Pre-heating Furnaces for Forging Operations

Otto Junker supplies high-performance continuous belt conveyor furnaces for heating aluminium ingots/ billets to the forging temperature.

These furnaces provide holding capacities up to 60,000 kg at throughput rates of 8,000 kg/h. A forced convection system with individually adapted flow management ensures that all parts placed on the conveyor will be heated in a most uniform and reproducible manner.

The furnaces are heated either electrically or with natural gas, depending on the customer's choice. Heating is achieved by intense recirculation of the furnace atmosphere covering the entire surface area. However, to ensure optimum heating conditions, the atmosphere flow regime must be adapted to the geometry of the forgings and specifically to their loading pattern on the conveyor belt.

Small parts are commonly loaded automatically from a magazine. Larger parts are typically fed into the furnace by a robot; their subsequent removal and delivery to the forging press being likewise robotized. For very large forgings, travelling manipulators are used.

To minimize the length of the system, dual-track plate conveyor systems with mutually autonomous track control may be employed.

This furnace type is used also in wheel manufacturing for heating the cast or forged wheel blanks before the flow forming operation.

• A plate conveyor made of highly alloyed CrNi steel is designed to support large weights and diverse part geometries and sizes.
• Even high belt tension is accommodated uniformly and over the entire conveyor width. A long service life and high operating reliability are thus ensured. Full-area conveyor supports made of solid cast elements with good anti-friction properties provide additional wear resistance and improved maintenance-friendliness.
• Conveyor can be run in oscillating mode.
• The use of recuperative burners results in substantial energy cost savings.
• Input of the heating gas via manifolds and mixing devices ensures high flow temperature uniformity. Localized hot currents – and hence, overheating – are thus avoided.
• Intense forced circulation of the furnace atmosphere, covering the entire surface area, ensures high temperature accuracy.
• The interior furnace casing, plenum ducts, air baffles and fans are made of high chromium-nickel steel. Wear of heat-resistant components and the entrainment of oxide or insulation particles are prevented or minimized.
• The furnace insulation is essentially made up of heat-resistant mineral fibre panels with a low thermal inertia.
• Consistent with tough forging environments, all furnaces are of very rugged, heavy-duty design.