The invention relates to the art of mechanical treatment of metal by pressure, i.e. to production of rolled products, in particular it relates to controlling of rolling mills and handling of the produced articles in the course of their treatment, and more particularly it relates to the rolling mill's monitoring and adjusting devices that are operable to respond to different variables of the rolled sheets. To a certain extent, the invention relates to auxiliary operations for treatment of metal in the course of rolling thereof.
The invention is particularly intended for optimizing the process of hot and/or cold rolling of strips.
Known is the method for adjusting the rolling process, comprising the steps of measuring thickness of a rolled strip, and carrying out the correcting actions as to actuators of the roll drives when a rolled strip thickness deviates from predetermined values (patent RU No. 2125495, assigned to SMS Schloemann-Siemag AG, IPC B 21 B 37/00, 1999). This method provides for measurement of only one parameter, and does not provide for taking into account a change in speed of a rolled strip.
Known is the method for adjusting the rolling process, comprising the steps of measuring the strip rolling process parameters by measuring instruments at a number of points along a mill, and outputting appropriate correcting actions as to actuators (patent RU No. 2078626, assigned to Siemens AG, IPC B 21 B 37/00, 1997). Said method does not include the step of tracking the relationship between the monitored process parameters and particular length values of a rolled strip. For that reason, any exact moment for applying the correcting actions cannot be determined while selecting said correcting actions.
Also known is the method of adjustment of the rolling process, comprising the steps of discretely measuring the monitored strip rolling process parameters at a number of points along a mill, measuring angular velocities of the stand working rolls and table rolls, basing on which measurements a strip linear speed is determined; defining, according to the obtained data, a certain number of equally sized strip sections for subsequent averaging of at least three values of the measured monitored variables at each given section, and determining the required correcting actions as to actuators on the basis of the averaged values of the monitored parameters for a given section (patent RU No. 2177847, cl. B 21 B 37/00, 2002). In the applicant's opinion, this method is the art that is the most pertinent to the claimed invention.
The invention is based on the concept of continuous, more exactly: quasi-continuous measurement of such process parameters as, for instance, consumer properties of a rolled strip along its length in the course of rolling. These properties can be as follows: ultimate strength (σus) yield strength (σy), and/or elongation (δ) of a rolled strip, etc.
According to the invention: the monitored parameters are measured when a strips moves under an appropriate sensor, and/or at an appropriate measuring arrangement; further, for excluding a possibility that the measurement results would be affected by any occasional fluctuations of measured quantities, which are inevitable under conditions of high temperatures and large masses of a moving metal, at least three values obtained at adjacent measurement points are averaged, the obtained averaged values of the process parameters of a rolled article are compared with the standard values, and when said quantities do not coincide, the correcting actions are effected at the relevant sections of a mill. Such action may consist in modifying the gap between rolls, or the cooling action.
More particularly, according to the invention, implemented is a method for optimizing the rolling process by way of determination of settings for a mill, provision of sensors and measuring arrangements at a mill (for example, for selecting specimens of a rolled material) to determine parameters of a rolled strip while a strip is moving, to read and automatically process the sensor indications or the sampling results, and for determining the controlling actions to be performed as to the rolling process. Further, the rolling process parameters that should be monitored according to production specification of a given rolled products' batch are preset. The invention also provides for systematic measuring of the preset parameters' quantities in the course of movement of a rolled strip over a rolling mill. In this context, the “systematic” term means as frequent measurements of parameters as the used instruments allow such frequency, or as required by the monitoring conditions. Then, a number or length of sections of a rolled strip are defined; for each one of the sections, values of the rolling parameters' measured quantities should be obtained separately. Under conditions of the Examples described below, number of sections of the 800-meter (at exit) strip was 50 sections, so that, accordingly, one section was 16 m long. After that, the measured quantities relating to a given section of a rolled strip are averaged, the averaged quantities of the measured parameters are compared with the quantities defined in conformity with production specifications of a given batch of rolled articles. When the compared quantities do not coincide to an extent beyond certain tolerances, then the mill settings are corrected for rolling of next strip, in respect of which next strip these steps are repeated. When the comparison result is positive, the existing settings remain for rolling of next strip.
More specifically, the invention further comprises the steps of: discrete measuring of the strip rolling process parameters, measuring of the angular velocities of the stand working rolls and tables rolls, determining the strip linear speeds; defining a certain number of equally sized strip sections for subsequent averaging of at least three values of the measured process parameters at each given section, setting a rated portion of the strip length subdivided into sections; for a given rolled products range, further defining the consumer properties at each one of the rolled strip sections depending on the averaged values of each section's measured process parameters; comparing the defined consumer properties with the preset limits of the consumer properties; defining a strip length portion wherein the consumer properties are within the preset limits, and establishing these process parameters as the primary standard for rolling of strips of the same or proximate product range—when this defined strip length portion is not less than the rated portion, or amending the process parameters on a new strip—when said defined strip length portion is less than the rated one.
The method was carried out at a continuous wide-strip hot mill. Strips 800 m long, made of steel 08nc (semi-killed steel), 4 mm thick, were rolled. Chemical composition of the rolled steel was indicated in the heat log issued by the steel-making unit: Table 1.
The monitored process parameters were the rolling termination temperature (Tre) and coiling temperature (Tco). For measuring the strip rolling termination temperature, a pyrometer positioned at exit from the last finishing stand in the start of the run-out table was used; and the coiling temperature was measured by a pyrometer positioned upstream of the coiler. The strip temperature downstream of the final roughing stand (the sixth stand, T6) was measured by a pyrometer positioned in the start of the span between the roughing and finishing groups of the mill stands. Strip thickness was measured by an X-ray thickness gauge at exit from the mill finishing group; strip parameters were measured discretely 10 times/s by pyrometers and thickness gauge. Angular velocities of working rolls of the final finishing stand, final roughing stand, of the run-out table and intermediary tables' rolls were measured by tachometers mounted on the respective drives. Basing on the angular velocity measurements, taking into account diameters of the stands and table rolls, the strip linear speed was measured, which speed had the following values: 2 m/s within the span between the roughing and finishing groups, and 6.5-11.2 m/s downstream of the stands' finishing group. For each one of 50 sections 16 m long, basing on a value of the strip linear speed: a set of the measured values relating to the time, when each one of said strip sections has passed under a relevant sensor, was determined. The number of sections selected in this case was determined, on the one hand, by the response speed of the used measuring systems and actuators and, on the hand, by the required adjustment accuracy. The measured discrete values of instrument indications were averaged for each section. As the averaged values were within the tolerances of the rolled products range, next strips were rolled under the same settings.
Under the same initial conditions as were used in Example 1, part from the process parameters mentioned in said Example: values of σ (ultimate strength) and δ (elongation) were determined for each one of the strip sections to check them upon their compliance with requirements of the applicable standards (the general standards and those demanded by a customer).
The obtained data are summarized in Table 2.
It follows from Table 2 that the strip length portion wherein the consumer properties' values are within the preset limits, exceeds the strip length rated portion having the consumer properties' values within the preset limits (every rolled product range is rated by the engineering specifications on the basis of previous investigations), i.e. for a given chemical composition of steel, the rolling termination temperature of 886° C. and that of coiling of 680° C. provided the strip mechanical properties required by the applicable standard. These values were subsequently used as the primary standard for strip rolling of the same or proximate range of rolled products (having a proximate metal composition and thickness). For subsequent rolling of strips of the same or proximate product range, the established primary standard was used for setting Trt and Tro process values.
Under the initial conditions of Example 2, strips selected from a group having a somewhat different chemical composition were rolled. Data on the same measurements for this strip are summarized in Table 3.
Table 3 shows that values of σus (ultimate strength) exceed the standard values by 32% of the strip length, while the allowed excessive value is 8%. For this reason, for rolling of next strip of that group, the correcting action to be effected at its relevant sections was modified, and said measurement procedure was entirely repeated so that the needed fitness of the strip's rated portion was provided; then the defined mode was being maintained in the course of rolling of other homogeneous blanks.
The invention can be suitably used first of all for rolling of groups of homogeneous blanks, and also can be used for rolling of single blanks, particularly in the cases when subsequent use of separate portions of a rolled sheet for different purposes or different subsequent processes is anticipated.
Number | Date | Country | Kind |
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2002114912 | Jun 2002 | RU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/RU03/00224 | 5/22/2003 | WO | 00 | 11/23/2004 |
Publishing Document | Publishing Date | Country | Kind |
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WO03/104099 | 12/18/2003 | WO | A |
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20050178481 A1 | Aug 2005 | US |