N₂-GEN^® – HTS Nitrogen Generation System

Nitrogen Generator for Annealing: Annealing is heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired microstructure (for subsequent operations) or obtaining desired mechanical, physical, or other properties. Annealing can be performed in a variety of different furnace atmospheres depending on the material involved including products of combustion, nitrogen, nitrogen/hydrogen blends, Exothermic and Endothermic gas, dissociated ammonia (or nitrogen-diluted dissociated ammonia), hydrogen, and vacuum. Other common names and related subjects are: isothermal annealing, sub-critical annealing, process annealing, malleabilizing, recrystallization annealing, and spheroidizing.

Nitrogen Generator for Blanketing (Covering) Gas: A term used to describe an inert gas such as nitrogen or argon introduced into a furnace to prevent oxidation of the component parts being heat-treated. The flowrate and pressure of the atmosphere and the equipment type (i.e. gas-tight construction) must be sufficient to limit the influx of air.

Nitrogen Generator for Blending / Gas Dilution: Blending (aka gas dilution) involves the mixing of two or more gases to create a furnace atmosphere. Often the primary atmosphere (for example, hydrogen, dissociated ammonia, Exothermic or Endothermic gas) is mixed with nitrogen to create a fixed percentage of reactive gas (e.g. hydrogen). Economic benefits (i.e. cost savings) are often the principal driver in gas blending.

Nitrogen Generator for Brazing: Brazing consists of joining metals by flowing a thin capillary layer of non-ferrous filler metal into the space between them. Bonding results from the intimate contact produced by dissolution of a small amount of base metal into the molten filler metal, without fusion of the base metal. The term brazing is used when the temperature exceeds some arbitrary value, typically 475ºC (880ºF). Furnace atmospheres for brazing include Exothermic and Endothermic gas (including nitrogen-diluted Endothermic gas), nitrogen, nitrogen/hydrogen mixtures, dissociated ammonia (including nitrogen-diluted dissociated ammonia), hydrogen, and vacuum (partial pressure). The term soldering is used when the temperature is lower than this arbitrary value. Welding is another joining process that is performed at temperature in which melting of both the base metal and the filler metal occur.

Nitrogen Generator for Case hardening: Hardening a ferrous alloy so that the outer portion, or case, is made substantially harder than the inner portion, or core. This is accomplished by increasing the surface carbon content and quenching or by selectively hardening the surface using applied energy techniques (flame, induction, laser). Typical furnace atmospheres are Endothermic gas or nitrogen-methanol with the addition of a hydrocarbon and/or air to maintain a predetermined surface carbon in the material.

Nitrogen Generator for Emergency Purge: The introduction of an inert gas, typically nitrogen, into a furnace in which an abnormal condition has developed due to, for example, a power failure or load transfer malfunction. Often times a smaller nitrogen generator package can be paired with a larger nitrogen storage tank to accommodate an emergency purge to cover all furnaces in the plant. Contact us with help in sizing an Emergency Purge System for your facility.

The purposes of an emergency purge are:
• to maintain the furnace under positive pressure
• to limit air egress
• to remove a combustible atmosphere from the unit and replace it with a non-flammable one, often over a concern that the furnace temperature will drop below the atmosphere self-ignition temperature of 760ºC (1400ºF)

Nitrogen Generator for Gas Quenching: A term that applies to the use of a type of circulated gas to rapidly cool a workload. Typical methods of circulation include fans or gas nozzles. Gas quenching can be done by recirculating the existing furnace atmosphere (typically cooled or sent through a heat exchanger to remove the heat absorbed) or the introduction of a new gas (e.g. nitrogen) under given pressure or flow conditions. A variation of gas quenching is so-called high pressure gas quenching (HPGQ) typically performed in vacuum furnaces. Nitrogen is the most commonly used gas for HPGQ. This form of quenching can be described as “accelerating the rate (speed) of quenching by densification and cooling of gas.” One of the many reasons for the intense interest in this quenching technique is related to improved part distortion with full hardness. A critical concern in using this technology is to avoid sacrifice of metallurgical, mechanical, or physical properties, that is, retain the ability to transform a material to a microstructure that is similar, identical or superior to that of a known quenching medium (e.g. oil or salt).

Nitrogen Generator for Hardening: Increase in the hardness of a material by suitable treatment, usually involving heating and rapid cooling. The furnace atmosphere in use must be one that is neither oxidizing or reducing nor carburizing or decarburizing to the surface of the material being processed. Other common names and related subjects are: neutral hardening, quench hardening, direct hardening, surface hardening, and hardening by applied energy (induction, flame, laser).

Nitrogen Generator for Normalizing: Heating a ferrous alloy to a suitable temperature above the transformation range (and typically above the suitable hardening temperature) and then cooling in the equivalent of still air to a temperature substantially below the transformation range. Normalizing can be performed in a variety of different furnace atmospheres including products of combustion, nitrogen, nitrogen/hydrogen blends, dissociated ammonia (and nitrogen diluted dissociated ammonia), hydrogen, and vacuum.

Nitrogen Generator for Sintering: The bonding of adjacent powder particle surfaces in a mass of metal powders or a compact, by heating. Sintering is typically performed in a furnace atmosphere consisting of Nitrogen/hydrogen, dissociated ammonia (or diluted dissociated ammonia), hydrogen, or vacuum. Other common names and related subjects are: cold/hot isostatic pressing, liquid phase sintering, metal injection molding.

Nitrogen Generator for Solution Treating: Heating an alloy to a suitable temperature, holding at that temperature long enough to allow one or more of the constituents to enter into solid solution and then cooling rapidly enough to hold the constituents in solution. Furnace atmospheres for use with this process typically include air, nitrogen, and vacuum (partial pressure). The alloy is left in a supersaturated, unstable state, and may subsequently exhibit quench aging. Solution treating is most often followed by an aging treatment.

Nitrogen Generator for Stress Relief: A process consisting of heating to a suitable temperature, holding long enough to reduce residual stresses and then cooling slowly enough to minimize the development of new residual stresses. Furnace atmospheres for use with this process typically include air, products of combustion, Exothermic gas, and nitrogen (in instances where scale formation is undesirable). Other common names and related subjects are: stress relieving, stress relaxation.

Nitrogen Generator for Tempering: Reheating a quench hardened or normalized ferrous alloy to a temperature below the transformation temperature and then cooling at any rate desired. Furnace atmospheres for use with this process typically include air and nitrogen. A reduction in strength and increase in ductility properties of the material generally results. Other common names and related subjects are: draw, drawing, and temper.