How to harden 40x steel

Hardening steel 40x: hardness, modes, time, temperature, technology - Website about

17.12.2019

Of all the materials used in mechanical engineering, machine tool building, instrument making and other industrial fields, steel is the most widely used. The choice of its grades is huge; depending on its composition, any steel has certain qualities and belongs to different groups according to its indicators. Steel 40X belongs to the class of structural alloy steels.

Chemical components included in the composition

If we consider the percentage composition of the presented alloy, the number 40 means that it contains a percentage of carbon up to 0.44%, the letter X determines the presence of an alloying additive - chromium up to 1.1%. A more detailed composition of the chemical components is presented in the table below. An equivalent replacement for this grade can be alloys such as 40ХН, 45Х, 40ХН, 40ХС.

Alloy steels are produced by remelting or production using fresh charge.

If a charge is used, a preliminary calculation of the chromium content in it should take into account losses during smelting, but this value should not exceed 0.4%, otherwise the process will produce highly alloyed waste.

Refining of the metal with alloying elements is carried out with strong deoxidizers, after which slag treated with carbon and silicon is introduced. After exposure to the reducing slag, the structural steel is well deoxidized, which ensures good hardening.

Heat treatment

For 40X steel, the heat treatment sequence is as follows. First, quenching is carried out in an oil environment, and then tempering in oil or air. For each part, its own heat treatment mode is selected; it depends on the loads under which this part is used, since different modes give different hardness of the product.

The heat treatment mode is calculated depending on the critical points, reaching which the material undergoes physical and chemical changes and changes its properties and characteristics. Steel 40X has the following critical points: Ac1 = 743, Ar1 = 693 Ac3 = 782, Ar3 = 730. Hardening is carried out at a temperature of 860 ºС, the medium is oil, the hour interval is 4 hours.

Then a low tempering is performed at a temperature of 200 ºC in air, or you can use a temperature parameter of 500 ºC and carry out the treatment in an oil environment. After this heat treatment regime, the following strength of steel is achieved: NV - 217 and HRC - 45.

Qualitative indicators

A durable and hard material that can withstand heavy loads and not be destroyed - this is how 40X steel can be assessed. Characteristics it has:

• good corrosion properties;
• resistance to temperature fluctuations;
• high strength indicators;
• aesthetic qualities.

But in addition to positive indicators, 40X steel also has negative properties. This may include:

• tendency to form flakes;
• temper brittleness;
• poor weldability.

Flock sensitivity

This is a defect that occurs during accelerated cooling of the alloy after casting, in the form of internal cracks. It can occur during hot deformation of alloy steel. It can also appear on the surface in the form of clear oval or zigzag areas.

The formation of this defect can occur due to an excess of hydrogen evolution during heat treatment. This disadvantage can be combated using high-temperature heat treatment and optimal cooling mode.

You can also use the method of vacuumizing the alloy, which will help reduce the hydrogen content as a percentage.

Tempering brittleness

It occurs during slow cooling of alloyed structural steels after tempering and is caused by a sharp decrease in viscosity.

For comparison, the viscosity value can drop by 5-10 times compared to the same indicator when the steel is rapidly cooled. Slow cooling only affects the impact strength; it does not reduce the other characteristics of the steel.

Cooling too quickly can cause internal stresses, which can lead to deformation of the product.

Welding difficulties

Steel 40X belongs to the fourth group in terms of weldability. Welding seams can lead to the formation of cracks. The manifestation of these defects can be reduced by preheating. Preliminary edge preparation is also required.

Welding work of this brand can be performed using arc welding: manual or electroslag; you can also use resistance welding. After contact point, additional heat treatment will be required. For manual welding, special electrodes for alloy steels E85 UONI-13/85 are used.

The type and position of the welded seam can be any.

Application area

This grade of steel has a number of properties, thanks to which it covers a fairly wide range of applications.

It is used to produce billets of long and shaped metal products of various profiles, and also to produce sheets, pipes, and forgings obtained by forging. This type of rolled metal is used for cutting tools.

Steel 40, which has not been subjected to heat treatment, is very advantageous to use for non-working tail parts - tap bodies, nozzles, reamers.

An improved alloy obtained by heat treatment, which we discussed earlier, is used for critical structures.

These include: gear rims, shafts, axles, bushings, bolts, plungers.

This brand has found its application in structures that are operated at low temperatures in the open air; it is used in northern latitudes for the construction of railway and road bridges.

Source: https://nzmetallspb.ru/tehnologii/zakalka-stali-40h-tverdost-rezhimy-vremya-temperatura-tehnologiya.html

Steel hardening methods of the 40s and their features: types and technology

In the process of manufacturing various metal structures, the metal is subjected to procedures, including heat treatment. It is very important to competently approach this operation, fulfilling the requirements of the technology, which will give the final product improved mechanical properties.

This topic is quite extensive and includes a fairly large number of important issues. However, we would like to consider the features of the steel hardening procedure, its application and technology. It may seem at first that heat treatment is quite a complex procedure, but upon closer inspection it becomes clear that this is not the case at all.

Some general information

Hardening is understood as a procedure during which the crystal lattice of steel and its alloys changes , due to which it is possible to maintain a critical temperature, and the latter is selected for a specific material on an individual basis. Typically, upon reaching the required temperature level, the workpiece is subjected to rapid cooling. To complete this step, use water or oil.

An important point is that in relation to tool steels, incomplete hardening is performed. It is based on heating to a temperature at which it is possible to cause the appearance of excess phases. A number of other steel grades require full hardening.

They are heated to a level 50 degrees higher than the temperature that is maintained during incomplete hardening.

In the case of processing non-ferrous metals, there is no need to bring the heat treatment to a polymorphic transformation, but for steel, a polymorphic transformation is a mandatory requirement.

Removing the hardening

In accordance with the technology, when cooling the product, a vacation must be carried out. Its purpose is to increase the ductility and reduce the brittleness of the material. At the same time, it is important to ensure the constant strength of the workpiece. This problem is solved by keeping the product in an oven heated to a temperature of 150 to 650 degrees , where it gradually cools. It is customary to distinguish three types of vacations:

• Low temperature. The main effect here is to give the workpiece increased wear resistance characteristics. At the same time, such steel can better withstand dynamic loads. The treatment procedure itself takes place at a temperature of 260 degrees. This type of tempering is carried out for products made of low-alloy and carbon steels.
• Medium temperature. To carry it out, the temperature is maintained in the range from 350 to 500 degrees. It is usually used in relation to springs, leaf springs, dies, etc. The effect of such tempering is to increase the elasticity and endurance of the product.
• High temperature. It is carried out at temperatures of 500 and 680 degrees. Such processing allows you to give the product higher strength and ductility. This procedure is usually carried out on parts that will subsequently experience significant loads.

Hardening steel at home

There are situations when a home craftsman is faced with the problem of increasing the strength characteristics of a household tool. Moreover, to solve this problem there is no need to contact specialists, since he can do everything himself . You can cope with this task with a minimum of equipment and knowledge.

Let's take a closer look at the situation on the axe. If you are considering a Soviet-made instrument , then there is no doubt about its high quality of workmanship. At the same time, the same cannot be said about the products that are sold today. If there are signs of jamming or chipping, then from this we can conclude that the requirements of the hardening technology have been violated. However, it is within the power of every master to correct this situation.

The first thing to do is light a fire with coals. It is advisable to bring it to such a state that the coals are as white as possible. This way you can understand that they have heated up to the highest possible temperature. In addition, we will need two containers. In the first one we will pour oil, which can be used as regular machine oil. The other tank should be filled with clean cold water.

After waiting until the edge of the tool turns crimson, the ax is removed from the fire. To avoid burns due to exposure to high temperatures, it is recommended to use blacksmith's tongs or any other alternative.

After this, you need to quickly place the ax in a container with oil and hold it there for 3 seconds . After this time, the ax is removed, allowed to cool for the same 3 seconds, after which the operation is repeated.

The procedure of immersing the ax in oil must be carried out until the tool loses its bright light.

Next, we have to immerse the ax in a container of water, and it is important to stir the liquid periodically. This operation completes the hardening of steel at home.

Details about heating metal

If you follow the technology, metal hardening requires 3 stages:

• Heating steel;
• Excerpt. Thanks to this operation, it is possible to complete all structural transformations and ensure through-through heating;
• Cooling.

If you have to deal with structures made of carbon steels, then they are hardened in chamber furnaces . A special feature of this procedure is that there is no need for preheating.

This is due to the ability of the material to perfectly tolerate such unpleasant phenomena as warping and cracking. If it is necessary to harden such complex structures as sharp transitions and thin edges, then preheating is indispensable.

This procedure can be performed in two ways:

• Using salt furnaces, in which the workpiece must be immersed for 3-4 seconds in three stages;
• Using separate ovens, in which a temperature regime of 400-500 degrees Celsius should be created.

An important point in hardening metal is that this procedure must be carried out with uniform heating. It happens that such a problem cannot be solved in one session. In this case, the conditions for through heating must be maintained. Particular attention should be paid to the number of products that are planned to be hardened.

As their number increases, it is necessary to increase the duration of their heating. For example, if a disk cutter with a diameter of 2.4 cm , then it must be heated for 13 minutes.

If it is planned to subject a dozen similar products to such processing, then the heating time should be increased to 18 minutes.

Steel hardening methods

The following methods have become most widespread recently:

Quenching in one cooler

This method is based on immersing the workpiece in a quenching liquid, where it is kept until it cools completely. The peculiarity of this method is that it can be used by the average consumer.

Hardening in two environments

This method is applicable to products made of carbon steels. The main operations involve immersing the workpiece in water, after which it is dipped in oil.

Streaky

Here the workpiece is exposed to a jet of water. This hardening method is used in situations where only part of the part has to be hardened. This hardening option is characterized by the absence of a steam jacket, which has a positive effect on the effectiveness of such hardening.

Stepped

For metal processing, a quenching environment is used, in which the temperature is maintained above the martensitic temperature. Next, the workpiece is kept at the created temperature regime . It is very important to ensure the same temperature at each section of the workpiece, which should not differ from the temperature maintained in the quenching bath.

Protecting the product from external influences

There are often situations when it is necessary to solve the problem of protecting steel from harmful effects that can be created as a result of the appearance of scale or loss of carbon.

A solution to this problem can be special gases , which are supplied to the furnace where the part being processed is located. But it should be remembered that such a procedure can be performed provided that the oven has a sealed design.

Most often, a special generator is used as a gas source, the fuel for which is hydrocarbon gases, for example, methane.

When carrying out complete hardening of a metal workpiece, it is important to provide it with protection . In some situations it is not possible to supply gas. Then this operation can be carried out in an airtight container. The sealant here can be clay, which can prevent air from penetrating inside. But even before starting this procedure, it is recommended to cover the workpiece with a layer of cast iron shavings.

Conclusion

The vast majority of metal structures used in construction must have increased strength characteristics. This problem can be solved through a procedure such as hardening, which is carried out for all products at the stage of their manufacture. It is not recommended to neglect it, since this makes it possible to give them improved properties that expand the range of applications of the products.

An important point that should be given special attention when hardening metal structures is compliance with the technology for carrying out this work. The required temperature must be precisely maintained, which largely determines how high the strength characteristics of the processed product will be. This, in turn, affects the maximum service life of the structure, which will be made of steel processed in this way.

Source: https://stanok.guru/stal/metody-zakalki-stali-40h-i-ih-osobennosti.html

Hardening steel 40Х

When heated strongly, almost all materials change their physical characteristics. In some cases, heating is carried out purposefully, since in this way it is possible to improve some performance qualities, for example, hardness. Heat treatment has been used for many years to increase the surface hardness of steel.

Hardening should be carried out taking into account the characteristics of the metal, since the technology for increasing surface hardness is created based on the composition of the material. In some cases, hardening can be carried out at home, but it is worth considering that steel is a difficult-to-process material and in order to impart plasticity it is necessary to carry out strong heating to high temperatures using certain equipment.

In this case, we will consider the features of heating 40X steel to increase ductility and conduct quenching or tempering.

Circle made of steel 40X

Steel 40Х

As previously noted, for proper quenching and tempering of steel, its composition and many other features should be taken into account. You can choose the right heat treatment modes taking into account the following information:

1. The steel in question belongs to the structural alloy group. The alloy group is characterized by the content of a large number of impurities, which determine changes in performance properties, including hardness.
2. Used in industry to create shafts, axles, rods, mandrels, racks, bolts, bushings, gears and other parts.
3. Hardness index before heat treatment HB 10-1 = 217 MPa.
4. The temperature of the critical points determines the moment at which 40X steel begins to lose its qualities due to heat treatment: c1 = 743, Ac3(Acm) = 815, Ar3(Arcm) = 730, Ar1 = 693.
5. At a tempering temperature of 200 °C, HB = 552.

The interpretation of 40X steel indicates that the material contains 0.40% carbon and 1.5% chromium.

Download GOST 4543-71 “Rolled products from alloy structural steel 40X”

Hardening process

The process of treating 40X steel and other alloys at high temperatures is called hardening. It is worth considering that heating is carried out to a certain temperature, which was determined through numerous tests. The holding time after which cooling is carried out, as well as other points, can be found in special tables. Heating at home is quite difficult, since in the case under consideration it is necessary to reach a temperature of about 800 degrees Celsius.

Chemical composition of steel 40Х

The result of strong heating and exposure of 40X metal for a certain time, followed by sharp cooling in water, is an increase in hardness and a decrease in ductility. The result depends on the following indicators:

1. metal heating speed 40X;
2. holding time;
3. on the cooling rate.

When working at home, the processing temperature and cooling time should be taken into account.

Mechanical properties of 40X steel depending on tempering temperature

When choosing a surface heating method, you should pay attention to HDTV. This method is more popular than conventional volumetric processing due to the fact that the required temperature is achieved in a shorter time.

At home, HDTV is used extremely rarely. After carrying out the work, using HDF increases the operational strength of the part, which is associated with the appearance of surface compressive stresses.

You can carry out 40X hardening using the example of an M24 bolt product as follows:

1. the electric oven is heating up;
2. it should be heated to 860 °C, which in some cases requires 40 minutes;
3. the time required for austenitization, after which cooling is carried out, is 10-15 minutes. The uniform yellow color of the product is a sign of the correct completion of the 40X hardening process;
4. The final stage is cooling in a bath of water or other liquid.

It is impossible to independently determine the moment after which the metal should be cooled in industrial and domestic conditions. That is why, according to research, it was accepted that heating metal in electric furnaces requires 1.5-2 minutes per millimeter, after which the structure can be overheated.

Hardness determination is carried out using the Rockwell method. The improvement made by tempering or quenching can be measured using the HRC designation. Standard designation HR, to which a letter is added according to the type of test performed. The designation HRC is the most common, the last letter indicating the use of a 120° diamond cone when testing.

Tempering is carried out immediately after completion of hardening, since there is a high probability of cracks occurring in the structure. In this case, the product is heated to a point below the critical point, held for a certain period of time, and cooled. Tempering improves the structure, eliminates stress and increases ductility, eliminating the brittleness of 40X steel.

Mechanical properties of 40X steel depending on tempering temperature

There are three types of heat treatment under consideration:

1. Low tempering determines the heating of the surface to 250 °C with exposure and cooling in air. It is used to relieve stress and slightly increase ductility with virtually no loss of hardness. In the case of a structural alloy, it is used extremely rarely.
2. The average tempering allows the product to be heated up to 500 °C. In this case, the viscosity increases significantly and the hardness decreases. This heat treatment method is used to produce springs, leaf springs and some tools.
3. High allows you to heat the part up to 600 °C. In this case, martensite decomposes to form sorbitol. This structure is represented by the best combination of strength and ductility. Impact strength also increases. This heat treatment method is used to produce parts used under shock loads.

Another type of common heat treatment is normalization. Normalization is often carried out by heating the metal to the upper critical point, followed by holding and cooling in a normal environment, for example, in the open air. Normalization is carried out to impart a fine-grained structure, which leads to increased ductility and toughness.

Source: https://stankiexpert.ru/spravochnik/materialovedenie/zakalka-stali-40h.html

Products – Tekhmashholding – group of companies, official website

In the process of manufacturing various metal structures, the metal is subjected to procedures, including heat treatment. It is very important to approach this operation competently, fulfilling the requirements of the technology, which will give the final product improved mechanical properties. This topic is quite extensive and includes a fairly large number of important issues. However, we would like to consider the features of the steel hardening procedure, its application and technology. It may seem at first that heat treatment is quite a complex procedure, but upon closer inspection it becomes clear that this is not the case at all.

Hardening steel 40x13 at home: heat treatment and nitriding

Many craftsmen think about how to harden metal at home. First of all, we are talking, of course, about steel. Recently, the Russian market has been flooded with cheap Chinese products. Low quality metal often looks nice but is soft. In order for a metal tool to be suitable for use, the steel must be hard. This problem is usually successfully solved with the help of appropriate heat treatment - hardening.

Why is steel hardening and tempering needed?

As a rule, steel products go on wide sale after hardening. Hardening is carried out in special furnaces at metallurgical plants and is the final stage of preparing the metal for the manufacture of various products (chef's and hunting knives, scissors, surgical instruments).

Modern technologies make it possible to carry out this procedure quickly and safely, while the product does not become fragile due to sudden temperature changes. As a rule, furnaces that are installed in factory and factory workshops at steel mills have several operating modes, so the product is cooled gradually (and this is very important for preserving the structure of the metal). Nitriding is used quite often.

The main disadvantage of these methods is that they are not suitable for use at home. However, situations often arise when steel products purchased in a specialized store require additional processing, namely strengthening. Hardening of steel followed by tempering is necessary because:

• A product that has been subjected to heat treatment will retain its hardness for a long time;
• Hardening is an excellent protection against metal corrosion. Experts say that the likelihood of rust on hardened products is significantly reduced;
• Piercing and cutting objects, hardened at home or in a factory (factory), begin to better perform their main function. They become sharper and do not become dull for a long time, even with active use;
• Heat treatment also has a positive effect on the appearance of the metal product.

Most often, ATs40ХМ metal is used for the manufacture of products needed in everyday life. For mechanical engineering, the 40KhGM grade is most often used. For the manufacture of surgical instruments - grade 40x metal. Hardening metal at home, subject to all technologies, is no less effective than strengthening steel in production.

When working with metal, especially at high temperatures and in the presence of open flame sources, safety precautions should be strictly observed. This applies to both the steel mill worker and the home craftsman.

Experts categorically do not recommend hardening steel using chemicals, as there is a risk of serious burns or severe poisoning. At home, it is best to use a thermal method of strengthening steel products, when metal molecules are more closely attracted to each other due to the active release of thermal energy. All work must be carried out outdoors or in a specially equipped room.

Main advantages

You can harden metal yourself. The main thing is not to forget about tempering the metal, which must be carried out after hardening and temperature normalization. Sometimes this procedure is also called "annealing".

The procedure of strengthening metal with oil or the so-called “hardening in two environments” - in water and oil - is very popular.

But a person who does not have experience should not undertake hardening using hot liquids, as serious injury can occur if safety precautions are violated.

The lack of tempering of the metal after hardening often leads to the fact that, due to a sharp temperature change, the metal becomes harder, but more brittle and brittle. If hardening occurs at the factory, the tempering procedure occurs in full accordance with GOST standards.

Here are the main advantages of hardening steel at home:

• You don't need any special equipment to work. A regular fire or gas burner will do;
• Heat treatment does not take much time. If metal is hardened over a fire, the degree of hardening can be easily determined by the appearance of the product placed in the fire;
• You don't need a lot of space to complete this procedure. You can make a fire or install a muffle stove in the far corner of your summer cottage so as not to disturb anyone;
• You can harden steel objects of any size at home, from large saws and axes to small, delicate surgical instruments.

If a fire is used as a source of open fire, steel hardening should be carried out in calm weather so that an accidental gust of wind does not cause a fire. It is imperative to protect your eyes with special glasses, since prolonged observation of a bright flame can adversely affect your vision. It is also necessary to wear protective clothing made of fire-resistant material.

How to make an ax stronger

To improve the quality of the metal from which the ax blade is made, you can easily harden it at home. It is best to harden piercing and cutting products made from steel grade 45. There should also be no problems with products made from metal grade 40×13.

You can increase the hardness of the blade by simply lowering it into the fire. Experienced craftsmen can easily determine the degree of hardening by the color of the ax lowered into it. Typically, a product made from 40x steel first turns bright red, and then the color gradually begins to fade.

The color of the metal blade changes depending on the heating temperature approximately as follows:

• Bright red color when the product is heated to 300 degrees;
• Orange color at about 400 degrees;
• Rich yellow color when heated to 500−600 degrees;
• Light yellow, almost white color at the final stage, when the incandescence temperature reaches approximately 750-800 degrees.

Next, as a rule, follows the tempering of the metal - its gradual cooling. If you neglect this stage, in the future the ax blade can easily break even under light load.

How to harden a steel knife

Heat treatment of steel knives, scissors or surgical instruments can be carried out in a muffle furnace. This furnace is well suited for small-sized products made of 40x steel. Some craftsmen also use a gas burner for this purpose, but this method is not safe, as a fire may occur.

The main advantage of a muffle furnace is that it can carry out not only hardening, but also tempering. You can construct this simple device for heat treatment of metal with your own hands. Hardening steel at home in a muffle furnace is a safe way to increase the hardness of the metal without the use of chemicals (such as nitrogen). To harden a knife made of 40x steel, it must be placed in the oven while it is still warm.

Next you need:

• Set the oven to gradual heating mode to the required temperature;
• Cut the sealing wax several times with a steel knife;
• Do the same, but with a gradual decrease in temperature;
• When the knife has cooled, carefully clean it of any remaining melted sealing wax.

This method is often used by surgeons to harden steel scalpels at home. Also, a muffle furnace is often used to strengthen metal parts used in the assembly and repair of cars and trucks.

Hardening metal is a great way to extend the shelf life of a metal product. Of course, it is better to immediately purchase hardened parts and tools. But if this is not possible, you can easily increase the hardness of the material yourself. With certain skills and basic knowledge of metallurgy, a good owner can easily cope with this important task. The main thing is to follow safety precautions and not forget about such an important stage of hardening as tempering or annealing.

Source: https://obrabotkametalla.info/stal/zakalka-stali-40x-v-domashnix-usloviyax

Heat treatment of steel 45, 40x, 20, 30xgsa, 65g, 40, 40xn, 35, and steel 20x13

In mechanical engineering steel 45 (as a substitute for 40Х, 50, 50Г2), steel 40х (as a substitute for steel 38х, 40хр, 45х, 40хс, 40хф, 40хн), steel 20 (as a substitute for 15, 25), are most often subjected to heat treatment. steel 30khgsa (substitutes 40khfa, 35khm, 40khn, 25khgsa, 35khgsa), steel 65g, steel 40khn, steel 35, and steel 20x13, also

Heat treatment of steel 45

Heat treatment of steel 45 - structural carbon. After preliminary heat treatment of steel 45 - normalization, it can be machined quite easily. Turning, milling, etc. Parts are obtained, for example, such as pinion shafts, crankshafts and camshafts, gears, spindles, bandages, cylinders, cams.

After the final heat treatment of steel 45 (hardening), the parts acquire high strength and wear resistance. Often sanded. The high carbon content (0.45%) ensures good hardenability and, accordingly, high surface hardness and strength of the product. 45 steel is hardened “on water”. That is, after calcination, the part is cooled in water. After cooling, the part is subjected to low-temperature tempering at a temperature of 200-300 degrees Celsius.

With this heat treatment of steel 45, a hardness of about 50 HRC is obtained.

Heat treatment of steel 45 and use of products: The jaws of machine chucks, according to GOST instructions, are made from steels 45 and 40X. Hardness Rc = 45 -50. In the jaws of four-jaw chucks, the thread hardness should be in the range Rc = 35-42. Tempering of cams from steel 45 is carried out at a temperature of 220-280°, from steel 40X at 380-450° for 30-40 minutes.

Interpretation of steel grade 45: grade 45 means that the steel contains 0.45% carbon, C 0.42 - 0.5; Si 0.17 - 0.37; Mn 0.5 - 0.8; Ni up to 0.25; S up to 0.04; P up to 0.035; Cr up to 0.25; Cu up to 0.25; As up to 0.08.

Heat treatment of steel 40Х

Heat treatment of steel 40X - alloy structural steel is intended for high-strength parts such as axles, shafts, gear shafts, plungers, rods, crank and cam shafts, rings, spindles, mandrels, racks, sponge rings, bolts, axle shafts, bushings and other parts increased strength. 40X steel is also often used to produce forgings, stampings and pipe fittings. However, the last listed parts require additional heat treatment, which consists of quenching through water in oil or simply in oil, followed by tempering in oil or air.

Decoding steel grade 40X. The number 40 indicates that the steel contains 0.4% carbon. Chromium content is less than 1.5%. In addition to the usual impurities, it contains specially introduced elements in certain quantities, which are designed to provide specially specified properties. In this case, chromium is used as an alloying element, as indicated by the corresponding marking.

Heat treatment of steel 20

Heat treatment of steel 20 - high-quality structural carbon steel. Widely used in boiler making, for pipes and heating pipelines for various purposes; in addition, the industry produces rods and sheets. The starting temperature for forging steel 20 is 1280° C, the end temperature is 750° C, the forging is cooled by air.

Steel 20 is non-floczen sensitive and not prone to tempering.

After carburization and cyanide plating, steel 20 can be used to produce parts that require high surface hardness and allow low core strength: cam rollers, fasteners, spindles, sprockets, studs, rod forks and gear shift shafts, valve lifters, oil pump shafts.

Steel 20 is used for the production of lightly loaded parts (pins, axles, copiers, stops, gears), cemented parts for long and very long service (operation at temperatures not exceeding 350 ° C), thin parts exposed to abrasion and other parts of automotive and agricultural mechanical engineering.

Heat treatment of steel 30khgsa

Heat treatment of steel 30xgsa - refers to medium-alloy structural steel.

Steel 30xgsa undergoes improvement - hardening followed by high tempering at 550-600 ° C, therefore it is used in the creation of improved parts (except for aircraft parts, these can be various casings, axles and shafts, blades of compressor machines that operate at 400 ° C, and much more), levers, pushers, critical welded structures operating under alternating loads, fasteners operating at low temperatures.
Steel 30xgsa has good endurance, excellent impact strength, and high strength. It also has excellent weldability.

Welding 30xgsa steel also has its own characteristics. It is carried out with preheating of the material to 250-300 ° C, followed by slow cooling. This procedure is very important because cracks may appear due to the sensitivity of the steel to sudden temperature changes after welding.

Therefore, upon completion of welding work, the torch should be withdrawn slowly, while heating the material at a distance of 20-40 mm from the welding site. Also, no more than 8 hours after completion of welding, welded joints of 30KhGSA steel require quenching with heating to 880 °C, followed by high tempering. Next, the product is cooled in oil at 20-50 °C.

Tempering is carried out by heating to 400 - 600 ° C and cooling in hot water. Welding must be performed as quickly as possible in order to avoid burnout of alloying elements.

After undergoing thermomechanical low-temperature treatment, 30KhGSA steel acquires a tensile strength of up to 2800 MPa, impact strength doubles (in contrast to conventional heat treatment of 30KhGSA steel), and ductility increases. 

Heat treatment of steel 65g 

Heat treatment of steel 65g - Structural spring steel. Springs, leaf springs, thrust washers, brake bands, friction discs, gears, flanges, bearing housings, clamping and feed collets and other parts that require increased wear resistance and parts that operate without shock loads are used in industry. (substitutes: 70, U8A, 70G, 60S2A, 9HS, 50HFA, 60S2, 55S2).

Heat treatment of steel 40 - High-quality carbon structural steel. Industrial use: pipes, forgings, fasteners, shafts, discs, rotors, flanges, gears, bushings for long and very long service at temperatures up to 425 degrees.

Heat treatment of steel 40xn - Structural alloy steel Use in industry: axles, shafts, connecting rods, gears, excavator shafts, couplings, gear shafts, spindles, bolts, levers, rods, cylinders and other critical loaded parts subject to vibration and dynamic loads , which are subject to requirements for increased strength and toughness. Rolls of rail and beam and large-section mills for hot rolling of metal.

Heat treatment of steel 35 - High-quality carbon structural steel. Use in industry: parts of low strength that experience low stress: axles, cylinders, crankshafts, connecting rods, spindles, sprockets, rods, rims, traverses, shafts, tires, discs and other parts.

Heat treatment of steel 20Х13 - Corrosion-resistant, heat-resistant steel.

Use in industry: power engineering and furnace making; turbine blades, bolts, nuts, fittings for cracking units with a long service life at temperatures up to 500 degrees; martensitic class steel Steel grade 20Х13 and other martensitic class steels: heat-resistant martensitic chromium steels are used in various power plants; they operate at temperatures up to 600° C. Rotors, disks and turbine blades are made from them, and recently they have been used for ring parts large thicknesses. There are a large number of steel grades of this class. Common to all is a reduced chromium content, the presence of molybdenum, vanadium and tungsten. They are effectively strengthened by conventional heat treatment methods, which are based on the y-a transformation and provide for the formation of martensite in the structure with subsequent improvement depending on the technical requirements. (substitutes: 12Х13, 14Х17Н2)  

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How to harden 40x steel at home

In the process of manufacturing various metal structures, the metal is subjected to procedures, including heat treatment. It is very important to competently approach this operation, fulfilling the requirements of the technology, which will give the final product improved mechanical properties.

This topic is quite extensive and includes a fairly large number of important issues. However, we would like to consider the features of the steel hardening procedure, its application and technology. It may seem at first that heat treatment is quite a complex procedure, but upon closer inspection it becomes clear that this is not the case at all.

Steel grade 40X: characteristics, hardening, GOST standards and industrial use

Mechanical engineering, instrument making, machine tool building and other areas of industry in the production process use a huge amount of materials, both classical, known for decades and hundreds of years, and completely new, modern ones.

Steel is one of the classic and widely used materials.

The classification of steels by chemical composition provides for their division into alloyed (with the introduction of alloying elements that provide the alloy with the necessary mechanical and physical properties) and carbon.

Steel 40x is a structural alloy alloy. The word “structural” indicates that the material is used for the manufacture of various mechanisms, structures and parts used in mechanical engineering and construction, and has a certain set of chemical, physical and mechanical properties.

Chemical composition

The number 40 in the marking indicates that the percentage of carbon in the alloy ranges from 0.36 to 0.44, and the letter x indicates the presence of the alloying element chromium in an amount of no less than 0.8 and no more than 1.

1 percent. Alloying steel with chromium gives it the property of resistance to corrosion in an oxidizing environment and atmosphere. In other words, steel acquires stainless properties .

In addition, chromium determines the structure of the alloy, its technological and mechanical characteristics.

The remaining chemical elements are included in steel x 40 in the following quantities:

• no more than 97% iron;
• 0.5 - 0.8% manganese;
• 0.17 - 0.37% silicon;
• no more than 0.3% copper;
• no more than 0.3% nickel;
• no more than 0.035% phosphorus;
• no more than 0.035% sulfur.

physical characteristics

Almost all physical properties of metals depend directly or inversely on temperature . Indicators such as resistivity, coefficient of linear expansion and specific heat capacity increase with increasing temperature, while the density of steel, its modulus of elasticity and thermal conductivity, on the contrary, decrease with increasing temperature.

Another physical characteristic, called mass, does not depend on practically anything. The sample can be subjected to heat treatment, cooled, processed, given different shapes, and the mass will remain unchanged.

The physical characteristics of all known grades of domestic steels and alloys, including the grade described, are summarized in tables and placed in reference books on metal science.

Steel in its original state is a fairly plastic mass and can be processed by deformation. It can be forged, stamped, rolled.

To change the mechanical properties and achieve the required qualities, heat treatment of the metal is used. The essence of thermal or heat treatment is the use of a set of operations for heating, holding and cooling hard metal alloys. As a result of such processing, the alloy changes its internal structure and acquires certain properties necessary for the manufacturer and consumer.

Critical points

Critical points are temperatures at which the structure of steel and its phase state change. Calculated in 1868 by Russian metallurgist and inventor Dmitry Konstantinovich Chernov , which is why they are sometimes called Chernov points.

Such points are designated by the letter A. The lower point A1 corresponds to the temperature at which austenite turns into pearlite when cooled or pearlite into austenite when heated. Point A3 is the upper critical point, corresponding to the temperature at which ferrite begins to separate during cooling or its dissolution ends when heated.

If the critical point is determined during heating, then the index “c” is added to the letter “A”, and when cooling, the index “r” is added.

For this steel, the following critical point temperatures are determined:

• 743*C - Ac1;
• 815*C - Ac3;
• 730*C - Ar3;
• 693*C - Ar1.

Algorithm for heat treatment of steel and alloys:

• annealing:
• hardening;
• vacation;
• normalization;
• aging;
• cryogenic treatment.

Heat treatment for 40x steel . Characteristics of the temperature regime in accordance with the requirements of GOST 4543–71:

• hardening of steel 40x in an oil environment at a temperature of 860*C;
• tempering in water or oil at a temperature of 500*C.

As a result of this heat treatment, this steel acquires increased hardness (HB hardness number no more than 217), high tensile strength (980 N/m2) and impact strength of 59 J/cm2.

Yield strength

Speaking about mechanical properties, it is necessary to mention such an important characteristic as the yield strength. If the applied load is too great, then the structure or its parts begin to deform and not elastic (completely disappearing, reversible), but plastic (irreversible residual) deformations appear in the metal. In other words, the metal “flows.”

The yield point is the boundary between elastic and elastoplastic deformations. The value of the yield strength depends on many factors: heat treatment mode, the presence of impurities and alloying elements in the steel, microstructure and type of crystal lattice, temperature.

In metallurgy, a distinction is made between the concepts of physical and conditional yield strength.

The physical yield strength is the stress value at which the deformation of the test specimen increases without increasing the applied load. In reference books, this value is designated σt and for grade 40x its value is no less than 785 N/mm2 or 80 KGS/mm2.

It should be noted that plastic (irreversible) deformations do not appear in the metal instantly, but increase gradually, with increasing applied load. Therefore, from a technology point of view, it is more appropriate to use the term “conditional (technical) yield strength.”

The conditional (or technical) yield strength is the stress at which the prototype receives a plastic (irreversible) elongation of its calculated length by 0.2%. In the tables this value is designated as σ 0.2 and for steel 40x it is:

• at temperatures from 101 to 200*C - 490 MPa;
• at temperatures from 201 to 300*C - 440 MPa;
• at temperatures from 301 to 500*C - 345 MPa.

Technological characteristics

To summarize, 40x steel can be characterized as a hard and durable material that can withstand heavy loads without breaking. PC positive properties include:

• resistance to temperature fluctuations;
• excellent corrosion properties;
• high strength indicators.

Along with these qualities, this material, unfortunately, also has disadvantages. These include:

• difficulties when welding;
• tendency to temper brittleness;
• sensitivity to floc formation.

After heating followed by heat treatment, the steel described is amenable to manual arc welding (MAW) and electroslag welding (ESW). If resistance spot welding (KSW) is used, then subsequent heat treatment is necessary.

Slow cooling of 40x structural alloy steel after tempering leads to its brittleness. This disadvantage does not occur with rapid cooling, but in this case internal stresses may arise, causing deformation.

Flock sensitivity is the tendency of a metal to form internal defects (cavities and cracks), the so-called flakes. To eliminate this drawback, the alloy is evacuated in a ladle with simultaneous argon purging and electric arc heating.

40x steel is produced and marketed in the following forms:

• long products (including shaped sections) in accordance with GOSTs 4543−71, 2591−2006, 2590−2006, 10702−78 and 2879−2006;

Source: https://tokar.guru/metally/stal/harakteristiki-osobennosti-termoobrabotki-i-primenenie-stali-40h.html

Maximum hardness of steel 40x after hardening

• Steel 40Х
• Hardening process
• Vacation and normalization

When heated strongly, almost all materials change their physical characteristics. In some cases, heating is carried out purposefully, since in this way it is possible to improve some performance qualities, for example, hardness. Heat treatment has been used for many years to increase the surface hardness of steel.

Hardening should be carried out taking into account the characteristics of the metal, since the technology for increasing surface hardness is created based on the composition of the material. In some cases, hardening can be carried out at home, but it is worth considering that steel is a difficult-to-process material and in order to impart plasticity it is necessary to carry out strong heating to high temperatures using certain equipment.

In this case, we will consider the features of heating 40X steel to increase ductility and conduct quenching or tempering.

Characteristics, features of heat treatment and use of 40X steel - we understand in detail

The physical properties of materials can be changed by thermal treatment at a high degree of heating and subsequent cooling. This primarily applies to metals that are subjected to hardening. To properly harden steel, you need to know its grade: it reflects the full chemical composition of the solid. Thus, heat treatment of 40x steel has its own nuances associated with the type of impurities contained in it.

If we take the exact definition of the type of steel to which 40x belongs, then this is a classic type of alloyed material, where the percentage of carbon is inferior to the percentage of chromium impurity. These elements here range from 0.44 to 0.36 and from 1.1 to 0.8, respectively. Chromium in the metal contributes to its resistance to aggressive oxidizing environments and gives it the ability not to rust. In addition, chromium affects the mechanical properties of 40x steel, transferring it to the category of structural steel.

Decoding steel 40X

In the CIS, the GOST 4543-2016 standard is used, which allows you to determine not only the chemical composition, but also the various performance qualities of the material.

Download GOST 4543-2016

Steel 40X GOST defines the following substances in its composition:

1. The first number 40 is used to indicate the main element in the composition, which is carbon. As a rule, most of the composition is iron, and carbon, the concentration of which is 0.44%, determines the main performance characteristics.
2. The next letter X indicates that the composition contains an alloying element represented by chromium. The absence of a number after the letter indicates that the concentration of the element is 1.1%. As previously noted, chromium increases the corrosion resistance of the structure. However, the steel grade in question, 40X, is not characterized by high anti-corrosion qualities.
3. Considering 40X GOST, we note that the composition includes a fairly large amount of nickel, silicon and manganese. They determine some of the performance characteristics of the metal, but they are not noted in the markings.

Deciphering allows you to determine the chemical composition and basic performance qualities of the material. It is worth considering that foreign manufacturers use different standards when labeling materials, but the chemical composition of analogues is approximately similar.

: Characteristics and composition of stainless steel

Steel 40X. Application in production

40X steel is a structural carbon alloy steel.

After hardening and appropriate tempering, Steel 40X acquires high strength while maintaining sufficient ductility, allowing it to be used in the production of gear shafts of the first stage of RM type gearboxes, such as the RM 250 gearbox, the RM 350 gearbox, the RM 750 gearbox, the RM 850 gearbox and the gearbox RM 1000. Also, gear wheels of Ts2N type gearboxes are made from Steel 40X. These are the Ts2U 400 gearbox, the Ts2N 450 gearbox, the Ts2N 500 gearbox, the Ts2N 630 gearbox and the Ts2N 710 gearbox. All detailed characteristics of these mechanisms are given in our catalog.

Chemical composition of steel

The main indicators of the chemical composition of Steel 40X are specified in its marking - from 0.36 to 0.44%, and the letter X means the presence of the alloying element - chromium, the share of which in the composition is from 0.8 to 1.1%. Below is the full lineup:

• iron (Fe) – up to 97%;
• silicon (Si) – from 0.17 to 0.37%;
• manganese (Mn) – from 0.5 to 0.8%;
• nickel (Ni) – up to 0.3%;
• sulfur (S) – up to 0.035%;
• phosphorus (P) – up to 0.035%;
• chromium (Cr) – from 0.8 to 1.1%;
• copper (Cu) – up to 0.3%;

Existing GOST standards for Steel 40Х

Due to the wide variety of existing rolled products and billets made of Steel 40X, the quality and characteristics of the entire product range are regulated by the following GOSTs:

• circle Sal 40Х GOST 2590-2006 (GOST 2590-88) hot-rolled steel circle (bar);
• circle Steel 40X GOST 7417-75 calibrated circle (rod);

Source: https://tpspribor.ru/vidy-metalla/specifika-termoobrabotki-stali-40h.html