A pusher furnace is kind of a continuous furnace in which the product that is being worked on is moved on the hearth with the help of an electrical or a hydraulic pusher, placed behind the charge. A pusher furnace, for continuous type heat treatment, is used in metallurgical and machine-building industries, where metal pieces are required to be heated up to a high temperature for the purpose of shaping them into their desired forms. These furnaces can work up to temperatures between 400℃ to 1400℃.
How Does a Pusher Furnace Work?
A pusher furnace for continuous type heat treatment has two openings at its two ends. These are kept closed by two shutters or doors. At one end, the charge is placed in front of the electrical or hydraulic pushers that push the charge into the furnace and is heated up in the closed furnace until the desired temperature is reached.
Then, from the other end, the charge is removed by another set of pushers that push the charge out of the furnace. The charge is then placed into a cooling pit, containing a liquid like oil and is allowed to cool. The use of pushing to get the charge inside the furnace is the easiest way for it to function, as it requires much less equipment and mechanical gadgets.
Although pushing of the charge inside is the easiest method, it can damage the products by causing them to scrape against the hearth. This can be countered by adding trays or lining on the hearth so that the charge does not scrape against it when pushed.
A pusher furnace is typically classified according to its design features. Large pusher furnaces are commonly found in rolling mills where wheel rolling or forging is done by pushing the wheel inside the furnace alongside guides that are U-shaped in its cross-section. Smaller articles are rolled or pushed in using trays and can sometimes be covered with a muffle while being pushed.
Normally, a pusher furnace is used in processes like carburizing and hardening where thermochemical heat treatment of parts that are of high volumes and less in product variety are conducted. It is also used for other processes like annealing, stress relieving, solution treating and aging, and so on. These processes are often used in the manufacturing of parts like axle rods, gear shafts, axle components, transmission parts, engine components, and others.
Benefits of Using a Pusher Furnace
The use of a pusher furnace for continuous type heat treatment is typically well-suited since it comes with a stable hearth structure that is designed for heavy loads. Using a pusher furnace has the following advantages:
- There is a higher operational safety guaranteed by the sturdy structural design of the furnace.
- There is an excellent recirculation of the protective atmosphere inside, so as to ensure that it is evenly distributed.
- It is a very cost-efficient solution to treat large volumes of charge materials.
- It has optimum repeatability.
- It contains multiple rows that allow for an efficiently working system.
- The doors open at the bottom as this saves energy in the process of heat treatment and makes bottom-loading possible.
- These furnaces use oil pits that are mounted on the floor for quenching the metal. This makes it easier to eliminate the need of building in costly pits.
Normally, a push furnace would be manufactured according to the custom designs requested by the clients of a manufacturer. Depending on this, the client can order for a variety of versions of the pusher furnace that would be suitable for their purpose.