How to harden metal at home

How to properly harden metal: methodology, recommendations, heat treatment at home and at the stake

The need to harden steel can arise at any time. There are a large number of different tools sold on the market that may not have been hardened during manufacture or, on the contrary, were overdone with the temperature during heat treatment. For example, you can recall the well-known drill bits. If the steel is not properly hardened, it will bend. If the steel is too hardened, the drill will most likely begin to crumble.

A similar description applies to any steel materials. Naturally, it won’t be possible to check metal in a store. In this case, there is only one option left, we are talking about hardening steel at home.

Checking metal for quality at home

The first step after purchasing a metal item is to check its quality. This can be done using a simple soldering iron. The end of the soldering iron is passed over the metal to identify defects when developing the tool.

If the soldering iron sticks to the surface, it means the steel is not hardened, and with frequent use the tool will become deformed. If, on the contrary, the tip of the soldering iron passes smoothly over the steel and almost bounces off it, then the metal is too hardened.

In this case, you need to heat treat the steel tool to increase its strength.

Hardening technique

On the Internet you can find a large number of methods and videos of hardening metal objects, but most of them require special equipment, but there are ways that help improve the quality of steel using improvised means.

First you need to determine what steel hardening is. The main process is divided into two parts, or more precisely, heating the metal to a high temperature and subsequent cooling.

The process looks simple only at first glance, but you have to take into account the structure and characteristics of the metal . If you start heating the steel without analyzing it, the material will most likely deform.

Deformation occurs especially often with low-carbon steel, so if the structure of the metal is unknown, it is better not to use heat treatment.

Hardening of steel is justified only in some cases.

1. The need to increase the strength of the tool . For example, it could be an ordinary kitchen utensil, a chisel or a chisel.
2. Increasing the ductility of the metal also requires heat treatment to further simplify the work during hot forging.

You can also order steel hardening services from specialists, especially since the cost is reasonable. For 1 kg of metal of a large structure, blacksmiths usually charge no more than 100–150 rubles. If you harden small parts, the prices are about 6–20 rubles. This will not guarantee the quality of the instruments, which is why many try to use heat treatment at home in order to independently monitor the process.

The first thing you need to remember when heating steel is some rules. Steel can be damaged if the temperature of the metal is raised above normal.

In this case, the tool may acquire a black or blue tint , which in the end cannot even be sanded off with sandpaper.

In order for such a defect to not occur, the metal must have a sufficient amount of carbon in its structure, and one must not overdo it with increasing temperature. Typically, steel is considered hot if a red tint appears.

For heat treatment of steel tools, a cutter, blowtorch, electric or gas stove may be suitable. In some cases, metal can be heated over a fire . In fact, there is no difference in where it is better to heat a metal product. Simply in the open air, when heated by a fire, there may not be enough heat energy to achieve the required temperature. Therefore, it is important to clarify the melting and hardening temperature of the material in advance.

It is also necessary to decide on the coolant during heat treatment. Any container with water is suitable for this, the main thing is that the tool fits completely. If steel consumables are being hardened, then a simple cut bottle can be used. In the case of heat treatment of an ax, crowbar and other similar tools, you need to choose a container with a large volume. In some cases, even a bathtub may be suitable, especially since there is no risk of its deformation.

The cooler is selected not only taking into account the size of the steel object, but also the method of heat treatment. Sometimes only a certain area needs to be hardened , in which case only jet cooling can be used.

More precisely, plain water is poured onto the material in drops into the area that requires hardening. This method is especially often used when heat treating a drill bit for a drill or on nails to improve the quality of the tip.

The hardening technique can be divided into several levels.

The following cooling levels are distinguished:

• sharp;
• one-time;
• gradual.

For single cooling, a simple container of water is most often used. If two-stage cooling is used, then two different means are used in the process.

This, in turn, increases not only the quality, but also the release of steel material. First of all, the steel is immersed in plain water, and then transferred to machine or mineral oil for further cooling .

The process is quite dangerous, because you need to cool the product in water to prevent the oil from igniting.

Hardening steel over an open fire

How to harden metal at home over an open fire? The question is quite common, and there are many methods. Heat treating over an open fire may not be as effective, but it reduces the risk of fire , especially when using oil while cooling the steel material.

The first thing you need to do is prepare your tools. You need to take steel material that will undergo heat treatment, forging tongs or an analogue tool and two containers. Water should be poured into one container, and machine or diesel oil should be added to another container.

After this, you should make a fire, using a large amount of coal. Unlike most methods of heating metal, here the material must be placed directly on the coals and it is desirable that they be white, because they are the ones that produce the highest temperature.

The fire that will envelop the steel must be crimson in color. If a white fire appears, then we can assume that the steel material has begun to burn .

In this case, it is impossible to save it, so it is better not to bring the hardening to this stage of melting.

You should also not allow black or blue spots to appear on the metal product. A blue color indicates that the steel has softened too much and has begun to deform, so it is worth checking the shade of the material from time to time. Complete deformation of the metal occurs when the object turns white.

After the steel material has heated up, you need to remove it from the fire and lower it into the oily liquid. The metal should be dipped several times at intervals of three seconds, gradually increasing this time.

The main thing is to do everything without haste, but you can’t hesitate either, because you can dip steel only if the material has the appropriate heat shade . After this, the metal product is placed in plain water, but you should be extremely careful here, as the remaining drops of oil may simply burst into flames.

If the procedure is carried out taking into account all the recommendations, the metal product can simply be left in water until it cools completely.

It is also important to remember that, unlike conventional tools, elongated objects, such as drills or nails, cannot be lowered into water sideways , since the lower part may simply flatten due to high temperature and sudden contact with water. Such elongated objects are lowered vertically into the water, with the end that has a larger diameter.

Hardening steel at home on a stove or fire is only suitable in cases where a simple type of material is used. When hardening non-ferrous metal, the temperature required is too high, which is 600–900 degrees. This result can be achieved using blast furnaces, but not at home.

Conclusion

The use of metal heat treatment can improve the quality of tools or consumables. When hardening steel at home, it is important to remember the basic recommendations so as not to deform the material.

Source: https://stanok.guru/metalloobrabotka/termoobrabotka-metalla/kak-pravilno-v-domashnih-usloviyah-zakalyat-metall.html

Products – Tekhmashholding – group of companies, official website

If you know how to harden metal correctly, then even at home you can increase the hardness of products made from it two to three times. The reasons why there is a need for this can be very different. Such a technological operation is required, in particular, if the metal needs to be given hardness sufficient for it to cut glass. Hardening metal at home Most often, a cutting tool needs to be hardened, and heat treatment is performed not only if it is necessary to increase its hardness, but also when this characteristic needs to be reduced. When the hardness of a tool is too low, its cutting part will jam during operation, but if it is high, the metal will crumble under the influence of mechanical loads. Few people know that there is a simple way to check how well a steel tool is hardened, not only in industrial or home conditions, but also in the store, when purchasing. In order to perform this test, you will need a regular file. It is passed along the cutting part of the purchased tool. If it is poorly hardened, then the file will seem to stick to its working part, and in the opposite case, it will easily move away from the tool being tested, while the hand in which the file is located will not feel any irregularities on the surface of the product. Dependence of steel hardness on the heat treatment mode If it turns out that you have at your disposal a tool whose hardening quality does not suit you, there is no need to worry about this. This problem can be solved quite easily: you can harden metal even at home, without using complex equipment and special devices. However, you should know that low-carbon steels cannot be hardened. At the same time, the hardness of carbon and tool steel alloys can be easily increased even at home.

Technological nuances of hardening

Hardening, which is a type of heat treatment of metals, is performed in two stages. First, the metal is heated to a high temperature and then cooled. Different metals and even steels belonging to different categories differ from each other in their structure, therefore their heat treatment modes do not coincide. Heat treatment modes for some non-ferrous alloys Heat treatment of metal (quenching, tempering, etc.) may be required for:

• its strengthening and increasing hardness;
• improving its ductility, which is necessary when processing by plastic deformation.

Many specialized companies harden steel, but the cost of these services is quite high and depends on the weight of the part that needs to be heat treated. That is why it is advisable to do this yourself, especially since you can do it even at home.

If you decide to harden the metal on your own, it is very important to correctly carry out such a procedure as heating. This process should not be accompanied by the appearance of black or blue spots on the surface of the product. The bright red color of the metal indicates that heating is occurring correctly. This video demonstrates this process well, which will help you get an idea of ​​the degree to which to heat the metal subjected to heat treatment.

As a heat source for heating the metal product that needs to be hardened to the required temperature, you can use:

• a special oven powered by electricity;
• blowtorch;
• an open fire that you can make in the yard of your house or in your country house.

Hardening a knife on open coals

The choice of heat source depends on the temperature to which the metal to be heat treated must be heated.

The choice of cooling method depends not only on the material, but also on the results to be achieved. If, for example, it is not necessary to harden the entire product, but only a separate section of it, then cooling is also carried out pointwise, for which a stream of cold water can be used.

The technological scheme by which metal is hardened may include instant, gradual or multi-stage cooling.

Rapid cooling, which uses one type of coolant, is optimal for hardening steels classified as carbon or alloy. To perform such cooling, you need one container, which can be a bucket, barrel, or even an ordinary bathtub (it all depends on the size of the item being processed).

Cooling the knife blank in oil

In the event that steels of other categories need to be hardened or if, in addition to hardening, tempering is required, a two-stage cooling scheme is used. With this scheme, a product heated to the required temperature is first cooled with water and then placed in mineral or synthetic oil, in which further cooling occurs. Under no circumstances should an oil-based cooling medium be used directly, as the oil may ignite.

In order to correctly select the hardening modes of various steel grades, you should focus on special tables.

Heat treatment modes for high-speed steels

Heat treatment modes for alloy tool steels

Heat treatment modes for carbon tool steels

How to harden steel over an open fire

As mentioned above, you can harden steel at home, using an open fire for heating. Naturally, such a process should begin by starting a fire, in which a lot of hot coals should form. You will also need two containers. You need to pour mineral or synthetic oil into one of them, and ordinary cold water into the other.

In order to remove hot iron from a fire, you will need blacksmith tongs, which can be replaced with any other tool of a similar purpose. After all the preparatory work has been completed, and a sufficient number of hot coals have formed in the fire, objects that need to be hardened can be placed on them.

The color of the formed coals can be used to judge the temperature of their heating. Thus, coals whose surface has a bright white color are hotter. It is also important to monitor the color of the fire’s flame, which indicates the temperature regime in its interior. It is best if the fire flame is colored crimson rather than white. In the latter case, indicating that the flame temperature is too high, there is a risk of not only overheating, but even burning the metal that needs to be hardened.

Heated steel colors

The color of the heated metal must also be carefully monitored. In particular, black spots must not be allowed to appear on the cutting edges of the tool being processed. Blue discoloration of the metal indicates that it has softened greatly and become too flexible. It cannot be brought to such a state.

After the product has been calcined to the required degree, you can proceed to the next stage - cooling. First of all, it is lowered into a container with oil, and this is done often (every 3 seconds) and as sharply as possible. Gradually the intervals between these dives increase. As soon as the hot steel loses its brightness, you can begin to cool it in water.

Steel tarnish colors

When cooling metal with water on the surface of which droplets of hot oil remain, care should be taken, as they may burst into flames. After each dive, the water must be agitated to ensure it remains cool at all times. A training video will help you get a clearer idea of ​​the rules for performing such an operation.

There are certain subtleties when cooling hardenable drills. So, they cannot be lowered flat into a container with coolant. If you do this, then the lower part of the drill or any other metal object that has an elongated shape will cool sharply first, which will lead to its compression. That is why it is necessary to immerse such products in coolant from the wider end.

For heat treatment of special grades of steel and smelting non-ferrous metals, the capabilities of an open fire are not enough, since it will not be able to heat the metal to a temperature of 700–9000. For such purposes, it is necessary to use special furnaces, which can be muffle or electric. If it is quite difficult and expensive to make an electric furnace at home, then with muffle-type heating equipment this is quite feasible.

Self-production of a chamber for hardening metal

A muffle furnace, which is quite possible to make yourself at home, allows you to harden various grades of steel. The main component that is required to make this heating device is refractory clay. The layer of such clay that will cover the inside of the oven should be no more than 1 cm.

Diagram of a chamber for hardening metal: 1 - nichrome wire; 2 - inner part of the chamber; 3 — outer part of the chamber; 4 - rear wall with spiral leads

In order to give the future furnace the required configuration and desired dimensions, it is best to make a mold from cardboard impregnated with paraffin, onto which fireproof clay will be applied.

Clay, mixed with water to a thick, homogeneous mass, is applied to the wrong side of the cardboard form, from which it will peel off after complete drying.

Metal products heated in such a device are placed into it through a special door, which is also made of refractory clay.

After drying in the open air, the chamber and door of the device are additionally dried at a temperature of 100°. After this, they are fired in a furnace, the temperature in the chamber of which is gradually raised to 900°. When they have cooled after firing, they must be carefully connected to each other using metalworking tools and emery cloth.

Clay heater with a walled nichrome spiral

Nichrome wire is wound onto the surface of the fully formed chamber, the diameter of which should be 0.75 mm. The first and last layers of such winding must be twisted together.

When winding the wire around the camera, you should leave a certain distance between its turns, which also needs to be filled with fireproof clay to eliminate the possibility of a short circuit.

After the layer of clay applied to provide insulation between the turns of nichrome wire has dried, another layer of clay is applied to the surface of the chamber, the thickness of which should be approximately 12 cm.

After complete drying, the finished camera is placed in a metal case, and the gaps between them are filled with asbestos chips. In order to provide access to the inner chamber, doors, lined with ceramic tiles on the inside, are hung on the metal body of the oven. All existing gaps between structural elements are sealed using refractory clay and asbestos chips.

Ready homemade camera

The ends of the nichrome winding of the camera, to which electrical power must be supplied, are brought out from the rear side of its metal frame.

In order to control the processes occurring in the inside of the muffle furnace, as well as measure the temperature in it using a thermocouple, two holes must be made in its front part, the diameters of which should be 1 and 2 cm, respectively.

From the front part of the frame, such holes will be closed with special steel curtains. The homemade design, the manufacture of which is described above, allows you to harden metalworking and cutting tools, working elements of stamping equipment, etc. at home.

Self-manufacturing of such a furnace (as well as other types of hardening equipment) allows you not only to get at your disposal a device that fully meets your needs, but also to save a lot of money, since serial models are quite expensive.

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Source: https://pellete.ru/stal/kak-pravilno-zakalit-stal.html

How to harden metal yourself at home

Heat treatment of metals is one of the main ways to improve their mechanical and physical-chemical characteristics: hardness, strength and others.

One type of heat treatment is hardening. It has been successfully used by man in a handicraft way since ancient times. In the Middle Ages, this method of heat treatment was used to improve the strength and hardness of metal household items: axes, sickles, saws, knives, as well as military weapons in the form of spears, sabers and others.

And now they use this method of improving the characteristics of metal, not only on an industrial scale, but also at home, mainly for hardening metal household items.

What is metal hardening and its types

Hardening is understood as a type of heat treatment of a metal, consisting of heating it to a temperature, upon reaching which a change in the structure of the crystal lattice occurs (polymorphic transformation) and further accelerated cooling in water or an oil medium. The purpose of this heat treatment is to increase the hardness of the metal.

Hardening is also used, in which the heating temperature of the metal prevents a polymorphic transformation from taking place. In this case, its state is recorded, which is characteristic of the metal at the heating temperature. This state is called a supersaturated solid solution.

Polymorphic transformation hardening technology is used mainly for products made of steel alloys. Non-ferrous metals are subjected to hardening without achieving a polymorphic change.

After such treatment, steel alloys become harder, but at the same time they become more brittle, losing their ductility.

To reduce unwanted brittleness after heating with polymorphic change, a heat treatment called tempering is used. It is carried out at a lower temperature with gradual further cooling of the metal. In this way, the stress of the metal is relieved after the hardening process, and its fragility is reduced.

When hardening without polymorphic transformation, there is no problem with excessive brittleness, but the hardness of the alloy does not reach the required value, therefore, during repeated heat treatment, called aging, it is, on the contrary, increased due to the decomposition of the supersaturated solid solution.

Features of steel hardening

Mainly stainless steel products and alloys intended for their manufacture are hardened. They have a martensitic structure and are characterized by increased hardness, leading to brittleness of products.

If you heat treat such products by heating to a certain temperature followed by rapid tempering, you can achieve an increase in viscosity. This will allow the use of such products in various fields.

Types of steel hardening

Depending on the purpose of stainless steel products, it is possible to harden the entire item or only that part of it that must be functional and have increased strength characteristics.

Therefore, hardening of stainless steel products is divided into two methods: global and local.

Cooling medium

Achieving the required properties of stainless materials largely depends on the choice of cooling method.

Different grades of stainless steel undergo cooling differently. If low-alloy steels are cooled in water or its solutions, then for stainless alloys oil solutions are used for these purposes.

Important: When choosing a medium in which to cool the metal after heating, it should be taken into account that cooling occurs faster in water than in oil! For example, water at a temperature of 18°C ​​can cool an alloy by 600°C in a second, but oil by only 150°C.

In order to obtain high metal hardness, cooling is carried out in running cold water. Also, to increase the hardening effect, a brine solution is prepared for cooling by adding about 10% table salt to the water, or an acidic medium containing at least 10% acid (usually sulfuric) is used.

In addition to the choice of cooling medium, the cooling mode and speed are also important. The temperature decrease rate must be at least 150°C per second. Thus, in 3 seconds the temperature of the alloy should drop to 300°C. A further decrease in temperature can be carried out at any speed, since the structure fixed as a result of rapid cooling will no longer be destroyed at low temperatures.

Important: Cooling the metal too quickly leads to its excessive fragility! This should be taken into account when hardening yourself.

The following cooling methods are distinguished:

• Using one medium, when the product is placed in a liquid and kept there until completely cooled.
• Cooling in two liquid media: oil and water (or saline solution) for stainless steels. Products made of carbon steel are first cooled in water, since it is a fast cooling medium, and then in oil.
• Using the jet method, when the part is cooled with a stream of water. This is very convenient when you need to harden a specific area of ​​the product.
• Using the method of step cooling in compliance with temperature conditions.

Temperature

The correct temperature regime for hardening stainless steel products is an important condition for their quality. To achieve good characteristics, they are uniformly heated to 750-850°C, and then quickly cooled to a temperature of 400-450°C.

Important: Heating the metal above the recrystallization point leads to a coarse-grained structure, which worsens its properties: excessive brittleness, leading to cracking!

To relieve stress after heating the metal to the desired hardening temperature, step-by-step cooling of products is sometimes used, gradually lowering the temperature at each heating stage. This technology allows you to completely remove internal stress and obtain a durable product with the required hardness.

How to harden metal at home

Using basic knowledge, you can harden steel at home. Heating of metal is usually carried out using a fire, electric muffle furnaces or gas burners.

Hardening an ax at the stake and in the oven

If you need to give additional strength to household tools, for example, to make an ax more durable, then the easiest way to harden it can be done at home.

During manufacture, axes are stamped with a mark by which you can identify the grade of steel. We will look at the hardening process using U7 tool steel as an example.

The technology must be performed in compliance with the following rules:

1. Annealing . Before processing, dull the sharp edge of the blade and place the ax in a burning brick oven to heat. The heat treatment procedure must be carefully monitored to prevent overheating (permissible heating is 720-780°C). More advanced craftsmen recognize the temperature by the color of the heat.

And beginners can find out the temperature using a magnet. If the magnet stops sticking to the metal, it means the ax has heated up above 768°C (red-burgundy color) and it’s time to cool down.

Use a poker to move the hot ax to the oven door, remove the heat deeper, close the door and valve, leave the heated metal in the oven for 10 hours. Let the ax gradually cool down with the stove.

2. Hardening of steel . Heat the ax over a fire, potbelly stove or stove until dark red - temperature 800-830°C (the magnet has stopped magnetizing, wait another 2-3 minutes).

Quenching is performed in heated water (30°C) and oil. Lower the ax blade into the water 3-4 cm, moving it vigorously.

Next, place the ax in a container with oil; if the oil catches fire, cover the container with a thick cloth. Keep in oil until completely cool.

3. Release of the ax blade . Tempering reduces the brittleness of steel and relieves internal stress. Sand the metal with sandpaper to better distinguish the colors of the paint.

Place the ax in the oven for 1 hour at a temperature of 270-320°C. After standing, remove and cool in air.

heat treatment of an ax at home, three stages: annealing, hardening, tempering.

Hardening the knife

It is advisable to use furnaces to harden metals yourself. For household items in the form of knives, axes, drills and others, small muffle furnaces are the most suitable. In them you can achieve a hardening temperature much higher than on a fire and it is easier to achieve uniform heating of the metal.

You can make such a stove yourself. You can find many simple design options on the Internet. In such ovens, a metal product can be heated to 700-900°C.

Let's look at how to harden a stainless steel knife at home using an electric muffle furnace. For cooling, instead of water or oil, melted sealing wax is used (can be obtained from a military unit).

The sequence of the hardening process is as follows:

• the knife (without a handle, if it is wooden) is placed in a cold oven;
• turning on the closed oven, heat it together with the knife until the blade turns bright red (800-900°C);
• Using a hot knife blade, cut the sealing wax up to 10 times, plunging 1.5 cm into it;
• the procedure is repeated up to 5 times, heating the knife blade and cooling in wax;
• Remains of sealing wax are removed with turpentine using a dampened cloth.

It is better to do the procedure in the fresh air; sealing wax smells terrible when melted. Also, the knife blade can be heated over an open fire.

other ways to harden a knife at home.

Source: https://plavitmetall.ru/obrabotka/zakalka-stali-v-domashnix-usloviyax.html

Hardening metal at home: hardening steel correctly

If you know how to harden metal correctly, then even at home you can increase the hardness of products made from it two to three times. The reasons why there is a need for this can be very different. Such a technological operation is required, in particular, if the metal needs to be given hardness sufficient to enable it to cut glass.

Hardening metal at home

Most often, a cutting tool needs to be hardened, and heat treatment is performed not only when its hardness needs to be increased, but also when this characteristic needs to be reduced. When the hardness of the tool is too low, its cutting part will jam during operation, but if it is high, the metal will crumble under the influence of mechanical loads.

Few people know that there is a simple way to check how well a steel tool is hardened, not only in production or at home, but also in a store when purchasing. In order to perform this test, you will need a regular file.

It is passed along the cutting part of the purchased tool.

If it is poorly hardened, then the file will seem to stick to its working part, and in the opposite case, it will easily move away from the tool being tested, while the hand in which the file is located will not feel any irregularities on the surface of the product.

Dependence of steel hardness on heat treatment mode

If it turns out that you have at your disposal a tool whose hardening quality does not suit you, there is no need to worry about it.

This problem can be solved quite easily: you can harden metal even at home, without using complex equipment and special devices. However, you should know that low-carbon steels cannot be hardened.

At the same time, the hardness of carbon and tool steel alloys can be easily increased even at home.

How to harden a knife or other steel at home: types of hardening, their features and instructions

How to harden a knife at home? This question arises for many home craftsmen. Metal hardening is a type of heat treatment that allows you to deform and change the state of a substance.

This method of improving the properties of weapons has been used since ancient times. For example, in the Middle Ages, hardening was used to increase the strength and hardness of various objects: from ordinary knives to axes and sickles.

Thanks to the development of technology, this heat treatment is now available not only at industrial enterprises where there is special equipment, but also at home. We will talk about this in detail in this article.

Proper cooling (holiday)

In order to achieve the necessary properties of the metal, you need to responsibly choose the cooling medium in which this process will take place.

The list of cooling media that are suitable for our business is as follows:

• One medium with liquid. Cold water is best. The body is placed inside and remains there until it cools completely.
• Two environments with different liquids. As in the first case, water is placed in the first medium, and the product is sent there first. After initial cooling, it is placed in oil or saline solution.
• Next comes standard jet cooling. There is nothing complicated or special here: the product is simply placed under running cold water until cooled. Perfect for cases when it is necessary to heat a separate element of the entire product.
• A special staged cooling method that uses several different temperature conditions.

Correct temperature

Before starting the process of hardening steel at home, it is necessary to understand the temperature regime, which must be observed to achieve a high-quality result. The product must be uniformly heated to a temperature of about 700−850 degrees Celsius, and then quickly released to 400−500 using one of the methods described above.

There are a large number of methods, involving various techniques and other devices. However, in this article we will look at the two most popular ones, which are best suited for home use: in a stove or oven and over a fire.

There is no fundamental difference between these methods. The main thing is to place the knife or other product in the oven or fire and monitor its temperature.

The first step is annealing, that is, the main step of heat treatment. It is important to monitor the temperature of the steel and prevent overheating. If there is no special device that can be used to measure its current indicator, you can evaluate it by the color of the heat:

• Orange - from 950 to 1000 degrees;
• Red-orange - from 900 to 950;
• Red - from 800 to 900;
• Darkish red - from 750 to 800 degrees;
• Red-burgundy - from 700 to 750;
• Burgundy - from 650 to 700;
• Brown-red - from 550 to 650;
• Reddish brown - 500 to 550 degrees.

You can also check the readiness of hardening using a regular magnet. If it stops “sticking” to the metal, then its temperature is about 760 degrees, and it is necessary to proceed to cooling as quickly as possible.

For a more convenient holiday, you can also check the color of the product, thus:

• Gray - 350 degrees;
• Blue - 300−350 degrees;
• Blue - 300 degrees;
• Purple - 280 degrees;
• Red-brown - 260 degrees;
• Yellow-brown - 250 degrees;
• Straw yellow - 240 degrees;
• Light yellow - 200−240 degrees.

So, as you can see, it is quite easy to harden a steel product at home. However, you should always remember safety precautions and also keep in mind the instructions described in this article.

Source: https://tokar.guru/metally/sovety-po-zakalke-stali-v-domashnih-usloviyah.html

How to harden steel at home

Hardening the metal increases the hardness of the product by 3-4 times.

The need for this procedure arises when you need a metal object to cut glass without effort.

It happens that the need to harden a metal tool arises due to the fact that it is either not hardened to the required degree, or, conversely, it was overdone in hardening it.

In the first case, metal objects, such as drills, become jammed, in the second they literally crumble.

It is unlikely that you will be able to check in the store how well a metal tool is hardened.

Although the possibility of such verification exists. You need to take a file and run it along the edge of a cutting object - a knife or an ax.

The fact that the file sticks and sticks to the metal means that the product has not been hardened enough.

In this case, its edge will be too soft and pliable.

If the file moves away from the object with ease and seems to be stroking it, and the hand does not feel any uneven places while pressing, then the product has become overloaded on the face.

If you still have metal equipment in your hands that needs additional hardening, then it’s okay.

You can harden a knife with your own hands, even without resorting to complex technologies, that is, at home.

The only thing you need to remember: it is forbidden to harden low-carbon steels.

But it is quite possible to increase the strength of carbon and tool steels.

How to make a chamber for hardening metal?

A homemade muffle furnace is a must-have in the household today. It allows you to heat treat the product without unnecessary steps.

To make a stove with your own hands, you will need fireproof clay, which is used to cover boilers. A chamber no more than 1 cm thick is created from this material.

And its dimensions must fit into the following parameters of length, height and width - 210 * 105 * 75 mm.

When fashioning a muffle furnace with your own hands, you need to have a mold made from cardboard in advance. It is better to soak it in paraffin so that it does not stick.

The clay is spread on the mold from the wrong side, because this way it will not shrink during drying. When the clay hardens, it will move away from the edges of the mold on its own.

The same refractory clay will serve as the material for making the oven door. Then the homemade muffle furnace in the form of two parts should dry in the open air.

Then it is completely dried in an oven at a temperature of one hundred degrees.

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Then the door and chamber are fired, gradually increasing the temperature to 900 degrees. These parts should then gradually cool in the oven itself.

  U-shaped steel profile

Then the door is attached to the oven, carefully using a file and sanding the surface with sandpaper.

You need to wind 18 meters of nichrome wire around the camera. Its thickness should be 0.75 mm. The first and last turns are twisted.

A homemade muffle furnace made by yourself is placed in a metal frame measuring 270*200*180 mm.

To make the case easy to assemble, it is better to make it with two removable covers, which are secured with screws.

A door is attached to the front lid on a hinge; it should open horizontally. It is necessary to install a ceramic part on this door using bolts and gaskets.

The remaining gaps are again filled with clay, and the edges of the wire are removed onto the back cover of the frame.

Then a connector and a standard cord with a plug are prepared. All holes between the heating elements and the frame must be filled with asbestos chips.

To install a thermocouple and be able to monitor the heating process, it is advisable to make two holes in the chamber.

The first is 1 cm in diameter, the second is 2 cm. Closable metal curtains need to be attached to these holes.

The homemade stove design weighs 10 kg and can heat up to 950 degrees within an hour.

Its presence facilitates the process of hardening a drill, file, matrix and many other metal products. How a homemade stove hardens metal equipment is shown in the video.

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Although muffle equipment that hardens metal is not the only option. Heat treatment can be performed by chamber and flame equipment, electric furnace, thermal furnace, as well as bath furnaces.

In any case, making a hardening device yourself is more profitable than buying it. For example, the average price of a muffle furnace is 40 thousand.

An electric furnace is used to harden metal at a temperature of about 1300 degrees and the electric furnace costs much more.

Source: https://steelfactoryrus.com/kak-zakalit-stal-v-domashnih-usloviyah/

How to harden metal at home: improving the properties of a knife, chisel and ax

Heat treatment of metal has been carried out for many centuries. It allows you to significantly improve the performance properties of the material and change some properties. Hardening is a type of heat treatment.

Even before the advent of firearms, blades were strengthened by hardening the metal used during their manufacture. Today, at home, you can harden a bolt, axe, chisel, blade, wire and many other products.

It is worth considering in more detail how you can harden metal at home, and what difficulties may arise.

The essence of hardening metal products

In order to properly harden iron and other metals, you should consider the essence of this process.

The features of this type of heat treatment include the following:

• Quenching means heating a material to a temperature that can change its structure. In metals, the structure is represented by a crystal lattice.
• The process also involves cooling the material, for which oil or water can be used.

The purpose of such heat treatment is to increase the hardness of the structure of steel or other alloy.

Hardening is also associated with a process called tempering. It is carried out in order to reduce the fragility of the structure after heat treatment. Vacation is carried out at a lower temperature, and cooling takes much longer. The importance of this process is great, otherwise serious defects may form in the structure.

What metals can be hardened

It should be borne in mind that not all metals are suitable for such heat treatment. Very often, the physical and mechanical qualities of structural steels are improved, for example, steel 45, as well as some alloyed alloys (65G, U7Kh).

Aluminum and many other non-ferrous alloys undergo heat treatment, during which the crystal lattice remains unchanged. This can be achieved by heating to low temperatures followed by rapid cooling in a different environment.

Features of the technology

There are 3 main stages of heat treatment of steel:

1. Annealing. First, the structure is heated to a temperature that is selected depending on the type of material being hardened (for U7 80°C). After heating, the metal is left in the furnace to cool slowly.
2. Hardening. After annealing, the hardening stage begins. Depending on the type of metal, the heating temperature can vary between +800+1000°C and above. At home, you can only reach +800°C or slightly higher. Heating is carried out until the metal becomes completely red, while the graphite and the entire crystal lattice are rearranged. Cooling can take place in water, but it is better to use oil, which will reduce the likelihood of serious defects in the structure. It should be borne in mind that when the oil is heated, smoke and other combustion products that are harmful to humans may be formed.
3. Vacation. Tempering can significantly reduce the fragility of the structure, while the product is kept in the oven for 1 hour or more at a temperature not exceeding +320°C. It is important to consider that at this stage the crystal lattice should not be rearranged, since strong heating can lead to a decrease in the hardness of the surface layer.

Hardening a knife at home is feasible; all you need is a regular oven, a place to do the work, and a container of oil or water to cool the metal.

Much attention is paid to the choice of steel cooling method. The following methods are distinguished:

• Application of one environment.
• Cooling when using two liquids.
• Jet method of reducing metal surface temperature.
• A step cooling method used to reduce stress in the structure of a material.

When hardening at home, it should be taken into account that too rapid cooling causes increased fragility of the structure. It is important to ensure uniform cooling, which allows for a uniform structure.

Be careful when working with hot steel. Such work should not be carried out near flammable materials.

Source: https://obrabotkametalla.info/splavy/kak-pravilno-zakalit-metall-v-domashnix-usloviyax

How to harden metal at home

The process of hardening steel allows you to increase the hardness of the product by about 3-4 times. Many manufacturers carry out a similar process at the time of production, but in some cases it must be repeated because the hardness of the steel or other alloy is low. This is why many people wonder how to harden metal at home?

Hardening metal at home

Methodology

In order to carry out the work of hardening steel, you need to take into account how such a process is carried out correctly. Hardening is a process of increasing the hardness of the surface of an iron or alloy, which involves heating a sample to a high temperature and then cooling it. Despite the fact that at first glance the process in question is simple, different groups of metals differ in their unique structure and characteristics.

Heat treatment at home is justified in the following cases:

1. If necessary, strengthen the material, for example, at the cutting edge. An example is the hardening of chisels and chisels.
2. If it is necessary to increase the plasticity of an object. This is often necessary in the case of hot forging.

Professional hardening of steel is an expensive process. The cost of 1 kg of increasing surface hardness costs approximately 200 rubles. It is possible to organize hardening of steel at home only taking into account all the features of increasing surface hardness.

Process Features

Steel can be hardened taking into account the following points:

1. Heating should occur evenly. Only in this case the structure of the material is homogeneous.
2. The steel should be heated without the formation of black or blue spots, which indicates severe overheating of the surface.
3. The sample cannot be heated to an extreme state, since changes in the structure will be irreversible.
4. The bright red color of the metal indicates that the steel has been heated correctly.
5. Cooling must also be carried out evenly, for which a water bath is used.

Temperature of the workpiece depending on the color when heated

It is recommended to take these points into account when considering how to harden at home.

Modes of hardening and tempering of steels

Equipment and features of the process

Special equipment is often used to heat the surface. This is due to the fact that heating steel to the melting point is quite difficult. The following equipment is often used at home:

1. electric oven;
2. blowtorch;
3. thermal oven;
4. a large fire that is surrounded to redirect the heat.

Mobile forge for heating parts

When choosing a heat source, you should take into account the fact that the part must be completely placed in the oven or fire on which the heating is carried out. It will also be correct to select equipment based on the type of metal that will be processed. The higher the strength of the structure, the more the alloy is heated to impart plasticity.

In cases where only part of the part needs to be hardened, jet hardening is used. It provides for a jet of cold water to hit only a certain part of the part.

A water bath or barrel or bucket is often used to cool steel. It is important to take into account the fact that in some cases gradual cooling is carried out, in others it is rapid and abrupt.

In everyday life, hardening is often carried out over an open fire. This method is only suitable for a one-time process of increasing surface hardness.

All work can be divided into several stages:

1. First you need to make a fire;
2. at the time of lighting the fire, two large containers are prepared that will correspond to the size of the part;
3. In order for the fire to produce more heat, you need to provide a large amount of coals. they give a lot of heat for a long time;
4. one container should contain water, the other should contain motor oil;

Source: https://stankiexpert.ru/spravochnik/materialovedenie/kak-zakalit-metall-v-domashnikh-usloviyakh.html

How to harden a knife or other steel at home: types of hardening, their features and instructions - Machine

Surface hardening of the knife provides additional strength to the cutting base. Heat treating a steel billet significantly improves the mechanical and physical properties of that item.

If you neglect this requirement, then the risk of quickly erasing the metal plate increases. In simple terms, the knife will constantly become dull, which will affect its performance.

In our material we will talk about how to harden a knife at home. Here are recommendations from professionals who know all the intricacies of working with metal.

What material are knives made of?

An alloy of carbon and iron is used to produce knives. When these components are heated, high carbon steel is formed.

This material is able to cope with sudden changes in temperature. In addition, it is characterized by high density and resistance to various mechanical influences.

Products made from pure carbon steel are quite expensive. To reduce the cost of materials and components, many craftsmen prefer to add special additives.

To do this they use the following substances:

• Molybdenum;
• Vanadium;
• Zinc;
• Tungsten;
• Calcium.

If the workpiece contains a minimum amount of carbon steel, then which products are elastic? They require proper hardening, which will provide them with additional strength.

We make a chamber for hardening metal

Before you begin processing the metal base, you need to prepare the appropriate equipment. It is recommended to pay special attention to the oven in which high-temperature processing will be carried out.

The oven chamber should have dimensions of 30 cm x 20 cm x 10 cm. It is made of refractory clay and brick. The clay composition should not contain any impurities.

The design of the furnace is a rectangle. The walls and back panel are on the same level. A metal door on hinges is installed in front. This will maintain the temperature inside the furnace structure.

To harden steel you will need from 300 to 900 degrees. This parameter directly depends on the material from which the metal product is made. For example, to harden a knife from a file, you will need a temperature of 500 degrees.

The composition of this material contains a high steel content and a minimal amount of tungsten. The finished item is quite strong and durable.

The process of hardening steel at home

The easiest way to harden a workpiece is an open fire. Our ancestors used a similar method more than 100 years ago. The processing process is carried out “by eye”.

For the work process you will need the following materials and tools. These include:

• Fire;
• Large container with oil;
• Bucket of cold water;
• Metal pliers with long handles. They will help you carefully remove and lower the iron for further heating.

The first step is to achieve the desired temperature. We send combustible material in the form of firewood and coal to the oven. The flame begins to change its hue from bright orange to crimson.

At this time, wood and combustible material are added to the fire. When the flames change their color to white, you can proceed to hardening the metal product.

Place the base of the knife on burning coals and leave until the metal turns red. On average, this will take from 5 to 15 minutes. When the product acquires a bright red hue, it is immersed in oil.

Tempering a knife with oil helps add ductility and strength. After the first dive, similar manipulations are carried out 5 more times. Next, he sends the metal blade back to the heating furnace

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The next step is cold water quenching. This procedure is final. It adds strength to the metal product. The hot workpiece is placed in ice water for 20 minutes. A photo of knife hardening shows this manipulation.

We present to your attention a detailed video of knife hardening. Here is presented all the regular actions and manipulations with carbon steel.

Photo of knife hardening

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Source: https://regionvtormet.ru/beton/kak-zakalit-nozh-ili-druguyu-stal-v-domashnih-usloviyah-vidy-zakalki-ih-osobennosti-i-instruktsiya.html

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