Controlled atmosphere front load furnace:
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- There are many vertical and horizontal tube furnaces suppliers, but few suppliers of front load, bottom load, and top hat furnaces specially designed for processing in inert atmospheres. To do so, the furnace must be sealed: the element ports, thermocouple ports, and door access. Gas inlets will allow purging in any furnace, but to operate in different atmospheres, the room air in the furnace must be displaced by the desired gas or gas mixture. Gases may include argon, nitrogen, oxygen, and hydrogen mixtures.
- Tube furnaces are ideal for applications requiring relatively small workspaces and features such as multiple zones, independently controlled. Alumina tubes are required for high-temperature operation, but they are subject to thermal shock. The smaller the diameter of the process tube, the better. Deltech manufactures tube furnaces for operating temperatures up to 2000 degrees centigrade. In addition to vertical and horizontal tube models, we offer a bottom-loading vertical tube and combination units that allow the tube to be placed either vertically or horizontally. Water-cooled end caps and gas mixing systems are optional.
- Controlled atmosphere tube furnaces designed for operation at 3600 degrees Fahrenheit require the use of a zirconia tube.
- Deltech sealed atmosphere furnaces are called “atmosphere envelopes”. They are available in bottom load, front load, and top hat models, in most any size and configuration that the application requires. They operate at pressures up to .022 atmosphere. Vacuum-assisted evacuation is optional, allowing the user to remove the room air before backfilling with the desired gases.
- Element limitations reduce the recommended operating temperatures in furnaces using molydisilicide heating elements. In inert atmospheres, there is a 100 degrees centigrade reduction. In even 5% hydrogen mixtures, it is much lower. The use of moist hydrogen improves on this by 300 degrees centigrade.
Applications for controlled atmosphere furnaces
Controlling the gas in the hot zone prevents oxidation, decarburization and contamination during high-temperature processing. Common uses include:
- Heat treating metals: annealing, carburizing and nitriding, where the atmosphere protects the surface and microstructure.
- Bonding and brazing: a stable atmosphere keeps oxidation away from the joint.
- Curing and sintering: polymer curing and ceramic sintering need steady temperature and gas flow to limit porosity and surface defects.
- Materials synthesis and chemical research: labs control gas composition, temperature and pressure to make advanced materials and run reactions without outside contamination.
Choosing the right atmosphere
Inert gases such as argon give a fully neutral environment. Nitrogen-hydrogen blends are common for oxidation-sensitive processes. Keep the element limits above in mind: molydisilicide elements lose about 100 degrees centigrade of rating in inert gas, and more in hydrogen mixtures.
Getting consistent results
Uniform heating comes from multizone designs, good insulation and real-time temperature monitoring. Programmable controllers and PLCs regulate gas flow and automate cycles, and sealed doors and access points keep the atmosphere intact during loading. Routine gas flow checks, sensor inspections and refractory assessments keep the furnace performing over time.
Related Deltech products: furnaces built for controlled atmospheres include horizontal tube furnaces (inert, reducing or vacuum), front load furnaces and top hat furnaces with an Atmosphere Envelope.