[b]1 Introduction[/b] The automated control system for the No. 1 80-ton converter in the Laiwu Steel Yinshan Qianqu area comprises seven subsystems: converter body, vaporization cooling, bulk material feeding, ferroalloy feeding, circulating water pump station, dry dust removal, and gas recovery. Each subsystem is controlled by a SIMATIC S7-400 series PLC. PLCs communicate with each other and with HMIs via industrial Ethernet, while PLCs communicate and control with field distributed I/O and frequency converters via PROFIBUS-DP bus. The secondary system manages the converter system and issues timely steelmaking plans and commands. 2 System Composition 2.1 Overview of Converter Control The Laiwu Steel Yinshan Qianqu No. 1 80-ton converter production line has a designed capacity of 800,000 tons/year. The level of its automation control directly affects product quality. Achieving intelligent automatic control of the converter plays a crucial role in reducing energy consumption, improving product qualification rate, and reducing the labor intensity of workers. The steelmaking production line mainly controls the weighing and addition of bulk materials and ferroalloys, the tilting of the converter body, the raising and lowering of the oxygen lance, the application of steelmaking media, the circulation, cooling, and purification of circulating water, and the absorption, cooling, dust removal, and pressurized storage of steelmaking flue gas. The process of bulk materials moving from the underground receiving silo to the high-level silo is called the bulk material feeding system; the process of moving from the high-level silo to the collection hopper and into the converter is called the bulk material charging system. Each converter's bulk material charging system has 10 high-level silos, each equipped with a vibrating feeder. The system also has three weighing hoppers and two collection hoppers (with weighing functions). The weight of the bulk materials is measured by the weighing hoppers, and the required amount can be provided by computer based on the steelmaking raw material conditions or set manually. When the converter oxygen lance descends and oxygen blowing begins, the signal for adding the first batch of bulk materials is given, and the second batch of billets is weighed; when the oxygen blowing rate reaches the preset oxygen level (30-40%), the signal for adding the second batch of bulk materials is given. Pressing the automatic button automatically adds various bulk raw materials in batches. The ferroalloy charging system includes 20 high-level silos and 6 weighing hoppers. After baking, the ferroalloy material is weighed according to set values ​​and then added to the converter based on production needs. The converter body primarily achieves molten iron addition, scrap steel addition, steel tapping, and slag removal through tilting. Oxygen lance lifting and lateral movement enable oxygen blowing for steelmaking and nitrogen blowing for slag splashing and furnace protection. The system allows for rapid, slow, and reverse tilting of the converter based on its tilting angle. It also features a torque self-balancing function for converter tilting and an automatic oxygen lance return function in case of steelmaking medium safety parameter failures. The waste heat boiler vaporization cooling system mainly controls the accumulator water supply valve, low-pressure forced circulation pump, medium-pressure forced circulation pump, deaerator emergency drain valve, chemical dosing pump, solution agitator, and other equipment. It achieves the circulation, cooling, and purification functions of the converter steelmaking water medium. The circulating water supply covers the entire converter area and continuous casting area. Dry dust removal control mainly adjusts the fan speed, the intake of converter flue gas, the temperature of the evaporative cooler, the electrostatic precipitator, the coarse ash conveying system, the fine ash conveying system, and the gas cooler to cool the recovered gas, based on the converter smelting conditions. By controlling the interlocking operation of the gas compressor and the regulating valves before and after the compressor, pressurized gas storage is achieved to meet the production requirements for gas absorption and supply. 2.2 System Composition: The system hardware configuration adopts the SIEMENS WinCC/S7-400 control system. This control system is an open system built on the S7-400 controller and Pentium IV industrial computer platform. The S7-400 is a modular large-scale PLC system using standard Ethernet communication. The DELL industrial computer uses a 2.5GHz Pentium IV CPU, 512MB SDRAM memory, and an 80GB UltraSCSI interface hard drive. The S7-400 controller and the industrial computer communicate via Ethernet at a rate of 100Mbps, using multimode fiber optic connection. The converter body, vaporization cooling, bulk material feeding, ferroalloy feeding, circulating water pump station, dry dust removal, and gas recovery stations (each station includes a power module, one CPU, one CP443 communication interface module, and a varying number of analog input, analog output, digital input, and digital output modules) adopt industrial Ethernet ring network communication, a client and redundant server structure, with a total of two servers, 11 clients, and 8 frequency converters. The frequency converters and controllers use PROFIBUS-DP communication. (See Figure 1) [b]3 Automatic Control System Control Method and Control Difficulties:[/b] 3.1 Engineering Station Based on SIMATIC STEP7 programming software, the engineering station completes the hardware configuration, address and station address allocation of the 7 PLC station systems, as well as the design, development, and debugging of user programs. The program design adopts modular and structured programming, using OB, FC, FB blocks and related data blocks DB to form the entire control system, and anti-interference measures are adopted in the software design. 3.2 Operator Station The operator station serves as the human-machine interface for the entire system. It utilizes a general-purpose industrial PC and is equipped with SIMATIC WinCC screen configuration monitoring software. Process monitoring of field equipment is achieved via Ethernet. WinCC enables dynamic display of process data, parameter setting, and operation control. It also features process information archiving, sequential display of alarm information, and report printing, providing strong real-time performance. 3.3 Key Control Challenges 1) Furnace Body Tilting The converter body PLC station primarily handles the furnace door operation and furnace body tilting, furnace tilting and ladle/slag removal operations, hood lifting and lowering operations and cooling water flow and pressure control, oxygen lance lifting and lowering operations and oxygen lance positioning and cooling water flow and pressure interlock control, oxygen lance lateral movement and lance changing operations, material loading and weighing, and feeding operations. It also collects real-time data on temperature changes at 48 temperature measurement points in the water-cooled systems (converter water-cooled hood, water-cooled furnace wall, water-cooled oxygen lance, etc.) and monitors and alarms for over-limit and accident events related to cooling water system pressure and flow. Real-time data transmission between the PLC and the operator station is achieved via Ethernet, with production process monitoring completed through a human-machine interface. The load balancing of the four converter tilting motors was the most technically challenging aspect of the project, requiring high-speed response, high control precision, and high safety and reliability. The drive control device used in the design is the Siemens MASTERDRIVE 6SE70 series all-AC frequency converter, which, in conjunction with Siemens' PLC, PROFIBUS-DP, and SIMO-LINK communication network, constructs a high-performance drive system. This fully leverages the multi-functionality and high performance of Siemens products, effectively solving the technical difficulties and significantly improving the response speed of the converter tilting system. The converter tilting is operated from two locations: the main control room in front of the furnace and the control room behind the furnace. Only one of these two locations can be operated at a time. A command conversion switch is installed in the main control room. The converter tilting operation includes fast, slow, forward/reverse, and signal displays, as well as a furnace tilt angle display. The converter tilting speed is 0.12 r/min to 0.998 r/min, and the converter operates with full positive torque. The maximum tilting torque is 240 ton-meters. 2) Oxygen Lance Positioning: The oxygen lance system is a dual-cart, dual-hoist system, with one set in operation and the other on standby. The oxygen lance lifting is driven by an AC motor with variable frequency speed control. The lifting speed is 40 m/min for fast and 5 m/min for slow. In case of power failure, the lance is lifted using a pneumatic motor. The CRT displays the actual lance position, which can be controlled via a computer keyboard. Oxygen lance position control has two modes: automatic and manual. The automatic mode uses a PLC and automatically operates according to the set lance position. In manual mode, if the automatic mode malfunctions, the instruction conversion switch on the control panel is used. After receiving the lowering command, the oxygen lance quickly descends from the waiting position (+16.00 m) to the oxygen start point (+14.20 m), at which point the oxygen quick-cut-off valve automatically opens to supply oxygen. It descends to the speed change point (+12.20 m) and then slows down until it reaches the blowing point (0.30-10.00 m). Upon receiving the lifting command, the oxygen lance is quickly lifted to the oxygen shut-off point (+12.20m), where the oxygen cut-off valve automatically closes, stopping oxygen supply. It then quickly rises to the speed change point (+15.30m), slowly rises to the waiting position (+16.00m), and stops lifting. Upon receiving the replacement lifting command, the oxygen lance quickly rises from the waiting position (+16.00m) to the speed change point (+21.00m), slows down to the replacement position (+24.9m), and automatically replaces the lance. Upon receiving the pressing command, it slowly descends from the replacement position to the speed change point (+21.00m), quickly descends to the speed change point (+16.50m), and slowly descends to the waiting position (+16.00m), stopping lowering. When the tension of a single hoist wire rope is ≥6 tons, the lance automatically interlocks and stops. After the oxygen lance is activated, both the lance raising/lowering and the furnace tilting are locked. The system must be switched to maintenance mode or manually positioned before the lance can be moved. The furnace tilting can only be moved after the interlock is released. Once the lance activation condition is resolved, the activation unlock button can be clicked to restore the linkage operation. 4. Main Technologies and Functions 4.1 Multi-Client Technology The multi-client architecture allows one client to access data from multiple servers; it also allows multiple clients to access several servers simultaneously. Operations can be completed concurrently. Project data, process variables, archived data, alarms, and messages are all obtained from the multi-client servers. This allows data to be distributed across several servers, with multiple clients accessing it through a common operation, thereby improving system availability. 4.2 Redundant Server Technology The redundancy option enables two redundant WinCC servers to run simultaneously to ensure continuous process and operator control. If one of the two stations fails, the other takes over report transmission and process value archiving. When the failed station resumes operation, all process value archives and messages collected while that station was not operating are copied to the now-operating station. Thus, two identical WinCC stations can once again run simultaneously. This concept is used to configure all process value files and messages under redundant management, thus ensuring data integrity. In client/server mode, the client automatically switches from a failed server to a redundant cooperating station. After a short switching cycle, all running stations resume operation. To simplify configuration, a project replicator can be used, which copies all configuration data to the cooperating stations and matches them accordingly. 4.3 PROFIBUS Fieldbus Technology Communication between the controller and the frequency converter adopts PROFIBUS-DP. PROFIBUS fieldbus is the most widely used fieldbus technology in the world, mainly including the high-speed bus PROFIBUS-DP (H2) with a maximum baud rate of up to 12 MHz and the intrinsically safe low-speed bus PROFIBUS-PA (H1) for process control. The perfect combination of DP and PA makes PROFIBUS fieldbus superior to other fieldbuses in terms of structure and performance. Replacing a large number of traditional transmission cables with a pair of twisted-pair wires greatly saves cable costs and reduces the failure rate. 4.4 Ethernet Ring Network Communication Technology The S7-400 controller and DELL industrial computer adopt an Ethernet ring network with a communication rate of 100Mbps, using multimode fiber optic connection. All controllers are connected to the Ethernet ring network, and the ring network forms a loop in the field. If a point on the ring network breaks for some reason, the controller can communicate in another direction without affecting the normal operation of the system. [b]5 Conclusion[/b] Since its commissioning, the system has been operating stably and reliably. The implementation of this computer control system, with its advantages of high performance, high reliability, small size, low price, powerful computing function, and ease of implementing complex control functions, has effectively improved product quality and output, saved a large amount of electricity and water resources, reduced environmental pollution, extended equipment lifespan, reduced labor intensity for workers, and improved the operating environment. References 1 Li Leting, Wang Hongcai. *Design Manual for Process Detection and Control Automation in Iron and Steel Enterprises*. Beijing: Metallurgical Industry Press, 2000. 2 Wang Changli, Liao Daowen. *Design and Application of Distributed Control Systems* [M]. Beijing: Tsinghua University Press, 1993. Edited by: He Shiping