| The term "flame heating" refers to processes where heat is transferred to the work piece by means of a gas flame without the work piece melting or material being removed. Examples are flame straightening, flame hardening, hot forming, as well as heating in conjunction with welding, spot heating and fusing of flame-sprayed coatings.
Flame straightening is employed to restore the shape of parts or assemblies that have been distorted, mainly by welding. Flame hardening can be used to achieve partial surface hardening of, for example, bearing seats on shafts or the wearing surfaces on rolls. In hot forming, the part to be formed is heated locally and then formed by the application of an external force. In welding of certain alloyed steels, especially with thick pieces, preheating must be carried out to avoid hardening cracks. After welding, stress relief heat treatment may be necessary in order to reduce welding stresses. Fusing of flame-sprayed coatings involves heating of the coating to the melting temperature, which strengthens the bond between the coating and the substrate. This heating is normally carried out with a flame.
Many different factors must be considered when choosing a fuel gas for the various flame processes with respect to the application, such as rapid local heating or homogenous annealing of the entire work piece. In the former case, it is the flame temperature and the intensity of the fuel gas that are most important. In the latter case, the fuel gas that provides the lowest costs per unit emitted energy can be chosen, also taking into account the oxygen requirements.
Working with fuel gases and oxygen can be risky if the person using the equipment does not have sufficient knowledge of the equipment and its installation, handling and care.
Flame Straightening
Soldering & Brazing |
