Patent Application
20100219567
The present invention relates to an apparatus and method for controlling a process line such as a continuous annealing line or a plating line in which steel materials are continuously processed.
In general, in a line called a process line, annealing or plating is performed on steel materials. The annealing is a process of heating a cold-rolled and hardened steel material to about 700 to 900° C. for softening so that the steel material can be easily processed during a postprocess. In this case, the heating allows iron atoms to move easily, recovering and recrystallizing steel crystals hardened by the processing. New crystal grains of a size corresponding heating and temperature maintenance conditions are generated and grown.
A conventional technique places a coil directly into a box-shaped furnace for annealing (this is called batch annealing). However, in recent years, a continuous annealing line (CAL) for continuous annealing has often been used for treatment. This is because a CAL provides higher productivity.
The quality of the above steel material includes strength and ductility, which are called mechanical properties. The mechanical properties are determined by a metallic structure such as a crystal grain size. Thus, determination of the metallic structure such as the crystal grain size enables the mechanical properties to be calculated.
However, the measurement of the crystal grain size requires steps of cutting out, polishing, and microscopically observing specimens. This requires much time and effort. Thus, the nondestructive measurement of the crystal grain size has been strongly desired. One method for nondestructively measuring the crystal grain size uses ultrasonic vibration.
For example, Patent Document 1 discloses a method for measuring the crystal grain size or texture of a material on the basis of detection values for a variation in the intensity of an ultrasonic wave applied into the material or for a speed at which the ultrasonic wave propagates.
A recently developed laser ultrasonic apparatus or electromagnetic ultrasonic apparatus may be used to transmit and receive ultrasonic waves. For example, Patent Document 2 discloses an example of the laser ultrasonic apparatus. A measuring apparatus using electromagnetic ultrasonic waves needs to contact the steel material. However, the laser ultrasonic apparatus is characterized by being able to set a long distance between a surface of the material and a head of the apparatus and offers a particularly high utility value when hot measurements and online measurements are required.
The material sensor is desirably of a non-contact and nondestructive type in terms of durability or the like. It is possible to use not only a sensor directly measuring the quality of a material such as magnetic permeability but also a sensor making indirect measurements by detecting a physical quantity such as electric resistance, an ultrasonic propagation property, or a radiation scattering property which exhibits a strong correlation with the material and converting the physical property into a material quality such as the crystal grain size or formability. There are various such sensors, and Patent Document 3 discloses an apparatus measuring the transformation quantity of a steel material from a flux intensity detected by a flux detector.
Moreover, Patent Document 4 discloses a method for measuring an r value (Lankford value) utilizing electromagnetic ultrasonic waves. Here, the r value is the ratio of distortion in a plate width direction to distortion in a plate thickness direction which is observed when a steel material is deformed by applying a tensile stress to the material. The r value is an index representing deep drawability. A larger r value increases a reduction in plate width more sharply than a reduction in plate thickness. This makes it possible to inhibit fracture and a decrease in strength during deep drawing, allowing the formability, particularly the deep drawability to be improved.
Proposed methods for nondestructively measuring the crystal grain size utilize Rayleigh scattering, the ultrasonic propagation speed, or the like.
A CAL and a CGL may use the crystal grain size or r value of the steel material measured after annealing in order to check whether or not a desired product quality has been obtained. In general, the crystal grain size is desirably large and uniform and the r value is preferably large. Patent Document 5 shows a method for directly measuring these values to control heating temperature.
Patent Document 1: Jpn. Pat. Appln. KOKAI Publication No. 57-57255
Patent Document 2: Jpn. Pat. Appln. KOKAI Publication No. 2001-255306
Patent Document 3: Jpn. Pat. Appln. KOKAI Publication No. 56-82443
Patent Document 4: Jpn. Pat. Appln. KOKOKU Publication No. 6-87054
Patent Document 5: Japanese Patent No. 2984869
However, the method shown in Patent Document 5 has the following problems.
Patent Document 5 illustrates a sensor utilizing laser ultrasonic waves as a device measuring the grain size of ferrite described in Paragraph No. 0014. However, a CAL and the like have achieved a maximum speed of about 1,000 m/min. It is difficult for the current techniques to measure the crystal grain size of a steel material moving at such a high speed. High-frequency vibration may occur during high-speed movement, resulting in much noise.
Thus, an object of the present invention is to provide an apparatus and method for controlling a process line which can improve the quality of a steel material.
To accomplish the object, an invention corresponding to claim 1 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace and controlling the temperature of the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 3 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace as well as between positions succeeding the heating process and preceding the cooling process in the annealing furnace and controlling the temperature of the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 5 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace and controlling a conveyance speed for the steel material in the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 7 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace as well as between positions succeeding the heating process and preceding the cooling process in the annealing furnace and controlling a conveyance speed for the steel material in the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 9 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace and controlling the temperature of the annealing furnace and a conveyance speed for the steel material in the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 11 provides a process line control apparatus which controls a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the apparatus using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace as well as between positions succeeding the heating process and preceding the cooling process in the annealing furnace and controlling the temperature of the annealing furnace and a conveyance speed for the steel material in the annealing furnace on the basis of measurement results for the quality of the steel material.
To accomplish the object, an invention corresponding to claim 14 provides a method for controlling a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the method being characterized by comprising a step of using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace, checking measurement results to determine whether or not the material is acceptable on the basis of determination criteria, and recording, in a database, those of the determinations which indicate the acceptability of the material, the determinations corresponding to processing conditions including set and/or actual values for heating and cooling temperatures at the corresponding positions in the annealing furnace and/or a set value for a conveyance speed for the steel material, and a step of reading the processing conditions recorded in the database and indicating the acceptability of the material to apply the processing conditions to the annealing furnace.
To accomplish the object, an invention corresponding to claim 15 provides a method for controlling a process line comprising an annealing furnace which continuously executes heating and cooling processes on a steel material, the method being characterized by comprising a step of using a material quality measuring apparatus to measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the annealing furnace as well as between positions succeeding the heating process and preceding the cooling process in the annealing furnace, checking measurement results to determine whether or not the material is acceptable on the basis of determination criteria, and recording, in a database, those of the determinations which indicate the acceptability of the material, the determinations corresponding to processing conditions including set and/or actual values for heating and cooling temperatures at the corresponding positions in the annealing furnace and/or a set value for a conveyance speed for the steel material, and a step of reading the processing conditions recorded in the database and indicating the acceptability of the material to apply the processing conditions to the annealing furnace.
The present invention will be described below on the basis of embodiments with reference to the drawings. The description below is intended for the continuous annealing line (CAL) shown in
Material quality measuring apparatuses 6, 7 described below are arranged in the inlet stage 1 and the outlet stage 5, respectively. Specifically, a crystal grain size and an r value are measured as the quality of a steel material before the material is carried into the furnace 3 and while the material is being carried out of the furnace 3.
A measurement result from the material quality measuring apparatuses 6 is input to heating apparatus feed-forward (FF) control means 112. On the basis of the measurement result from the material quality measuring apparatus 6, the heating apparatus feed-forward (FF) control 112 means determines that it is proper to set, for example, 830° C. for the heating apparatus in the furnace 3. The heating apparatus FF control means 112 outputs +30° C. to the heating apparatus in the furnace 3. Further, a measurement result from the material quality measuring apparatuses 6 is input to cooling apparatus feed-forward (FF) control means 113. On the basis of the measurement result from the material quality measuring apparatus 6, the cooling apparatus feed-forward (FF) control means 113 determines that it is proper to set, for example, 290° C. for the cooling apparatus in the furnace 3. The cooling apparatus FF control means 113 outputs −10° C. to the cooling apparatus in the furnace 3.
A measurement result from the material quality measuring apparatuses 7 is input to heating apparatus feed-forward (FF) control means 114. On the basis of the measurement result from the material quality measuring apparatus 7, the heating apparatus feed-forward (FF) control 114 means determines that it is proper to set, for example, 810° C. for the heating apparatus in the furnace 3. The heating apparatus FF control means 114 outputs +10° C. to the heating apparatus in the furnace 3. Further, a measurement result from the material quality measuring apparatuses 7 is input to cooling apparatus feed-forward (FF) control means 115. On the basis of the measurement result from the material quality measuring apparatus 7, the cooling apparatus feed-forward (FF) control means 115 determines that it is proper to set, for example, 295° C. for the cooling apparatus in the furnace 3. The cooling apparatus FF control means 115 outputs −5° C. to the cooling apparatus in the furnace 3. In the embodiment in
With this configuration, in a process line comprising the furnace 3 including the heating and cooling apparatuses continuously executing heating and cooling processes on a steel material, the material quality measuring apparatuses 6, 7 measure the quality of the steel material at positions preceding the heating process and succeeding the cooling process in the furnace 3. Then, on the basis of the measurement results for the quality of the steel material, the heating and cooling apparatuses in the furnace are controlled. This enables the quality of the steel material to be improved.
Here, an example of the material quality measuring apparatuses 6, 7 will be described with reference to
Pulse laser light 61a from the ultrasonic oscillator 61 has its beam diameter reduced to an intended value by a lens (not shown). The pulse laser light 61a is then applied to a surface of a measurement target material to be processed by a hot rolling mill, that is, a steel material 62. An ultraviolet pulse 62a generated at the surface of the steel material 62 propagates through the steel material 62 to vibratorily displace a back surface of the steel material 62, while repeating multiple reflections by reciprocating through the steel material 62. Thus, the vibratory displacement (ultrasonic detection laser light) 62a′ at the back surface of the steel material 62 is detected by an ultrasonic detector 63 using a continuous wave laser. A detection signal 63a is loaded into a digital waveform storage (not shown; for example, a digital oscilloscope) or the like and processed by an ultrasonic signal processing device 64 to obtain a waveform characteristic parameter identification result (multidimensional function coefficient vector) 64a.
The waveform characteristic parameter identification result 64a is input to a crystal grain size calculating device 65′, which then calculates the crystal grain size. The calculated crystal grain size is input to a crystal grain size correcting device 65, which corrects the crystal grain size on the basis of the volume fraction of each substructure from a material quality model 67 described below. A crystal grain size output device 68 allows the corrected crystal grain size to be, for example, audibly or visually perceived by users or to be externally read.
Here, for example, a photorefractive interferometer is used as the ultrasonic detector 63. The type of the interferometer is not limited to the photorefractive interferometer but may be a Fabry-Perot interferometer. Alternatively, a Michaelson interferometer may be used provided that the surface of the steel material is not rough.
Thus, with the ultrasonic vibration generated at the surface of the steel material 62, since an optical path changes between reference light and reflected light, the intensity of interference light changes according to the vibratory displacement of the surface of the steel material 62.
Now, description will be given of the frequency property and reliability of the interferometer. That is, for a frequency range of about several tens of MHz to 100 MHz, used to measure a grain size of 1 to 10 microns, the Fabry-Perot interferometer is more sensitive and advantageous than the photorefractive interferometer. However, experiments show that the photorefractive interferometer poses no problem in a practical sense.
On the other hand, for reliability, the Fabry-Perot interferometer requires a precise control mechanism because the interferometer must sequentially operate two opposite mirrors so as to accurately maintain an appropriate gap between the mirrors. Consequently, the Fabry-Perot interferometer is slightly unreliable in terms of the probability of a defect. In contrast, the photorefractive interferometer causes reference light and reflection light to interfere with each other in the crystal. This results in the need for a reduced number of mechanical sections, enhancing the reliability in terms of the probability of a defect.
Now, a processing operation performed by an ultrasonic signal processing device 64 will be described with reference to a block diagram in
A crystal grain size measured value do measured before corrections based on the volume fraction of each substructure is calculated from the coefficient vector of the multidimensional function obtained by fitting the quartic curve to the decay constant and a scattering coefficient S obtained from the steel material 62 for calibration.
As described above, the ultrasonic detector 63 measures ultrasonic pulse trains including a first ultrasonic pulse, a second ultrasonic pulse, . . . . An example of the ultrasonic pulse train is shown in
Here, a typical method utilizing decay resulting from scattering (Rayleigh scattering) of the ultrasonic wave caused by crystal grains by means of will be shown.
The ultrasonic wave is classified into a longitudinal wave (P wave=bulk wave), a transverse wave (S wave), a surface wave (L wave=Rayleigh wave, Love wave), and a plate wave (SO mode, AO mode) according to the vibration form of the wave. The grain size measuring method utilizing Rayleigh scattering uses the longitudinal wave (bulk wave).
The decay of the bulk wave is expressed by Equation 1 using a decay constant a.
P=Po·exp(−a·x) (1)
x: propagation distance in the steel material, and
P, Po: sound pressure.
If the frequency of the bulk wave falls within a “Rayleigh region”, the decay constant a is approximated by a quartic function of an ultrasonic frequency f as shown in:
a=a1·f+a4·f4 (2)
where f: bulk wave frequency, and
a1, a4: coefficients.
(Here, the first item of Equation 2 is an absorptive decay item, and the second item is a Rayleigh scattering item)
The term “Rayleigh region” refers to a region in which the crystal grain size is sufficiently small compared to the wavelength of the bulk wave, for example, a range expressed by Equation 3 (see Patent Document 5).
0.03<d/λ<0.3 (3)
d: crystal grain size, and
λ: wavelength of the bulk wave.
Further, a quartic coefficient a4 in Equation 2 is known to be proportional to the third power of the crystal grain size d as shown in:
a4=S·d3 (4)
where S: scattering constant.
The waveform of the bulk wave transmitted by a transmitter contains a certain distribution of frequency components. Consequently, analyzing the frequency of the received waveform enables the decay rate of each frequency component to be obtained. Moreover, the propagation distance in the steel material is determined from a variation in the time required for transmission or reception. Thus, each of the coefficients in Equation 2 can be determined on the basis of the propagation distance and the decay rate of each frequency component. Moreover, the scattering constant S predetermined using standard samples allows the crystal grain size d to be obtained on the basis of Equation 4.
The energy decays according to Equation 1. The amount of decay between the first and second ultrasonic pulses is determined as a difference in power spectrum between the first and second ultrasonic pulses. This curve corresponds to the decay constant a in Equation 2 multiplied by a difference 2t in propagation distance. Thus, the coefficients of Equation 2 for a unit propagation distance are determined by the least square method or the like. Then, the scattering constant S predetermined using the standard sample and a4, one of the coefficients determined as described above can be used to Equation 3 to determine the crystal grain size measured value do measured before corrections with the volume fraction of each substructure. However, the present embodiment is different from the conventional embodiments in that the present embodiment has a subsequent step of predictively calculating the material quality on the basis of the material model 67 to make corrections in accordance with the composition of each phase, that is, the volume fraction of each substructure.
As shown in
As shown in
The material quality predictive calculation is executed, for example, as follows. As shown in
The hot processing model 671 formulates dynamic recrystallization occurring during drafting performed by a roll and subsequent phenomena such as recovery, static recrystallization, and grain growth to calculate the grain size (grain boundary area per unit volume) during and after the rolling and a residual dislocation density, for example, an austenite state. The hot processing model 671 uses the austenite grain size, temperature and inter-pass time information based on temperature and speed, and equivalent strain and strain speed information based on a drafting pattern to make calculations (rolling austenite grain size, dislocation density, and the like).
The temperature and inter-pass time information and the equivalent strain and strain speed information are calculated on the basis of rolling conditions (inlet plate thickness, outlet plate thickness, heating temperature, inter-pass time, roll diameter, and roll rotation number).
The transformation model 672 estimates the structural state after transformation such as the grain size and the fractions of pearlite and bainite for each generation and each growth.
The transformation model 672 uses temperature information based on a cooling pattern in a runout table for the hot rolling machine (not shown) to output calculation results (ferrite grain size and the structural fraction of each phase). The temperature information is calculated on the basis of cooling conditions (air and water cooling sections, water amount density, plate passage speed in the cooling apparatus, and components) and the amount of transformation provided by the transformation model. Instead of the above model, a precipitation model taking the effects of precipitated grains into account may be appropriately used if a trace amount of additional elements such as Nb, V, and Ti may be effective. Some metal materials such as aluminum and stainless are not transformed. Thus, no transformation model may be used for these materials.
The above calculations can be used to estimate (calculate) the volume fraction of each substructure (673). The resulting volume fractions are used in the equation shown below together with the grain size do, obtained by the ultrasonic vibration measurement.
d=do(1+k×R/100) (5)
d: crystal grain size measured value (μm),
do: crystal grain size measured value (μm) measured before corrections with the volume fraction of each substructure,
k: influence coefficient (a large number of samples are pre-measured and pre-identified) (−%), and
R: substructure volume fraction (%).
As shown in the above equation, the grain size obtained by the ultrasonic vibration measurement can be corrected to improve the measuring accuracy of the ultrasonic vibration measurement. In the description below, the measured crystal grain size refers to the value d resulting from the correction based on Equation 5 or the uncorrected value do. These values are collectively denoted by symbol D.
The above embodiment uses an optical fiber transmission path as a transmission path from a reception head to an interferometer and a reception laser light source. This advantageously makes the reception head compact to increase the degree of freedom of the location and direction of a measurement surface. Further, this advantageously requires that only the small reception head be cooled even under measurement conditions in which the material is continuously exposed to high temperatures. The material quality measuring apparatuses 6, shown in
The heating apparatus FF control means 112 and the cooling apparatus FF control means 113 control the set temperatures for the heating and cooling apparatuses or the conveyance speed for the steel material in a feed-forward (FF) manner on the basis of the measurement result from the material quality measuring apparatus 6. For example, it is assumed that the measurement result from the material quality measuring apparatus 6 indicates an actual crystal grain size value Di and that the initial set temperature for the heating apparatus is calculated on the assumption of a crystal grain size Do. A modification ΔTH for the set temperature for the heating apparatus is expressed by:
where (∂T/∂D)1 is an influence coefficient indicating the effects of the crystal grain size on the temperature and is generally determined in the form of the inverse of (∂D/∂T), that is, an influence coefficient indicating the effects of the temperature on the crystal grain size.
Although the influence coefficient is described as a linear variable, the coefficient may be obtained from a mathematical model and determined using a control method in accordance with the present invention described below.
The temperature for the cooling apparatus may be similarly modified. The modification of the conveyance speed affects all the steel materials in the furnace and is not always effective. However, the modification is applicable if for example, the measurement result for the crystal grain size obtained by the material quality measuring apparatus 6 indicate a gradual and uniform variation. The speed may be changed taking into account a heat balance to which the steel material is subjected when the temperature is changed and a heat balance to which the steel material is subjected when the temperature is changed and a heat balance to which the steel material is subjected when the speed is changed.
The heating apparatus FB control means 114 and the cooling apparatus FB control means 115 control the set temperatures for the heating and cooling apparatuses or the conveyance speed for the steel material in a feedback (FB) manner on the basis of the measurement result from the material quality measuring apparatus 7. For example, it is assumed that the measurement result from the material quality measuring apparatus 7 indicates an actual crystal grain size value Do and that a target crystal grain size is defined as Daim. The modification ΔTH for the set temperature for the heating apparatus is expressed by:
where (∂T/∂D)2 is an influence coefficient indicating the effects of the crystal grain size on the temperature as is the case with Equation 6.
The heating apparatus FF control means 112 and the heating apparatus FB control means 114 modify the set temperature preset for the heating apparatus by the temperature and speed setting means 111 of the heating and cooling apparatuses. The cooling apparatus FF control means 113 and the cooling apparatus FB control means 115 modify the set temperature preset for the cooling apparatus by the temperature and speed setting means 111 of the heating and cooling apparatuses. Alternatively, the heating apparatus FF control means 112, the heating apparatus FB control means 114, the cooling apparatus FF control means 113, and the cooling apparatus FB control means 115 modify the conveyance speed setting for the steel material in the heating and cooling furnaces preset by the temperature and speed setting means 111 of the heating and cooling apparatuses.
The steel material in the inlet stage 1 must be stopped while the welding machine 13 is performing a welding operation. However, the in-furnace conveyance speed needs to be kept constant for appropriate annealing. Thus, the inlet looper 2 is an apparatus which stores the steel material in order to maintain the in-furnace conveyance speed and which pays out the steel material at a constant speed. The inlet looper 2 comprises an inlet looper main body 22.
The furnace 3 comprises a bridle roll 31, a heating section 32, a soaking section 33, a cooling section (1)34, and a cooling section (2)35. Each of the sections sets the temperature at a desired value to control the temperature of the passing steel material.
Since the steel material may be stopped in the outlet stage 5 as is the case with the inlet looper 1, the outlet looper 4 comprises an outlet looper main body 42 in order to keep the in-furnace conveyance speed constant.
The outlet stage 5 comprises a bridle roll 51, a skin pass mill 52, a tension leveler 73, a bridle roll 54, an end cutting machine 55, an inspection apparatus 56 including a plate thickness and width sensor, a bridle roll 75, an oil attaching machine 58, a cutting machine 59, and a winding machine 50. The outlet stage may decelerate or stop so as to allow the inspection apparatus 56 to perform inspections or may stop so as to allow the end cutting machine 55 and the cutting machine 59 to cut the steel material. This varies the steel material conveyance speed.
In a plating line (continuous galvanized line [CGL]), for example, a hot-dip plating line, an annealing process is usually executed before a plating process. The steel material is heated to obtain material properties similar to those obtained in the case of a CAL. The surface of the steel material is reduced by gas and activated so that the material can be easily plated. The configuration of a CGL often corresponds to the CAL in
Here, the specific installation range for the material quality measuring apparatus 6 is such that the material quality measuring apparatus 6 is installed in the inlet stage 1 at an appropriate position between the rear end of the welding machine 13 and the rearmost end of the group of the bridle roll 14, washing apparatus 15, and bridle roll 16. Further, the specific installation range for the material quality measuring apparatus 7 is such that the material quality measuring apparatus 7 is installed in the outlet stage 5 at an appropriate position between the front end of the bridle roll 51 and the rearmost end of the group of the skin pass mill 52, the tension leveler 53, the bridle roll 54, the end cutting machine 55, the inspection apparatus 56, the bridle roll 57, the oil attaching machine 58, and the cutting machine 59.
According to the first embodiment described above, the material quality measuring apparatus 6 is installed in the inlet stage 1, and the material quality measuring apparatus 7 is installed in the outlet stage 5. The material quality measuring apparatuses 6, 7 are used to measure the crystal grain size or the r value. The quality of the steel material can thus be improved. This will be specifically described below. The inlet stage 1 is installed in front of the heating process apparatus in the annealing furnace 3, and the steel material is stopped in the inlet stage 1. This is because the steel material needs to be stopped in the inlet stage 1 while the pieces of the steel material from the payout reel 11 are welded together. Thus, even with the use of a laser ultrasonic measuring apparatus measuring the crystal grain size, an example of the material quality measuring apparatus 6, in a process line for a steel material moving at, for example, 1,000 m/min., the stopped steel material prevents the adverse effect of much noise resulting from high frequency vibration in the moving steel material. This enables the crystal grain size of the steel material to be accurately measured. Further, even with the use of an electromagnetic ultrasonic measuring apparatus measuring the r value, an example of the material quality measuring apparatus 6, the steel material stopped in the inlet stage 1 is prevented from being damaged even when the r value for the steel material is measured by contacting a contactor with the steel material.
Moreover, since the outlet stage 2 has the inspection apparatus 56, the steel material is decelerated or stopped when the inspection apparatus 56 performs inspections. Furthermore, since the outlet stage 2 has the cutting machine 59, the steel material is stopped so as to allow the cutting machine 59 to perform a cutting operation. Thus, as is the case with the material quality measuring apparatus 6, even though a laser ultrasonic measuring apparatus, an example of the material quality measuring apparatus, is used as the material quality measuring apparatus 7, installed in the outlet stage 2, the stopped steel material prevents the adverse effect of much noise resulting from high frequency vibration in the moving steel material. This enables the crystal grain size of the steel material to be accurately measured. Further, even with the use of an electromagnetic ultrasonic measuring apparatus measuring the r value, an example of the material quality measuring apparatus 6, the steel material is prevented from being damaged even when the r value for the steel material is measured by contacting the contactor with the steel material.
Moreover, the first embodiment enables modeling on the basis of actual information on the material quality measured by the material quality measuring apparatuses 6, 7 as well as actual information on the line. This allows a model suitable for the characteristics of the line to be constructed and used for control. This in turn enables more precise control, providing high-quality products. In connection with the determination of whether or not the material quality is acceptable, the need for manual operations for downstream steps is eliminated.
The second embodiment configured as described above exerts effects similar to those of the first embodiment, described above.
Speed setting means 118 sets the conveyance speed for the steel material in the furnace 3 at a set value of, for example, 10 m/s.
The material quality measuring apparatuses 6, 7 are arranged in the inlet stage 1 and outlet stage 5, respectively. Measurements are made of the quality of the steel material, specifically, the crystal grain size and r value of the steel material before the material is carried into the furnace 3 and while the material is being carried out of the furnace 3.
A measurement result from the material quality measuring apparatuses 6 is input to heating apparatus feed-forward (FF) control means 122. On the basis of the measurement result from the material quality measuring apparatus 6, the heating apparatus feed-forward (FF) control 122 means determines that it is proper to set the conveyance speed for the steel material in the furnace 3 at, for example, 10.1 m/s. The heating apparatus FF control means 122 outputs +0.1 m/s to a speed control apparatus for the furnace 3. Further, a measurement result from the material quality measuring apparatuses 6 is input to cooling apparatus feed-forward (FF) control means 123. On the basis of the measurement result from the material quality measuring apparatus 6, the cooling apparatus feed-forward (FF) control means 123 determines that it is proper to set, for example, 9.9 m/s for the speed cooling apparatus for the furnace 3. The cooling apparatus FF control means 113 outputs −0.1 m/s to the speed control apparatus for the furnace 3.
A measurement result from the material quality measuring apparatuses 7 is input to heating apparatus feed-forward (FF) control means 124. On the basis of the measurement result from the material quality measuring apparatus 7, the heating apparatus feed-forward (FF) control 124 means determines that it is proper to set, for example, 10.2 m/s for the speed control apparatus for the furnace 3. The heating apparatus FB control means 124 outputs +0.2 m/s to a speed control apparatus for the furnace 3. Further, a measurement result from the material quality measuring apparatuses 7 is input to cooling apparatus feedback (FB) control means 125. On the basis of the measurement result from the material quality measuring apparatus 7, the cooling apparatus feedback (FB) control means 125 determines that it is proper to set, for example, 9.8 m/s for the speed cooling apparatus for the furnace 3. The cooling apparatus FF control means 125 outputs −0.2 m/s to the speed control apparatus for the furnace 3. In the embodiment in
With this configuration, in the process line comprising the furnace including the heating and cooling process apparatuses continuously executing heating and cooling processes, respectively, on the steel material, the material quality measuring apparatus measures the quality of the steel material at the positions preceding the heating process and succeeding the cooling process in the furnace, and on the basis of the measurement result for the quality of the steel material, the conveyance speed for the steel material in the furnace is controlled. This enables the quality of the steel material to be improved.
On the basis of the measurement result from the material quality measuring apparatus 8, the set temperature for the heating apparatus 3a is controlled in a feedback (FB) manner. The concept of the control method is similar to that shown in
Cooling apparatus intermediate control means 127 controls the set temperature for the cooling apparatus in the feed-forward (FF) manner on the basis of the measurement result from the material quality measuring apparatus 8. The control method is similar to that described above. When it is assumed that after heating, the measurement result from the material quality measuring apparatus 8 indicates the actual crystal grain size value Di and that the initial set temperature for the heating apparatus has been calculated on the assumption of the crystal grain size Do, ΔTH can be determined in the same manner as shown in Equation 6.
In
That is, the method for controlling the process line comprising the furnace 3 which continuously executes heating and cooling processes on the steel material comprises, as shown in
The above control method is applicable not only to
Material quality acceptability determining means 132 determines whether or not the steel material is acceptable on the basis of material quality data on the steel material obtained from the material quality measuring apparatus 7 or material quality data on the steel material checked for quality in a downstream step on the line, the data being included in various pieces of information collected in the database 131. In
That is, the method for controlling the process line comprising the furnace 3 which continuously executes heating and cooling processes on the steel material comprises a step of using the material quality measuring apparatuses 6, 7 to measure the quality of the steel material at the positions preceding the heating process and succeeding the cooling process in the furnace 3, recording the measurement results for the quality of the steel material in the database 131, and recording, in the database 131, the set and actual values for the heating and cooling temperatures at the appropriate positions in the furnace 3 and/or the set and actual values for the conveyance speed for the steel material as well as information such as the plate thickness and width of the steel plate which is required to determine whether or not the material quality is acceptable, a step of determining whether or not the material quality is acceptable on the basis of the information recorded in the database 131 and recording, in the database 131, those of the pieces of information which have been determined to be acceptable, the information indicating the temperature settings for the heating and cooling processes in the furnace and the conveyance speed for the steel material, and a step of, for a steel material to be processed after the step of recording the information in the database 131 is completed, applying, to the process line, processing conditions similar to those for the steel material determined to be acceptable which are recorded in the database 131.
The above control method is applicable not only to
As described above, the processing conditions for the steel material determined to be qualitatively acceptable are recorded in the database 131. This enables the processing conditions for the steel material to be read and reflected in the settings for the furnace 3 for the subsequent steel materials. In this case, when the processing conditions for the steel materiel determined to be acceptable are read, it may be necessary to execute, for example, a process of averaging a plurality of processing conditions.
The following method is an example of determination of the influence coefficient for the effect of the temperature on the crystal grain size, described in Equation 1.
When it is assumed that the furnace has n sections for the heating and cooling apparatuses, heat input to the steel material and determined from the actual temperature values and conveyance speeds obtained from the respective sections is defined as Qi (i=1 to n). The crystal grain size measured by the material quality measuring apparatus 6 is defined as Di, and the crystal grain size measured by the material quality measuring apparatus 7 is defined as Do. Then, a regression equation is defined by Equation 8.
Do=a(0)+a(1)Q(1)+a(2)Q(2)+ . . . +a(n)Q(n)+a(n+1)Di (8)
Here, Q(i) (i=1-n) denotes, when it is assumed that the furnace has n sections for the heating and cooling apparatuses, the heat input to the steel material and determined from the actual temperature values and conveyance speeds obtained from the respective sections. Di denotes the crystal grain size measured by the material quality measuring apparatus 6. Do denotes the crystal grain size measured by the material quality measuring apparatus 7. a(0), a(1), . . . , a(n), a(n+1) denotes an influence coefficient for the effect of the heat quantity on the outlet crystal grain size in each section of the heating furnace.
By determining each of the coefficients of Equation 8 on the basis of the data stored in the database 131, it is possible to determine the influence coefficient for the effect of the heat quantity on the outlet crystal grain size in each section. The conversion of the heat quantity into the temperature and speed can be based on a common idea. This is applicable not only to the crystal grain size but also to the r value. Further, the multiple regression equation need not be used but, for example, a neural network may be used. With the neural network, an input layer is defined as the input heat, the crystal grain size Di, or the like, and an output layer is defined as Do. The neural network may be allowed to learn a measured Do as a teaching signal.
Furthermore, the relationship between the crystal grain size or r value and the annealing temperature for the steel material is partially modeled using equations. However, actual annealing stages are very long and must thus be treated as distributed parameter systems. Thus, the temperature setting cannot be easily calculated using the equations.
Thus, the material quality measuring apparatuses 6, 7, and/or 6, 7, 8 measure the quality of the steel material and record the results in the database 131. Further, the actual values for the heating and cooling temperatures at the appropriate positions in the furnace 3, the actual value for the conveyance speed for the steel material, and the required information such as the plate thickness, plate width, and chemical components of the steel material are also recorded in the database 131. Moreover, a determination is made of whether or not the desired material quality has been obtained at the temperature settings for the heating and cooling apparatuses and the conveyance speed for the steel material. The determination is also recorded in the database 131. A heating process, a cooling process, and a conveyance speed meeting conditions similar to those determined to be acceptable are retrieved from the database 131 and applied to the steel materials to be subsequently processed. This enables the appropriate steel material quality to be obtained.
Further, a model for the quality of the steel material, the temperature settings for the heating and cooling apparatuses, and the conveyance speed for the steel material is automatically generated from the information recorded in the database 131 and used for control.
In the above description, the material quality measuring apparatus in
The present invention makes it possible to provide an apparatus and method for controlling a process line, which can improve the quality of the steel material.
The present invention is applicable not only to a continuous annealing line but also to a plating line involving an annealing process and other stages involving a heating or cooling process.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/052393 | 2/9/2007 | WO | 00 | 5/12/2008 |
