Differences between vacuum furnace and pit furnace

Vacuum furnace and pit furnace differ in many aspects, as follows:
1. Working principle and structure
Vacuum furnace is an industrial heating equipment that performs heating treatment in a near-vacuum environment. This furnace uses a vacuum system (including vacuum pump, vacuum measuring device and vacuum valve, etc.) to reduce the pressure inside the furnace chamber to much less than a standard atmospheric pressure, thereby creating a vacuum environment. There are many advantages to heat treatment in such an environment, such as preventing material oxidation and decarburization, and improving heating efficiency and temperature control accuracy. Common vacuum furnace structures include pit or box furnace shells made of welded steel plates and steel sections, furnace linings with energy-saving composite fiber or full fiber insulation structures, and high-temperature resistant resistance alloy elements as electric heating elements. In addition, vacuum furnaces also have strict vacuum sealing structures to ensure the vacuum environment in the furnace.
Pit furnaces are a type of periodic operation furnace, suitable for heat treatment of rods and long shaft parts. Its structural feature is that the furnace body is a cylindrical deep well, and the workpiece is vertically loaded into the furnace by a special crane for heating. The pit furnace is generally placed below the workshop floor, but some are placed above the floor, or half above and half below the floor. The pit furnace is mainly composed of an outer cover, an inner tube, a convection tube, a burner, a furnace bottom stirring circulation fan, a forced cooling fan, etc. The outer cover is the structural support of the entire furnace body, and the inner tube separates the flue gas flow space from the controllable atmosphere flow space where the workpiece is located.

2. Application and heating method
Due to its unique working principle and environment, the vacuum furnace is widely used in many fields, such as metal heat treatment (vacuum quenching, vacuum tempering, vacuum annealing, etc.), vacuum brazing, vacuum sintering, vacuum melting, vacuum coating, and semiconductor manufacturing. Its heating method is mainly through radiation. Heating elements such as resistance wires, induction coils or electron beams convert electrical energy into thermal energy and transfer heat to surrounding objects in the form of radiation.
Pit furnaces are mainly used for heat treatment of rods and long shaft parts, such as quenching and annealing. Its heating method can be gas or liquid fuel combustion, or electric heating. When gas fuel is used, there are usually multiple small energy burners installed along the tangent direction of the inner wall of the furnace to uniform the furnace temperature. When electric heating is used, it is called a pit-type resistance furnace.

3. Performance characteristics
The main performance characteristics of vacuum furnaces include precise design, strict manufacturing process, good vacuum sealing, high efficiency of heat preservation and energy saving, and high temperature control accuracy. In addition, the temperature range of vacuum furnaces is wide, and very high temperatures can be reached, and the temperature control accuracy is high.
The pit-type furnace has the advantages of compact structure, small footprint, simple operation and low failure rate. At the same time, the temperature uniformity in the furnace is good, the heating efficiency is high, and a variety of heating methods can be used to meet different process requirements. However, compared with vacuum furnaces, pit-type furnaces may have certain limitations in preventing material oxidation and decarburization, and improving heating efficiency and temperature control accuracy.

In summary, there are obvious differences between vacuum furnaces and pit-type furnaces in terms of working principle and structure, use and heating method, and performance characteristics. Which furnace to choose depends on the specific process requirements and workpiece type.

Back News