DIY crucible for melting lead, aluminum, gold

Cooling system equipment

Industrial units for melting metal are equipped with special cooling systems using antifreeze or water.
Equipping these important installations in homemade HDTV stoves will require additional costs, which is why the assembly can put a significant dent in your wallet. Therefore, it is better to provide a household unit with a cheaper system consisting of fans. Good to know: types of antifreeze.

Air cooling with these devices is possible when they are located remotely from the furnace. Otherwise, the metal windings and fan parts can serve as a loop for short-circuiting eddy currents, which will significantly reduce the efficiency of the equipment.

Terms of use

For experienced radio technicians, assembling an induction furnace according to the diagrams with your own hands may seem like an easy task, so the device will be ready quite quickly, and the master will want to try his creation in action

It is worth remembering that when working with a homemade installation, it is important to follow safety precautions and not forget about the main threats that may arise during operation of an inertial furnace:

Liquid metal and heating elements of the device can cause severe burns.
Lamp circuits consist of high-voltage parts, so during assembly of the unit they must be placed in a closed box, thus eliminating the possibility of accidental touching of these elements.
The electromagnetic field can influence even those things that are outside the installation box. Therefore, before turning on the device, you need to put away all complex technical devices, such as mobile phones, digital cameras, MP3 players, and also remove all metal jewelry. People with pacemakers are also at risk: they should never use such equipment.

These furnaces can be used not only for smelting, but also for quickly heating metal objects during forming and tinning. By changing the output signal of the installation and the parameters of the inductor, you can configure the device for a specific task.

For melting small volumes of iron, homemade stoves are used; these effective devices can operate from ordinary sockets. The device does not take up much space; it can be placed on a desktop in a workshop or garage. If a person knows how to read simple electrical diagrams, then he does not need to purchase such equipment in a store, because he can assemble a small stove with his own hands in just a few hours.

Radio amateurs have long discovered that they can make induction furnaces for melting metal with their own hands. These simple diagrams will help you make a HDTV installation for home use. However, it would be more correct to call all the described designs “Kukhtetsky’s laboratory inverters,” since it is simply impossible to independently assemble a full-fledged stove of this type.

MAKING A POWERFUL MELTING – DIY

Hamsters welcome you friends!

Today's post will be about a homemade jewelry smelter that can melt silver, gold and even copper! Despite the simple design, this project turned out to have a lot of pitfalls that we have to deal with. The post promises to be as hot as chebureks in the summer high season.

This story begins with the fact that one fine day Sanya “Chemist”, a man of legend, offered to continue his project to create a crucible furnace for melting metals.

Speaks:

- Listen, I have a ready-made homemade glass, here you go! There is no time to deal with this topic!

— Of course, I was happy looking at this masterpiece and the work began to boil.

The gray color is due to the fact that it was pre-coated with high-temperature sealant. The heating coil was wound independently from fechral, using a knitting needle and a screwdriver. In short, complete “Handmade” so to speak.

The first thing that needed to be designed for the fallen goblet of fire was a good thermal insulation box so that the spiral would not unnecessarily heat up the air in the room, which would cause colossal heat loss.

As a fur coat, a fire-resistant mullite-silica plate from an old gas water heater was used, a possible brand of plate MKRP-340 or ShPGT-450. The material is unique in that, due to its porosity and low thermal conductivity, one centimeter of such a heat insulator can literally stop the flame of a gas burner. In general, we cut this mat into pieces, and with the help of a file we process the edges, trying to make something like a heat-insulating bowl.

You can strengthen the outside of the bowl using asbestos fabric, which is pre-impregnated with liquid glass. Why is this needed?! During these procedures, an asbestos rag acquires ceramic strength, while the same fabric, without treatment, tears like an old sheet. We wrap the glass with this noodle and wait until it completely dries. The cup turned out just right! Let's try on a matryoshka made from glasses. Everything goes according to plan.

We fill the cracks of the future thermal box with fireproof silica wool. This is exactly how the design of the crucible heater was imagined, which should heat the metal to temperatures above 1000 degrees.

The next step is to create the outer casing for the smelter. We cut it out of a stainless pipe for the air duct, with a diameter of 140 mm. Cutting stainless steel is quite a task; I had to dance with a tambourine and a hacksaw for a couple of hours. The grinder discs for the drill had to be changed one by one; they instantly turned into dust and settled on the walls of my lungs. Half a day of work as a tinsmith and the body began to take on its appearance!

At the bottom there is a black pedestal made from a steel box purchased at a local radio market, inside of which a common PID is mounted - the ReX-C100 regulator.

A heater and a thermocouple are connected to it, which must be somehow removed in advance so that it is placed inside the thermostat. The bowl itself will be wrapped several times in thermal insulating wool. Not a single extra degree should leave the walls of our device.

The stove is almost ready. The only thing it lacks is a heat-protective casing, so that in case of accidental contact with the body you don’t burn your hands, tongue or anything else...

We will make the thermal protection from a perforated cassette for suspended ceilings, I don’t remember where I got it from, but I have plenty of such junk! We cut off the desired piece using the same drill. We roll the resulting sheet into a roll and then everything follows the knurled pattern.

PID - S-100 regulator. There are many manufacturers that produce them. This option was created by Berm. I don’t remember where I got it, but two years later it works like clockwork! Yes, yes, the material was filmed long before you saw it.

PID - the regulator controls the load through a so-called solid-state relay, with a maximum allowable current of up to 40 amperes. I believe that with such a real load, all the wiring in the house will burn out faster.

Whatever device you assemble, ensure good electrical insulation of the wires. God forbid something shorts out during work, it will be a disaster.

Connecting the power! Blue wires are mains voltage, red/black are solid state relay control. We clamp the thermocouple into the terminals. The measured resistance of the fechral heater was 62 ohms. Power consumption 737 W. The device looks quite simple, which is called connect ready-made modules with wires.

Let's check how it all works. PID - the S-100 regulator operates directly from the 220 network, inside it there is a step-down power supply for its own electronics, convenient! After turning on the indicator, we see two temperatures. The one on top is the current one, and the one on the bottom is a value that you can change. We set the temperature to 150 degrees and the regulator quickly begins to increase it. Amazing! We assemble the device, tighten the screws and see how everything works together.

The limit value of this PID temperature controller is 1350 degrees. Since this is the first activation, we will set the shelf to 1100 degrees. At these values, silver should melt.

A fan stands next to the open window and blows out the smoke that comes out of the kaolin wool. It was bought new and the first calcination was stinking. After about ten minutes, the stove returned to normal. Inside the smelter one could see the red-hot heart of the volcano, eager to smelt metal.

A couple of days before filming these shots, I asked a good friend for an infrared camera so that I could evaluate the heat loss of the assembled crucible smelter. How I regretted it later...

Meet the famous Flir infrared camera for connecting to a mobile phone. It has a built-in battery on board and two matrices, one of them is infrared, and the second is conventional for combining the contours of observed objects from the real world. My happiness knew no bounds. You feel like an alien from the movie "Predator"

A couple of hours before the smelter started heating, the camera needed to be charged, since it only lasts for an hour of continuous operation, despite the fact that lying on a shelf it self-discharges quite quickly. But as soon as it came to filming, for some reason the camera did not want to turn on. Zero response to the button. Another attempt at charging did not lead to anything good. Meanwhile, the stove reached 1100 degrees. I fiddle with the camera and see that the smelter began to lose temperature 900...800...700, something clearly went wrong.

While I was tinkering with the stove, the camera recharged a little, but when I connect it to the phone, the power button still refuses to respond. After reading the forums, it turned out that this is a common problem and the camera needs to be sent to a service center. This problem was related to the charge controller, which had failed. I collect documents and begin to study them. At the time of the breakdown, the warranty repair was apparently expired, but if you register on the Flir website, the warranty is extended for another two years. As a result of correspondence with the manufacturer, it turned out that the nearest warranty service center is in Estonia and I need to go to some nearby EMS post office. Screw him, I thought! The camera is not mine and costs a fortune, I’ll have to pack for a hike.

A little while later. What happened to our stove? Everything inside her seems to have gone through hell! Everything that began to fade during the work settled in a thick gray layer on the kaolin wool.

Now let's look at the mistakes that can be made when designing such devices. There is no need to connect the wire to the end of the heater through the brass clamp terminal block. At temperatures above 900 degrees it is likely to melt. The main problem here lay in the fechral heater and the insulating glass.

It turned out that the heat-resistant sealant with which the glass was coated reacted with the metal of the spiral at high temperatures, causing its partial oxidation and destruction. It turns out that the sealant became a kind of flux, which destroyed the protective oxide film of the fechral and turned the spiral into fragile ruins.

In general, a week of work wasted. No stove, no infrared camera. Black line…

I throw on a glass and order a special thermally insulating glass from China along with a graphite crucible for induction melting . And in general, it is suitable for any swim.

Sanya “Khimik”, having learned about the accident during the testing of the installation, immediately wound another heating element from fechral so that the experiments could be continued. Just respect for the efficiency. The glass itself is ceramic based on aluminum oxide. The only thing missing here is some grooves to prevent the heater from crawling back and forth. We draw a spiral with a marker, and then using a grinding stone and a drill we drill channels and wind the spiral into a stretch. This is what the main differences between the new and old glasses look like.

We place it in a thermal insulation box made from old slabs from a gas water heater. We fill all excess cracks with kaolin wool. This time we solder the ends of the heater using silver-containing solder. I love working with fire and high temperatures. We wrap the thermal glass in a blanket and place it back into the stainless steel case. We repeat the assembly procedure.

During repeated tests, the stove returned to normal, worked for several minutes and again began to lose the temperature it had gained. You can't even imagine my emotions at this moment #%@!&. And so it all started well...

Unlike the previous case, there was a distinct smell of burnt insulation in the room. Having unscrewed the case, the first thing that caught my eye was the wires stuck to each other. What could possibly go wrong here again?! When examining the heater, it became clear that during operation it lost its springiness and the hot coils slid onto each other, shorted in places and, in general, it was a fiasco, bro.

Meanwhile at work. At some point, I became so uncomfortable that I simply had to hide at the sight of the man who lent me his infrared camera. Looking ahead, I will say that the situation with the infrared camera dragged on for half a year. The service center received the parcel in Estonia on the fifth day after I sent it, and then the bureaucracy began. Either some documents needed to be filled out, then wait until the camera appeared in the warehouse, or wait until the unicorn constellation was on a par with the general parade of planets. In general, the correspondence with the Flir company lasted for ages, to infinity and beyond. And when all this hell ended and the new camera arrived in my mail, I had to clear it through customs and pay duty. This is a good example of why you shouldn’t take other people’s things for use. Draw your own conclusions about the Flir company.

Let's return to our smelter. Despite the fact that the coil sagged like snot, I was confused by the fact that the heater was torn off in one place. Curious. Upon closer inspection, an interesting point emerged. Kaolin wool, like that high-temperature sealant, upon contact with fechral, also destroys its surface protective layer and turns the metal into some kind of powder.

I’m sure many will ask: why not use nichrome in this matter? I answer: because! It has lower operating temperatures compared to fechral. The most interesting thing is that after digging through the Google archives, we found interesting photos of a Chinese smelter that experienced identical problems with the heater.

In general, after much thought, the path to the heights of triumph was found in the vastness of Aliexpress. As it was written on the website, this is a ceramic heater with an internal adjustable diameter from 55 to 80 mm. Heating element power 700 W.

The internal diameter is adjustable using a bolt, which allows this structure to move freely back and forth. The outer casing is made of stainless steel. But the Chinese forgot to mention that they use beryllium ceramics, which is slightly toxic if you cut it with a file and inhale it greedily. In general, in the 90s this would have been a good alternative to a soldering iron. Interrogations and signing of some documents would become much faster and more practical)

The internal space between the pink ceramic and stainless steel has a thin cotton candy lining. At this moment, I began to have some doubts about the reliability of this design, since upon a detailed inspection of the heating element spiral, fine dust caught my eye and shrouded everything around in fine hairs.

In some places, ceramics greedily tried to devour cotton wool, this is no good. I was also surprised by the ceramic terminal block, inside of which there is the same brass that will leak at 900 degrees. Although the heater on the website promises to reach temperatures up to 1200 degrees. In its bare form, the design of the heater looks like this: bricks made of pink ceramics, inside of which a spiral, presumably made of fechral, with a diameter of 0.4 mm is wound. Now we need to get rid of any hints of dust that the insulation wool left behind.

We will do this using alcohol-gasoline and an ultrasonic bath, the development of which has been going on for three years now. The emitter power here is 100 W. There is heating, degassing, power adjustment, blowing of power elements, two types of overheating protection and much more, including touch control.

Since alcohol-gasoline has a low density, when the heater is removed, the liquid turns into a continuous stream of a fountain, which is just waiting for someone nearby to light a match, just kidding. After the ultrasonic procedures, we place the heating element back into the stainless casing. We throw the cotton wool that was there in the trash!

Looking ahead, I will say that placing a thermocouple directly next to the walls of a graphite crucible will most likely lead to emergency situations associated with the inertia of heat transfer from the heater. When the temperature of the walls of the graphite crucible is 1000 degrees, the fechral around the aluminum oxide glass can reach temperatures of 1300 degrees and inadvertently melt itself at any opportunity. The closer the thermocouple is to the heating element, the better.

We place a heat-resistant glass inside the heating element and secure it well with a tightening bolt. Then we repeat the same procedure as before, wrap the insides in a fur coat and place them back into the stainless case.

After half a year, the crucible smelter acquired the appearance that is now presented on your screens. A few days after taking these shots, I finally received a new infrared camera that can break at the slightest breath of wind. It would probably be worth wearing antistatic gloves and a tin foil hat, otherwise you never know...

As Sanya “Khimik” said, the graphite crucible needs to be drilled before starting melting. Follow the instructions and add borax. It protects the metal surface from various types of oxidation, creating a kind of glassy film around a hot liquid drop. It also protects the inner walls of the graphite crucible from burning out in oxygen. Let's prepare several silver ingots for melting down.

The smelter has returned to normal. On the infrared camera, the places of maximum heat loss are clearly visible; they mainly go through the mounting posts that hold the thermal protective casing. The temperature in these places does not exceed hundreds of degrees. The thermal insulation of the body was so successful that you can safely touch the lid of the smelter with your hand, it is so warm. At the same time, everything inside is heated to white!

And so, the moment of truth. The stove worked at 1100 degrees for about 40 minutes. Heating remains stable. We place a piece of silver into a red-hot heart and watch it melt before our eyes, as if the eye of Sauron is looking into your soul)

We take special crucible tongs We repeat the melting procedure several times to make sure that the Chinese heater works properly at the temperatures indicated on the website. Experiments with silver continued day and night.

After an endless number of meltdowns of the same silver, I began to wonder whether a homemade smelter, assembled literally from shit and knee sticks, was capable of melting copper, the melting point of which is 1085 degrees. The metal used was scraps of industrial power wire with a cross-section of 4 squares; it seems that the metal used in such products is quite pure and with minimal admixtures of alloying elements.

In 20 minutes at a temperature of 1150 degrees, the copper did not melt at all. Individual pieces of wire barely tried to stick to each other with the help of borax, nothing more. This result does not suit us for two reasons. The first is an interest in finding out the maximum critical temperatures of a Chinese heater, the second is to defeat copper at any cost.

We set the maximum possible temperature on the PID controller to 1300 degrees and leave this dish to simmer over high heat. After 15 minutes, there was a distinct aroma of fried copper in the room - this was the smell of the wiring in the walls of my Khrushchev building. Just kidding, Khrushchev buildings have aluminum wires by default. Basically, the copper melted into a beautiful drop in the recess of the graphite jewelry mold. After boiling the ingots in citric acid, we got 2 beautiful drops of metal.

Looking ahead, I will say that absolutely any crucibles for various technical tasks can be placed in the oven. Whether it's evaporating crystalline water from copper sulfate to try to obtain anhydrous alcohol to cooking fried potatoes. Everything will depend on your imagination.

An aluminum oxide crucible can withstand temperatures of 1800 degrees, a quartz crucible 1750 degrees, and a porcelain crucible with a lid up to 1200 degrees. Potatoes, in these cases, will probably turn into carbon. Like the oil in which it was fried.

Graphite crucibles are good because they operate at temperatures above 2000 degrees, but they have one significant drawback. Graphite burns out in an oxygen atmosphere with high heat, and you need to work here either in a vacuum or in a protective gas environment.

When choosing, be sure to pay attention to the grain size of the graphite chips. Two types of crucibles passed through my hands, one of them crumbled literally before my eyes after 10 meltings of silver. A large crumb is still disgusting.

For reference. The filming of this episode, as befits the traditions of the channel, took 3 months. Due to constant technical problems with the infrared camera and other difficulties, this issue settled in the bottom sediments of the hard drive and was released 2 years after filming. This is a common thing, considering that behind the scenes the filming of the next dozen episodes on various topics is taking place.

I thank Sanya “Khimik” for the donated heater, which in the end did not work, but led to invaluable experience in the process of experimentation. I also want to express my deep gratitude to Vovanchik, who was sympathetic to the camera breakdown, the problem of which arose due to the crooked engineers of the Flir company and the same support service, who fed me breakfast for six months. During this time, my hamsters managed to reproduce three times!

Today's jewelry smelter cost about 100 bucks at cost. For comparison: the previous issue about a moonshine still cost +1000 bucks, and the development of the first prototype of an ultrasonic bath cost +4000 greenbacks, not to mention the time spent. The creation of any complex devices requires complex technical solutions with considerable financial investments. I’m already silent about the time that we all already have limited. Let everyone decide for themselves what to spend it on. There is only one life, as they say.

Full video of the project on YouTube

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Features of the technological process

A crucible is a refractory container for heating metal. Products made from the following materials are used:

Porcelain.
Steel.
Cast iron.
Corundum.

At home, a ready-made crucible or container made from a wide iron pipe is used. To make it, you will need a grinder and welding equipment. The volume of the crucible is selected individually, the container is heated evenly, and the crushed metal melts as a result of heat transfer.

Before heat treatment, it is necessary to reduce the melting temperature so that the state of the metal changes faster. To do this, aluminum is crushed into small fragments. Ignition or oxidation occurs frequently after such grinding. The state of the resulting aluminum oxide changes at higher temperatures. This substance is removed along with other slags after remelting the base metal.

During the heat treatment process, you will have to avoid liquid getting into the crucible. The sudden evaporation of water causes an explosion. When immersing metal in a container, you must make sure that there is no moisture on it. Aluminum wire is most often melted. First, the material is divided into fragments with scissors, then compressed with pliers. This method prevents the exposure of oxygen to the metal. If there is no need to obtain high-quality parts, there is no need to grind raw materials.

How to melt aluminum at home?

Aluminum and duralumin waste can be easily melted literally at home. And for this there is no need to build blast furnaces or create draft, as is customary in accordance with standard conditions.

Melting aluminum in a ladle

The author of the method of melting aluminum on a gas stove uses a stainless steel ladle as a crucible. The melting point of aluminum is 660 degrees. A gas stove cannot provide such heating.

First, the crucible with its contents is heated for 15 minutes, then the gas burner is turned on, which provides the temperature necessary to melt the aluminum. Ready-made melting furnaces in this store.

Products for inventors.

Making a crucible from clay

You can make a crucible from fireclay clay. This is an inexpensive option and also highly resistant to high temperatures. This clay is used for laying stoves and can be purchased at any hardware store. Fireclay clay can withstand temperatures up to 1600 degrees Celsius.

So, you will need fireclay clay (sold in bags in hardware stores), liquid glass (sold there) and ground fireclay. It can be bought or made from fireclay bricks.

In order to make a mixture from which a crucible will be fashioned in the future, take 7 parts of clay, 3 parts of fireclay and 10 tablespoons of liquid glass per liter of dry mixture. Fireclay and clay are mixed until smooth. After this, water is slowly added. In order not to spoil the workpiece, you can pour out part of the mixture, and if there is a large amount of water, add dry powder. You need to knead until the clay stops sticking to your hands.

Only after the clay of the desired consistency has been mixed can glass be added. When adding glass, you need to thoroughly knead everything until the clay stops cracking. It is best to add glass to a lump of clay and roll it into a roll, then fold it several times and repeat the procedure until it stops cracking. The material for the crucible is ready. Until the moment when it is used, it must be stored in several layers of cellophane.

There is clay, now to make a crucible you need to take a mold, the easiest way is to use a plaster mold. How to make such a form can be found on any website on plaster modeling. So, directly making the crucible.

Before you start sculpting, you need to knock all the air out of the clay; to do this, you can lay a newspaper on the floor and forcefully throw a lump on it several times, ten times will be enough. Now take a lump of clay and carefully press it into the bottom of the mold, after which the walls of the product are formed in small lumps. Their thickness can be controlled along the edge of the mold

It is very important to carefully press the clay into the mold so that no air cushions form there. After the crucible is molded, you need to make the inner surface smooth

To do this, just moisten the clay with water.

After this comes the moment of drying. The mold with clay is placed in a cardboard box and covered with a lid. After seven hours, all the water from the clay will evaporate and the shape of the future crucible will “shrink” a little, so getting it out of the mold is not particularly difficult. After this, the crucible continues to dry in the same box; as it dries, all defects will be eliminated by themselves and the pot will acquire a gray color. Sometimes small cracks may appear. They can be covered with wet clay. Next, the pots are fired at a temperature of 800 degrees in a muffle furnace. After firing, the crucible is ready for use.

Crucible furnace structure

An induction melting furnace consists of a frame, an inductor, a heating chamber, a tilting mechanism, and a vacuum system. The unit does not have a core; a cylindrical melting crucible is placed directly in the cavity of the inductor. The mixture of starting materials is melted in a crucible under the influence of electromagnetic energy. All components are enclosed in a casing - this frame provides structural rigidity and prevents power dissipation.

Appearance of induction melting furnace

Simpler are the designs of crucible furnaces operating on the basis of solid fuel, for example, charcoal - they are easier to make with your own hands from scrap materials. The metal cylinder body is reinforced with a fireproof layer of concrete or fireclay clay with sand. Fuel is subsequently placed into this shaft. Place a crucible on top, for example, a teapot, a tin can with thick walls, or any strong stainless steel container.

In the lower sector of the shaft there is a hole intended for air supply, and a lattice base is also located here. These elements allow you to maintain the combustion process and change the temperature. Excess air is removed through the damper. For injection, a vacuum cleaner pipe or a hair dryer is usually used.

Crucible furnaces, designed for simultaneous melting of more than 10 kg of aluminum, are equipped with a lid so that the metal is heated evenly. All elements of primitive models are made of cast iron or steel - these materials do not deform when heated in artisanal conditions.

Basic types of reverberatory furnaces

The basic types of gas reverberatory furnaces for melting aluminum are [1]:

Dry hearth reverberatory furnaces, in which the metal is heated on an inlet inclined hearth before being melted (Figure 1).
Wet bath reverberatory furnaces , in which metal is loaded directly into the aluminum melt, usually without preheating (Figure 2).
Shaft smelting furnaces (stack (shaft) furnaces) are characterized by increased energy efficiency, as they use the heat of exhaust gases to heat the loaded aluminum charge (Figure 3). Shaft furnaces are a modified version of reverberatory furnaces

Figure 1 – Gas reverberatory melting furnace with dry hearth [2]

Figure 2 – Bath-type gas reverberatory melting furnace [3]

Figure 3 – Gas shaft melting furnace [4]

Another type of gas furnace is crucible furnace, which is used for small casting volumes, as well as for special alloys. These furnaces require separate consideration.

Classification of muffle furnaces

Based on the type of heating elements, muffle furnaces are divided into:

electrical;
gas.

By purpose they are divided into:

for metal melting;
for firing ceramics;
for melting glass;
for hardening metal;

There are also industrial and homemade muffle furnaces.

Industrial muffle furnace with automation

But it is impossible to make gas-powered stoves at home, although gas is cheaper than electricity, since such experiments are prohibited by law. Electric oven control provides convenient temperature control.

According to their design type, muffle furnaces are divided into:

horizontal (the simplest);
vertical or potted type;
bell-shaped;
tubular.

Heating can be carried out in air, in a vacuum or in a gas environment. At home, it is only possible to design a furnace with heat treatment of products in an air environment.

When you make a muffle furnace yourself, you can give it the desired shape and volume, and decorate it in a style suitable for the interior.

Main parts of the structure

The outer part of the furnace, the shell (body). It is convenient to use a disused gas stove, or rather an oven from it or an electric stove, as a body for a future muffle furnace. To use them, all plastic parts are dismantled. In cases where it is not possible to use such housing options, it is welded from sheet metal (thickness of at least two millimeters).
Thermal insulation layer. This part of the design is extremely important. The efficiency of the furnace and the heat loss it will incur depend on its quality. The inner layer of thermal insulation is a fireproof (fireclay) brick that can withstand temperatures up to one thousand degrees.
The outer layer, which reduces heat loss to the surrounding space, is laid from perlite or basalt wool. Asbestos is unsafe to use; when it is heated, carcinogenic substances are released into the atmosphere.
Elements that directly heat the workspace. The heating elements inside the muffle furnace are spirals twisted from nichrome or fechral wire. Thickness 1 mm. Nichrome (nickel-chrome) wire is very ductile and resistant to corrosion.
Fechral (aluminium, chrome, iron) wire is somewhat cheaper due to the absence of aluminum in the composition and also has the necessary properties for its use in a muffle furnace.

List of materials and tools for assembling the structure

grinder (machine for grinding and cutting materials) with cutting wheels for metal;
welding machine;
sheet steel >2mm thick;
metal corners;
fireclay fire-resistant brick;
fireproof mixture;
heat-resistant silicone;
basalt thermal insulator (cotton wool, density 200 kg/m3) or perlite;
safety glasses and respirator;
nichrome (fechral) wire with a cross section of 1 mm;
wire cutters or metal scissors.

Manufacturing of the device

In this case, we will tell you how to make a vertical muffle furnace for firing ceramics with your own hands.

To do this you will need the following tools:

angle grinder (grinder) and 1-2 wheels;
electric arc welding and electrodes;
metalworking tools, including wire cutters;
2mm nichrome wire.

and materials:

2.5 mm steel sheet or used oven body;
corner;
fittings;
basalt wool;
refractory fireclay brick;
fireproof mortar;
silicone sealant.

Melting metal at home

For a long time, men began to think about how to create their own furnace for melting metal at home. It must be portable and meet all conditions. The production facility has furnaces for melting large quantities of metal. At home, you can assemble a furnace for melting up to five kilograms of aluminum. Let's look at how to make a smelter at home.

Melting metal at home

Equipment and materials you will need

In order to melt metal, you need to buy the following components for manufacturing:

fire brick;
nails;
transformer;
copper wire;
graphite;
mica;
asbestos and cement tiles;
gas-burner;
crucible.

The dimensions will vary depending on the wishes of the person collecting it. It is better to create a small furnace for melting metals if you want to use it only for your needs. You will spend less time making it, and a small amount of kilowatts will be spent heating it. If you do it using diesel fuel or coal, then do not forget about installing thermal insulation and air supply.

Homemade crucibles

Metals such as iron, nickel, tin, and copper are melted in an electric furnace. The output voltage in an electric furnace should be greater, which means the distance between the electrodes will increase. Brushes from an electric motor are suitable instead of electrodes.

Step-by-step instruction

How to make a melting furnace at home - read the following instructions:

A high-frequency alternating current generator is installed.
Spiral winding. Made from copper wire.
Crucible.

All these elements are placed in one housing. The melting cup is placed in the inductor. The winding is connected to the power source. When the current is turned on, an electromagnetic field appears. The resulting eddy currents pass through the metal in the cup and heat it. Melting occurs.

Homemade muffle furnace

The positive properties of an induction furnace are that when melting metals, a homogeneous melt is obtained, alloying components do not evaporate, and melting occurs quite quickly. In addition, the installation of such a stove does not harm the ecosystem and is safe for the user.

Cooling can be done using a fan. Only the latter should be located as far as possible from the furnace, otherwise its winding will serve as an additional closure of the vortex flows. This will reduce the melting quality.

Wheel furnace

Features of melting some metals

In order to melt metal at home, this element must be placed in a small cup or crucible. The cup with the material is inserted into the oven. Then its melting begins. To melt the precious elements, they are placed in a glass ampoule. In order to make an alloy from several components, follow these instructions:

First, a refractory element - copper or iron - is placed in the melting cup.
Then a more fusible component is placed - tin, aluminum.

Melting aluminum in a homemade furnace

Steel is a refractory material. Its melting point is one thousand four hundred degrees Celsius. Therefore, to melt steel at home, you must follow the following instructions:

To melt steel at home, introduce additional regenerators. If the furnace runs on electricity, then electricity is used.
During induction heating, slags are added. They increase the speed of melting.
Constantly monitor instrument readings. If necessary, lower the melting temperature by switching to a more moderate mode.
It is always correct to determine whether the steel is ready for work or melting. Follow all the above steps. Only then will the resulting metal be of high quality.

Metal smelting

To melt iron at home, the furnace must be preheated. First, a large piece is placed, and then small ones. Iron must be turned over in time. A properly molten metal will have a spherical shape.

If you are going to make bronze, you must first place copper in the melting hole. Since this component is more refractory. When the copper is melted, tin is added.

Under no circumstances should elements such as cadmium, lead or zinc be melted. When burned, they produce toxic yellowish smoke.

And when melting aluminum, tin or iron, you must be careful. Rivet slowly and should be done with a small hammer. Heat the material frequently until reddened and cool in cold water. Only then will you get the perfect alloy at the end.

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Gas consumption of gas melting furnaces

Gas consumption during operation of melting furnaces depends on the gas burner. Low and medium pressure burners are installed on gas thermal furnaces. A correctly selected gas burner should provide:

supplying the required amount of gas and air to the combustion zone;
good mixing of the charge;
complete combustion of gas with a minimum excess air ratio;
good heat exchange inside the melting unit, eliminating local overheating;
stable operation within the required range of changes in thermal output.

Gas consumption when melting 1 ton of copper or aluminum charge ranges from 60 to 100 m3/hour.

Making a muffle

To construct a muffle furnace yourself, you should first make a fireproof chamber. Not every material is suitable for these purposes. A special chamber can be made from fireclay bricks. It is perfect for both rectangular and cylindrical ovens. True, it is quite difficult to lay bricks in the shape of a cylinder. To do this, you need to cut out identical trapezoids using a grinder. For a small stove you will need about 7 bricks.

Afterwards, you should connect them together with wire, and also check that they fit tightly. Unevenness can also be corrected using a grinder. Next, you should lay out the bricks in a row and make several grooves for the wire, which in the future will be the heating element

It is important to make the grooves in such a way that the wire does not touch anywhere. To do this, place recesses on one of the bricks at an angle

The grooves should be 7-8 millimeters wide, the distance between them should be at least 2 centimeters.

The bricks are connected using heat-resistant glue. You can also use a mixture of clay, fireclay brick powder and quartz sand.

Ordinary clay is also suitable for making a muffle, since a homemade furnace will not work with extreme temperatures. Clay needs pre-treatment. Construct a small rectangle from cardboard or a sheet of plywood, which will coincide in size with the intended muffle chamber. Be sure to calculate by size whether this chamber will fit freely into the furnace body.

The model of the chamber should be covered on the outside with clay several centimeters thick. The clay must dry within 5 days. Afterwards, the obligatory step is firing the clay structure. It is best to burn the material in a coal furnace, since a temperature of at least 700 degrees is required. If all conditions are met, the result will be a fairly strong and fire-resistant chamber.

Laboratory shaft furnaces SNOL

This equipment with a heating temperature of up to 900 degrees is an indispensable thing in any laboratory. The design of the working chamber allows you to safely work with heavy ceramic and metal products, as well as produce uniform heating without losing excess energy and heat. The dimensions and form factor of the device allow it to be easily placed in a small room, and a wide selection of additional peripherals, including fume hoods and shelving, opens up many possibilities for customization, allowing you to customize the process to the individual requirements of laboratory technicians.

Laboratory shaft furnace SNOL 10/900

A striking representative of this family is the SNOL 10/900 oven. A relatively compact device, measuring 860x750x800 mm, can fit even in the smallest laboratory, and a working 220 volt network will eliminate connection problems.

Main characteristics:

The dimensions of the working chamber 150x150x450 mm will allow you to conduct research on parts up to 45 cm in length.
Vertical loading will prevent deformation of long cylindrical samples.
The power of the heating element is 4.5 kW - the maximum possible for a two-phase connection, due to which the contents of the chamber are heated in the shortest possible time.

A furnace for melting aluminum with your own hands: how to make a furnace with a crucible for metal

This article brings together many different step-by-step instructions to help you make a great aluminum melting crucible. It will only take a couple of days and some money.

DENIAL OF RESPONSIBILITY

When melting aluminum at home, you will encounter fire and molten metal. Do not neglect safety equipment and protective clothing. Responsibility for any injuries caused lies solely with you! I have nothing to do with this.

Characteristics

The purity of materials determines their melting point. Aluminum is suitable for various technological procedures due to its low weight and good ductility. At high temperatures, interaction with oxygen occurs.

An oxide film appears on the surface of the metal, which protects it from corrosion and oxidation. Melting aluminum helps to change the structure of the substance, so the protective coating is beneficial for it.

Shrinkage and additional internal stress appear during sudden cooling.

Features of the technological process

A crucible is a refractory container for heating metal. Products made from the following materials are used:

Porcelain.
Steel.
Cast iron.
Corundum.

Aluminum wire is most often melted. First, the material is divided into fragments with scissors, then compressed with pliers. This method prevents the exposure of oxygen to the metal.

If there is no need to obtain high-quality parts, there is no need to grind raw materials.

You will have to model the casting technology yourself if you need to obtain molten aluminum at home. The material is pre-cleaned from dirt, impurities, and slags.

Large workpieces are divided into several small fragments. The casting method requires following the instructions: the most convenient method is used to melt the metal. Slag is removed from the surface of the fluid.

Liquid aluminum is poured into a mold, which breaks when it solidifies.

Using the crucible and auxiliary equipment

The previous method is good, but the jar cannot withstand more than one use and may burn out. In this case, there is a risk of metal spilling onto the burner.

To work in the furnace several times, it is recommended to prepare a special container - a crucible. It is made of steel. It is quite possible to use a piece of pipe whose bottom is welded.

A good device can be obtained if you use a cut-off fire extinguisher or a small oxygen cylinder with an oval profile.

In this case, it is worthwhile to provide for the presence of a side chute for draining molten aluminum.

Additional functions of gas furnaces

Each of these three basic oven types may have additional options, as well as elements common to other oven types, such as:

all three types of furnaces can have external wells for loading crushed charge, for example, shavings, into the melt;
inclined hearth furnaces and shaft furnaces may have additional loading windows for loading the charge directly into the melt;
bath furnaces and shaft furnaces can have a wide threshold or a short inclined hearth at the entrance to the furnace for preheating ingots and massive, for example, packaged scrap, as well as for the convenience of removing slag from the surface of the melt;
All types of furnaces can have a melt mixing system, both in the loading well and in the aluminum melt bath.

Types of crucible furnaces

The classification is usually based on the type of energy used to melt the metal. Thus, gas crucible furnaces, like electric ones, are widely used in the industrial sector; they are actively used for working with aluminum and other low-melting materials.

Models operating on solid fuel are common in relatively small workshops that do not have a narrow specialization (in particular, among home craftsmen, since this is the simplest configuration). Induction crucible furnaces that use an electromagnetic field are placed in a separate category; they are connected to an alternating current source.

Reasons for the demand for induction units:

high performance;
ease of management and maintenance, ample opportunities for process automation;
the possibility of draining the mass without residue, completely emptying the crucible;
ensuring rapid melting;
absence of intermediate heating elements.

Depending on the operating conditions, furnaces are distinguished:

compressor (create excess pressure),
vacuum,
open.

Induction crucible furnaces can be:

periodic,
continuous,
semi-continuous.

The melting crucible is:

ceramic (the best option, does not come into contact with the materials being processed);
conductive graphite (durable, suitable for working with precious scrap);
metal.

The latter is divided into water-cooled and conductive modifications.

What for?

A reader interested in home metallurgy “for general development” may have a question: why all this trouble? Not everyone wanders around with a metal detector in the forest after the rain, not everyone is keen on smelting damask steel at home, and not everyone has in mind hundreds of centners of old electronics, from which tens of grams of gold, platinum, and palladium can be extracted.

Let’s ask right there on the Internet how much lead bullion costs. Then, in the nearest fishing store, how many kilograms did you load from it? Let’s halve it so that the owner will certainly be tempted, and calculate the “gain.”

Surprised? You can go even steeper if you have artistic taste and lost-wax casting skills. The material for comparison is bronze scrap and figurines made from it.

But the rise will be even greater with bronze propellers for small vessels. True, making a propeller is much more difficult - you need to accurately maintain the profile, pitch and configuration of the blades. But in general, crucible melting of metal at home is a very profitable business. There would be a desire.

Below you can share your thoughts and results with our readers and regular visitors.

You can also ask questions to the author*, he will try to answer them.

Features of the technological process

A crucible is a refractory container for heating metal. Products made from the following materials are used:

Porcelain.
Steel.
Cast iron.
Corundum.

What heat source should I use?

For remelting aluminum at home, the following are used:

A muffle furnace that you can make yourself. This is an effective method for quickly melting aluminum.
A blowtorch can melt aluminum in small quantities.
Sometimes a gas cutter is used.

The hearth is built from bricks, the frame is made from a metal container. A hole is drilled on the side to supply oxygen. A vacuum cleaner, hair dryer or other device that pumps air is connected to the metal tube. After lighting the fire, the crucible is placed in the hearth.

To achieve better heat treatment, coals are also laid out on the sides. To avoid heat loss, you can build a lid and leave holes for smoke to escape. If the metal needs to be melted once, there is no need to equip a furnace. A simple gas stove will help heat aluminum to the desired temperature. Small pieces of metal melt in about half an hour.

Typically a tin can is used as a crucible. To achieve uniform temperature distribution, a container with aluminum is placed in another jar so that the gap between the walls is 1 cm. To ensure access to the flame, you need to make several holes in a large jar, 3-4 cm in diameter. It is not necessary to remove the divider on the burner. This way you can achieve uniform heating of the metal can. Cover the large tin with a lid to prevent heat from escaping.

Melting aluminum

Aluminum and its alloys are used in almost all areas of industry, as well as in the manufacturing of household items. At room temperature, a thin film of oxide (A12O3) forms on aluminum, firmly protecting it from subsequent oxidation. The oxidation time of aluminum increases sharply with increasing temperature. It is for this reason that in the process of melting aluminum and its alloys in melting furnaces, the surface of the melted material and the mirror of the bath are very quickly covered with an oxide film.

Furnaces for melting aluminum

Often, reverberatory (hearth) furnaces are used in the production of secondary aluminum. This type of furnace for melting aluminum has a large number of modifications. However, all of them are adapted for a standard reverberatory furnace, for special working conditions and a special charge.

Crucible furnaces are no less popular, especially in small industries. Secondary aluminum production often uses rotary furnaces as melting furnaces, especially in order to melt scrap with a high specific surface area, for example, aluminum shavings, as well as very dirty aluminum scrap.

All secondary aluminum producers are divided into two categories:

companies creating casting alloys for aluminum casting manufacturers
companies that create aluminum for steel deoxidation.

Both categories of companies use “old” scrap and production waste from foundries as raw materials. At such plants, in addition to introducing alloying components to refine a certain alloy, they use equipment to purify the aluminum melt and eliminate unwanted chemical elements and other impurities. Rotary melting furnaces are used by these aluminum scrap processors.

Aluminum melting in foundries that produce aluminum castings from recycled aluminum is carried out mainly in crucible furnaces - gas and electric, induction and resistance, both for melting and holding aluminum, as well as for pouring molten aluminum into prepared molds. The melting point of aluminum oxide is approximately 2050 ° C, which is almost three times higher than the melting point of metallic aluminum.

Today, the most popular is the smelting of aluminum in flame reverberatory furnaces, which operate on carbon fuel, and in electric furnaces. During the melting of aluminum in reverberatory flame furnaces and in chamber electric resistance furnaces, heating of individual pieces of the charge starts in the region of the highest temperatures, i.e. in the upper part. At the same time, the surface of the cage oxidizes at high speed and absorbs many gases.

Inside a channel induction electric furnace, the melting of pieces of aluminum is carried out in the region of highest temperatures under a layer of liquid metal, the surface of which is covered with a film of aluminum oxide. The region of highest temperatures in channel electric furnaces is located in a narrow channel and in the adjacent parts of the charge.

The metal on the surface of the shaft has the lowest temperature, as a result of which the resulting castings from channel electric furnaces contain a lower amount of oxides than castings from other types of furnaces. Crucible induction electric furnaces have the same advantage, in which, according to technological requirements, a certain amount of liquid metal remains in the crucible at the end of each melt, approximately 20-35% of the capacity of the furnace crucible.

An important property of liquid aluminum and its alloys is its ability to absorb gases, especially hydrogen. In combustion furnaces, a lot of hydrogen collects in the flue gases. In addition, it can be introduced into smelting furnaces of all types as a raw charge.

Liquid aluminum is a good solvent for many metals, such as iron. In this case, brittle compounds FeAl2 and Fe2Al7 are formed, which reduce the quality of castings.

Melting aluminum at home

It is very sad if small but important functional components in a house break down, for example, guides for roller shutters or sliding doors (they can burst), fittings, etc. Most often, such elements are created from aluminum. Finding a replacement for them is problematic, and sometimes a breakdown in the functionality of a door or window needs to be eliminated immediately, at least temporarily.

If you have experience in soldering, you can fix most of the breakdowns of aluminum fittings or profiles yourself. The main problem is obtaining the working material, that is, molten aluminum, with which the broken parts will be soldered. Many people do not know what the melting point of aluminum is. It is about 660 degrees. A standard gas stove is not capable of heating metal to such a temperature.

What to do? First you need to purchase an aluminum ingot, but you can also use scraps of an old profile. To melt aluminum you will need a portable gas torch or blowtorch. Different models of these devices are capable of giving temperatures in the range of 1000 - 1300 degrees. The prepared material must be placed in a refractory container, for example, made of stainless steel.

In addition, we need a calcined steel plate or another container into which we will pour the molten metal.

Sequence of work:

creating a small “well”. You will need to place a melting container on top
lighting a fire in the “well”. This is necessary to maintain the container in a heated state after using the burner. A fire will also help warm up the aluminum from below.
After the formation of hot coals, you can install a container with aluminum. The melting time of aluminum in this way is approximately 15 – 20 minutes. You can also leave the second container or plate to warm up here.
Next you need to turn on the gas burner to maximum and heat the aluminum from above
the melting of the metal begins almost instantly, but the goal has not yet been achieved. The task is to obtain uniform heating. To achieve this you need to shake the container periodically.
during the smelting process, aluminum oxide is formed, which forms scale
after this, the molten metal must be poured onto a calcined steel surface, carefully so that the scale does not spill out. Now the molten aluminum is ready for further work.