Tool Making & Mechanical Engineering – Furnaces for Hardening and Manufacturing

Heat Treatment in Tool Making and Mechanical Engineering

Tool making and mechanical engineering live on precision — and precision begins with correct heat treatment. An incorrectly hardened tool breaks prematurely. An inadequately annealed machine component distorts in machining. Stresses in a welded structure lead to cracks in service. Heat treatment is not a downstream process — it is an integral part of quality assurance.

NTH Therm supplies industrial furnaces for the full range of tool making and mechanical engineering requirements: from compact tempering furnaces for small press tools to heavy bogie hearth furnaces for large dies and machine beds.

Hardening Shop – Precision Heat Treatment of Tool Steels

Hardening tool steels requires tight temperature control. Austenitising temperature, hold time and cooling rate must be matched to the steel and the component.

High-speed steels (HSS) are austenitised at 1200–1280 °C — temperatures that demand precise control and good uniformity. The ICF series (to 1300 °C) is designed for these requirements.

Cold-work steels (D2, K110) are hardened at 1000–1060 °C, hot-work steels (H13) at 1000–1050 °C. Tempering is typically double or triple at 480–600 °C — the ICO forced-air furnace ensures the required uniformity.

Plastic mould steels often require a combination of pre-hardening, finish machining and final hardening with minimal distortion — an area where the multi-door furnace IRF plays to its strengths.

Heavy Loads – IWF Bogie Hearth Furnace

In tool and mould making, charge weights of 5 to 30 tonnes are not unusual: large forging dies for the forging industry, die-casting moulds for automotive, rolls for the paper and steel industries. The IWF bogie hearth furnace is built for these dimensions:

• Reinforced bogie construction for maximum load capacity
• Large-volume combustion chamber for even gas flow
• Side and floor-mounted burners for optimal temperature distribution
• High-performance circulation fans for homogeneous temperature throughout the charge space
• Heat-storage control for efficient energy use during long cycles

Mechanical Engineering – Annealing and Stress Relieving

Cast and welded machine bodies — machine beds, columns, beams — must be stress-relieved before precision machining. Residual stresses from casting and welding otherwise cause dimensional deviations that only appear weeks after machining.

Stress relieving of steel: 550–650 °C, slow heating and cooling rates (≤ 50 K/h for sensitive structures), adequate hold time (1–2 hours per 25 mm wall thickness).

Stress relieving of cast iron: 500–600 °C, even slower cooling to avoid cracking.

Normalising of forgings: 850–950 °C, air cooling — for even microstructure and reproducible mechanical properties before finish machining.

Flexibility with the IRF Multi-Door Furnace

Operations with varying production programmes value the versatility of the IRF multi-door furnace: the same system can run different processes at different temperatures and atmospheres. Multiple doors enable efficient logistics — loading and unloading without long interruptions to ongoing operation. Ideal for hardening shops serving a broad customer base.

Frequently Asked Questions