RU2252086C1 - Method for hot rolling - Google Patents

Abstract

FIELD: ferrous metallurgy, namely production of hot rolled strips.

SUBSTANCE: at finish rolling in mill at least in one intermediate pass at changing gap between rolls, rolled piece is produced. Said rolled piece has in its end portions thickened portions to removed in last pass where deformation is realized at constant gap between rolls. Inter-roll gap is changed simultaneously at changing rolling speed. At process of passing end portion of rolled piece and at its presence outside furnace in flat state, said portion of rolled piece is heat insulated with use of active or heat accumulating screens.

EFFECT: elimination of chilling of end portions of ready strip in comparison with temperature of its basic mass, enhanced quality of strips according to all controlled parameters.

9 cl, 12 dwg, 5 ex

Description

The invention relates to ferrous metallurgy, and more specifically to the production of hot-rolled steel strips in ferrous metallurgy.

One of the methods for the production of hot rolled strips in the iron and steel industry is rolling at Stekkel mills - at mills with winders in furnaces.

The range of hot-rolled strips produced at these mills is within the range of (2.0) 2.5 ... 20 mm in thickness, up to 2100 mm in width and up to 18 t / (m wide) in specific gravity of the roll. Thus, rolling on modern Steckel mills essentially covers most of the range of thicknesses of strips produced on wide-band hot rolling mills.

In recent years, for Stekkel mills, the thickness of the tackle is 25 mm; there is a desire to roll strips with a thickness of less than 2 mm on these mills.

In the classical Steckel mill, tackle is produced by reverse rolling in a roughing stand, followed by transfer to reverse rolling in a quarto stand with winders in furnaces (the latter determines the essence of the Steckel mill).

The finished strip after finishing rolling enters the discharge roller table, at the end of which at a temperature of 550 ... 650 ° C is wound into a roll.

The TSP scheme, using the Stekkel mill, provides for rolling in a cage with winders in furnaces by reverse rolling without reeling in a roll, and after receiving a rolling of 25 mm thick, reverse rolling is rolled to a finished strip with alternate reeling of an intermediate reel on a drum in furnaces. The TSP scheme was further developed in the form of two quarto stands with winders in ovens covering these two stands (i.e., with two ovens remaining on the mill).

[Detailed information about the Stekkel mills can be found in the article by A. Lederer, “The Current Level of Development of the Stekkel Mills”, “Ferrous Metals”, 1993, No. 4, pp. 39-48, in Russian].

Ultimately, the development of the Stekkel mills led to the fact that they began to fully satisfy the existing requirements regarding the quality of finished strips and the costs of their production, which created favorable conditions for connecting these mills with modern processes for casting thin slabs and strips [see, for example, “Economic production of strips of corrosion-resistant steel at Stekkel mills”, G. Kneppe, V. Rode, “Ferrous metals”, 1993 (No. 7 - original; December 1993 - in Russian, p. 33-43)] .

Significant improvements are made to the Steckel mill without changing the essence of the rolling process implemented on it [see, for example, A. Bohlin, Y. Nygren et al. “New Technologies at the Steckel Rolling Mill” (MRT International. 2002, No. 6, p. 56-62; in Russian by OJSC Chermetinformatsiya Iron and Steel News Abroad. 2003, No. 3, p. 53-55)].

However, a significant drawback is inherent in Stekkel mills: due to the necessity of rolling on these mills themselves, it is necessary to slow down the roll, until it stops, and then accelerate the mill with temporarily leaving the end of the roll outside the furnace in a flat state, these parts of the strip cool significantly, in comparison with its main part. As a result, the end parts of the strip turn out to be 200 ... 220 ° C colder than the main part of the strip (see the indicated publications by A. Lederer, G. Kneppe).

The present invention is directed to the elimination of this significant drawback.

A known method of hot rolling, implemented on a mill with winders in furnaces, including the deformation of metal from a hard-to-deform strip with reverse rolling and with alternate temporary placement of the main part of the intermediate roll in the furnace in the form of a roll, the roll, including its end parts, is heated in the process of passing the section between the winder and the cage, on both its sides, and additionally electrically heat the rolls [see, for example, Japanese application 63-180311. Declared January 22, 87. Published on July 25th, 2018 in Kokai Tokkyo Koho. Ser. 2 (2). # 1988, # 48, pp. 55-57].

In the known method, the problem of a significant increase in the temperature of the end sections of the roll is not solved in comparison with its main part (the noted applies to the finished strip), because, firstly, the total residence time of the end of the roll in a flat state in the area between the stand and the furnace very short-term (maximum 9-10 seconds), which excludes the necessary heating of the metal [see, for example, “Heating the metal before rolling” Steel Times International, issue in Russian, May, 2000, p.10 ... 18] secondly, the heating of the rolls cannot be significant, so as to significantly affect l on heat transfer between the roll and the rolls [for example, according to Steel, 1977, No. 2, pp. 151-154, increasing the temperature of the roll by 100 degrees reduces its cooling effect on the strip by 10%].

A known method of hot rolling in the Steckel mill, including the stage of final deformation in the form of a series of passages with reverse roll and alternately temporarily placing the roll in the furnace in the form of a roll, the end part of the roll is rolled at a lower speed relative to the rolling of the main part of the roll and left in a flat state outside furnaces [see, for example, the cited publication by G. Kneppe and V. Rode in the World Cup, 1993, December, p. 33 ... 49].

The known method of rolling at the Steckel mill for essential features is closest to the proposed method of rolling, therefore, adopted as a prototype.

However, other known analogues of the rolling methods at the Steckel mill are not analyzed, since the essential features of the prototype noted in them are fully preserved. Methods of producing rolled products are also not analyzed: in a roughing reverse stand, by rolling on a Steckel mill without reeling in the furnaces in a roll (TSP scheme), on a combined casting and rolling unit, since they do not change the noted essential features of the hot rolling method on the Steckel mill.

The known method of hot rolling at the Steckel mill already has a significant drawback: a significant overcooling of the end parts of the strip in comparison with its main part, which makes it difficult to obtain high-quality hot-rolled strips on these mills.

The proposed method of hot rolling in the Steckel mill is free from the indicated disadvantage of the known method. It technically solved the problem of increasing the temperature of the end parts of the strip to a level close to or even slightly higher than the temperature level of the main part of the strip. Thus, high-quality hot-rolled strips are obtained in all controlled parameters.

These technical results are obtained due to the fact that in the proposed method of hot rolling at the Steckel mill, which includes the stage of final deformation in the form of a series of passes with reverse roll and with alternate temporary placement of the main part of the intermediate roll in the furnace in the form of a roll, while the end part of the roll is rolled with a speed reduced relative to the rolling of the main part of the roll, and left flat outside the furnace, according to a proposal in at least one of the intermediate passages Then, changes in the gap between the rolls produce a roll with a thickening of at least one of its end parts, while in the last pass the deformation is carried out with a constant gap between the rolls. Moreover, the specified change in the gap between the rollers during the passage of the end sections of the roll is carried out in the third or fourth pass from the last pass, which is taken in this case as the first. In addition, the specified change in the gap between the rolls is carried out simultaneously with the change in the rolling speed of the roll. In addition, in at least one of the intermediate passages, the thickening of the end portion of the roll formed in the previous passages is reduced. In addition, in the process of passing the end part of the roll with a variable speed and finding this part of the roll outside the furnace in a flat state, this part of the roll is thermally insulated from the environment by screens. In this case, the surface temperature of the screens is preliminarily raised to the level of the surface temperature of the screened part of the roll. In addition, the screened part of the roll is thermally insulated from the environment by screens, the surface temperature of which is formed during the passage under the screens of the main part of the roll. Moreover, after passing the end of the roll, the screens are removed from the thermal interaction with the roll surface. The end part of the roll is also insulated from the environment in only one or two of the last passages.

The combination of the above methods increases the temperature of the end parts of the roll, firstly, by transferring part of the work of deformation and, accordingly, due to this work of heating the end parts of the roll into the last deformation passes, and secondly, they reduce the cooling of the end parts when they are outside the furnace due to the greater their thickness, thirdly, maximally reduce (especially in the last passes) cooling of the end parts of the roll due to shielding. Ultimately, the temperature of the end of rolling of the end parts of the finished strip is raised to a level close to the temperature of the end of rolling of the main part of the strip, which together improve the quality of the hot rolled strips.

The proposed method of hot rolling in the Steckel mill is explained by a number of schematic drawings and graphs.

Figure 1 shows a diagram of a Steckel mill; figure 2 - sequence of operations for changing the thickness of the roll through the aisles (indicated by Roman numerals) when rolling the rolled 25 mm thick onto a strip 2.0 mm thick in the known method; figure 3 - the same sequence of operations to change the thickness of the roll through the aisles (indicated by Roman numerals) in the proposed method of rolling; figure 4 shows a diagram of a TSP with a Stekkel mill with two stands; figure 5 is a sequence of operations to change the thickness of the roll along the aisles (indicated by Roman numerals) when rolling the rolled 25 mm thick onto a strip 1.5 mm thick in the TSP scheme when implementing the known method; Fig.6 is the same sequence of operations for changing the thickness of the roll along the aisles (indicated by Roman numerals) in the TSP scheme when implementing the proposed rolling method; Fig.7 - heating of the strip due to the work of deformation (Δt) when P _c changes from the thickness of the roll for carbon steels (according to A. Lederer, Fig. 5); on Fig - dependence of the cooling speed of the roll at t = 1000 ° C on the thickness of the roll; figure 9 - the use of active screens on the Steckel mill; figure 10 is a view of figure 9; figure 11 - the use of heat storage screens on the Steckel mill; Fig.12 is a view of B in Fig.11.

The Stekkel mill contains a quarto mill with support 1 and working 2 rolls (figure 1). On both sides of the cage there are kilns 3 with drums for alternately winding the main part of the intermediate peals into a roll 4, while the end part of peals 5 remains outside the furnace, so that the “tail” of the peal is in the tribrader 6. The tackle comes, for example, in the direction 7, the finished strip leaves the mill in direction 8. The deformation process in a known manner is carried out by reverse rolling, deforming the tackle 9 to the finished strip 10 in several passes (transitions, see figure 2, are indicated by Roman numerals). Moreover, according to the proposed method, the tackle 9 is also deformed into the finished strip 10 for several transitions shown in figure 3 in roman numerals, making changes to the deformation of the end parts of the peals.

The specificity of the TSP scheme (Fig. 4) consists, firstly, in that the mill stand is used to produce tackle 9, i.e. rough reverse passages are carried out without feeding the roll into the furnace and rolling it into a roll, and secondly, in the use of two quarto stands with supporting 1 ’and 1’ ’and working 2’ and 2’’ rolls. In this case, vertical rolls 11 can be installed between the stands. The sequence of operations for rolling the rolled 9 into the finished strip 10 is shown in FIG. 5 (known method) and in FIG. 6 (proposed method) and does not fundamentally differ from those shown in FIGS. 2 and 3 accordingly, not counting the implementation of the continuous rolling process in two stands. The implementation of continuous rolling in the TSP scheme requires the presence on the Steckel mill loop holder 12 (figure 4).

In the process of deformation, a rolling force is applied to the metal, the average value of which (P _cf in Fig. 7) during the deformation of carbon steels varies depending on the thickness of the roll as shown in Fig. 7. The application of rolling force to a metal leads to an increase in its temperature due to the strain energy, which can be determined, for example, by the formula:

where R _cf - see Fig.7;

h ₀ is the thickness of the roll before the passage (deformation);

h ₁ - the thickness of the roll after the passage (deformation);

ρ is the density of the rolled metal;

C is the specific heat of rolled metal;

A is the coefficient of transition from mechanical to thermal energy.

The heating curve Δt _{d of a} strip of different thicknesses depending on its deformation for carbon steel is shown in Fig.7.

In the process of finding the metal outside the deformation zone and outside the furnace, it cools. Its main cooling occurs due to heat radiation. In this case, convective heat transfer can be neglected, since the realized rolling speeds are quite low, and besides, taking them into account does not change the essence of the rolling process. The degree of metal cooling due to radiation depends on the thickness of the roll and its temperature level. Since the furnaces in the Steckel mill maintain the metal temperature at t = 1020 ° C, there is reason to consider metal cooling at t = 1000 ° C. The cooling rate of the roll of different thicknesses of carbon steel at a temperature of 1000 ° C is shown in Fig. 8.

In the process of finding the metal in the deformation zone, it is cooled due to heat exchange with work rolls. This heat transfer depends on the temperature level of the metal and rolls, the thickness of the metal in the deformation zone, the length of the gripping arc, the degree of deformation, and the rolling speed. Temperature losses of metal during the roll gap passage by heat exchange with the working rolls _in Δt may be, for example, defined by the formula

where t ₀ is the temperature of the metal (in our case, 1000 ° C);

lg is the length of the capture arc;

h _cf - the average thickness of the roll;

ε is the degree of deformation;

V is the rolling speed.

The Stekkel mill is equipped on both sides of the mill with shielding units (Figs. 9-12). Their purpose is to reduce heat loss by the end parts of the peals, especially in the last passes, due to radiation at the moment when the end of the peel in a flat state 6 is outside the furnace 3.

Apply a shielding installation with active screens (Fig.9 and 10) or with accumulating screens (Fig.11 and 12).

In both cases, the heat storage installation by shielding is shifted towards the rolling mill line to the area between the cage and the furnace. To do this, the installation of active screens 13 is equipped with a drive 14 (Fig.9). The active screens themselves are made in the form of insulated membranes 15, to which an electric current is supplied briefly. By passing a current, the temperature of the membranes 15 is raised to the level of the surface of the roll in a flat state 6 and the installation 13 is brought into thermal contact with the end of the roll 6. When rolling the main part of the strip and its tail, the screens are diverted from the mill technological line. The shielding units 13 on both sides of the stand work, respectively, alternately.

Heat storage screens 16 (11) work on the accumulation of heat emitted by the main part of the roll. They are equipped with a drive 17 for moving them to the rolling technological line. Being in long-term thermal contact with the roll, the membrane 18 of the screens accumulates heat and heats up to a temperature of about 900-950 ° C. When passing the end of the roll, the screens give the roll accumulated heat. The heat storage screens 16 operate alternately, but from the description of the principle of their operation it is clear that their thermal contact with the roll is significantly different from contact with the roll of active screens.

The totality of the materials presented allows us to present the proposed method of hot rolling at the Steckel mill.

The method of hot rolling in the Steckel mill is as follows.

The basis of the proposed rolling method is to obtain, in at least one of the intermediate passages, a roll with a thickening of at least one of its end parts and the subsequent rolling of such a roll into a finished strip with a constant thickness along its length. Getting roll with a thickening of the end parts is carried out by changing the gap between the work rolls in the process of deformation of the metal.

The marked change in the gap between the rollers and, accordingly, the production of a roll with thickened end parts can be carried out starting from the first pass, and thereby reduce heat loss by radiation from the end parts of the roll.

However, given that the main metal losses of heat by radiation and heat exchange with work rolls in the Steckel mill in Fig. 1 take place in the last two passes, in this case, the formation of a peal with thickened end parts is preferably carried out in the third or fourth from the last pass, counting in in this case, the last pass first. Thus, the production of a roll with a thickening of the end parts (possibly in some passages with a thickening of one end portion, see, for example, the first pass in FIGS. 3 and 6) is carried out in at least one of the intermediate passages.

Moreover, since the work spent in the process of deformation of the rolled of the same thickness into the finished strip of the same thickness is the same, the essence of the proposed method is to redistribute this work to the end parts of the roll: to shift it towards the end of the strip rolling process by become. According to formula (1), in this case, towards the end of the strip rolling, the temperature Δt _d increases accordingly due to deformation, which at the same time concentrates on the end sections of the finished strip.

According to Fig. 8 and formula (2), with a decrease in the thickness of the roll, Δt _and - cooling of the metal due to radiation increase (see the curve in Fig. 8), and Δt _в - cooling of the metal due to heat exchange with work rolls.

The indicated thickening of the ends of the roll reduces their cooling by heat radiation, and the already noted metal cooling components partially (or completely) compensate for the already noted components of the metal cooling (Δt _в and Δt _и ) by shifting the work of deformation of the end parts of the strip to the end of rolling and the increased heating of these parts of the rolled products.

Since the speed of filling / unwinding the ends of the roll to / from the drum of the furnace 3 is taken equal to 2 ... 3 m / s, then at a realizable speed of rolling the main part of the roll at a level of up to 8 ... 10 m / s (and even 15 m / c) at the end of each pass, the rolling speed is reduced, up to zero, the speed of the roll when the tail section is left in the flat state 6 and in the tribrachboard 5. Accordingly, the process of starting the end of the roll each time starts from zero, raising the rolling speed of the main part of the roll ( finished strip) to the specified values.

The noted variation in the rolling speed and the residence time of the roll in a flat state 6 outside the roll 4 of the furnace 3 increases the components of the heat loss by the roll. This increase is greater than the thinner the roll [see Fig. 8 and formula (2)]. Therefore, in the proposed rolling method, the change in the gap between the rollers to obtain thickenings at the ends of the roll is carried out simultaneously with the specified change in the rolling speed.

To reduce the cooling of the end sections of the roll due to heat radiation, in some cases, a thickening of the end sections of the roll is formed from the first pass (Fig. 3). In these cases, it may be necessary to over-compress in the last aisles, resulting in forces that are unacceptable to the rolling stand. In these cases, at least in one of the intermediate passages, the thickening of the end portion of the roll formed in the previous pass is reduced (see, for example, FIG. 3, compression from 15 mm to 12.5 mm and from 12.5 mm to 5 mm) .

It has already been noted that the main heat loss by the rolled metal occurs due to radiation and these heat losses most significantly affect the temperature level of the metal in the last two to three passes.

The indicated metal temperature loss in the last 2 ^x -3 ^x passes at the end sections of the roll (reaching 80 ... 100 degrees or more) is significantly reduced by screening the roll in position 6 (Fig. 1), when the metal stops and for a certain time without deformation, is in a flat state.

The screening is carried out by the transverse displacement of a part of the roller table between the furnace 3 and the cage (1 and 2) and the installation of active screens instead of it (Fig. 9). The essence of the active screens is shown in view A (Fig. 10) and consists in preheating the shielding membranes 15 to the surface temperature of the end portion of the roll in position 6. Thus, the indicated cooling of the end parts of the roll is almost completely (up to 90-95%). The marked operation is carried out alternately on both sides of the rolling stand. During the rolling of the main part of the roll, the screens 13 are transversely displaced from the drive 14 from contact with the metal, replacing them with a roller table.

Shielding can be carried out using heat-accumulating screens 16 (11 and 12). In this case, also, a part of the roller table between the furnace 3 and the cage is pushed away by a lateral displacement from the rolling line and heat storage screens from the drive 17 are introduced instead (see Figs. 11 and 12). In this case, unlike active screens, heat-accumulating screens are in thermal contact with the roll during rolling of the main part of the roll and the end part of the roll is in position 6 (Figs. 1 and 4). After passing the end of the roll 6 in the opposite direction, the screens 16 from the actuator 17 are displaced to an inoperative position (see Fig. 11). At this time, similar screens are introduced into the working position from the other side of the stand, solving a similar problem of preserving heat by the other end part of the roll.

In this case, the membranes 18 of the heat-accumulating screens 16, when passing through the main part of the roll, are heated to 900 ... 950 ° C from the heat of the roll and thereby reduce the temperature decrease of the end parts of the roll due to radiation by 70 ... 80%.

Both types of shielding are used in the proposed method in the production of thin (1.8 ... 3.0 mm) and especially thin (1.0 ... 1.8 mm) strips when the cooling of the end parts of the roll due to heat radiation Δt _and in position 6 it can be so significant that, together with the cooling effect of the work rolls (Δt _and + Δt _c ), it can significantly prevail over the heating of the end part of the roll due to the strain energy (Δt _u ).

When implementing both types of shielding, the proposed method proposes:

- firstly, to preserve the use of the rolling table with the tapper 5, absolutely necessary when rolling thick finished strips, when the need for shielding is not relevant;

- secondly, to provide for the described shielding systems the presence of the tribapapper 5, necessary for organizing the start of rolling,

Example 1. At the Steckel mill (FIG. 1), 2.0 mm thick strips are made from carbon steel (10 in FIG. 2) from a blank 9 of 25 mm thickness. The billet is fed to the mill, for example, in direction 7. The four-roll mill stand is equipped with work rolls of 2 × 800 mm, supported by support rolls 1. Furnaces 3 are located from the axis of the mill stand at a distance of 9000 mm, the drawer units 5 at a distance of 5500 mm. The rolling process is carried out in 5 passes, placing the main part of the intermediate roll in the furnace 3 in the state wound into a roll 4. By placing the metal in the furnace 3, the temperature of the main part of the roll at the outlet of the furnace is provided at a level of 1020 ° C, so that the metal enters the crate at each pass at a temperature close to 1000 ° C.

Metal filling in the furnace winder is carried out at a speed of 2.5 m / s; the rolling speed of the main part of the strip varies, providing 10 m / s in the last pass.

Starting from the first pass (I in Fig. 3), by changing the gap between the rollers, peals are formed with a thickening of the end parts of the peel within the limits indicated in Fig. 3. As rolling in the III and IV passes, the thickening is first reduced to 12.5 mm, then to 5.0 mm. Changing the gap between the rollers is carried out, starting with a decrease in the rolling speed of the end part of the peals. In the last, fifth, pass, the deformation is carried out with a constant gap between the work rolls, which provides a finished strip with a thickness of 2.0 mm

According to equation (1) and the data in Fig. 7, the total heating of the ends of the strip due to the strain energy Δt _d will be 220 deg, but the main heating will occur in IV (Δt _d = 87 deg) and V (Δt _d = 89 deg) passes. In the same aisles, due to the thicker ends of the peal, their cooling will decrease due to radiation by 70 degrees in the V passage and by 50 degrees in the IV pass.

Ultimately, the implementation of the hot rolling method discussed in FIG. 3 at the Steckel mill allows the temperature of the end of the rolling of the ends of the strip to be lower in comparison with the temperature of the main part of the strip by only 40-50 degrees.

Example 2. At the Steckel mill under the conditions described in example 1, carry out rolling of carbon steel strips with a thickness of 2.0 mm by a known method (figure 2).

In this case, the heating of the ends of the strip due to the strain energy will also be 220 ° C; for the highest temperature increase (Δt _d = 65 deg) takes place in the III pass, decreasing to the V pass to 35 deg.

Ultimately, the implementation of the Steckel mill of the known method (figure 2) leads to the fact that the end parts of the finished strip have a temperature of 180 ... 190 degrees below the temperature of the main part of the strip.

Example 3. At the Steckel mill with two stands, use the parameters and equipment according to figure 4. Rolling stands are equipped with work rolls ⌀ 800 mm. The mill produces strips 1.5 mm thick from carbon steel from rolled steel 25.0 mm thick. Tackle 9 arrives, for example, in direction 7. The finished strip leaves the mill in direction 8. The rolling process is carried out in three double passes (i.e., only 6 passes), placing the roll after each double pass in furnace 3 in the form of a roll 4 with the leaving the end of the roll outside the furnace in a flat state 6. Since the rolling process is continuous, it is carried out with a slight tension between the stands, maintaining its constancy using the loop holder 12.

During the rolling process, the ends of the roll are charged into the furnace at V = 2.5 m / s, the main part of the strip is rolled at 8 m / s; on the last pass - at V = 10 m / s.

The hot rolling method is implemented according to FIG. 6, forming from the first stand a thickening of at least one end of the roll (I in FIG. 6), which then begins to decrease to h = 9.0 mm in the IV pass, to h = 4.0 mm in the V pass and in the last pass (VI in FIG. 6), they are completely removed by rolling with a constant gap between the rollers, providing a finished strip with a thickness of 1.5 mm Changing the gap between the rollers is carried out, starting with varying the rolling speed due to the filling of the corresponding end of the roll into the furnace 3 (described in more detail in example 1).

According to equation (1) and the data in Fig. 7, the total heating of the ends of the strip due to the strain energy will be ≈300 degrees, however, the bulk of the strain energy will be concentrated at the ends of peals in IV (Δt _d = 47 degrees), V (Δt _d = 90 degrees ) and VI (138 deg) passes.

The noted specificity allows you to finish rolling almost at a quasi-stable temperature along the length of the finished strip with a thickness of 1.5 mm.

Example 4. Under conditions analogous to Example 3, in a Steckel mill, carbon steel 1.5 mm thick is rolled by a known method (FIG. 5).

The implementation of the known rolling method on the Steckel mill in this case (Fig. 5) leads to a decrease in the temperature of the front and rear ends of the finished strip with a thickness of 1.5 mm in comparison with its main part by 210 ... 220 degrees.

Example 5. Implement the rolling process in accordance with the conditions and parameters given in example 1.

Carry out the shielding of the end parts of the roll in the penultimate and last passes.

Completely eliminate the lowered temperature of the end sections of the finished strip in comparison with the temperature of its main part. Moreover, depending on the degree of shielding, they provide 20 ... 30 degrees higher temperature of the ends of the strip, which favorably affects the process of its cooling in a roll on a coiler for finished strips.

Thus, the proposed method of hot rolling at the Steckel mill allows eliminating the organic disadvantage of the rolling process at these mills: a significant coldness of the end sections of the finished strip in comparison with the temperature of its bulk, reaching 200 degrees or more for thin and thin stripes. The elimination of this limited drawback opens up wide possibilities for the application of Stekkel mills, especially TSP schemes, in modern casting and rolling modules combined with continuous casting machines. The effectiveness of the application of the developed method on modern existing Steckel mills equipped exclusively with a hydraulic system for changing the roll gap is obvious.

Claims (9)

1. The method of hot rolling at the Steckel mill, comprising the stage of final deformation in the form of a series of passages with reverse roll and with alternate temporary placement of the main part of the intermediate roll in the furnace in the form of a roll, while the end part of the roll is rolled at a lower speed relative to the rolling of the main part of the roll left in a flat state outside the furnace, characterized in that at least in one of the intermediate passages by changing the gap between the rollers get rolling with a thickening of at least one of its end parts, while in the last pass the deformation is carried out with a constant gap between the rolls. 2. The hot rolling method according to claim 1, characterized in that the said change in the gap between the rollers during the passage of the end sections of the roll is carried out in the third or fourth pass from the last pass, taken in this case as the first. 3. The hot rolling method according to claim 2, characterized in that said change in the gap between the rolls is carried out simultaneously with a change in the rolling speed of the roll. 4. The hot rolling method according to claim 1, characterized in that in at least one of the intermediate passages, the thickening of the end portion of the roll formed in the previous passages is reduced. 5. The hot rolling method according to claim 1, characterized in that in the process of passing the end part of the roll with a variable speed and finding this part of the roll outside the furnace in a flat state, this part of the roll is thermally insulated from the environment by screens. 6. The hot rolling method according to claim 5, characterized in that the surface temperature of the screens is preliminarily raised to the surface temperature level of the screened portion of the roll. 7. The hot rolling method according to claim 5, characterized in that the shielded part of the roll is thermally insulated from the environment by screens whose surface temperature is formed during passage under the screens of the main part of the roll. 8. The hot rolling method according to claim 6, characterized in that after passing the end of the roll, the screens are removed from thermal interaction with the roll surface. 9. The hot rolling method according to claim 5, characterized in that the end part of the roll is insulated from the environment in only one or two of the last passes.

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