Yuantuo carbon steel and low-alloy steel bar quenching & tempering line is designed for continuous induction quenching and tempering of round steel bars with diameter from φ40 to φ105 mm and length from 3 to 12.3 m. In heat treatment industry, quenching and tempering temperature directly determine the metallographic structure, hardness and mechanical properties of finished products. Traditionally, operators judge temperature by observing the color of hot steel bars and adjust equipment parameters manually based on practical experience. This manual control mode is highly subjective with large measurement errors. During mixed production of multi-specification steel bars, temperature fluctuation often occurs, resulting in uneven hardness and abnormal metallographic structure. Meanwhile, core processes rely heavily on senior technicians, and staff turnover may lead to process interruption, which is a common industry problem. To solve the above pain points, Yuantuo steel bar quenching & tempering line is standardly equipped with two sets of infrared temperature measurement systems and main PLC console, which are linked to build a full-automatic closed-loop temperature control system and completely get rid of dependence on manual experience.

On this Yuantuo induction quenching and tempering line, two independent infrared temperature measurement systems are installed at the induction heating section for quenching and the induction heating section for tempering respectively. The devices collect real-time surface temperature data of steel bars around the clock, accurately monitoring the quenching temperature range of 800–950 °C and tempering temperature range of 500–700 °C. Compared with manual visual temperature judgment, infrared temperature measurement is not affected by workshop light, viewing angle and human factors. It features high detection accuracy and fast signal response, providing reliable data support for automatic regulation.

Real-time temperature signals collected by infrared temperature measurement devices are transmitted to the main PLC console to implement closed-loop automatic control. Once the measured temperature deviates from the preset process value, the PLC will automatically send control commands to dynamically adjust the output power of IGBT induction heating power supplies, as well as the operating speed of variable-frequency idler rollers on feed roller tables and conveying roller tables. When the temperature is too high, the heating power is reduced and the conveying speed is increased; when the temperature is too low, the power is raised and the conveying speed is decreased. The whole regulation process runs automatically without manual intervention, keeping steel bars within the standard temperature range stably.

The built-in PLC control system has complete functions, which supports setting, storage, adjustment, modification and statistics of 20 groups of process parameters. For different steel grades such as bearing steel, spring steel, 42CrMo, 35CrMoA, 40Cr and 45# steel, as well as round steel bars in four diameter ranges, technicians can input and classify corresponding process parameters in advance. When switching production specifications on Yuantuo steel bar tempering line, operators only need to call preset parameters with one click. The equipment can quickly match the temperature control logic and conveying rhythm, greatly shortening the commissioning time for product changeover and fully meeting the demands of multi-variety and mass continuous production.

Benefiting from the automatic temperature control scheme of linked infrared temperature measurement and PLC, Yuantuo induction heating tempering line realizes standardized heat treatment processes. Unified temperature control standards effectively avoid quality defects such as local overheating and performance deviation, and keep product quality stable. Digitally stored process parameters are permanently preserved to prevent technology loss, supporting large-scale and standardized production of enterprises.