What are the main characteristics of a atmosphere furnace?
2024-03-26
Atmosphere furnace Its characteristic is that, at a specified temperature, a specially formulated atmosphere of controlled composition is introduced into the furnace to achieve specific heat-treatment objectives, such as gas carburizing, carbonitriding, bright quenching, annealing, and normalizing. Atmosphere furnaces are primarily characterized by the following features:
Sealability
To control the furnace atmosphere and maintain the desired pressure, the furnace working space must be kept completely isolated from the ambient air, with leakage and air ingress minimized. Therefore, sealing devices are required for the furnace shell, refractory lining, furnace door, and all external connection components, such as blowers, thermocouples, radiant tubes, and pusher/withdrawal mechanisms.
Atmosphere control
To maintain a specified carbon potential within the furnace, in addition to ensuring the stability of the atmosphere composition, it is also necessary to monitor the furnace conditions.
The furnace atmosphere must be automatically controlled. To this end, various control instruments (as shown in Figure 1) are required to continuously or periodically measure the furnace atmosphere and adjust the supply of combustion air accordingly.
Heating method
To ensure atmospheric stability, atmosphere furnaces are classified into muffle furnaces and non-muffle furnaces. In a muffle furnace, the flame is located outside the muffle, and the workpiece is heated indirectly within the muffle; in a non-muffle furnace, various flame-fired radiant tubes or electric radiant heaters are used to isolate the flame or electric heating elements from the furnace atmosphere, thereby preventing disruption of atmospheric stability inside the furnace.
Explosion-proof device
When reducing gases are mixed with air to a certain molar ratio, they can easily ignite and explode at specific temperatures. Therefore, explosion-proof devices are installed in the furnace’s preheating chamber, post-heating chamber, quenching chamber, and slow-cooling chamber, and the furnace’s gas supply and exhaust control system must also incorporate explosion-proof measures.
Refractory materials
The muffle-free atmosphere furnace employs a reducing gas; to ensure the service life of the masonry and maintain the integrity of the furnace atmosphere, the furnace chamber masonry must be constructed from carburization-resistant refractory materials.
Level of automation
Various types of atmosphere furnaces have stringent sealing requirements, and their loading and unloading operations are complex. To maximize furnace versatility and accommodate high-volume production, they are often configured as large-scale, dedicated or dual-purpose heat-treatment units, thereby necessitating a high degree of mechanization and automation.
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