RU2210443C2 - Method for cold rolling of strip in mill with four-high stands driven through backup rolls - Google Patents

Abstract

FIELD: metallurgical industry branches, namely processes for cold rolling of strip in wide-strip cold rolling mill having four-high stands with main drive through backup rolls. SUBSTANCE: method for cold rolling of strip in mill with four-high stands driven through backup rolls at emulsion lubricating of rolls during rolling process comprises steps of controlling in separate stands of mill such parameters as reduction and(or) tension values while taking into account known beforehand parameters such as diameters Dr, Db of rolling and backup rolls respectively; length Lb of barrel of backup rolls; length of slopes of barrels of backup rolls; diameters d_b.r, d_b.b of bearing units of rolling and backup rolls respectively; horisontal shift of axis of rolling rolls relative to axis of backup rolls in rolling direction Xr; friction coefficients f_r, f_b in bearing units of rolling and backup rolls respectively; in addition taking into account parameters measured directly at rolling process, namely: power Ndr consumed by electric motors for rotating driven rolls, angular velocity ω_p of rolling rolls, rolling effort P, thickness h₁ of rolled piece, thickness h₀ of initial blank, back tension To of strip, front tension T1 of strip; at rolling process measuring in addition concentration C of emulsol in used emulsion; using above mentioned parameters calculating tgβ being tg of inclination angle of interroll effort relative to axial plane of rolls and coefficient f₀ of rest friction at roll contact according to empiric dependence; then for each stand of mill testing if condition tgβ<0,9f₀ is satisfied; when said condition is not satisfied at least for one stand, increasing reduction value in said stand and(or) increasing front tension or lowering back tension of strip in said stand. EFFECT: elimination of emergency state of mill caused mutual slipping between rolling and backup rolls at rolling process.

Description

 The invention relates to the metallurgical industry, in particular to a method for cold rolling strips on broadband cold rolling mills having four-roll stands with a main drive through backup rolls.

 Known and closest in technical essence to the invention, the method of cold rolling strips on a mill with four-roll stands with a drive through the backup rolls and with emulsion lubrication of the rolls during rolling / 1 /.

The known method includes the regulation in individual mill stands of such parameters of the rolling process as compression and / or tension, taking into account the known process characteristics:
- diameters of the workers D _p and supporting D _op rolls;
- the length of the barrel of the backup rolls L _op ;
- the length of the bevels on the barrels of the backup rolls with;
- the diameters of the trunnions of the bearings of the workers d _{subsh p} and supporting d _{under w sh op} rolls;
- horizontal displacement of the axis of the work rolls relative to the axis of the backup rolls in the rolling direction X _g ,
- the coefficient of friction in the bearings of the workers f _p and supporting f _o rolls,
and measured directly during the rolling process:
- the power spent by the electric motors on the rotation of the drive rolls N _priv ;
- the angular velocity of rotation of the work rolls ω _p ,;
- the rolling force P;
- thickness of the rolling h ₁ ;
- the thickness of the rolled h ₀ ;
- the rear tension of the strip T ₀ ;
- front tension strip T ₁ .

 At the same time, when rolling the compression in the mill stands, they are distributed based on the condition of their uniform loading.

 However, in the known method, rolling is carried out without taking into account factors that can lead to slippage in the roll contact between the backup and work rolls. As a result, with improperly selected modes of rolling on the mill in the stands, slipping in the roll contact is possible, which causes intense wear of the rolls.

 The objective of the invention is to eliminate the emergency situation at the mill due to mutual slippage between the work and backup rolls during the rolling process.

- плечо усилия прокатки по формуле:

где N_пр - мощность прокатки, равная мощности, затрачиваемой на вращение приводных опорных валков N_прив;
- радиус круга трения в подшипниках рабочих и опорных валков по формуле

где f - коэффициент трения в подшипниках,
- плечо трения качения в контакте валков по формуле:
e=0,10•b
где b - полуширина площадки сплющивания валков, определяемая по формуле:

здесь

- нормальное напряжение в межвалковом контакте по формуле:

- тангенс угла наклона межвалкового усилия к осевой плоскости этих валков по формуле:

- коэффициент трения покоя в контакте валков по эмпирической зависимости:

после чего для каждой клети стана проверяют выполнения условия:
tgβ<0,9f₀ (10)
и в случае, если оно не выполняется хотя бы для одной клети, увеличивают обжатие в этой клети и/или увеличивают переднее либо уменьшают заднее натяжение полосы в этой клети.This problem is solved by the fact that in the method of cold rolling strips on a mill with four-roll stands driven through backup rolls and lubricating the rolls during rolling, which includes adjusting the parameters of the rolling process, such as compression and / or tension, in individual stands of the mill, taking into account while as known in advance process characteristics:
- diameters of the workers D _p and supporting D _op rolls;
- the length of the barrel of the backup rolls L _op ;
- the length of the bevels on the barrels of the backup rolls with;
- diameters of the trunnions of the bearings of the workers d _{under w p} and support d _{under w op} rolls;
- horizontal displacement of the axis of the work rolls relative to the axis of the backup rolls in the rolling direction X _g ;
- coefficient of friction in the bearings of the workers f _p and supporting f _op rolls,
and measured directly during the rolling process:
- the power spent by the electric motors on the rotation of the drive rolls N _priv ;
- the angular velocity of rotation of the work rolls ω _p ;
- the rolling force P;
- thickness of the rolling h ₁ ;
- the thickness of the rolled h ₀ ;
- the rear tension of the strip T ₀ ;
- front tension strip T ₁
according to the invention, in the process of rolling the strip, the concentration C of the emulsol in the emulsion used is additionally measured;
calculate for each mill stand:
- the angular velocity of rotation of the work rolls ω _op according to the formula
ω _op = ω _p D _p / D _op (1)
- the angle of inclination of the plane passing through the axis of the rolls to a vertical plane according to the formula:

- shoulder rolling force according to the formula:

where N _CR - rolling power equal to the power spent on rotation of the drive backup rolls N _priv ;
- the radius of the friction circle in the bearings of the workers and backup rolls according to the formula

where f is the coefficient of friction in the bearings,
- the rolling friction shoulder in the contact of the rolls according to the formula:
e = 0.10 • b
where b is the half width of the flattening rolls, determined by the formula:

here

- normal voltage in the roll contact according to the formula:

- the tangent of the angle of inclination of the inter-roll effort to the axial plane of these rolls according to the formula:

- the coefficient of friction of rest in the contact of the rolls according to empirical dependence:

after which, for each mill stand, the conditions are satisfied:
tgβ <0.9f ₀ (10)
and if it is not performed for at least one stand, increase the compression in this stand and / or increase the front or decrease the back tension of the strip in this stand.

 This technical solution eliminates the emergency situation at the mill due to mutual slippage between the work rolls and backup rolls during the rolling process. It is known that if the tangent of the angle of the roll-to-roll force exceeds the rest friction coefficient, then idle work rolls stop. However, it was experimentally established that the regime of full slip of the idle roll is preceded by the regime of partial slip, which occurs when the tangent of the angle of inclination of the roll force equal to 92-95% of the value of the coefficient of rest friction. To ensure guaranteed operation of the mill without slippage of the rolls, as we have established, it is necessary that the tangent of the calculated angle of inclination of the roll-to-head force does not exceed 90% of the rest friction coefficient (safety factor is 0.90).

 If the tangent of the roll angle of the inter-roll force exceeds 90% of the value of the coefficient of rest friction, for these working conditions of the stand, it is necessary to adjust the parameters of the rolling mode in order to reduce the tangent of the angle of the roll-to-roll effort.

 To do this, you can increase the compression in the stand, where the condition (10) is not satisfied. In this case, tgβ calculated by formula (8) will decrease, since with an increase in compression the rolling force increases, and with an increase in rolling force in formula (8), the numerator decreases and the denominator increases; and / or increase the front tension or decrease the back tension of the strip - in this case, the numerator decreases and the denominator increases in formula (8), which means that tgβ decreases.

 Then it is necessary to recount according to the proposed methodology.

- угловой скорости вращения приводных валков ω (30-50 с^-1),
- концентрации эмульсола ("Квакерол") в используемой эмульсии С (0-2,5%).The proposed empirical dependence of the rest friction coefficient on four rolling parameters that most affect the level of rest friction in the contact of steel rolls has been experimentally obtained for real stands of broadband cold rolling mills and is reliable in the following parameter ranges:
- the magnitude of the normal stress in the contact of the rolls p ₀ (550-900 MPa);
- the ratio of the diameters of the backup and work rolls

- the angular velocity of rotation of the drive rolls ω (30-50 s ^-1 ),
- the concentration of emulsol ("Quakerol") in the used emulsion C (0-2.5%).

The following is a specific example of the implementation of the method according to the invention. We carry out strip rolling on a cold rolling mill equipped with four-roll stands with drive through backup rolls. The stands of the mill have the following structural characteristics:
- the diameter of the barrel of the work rolls D _p = 300 mm;
- the diameter of the barrel of the backup rolls D _op = 1200 mm;
- the length of the barrel of the backup rolls L _op = 1300 mm;
- the length of the bevels on the barrels of the backup rolls with = 100 mm;
- the diameter of the trunnion of the bearings of the work rolls d _{subsh p} = 200 mm;
- the diameter of the trunnion of the bearings of the backup rolls d _{subsh op} = 650 mm;
- horizontal displacement of the axis of the work rolls relative to the axis of the support in the rolling direction X _g = 6 mm;
- the coefficient of friction in the bearings of the workers f _p and the supporting f _op rolls - 0,005.

During the rolling process, the following parameters were measured (on the example of the last mill stand, where there is a danger of roll slippage):
- the power expended by the electric motor to rotate the drive backup rolls N _priv = 0.08 MN • m / s;
- the angular velocity of rotation of the work rolls ω _p = 120 s ^-1 ;
- rolling force P = 1.35 MN;
- rolled thickness h ₁ = 0.62 mm;
- rolled thickness h ₀ = 0.60 mm;
- the back tension of the strip T ₀ = 0.26 MN;
- the front tension of the strip T ₁ = 0.04 MN;
- the concentration of emulsol "Quakerol" C = 2.0%.

1. By the formula (1) determined the angular velocity of rotation of the work rolls ω _op = 30 s ^-1 .
2. Using the formula (2), we calculated the angle of inclination of the plane passing through the axis of the rolls to the vertical plane γ = 0.46 ^o .

 3. Using the formula (3), we determined the shoulder of the rolling force a = 0.278 mm.

 4. Using the formula (4), we calculated the radius of the friction circle in the bearings of the work rolls ρ = 0.5 mm.

 5. By the formula (6), the half-width of the flattening area of the rolls was determined to be b = 1.2439 mm.

 6. Using the formula (5), the rolling friction shoulder in the roll contact e = 0.1244 mm was calculated.

7. Using the formula (7), we determined the normal stress in the inter-roll contact p ₀ = 559 MPa.

 8. Using the formula (8), we calculated the tangent of the angle of inclination of the roll force to the axial plane of these rolls tgβ = 0.09493.

9. By the formula (9), the coefficient of rest friction was calculated f ₀ = 0.10413, which, taking into account the safety factor of 0.9, amounted to 0.09372.

 10. Verification of condition (10) showed that in the stand under consideration there is a danger of slipping of the rolls, so the back tension of the strip was changed from 0.26 to 0.24 MN.

 When recalculating according to the proposed algorithm, the tangent of the angle of inclination of the inter-roll force to the axial plane of these rolls was tgβ = 0.08654 - condition (10) is satisfied.

Literature
1. Technology of rolling production. In 2 books. Prince 2. Reference: Benyakovsky M. A., Epiphany K. N., Vitkin A. I. et al. M.: Metallurgy, 1991.442 s., p. 641

Claims (1)

A method of cold rolling a strip in a mill with four-roll stands driven through back-up rolls and with emulsion lubrication of the rolls during rolling, which includes adjusting the rolling process parameters such as compression and / or tension in individual mill stands, taking into account previously known characteristics process: working diameter D _p and D _op supporting rolls, barrel length L _op supporting rolls, the length of the bevel on the support rollers, the diameters of the barrels trunnion bearings working _hem d _p and d _hem reference _op rolls horizontal displacement of and the work rolls with respect to the axis of the backup rolls in the rolling direction X _g, the coefficient of friction in the bearings of the working f _p and the reference f _op the rolls and measured directly in the rolling process parameters: power expended by the motors to rotate the drive roller N _pref, the angular speed of the working rolls ω _p , rolling force P, rolling thickness h ₁ , rolling thickness h ₀ , rear tension of the strip T ₀ , front tension of the strip T ₁ , characterized in that the concentration C is additionally measured during rolling of the strip emulsol used in the emulsion, is calculated for each mill stand: the angular velocity ω of rotation of the working rolls _op formula _OP ω = ω _p D _p / D _op, the angle of inclination of a plane passing through the axes of the rolls, to a vertical plane by the formula

shoulder rolling force according to the formula

where N _CR - rolling power equal to the power expended on the rotation of the drive rolls N _PR , the radius of the friction circle in the bearings of the workers and backup rolls according to the formula

where f is the coefficient of friction in the bearings, the rolling friction shoulder in the contact of the rolls according to the formula e = 0.10 • b, where b is the half-width of the flattening area of the rolls, determined by the formula

here

normal voltage in the roll contact according to the formula

the tangent of the angle of inclination of the inter-roll force to the axial plane of these rolls according to the formula

empirical dependence of the static friction coefficient in the contact of the rolls

after which, for each mill stand, the conditions tgβ <0.9f _{0 are} checked and if it is not fulfilled for at least one stand, increase the compression in this stand and / or increase the front or decrease the back tension of the strip in this stand.