Do-it-yourself gas oven for forging. DIY forge gas forge

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Well, how much we love wild abstruse definitions: special heating devices for the purpose of increasing the plastic characteristics of the metal. Let's try to translate all this disgrace into human language.

A forge is essentially a stove. It is clear that with its own characteristics, varieties and technological nuances, but it’s still a stove. It is needed to heat metal parts to a temperature so that they can be forged, that is, subjected to deformation.

This is the main and general fact for all kinds of forges - from primitive country crafts on bricks to industrial furnaces with many technological features of application and purpose.

Two main and only properties are required from a forge furnace: give a very high temperature, up to 1200 - 1500°C and the ability to maintain desired temperature for a certain time. In other words, we need strong and even heat.

At what temperature do metals become forgeable, that is, begin to be ductile? This is different for all metals and alloys. Here's a visual sign that metal part heated to the required temperature, also common - this is the orange color of the part.

All metals respond to heat by changing color from dark red to piercing white. So the orange color is a signal that you can start real blacksmithing work on metal.

Drawing of a blacksmith's forge.

The only metal that behaves quite meanly and does not change its color when heated is aluminum. It is not the easiest metal to forge and weld in principle; with aluminum you need to know and apply many special requirements.

So here's the absence orange color while it has already warmed up for forging - a significant factor making it difficult to work with this capricious metal and its alloys. After all, you can’t overheat. Underheating is also no good.

Classification of forges

There are several criteria by which you can classify all these stoves into neat types.

Most often, forges are divided according to the type of fuel on which they operate:

Solid fuel forges

They run on coal. Their use is becoming less and less common, since coal is a fuel that does not provide a stable and even fire, which is the most important requirement to the blacksmith's forge. Not only that, such stoves require not just coal, but high-quality coking wood coal or hard coal of the same quality.

There are lovers of such exotic things, so below we will focus on a couple of tips for arranging such a stove.

Gas forges

We’ll talk about this type of stove in detail: they are the most common in both home handicraft workshops and professionally equipped forging centers. The gas forge is, without a doubt, the favorite tool of domestic blacksmiths.

Liquid

Here the main type of fuel is fuel oil.

Coal forge forge.

According to the design decision, forges are divided into closed and open. In size they come in small, medium and large. That, in fact, is the entire classification of forges. A homemade forge for forging is a very real thing and, most importantly, necessary on the farm.

The main thing is to decide which kind of forge suits you. And to do this, you must clearly know what kind of forging products you are going to make, for whom and in what quantities.

Basic design of a homemade forge

The first question is: what kind of forge should I make - open or closed? The answer will depend on your plans - what are you going to do in your blacksmith shop? If this is a hobby in the form of artistic forging in small quantities exclusively for the home and gifts for relatives, then it will be quite enough for you to acquire an open forge.

It is much simpler and will cost you less in terms of money and labor costs. An open forge makes it easier to heat massive or long parts.

If you plan to work with metals seriously, for example, to earn money, then we would advise you to build a closed forge with your own hands.

These are the parts that make up a well-assembled forge:

frame on racks for support, everything must be made of steel;
under – bottom or Bottom part forge walls;
slide-type damper with special holes to accelerate metal heating and save fuel;
fan;
smoke exhaust pipe
linings – thermal protection of the stove in the form of fireclay bricks;
recuperator - a special device for returning the generated heat in the form of furnace gases and, thus, effective use resources.

Building a solid fuel forge

The main disadvantage of solid fuel forges is that coal itself cannot produce the required temperature above 1000°C. Therefore, such stoves always require a feed air jet. Previously, these were bellows, now more often the air is supplied through a pipe with a welded end, also made of steel.

The easiest way is to dig such a stove directly in the ground - just line the hole with fireproof bricks. A homemade forge can be made differently: from a steel plate of decent thickness, build a table with a grate made of cast iron or steel.

Grate for the forge.

The plate for the table must be made from a blank with a thickness of at least 5 mm. If you install an open-construction furnace outdoors, you will not need to deal with special ventilation.

Here are the main stages of construction homemade forge coal-fired:

Build a platform for the foundation with concrete and reinforced rods.
Fold the bricks into a rectangular base; the table surface can be of any height.
Make a hole in any wall of the base for the blower.
Assemble the floor from special refractory bricks onto the base.
Install a grate with holes, which must also be made of fire-resistant material, for which a cast-iron door from an old stove is perfect.
After installing the grate, add walls made of the same refractory brick.
Do not forget to leave a hole in one wall for air supply; it is better to do this immediately when laying bricks.
Install a fan into the air supply pipe.
If you do closed design, be sure to build a chimney, which is absolutely necessary for draft.

Such a forge can be made mobile - it all depends on you. Excellent frame An old gas stove can serve as a solid fuel forge.

Building a gas forge

Before you start building a gas forge with your own hands, you need to determine the parameters of the hearth - its area.

There is a clever formula for this:

N is the productivity of the hearth, which depends on the tension H and the hearth area F. It has been calculated that the gas supply speed in the range from 1 to 1.5 m/sec is sufficient to optimally maintain the required temperature in the hearth.

Diagram of a gas burner for a forge.

You know the area of your workshop and the approximate number of forging parts in kilograms that you plan to produce. With this data you derive the hearth tension with a maximum permissible upper limit of 150 kg/m².

Necessary materials you need to get started:

fire-resistant brick such as dinas or chamotte;
plates with a thickness of at least 5 mm made of heat-resistant steel;
steel profile for the racks, frame and valve of the hearth;
chimney pipe and ventilation duct of steel;
putty for sealing cracks between bricks with heat-resistant properties;
sheet metal or an additional layer of fire bricks for lining with outside;
from high-power double-circuit boilers;
fan;

Gas forges can also be open. With it everything is much simpler; it will be enough to install grate bars with air supply for greater heating efficiency. In this case, combustion substances are removed by a fan made of heat-resistant metal.

It is better to place the support frame close to one of the walls of your workshop. The choice of wall must be made taking into account the need for a chimney and ventilation tube, so it is better not to use adjacent walls, if any.

The most important condition is strict adherence to the rules fire safety which consists in using only fireproof and heat-resistant materials. It doesn't hurt to check what your workshop walls are made of. We treat various types of plasterboard structures with great caution.

It is better to weld the racks and the frame itself from low-alloy steel according to drawings that can be downloaded on the Internet. Low-alloy steel is strong, lightweight and, most importantly, resistant to specific high-temperature corrosion. The external lining must be thought out in advance so that holes for its fastening are immediately made in the support frame.

Now about refractory bricks and masonry. It is important to buy real certified fireclay bricks made in accordance with GOST 390-79. If you purchase a brick that does not meet the standard, you risk that ordinary bricks will begin to melt at a temperature of 1000°C.

Real fireclay bricks are cream-colored with small pores in small quantities; they are much heavier than ordinary ceramic ones; the weight of one large fireclay brick reaches 5 kg. The most suitable brands of fireclay are ShB, ShA and ShPD.

Construction of a forge.

The second type of refractory bricks is dinas. These bricks are more expensive, but more resistant to high temperatures: they can withstand temperatures of 1800°C. They are lighter than fireclay bricks due to the high proportion of silicon salts in their composition.

If you have the opportunity, it is better to line the forge with silica brick: forges made of refractory silica brick are more durable and can withstand the most severe temperature conditions.

The bricks are laid with a mortar of refractory clay with the addition of fireclay and silica powder in a precise proportion of 60:40. Treat the chimney and fan around the perimeter with metal corners.

The most important final stage is drying the entire structure. After this, you need to check how the fans for the forge work. And only then will it be possible to perform a test run.

How to make a burner for a gas forge

Besides general instructions how to make a forge, there are rules for installing a gas burner. gas forge can be purchased in a store, or can be made independently.

You need to make a gas forge burner yourself, taking into account the requirements for it:

ignition of gas should be completely safe;
combustion must be stable;
resistance to humidity inside the furnace;
safety in case of changes in thrust and the risk of explosion of a flammable substance.

The burner is installed through a pre-prepared lining hole. The mouth of the burner is attached to a confuser, which is pulled through a steel gasket. Then pipes for supplying gas and air are installed.

Gas is supplied from or the network under the control of regulators. A test run of gas is carried out to check the regulators and pressure, and monitor the smell.

In blacksmithing, a forge is used to heat and preheat metal blanks before heat treatment. The operating temperature in this device rises to 1200 degrees. By design, the device can be stationary and mobile (that is, placed directly in a specially equipped forge or transported to a place convenient for work). Equipment for industry is completed various devices, For household use The forge is produced in its simplest form.

Features of a household forge

Due to the high cost of smelting plants, not every user can buy such equipment special purpose. For household needs, it is not difficult to assemble a gas forge with your own hands. subject to correct determination of the shape, power and design of the supercharging system. A simple household forge for artistic forging or casting of non-ferrous metal can be assembled from several fireclay bricks and sheet steel.

Making a forge at home for working with ferrous metal is not difficult. Make the simplest design possible from metal container, in the side of which it is necessary to make a hole for a gas burner. The fuel supply system can be assembled from a piece of pipe and coupling; long bolts are suitable for the supporting structure under the container. The lining of a gas fireplace is carried out by filling a solution of alabaster or gypsum, sand and water.

The forge must be equipped protective casing, ceramic tube or suitable sized bottle. After lining and drilling a hole for the gas supply, the device is installed in a convenient place, but at a distance from flammable materials. The advantages of the design include the ability to move the furnace and regulate the degree of heating of the workpiece, which is especially convenient when working with different forging materials.

Operating principle of the installation

Before you begin assembling the thermal unit, you need to understand the principles of operation of a homemade forge for forging metal to simplify the design of the furnace for home use. The operation of the device is based on the energy output when burning a mixture of carbon and oxygen, the percentage of metal released in molten form. During the smelting process, carbon stops the oxidation reaction of the metal; constant injection of gas into the fuel quickly increases the temperature in the forge.

The process of heating metal requires certain skills and specific knowledge. It is not enough to assemble a mini-forge with your own hands; you need to learn how to control the supply of oxygen to the fuel, the volume of which should be no more than 95%. If the workpiece overheats, carburization of the metal occurs, the steel becomes brittle, turning into cast iron.

When developing a drawing of a future blacksmith's device, special attention should be paid to the type of energetic substance that affects the design of the hearth. The type of fuel for the forge is:

gas (butane, propane);
liquid (diesel oil, fuel oil);
solid (charcoal, coke);
mixed (gas-liquid).

Depending on the planned work and the size of the workpiece, the thermal furnace can have an open or closed hearth zone. For the home handyman it should be remembered that domestic gas can be used in a furnace only after preliminary purification from sulfur using the method of “driving” through liquid naphthalene. Products made from heated gas burner metal cannot be used as loaded parts.

The main requirement for ensuring the security of the master is the installation of a powerful forced ventilation system, even if a household soldering apparatus running on bottled gas is used to construct the forge. The device will allow you to manufacture decorative elements interior and exterior in your own garage.

Making a stove from a blowtorch

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

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

Solid fuel device for forge

The simplest model of a solid fuel device for a private forge is an outdoor open stove, which does not require the installation of a ventilation system. The construction of the structure involves pouring reinforced concrete base, at the base of the structure it is necessary to lay wall bricks. The table is installed at a convenient height, a hole is left in one wall for the blower.

The mountain pit is laid out of fireclay bricks supported on steel corners; a cavity for the grate is left in the middle part of the structure. A chimney or probe will help ensure sufficient draft in the fireplace; the air supply system is installed at the final stage construction work. Installing an electric fan in the chimney or installing blacksmith bellows will help increase the draft.

In a home forge, the tank for hardening parts and the gas-air chamber are not mandatory elements. They can be useful in cases where thermal or shock hardening is required when working with damask steel. In the gas-air chamber the following is carried out:

drying and heating oxygen;
filtering oxygen from condensate and foreign impurities;
mixing air with additives for alloying steel.

To melt precious metals and create an alloy of non-ferrous metals, it is necessary to make a crucible from a heat-resistant material. The device, made in the form of a cap, allows you to increase the operating temperature in the furnace without the risk of overheating the workpiece and the formation of soot.

Home gas forge

To make a simple home gas forge, you can use parts from an old bicycle. If on lathe grind the sprocket from the gearbox; the device can operate on butane or propane and heat closed furnaces of small volume. An important condition use portable design is prohibited from operating the burner with acetylene, since heat the flame can burn the former “star”, and the oven will simply explode.

It is not difficult to assemble such a device, and a homemade forge for forge is not much inferior to industrial ones, but is much cheaper. The main thing is to follow safety rules during manufacture and use.

If you are involved in forging, then you have probably had to think about heating the metal more than once. If you don’t yet have the financial opportunity to purchase a forge, then try making a forge with your own hands.

Types of forges:

by type of fuel - forges can operate on solid, liquid or gaseous fuel
by type of installation - portable or stationary models forges
according to the design of the hearth - open or closed type
according to the principle of operation - fuel or electric
according to the method of air supply - with a side nozzle or a central lance
by hearth size ( effective surface) – small, medium and large.

The general structure of the forge is shown in the figure below.

Stages of making a forge with your own hands

1. The production of a forge begins with a table, the height of which will be 0.7-0.8 m, the surface will be 0.8 * 0.8 m or 1.0 * 1.5 m.
2. A furnace nest is placed in the center, consisting of a tuyere or grate for air supply. The grate is often made of cast iron. It is inserted into the hole of the table with a tight fit. If the brick is pre-soaked in water, it will be easier to process.
3. Next, you need to install the air blowing mechanism. This can be a mechanical foot blower, although it is better to use a fan, which is often taken from vacuum cleaners. Its speed is quite enough for work and, moreover, it does not produce much noise. You can make a fan from a blower from a hand siren or use a fan from a car heater.

What kind of fuel can be used in a forge? There are many options. This can be charcoal, hard coal, coke (preferably fine fractions), bottled gas or main gas, liquid fuel, most often fuel oil.

In the next video we will see how a craftsman made a forge with his own hands from an ordinary cast iron duckling. Holes with a diameter of 8 mm were drilled in the bottom of the ducklings. A galvanized pipe is inserted into the pan, filled with expanded clay concrete, and air is blown in.

This video presents a forge made by hand with minimal investment. A detailed story from the master about how he made this forge.

The next video is about a quick and cheap way to make a forge with your own hands. Available to everyone and inexpensive materials for making: bricks, metal bracket, wire, pump from a rubber boat.

If you are one of those people who melts metal in your hands and you dream of having your own forge, then you need a forge. We invite you to use our example, and you will be able to make a forge for yourself with your own hands, which will help you master the art of blacksmithing.

Carpentry or carpentry is, of course, good. Wood processing is traditional for Rus'. But we want to talk about metal. More precisely, about metal forging. What do you need to start forging? The first is a blacksmith's forge.

You might be surprised, but the forge is the easiest thing to organize a forge.

The task of the forge is to heat a piece of metal to a temperature that will allow it to be crushed without destruction.

The forge is, of course, fire. You can burn gas, liquid fuel, fuel oil or crude oil, coal and firewood. Only the firewood produces little heat until it turns into coal. Firewood can only be considered as a raw material for obtaining charcoal, but charcoal is an excellent fuel for a forge. Perhaps the best, but also the most expensive, although also the most accessible. Charcoal for grills and barbecues is sold in any supermarket. So we’ll stick to the coal option.

If we talk about a coal-fired forge, then there are two options: with side blast and with bottom blast. Side blowing is ideal for charcoal, and is also the easiest to implement. The simplest option- a hole in the ground where air is supplied through a pipe. You can also line the forge out of brick and cover it with earth.

With the help of such a forge, novice blacksmiths try their hand. A hose is inserted into the pipe and connected to the blowing hole of the vacuum cleaner.

The disadvantage of this forge is that you have to work while squatting, and this is not very comfortable. However, you can put together a box of the required height, fill it with earth and make a forge in it. But since we are going this route, it is worth doing something more thorough. There is one more point. A forge with side blast is not very suitable for coal, while a forge with bottom blast through a grate is more versatile in this regard. That is, a forge with bottom blast can work on both charcoal and stone. But the design will be more complicated.

We will need:

steel sheet five millimeters thick, about 100x100 cm;
sheet steel 2 mm thick;
corner 30x30;
six fireclay bricks ШБ-8;
angle grinder, popularly called “grinder”;
cleaning wheel;
cutting wheels for cutting steel and stone;
welding machine and electrodes;
two wing screws (eye nut).

The forge consists of a table with a forge nest. Below, under the furnace nest, there is an ash chamber into which air is supplied. The table is made of steel sheet five millimeters thick. The size of the table is arbitrary, but it is more convenient when you can freely place working pliers, a poker and a scoop on it so that they are at hand. We cut a strip 125 mm wide from a five-millimeter sheet; we will need it later, and from the remaining piece we make a table.

Scheme of a forge with a forge nest

Cut out in the middle square hole under the future forge nest. You need to decide on the size of the nest. A large nest will require a lot of coal. A small one will not allow heating large workpieces. The depth of the nest to the grate also matters. Without going into details, let's say that a depth of ten centimeters will be optimal, regardless of the size of the nest in plan.

To prevent the metal from burning through, it must be lined (covered) with fireclay bricks. We use ShB-8 brick. Its dimensions are 250x124x65 mm. These dimensions will determine the size of the forge nest - 12.5 cm at the grate, 25 at the top, 10 cm deep. Considering the thickness of the brick, the size of the hole in the table will be 38x38 cm.

From the cut piece we cut out a square with a side of 25 cm. In the center of the square we cut out a square hole with a side of 12 cm. We also need four plates in the shape of an isosceles trapezoid with base lengths of 38 and 25 cm, a height of 12.5 cm. So the previously cut strip came in handy . Now you need to cook it all.

From two millimeter steel we roll square pipe with a side of 12 and a length of 20-25 cm. This will be an ash receptacle. In the middle of one of the walls we make a hole for the air duct. We weld a pipe into the hole. We use a piece of ordinary water pipe 40.

The ash receptacle from below is closed with a lid. We do it with thumbscrews.

The table is ready. All that remains is to place it on the base or weld the legs from the corner to it. You can make the base from foam concrete blocks.

Pay attention to the opening. An air duct will pass through it.

Using a grinder with cutting disc We cut out the lining from the brick using the stone. Be sure to use a respirator and safety glasses. And follow safety precautions when working with angle grinders.

You can connect a vacuum cleaner and try to light the forge.

First, we lay down wood chips and finely chopped firewood. We set them on fire with a weak blow, and when the wood burns well, add coal. Now you can increase the blowing.

The vacuum cleaner can be connected not directly to the air duct of the forge, but through a homemade air supply regulator. This device allows you to regulate the amount of air supplied to the forge, that is, reduce or increase the blast.

Typically, a damper is installed to regulate the air supply into the duct. But blocking the flow increases the load on the vacuum cleaner motor. An old vacuum cleaner is usually used, and in order not to overload it, an air supply regulator is built. The air flow is not blocked, but is diverted into another duct. For this purpose, a box with three pipes was made. Two opposite each other - the entrance from the pump and the exit to the furnace. The third pipe, on the top wall, is where excess air is discharged. The third pipe is shifted relative to the first two by the diameter of the holes.

Inside is a plate bent at a right angle, half the length of the box wide. The plate can be moved from one extreme position to another using a wire rod. As far as the air supply hole into the forge is blocked, the discharge hole will open to the same extent.

The box is closed with a lid with a hole for traction.

We now have a working forge suitable for outdoor use. To protect from rain, you need a canopy, which must be non-flammable. And the forge needs an umbrella and a pipe to collect and remove smoke.

We make the umbrella from sheet iron two millimeters thick. Firstly, such an umbrella will last longer, and secondly, it is more difficult to weld thinner iron using manual arc welding.

For an umbrella to be as effective as possible, the slope of its walls must be at least sixty degrees to the horizon. The umbrella should be positioned above the fireplace so that an imaginary beam directed from the point closest to the edge of the fireplace, inclined outward at an angle of sixty degrees to the plane of the table, falls inside the umbrella. This means that the higher the umbrella is above the fireplace, the larger it should be. On the other hand, the lower the umbrella is above the table, the more inconvenient it is to work. Here we must proceed from the available material and our anthropometric data.

The umbrella is supported by angle steel posts. We place a pipe on top of the umbrella, which we also weld from a two-piece steel sheet. The pipe must be covered with a spark arrester, which we make from metal mesh.

If you direct the air discharged from the throttle through the air duct (it will go water pipe 1 inch) to the beginning chimney, then you get an ejector that increases the efficiency of flue gas removal.

A forge is an indispensable attribute of workshops engaged in the production of various products using the method of hand-made artistic forging. Only a certain number of forged elements can be produced by plastic deformation of metals at room temperatures. In most cases, heating is required. For steel, in particular, the range of optimal forging temperatures is (depending on the steel grade) from 800...900 0 C to 1100...1200 0 C. A forge is the simplest type of heating device, which is quite suitable for these purposes.

Invented by the ancient Khalibs for forging copper knives and scrapers (Middle East, 6th millennium BC), the first forge was made in the form of a primitive depression in the ground measuring about 700 mm. The pit was surrounded stone wall, in which a hole was provided for air injection. Air injection (which is necessary for stable combustion of fuel) was carried out using blacksmith bellows. They consisted of a cavity made of goat skins, into which air was blown through levers through an air valve. The reverse movement of the lever was ensured by a stone, which was installed on the top plate of the bellows, and the operation of the valve was carried out due to the difference in pressure of cold and hot air.

Existing forge designs are determined by the following factors:

Fuel, on which the device operates: coke, fuel oil, coal or gas.
Design fuel burning device.
Required sizes workspace.
Purpose, since, in addition to heating for forging, forges are also used for some heat treatment operations of finished forgings - carburizing, tempering and even hardening.

For safety reasons, forges are often fired with coal.

Coke is expensive, fuel oil has unsatisfactory environmental operating conditions, and gas furnaces require especially careful routine maintenance. At the same time gas furnaces are characterized by higher efficiency, and also allow for fairly convenient mechanization of some heating control processes - in particular, ignition of gas in the burner or burners.

Common disadvantages blacksmith forges are considered:

Uneven heating metal placed on the surface;
Impossibility practical temperature control heated workpiece;
Unwanted saturation surface layers heated metal sulfur compounds, resulting in increased fragility of the workpiece.

However, an experienced blacksmith is able to estimate the temperature of the metal by the color of its surface, and the problem of sulfurization is solved by using a higher quality type of fuel.

Fuel consumption during the operation of forges is 40...150% of the mass of the heated metal, with its surface loss of 4...7% (depending on the duration of heating). Modern forges are predominantly of the closed type, since otherwise the efficiency of the heating device drops to 5...10%.

Coal fired forges

The design of a heating device of this type includes:

Arch and side walls, which are laid out from refractory bricks (fireclay or dinas).
Horn nest, formed by the upper surface of the arch, where the workpieces are heated.
Umbrella, equipped with folding curtains, and designed to improve natural traction in the workspace.
Rear wall (firewall), which provides openings for supplying source air.
Air valve, designed to turn on the air supply to the forge socket.
Protective box made of heat-resistant steel, which connects the inlet cavity at the air supply valve with the forge socket.
Quenching tank(it can be steel or brick), designed to cool the workpieces during heat treatment or to cool the hearth nest itself from overheating and subsequent formation of temperature cracks.
Chimney, through which fuel combustion products are removed.
Coal storage tanks and various blacksmith tools.

Schematic diagram of the operation of a forge

A solid fuel forge is a rather capricious heating device, and heating it requires a certain amount of practical experience from the blacksmith. It is especially difficult to ignite a forge that has not been used for a long time, and also if the external temperatures and air pressure are quite low. Coal, which is used in such forges, must comply requirements of GOST 8180.

Preparing the forge for heating metal is done in the following sequence:

Their furnace nest removes waste, leftovers forged metal, ash and scale (this should be done even when the surface has been thoroughly cleaned after completion of work);
Chimneys and air supply channels are purged compressed air (for small forges you can use a vacuum cleaner);
A small layer of coal is poured onto the surface of the forge nest., and the opening of the protective box should not be completely blocked;
Top on coal place the rags, soaked in flammable liquid or sawdust;
After ignition when combustion becomes stable, add the next portion of coal(the fraction may have an increased size compared to the original);
The air supply valve opens, and is installed in the middle position;
As it burns out, the blast intensity is gradually increased.

The required quality of heating the workpiece for forging in an open forge is ensured formation of a superficial crust, which is formed during fuel combustion.

The temperature inside the crust is always higher, so the workpiece is placed inside and covered with another dose of coal on top. At the same time, they try not to destroy the upper surface of the crust, since otherwise heating will be slower, and metal waste and scaling will increase. Sometimes, to weaken the processes of carburization of the metal, the crust is sprayed with water.

In open forges, the least intense heating of the metal occurs at the periphery of the forge nest, therefore fresh coal is poured precisely along the perimeter of the heated workpiece. If the crust layer becomes too thick (more than 5...10 mm), it is broken, because in this case, the thermal conductivity to the workpiece decreases.

The workpiece is periodically heated during heating. turn to provide all its parts with the same heating conditions. The flame when burning coal should have a uniform color with a minimum of soot.

Colors of heated steel at different temperatures are:

Dark cherry colors – 700...750 0 C;
Cherry red – 750...800 0 C;
Red – 800…850 0 C;
Light red – 850…900 0 C;
Orange – 900…1050 0 C;
Dark yellow – 1050…1150 0 C;
Light yellow – 1150…1250 0 C.

Overheating of the metal above the specified temperatures is unacceptable. Overheated metal is characterized by a coarse-grained structure, which is less susceptible to forging, especially when forming complex forged elements.

Gas-powered forges

Gas furnaces are brought to the design mode much easier, and this is their advantage over solid fuel heating devices. Typical design such a forge is next:

Camera, made of fire-resistant material, and externally lined with thick sheet heat-resistant steel.
Front flap, opening with hinges or a counterweight, and equipped with a viewing window.
Under, made of heat-resistant fireclay bricks.
Burner. Burner type is determined calorific value gas used. For example, for a propane-butane mixture, diffusion combustion burners are effective, in which mixing of air and gas occurs only after the gas and air leave the device, and mixing of the components occurs due to diffusion processes. Such burners provide the most uniform heating of workpieces (especially long ones), and minimal metal waste is achieved due to the fact that there is always a protective layer above its surface.
Mixing reducer, providing mixing of air and gas (included in the structure of the liquefied gas cylinder).
Nozzle, the configuration of which is determined by the shape of the billets heated in the forge.
Grate, designed to improve traction and collect scale.
Fan, ensuring the injection of air in the required volume with its subsequent supply to the burner coverage area.

To operate such forges, a stationary source of electricity is required. It is advisable to use gas forges for heating parts of long workpieces for forging: heating occurs much faster, and therefore, scaling is less.

When using a gas forge, the following safety requirements must be strictly observed:

Thoroughly ventilate the forge room. Avoiding stagnant zones where flammable gas can accumulate;
Do not use oxygen or oxygen-containing mixtures that are prone to spontaneous combustion and self-ignition near the operating device;
Provide for complete afterburning of gas in the working space of the hearth (determined by a gas analyzer, which is required during a test run of the gas hearth);
Thoroughly clean the grate after turning off the gas supply to the device.

In order to reduce scale formation, they are also used to heat workpieces for forging. and electric resistance heaters, but such devices can be called “forges” with great reserve.

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