Applications
Heat treatment: the key technology for superior performance
Heat treatment furnaces are essential industrial plants used in a wide range of sectors: from the most demanding ones, such as automotive and aerospace, to the most common applications in precision mechanics and tool production. These systems play a crucial role in the transformation of metal products. Through controlled heating and cooling cycles, the metal changes its internal structure, acquiring the mechanical and physical properties required to ensure high performance, reliability and durability.
Requirements:
Thermal process temperature control
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Digital recording of process variables
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High temperature furnace safety threshold
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Control of electrical heating loads
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Measurement of thermal process temperature
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Requirement:
Thermal process temperature control
Temperature is the most critical variable in the heat treatment of metals.
Precise and repeatable control is essential to ensure consistent, high-quality production. This is particularly important in the aerospace and aeronautical sectors, where accuracy must comply with standards such as AMS2750 and CQI-9.
In continuous furnaces, the temperature control system consists of a series of PID controllers, which must precisely manage the individual zones of the furnace. This ensures compliance with the thermal profile required by the metallurgical specifications of the finished product and, consequently, the conformity of the final product.
Solution:
The 1850 PID Controller is the ideal solution for precise and reliable furnace temperature control. Thanks to a highly efficient control algorithm, it ensures compliance with the thermal specifications required by the materials being treated. Certified according to AMS2750 standards for the aerospace industry and CQI-9 for the automotive industry, the 1850 controller is suitable for these applications that require a high level of precision in thermal control.
Main features:
- Control outputs for SSRs and motorised valves
- Colour LCD interface
- Ethernet and serial connectivity (master/slave)
- Multilingual diagnostic messages
- Logic and math functions
Requirement:
Digital recording of process variables
Recording temperatures during heat treatments is essential to ensure the quality and safety of the materials being treated. Accurately monitoring and documenting thermal parameters ensures that the treatment cycle meets the required specifications, preventing defects and variations in the final product.
Furthermore, temperature recording is a fundamental requirement for compliance with industry regulations and standards, such as AMS2750 and CQI-9, which are particularly strict in the aerospace and automotive sectors. This process also allows each production batch to be traced, ensuring total reliability of the production process.
Solution:
Gefran’s solution for recording temperature variables is the 3850T multifunction controller, a device that integrates several features, including an efficient data logger function compliant with ASM2750 and CQI-9 specifications. This function, combined with the Real Time Clock, is capable of storing process data, digital input/output signals and alarm statuses.
Main features:
- Touch screen graphic interface;
- Storage in open or encrypted format;
- Local or Ethernet network file export;
- Data export in CSV or PDF format;
- Remote VNC connection.
Requirement:
High temperature furnace safety threshold
To protect the system and ensure operator safety in the event of overheating, it is necessary to use appropriate devices, known as safety thresholds.
Excessive heat can compromise the integrity of the furnace, damaging heating elements, sensors and refractory linings, with the risk of fire, explosion or mechanical failure. In the event of a malfunction of the primary system and exceeding the set threshold, the safety system automatically intervenes by activating alarms and shutting down the system, preventing damage and protecting personnel.
In the American market, Factory Mutual (FM) regulations require certified devices to guarantee correct operation in the event of the permitted temperature being exceeded.
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The 650L (48×48 format) and 1250L (48×96) safety indicators, certified by Factory Mutual (FM), are devices designed to detect overheating in industrial heating processes and activate a signal that puts the system in safety mode.
To facilitate installation and use, they are supplied with a factory-set configuration ready for use, including an alarm memory function that requires acknowledgement by the operator. Acknowledgement can be made via a dedicated front button (red R), optional digital input or serial line. The LCD display shows clear messages that guide the operator in identifying the status of the system, making intervention simple and immediate.
Main features:
- Factory Mutual (FM) certification for use as a safety indicator in heating processes;
- Industry standard formats: 48×48 (650L) and 48×96 (1250L);
- Retentive alarm function with operator acknowledge;
- Highly legible LCD display;
- Factory configuration ready for use;
- Alarm acknowledge via front button, digital input or serial line.
Requirement:
Control of electrical heating loads
In industrial electric heating, power management is crucial to ensure temperature uniformity, energy efficiency and operational continuity. Applications require systems capable of adapting to different types of loads – from linear resistors to transformers – while maintaining stability even in the presence of process variations. To meet these needs, solutions are required that offer configuration flexibility, advanced diagnostics for predictive maintenance and compatibility with the latest communication protocols.
Effective I/O integration enables signal management, from command retransmission to process variable monitoring.
Finally, the need for installations in confined spaces makes compact and robust systems essential, capable of ensuring safety, efficiency and reduced downtime.
In electric heating, to guarantee treatment temperatures above 1000°C, Gefran offers the Power Controllers of the series GRC, intelligent devices that manage electrical power with precision and efficiency.
Main features:
- Current ratings from 25 to 150 A;
- Single, two-phase and three-phase configurations;
- Configurable control modes;
- Integrated diagnostics;
- Fieldbus connectivity.
Requirement:
Measurement of thermal process temperature
Temperature is the most critical variable in heat treatment processes. Accurate control is essential to ensure the required mechanical properties, process repeatability, compliance with quality standards and operational safety. Temperature probes must operate in high-temperature environments, ensuring stable and continuous measurement. The sheath that protects the sensitive element — usually thermocouples — is fundamental. In addition to withstanding high temperatures, it must also withstand the action of the process atmospheres present in the furnace, as in the case of nitriding. For this reason, it is necessary to choose a suitable coating material that can guarantee reliability and long life.
Solution:
TC6M series temperature probes, equipped with a thermocouple sensing element, are an ideal solution for heat treatment applications with temperatures up to 1000°C. The possibility of choosing the type of thermocouple, the measurement range, the installation length and the sheath material allows for a wide range of uses. For example, an AISI 316 steel sheath is suitable for medium temperatures in non-aggressive atmospheres, while INCONEL 600 alloy (nickel-chromium-iron based) is more suitable for high temperatures in aggressive environments, thanks to its resistance to reactive gases.
Main features:
- Measures temperatures up to 1000 °C with thermocouple sensing element;
- AISI 316 or INCONEL 600 sheath to withstand different environments and temperatures;
- Reliability and measurement stability even in extreme thermal conditions.
Operating principle
When it comes to heat treatment, continuous furnaces are the most widely used and appreciated solution due to their high productivity, particularly in the treatment of large volumes. In these systems, the pieces move through the heating chamber in a continuous flow. Continuous furnaces consist of an insulated tunnel, divided into several independent heating zones, and a conveyor system — belt or push — that allows the material to pass through its structure, ensuring an uninterrupted and efficient heat treatment process. With temperatures that can reach 1000°C, continuous furnaces are ideal for a wide range of heat treatments, such as hardening, annealing, tempering and normalising.
Each process is managed according to a specific thermal profile, which is provided by the movement of the material through the different individually controlled temperature zones, a fundamental feature for achieving the desired metallurgical properties.
Requirements and technology
In heat treatment, temperature is the most critical parameter: it must be managed with absolute precision and constant stability to ensure reliable results that comply with the highest standards.
For this reason, modern systems rely on advanced PID controllers, equipped with optimised algorithms and autotuning functions, which simplify management and ensure intuitive and efficient control of the entire process.
Heating can be provided by electric heating elements or gas burners: in the first case, the controller communicates with the Power Controllers, which modulate the thermal energy with extreme precision; in the second case, it directly manages the gas valves,ensuring responsiveness and safety. In addition to control, it is also essential to record and monitor temperature trends, especially in highly specialised sectors such as aerospace and automotive, where process traceability is essential for certifying quality and complying with the most stringent regulations.
Finally, to protect the plant and ensure operator safety, it is essential to integrate dedicated protection devices, such as safety thresholds against overheating, which intervene promptly to avoid critical situations.
