Building a finishing gauge for round steel. Caliber design

The dimensions and tolerances of the caliber are somewhat different from the dimensions and tolerances of the rolled profile, which is explained by the different coefficients of thermal expansion of metals and alloys when heated. For example, sizes finishing gauges for hot rolling steel profiles should be 1.010-1.015 times the size of the finished profiles.

The dimensions of the calibers increase during rolling, which is due to their development. Upon reaching dimensions equal to the nominal plus tolerance, the caliber becomes unsuitable for further work and is replaced with a new one. Therefore, the greater the tolerance on the dimensions of the profile, the longer the service life of the calibers, and, consequently, the productivity of the mills. Meanwhile, the increased tolerance leads to an excessive consumption of metal for each meter of the length of the products. It is necessary to strive to obtain profiles with dimensions that deviate from the nominal in a smaller direction.

In practice, calibers are built not with positive ones, but with average tolerances or even with some minus. The improvement of rolling mill equipment, the improvement of production technology and the introduction of automatic equipment for setting rolls will contribute to the production of rolled products with increased accuracy.

GOST 2590-71 provides for the production round steel diameter from 5 to 250 mm.

The rolling of this profile, depending on the steel grade and dimensions, is carried out in different ways (Fig. 116).

Methods 1 and 2 differ in the options for obtaining a pre-finishing square (the square is precisely fixed diagonally and it is possible to adjust the height). Method 2 is universal, as it allows you to get a number of adjacent sizes of round steel (Fig. 117). Method 3 is that the prefinishing oval can be replaced by a decagon. This method is used for rolling large circles. Method 4 is similar to method 2 and differs from it only in the shape of the rib gauge. The absence of sidewalls in this caliber contributes to better descaling. Because this way allows wide adjustment of the dimensions of the strip coming out of the rib gauge, it is also called universal gauge. Methods 5 and 6 differ from the rest in higher hoods and greater stability of the ovals in the wiring. However, such calibers require precise adjustment of the mill, since even with a small excess of metal, they overflow and form burrs. Methods 7-10 are based on the use of an oval-circle sizing system.

A comparison of possible methods for producing round steel shows that methods 1-3 make it possible in most cases to roll the entire range of round steel. Rolling of quality steel should be carried out according to methods 7-10. Method 9, as it were, is intermediate between the oval-circle and oval-oval systems, it is most convenient in terms of regulating and adjusting the camp, as well as preventing sunsets.

In all considered methods of rolling round steel, the shape of the finishing and pre-finishing passes remains almost unchanged, which contributes to the establishment of general patterns of metal behavior in these passes for all cases of rolling.

Building fine gauge for round steel is carried out as follows.

Determine the estimated diameter of the caliber (for a hot profile when rolling to minus) d g \u003d (1.011 ÷ 1.015) d x - part of the tolerance +0.01 d x, where 0.01d x, - magnification diameter for the above reasons; d x \u003d (d 1 + d 2 / 2) - diameter round profile in a cold state. In practice, when calculating the second and third members of the right side of the equality can be considered approximately the same, then

d g \u003d (1.011 ÷ 1.015) (d 1 + d 2) / 2,

where d 1, d 2 are the maximum and minimum allowable diameter values ​​according to GOST 2590-71 (Table 11).

Depending on the size of the rolled circle, the following angles of inclination of the tangent α are chosen:

We accept the value of the gap t (according to rolling data), mm:

Based on the data obtained, a caliber is drawn.

Example. Build a finishing gauge for rolling round steel with a diameter of 25 mm.

1. Let's determine the calculated diameter of the caliber (for a hot profile) according to the equation above.
   We find from the table: d 1 \u003d 25.4 mm, d 2 \u003d 14.5 mm; whence d g \u003d 1.013 (25.4 + 24.5) / 2 \u003d 25.4 mm.
2. We choose α=26°35′.
3. We accept the gap between the rolls t=3 mm.
4. Based on the data obtained, we draw a caliber.

Pre-finishing gauges for a circle are designed taking into account the accuracy required for the finished profile. The more the shape of the oval approaches the shape of a circle, the more accurately the finished round profile is obtained. Theoretically, the most suitable profile shape to obtain the correct circle is an ellipse. However, such a profile is rather difficult to hold at the entrance to the finishing round gauge, so it is used relatively rarely.

The flat ovals hold the wires well and, in addition, provide large swages. But the thinner the oval, the lower the accuracy of the resulting round profile. This is due to the degree of broadening that occurs during compression. The broadening is proportional to the compression: where there are small reductions, there is also a small broadening. Thus, at small reductions of the oval, the possibilities of size fluctuations in a round gauge are very small. However, the opposite phenomenon is true only for the case when a large oval and a large hood are used. The oval for small sizes of round steel is close in shape to the shape of a circle, which makes it possible to use an oval of single curvature. The profile of this oval is outlined with only one radius.

For round profiles of medium and large sizes, the ovals, outlined by one radius, turn out to be too elongated along the major axis and, as a result, do not provide a reliable grip of the strip by the rolls. The use of sharp ovals, in addition to not providing an accurate circle, adversely affects the stability of the round gauge, especially in the output stand of the mill. The need for frequent replacement of rolls sharply reduces the productivity of the mill, and the rapid development of calibers leads to the appearance of second grades, and sometimes marriage.

The study of the causes and mechanism of the development of calibers produced by N.V. Litovchenko showed that the sharp edges of the oval, which cool faster than the rest of the strip, have significant resistance to deformation. These edges, entering the caliber of the finishing stand rolls, act on the bottom of the caliber as an abrasive. Rigid edges at the tops of the oval form hollows at the bottom of the gauge, which lead to the formation of protrusions on the strip along its entire length. Therefore, for round profiles with a diameter of 50-80 mm and more, a more accurate profile execution is achieved by using two- and three-radius ovals. They have approximately the same thickness as an oval outlined by one radius, but due to the use of additional small radii of curvature, the width of the oval decreases.

Such ovals are flat enough to hold them in wires and provide a secure grip, and a more rounded contour of the oval, approaching the shape of an ellipse in its shape, creates favorable conditions for uniform deformation across the width of the strip in a round gauge.

The assortment of round and square profiles is very wide due to the wide variety of its use. Products square section(made of steel) are rolled with a side of a square from 6 to 200 mm or more, of a round section - from 5 to 300 mm in diameter. Dimensions (diameters) from 5 to 9 mm correspond to rolling wire, on wire mills (rolled wire); the interval of their sizes through 0.5 mm. Product sizes from 8 to 380 mm are rolled on small section mills with an interval of 1 and 2 mm; from 38 to 100 mm - on medium section mills with an interval of 2-5 mm and from 80 to 200 mm - on large section mills with an interval of 5 mm. Larger sizes of products are rolled on a rail and beam mill.

The most convenient for rolling a round profile are oval gauges (Further "caliber" - "K.";), alternating with square ones according to the system square-oval-square (Fig. 3.11, a) or by system square - rhombus - square (Fig. 3.11, b); in both cases, the square calibers in the rolls are located on the edge. Such a distribution and alternation of k. contributes to a better compression and study of all layers of metal.

When rolling products with a circular cross section with a diameter of 5 to 20 mm, the K system, alternating, square - oval (Fig. 3.11, a). Rolled round with a diameter of more than 20 mm is carried out in calibers, alternating according to the system square-rhombus (Fig. 3.11, b). In both systems, the last three K. are common:

• prefinishing square;
• prefinishing oval;
• clean circle.

Since rolling is carried out in a hot state, to obtain products of the required diameter (which is measured cold) the dimensions of the finishing gauge should be corrected for shrinkage.

Due to the large cooling effect of the rolls in the vertical direction, the temperature shrinkage of the vertical diameter is less than that of the horizontal one. Correction of the dimensions of the finishing K. is provided if the vertical diameter of the caliber is taken d in \u003d 1.01 d x, and the horizontal d g \u003d 1.02 d x.

The gap between the rolls, depending on the diameter of the roller, is taken in the range from 1 to 5 mm; the radius of rounding of the corners of the rolls near the gap r is 0.1d x (Fig. 3.11, e).

Rolling of products of square section is carried out in calibers, alternating system rhombus-square (Fig. 3.11, c). This system is often used for rolling square profiles larger than 12 mm. Calibration begins with the determination of the dimensions of the finishing K., taking into account the unequal temperature shrinkage in the vertical and horizontal directions. To do this, the angle at the top of the finishing gauge is taken equal to 90 ° 30 "or 181/360 rad (Fig. 3.11, e).

Then the vertical diagonal of the finishing K. d in \u003d 1.41 C mountains, and the horizontal d g \u003d 1.42 C mountains, where C mountains is the side of the square in the heated state, equal to 1.013 C n. The profile that came out of such a K., when solidified, will have an exact square shape. The corners of a fine square K. are not rounded. The gap between the rolls is assumed to be from 1.5 to 3.0 mm.

Vinogradov Aleks, head of a chair, candidate of technical science, associate professor

Marina Anatolyevna Timofeeva, candidate of technical science, associate professor

Cherepovets State University, Russia

Championship participant: the National Research Analytics Championship - "Russia";

A new technique for the analysis of roll calibration systems has been proposed section mills. As criteria, it is proposed to use the coefficients of non-uniformity and efficiency, which determine the degree of development of the structure during the rolling of profiles. On the example of calibration systems for the production of a round profile with a diameter of 28 mm, possible deformation schemes are analyzed, as well as the advantages and weak spots each of them.

Keywords: gauge systems, section rolling, efficiency criterion.

A new technique for the systems analysis ofsection mill roll’s calibrations was proposed. The following criteria for analysis were proposed to use: the coefficients of uniformity and coefficient of efficiency, they determine the maturity structure at the profile rolling. Example of calibration systems for the production of round profile 28 mm was analyzed for possible scheme of deformation, as well as strengths and weaknesses of each scheme.

keywords: system calibration, rolling of sections, the efficiency criterion.

Formulation of the problem. Building rational calibration rolls of a section rolling mill is a difficult task. And its complexity is determined by the priority of one or another expected result. It is known that some calibrations are “sharpened” for the fastest possible shaping, others for a better study of the structure. Calibrations exist that provide more accurate cross-sectional dimensions or enable energy-efficient deformation modes.

Calibration systems known from literary sources have many varieties, subcircuits, and sometimes, solving one problem, significantly worsen the conditions of another. Therefore, the development of a methodology for analyzing a calibration system based on reasonable criteria is an urgent scientific task.

The methodology of the work. For the analysis of calibration systems, pairs of successive calibers were selected, which, on the one hand, allow us to consider all possible combinations of calibers, and, on the other hand, provide research into the division limit of a complex system, such as the calibration of rolls of a continuous section mill.

The non-uniformity coefficients are chosen as the system efficiency criteria K inf and efficiency To ede, which determine the degree of elaboration of the metal structure:

(1)

(2)

Where ? i= b i/ a i- component of the forming matrix;

a i, b i are the lengths of the radius vectors in i-th point of the cross section of the workpiece and the outgoing strip, respectively;

n- the number of radius vectors.

Coefficients of non-uniformity and efficiency of forming, which determine the degree of development of the metal structure, largely depend on the shape of alternating calibers, the ratio of the lengths of the axes of unequal calibers. The wrong choice of the ratio of the axes leads to the appearance of cracks and breaks in the strip during the rolling of profiles, especially from hard-to-deform steels.

There are two main stages in the process of rolling any section profile: rolling of a square continuously cast billet in the roughing and intermediate stands of the mill in order to obtain a roll of the required shape and dimensions for the finishing group of stands and rolling in the finishing stands. When constructing a rational calibration of the rolls of a rolling mill, it is necessary to strive to use the same calibers in the roughing and intermediate stands when obtaining rolled products of a wide profile assortment.

So, when rolling round steel with a diameter of 25-105 mm and hexagonal steel No. 28-48 on the medium-section mill "350" of the CherMK JSC "Severstal", the calibration systems used differ only in the finishing and some intermediate stands.

Let's try, based on the criteria for the efficiency of forming, to analyze the development of the structure for various calibration systems. As an example, consider the rolling of round steel with a diameter of 28 mm.

When modeling, the following conditions were taken as boundary conditions: ensuring the capture of the strip by rolls, i.e. ? i ≤ [?] i , ensuring the stability of the roll in the caliber and ensuring the required width of the roll.

Work results. The results of mathematical modeling for possible combinations of calibers are presented in the form of graphical dependencies in Figures 1-4.

Coefficient K inf(Fig. 1) characterizes the non-uniformity of metal deformation along the cross section of the profile. Greater value coefficient indicates a greater non-uniformity of such deformation when obtaining the same profile and, as a result, better workability of the metal structure. For the compared calibration schemes, non-equiaxed gauges known from the literature (for example, oval, rhombic), with different ratios of the axes, were used.

Rice. 1. Coefficient of integral non-uniformity of forming K inf:

1- oval-circle; 2 - flat oval-circle; 3 - oval-square; 4 - oval-rib oval;

5 - rib oval-oval; 6 - rhombus square.

When rolling a round profile in a finishing pair of calibers, it is possible to use the oval-circle and flat oval-circle systems. As shown in figure 1 (lines 1,2) the value of the maximum value of the coefficient K inf 1.4-1.5 times more when used as a pre-finishing flat oval caliber.

Thus, from the point of view of a better study of the structure, the flat oval-circle system is the most preferable. In doing so, it must be taken into account that this system in the production of small-sized round steel, it requires a high accuracy of setting the mill to eliminate defects in the round profile “mustache” or “lampas”, as well as “flat edges” arising from overfilling or underfilling of calibers.

In the production of round and hexagonal steel, intermediate and pre-finishing stands often use ribbed oval gauge systems, such as oval-ribbed oval and ribbed oval-oval. In these systems, as studies have shown, the value of the coefficient of uneven shape change K inf largely depends not only on the ratio of the axes of a single-radius oval gauge (Fig. 1, lines 4 and 5), but also on the ratio of the axes of the ribbed oval. As the simulation results showed, best conditions deformation is provided by the “rib oval” caliber, the shape of which is close to a circle, i.e. the ratio of the axes of the rib oval in the intermediate and pre-finishing stands is 0.94-0.96. With such a ratio of the axes of the rib oval, the area of ​​high-altitude deformation becomes commensurate with the area of ​​transverse deformation, which leads to an increase in the value of the coefficient K inf. By changing the ratio of the axes of the rib oval from 0.75 to 0.95, the shape change coefficient changes from 0.038 to 0.138. In the task of rolling an oval shape with an axis ratio of 1.5 to 2.65 into an oval rib pass, the ratio of the axes of which is 0.95, the coefficient K inf changed from 0.06 to 0.31. Thus, the intensity of growth of deformation unevenness in the rib oval-oval system is greater than in the oval-rib oval system.

In the intermediate stands of a section mill, in the production of a round profile, it is possible to use the oval-square gauge system, in which, as shown by modeling, the ratio of the axes of the oval roll can be 1.5 times greater than in the oval-circle system at the same elongation ratios. This leads to more than a doubling of the coefficient K inf(lines 1, 3 Fig. 1), which provides a better study of the metal structure.

In the rhombus-square gauge system, which can also be used in intermediate stands, the coefficient of integral shape change unevenness is approximately 3 times less than in the oval-square system, since the ratio of the axes of the rhombic gauge can be 1.2-1.8, and the oval gauge 2-2.7. Such a ratio of the axes of the rhombic caliber is due to the restriction on the capture condition. Therefore, in the production of round steel, it is more expedient to use an oval-square caliber system as an exhaust one.

Analysis of data on the coefficient of efficiency of deformation in the elements of the caliber To ede(Fig. 2), which makes it possible to assess how rational this system of calibers is in terms of elongation, shows that the maximum coefficients occur in the oval-square system (Fig. 2, curve - 3), the value of which, on average, is 2 times higher than the values ​​of the coefficients To ede for other systems.

When comparing the oval-circle and flat oval-circle systems (Fig. 2, lines 1 and 2), it can be seen that the deformation is more effective in the oval-circle system, where the value of the coefficient To ede with the same ratios of the axes of oval calibers, 1.5-1.8 times more.

Rice. 2. Form change coefficient K ede: 1- oval-circle; 2 - flat oval-circle;

3 - oval-square; 4 - oval-rib oval; 5 - rib oval-oval; 6 - rhombus square.

When using a ribbed oval pass, the coefficient of deformation efficiency in the elements of the pass is greater when rolling in the oval-ribbed oval system than in the latter ribbed oval-oval system (Fig. 2, lines 4 and 5). So, changing the ratio of the axes of the rib oval from 0.75 to 0.95 in the rib oval-oval system, the coefficient of shape change K ede varies from 0.06 to 0.11. In the task of rolling an oval shape with an axis ratio of 1.5 to 2.65 into an oval rib pass, the ratio of the axes of which is 0.95, the coefficient K ede changed from 0.017 to 0.154.

Thus, the intensity of growth of the deformation efficiency in the oval-ribbed oval system is greater than in the ribbed oval-oval system.

Taking into account the noted regularities in the distribution of the coefficients of shape change in various systems of calibers, four variants of calibration schemes for intermediate, pre-finishing and finishing stands of the 350 medium-section mill when rolling round steel with a diameter of 28 mm are proposed (see Table 1). The proposed options differ in the systems of calibers in the intermediate and pre-finishing stands. In all variants, the maximum possible coefficients of forming efficiency were obtained K inf And To ede on the stands of the mill "350" when the boundary conditions are met.

The distribution of efficiency coefficients by mill stands is shown in fig. 3, 4. To compare the proposed options, the average values ​​of the coefficients of shape change were calculated K inf, To ede and drawing ratio for six stands of mill No. 7-12. The calculation results are presented in Table 2.

From Table. 2 shows that the maximum average value of the coefficient K inf takes place in variant 4 when using the oval-rib oval gauge system in intermediate stands, the maximum average value of the coefficient To ede and elongation ratio in variant 2, when using the oval-square and oval-circle systems.

Thus, rolling using the calibration scheme of option 4 will provide the maximum workability of the metal structure compared to other options, and hence the minimum grain size of the metal structure of the finished profile.

The third option is characterized by the minimum average values K inf And To ede, which ensures minimal energy consumption and can be recommended for the assortment subjected to subsequent heat treatment, leveling the difference in the resulting structures.

Fig.3. The distribution of the coefficient of shape change K inf during rolling of a round profile with a diameter of 28 mm on the mill "350".

Rice. Fig. 4. Distribution of the coefficient of form change K ede during rolling of a round profile with a diameter of 28 mm on the mill "350"

Table 1 - Options for sizing rolls of a medium-section mill "350" in the production of a round profile with a diameter of 28 mm.

Note: () - the ratio of the axes of the unequal caliber

Table 2 - Average values ​​of deformation indices and coefficients of form change during rolling of a round profile according to various calibration schemes

* - ?cp 7-12 - average hood for stands No. 7-12; ? ? - total extract for stands No. 7-12

Option 2 is a compromise and can be used to obtain profiles with low requirements for the structure, but allows to reduce energy costs for rolling profiles.

Conclusion. Thus, the analysis and modeling of the calibration of the rolls of the section mill "350" by varying such parameters as the ratio of the sides of non-equiaxed calibers (oval, rib oval) and the elongation coefficients in the pre-finishing and finishing stands showed the possibility of developing rational calibration schemes according to the criteria "better workability of the structure" or "maximum energy efficiency".

Literature:

1. A.I. Vinogradov, S.O. Korol On the issue of creating calibration rolls that increase the efficiency of production of profiles from hard-to-deform materials / Bulletin of Cherepovetsky state university. - 2010.- №3(26).- p.116-120

2. B.M. Ilyukovich, N.E. Nekhaev, S.E. Merkuriev Rolling and calibration. Reference book in 6 volumes, volume 1, Dnepropetrovsk, Dnepro-VAL.-2002

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Dear Alexey Ivanovich and Marina Anatolyevna! Let's talk right away. In order to give a competent commentary on this report, one should be at least an expert in the field of rolling production. And since we are not such, we are forced to comment on the report from the position of just metallurgists. In our opinion, in connection with the constantly growing requirements for improving the efficiency of section rolling mills, the choice of a rational system (scheme) for sizing rolls is an important problem for manufacturers. The simpler and more accessible its solution, in this case, through the use of mathematical modeling, the greater its attractiveness for factory workers. The authors chose one of the most important parameters of efficiency - the degree of elaboration of the metal structure, characterized by two coefficients: unevenness and efficiency (the indexes of the coefficients are incomprehensible - "inf." and "ede"). Of course, it was possible to choose several parameters at once as an optimality criterion, for example, related to minimizing costs: the minimum energy consumption for deformation, the minimum number of passes and tilts, the minimum wear of calibers, etc. But, obviously, this would complicate the solution of the problem, although and would optimize it more. Without knowing anything about other available methods for calculating roll calibration systems for section rolling mills, it is difficult to assess the degree of its novelty and advantages. However, it is important that the methodology developed by the authors made it possible to determine rational calibration schemes for a particular mill of a particular enterprise. In the development of the work and to confirm the effectiveness of the schemes determined as a result of modeling and the performed calculation, it is possible to recommend the authors to carry out real rolling with metal sampling to determine the microstructure (grain size, etc.), successively at various stages of metal advancement in the rolling process (after ferrous, intermediate and finishing group of stands). In addition, in our opinion, in order to improve the quality of manufactured metal products and improve rolling conditions, it is advisable to contact steelworkers in this direction, since the latter have a large arsenal of tools that ensure the optimization of the structure and level of physical and mechanical properties of cast CW. Obviously, it is important, together with them, to select the optimal profile (for example, a square with rounded corners, etc.) in terms of shortening cycles and “facilitating” subsequent rolling operations. But this is so - the reflections that your report led us to. It was nice to be in the section not alone. Good luck on your way to improving technological parameters and rolling modes. Titova T.M., Titova E.S.

This is not the first attempt to use the coefficient of efficiency and unevenness in the calibration of rolls of rolling mills. But in the long case there is a deep system analysis in combination with a mathematical justification. One can only welcome the efforts of the author in our time, when interest in technical science is waning. A. Vykhodets

Goal of the work: familiarization with the principles of sizing rolls for rolling square and round profiles.

Theoretical information

I. General issues of roll sizing.

Long products are obtained as a result of several: consecutive passes, the number of which depends on the ratio of the sizes and shapes of the initial and final section, while in each pass the section changes With a gradual approach to the finished profile.

Rolling of section metal is carried out in calibrated rolls: i.e. in rolls with special cutouts corresponding to the required configuration of rolled stock in a lath pass. Annular cut in one roll / fig. 4".L/ is called stream I, and the gap between two streams located one above the other working together, taking into account the gap between them, is called gauge 2.

Rolling in calibers, as a rule, is an example of a pronounced non-uniform deformation of the metal and V most cases by constrained broadening.

When calibrating rolling rolls, the amount of reduction by passes has to be taken simultaneously with the determination of the successive shapes and sizes of the calibers /Fig. 42.2/, providing high-quality rolled products and accurate profile dimensions.

Gauges used in rolling are divided into the following main groups depending on their purpose.

Crimp or draw gauges - designed to reduce the cross-sectional area of ​​the billet mm mm. Drawing calibers are square with a diagonal arrangement, rhombic, oval. A certain combination of these calibers forms caliber systems, for example, rhombus-square, oval-circle, etc. /Fig.42.3/.

Rough go preparatory calibers", in which, along with a further reduction in the section of the rolled product, the profile is processed with a gradual approximation of its dimensions and shapes to the final section.

Finishing or finishing gauges , to complete the profile. The dimensions of these calibers are 1,2...1,5% more finished profile; the allowance is given for the shrinkage of the metal when it is cooled.

2. Caliber elements

Gap between rolls. The height of the caliber is the sum of the depth of the virez in the upper h t and lower h2, rolls and magnitudes S between rolls

During rolling, the pressure of the metal tends to push the rolls apart, while the gap 5 increases, which is called the recoil, or spring, of the rolls. Since the gauge drawing is displayed compresses its shape and dimensions at the time of the strip passage, then the gap between the rolls when installed in the stand is reduced less than the gap indicated in the drawing by the amount of return of the rolls. At the same time, it is necessary to take into account the fact that during operation the distance between the rolls change in steel grade, wear of rolls, etc. / have to be changed in order to adjust the mill. This setting can be carried out if there is a gap between the rolls, which is accepted for shrinking mills I...I.5%, for other mills 0.5..1 % on the roll diameter.

Issue caliber. The side walls of the box caliber / fig. 42.3 "have some slope To roll axes. This inclination of the walls of the caliber is called release. During rolling, the release of the pass provides a convenient and correct insertion of the strip into the pass and the free exit of the strip from the pass. If the walls of the caliber are perpendicular to the axis of the rolls, a strong pinching of the strip would be observed, and there would be a danger of binding the rolls, since broadening almost always accompanies the rolling process. Typically, the release of the caliber is squeezed in percent /~ 100 %/ or in degrees µ and is accepted for box gauges 10..20%

Top and bottom pressure It is very important during rolling to ensure a straight exit of the strip from the rolls. For this purpose, wires are used, since during rolling there are reasons that caused the strip to bend towards the upper and lower rolls, this requires the installation of wires on the lower and upper rolls. But this setting

can be avoided if the strip is given a certain direction in advance, which is achieved by using rolls with different diameters. The difference between the diameters of the forks is conventionally called "pressure", Will the diameter of the upper roll is larger, they speak of "upper pressure" / fig. 42.4/,

if the diameter of the lower roll is assumed to be large, then in this case there is "neither lower pressure". The pressure value is expressed as a difference in diameters in millimeters. For long sections, they tend to have an upper pressure of more than I % from the average diameter of the rolls.