The three general equipment classifications for thermal processing equipment are:
-
batch
-
semi-continuous
-
continuous
Classification used depends upon the scope of production and the nature of the business.
While the science behind heat treatment remains principally the same, certain advantages can be achieved from particular oven and furnace types.
As an example it is possible to carry out the annealing process in air furnaces, vacuum furnaces, and gas purged retort furnaces, amongst others.
Similarly the surface chemistry process of carburizing can be carried out in a range of equipment types including batch and continuous atmosphere controlled furnaces, pusher furnaces, or vacuum furnaces.
The range of furnace types is extremely diverse.
So, if the furnace equipment type does not define the process, why should there be so many different options for users to choose from?
Other issues that influence the choice of processing equipment include:
-
Captive shops: These are in-house processes usually carrying out work of a similar nature where continuous processes and large-scale batch processes can be most economically employed.
-
Commercial shops: Usually carry out a variety of work for external customers where batch production allows the flexibility required to meet the demands of a wide number of processes.
-
The desire to achieve the final finished product compliance without the need for further processing.
-
Physical size of the component.
-
Mixed batch production.
-
Reduced surface oxidation.
-
Final surface finish for wear, corrosion and fatigue resistance
-
Reduced component deformation.
For example:
Automotive gears have been hardened and tempered for many years in standard gas carburizing and draw furnaces. Recent
advances in Low Pressure Carburizing for these components in a vacuum furnace have brought advantages to production cycle integration and component quality.
Aircraft components can equally be annealed in gas purged retort furnaces or in vacuum furnaces. The distinction often lies in the stage of the process, with annealing of raw or core material being carried out under controlled atmospheres, while finished components are processed in vacuum where there is a much greater need to maintain control of components shape, dimension and surface finish as well the material properties.
