Nitempering Furnace

Nitemper® is Ipsen's patented, internationally acclaimed process of ferritic nitrocarburizing that uses a 50% Endogas + 50% NH3 atmosphere. Contrary to conventional nitriding, both carbon and nitrogen are diffused into the steel at a low temperature while the steel is in the ferritic phase. Instead of Endogas, other carbon-evolving gases, such as CO2, can also be used (e.g., CO2+N2+NH3).

Because of the low temperature - typically 570 °C - carbon solubility is low and so very small amounts of carbon are transferred to the steel surface. A Nitempered surface has unique properties that find application in diverse areas.

Improved abrasion and wear resistance
A Nitempered surface is resistant to wear and abrasion. If the steel has nitride-forming alloying elements, wear resistance can be further improved.

Tribological and corrosion resistance properties
A Nitempered surface has tribological properties (i.e., it can display self-lubrication). Thus, it finds niche applications in the precision or fine engineering industry for watch parts, instrument parts, etc., as well as for internal combustion engine crankshafts. The Nitempered surface is also corrosion resistant and can be made more so through a process of post-oxidation as a continuation of the basic Nitemper cycle.

Equipment flexibility - many processes in one batch
Ipsen's dedicated Nitemper furnace can be used for preheating, tempering, Nitempering and fast atmosphere cooling inside the furnace. Ipsen Sealed Quench Furnaces can also be equipped (or retrofitted) with Nitemper® capabilities. Hence, it is possible to first do the basic hardening in the conventional way and then carry out Nitemper® in the same furnace on the same batch load.

Distortion-free heat treatment
For steels or charge geometries that are prone to distortion, Nitemper is a good option as it involves a process where the substrate is pre-hardened to a medium extent and then a Nitemper operation is carried out on the surface. Plus, the low Nitemper® temperatures mean almost zero distortion.

Pre- and Post-Oxidation
The Nitemper process can be modified to include a stage of pre-oxidation and one of post-oxidation. While pre-oxidation helps to activate the surface and improve reaction kinetics, post-oxidation creates a layer of oxide on the surface which dramatically improves corrosion resistance (up to 500 hours of salt spray test, typically). Post-oxidation can be done by air or water injection.

Ipsen's patented sensor-based, oxygen-potential-controlled post-oxidation process for defined iron oxide layers.

Latest "flameless" ignition of flame curtain
In conventional designs, a pilot burner flame burns continuously at the unloading door to ignite the flame curtain whenever the door opens; however, this often wastes expensive gas. In the Ipsen design, an ignition device is automatically activated whenever the door is to be opened. This allows the gas to automatically flow when the ignition is activated, resulting in the flame curtain. Thus, the gas is consumed once in a cycle instead of throughout the day.

Unique rear door design
In the Ipsen Sealed Quench furnace, the rear (unloading) door moves inside a frame that can be moved away or clamped with respect to the furnace shell by four cylinders. While opening the doors, the frame is first pushed away and then the door is lifted, so that the seals are not worn or rubbed down. After the door is closed, the cylinders retract, effectively drawing the door onto the seals and clamping down, allowing for better sealing.

Floor-mounted atmosphere circulation fan
The heat-resistant recirculation fan is installed between the furnace floor and the hearth roller track. Because nascent nitrogen atmospheres are heavy, this is the best method to ensure atmosphere and temperature uniformity. No other design offers this feature.

Rear-mounted radiant tubes for indirect heating
The heating system is located at the back of the furnace and consists of several vertical radiant heating tubes, which can be gas or electric heated. An insulated heat-resistant steel radiation wall separates the furnace chamber from the heaters for indirect heating. No soft spots, no hot spots. Just uniform properties.

Fast cooling furnace system
The furnace is provided with a top mounted, gas-tight cooling hood, consisting of a pneumatically lowered / lifted stainless steel heat exchanger through which atmosphere is circulated for cooling the charge. While heating or a process is on, the hood is isolated from the furnace chamber by an insulated hatch which is lowered pneumatically into the heating chamber during the cooling period. The baffle-guided gas flow then discharges heat through the heat exchanger.