SU1405911A1 - One-piece slab - Google Patents

Abstract

The invention relates to rolling production and can be used on hot rolling broadband mills. The purpose of the invention is to expand the range of energy consumption for lateral compression during rolling, to increase the productivity of machines for continuous casting. The slab has a cross section in the form of an octagon stretched in a horizontal direction, symmetric with respect to the shown orthogonal axes. The sides of this octagon belong to the slab surface: side 1 is the horizontal face; 2 - the boundary surface of the transition region; 3 - side face (edge). The axial dimensions of the slab (width .fif and the thickness of He) follow from the gauge of this mill, the width of the transition region is 0.53-1.34 from the thickness, the slabs and the thickness monotonically decreasing to the lateral face 0.40-0.64 of the thickness of the slab. 9 silt, 2 tab. (5 (L

Description

/ 7a7 a / 7cfc / L /

 Ate

with

cfiue.l

The invention relates to rolling production and can be used: on wide-strip mills for hot rolling.

The purpose of the invention is to increase the range of widths of the strips rolled from the slab of the same width, reduce the energy consumption for lateral reduction during rolling, and increase the productivity of continuous slab casting machines.

FIG. Figure 1 shows schematically the proposed slab with a concave cross-sectional shape of the transition region; pas figs. 2 - the same, with a straight sectional shape; in fig. 3 - the same, with a convex section shape; in fig. 4 shows a scheme for determining the dimensions of the transition regions, ensuring that they require an increase in the marginal lateral compression; in fig. 5 - diagram of compression of slab in vertical rolls; in fig. 6 is a diagram for determining the ratio of the sizes of the transition regions, taking into account the particular shape of the high bands; in fig. 7-9 are graphs for finding the preferred ratios of the sizes of the transition regions for each variant of the cross-section corresponding to.

The slab has a cross-section in the form of an octagon stretched out in a horizontal direction, symmetrical about the shown orthogonal axes (Figures 1-3). The sides of this octagon belong to the slab surface; side 1 - the horizontal side; side 2 - the boundary surface of the transition region; side 3 - side face (edge). The axial dimensions of the slab (width W and thickness He) follow from the gauge yes) of the single mill, and the dimensions of the transition region (width Wpo 1, g.z and the trough depth at the edge of Yak 1,2,3 are determined by the pointer ratios. The main feature This effect is caused by the positive volume redistribution of the mixed volume due to the introduction of transition regions whose thickness decreases to the lateral faces of the slab (Fig. 1-3) .It is known that the offset bemsya - the most important characteristics of the plastic shaping

energy process parameters significantly depend on. The work and consumption of the energy produced during rolling are proportional to the mixed volume and, in turn, unambiguously determine the average specific pressure and rolling moment. Therefore, using this slab, it is possible, without overloading the stand with vertical rollers, to increase, in accordance with the purpose of the invention, the limiting lateral reduction

Bi.

.

1,2,3 is an embodiment of the transition region represented in fig. 1, 2 or 3 respectively;

, DV max-limiting lateral compression of the proposed and known slabs, respectively; p, - is the coefficient of increase of the limiting lateral reduction, determined from the condition

, (2)

where l / cMi, I / CM is the mixed volume (from the side of one vertical roll per unit slab length) with lateral reduction of the proposed and known slabs, respectively.

In condition (2), taking into account the symmetry of the slab, we have (in Fig. 4, the mesh hatching highlights the part of the displaced volume, which is common for the proposed and well-known slab);

Lj l n abhatx

u ...) dx; (3)

VCM

E

/

// cAvmax

(four)

where Hi (x) is a function describing the shape of the upper (lower) boundary of the transition region in the range of values x (0, B „o,)

g - Bi max

B, (

The relation (5) means that lateral compression does not extend beyond the nepexojiibi.x areas.

As a necessary function in the first embodiment (Fig. 1), we take the quadratic dependence of the form

N / x;

, // c-I,

(6)

2Guy 1

in the second variant (fig. 2) - linear dependence

hell

,,,

: 2

2S.,

and in the third variant (fig. 3) the quadratic dependence

I.(.),

2B p

(7) other

(eight)

Vlog

The expressions presented are constructed from the following, their grapical conditions;

 / UK 1

//, l - 0) 0; / - /, (,,)

dH, (x dH., (x),

--7

dx

.0.

five

Substitute the expressions of the function (6), (7), (8) in equation (3) and (4), integrating and substituting the results into condition (2), after elementary transformations, for the transition region with a concave cross-sectional shape

, 12bf-Bi |

with my form

() p |

4b2-p2

  (4b - /; jBi

with convex shape

. 6b, (2b ,.

V 6ba (2b, -l) where

/ g.

Ht

is the dol that is the thickness at the edge of the proposed slab of its thickness g

(13)

/,

 A o

Zad shaks

- This is the ratio between the width of the transition region and the extreme lateral compression of the slab. From expression (5) it follows that fc, 0.5.

Formulas (9), (10), (11) establish for transition regions of various shapes the interrelation of their dimensions ratios, including limiting lateral reduction with a certain coefficient of its increase, i.e. from the point of view of realizing the objective of the invention. If p, 1 (lateral reduction is not increased), all formulas give hi. This means that the thickness at the edge is equal to the slab thickness, and, therefore, the proposed slab becomes known. All three values hi-h, hz and Lz have the same limit.

11sh / g, / -,

; i4)

fct- i

whence for the final transition region when we have

/one,. PI

Searches for size transition

These areas should not only allow an increase in lateral compression of the slab, but also take into account the peculiarity of its change in vertical rolls as a high strip. The transitional regions create an additional metal-free space adjoining their upper and lower boundaries (see Fig. 5, the outlines of the section of the slab before crimping are shown with dotted lines). The volume of this free space must be such that when the slab 1 is compressed by vertical rolls 2, the contact flows 3 fill it, not beyond the horizontal faces of the slab. Then the cross section tends to be rectangular and there is no additional broadening during the subsequent rolling in horizontal rolls. Consequently, the final effect of lateral crimping on the width of the roll increases to 100%, which meets the purpose of the invention.

Quantitatively, the condition for taking into account the features of shaping high bands is presented as (see Fig. 6)

. Uk1 | Usm1 (16)

where CC is the compensating volume (additional free space

ten

20 25

thirty

35

40 45 0

55

on the side of one vertical roll per unit length of slab ba) for placing a contact junction; e - the proportion of displaced volume going

in contact flow In condition (16), taking into account the symmetry of slab, we have

l | m kgftwt

/ к1 (Yas-Yak |) (Vpo1-ti -Ч hi (.

t lmiK / 2. (7)

Substituting the expressions of functions (6), (7), (8) into equations (3) and (17), integrating and substituting the results into condition (16), after elementary transformations, we obtain: for a transition region with a concave cross-sectional shape

{, 4 (4 & i-3) -fl- "-46f 46: -3 (l-s) -fr with my own form

, (2b,

 (2b-2-lY + l ()

(18)

(nineteen)

,, f with a convex shape

CH1Y

(126 -66з + 1), (N)

(20)

Formulas (18-20) establish a relationship between the ratios of the sizes of the transition regions, including limiting lateral reduction, which takes into account the condition for creating the necessary compensating volume to accommodate the contact flow. The use of this connection makes it possible to increase the final effect of lateral reduction on the width of the rolled metal and, therefore, better realize the purpose of the invention. With small lateral collapses (the ratio of the average width of the peal to the length of the deformation zone is 9-12), the entire volume of metal displaced in the vertical rolls goes into contact buckling, stretching is absent and 1. This design provides for the realization of high and ultrahigh lateral reductions (this ratio is 3-6), then, along with a bulging, the stretching and e. For this case, the value of I is approximately characterized as the ratio of the additional broadening of the roll when rolling in horizontal rollers, which fully occurs as a result of the compression of the zones of contact buckling, to the previous compression in vertical rollers. The computational analysis determines the estimate of the required value | 0.3.

To find the preferred ratios of the sizes of the transition regions of various shapes, use a graphical representation of the dependences (9) and (18) on the / rI-b plane (see Fig. 7); (10) and (19) - on the / i2-b-2 plane (see Fig. 8); (11) and (20) - on the hz-63 plane (see Fig. 9). In each case, the corresponding

graphs for the values of the coefficient of increase of the limiting lateral reduction p, -, 50; 1.75; 2.00; 2.25 (dashed lines) and a graph that takes into account the required compensating volume (solid line). The range of values of the coefficient is taken from the considerations of ensuring high efficiency of the proposed technical solution. The limitation of the upper value of this coefficient follows from the equality (15) .-

The value of / i, - affects the thermal condition of the proposed slab. When it moves from the heating furnaces (or from the caster to direct rolling) to the cage with vertical rolls, the surface of the thinned transition regions cools down due to heat radiation and convection somewhat faster than horizontal faces. This leads to a corresponding temperature gradient over the cross section of the slab at the entrance to the cage, which can cause cracking of the slab edges during lateral reduction. The possible values of this gradient are estimated using the equation of G. P. Nvantsov - MM Safs taking into account the correction for convective heat transfer. In order to ensure small values of the gradient (no more than 20-25 ° C) and, therefore, prevent cracking of the side edges of the proposed slab, the value of / i, should not be less than 0.4. Then p ,, 5.

The preferred ratios of the sizes of the transition areas include those that satisfy the following requirements: they provide an increase in the limit of lateral reduction of | 3, - 1.5; creating the necessary compensating volume to accommodate the contact flush; have a value of / 1, 4. Accordingly, preferred aspect ratios are given in each of FIG. 7-9 is a marked area with a solid curve, the lower boundary of which is a point with ordinate / g, 0.4, and the upper one is a dotted line, 5. Obtained for a transition region with a concave cross-sectional shape (see Fig. 7), 40-0.64,, 84- - 1.11; with direct form (see fig. 8) / g2 0.40-0.58, 03-1.28; with a convex shape (see Fig. 9) /1.,40-0,55, & h 1.48-1.78.

The value of p, at the lower boundary of the plots, is determined from equations (9-I). Substituting the corresponding values of / g ,, b, -, get, 12; , 83; 73

The sh Irina of the transition region is expressed in fractions of the slab thickness by the formula

, -Ь „(2)

ne

(22)

/ g

D to max

ITT

(23)

5 p 5

0 5 d 5

0

five

The validity of formula (21) proves the substitution of the values of p, (1) and b, - (13), which turns it into an identity. The literature coefficient k is 0.3-0.5. Substituting in the formula (21) the extreme values of this coefficient, as well as the indicated upper and lower limits of the magnitude and, and the corresponding limits of the coefficient Pi, are found for the transition region with a concave cross-sectional shape & j 0.53- -0.83; with straight form, 57-0.96; with convex shape i), 77-1.34.

The c and b with the convex cross sectional shape of the transition regions (Fig. 1) is distinguished by the smooth mating of their boundary surfaces 2 with horizontal faces 1 and, accordingly, the greater width of the transition regions. Such a form can be recommended for crack-sensitive steels (high carbon and alloyed). The straight cross-sectional shape of the transition regions (Fig. 2) is suitable for medium to low carbon steels, and the concave shape (Fig. 3) for highly elastic low carbon steels.

Summarizing the results for all the considered variants, we conclude that the transition region has a thickness that monotonously decreases to the lateral face to values from the thickness of the slab in the center of 0.40-0.64, and the width being 0.53-1.34 from the thickness sl ba When rolling a slab, the displacement by vertical rolls of a similar limiting volume, as in the rolling of the known, leads to an increase in the limiting lateral reduction in | 3; time. This means that approximately at the same energy consumption for rolling in vertical rolls, it is possible to obtain p, - once more reduction, or previous compression is achieved with smaller by p, - times the energy consumption. In addition, the achieved reduction in width is maintained during subsequent rolling in a cage with horizontal rollers, since the near-edge beadings do not extend beyond the horizontal edges of the slab. Offsets in the additional broadening in this stand no longer occur, and the corresponding energy consumption is saved. We also note the positive shape of the deformation zone during lateral reduction of the proposed slab. The height of the contact surface with the vertical rolls MI increases in the direction of rolling, and the more, the greater the reduction. This causes an increase in the area of the advance zone, as well as a shift in the resultant metal pressure on the rolls towards the exit from the deformation zone. Accordingly, the reserve friction forces acting in the advance zone increase, and the component force directed against the rolling movement decreases.

Example. Define and compare ranges of reductions that can be implemented by energy-power parameters during rolling

known and proposed slabs in a cage with vertical rollers. We also estimate the residual decrease in the width of the roll after the cage with horizontal rollers in either case. On the basis of the data obtained, we choose the width gradation of the proposed slabs for a specific assortment. Characteristics of cast slabs: steel grade Art. FPA; dimensions of traditional slab / V, mm; Sun 750-1850 mm. Such a slab assortment is provided for NSHSPS 2000.

Consider the rolling stand - vertical descaler at the entrance of the draft group. In this stand, the roll diameter is 1200 mm; barrel length 650 mm; rolling speed 1 m / s; maximum rolling force 600 ts; maximum rolling moment 120 ts-m; main drive power 2X630 kW. Calculations of the force and moment of rolling slabs in vertical rolls are performed by the method of M. Ya. Brovman - A.I. Gertsev. This technique is applicable for the ratio of the thickness of the slab to the length of the deformation region 0.3-2.5. A variant of the method of thermomechanical coefficients is used to find the resistance of the metal to deformation. The temperature of the slab during compression in a vertical descaler is 1210 ° C.

The calculation results for the known slab are presented in Table. one.

The ratio of the slab thickness to the length of the deformation zone is 1.44-0.81, i.e., it is within acceptable limits. The limiting factor for lateral reduction is rolling moment. The ultimate compression, at which the moment becomes the maximum allowable, is 100 mm. The residual decrease in slab width after with horizontal rolls is determined by the formula M. Ya. Brovman and others. It is valid when the ratio of the average slab width to the length of the deformation zone is 4.5–12.0. All design variants with a maximum width (1850 mm) correspond to this interval, and with a minimum width (750 mm) they go beyond its lower limit. Therefore, in each case, the lower width is taken from the NSHPS 2000 MMK assortment so as not to go beyond the lower limit of the permissible interval.

The proposed slab is taken for comparative calculations of similar dimensions as that known with transition regions having a straight cross-sectional shape (Fig. 2). The ratios of the sizes of the transition regions are taken according to the corresponding schedule (see Fig. 8), 5; ,sixteen. For this point, the coefficient of increase in limiting lateral reduction is 6 (its value is estimated from the graphs of Fig. 8 or is found from equation (10)). According to the results of the calculation for the known slab, 4. Then the formula (21) gives, 74. Get the size of the transition regions Yak2

/ r2. mm; In „dg-b l-Hs mm. The calculations of the force and rolling moment of the proposed slab have features in connection with its variable thickness in the transition regions. The calculated thickness is determined by the displaced volume.

. -5 (24)

.arasch. --SHT2

where Vc.v2 is the displaced volume on the side of one vertical roll per unit length of slab; DV2 - lateral compression. Consequently, the calculated thickness is the average thickness of the cross section of the transition region in the area of lateral reduction. From formula (24) with regard to expressions (3) and (7), we have

Ya2rasc. Yak2 + ts7 AD2. (25)

Honor

When determining the rolling moment, a coefficient is introduced that takes into account the shift of the resultant metal pressure on the rolls towards the exit from the deformation zone as a result of the variable thickness of the slab in the lateral reduction zone. This coefficient for the design reductions is 0.98-0.94.

The calculation results for the proposed slab are presented in Table. 2

The ratio of the calculated thickness of the area to be crimped to the length of the deformation zone (0.77-0.49) does not go beyond the allowable interval. The ultimate in rolling moment is a lateral reduction of 160 mm. The residual decrease in the width of the strip after the stand with horizontal rollers coincides with the lateral compression in the vertical stand — this is one of the positive features of the proposed slab (we do not consider a slight natural broadening in the stand with horizontal rollers).

Comparison of the results shows the following. Direct calculation according to the table. 1 and 2 gives the magnitude of the coefficient of increase in limiting lateral reduction, 6. This confirms the validity of the prerequisites for increasing the marginal lateral reduction inherent in the disassembly of this slab. With the same side reductions, the force and moment of rolling for the proposed slab are 1.9-1.6 times less than for the known slab. Since the energy consumption is proportional to the rolling moment, the energy consumption for lateral compression of the proposed slab, all other conditions being equal, is much less than for the compression of the known. The reduction in rolling force is important from the point of view of maintaining the stability of the proposed sl l with ultra-high compression in vertical rolls. For example, when limiting compression (160 mm) of the proposed slab, the rolling force is approximately the same as when compressing the known slab by 80 mm (350 and 358 ts, respectively). When comparing the residual width reduction after the stand with horizontal rollers (see Tables 1 and 2), the advantage of the proposed slab increases. The limiting residual decrease in its width is 2.3–2.7 times greater than the known slab. If we compare the compression of 80 mm realized on the well-known slab with the equivalent for the moment of rolling, compression of 130 mm on the proposed one, then the residual decrease in the width of the latter in this case is 2.3-2.9 times greater. The performed calculations prove the possibility of increasing the gradation of the NSHPS 2000 slab width to 130–150 mm using the proposed slab instead of the known one. Then the number of slave sizes required is reduced to 9 (& 880, 1010, 1140, 1270, 1400, 1530, 1660, 1790, 1920 mm) or to 8 (Sun 900, 1050, 1200, 1350, 1500, 1650, 1800, 1950 mm), i.e., about 2 times.

five

0

The invention makes it possible to increase the productivity of the continuous casting machine, to improve the conditions for the realization of the energy saving technology of hot sheet rolling.

Claims (1)

Invention Formula Cast slab, having vertical and horizontal edges with a width-to-thickness ratio of 3-12, characterized in that, in order to increase the range of widths of the strips rolled from slabs of the same width, reduce the energy consumption for lateral compression during rolling, increase productivity machines for continuous casting of slabs, transitional sections are made between horizontal and vertical edges with a monotonous decrease in thickness to the vertical faces to 0.40-0.64 of the thickness of its central part, and the width of transitional sections is 0,53-1,34 thickness of the slab in the central part. The length of the deformation zone, mm 173.2 219.1 mc 3.640 4.082 4.313 6.315 6.539 b, 681 273.4 358.2 409.2 e e 56.8 94.2 800 W50 1850 1850 23.7 44.8 Table 1 245.0 279.3 300.0 309, 4.602 4.766 4.842 6.875 6.992 7.045 480.0 524.4 545.6 120.3 160.9 188.8 202.9 1850 1350J 450 18501850 1850 81.9 97.2 104.9 eleven The length of the deformation zone, mm Calculated thickness, mm Metal deformation resistance, kg / mm Average specific pressure, kg / mm Effort of rolling, tf Moment of rolling, tf, m The residual reduction in width after the stand with horizontal rollers, mm 173.2 219.1245,0279.3 300.0 309.8 133.4 138.5141.9147,0150.3 152.0 4.398 4.905 5.153 5.432 5.583 5.650 50 80 100 130 150 160 1405911 12 Table 2 5.153 5.432 5.583 5.650 100 130 150 160 Phie.: 5 / Tereha d / e ff / 7aC / 7TU (Pig 7 FIG. eight ABOUT 0.5 1.0 9 and 9 1.5