How to harden a screwdriver at home. How to temper metal at home? How metal is tempered
If you know how to harden metal correctly, then even at home you can increase the hardness of metal products by two to three times. The reasons why this is necessary can be very different. Such a technological operation, in particular, is required if the metal must be hardened enough to be able to cut glass.
Most often, it is necessary to harden the cutting tool, 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 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 an easy way to check how well a steel tool is hardened, not only in production or at home, but also in a store when buying. In order to perform such a check, you need a regular file. They are carried out along the cutting part of the purchased tool. If it is hardened badly, then the file will seem to stick to its working part, and in the opposite case, it will easily move away from the tested tool, while the hand in which the file is located will not feel any irregularities on the surface of the product.
If, nevertheless, it turned out that you had a tool at your disposal, the quality of hardening of which does not suit you, you should not worry about this. This problem is solved quite easily: it is possible to harden metal even at home, without using sophisticated equipment and special devices for this. However, you should be aware that low-carbon steels cannot be hardened. At the same time, the hardness of the carbon and easy enough to increase even at home.
Technological nuances of hardening
Tempering, which is one of the types of heat treatment of metals, is carried out 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, so their heat treatment modes do not match.
Heat treatment of metal (hardening, tempering, etc.) may be required for:
- its hardening and increase in hardness;
- improving its plasticity, 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 it 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 properly 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 fact that the heating is happening correctly is evidenced by the bright red color of the metal. This process is well demonstrated by a video that will help you get an idea of how much to heat the metal being heat treated.
As a heat source for heating to the required temperature of a metal product that needs to be hardened, 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 the country.
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 what results are to be achieved. If, for example, it is not necessary to harden the entire product, but only its separate section, then cooling is also carried out pointwise, for which a jet can be used cold water.
The technological scheme, according to which the metal is hardened, may provide for instantaneous, gradual or multi-stage cooling.
Fast cooling, using one type of cooler, is optimal for hardening steels in the carbon or alloy category. To perform such cooling, one container is needed, which can be a bucket, a barrel, or even an ordinary bath (it all depends on the dimensions of the object being processed).
In the event that other categories or if, in addition to hardening, tempering is required, a two-stage cooling scheme is used. With this scheme, the product heated to the required temperature is first cooled with water, and then placed in mineral or synthetic oil, in which further cooling takes place. Under no circumstances should an oil coolant be used immediately, as the oil may ignite.
In order to correctly select the hardening modes for various steel grades, one should be guided by special tables.
How to harden steel over an open fire
As mentioned above, it is possible to harden steel at home, using an open fire for heating. Naturally, such a process should begin with a fire, in which a lot of hot coals should form. You will also need two containers. Mineral or synthetic oil must be poured into one of them, and ordinary cold water into the other.
In order to extract red-hot iron from a fire, you will need blacksmith tongs, which can be replaced with any other tool of a similar purpose. After everything preparatory work completed, and a sufficient amount of hot coals has formed in the fire, you can put objects that need to be hardened on them.
By the color of the coals formed, one can judge the temperature of their heating. So, coals are hotter, the surface of which has a bright White color. It is also important to monitor the color of the fire flame, which indicates temperature regime in its interior. It is best if the fire flame is painted crimson, not white. In the latter case, indicating a too high temperature of the flame, there is a risk not only of overheating, but even of burning the metal to be hardened.
The color of the heated metal must also be carefully monitored. In particular, black spots should not be allowed to appear on the cutting edges of the machined tool. The blue color of the metal indicates that it has softened a lot and become too ductile. It cannot be brought to such a state.
After the product is 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 (with a frequency of 3 seconds) and as sharply as possible. Gradually, the intervals between these dives increase. As soon as the red-hot steel loses the brightness of its color, you can start cooling it in water.
When cooling metal with water, on the surface of which droplets of hot oil remain, care should be taken, as they can flare up. After each dive, the water must be shaken to keep it cool at all times. To get a better idea of the rules for performing such an operation, a training video will help.
There are certain subtleties in the cooling of hardened drills. So, they cannot be lowered flat into a container with coolant. If you do it this way, then Bottom part a drill or any other metal object that has an elongated shape will cool first, which will lead to its compression. That is why it is necessary to immerse such products in the coolant from the side of the wider end.
For heat treatment of special grades of steel and smelting of non-ferrous metals, the possibilities of an open fire will not be enough, since it will not be able to provide heating of 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-made 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 will be required for the manufacture of this heating device is refractory clay. The layer of such clay, which will cover the inside of the furnace, should be no more than 1 cm.
Scheme of a chamber for hardening metal: 1 - nichrome wire; 2 - the 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 the desired dimensions, it is best to make a mold from cardboard impregnated with paraffin, on which refractory 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 itself will lag behind 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.
The chamber and the door of the device after drying in the open air are additionally dried at a temperature of 100 °. After that, they are fired in a furnace, the temperature in the chamber of which is gradually brought up to 900 °. When they have cooled after firing, they must be carefully connected to each other using locksmith tools and sandpaper.
On the surface of a fully formed chamber, a nichrome wire is wound, the diameter of which should be 0.75 mm. The first and last layer of such winding must be twisted together. When winding the wire around the chamber, a certain distance should be left between its turns, which must also be filled with refractory clay in order to exclude the possibility of a short circuit. After the layer of clay applied to provide insulation between the turns of nichrome wire dries, another layer of clay is applied to the surface of the chamber, the thickness of which should be approximately 12 cm.
The finished chamber, after complete drying, 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 finished from the inside are hung on the metal body of the furnace. ceramic tiles. All existing gaps between structural elements are sealed with refractory clay and asbestos chips.
The ends of the nichrome winding of the camera, to which it is necessary to supply electrical power, are output 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 to 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 of the frame, such openings will be closed with special steel curtains. A home-made design, the manufacture of which is described above, allows you to harden locksmith and cutting tools, working elements of stamping equipment, etc. at home.
May appear at any time. There are a large number of different tools on the market that could not be hardened during manufacture or, conversely, overdo it with the temperature during heat treatment. For example, we can recall the well-known drills for a drill. If the steel is not hardened to the norm, it will bend. If the steel is hardened too much, the drill will most likely start to crumble.
A similar description applies to any steel material. Checking the metal in the store, of course, does not work. 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 buying a metal item is to check its quality. This can be done using simple soldering iron. The end of the soldering iron is held on metal to find out defects in tool development. If the soldering iron sticks to the surface, then the steel is not hardened, and with frequent use the tool is deformed. If, on the contrary, the tip of the soldering iron runs smoothly over the steel and almost bounces off it, then the metal is too hardened. In this case, it is necessary to make a thermal treatment of the steel tool to increase its strength.
Hardening technique
On the Internet you can find a large number of methods and videos for hardening metal objects, but most of them require special equipment, but there are ways that help improve the quality of steel with improvised means.
First you need to define what steel hardening is. The main process is divided into two parts, or rather, speaking, heating the metal to a high temperature and subsequent cooling. The process looks simple at first glance, but have to take into account the structure and characteristics of the metal. If, without analysis, they begin to heat it up, the material is likely to deform. Particularly often deformation occurs with mild steel, so if the structure of the metal is unknown, it is better not to apply heat treatment.
Tempering steel is justified only in some cases.
- The need for increased tool strength. For example, it can be ordinary kitchen utensils, a chisel or a chisel.
- Increasing the plasticity of the metal also requires heat treatment to further simplify hot forging operation.
You can also order a steel hardening service from specialists, especially since the cost is acceptable. Blacksmiths usually charge no more than 100-150 rubles for 1 kg of metal of a large structure. If you harden small parts, then the prices are about 6–20 rubles. This will not guarantee the quality of the instruments, which is why many people try apply heat treatment at home to follow the process.
First of all, when heating steel, you need to remember some rules. Steel can be damaged if the temperature of the metal is raised above normal. In this case the instrument may be black or blue tint , which in the end can not even be ground off with sandpaper. In order to avoid such a defect, the metal must have a sufficient amount of carbon in its structure, and one should not overdo it with an increase in temperature. Usually, steel is considered hot if a red tint appears.
For heat treatment of steel tools, a cutter, blowtorch, electric or gas stove. In some cases heating of metal can also be done on a fire. In fact, there is no difference in where it is better to heat up a metal product. Just in the open air, when heated with a fire, there may not be enough heat energy to reach the required temperature. Therefore, it is important to clarify in advance the melting and hardening temperatures of the material.
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 consumable steel is hardened, then a simple cut bottle can also be used. In the case of heat treatment of an ax, scrap and other similar tools, you need to choose a container with a large volume. In some cases, even a bath 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 you need to harden only a certain area, in which case only jet cooling can be used. More precisely, droplets are poured onto the material plain water to the area that needs to be hardened. Especially often this method is used in the heat treatment of a drill for a drill or on nails to improve the quality of the tip. The hardening technique can be divided into several levels.
There are the following levels of cooling:
- sharp;
- one-time;
- gradual.
For single cooling, a simple container of water is most often used. If two-stage cooling is used, two different means are used in the process. This, in turn, improves not only the quality, but also the tempering of the steel material. First of all, steel is immersed in plain water, and then rearranged for further cooling in machine or mineral oil. The process is quite dangerous, because you need to cool the product in water so that the oil does not ignite.
Tempering steel over an open fire
How to harden metal at home on an open fire? The question is quite common, and there are many methods. Conducting heat treatment on an open fire may not be as effective, but at the same time the risk of fire is reduced, especially when using oil during the cooling of the steel material.
The first step is to prepare the tools. It is necessary to take a steel material that will undergo heat treatment, blacksmith tongs or an analog tool and two containers. Water should be poured into one container, and engine or diesel oil should be added to another container.
After that, you should make a fire, while using a large amount of coal. Unlike most metal heating methods, here the material must be placed directly on the coals and it is desirable that they be white, because they give out the highest temperature. The fire that will envelop the steel must be crimson. If a white fire appears, then we can assume that steel material started to burn. It is impossible to save it in this case, therefore it is better not to bring the hardening to such a stage of melting.
It is also impossible to allow black or blue spots to appear on a metal product. The blue color indicates that the steel has softened too much and 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 becomes white.
After the steel material has warmed up, you need to pull it out of the fire and lower it into the oily liquid. The metal should be dipped several times with an interval of three seconds, gradually increasing this time. The main thing is to do everything without haste, but you can’t hesitate either, because steel can be dipped only if the material has an appropriate heat tone. After that, the metal product is placed in plain water, but here you should be extremely careful, as the remaining drops from the oil can simply flare up. If the procedure is carried out taking into account all the recommendations, the metal product can simply be left in the water until it cools completely.
It is also important to remember that, unlike conventional tools, elongated objects, such as drills or nails, must not be lowered sideways into the water, since the lower part can simply flatten due to high temperature and sudden contact with water. Such elongated objects sink vertically into the water, and the end, which has a larger diameter.
Tempering steel at home on a stove or fire is only suitable when a simple type of material is used. When hardening non-ferrous metal, too much heat, which is equal to 600-900 degrees. This result can be achieved with the help of blast furnaces, but not at home.
Conclusion
The use of metal heat treatment can improve the quality of tools or consumable. When hardening steel at home, it is important to remember the basic recommendations so as not to deform the material.
In a simplified form, the process of metal hardening consists in raising the temperature of the sample to large values and then cooling it down. But not everything is so simple. And this is due to the fact that different kinds metals differ in their structure, and, accordingly, specific properties. Therefore, certain methods (and temperatures) are used for their hardening. We will talk about them, as well as the specifics of the corresponding operations.
First of all, it is worth noting that heat treatment (hardening) of metal products (or blanks) is carried out in two cases.
First, if necessary, increase the strength of the material (several times). Almost everyone faces this in everyday life. For example, to "reinforce" the cutting edges kitchen utensils(knives, hatchets for chopping meat) or tools (chisels, chisels, etc.).
Secondly, to give the metal some plasticity, which greatly facilitates further work with the material ("hot" forging). This is well known to those who are engaged in blacksmithing. Consider all the stages of the technology of hardening metal products at home.
Heat
The main condition for high-quality hardening is its uniformity, without dark spots on the sample (blue or black). The metal should not be heated to a "white heat". A sign of optimal warming up is the acquisition of a bright crimson (red) color. Anything can be a source of heat - a blowtorch, an electric stove, a gas burner, an open fire. Its choice depends on the temperature that must be reached for a given steel grade.
Cooling
There are several methods for carrying out this technological operation. It can be both sharp and gradual, stepped. The specificity is determined by the type of metal.
Jet hardening
It is used if it is necessary to process not the entire sample, but a separate area of the surface. A jet of cold water is sent to it.
With one "cooler"
It is clear that a suitable container (bucket, barrel, bath) is pre-installed. Typically used for alloy or carbon steel workpieces.
With two
As a "cooler" are used media with different ability to lower the temperature of the material. Therefore, the process is a two-stage process, thus ensuring the "vacation" of the metal. For example, first cooling is carried out in water, and then in oil (for example, machine or mineral), since it can ignite from high temperature.
There are other ways, but they are usually used by craftsmen who work on professional level and well versed in metals. For example, hardening is isothermal. It makes no sense to dwell on them in detail, since first you have to explain what martensitic and austenitic steels are.
What to cool?
We have already mentioned that most often this is done with cold water and oil. But these are not the only possible "coolers". The fact is that with such hardening, some grades of steel become brittle. Therefore, in practice, other media are also used that can intensively lower the temperature of the metal.
For example, liquid wax. It is more suitable for working with flat blanks, which, after bringing their temperature to the required value, are completely immersed in it, and sequentially, several times in a row, until the sealing wax mass completely hardens.
Masters also use substances such as alkalis, solutions with a strong salt concentration and a number of others, even molten lead, as “coolers”.
How to check the quality of hardening? There is a fairly simple way - using an ordinary file.
- If, when processing the workpiece, it literally “bounces” from it, then it turned out to be “glass”. Such metal is overheated and will crumble easily.
- But the “sticking” of the tool indicates that the metal turned out to be soft (“plasticine”), not hardened enough, and the strength of the part made from it is highly doubtful.
- All metal products that we encounter in practice are heterogeneous in composition. There are several types of steel, and not all of them can be heat treated. For example, low-carbon steel is not hardened.
- If in everyday life it is necessary to give strength to a table knife or an ax, then special knowledge in the field of metallurgy is not necessary. But a novice blacksmith should be reminded that before proceeding with the heat treatment of the workpiece, it is necessary to figure out what kind of material it is (grade of steel). The corresponding reference table will help you with this, in which for each of them the duration of thermal exposure, temperature, and the optimal cooling method are indicated.
Our market is simply littered with low-quality Chinese tools. And the point here is not even the manufacturer, but rather the resellers who massively carry cheap Chinese screwdrivers, passing them off as a brand. There is also an excellent, high-quality Chinese instrument, but it is quite difficult to find it.
We will not talk much about what and how, but we will try to improve the quality of a screwdriver or screwdriver with interchangeable bits.
I will be hardening the bits. Hardening aims to increase the strength of steel, change the properties of the metal, making it harder, but more brittle.
How to harden metal with your own hands
The hardening process is extremely simple and does not require special knowledge or special work techniques from you. But you will have to be especially careful when working with hot metal and a gas burner.So, what do you need for hardening?
- - The beats themselves first.
- - Heater. Ideally, use it, but if you don't have one, you can use a gas burner like me.
- - Machine oil. Any will do, it's even better to use a used one, as it is thinner.
In principle, you can simply hold the thick end of the bit with pliers so that only the part of the bit that interacts with screws and screws is hardened.
We light gas burner. We bring the bat and begin to heat up the metal.
We warm to a bright pinkish color. It is not recommended to warm up to white, although on such a burner you are unlikely to succeed.
As soon as everything is warmed up, quickly lower it into the oil, for 5-6 seconds. Then we take it out.
You can use another process: 4 seconds in oil and then abruptly in cold water, they say the effect is better, but, again, I have not tried it.
That's all. Process completed. It remains only to wipe the bit from the oil and start using it.
She appeared to be darker.
I want to add that not all bits can be hardened. I don’t know what is mixed in them, but there are instances that hardening not only does not affect, but even destroys them, and they become like plasticine after heat treatment.
I would also like to add that this method does not lie in any way with factory hardening, so you do not need to wait for the same hardness of the metal. Since even the metal is not the same as the factory. But the effect of increasing hardness, and hence the operating time, is still there.
Many are interested in how to properly harden metal at home and in what cases is this process required? Hardening of products from this material is carried out if it is necessary to increase its strength. For example, to harden the edges for cutting kitchen utensils (knife, secateurs) or tools (chisel, chisel, etc.). In addition, the metal acquires a certain amount of plasticity, which facilitates the processing of the material. Blacksmiths are well aware of this rule. The article will describe how to harden metal at home.
What is hardening for?
Hardening of the metal contributes to an increase in the hardness of the product by about 4 times. In this case, an object made of this material can easily cut the glass surface. Hardening is required due to insufficient strength of the object or vice versa. In the first case, metal products will be crushed, and in the second, they will crumble.
Checking the level of hardening of a metal product
To check the level of hardening of a metal product, take a file and run the tool along the edge of the object to be cut, for example, an ax or a knife. If you feel that the file begins to stick or stick to the metal, then this indicates that the product is not hardened enough. At the same time, its edge will be soft and pliable.
If the tool easily moves away from the object and it feels like it is stroking it, and the hand does not feel irregularities, then this means that the metal is overhardened.
It is possible to harden metal at home. In this case, you should not turn to complex technologies. The process is done by hand.
It should be remembered that low-carbon steels are not subject to the process. But to achieve an increase in the strength of carbon products or really.
How is hardening done?
Hardening technology involves two processes - heating a metal product to a high temperature and subsequent cooling.
Heat treatment of the surface is advisable if:
- there is a need to give the metal additional strength;
- an increase in the level of plasticity is required, for example, for subsequent hot forging.
The price of hardening a metal product at a professional level is 200 rubles. for 1 kg. Fire treatment of small parts is cheaper. The price for this service is 20 rubles.
How to harden metal at home? It is necessary to familiarize yourself with some of the nuances of this case.
Heating should be uniform. There should be no spots of black or of blue color. Do not heat the product to the extreme temperature. The appearance of a bright red color indicates that the process is proceeding correctly.
What equipment is used for hardening?
For example, in order to harden metal at home in the form of a drill, an electric or soldering lamp or a fire is used. What is suitable in a particular case depends on what temperature indicator is required for the material being processed.
Cooling of various tools
The rules for cooling instruments may be different. The process can be carried out in one or more steps. It all depends on the type of metal.
How to harden metal not over the entire surface, but only in a certain place? In this case, the jet type of hardening is used. It implies the direction of a jet of cold water on an object pointwise.
If the action is carried out with one cooler, then specialized devices are required in the form of a barrel or bucket. For this purpose, even a bath is used. This cooling method is suitable for objects based on carbon or alloy steel.
If a two-stage cooling scheme is required to lower the product temperature, then different media are used. This process provides metal tempering. Initially, drills or discs are cooled with water, then with machine or mineral oil. Cooling with its help is the second stage of the process, since there is a risk of ignition under the influence of high temperature.
Application of water for cooling
The main cooling liquid is water. If you add a little salt or soap to it, then the cooling rate will change. Therefore, the tempering tank cannot be used for hand washing. To ensure the same hardness index on the metal surface, the temperature of the liquid should be maintained at 20–30 °C. You can not often change it in the tank. It is forbidden to cool the product in running water.
The disadvantage of hardening with water is the appearance of many cracks on the surface of the metal. In this way, objects of a simple shape or cemented should be subjected to the process.
What is used to harden parts of complex shape?
How to harden metal of complex shape? For use, a fifty percent solution of caustic salt is used cold or heated to 50 - 60 ° C. Parts heated in a salt bath and hardened in it come out bright. The solution temperature must not exceed 60 °C.
The vapors that arise during hardening are harmful to health, so the bath must be equipped with a ventilation hood.
How is alloy steel hardened?
How to harden metal? At home, alloy steel is processed in a mineral oil bath. Thin objects made of carbon steel are hardened in the same way. The advantage of oil baths is that the cooling rate does not depend on the temperature of the oil. It will proceed equally quickly at any of its indicators.
How to harden metal in oil correctly? Water should not get into such a bath, as this can cause cracks to appear on the surface of a metal object. It is noted that if the oil is heated to a temperature of 100 ° C, then the ingress of water will not cause cracking of the product.
Cons of an oil bath
- During hardening, toxic gases are released.
- A plaque is formed on the subject.
- The oil may ignite.
- The quality of hardening in an oil bath gradually decreases.
How is metal tempered?
All hardened parts are tempered. This relieves internal stress. As a result of this process, the hardness decreases and the ductility of the material increases.
How to release hardened metal? Depending on the desired temperature, the process is carried out:
- in baths with oil;
- in baths with saltpeter;
- in furnaces with air circulation;
- in alkaline baths.
What determines the choice of tempering temperature?
How to loosen hardened metal correctly, what should be considered? An important factor is the tempering temperature. It depends on the type of steel and the required hardness index of the product. For example, a product for which an HRC indicator of 59 - 60 is required is tempered at a temperature of 150 - 200 ° C. In this case, the internal stress decreases, and the hardness practically does not change.
Lowered at a temperature of 540 - 580 ° C. This process is called secondary hardening. Its result is an increase in the hardness of the product.
The metal is tempered to a tint color. It is heated in ovens or hot sand. The oxide film that appears when heated is colored in different colors. In this case, the surface of the metal product is cleaned of scale, soot and oil.
After tempering, the metal is usually cooled in air. Chrome-nickel products are cooled in water or oil, since the slow cooling of these grades leads to temper brittleness.
on an open fire?
How to harden metal on fire? For easy holding the process of hardening metal at home, make a fire and prepare two containers large capacity. There should be a lot of hot coals in the fire.
Fill one container with diesel or engine oil, and the other with clean water. Better if it is a well. Initially, a tool is prepared with which the metal, heated to the limit, will be held. Blacksmith pliers are used. But if they are not, then you can use something similar.
After doing the preliminary work, metal drills or other tools are placed in the center of the flame on hot coals. White coals are much hotter than the rest. The hardening process must be observed carefully. The fire flame should be crimson. If the fire turns white, then there is a threat of overheating and even combustion of the metal.
It is necessary to ensure that the crimson color is evenly distributed over all areas of the fire. Black spots should not appear on the edge of a metal product. If blue spots appear on the material, this indicates excessive softening of the material and its excessive plasticity. This cannot be allowed.
After calcining a metal product in a fire, it should be removed from the hotbed. A red-hot object is lowered into a container of oil many times with an interval of 3 seconds. The time interval is gradually increased. You can't delay at this stage. The operation is carried out quickly and abruptly. The product is dipped in oil until its color is no longer bright and saturated.
Then the object is immersed in a bucket of water, which needs to be shaken a little. At this stage, you should be extremely careful, since drops of oil on a knife or ax can be dried when immersed in an aquatic environment. Drills should be lowered into the liquid with a thick end.
You already know how to temper metal correctly. If you follow all the recommendations, then the process will bring the desired effect.
When is an electric oven used?
At home, you have to harden products made of non-ferrous metals or steel. In this case, a very high temperature of up to 900 ºС and above will be required.
Only an electric or muffle furnace can heat a metal product to such an indicator. The latter can be made with your own hands, but it is impossible to make an electric one.
How to make a muffle furnace?
How to harden metal at home using a do-it-yourself muffle furnace? Such a device will become very necessary in the household. It will allow for heat treatment of metal products without unnecessary manipulations. Making a do-it-yourself oven requires refractory clay used for coating. From this material, a chamber is created with a thickness of not more than 1 cm. Its dimensions should be 210x105x75mm.
When sculpting a muffle furnace with their own hands, they resort to using a pre-prepared cardboard mold. So that it does not stick, it is impregnated with paraffin.
Clay is smeared on the form from the inside out. In this case, during drying, it will not shrink. When hardening, the material itself will move away from the edges of the mold. Refractory clay can become the basis of the furnace door.
A homemade muffle furnace should be allowed to dry in the open air. Then it is dried to the end in an oven at 100 ºС. The doors and chamber are fired gradually as the temperature rises to 900 ºС.
The parts should be allowed to cool without removing them from the oven. Then a door is attached to it. Its surface is polished with a file.
18 m of nichrome wire is wound on the camera. Its thickness should be 0.75 mm. The first and last turns must be twisted. To prevent a short circuit, the distance between the turns is coated with clay. On a dry layer of material it is necessary to spread another layer 12 cm thick.
A do-it-yourself muffle furnace consists in metal carcass, the size of which is 270x200x180 mm.
For easy assembly of the case, it should be designed with two removable covers fixed with screws.
A door is attached to the front cover with a hinge. It should open horizontally. A ceramic part must be installed on this door using bolts and gaskets.
All gaps are covered 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 made. All holes between the heating parts and the frame are filled with asbestos chips.
To install a thermocouple and be able to monitor the process of metal hardening in the chamber, it is necessary to drill two holes. The diameter of the first should be 1 cm, and the second 2 cm. Closable metal curtains are attached to them.
The weight of a homemade muffle furnace is 10 kg. It heats up to a temperature of 900 ºС within an hour. With its help, you can facilitate the process of hardening drills, files, matrices and many other metal products.
Muffle equipment for metal hardening is not the only device. For this purpose, a chamber device, an electric or thermal oven, as well as a bath oven are used. Making a muffle furnace with your own hands is more profitable than buying ready-made equipment. For example, the average price of such a device on the market is 40,000 rubles.
