How to roll a square out of a circle yourself. Development of rational schemes for roll calibers of section mills

1. The profile of the hole, images, adjacent grooves of the rolling rolls in the working position and the gaps between them, serves to give the specified shape and size to the section of the roll. Usually the roll is formed by two, less often by three or four rolls. The shape of the boxes can be simple - rectangular, round, square, diamond-shaped, oval, strip, hexagonal, lancet and shaped - corner, I-beam, channel, etc. By design, i.e. position of the parting line, they are divided into open. and closed, according to location on the rolls - open, closed, semi-closed. and diagonal. By appointment - crimping, drawing, roughing, pre-finishing and finishing. Main. el-you k. - gap between the rollers, outlet k., connector, collars, rounding, neutral. line. Types of circuits are shown in Fig. 2. Replaceable technological tool, fastened on the work roll. 3. A scale-free measurer, a tool for controlling the size, shape and relative position of parts of a product by comparing the size of the product with the k. according to the occurrence or degree of fit of their surfaces:
beam gauge - k. (1.) for rolling rough and finishing I-sections. Use b. to. straight closed, open, inclined, and universal. Usually two-rollers are used, less often - universal ones. four-roll b. K. Naib, dist. straight closed b. j. Open b. They are used as split and rough steels when rolling large I-beams. In tilt, b. to. roll I-profiles with reduction. internal slopes shelf edges and high flange heights. To the university b. they roll large-sized wide-flange I-beams and para-rall I-beams. shelves. When rolling lightweight I-beams, use a horizon positioned diagon. b. To.;
drawing gauge - a (1.) simple form for reducing the cross-section and drawing (1.) of the roll with a given alternation of two or one gauge of the same type. In some cases c. they give the roll dimensions, at which the formation of a given profile begins. When rolling simple profiles, they are usually rough gauges. As a rectangular, square, rhombic, oval, hexagonal are used. and other calibers. Depending on the rolling conditions and requirements, the cross section of the roll. to. are located in a certain position. last name exhaust gauge system;
diagonal gauge - closed k. (1.) with diagonal. (different in height) location of the bed. connectors. D.K. usually cut into rolls at an angle and are used for oblique calibration of I-beams, profiles and rails. Horizon, d.k. is used when rolling I-beams, profiles on continuous mills and Z profiles. D.K. facilitates the exit of the rolled product from the rolls, but creates undesirable material. lateral forces;
closed pass - a roll (1.), in which the parting line of the rolls is outside its contour. 3. K. is usually used for rolling shaped profiles; it, as a rule, has one rotation, an axis of symmetry;
Rib oval gauge
rhombic gauge - k. (1.) rhombic. config., cut into the rolls along a small diagonal. Calculation, dimensions: C, = 5K/2sinp/2, B - B - Sa, height taking into account roundings

Diamond caliber
I, = I, -2K(1 + l/ek2) -1), a = I/I, = = tgp/2, / = (0.15-nO,20)R1, l, = (0.10 +0.15)R„ P = 2(R,2 + R,2)"2, in, = 1.2*2.5 (Fig.). R.K. is used in the rhombus-rhombus and rhombus calibration system - square. The angle at the top of the caliber p varies from 90 to 130°, with an increase in the angle of updraft in the caliber, on average, 1.2-1.3. Recommended degree of filling of the caliber 0.8 -0.9;
Ogival square gauge
lancet square gauge - k. (1.) with the outline of a square with concave sides, cut into the rolls diagonally. Calculation, dimensions: Vk = R, = 1.41 C; R = = (C,2 + 4D2)/8D; g = (0.15+0.20)С; B = 5K-- (2/3)5. Area F = C, (C, + (8/3) D), where D is the size of one side. convexity, C, is the inscribed side of a square (Fig.). Max, side size c. k.k. C^ = = C, + 2D. S. k. k. is used when necessary. transfer a large amount of metal to the finishing passes. At the same time, the values ​​are preserved. rolling temperature, because there are no sharp corners. S. k. k. - exhaust in the oval-arrow square caliber system and sometimes pre-finishing for circles;
rough gauge - k. (1.), approx. cross-section of the workpiece or roll to the configuration of the finished profile. The black parts of shaped profiles during rolling approach the shape of the finished steel. The shape of the black parts when rolling simple profiles is determined by the exhaust system of the metal;
finishing gauge i-k. (1.) to give the rolled product a final profile, i.e. for manufacturing rolled from the end transverse dimensions sections. When designing h.c. take into account thermal expansion. metal, uneven distribution rolling temperatures, wear of calibers, additional profile adjustment and other factors;
hex gauge - k. (1.) hex. contour, cutting, into the rolls along a large diagonal. Connector w. k. located on its sides. Dimensions w. k. expression through vpi-

Hex gauge
rank circle dia. d: side C = 0.577d, area -F = 0.866d2, height H, = 2 C (fig.). Appl. The quality is clean, the caliber when rolling is hexagonal. steel and black when rolling hexagons. drill steel, when uniform and low compression along the passes is required;

Sss carbon caliber
hexagonal gauge - k. (1.) hexagonal. contour, plunge, into the rolls along the minor axis; appl. in the exhaust system of calibers hexagon-square and as pre-clean. when rolling hexagonal profiles. Calculation, dimensions: 5D = 5K - I; B = 5K - S; ak = BJH, = 2.0+4.5; g = g, = (OD5+0.40)R; P = 2(Bf + 0.41R) (Fig.). Predchistova highway they are built like a regular hexagonal one, but for compensation. expansion of the metal and preventing the convexity of the side walls is clean. hexagon bottom of the caliber is made with a convexity of 0.25-1.5 mm, depending on the size of the profile. Filling degree w. k. take 0.9;
l

Box gauge
box gauge - k. (1.), image. trapeze cutting into rolls, for rectangular rolling. and square, profiles. Design dimensions: 5d = (0.95+1.00) В„; B = Poison + (I, -- S)tg(p; g = (0.10h-0.15)I,; g, = (0.8+1.0)/-, ok = = 4/I , = 0.5+2.5; />* 2(R, + B) (Fig.).The depth of cut-in of the cell I, depends on the ratio of dimensions (R,/R0) of the profile specified in it. They are mainly used on blooming, crimping and continuous billet mills, crimping and ferrous stands of section mills and for producing commercial billets on rail and beam and large-section mills.
square gauge - k. (1.)
square, contour, cut into the rolls along the dia
drove. Depending on the requirements, rental profile
performed with a rounded or sharp tips
us. Calculation, dimensions: Hk= Bf= 21/2 C I, =
= 21/2 C. - 0.83g, B =B-s;r= (0.1+0.2)^;
/-,= (0.10^0.15)I,; P = 2-21/2R, (Fig.). K.K. -
finishing when rolling square pros
lei and exhaust in rhombus-square systems,
oval-square and hexagon-square. In black
new calibers perform significant
the rounding of the vertices with a radius r. The height and width of the coque are, respectively, 1.40 and 1.43 of its sides.
When rolling squares with sharp corners, the square has an angle at the apex of the example, but 91-92° taking into account
volume of thermal shrinkage of the profile; L"" "°t -""" " "" and
control gauge - k. (1.), for small high-altitude compression and control of the dimensions of the part. el-tov roll; used when rolling a number of shaped and complex profiles, for example, I-beams, for wheel rims, door hinges, etc. K. are made closed and semi-closed. A closed k.k. provides more accurate dimensions of the rolled elements, but more often they work with semi-closed k.k.
round gauge- k. (1.) with a circle outline on the main part of the perimeter; finishing during rolling round steel and exhaust in the oval-circle system. K.K. of all types have release or collapse. When constructing a finishing k.k., they usually take an outlet of 10-30° or 20-50°, depending on the diameter. rolled circle. Design dimensions: Bf = rf/cosy, B" = Yak-.Stgy, g, = (0.08+0, lO)d, P = = tk/(fig.). Because they tend to roll round steel with minus, tolerance D on dia., then for finishing k.k. taking into account thermal expansion, take d = 1.013, where rfxon "~ Diam. circle in a cold state;
multi-roll gauge - a roll (1.) with a contour formed by three or more rolls, the axes of which lie in the same plane. In the m.c., the metal is compressed in the vertical-transverse direction. with advantage all-round compression, which allows the deformation of low-plasticity materials. M. k. provide. high dimensional accuracy of profiles, therefore they are widely used in finishing stands of small-section and wire mills for rolling steel and non-ferrous materials. metals Four-roll open and closed gauges are often used at mountains. and cold rolling of high-precision shaped profiles;
crimp gauge - k. (1.) for reducing the cross-section of the rolled product and obtaining blanks for section mills. As o. because on blooming, crimping and blanking mills, box gauges are used. Deformation in o. K. is not always accompanied by creatures, hood, as, for example, in the first passes on blooming. However, to Fr. c. sometimes calibers are partially or completely attributed exhaust systems calibrations The subsection of gauges for crimping and drawing depends on the purpose of the rolling mill, the gauge system and the individual gauge;
oval gauge - (1.) an oval or close to it contour, cut into the rolls along the minor axis. O.K. is used as a pre-finishing agent for rolling round profiles and exhaust in the oval - rib oval system, etc. Depending on the purpose of the caliber and the size of the rolls, they use: 1. Single-radius o. k. (ordinary o.k.), appl. as a pre-finishing agent when rolling round steel. Their calculated dimensions (Fig.): R = = R, + (1 + O/4; B = (R, - S) 1/2; r, = (0.10+0.40)^; P = 2 [B* + + (4/3)R,2]1/2; a^ = Bk/H, = 1.5 + 4.5. Elliptic and two- or three-radius o.c., used as pre-finishing when rolling large circles and in oval-circle and oval-oval systems; flat o.c., used in the same place as elliptical o.c. and as pre-finishing when rolling periodic reinforcing profiles, in of which B = = OD; r = 0.5R,; r, = (0.2+0.4)R; O|t = = 1.8+3.0; modified flat o.c., the contour of which is an image, a rectangle and lateral curved triangles, taken as parabolic segments; trapezoidal (hexagonal) o.k. with straight outlines, used for good retention of the roll and alignment of hoods
open gauge - k. (1.), the parting line of which is within its contour; image, cuts in two or more rolls, cut in one roll and a smooth barrel or smooth barrels. In simple o. to. connector image, approximately in the middle of the caliber and the side sections of the shaped roll. the shoulders of two rolls. In some shaped o. because they are formed. the walls of the stream in only one roll;
semi-closed gauge - shaped connector (1.) with a connector located on the side wall near the top of the stream; used as a control when rolling channels, strip-bulb, I-beam and other profiles. Compared to the closed control gauge, it has a larger outlet and a small plunge depth of the closed groove, which weakens the roll less in diameter, allows the flanges of the rolls to be compressed in thickness, increases the number of regrinds and the service life of the rolls;
pre-finishing gauge - k. (1.) for penultimate. skipping the roll; to prepare the roll for forming. final profile. When rolling shaped
profiles are very close in shape and/or size to the finished one, but when rolling simple profiles it may differ. As p.c., rib gauges are often used when rolling strip profiles and control gauges when rolling flange profiles;
split gauge - 1. K. (1.) with a ridge in the middle part, for initial. for-world. from blanks of flanged rolled elements; for example, when rolling I-beams from rectangles. The workpiece forms sections of flanges and walls, and when rolling rails, sections for the sole and head are formed. Use open and closed rivers. k. Closed rivers They are performed on rollers of large diameter. for manufacturing large flanges. Open symmetrical R. K. with blunt ridges are often used for rolling beam blanks from slabs. 2. K. for longitudinal separation of double rolls;
Rib gauge
rib gauge - k. (1.), cut-in, into large-sized rolls; used, in particular, when rolling steel strips to regulate the width of the roll. Predchistovaya R. It also forms rolled edges. When rolling strips with straight edges, the convexity of the bottom of the pre-finishing river. k.D = = 0.5-5-1.0 mm, roll gap< 1/3 высоты полосы и выпуск 0,05+0,10 (рис.);
T
rib oval gauge - k. (1.) oval contour, cut into the rolls along the major axis. Calculation, dimensions: R = 0.25/^(1 + + 1/a2), V = V- 2L, r = = rt = (0.10+0.15)5, ak = 4/R, = 0 .75*0.85, P = 2(R,2 + (4/3)r,T2 (Fig.). Used as an exhaust oval in the system - rib oval;

Calibration of rolls for rolling round profiles

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

Rolling of this profile, depending on the steel grade and dimensions, is carried out in different ways (Fig. 2.7 ).

Figure 2.7. MethodsI -X rolling round steel:

I – oval, rhombus or hexagon;II . IV. V – smooth barrel or boxcaliber;III – decagonal or box calibers; VI – square or hexagonal gauges; VП – circle, etc.; VIII– lancet caliber, smooth barrel or box caliber; IX, X- oval, etc.

Methods 1 And 2 They 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 obtain a number of adjacent sizes of round steel (Fig. 2). Method 3 is that the pre-finishing oval can be replaced with 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 side walls in this caliber allows for better scale removal. Because this method allows you to widely adjust the size of the strip coming out of the rib gauge, it is also called universal gauge. Methods 5 and 6 differ from the others in higher hoods and greater stability of the ovals in the wiring. However, such calibers require precise adjustment of the mill, since with a slight excess of metal, they overflow and form burrs. Methods 7-10 are based on the use of an oval-circle calibration system

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

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

Drawing2.8 Example of calibration of round steel using method 2

The construction of a finishing gauge for round steel is carried out as follows.

Determine the calculated diameter of the gauge (for a hot profile when rolling at minus) dG = (1,011-1,015)dX– this is part of the tolerance +0.01 dX where 0.01 dX– increase in diameter for the above reasons: dX = (d 1 + d 2 )/2 – diameter of a round profile in a cold state. Then

dG = (1,011-1,015) (d 1 + d 2 )/2

Where d 1 And d 2 – maximum and minimum permissible diameter values.

Pre-finishing gauges for the wheel are designed taking into account the accuracy required for the finished profile. The closer the oval shape approaches the shape of a circle, the more accurate the finished round profile is. Theoretically, the most suitable profile shape for obtaining a perfect circle is an ellipse. However, such a profile is quite difficult to maintain when entering a finishing round gauge, so it is used relatively rarely.

Flat ovals are well held by wires and, in addition, provide large compressions. With small oval compressions, the possibility of size fluctuations in a round gauge is very insignificant. However, the opposite phenomenon is true only for the case when a large oval and a large hood are used.

For round profiles of medium and large sizes, ovals outlined by one radius turn out to be too elongated along the major axis and, as a result, do not provide reliable grip of the strip by the rolls. The use of sharp ovals, in addition to the fact that it does not ensure an accurate circle, has a detrimental effect on the durability 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 production of calibers leads to the appearance of second grades and sometimes defects.

A study of the causes and mechanism of caliber production 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 groove of the finishing stand rolls, act on the bottom of the groove as an abrasive. The hard 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 above, 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 is reduced.

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

Calibration of profiles and rolls intended for rolling round and square steel

TO hot rolled round steel according to GOST 2590-71, they include profiles that have a circular cross-section with a diameter of 5 to 250 mm.

In general, the calibration scheme for round steel can be divided into two parts: the first is calibration for roughing and middle groups of stands and satisfies a number of profiles, being in this sense common to several final profiles of different sections (square, strip, hexagonal, etc.) , and the second is intended as a specific system for the last three to four stands and is characteristic only of this round steel profile. In roughing and middle groups of stands, gauge systems can be used: rectangle - box square, hexagon - square, oval - square, oval - vertical oval.

For the last three to four profiling stands, the gauge system is also not constant. A certain pattern is observed only in the last two stands: the finishing stand has a round gauge, the pre-finishing stand has an oval gauge, the gauge of the third stand from the end of rolling can be of different shapes, on which the calibration system depends.

General caliber diagrams of the last four passes when rolling round steel. From these diagrams it follows that oval gauges of two shapes are used as pre-finishing gauges: single-radius and with rounded rectangles - the so-called “flat” gauges. The first scheme is used when rolling round steel of most profile sizes, the second - mainly for round steel of large diameters and reinforcing steel.

According to the first general rolling scheme, seven types of gauges used in the pre-oval stand can be noted. According to the second general scheme, only two types of gauges have found the greatest use: box square 1 and square 3, embedded in the roll barrel when positioned diagonally.

The systems and shape of the gauges used for roughing and middle groups of stands can be very diverse and depend on a number of factors, the main ones being the type of mill and the design of its main and auxiliary equipment.

Currently, there are a number of techniques for constructing a finishing gauge for round steel: outlining the gauge with two radii from different centers; chamfering at the roll connectors in order to prevent stripping of small-thickness undercuts of the rolled material by caliber collars; formation of release by the outline of the caliber along the connector, etc. Practice shows that a finishing gauge, outlined by one radius and having only one size - the internal diameter, does not satisfy the requirements for obtaining a geometrically correct high-quality profile, especially a large-diameter profile. As a rule, in such a caliber, even with the most insignificant change in technological conditions (lowering the rolling temperature, producing pre-finishing caliber rolls, increasing the height of the oval, etc.), the streams become overfilled with metal. Obtaining a profile in accordance with the shape of the finishing gauge requires constant monitoring of the dimensions of the pre-finishing oval roll. In cases where the gauge is overfilled, it is not always possible to maintain the profile diameter, even within the plus tolerance.

In order to eliminate the noted shortcomings, it is recommended to design a finishing gauge with a camber (release) for a round steel profile, i.e., provide a slightly larger horizontal diameter compared to the vertical one. This is also necessary due to the fact that the oval-section rolled product entering the finishing gauge has a lower temperature at the ends of the major axis and the thermal shrinkage of the finished profile upon cooling in the direction of the horizontal diameter is somewhat greater than in the direction of the vertical diameter. Intensive wear of the finishing gauge of round steel vertically due to greater compression also contributes to the size exceeding the horizontal diameter by 1-1.5% over the vertical.

Domestic factories tend to roll round steel to minus tolerances.

Determining the size of the horizontal diameter using the finishing gauge connector is recommended using analytically derived equations (N.V. Litovchenko) taking into account the dimensions of the profile diameters.

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 analyzing calibration systems for section mill rolls is proposed. As criteria, it is proposed to use the coefficients of unevenness and efficiency, which determine the degree of elaboration of the structure when rolling sections. Using the example of calibration systems for the production of a round profile with a diameter of 28 mm, possible deformation patterns 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 of section 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. Construction rational calibration rolls in a section rolling mill is a complex 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 change in shape, others for better elaboration of the structure. There are calibrations that provide more accurate cross-sectional dimensions or allow energy-efficient deformation modes.

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

Methodology of work. To analyze calibration systems, pairs of sequential gauges were selected, allowing, on the one hand, to consider all possible schemes of combinations of gauges, and on the other, to provide research into the division limit of a complex system, such as the calibration of rolls of a continuous section mill.

Unevenness coefficients were selected as system efficiency criteria To 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- lengths of radius vectors in i-th point of the cross section of the workpiece and the exiting strip, respectively;

n- number of radius vectors.

The coefficients of unevenness and efficiency of forming, which determine the degree of development of the metal structure, largely depend on the shapes of alternating gauges and the ratio of the lengths of the axes of non-equiaxial gauges. An incorrect choice of axial ratio leads to the appearance of cracks and breaks in the strip when rolling profiles, especially from hard-to-deform steels.

In the process of rolling any section profile, two main stages can be distinguished: rolling a square continuously cast billet in roughing and intermediate stands of the mill in order to obtain a rolled product of the required shape and size for the finishing group of stands, and rolling in the finishing stands. When constructing a rational calibration of rolling mill rolls, it is necessary to strive to use the same calibers in roughing and intermediate stands when producing rolled products of a wide profile range.

Thus, when rolling round steel with a diameter of 25-105 mm and hexagonal steel No. 28-48 on the medium-grade mill “350” of CherMK OJSC 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 under different calibration systems. As an example, consider rolling round steel with a diameter of 28 mm.

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

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

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

Rice. 1. Coefficient of integral unevenness of shape change 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 gauges, it is possible to use oval-circle and flat oval-circle systems. As shown in Figure 1 (lines 1,2) the maximum value of the coefficient To inf 1.4-1.5 times more when used as a pre-finishing flat oval gauge.

Thus, from the point of view of better elaboration of the structure, the most preferable is the flat oval-circle system. It must be taken into account that this system in the production of round steel of small sizes, it requires high precision in setting the mill to eliminate defects in the round profile “mustache” or “lamps”, as well as “flat edges” that arise due to overfilling or underfilling of the gauges.

In the production of round and hexagonal steel, ribbed oval gauge systems such as oval-ribbed oval and ribbed oval-oval are often used in intermediate and finishing stands. In these systems, as studies have shown, the value of the coefficient of unevenness of shape change To inf largely depends not only on the ratio of the axes of the single-radius oval caliber (Fig. 1, lines 4 and 5), but also on the ratio of the axes of the rib oval. As the simulation results showed, best conditions deformation is ensured by the “rib oval” caliber, the shape of which is close to a circle, i.e. The ratio of the rib oval axes in the intermediate and finishing stands is 0.94-0.96. With this ratio of the axes of the rib oval, the area of ​​​​altitude deformation becomes commensurate with the area of ​​\u200b\u200btransverse deformation, which leads to an increase in the value of the coefficient To inf. By changing the ratio of the axes of the rib oval from 0.75 to 0.95, the coefficient of change in shape changes from 0.038 to 0.138. When faced with the task of rolling an oval shape with an axial ratio from 1.5 to 2.65 into a rib oval gauge, the axial ratio of which is 0.95, the coefficient To inf varied 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 when producing round profiles, it is possible to use an oval-square gauge system, in which, as modeling has shown, the ratio of the oval roll axes can be 1.5 times greater than in the oval-circle system at the same drawing ratios. This leads to a more than doubling of the coefficient To inf(lines 1, 3 of Fig. 1), which provides better elaboration of the metal structure.

In the rhombic-square gauge system, which can also be used in intermediate stands, the coefficient of integral unevenness of the form change 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 ratio of the oval gauge 2-2.7. This ratio of the axes of the rhombic caliber is due to the limitation on the capture condition. Therefore, when producing round steel, it is more expedient to use an oval-square gauge system as a drawing system.

Analysis of data on the deformation efficiency coefficient in caliber elements To ede(Fig. 2), which allows us to assess how rational a given system of gauges is in terms of drawing capacity, shows that the maximum coefficients occur in the oval-square system (Fig. 2, curve - 3), the value of which is on average 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 is clear that deformation is more effective in the oval-circle system, where the value of the coefficient To ede with the same axial ratios, oval calibers are 1.5-1.8 times larger.

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

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

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

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

From the table 2 it is clear that the maximum average value of the coefficient To inf occurs in option 4 when using the oval-rib oval gauge system in intermediate stands, the maximum average value of the coefficient To ede and the draft coefficient in option 2, when using the oval-square and oval-circle systems.

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

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

Fig.3. Distribution of the forming coefficient K inf when rolling a round profile with a diameter of 28 mm on a 350 mill.

Rice. 4. Distribution of the coefficient of forming K ede when rolling a round profile with a diameter of 28 mm on the 350 mill

Table 1 - Options for calibrating rolls of the medium-grade mill “350” in the production of round profiles with a diameter of 28 mm.

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

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

* - ?av 7-12 - average hood for cages No. 7-12; ? ? - total exhaust for cages No. 7-12

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

Conclusion. Thus, the analysis and modeling of the calibration of rolls of the section mill “350” when varying such parameters as the aspect ratio of unequal passes (oval, ribbed oval) and drawing coefficients in the pre-finishing and finishing stands showed the possibility of developing rational schemes calibration according to the criteria of “best structure elaboration” or “maximum energy efficiency”.

Literature:

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

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

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Dear Alexey Ivanovich and Marina Anatolyevna! Let's make a reservation right away. In order to give an intelligent commentary on this report, you should at least be a specialist in the field of rolling production. And since we are not such, we are forced to comment on the report from the position of simply metallurgists. In our opinion, due to the ever-increasing requirements for increasing the efficiency of section rolling mills, the choice of a rational system (scheme) for calibrating 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 indices for the coefficients are unclear - “inf.” and “ede”). Of course, it was possible to select several parameters at once as an optimality criterion, for example, those related to minimizing costs: minimum energy consumption for deformation, minimum number of skips and turns, minimum wear of gauges, 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 specific mill of a specific enterprise. To develop the work and to confirm the effectiveness of the schemes determined as a result of modeling and calculations, we can recommend that the authors carry out real rolling with metal sampling to determine the microstructure (grain size, etc.), sequentially at various stages of metal advancement during 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 modes, it is advisable to contact steel smelters and casters in this direction, since the latter have a large arsenal of tools that ensure optimization of the structure and level of physical and mechanical properties of cast continuous castings. Obviously, it is important, together with them, to select the optimal profile (for example, a square with rounded corners, etc.) from the point of view of reducing cycles and “facilitating” subsequent rolling operations. But this is so - the thoughts that your report led us to. It was nice to not be alone in the section. Good luck to you on your path 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 non-uniformity in the calibration of rolls of rolling mills. But in this case, a deep system analysis takes place in combination with mathematical justification. One can only welcome the author’s efforts in our time when interest in technical sciences is waning. A.Vykhodets