JP2017133043A - Center speed control method and device for continuous heat treatment line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a center speed control method and device of a continuous heat treatment line capable of achieving maximum production efficiency with securing quality by preventing plate temperature from going out of tolerance even when acceleration and deceleration with large speed change is generated and setting necessary and sufficient acceleration and deceleration rate.SOLUTION: A limit fuel speed is calculated per steel band unit based on a facility performance control condition of a continuous heat treatment line and a quality securing limitation condition due to quality of a steel band, the limit fuel speed calculated per the steel band unit is connected in order to calculate center speed limit schedule with a horizontal axis as a steel band longitudinal position, acceleration and deceleration rate is corrected at a point where center speed is changed to a threshold or more in the center speed limit schedule, rescheduling for calculating the center speed limit schedule based on the corrected acceleration and deceleration is conducted by the center speed limit schedule is converged and center speed is controlled according to the finally calculated center speed limit schedule and the acceleration and deceleration rate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method and an apparatus for controlling the central speed of a continuous heat treatment line for controlling the central speed of the continuous heat treatment line.

  In a continuous heat treatment line that inserts a coiled metal strip (hereinafter also referred to as a steel strip) and manufactures products with different dimensions and materials according to the customer's order, the product is continuously secured while maintaining a predetermined material. In order to maximize the metal band conveyance speed (hereinafter, also referred to as line speed, furnace speed, or simply speed) in the heat treatment line, techniques for controlling the plate temperature and speed have been disclosed so far.

  For example, the “Line speed acceleration / deceleration rate automatic setting system in the continuous annealing line” of Patent Document 1 describes that when the line speed change operation is performed by the operator, the plate temperature control circuit responds to an operation condition change processing command. The deceleration rate is repeatedly set and calculated at a predetermined cycle, and the setting calculation result is periodically returned to the line control circuit as an acceleration / deceleration rate control signal. The line control circuit sets the line speed and combustion amount based on the acceleration / deceleration rate control signal. And a method for outputting a line speed change command to the line speed control mechanism and a combustion amount change command to the furnace condition change control mechanism is disclosed.

  In addition, the “central speed control method for continuous processing line” in Patent Document 2 describes the input side looper restriction speed received from the input side looper capacity and the furnace load when metal strips of different varieties and dimensions are transferred between the loopers. The central restriction speed received from capacity, soaking time, overaging treatment time, etc., the outgoing looper restricted speed received from the outgoing looper capacity, the maximum and minimum speeds on the equipment such as motor capacity, and the operator setting Predict the common constrained speed received from the upper and lower speed limits and the speed change timing to satisfy all these speeds, and the tail end passes after the tip of the metal band reaches the constrained range where each constrained speed is added In the meantime, a method of changing the speed of the central speed so as to reach the maximum speed satisfying all the restricted speeds is disclosed. The speed determined based on the constraint condition (line speed determined so as to satisfy the constraint condition) is hereinafter referred to as the constraint speed.

  Further, the “speed control method, apparatus, and computer program for continuous heat treatment equipment” disclosed in Patent Document 3 includes restrictions on equipment capacity in each heat treatment furnace and manufacturing specifications including the width and thickness of the metal strip. Based on the conditions, calculate the theoretical constraint speed of each heat treatment furnace using the mathematical model of each heat treatment furnace, create a speed schedule based on the speed change timing and speed change rate of multiple patterns prepared in advance, and each speed Method for determining speed change timing and speed change rate using evaluation function including plate temperature, target plate temperature, and speed change rate obtained by simulator simulating each heat treatment furnace included in heat treatment equipment for schedule Is disclosed.

JP 2003-226911 A Japanese Patent No. 2910506 Japanese Patent No. 4833614

  However, the above prior art has the following problems.

  That is, when the line speed changing operation of Patent Document 1 is performed, the technique of sequentially changing the acceleration / deceleration rate does not perform a predictive calculation based on the constrained speed schedule that is the theoretical maximum speed. As a result of sequentially changing the acceleration / deceleration rate according to the results, there is a concern that the production efficiency may be hindered.

  In the technique of changing the speed of the central speed so as to reach the maximum speed satisfying all the restricted speeds in Patent Document 2, the line speed and the plate thickness are used to determine the acceleration / deceleration rate. The speed change width, which is the absolute value of the difference between the speed and the speed after the speed change, is not considered. Therefore, there is a concern that the plate temperature may deviate from the target value in the case where the speed change width becomes large even at the same acceleration / deceleration rate.

  Furthermore, the technology of calculating the speed change timing and the speed change rate by calculating the neck speed schedule from the equipment capacity and coil specifications of Patent Document 3 and performing the plate temperature prediction simulation based on the schedule, Dynamic constraints other than heat treatment equipment such as outage time and looper consumption have not been taken into account, so the optimum addition to prevent the plate from coming off when an unexpected pattern of operation is performed. There is no guarantee that the deceleration rate is set, and there is a concern that the plate temperature may be out of the threshold. Further, there is no guarantee that the plate temperature simulation sufficiently shows the actual plate temperature behavior.

  The present invention has been made in view of such a conventional problem, and even when acceleration / deceleration with a large speed change width occurs, it prevents the plate temperature from falling off, and by setting a necessary and sufficient acceleration / deceleration rate, It is an object of the present invention to provide a method and an apparatus for controlling the central speed of a continuous heat treatment line capable of achieving the maximum production efficiency capable of guaranteeing quality.

  The above problems can be solved by the following invention.

[1] In a continuous heat treatment line with loopers on the entry and exit sides and heat treatment equipment arranged between these loopers,
Based on the equipment capacity restriction conditions of the continuous heat treatment line and the quality assurance restrictions attributed to the quality of the steel strip, the restricted furnace speed is calculated for each steel strip,
By connecting the constrained furnace speeds obtained in units of steel strips in order, the central speed constraint schedule is obtained with the horizontal axis as the steel strip longitudinal position,
The acceleration / deceleration rate is corrected at the point where the central speed is changed to a threshold value or more in the central speed constraint schedule,
Rescheduling to find the central speed constraint schedule based on the corrected acceleration / deceleration rate until the central speed constraint schedule converges,
A central speed control method for a continuous heat treatment line, wherein the central speed is controlled according to a finally determined central speed restriction schedule and acceleration / deceleration rate.

[2] In the central speed control method of the continuous heat treatment line as described in [1] above,
In correcting the acceleration / deceleration rate,
A central speed control method for a continuous heat treatment line, wherein an acceleration / deceleration rate corresponding to a heat treatment condition is set to a table value from a predetermined table, or a calculation formula using a time constant in temperature change of heat treatment equipment is used.

[3] In a continuous heat treatment line with loopers on the entry and exit sides and heat treatment equipment arranged between these loopers,
Based on the equipment capacity constraint condition of the continuous heat treatment line and the quality assurance constraint condition caused by the quality of the steel strip, means for calculating the restricted furnace speed in steel strip units,
Means to connect the constrained furnace speed obtained in units of steel strips in order, and to obtain a central speed constraint schedule with the horizontal axis as the steel strip longitudinal position,
Means for correcting the acceleration / deceleration rate at a point where the central speed is changed to a threshold value or more in the central speed constraint schedule;
Means for rescheduling the central speed constraint schedule based on the corrected acceleration / deceleration rate until the central speed constraint schedule converges;
A central speed control device for a continuous heat treatment line, comprising a central speed restriction schedule finally obtained and means for controlling the central speed in accordance with an acceleration / deceleration rate.

[4] In the central speed control device for the continuous heat treatment line according to [3] above,
In the means for correcting the acceleration / deceleration rate,
A central speed control device for a continuous heat treatment line, comprising a table in which acceleration / deceleration rates according to heat treatment conditions are determined in advance, or a calculation formula using a time constant in changing the temperature of heat treatment equipment.

  According to the present invention, the acceleration / deceleration rate is dynamically changed according to the speed change width of the central speed, so that the temperature can be prevented from falling off and the quality can be guaranteed by setting the necessary and sufficient acceleration / deceleration rate. Maximum production efficiency can be achieved.

It is a figure which shows an example of the equipment row | line of the continuous heat processing line to which this invention is applied. It is a figure which shows the process sequence example in the central speed control method of the continuous heat processing line which concerns on this invention. It is a conceptual diagram explaining correction of a central speed restriction schedule. It is a figure which shows the central speed restrictions schedule before and behind correction of an acceleration / deceleration rate.

  FIG. 1 is a diagram showing an example of an equipment row of a continuous heat treatment line to which the present invention is applied. Furthermore, FIG. 2 is a figure which shows the example of a process sequence in the central speed control method of the continuous heat processing line which concerns on this invention.

  In FIG. 1, 1 is a payout reel (payoff reel), 2 is an entry side equipment, 3 is an entrance side looper, 4 is a heat treatment equipment, 5 is an exit side looper, 6 is an exit side equipment, 7 is a take-up reel (tension reel) ) And 8 represent process computers, respectively.

  A coil (hereinafter also referred to as a metal strip or a steel strip) is delivered from a delivery reel 1 provided at the forefront of the continuous heat treatment line. At this time, in order to continuously heat-treat steel strips having different plate thicknesses, plate widths, or target plate temperatures, a plurality of pay-out reels 1 (not shown) are provided. A continuous heat treatment is performed as a series of steel strips by welding with a welding machine which is one of the facilities 2.

  Since it is necessary to perform welding with the coil stopped by the welding machine, the entry-side looper 3 stores a steel strip that is sent to the subsequent heat treatment equipment 4 at least during the time required for welding. Usually, an amount of steel strip corresponding to the required welding time is sent to the subsequent stage so that the line speed in the heat treatment equipment 4 can be kept constant during the time required for welding.

  The heat treatment facility 4 is a heat treatment furnace in which any one of a pre-tropical zone, a heating zone, a soaking zone, and a cooling zone is combined in series. The process computer 8 performs furnace temperature control and line speed control so that the steel strip fed from the entry-side looper 3 reaches the target plate temperature.

  The steel strip exiting the heat treatment facility 4 passes through the exit side looper 5, is cut by a cutting machine that is one of the exit side facilities 6, and is wound in a coil shape by the take-up reel 7. Although not shown, a plurality of take-up reels 7 are provided in the same manner as the payout reel 1.

  In order to cut a series of welded steel strips in the cutting machine, and in order to change from the reel that has been wound up to the next reel in the take-up reel 7, the movement of the steel strip has to be stopped. In the exit side looper 5, the steel strip for the amount sent from the heat treatment equipment 4 is stored at least during the time required for stopping. Usually, an amount of steel strip corresponding to the stop time is stored during operation so that the line speed in the heat treatment equipment 4 can be kept constant during the stop time.

  Generally, the time constant in changing the temperature of the heat treatment equipment is larger than the time constant in changing the speed of the central speed, and the unsteady period until the furnace temperature reaches a desired temperature becomes longer. In particular, in a heat treatment facility having a relatively large time constant such as a radiant tube furnace, the difference between the two becomes large.

  And the larger the speed change width, the longer the unsteady period until the furnace temperature reaches the desired temperature, and there is a greater concern that the steel strip temperature to be heated will deviate from the target and the target quality cannot be secured. Become. This tendency is particularly remarkable in a thin steel strip having a thickness of 0.15 mm. From such a problem consciousness, the present invention has been conceived in consideration of the fluctuation range of the central speed.

  The processing procedure in the present invention will be described below with reference to FIG. First, in Step 01, the restricted furnace speed is calculated for each steel strip. Here, the constrained furnace speed, which is the theoretically possible maximum furnace speed, is calculated based on the equipment capacity constraint conditions of the continuous heat treatment line and the quality assurance constraint conditions caused by the quality of the steel strip such as the heat treatment temperature and time.

  Here, the constraint condition resulting from the facility capacity is a constraint condition of the furnace heating capacity (furnace combustion load), the path length in the furnace, the maximum speed associated with the motor limitation, and the looper capacity on the input / output side.

  The constraints caused by the steel strip include steel strip dimensions such as plate thickness, strip width, steel strip insertion length, and split length, as well as the composition and structure of the steel strip, and the target material ( This is a constraint condition of manufacturing conditions such as soaking temperature and soaking time necessary for obtaining (component / structure).

For example, the maximum furnace heating capacity is K (kg / h), the steel strip dimensions are the plate thickness t (m), the plate width w (m), and the density ρ (kg / m ^3). However, if there are no other restrictions, the theoretically possible maximum furnace speed V (m / h) is given by K / (ρ × t × w).

  Actually, it is not possible to determine the restricted furnace speed from a single restriction such as the heating capacity of the furnace, but the restriction on the inlet part of the heat treatment furnace, the heat treatment furnace that is the central part, and the outlet part of the heat treatment furnace. It is preferable to select the maximum furnace speed that satisfies all these constraints.

  There are roughly four types of restricted furnace speeds defined by each restriction, namely, an entry-side restricted furnace speed, a central restricted furnace speed, an outgoing-side restricted furnace speed, and other restricted furnace speeds.

  First, as the input side restricted furnace speed, the restricted furnace speed so as not to become the looper short end (lower limit) at the time of coil switching, the restricted furnace speed to recover the looper after coil switching, and the time required for preparing the inlet side next coil There are constraints such as furnace speed.

  Further, as the centrally constrained furnace speed, there are a constrained furnace speed due to the heating capacity of the furnace, a constrained furnace speed for suppressing throttling by changing the heat pattern, and a constrained furnace speed for securing the in-furnace time.

  In addition, as the outlet side restricted furnace speed, the restricted furnace speed is set so that the looper does not reach the long end (upper limit) when the coil is switched, the restricted furnace speed is used to restore the looper after the coil is switched, and the next use tension reel is prepared for winding. There is a restricted furnace speed to secure time.

  Further, as other restricted furnace speeds, common restricted speeds received from the upper and lower limit speeds set by the operator (for example, restricted furnace speeds for each coil that can be forcibly set by the operator, the operator can be set for the entire continuous coil. Status-restricted furnace speed, etc.), and restricted furnace speed in order to be in time for temperature increase / decrease described later.

  The restricted furnace speed that satisfies all the above restricted furnace speeds is calculated. And each restricted furnace speed is calculated in order about a plurality of different steel strips which are going to be inserted into a continuous heat treatment line.

  Next, in Step 02, a central speed restriction schedule is calculated. Connect the constrained furnace speeds obtained in units of steel strips in order, and obtain a central speed constraint schedule with the horizontal axis as the steel strip longitudinal position.

  In Step 03, it is determined whether the reschedule has converged. This determination step is to determine the end of the process when the schedule is no longer changed when the re-scheduling of the central speed restriction schedule is repeated. If the previous Step 02 is the central speed constraint schedule obtained first, the process proceeds to the next Step 04 unconditionally.

  In Step 04, it is determined whether or not the speed change width at acceleration / deceleration is greater than the threshold value. At the point of changing the central speed, a speed change width (absolute value of the speed change amount) is calculated, and if this speed change width exceeds a predetermined threshold value, the acceleration / deceleration rate is corrected.

  FIG. 3 is a conceptual diagram illustrating the correction of the central speed constraint schedule. FIG. 3 (a) shows the central speed restriction schedule obtained in Step 01, and FIG. 3 (b) shows the time point at which the acceleration / deceleration rate should be corrected or not corrected.

  In the central speed restriction schedule of FIG. 3 (a), there are three places (acceleration / deceleration start 1 to 3) where acceleration or deceleration is performed, but the speed change width of acceleration / deceleration exceeds a predetermined threshold, the steel strip longitudinal direction These two points indicate that the acceleration / deceleration rate is to be corrected (see FIG. 3B).

  If the threshold value is not exceeded in Step 04, the process is terminated. If the threshold value is exceeded in Step 04, the acceleration / deceleration rate is corrected in Step 05. In the correction of the acceleration / deceleration rate, the acceleration / deceleration rate corresponding to the size of the steel strip and the heat treatment condition is set as a table value from a predetermined table, or the time constant in the temperature change of the heat treatment equipment is used, for example, ( The acceleration / deceleration rate is calculated according to equation (1).

  FIG. 4 is a diagram showing a central speed restriction schedule before and after the acceleration / deceleration rate is corrected. FIG. 4 (a) shows a central speed restriction schedule before the acceleration / deceleration rate is corrected. The portion where the speed fluctuation width at the center of the steel strip longitudinal position is small is not subject to correction, and the acceleration / deceleration portions on both sides are not subject to correction. It is a correction target. In the central speed restriction schedule after the acceleration / deceleration rate correction in FIG. 4B, the acceleration / deceleration rates in the correction targets on both sides are corrected to be small.

  Although FIG. 4B shows an example in which only the acceleration / deceleration rate is changed, in actuality, changing the acceleration / deceleration rate changes the storage / consumption amount of the looper and the arrival timing of the heat treatment equipment. Review (rescheduling) is required. Therefore, after correcting the acceleration / deceleration rate in Step 05, rescheduling after Step 06 is performed.

  Step 02 Iterates from the central speed restriction schedule until it becomes Yes in Step 03 or No in Step 04, and the central speed according to the finally obtained central speed restriction schedule and acceleration / deceleration rate is determined. Based on the determined central speed, the central speed of the heat treatment equipment is controlled.

  Note that the rescheduling convergence determination in Step 03 is performed because the difference between the acceleration / deceleration start and end points before and after rescheduling is within a certain range.

DESCRIPTION OF SYMBOLS 1 Dispensing reel 2 Entry side equipment 3 Entry side looper 4 Heat treatment equipment 5 Delivery side looper 6 Delivery side equipment 7 Take-up reel 8 Process computer

Claims (4)

In a continuous heat treatment line with loopers on the entry and exit sides and heat treatment equipment arranged between these loopers,
Based on the equipment capacity restriction conditions of the continuous heat treatment line and the quality assurance restrictions attributed to the quality of the steel strip, the restricted furnace speed is calculated for each steel strip,
By connecting the constrained furnace speeds obtained in units of steel strips in order, the central speed constraint schedule is obtained with the horizontal axis as the steel strip longitudinal position,
The acceleration / deceleration rate is corrected at the point where the central speed is changed to a threshold value or more in the central speed constraint schedule,
Rescheduling to find the central speed constraint schedule based on the corrected acceleration / deceleration rate until the central speed constraint schedule converges,
A central speed control method for a continuous heat treatment line, wherein the central speed is controlled according to a finally determined central speed restriction schedule and acceleration / deceleration rate. In the central speed control method of the continuous heat treatment line according to claim 1,
In correcting the acceleration / deceleration rate,
A central speed control method for a continuous heat treatment line, wherein an acceleration / deceleration rate corresponding to a heat treatment condition is set to a table value from a predetermined table, or a calculation formula using a time constant in temperature change of heat treatment equipment is used. In a continuous heat treatment line with loopers on the entry and exit sides and heat treatment equipment arranged between these loopers,
Based on the equipment capacity constraint condition of the continuous heat treatment line and the quality assurance constraint condition caused by the quality of the steel strip, means for calculating the restricted furnace speed in steel strip units,
Means to connect the constrained furnace speed obtained in units of steel strips in order, and to obtain a central speed constraint schedule with the horizontal axis as the steel strip longitudinal position
Means for correcting the acceleration / deceleration rate at a point where the central speed is changed to a threshold value or more in the central speed constraint schedule;
Means for rescheduling the central speed constraint schedule based on the corrected acceleration / deceleration rate until the central speed constraint schedule converges;
A central speed control device for a continuous heat treatment line, comprising a central speed restriction schedule finally obtained and means for controlling the central speed in accordance with an acceleration / deceleration rate. In the central speed control device of the continuous heat treatment line according to claim 3,
In the means for correcting the acceleration / deceleration rate,
A central speed control device for a continuous heat treatment line, comprising a table in which acceleration / deceleration rates according to heat treatment conditions are determined in advance, or a calculation formula using a time constant in changing the temperature of heat treatment equipment.