Ask the Expert: Do I need Convection Heating?

Convection heating increases temperature uniformity and decreases cycle times for large cross-section parts, alloys with a low heat-transfer rate, and parts with complex geometries. Before we go into convection heating, it is important to understand the most common type of heating used in vacuum furnaces: radiant heating.

What is radiant heating?

Radiant heating is most common in vacuum furnaces. This type of heating does not rely on direct contact between the heat source (heating elements) and the parts being heated. Instead, it heats anything in its path (like how the sun heats the earth), and the effects are felt without actually touching the heat source. Parts that are in the “shade” receive heat from surrounding parts, which become hot and re-radiate heat.

What is convection heating?

Convection heating uses gas (typically nitrogen or argon) and a fan to circulate heat to all parts in the load. Unlike radiant heating, parts do not have to be in the direct sight line of the heating elements to feel the effects, resulting in better uniformly of heating.

The gas path for the TurboTreater vacuum furnace with the added option of convection heating
The gas path for the TurboTreater® vacuum furnace with the added option of convection heating

How does convection heating work?

The furnace is loaded, then pumped down to at least 80 microns. Inert gas is backfilled into the furnace under partial or slightly positive pressure (1-2 bar). A fan or pulsejet circulates hot gas throughout the load while heating up. The circulation of hot gas increases the heat transfer to the parts, including “hidden” areas in parts with complex geometries. This shortens the total heat-up time and provides more uniform heating. Convection heating, when used in conjunction with radiant heating, can help you reach your maximum temperature more quickly and efficiently.

What are the benefits of convection heating?

Convection heating is beneficial for parts with complex geometries, alloys with a low heat-transfer rate, and parts that require a tight temperature uniformity range. Ipsen’s patented flapper nozzles remain closed, unless the furnace is in cooling mode, which helps keep heat from escaping the hot zone and further improves temperature uniformity. This technology decreases cycle times (especially for large, dense loads) and reduces energy consumption, helping you save time and money.

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