My first knife made from springs without forging or equipment

You can buy this equipment or make it yourself. This is a special oven that allows you to reach high temperatures. Let's see if it can be made at home.

Instructions for making a simple forge

• Buy fireclay bricks, they are resistant to heat up to 2500 degrees.
• Inside the pipe is a cylinder with a diameter of about 10 cm.
• Brick cladding on the outside.
• Use steel angles for reinforcement.
• Install a cast iron grate on top of the cylinder, in the middle of the hearth.
• Attach a fan and a plug to the bottom of the pipe to clean out the ash.
• Equip the system with valves so that it can be cleaned if necessary.
• Place the new equipment on legs according to the height of the master.

How to heat metal yourself

Instructions for using the oven:

Possibility of procedure at home

Let's look at the video of how hardening was done at home independently without additional equipment:

Making a hardening chamber

The name of this design is a muffle furnace. It is made from fireproof clay, which must be poured into any form, for example, prepared from cardboard. The layer should be 0.8-1 cm. The heating element is a nichrome spiral made of wire. Let's watch a video with detailed instructions:

Hardening equipment and features

The houses can be used:

• electric or muffle furnace;
• soldering iron;
• big fire outside.

The choice must be made according to the size of the part, the type of alloy, and the maximum heating temperature.

Increased hardness over open fire

If you don’t want to make a forge with a blower, you can use a regular barbecue or fireplace, let’s see how they do it in the video:

In the article we told you how to make hardened steel. Since the procedure is risky, please follow safety precautions.

Source: www.rocta.ru

Pros of steel 65g

Undoubtedly, this steel is very popular not only due to its low production cost, but also for other important reasons:

• Very high hardness. This means that under significant loads the material will not deform, break or collapse.
• Great resistance to impacts and deformations. It is for this quality that such steel is usually used for throwing knives, blades, and less often for medical instruments.
• Easy to sharpen.
• High tear resistance.

It is worth noting that the number “65” in the name means the percentage of carbon in the alloy in hundredths. The letter “G” indicates that the main alloying element is Manganese. It is thanks to him that the alloy acquires most of the properties described above.

Heat treatment of steel 65G

Structural high-carbon steel grade 65G, supplied in accordance with the technical requirements of GOST 14959, is a steel of the spring group. It must combine high surface hardness (for which up to 1% manganese is added to its composition) and increased elasticity. All these characteristics are ensured as a result of proper heat treatment of products made from the steel in question.

Initial chemical composition of steel and requirements for parts made from it

Belonging to the category of sparingly alloyed steel, 65G steel is relatively cheap, which makes it widely and effectively used. Among its main components are:

1. carbon (within 0.62...0.70%);
2. manganese (within 0.9…1.2%);
3. chromium and nickel (up to 0.25...0.30%).

All other components are copper, phosphorus, sulfur, etc. – refer to impurities, and are allowed in the chemical composition of this material in quantities limited by the state standard.

With sufficient hardness (for example, after surface normalization it should be at least 285 HB) and tensile strength (not lower than 750 MPa), 65G steel has a fairly high impact strength for its class - 3.0...3.5 kg∙m /cm 2. This makes it possible to use the material for the production of critical parts of lifting and transport equipment (in particular, running wheels of overhead cranes, rollers), as well as spring washers and springs for non-critical purposes.

It is worth noting that spring parts made of 65G steel are poorly welded and cannot withstand periodically occurring tensile stresses (relative elongation does not exceed 9%), and therefore cannot be used in one-piece structures of machines and mechanisms. When carrying out cold plastic deformation processes, steel becomes very low-plasticity even at small (up to 10%) deformations, therefore, if it is necessary to manufacture large-sized springs from it, it is necessary to use heating of the original blanks, even for sheet stamping. However, even in the hot state, the maximum degree of deformation of 65G steel does not exceed 50...60%.

Chemical composition of steel 65G

Despite the fact that during strain hardening the ultimate tensile strength of the material increases to 1200...1300 MPa, these indicators are not enough to give the final product (for example, springs) the necessary operational strength. Therefore, quenching and tempering of 65G steel is mandatory.

Main characteristics

Steel 40X13, sometimes referred to as 4X13, is classified as a corrosion-resistant, heat-resistant grade. The domestic substitute is steel 30X13. The chemical composition of this material includes:

• carbon up to 0.45%;
• chromium up to 14%;
• other materials (silicon, manganese, etc.) up to 0.8%.

This composition allows the following products to be manufactured from this steel:

• cutting and measuring tools;
• medical, including surgical instruments;
• structural elements operating in mildly aggressive environments.
• springs, fasteners, shafts and bearings capable of operating in aggressive environments, including temperatures up to 450 ºC.

This material is produced in open kilns. Induction furnaces are most often used. Steel is melted at temperatures from 850 to 110 degrees Celsius. This mode ensures its complete deformation. To prevent the formation of cracks and other defects, various temperature conditions are used alternately. By the way, to use parts made of grade 40X13 in aggressive environments, in order to increase their resistance to corrosion, it is recommended to grind their surface.

Among the imported analogues of 40x13 steel, the following can be mentioned:

• USA - 420;
• Germany - 1.4031;
• China - 4С13.

GOST

The metallurgical industry produces the following assortment - sheet (GOST 5582-75), rod GOST 18907-73, wire (GOST 18143-72).

Optimal technological processes for heat treatment of materials

The choice of heat treatment mode is dictated by production requirements. In most cases, to impart proper physical and mechanical characteristics, the following is used:

• normalization;
• hardening followed by tempering.

The temperature-time parameters of heat treatment and the choice of its type depend on the initial structure of the steel. This material belongs to the hypoeutectoid type steels, therefore, at temperatures above the lower point of the austenitic transformation - 723 ° C - by 30...50 ° C it contains austenite in the form of a solid mechanical mixture with a small amount of ferrite. Since austenite is a harder structural component than ferrite, the quenching temperature range for 65G steel will be significantly lower than for structural steels with a lower percentage of carbon. Thus, the temperature range for hardening steel of this grade should be within the range of no more than 800...830 °C.

Approximately the same temperature range is used to carry out normalization - a technological heat treatment operation, which is used to correct the structure of the material of the product, to relieve internal stresses, and during subsequent mechanical processing of the semi-finished product - to improve its workability.

Since the impact strength of hardened steel 65G is reduced, after hardening, products made from it, in particular springs, must undergo a high tempering. The martensitic-austenitic transformations that occur during tempering reduce the level of internal stresses arising during hardening, reduce brittleness and slightly increase impact toughness.

The transition to high tempering is excluded from the mode only when the workpiece undergoes isothermal hardening. As a result of high tempering, 65G steel acquires a sorbitol structure, the characteristic features of which are the fine dispersion of the structure while maintaining initially high hardness values, which fully meets the operational requirements.

Characteristics and properties

Having in its chemical composition 0.75...0.85% carbon, as well as a small amount of other elements - silicon, manganese, chromium, nickel and copper - U8 steel is ectectoid. With reduced manganese and silicon contents, the critical cooling rate always increases. Therefore, in practice, U8 steel is used only for the manufacture of metalworking tools with small overall dimensions. Hardening of steel of this type allows the use of very harsh cooling media (water or aqueous solutions of salts). Thus, this steel is not hardenable: the core remains viscous, and the hardness obtained as a result of preliminary annealing of the workpieces remains almost the same.

Scheme of structural transformations of U8

Quenching in water also has other negative consequences - with an increase in the cooling rate, the structure of the steel remains coarse-grained. During further processing (for example, forging), this feature can cause cracking of the forging, especially at significant degrees of deformation. Often, when quenched in water, the product loses its dimensions and warps, which forces additional calibration of the tool.

The temperature of the critical points of U8 steel is:

1. The beginning of the austenitic transformation from the initial pearlite when heated is 720 °C.
2. The end of the austenitic transformation is 740 °C.
3. The temperatures at which the transformation of austenite into pearlite begins and ends upon cooling coincide and are within 700 °C.
4. The martensitic transformation, starting at 810 °C, ends at 245 °C.

Hardness of steel after heat treatment

Hardening modes of steel 65G

To comply with the characteristics specified by the technical conditions for the operation of parts, when choosing a hardening mode, the following components are taken into account:

1. method and equipment for heating products to the required temperatures;
2. establishing the required hardening temperature range;
3. choosing the optimal holding time at a given temperature;
4. selection of the type of quenching medium;
5. technology for cooling the part after hardening.

The intensity of heating determines the quality of the resulting structure. For low-alloy steels, the process is carried out quite quickly, since this minimizes the risk of decarburization of the material, and, as a consequence, the loss of the part’s strength parameters. However, too rapid heating causes other problems. In particular, for large parts with large differences in cross sections, this can cause uneven heating of the metal, with the prospect of further appearance of hardening cracks, chipping of corners and edges.

Temperature of the workpiece depending on the color when heated

To achieve the maximum degree of heating uniformity, the steel is first heated in the preliminary chambers of thermal furnaces to temperatures slightly lower than hardening temperatures - from 550 to 700 ° C, and only then the part is sent directly to the hardening furnace. Heating occurs fastest in molten salts, slower in gas furnaces, and even slower in electric furnaces. That is why surface hardening of 65G steel products in induction furnaces is performed quite rarely. The inductor, as a hardening unit, is used only for products with a small cross section. When choosing the type of heating device, the composition of the atmosphere that is created in it is also important. In particular, for thermal furnaces operating on gas, they try in every possible way to reduce the duration of the part’s stay in the furnace, since otherwise some of the carbon in the surface layer will burn out.

Based on the quenching temperature normalized for 65G steel at 800...820 °C, the maximum value of the decarbonized layer should not be more than 50...60 µm.

The temperature range of quenching temperatures can be adjusted depending on the product configuration. For example, if the part has complex shapes, small dimensions and is made of sheet metal, then the optimal temperature will be the lower limit of the above range. By controlling the hardening temperature (for example, using automatic temperature sensors), you can change the thickness of the hardened layer and the size of the zone that is less hardened than others. Such technical solutions are resorted to when different parts of a part operate under different operating conditions.

Steel 65G is not afraid of overheating, however, when hardening at the upper value of the temperature range, the impact strength of the material begins to decrease, which is accompanied by the growth of grains in the microstructure.

To reduce warping of parts that have thin ribs and bridges, they are heated in salt quenching baths. More often, a melt of sodium chloride is used, and for deoxidation, borax or ferrosilicon is added to the working volume of the bath.

When hardening products made from steel 65G, holding at a given temperature range occurs until the pearlite transformation completely occurs. This process depends on the cross-sectional size of the part and the heating method. For the most common cases, you can use the table data:

Heating and holding time depending on the quenching medium and dimensions of the workpiece
Largest overall dimension of the part, mm

Hardening in a fiery furnace		Hardening in an electric furnace
Heating time, min	Holding time, min	Heating time, min	Holding time, min
Up to 50	40	10	50	10
Up to 100	80	20	88	20
Up to 150	120	30	130	30
Up to 200	160	40	175	40

Cooling of products after hardening is carried out not in water, but in oil, this avoids the possible danger of cracking.

Processing methods

The steel in question is subjected to two main types of processing: thermal and mechanical. Heat treatment of 40x13 steel is used to give it the appropriate technological properties. Mechanical - to create the required shape, solve the assigned technical problems.

Experts classify such metal into the category of materials that require a certain specific approach during heat treatment. It is this type of processing that gives the required properties.

Steel 40x13 in a hardening oven

The main types of heat treatment are:

• sequential hardening;
• slow release after heating;
• hot and cold plastic deformation;
• annealing.

After hardening, the following components are formed in the structure:

• carbides;
• martensites;
• some remains of so-called austenites.

The first two processing methods make it possible to give steel good corrosion resistance and excellent mechanical properties. This is possible due to the fact that it has good plastic deformation. Hardening of such steel occurs by gradual heating to a temperature of more than 950 °C, but not more than 1100 °C. Consistent heating is necessary because this grade of steel is highly sensitive to cracks. To avoid negative consequences, a metal part (especially one with a thickness of more than 100 millimeters) must be heated for more than 10 minutes.

To avoid the appearance of cracks, including in the depths of the metal, the sample is subjected to so-called tempering. That is, a gradual decrease in temperature and keeping the sample at temperatures up to 300 °C. In this case, the steel acquires its maximum strength characteristics. If the temperature regime is not maintained and the process occurs at 450 °C, the steel will lose its impact strength characteristics. It acquires the best corrosion properties and good ductility if the following parameters are observed. Sequential heating to a temperature of 700 °C, subsequent holding for 20 minutes, cooling in a container with oil.

The so-called annealing is used as a softening heat treatment. The part is heated to a temperature of 800 °C. Next, slow cooling is carried out in the furnace itself to a temperature of about 500 °C.

Temperature of quenching and tempering of steel 40x13

As an alternative to the standard type of heating, heating with high frequency currents is used to carry out heat treatment. This method is especially used when it is necessary to harden the surface layer of a part. These are parts that are included in mechanisms with friction and rolling units, and in elements of pipeline fittings. Typically, such hardening is applied only to parts whose thickness exceeds 15 millimeters. With its help, it is possible to achieve a hardness indicator after hardening equal to 36.5 HRC units.

It is subjected to the following types of mechanical processing:

• drilling holes;
• sharpening;
• milling;
• forging.

Carrying out these operations is associated with certain difficulties:

• Hardening of the surface layer (this is due to additional heating of the workpiece at the time of cutting or drilling).
• Problems with the removal of metalworking waste (the resulting metal shavings form a long, narrow, twisted strip). This causes certain inconveniences during long-term processing. This problem is solved by installing special devices on metal-cutting tools. They produce periodic chip breakage.
• Increased wear of the cutting edge. This is due to an increase in the temperature of the part at the point of contact with the edge of the cutting tool. In this case, the presence of crystalline compounds (carbides and martensites) in this grade creates the effect of the presence of abrasive elements in it, which leads to rapid wear of the cutting edge.

https://youtube.com/watch?v=u262HjEbaEY

In addition, difficulties arise when sharpening cutting tools made from this steel. At the moment of sharpening, the temperature of the sharpened edge increases and a so-called metallic influx is formed. This leads to uneven hardening of the edge of the sharpened surface.

After this operation (hot deformation), only slow cooling followed by low-temperature annealing is allowed.

Unfortunately, welding is not included in the available list of mechanical processing. The fact is that this grade of metal belongs to the category of difficult-to-weld materials. Therefore, this processing method is not used to connect structures made from this material.

Subsequent release technology

As already indicated, to obtain the sorbitol structure, products made from 65G steel are subjected only to high tempering at temperatures of 550...600 °C, with cooling in still air. For particularly critical parts, an additional low holiday is sometimes carried out. Its temperature range is 160...200 °C, followed by slow cooling in air. This technology avoids the accumulation of thermal stresses in the product and increases its durability. For tempering, you can use not only flame, but also electric furnaces equipped with devices for forced air circulation. The holding time of products in such furnaces is from 110 to 160 minutes (increased time standards correspond to parts with complex configurations and large cross sections).

It is not recommended to use water and aqueous solutions of salts as working media when hardening 65G steel. The acceleration of the cooling process caused by water is often accompanied by uneven calcination.

The final quality control of hardening consists of assessing the macro- and microstructure of the metal, as well as determining the final hardness of the product. The surface hardness of products made from 65G steel should be within 35...40 HRC after normalization, and 40...45 HRC after quenching with high tempering.

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Source: stankiexpert.ru

Technology of hardening and tempering of spring steel

To obtain metal with the desired physical properties, spring steel is tempered and hardened. Each stage has its own technological features:

• First, the spring steel is hardened at high temperatures. Thanks to hardening, the yield strength of the material increases significantly, which makes the steel elastic, malleable, and stable.
• However, during high-temperature hardening, martensitic compounds are formed inside the alloy, which sharply worsen the elasticity of the material, making it unusually brittle and hard.
• To get rid of martensitic compounds, spring steel should be tempered at low temperatures. During such processing, martensites are destroyed, which makes it possible to obtain a material with the desired properties.

Please note that the temperature and processing time at each stage depend on what grades of spring steel are used. For example: spring steel grade 65G must be hardened at a temperature of +800-850 degrees, tempered at +200-300 degrees. In some cases, hardening and tempering are combined with the metal normalization procedure

This procedure allows you to get rid of excess stress inside the metal, but in most cases normalization occurs on its own as the material cools. Therefore, additional processing by normalization is usually not required.

In some cases, hardening and tempering are combined with the metal normalization procedure. This procedure allows you to get rid of excess stress inside the metal, but in most cases normalization occurs on its own as the material cools. Therefore, additional processing by normalization is usually not required.

Thermal hardening

Hardening of spring steel is carried out taking into account the following parameters:

• Method of heating metal, nature of cooling of material, ambient temperature.
• Metal composition, presence and type of alloying additives, total carbon concentration.
• A method of maintaining the required temperature range for hardening.
• Method of cooling the material after hardening, method of storing the material.

Low alloy steels are recommended to be heated quickly. After all, with slow heating, carbon gradually evaporates, which is critical for low-alloy materials. However, you don’t need to overdo it with the heating speed. If heating proceeds very quickly, then uneven heating of the material may occur. Because of this, the risk of the formation of various metal defects (cracks, edges, destruction of corners) increases.

The optimal heating method is to use two ovens. In the first furnace, the material is gradually heated to 500-700 degrees, and then it enters the second furnace, where final hardening occurs.

It is recommended to use gas ovens for heating. However, during heating, you should monitor the heat distribution to avoid the appearance of “thermal islands” on the metal. Electric ovens heat up quite slowly, so their use in this case is problematic from a practical point of view. The only exception to this rule is the hardening of thin metals, which do not require additional uniform heating for obvious reasons.

The holding time depends on many parameters, but on average the total hardening time is 80 minutes for combustion furnaces and 20 minutes for electric installations. The shape of the product also has a certain significance. When working with flat sheets, hardening can be carried out quickly. Whereas in the case of a material with a complex shape, it is recommended to perform additional heating. The best way to cool the material is in the open air.

Final thermal holiday

To avoid the appearance of hard martensitic fractions, it is necessary to perform thermal tempering immediately after quenching. The temperature regime also depends on what grade of spring steel has been hardened. Both combustion and electric furnaces can be used for tempering. The type of oven will also affect the length of the holiday.

Example: 65G steel is recommended to be subjected to high tempering at a temperature of +500-600 degrees. The cooling method is air. The holding time is 30-150 minutes depending on the type of oven. After hardening, it is recommended to carry out control measures. However, this should be done only after the material has completely cooled, so as not to damage the alloy.

Forging a knife from a spring takes place in several stages

Stage 1.

First of all, you need to collect all the materials for work so that they are ready. The author's source material was a spring leaf from an old car.

Since the spring is made in a curved shape, it must be bent. This is done like this: the metal is heated, after which it gradually cools. A burner is suitable for heating, or you can simply place a leaf of spring in a well-lit fire. After the workpiece has cooled, you need to take a hammer and an anvil and process the spring so that it becomes a straight plate. After tempering, the metal has become softer, it will be easy to cut, drill, etc.

Stage 2.

First you need to make a knife template. The author used a ready-made template from the Internet. If there is a desire, it can be improved. After printing the template, you need to glue the paper onto the cardboard and cut out the template with scissors. Holding it in our hands, we can imagine what a knife made from a spring will look like. After this, you need to attach the template to the metal and circle it with a marker.

Stage 3.

Now we are starting the most difficult stage of the work - we need to cut out the profile of the knife. This is done using a grinder - when using this tool, it is not recommended to overheat the metal. If the steel begins to change color at the cutting site, this means that it is overheating. In this case, the metal must be poured with water. In those places where it is impossible to cut, the metal can be drilled in a row of holes and then this part can be broken off.

Stage 4.

This is the final stage of shaping the main profile of the blade. For such work, a belt sanding machine is very convenient and simple. Craftsmen with extensive experience can use an angle grinder. The outer plane of the knife should be sanded so that it shines. The author used a block to press the workpiece against the sanding belt. Here you also need to ensure that the metal does not overheat.

Another important aspect of grinding is making bevels on the knife.

Stage 5.

To securely secure the lining to the handle, this knife uses 4 pins. You need to drill holes for them. To select the diameter, we focus on the existing pins, which are traditionally used as brass rods. For this case, regular steel nails are also suitable.

Stage 6.

After hardening, the blade becomes hard and does not dull for a long time. To harden the blade, you need to take oil - motor or vegetable oil, a stove or a good fire will do. The metal must be heated to such a state that a permanent magnet will not be attracted to it. As the author notes, when heated, the metal has a dull red color. After this, you need to lower the workpiece into the oil. Be careful as the oil often ignites with smoke and spray flying in all directions. The container for hardening should be made of metal.

It happens that during hardening the metal begins to deform. This situation can be corrected. To solve the problem, you need to heat the workpiece, level it, and then try to harden it again.

Stage 7.

To make handle linings, we take two boards of small thickness. We cut them to the required size and drill holes in them for the pins.

Now we glue the blanks together using epoxy glue, applying a good layer on both pads. Then you need to insert the pins and clamp the handle well with a clamp. Leave it like this for 24 hours so that the glue is completely dry. Immediately take a rag or toilet paper to remove any remaining glue.

After the glue has dried, you need to take out the knife and finally shape the shape of the handle. For these works we use a belt sanding machine.

At the final stage, we polish the knife, if necessary, we make the surface of the blade mirror-like. You can also polish the handle, so it will become smooth. Wooden overlays must be impregnated with linseed oil or other impregnations. Sometimes this is done by heating beeswax and mixing it with linseed oil.

At the end of the work, our knife, a knife made from a spring, should be sharpened well with your own hands. The most affordable option is fine-grain sandpaper.

Source: www.umeltsi.ru

The use of spring steel for making a knife

Spring material 65G is used by amateur knife makers to make knives. Thanks to its unique characteristics, the metal finds its application in various fields.

Blades for the kitchen, hunting, tourism - all show excellent cutting qualities. If there is a special need, you can actually forge a sword or an ax. After hardening, the steel acquires good rigidity, which allows the product to be cut.

Examples of using spring steel:

1. Kitchen knife. In difficult times for the country, after the collapse of the USSR, not all people could afford a good set of kitchen knives. I had to get out. Springs and plates made of 65G steel were easily accessible. In the kitchens of the post-Soviet space, homemade products were often found. The handle was made from improvised material: wood, simple epoxy, and electrical tape - which did not prevent the knives from remaining at their height.

1. Tourist knife. The disadvantage of spring metal is that it is susceptible to corrosion and requires constant care after use. The knife is suitable for use in hiking conditions. An important point is hardening. If it is weak, the blade will quickly become dull on the tin can. You should know the hardness of the knife.
2. Army. Tactical or, nowadays, military knives do their job well. Serrated sharpening will increase the scope of use of the blade. Withstands piercing blows without problems. In everyday conditions it will become a valuable assistant for a fighter or a “survivalist”.
3. Axe, machete or sword. Alloy 65G and analogs allow you to make truly formidable weapons. The thickness of the product certainly plays a significant role. When producing such a masterpiece, you need to stock up on springs from a truck, or get a long plate.

With proper processing of the metal, we are guaranteed to get an excellent blade. Little experience with the manufacture of steel products is nonsense. Further, in the article we will provide a detailed description of the manufacture of knives from springs using various methods.

Hardening of spring steel 65g

And cold weapons warm the soul. Ara Baghdasaryan

The Zbroevy Falvarak workshop has been manufacturing swords and other bladed weapons for knightly festivals for several years. The main grade of steel that our workshop works with is 65g steel.

Due to its properties, this steel is considered one of the best for the manufacture of long-bladed weapons intended for knightly tournaments.

However, the properties of steel that are acquired during the manufacture of a sword are largely the result of proper heat treatment. So how is 65g steel hardened?

Heating of steel, color depending on temperature

According to the reference book, heat treatment of the blade should occur at the following rates: hardening 830 (oil), tempering 470 (air) HRC 38-45 hardening 810 (oil), tempering 360 (air) HRC 44-49 hardening 830 (oil), tempering 200 ( air) HRC 44-49 Depending on the thickness and area of ​​the part, when tempering from 200 to 400 degrees, a hardness of 55 units can be obtained. In the case of our workshop, we harden the blade at 52-55 units , respectively, the blade is hardened at a temperature of 830, and tempered at 200 degrees. Of course, this is a lot of hardness for 65g steel; in this process, the main thing is the experience of the thermist, because an incorrectly heated blade will become brittle. The blade needs to be soft enough, i.e. When hitting the edge of the blade, there were no chips; the edge should dent and not break off. Tests in our workshop have shown that our blades meet these requirements. But once again, I would like to repeat that in the matter of heat treatment, the most important thing is the experience of the thermist. The process of heat treatment of steel itself occurs as follows: Before hardening, the blade must be heated, and then placed on a box-shaped or U-shaped baking sheet and covered with a layer of spent charcoal carburizer (borax can also be used, it has positive properties. The blade after heat treatment in the environment Borax requires less grinding. Then the stove is heated to a temperature of 830 degrees and held for a certain time, depending on the thickness of the workpiece, in our case the blade. Then the sword is taken out of the stove and immersed in a tank of oil. It must be remembered that hot parts with coal can catch fire and therefore you need to be careful when performing this process. Also, you must not forget that the parts should not have time to cool down after they are removed from the furnace. That is, the oil tank should be at a very close distance from the furnace. It will be correct, after quenching in oil, degrease the workpiece in a hot (90 degrees) aqueous solution of a surfactant, for example “Feri” or cheaper analogues. As a last resort, you can degrease the blade in this way: let the oil drain and dry at a temperature of about 300 degrees for 2 hours, as a result the oil will dry, after which you can temper it to the specified hardness. Small workpieces are cooled in air, large ones - in a confined space (box). If there are no requirements for hardness, then you don’t have to heat it at all. Perform annealing-normalization. Get a fine-grained, even texture. As for vacation time, there is a rule. The more carbon in the steel, the lower the heating rate should be (this rule applies to annealing and hardening). Overall, this process requires a lot of experience, i.e. In this case, it will not be possible to do everything according to the instructions. Therefore, look for a good thermist or get ready for a serious test and material costs.

Source: zbroevy-falvarak.by

Pre-treatment - annealing

During annealing, the first and second main transformations of steel occur: pearlite to austenite and austenite to pearlite. The heating temperature should be only slightly above Ac1 in order to keep most of the excess carbides undissolved and obtain the structure of granular pearlite. The heating temperature during annealing of 9KhVG steel in accordance with Table 2 is 770-800°C.

Holding for 30-60 minutes after heating ensures the dissolution of that part of the carbides that can be converted into austenite at a given temperature, and also ensures equalization of the concentration of carbon and alloying elements in it.

Two cooling modes are possible:

1. Slow, providing hardness as in the delivered state. The workpiece is cooled at a rate of 50–60°C/h to the isothermal holding temperature (670–720°C), and then held to complete the decomposition of austenite with the formation of a ferrite-carbide structure. The decay time of austenite at the isothermal holding temperature ranges from 20 to 60 minutes. Further cooling can be done in air. However, to reduce stress, it is recommended to cool workpieces of complex shapes in a furnace to 550-600°C.

2. Very slow cooling at a rate of 20-30°C/h to the same isothermal holding temperatures. After the end of the exposure, slow cooling 60-80°C/h to 500°C follows again, and then in air or with a furnace. The hardness after annealing according to the specified regime is 15-20 HB lower than the hardness in the delivered condition. In this case, the yield strength and strength are further reduced.

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.

Heating the metal

All steel hardening methods consist of:

• heating steel;
• subsequent holding to achieve through-heating of the product and completion of structural transformations;
• cooling at a certain speed.

Carbon steel products are heated in chamber furnaces. In this case, preheating is not required, since these steel grades are not subject to cracking or warping.

https://youtube.com/watch?v=I-br0B8ocpI

Complex products (for example, a tool with protruding thin edges or sharp transitions) are preheated:

• in salt baths by immersing two or three times for 2 - 4 seconds;
• in separate ovens up to a temperature of 400 - 500 degrees Celsius.

Heating of all parts of the product should proceed evenly. If this cannot be achieved in one step (large forgings), then two holding times are made for through heating.

If only one part is placed in the oven, the heating time is reduced. For example, one 24 mm thick disk cutter heats up within 13 minutes, and ten such products heat up within 18 minutes.

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

General information about steel 65g

This steel is very popular due to its relatively low cost. It belongs to the spring-spring type and passes the bluing and blackening procedures very well. Due to its characteristics, it is used to make throwing knives; it is extremely rarely used to create cutting knives. This is due to the fact that such steel oxidizes extremely quickly and becomes rusty.

If we talk about hardening, then this material is not afraid of overheating. However, if the temperatures are high enough, the toughness decreases quite quickly, which in turn inevitably leads to large grain growth in the fine texture of the fibers.

Due to the addition of Manganese, such an alloy is also called deoxidized steel; this applies to absolutely all materials containing such a component. Knives acquire their properties in cases where pearlite transformation has been achieved during the hardening process.

How to harden steel over an open fire

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

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

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

Heated steel colors

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

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

Steel tarnish colors

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

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

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

Classification of hot steel

Types of steel hardening are classified according to the type of heating source and method of cooling the metal. The main equipment for heating parts before hardening is still muffle furnaces, in which metal products of any size can be evenly heated. A high heating rate during continuous processing of products is ensured by hardening using high-frequency currents (induction hardening of steels) (see photo below). To harden the top layers of steel products, fairly inexpensive and effective gas-flame hardening is used, the main disadvantage of which is the inability to accurately set the heating depth. Laser hardening does not have these disadvantages, but its capabilities are limited by the low power of the radiation source. Methods for cooling a hardened part are usually classified according to the type of cooling medium, as well as sets and cycles of work operations. Some of them include tempering procedures, while others, such as various types of isothermal hardening, do not need it.

Hardening in one environment

With this method of hardening, a steel product heated to a given temperature is placed in a liquid, where it remains until it cools completely. Water is used as a quenching medium for carbon steels, and mineral oil is used for alloy steels. The disadvantage of this method is that after such hardening, significant stresses remain in the metal, so in some cases additional heat treatment (tempering) may be required.

Step hardening

Step hardening takes place in two stages. In the first step, the product is placed in an environment with a temperature several tens of degrees higher than the point at which martensite begins to appear. After the temperature is equalized throughout the entire volume of the metal, the part is slowly cooled, as a result of which a martensitic structure is uniformly formed in it.

Isothermal hardening

During isothermal hardening, the product is also kept in a hardening bath at a temperature above the martensite point, but slightly longer. As a result, austenite is transformed into bainite, a type of troostite. This steel combines increased strength with ductility and toughness. In addition, after isothermal hardening, the residual stresses in the product are reduced.

Hardening with self-tempering

This type of heat treatment is used to harden the impact tool, which must have a hard surface layer and a viscous middle. Its peculiarity is that the product is removed from the quenching container when it is not completely cooled. In this case, its internal part still contains enough heat to warm the entire volume of metal to the tempering temperature. Since reheating of the product is carried out without external influence due to internal thermal energy, this type of heat treatment is called quenching with self-tempering.

Light hardening

Light hardening is used for steel products whose surfaces should not be subject to oxidation during heat treatment. With this heat treatment, steel is heated in vacuum furnaces (see photo below) or in inert gas environments (nitrogen, argon, etc.), and cooled in non-oxidizing liquids or melts. This method is used to harden products that should not be subjected to further grinding, as well as parts that are critical to the carbon content in the surface layer.

Self-production of a chamber for hardening metal

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

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

In order to give the future furnace the required configuration and desired dimensions, it is best to make a mold from cardboard impregnated with paraffin, onto which fireproof clay will be applied. Clay, mixed with water to a thick, homogeneous mass, is applied to the wrong side of the cardboard form, from which it will peel off after complete drying. Metal products heated in such a device are placed into it through a special door, which is also made of refractory clay.

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

Clay heater with a walled nichrome spiral

Nichrome wire is wound onto the surface of the fully formed chamber, the diameter of which should be 0.75 mm. The first and last layers of such winding must be twisted together. When winding the wire around the camera, you should leave a certain distance between its turns, which also needs to be filled with fireproof clay to eliminate the possibility of a short circuit. After the layer of clay applied to provide insulation between the turns of nichrome wire has dried, another layer of clay is applied to the surface of the chamber, the thickness of which should be approximately 12 cm.

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

Ready homemade camera

The ends of the nichrome winding of the camera, to which electrical power must be supplied, are brought out from the rear side of its metal frame. In order to control the processes occurring in the inside of the muffle furnace, as well as measure the temperature in it using a thermocouple, two holes must be made in its front part, the diameters of which should be 1 and 2 cm, respectively. From the front part of the frame, such holes will be closed with special steel curtains. The homemade design, the manufacture of which is described above, allows you to harden metalworking and cutting tools, working elements of stamping equipment, etc. at home.

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

Source: met-all.org

Quenching and tempering of steel 65G

Structural high-carbon steel grade 65G, supplied in accordance with the technical requirements of GOST 14959, is a steel of the spring group.

It must combine high surface hardness (for which up to 1% manganese is added to its composition) and increased elasticity.

All these characteristics are ensured as a result of proper heat treatment of products made from the steel in question.

HDTV hardening

Self-manufacturing and hardening of springs

To harden a spring means to subject it to heat treatment in order to increase the strength, elasticity, hardness and ductility of the product, which will ultimately affect the physical and chemical properties and service life.

The essence of the process is heating to a temperature at which the metal structure transforms into a special state, and high-speed cooling in various environments, including cooling in air.

The choice of hardening technology depends on the grade of steel from which the spring is made and the diameter of the wire. This operation is performed in industrial and home conditions.

A homemade spring is not recommended for use in devices operating under increased loads.

Requirements for wire and its diameter

Steel wire for the manufacture of a spring, which will subsequently be hardened, must meet the requirements specified in GOST 14963-78. According to the document, it is classified according to the following criteria:

• winding method (cold and hot);
• method of surface finishing (without finishing and with finishing);
• manufacturing accuracy (normal and increased);
• class of mechanical properties (general and critical use);
• diameter (from 0.5 to 14 mm);
• type of delivery (in rods or coils).