# Steelmaking - continuous casting production schedule control system research

[Abstract] efficient steelmaking - continuous casting production schedule control system for steel enterprises to improve productivity is important. In this paper, a large steel company continuous casting production scheduling problem, a process characteristics of the company with the schedule model, combined with the equipment, parts, orders due to dynamic events, the development progress of the control system. The actual data tests to demonstrate the effectiveness of the algorithm and control the system's utility.

## 1 Introduction

Iron and steel manufacturing process, steelmaking - continuous casting process for ensuring coordination between the continuity and stability of production has a very important influence. Therefore, many domestic and foreign experts conducted in-depth study of the issue. Li CY, etc. BOF, refining and continuous casting process as the research object, the establishment of an order for steelmaking - continuous casting plan optimization mathematical model, and with two stage heuristic algorithm to solve the model [1]. Liu Hang, LI Tie-grams have parallel machine for multi-stage production environment, the establishment of comprehensive consideration heats equipment assignments and job sorting mixed integer linear programming model is proposed for the practical application of the heuristic algorithm to match the device heats and ease the resource assignment rules conflict [2]. Tian Zhibo other matching against non-commissioned slab, established a multi-objective optimization of 0-1 integer programming model [3]. Numao and Morishita expert system used in steelmaking and continuous casting production scheduling, and improve the continuous casting ratio [4]. Ivan Ferretti wait for the casting floor stock cooling problem, a solution model and the use of ant colony algorithm, making the production levels were significantly improved [5]. Cowling, etc. Multi-Agent method used to develop the dynamic scheduling scheme rolling mill, according to real-time information and to schedule an emergency repair [6].

## 2.1 Problem description and analysis

A new company on a wide plate (PM) casting machine, a LF refining furnaces, a RH refining furnace. Since the original CSP production line and production of PM is different, some still need to go through two refining molten steel, resulting in increased difficulty scheduling papers converter download.

According to Figure 1, A company has two converters, three refining furnace, two continuous casting machines. 2 caster shared two converter provides steel, RH refining furnace is mainly for special steel for refining. As a # # BOF converters and two shared a crane lifting scrap and molten iron, so two converter starts blowing time difference of at least 15 minutes. 1 # refining furnace 1, 2, 2-position, but share a heating device, therefore, a # refining furnace two-station is only five minutes at most refining time overlap, 2 # refining furnace is also true. In addition, from the converter to the casting of the molten steel storage tank between machines bits is limited.

## 2.2 Scheduling Model

According to Company A continuous casting process route and the characteristics of each process, the establishment of the schedule model. For convenience introduce the following notation:
i is the order number of the furnace, i = 0,1,2, ..., N; j the device serial number, j = 1,2, ..., 7, respectively converter number 1 No. 2, converter, East refining LF1, LF2 refined East Western Refining LF1, West refining LF2, RH furnace; k is step number, k = 1,2,3,4, respectively, blowing, LF refining, RH refining, casting; n is placed between the converter to the molten steel casting machine the total number of cans; di pouring times as i planned to reach casting machine heats the expected time; Q is pouring in through the second sub-set of RH refining furnace; P is pouring times in RH refining furnace without a second collection; Ti , k is the k i furnace process in the processing time; t12 is the converter to the transit time of LF; t23 is in LF to RH furnace transit time; t24 LF furnace to the casting machine is the transit time; t34 is RH furnace to cast machine transport time; SIj, ki is the device i j tight heats after heats; SMi, j is the j i on the device after the device heats tight; Yi, k is the k i furnace process start time; Sk k is the process of adjustment time; N is the total number of furnaces by pouring the pilot program to determine, Xi, j i j in times when the furnace processing device 1, and 0 otherwise.

## Objective function:

Wherein the formula (1) represents the case of continuous casting continuously poured, pouring the last start time of a furnace and the first smelting furnace start time is minimum, is Minimizing the Make-Span. Equation (2) represents any one workpiece is being blowing and only once, once refined, cast again. Equation (3) any device that heats the starting time of two adjacent intervals of not less than the machining time of a furnace and the sub-time, and adjust the machine. Equation (4) means that each furnace LF refining furnace and converter on the difference between the start time is not less than the heats blowing time and from the converter to the LF refining furnace and transport time. Equation (5) means that each furnace LF refining furnace casting machine and the start time is not less than the difference between the heats of LF refining time and from LF refining furnace to the casting machine and transport time. Equation (6) means that each furnace RH refining furnace casting machine and the start time is not less than the difference between the heats of the RH refining time and from RH refining furnace to the casting machine and transport time. Equation (7) represents LF refining the casting time is less than the total processing time of delivery. Equation (8) represents the casting from the LF refining the processing time is less than the total delivery time. Equation (9) represents any one of two adjacent device heats the start time interval is not less than the machining time of a furnace and the sub-time, and adjust the machine. Equation (10) is pot position constraint, that the converter and continuous casting machine molten steel between the maximum number of cans stored number n. Equation (11) is parallel converter constraints, which means that if two conditions converter also have against the iron, the latter against the iron converter wait at least 15 minutes before start against the iron. Equation (12) is parallel constraint refining furnace, refining furnace represents a # and 2 # refining furnace respective two stations at most five minutes of overlap time.

## 2.3 processing time deviation from the plan

Dynamic event processing time deviation from the plan, when the steel composition or temperature does not comply, change orders three kinds. This article analyzes the processing time when the deviation from the plan, the system how to handle this dynamic event. Processing time deviation from the plan, there are two situations in advance and delay.

(1) When a workpiece is processed ahead of time, Ti, k becomes small, i.e. k i furnace shortened machining processes. If the job is on the critical path (ie, the relaxation time of the device is zero), then according to the furnace immediately after the heats and after tightening devices FF (front to a free safety time, free safety time that a device or piece of relaxation time) determine the minimum value. FF is calculated as:

## After tightening heats heats FF = tight after the earliest start time - end time of the latest current workpiece - machine adjustment time;

FF = tight tight after the device heats after the earliest start time - end time of the latest current device - transit time.
When the lead time is less than tight after heats (SIj, i) and after tightening device (SMi, j) of the FF minimum, then the job after the sequence job chain (from tight tight after the device or start a job after heats chain) start time pan forward until it encounters the FF 0 jobs. When the time is greater than or equal to the advance after the heats and tight after tightening devices FF minimum value, then the operation sequence after the start time of the job chain shift forward after tightening after tightening device heats and the minimum value of FF. When the job is not in the critical path is not processed.

(2) When a processing operation is postponed, Ti, k becomes large, i.e. i furnace prolonged processing time of step k. According tight tight after the heats and equipment after BF (free safety time backward) the minimum value judgments, BF is calculated as:

tight after heats the workpiece after BF = tight tight heats after the earliest start time - immediately after the workpiece latest end time - the machine to adjust the time;
BF = tight tight after the device immediately after the workpiece equipment after the earliest start time - immediately after the workpiece latest end time - transit time.

When the delay time is less than or equal to the tight tight after the heats and BF equipment after the minimum, then the sequence after the job start time jobs are backward shift of the extension of time. When the delay time is greater than tight tight after the heats and BF equipment after the minimum, there may be poured off, casting speed must be reduced only solution.

## 3 progress control system to achieve

Schedule control system uses SQL Server database technology needed for progress control actual data storage and processing, the use of VC technology will work rules and job processing method for compiling a software function modules. SQL databases are mainly three functions: First, the database as a data transfer interface, three systems store incoming data in the data table, schedule control system on a regular basis to read the data in the table; Second, the discharge into the schedule database, provide the basis for subsequent research work; Third, the software error information stored in the database. Program using VC + + language, namely the control room personnel, production management and technical personnel and software debugging and monitoring personnel designed the main window, and commissioning schedules statistics window dedicated window. The main window interface to reflect the program's human-computer interaction, clarity, and clearly express the scheduling result. Schedule integrity analysis statistics window including window and evaluation window. Integrity analysis window through the device complete schedule time span into each state unit of time, are classified statistics, enabling managers to more clearly see the status of the production equipment and production rhythm, to provide support for decision-making. Debug debugging windows dedicated window including converter, ladle furnace and casting machine debug window debug window. Schedule control system interface shown in Figure 2.

## 4 Conclusion

Based on the steel-making - continuous casting process characteristics, the establishment of a typical scheduling model and actual production in the case of Company A, the new constraints parallel converter, ladle furnace and tank-bit parallel constraint constraint. Deviation from the plan for the processing time of the dynamic event, presented the calculation of FF and BF. FF based calculation, the problem of processing of the dynamic events ahead of time; BF on the calculation method to solve the processing time delay of the dynamic event. FF and BF with the calculation method, capable of re-scheduling scheduling results, and can effectively reduce the step of rescheduling. The schedule control system is now used in Company A.

## Main references

[1] Li Chong, Su Li Jian, Xie. Orders for steelmaking - continuous casting Planning Optimization Model and Algorithm [J]. Logistics Technology, 2007,26 (10) :62-64.

[2] Liu Hang, Li Tie grams. Steelmaking - Continuous Casting Production Scheduling Model and Heuristic Algorithm [J]. Systems Engineering, 2002, 20 (6) :44-48.

[3] Tianzhi Bo, Tang Lixin, Ren Yiming, et al. Based on synthetic neighborhood did not entrust slab ant colony algorithm matching [J]. Automatica Sinica, 2009,35 (2) :186-192.

[4] M Numao, S Morishita. Cooperative Scheduling and Its Application to Steelmaking Processes [J]. IEEE Transactions on Industrial Electronics, 1991,38 (2) :150-155.

[5] Ivan Ferretti, Simone Zanoni, Lucio Zavanella. Production-inventory Scheduling Using Ant System Metaheuristic [J]. International Journal of Production Economics, 2006,104 (2) :317-326.

[6] P I Cowling, D Ouelhadj, S Petrovic. A Multi-Agent Architecture for Dynamic Scheduling of Steel Hot Rolling [J]. Journal of Intelligent Manufacturing, 2003, 14 (5) :457-470. Links to free download http://eng.hi138.com