Developing a Three-Row Pusher Furnace with a Small Footprint

Mercedes-Benz recently procured a special atmosphere heat-treating system from Ipsen for the thermal processing of drive pinion wheels, crown wheels and gearbox parts. In addition to delivering superior performance, the three-row Pusher system consumes less power and occupies relatively less floor space.

Challenges Faced by Ipsen

The limited space available made the installation of the new heat treatment system somewhat of a challenge. Nevertheless, Ipsen solved the problem by connecting the low- and high-temperature furnaces, quenching equipment and cleaning systems into sophisticated units.

This setup offered the flexibility necessary for accommodating different kinds of components, as well as reduced the amount of space required. Finally, a highly integrated transfer mechanism was used to service the whole system and necessary parts, all of which was done in the compact area.

System Configuration and Operation

The following units are featured in the complete Ipsen heat-treating system:

  • Pre-oxidation furnace with an operating temperature of 842°F (450°C)
  • High-temperature heat treatment furnace with an optimal operating temperature of 1,742°F (950°C) and has the following parts:
    • Entry gate
    • Three-row heating zone
    • Three-row carburizing zone
    • Single-row hardening zone
    • Gas-tight intermediate doors
    • Discharge station for individual, press-hardened parts
  • Oil bath with two separate immersion baths
  • Fully automatic Heess press-hardening system
  • Three-zone post-washing machine
  • Tempering furnace
  • Multiple transport units

The semi-automatic powered roller tracks that come with the three-row Pusher atmosphere furnace are used to load and unload components. Roller track feed the components into the system  prior to transferring them into automatic load storage conveyors. The loads are preheated in the pre-oxidation furnace to 842°F (450°C), after which they are moved into the entrance vestibule of the high-temperature furnace by means of an intermediate transfer system.

After leaving the entrance vestibule, the components reach the three-row heat treatment chamber where they are heated to a temperature of more than 1,652°F (900°C). The components of multiple loads are then carburized in the three-row heating zone until the surface achieves the required carbon specifications. Three-rows enable simultaneous treating of multiple loads, thereby increasing productivity and profitability.

The carburized loads are then fed into a single-row pre-quench soak zone. After leaving the pre-quench soak zone, the loads are fed into a fully automatic press quenching system or free quenched in oil. This yields a distortion-free finish for large components, while ensuring the finished parts are the appropriate size.

Finally, all the quenched components are transported by a fully automated transfer system for any further processing they might have to undergo. In some cases, the components are removed for certain processes, such as straightening, prior to transferring into the two-row tempering furnace. After tempering and subsequent cooling, the components are passed through a load handling system for final cooling and storage.

Salient Features of Ipsen's Atmosphere Pusher Furnace

The main operating zones of this atmosphere heat-treating Pusher furnace all have three rows. In addition, the new system is Ipsen’s first continuous heat treatment furnace to feature the newly patented Lock up system. As part of this new system, both the entrance vestibule and oil bath are separated from the heat treatment chamber by gas-tight doors.

It is also now possible for loads to be fed in and out the Pusher furnace without affecting its atmosphere, due to the special gas-guiding systems. This yields precise, straight-line characteristic that are easily observable and adjustable.

The need for a protective atmosphere is also reduced by maintaining a constant pressure level in the heat treatment chamber while feeding the loads in and out. The reduced intergranular oxidation (IGO) on the components is another advantage of the Pusher furnace, making it suitable to process high-quality precision gearbox components.

Patented EcoFire Process

Ipsen’s patented EcoFire process significantly improves efficiency by using the endogas exhausted from the preheating furnace as a combustion gas through carefully controlled process steps. The use of the process gas allows the system to achieve considerable cost savings.

Sophisticated Circulation Equipment

The advanced circulation equipment not only homogenously distributes protective gas in the heat treatment chambers, but it also allows a sufficient flow of reactive gases around the components. This combination of sophisticated burner technology and improved airflow characteristics yields unprecedented temperature stability and superior reproducibility of specific heat treatment results.

Ipsen’s New Insulation Technology

Ipsen’s new insulation technology ensures the cost-effective operation of the atmosphere furnace system. Time-tested, durable Ipsen masonry consisting of refractory bricks are utilized as hot face insulation for the floor, walls and ceiling. The use of high-strength silicon carbide materials for making the support components provides prolonged service life.

The use of microporous material as backup insulation in the major sections of the furnace system helps provide unprecedented insulation with a temperature resistance of 2,012°F (1,100°C). As a result, this design reduces waste heat by 30% when compared to traditional designs, thereby significantly lowering process costs.

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This information has been sourced, reviewed and adapted from materials provided by Ipsen.

For more information on this source, please visit Ipsen.


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