SU1690868A1 - Strip rolling method - Google Patents

Abstract

The invention relates to rolling production and can be used in rolling strip steel. The purpose of the invention is to increase the productivity of the mill by increasing the total stretch in one stand. During the strip rolling between the working and intermediate rollers, the front end of the strip is rolled and set in succession to successive deformation centers at a controlled ratio of the peripheral speeds of the first and second rolls. . After the start of rolling the strip in the second pair of rolls, the tension of the strip between the strain points is set in the range from 0.05 to 0.15 of the yield strength of the metal. 2 tab., 1 Il,

Description

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The invention relates to rolling production and can be used in rolling strip steel.

The purpose of the invention is to increase the productivity of the mill by increasing the total stretching of the strip in one stand.

The drawing shows schematically the process of rolling a strip in a six-high stand.

The rolling stand 1 contains 2.3 support rolls, 4.5 work rolls and intermediate rolls 6.7,

The method is carried out as follows.

Set the required gap between the rollers and set the strip alternately in the deformation centers, k, m, n. Deformation centers k, m, n are located in the vertical

plane one below the other. Since the forces P4 and PS acting on the work rolls are equal to each other, they do not have an elastic deflection and the active forming rolls across the width of the strip are almost identical to the original grinding profile of their forming. Thus, if there are three deformities located one above the other, only the RA and PS forces act on the support rolls from the deformation foci k, etc. This contributes to the formation of strips with a small transverse thickness difference when the strip is deformed with a stretching factor of / 1.8-6.

When rolling a strip in rollers 3,4, the bending of the front end of the strip occurs on roller 4, since roller 3 is driven and has a greater speed than idle waO O O 00 O 00

block 4. In this case, the front end of the strip is directed to the deformation zone m between the rolls 4,5. To ensure the task of the front end of the strip to the deformation zone p between the rollers 5, 6, the circumferential speed Ouse (roller 3) is 1.1-1.3 times the peripheral speed VG (roller 6). This ensures the bending of the strip on the roll 5. After exiting the deformation n and at the end of the strip, tension is created Ti (with a coiler or a subsequent stand).

As the strip thickness decreases, the yield strength of the metal increases, and the reduction value decreases. If the speeds of the drive rolls 3 and b in the steady state process are the same, then the second volume of metal from the first deformation zone to the third (center n) decreases, i.e. Vkhk Vmhm Vnhn. where Vk, Vm, Vn are the average rolling speeds of nonocbi; hk, hm, Hn are the average strip thicknesses in the corresponding deformation areas. During such rolling between the foci of deformation, loop loops are formed and the strip is rolled without tension. In this case, the rolling process is unstable and the strip is displaced along the length of the rolls. Adjusting the loop size by tensioning the ends of the strip can be carried out with significant values of To and TL, which leads to rupture of the strip and limiting the coefficients of stretching. The elimination of the loops and rolling with adjustable tension between the deformed foci is achieved, besides creating tension To and Ti, by changing the speed mode of the drive roller 6. This mode provides for the increase in speed Vi after a seizure of strip 1 by rolls 5, and in the established rolling process, the ratio

Vi / Va p-fik

where I is the total stretch ratio in all deformation foci ;.

jMk is the stretch ratio in the deformation zone k, which ensures the equality of the second volumes of metal coming out of the three deformation zones, and the tension of the band within Ots / crf 0.05-0.15, which is sufficient to stabilize the position of the band. in rolls (7t / 0n - the yield strength of the metal and the specific tension of the strip between the deformation sites).

The optimality of the values of cnc / From 0.05 to 0.15 is that at He / From 0.05, the strip is shifted when rolled to the edge of the roll barrel, and

at 0.15, a band break occurs (Table 1).

Adjusting the distribution of the tensile stresses across the width of the strip is accomplished by creating an appropriate thermal profile of the rolls. This is favored by rolling the strip covering the rolls 4 and 5. Thus, when creating a convex profile of the forming roll 4, the thickness of the strip in the middle decreases not only by reducing the gap in the middle of the width of the strip, but also by increasing the diameter of the roll in the middle part of the barrel, which makes it appear in the middle of the strip width

larger values of tensile stresses than on edges. The action in this non-uniformity of stresses also contributes to reducing the strip thickness in the middle of the width. Such a method of adjusting the transverse thickness variation and flatness of the strip is more effective, which is a simple adjustment by changing the roll forming in the normal rolling process.

The period of seizure of the strip by the rollers is carried out with small reductions, after the strip leaves the rollers 5 and 6 (steady state), the total stretch ratio is increased to, and 1.8-6.

The method was tested in a six-roll stand with a diameter of 60–85 mm working and intermediate rolls and 100 mm supporting rolls. The number of revolutions of the work rolls is 60 rpm. Rolled strip widths B of aluminum with the original thickness of H 1.5 mm. Emulsol T was used as a lubricant. A usual rolling process with a single deformation zone between

rolls 4,5. The results of the experiments are presented in table 2,

As follows from the table.2, when rolling with compression of the strip between the work rolls 4 and 5 (normal process, experiments 1-3) force

rolling increases with stretching and at / g 3.02, force P is equal to Р Р4 Рб 58.8 kN. When rolling by the proposed method with stretching ratio fi 2.85 (test4), the rolling force is significantly

less than and equal to P 16.5 kN, which is 3.5 times less than in experiment 3 for the usual rolling process. This is due to the fact that some of the forces arising in the process of deformation of the strip closes

among themselves (P4, RB). When rolling with a draw ratio / 4 6.0, the rolling force is 2.3 less than in a conventional process (experiment 3), and this ensures a reduction in elastic deformations and an increase in rolling accuracy. In the case of rolling in Experiment 5 (Oz / Oe 1.0), the front end of the strip bends on roller 4 and freely enters the deformation zone t. At the exit from the deformation zone t, the front end bends also on roller 4 or leaves roller 4 and 5 exactly . When using rolls with the ratio Oz / 0b 1.1 -1.30 (experiments 6.7), the front end at the exit of the deformation zone m bends onto the roll 5 and freely enters the deformation zone of the section. When rolling from Oz / Oe 1 , 42 (experiment 8), the front end of the strip gets a significant bend when it leaves the deformation zone n, which makes it difficult for the strip to enter the rolls 5.6.

Thus, unhindered seizure of the strip into subsequent deformation sites is provided by using Oxy De rolls with a ratio of 1.2-1.3. In addition, the proposed rolling method provides higher draw ratios with significantly lower rolling force values, which allows to increase rolling accuracy and mill productivity in proportion to the increase in thickness and decrease in the length of the original strip. Increasing the initial thickness H of the strip when AH const increases the value of the second volume of metal in the deformation zone k and allows proportionally speeding up the process of winding the strip from the unwinding winder in front of the mill and releasing it to accept the following

The results of the experimental determination of the boundary values of the values of the tension of the strip between the deformation sites (strip width 100 mm)

 2

Note: & g when conducting experiments was 105 N / mm.

roll. Since the second volume of the metal is

With Vk hit,

then, as hk increases, for example, by 1.3 times, the number of rolled rolls per unit of time increases to the same extent. The use of the proposed method with an increased thickness of the initial hot rolled strip also ensures an increase in the productivity of continuous broadband hot rolling mills.

Claims (1)

The invention of the method of rolling strips, including compression in the cage with intermediate and support rolls with three metal deformation sites located in a common vertical plane, the adjustment of the speeds of the rolls and the tension of the strip, in order to increase the productivity of the mill due to increase the total stretching of the strip in one stand, when rolling the front end of the strip and its task successively into successive deformation centers, the circumferential speed of the first one during the rolling of the drive roll is set 1.1-1.3 times more is poured than the speed of the second drive roll, and after the strip starts rolling in the second pair of rolls, the circumferential speed of the second drive roll is increased relative to the first one before the strip is tensioned between the strain points within 0.05-0 , 15 from the yield strength of the metal. Table 1 The results of the experiments on rolling strips for various options. Width strips 50 mm Table 2