Method for continuous cold rolling of strip tension

 

(57) Abstract:

The invention relates to rolling production and can be applied on a continuous broadband cold rolling mills. The technical result - the sustainable position of the work rolls fluctuations in the tension and effort rolling. The method includes determining the yield strength of the stripteach interstand interval for different steel grades in maintaining the volume of specific tension nby setting the value of Krepresenting the relationntoT. The new method is that set maximum allowable value for= KCRadditionally for each stand to determine the factor KTinstability of tension as the ratio of the largest variance among the front and rear tension from the nominal technologically given their size to that of the nominal value of the tension, the angle between the line connecting the centers of the working and backup rolls, and vertical angle3between the line connecting the centers of the working and backup rolls, and the line of action of mivakulova efforts at slowing mill, measure the thickness of strip and rolling forces in each stand. P ratios:

the value of the specific tension before the first crate, PA;i+1the value of the specific tension for the i-th stand, PA; PCR- roll force, N; b - band width, m; hithe thickness of the strip before the i-th stand, m; hi+1- strip thickness for the i-th stand, m; - [rad];3- [rad]. 1 Il., table 1.

The invention relates to rolling production and can be applied on a continuous broadband cold rolling mills.

The prior art method for continuous cold rolling of strip tension [1] , in which the value of the specific tensionnin interstand intervals prescribed with a gradual increase from the first to the last stand within then= (0,35-0,7)t. The application of this method of rolling reduces the likelihood of slippage and improve the flatness of the car.

The disadvantage of this method of rolling is a high probability of gusts of the bands at the existence of non-metallic inclusions and the presence of hub tension on the strip edge.

A known method for continuous cold rolling of strip tension [2], including the definition of ateach interstand interval for different grades of steel, and in which velicolepniintot. The value of the coefficient kfor the first crate support equal to 0.2, and in the last interstand interval is equal to 0.16. The value of the specific strip tension in a separate interstand intervals prescribed on the basis of descending order of the magnitude of the coefficient kfrom the first to the last stand. Application of a known method of rolling reduces pariwest bands in interstand the gaps and smooth out the original thickness of the steel.

This method can be adopted for the prototype of the invention.

The disadvantage of this method is the unstable position of the work rolls during rolling, which affects the surface quality of rolled strip (defect type "ribbing").

The unstable position of the work rolls during rolling may be the case when polprasert tensions close in value to the value of the horizontal projection of the efforts of the current between the working and support rolls. In this case, fluctuations in the tension and rolling forces, as well as during acceleration and deceleration of the mill can move the work roll in the horizontal plane in the direction from the coil to uncoiler and nab the texts are accompanied by changes mivakulova gap, which impairs the surface quality of cold rolled strips.

At the same time, the radial load acting on the bearing assemblies of the work rolls is a function of the front and rear tension; its large size causes a reduction in durability of the bearings.

The objective of the invention is the provision of the stable positions of the work rolls fluctuations in the tension and effort rolling, as well as during acceleration and deceleration of the mill and thereby improving the surface quality of cold-rolled strip and at the same time maintaining a low probability of gusts of the bands at the existence of non-metallic inclusions and the presence of hub tension on the strip edge.

This task is solved in that in the method of continuous cold rolling the strip to tension, including the definition of the yield strength of the stripteach interstand interval for different steel grades and maintaining the volume of specific tensionnby setting the value of the coefficient krepresenting the relation ntotaccording to the invention set maximum allowable value = KCRadditionally for each stand to determine the tension of the nominal technologically given their size - this nominal tension, the angle between the line connecting the centers of the working and backup rolls, and vertical angle3between the line connecting the centers of the working and backup rolls, and the line of action of mivakulova efforts at slowing mill, measure the thickness of strip and rolling forces in each stand, then the value of the specific tensions in a separate interstand the support intervals, based on the following ratios:

< / BR>
i= knpTwheni>knpT,

whereithe value of the specific tension before the first crate, PA;i+1the value of the specific tension for the i-th stand, PA; PCR- roll force, N; b - band width, m; hithe thickness of the strip before the i-th stand, m; hi+1- strip thickness for the i-th stand, m; - [rad];3- [happy].

For explanation of the invention the drawing shows a diagram of the forces on the strip and the rolls during rolling.

Radial force acting on the cushion of the work roll of the reference planes and represents the amount of support reactions, balancing polprasert rear and front tension band and horizontal projection mivakulova efforts, as well (see drawing):

< / BR>
jednego tension, H; Ponthe force acting between the work and support rolls (magalloway force), N; is the angle between the line connecting the centers of the rolls, and vertical, happy; - the angle between the line connecting the centers of the rolls, and the line of action of the force PonI am.

The force acting between the rollers:

< / BR>
The angle can be determined by the following formulas:

- at constant speed rolling force (Pondirected tangentially to the circle of friction in the bearings supporting the rolls, this case is not shown):

< / BR>
- when accelerating mill:

< / BR>
- when the deceleration of the mill:

< / BR>
where m is the shoulder of rolling friction, m;on- the radius of the circle friction bearings supporting the roll, m; Ronis the radius of the support roll, m; RCR- roll force, N; MJn.op- moment of inertia of the rotating support roll, Nm.

In turn, the angle can be determined from the expression:

< / BR>
where Rslaveis the radius of the work roll, m; e is the distance between the vertical axial plane of the working and backup rolls, m

As can be seen from the drawing, and expression (1), if polprasert tension band more horizontal projection mivakulova efforts, the radial force acts on napra force directed in the opposite direction.

In the process of rolling the tension of the strip is not permanent, under the influence of the oscillation modes of rolling are variations of tension, which, depending on the type of mill can be up to 20% from the nominal values. By setting the maximum for standard deviation values of the tension from the corresponding nominal values of maximum, minimum and average (nominal) tension can be linked by the following relations:

< / BR>
where kT- coefficient instability tensions; T0maxT0min- maximum and minimum value of the back tension, N; T1maxT1min- maximum and minimum value of the front tension, N; T0T1- the average (nominal) value of the tension established technological instruction, N.

When the tension variation, as well as during acceleration and deceleration of the mill may change the direction of the radial forces, which reduces the surface quality of rolled strip due to the unstable position of the work rolls in the cage and fluctuations mivakulova gap.

Values of specific tensions that ensures a stable position of the roller in the cage, determined from the t produced for the most unfavourable.

1. If polprasert tensions more horizontal projection mivakulova efforts, the radial force acts on the bearings in the direction of rolling, and the smallest possible difference of tension during acceleration of the mill will be equal to (T0min-T1max); in this case, the condition for the stability of the work roll is:

< / BR>
2. If polprasert tensions less horizontal projection mivakulova efforts, the radial force acts on the bearings against the direction of rolling, and the greatest possible difference of tension during deceleration of the mill will be equal to (T0max-T1min); in this case, the condition for the stability of the work roll is:

< / BR>
If technological instruction mill is set to the nominal value of the front tension T1then the nominal value of the back tension T0guaranteeing stable position of the work roll in the cage, can be determined from the following inequalities obtained by converting expressions(1), (2), (7), (8), (9):

< / BR>
< / BR>
Given thaty>3, in order to prevent gusts strip during rolling due to the high level of specific interstand tensions the magnitude of the back tension for each stand is prescribed on the basis of conditions (11 expression to determine the value of specific rear tension.

By setting the maximum allowable value of k= kCRthat limited the possibility of gusts of the bands at the existence of non-metallic inclusions and the presence of hub tension on the strip edge. If defined specific tension does not exceed the product of kCRthe yield strength of the striptthe danger of gusts strip is missing. If defined specific tension more works of kCRthe yield strength of the strip tthe danger of gusts band exists in this case to prevent gusts accept specific tension is equal to the product of the coefficient kCRthe yield strength of the stript.

A specific example of the method for continuous cold rolling of strip tension below in the table.

As can be seen from the table, the described method allows to provide a stable position of the work rolls fluctuations in the tension and effort rolling, as well as during acceleration and deceleration of the mill, which provides a high surface quality of cold rolled strips and low probability of gusts of the bands at the existence of non-metallic inclusions and the calculation of machines and mechanisms rolling mills. - M.: Metallurgy. 1985. S. 51-52.

2. A. F. Pimenov, O. N. Soskovets, A. I., Trina and other Cold rolling and finish tin. - M.: Metallurgy. 1990. S. 104-105 (prototype).

Method for continuous cold rolling of the strip under tension, including the definition of the yield strength of the stripteach interstand interval for different steel grades and maintaining the volume of specific tensionnby setting the value of Krepresenting the relationntot, characterized in that the set maximum value to a= KCRadditionally for each stand to determine the factor Ktinstability of tension as the ratio of the largest variance among the front and rear tension from the nominal technologically set their values to the nominal value of the tension, the angle between the line connecting the centers of the working and backup rolls, and vertical angle3between the line connecting the centers of the working and backup rolls, and the line of action of mivakulova efforts at slowing mill, measure the thickness of strip and rolling forces in each stand, then the value of the specific tensions in a separate interstand intervals support, SUB> the value of the specific tension before the first crate, PA;

i+1the value of the specific tension for the i-th stand, PA;

PCR- roll force, N;

b - band width, m;

hithe thickness of the strip before the i-th stand, m;

hi+1- strip thickness for the i-th stand, m;

- [rad] ;

3- [rad] .

 

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