What is metal tempering

Tempering of steels

Tempering is a heat treatment process consisting of heating hardened steel to temperatures below the Ac1 point in order to obtain an equilibrium structure and a given set of mechanical properties.

After hardening, the steel has a structure based on martensite with a tetragonal distorted crystal lattice and retained austenite, the amount of which depends on the chemical composition of the steel. When hardened steel is heated, phase transformations occur in its structure, which can be shown in the form of a diagram.

Scheme of phase transformations during steel tempering

Low steel tempering

Low tempering of steel is done at temperatures up to 250°C. During this process, some of the excess carbon is released from martensite to form tiny carbide particles (ε-carbides). ε-carbides precipitate in the form of plates or rods and they are coherently bonded to the martensite lattice.

The decomposition of retained austenite during low tempering occurs according to the mechanism of bainite transformation: a heterogeneous mixture of low-carbon martensite crystals and dispersed carbides is formed.

 The product of low tempering is tempered martensite, which differs from quenched martensite by its lower carbon concentration and the presence of carbides (ε-carbides) in it, which are coherently bonded to the martensite lattice.

At a temperature of about 250°C, the transformation of carbide into cementite begins; in this case, the coherence of the lattices of the α-solid solution of martensite and carbides is disrupted.

Iron-carbon tool materials (cutting and measuring tools), as well as steels that have been carburized or nitrocarburized, are subjected to low tempering. Low tempering is often done for steels after heat treatment with high frequency currents.

Average holiday

Average tempering is carried out at temperatures of 350–400 °C. In this case, all excess carbon is released from martensite with the formation of cementite particles. The tetragonality (degree of tetragonality) of the iron lattice decreases, it becomes cubic.

As a result, ferrite remains instead of martensite. Such a ferrite-cementite mixture is called tempering troostite, and the process leading to such changes is called medium-temperature tempering.

 With medium tempering, the dislocation density decreases and the internal stresses in the steel decrease.

Medium tempering is used for heat treatment of elastic parts: leaf springs, springs, etc.

High holiday

During high tempering (450-550°C and above), structural changes occur in carbon steels that are not associated with phase transformations: the shape, size of carbides and ferrite structure change. With increasing temperature, coagulation occurs - the enlargement of cementite particles. The shape of the crystals gradually becomes spherical - this process is called spheroidization.

Coagulation and spheroidization of carbides begin to occur more intensely at a temperature of 400°C. The ferrite grains become large and their shape approaches equiaxial. The ferrite-carbide mixture, which is formed after tempering at a temperature of 400–600 ° C, is called tempering sorbitol. At a temperature close to point A1, a fairly coarse ferrite-cementite mixture is formed - pearlite.

High tempering at temperatures of 450-550°C is used for most structural steels. It is widely used in the heat treatment of various bushings, supports, fasteners operating in tension-compression and other products that experience static loads.

Temper brittleness phenomenon

When tempering some steels, processes may occur that reduce the impact strength of the steel without changing other mechanical properties. This phenomenon is called temper brittleness and is observed in the tempering temperature ranges at 250–400ºС and 500–550ºС.

The first type of brittleness is called type 1 temper brittleness and is irreversible, so tempering steels at these temperatures should be avoided. This type is inherent in almost all steels alloyed with chromium, magnesium, nickel and their combination, and is due to the heterogeneous precipitation of carbides from martensite.

 The second type of temper brittleness, temper brittleness of the ΙΙth kind, is reversible. Temper brittleness of the ΙΙ-th kind manifests itself when alloy steel is slowly cooled at a temperature of 500–550°C. This brittleness can be eliminated by repeated tempering at a high cooling rate (in water or oil).

In this case, the cause of this brittleness is eliminated—the precipitation of carbides, nitrides, and phosphides along the boundaries of former austenite grains. It is possible to eliminate the temper brittleness of alloy steels by introducing small additions of molybdenum (0.2–0.3%) or tungsten (0.5–0.7%) into them.

Graphically, these types of fragility look as shown in the figure.

Manifestation of temper brittleness in steels during tempering

Almost all steels obey the law: an increase in tempering temperature leads to a decrease in strength characteristics and an increase in plasticity, as shown in the figure below.

Effect of tempering temperature on the mechanical properties of steel

This pattern does not apply to high-speed tool steels alloyed with carbide-forming elements.

Tempering of high-speed tool steels

The main alloying elements of high-speed steels (P18, P6M5, etc.) are tungsten, molybdenum, cobalt and vanadium - elements that provide heat resistance and wear resistance during operation. High-speed steels belong to the carbide (ledeburite) class. For hardening, these steels are heated to a temperature above 1200°C (P18 to a temperature of 1270°C, P6M5 to a temperature of 1220°C).

 High quenching temperatures are necessary for more complete dissolution of secondary carbides and obtaining austenite highly alloyed with chromium, molybdenum, tungsten, and vanadium. This ensures that heat-resistant martensite is obtained after quenching. Even at very high heat, only part of the carbides dissolves.

These steels are characterized by the preservation of fine grains at high heating temperatures.

Iron and “quick-cut” alloying elements have very different thermal conductivity properties, therefore, when heating, temperature stops should be made to avoid cracks. Typically at 800 and 1050°C. When heating a large instrument, the first exposure is made at 600°C. The holding time is 5-20 minutes.

Holding at the quenching temperature should ensure the dissolution of carbides within the limit of their possible solubility. Cooling of the instrument is most often done in oil. To reduce deformation, stepwise hardening is used in molten salts at a temperature of 400-500°C.

 The structure of “quick cuts” after quenching consists of highly alloyed martensite containing 0.3-0.4% C, undissolved excess carbides and retained austenite. The higher the quenching temperature, the lower the position of points Mn, Mk and the more retained austenite.

In R18 steel there is approximately 25-30% retained austenite, in R6M5 steel - 28-34%. To reduce austenite, cold treatment can be done, but as a rule this is not required.

After quenching, tempering follows at 550 - 570°C, causing the transformation of retained austenite into martensite and dispersion hardening due to the partial decomposition of martensite and the release of dispersed carbides of alloying elements. This is accompanied by an increase in hardness (secondary hardness).

During the holding process during tempering, carbides are released from the retained austenite, which reduces its alloying, and therefore, upon subsequent cooling, it undergoes a martensitic transformation (Mn ~ 150°C). During a single tempering process, only part of the retained austenite is transformed into martensite. In order for all the austenite to transform into martensite, two and three times tempering is used.

The holding time is usually 60 minutes.
When assigning a regime, it is necessary to take into account the chemical properties of the elements and the frequency of carbide release depending on temperature. For example, the maximum hardness of R6M5 steel is obtained through 3-stage tempering. The first tempering is at a temperature of 350°C, the next two at a temperature of 560-570°C.

At a temperature of 350°C, cementite particles are released, evenly distributed in the steel. This contributes to the uniform release and distribution of special M6C carbides at a temperature of 560-570°C.

Source: https://HeatTreatment.ru/otpusk-stalej

Steel tempering: types and characteristics, technology features and temper brittleness, heat treatment of alloys

Metal tempering is the technological process of heat treatment of a hardened steel alloy. It makes it possible to complete phase transformations in the microstructure (martensite), which acquires the most stable state.

The fact is that during the hardening process, internal stresses arise in the metal - axial, radial, tangential.

To eliminate their negative consequences such as fragility and low ductility, products are heated in ovens at different temperatures (from 250 °C to 650 °C), kept for a specified time (from 15 minutes to 1.5 hours), and then slowly cooled.

The complex of these measures leads to the release of excess carbon, restructuring and ordering of the metal structure, and the elimination of defects in its crystalline structure. The processed materials acquire a given set of mechanical properties, among which the main ones are an increase in ductility and a decrease in fragility while maintaining a sufficient level of strength.

Types of steel tempering

1. Short.
2. Average.
3. High.

Low holiday concept.

To reduce internal stresses, low tempering of steel is usually carried out by heating to 250 °C for 1 to 2.5 hours. During the process of diffusion, some of the excess carbon is released from the metal, from which carbide particles are formed in the form of plates and rods. The nonequilibrium structure of quenched martensite transforms into equilibrium tempered martensite. This achieves stabilization of product dimensions , increases viscosity and strength, and hardness indicators practically do not change.

Iron-carbon and low-alloy steels are subjected to low-temperature tempering to produce cutting and measuring tools that do not experience dynamic loads. It is mainly performed for steels hardened by high-frequency currents, as well as for alloys whose surface was previously saturated with carbon and nitrogen.

Features of an average vacation.

It is carried out at temperatures from 350 °C to 500 °C and provides high elasticity and relaxation resistance. All excess carbon is released from the steel, and the carbide turns into cementite.

Martensite has already completely decomposed, and the restructuring of the metal structure (polygonization) and its improvement (recrystallization) have not yet begun. The new combination is called troostomartensite and is characterized by accelerated diffusion processes.

In this case, the crystal lattice of the alloy turns into a cubic lattice, and internal stresses decrease even more.

The metal is cooled in water, which also increases the endurance limit. Medium-temperature tempering is necessary in the production of elastic parts: springs, impact tools and springs.

High release technology.

At temperatures above 500 °C, structural transformations occur in carbon alloys, which are no longer phase transformations. The configuration and dimensions of crystal particles undergo changes, their grains become larger, and their shape tends to be equiaxed.

Complex heat treatment, including hardening and high tempering of steel, is called improvement in materials science, and the crystalline structure of the metal after this is called sorbitol tempering. It is considered the most effective, since an ideal combination of viscosity, ductility and strength of the alloy is achieved.

However, the hardness decreases somewhat, so there is no hope for improved wear resistance.

https://www.youtube.com/watch?v=0vueOUKzTe4

The duration of high tempering varies from 1 to 6 hours and depends on the sizes of gears, bearings, crankshafts, bushings, bolts and screws made of structural and medium carbon steels. During operation, these products absorb shock loads and work under compression, tension and bending, and special requirements are placed on their strength, endurance, fluidity and impact strength.

What is hardening, tempering of steel and tarnish color

You may have heard these terms more than once when talking about forged knives, and steels in general. It's time to figure out what they mean.

Hardening, in its essence, is heating the finished product to a certain temperature, followed by cooling at a certain speed, and tempering is additional heating following hardening to lower temperatures with a different cooling mode; exactly which one depends on the grade of steel. The speed is regulated by the so-called. “quenching medium” - a liquid in which the blade is cooled at a certain speed: machine oil, saline solutions, air flow, etc. For example, oil cools at a rate approximately 6 times slower than circulating water.

To get to specific numbers, you need to understand why these two processes are needed at all.

What does proper hardening of steel improve?

If you ask the average person who has nothing to do with knife forging, the question “What does hardening give?” he will first talk about strength. In general, he will be right, although of the several qualities that hardening improves, hardness will still be the leader. But first things first.

• The hardness of blade steels is typically measured using the Rockwell Hardness Scale (HRC); European knives barely reach 60 HRC, Asian knives slightly exceed this mark. If we scratch two identical alloys of different hardness against each other, marks will remain on the softer one; Thus, hardness gives us an idea of ​​how well an alloy resists mechanical damage.
• Strength usually means steel’s resistance to destruction (bending, impact, etc.) - for a knife this is important when, for example, we test it “for bending”. If the steel is damp, the blade will remain partially deformed after bending. True, if the steel is overheated, it will be even worse - the blade will break; Therefore, when hardening, it is important to maintain a golden mean.
• Elasticity. This is exactly what we talked about a little higher - the ability to return to its original shape after removing the load. If the hardening is done according to all the rules, everything will be fine with this indicator: when bent by about 10 degrees (and for thin kitchen knives up to 30), the blade will return to its original shape.
• Wear resistance. The correct hardening regime improves all the indicators that are included in this concept: the ability to resist mechanical and abrasive wear, the ability to hold an edge and resistance to shock loads.

The main thing in the pursuit of all these qualities is to achieve by hardening such a compromise of all the above properties so that the knife cuts well and is durable.

How to do hardening and tempering

After the blade blank has been given the required shape, it is hardened. Of course, everything is very individual for different grades of steel, for specific products, but on average, craftsmen call the heating temperature for hardening about 700–800 degrees Celsius. The optimal color of the product in this case will be scarlet or cherry.

If the redness goes away, giving way to orange and yellow hues, the temperature has most likely exceeded 1,100 degrees - this is already too much for most steels.

The white color indicates that the temperature has reached at least 1,300 degrees, and it is not suitable for hardening - it will cause overheating; in this case, it will be impossible to restore the strength of the steel.

It is these colors that are called the colors of incandescence. We will meet with them again when we consider a vacation.

The heat colors show us the temperature the workpiece has reached. They should not be confused with tarnished colors - shades of oxides

When a blade is hardened, it gains high hardness, but at the same time loses strength. Now the strength must be restored: vacation serves this purpose. Vacation, as we remember, is reheating to lower temperatures followed by cooling; Let's add to this that between repeated heatings the blade must cool completely - naturally or by cooling it in a saline solution or oil. We select the heating temperature for tempering as follows.

• Most likely, we do not need high-temperature tempering - it is done for parts that are subjected not so much to deformation as to shock loads, and this clearly does not apply to knives. However, let’s say about it that its temperature limits are 500–680 degrees.
• Medium-temperature tempering is heating to 350–500 degrees; This is also a lot, only suitable for throwing knives.
• Low temperature holiday is what you need. Warming up here goes up to 250 degrees. Of course, the knife will not be so resistant to lateral impact loads, but we don’t need this: we have already achieved the required hardness during hardening, and now we are interested in strength. At this temperature it will turn out just right.

The desired temperature will again be shown by the heat colors: the optimal color in this case (for the knife) will be light yellow.

After each stage at which oxide products (tarnish) appear, the product should be cooled in salt water or oil. In clean water, the workpiece should not be cooled either after hardening or during tempering - due to too high a cooling rate, the product may crack.

Neither water nor oil fully meets the necessary requirements for hardening carbon steel: rapid cooling to 550 °C and slower cooling from 300 °C to 200 °C. Therefore, water is used in combination with oil: first into water, and then into oil. This method is used on tool steels and is called “into oil through water.”

But alloy steels can only be hardened in oil.

The colors of tarnish on the blade of the “Zombie” collection knife are oxides that were not removed after tempering

Selection of steel for hardening

To begin with, let’s conditionally divide all steels into high-carbon and alloyed.

All steels are alloys of iron with carbon and various alloying elements; The name of the steel will depend on whether one carbon predominates in it or whether alloying elements are present in significant quantities.

It cannot be said that this or that group is worse or better at hardening; They initially have very different characteristics and different tasks, so we will simply talk about the hardening of both steels.

Hardening of carbon steels

We have accumulated vast experience working with this steel, as well as with products made from it. By itself, it requires lower quenching temperatures than those alloyed with various elements - it already has fairly high hardness and strength indicators, which are so valued on the market.

• Low-carbon steels are hardened at temperatures from 727 to 950 °C.
• Medium and high carbon steels are hardened at temperatures from 680 to 850 °C.

It must be remembered that steels with very low carbon content cannot be hardened at all.

If we want to make and harden a blade from carbon steel at home, the following brands are suitable for us.

Russian:

American:

These grades, when properly heat treated, are characterized by great strength and hardness, although low resistance to corrosion.

Hardening of alloy steels

In addition to iron and carbon, such steels contain a significant amount of various alloying elements, which give the alloy special properties needed in a particular area.

• Chromium makes steel corrosion-resistant if its content exceeds 12–16%.
• Molybdenum and nickel increase the strength of steel and its ability to withstand high loads.
• Vanadium improves the wear resistance of the alloy and gives its blades the ability to hold an unusually sharp edge.

Due to the presence of these elements in the alloy, steel has worse thermal conductivity than pure carbon steel, therefore: 1) it will take more time to heat and cool - if the process is artificially accelerated, then cracks may appear in the alloy; 2) for hardening it needs a high temperature - from 850 to 1,100 ° C.

Unfortunately, correct heat treatment of complex alloy steels is quite difficult, since to give the blade high performance properties, both precise temperature and special equipment for deep cooling are needed. Therefore, it will not be possible to harden them qualitatively “by eye”.

The most common brands include the following:

• 420;
• 440A;
• D2;
• ATS34;
• CPM S320V.

We can say about the last sample that it is extremely wear-resistant.

Hardening knife steel at home

For simple carbon steels, even in artisanal conditions, satisfactory hardening can be done, the main thing is to arm yourself with the right knowledge.

Used tools, springs and files can be used as sources; Make sure there is no rust on them. A workpiece made from brand new melted metal is, of course, better, since parts that have served for a long time have a quality called fatigue, which reduces their strength.

Although for high-quality materials it is enough to carry out annealing, which consists of heating the steel, holding it at a certain temperature and then slowly cooling it with a furnace or in sand at a speed of two to three degrees per minute.

As a result of annealing, a stable structure is formed, free from residual stresses.

For both annealing and heating the part for hardening, you can use a homemade forge made from a pit lined with bricks, a blowtorch and a pipe. Ideally, of course, use a muffle furnace.

It’s easy to check at home whether the hardening has reached the required degree: you can run a file over the hardened product - if the hardening is not complete, the file will simply stick to the knife. Overheating can be checked in artisanal conditions by a strong blow of the workpiece against a hard object - a stone or a rail: the overheated blade shatters into pieces with such a blow.

Source: https://www.tojiro.ru/clients/blog/kukhonnye-nozhi/zakalka-i-otpusk-stali-tsveta-kaleniya-i-pobezhalosti/

How to temper hardened steel at home?

Technologies for imparting greater hardness to metals and alloys have been improved over many centuries. Modern equipment makes it possible to carry out heat treatment in such a way as to significantly improve the properties of products even from inexpensive materials.

Hardening of steel and alloys

Hardening (martensitic transformation) is the main method of imparting greater hardness to steels. In this process, the product is heated to such a temperature that the iron changes its crystal lattice and can be additionally saturated with carbon. After holding for a certain time, the steel is cooled.

This must be done at high speed to prevent the formation of intermediate forms of iron. As a result of rapid transformation, a solid solution supersaturated with carbon with a distorted crystal structure is obtained. Both of these factors are responsible for its high hardness (up to HRC 65) and brittleness.

When hardening, most carbon and tool steels are heated to a temperature of 800 to 900C, but high-speed steels P9 and P18 are heated at 1200-1300C.

Microstructure of high-speed steel R6M5: a) cast state;
b) after forging and annealing; c) after hardening; d) after vacation. ×500.

Quenching modes

The heated product is lowered into a cooling medium, where it remains until it cools completely. This is the simplest hardening method, but it can only be used for steels with a low carbon content (up to 0.8%) or for parts of simple shape. These limitations are associated with thermal stresses that arise during rapid cooling - parts of complex shapes can warp or even crack.

With this method of hardening, the product is cooled to 250-300C in a saline solution for 2-3 minutes to relieve thermal stress, and then cooling is completed in air. This helps prevent cracks or warping of parts.

The disadvantage of this method is the relatively low cooling rate, so it is used for small (up to 10 mm in diameter) parts made of carbon or larger ones made of alloy steels, for which the hardening rate is not so critical.

It begins with rapid cooling in water and ends with slow cooling in oil. Typically, such hardening is used for products made of tool steels. The main difficulty lies in calculating the cooling time in the first environment.

• Surface hardening (laser, high frequency currents)

Used for parts that must be hard on the surface, but have a viscous core, for example, gear teeth. During surface hardening, the outer layer of the metal is heated to supercritical values, and then cooled either during the heat removal process (with laser hardening) or by liquid circulating in a special inductor circuit (with high-frequency current hardening)

Vacation

Hardened steel becomes excessively brittle, which is the main disadvantage of this hardening method. To normalize the structural properties, tempering is carried out - heating to a temperature below the phase transformation, holding and slow cooling.

During tempering, a partial “cancellation” of hardening occurs, the steel becomes slightly less hard, but more ductile.

There are low (150-200C, for tools and parts with increased wear resistance), medium (300-400C, for springs) and high (550-650, for highly loaded parts) tempering.

Temperature table for quenching and tempering steels

No.	steel grade	Hardness (HRCe)	Temperature hardening, degrees C	Temperature holidays, degrees C	Temperature zak. HDTV, deg.C	Temperature cement., deg. C	Temperature annealing, degrees C	Temper. Wednesday	Note
1	2	3	4	5	6	7	8	9	10
1	Steel 20	5763	790820	160200	920950	Water
2	Steel 35	3034	830840	490510	Water
3335	450500
4248	180200	860880
3	Steel 45	2025	820840	550600	Water
2028	550580
2428	500550
3034	490520
4251	180220	Sech. up to 40 mm
4957	200220	840880

Source: https://varimtutru.com/kak-otpustit-zakalennuyu-stal-v-domashnih-usloviyah/

Average metal tempering

Medium tempering (medium temperature tempering) is a type of heat treatment of metal in which heating occurs to temperatures in the range of 300 - 480°C, holding after reaching the specified temperatures and subsequent slow or accelerated cooling in air or in an aqueous environment.

Purpose of medium temperature tempering as a type of heat treatment of metals

Steels are subjected to medium-temperature tempering to significantly reduce hardness and residual internal stress after hardening while simultaneously acquiring increased viscosity, elasticity, ductility and relaxation resistance by the metal, as well as to relieve stress after straightening.

Parts made of medium-carbon steel (0.4 - 0.8%) that are subjected to shock and variable loads, where high thresholds of strength and elasticity with average hardness values ​​are of great importance, are most often treated with this thermal treatment method. These are springs, leaf springs, impact tools such as a chisel or hammer, and some types of dies.

Conditions and mode of conducting the average steel holiday

When carrying out medium tempering of metal, the correct selection of temperature conditions plays an important role. Otherwise, processes of irreversible temper brittleness may develop in steels. The permissible heating temperature range lies within Tn = 300 - 480°C. After holding, cooling is carried out. It can be slow or accelerated, carried out in an aquatic environment or in air.

The Perm Heat Treatment Plant conducts medium steel tempering in a modern chamber-type electric tempering furnace with a maximum charge weight of 5000 kg and the ability to process metal products up to 9200 mm in length.

Uniform heating of the furnace atmosphere, charge and subsequent strict control of the heat treatment regime are ensured by high technology of the equipment and the possibility of computerized monitoring and control of all processes.

Among the advantages of our equipment:

• uniform temperature distribution at all points
• various heat treatment modes
• forced circulation system of furnace atmosphere
• temperature control
• control of the composition of the gas environment
• equipment that ensures the safety of heat treatment

Structural changes in steels during medium tempering

Steels heat-treated by the medium tempering method undergo accelerated diffusion processes. When the temperature of hardened carbon steels rises to 400°C, the process of carbon separation from martensite is completed. The coherent connection of fine carbide particles with the martensite lattice is disrupted. Martensite disintegrates and the steel acquires a fine ferrite-cementite structure.

With subsequent heating to the maximum temperature values ​​inherent in this type of tempering, cementite particles grow and their shape changes.

As a final result, the steel acquires the structure of granular tempered troostite or troostomartenite with hardness values ​​ranging from 40 to 50 HRC.

Due to the complete release of carbon from martensite in steel, internal hardening stresses are relieved, and the increase in ductility, elasticity and endurance is due to the beginning of the process of enlargement of cementite and ferrite, accompanied by a decrease in the level of hardness.

The Perm Heat Treatment Plant carries out chemical-thermal treatment of metal products using the most modern equipment in the region. Our experience in this field is more than 10 years.

We clearly understand the needs of our clients and strictly adhere to deadlines and scope of work.

The most modern computerized equipment for heat treatment of metals, highly qualified personnel and strict quality control allow us to achieve the best results in the field of heat treatment of metals in the Perm region.

You can order a high-quality service for metal processing using the medium tempering method using a convenient feedback form or by calling us on the website.

Source: http://pzto.pro/services/sredniy_otpusk.html

Steel tempering: types and purposes

Tempering is the final stage of heat treatment of steel. Performed after hardening. The quality and service life of the part depends on it.

The task is to heat the steel billet to a temperature below the critical level, after which the value is maintained for a certain period of time and slowly (or quickly, depending on the specifics of the technical process) tempered to the desired value.

The following actions are performed:

1. Possible stress in the steel workpiece is reduced or completely eliminated.
2. The viscosity of the metal increases to the value required by operating conditions.
3. The hardness of the workpiece decreases, this is important for its processing.

The main processes during the operation are: decomposition of martensite, subsequent polygonization, recrystallization.

The product is heated in an oven from 150-250 to 370-650 ºC, the value is controlled smoothly, sudden changes in indicators are unacceptable.

Short

The procedure is carried out taking into account heating in the oven to 150-250 ºC. Next, a long exposure is carried out, taking into account the temperature value; the final stage is cooling the workpiece in the open air.

When a steel billet is seasoned, martensite takes the form of tempering within a specified temperature range. The previously formed stress in the structure will be relieved, and the residual austenite will transform into martensite of a similar shape. If the steps are carried out correctly, the strength of the part is achieved, and it can be easily processed to obtain the required shape and dimensions.

Upon completion of the operation, the metal remains hard, but in some cases, the indicator increases. The result is achieved due to the decomposition of retained austenite. In parallel with the preservation of hardness, the brittleness of hardening is localized.

This type of operation is used in the manufacture of various products and cutting tools, provided that high hardness of the structure is ensured. Thanks to the transformation of martensite, the dimensions of the workpiece are stabilized.

This is relevant provided that the parameters of the measuring instrument, in the manufacturing process of which tool steel is used, are observed. When making an instrument, this type of operation is performed.

Average

A temperature of 300-500 ºC is required. The hardness at the last stage rapidly decreases, but the viscosity value increases. It is possible to obtain tempered troostite, the hardness of the metal increases to 43 HRC.

It is used in the production of springs, leaf springs, special technological tools, which are characterized by high strength and elasticity.

In this case, the hardness is set at an average level, this will allow the workpiece to be processed and given the desired characteristics.

High

It is carried out taking into account the temperature regime of 500-600 ºC. The main purpose is to obtain maximum toughness with an optimal combination of strength and elasticity of the steel structure. In practice, this is used in the manufacturing process of parts made from structural grades. While performing work, they are exposed to high voltage. This is relevant when the metal structure is exposed to shock loads during casting.

During the manufacture of parts designed for the use of various types of mechanisms and machine tools, it is customary to use heat treatment. The essence is to harden the workpiece with further high tempering. It is carried out taking into account the preservation of temperature, which ensures the production of sorbitol, excellent ductility and strength of the metal. The processing process is called “improving the characteristics of the metal.”

 Heating in the metal may also be provided. It is performed exclusively in furnaces used in production when carrying out other methods of processing the workpiece. It will be necessary to ensure uniform temperature throughout the entire stage, while simultaneously accurately monitoring the condition of the metal.

Tempering brittleness

In parallel with the increase in the tempering temperature, the impact strength increases; cooling does not affect the characteristics. For certain steel grades, a decrease in this indicator is typical; the defect is called “temper brittleness.”

There are two types of phenomena, each of which is distinguished by the specifics of its formation and subsequent result. Pay attention to the features of each of them; the development of the technological process for creating the workpiece depends on this.

Type 1 temper brittleness

Occurs when the temperature range passes 300 ºC. This is not related to the cooling parameters of the workpiece at the final stage of processing. This manifestation is caused by the difference in the levels of martensite transformation in the workpiece being created. The measured value of fragility is irreversible; even if this element is heated again, it will not appear, therefore, the structure remains in a stable state.

Tempering brittleness 2nd kind

The phenomenon manifests itself in the structure of alloy steels when they are slowly cooled. The temperature is set to 450-650 ºC. When a high tempering takes place during the casting of a workpiece, the separation of dispersed inclusions of carbides is noted along the boundaries of the metal. Upon examination, the border zone is united due to the presence of alloying components.

When smooth cooling occurs, diffusion is formed; it manifests itself more sharply towards the grain boundaries. Parts of the structure in the border region are enriched in phosphorus. This manifestation will reduce the level of toughness as well as strength.

It is noted as a reversible process; with secondary heating, smooth cooling to the desired value, if an interval dangerous for the indicators is set, the defect has every chance of reoccurring.

Steels that tend to develop this type of brittleness in their structure cannot be heated to 650 ºC.

A decision is made to conduct a vacation of one type or another, depending on the characteristics of the workpiece, performance indicators, as well as the needs of the production process. It is important to maintain the temperature and subsequently carry out natural cooling of the workpiece, which will allow you to achieve an impressive result. There is nothing complicated in the process if you work out a map of technological operations in advance.

Source: https://prompriem.ru/metalloobrabotka/otpusk-stali.html

Steel tempering

Tempering consists of heating hardened steel to temperatures below A c1, holding it at a given temperature and then cooling it at a certain rate. Tempering is the final heat treatment operation, as a result of which the steel obtains the required mechanical properties.

In addition, tempering completely or partially eliminates the internal stresses that arise during hardening. These stresses are relieved more completely the higher the tempering temperature. For example, axial stresses in a cylindrical sample made of steel containing 0.3% C are reduced from 60 to 8 kgf/mm2 as a result of tempering at 550 °C.

Tangential and radial stresses are also greatly reduced.

The stresses decrease most intensively as a result of holding at 550 °C for 15–30 minutes. After holding for 1.5 hours, the stresses are reduced to the minimum value that can be achieved by tempering at a given temperature.

The cooling rate after tempering also has a great influence on the magnitude of residual stresses. The slower the cooling, the lower the residual stresses. Rapid cooling from 600 °C creates new thermal stresses.

For this reason, products with complex shapes should be cooled slowly to avoid warping after tempering at high temperatures, and products made of alloy steels prone to reversible temper embrittlement should in all cases be cooled quickly after tempering at 500–650 °C.

The main influence on the properties of steel is the tempering temperature. There are three types of vacation.

 Low temperature tempering of steel

Low-temperature (low) tempering is carried out with heating to 150–200 °C, less often to 240–250 °C.

At the same time, internal stresses are reduced, quenched martensite is converted into tempered martensite, strength increases and toughness improves slightly without a noticeable decrease in hardness.

Hardened steel (0.5–1.3% C) after low tempering retains a hardness within HRC 58–63, and therefore high wear resistance. However, such a product (if it does not have a viscous core) cannot withstand significant dynamic loads.

Therefore, cutting and measuring tools made of carbon and low-alloy steels, as well as parts that have undergone surface hardening, carburization, cyanidation or nitrocarburization, are subjected to low-temperature tempering. The duration of the tempering is usually 1–2.5 hours, and for products with large sections and measuring instruments, a longer tempering is prescribed.

 Medium temperature tempering of steel

Medium temperature (medium) tempering is performed at 350–500 °C and is used mainly for springs and leaf springs, as well as for dies. Such tempering provides high elasticity limit, endurance limit and relaxation resistance. The structure of steel (0.45–0.8% C) after medium tempering is tempered troostite or troostomartensite with a hardness of HRC 40–50. The tempering temperature must be chosen in such a way as not to cause irreversible temper embrittlement.

Cooling after tempering at 400–450 °C should be carried out in water, which promotes the formation of compressive residual stresses on the surface, which increase the endurance limit of the springs.

 High temperature tempering of steel

High temperature (high) tempering is carried out at 500–680 °C. The structure of steel after high tempering is sorbitol tempering. High tempering creates the best ratio of strength and toughness of steel.

Quenching with high tempering, compared with the normalized or annealed state, simultaneously increases the strength and yield limits, the relative contraction, and especially the impact strength (Table 1). Heat treatment, consisting of quenching and high tempering, is called improvement.

Medium-carbon (0.3–0.5% C) structural steels, which have high requirements for yield strength, endurance limit and impact strength, are subject to improvement. However, the wear resistance of improved steel due to its reduced hardness is not high.

Table 1 — The influence of heat treatment on the mechanical properties of carbon steel with 0.42% C* Heat treatmentσвσтδψAn,kgf m/cm2kgf/mm2%

Annealing at 880 °C	55	35	20	59	9
Quenching from 880 °C (cooling in water) and tempering at 300 °C	130	110	12	35	3
Quenching from 880 °C (cooling in water) and tempering at 600 °C	62	43	22	55	14
* Workpiece with a diameter of 12 mm.

The improvement significantly increases the structural strength of steel, reducing sensitivity to stress concentrators, increasing the work of plastic deformation during crack movement (work of crack propagation) and reducing the temperature of the upper and lower thresholds of cold brittleness.

Tempering at 550–600 °C for 1–2 hours almost completely removes the residual stresses that arose during hardening. Most often, the duration of high tempering is 1–6 hours, depending on the overall dimensions of the product.

Source: http://weldworld.ru/theory/term-obrab/otpusk-stali.html

Metal release

Tempering is a heat treatment operation consisting of heating hardened steel to a temperature below the critical point AC1, holding at this temperature, and then cooling.

Depending on the heating temperature, two types of tempering are distinguished:

Low Vacation

Low tempering is characterized by heating in the range of 120-200°, holding and subsequent cooling in air. This type of tempering is used for tools and precision parts made from tool steel, for which high hardness and dimensional stability are important.

The cutting tool is subjected to low tempering at temperatures of 160-200°.

As a result of tempering, the steel retains high hardness, and sometimes increases it due to the decomposition of retained austenite.

Measuring tools and precision parts are subjected to low tempering at temperatures of 120-160°. After such a tempering (sometimes called artificial aging ), the dimensions of the product do not change.

After low tempering, steel retains high strength properties, but acquires low plastic properties.

Equipment for heat treatment of fasteners, hardware and parts

Complex heat treatment of metals is a process of changing the structure of steel, non-ferrous metals, alloys during heating and subsequent cooling at a certain speed. Heat treatment (heat treatment) leads to significant changes in the properties of steel, non-ferrous metals, and alloys. The chemical composition of the metal does not change.

Heat treatment ( heat treatment ) of steel and alloys can be of the following types: annealing , normalization , hardening , tempering .

• Annealing is a thermal treatment (heat treatment) of a metal that involves heating the metal and then slowly cooling it. This heat treatment (i.e. annealing) comes in different types (the type of annealing depends on the heating temperature and the cooling rate of the metal).
• Hardening is a heat treatment (heat treatment) of steel and alloys, based on the recrystallization of steel (alloys) when heated to a temperature above critical; After sufficient exposure to the critical temperature to complete the heat treatment, rapid cooling follows. Hardened steel (alloy) has a nonequilibrium structure, so another type of heat treatment is applicable - tempering.
• Tempering is a heat treatment (heat treatment) of steel and alloys, carried out after hardening to reduce or relieve residual stresses in steel and alloys, increasing toughness, reducing the hardness and brittleness of the metal.
• Normalization is a heat treatment (heat treatment) similar to annealing. The differences between these heat treatments (normalization and annealing) are that during normalization the steel is cooled in air (when annealing, it is cooled in a furnace).

ANNEALING OF STEEL

Annealing is a metal heat treatment process that involves heating and then slowly cooling the metal. Transition of a structure from a nonequilibrium state to a more equilibrium one.

Annealing of the first kind , its types: return (also called metal rest), recrystallization annealing (also called recrystallization ), annealing to relieve internal stress , diffusion annealing (also called homogenization ).

Annealing of the second type is a change in the structure of the alloy through recrystallization near critical points in order to obtain equilibrium structures. Annealing of the second kind, its types: complete , incomplete , isothermal annealing . Annealing and its types in relation to steel are discussed below.

• Return (rest) of steel - heating to 200 - 400°C, annealing to reduce or remove hardening. Based on the results of annealing, a decrease in the distortion of crystal lattices in crystallites and a partial restoration of the physicochemical properties of steel are observed.
• Recrystallization annealing of steel (recrystallization) - heating to temperatures of 500 – 550°C; annealing to relieve internal stress – heating to temperatures of 600 – 700°C. These types of annealing relieve internal stresses in the metal of castings due to uneven cooling of their parts, also in workpieces processed by pressure (rolling, drawing, stamping) using temperatures below critical. As a result of recrystallization annealing, new crystals grow from the deformed grains, closer to equilibrium ones, therefore the hardness of the steel decreases, and the ductility and toughness increase. To completely remove the internal stresses of steel, a temperature of at least 600°C is required. Cooling after holding at a given temperature must be quite slow: due to the accelerated cooling of the metal, internal stresses arise again.
• Diffusion annealing of steel (homogenization) is used when the steel has intracrystalline segregation. Leveling the composition in austenite grains is achieved by the diffusion of carbon and other impurities in the solid state, along with the self-diffusion of iron. According to the results of annealing, the steel becomes homogeneous in composition (homogeneous), therefore diffusion annealing is also called homogenization. The homogenization temperature should be high enough, but overburning and melting of the grains should not be allowed. If the burnout is allowed to occur, the oxygen in the air oxidizes the iron, penetrating into its thickness, and crystallites are formed, separated by oxide shells. Overburning cannot be eliminated, therefore overburnt workpieces are a final defect. Diffusion annealing of steel usually results in too much grain coarsening, which should be corrected by subsequent full annealing (to fine grains).
• Complete annealing of steel is associated with phase recrystallization, grain refinement at temperatures of points AC1 and AC2. Its purpose is to improve the structure of steel to facilitate subsequent processing by cutting, stamping or hardening, as well as to obtain a fine-grained equilibrium pearlite structure of the finished part. For complete annealing, the steel is heated 30-50°C above the GSK line temperature and cooled slowly. After annealing, excess cementite (in hypereutectoid steels) and eutectoid cementite have the form of plates, which is why pearlite is called lamellar
• When annealing steel onto lamellar perlite, the workpieces are left in the furnace until cooled, most often with the furnace partially heated with fuel, so that the cooling rate is no more than 10-20°C per hour. Annealing also achieves grain refinement. A coarse-grained structure, for example, of hypoeutectoid steel, is obtained during solidification due to the free growth of grains (if the cooling of the castings is slow), as well as as a result of overheating of the steel. This structure is called Widmanstätten (named after the Austrian astronomer A. Widmanstätten, who discovered such a structure on meteoric iron in 1808). This structure imparts low strength to the workpiece. The structure is characterized by the fact that inclusions of ferrite (light areas) and pearlite (dark areas) are located in the form of elongated plates at different angles to each other. In hypereutectoid steels, the Widmanstätten structure is characterized by a streak-like arrangement of excess cementite. Grain refinement is associated with the recrystallization of alpha iron into gamma iron; Due to cooling and the reverse transition of gamma iron to alpha iron, the fine-grained structure is preserved. Thus, one of the results of annealing on lamellar pearlite is a fine-grained structure.
• Incomplete annealing of steel is associated with phase recrystallization only at point temperature A C1; partial annealing is used after hot pressure treatment, when the workpiece has a fine-grained structure.
• Annealing steel into granular pearlite is usually used for eutectoid and hypereutectoid steels to increase the ductility and toughness of steel and reduce its hardness. To obtain granular pearlite, the steel is heated above the AC1 point, then held for a short time so that the cementite does not completely dissolve in the austenite. Then the steel is cooled to a temperature slightly below Ar1 and maintained at this temperature for several hours. In this case, the particles of the remaining cementite serve as crystallization nuclei for all the released cementite, which grows as rounded (globular) crystallites dispersed in the ferrite. The properties of granular pearlite differ significantly from the properties of lamellar pearlite in the direction of lower hardness, but greater lamellarity and viscosity. This especially applies to hypereutectoid steel, where all cementite (both eutectoid and excess) is obtained in the form of globules.
• Isothermal annealing - after heating and holding, the steel is quickly cooled to a temperature slightly below point A 1, then maintained at this temperature until the austenite completely decomposes into pearlite, after which it is cooled in air. The use of isothermal annealing significantly reduces time and also increases productivity. For example, ordinary annealing of alloy steel lasts 13-15 hours, and isothermal annealing - only 4-7 hours.

HARDENING OF STEEL

A distinction is made between hardening with polymorphic transformation, for steels, and hardening without polymorphic transformation, for most non-ferrous metals. The hardened material acquires greater hardness, but becomes brittle, less ductile and viscous if more repetitions of heating and cooling are performed.

To reduce brittleness and increase ductility and toughness, tempering is used after hardening with a polymorphic transformation. After hardening without polymorphic transformation, aging is applied. During tempering, there is a slight decrease in the hardness and strength of the material.

Source: https://www.metiz.com.tw/heat_information.htm

Steel tempering: types and characteristics, technology features and temper brittleness, heat treatment of alloys - Machine

Heat treatment of steel allows you to give products, parts and workpieces the required qualities and characteristics. Depending on the stage at which heat treatment was carried out in the manufacturing process, the workpieces’ workability increases, residual stresses are removed from the parts, and the parts’ performance qualities increase.

Steel heat treatment technology is a set of processes: heating, holding and cooling with the aim of changing the internal structure of the metal or alloy. In this case, the chemical composition does not change.

Thus, the molecular lattice of carbon steel at a temperature of no more than 910°C is a body-centered cube. When heated above 910°C to 1400°C, the lattice takes the shape of a face-centered cube. Further heating turns the cube into a body-centered one.

Heat treatment of steel

The essence of heat treatment of steels is a change in the grain size of the internal structure of the steel.

Strict adherence to temperature conditions, time and speed at all stages, which directly depend on the amount of carbon, alloying elements and impurities that reduce the quality of the material.

During heating, structural changes occur, which upon cooling occur in the reverse order. The figure shows what transformations occur during heat treatment.

Change in metal structure during heat treatment

Purpose of heat treatment

Heat treatment of steel is carried out at temperatures close to critical points. Here's what happens:

• secondary crystallization of the alloy;
• transition of gamma iron to the alpha iron state;
• transition of large particles into plates.

The internal structure of a two-phase mixture directly affects performance and ease of processing.

Formation of structures depending on cooling intensity

The main purpose of heat treatment is to give steels:

• In finished products:
  1. strength;
  2. wear resistance;
  3. corrosion resistance;
  4. heat resistance.

• In blanks:
  1. relief of internal stress after
     • casting;
     • stamping (hot, cold);
     • deep drawing;
  2. increased plasticity;
  3. facilitating cutting.

Heat treatment is applied to the following types of steels:

1. Carbon and alloyed.
2. With varying carbon contents, from low carbon 0.25% to high carbon 0.7%.
3. Structural, special, instrumental.
4. Any quality.

Classification and types of heat treatment

The fundamental parameters affecting the quality of heat treatment are:

• heating time (speed);
• heating temperature;
• duration of holding at a given temperature;
• cooling time (intensity).

By changing these modes, you can obtain several types of heat treatment.

Types of heat treatment of steel:

• Annealing
  1. I – kind:
     • homogenization;
     • recrystallization;
     • isothermal;
     • removal of internal and residual stresses;
  2. II – kind:

Heating temperature of steel during heat treatment

3. High release

With high tempering, sorbitol crystallizes, which eliminates stress in the crystal lattice. Critical parts are manufactured that have strength, ductility, and toughness.

Annealing steel

Processing modes:

Heating to a temperature of 450°C, but not higher than 650°C.

Annealing

The use of annealing makes it possible to obtain a homogeneous internal structure without stress on the crystal lattice. The process is carried out in the following sequence:

• heating to a temperature slightly above the critical point, depending on the grade of steel;
• holding with constant temperature maintenance;
• slow cooling (usually cooling occurs together with the furnace).

1. Homogenization

Homogenization, otherwise known as diffusion annealing, restores the non-uniform segregation of castings. Processing modes:

• heating to a temperature from 1000°C, but not higher than 1150°C;
• exposure – 8-15 hours;
• cooling:
  • oven – up to 8 hours, temperature reduction to 800°C;
  • air.

Recrystallization, otherwise low annealing, is used after plastic deformation treatment, which causes hardening by changing the grain shape (hardening). Processing modes:

• heating to a temperature above the crystallization point by 100°C-200°C;
• holding – ½ – 2 hours;
• cooling is slow.

3. Isothermal annealing

Alloy steels are subjected to isothermal annealing to cause austenite decomposition. Heat treatment modes:

• heating to a temperature of 20°C - 30°C above the point;
• holding;
• cooling:
  • fast - not lower than 630°C;
  • slow – at positive temperatures.

4. Annealing to eliminate stress

Removal of internal and residual stresses by annealing is used after welding, casting, and machining. With the application of work loads, parts are subject to destruction. Processing modes:

• heating to a temperature of – 727°C;
• holding - up to 20 hours at a temperature of 600°C - 700°C;
• cooling is slow.

5. Complete annealing

Full annealing makes it possible to obtain an internal structure with fine grains, which contains ferrite and pearlite. Full annealing is used for cast, forged and stamped workpieces, which will subsequently be processed by cutting and subjected to hardening.

Complete annealing of steel

Processing modes:

• heating temperature – 30°C-50°C above point ;
• excerpt;
• cooling to 500°C:
  • carbon steel – temperature decrease per hour is no more than 150°C;
  • alloy steel – temperature decrease per hour is no more than 50°C.

6. Incomplete annealing

With incomplete annealing, lamellar or coarse pearlite is transformed into a ferrite-cementite grain structure, which is necessary for welds produced by electric arc welding, as well as tool steels and steel parts subjected to processing methods whose temperature does not provoke grain growth of the internal structure.

Processing modes:

• heating to a temperature above the point or, above 700°C by 40°C - 50°C;
• curing - about 20 hours;
• cooling is slow.

Hardening

Hardening of steels is used for:

• Promotions:
  1. hardness;
  2. strength;
  3. wear resistance;
  4. elastic limit;

• Reductions:
  1. plasticity;
  2. shear modulus;
  3. compression limit.

The essence of hardening is the fastest cooling of a thoroughly heated part in various environments. Heating is performed with and without polymorphic changes. Polymorphic changes are possible only in those steels that contain elements capable of transformation.

Steel hardening

Such an alloy is heated to a temperature at which the crystal lattice of the polymorphic element undergoes changes, due to which the solubility of alloying materials increases. As the temperature decreases, the lattice changes structure due to an excess of alloying element and takes on a needle-like structure.

The impossibility of polymorphic changes during heating is due to the limited solubility of one component in another at a rapid cooling rate. There is little time for diffusion. The result is a solution with an excess of undissolved component (metastable).

To increase the cooling rate of steel, the following media are used:

• water;
• water-based brine solutions;
• technical oil;
• inert gases.

Comparing the rate of cooling of steel products in air, cooling in water from 600°C occurs six times faster, and from 200°C in oil 28 times faster.

Dissolved salts increase the hardening ability. The disadvantage of using water is the appearance of cracks in places where martensite forms.

Industrial oil is used to harden alloy alloys, but it sticks to the surface.

Metals used in the manufacture of medical products should not have a film of oxides, so cooling occurs in an environment of rarefied air.

To completely get rid of austenite, which causes high brittleness in steel, products are subjected to additional cooling at temperatures from -40°C to -100°C in a special chamber. You can also use carbonic acid mixed with acetone. This processing increases the accuracy of parts, their hardness, and magnetic properties.

If parts do not require volumetric heat treatment, only the surface layer is heated using HDF (high-frequency current) installations. In this case, the depth of heat treatment ranges from 1 mm to 10 mm, and cooling occurs in air. As a result, the surface layer becomes wear-resistant, and the middle is viscous.

The hardening process involves heating and holding steel products at temperatures reaching about 900°C. At this temperature, steels with a carbon content of up to 0.7% have a martensite structure, which, during subsequent heat treatment, will transform into the required structure with the appearance of the desired qualities.

Normalization

Normalization produces a fine grain structure. For low-carbon steels this is a ferrite-pearlite structure, for alloyed steels it is a sorbitol-like structure. The resulting hardness does not exceed 300 HB. Hot-rolled steels are subjected to normalization. At the same time, they increase:

• fracture resistance;
• processing performance;
• strength;
• viscosity.

Steel normalization process

Processing modes:

• heating occurs to a temperature of 30°C-50°C above the point ;
• maintaining in a given temperature range;
• cooling - in the open air.

Benefits of Heat Treatment

Heat treatment of steel is a technological process that has become a mandatory step in obtaining sets of parts made of steel and alloys with specified qualities. This can be achieved by a wide variety of modes and methods of thermal exposure. Heat treatment is used not only for steels, but also for non-ferrous metals and alloys based on them.

Steels without heat treatment are used only for the construction of metal structures and the manufacture of non-critical parts, the service life of which is short. There are no additional requirements for them. Everyday operation, on the contrary, dictates stricter requirements, which is why the use of heat treatment is preferable.

In thermally untreated steels, abrasive wear is high and proportional to its own hardness, which depends on the composition of chemical elements. Thus, non-hardened die matrices are well combined when working with hardened punches.

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What steel tempering technologies exist?

When metals are hardened, internal stress is generated. If it is not eliminated, the finished product will have a high fragility rating. Plasticity will be significantly below normal. To eliminate these problems, steel tempering is used. It is one of several heat treatment processes for metals.

What is a vacation?

Metal tempering is a thermal process that is used for all hardened parts. Many novice craftsmen do not understand how important the set of heat treatment stages is for a material. Heat treatment of metals improves the characteristics of a metal part. During such processing, the structure of the steel changes. Because of this, individual properties of the material deteriorate or improve.

This heat treatment allows you to relieve the internal stress that forms after hardening the steel. If this is not done, the material will be fragile and will not withstand serious loads. In addition to relieving internal stress, this process increases the hardness of the steel. This is an important feature in the manufacture of tools and parts for industrial equipment.

The temperature regime is selected depending on what grade of material will be processed. Based on this, the metal can be cooled in different solutions:

• in containers filled with molten alkali;
• in baths filled with saltpeter;
• in containers with oil or water.

In production, metal parts are cooled in ovens.
In this case, a forced ventilation system is installed on the equipment. REMOVAL OF STEEL THE SIMPLE METHOD

Kinds

The steel tempering temperature is considered the most important parameter when carrying out this technological process. There are three types of tempering heat treatment. Features of the technological process depend on the type of heat treatment.

Heat treatment of tool alloys

Tool alloys or high-speed metals used for the manufacture of wear-resistant tools must be heat treated. As temperatures increase, their ductility does not increase and strength does not decrease.

To improve the characteristics of tool alloys, alloying additives are added to their composition - tungsten, molybdenum, vanadium or cobalt. Next, the workpieces are hardened at a temperature of 1200 degrees.

Tempering is considered one of the key stages of heat treatment. It allows you to relieve internal stress and increase the strength of the metal. It is important to choose the correct temperature regime and cooling rate of the workpiece. For cooling, containers with various solutions are used.

Source: https://metalloy.ru/obrabotka/termo/otpusk-stal