Field of the Invention. This invention relates to the hot rolling of metals on a rolling mill, more specifically, to rolling on a continuous wide-strip hot mill and can be used for the development and improvement of continuous hot mills equipped with reheat furnaces.

Background Art. Currently, approximately 90% of hot rolled steel sheets are fabricated continuous wide-strip hot mills equipped with continuous reheat furnaces. Basic process requirements imposed on the reheat furnaces include the capability of heating the pieces to the rolling process temperature and providing the required temperature gradient across the rolled piece section. Reheating may have some restrictions, e.g. specific heating rate, maximum metal temperature gradient during heating, minimum metal surface exposure to high temperatures etc.

Known is a rolling mill hot rolling method (EP 0770433, publ. 02.05.1997). This method is implemented using a rolling line and comprises at least one descaling before feeding to the roughing stand of mill. After continuous casting the slabs are cut into specified length segments, pass the first descaling stage, are heated in the reheat furnace, pass the second descaling stage and are fed to the roughing mill.

The disadvantages of this method include:

- incomplete descaling of the bottom slab surface;

- the appearance of "dark spots" on the bottom slab surface that lead to nonuniform thickness of the final product.

The closest counterpart of this invention is the continuous wide-strip mill for hot rolling method (V.N. Khloponin, Methods of Reducing Feeding Strip Cooling in Strip Hot Rolling Mill Process Line, in: Metallurgical Heat Engineering: History, State of the Art and Future. One Hundredth Anniversary of M.A. Glinkov: Proceedings of the 3 ^rd International Research and Practical Conference, 1-3 February 2006, MISAA; Moscow; MISAA, 2006, p. 617-624).

Sheet rolling mills are equipped with pusher type, walking beam type or walking hearth type reheat furnaces. In large capacity rolling mills the furnace section may comprise 3 to 5 furnaces. Often, e.g. in 5000 type rolling mills, the reheat furnaces comprise bogie hearth chamber furnaces. Sheet rolling mills can roll slabs that are 100 - 400 mm in thickness, 400 - 4500 mm in width and 1500 - 12,000 mm in length. The rolling reheat temperature depends primarily on heated metal grade. For example, the reheat temperature is 1060 - 1200°C for alloy and high- quality steels, 1200 - 1250°C for ordinary steels and 1280 - 1300°C for sulfide transformer steels. According to said known method, after the furnace reheating the slabs are fed to the scale breaker, the roughing mill section, the preliminary coil-box, the cooler, the coilers or to the sheet finishing devices including cutting tools.

The disadvantages of said known method include:

- impossibility of providing highly uniform metal heating because the bottom slab surface has insufficiently heated areas, the "dark spots" produced by the exposure of the slabs to the water cooled components of the system of transport of metall;

- asymmetrical heat field across the slab thickness due to the different top and bottom slab heating conditions: the slabs are heated faster either at the top or at the bottom, and it is almost impossible to understand how heating actually occurs;

- large fuel consumption for metal reheating due to the necessity of spending heat for heating the large water cooled system of transport of metall installed in the reheat furnace;

- appreciable metal losses with the scale due to the long term metal exposure in the furnace which primarily concerns the 5000 type rolling mills that are used for rolling up to 400 mm thick slabs;

- large nitrogen oxide waste gas.

Disclosure of the Invention. The technical object of this invention is to provide a continuous rolling on a wide-strip hot mill rolling method achieving higher quality of the rolled metal, higher reheating efficiency and lower power consumption of the method.

The abovementioned technical result is achieved as follows.

According to the sheet rolling mill hot rolling method disclosed herein, prior to reheating the slabs are positioned vertically by putting them onto their longer edges and transferred to the slab surface examination chamber. Following that the slabs are transferred to the pusher type reheat furnace wherein they are moved in the vertical position along the roller hearth and heated with high efficiency gas burners at both sides. The heated slabs are sequentially descaled in the scale breaker and rough rolled in the roughing mill section. The as-roughed feeding strip is unwound in the preliminary coil-box and finally rolled in the finishing mill section. Following that the strip is cooled in the adjustable cooling section and coiled in the coiler.

After said slab surface examination chamber the slab surfaces are further treated before feeding the slabs to said pusher type reheat furnace.

Furthermore, after said pusher type reheat furnace the slabs are repositioned horizontally, descaled in the horizontal position and then rolled in the roughing mill section in the horizontal position.

Additionally, after said pusher type reheat furnace the slabs are descaled in the vertical scale breaker, transferred in the vertical position to the additional chamber for examination, high precision heating and complete scale removal from both surfaces, and following that chamber they are repositioned horizontally and passed through said roughing stand of mill.

Furthermore, after said additional examination, high precision heating and complete scale removal chamber the slabs in the vertical position are rolled in said vertical roughing mill section and coiled in the vertical preliminary coil-box following which the strip is repositioned horizontally and transferred to the finishing stands.

Additionally, after said vertical roughing mill section the feeding strip is passed through a pair of parallel vertical preliminary coil-boxes that work in sequence.

Furthermore, in said finishing device the strip is coiled or transferred to the sheet cutting device.

Brief Description of the Drawings. The invention will be further explained with the drawing where Figs. 1-4 show process lines for the implementation of the method according to this invention.

The drawing shows the following sections used in the continuous wide-strip rolling hot metal rolling process: continuous casting machine 1, first tilting gear 2, first examination device 3, first distributor 4, reheat furnace 5, second distributor 6, second tilting gear 7, vertical or horizontal scale breaker 8, horizontal or vertical roughing mill section 9, first preliminary coil-box 10 installed before the horizontal or vertical finishing mill section 11, adjustable strip cooling system 12, coilers 13, sheet finishing section 14, examination, edge heating and residual descaling chamber 15 and second coil-box 16 installed before the horizontal or vertical finishing mill section. Embodiments of the Invention. The method is implemented as follows. After the continuous casting machine 1 the slab is fed to the hot rolling mill on the horizontal roller conveyor, positioned vertically by the first tilting gear 2 and put onto its longer edge. In this position the slab passes through the first examination device 3 where its top and bottom surfaces are inspected visually and instrumen- tally. If the condition of the slab surfaces does not meet the process requirements, the slab after the device 3 is returned to the preparation section. If their condition is compliant with the process requirements, the slab is transferred in the vertical position to the reheat furnace 5 where it is moved on the rolled hearth and heated absolutely symmetrically at both sides with the special high efficiency gas burners.

In a general case the heated slabs are sequentially descaled in the scale breaker and rough rolled in the roughing mill section. The resultant feeding strip is unwound in the coil-box and finishing rolled in the finishing mill section. The strip is then cooled in the adjustable cooling section and coiled in the coil box.

In one embodiment of the method (Fig. 1) the heated slab after the furnace 5 is fed to the second tilting gear 7 which transfers it from vertical to horizontal position and is fed horizontally to the horizontal scale breaker 8. Then the slab passes the roughing mill section 9, the device 10, the finishing mill section 11 and the cooler 12. The rolled strip is then fed for finishing to the coiler 13 or to the sheet cutting line 4 where it is cut into required length sheets and stacked for shipment.

Figure 2 shows a specific embodiment of the method wherein the slabs after the reheat furnace 5 are descaled in the vertical scale breaker 8, transferred in the vertical position to the additional chamber 15 for examination, high precision heating and complete scale removal from both surfaces, following which the slabs are repositioned horizontally with the second tilting gear 7 and passed through the roughing mill section 9.

Figure 3 shows a specific embodiment of the method wherein the slabs after the additional chamber 15 the slabs in the vertical position are rolled in the vertical roughing mill section 9 and coiled in the vertical preliminary coil-box 10 following which the feeding strip is repositioned horizontally and transferred to the finishing mills 11 for finishing rolling.

Figure 4 shows a specific embodiment of the method wherein the slabs after the vertical roughing mill section 9 the feeding strip is passed through a pair of parallel vertical preliminary coil boxes 10, 16 that work in sequence. For that embodiment the feeding strip is first received by the first device 10 and then by the second one. Furthermore, when the second device 16 receives and coils the strip, the first device 10 transfers its strip to the finishing mill section 11. The process is then repeated: the first device 10 receives a new feeding strip while the second device 16 transfers its strip to the finishing stands section 11.

In the finishing device the strip is coiled in the coilers 13 or fed to the sheet cutting device 14.

Vertical slab heating in the furnace 5 with high efficiency gas burners provides for the absolutely symmetrical heating of the metal with the minimum possible temperature gradient across the slab thickness and width. By making use of the convective component and avoiding the cooling and screening effect of the conveyor system (the water-cooled skids and the support and mobile skids of the walking beam type hearth) this method reduces the time of metal heating, minimizes scale formation and reduces the nitrogen and carbon oxides in waste gas of the plant. The method provides for a simplified heating control because the radiation pyrometers installed in the furnace at both sides of the moving slabs scan the slab surfaces along their length and height (width) thus avoiding any longitudinal nonuniformity of slab heating or provide for the required temperature difference upon slab output from the furnace, i.e. the so-called thermal wedge effect when the trailing slab edge is overheated by several decades of degrees compared to the leading edge.

The vertical scale breaker 8 and the additional chamber 1 for examination, bottom support slab edge heating and residual descaling have for the first time in metallurgical practice provided for the same rolling conditions at the top and bottom slab surfaces. This will increase the quality of the product metal and avoid rolled-in scale defects.

Equipping the rolling mill with the roughing mill section 9 with vertical rollers and the vertical device 10 will increase the quality of the product metal and the output of the roller mills.