Heat Treating: What is a Rotary Retort Furnace

Rotary retort furnaces are designed to achieve consistent hardening performance required for uniform heat treating. Whether the furnace requires a batch or continuous retort, one of the goals is undoubtedly to get as much usage as possible before replacing the retort.

Since the mid-1990’s, fabricated retorts have been used in heat-treating industries – in both batch and continuous retort applications. Fabricated retorts are welded from wrought nickel alloys to the exact specifications required. A cast retort involves metal poured into a shape that ultimately becomes a rotary retort.

Although the end products might look similar, there are nuances to each type that effect the lifespan and investment.

Design Flexibility

Retorts can be custom fabricated using a combination of different nickel alloys. Because no casting patterns are required, the design can address specific aspects needed to maximize production and lifespan.

Optimal Material Selection

In a cast retort, the limitation is a specific metal poured into the mold which limits the ability to address failure points. Fabricated retorts can be made from wrought materials that have a lower carbon content than cast and have a tighter grain structure with greater ductility. The result is a greater resistance to thermal fatigue. If the retort has a weak section that needs additional strength, a different type of alloy can be incorporated to address that failure point.

Improved Performance

Fabricated retorts weigh less and heat up faster for shorter cycle times. Alloy Engineering has also found that fabricated retorts last anywhere from two to five years depending on the application, which translates into cost savings and better production performance.

In our experience, there aren’t many negatives associated with fabricated retorts. However, depending on the application sometimes cast will last longer. That’s why it’s important to work with an engineering team who will provide an unbiased review of your process and needs.

Fabricated retorts usually involve more labor and a larger up-front investment. But in our experience, we’ve seen fabricated retorts last two to three times longer than cast.

When it’s time to replace your retort, there are several factors to consider including design, materials selection and investment. Make sure you carefully consider these factors along with your specific needs. A reputable company will work with you to determine the best solution.

Alloy Engineering offers retorts custom-fabricated from corrosion-resistant alloys for use in high-temperature environments. To learn more, contact us here or call us at 440.243.6800.