Abstract : This paper addresses the problem of unstable casting speed in the continuous casting straightening machine at the TianTie Group steelmaking plant, and proposes specific improvement solutions. The adoption of Emerson frequency converters has resolved issues such as low control accuracy, poor stability, and low reliability, achieving good results. Keywords : Frequency converter, straightening machine, continuous casting, torque, frequency, overload modification 1 Introduction The No. 3 and No. 4 continuous casting machines at the TianTie Group steelmaking plant were put into operation in 1996. They are standard 6m arc-shaped continuous casting machines, with a Snecker straightening machine as the straightening machine. Each machine has only one drive motor, controlled by a 6SE7021-8EB10 series Siemens frequency converter. Instable casting speed frequently causes significant fluctuations in the liquid level within the crystallizer, hindering the normal formation of the billet shell. Leakage and overflow occur frequently, resulting in slag inclusions and uneven resistance in the produced billets, severely impacting continuous casting production efficiency and economic benefits. 2 Cause Analysis and Improvement Suggestions After extensive analysis and verification, the main factor restricting production is the heart of the continuous casting equipment—the straightening machine. Due to its chain drive, there is a transmission gap. This is the direct cause of unstable casting speed. Furthermore, the inverter's input and output control uses analog signals, resulting in low stability and reliability in stand-alone operation. This is particularly evident in: ① Inconvenient operation via English symbol menus; ② The only control method for running commands is external terminal control, relying on field selector switches to input switching signals. If the selector switches malfunction or have poor contact, the inverter will have difficulty starting and stopping, or may stop during operation; ③ Frequency setting relies on analog input terminals to input 0-10V DC voltage signals. Since analog signals are not suitable for long-distance transmission, this is a major factor contributing to unstable speed regulation; ④ The modified casting leveling machine was changed from being controlled by one inverter to being controlled by three inverters. These three inverters need to be synchronized. Siemens inverters cannot achieve this. In June, the TianTie Group Steel Plant and Hangxing Company jointly developed a continuous casting optimization system. The casting leveling machine is a double-frame 5-roll casting leveling machine with three drive motors and gear transmission, solving the constraints of the primary equipment. The No. 2 Continuous Casting Workshop and the Instrumentation and Electrical Workshop of the Steel Plant were responsible for the design, replacement, and installation of the electrical system. Emerson frequency converters, known for their high technology and cost-effectiveness, are widely used in metallurgical machinery due to their high-performance vector control technology and powerful network support. They achieve high-precision speed control, torque control, and position control for potential loads and loads with large dynamic changes. The following issues have been effectively addressed: ① They feature a Chinese menu, and parameters can be uploaded, copied, downloaded, and overwritten. ② Running commands are controlled via a built-in RS485 communication interface. Only one pulse signal is needed from the PLC to communicate with the frequency converter, and multiple frequency converters can be controlled simultaneously with reliable operation. ③ Frequency settings are also transmitted via PLC data. The PLC can receive field resistance signals without interference, ensuring synchronous operation of three frequency converters. [b][align=center]For more details, please click: Application of Emerson Frequency Converters in Continuous Casting Production[/align][/b]