Frequently Asked Questions

Which do I need… a FURNACE or an OVEN…?

The temperature you need to heat treat your material at will typically give you the answer: A FURNACE when you are above radiant heat (1300°F) and an OVEN with air recirculation when you are below.

How should I maintain my furnace or oven?

To maintain the utmost accuracy and extend the life of your heating elements, you should replace the thermocouples at least once a year. The sensing tips on the thermocouples degrade over time and begin to lose accuracy causing the heating element to work harder, shortening element life.

What replacement parts should I have on hand?

You should always have an extra heating element on hand to avoid unexpected downtime as well as the expense of overnight delivery.

Why use a protective atmosphere?

A protective atmosphere is used when exposure to air atmosphere may cause an undesirable chemical reaction with your parts. Note that if your parts are being cleaned or machined afterwards, the use of air atmosphere may be suitable. At Lucifer Furnaces we can provide you with a furnace using an inert protective atmosphere including nitrogen, argon or helium. Inert atmospheres can be used in a GT model furnace or an AM model furnace.

What is the difference between the GT and AM models?

Both our GT and AM models are designed for use with inert protective atmospheres. GT Models are designed with a continuously welded furnace shell and gasketed door for operation with a positive flow of inert atmosphere. GT Models are best suited for constant operation to maintain a dry refractory environment in the work area to minimize oxidation on workloads. GT Models are a less expensive alternative compared to AM Models

AM Models are equipped with an alloy muffle (retort) which separates the refractory and heating elements from the workload and atmosphere to minimize scale and oxidation on most tool steels. The design of the AM Models achieves lower dew points, reduced atmosphere consumption and allow shorter purge times.

Why use stainless steel foil wrap?

Stainless steel foil wrap will minimize decarburization and scale on most tool steels processed under normal air atmosphere.

Are your furnaces and ovens NADCAP approved?

NADCAP accreditation has to do with a company's compliance with certain specifications. There is no such thing as a NADCAP approved furnace or oven. Lucifer Furnaces can build your furnace or oven to comply with the requirements of AMS 2750D, a common furnace specification cited in NADCAP requirements for heat treating. It is your company or your process that becomes NADCAP accredited. If you are thinking about NADCAP accreditation, be sure to mention that when you are buying equipment.

Why are low watt density heating elements important?

With low watt density heating elements the heat is spread out over a greater surface area; the result being that low watt density heating elements burn out less frequently (they last longer) than higher watt density elements. Longer lasting elements reduce operating costs.

What is stress relief?

Stress relief is a process to remove residual (internal) stress which develops as a result of metal processing applications such as hardening, machining, forming, welding or casting.  Stress relief heat treating involves heating metal parts to a temperature below the "lower critical temperature" and holding for a set period of time. Following the hold period, parts are cooled at a slow rate to avoid re-formation of stress. Precise temperature, hold times and cooling rates are dependent upon several factors.  Lucifer Furnaces can meet your stress relief needs with an oven or furnace depending on the hold temperature required.

What is an annealing furnace?

An annealing furnace or oven is capable of heating material to a specific temperature under uniform heating conditions, generally associated with softening and/or involved with relieving stress.  The right furnace for your needs depends on the type of steel among other factors.  To prevent oxidation during annealing consider protecting your parts with foil wrap and/or heating in an atmosphere (ex. nitrogen).  An annealing furnace could be a batch (box) furnace or oven or a continuous (conveyor) furnace.

What is AMS 2750E

AMS (Aerospace Material Specifications) 2750E is a pyrometry specification (temperature driven) which used procedures, timelines, calibration information and record-keeping as well as specific thermocouple choices and temperature uniformity surveys.  When designing a furnace, an end user needs to make the builder aware of the need to meet AMS 2750E so that the furnace is built with those components that allow for the procedures/record-keeping, etc.... to be followed.