Construction of a finishing gauge for round steel. Rolling and calibration of rolls to produce round and square products
Oval-circle system
Figure 1.8. Diagram of metal rolling in a gauge system
"oval-circle".
The system is a special case of the “oval-rib-oval” system and, if necessary, allows you to create “universality” of calibration, ensuring round profiles standard diameters from intermediate working stands (during the rolling of metal in the mill), which reduces downtime of the mill for transshipment. However, the “universality” of roll calibration systems somewhat complicates the implementation of the metal compression mode on the mill, which to some extent can be attributed to the disadvantages of the system. The low stability of a single-radius oval in a round gauge prevents the rolling of metal while maintaining high values of the partial “draw” of the metal, and the value of the average “draw” of the metal in the “oval-circle” system is (). It is not rational to use the gauge system as an exhaust system, although it is indispensable as a finishing system, which is successfully implemented at the 350 OEMK mill.
Some elements of calibers of simple form are common to all types of calibers.
The gap between the rolls (roll collars), . Under the influence of forces from the rolled metal, the distance between the rolls increases due to the selection of gaps in the stand parts and the elastic deformation of the stand. At the same time, the height of the caliber will increase. Therefore, the drawing of the gauge should show its shape and dimensions at the time of rolling the strip, that is, together with the gap (Figure 5.1).
The gap allows you to change the height of the gauge during rolling, thereby changing the profile of the rolled metal. With a large gap, the contact zone between the metal and the rolls is small, the contour of the pass is not closed, and therefore the performance of the dimensions and shape of the rolled product deteriorates. For this reason, clearances in finishing gauges should be kept to a minimum.
The gap size is taken as a fraction of the nominal diameter of the rolls (Table 1.2.) or the height of the pass (strip height).
Table 1.2. Minimum gaps between roll collars
| Group of stands of small-section (medium-section) and wire line of mill 350 | No. of cages | , mm |
| Rough group |  |
|
| I intermediate | ||
| II intermediate | ||
| Finishing | ||
| Finishing block |  |
Figure 1.9. Scheme of construction and typical elements of a caliber: a – a geometric figure forming a caliber and the contours of the surfaces of a pair of smooth rolls (here the contours are two solid thin lines); b – roll streams with curves; c – position and dimensions of the rolled strip; d – final caliber diagram.
Caliber width represents a horizontal characteristic dimension relative to the roll axis (hereinafter horizontal and vertical will be implied relative to the roll axis) geometric figure forming a caliber (Figure 1.9.).
Caliber height- characteristic vertical size of the geometric figure forming the caliber (Figure 1.9.).
Gauge insertion width- this is the width of the geometric figure forming the caliber at the level of intersection with the line of the roll collar (Figure 1.9.).
Gauge plunge depth- this is the distance from the roll collar to the bottom point of the gauge (Figure 1.9.).
Radiuses of curvature along the bottom of the caliber and along the shoulders usually expressed in fractions of the caliber height. Curves make a smooth transition in places where there is a sharp change in the caliber contour or at the collar-caliber boundary (Figure 1.9.). Roundings are necessary to reduce stress concentrations in the roll elements.
Collar width between grooves (end flange) – the horizontal size of the uncut part of the roll barrel between adjacent grooves (between the last gauge and the edge of the working surface of the roll).
The width of the collar between the calibers:
End flange width:
, (1.4)
where is the length of the roll barrel (Appendix 1)
Number of streams on the roll barrel;
In expression (1.4) two quantities vary: . The resulting value must satisfy condition (1.5). Thus, in addition to finding the dimensions of the piles, the number of streams on the barrel is selected.
Caliber release. To ensure free exit of the strip from the rolls without pinching, the width of the stream should increase from the bottom to the center of the groove. Therefore, the side walls of the caliber are made inclined relative to the contour of the geometric figure forming the caliber. The tangent of the angle of inclination is called the caliber release. Sometimes caliber output is expressed as a percentage.
Strip height - vertical characteristic size of the strip emerging from the rolls.
The width of the line - horizontal characteristic size of the strip emerging from the rolls.
Dulling the stripe at the gauge connector (Figure 1.9) shows the vertical size of the part of the rolled strip free from contact with the rolls.
The width and bluntness of the strip are additional geometrically clear parameters that describe an important characteristic of rolling in calibers - degree of filling of the caliber with metal. The degree of filling is determined by the formula.
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)I1, 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;
Lancet square caliber
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 used mainly on blooming, crimping and continuous blanking mills, crimping, and ferrous stands. section mills and for obtaining 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 material when rolling round profiles and as a drawing material in the oval - rib oval system, etc. Depending on the purpose of the caliber and the size of the rolls, the following are used: 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;
Goal of the work: introduction to the principles of calibrating rolls for rolling square and round profiles.
Theoretical information
I. General issues of roll calibration.
Long products are obtained as a result of several: successive passes, the number of which depends on the ratio of the sizes and shapes of the initial and final sections, while in each pass the section changes with a gradual approach to the finished profile.
Rolling of high-quality metal is carried out in calibrated rolls: i.e. in rolls that have special cuts corresponding to the required configuration of rolled products in the line pass. Annular cutout in one roll /Fig. 4".L/ is called stream I, and the clearance of two streams located one above the other and working together, taking into account the gap between them, is called gauge 2.
Rolling in calibers, as a rule, is an example of pronounced uneven deformation of the metal and V in most cases, constrained by widening.
When calibrating rolling rolls, the reduction value by passes must be taken simultaneously with the determination of successive shapes and sizes of the calibers /Fig. 42.2/, ensuring the production of high-quality rolled products and accurate profile dimensions.
The gauges used in rolling are divided into the following main groups depending on their purpose.
Crimping or drawing gauges - designed to reduce the cross-sectional area of the ingot mm of the workpiece. Extraction gauges are square with a diagonal arrangement, rhombic, oval. A certain combination of these gauges forms caliber systems, for example, rhombus-square, oval-circle, etc. /Fig.42.3/.
Rough or preparatory calibers", in which, along with a further reduction in the cross-section of the rolled product, the profile is processed with a gradual approach of its dimensions and shapes to the final section.
Finishing or finishing gauges , giving the profile its final look. The sizes of these calibers are 1,2...1,5% more ready-made profile; allowance is given for the shrinkage of the metal as it cools.
2. Caliber elements
Gap between rollers. The height of the caliber is the sum of the depth of the virez in the upper h t and lower h2, rolls and magnitude S between rollers
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 drawing of the caliber display 
compresses its shape and dimensions at the moment of passage of the strip, 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 roll return. At the same time, it is necessary to take into account the fact that during operation the distance between the rolls for a number of reasons / change in steel grade, wear of rolls, etc. / have to be changed in order to adjust the mill. This setting can be made if there is a gap between the rolls, which is accepted for crimping mills I...I.5%, for other mills 0.5..1 %
from the roll diameter.
Caliber release. The side walls of the box caliber /Fig. 42.3" have some slope To roll axes. This inclination of the caliber walls is called release. When rolling, the release of the caliber ensures convenient and correct insertion of the strip into the caliber and free exit of the strip from the caliber. If the walls of the pass were made perpendicular to the axis of the rolls, there would be a strong pinching of the strip, creating the danger of binding the rolls, since widening almost always accompanies the rolling process. Usually the caliber release is suppressed as a percentage /~ 100 %/ or in degrees µ and is accepted for box calibers 10..20%
Upper and lower pressure When rolling, it is very important to ensure that the strip exits the rolls in a straight line. 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 installation
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”. If the diameter of the upper roll is larger, they speak of “upper pressure” /Fig. 42.4/,
if the diameter of the lower roll is taken to be large, then in this case there is “no 
lower pressure." The amount of pressure is expressed by the difference in diameters in millimeters. For long stakes, they tend to have an upper pressure of more than I %
from the average diameter of the rolls.
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Ministry of Education of the Republic of Belarus
Educational Institution Gomel State Technical University named after P.O. Sukhoi
Department: “Metallurgy and Foundry”
Explanatory note
For the course project
course: “Theory and technology of rolling and drawing”
on the topic: “Development of calibration of rolling rolls for a round profile with a diameter of 5 mm”
Completed by a student of group D-41
Rudova E.V.
Checked by Ph.D. assistant professor
Bobarikin Yu.L.
Gomel 2012
1. Introduction
2. Selection of finishing gauges and calculation of rolled cross-sectional areas
3. Selection of drawing gauges and calculation of roll sections
4. Determination of caliber sizes
5. Calculation of rolling speed
6. Calculation temperature regime rolling
7. Determination of friction coefficient
8. Calculation of rolling force
9. Calculation of rolling torque and power
caliber section profile rolling rolls
1 . Introduction
The basis of section rolling production technologies is plastic deformation of the metal in various types rolling mill roll calibers.
Sections are rolled from the workpiece in several passes in the calibers of rolling rolls, which give the rolled metal the required shape. To produce rolling metal assortments of simple and shaped profiles (round, square, hexagonal, strip, corner, channel, T-shaped, etc.), it is necessary to calculate the calibration of the rolling rolls.
Roll calibration is called the determination of the shapes of the sizes and the number of gauges measured on the rolls to obtain the finished profile.
Roll caliber- this is a gap formed by cuts in the rolls or a stream in a vertical plane passing through the axes of the rolls.
Calibration should ensure rolling from the workpiece of the required profile of the required shape and size within the accepted tolerances, as well as good quality rolled products, maximum rolling productivity, minimal wear and energy consumption spent on the operation of the rolling mill.
Rolling of the profile is first carried out in drawing passes, intended only to reduce the cross-sectional area of the rolled workpiece. When the cross-sectional area of the workpiece is reduced, the latter is extended in length without bringing the cross-sectional shape of the strip closer to the required one, which is why these gauges are called exhaust. After passing through the drawing passes, the workpiece is rolled in finishing passes. Finishing gauges are divided into pre-finishing and finishing gauges. In pre-finishing gauges (there may be several or one), with a further reduction in area, the cross-section configuration approaches the given shape of the finished profile, and its individual elements are formed. In the finishing gauge (there is always one), the required profile shapes and sizes are finally formed; it is placed on the last rolling pass.
2. Selection of finishing gauges and calculation of cross-sectional areaseniya peal
Selection of quantitiesmaterials and forms of finishing gauges
The number and shape of finishing gauges, i.e. finishing and pre-finishing gauges, depends on the shape of the finished or final profile and on the adopted calibration system for finishing gauges.
For a round profile, the finishing gauges are a pre-finishing oval gauge and a finishing round gauge. After the pre-finishing oval gauge, the oval profile roll is bent by 90° and enters the finishing round gauge, where the round profile is finally formed (Fig. 2.1). In this case, the shape of the pre-finishing oval gauge depends on the size of the finishing profile. The figure shows a pre-finishing oval gauge for medium and small finishing profile sizes.
Rice. 2.1 Scheme of round profile finishing gauges
Roll turning can be carried out using special turning guides between rolling stands for continuous mills or turning devices, between rolling passes for foundry mills. In addition, on continuous mills, the 90° turning condition can be achieved by alternating roll stands with horizontal and vertical roll axes.
For rolling round profiles in the group of finishing gauges, we use finishing round and pre-finishing oval gauges.
Determining the dimensions of the final profile while hotIresearch institute
To increase the service life of calibers, calculations are made to obtain a profile with minus tolerances in its dimensions. In order to take into account the reduction in the dimensions of a profile rolled in a hot state during cooling, it is necessary to multiply the size of the profile dimensions in a cold state by the coefficient 1,01-1,015 .
Taking a minus tolerance for a round final profile, we find the size of the circle in the cold state:
Hot finishing wheel size:
Determination of elongation coefficients in finishing gauges.
For finishing round gauge drawing coefficient where k is the number of finishing calibers, and also for the pre-finishing oval caliber we will determine according to the graph in Fig. 2.2.
Fig. 2.2 Dependence of the drawing coefficients in the finishing wheel, as well as in the pre-finishing oval, on the corresponding diameter of the wheel .
Note: if a round profile with a diameter of less than 12 mm inclusive is rolled, then the drawing coefficients in the finishing and pre-finishing gauges are determined according to practical recommendations for a specific profile. Taking into account the design features of the rolling mill 150 BMZ, we take the average draws equal to 1.25.
Determination of cross-sectional areas of profiles in finishing potsbrah.
The areas of profiles in finishing gauges will be determined by the dependencies:
where is the cross-sectional area of rolled products in the finishing gauge, determined by
according to hot dimensions of the final profile; - cross-sectional area of the roll in the last pre-finishing gauge; - cross-sectional area of the roll in the penultimate pre-finishing gauge. Let us determine the cross-sectional area of the strip in a finishing round gauge:
The cross-sectional area of the strip in the pre-finishing oval gauge is equal to:
The cross-sectional area in the last rough pass and, accordingly, in the last rolling pass of the drawing group of pass passes, is determined by the formula:
3. Selection of exhaust gauges andcalculation of cross-sectional areas of rolls
Selecting a draft system
As a rule, drawing calibers are formed according to certain systems, which are determined by the alternating uniform shape of the calibers.
Each drawing caliber system is characterized by its own pair of calibers, which determines the name drawing caliber system.
Pair of draw gauges- these are two successive gauges in which the workpiece moves from an equiaxed state in the first gauge to a non-equiaxed state, and in the second again to an equiaxed state, but with a decrease in cross-sectional area.
The following drawing gauge systems are used: rectangular gauge system, rectangle - smooth barrel system, oval - square system, rhombus - square system, rhombus - rhombus system, system square-square, universal system, combined system, oval-circle system, oval-rib oval system.
On small- and medium-sized modern continuous rolling mills, the following systems are more often used: diamond-square, oval-square, oval-circle and oval-rib oval.
These calibration systems ensure good quality of rolled products and stable position of the rolled products in the calibers.
When rolling in drawing rolls, the roll is always turned over or rotated around its longitudinal axis at a certain angle (usually 45° or 90 °) when the roll passes between stands from the first gauge of a pair of gauges to another gauge.
The turning can be replaced by alternating horizontal and vertical rolling stands, which provides the effect of turning without turning the workpiece.
Roll turning or alternation of horizontal and vertical rolling stands or rolls is necessary to transform the non-equiaxial state of the workpiece after passing the first pass of a pair of drawing passes into an equiaxed state in the second pass of the pair.
One of the most promising calibration systems is the oval - rib oval system, which ensures stable rolling conditions and good quality of rolled products.
In this system, in oval gauges, the workpiece goes into a non-equiaxial oval state with a large difference in the sizes of the oval axes, and in ribbed oval gauges - into an equiaxial oval state with a small difference in the sizes of the axes after deformation of the previous non-equiaxial oval along the major axis. Thus, the workpiece sequentially passes through the types of gauges: oval - ribbed oval - oval - ribbed oval, etc. until the required reduction in the cross-section of the workpiece is obtained.
Determination of average draft inarach drawing gauges and numbersrolling passes.
To determine the number of rolling passes n First, we determine the estimated number of pairs of exhaust gauges:
where is the cross-sectional area of the workpiece in the hot state;
The cross-sectional area of the workpiece in the last drawing pass.
Having determined the exact number of pairs of exhaust calibers, then it is necessary to establish a refined value of the average draft for a pair of exhaust calibers
The number of rolling passes in drawing passes is:
The number of rolling passes for the entire rolling technology is equal to:
Where To- number of finishing gauges.
Here it is necessary to check whether the total number of rolling passes will not exceed the number of rolling stands of the mill according to the inequality:
Where With- number of rolling stands of the mill.
The cross-sectional area of the workpiece in the hot state, taking into account a wide tolerance on the cross-sectional size, will be determined by the nominal cross-sectional size:
For the oval system - rib oval. Let's accept.
The estimated number of pairs of exhaust gauges is:
We will accept the exact number of pairs of exhaust gauges.
The adjusted average draw value for a pair of draw calibers is:
The number of rolling passes in drawing passes according to (3.3) is equal to:
The number of rolling passes is:
Let's check condition (3.4): .
The results of the distribution of rolling passes and types of gauges among the mill stands are recorded in Table 3.1.
Definition of hoods for pairs of hoods.
The draw of each pair of calibers is determined by the dependence:
where is the change in value
When making changes to the values of hoods for each pair of calibers, it is necessary to take into account the equality of 0 of the algebraic sum of all changes, i.e. the following condition must be met:
Let us determine the draws for each pair of calibers, taking into account their redistribution so that the initial pairs of calibers would have large values hoods, and the latter - smaller.
Let us make changes for each pair of calibers according to expression (3.5), remembering that the algebraic sum of these changes must be equal to 0:
Determination of drafts by rolling passes in the drawing systemandcalibers
Let us determine the hoods for the rib ovals with the known formula:
We determine the hoods for ovals using the formula:
Using formulas (3.7) and (3.8), we determine the numerical values of the draws for all rolling passes along the draw passes:
For j= 7(14;13)
We enter all values of hoods for exhaust and finishing calibers in Table 3.1.
Determination of cross-sectional areas of rolled products in drawing gauges.
Let us determine the cross-sectional area of the rolled product after each rolling pass using the formula:
where is the cross-sectional area of the roll;
The area of the next section of the roll along the rolling path;
Drawing in the next caliber in the rolling process.
According to the condition, after the last, i.e., 26th, pass, the cross-sectional area of the roll should be equal to 28.35 . Thus, for.
The cross-sectional area of the workpiece before the first pass is equal to the cross-sectional area of the original workpiece. This value must be obtained from the product. However, due to the accumulation of rounding errors during calculations, in order to accurately obtain the value, it is necessary to adjust the extraction value in the first pass:
The obtained values of the rolled cross-sectional areas for all rolling passes are entered into Table 3.1.
Table 3.1 Calibration table
|
Type of caliber |
Sectional area of the roll F, |
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|
oval |
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|
Rib oval |
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|
oval |
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|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
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|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
|||||
|
oval |
|||||
|
Rib oval |
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|
oval |
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|
Rib oval |
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|
Pre-finishing oval |
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|
Finishing round |
4. Determination of caliber sizes
The diagram for constructing a finishing round K-th gauge is shown in Fig. 4.1. The diagram shows following sizes: - diameter or height of the gauge equal to the hot dimension of the diameter of the final profile round steel; - roll gap; - caliber release angle; - caliber width.
Fig. 4.1 Diagram of a round gauge
The size of the gap between the rolls is determined by the formula:
The width of the caliber and the width of the strip will be equal to the diameter of the caliber.
Values and select the following:
The diagram for constructing a pre-finishing oval (K-1) gauge for rolling an oval strip intended for subsequent rolling in a finishing round gauge of a round profile with a diameter of no more than 80 mm is shown in Fig. 4.2. We will calculate all the required dimensions:
Fig. 4.2 Diagram of an oval caliber
The height of the caliber is equal to the height of the strip, which is determined by the formula:
where is the cold diameter of the finished round profile being rolled;
Coefficient that takes into account the widening of the oval stripe in a finishing round gauge.
The dullness of the stripe is determined by the formula:
Rice. 4.3 Dependence of the coefficient on the width of the rib oval stripe, the preceding rib oval caliber
The bandwidth is determined by the formula:
where is the cross-sectional area of the oval strip after passing the pre-finishing oval gauge. The radius of the outline of the pre-finishing oval gauge is determined by the formula:
We assign the value of the gap between the rolls:
The width of the caliber is determined by the formula:
Determine the fill factor of the caliber:
The value must be within the limits.
We enter the main dimensions of finishing and pre-finishing gauges in Table 4.1.
Construction of exhaust gauges.
For the oval-rib oval drawing gauge system, we first build all the oval rib gauges according to the diagram in Fig. 4.4 and the calculation given below. When rolling a square profile, the last one during rolling is an equiaxed square gauge, which is also a pre-finishing gauge. square gauge. In our case, the initial profile of the rolled workpiece is square, then for convenient gripping of the workpiece, we build the first equiaxial gauge during rolling according to the diagram in Fig. 4.4. Then we build all the oval gauges according to the diagram in Fig. 4.2. and the calculation below.
Rice. 4.4. Scheme of rib oval caliber
For all ribbed oval gauges, i.e. for all calibers, the caliber dimensions are determined in the following sequence.
Example calculation for caliber 26.
Width of rib oval stripe
where is the cross-sectional area of the oval rib strip.
Height of rib oval stripe
The caliber width is
where is the fill factor of the caliber, equal to 0,92…0,99 , we will accept in advance.
Caliber outline radius
The dullness of the band is equal to:
The height of the roll gap is determined from the range where is the diameter of the rolls of the corresponding rolling stand.
In this case, the condition must be met
We carry out the calculation similarly for all other x calibers. We enter all the main dimensions of rib oval gauges in Table 4.1.
For all non-equiaxial gauges (Fig. 4.2.), the dimensions are determined against the rolling stroke.
For each non-equiaxial oval gauge, the dimensions are determined in the following sequence.
First, we determine the broadening in the equiaxed oval ribbed gauge next to the given gauge in the course of rolling using the formula:
where is the broadening determined from the graph in Fig. 4.6. depending on the width of the oval rib strip in question;
The diameter of the stand rolls for a given equiaxed pass.
Fig.4.6. Dependence of the magnitude of the widening of an oval strip in a ribbed oval gauge on the width of the ribbed oval strip during rolling in rolls.
The height of the oval stripe is:
The height of the caliber is equal to the height of the strip, i.e.
The dullness of the oval stripe is equal to:
where is the coefficient determined from the graph in Fig. 4.3.
Preliminary value of the width of the oval strip:
where is the cross-sectional area of the strip after passing the caliber in question.
The value of the average absolute compression of the metal in the oval gauge under consideration is equal to (for):
where is the width of the rhombic oval strip in the previous caliber under consideration.
The rolling radius of the roll is equal to:
where is the diameter of the rolls of the stand under consideration.
The average height of the strip at the exit into the considered caliber is equal to:
The broadening of the metal in an oval caliber is determined by the formula:
The width of the oval stripe is:
The radius of the caliber outline is determined by the formula:
We will assign a preliminary value of the roll gap from the range if the condition is met.
Caliber fill factor:
After this, we check the condition for normal filling of the caliber with metal.
Let us carry out the calculation for the 3rd non-equiaxial oval gauge using the above formulas.
We carry out the calculation similarly for all other calibers. We enter the main dimensions of all intermediate oval calibers in the table. 4.1.
Table 4.1. The penetration depth of the gauge is determined by the formula:
Table 4.1 Calibration table,
|
Rolling pass no. |
Strip height |
The width of the line |
Caliber height |
Caliber width |
Shaft clearance |
Cutting depth |
|
5. Calculation of rolling speed
We determine and enter into Table 5.1 all the values of the rolling diameters of the rolls. In this case, for oval gauges we will define them in terms of the radii determined by formula (4.31). For all other gauges, the rolling diameters of the rolls are determined by the formula:
where is the diameter of the roll barrel of the corresponding caliber;
The cross-sectional area of the strip at the exit from the corresponding gauge;
Bandwidth at the outlet of the caliber.
Let's carry out the calculation for caliber 2.
Then we determine the number of revolutions per minute of the rolls in the last stand during rolling according to the formula:
where is the rolling speed at the exit from the last stand, which is determined
working conditions of the mill, 8 0 m/s;
Rolling diameter n-oh cage, mm.
where is the cross-sectional area of the strip after passing n-th cage, i.e. final rolled products, .
To ensure some strip tension between the stands, the calibration constant for each rolling pass must be slightly reduced as we move from the first pass to subsequent ones. Therefore, the calibration constant for the penultimate pass is:
By analogy, against the rolling stroke, we determine the calibration constant for all rolling passes, i.e.
The rotation speed of the rolls for each pass is determined by the formula:
We enter all values in table 5.1.
The strip speed after each rolling pass is determined by the formula:
where in and in.
We enter all values in table 5.1.
We carry out the calculations similarly for all other calibers, and enter all the calculation results in Table 5.1.
Table 5.1. Calibration table
|
Rolling pass |
Rolling diameter of rolls, |
Calibration constant |
Roll rotation speed, |
Lane speed, |
|
6. Calculation of temperatour rolling mode
The task of calculating the temperature regime of rolling is to determine the temperature of the initial heating of the workpiece before rolling and to determine the temperature of the roll after each rolling pass.
Small section wire rolling mill 320 has the temperature of the billet at the furnace outlet before the first rolling stand 107 0 . When rolling in a 20-stand group and a wire block, the temperature of the rolled product at the exit from this block is 1010…1070 . The heating temperature of the workpiece for rolling a square profile made of steel 45, taking into account the table. 6.1. and technological capabilities of the mill furnace 320 we take equal 12 50 , and at the exit from the 20th stand the temperature of the rolled product is taken equal to 107 0 .
The rolling temperature for rolling passes is assumed to be equal to the average, i.e.
7. Determination of friction coefficient
The coefficient of friction during hot rolling of metals can be determined by the formula for each rolling pass:
where is a coefficient depending on the material of the rolling rolls; for cast iron rolls, for steel rolls;
A coefficient that depends on the carbon content in the rolled metal and is determined from table. 7.1. (m/u 2130 p. 60).
A coefficient that depends on the rolling speed or the linear speed of rotation of the rolls and is determined from the table. 7.2. (m/u 2130 p. 60).
Similarly, using formula (7.1), we calculate the friction coefficient for each rolling pass; we enter all the necessary data and calculation results in Table 7.1
Table 7.1
|
Rolling pass no. |
|||||
8. Calculation of rolling force
Determination of the area of metal contact with the roller.
Contact area of the rolled metal with the roller i caliber is determined by the formula:
where and are the width and height of the strip at the outlet of the caliber;
and - width and height of the strip at the outlet of the caliber;
The influence coefficient of the caliber shape, determined from the table. 8.1. (m/u 2130 p. 60). - radius of the roll along the bottom of the caliber.
The radius of the roll along the bottom of the groove is determined by the formula:
where is the diameter of the roll barrel; and - height and roll gap of the caliber. Let's calculate the first pass:
We calculate all values in the same way and enter them into the table. 8.1.
Determination of the stress state coefficient of the deformation zone.
The stress coefficient of the deformation zone during strip rolling for each rolling pass is determined by the formula:
where is a coefficient that takes into account the effect of the width of the deformation zone on the stress state;
Coefficient taking into account the influence of the height of the source;
Coefficient taking into account the effect of rolling in a caliber.
The coefficient is determined by the following dependence
The coefficient is determined by the dependence
where is the caliber shape coefficient for non-shaped calibers (square, rhombus, oval, circle, hexagon, etc.);
Gauge shape factor for shaped gauges.
Let's calculate the first pass:
Determination of resistance to plastic deformation.
The resistance to plastic deformation of the rolled metal for each rolling pass is determined in the following sequence.
Let's determine the degree of deformation
Then we determine the strain rate
where is the rolling speed in mm/s, we take from the table. 5.1.
determined by the formula:
Let's calculate the first pass:
We enter all values in the table. 8.1.
Determination of average pressure and rolling force.
The average rolling pressure for each rolling pass is:
Rolling force for each pass
Let's calculate the first pass:
We enter all values in table 8.1
Table 8.1. Calibration table
|
Rolling pass number |
Metal temperature |
Friction coefficient, f |
Contact area |
Stress factor states, |
|
Continued Table 8.1.
|
Rolling pass number |
Resistance to plastic deformation |
Average rolling pressure, |
Rolling force, P, kN |
Rolling moment |
Power pro- rollers N, kW |
|
9. Raseven torque and rolling power
The rolling moment is determined by the formula:
Similarly, we determine the moment of inertia for each rolling pass, and enter all the calculation results into the table.
Determination of rolling power
The rolling power is determined by the formula:
Calculation example for the first rolling pass:
Similarly, we determine the power for each pass, and enter all the calculation results in Table 8.1.
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| Article Index |
|---|
| Rolled steel production: classification of rolling machines, rolling processes |
| Pipe rolling mills and special purpose mills |
| Classification of rolling mills by number and location of rolls |
| Production of blooms and slabs |
| The main features of the technological process of rolling on blooming sheets |
| Production of billets on billet mills |
| Production of long products |
| Calibration of rolls for rolling square profiles |
| Calibration of rolls for rolling round profiles |
| Features of calibration of rolls for rolling angle steel |
| Production of rolled products on medium-size mills |
| Production of rails, beams, channels |
| Source material for rolling rails, beams and channels |
| Design and arrangement of equipment for rail and beam mills |
| Technological process of rolling rails |
| Rail quality control |
| Rolling of wide-flange I-beams |
| Characteristics of the equipment and its location on the universal beam mill |
| Wire rod production |
| Continuous wire mill 250 MMK |
| Unit for continuous casting and rolling of steel wire rod |
| Production of strips and tape |
| Rolling of hot strips and sheets |
| Source material and its heating |
| plate steel rolling process technology |
| Production of double-layer sheets |
| Cold rolling of sheets |
| Production of special types of rolled products |
| Production of periodic profiles |
| Finned tube production |
| All Pages |
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.
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