EP2662158A1 - Method for processing milled goods and milling system - Google Patents

Abstract

The method involves determining actual value (I) of a hardness of a rolling stock (6) i.e. slab, from an observation value (B) before entry of the rolling stock into a roll stand (4). Control variables (S) for the roll stand are provided on a basis of the actual value in order to control thickness of the rolling stock after passage through the roll stand to a set point value. The actual value is determined by measuring a parameter correlated with hardness. Rotation speeds or rotational torques of drives are used as control variables. An independent claim is also included for a rolling mill.

Description

The invention relates to a method for processing rolling stock and a rolling mill.

When rolling in a rolling mill, rolling stock, e.g. Rolled steel or various metals when passing through one or more stands. In this case, the rolling stock, which is present for example in the form of a strip to be rolled to a certain thickness. To achieve this thickness, the rolling stock undergoes a thickness control when passing through the individual rolling stands, which is carried out for example with the aid of a Gaugemeter or a mass flow controller.

With these known thickness rules, rolling stock of conventional metal grades in very good thickness quality is produced in single and multi-stand rolling mills. However, the metal-producing industry is increasingly developing modern metal grades that meet the requirements for lightweight construction with good formability and high ultimate strength. For steel, these are e.g. Dual phase and triple steels. A special feature of these metal grades is that their characteristic properties in addition to the alloy components are influenced by a specific cooling during and after rolling. Such changes in the temperature of the rolling stock can cause unwanted variations in the hardness of the rolling stock, e.g. Skid marks or tilting of crystal structures during ferritic rolling occur. The hardness of the rolling stock here means variable material properties of non-geometric type. These are, for example, inhomogeneities in the metallic structure, roughnesses of the surface of the rolling stock, the tensile strength.

In particular, due to deficiencies in the cooling of the rolling stock inhomogeneities in the metallic structure can arise, which influence the properties of the rolling stock itself and the forming behavior during rolling. The inhomogeneous metal structure affects as a variation of the hardness of the rolling stock and leads by appropriate Auffederungsänderungen the rolling stand to undesirable thickness errors.

Conventional thickness regulators, such as gauges or mass flow controllers, can only partially compensate for the effects of variations in the hardness of the rolling stock on the thickness quality of the rolling stock, since the variations in hardness can be very short-circuited, in particular when the crystal structure is tilted and in the area of the strip ends.

This leads, for example, especially during cold rolling to tolerance exceeded the cold rolled thickness of the rolling stock at the strip ends, so that these band ends must be cut and scrapped.

It is therefore an object of the present invention to propose a method for processing rolling stock, with which these disadvantages are avoided. Moreover, it is an object of the present invention to provide a rolling mill with which the method according to the invention can be carried out.

1. a) vor dem Einlauf des Walzguts in das Walzgerüst wird der Ist-Wert der Härte des Walzguts ermittelt,
2. b) in Abhängigkeit des Ist-Wertes wird zur Steuerung der Dicke des Walzguts nach Durchlauf durch das Walzgerüst auf einen Soll-Wert einer Stellgröße des Walzgerüsts voreingestellt.

The first object is achieved according to the invention with a method for processing rolling stock in a rolling mill with at least one roll stand, with the following steps:

1. a) before the entry of the rolling stock into the roll stand, the actual value of the hardness of the rolling stock is determined,
2. b) depending on the actual value is set to control the thickness of the rolling stock after passing through the rolling stand to a desired value of a manipulated variable of the roll stand.

The determination of the actual value of the hardness of the rolling stock is carried out continuously while passing through the rolling mill through the rolling mill before the rolling stock enters the rolling stand, so that an information of the hardness with respect to the considered Location of the rolling stock is obtained. In other words, therefore, a location-dependent hardness of the rolling stock is determined. As a result, fluctuations in the hardness of the rolling stock with respect to the location can be determined in particular.

Depending on the actual value of the hardness, ie in particular on the fluctuation of the actual value, manipulated variables of the following rolling stand are then preset in step b) such that the rolling stock, after passing through the rolling stand, reaches the desired value. According to the invention, therefore, information relating to the hardness of the rolling stock is used in the rolling process and the manipulated variables of the rolling stand are changed as a function of their dependence so that a predetermined desired value is maintained with regard to the thickness of the rolling stock. It thus be compensated for fluctuations in the hardness of the rolling stock, this has before passing through the rolling stand and would normally lead to a thickness error after passing through the rolling stand. The method according to the invention can be used both during cold rolling and during hot rolling.

In a preferred embodiment of the invention, the actual value of the hardness of the rolling stock is determined by measuring a parameter correlated with the hardness. Particularly advantageous can be determined as a correlated parameter, the tensile strength of the rolling stock before the inlet of the rolling mill by means of a suitable measuring device.

However, the actual value of the hardness can also be determined from an observation value at a preceding further rolling stand. Such an observation value can be determined based on at least one of the parameters rolling force of the preceding rolling stand, temperature of the rolling stock, strip tension, incoming thickness of the rolling stock in the preceding roll stand, expiring thickness or estimated value of the roll gap thickness at the roll gap of the preceding rolling stand. A measurement with a separate measuring device is then no longer necessary.

As a manipulated variable of the roll stand, the employment of the roll gap can be used. In particular, therefore, based on the knowledge of the actual value of the hardness and thus a hardness variation of the rolling stock in conjunction with the knowledge of the inlet side thickness of the rolling stock, the hydraulic adjustment, which moves the roll gap, pre-controlled. Thus, the expected Auffederungsänderung the rolling mill is compensated by the incoming strip thicknesses and hardness fluctuations in a timely manner.

Furthermore, it is possible to use as a manipulated variable and the rotational speeds or torques of the drives of the rolls of the rolling stand.

In the case of measuring the actual value of the hardness of the rolling stock already in the inlet of the rolling mill, this feedforward control can already be used in the first stand of a multi-stand rolling mill or in the first pass in a reversing single stand.

When ascertaining the actual value of the hardness or the hardness variation on the basis of an observation value of a preceding further rolling stand, the precontrol of the thickness can first act on the second stand or the second stitch. When passing through several scaffolds, the actual value of the hardness in each rolling stand can be observed again and this determined observation value can in turn serve as the basis of the feedforward control for controlling the thickness of the rolling stock in a subsequent roll stand. The same applies to the measurement of hardness.

In order to further improve a model of the rolling mill which is used for its regulation, the actual value of the hardness of the rolling stock determined in step a) can be used to adapt the model. In particular, the knowledge of the actual value of the hardness can be used to track the so-called material module CM. The material module CM together with the scaffold module is an important model for adaptation the controller dynamics of all other thickness controllers such as Gaugemeter, mass flow controller and monitor control.

The second object is achieved by a rolling mill with the features of claim 9. Advantageous embodiments are specified in the dependent claims. The advantages according to the invention have already been explained in connection with the method according to the invention.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in detail in conjunction with the drawings.

• Fig. 1 ein Walzwerk mit einem Walzgerüst und einem Messgerät zur Messung der Härte des Walzguts,
• Fig. 2 ein Walzwerk mit zwei Walzgerüsten.

For a further description of the invention reference is made to the embodiments of the drawings. Each shows in a schematic schematic diagram:

• Fig. 1 a rolling mill with a rolling stand and a measuring device for measuring the hardness of the rolling stock,
• Fig. 2 a rolling mill with two rolling stands.

Fig. 1 shows a rolling mill 2, in this case a cold rolling mill with a rolling stand 4 for processing rolling stock 6. The rolling stand 4 has two rollers 8, the distance of which define the roll gap w. The rolling stock 6, here in the form of a slab, has, prior to the passage of the rolling stand 4, an inlet-side thickness d ₀ and an outlet-side thickness d ₁ after passing through the rolling stand 4. The aim of the rolling process is that after passing through the roll stand 4, the rolling stock 6 assumes a predetermined outlet-side thickness d ₁ . In other words, the predetermined thickness d ₁ represents the target value I for the rolling process.

To ensure this, it is known to use thickness regulators such as gauges or mass flow controllers in rolling mills. Modern metal grades that meet the requirements of lightweight construction with good formability and high final strength, their characteristic properties are also influenced by a targeted cooling during and after the rolling process. By such temperature changes of the rolling stock 6, unwanted fluctuations in hardness, ie variable material properties of non-geometric nature such as inhomogeneities in the metallic structure, roughness of the surface or the tensile strength of the rolled material 6 can occur, which influence the rolling process in a rolling mill 4.

Conventional thickness regulators, such as gauges or mass flow controllers, can only partially compensate for the effects of variations in the hardness of the rolling stock on the thickness quality of the rolling stock, since the variations in hardness can be very short-circuited, in particular when the crystal structure is tilted and in the area of the strip ends.

In order to adjust the outlet side thickness d _{1 of} the rolling stock 6 to a desired value even with such metal grades, when using the method according to the invention in a step a) before the entry of the rolling stock 6 in the roll stand 4, the actual value I of the hardness of the rolling stock 6 determined.

In the in Fig. 1 In the case illustrated, a parameter correlated with the hardness, in this case the tensile strength of the rolling stock 6, is measured by means of a measuring device 10 before the inlet of the rolling stand 4. The actual value I of the hardness is detected as a function of the location, so that it also fluctuations of the hardness of the rolling stock are determined depending on the location.

The determined actual value I of the hardness of the rolling stock 6 is then further processed in a pilot control device 12. The pilot control device 12 is used as a function of the actual value I the hardness of the rolling stock 6 to determine a value of a manipulated variable S. This serves to control the thickness d _{1 of} the rolling stock 6 after passing through the roll stand 4 to a predetermined desired value.

In this case, the manipulated variable S is the setting of the roll gap w, which is moved with hydraulic cylinders 14. As a manipulated variable S but also, for example, the speeds or torques of the drives, not shown, of the rollers 8 of the roll stand 4 come into question. Depending on the actual value I of the measured hardness and also, for example, thickness d ₀ and the speed v ₀ with which the rolling stock 6 enters the roll stand 4, then the roll gap w can be moved such that the actual value I the outlet side thickness d _{1 of} the rolling stock 6 is controlled to a desired value. There are thus compensated for the expected Auffederungsänderungen of the roll stand 4 by the incoming fluctuations of the actual value I of the hardness of the rolling stock 6 before passing through the roll stand 4. By means of the method according to the invention is thus achieved that despite occurring variations in the hardness of the rolling stock 6 before entering the rolling stand 4, a homogeneous output-side thickness d _{1 is} achieved, which corresponds to the predetermined target value.

A further embodiment of the invention in a multi-stand rolling mill 2 shows Fig. 2 , The rolling mill 2 shown here has, in addition to the roll stand 4, a preceding further roll stand 4a. In the Fig. 2 used reference numerals corresponding to those from Fig. 1 , In the in Fig. 2 the situation shown, the rolling stock 6 is when passing through the previous roll stand 4a. Instead of like in Fig. 1 shown to measure the actual value I of the hardness of the rolling stock 6 with a measuring device 10, the actual value I of the hardness of the rolling stock 6 is determined from an observation value B at the preceding further rolling stand 4a. In order to obtain the observation value B, at least one of the parameters of rolling force of the preceding rolling mill 4, temperature of the rolling stock 6, strip tension, incoming thickness d _{-1 of} the rolling stock 6 is set into the previous roll stand 4a, tapered thickness d ₀ or estimated value of the roll gap thickness at the roll gap w of the preceding roll stand 4a detected metrologically. Based on this observation value B, the actual value I of the hardness of the rolling stock 6 is then determined by means of a computer unit 16.

The further method steps correspond to those associated with Fig. 1 explained steps. On the basis of the actual value I of the hardness to control the thickness d ₁ of the rolling stock 6 after passing through the rolling stand 4 to a desired value, in turn, the employment of the roll gap w of the roll stand 4 preset.

Although the invention has been further illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (11)

Method for processing rolling stock (6) in a rolling mill (2) with at least one roll stand (4), comprising the following steps: a) before the entry of the rolling stock (6) into the roll stand (4), the actual value (I) of the hardness of the rolling stock (6) is determined, b) depending on the actual value (I) is for controlling the thickness of the rolling stock (6) after passing through the rolling stand (4) to a desired value, a manipulated variable (S) of the rolling stand (4) preset. Method according to claim 1,
in which the actual value (I) is determined by measuring a parameter correlated with the hardness. Method according to claim 2,
in which the tensile strength of the rolling stock (6) before the inlet of the rolling stand (4) is measured as a correlated parameter. Method according to one of the preceding claims,
in which the actual value (I) is determined from an observation value (B) at a preceding further rolling stand (4a). Method according to claim 4,
in which the observation value (B) is based on at least one of the parameters rolling force of the preceding roll stand (4a), temperature of the rolling stock (6), strip tension, incoming thickness (d _-1 ) of the rolling stock (6) in the preceding roll stand (4) Thickness (d ₀ ) or estimated value of the roll gap thickness at the roll gap (w) of the preceding roll stand (4a) is determined. Method according to one of the preceding claims,
in which the adjustment of the roll gap (w) is used as the manipulated variable (S). Method according to one of the preceding claims,
in which the speeds or torques of the drives of the rollers (8) of the roll stand (4) are used as manipulated variable (S). Method according to one of the preceding claims,
in which the determined actual value (I) of the hardness is used to adapt a model of the rolling mill (2). Rolling mill (2) for processing rolling stock (6) with at least one rolling stand (4), a unit for determining the hardness of the rolling stock (6) and a pilot control unit (12) for controlling the thickness of the rolling stock (6) after passing through the rolling stand (4) to a target value. Rolling mill (2) according to claim 9,
in which the unit for determining the hardness is a measuring device (10). Rolling mill (2) according to claim 10,
in which the measuring device (10) is a measuring device (10) for the tensile strength of the rolling stock (6).

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