How to harden metal at home?
Many are interested in how to properly hardenmetal at home and when this process is required? Hardening products from this material is carried out if necessary, increase its strength. For example, for hardening edges for cutting kitchen utensils (knife, pruner) 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 acquainted with this rule. The article will describe how to temper the metal at home.
What is hardening for?
Hardening metal contributes toproduct hardness is about 4 times. In this case, an object made of this material can easily cut through the glass surface. Hardening is required due to insufficient strength of the object or vice versa. In the first case, metal products will be jammed, and in the second - crumble.
Check the level of quenching metal products
To check the level of hardening metal productsYou should take a file and hold the tool along the edge of the object for cutting, for example, an ax or a knife. If you feel that the file starts to stick or stick to the metal, then this indicates that the product is not sufficiently hardened. At the same time its edge will be soft and malleable.
If the tool easily moves away from the object and creates the feeling that he strokes it, and the hand does not feel irregularities, this means that the metal is hardened unnecessarily.
Hardened metal at home is possible. You should not turn to complex technologies. The process is carried out by hand.
It should be remembered that the process is not subject to low carbon steel. But to achieve an increase in the strength of products made of carbon or tool materials is real.
How is the hardening performed?
The quenching technology involves two processes — heating a metal product to a high temperature and then cooling it.
Thermal surface treatment is advisable if:
- there is a need to give the metal additional strength;
- An increase in ductility is required, for example, for subsequent hot forging.
The price of hardening metal products at a professional level is 200 rubles. for 1 kg. Processing by fire of small parts is cheaper. The price for this service is 20 rubles.
How to harden the metal at home? It is necessary to familiarize with some nuances of this business.
Heating should be uniform. On metal there should not be spots of black or blue color. Do not heat the product to the extreme temperature. The fact that the process proceeds correctly is indicated by the appearance of a bright red color.
What equipment is used for hardening?
For example, in order to temper the metal inat home, in the form of a drill, an electric or thermal oven, a soldering lamp or a fire is used. What is appropriate in a particular case depends on what temperature indicator is required for the material being processed.
Cooling various tools
Instrument cooling rules may vary. The process can be carried out in one or more techniques. It all depends on the type of metal.
How to harden the metal not over the entire surface, but only in a certain place? In this case, an ink-jet hardening method is used. It involves the direction of a jet of cold water on the subject point.
If the operation is performed with one cooler, thenSpecialized barrels or buckets are required. Even a bath is used for this purpose. This method of cooling is suitable for objects based on carbon or alloy steel.
If to lower the temperature of the product is requiredcooling scheme, which includes two stages, then use different environments. 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, as there is a risk of ignition under the influence of high temperature.
The main liquid for cooling is water. If you add a little salt or soap into it, the cooling rate changes. Therefore, the quenching tank cannot be used for hand washing. To ensure the same indicator of hardness 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 the help of water is the appearance of multiple cracks on the metal surface. In this way, it is necessary to subject the process to objects of simple form or cemented.
What is used for hardening parts of complex shape?
How to harden a metal of complex shape? For alloyed steel, a fifty percent caustic salt solution is used cold or heated to 50 - 60 ° C. Parts heated in a salt bath and quenched in it come out light. The temperature of the solution should not be above 60 ° C.
Couples that occur during hardening, are harmful to health, so the bath must necessarily be equipped with a ventilation hood.
How is the hardening of alloyed steel?
How to harden the metal? At home, the alloyed steel is subjected to a process in a mineral oil bath. Thin carbon steel objects are hardened in the same way. The advantage of oil baths is that the cooling rate is not dependent on the temperature of the oil. It will flow equally fast for any given indicator.
How to harden metal in oil correctly? Water should not get into such a bath, as this may cause cracks to appear on the surface of the metal object. It is noted that if the oil is heated to a temperature of 100 ° C, the ingress of water will not cause cracking of the product.
Cons of oil bath
- During hardening poisonous gases are emitted.
- On the subject of a raid.
- Oil may ignite.
- The quality of quenching in the oil bath gradually decreases.
How is the vacation metal?
All quenched parts are subject to tempering. This relieves internal stress. As a result of this process, the hardness decreases and the ductility of the material increases.
How to release the hardened metal? Depending on the desired temperature, the process is carried out:
- in baths with oil;
- in baths with saltpeter;
- in air circulation ovens;
- in alkaline baths.
What determines the choice of temperature vacation?
How to loosen the hardened metal correctly, thatshould be considered? An important factor is the temperature of the holidays. It depends on the type of steel and the desired hardness of the product. For example, a product for which HRC 59 - 60 is required is subjected to tempering at a temperature of 150 - 200 ° C. In this case, the internal voltage decreases, and the hardness practically does not change.
High-speed steel is lowered at a temperature of 540 - 580 ° С. This process is called secondary hardening. Its result is an increase in the hardness of the product.
The metal is hardened to tint color. It is heated on hotplates, in kilns or hot sand. The oxide film, which appears when heated, is painted in different colors. At the same time the surface of the metal product is cleaned from scale, scale and oil.
After tempering, the metal is usually cooled in air. Nickel-chromium products are cooled in water or oil, as slow cooling of these grades leads to temper brittleness.
How to temper steel on an open fire?
How to harden the metal on the fire? For easy carrying out the process of metal hardening at home, you should make a fire and prepare two large-capacity containers. In the fire should be a lot of hot coals.
In one tank should fill the diesel orengine oil, and other clean water. It is better if it is well. Initially a tool is prepared by which the metal, which is heated to the utmost, will be kept hot. Use blacksmith tongs. But if they are not, then you can use something similar.
After doing the preliminary work, drillmetal or other tools are placed in the center of the flame on hot coals. White coals are much hotter than others. The hardening process must be observed carefully. The flame of the fire should be crimson. If the fire becomes white, there is a threat of overheating and even burning of the metal.
It is necessary to ensure that the color is crimson.was distributed over all areas of the fire evenly. On the edge of metal products should not appear black spots. If blue spots appear on the material, this indicates excessive softening of the material and its excessive plasticity. This should not be allowed.
After burning a metal product in the fireit should be removed from the center of the heat. The red-hot object is lowered into the container with oil many times with an interval of 3 seconds. The time span is gradually increased. Delay at this stage is impossible. The operation is carried out quickly and abruptly. The product is dipped in oil until its color ceases to be bright and saturated.
Then the object is immersed in a bucket of water,which need a little shake. At this stage, one should be extremely careful, as the oil droplets on the knife or ax can be dried when immersed in an aqueous medium. Drills should be lowered into the fluid with a thick end.
How to harden the metal, you already know. If you follow all the recommendations, the process will bring the desired effect.
In what cases resort to the use of an electric oven?
At home, you have to harden products from non-ferrous metals or steel. In this case, a very high temperature is required up to 900 ºС and higher.
Only an electric or muffle stove can heat up a metal product to such an indicator. The latter can be made by hand, but the electric can not be done.
How to make a muffle furnace?
How to harden the metal at home whenthe help of a handmade muffle furnace? Such a device will become very necessary in the household. It will allow for heat treatment of metal products without unnecessary manipulation. For the manufacture of the furnace with your own hands you need refractory clay used for coating. A camera with a thickness of no more than 1 cm is created from this material. Its dimensions should be 210x105x75mm.
Carrying out the modeling of a muffle furnace with their own hands, they resort to using a pre-prepared form of cardboard. So that it does not stick, it is impregnated with paraffin.
Clay smeared on the form of the reverse side. In this case, it will not shrink during drying. When hardening, the material itself will move away from the edges of the form. Refractory clay can be the basis of the furnace door.
Self-made muffle stove must be allowed to dryoutdoors. Then it is dried to the end in an oven at 100 ºС. The doors and the chamber are burned gradually as the temperature rises to 900 ºС.
The parts should be allowed to cool without removing them from the oven. Then the door joins 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 coils must be twisted. To avoid a closure, the distance between the coils is covered with clay. On a dry layer of material it is necessary to spread another layer 12 cm thick.
Muffle furnace, made by hand, is in a metal frame, the size of which is 270x200x180 mm.
For a lightweight assembly of the case, it should be constructed with two removable covers that can be fixed with screws.
A door is attached to the front cover on the hinge. It should open horizontally. On this door with the help of bolts and gaskets you need to install a ceramic part.
All gaps are smeared with clay, and the edges of the wire are removed on the back cover of the frame.
Then the connector is made and a standard cord with plug. All holes between the heating parts and the frame are filled with asbestos chips.
To install the thermocouple and get the opportunityTo 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. They are attached to the closing of the curtain of metal.
The weight of the self-made muffle furnace is 10 kg. It is heated to a temperature of 900 ºС within an hour. With its help, you can facilitate the process of hardening drills, files, dies and many other metal products.
Muffle equipment for metal hardeningis the only device. For this purpose, a chamber fixture, an electric or thermal furnace, as well as an oven-bath 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.