RU2312721C2 - Cold rolling mill working roll exploitation method - Google Patents

Abstract

FIELD: operation processes of rolls of continuous, reversing and skin pass cold rolling mills.

SUBSTANCE: method comprises steps of reducing strip in successive row of four-high stands; acting upon active profile of working rolls due to hydraulic bending of their axes and correcting as backup rolls are worn initial profile of working rolls at their next exchange. Enhanced accuracy of selecting machine profiling of working rolls of four-high stand is achieved due to changing value of initial convexity of working rolls in proportion to metal volume rolled in stand from beginning of backup rolls mounting while correcting profile against actions of bending and counter-bending of rolls at each mounting of working rolls individually depending upon relation of width of rolled strip to active length of barrel of backup roll. Change value of initial profile is normalized by given mathematical expression.

EFFECT: improved modes of working rolls operation.

2 tbl, 1 ex

Description

The invention relates to sheet rolling production and can be used in the operation of rolls of continuous, tempering and reversing cold rolling mills.

There is a method of operating work rolls in contact with support rolls, in which, due to wear of the support rolls, it is necessary to increase the convexity of the work rolls as the amount of rolled metal by the support rolls increases [Efimenko S.P. Roller of sheet rolling mills. M .: Metallurgy, 1970, p.200].

The disadvantage of this method is the lack of regulation of the change in the value of the initial profiling of the work rolls with an increase in the number of rolled metal back-up rolls depending on the width of the rolled strips.

Closest in technical essence to the present invention is a method of operating a work roll with squeezing strips in a series of four-roll stands, including changing the size of the initial profiling of the work rolls when they are replaced as the backup rolls wear in proportion to the amount of metal rolled in the mill from the beginning of filling of the backup rolls during the campaign of operation of backup rolls, and profiling correction depending on the type of mill and the range of rolled strips [A.S. SU 1442287 A1, 12/07/1988. The method of profiling rolling rolls // L.V. Timoshenko, V.L. Mazur, V.V. Kostyakov, S.S. Samokhin, G.V. Rassomakhin, V.V. Shvetsov, Z.P. Karetny and A. D. Belyansky] - prototype.

A distinctive feature of this method is that the amount of deflection of the surfaces forming them (i.e., the value of the initial profiling) is successively changed in accordance with the expression:

where δ is the current value of the deflection of the generatrix of the work roll;

δ _Σ is the maximum change in the deflection of the generatrix of the work roll during the operation campaign of the backup roll;

Q is the current value of the rental volume;

Q _Σ is the value of the volume of rolled products, which determines the campaign of operation of the backup roll;

a = 0.2 ÷ 0.8 is a coefficient characterizing the standard size of the mill and the range of rolled products.

The disadvantages of this method are as follows.

1. The method involves the operation of rolls of a convex-concave profiling system (support - convex, workers - concave) and does not apply to other roll profiling systems (for example, workers - convex, support - cylindrical with bevels, etc.).

2. The prototype method does not take into account the effect of hydraulic bending of the axes of the work rolls on their profile.

3. The prototype method does not take into account the effect of the ratio of the width of the rolled strips to the length of the barrel of the backup rolls in contact with the work rolls on the change in the value of the initial profiling of the work rolls, although the deflection of the roll system depends on this parameter, and the size of the initial profiling of the work rolls depends on this.

The technical task of the invention is to improve the accuracy of the selection of the initial profiling of the work rolls during operation of the backup rolls in a rolling four-roll stand.

This technical problem is solved by adjusting the value of the initial profiling of the work roll in the direction of increasing its convexity depending on the number of rolled metal on the support rolls from the moment they are installed in the stand, the planned bending (anti-bending) axis of the work rolls and the ratio of the average strip width in the planned installation to the length of the barrel of the backup rolls in contact with the work rolls. This achieves the technical effect of increasing the stability of the mill, reducing the sorting and rejection of cold-rolled steel for defects "non-flatness", "kink", "weld sticking spots". In addition, the correct choice of the value of the initial profiling of work rolls reduces unplanned transshipment of work and backup rolls, lengthens their inter-transshipment campaign and, as a result of the above, reduces downtime of the mill, increases the time of its use, reducing the specific consumption of metal, electricity, emulsol and other indicators by 1 t of rolled metal, which generally improves the profitability of metal production.

The goal is achieved by applying the method of operating the working roll of a cold rolling mill with compression of the strip in a sequential row of four-roll stands, including changing the value of the initial profiling of the working rolls when they are replaced as the backup rolls wear in proportion to the amount of metal rolled in the stand from the beginning of filling of the backup rolls, and profiling correction depending on the range of rolled strips in the installation.

A distinctive feature of the method is that the profile of the work rolls is affected by the hydraulic bending of their axes, and the change in the value of the initial profiling Z _slave work rolls is carried out in accordance with the expression:

where Z _{slave 0} (B / L) -0.20 ÷ 0.20 is the value of the initial profiling of the work rolls at the beginning of the campaign of the support rolls of the stand, mm (depends on the ratio of the strip width to the length of the roll of the backup roll in contact with the work rolls, t .е. B / L), mm;

K _out = ( _0,030 ÷ 0,020) · 10 ^-3 - coefficient taking into account the influence of wear of the backup rolls on the change in the value of the initial profiling of the work rolls, mm / t;

Q - the amount of metal rolled in the stand from the beginning of the filling of the backup rolls, thousand tons;

P _izg and P _prig - the forces of bending and anti-bending of the rolls, respectively, t (the direction of action of the forces is taken into account by the signs ±);

K _bend = (3.0 ÷ 7.4) · 10 ^-4 - coefficient taking into account the change in the size of the profiling of the work rolls from the action of the mechanism of forced bending of the rolls (depends on B / L, the diameters of the rolls of the stand, the design features of the bending mechanism of the rolls on a particular mill etc.), mm / t;

K _prig = (4.0 ÷ 10.6) · 10 ^-4 - coefficient taking into account the change in the value of the initial profiling of the work rolls from the action of the roll bending mechanism, depending on B / L, stand roll diameters, design features of the roll bending mechanism on a particular mill etc.), mm / t;

0.05 - coefficient compensating for the change in the value of the initial profiling of the work rolls from the action of unaccounted factors, mm.

Known and proposed technical solutions have the following general technical features.

1. Both technical solutions are used for sheet metal rolling in four-roll stands.

2. Both methods involve changing the value of the initial profiling of the work rolls as the backup rolls wear and the amount of rolled metal increases.

3. Both methods provide for a change in the value of the initial profiling of the work rolls depending on the type of mill and range of rolled products.

The differences of the proposed method from the prototype are as follows.

1. According to the proposed method, when changing the value of the initial profiling of the work rolls, the planned force from the action of the mechanisms of forced bending of the rolls (bending force and anti-bending) is taken into account.

2. The type of mathematical dependencies in the prototype method and the proposed technical solution is different from each other.

These distinctive features increase the accuracy of choosing the value of the initial profiling of the work rolls, as a result of which the stability of the mill improves and the sorting and rejection of cold-rolled steel by shape and surface defects is reduced.

The essence of the invention is as follows.

Usually, a range of changes in the value of the initial profiling of the work rolls in each mill stand is recommended for the technological personnel of the mill. The change in the initial profiling of the work rolls is associated with constantly increasing wear of the backup rolls during their operation in the stand. The wear of the backup rolls, in turn, depends on many factors, the main of which are the operating time on the backup rolls, the width of the rolled strips, the bending and anti-bending forces of the rolls, etc. They, in turn, determine the range of variation of the value of the initial profiling of the work rolls. Within this range, the senior roll maker or shift mill master assigns the value of the initial profiling of the work rolls planned for filling in the cage. The main emphasis is on the personal experience and qualifications of personnel, which takes into account numerous objective and subjective factors (thickness, width and grade of rolled steel planned for rolling, the value of the initial profiling of work rolls rolled out of the stand, the achieved level of bending or anti-bending in the last stand camp, etc.). This creates a strong dependence of technology on the "human factor" and less on technological objective premises. In addition, under the conditions of a simultaneous change in many factors, even the most experienced technological personnel are not immune from errors.

When choosing the value of the initial profiling of the work rolls in this technical solution, it is proposed to adjust the value of the initial profiling of the work rolls from the moment of filling the support rolls into the mill to the moment of roll-out of the support rolls from the mill according to equation (2).

Since the wear of the backup rolls is linear (depending on the amount of metal rolled on the rolls), the proposed dependence is also close to a linear view. However, this additionally takes into account the average width of the strips rolled during installation (from transshipment to transshipment of work rolls), the level of bending (anti-bending) of the work rolls and some other indirect factors.

It was experimentally established that with an increase in the ratio of the width of the strips to the length of the back roll barrel (B / L), the initial convexity of the work rolls decreases. Physically, this is due to a decrease in the deflection of the work rolls under the strip with an increase in the width of the rolled strips. With a decrease in the B / L ratio, the deflection of the work rolls under the strip increases, and therefore, to compensate for it, it is necessary to increase the profile of the work rolls. The above is taken into account in the range of variation of the coefficient Z _slave0 (B / L) = - 0.20 ÷ + 0.20 mm in equation (2). Smaller values of the coefficient refer to wide bands, large ones to narrow ones. In addition, the specified range of changes in the value of the initial profiling of the work rolls takes into account the length of the roll barrel, diameter and its other design features. Wrong choice of the value of the initial profiling of the work rolls brings the system of hydraulic bending of the axes of the work rolls to saturation or close to it (100% load of the permissible values of the bending and anti-bending of the rolls).

The influence of wear of the backup rolls on the change in the value of the initial profiling of the work rolls is taken into account in equation (2) by the coefficient K _out , varying in the range (0.03 ÷ 0.02) · 10 ^-3 mm / t. Moreover, large values of this coefficient relate to the case of using rough rolls (maximum wear), smaller ones to the use of smooth rolls (minimal wear).

The B / L ratio also determines the bending stiffness of the roll system under the action of bending and anti-bending rolls. The influence of changes in the bending stiffness of the rolls when changing their diameters is taken into account in the interval values of the coefficients, taking into account the change in the value of the initial profiling of the work rolls from the action of the hydraulic bending axes of the work rolls. The coefficient K _arr in equation (2), taking into account the change in the value of the initial profiling of the work rolls from the action of the bending system of the rollers, varies in the range (3.0 ÷ 7.4) · 10 ^-4 mm / t. The coefficient K of _prig , taking into account the change in the value of the initial profiling of the work rolls from the action of the anti- _bending mechanism of the rolls, also depends on B / L, the diameters of the rolls, the design features of the anti-bending mechanism of the rolls on a particular mill, etc. K _prig varies in a wide range (4.0 ÷ 10.6) · 10 ^-4 mm / t. Moreover, large values of these coefficients relate to the case of using mills with low bending stiffness of roll systems for bending (small diameter of the working and backup rolls and lower values of the B / L ratio). On the contrary, lower values of the coefficients relate to the case of the use of large diameters of the work and backup rolls with increased bending stiffness, and with a larger ratio B / L.

All the moments described above are taken into account in the proposed technical solution and indicate that the proposed technical solution meets the criterion of "inventive step".

An example implementation of the invention

The testing of the proposed method was carried out on a continuous five-stand mill 2030 of endless rolling in sheet rolling production of OJSC "NLMK".

It should be noted that in this mill, the direction of the bending forces is taken as the direction of bending, which is opposite to the direction of movement of the stand pressing device when creating the rolling force. For the direction of action of the anti-bending - the direction of the force, which coincides with the movement of the pressing device of the stand when creating a rolling force. Thus, an increase in the bending force of the rolls compensates for the insufficient convexity of the work rolls, and an increase in the force of the bending of the rolls compensates for their insufficient concavity. This moment is considered as a special case, in relation to the systems of the camp on which it was tested.

Comparison of the proposed method and the prototype was carried out during experiments in the fifth mill stand during one campaign backup rolls for each method. Stand No. 5 was chosen as an example to determine the optimality of the initial profiling of the work rolls and the objectivity of the assessment, because the bending and anti-bending mechanisms in stand No. 5 are controlled by an automatic strip flatness control system (ARPA).

To determine the correct choice of the value of the initial profiling of the work rolls, we used corrections for changes in the bending and anti-bending of the rolls and the average flatness of the rolled strips in the I-Unit according to the readings of the measuring part of the SARP. Moreover, the higher the correction for bending or anti-bending of stand No. 5 was issued by the system, the greater was the amount of error made when choosing the value of the initial profiling of the work rolls (as the backup rolls wear and with a relatively stable transverse profile of the roll).

In the 5th mill stand, support rolls with a convex initial profiling of + 0.50 mm with bevels of 4 × 250 mm were used. The value of the initial profiling of the work rolls was calculated over the entire length of the campaign of the backup rolls, taking into account the development of the backup rolls and the range of rolled metal in accordance with equation (2) at zero values of bending and anti-bending of the rolls for three width groups:

- from 900 to 1300 mm inclusive (ratio B / L = 0.59 ÷ 0.85);

- from 1301 to 1600 mm inclusive (ratio B / L = 0.8503 ÷ 1.045);

- over 1600 mm (ratio B / L = 1,046 ÷ 1,21).

For stand No. 5 of a five-stand mill 2030 when using rough work rolls in it, which provoke intensive wear of the support rolls with bevels, equation (2) has the following form:

- Z _slave = [0.1118 + 0.020 · Q + 5.6 · 10 ^-4 · P _outg -5.2 · 10 ^-4 · P _prig ] ± 0.05, with the ratio B / L = 0.58 ÷ 0.85;

- Z _slave = [0.0618 + 0.019 · Q + 5.1 · 10 ^-4 · P _outg -5.0 · 10 ^-4 · P _prig ] ± 0.05, with the ratio B / L = 0.8503 ÷ 1,045;

- Z _slave = [- 0,0382 + 0,018 · Q + 4,8 · 10 ^-4 · P _mfd -4.8 · 10 ^-4 · P _prizg] ± 0,05, at a ratio of B / L = 1,046 ÷ 1 , 21.

The choice of the value of the initial profiling of the work rolls was carried out in accordance with these equations after calculating the average width of the metal rolled in the installation using the dependence:

where In _cf is the average width of the strips planned for rolling in installation, mm;

In _i - the width of the strips of each heat in the installation, mm;

M _i - the mass of each heat, t;

ΣM _i - mounting mass, t.

According to the prototype, the selection of the value of the initial profiling of the work rolls of stand No. 5 was carried out in accordance with equation (1) depending on the number of rolled metal with a rental volume of 45 thousand tons per roll campaign, the maximum change in the deflections of the work rolls forming the rolls campaign, equal to 0.85 mm, and the coefficient a = 0.5.

As an example, table 1 shows the comparative results of using the values of the initial profiling of the work rolls, calculated by the prototype method and the proposed method for the work rolls of stand No. 5 at the beginning, middle and end of two mounting rolls.

The difference in the values of the initial profiling work rolls according to the proposed method and the prototype method is associated with the use of various roll systems. The prototype used a system of "concave workers - convex support", in the proposed technical solution used convex backup rolls with bevels and work rolls mainly with convex profiling, except in cases where wide strips were rolled at the very beginning of the backup roll campaign. Profiling work rolls in such cases is cylindrical.

We take as a measure of the accuracy of the choice of the value of the initial profiling of the work rolls the correction issued by the system for automatically controlling the flatness of the rolled strip in stand No. 5. The obtained comparative characteristics are shown in table 1.

Analysis of table 1 showed the following.

According to the proposed option, the correction value issued by the system is in the range from +52 to -47% of the allowable anti-bending and bending forces, respectively, with an average value of corrections for hydraulic roll profiling systems of + 6%. At the same time, the actual average non-flatness of the cold-rolled strips was 2.824 I-Unit.

According to the prototype method, the amount of corrections issued by the system ranged from +91 to -87% of the allowable anti-bending and bending forces, respectively, with an average value of corrections for hydraulic roll profiling systems of + 26.9%. The actual average flatness of the cold-rolled strips was 3.943 I-Unit.

These circumstances indicate a more accurate choice of the value of the initial profiling of the work rolls of stand No. 5 and a higher flatness of the rolled strips by the proposed method in comparison with the prototype method.

To assess the effectiveness of the proposed method in comparison with the prototype, an experimental verification of the values of the initial profiling of the work rolls, determined over several months, was carried out.

Technical and economic indicators of the mill, downtime, power consumption, rolls, emulsol, as well as sorting of cold-rolled metal according to surface defects when working for 3 months according to the proposed option and prototype are shown in comparison with each other in table 2.

As follows from the data given in table 2, the lowest specific consumption of rolls, emulsol, electricity provides the proposed method of operating the work roll. So, the average specific consumption of electricity, work rolls, backup rolls and emulsol by the proposed method is 3.6%, 16.0%, 20.6% and 4.8%, respectively, less than the prototype. Accordingly, the average hourly productivity of the mill for these periods was 2.7% higher, and downtime lower by 0.7% when working on the proposed option in comparison with the prototype. An increase in mill productivity was achieved by increasing its stable operation and eliminating unscheduled transshipment of work rolls due to incorrect selection of the initial profiling of work rolls, as well as inefficient hydraulic bending in a saturation mode close to 100%.

The average removal rate during regrinding of the backup rolls was 4.5 mm when applying the proposed method of operation, and 5.2 mm for the prototype.

The analysis of sorting by defects "non-flatness", "kink" and "welding sticking spots" of strips rolled during the campaign of the backup rolls with the values of the initial profiling of the work rolls recommended by the proposed method and selected by the prototype method is carried out. As a result of the analysis, it was revealed that sorting by these defects by the proposed method is 0.145%, by the prototype method - 0.24% of the volume of rolled metal.

As can be seen from table 2, when applying the proposed method of operating rolls, metal consumption is on average 0.5 kg / t (on a five-stand mill) and 2 kg / t (throughout production) lower than by the prototype method. Metal savings have been achieved by reducing the number of substandard trimming at the end sections of strips rolled during transient operation of the mill, strips with reduced quality after transshipment, sections of the strip cut and transferred into subsequent scraps. The defect rate when applying the proposed method was reduced from 0.31% to 0.26% for the whole production due to the exclusion of coil turns welded in bell furnaces obtained when the flatness of the rolled strips deteriorates.

The total sorting of cold-rolled strips by defects in shape and surface when working on the proposed method compared to the prototype was reduced by 1.61 times. Sorting according to the defect “weld sticking spots” was reduced by 1.69 times, by the defect “kink” - by 1.51 times.

Technical appraisal and economic advantages of the proposed method for determining the initial profiling of work rolls are to increase the yield of metal (reducing scrap and reducing the specific metal consumption for redistribution), reducing downtime of equipment, power consumption, emulsol, work and backup rolls (by increasing the stable operation five-stand mill) and in reducing the sorting of cold-rolled annealed trained metal according to surface defects, which improves the profitability of production of cold rolled metal by 3-5%.

Table 1 No. p / p Proposed Technical Solution Prototype The operating time on the support rolls of the 5th stand, thousand tons Range of variation of bending and anti-bending forces from the permissible,% The average force of the hydraulic bending of the rolls from the permissible,% Average strip flatness rating, I-Unit The total value of the initial profiling of the work rolls (on both rolls), mm The operating time on the support rolls of the 5th stand, thousand tons Range of variation of bending and anti-bending forces from the permissible,% The average force of the hydraulic bending of the rolls from the permissible,% Average strip flatness rating, I-Unit Estimated total value of the initial profiling of the work rolls, mm * one 0 + 15 ÷ -29 -7 2.70 +0.10 0 + 65 ÷ -78 -21 3.60 -0,500 2 5 + 48 ÷ -47 +3 2.91 +0.15 5 + 65 ÷ -87 -33 4.1 -0.331 3 10 + 47 ÷ -31 +4 2.80 +0.30 10 + 66 ÷ -29 +43 3.9 -0.246 four fifteen + 37 ÷ -29 +7 2.66 +0.40 fifteen + 56 ÷ -61 +17 3.17 -0.142 5 twenty + 51 ÷ -14 +16 2.76 + 0.50 twenty + 31 ÷ -57 -12 2.94 -0.047 6 25 + 52 ÷ -19 +18 2.82 + 0.60 25 + 88 ÷ -74 +31 4.65 0,047 7 thirty + 42 ÷ -46 +6 2.84 +0.70 thirty + 82 ÷ -45 +29 3.67 0.142 8 35 + 0 ÷ -19 -8 2.79 + 0.80 35 + 46 ÷ -68 -8 3.17 0.230 9 40 + 38 ÷ -33 +5 2.92 +0.85 40 + 77 ÷ -58 +12 4.82 0.330 10 45 + 49 ÷ -24 +16 3.04 +0.95 45 + 91 ÷ -65 +63 5.41 0.425 Note * - in the fifth mill stand, from the moment of filling the back-up rolls, convex back-up and concave work rolls were used, and this column shows the total profiling for both rolls.

table 2 No. p / p Technical and economic indicators The method of determining the value of the initial profiling work rolls According to the prototype According to the proposed method one Mill production, t 512675 518631 2 Average hourly productivity of the mill, t / h 303.4 311.7 3 Downtime of the mill from the nominal operating time,% 13.6 12.9 four Specific consumption of work rolls per 1 ton of rolled products, kg / t 1.06 0.89 5 The average amount of removal during regrinding of the backup rolls, mm 5.2 4,5 6 Specific consumption of backup rolls per 1 ton of rolled products, kg / t 0.63 0.50 7 Specific energy consumption per 1 ton of rolled products, kW · h / t 60.9 58.7 8 The specific consumption of emulsol, kg / t 0.42 0.40 9 Specific metal consumption during cold rolling, t / t 1.005 1,0045 10 Specific consumption of metal as a whole in production, t / t 1,092 1,090 eleven General sorting of cold-rolled strips by defects associated with an incorrect choice of the value of the initial profiling of work rolls 1217 (0.24) 754 (0.145) 12 Sorting by defect “kink”, t (%) 766 (0.149) 510 (0,098) 13 Sorting by defect “sticking-welding spots”, t (%) 117 (0,023) 69 (0.013) fourteen Sorting by defect “non-flatness”, t (%) 324 (0,065) 175 (0,034) fifteen Defective yield, t (%) 1548 (0.31) 1348 (0.26)

Claims (1)

A method of operating a work roll of a cold rolling mill with compression of a strip in a sequential row of four-roll stands, including changing the value of the initial profiling of the work rolls when they are replaced as the backup rolls wear, in proportion to the amount of metal rolled in the stand from the beginning of filling of the backup rolls, and profiling correction depending from the range of rolled strips in the installation, characterized in that the active profile of the work rolls is affected by the hydrobending of their axes, and the change in the value of the original profiling Z _slave work rolls carried out in accordance with the expression

where Z _slave0 (B / L)) = - 0.20 ... 0.20 is the value of the initial profiling of the work rolls at the beginning of the campaign of the support rolls of the stand, depending on the ratio of the width of the strip to the length of the barrel of the backup roll B / L, mm; K _out = ( _0,030 ... 0,020) · 10 ^-3 - coefficient taking into account the influence of wear of the backup rolls on the change in the value of the initial profiling of the work rolls, mm / t; Q - the amount of metal rolled in the stand from the beginning of the filling of the backup rolls, t; P _izg and P _prig - the forces of bending and anti-bending of the rolls, respectively (the direction of action of the forces is taken into account by the signs ±), tf; K _izg = (3.0 ... 7.4) · 10 ^-4 - coefficient taking into account the change in the value of the initial profiling of the work rolls from the action of the mechanism of forced bending of the rolls, depending on B / L, the diameters of the stand rolls, design features of the roll bending mechanism on a specific mill, mm / t; K _prig = (4.0 ... 10.6) · 10 ^-4 - coefficient taking into account the change in the value of the initial profiling of the work rolls from the action of the mechanism of anti-bending of the rolls, depending on B / L, the diameters of the rolls of the stand, the design features of the mechanism of bending of the rolls on specific mill, mm / t; 0.05 - coefficient compensating for the change in the value of the initial profiling of the work rolls from the action of unaccounted factors, mm.