A Guide to Resistance Furnace
Resistance Furnace
A resistance furnace is an industrial heating device that uses electric current passing through resistive materials (heating elements) to generate Joule heating, thereby heating or thermally processing materials.A resistance furnace consists of three main parts: the furnace structure, the heating system, and the power & control system.
1. Furnace Structure
Furnace Shell and the Furnace Lining.
2. Heating System
The heating elements (the core components), namely the resistive elements, are the parts that convert electrical energy into heat. Commonly used materials include:
Metallic elements: such as FeCrAl and NiCr alloy wires. Suit for 800°C to 1200°C.
Non-metallic elements: such as SiC rods and MoSi₂ rods. Suit for above 1200°C.
3. Power & Control System
Includes the power supply system, temper. measurement system, and control system. Advanced furnace models are also equipped with a data recorder.
temper. measurement system: The most commonly used temper. sensors are thermocouples (e.g., type K, S, B).
Control system: The temper. controller serves as the core control unit. The most classic control algorithm is PID.
Types of Resistance Furnaces
Resistance Furnace (Standard Model)
Refers to a resistance furnace without a muffle chamber, consisting of a single chamber.
Muffle Furnace
A resistance furnace with a muffle chamber, featuring a “furnace-within-a-furnace” structure.
Furnace Shell → Furnace Lining → Heating Elements → Muffle → Sample Chamber.
Atmosphere-Protected Resistance Furnace
A resistance furnace capable of providing atmosphere protection, without a muffle chamber.
| Characteristics | Resistance Furnace (Standard Model) | Muffle furnace | Atmosphere Protection Furnace | ||
| Temper. Control Accuracy | Can be very high (depends on the temper. control system) | ||||
| Atmosphere Environment | Air (oxidizing) | Inert or protective atmosphere inside the muffle; heating elements surrounded by air | Entire furnace chamber filled with a controlled atmosphere | ||
| Temper. Uniformity | General | Good | Excellent | ||
| Heating Rate | Fast | Slow | Fast | ||
| Main Applications | Processes that do not require protective atmosphere, such as general annealing, tempering, preheating for quenching, sintering, ashing, and high-temper. material testing | Processes that require oxidation prevention, decarburization prevention, or specific atmospheres, such as bright annealing, brazing, sintering (magnetic materials, ceramics, etc.), and powder metallurgy | High-temper. sintering of cemented carbide tools, bright annealing of stainless-steel parts, and vacuum brazing of aerospace components | ||
| Model | TM 12 | TM 14 | TM 17 | TX3/TX4 Series | TX2 | TZH Series/TSZH Series |
| type | Muffle furnace | Muffle furnace | Muffle furnace | Muffle furnace | Resistance Furnace | Resistance Furnace TZH Series / Atmosphere Protection Resistance Furnace TSZH Series |
| Temper. Range | 1200 °C | 1400 °C | 1700 °C | 100–1200 °C | 1000 °C/1200 °C | 1000 °C/1200 °C |
| Temper. Accuracy | ±1 °C | ±1 °C | ±1 °C | ±1 °C | ±1 °C | ±1 °C |
| Max. Heating Rate | 30 °C/min | 25 °C/min | 10 °C/min | ≥30 °C/min | – | – |
| Thermocouple Type | N type | S type | B type | TX3: S type / B typeTX4: K type | K type | K type |
| Heating Element | Fe-Cr-Al Alloy doped by Mo | SiC rods | MoSi₂ rods | Alloy heating wire | Resistance wire | Resistance wire |
| Programmable Segments | 30 | 30 | 30 | 40 (P model) | optional | – |
1.Built-in Monitoring
Built-in ammeter and dual voltmeters for easy monitoring and troubleshooting.
2.Overheat Protection
Overheat protection shuts down the ceramic muffle if temperature is outside of acceptable range or when the thermal couple is broken or malfunctions
