How to harden metal at home?

Many people are interested in how to properly harden the 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 (a 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 familiar with this rule. The article will describe how to harden metal at home.

Why do I need hardening?

Hardening of the metal increases the hardness of the product by about 4 times. In this case, an object of this material can easily cut a glass surface. Hardening is required because of insufficient strength of the object or vice versa. In the first case, metal products will jam, and in the second - crumble.

Checking the hardness level of a metal product

To check the quenching level of a metal product, you should take a file and draw the tool along the edge of the cutting object, for example, an ax or knife. If you feel that the file begins 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 supple.

If the instrument easily moves away from the object and creates the feeling that it is stroking it, and the hand does not feel any unevenness, then it means that the metal is too hardened.

Hardening metal at home is possible. In this case, one should not resort 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 hardening done?

The quenching technology involves two processes: heating the metal product to a high temperature and then cooling.

Thermal surface treatment is advisable in the event that:

• There is a need to give the metal additional strength;
• An increase in plasticity is required, for example, for subsequent hot forging.

The cost 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 black or blue spots on the metal. Do not heat the product to the extreme temperature. The fact that the process is proceeding correctly is indicated by the appearance of a bright red color.

What equipment is used for hardening?

For example, in order to harden metal at home in the form of a drill, an electric or thermal furnace, a soldering lamp or a fire is used. What is appropriate in a particular case depends on what temperature index is required for the material being processed.

Cooling of different tools

Rules for cooling instruments can be different. The process can be carried out in one or more receptions. It all depends on the type of metal.

How to harden metal not on the whole surface, but only in a certain place? In this case, the jet type of hardening is used. It implies the direction of the jet of cold water on the object point.

If an action is carried out with a single coolant, specialized devices in the form of a barrel or a bucket are required. For this purpose, even a bath is used. This cooling method is suitable for items based on carbon or alloy steel.

If a cooling scheme involving two stages is required to lower the temperature of the product, different media are used. This process ensures the release of metal. Initially, drills or discs are cooled by water, then by 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.

Use of water for cooling

The main liquid for cooling is water. If you add a little salt or soap in it, the cooling rate will change. Therefore, the hardening tank can not be used for washing hands. To maintain the same hardness index on a metal surface, the liquid temperature should be maintained at 20-30 ° C. You can not change it often in the tank. Do not cool the product in running water.

The downside of hardening with the help of water is the appearance on the metal surface of many cracks. In this way, simple form or cemented objects should be subjected to the process.

What is used to harden parts of complex shapes?

How to harden a complex metal? For alloy steel , a 50% solution of caustic salt is used in a cold form or heated to 50-60 ° C. The details heated in the salt bath and passed through it are quenched, they come out bright. Do not allow the temperature of the solution to be above 60 ° C.

The vapors that occur during hardening are harmful to health, therefore the bath must necessarily be equipped with a ventilation hood.

How is the alloyed steel hardened?

How to harden metal? At home, the alloyed steel is subjected to a process in a bath with mineral oil. Thin objects made of carbon steel are quenched in the same way. The advantage of oil baths is that the cooling rate does not depend on the oil temperature. It will flow equally fast for any of its indicators.

How to harden the metal in oil correctly? In such a bath should not get water, as this can provoke the appearance on the surface of a metal object cracks. 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.

Oil bath accidents

• At hardening, toxic gases are released.
• On the subject a plaque is formed.
• The oil can ignite.
• The quality of quenching in the oil bath is gradually decreasing.

How is the metal released?

All the parts that have been tempered undergo tempering. This removes the internal tension. As a result of this process, the hardness decreases and the plasticity of the material increases.

How to release tempered metal? Depending on the desired temperature, the process is carried out:

• In baths with oil;
• In bathtubs with nitrate;
• In ovens with air circulation;
• In alkaline baths.

What determines the temperature of tempering?

How to weaken the 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 requiring HRC 59 - 60 is tempered at a temperature of 150 - 200 ° C. In this case, the internal tension decreases, and the hardness remains practically unchanged.

High-speed steel is 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.

Metal is hardened by the color of tarnishing. It is heated on an electric stove, in ovens or hot sand. The oxide film, which appears when heated, is colored in different colors. In this case, the surface of the metal product is cleaned from scale, carbon and oil.

After tempering, the metal is usually cooled in air. Chromium-nickel products are cooled in water or oil, as the slow cooling of these grades leads to temper brittleness.

How to temper steel on an open fire?

How to harden metal on fire? For easy carrying out of process of hardening of metal in house conditions it is necessary to build a fire and prepare two packings of the big capacity. In the fire there must be a lot of hot coals.

In one container it is necessary to pour diesel or engine oil, and in another pure water. It is better if it is well. Initially, a tool is prepared, with the help of which the metal, which is heated to the limit, will be held. They use blacksmith's tongs. But if they are not, then you can use something similar.

After doing preliminary work, metal drills or other tools are placed in the center of the flame on hot coals. White coals are much hotter than others. It is necessary to observe carefully the process of hardening. The flame of the fire must be crimson. If the fire becomes white, that is the threat of overheating and even the burning of metal.

It is necessary to ensure that the crimson color is distributed evenly throughout the campfire. On the edge of the metal product, there should be no black spots. If the material shows blue spots, this indicates excessive softening of the material and its excessive plasticity. This can not be allowed.

After calcination in the fire of a metal product, it should be removed from the hot spot. The incandescent object is lowered into the container with oil many times with an interval of 3 seconds. The time interval is gradually increased. To delay at this stage is impossible. The operation is carried out soon and abruptly. The product is immersed in oil until its color ceases to be bright and saturated.

Then the object is immersed in a bucket of water, which must be shaken slightly. At this stage, you should be extremely pointed, since oil droplets on the knife or ax can be dehydrated when immersed in an aqueous medium. The drill should be lowered into the liquid with a thick end.

How to properly harden the metal, you already know. If you follow all the recommendations, the process will bring the desired effect.

In what cases do you use an electric oven?

At home, you have to harden products made of non-ferrous metals or steel. In this case, a very high temperature of 900 ° C or more is required.

Preheat the product from metal to such an indicator in the state of only an electric or muffle stove. The latter can be made by hand, but it is impossible to make an electric one.

How to make a muffle furnace?

How to harden metal at home with a muffle furnace made by yourself? Such adjustment will become very necessary in the household. It will allow the thermal processing of metal products without unnecessary manipulation. For the manufacture of the oven with their own hands, refractory clay used for coating is required. From this material a chamber with a thickness of not more than 1 cm is created. Its dimensions should be 210x105x75 mm.

Carrying out the molding of the muffle furnace with his own hands, resort to the use of a pre-prepared cardboard mold. That it is not lather, it is impregnated with paraffin.

The clay is spread on the mold from the wrong side. In this case, during drying, it will not shrink. When solidified, the material itself will depart from the faces of the mold. Refractory clay can become the backbone of the oven door.

A homemade muffle furnace should be allowed to dry out in the open air. Then it is dried to the end in an oven at 100 ° C. Doors and the chamber are fired gradually when the temperature rises to 900 ° C.

The parts should be allowed to cool without taking them out of the oven. Then the door joins it. Its surface is ground with a file.

18 m of wire from nichrome 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 turns is smeared with clay. On the dry layer of the material, one more layer of 12 cm thick should be spread.

The muffle furnace, made by own hands, consists in a metal frame, the size of which is 270х200х180 mm.

For easy assembly of the enclosure, it should be designed with two removable covers fixed with screws.

To the front cover, a door is attached to the hinge. It should open in the horizontal direction. On this door with the help of bolts and gaskets you need to install a ceramic part.

All gaps are covered with clay, and the edges of the wire are removed to the back cover of the frame.

Then make a connector and a standard cord with a plug. All the holes between the heating parts and the frame are filled with asbestos crumb.

To install the thermocouple and to be able to track the process of hardening the metal in the chamber, it is necessary to drill two holes. The diameter of the first should be 1 cm, and the second 2 cm. Closer curtains of metal are attached to them.

The weight of the self-made muffle furnace is 10 kg. It is heated up to a temperature of 900 ° C for an hour. With its help it is possible to facilitate the process of hardening drills, files, matrices and many other metal products.

Muffle equipment for hardening metal is not the only device. For this purpose, a chamber device, an electric or a thermal furnace, and a bath oven are used. Make a muffle furnace with your own hands is more profitable than to buy ready-made equipment. For example, the average price of such a device on the market is 40,000 rubles.