product mix.

EXAMPLE I

A 48.99 inch wide.times.0.040 inch thick sheet in coil form is produced from a 5 1/2 inch cast slab in accordance with the following rolling schedule:

EXAMPLE I (TANDEM REVERSING MILL)

__________________________________________________________________________24.495 TONS 1000. PIWROLLING SCHEDULE HSM - 48.99-5.5000/.0400__________________________________________________________________________ MILLPASS STAND GAUGE % DRAFT BITE LENGTH ELAPSEDNO. NAME IN. RED IN. ANGLE DEG. FT. TIME SEC.__________________________________________________________________________0 FCE: 5.5000 .0 .000 .00 53.5 .001 TF1: 3.9350 28.5 1.565 17.99 74.8 9.092 TF2: 2.4300 38.2 1.505 17.64 121.2 14.863 TF2: 1.3700 43.6 1.060 14.79 214.9 50.474 TF1: .6400 53.3 .730 12.26 460.1 55.395 TF1: .3250 49.2 .315 8.05 906.1 132.766 TF2: .1788 45.0 .146 5.48 1646.9 136.857 TF2: .1073 40.0 .072 3.83 2744.4 264.828 TF1: .0697 35.0 .038 2.78 4224.8 268.439 TF1: .0470 32.6 .023 2.16 6265.3 466.7610 TF2: .0400 14.9 .007 1.20 7361.8 466.76__________________________________________________________________________ MILL ENTRY EXIT ROLL RMSPASS STAND GAUGE TEMP. TEMP. FORCE TORQUE HORSE LOAD TIMENO. NAME IN. DEG. F. DEG. F. LB .times. 10**6 LB-FT .times. 10**6 POWER RATIO SEC.__________________________________________________________________________0 FCE: 5.5000 2250.00 2250.00 .0000 .0000 0. .0000 .001 TF1: 3.9350 2207.52 2200.11 2.7560 1.1437 12842. 1.9441 34.352 TF2: 2.4300 2197.20 2204.63 3.2310 1.3135 23883. 2.2326 45.303 TF2: 1.3700 2143.36 2121.95 3.6420 1.2393 13158. 2.1064 157.964 TF1: .6400 2107.87 2127.08 4.0939 1.1498 26134. 1.9544 129.335 TF1: .3250 2068.29 2014.94 4.0374 .7352 13789. 1.2496 120.826 TF2: .1788 2000.37 2014.71 3.5497 .4304 14673. 1.0481 82.767 TF2: .1073 1928.23 1934.41 3.5588 .2906 9652. .6895 60.838 TF1: .0697 1847.25 1855.03 3.7157 .2076 10617. .7583 72.429 TF1: .0470 1752.82 1752.20 4.9793 .1901 8272. .5909 69.2510 TF2: .0400 1725.05 1702.53 3.0653 .0556 2846. .2033 8.11__________________________________________________________________________ Distance/Length Ratio: .5000 Reversing Tandem Mill Peak Production: 188.93 TPH Coiling Begins at Pass Number: 4 *TF1* Tandem Passes Begin at Pass Number: 1 *TF1* Distance Between CFce #1 and Mill: 35.00 ft. Distance Between Mill and CFce #2: 35.00 ft. Coiling Furnace Diameter: 54.00 in. Coiling Furnace Temperature: 1650.00 Deg. F. Acceleration/Deceleration Rate: 250.00 FPM/sec. Final Body Temperature at TS: 1702.53 Deg. F.

Example I illustrates one of a wide variety of product types which can be rolled with the present system. As illustrated in this Example, the present mill can economically hot roll down to 0.040 inch thick. The provision of the twin stands allows for accurately rolling down to these light gauges for which there is an increased market demand.

EXAMPLE II

A 55 inch wide.times.0.060 inch thick sheet in coiled form is produced from a 5 1/2 inch cast slab in accordance with the following rolling schedule:

EXAMPLE II (TANDEM REVERSING MILL)

__________________________________________________________________________27.5 TONS 1000. PIWROLLING SCHEDULE HSM - 55.00-5.5000/0.0600__________________________________________________________________________ MILLPASS STAND GAUGE % DRAFT BITE LENGTH ELAPSEDNO. NAME IN. RED IN. ANGLE DEG. FT. TIME SEC.__________________________________________________________________________0 FCE: 5.5000 .0 .000 .00 53.5 .001 TF1: 3.9480 28.4 1.560 17.97 74.7 8.592 TF2: 2.5700 34.8 1.370 16.83 114.6 14.223 TF2: 1.6000 37.7 .970 14.14 184.0 42.794 TF1: .8500 46.9 .750 12.43 346.4 47.495 TF1: .4750 44.1 .375 8.78 619.9 106.786 TF2: .2470 48.0 .228 6.84 1192.2 110.947 TF2: .1480 40.1 .099 4.51 1989.7 218.888 TF1: .0941 36.4 .054 3.33 3129.3 222.599 TF1: .0706 25.0 .023 2.20 4171.0 371.8410 TF2: .0600 15.0 .011 1.47 4907.8 371.84__________________________________________________________________________ MILL ENTRY EXIT ROLL RMSPASS STAND GAUGE TEMP. TEMP. FORCE TORQUE HORSE LOAD TIMENO. NAME IN. DEG. F. DEG. F. LB .times. 10**6 LB-FT .times. 10**6 POWER RATIO SEC.__________________________________________________________________________0 FCE: 5.5000 2250.00 2250.00 .0000 .0000 0. .0000 .001 TF1: 3.9480 2208.27 2201.51 3.0812 1.2766 15141. 2.1699 40.462 TF2: 2.5700 2198.78 2204.63 3.3368 1.2942 23531. 2.1997 41.583 TF2: 1.6000 2154.98 2138.02 3.5295 1.1492 13876. 1.9534 109.024 TF1: .8500 2127.11 2140.93 4.0143 1.1449 26023. 1.9461 102.405 TF1: .4750 2096.08 2104.49 3.6429 .7284 12912. 1.2380 90.896 TF2: .2470 2092.28 2107.45 3.0257 .5876 20038. 1.4313 117.097 TF2: .1480 2024.39 2027.03 3.4411 .3386 9785. .6990 52.748 TF1: .0941 1958.84 1955.66 3.5483 .2473 11241. .8029 68.319 TF1: .0706 1854.68 1842.76 3.0025 .1305 5041. .3601 19.3510 TF2: .0600 1818.74 1795.94 2.1214 .0579 2634. .1882 5.21__________________________________________________________________________ Reversing Tandem Mill Peak Production: 266.20 TPH Coiling Begins at Pass Number: 4 *TF1* Tandem Passes Begin at Pass Number: 1 *TF1* Distance Between CFce #1 and Mill: 35.00 ft. Distance Between Mill and CFce #2: 35.00 ft. Coiling Furnace Diameter: 54.00 in. Coiling Furnace Temperature: 1650.00 Deg. F. Acceleration/Deceleration Rate: 250.00 FPM/sec. Final Body Temperature at TS: 1795.94 Deg. F.

Example II, like Example I, illustrates the versatility of the present system in hot rolling thin gauges. These hot rolled narrow gauge products, such as about 0.040 inch and about 0.060 inch thick, are able to be utilized as final end products in situations in which the final end product is generally not exposed and does not require any surface finishing. Metal construction studs, for example 0.040 inch galvanized studs, represent one final end product that can be hot rolled by the present invention. This is a distinct advantage over the known prior art which would generally hot roll somewhere above 0.080 inch thick then pickle and finish the product on a cold mill with a subsequent anneal and temper rolling.

EXAMPLE III

A 62 inch wide.times.0.090 inch thick sheet in coil form is produced from a 10 inch outsourced slab in accordance to the following schedule:

__________________________________________________________________________31 TONS 1000. PIWROLLING SCHEDULE HSM - 62.00-10.00/0.0900__________________________________________________________________________ MILLPASS STAND GAUGE % DRAFT BITE LENGTH ELAPSEDNO. NAME IN. RED IN. ANGLE DEG. FT. TIME SEC.__________________________________________________________________________0 FCE: 10.0000 .0 .000 .00 29.5 .001 TF1: 8.5500 14.5 1.450 17.32 34.4 3.112 TF2: 7.1000 17.0 1.450 17.32 41.5 8.183 TF2: 5.6500 20.4 1.450 17.32 52.1 12.384 TF1: 4.2000 25.7 1.450 17.32 70.1 17.695 TF1: 2.9300 30.2 1.270 16.20 100.5 26.696 TF2: 1.8700 36.2 1.060 14.79 157.5 32.377 TF2: 1.12000 40.1 .750 12.43 262.9 62.218 TF1: .6600 41.1 .460 9.73 446.2 66.309 TF1: .3878 41.2 .272 7.48 759.4 119.0110 TF2: .2521 35.0 .136 5.28 1168.2 122.8011 TF2: .1765 30.0 .076 3.94 1668.6 192.4312 TF1: .1324 25.0 .044 3.01 2224.3 195.9113 TF1: .1059 20.0 .027 2.33 2780.9 276.4614 TF2: .0900 15.0 .016 1.81 3272.2 276.46__________________________________________________________________________ MILL ENTRY EXIT ROLL RMSPASS STAND GAUGE TEMP. TEMP. FORCE TORQUE HORSE LOAD TIMENO. NAME IN. DEG. F. DEG. F. LB .times. 10**6 LB-FT .times. 10**6 POWER RATIO SEC.__________________________________________________________________________0 FCE: 10.0000 2250.00 2250.00 .0000 .0000 0. .0000 .001 TF1: 8.5500 2227.38 2225.39 3.2570 1.3008 19641. 2.2110 15.212 TF2: 7.1000 2224.30 2226.34 3.2540 1.2996 23630. 2.2090 15.183 TF2: 5.6500 2220.03 2217.71 3.2821 1.3108 22147. 2.2281 20.894 TF1: 4.2000 2215.05 2218.71 3.2788 1.3095 29763. 2.2258 20.845 TF1: 2.9300 2194.47 2198.55 3.5122 1.3115 19976. 2.2292 44.726 TF2: 1.8700 2195.76 2193.42 3.8134 1.2987 30993. 2.2138 44.107 TF2: 1.1200 2125.80 2135.32 4.1445 1.1833 22189. 2.0114 120.708 TF1: .6600 2121.51 2113.87 4.0563 .9016 28689. 2.0492 117.669 TF1: .3878 2076.96 2087.73 3.9993 .6770 17504. 1.2503 82.4010 TF2: .2521 2077.75 2084.45 3.2680 .3843 15284. 1.0917 60.6211 TF2: .1765 2030.67 2032.36 2.9640 .2547 10858. .7755 41.8812 TF1: .1324 1976.73 1976.45 2.6926 .1722 9786. .6990 33.1413 TF1: .1059 1916.07 1907.90 2.4442 .1177 5683. .4059 13.2714 TF2: .0900 1893.44 1880.60 1.9862 .0718 4081. .2915 6.67__________________________________________________________________________ Reversing Tandem Mill Peak Production: 403.72 TPH Coiling Begins at Pass Number: 8 *TF1* Tandem Passes Begin at Pass Number: 1 *TF1* Distance Between CFce #1 and Mill: 35.00 ft. Distance Between Mill and CFce #2: 35.00 ft. Coiling Furnace Diameter: 54.00 in. Coiling Furnace Temperature: 1650.00 Deg. F. Acceleration/Deceleration Rate: 250.00 FPM/sec. Final Body Temperature at TS: 1880.60 Deg. F.

EXAMPLE III (TANDEM REVERSING MILL)

Example III illustrates the flexibility of the present system which can receive outsourced slabs for further processing. Such outsourced slabs may be, as here, slabs which are too thick to be cast in the intermediate thickness caster or slabs which have a specialized composition limiting where they may be produced or simply additional slabs to supplement the caster product. The rolling of outsourced slabs and the ability to store cast slabs allows the casting and rolling to be decoupled and operated independently of each other.

EXAMPLE IV

A 48 inch wide.times.0.125 inch thick sheet of high carbon steel (0.51-0.95 carbon) in coil form is produced from a 5 1/2 inch thick cast slab in accordance to the following rolling schedule:

__________________________________________________________________________24.000 TONS 1000. PIWROLLING SCHEDULE HSM - 48.00-5.5000/.1250__________________________________________________________________________ MILLPASS STAND GAUGE % DRAFT BITE LENGTH ELAPSEDNO. NAME IN. RED IN. ANGLE DEG. FT. TIME SEC.__________________________________________________________________________0 FCE: 5.5000 .0 .000 .00 53.5 .001 TF1: 3.9350 28.5 1.565 17.99 74.8 8.762 TF2: 2.5200 36.0 1.415 17.10 116.9 14.983 TF2: 1.6500 34.5 .870 13.39 178.5 39.524 TF1: .9850 40.3 .665 11.70 299.0 44.035 TF1: .5600 43.1 .425 9.35 525.8 87.356 TF2: .3500 37.5 .210 6.57 841.3 91.407 TF2: .2450 30.0 .105 4.64 1201.9 153.788 TF1: .1830 25.3 .062 3.57 1609.1 157.519 TF1: .1470 19.7 .036 2.72 2003.2 230.6010 TF2: .1250 15.0 .022 2.12 2355.8 230.60__________________________________________________________________________ MILLPASS STAND GAUGE ENTRY TEMP. DEG. F. EXIT TEMP. DEG. F.NO. NAME IN. Front Tail Diff. Front Tail Diff.__________________________________________________________________________0 FCE: 5.5000 2250.0 2250.0 .0 2250.0 2250.0 .01 TFI: 3.9350 2225.0 2214.4 10.7 2213.6 2209.5 4.12 TF2: 2.5200 2208.4 2206.1 2.3 2216.4 2215.6 .83 TF2: 1.6500 2131.5 2208.1 76.6 2125.0 2173.8 48.84 TFl: .9850 2120.1 2161.8 41.7 2135.6 2171.0 35.55 TFl: .5600 2119.4 2025.2 94.2 2123.6 2045.4 78.36 TF2: .3500 2093.5 2036.7 56.9 2094.6 2053.5 41.17 TF2: .2450 1879.0 2014.6 135.6 1892.8 2000.6 107.88 TF1: .1830 1882.3 1954.2 71.9 1891.6 1938.4 46.89 TF1: .1470 1835.9 1776.8 59.1 1811.6 1780.2 31.410 TF2: .1250 1762.7 1767.6 4.9 1736.9 1765.0 28.2__________________________________________________________________________ MILLPASS STAND GAUGE ROLL FORCE LB .times. 10**6 TORQUE LB-FT .times. 10**6NO. NAME IN. Front Tail Front Tail__________________________________________________________________________0 FCE: 5.5000 .0000 .0000 .0000 .00001 TF1: 3.9350 3.3819 3.3961 1.4016 1.40762 TF2: 2.5200 3.7790 3.7821 1.4872 1.48843 TF2: 1.6500 3.6795 3.4730 1.1318 1.06834 TF1: .9850 3.9123 3.7526 1.0476 1.00485 TF1: .5600 3.9918 4.4220 .8474 .93876 TF2: .3500 3.4093 3.6004 .5011 .52927 TF2: .2450 3.5301 3.0166 .3596 .30738 TF1: .1830 2.9834 2.7839 .2282 .21299 TF1: .1470 2.6765 2.8334 .1515 .159510 TF2: .1250 2.4248 2.2978 .1027 .0980__________________________________________________________________________ MILLPASS STAND GAUGE HORSEPOWER LOAD RATIO RMS TIMENO. NAME IN. Front Tail Front Tail SEC.__________________________________________________________________________0 FCE: 5.5000 0. 0. .0000 .0000 .001 TF1: 3.9350 16321. 16390. 2.3824 2.3925 49.952 TF2: 2.5200 27040. 27062. 2.5278 2.5299 56.053 TF2: 1.6500 18428. 17393. 1.9238 1.8158 85.814 TF1: .9850 28572. 27405. 2.0408 1.9575 90.355 TF1: .5600 19680. 21801. 1.4403 1.5955 99.816 TF2: .3500 18623. 19667. 1.3302 1.4048 76.837 TF2: .2450 12209. 10433. .8721 .7452 40.798 TF1: .1830 10373. 9679. .7409 .6914 30.959 TF1: .1470 5855. 6164. .4182 .4403 13.4710 TF2: .1250 4669. 4454. .3335 .3181 7.50__________________________________________________________________________ Reversing Tandem Mill Peak Production: 374.68 TPH Coiling Begins at Pass Number: 4 *TF1* Tandem Passes Begin at Pass Number: 1 *TF1* Distance Between CFce #1 and Mill: 35.00 ft. Distance Between Mill and CFce #2: 35.00 ft. Coiling Furnace Diameter: 54.00 in. Coiling Furnace Temperature: 1650.00 Deg. F. Acceleration/Deceleration Rate: 250.00 FPM/sec. Final Front Temperature at TS: 1736.86 Deg. F. Final Tail Temperature at TS: 1765.03 Deg. F.

EXAMPLE IV (TANDEM REVERSING MILL)

EXAMPLE V

A 60 inch wide.times.0.100 inch thick sheet in coil form is produced from a 5 inch cast slab of low carbon steel according to the following rolling schedule:

__________________________________________________________________________30.000 TONS 1000. PIWROLLING SCHEDULE HSM - 60.00-5.0000/.1000__________________________________________________________________________ MILLPASS STAND GAUGE % DRAFT BITE LENGTH ELAPSEDNO. NAME IN. RED IN. ANGLE DEG. FT. TIME SEC.__________________________________________________________________________0 FCE: 5.0000 .0 .000 .00 58.9 .001 TF1: 3.7000 26.0 1.300 17.37 79.6 9.202 TF2: 2.4000 35.1 1.300 17.37 122.7 15.293 TF2: 1.3750 42.7 1.025 15.41 214.1 40.094 TF1: .8250 40.0 .550 11.28 356.9 44.525 TF1: .4580 44.5 .367 9.21 642.9 87.666 TF2: .2920 36.2 .166 6.19 1008.4 92.027 TF2: .2085 28.6 .083 4.39 1412.2 154.388 TF1: .1500 28.1 .058 3.67 1963.0 158.359 TF1: .1176 21.6 .032 2.73 2503.8 230.9910 TF2: .1000 15.0 .018 2.01 2944.5 230.99__________________________________________________________________________ MILL ENTRY EXIT ROLL RMSPASS STAND GAUGE TEMP. TEMP. FORCE TORQUE HORSE LOAD TIMENO. NAME IN. DEG. F. DEG. F. LB .times. 10**6 LB-FT .times. 10**6 POWER RATIO SEC.__________________________________________________________________________0 FCE: 5.0000 2300.00 2300.00 .0000 .0000 0. .0000 .001 TF1: 3.7000 2257.40 2245.50 2.6914 .9614 12731. 1.4293 16.912 TF2: 2.4000 2240.90 2244.50 3.1851 1.1359 23190. 1.6888 26.323 TF2: 1.3750 2150.30 2149.90 3.8551 1.2119 27833. 1.8817 76.114 TF1: .8250 2146.10 2156.40 3.2415 .7469 28591. 1.2744 35.965 TF1: .4580 2133.40 2040.00 3.9262 .7340 23884. 1.0912 50.886 TF2: .2920 2014.20 2008.40 3.1308 .3886 19835. .8855 30.507 TF2: .2085 1857.00 1844.40 2.9526 .2559 11744. .5243 14.698 TF1: .1500 1856.80 1845.10 2.8790 .2052 13091. .5814 19.469 TF1: .1176 1790.80 1757.90 2.6673 .1368 7420. .3313 7.4310 TF2: .1000 1712.50 1677.20 12.2102 .0801 5110. .2281 3.12__________________________________________________________________________ Reversing Tandem Mill Peak Production: 467.52 TPH Coiling Begins at Pass Number: 4 *TF1* Distance Between CFce #1 and Mill: 27.00 ft. Distance Between Mill and CFce #2: 27.00 ft. Coiling Furnace Diameter: 54.00 in. Coiling Furnace Temperature: 1750.00 Deg. F. Acceleration/Deceleration Rate: 250.00 FPM/sec. Final Temperature at TS: 1677.17 Deg. F.

EXAMPLE V (TANDEM REVERSING MILL)

Examples IV and V show the range of grades producible on the present invention providing the broad product mix needed for a competitive mill.

Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.

Claims

1. An intermediate thickness slab caster and inline hot strip and plate line comprising:

a) an intermediate thickness continuous strip caster;

b) an inline cutoff downstream of said caster for cutting an intermediate thickness slab to a desired length;

c) a slab conveyor table inline with said cutoff;

d) a slab transfer means adjacent said slab conveyor table operable transverse of said slab conveyor table;

e) a feed and run back table positioned in communication with said slab transfer means;

f) a slab collection and storage area adjacent said slab transfer means adapted to selectively receive slabs therefrom;

g) a first reheat furnace positioned between said feed and run back table and said slab conveyor table;

h) a second reheat furnace downstream of and adjacent said first reheat furnace and having an entry end inline with said slab conveyor table and an exit inline with said feed and run back table;

i) a hot reversing mill means inline with said feed and run back table for reducing a slab on said feed and run back table to an intermediate product of a thickness sufficient for coiling in a number of flat passes; and

j) a pair of coiler furnaces positioned inline with said feed and run back table, one located upstream of said hot reversing mill means and the other located downstream, said coiler furnaces capable of receiving and paying out said intermediate product as it is passed between said coiler furnaces and through said hot reversing mill means so as to be reduced to an end product.

2. The apparatus of claim 1 wherein said first reheat furnace has an entry end inline with said feed and run back table and an exit inline with said slab conveyor table.

3. The apparatus of claim 1 wherein said hot reversing mill means includes a pair of rolling mill stands operated in tandem.

4. The apparatus of claim 3 further including an adjustable vertical edger positioned between said pair of rolling mill stands.

5. The apparatus of claim 1 wherein said slab transfer means includes a first slab transfer table positioned between said slab conveyor table and said feed and run back table, and a second slab transfer table positioned between said feed and run back table and said slab collection and storage area.

6. An intermediate thickness slab caster and inline hot strip and plate line comprising:

a) an intermediate thickness continuous strip caster;

b) an inline cutoff downstream of said caster for cutting an intermediate thickness slab;

c) a slab conveyor table inline with said cutoff;

d) a slab loading and unloading means adjacent said slab conveyor table for removing and supplying slabs thereto;

e) a slab collection and storage area adjacent said slab loading and unloading means for receiving and supplying slabs thereto;

f) at least one reheat furnace having an entry end inline with said slab conveyor table for receiving slabs therefrom;

g) a feed and run back table positioned at an exit end of said at least one reheat furnace;

h) a hot reversing mill inline with said feed and run back table for reducing a slab on said fed and run back table to an intermediate product in a number of flat passes, said hot reversing mill including a pair of rolling mill stands adapted to be operated in tandem; and

i) a pair of coiler furnaces positioned inline with said feed and run back table, one located upstream of said hot reversing mill means and the other located downstream, said coiler furnaces capable of receiving and paying out said intermediate product as it is passed between said coiler furnaces and through said hot reversing mill means so as to be reduced to an end product.

7. The apparatus of claim 6 wherein said slab loading and unloading means includes:

i) a first slab transfer means adjacent said slab conveyor table operable transverse of said slab conveyor table, wherein said feed and run back table is positioned adjacent an end of said first slab transfer means; and

ii) a second slab transfer means adjacent said feed and run back table, wherein said slab collection and storage area is adapted to receive slabs from said second slab transfer table.

8. The apparatus of claim 6 further including a reheat furnace having an entry end inline with said feed and run back table and an exit end inline with said slab conveyor table.

9. The apparatus of claim 6 further including an adjustable vertical edger positioned between said pair of rolling mill stands.

10. A method of processing metal slabs comprising the steps of:

a) providing an intermediate thickness continuous caster and inline cutoff for casting an intermediate thickness strand and cutting said strand into a slab of predetermined length;

b) providing a slab loading and unloading means adjacent a slab collection and storage area for moving slabs between a position inline with said intermediate thickness caster and said slab collection and storage area;

c) feeding a slab to be worked into an inline heating furnace wherein said slab to be worked is from either said intermediate thickness caster or said slab collection and storage area;

d) extracting said slab to be worked from said inline heating furnace onto a continuous processing line including a hot reversing mill having a coiler furnace on each of an upstream and downstream side thereof;

e) flat passing said slab to be worked back and forth through said mill to form an intermediate product of a thickness sufficient for coiling;

f) coiling said intermediate product in one of said coiler furnaces; and

g) passing said coiled intermediate product back and forth through said mill to reduce said coiled intermediate product to an end product of desired thickness, said intermediate product being collected in and fed out of each of said coiler furnaces on each pass through said hot reversing mill.

11. The method of claim 10 including casting said strand to a thickness between 3.50 and 5.50 inches.

12. The method of claim 10 further including supplying at least one slab to be worked to said heating furnace and said continuous processing line from said slab collection and storage area which was not cast in said intermediate thickness caster.

13. The method of claim 12 wherein said at least one slab to be worked which was not cast in said caster has a thickness greater than said slabs cast by said caster.

14. The method of claim 10 further including the step of surface conditioning at least one slab in said slab collection and storage area.

15. The method of claim 10 wherein said hot reversing mill includes a pair of rolling mill stands operated in tandem.

16. The method of claim 15 further including an adjustable vertical edger positioned between said pair of rolling mill stands.

17. The method of claim 10 further including a second heating furnace adjacent said inline heating furnace.

18. The method of claim 10 wherein said intermediate product is formed after no more than three flat passes through said hot reversing mill when said slab to be worked is cast in said caster.

19. The method of claim 10 wherein said end product has a thickness of equal to or less than 0.060 inch.

20. The method of claim 19 wherein said end product has a thickness of about 0.040 inch.

21. A method of processing metal slabs comprising the steps of:

a) continuously casting an intermediate thickness strand;

b) cutting said strand into a slab of predetermined length;

c) feeding said slab into at least one inline heating furnace;

d) extracting said slab to be worked from said inline heating furnace onto a continuous processing line including a hot reversing mill having a coiler furnace on each of an upstream and downstream side thereof;

e) flat passing said slab to be worked back and forth through said mill to form an intermediate product of a thickness sufficient for coiling;

f) coiling said intermediate product in one of said coiler furnaces; and

g) passing said coiled intermediate product back and forth through said mill to reduce said coiled intermediate product to an end product of a thickness of equal to or less than about 0.060 inch, said intermediate product being collected in and fed out of each of said coiler furnaces on each pass through said hot reversing mill.

22. The method of claim 21 wherein said end product has a thickness of about 0.040 inch.

23. The method of claim 21 wherein said hot reversing mill includes a pair of rolling mill stands operated in tandem.

24. A method of processing metal slabs comprising the steps of:

a) continuously casting an intermediate thickness strand;

b) cutting said strand into a slab of predetermined length;

c) selectively feeding said slab to either

i) a continuous processing line including a hot reversing mill having a coiler furnace on each of an upstream and downstream side thereof, or

ii) an inline furnace from which said slab exits to said continuous processing line, or

iii) a slab collection and storage area and subsequently transferring said slab to said furnace;

d) flat passing said slab to be worked back and forth through said mill to form an intermediate product of a thickness sufficient for coiling;

e) coiling said intermediate product in one of said coiler furnaces; and

f) passing said coiled intermediate product back and forth through said mill to reduce said coiled intermediate product to an end product of desired thickness, said intermediate product being collected in and fed out of each of said coiler furnaces on each pass through said hot reversing mill.