Which Industrial Furnace for Which Process?
Selecting an industrial furnace starts with the process, not the furnace. Process temperature, atmosphere and charge weight together make the furnace type almost self-evident – this matrix gets you there in three steps.
Three questions lead to the furnace type
- At what temperature does the process run? This separates air-circulation furnaces from radiant ones – the boundary sits at roughly 860 °C.
- What atmosphere is needed? Air, protective gas, vacuum or carburising.
- How heavy and how large is the charge? This decides between bench-top unit, chamber furnace and bogie hearth furnace.
Selection matrix by process
| Process | Temperature | Atmosphere | Suitable furnace type |
|---|---|---|---|
| Drying | 50–350 °C | Air | Low-temperature chamber furnace, Drymatic systems |
| Tempering | 100–700 °C | Air, opt. protective gas | ICO · IWO |
| Preheating | 80–1200 °C | Air | IWO · IWF · Conveyor |
| Annealing | 450–1100 °C | Air, protective gas | ICF · IWF · Bell-type |
| Hardening | 750–1100 °C | Protective gas, opt. vacuum | ICF + Quenching furnace |
| Carburising | 850–1000 °C | N₂ / methanol / propane | Carburizing furnace |
| Sintering | up to 1300 °C | Protective gas, opt. vacuum | ICF · IWF · TH1 |
Step 1 – The 860 °C boundary
Below roughly 860 °C, moving air transfers heat effectively. Forced circulation gives the best uniformity there: the ICO and the IWO achieve below ±5 °C across 50–860 °C.
Above it, radiation dominates. A circulation fan would lose its effect and wear out, which is why the ICF and the IWF use freely radiating tube heating elements up to 1300 °C – on the ICF from three sides, two side walls and the floor.
Step 2 – The atmosphere
| Atmosphere | Used for | Design consequence |
|---|---|---|
| Air | Tempering, annealing in air, drying, preheating | Standard design |
| Protective gas (N₂, Ar) | Scale-free annealing, sintering | Gas-tight design, gas train, purge programme |
| Vacuum | Materials research, oxidation-sensitive materials | Pumping system – on the TH1 optionally to 10⁻⁶ mbar |
| Carburising | Case hardening | Carbon potential control and full explosion protection |
Step 3 – Charge weight and design
| Charge | Design | Range |
|---|---|---|
| Material samples, small batches | Bench-top unit | IBF – to 1300 °C, 3-sided heating |
| Samples in tube form, wire, powder | Tube furnace | TH1 – 50–1200 °C, inner diameters 15–100 mm |
| up to approx. 1 t | Chamber furnace | ICO · ICF |
| up to 30 t, bulky | Bogie hearth furnace | IWO · IWF |
| Coils, rings, bundles | Bell-type furnace | Bell-type – 1,000–10,000 litres |
| Series production, high throughput | Conveyor furnace | Conveyor – 260–1100 °C |
The detailed comparison of the two most common designs is at Chamber or bogie hearth furnace.
When several processes are run
Operations working both below and above 860 °C do not necessarily need two plants. The multi-door chamber furnace IRF combines an air-circulation chamber to 860 °C and a high-temperature chamber to 1200 °C in one housing, with separate doors and control loops.
If a qualification to standard is also on the table, settle it before the design is fixed – the reasons are at AMS2750, CQI-9 and NADCAP.
Frequently Asked Questions
Which furnace is suitable for tempering?
Tempering runs at 100–700 °C and therefore squarely in the air-circulation range. A chamber furnace ICO or a bogie hearth furnace IWO with forced air circulation achieves uniformity below ±5 °C there – exactly what tempering needs, because toughness depends directly on temperature.
Which furnace is suitable for sintering?
Sintering requires up to 1300 °C and often a protective atmosphere. Suitable options are the chamber furnace ICF with 3-sided radiant heating, the bogie hearth furnace IWF for heavy charges, and the tube furnace TH1 for samples under vacuum or inert gas.
Do I need a separate quenching furnace for hardening?
For austenitising at 750–1100 °C a chamber or bogie hearth furnace is enough. Where a defined quench rate matters, a quenching furnace with a fast-opening door and air, water or oil quenching is the right choice: the time between furnace and medium determines the hardness result.
Which furnace covers several processes at once?
The multi-door chamber furnace IRF: two independent process chambers in one housing, forced circulation to 860 °C on the left for tempering and ageing, high temperature to 1200 °C on the right for sintering and high-temperature annealing.
Which matters more in selection – temperature or atmosphere?
Both narrow the field, but atmosphere is the more expensive factor. Temperature fixes the insulation and heating type; a protective, vacuum or carburising atmosphere additionally demands gas tightness, a gas train, control and possibly explosion protection.