RU2089307C1 - Method of supercompact production of endless hot strip on continuous-reversing casting-rolling unit - Google Patents

Abstract

FIELD: production of endless hot strip on continuous-reversing casting-rolling unit. SUBSTANCE: the offered method includes continuous casting of metal into thin slab; accumulation and heating of slab, its reversing rolling into endless strip by successive sections for several passes with return of rolled section to zone of accumulation; cooling of rolled strip, cutting and coiling. After each pass, except for the last, rolled section is simultaneously heated and accumulated. Accumulation is effected by two-inlet coiling into intermediate roll with its simultaneous motion in direction of production process flow of metal. In course of return of strip, roll is uncoiled with simultaneous motion against metal flow. After the last pass, rolled section of strip is simultaneously accumulated and heat-insulated between zones of heating-accumulation of rolled section of strip and cooling. Further on, for the cycle of rolling of the next section of slab, rolled section of strip is continuously fed to cooling zone. EFFECT: higher efficiency. 2 cl, 19 dwg, 2 tbl

Description

 The invention relates to the field of rolling production and can be used in the shops of hot sheet rolling of metallurgical plants.

 A known method for the production of hot rolled strips, including continuous casting of a thin slab on a continuous casting machine, cutting it into sections of a certain length, heating cut sections of the slab in a continuous heating furnace, rolling them into strips on a multi-strand continuous mill, cooling the strips in a cooling device, and winding them onto final winder (see application EP N 0266564, CL B 21 B 1/46, 1988).

 The disadvantage of this method is the relatively low speed of rolling in a continuous multi-bench mill in the absence of special technical means of controlling the temperature regime of rolling, which limits the ability to maintain the temperature of the strip in a narrow range.

 Thermal insulation of the rolled strip between rough and finish rolling is known on the intermediate roller table of a broadband hot rolling mill (see, for example, Salganik V.M. Gun I.G. Development of broadband hot rolling mills // Ferrous metallurgy. Bull. In-ta Chermetinformation). M. 1990. Issue 3). In the known method, this operation is designed to reduce the power parameters of rolling by increasing the average temperature of the roll before finishing rolling.

 The accumulation of the strip after rolling on the mill before winding into finished rolls on final winders is also known (see ed. St. USSR N 737033, class B 21 B 1/24, 1980). In the known method, this operation provides increased mill productivity.

 Closest to the claimed method in technical essence is a method for the production of hot-rolled strips on a continuously reversible casting and rolling unit, including continuous casting of metal into a thin slab, its heating and accumulation by two-input winding into an intermediate roll, periodic delivery from the accumulation zone in successive sections, rolling into the strip by these separate sections for several passes on the rolling mill with the return of the rolled section of the strip into the accumulation zone, cooling of the strip, cutting and winding in rolls ready (see. application WO N 92/00079, cl. B 21 B 1/46, 1992). Moreover, the accumulation of the slab in the known method is carried out by two-input winding into an intermediate roll while moving this roll against the process metal stream. These operations, as well as the sequence of their implementation, exhibit a technical effect in the known method, which consists in coordinating the performance of a continuous casting machine for thin slabs and a reversing rolling mill in the production of an endless strip.

 However, the delivery in the described method of the rolled section of the strip during the rolling process directly to the discharge roller table and the final winder leads to the fact that during the passage of each section of the strip in the direction of the metal flow and return to the accumulation zone, it is intensively cooled. In addition, when returning the strip, you have to reverse the final winder, unwinding the finished strip from it. As a result of significant temperature losses of the metal during movement along the discharge roller table, the energy and power parameters of rolling increase and the energy consumption for it increases. The resulting non-uniformity of the temperature and power parameters of rolling along the length of the strip section can be significant and unavoidable in subsequent passes and can lead to uneven mechanical properties and geometric characteristics of the rolled strip. The unwinding of the hot-rolled strip from the final winder and, as a consequence, its additional cooling also lead to significant instability of the temperature regime of the winding of the finished hot-rolled strip and significant unevenness along the strip length of its physical and mechanical properties, that is, to a decrease in the quality of the finished rolling. Reversing the final winder and intensive cooling of the rolled strip section narrows the range of hot rolled strips produced on the unit. The implementation in the prototype of the accumulation on one end winder and the rolled section of the strip and the final product leads to a negative temperature effect on each other and causes significant loss of under-rolled metal due to its rapid supercooling in the event of delays on the rolling mill.

 The basis of the invention is the task of creating such a method of ultra-compact production of an endless hot rolled strip on a continuously reversible casting and rolling unit, which, by improving the temperature regime of rolling by eliminating intensive cooling of the rolled section of the endless strip in the process of issuing it from the rolling zone in the direction of the metal flow and return to the accumulation zone, as well as by stabilizing the temperature regime of the winding of the rolled strip will provide an increase achestva finished products. Moreover, unlike the prototype, in the process of winding the strip, the intermediate roll is not moved against, but in the direction of the metal flow. Thermal insulation and accumulation of the strip section is carried out only after the last pass, and delivery to the cooling zone is carried out continuously and at a constant speed.

 The problem is solved in such a way that in the claimed method of supercompact production of an endless hot rolled strip on a continuously reversible casting and rolling unit, including continuous casting of metal into a thin slab, accumulation and heating of the slab, its rolling into an endless strip in successive sections in several passes with the return of the rolled section into the accumulation zone, cooling the rolled strip, cutting and winding into rolls, according to the invention, after each, except the last, passage in the direction and the metal process stream, the rolled section is simultaneously heated and accumulated, and the accumulation is carried out by two-way winding into the intermediate roll with its simultaneous movement in the direction of the metal flow, and in the process of returning the rolled section of the strip, it is unwound from this intermediate roll with its simultaneous movement against the direction of the technological metal flow, and after the last pass, the rolled portion of the strip simultaneously accumulates and liruyut between heat-accumulation zones of the rolled strip portion and the cooling cycle and the next rolling slab continuous portion is provided in the cooling zone.

 In this case, the rolling of each successive section of the strip is carried out reversely.

 In the inventive method, the new sequence and modes of operations allow the manifestation of a new technical effect, which consists in stabilizing the temperature regime of the winding of an endless hot rolled strip. This is achieved as a result of the fact that the accumulation with simultaneous heating, carried out in the accumulation zone of the rolled strip section, allows during rolling the strip section in the direction of the metal flow, except for the last pass, and its return to the accumulation zone of the slab, to improve the rolling temperature by eliminating the stage intensive cooling of the rolled strip section on the discharge roller table. In addition, the accumulation with simultaneous thermal insulation of the rolled section of the endless strip in the accumulation zone before cooling and winding onto the final winder allows, by eliminating the winding into one roll on the final winder and the already rolled strip, and the rolled section to eliminate additional temperature losses of the latter, thereby to stabilize the temperature regime of the winding and, therefore, to provide an improvement in the physical and mechanical properties of the finished strip, that is, an increase in its quality. In addition, in the event of a delay in the rolling mill, the simultaneous accumulation and heating of the rolled strip section, in contrast to the prototype, where this section is cooled on the discharge roller table and the final winder, allows the rolling process to continue without loss due to overcooling after eliminating the delay.

 Figure 1 shows a General view of a continuously reversible casting and rolling unit for implementing the inventive method; figure 2 the beginning of the first pass of the first section of the strip; figure 3 the moment of the beginning of the formation of the intermediate roll in the first pass; in Fig.4 the beginning of the second passage of the first section of the strip; figure 5 the moment of completion of the unwinding of the strip from the intermediate roll during the second pass; in Fig.6 the beginning of the third passage of the first section of the strip; in Fig.7, the moment of the beginning of the formation of the intermediate roll in the third passage; on Fig the beginning of the fourth passage of the first section of the strip; in Fig.9 the moment of completion of the unwinding of the strip from the intermediate roll during the fourth pass; figure 10 the beginning of the fifth passage of the first section of the strip; 11, the initial stage of accumulation of the rolled (i-1) -th section of the strip in the loop former and issuing it to the discharge roller table; on Fig the moment of the beginning of the formation of the intermediate roll during the first pass of the i-th section of the strip, the moment of completion of filling the looper with the rolled (i-1) -th section of the strip and the stage of issuing it to the discharge roller table; on Fig the beginning of the second pass of the i-th section of the strip and the stage of issuing a rolled (i-1) -th section of the strip on the discharge roller table; on Fig the end of the second pass of the i-th section of the strip and the stage of issuing the rolled (i-1) -th section of the strip on the discharge roller table; in FIG. 15 the beginning of the third pass of the i-th section of the strip and the stage of issuing the (i-1) -th rolled section of the strip to the discharge roller table; in FIG. 16 the moment of the beginning of the formation of the intermediate roll during the third pass of the i-th section of the strip and the stage of issuing the rolled (i-1) -th section of the strip to the discharge roller table; on Fig the beginning of the fourth passage of the i-th section of the strip and the stage of issuing the rolled (i-1) -th section of the strip on the discharge roller table; in Fig.18 - the end of the fourth passage of the i-th section of the strip and the final stage of issuing a rolled (i-1) -th section of the strip on the discharge roller table; on Fig the beginning of the first pass of the (i + 1) -th section of the strip, the end of the issuance on the discharge roller table of the (i-1) -th section of the strip and filling the looper with the ith section of the strip.

 The casting and rolling unit for implementing the method of ultra-compact production of an endless hot-rolled strip includes a sequentially located machine 1 (Fig. 1) for continuous casting of thin slabs of known design, a passage device 2 for heating and accumulating a slab and a rolled section of a strip of known design, a reversible rolling mill 3 for rolling a slab into a strip in separate sections in several passes, a device 4 for heating and accumulating a rolled section of a strip, a device 5 for accumulating, and heat insulation of the rolling section of the strip, a device 6 for cutting an endless strip, a device 7 for cooling the strip and the final winder 8 for winding the rolled strip into finished rolls. The device 4 may include a roller furnace 9 and a device 10 for forming and moving an intermediate roll. The device 10 includes a trolley 11 located on the outside of the furnace 9, and a drive drum 12 and two pairs of pulling rollers placed inside the furnace 13. The device 5 can be made in the form of a loop former placed inside a heat-insulating casing 14. The looper contains several pairs (for example, five ) pulling rollers 15 and several (for example, four) forming rollers 16, which are made with the possibility of movement in a vertical plane.

In Fig.1, the following notation is adopted: L _{1 the} distance from the exit from the continuous casting machine to the rolling mill; L _{2 the} distance from the rolling mill to the exit of the device 4; L _{3 the} distance from the exit of the device 4 to the exit of the device 5. In FIG. 2-19 the following designations are adopted: V _i the rolling speed in the i-th passage, i varies from 1 to 5; V _{I i} - the speed of entry of the metal into the stand in the i-th passage; V _{b the} speed of rotation of the drum coiler; V _m speed of winder movement along the furnace.

A detailed description of a specific embodiment of the proposed method is given for the case of reverse rolling of each section of the slab in five passes. After casting in a continuous casting machine, a thin slab enters the device 2 (see figure 1) with a casting speed. After the passage of the device 2 begin the first pass on the rolling mill 3 (Fig.2) of the first section of the slab and compress it from a thickness h ₀ to a thickness h ₁ . During the first pass, the rolled section of the strip moves in the furnace 9 (Fig. 3) through the gaps of the pulling rollers 13 and the slot of the drum 12 of the device 10 until it leaves the furnace at a speed of V ₁ . At the moment of approaching the front end of the rolled section to the exit from the furnace 9 (Fig. 3), they start winding the strip into an intermediate roll at a speed of V _b V _1/2 while moving it in the direction of the process metal stream at a speed of V _m V _1/2 . The front end of the strip lies at the exit of the furnace 9. In the particular case, when the length of the rolled section is less than L ₂ , it is placed in the furnace without winding into an intermediate roll. At the end of the first pass, the formation of an intermediate roll ends, the rolling mill is reversed, the roll gap is reduced, and the second pass of the first section of the rolled strip is started with compression from thickness h ₁ to thickness h ₂ . At the same time, the device 10 (Fig. 4) begins to unwind the intermediate roll at a speed of V _b = V _in2 / 2 and move it against the direction of the process metal stream at a speed of V _m = V _in2 / 2. At the end of the unwinding device 10 (figure 5) stops, and the front end of the rolled section begins to move against the direction of the process metal flow with a speed of V _in2 . At the end of the second pass, the rolling mill is reversed and its roll gap is reduced (Fig.6). Next, the rolling of the first section of the rolled strip in the third and fourth passes is carried out similarly to its rolling in the first and second passes. The sequence of operations shown in Fig.7-9. At the end of the fourth pass, the rolling mill is reversed, its roll gap is reduced, and the fifth pass of the first section of the rolled strip is started with compression from thickness h ₄ to thickness h ₅ . During the fifth pass, the rolled section of the strip moves in the furnace 9 (Fig. 10) through the gaps of the pulling rollers 13 and the slot of the drum 12 of the device 10 until it leaves it, then until it leaves the device 5. At the moment the front end of the rolled section of the strip approaches the exit from of device 5, it is braked from speed V ₅ to the speed of issuing the rolled strip to the cooling zone v _cm1 = (l ₅ - L ₂ - L ₃ ) / τ _c , where τ _{c is} the rolling cycle of the strip section, l _{5 the} length of the strip section after the fifth pass ( 11). In this case, the device 5 begins the accumulation and thermal insulation of the rolled strip, which enters it with a speed of V ₅ . At the end of the fifth passage of the first section of the strip, the first passage of the second section of the strip begins, which is carried out similarly to the first passage of the first section of the strip, while the remaining part of the rolled first section of the strip continuously enters the device 5 from the side of the rolling mill, and continuously from the device 5 to the discharge roller a rolled strip is issued. At the moment of stopping the front end of the second section of the rolled strip, the receipt of the section of the rolled strip in the device 5 (Fig.12) stops. At the end of the first pass of the second section of the rolled strip, its second passage begins similarly to the second pass of the first section of the rolled strip (Fig. 13). During the second pass at the moment the front end of the second section of the strip begins to move against the direction of the metal process stream from the device 5 from the side of the rolling mill, delivery of the rolled strip to the furnace 9 (Fig. 14) begins. After the second pass, rolling in the third and fourth passes is carried out similarly to rolling in the first and second passes, as shown in FIG. 16-17. At the end of the fourth passage of the second section of the strip from the device 5 completely issued a rolled section of the strip with a length of L ₅ -L ₂ -L ₃ . At the beginning of the last fifth pass of the second section of the strip at the exit of the device 5, the rolled strip accelerates to a speed of v _cm = l ₅ / τ _c . In the process of the fifth pass, the device 5 is filled with a rolled strip (Fig. 19). Moreover, the rolled strip is issued to the discharge roller table from the device 5 with a speed of V _cm when rolling all other sections of the strip. From the moment the first pass of the third and other sections of the strip begins, all operations are repeated similarly to the operations during rolling of the second section shown in FIG. 11-19.

 The cooled rolled strip coming from the discharge roller table is divided depending on the specific requirements for the weight of the finished roll and is wound onto the final winders in turn.

 To justify the technical advantages of the proposed method compared to the continuous cast prototype, a thin slab of steel 08 with a thickness of 20 mm was rolled with various compressions and speeds (Table 1) into a strip 2.5 mm thick in five passes in successive sections.

 Five sections were identified on each section of the strip, for which the temperature of the end of rolling along the aisles was calculated. The calculation results are summarized in table 2.

 Analysis of the temperature of the rolling (see table 2) shows that, in contrast to the prototype in the present method there is a uniform temperature distribution along the length of the strip. In addition, the temperature of the end of the rolling of all sections of the strip in the present method is in the allowable range, and in the prototype the temperature of most of the strip is below the allowable.

 Thus, when implementing the proposed method, in contrast to the prototype, the stage of intensive cooling of the rolled strip on the discharge roller table is eliminated and, as a result, the quality of the finished product increases. The inventive method of ultra-compact production of an endless hot rolled strip on a continuously reversible casting and rolling unit compared to analogues used in industry today makes it possible to obtain strips in rolls of almost any desired mass without changes in technology and equipment.

 Based on the foregoing, we can conclude that the inventive method of contactless production of an endless hot rolled strip on a continuously reversible casting and rolling unit is efficient and eliminates the disadvantages that occur in the prototype solution, which is confirmed by an example of a specific implementation. Accordingly, the claimed solution can be applied in the shops of hot sheet rolling of metallurgical plants.

Claims (2)

 1. The method of ultra-compact production of an endless hot rolled strip on a continuously reversible casting and rolling unit, including continuous casting of metal into a thin slab, accumulation and heating of the slab, rolling it into an endless strip in successive sections in several passes with the rolled section being returned to the accumulation zone, cooling the rolled strip, cutting and winding into rolls, characterized in that after each, except the last, passage in the direction of the metal flow, the rolled section is one temporarily heated and accumulated, and the accumulation is carried out by two-way winding into an intermediate roll with its simultaneous movement in the direction of the metal flow, and in the process of returning the rolled section of the strip it is unwound from this intermediate roll with its simultaneous movement against the direction of the metal flow, and after the last the passage, the rolling section of the strip is simultaneously accumulated and insulated between the heating zones of the accumulation of the rolled section strip and cooling and for the rolling cycle of the next section of the slab continuously issue in the cooling zone.  2. The method according to claim 1, characterized in that the rolling of each successive section is carried out reversely.

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