How to Choose melting furnace for sale, melting furnace?

31, Mar. 2025

 

Choosing the Right Melting Furnace | Inductotherm

Foundries selecting a new furnace will consider production goals, equipment maintenance, safety standards, and product lifespan, among other factors, but finally the choice will come down to identifying a furnace that can match a high-throughput target while withstanding the foundry’s harsh environmental conditions. The Heavy Steel Shell Furnace and Steel Frame Furnace (Figure 1) from Inductotherm are designed according to those guiding principles, to achieve high output and to last for years of reliable service. There are some similarities and key differences between these two furnaces.

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Both furnace designs offer superior performance and outstanding durability that will meet the demanding requirements of foundry applications and environments. Each combines strength and accessibility to provide maximum furnace rigidity and strength for long lining life and serviceability. But there are distinctions.

Each furnace provides effective shunt coverage of more than 50% of the coil’s circumference which redirects the electromagnetic field into the melt (Figure 2). The shunts are carefully designed to provide positive support of the coil, held in place by multiple shunt bolts. Vertical tie rods are used to create a clamping force and hold the coil in place.

Both are designed with a high freeboard to provide extra space for solid charge materials, allowing the furnace’s optional cover to close easily as the charge melts, greatly reducing heat loss, and providing better protection and safety for the operators (Figure 3). Using a high freeboard also ensures molten metal is contained within the active section of the coil. Consistently containing the molten bath within the active section of the coil allows maximum stirring, inclusion of scrap material when nearing the end of the melt.

Every Inductotherm furnace is designed for structural strength with the aid of custom computer-aided software. Using application specific information, Inductotherm engineers will use this information to predict how the furnace will perform before it is released for production (Figure 4).

Both designs use heavy-wall, water-cooled extruded copper tubing designed especially for induction melting (Figure 5). Inductotherm engineers design coils with optimal space between turns to minimize resistance and maximize electrical efficiency, ensuring more energy goes into the melt, which results in more metal, faster. The coils are designed with space between turns to enhance their current-carrying efficiency and allow moisture to dissipate easily from the refractory, resulting in lower ground leakage. This space also eliminates the possibility of resistance losses caused by interference from the magnetic fields – a common problem in furnaces that uses closely spaced tubing.

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Taking advantage of Inductotherm’s patented extended coil design, which extends the induction coils well below the bottom of the refractory, the resulting magnetic field improves furnace efficiency by coupling with the load much more evenly from top to bottom. Traditional coil designs produce magnetic fields that are especially curved in the bottom of the furnace, and the resulting stirring action is responsible for premature lining erosion in the bottom corners of the refractory, commonly known as “Elephant’s Foot Erosion” (Figure 6).

Both furnace designs have stainless steel cooling sections at the top and bottom of the power coil to provide uniform temperature gradients that extend furnace lining life.

The Steel Frame furnace has an open-frame design providing easy visibility and access to the coil, shunts, and other furnace components for scheduled maintenance or unexpected production interruptions, decreasing downtime. In contrast, the Heavy Steel Shell furnace is fabricated with a rolled steel shell, which creates what is called “Hoop” strength. The shunt bolts pass through the shell to create a clamping force, and the additional hoop strength from the rolled steel shell maximizes support for the shunts and creates a rigid structure to support the coil and refractory lining.

The inductive magnetic field exerts an outward force on the coil, causing an insufficiently supported coil to expand over time. In addition to the shunts, vertical tie rods secure the coil in place and provide high strength with flexibility, resisting refractory expansion while keeping the coil in compression. Using advanced composite materials, our coil stabilizer system locks each turn of the coil firmly in place, eliminating turn-to-turn arcing as well as minimizing distortion during tilt, pour, and lining push-out operations. All these factors result in longer lining life with each melting campaign and increased yield per melt.

The Heavy Steel Shell furnace shields the coil and shunts to protect them from stray scrap, sparks, and metal splash. Heavy steel splash shields (Figure 7) and covers bolted on to the exterior of the shell can be removed for scheduled maintenance or to reveal a service opening large enough to examine the interior components. This ensures that interior components of the shell are always protected. The Heavy Steel Shell is not only stronger than competing frame-based designs, but significantly quieter as the shell’s design characteristics will contain ambient noise within the shell.

Careful consideration of the advantages of the Heavy Steel Shell and Steel Frame furnaces will allow you to choose what is right for your foundry. The Inductotherm designs offer high efficiency, high productivity, and increased durability, adapted to specific application and production requirements, and combined with low life-cycle cost, to give you a competitive advantage for years to come.

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A melting furnace for a newcomer - The Home Foundry

Hi

I am Werner from South Tyrol Italy.

Would like to build me a melting furnace.

I am a complete novice, but I have a friend who casts at home, complete 2 stroke cylinders.

He has already given me many tips for my first mold.

Would now like to build myself a furnace.

I'm not sure if I should start with just a small propane furnace for aluminum, or design the furnace to handle cast iron as well.

For an aluminum casting of about 2-2.5kg without basin sprue or riser, how big does the crucible need to be.

How would a possible simple melting furnace look like if it only has to reach the temperature for aluminum.
200lt and 60lt metal drums would be available....

Translated with www.DeepL.com/Translator (free version)
Ciao / Gruetzi Werner!

I have just started casting Alu with a 6kg kit from Amazon which is really more like 1.5kg Alu once you figure the bronze to aluminum conversion and moving a smaller crucible to be in a better place from the burner. Also being so close to capacity makes it had to pull the crucible out with the supplied tongs and I have longer pieces of good scrap that stick up.

Sometimes my casting the gating is as much as the part in weight.

So maybe I need a bigger furnace too...I am not an expert but maybe if we have some more numbers people can read and comment.

From Alibaba:
innopack-steel drum
oil paint bucket/dyestuff bucket
60 liter steel drum
415*395*480mm [ 16.25 x 15.5 x 18.875 inches]

75mm [3"] top, 75mm [3"] bottom, 50mm [2"] each side insulation,
leaves 295mm [10.5"] diameter and 330mm [13"] interior.

Need space along sides for hot gases and lifting tongs. Need space at the top for hot gases and longer pieces of clean scrap Alu to stick up before they melt. So if we allow say 35mm [1.375"] per side and 75mm [3"] on the top, crucible max is 225mm [8.75"] diameter and 260mm [10.25"] tall.

So a Salamander A20 crucible would be about max height but only 1/2 full and A10 the smallest very full to have 5kg Alu 2.5 Kg [5.5#] part and 2.5 Kg [5.5#] gating system) assuming Alu is about 1/3 dense as bronze.

You may want to check my math before ordering anything, still first cup of coffee...

PS Something like this with the barrel, insulation, and A20 dims above:

Welcome Werner,
The biggest question is what type of refractory material is available for your furnace lining. Commercial products specifically made for foundry furnaces is highly recommended if you can get them. Not fireplace cement, but foundry furnace refractory. We have an active member here who lives in Austria so maybe he will have some recommendations for buying refractory materials and crucibles.

Melting cast iron with propane is possible, but you would find it to be difficult. Aluminum and copper alloys are much easier.

Your furnace bore size will be determined by your required crucible size, so I’d recommend finding an available crucible before building the furnace. Buying a commercially made crucible is highly recommended. Steel crucibles can be used for aluminum but are not great. For a 2.5kg casting, you’ll want a capacity of about 2 liters to accommodate sprue and gating. (2.7kg/liter). The furnace bore diameter will be 100mm larger than the crucible diameter.

There are several ways to approach this, so finding out what materials are available to you before you begin will save much time, money, and aggravation.
A list of potential materials:
Refractory cement (castable or plastic)
Ceramic fiber insulation
Refractory mortar
Dense firebrick
Insulating firebrick
Crucibles


Pete
that's just the point.
On the Internet, of course, there are many instructions, but usually some specific building material is used. I have to see if I can buy the building material here in Italy or Austria.

Work as an agricultural machinery mechanic, dirty diesel, and waste oil would always be available.
but first the melting furnace, before I take care of the burner.

I think if an A20 fits straight in there that would be great.

I would still like the version with the poured barrel best I think.

Maybe just poured with a castable refractory cement ?
Ah, we have some new information. You may start out with propane, but you will not want to pay for it for very long. If you have diesel and oil available for free, that is what you will end up using. That is important because if you build a light duty furnace that will handle propane you will likely destroy it when you switch to oil. So here is a specific recommendation: your furnace should have 50mm of ceramic fiber insulation and 25mm commercial castable refractory cement rated to F. It will be bulletproof.
The bottom of the furnace can be solid 50mm thick or can have a ring of insulation, but it should be solid in the center portion kind of like a doughnut so there is solid support in the center. Your crucible will sit on a pedestal (plinth) which will be about 100mm tall. I agree with Kelly that a #10 is a good starter size but if you only want to build one furnace you might as well build for a larger crucible. A #20 would be the maximum in aluminum I would pour by myself. A #20 from my supplier is 190mm diameter by 228mm tall. Yours may be different. Make sure of your size before you start. So your steel shell should be about 440mm diameter. It should be 428mm tall. That leaves 50mm between the top of the crucible and the bottom of the lid. The lid should be 75-100mm thick with a 100mm exhaust hole.

Pete