Car Bottom Heat Treatment Furnaces
Car bottom annealing furnaces are used within the heat treatment of ready-made products in forging and pressing shops, as well as for the heat treatment of castings and weldments. Bulky parts are annealed while resting on annealing supports mounted on the furnace car, while smaller ones are loaded as stored in baskets or on grates. These furnaces are used for many various types of heat treatment – normalization, process annealing, heating for hardening or austenization, further for tempering or for annealing to release internal stresses after molding or welding. Commensurate to the above is the range of operating temperatures, from 250 °C to 1,150 °C, exceptionally up to 1,250 °C in the event of special materials. Where required, furnaces are fitted with a cooling system that will make it possible to carry out heat processing as a whole process, including controlled cooling zones and intense final cooling of the charge in the closed furnace without the need to open the door or to move the car out of furnace.
Car bottom furnaces are available in all sizes as required by customers. The largest furnace we have ever made had a working space sized 9×12×5 m (clear dimensions w×l×h) and can accommodate a charge of 570 tonnes. A universal car hearth furnace with a clear length of 22 m has been supplied for the processing of long rotors and shafts, including controlled and intense cooling, allowing also heating for forging at up to 1,250 °C.
Properly selecting the types and locations of burners along with optimum control of the heating system, sufficient sealing of the furnace and pressure stabilization in the furnace will ensure a highly homogenous nature of the temperature field in the working space of the furnace.
In respect of waste heat utilization, an optimal arrangement of the heating system is selected, depending on the prevailing temperatures of the heat treatment processes, furnace capacity, expected plant factor and other operating conditions. Either burners with cold combustion air inflow, burners with air preheated in a central recuperator, or recuperative burners, which provide utmost utilization of the heat from outgoing fumes for furnaces of this type, can be used.
Where justified, car bottom annealing furnaces are equipped with electrical resistance heaters instead of gas-fired systems and – where necessary –forced air circulation is used to ensure homogenous distribution of temperatures throughout the field and intensified convective heat transfer across the charge contents.