Do-it-yourself gas furnace for hardening metal

do-it-yourself, furnace, hardening, metal

DIY Heat treating oven (build video)

How to make a heating element?

Wire is used as a heating element. You can use nichrome or fechral. Nichrome wire withstands up to 1100 degrees. But nichrome can burn out from the slightest contact with air. Fechral can withstand temperatures up to 1300 degrees, while the air does not spoil the wire. The minimum wire size to be used is 1 mm. Depending on the type of the muffle chamber, there are different ways to attach the heating element.

Ceramics muffle wind wired

Propane forge/heat treat oven build for annealing hardening and tempering

The heating element is fixed on the casing with clay, the distance between each turn should be about 2 millimeters. The bonding layer should also be dried for several days and fired in a charcoal kiln.

It is necessary to install a heating coil in the fireclay muffle. It can be made independently from nichrome or fechral wire. To do this, it is necessary to evenly wind the wire around a cylindrical object. Suitable pencil, thin metal rod or welding electrode. The diameter of the spiral should be 6 mm.

Be sure to ensure that the turns do not touch each other, otherwise a short circuit will occur. The spiral must be carried out in special recesses made in fireclay bricks. Be sure to fasten the coils. This can be done with wire or putty. Clay can be used for putty. Holes are drilled in the body through which it is necessary to bring the ends of the wire. To connect the spiral to the network, you need to use a cable.

What is a muffle furnace

A muffle furnace is a thermal device designed to heat materials to a predetermined temperature. It consists of a heating chamber and a capsule (muffle) in which the object to be processed is placed.

The scope of the devices is quite extensive:

  • Laboratory analysis. The properties of many minerals are manifested at high temperatures.
  • blacksmith craft. Heating of workpieces while maintaining their shape and the absence of scale.
  • Metal hardening. During heat treatment, the crystal structure changes, strength and rigidity increase.
  • Fuse. Isolation of the desired substance from heterogeneous raw materials. This is how ingots of aluminum, gold and silver are obtained.
  • Annealing. Contributes to the achievement of a given microstructure when creating parts from several components.
  • Burning. Giving objects the desired properties, such as hardness, presentability, resistance to moisture and chemicals.
  • heat treatment. Removal of water, acids, oils and other liquids from the substance for the purpose of complete drying.
  • Vacation. Removal of internal stresses after melting or hardening, achieving plasticity.
  • Ashing. Removal of foreign matter by incineration. Determination of the presence of minerals in the investigated alloy.

Using the functions of devices allows you to get beautiful ceramics, souvenirs, unique metal products.


The handles are made of dielectric plastic. The muffle furnace is a potential hazardous device requiring the following safety precautions:

  • the turns should not touch each other, otherwise a short circuit will occur;
  • clay or heat-resistant silicone can be used for putty;
  • handles must be made of dielectric plastic.

Efficient ventilation must be used when working with the stove.

Do-it-yourself muffle furnace. features, calculations, useful tips

The muffle furnace allows you to raise the temperature of objects to high values ​​​​impossible in conventional heaters. This is an integral element of jewelry or pottery workshops, other small enterprises. Home craftsmen are often faced with the need to melt metal or provide thermal bonding of glass and ceramics, fire glaze, temper metal, etc.P.

All these procedures require the participation of a muffle furnace, but it is not available. Sometimes this is the only problem stopping an important creative or repair process. However, there is a way out. you need to make a muffle furnace with your own hands. Consider the features and specifics of this process.

DIY muffle furnace

Muffle furnaces are a design, the heating elements of which allow you to achieve the temperature required for firing ceramics, melting metals, hardening steel in a personal workshop. Jewelers and other craftsmen whose workshop is located at home understand the value of such a design. And given the high cost of factory-produced muffle furnaces, such a furnace, made independently, is of particular importance.

The device of the muffle electric furnace

Furnace for melting and hardening

The people asked for a post about the oven and here it is, keep it.It all started with the fact that I needed a furnace for. any. I wanted to melt and heat steel and burn my hands, a complete set, in short. I decided to go the easy way and ordered this one from Ali for 10k (5k shipping):

DIY Heat treating oven- build video

She worked exactly two heats _ after which the spiral flowed and spoiled the muffle:

In general, I strongly advise against taking stoves from the Chinese. suffocate for one or two. However, I managed to fully refund the cost, or Ali took my side. But without shipping. It seems like he hit 5 thousand, but what was left of the furnace remained on his hands, namely: a graphite crucible, a bunch of refractories, a thermocouple and a regulator, as well as fashionable tongs. As a result, almost a draw, probably.The furnace is dead, long live the new furnace!I already assembled this one myself from this: Fireclay brick SHL. 1 (seemingly, I don’t remember exactly which number):

It is precisely light fireclay that is needed, since it is very convenient to cut grooves for a spiral in it, and it is also really very light (very brittle, on the other hand). Cut into 4 bricks of grooves so that the spiral is obtained, rising from the bottom up to put into this spiral, already another spiral (exibut would be happy), from Fehehral. I made the bottom from a pair of the same bricks, and cut a couple more into plugs in the corners of the furnace. Glue everything in place can be a refractory composition for masonry of fireplaces and furnaces, refractory sealant or refractory glue.

Then, be sure to need a fechral, ​​and better suede. Nichrome does not fit, it burns apart when contacting air. I bought such a skein in Novosibirsk (do not pay attention to what is on top):

They sell it by weight and then 3 kg _ the resistivity of this wire is 1.78 microohm per meter. The calculation of the required wire length is very simple: the square of the voltage divided by the power (I needed 1.5 kW) and resistivity. That is, in my case: 220220/1500 = 32 ohms. 32/1.78=18 meters. In total, we take 18 meters of wire and wind it on some bar of the desired diameter. so that it fits well into the grooves sawn in bricks. You can quickly wind up, for example, using an electric screwdriver. I waved my hands %-)

The spiral will need to be stretched so that the turns do not touch each other and put into the grooves

The tighter you can lay the spiral in the grooves and corners, the better. Fethraral when heated becomes softer and can be saved and fall out of the hollow. The spiral comes out from above and below (the photo above shows the exit from above). It is worth twisting the outputs in half so that the wire does not get very hot there. I connected the ends with copper wires to the electronic remains of a Chinese stove. I will not disassemble my stove to take pictures, but such regulators are sold in large stores of radio components (escor in Barnaul, for example). They look like this (on the left):

In principle, it is already possible to include everything, in theory, will work (for smelting aluminum should be enough). However, with more or less long-term use there will be large heat loss and it will not be possible to develop the temperature for melting copper, for example. In this case, mullite-silica wool, the same felt or some kind of ceramic fiber will help. All this is sold in online refractories stores and is quite affordable per kg. It must be wrapped around the working chamber and generally plugged all the holes with it so that the heat does not leave the chamber anywhere. In theory, the lid is best made again from light fireclay and cotton wool to stuff more and so that it fits snugly%.) In short, make the camera as isolated as possible from the outside world.True, my hands still do not reach the lid, so I just put the ceramic fiber from the Chinese oven in three layers on top (at 1000 degrees inside, you can easily press the fiber from above with an unprotected hand).Oh yes, I forgot something. mullite-silica wool is impregnated with some oily stuff to make it easier to install. When heated, it burns out and stinks quite significantly, at first wata will smoke, then the norm.

Something else. thermocouple (it is the same thermometer) should not be exactly located on top, like mine. The fact is that in this position it is lying about temperature, shows, in my case, about 100 degrees are lower than in the working area where the blank is hanging in the photo above.And, of course, keep in mind that current flows in a spiral. Before climbing into the oven, you should turn off the power or take extreme care not to touch the energized coil.If you have any questions or clarifications (you never know, I forgot to write something or confused something), do not hesitate to write in the Комментарии и мнения владельцев.

Melting of metal and cast iron

The furnace for melting metal is a body made of fireclay bricks. The binding element is clay. The furnace is designed for burning coal. A hole is provided below through which air is blown into the ashes. Below is a cast-iron grate, which is called a grate. Coke or coal is laid out on it. It can be removed from the old furnace. Sometimes refractory bricks, when forming the hull, are placed on the edge. The finished structure is fastened on the outside with a metal belt.

The furnace for melting metals must have a crucible. It can be an enameled or cast iron cauldron. Location of Tigers. Next to Burning Coke. In order to improve the imagination, the fan is installed nearby. Equipment is used for steel smelting, but you can use as a furnace for smelting cast iron.

Making a solder lamp furnace

When making a hearth for forging with your own hands, you need to install a blowtorch in a recess, along the perimeter of which lay a fireclay brick with a grate. When laying refractory bricks, it is necessary to observe the distance between the enclosing elements in order to ensure the entry of air masses into the combustion chamber. The angle of location relative to each other blocks of building material is determined by the master.

Charcoal or coke is poured into the recess, equipped with bricks on the grate, a pipe is put on the blowtorch, which is brought under the grate. The blank for forging is placed in the gap between the brickwork, the coal concentrate is ignited from below. To remove smoke, a probe, tent or chimney is installed above the grate.

DIY Tips

When creating from fireclay bricks, any pottery hardening needs to use a heating element. And if there is a need to place an appropriate solution, then it will be necessary to make cuts and technical cavities in the ceramic material. It is best to pre-mark the entire location of the element and only then resort to making cuts. All this can be done at home using simple power tools.

It is worth starting with sawing the seams, using a cutting machine, with a special diamond wheel. And then it will be necessary to remove the obtained areas of ceramics. And here it is best to apply a drill peuorator. Since this will avoid cracking and damage to the material and each of the elements. Do not use the hammer and chisel, because when you hit, cracks may form, which will later lead to the dissent of each of the elements.

Selected and created home-made stoves must be obtained with an understanding of the technical processes in which they will take part. And then a natural question arises, to create a more voluminous furnace or to perform a more miniature solution. In the case of jewelry remelting, a minimum amount of internal space will suffice. This will allow more practical use of products and will not require additional space.

But in the case of blacksmithing, it will be necessary to create more significant design solutions that will allow melting and hardening of metal.

Watch the video in which the user demonstrates in detail the device of a muffle furnace made by himself:

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