EP0532560A1 - Process for the production of low-residual-stress rolled strip. - Google Patents

Abstract

The invention relates to the production of a strip with low internal stress and applies to the field of metal shaping. According to the invention, the extent of fine rolling divided into n strips is adjusted each time, during rolling, by adjusting members, to DELTASi setting values, without the number n of the measuring sections necessarily coinciding with the number of adjustment sections, the DELTASi adjustment values being continuously calculated for the different bands taking into account the flow limit line, in such a way that we calculate, with the start of the pass or at this instant , the average reduction at the different epsilon passes (Boolean not) h, ges and the partial reduction epsilon (Boolean not) h, k which characterizes the reduction from the flow limit line to the exit of the right-of-way. The quotient of these two quantities epsilon (Boolean not) h, ges / epsilon (Boolean not) h, k gives, after a multiplicative connection with the final thickness h1, a fixed value valid for each rolling pass. After a multiplicative connection of this fixed value with the effective values of elongation or crushing DELTASg (e) l, i of the strap obtained by the device for measuring the tension of the strap for each band i, the setting values are obtained. DELTASi, required for fine adjustment of the edges of the right-of-way, in the form of a reference value for the fine adjustment of the edges of the right-of-way which is carried out by means of adjustment members.

Description

 Process for producing low-tension strip during rolling ------------------------------------------ -------------------------------------------------- ---------------------

The invention relates to the production of low-tension band and is applicable in the field of metal forming.

The aim of rolling strip is to reduce strip ripple

avoid and ensure that the strip is low in residual stress after rolling in the longitudinal direction across the strip. Recently, this has become

different actuators for setting the fine roll gap

purposefully used. Serve as such actuators. a.

Waizen bending devices. displaceable in the axial direction

Intermediate rolls with symmetrically or asymmetrically shaped

Roll bales, sliding work rolls, devices for

Inclination of the rollers, furthermore the influence of the thermal

Profiles of the rolls through defined local coolant supply

as well as support rollers that vary in the profile of the rollers. at

20-roll mills also become the support saddles for the outer ones

Support rollers used to adjust the fine roll gap (H. Galla. H. Jung: "Rolling flat products". German Society for

Metallurgy. Information society. Verlag 1966).

In order to be able to use these actuators sensibly for profile control of the fine rolling gap with the aim of producing low-tension strip, additional measuring devices are used in modern rolling plants to record the strip longitudinal tension curve over the strip width

used. These measuring devices record the band tension curve u. a. with special measuring rollers, styli or via electromagnetic force effects.

From the measured strip tension curve δli can be eliminated by eliminating the longitudinal tension applied from outside (e.g. by reel pull) during rolling the residual stress curve Δ l. i in the relieved band strip Δδl, i = δl, i - l (1)

+ Residual compressive stresses

 - Intrinsic tensile stresses and according to Hooke's law the longitudinal expansion or

-St also amounts

Aε l, i =

 + Longitudinal compression amounts

- Amounts of longitudinal expansion are determined (Figure 1). The aim is to use the actuators mentioned to set the fine roll gap using the signals continuously generated by the measuring devices in such a way that band ripple is avoided and

 low-tension band is generated.

For the correct conversion of the tape tension measurement values Δδ _{ℓ, i} or

Longitudinal elongation and compression measurement values Δε _{l, i} in the setting values Δ S _i required for the correction of the fine rolling gap require separate transfer functions.

So far it has been assumed that if there is no or only slight spreading of the strip during the rolling pass a

Proportionality between the Δε _{ℓ, i} values and those from the

 Thickness profiles of the incoming and outgoing strip derived

Deformation values Δε _{h, i} according to Δ £ l. i = Δ £ h, i (3) and consequently the thickness values can be derived from the Δε _{ℓ, i} measured values.

The picture is 2

and

However, rolling practice has shown that the values for the reduction of the longitudinal stresses from the measured longitudinal expansion and elongation values Δε _{ℓ, i}

with the inclusion of equation (3) determined thickness values Δ Si, do not lead to the desired goal. Special investigations (Bernsmann, G.P .; Iron and Steel Engineer, 1972/3, pages 67-71). (Becker, H .;

Freundel. P .; Wiss. Journal of TU-Magdeburg 19, 1975, issue 7/8, pages 753-761), (Köpstein, E .; Grigorjan, GG; Zeleznow, Ju. D .; Neue Hütte 1975, 4, pages 226-226) with inclusion of the one and

band profile (see Fig. 2) resulted in very large and strongly scattering deviations, which are used as a correction factor K _M in the relationship were introduced (Eq. (7) is analogous to Eq. (2) with Eq. (3) in

Connection).

These correction factors include value ranges K _M = 0.05 .... 0 .1

... 0.2. Similarly, it was found that measured with Bandspannungsmeßgeräten longitudinal tension values (Δδ _{l, i) in accordance with} are much lower than that calculated from the Dickenorofilen longitudinal stress changes _{(Δδ ℓ, i) calc.}

This is the difference according to Köpstein

A dependency of these strongly fluctuating correction factors on characteristic rolling conditions could not be recognized. Therefore, there are currently very large uncertainties and inaccuracies in the determination of the for setting the fine rolling gap

required setting values ΔSi, from the Δε _{l, i} and Δε _{l, i} measured values obtained from strip tension measuring devices. so that the rolling of

 Low tension belt causes considerable problems. The resulting quality deficiencies of the rolled strips reduce the value in use and result in economic losses.

The aim of the invention is the employment opportunities for the

 Use the fine roll gap in such a way that low-tension strip can be produced, thereby creating the conditions so that a higher strip quality is achieved during rolling and fewer technological difficulties arise when processing the strips and sheets.

The invention is based on the technical problem in the production of low-tension strip, where rolling is carried out in the usual way, using actuators for adjusting the fine rolling gap and measuring devices for the course of the strip length tensions over the strip width, so that the strip rolling process Adjustment values Δ Si corresponding to the real rolling conditions for setting the fine rolling gap in the production of low-tension strip are determined and used.

According to the invention the object is achieved in that during the rolling by actuators the fine wagging gap in n strip elements is set by actuating amounts ΔSi, however, the number n of measuring sections does not necessarily have to match the number of actuating sections, the actuating amounts Si for the individual Strip elements, including the flow sheath (Fig. 1), are continuously determined in such a way that the average stitch decrease and the partial acceptance amount before or at the start of the stitch

which marks the decrease from the flow sheath to the roll gap exit. The one made from both sizes

The quotient gives a multiplicative link

with the final thickness hi, one valid for the respective roll pass

Fixed amount

After multiplicative linking of this fixed amount with that of

Strip tension measuring device for the current strip elongation or compression values Δε _l, i obtained for the respective strip element _i result in the necessary for the fine adjustment of the roll gap contour

Actuating amounts ΔS _i as the default value for the fine adjustment of the

Roll gap contour. which takes place by means of an actuator.

In cases in which the strip tension measuring device for the respective strip elements i does not display the measured values as the current strip elongation or compression values Δε _{l, i} , but rather as strip longitudinal tensions

Δδ _{ℓ, i} , these tension values are first converted into band elongation or compression values according to Hooke's law.

The invention will be explained in more detail in the following embodiment, the following sizes being included (see also Figure 2): h _{o, i} local thickness before the stitch in the i-th strip strip element. h _{i, i '} local thickness after the stitch in the i-th strip strip element. h _o average tape thickness before the stitch, hi average tape thickness after the stitch, h _k average thickness on the flow sheath (Fig. 1).

L _k Distance of the flow sheath from the roll gap exit.

L _d Printed length of the roll gap.

R radius of the work rolls.

Picture 1 illustrates the rolling process.

A metal strip made of deep-drawing steel with a width of 300 mm is changed from an average starting thickness h = 0.47 mm to an average final thickness h _i = 0.34 mm on a 20 roller mill with a work roll radius

R = 21 mm rolled. Here, the external longitudinal tension δ ₄ = -180N / _mm 2 applied by the tension reel to the outgoing band. From a strip tension measuring device, strip elements evenly distributed over the bandwidth in n = 11 are given in Table 1, column 2 measured longitudinal stress registered. According to Eq. (1) for one

Current state of the longitudinal stress Δδ _{l, i} is in

Column 3 of Table 1 is shown. Hence the

Longitudinal expansion or compression amounts Δε _{l, i} according to Eq. (2) in column 4 of Table 1.

According to the invention, the following are determined before or at the beginning of the tich:

- the flow sheath height h _k according to known equations (e.g.

Knuschner, A .; Freiberg Research Books B 267, VEB Dt. Publishing house for basic materials industry. Leipzig 1969 or Neue Hütte 1961, 3rd pages 94-99). h _k = h ₁ + 2 R [1-cos [arc sin (l _k / l _d . L _d / 2R)]] (9)

In the present example, the

Flow sheath L _k / L _d = 0.3 the flow sheath according to Eq. (9) to

h _k = 0.3517 determined.

- which is the average decrease from the flowing sheath to

 Partial purchase amount characterizing roll gap exit

In the example is = 0.0249.

 - the fixed amount valid for this roll pass

 takes the value 3.7773 in the example.

During the roll pass, the respective actuating amounts ΔS _{i are determined} as default values for the fine adjustment of the roll gap contour, by continuously multiplying the fixed amount of 3,777 valid for this roll pass with the current elongation and compression amounts Δε _{L, i} determined by the strip tension measuring device

In this way, the employment amounts ΔS _i are obtained in column 5, table 1.

If the Δs _i values are negative, the fine roll gap height h1, i in the associated strip elements is narrowed by the specified values ΔS _i using suitable actuators. In contrast, positive AS _i values require an increase in the roll gap height h ₁ , _j by the specified ΔS _i values. After this correction of the fine roll gap, the strip is low in tension. If the measured values Δε _{L, i} change on the belt tensioner _{, the} ΔS _i values must be determined again in the manner specified.

Claims

Claims

1. A method for producing low-tension strip during rolling, in which rolling is carried out in the usual way and actuators for setting the Treinwalz gap as well as measuring devices for the course of the longitudinal tension across the width are used,

 characterized,

that during the rolling by actuators, the fine rolling gap in n strip elements is set by incremental amounts ΔS _i , however, the number n of measuring sections does not necessarily have to match the number of adjusting sections. the actuating amounts ΔS _i for the individual strip elements below

Inclusion of the flow sheath can be determined continuously in such a way that, before or at the beginning of the stitch, the mean stitch decrease and the partial decrease amount of the decrease of of the flow sheath until the roll gap emerges, the quotient formed therefrom, with which

average final thickness h ₁ multiplicatively linked and this fixed amount ₁ valid for the respective roll pass

multiplicative linkage with the current strip elongation or compression value Δε _L, i obtained from the strip tension measuring device for the respective strip element _{i represents} the respective actuating amounts ΔS _i for the fine adjustment and is used for the adjustment.

2. The method according to claim 1,

 characterized,

that in cases where the strip tension measuring device for the respective strip elements i does not display the measured values as current strip elongation or compression values Δε _{ℓ, i} , but as

Longitudinal strip voltages Δδ _{l, i} these voltage values after

 Hooke's law can first be converted into band elongation or compression values.