Do-it-yourself spring manufacturing and hardening technology
Almost every home craftsman knows that it is possible to make a spring from almost any wire and successfully use it in everyday life. Basically, there are no problems with making the part yourself. However, sometimes situations arise in which it is necessary to either make a spring of non-standard dimensions, or give it increased strength and elasticity.
To do this, you should resort to heat treatment operations. It is quite possible to harden a spring at home. It goes without saying that a homemade part should not be used in particularly critical devices operating under increased load. For such purposes, it is recommended to use factory-made springs.
But for home use in a device operating in a lightweight mode, the technology in question is quite suitable.
Required tools and materials
In order to make and harden a wire spring with your own hands, you need:
- Steel wire. The diameter is selected based on the necessary characteristics of the future product.
- Ordinary gas burner.
- Metalworking tools: pliers, hammer, etc.
- Vise.
- Stove. This may be, if available, a special one or an ordinary household one.
Additional devices that are selected individually in accordance with the size and stiffness of the spring can facilitate the process of winding the spiral.
If the use and hardening is intended to be made from wire with a diameter of less than 2 millimeters, then it may not be preheated. It will bend without any problems without this operation. However, before starting winding, it is recommended to straighten it along its entire length and completely level it.
When using wire with a diameter of more than 2 millimeters, it should be burned before starting work. Without this operation, aligning and winding it will be problematic.
Features of the operation
- The right foundation is the key to success. In factory conditions, an alloy of non-ferrous metals (65G, 60HFA, 60S2A, 70SZA, Br. B2), alloy or carbon steel is used for production. During home production, the optimal base will be an old spring of the required diameter.
- A special furnace is best suited for annealing. If this is not available, brick or metal will do.
- For cooling after heating, it is recommended to use transformer oil. If it is not available, a spindle will do.
Sequencing
1. Before tempering the spring wire, you should check the base material and make sure that the wire used is carbon steel.
2. The annealing procedure, as mentioned earlier, can add plasticity. This will make the process of alignment and winding onto the mandrel easier. You can use a special oven or any suitable oven for this.
In everyday life, it is possible to harden in the most suitable structure (metal or brick). To do this, a regular fire is lit and then the future spring is placed in the coal. After heating the workpiece red-hot, the wire must be removed and allowed to cool naturally.
The cooled wire will be much softer and you can work with it comfortably.
3. The softened wire should be completely aligned and begin winding onto a mandrel of a suitable diameter. During the procedure, you need to control the tight arrangement of the turns to each other. To make it easier, you can use a screwdriver.
4. To impart the required elasticity, hardening will be required. Thanks to this heat treatment, the part is harder and more durable. Hardening springs involves heating them to a temperature of 830 to 870 degrees. To do this, you can use a gas burner. Earlier we talked about hardening metal at home.
It is unlikely that you will find a suitable thermometer at home that can accurately determine the temperature of a part. Therefore, you can navigate by the color of the metal. When the required temperature is reached, the workpiece will turn light red. We recommend watching a video with a detailed description of the heating temperature. After this, the spring is placed in a cooling medium (oil).
5. Afterwards, the hardened spring must be kept in a compressed state. This requires from 20 to 40 hours.
6. Finally, process and adjust to the required dimensions.
Correct implementation of such hardening will allow you to successfully use the spring in home mechanisms.
Do-it-yourself spring manufacturing and hardening technology Link to main publication
Source: https://oxmetall.ru/termo/tehnologiya-izgotovleniya-i-zakalki-pruzhiny-svoimi-rukami
Features of steel hardening
Heat treating a metal changes its characteristics. Tempering steel makes it harder and stronger. In some cases, heat treatment is carried out to refine the grain and level the structure. A simple heating and rapid cooling technology for small parts can be done at home. It is necessary to know the grade of steel and its heating temperature for hardening.
What is metal hardening?
One type of heat treatment is metal hardening. It consists of several stages performed in a certain sequence:
- Heating metal to a certain temperature. Dwell time for leveling over the entire depth of the part.
- Fast cooling.
- Tempering to relieve stress and correct hardness to a specified value.
During the manufacturing process, complex parts can undergo several different types of hardening.
Based on the depth of treatment, hardening is divided into two types:
Basically, in mechanical engineering, volumetric heat treatment is used, when the part is heated to its entire depth. As a result of sudden cooling, after the completion of heat treatment, the hardness inside and outside differs by only a few units.
Surface hardening is used for parts that must be hard on top and ductile on the inside. The inductor heats the steel to a depth of 3–20 mm and immediately behind it there is a sprayer that pours water on the hot metal.
The steel is heated to austenite state. Each brand has its own temperature, determined from the table of the state of iron-carbon alloys. During sudden cooling, carbon remains inside the grain and does not enter the intercrystalline space. The transformation of the structure does not have time to occur, and the internal structure contains pearlite and ferrite. The grain becomes finer, the metal itself becomes harder.
What steels can be hardened?
When heated and rapidly cooled, internal changes in structure occur in all steels. Hardness increases only with carbon content greater than 0.4%. St. 35 according to GOST has it 0.32 - 0.4%, which means it can “get hot” - slightly change the hardness if the carbon is located at the upper limit.
Steels starting from CT45 and higher in carbon content are considered hardenable. At the same time, hardening of stainless steel with low carbon content, type 3X13, is possible. Chromium and some other alloying elements replace it in the crystal lattice and increase the hardenability of the metal.
High-alloy carbon steels contain substances that accelerate the cooling process and increase the steel's ability to harden. They require a complex step cooling system and high temperature tempering.
Temperature and heating rate
The heating temperature for hardening increases with the content of carbon and alloying substances in the steel. For St45 it is, for example, 630–650⁰, St 90HF - more than 800⁰.
High-carbon and high-alloy steels, when heated quickly, can “crack” - form small cracks on the surface and inside. They are heated in several stages. At temperatures of 300⁰ and 600⁰, exposure is done. In addition to equalizing the temperature throughout the depth, there is a structural change in the crystal lattice and a transition to other types of internal structure.
Properties of steel after hardening
After hardening of parts, structural changes occur that affect the technical characteristics of the metal:
- increases hardness and strength;
- grain decreases;
- flexibility and ductility decreases;
- fragility increases;
- abrasion resistance increases;
- fracture resistance decreases.
It is easy to obtain a high class of cleanliness on the surface of a hardened part. Raw steel is not polished, it drags on and on.
Types of steel hardening
The main parameters for hardening steel: heating temperature and cooling rate. They completely depend on the grade of steel - carbon content and alloying substances.
Hardening in one environment
When hardening steel, the environment determines the cooling rate. The greatest hardness is obtained when the part is dipped in water. This way you can heat medium-carbon low-alloy steels and some stainless steels.
If the metal contains more than 0.5% carbon and alloying elements, then when cooled in water, the part will crack - become covered with cracks or completely collapse.
High-alloy steels increase their hardness even when cooled in air.
When quenching in water, alloy steel is heated to 40–60⁰. The cold liquid will bounce off the hot surface, forming a steam jacket. The cooling rate will be significantly reduced.
Step hardening
Hardening of steels with complex composition can be carried out in several stages. To speed up the cooling of large parts made of high-alloy steels, they are first dipped in water. The residence time of the part is determined by several minutes. After this, quenching continues in oil.
Water quickly cools the metal on the surface. After this, the part is dipped in oil and cools to the critical temperature of structural transformations of 300–320⁰. Further cooling is carried out in air.
If you heat massive parts only in oil, the temperature from the inside will slow down the cooling and significantly reduce the hardness.
Isothermal hardening
It is difficult to harden metal with a high carbon content, especially tools made of tool steel - axes, springs, chisels. When rapidly cooled, strong stresses are formed in it. High temperature tempering removes some of the hardness. Hardening is carried out in stages:
- Normalization to improve structure.
- Heating to hardening temperature.
- Dipping into a bath of saltpeter, heated to 300–350⁰, and soaking in it.
After hardening in a saltpeter bath, tempering is not necessary. Stresses are released during slow cooling.
Light hardening
There is no technical term for “light hardening”. When alloy steels are hardened, including heating, in a vacuum or inert gases, the metal does not darken. Hardening in a protective gas environment is expensive and requires special equipment separately for each type of part. It is used only for mass production of the same type of product.
In a vertical furnace, the part is heated, passing through an inductor, and immediately lowered below - into a salt or nitrate bath. The equipment must be sealed. After each cycle, the air is pumped out of it.
Hardening with self-tempering
During rapid cooling during the hardening process of steel, heat remains inside the part, which gradually leaves and releases the material - relieving stress. Self-tempering can only be done by specialists who know how much the time a part remains in the coolant can be reduced.
Self-tempering can be done at home if you need to slightly increase the hardness of fasteners or small parts. It is necessary to lay them on heat-insulating material and cover with asbestos on top.
Cooling methods during hardening
Methods of cooling metal during water and oil quenching are widely used in industry. The most ancient composition for hardening swords and other thin-walled objects is saline solution. Hardening was carried out by blacksmiths using forging heat and the heat generated by deformation.
Red sabers, swords, knives were dipped into the urine of red-haired guys. In Europe they were simply stuck into the bodies of living slaves. The colloidal composition containing salts and acids made it possible to cool the steel at an optimal speed and not create unnecessary stresses and leads.
Currently, various sodium salt solutions, saltpeter and even plastic shavings are used.
How to harden steel at home
The decision on how to heat metal is made based on several parameters:
- steel grades;
- required hardness;
- operating mode of the part;
- dimensions
Not all heat treatment methods are available to amateurs. You should choose the simplest ones. Most often, at home, you have to harden stainless steel when making knives and other home cutting tools.
The hardening temperature of chromium-containing steels is 900–1100⁰C. Heating should be checked visually. The metal should have a light orange - dark yellow color, uniform over the entire surface.
You can dip a thin stainless steel into hot water, lifting it into the air and lowering it again. The higher the carbon content, the more time the steel spends in air. One cycle lasts approximately 5 seconds.
Plain weldable steels are heated to a cherry color and cooled in water. Medium alloy materials should have a red color before immersion in water. After 10–30 seconds, they are transferred to oil, then placed in the oven.
When hardening, the maximum hardness that steel gives with this technology is obtained. Then it is reduced to the required value by high-temperature tempering.
Hardening at home
Equipment
Metal is heated in various ways. You just need to remember that the combustion temperature of wood cannot provide heating to the metal.
If you need to improve the quality of 1 part, just light a fire. It must be lined with bricks around the perimeter and, after laying the workpiece, partially closed on top, leaving gaps for air access. It's better to burn coal.
A separate area and a small part are heated with a gas and kerosene burner, constantly running the flame and heating it from all sides.
Making a muffle furnace requires a lot of time and resources. It is advisable to build it for constant use.
The coolant can be in a bucket or any other container that will ensure complete immersion of the part with an oil thickness of the 5 largest sections of the part:
- one part under the hardened product;
- two on top.
The part must be moved slowly in the coolant. Otherwise, a steam jacket will form.
Self-production of a chamber for hardening metal
The simplest semblance of a muffle furnace is made from refractory brick, fireclay clay and asbestos:
- Wind copper wire onto the mandrel. For home voltage, a cross section of 0.8 mm is suitable. Leave long ends.
- Place the spiral inside the bricks and fix it with clay, coating the entire inner surface.
- Make a pallet inside - a platform for placing workpieces. To do this, you need to mix clay with asbestos.
- Thermal insulating material can also be placed outside, reducing the heat transfer of the walls.
- Connect the ends of the wire to the wires with a plug.
- At the back, seal the hole between the bricks hermetically.
- Build a lid in front that will open.
All materials should dry at room temperature.
This will take several days. Then you can lay the part on the insulating material and heat it. Hardening an ax at home.
Defects during hardening of steel
When hardening steel, 2 groups of defects arise:
The first are associated with uneven, spotty hardening and the discrepancy between the resulting hardness and the requirements in the drawing. Such defects are mainly caused by improper cooling or poorly performed heat treatment.
Uncorrectable items include chips, cracks, and complete destruction of parts. The reason most often lies in low-quality metal.
Hardening significantly changes the structure and performance properties of the metal. You can do it yourself using simple parts. It is necessary to know exactly the grade of steel, its hardening temperature and the cooling medium.
Source: https://metalloy.ru/obrabotka/termo/zakalka-stali
How to harden metal at home?
[Metal hardening] 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.
Hardening technique
Simply put, hardening technology consists of two actions - heating the sample to a high temperature and cooling it.
Just don’t assume that everything is elementary, because groups of metals differ in their unique structure and characteristics.
Do-it-yourself heat treatment of metal is justified if:
- there is an urgent need to strengthen the material, for example, to “strengthen” the cutting edges of kitchen utensils or tools, such as a chisel or chisel;
- it is necessary to increase the ductility of the object, which makes it easier to work with metal, for example, the hot forging process.
The price of professional hardening of 1 kg is 100-200 rubles. Hardening small parts will cost less. The price for this service ranges from 6 to 20 rubles.
If you harden equipment at home, it is important to know some of the subtleties of this process.
Heating requires uniformity; it must occur without the appearance of black or blue spots on the object. Under no circumstances should the sample be heated to extreme levels.
The fact that the product is heating up correctly will be indicated by its coloring in a bright red color.
For hardening a metal object such as a drill, equipment such as an electric furnace or thermal oven, as well as a blowtorch and a large fire are suitable.
IMPORTANT TO KNOW: How to make a snail for cold forging with your own hands?
What is more suitable - a furnace, an electric furnace or an open fire depends on the temperature required by the type of metal being processed.
When it is necessary to harden not the entire surface of a metal object, but only a certain place, jet hardening is used. It assumes that a stream of cold water is directed at the object pointwise.
The cooling method for a drill, screwdriver, chisel or crimp may vary. It can be carried out in several stages, one-time and abruptly, or gradually. It all depends on the type of metal.
If you plan to carry out an operation with one cooler, then special equipment, such as a bucket or barrel, is prepared. Even a bath is suitable for this.
This cooling method is ideal for products made from carbon or alloy steel.
When a two-stage cooling scheme is needed to lower the temperature of a metal object, two different media are used. This procedure also ensures the tempering of the metal.
So, first, drills or disk parts are cooled with water, then with oil, which can be machine or mineral.
Cooling with oil is carried out secondarily, since there is a risk of ignition due to high temperature.
Temperature conditions and other hardening indicators are reflected in the table below.
Hardening steel over an open fire
It is possible to harden metal at home. For an easy and useful hardening process, you need to light a fire and prepare two large containers. There should be a lot of hot coals in the fire.
Diesel or motor oil is poured into one container, clean water, preferably from a well, is poured into the other. You should first prepare a tool with which you will need to hold the hot product.
It is advisable to find blacksmith pliers, but if they are not among the tools, you can arm yourself with something else similar to pliers.
When the preliminary work is done, metal drills or other objects are placed in the very center of the flame, that is, on hot coals.
The rich white coals are hotter than the rest. It is important to watch the hardening process - the flame should be crimson, not white. If the fire is painted in the latter color, there is a risk of overheating and even burning of the metal.
It is necessary that the color is distributed evenly across the entire area of the fire. Black spots should not appear on the edge of the product that is being hardened.
And if the metal turns blue in places, this indicates that the material has softened too much and become too plastic. This should not be allowed under any circumstances.
IMPORTANT TO KNOW: Technique of artistic metal forging
Therefore, the process requires increased care, because you can overdo it and heat the ax blade white-hot.
When the metal equipment is heated in the fire, it is time to remove it from the high heat.
A hot object must be lowered into a container of oil many times with a frequency of 3 seconds, gradually increasing this period of time.
You cannot hesitate with these actions; you need to carry out operations to harden the metal edge quickly and sharply.
When working with your own hands, the element should be dipped into a container with liquid until the color loses its saturation and brightness.
Next, the object is immersed in a bucket filled with water, which will have to be shaken a little.
At this stage, do not forget to be careful, as oil droplets on a knife or ax may burst into flames if they end up in water.
The table shows how to correctly and incorrectly immerse various parts, including drills and disc cutters, in water:
Very often there is a need to harden drills. It is not recommended to immerse thin long elements flat into water, otherwise the lower layer of metal, cooled first, will shrink.
Drills should be lowered into the liquid with the thicker end.
If you follow all the rules and precautions, then hardening yourself will not seem like a complicated and dangerous procedure. It will bring the desired guaranteed effect.
But sometimes at home you have to harden steel equipment or melt non-ferrous metal. Such operations require extremely high temperatures, 700-900 degrees.
And only a muffle furnace or an electric furnace can heat metal objects to this level. You can make a muffle furnace yourself. It is unlikely that you can make an electric oven at home.
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.
IMPORTANT TO KNOW: Secrets of copper plating at home
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.
Then the door and chamber are fired, gradually increasing the temperature to 900 degrees. These parts should then gradually cool in the oven itself.
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.
To avoid the risk of a short circuit, the distances between the turns of the wire are smeared with clay. Another layer about 12 cm thick is spread on the dried layer of clay.
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.
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://rezhemmetall.ru/zakalka-metalla-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.
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 (hardening, 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.
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.
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.
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.
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
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
.
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
How to temper wire at home? — Machine tools, welding, metalworking
Almost every home craftsman knows that it is possible to make a spring from almost any wire and successfully use it in everyday life. Basically, there are no problems with making the part yourself. However, sometimes situations arise in which it is necessary to either make a spring of non-standard dimensions, or give it increased strength and elasticity.
To do this, you should resort to heat treatment operations. It is quite possible to harden a spring at home. It goes without saying that a homemade part should not be used in particularly critical devices operating under increased load. For such purposes, it is recommended to use factory-made springs.
But for home use in a device operating in a lightweight mode, the technology in question is quite suitable.
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
How to temper hardened steel at home?
Technologies for imparting greater hardness to metals and alloys have been improved over many centuries. Modern equipment makes it possible to carry out heat treatment in such a way as to significantly improve the properties of products even from inexpensive materials.
Hardening of steel and alloys
Hardening (martensitic transformation) is the main method of imparting greater hardness to steels. In this process, the product is heated to such a temperature that the iron changes its crystal lattice and can be additionally saturated with carbon. After holding for a certain time, the steel is cooled.
This must be done at high speed to prevent the formation of intermediate forms of iron. As a result of rapid transformation, a solid solution supersaturated with carbon with a distorted crystal structure is obtained. Both of these factors are responsible for its high hardness (up to HRC 65) and brittleness.
When hardening, most carbon and tool steels are heated to a temperature of 800 to 900C, but high-speed steels P9 and P18 are heated at 1200-1300C.
Microstructure of high-speed steel R6M5: a) cast state;
b) after forging and annealing; c) after hardening; d) after vacation. ×500.
Quenching modes
The heated product is lowered into a cooling medium, where it remains until it cools completely. This is the simplest hardening method, but it can only be used for steels with a low carbon content (up to 0.8%) or for parts of simple shape. These limitations are associated with thermal stresses that arise during rapid cooling - parts of complex shapes can warp or even crack.
With this method of hardening, the product is cooled to 250-300C in a saline solution for 2-3 minutes to relieve thermal stress, and then cooling is completed in air. This helps prevent cracks or warping of parts.
The disadvantage of this method is the relatively low cooling rate, so it is used for small (up to 10 mm in diameter) parts made of carbon or larger ones made of alloy steels, for which the hardening rate is not so critical.
It begins with rapid cooling in water and ends with slow cooling in oil. Typically, such hardening is used for products made of tool steels. The main difficulty lies in calculating the cooling time in the first environment.
- Surface hardening (laser, high frequency currents)
Used for parts that must be hard on the surface, but have a viscous core, for example, gear teeth. During surface hardening, the outer layer of the metal is heated to supercritical values, and then cooled either during the heat removal process (with laser hardening) or by liquid circulating in a special inductor circuit (with high-frequency current hardening)
Vacation
Hardened steel becomes excessively brittle, which is the main disadvantage of this hardening method. To normalize the structural properties, tempering is carried out - heating to a temperature below the phase transformation, holding and slow cooling.
During tempering, a partial “cancellation” of hardening occurs, the steel becomes slightly less hard, but more ductile.
There are low (150-200C, for tools and parts with increased wear resistance), medium (300-400C, for springs) and high (550-650, for highly loaded parts) tempering.
Temperature table for quenching and tempering steels
| No. | steel grade | Hardness (HRCe) | Temperature hardening, degrees C | Temperature holidays, degrees C | Temperature zak. HDTV, deg.C | Temperature cement., deg. C | Temperature annealing, degrees C | Temper. Wednesday | Note |
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 1 | Steel 20 | 5763 | 790820 | 160200 | 920950 | Water | |||
| 2 | Steel 35 | 3034 | 830840 | 490510 | Water | ||||
| 3335 | 450500 | ||||||||
| 4248 | 180200 | 860880 | |||||||
| 3 | Steel 45 | 2025 | 820840 | 550600 | Water | ||||
| 2028 | 550580 | ||||||||
| 2428 | 500550 | ||||||||
| 3034 | 490520 | ||||||||
| 4251 | 180220 | Sech. up to 40 mm | |||||||
| 4957 | 200220 | 840880 |
Source: https://varimtutru.com/kak-otpustit-zakalennuyu-stal-v-domashnih-usloviyah/
