EP3168312A1 - Engineering steel with bainitic structure, forged part produced therefrom and method for making a forged part - Google Patents

Abstract

The invention provides a steel having a high strength without the need for complex heat treatment processes, while having a low tendency to warp. The noble steel steel according to the invention consists of (in% by weight) up to 0.25% C, up to 0.45% Si, 0.20-2.00% Mn, up to 4.00% Mn, 0, 6 - 3.0% Mo, 0.004 - 0.020% N, up to 0.40% S, 0.001 - 0.035% Al, 0.0005 - 0.0025% B, up to 0.015% Nb, up to 0.01% Ti, up to 0.10% V, up to 1.5% Ni and up to 2.0% Cu, remainder iron and unavoidable impurities, the Al content being% Al, the Nb content being% Nb, the Ti Content% Ti, the V content% V and the N content% N of the structural steel respectively satisfy the following condition:% Al / 27 +% Nb / 45 +% Ti / 48 +% V / 25>% N / 3, 75 The engineering structural steel according to the invention has a yield strength of at least 750 MPa, a tensile strength of at least 950 MPa and a microstructure consisting of at least 80% by volume of bainite and a total of at most 20% by volume of retained austenite, ferrite, perlite and / or martensite. Due to its property profile of the steel according to the invention is particularly suitable for the forging technology production of forgings with over its length large cross-sectional changes. The invention also discloses a method of making such forging components.

Description

The invention relates to a structural steel with high strength and a structure which consists of at least 80 vol .-% of bainite.

Furthermore, the invention relates to a forged part, which is made of such a structural engineering steel.

Finally, the invention relates to a method for producing a forged component from a noble structural steel according to the invention.

If "%" information is given below on alloys or steel compositions, these are in each case based on the weight, unless expressly stated otherwise.

All of the mechanical properties of the steel according to the invention and of the steels which may be mentioned for comparison have been determined according to DIN EN ISO 6892-1, unless stated otherwise.

As described by Dipl.-Ing. Christoph Keul et al. in the article "Development of a high-strength ductile bainitic (HDB) steel for highly stressed forging components", published in the Schmiede-Journal, issue September 2010 , published by Industrieverband Massivumformung eV, reports that there is a demand in the forging industry for steel material concepts that offer the possibility of high strength and to realize toughness with a simultaneously shortened process chain of their production. Further, the article states that promising materials with a bainitic structure have been found to combine good strength and toughness properties without the need for additional heat treatment resulting in tensile strengths greater than 1200 MPa, a yield strength of more than 850 MPa and an elongation at break of more than 10% at a impact energy of 27 J at room temperature. As an example of alloy concepts offering such properties, the article contains a steel having (in wt%) 0.18% C, 1.53% Si, 1.47% Mn 0.007% S, 1.30% Cr , 0.07% Mo, 0.0020% B, 0.027% Nb, 0.026% Ti, 0.0080% N, balance iron and unavoidable impurities and a steel with 0.22% C, 1.47% Si, 1, 50% Mn, 0.006% S, 1.31% Cr, 0.09% Mo, 0.0025% B, 0.035% Nb, 0.026% Ti, 0.0108% N, balance iron and unavoidable impurities presented.

Another development, which also aims at a steel for the production of drop forged parts, which have a high strength and high toughness without an additional heat treatment, is in the EP 1 546 426 B1 described. The steel known from this patent contains (in% by weight) 0.12-0.45% C, 0.10-1.00% Si, 0.50-1.95% Mn, 0.005-0.060% S, 0.004-0.050% Al and Ti each, up to 0.60% Cr, Ni, Co, W, Mo and Cu, up to 0.01% B, up to 0.050% Nb, 0.10-0.40% V, 0.015-0.04% N and balance iron and unavoidable impurities with the proviso that the product of the V and N contents of the steel is 0.0021-0.0120, that the S content is% S, the Al content% Al, the Nb content% Nb and the Ti content% Ti, the condition 1.6 x% S + 1.5 x% Al + 2.4 x% Nb + 1.2 x% Ti = 0.040-0.080% and the Mn content% Mn, the Cr content% Cr, the Ni content% Ni, the Cu content% C and the Mo content% Mo the condition 1.2 ×% Mn + 1 , 4 x% Cr + 1.0 x% Ni + 1.1 x% Cu + 1.8 x% Mo = 1.00 - 3.50%.

It is regarded as essential that the necessary toughness improvement is achieved by lowering the carbon content in the steel. The strength loss associated with this in principle according to the prior art is compensated by the other alloying elements, the contents of which are adjusted so that solidification by solid solution formation takes place.

Furthermore, from the DE 697 28 076 T2 ( EP 0 787 812 B1 ) discloses a production method of a steel forgings in which a steel having (in wt.%) 0.1-0.4% C, 1-1.8% Mn, 0.15-1.7% Si, up to 1 % Ni, up to 1.2% Cr, up to 0.3% Mo, up to 0.3% V, up to 0.35% Cu and each optionally 0.005-0.06% Al, 0.0005-0 , 01% B, 0.005 - 0.03% Ti, 0.005% - 0.06% Nb, 0.005 - 0.1% S, up to 0.006% calcium, up to 0.03% Te, up to 0.05% Se, up to 0.05% Bi and the remainder cast iron and unavoidable impurities to a semi-finished product, which is then hot-forged to a forging in a conventional manner. Subsequently, the forging is subjected to a heat treatment comprising cooling at a cooling rate Vr of more than 0.5 ° C / sec from a temperature at which the steel is austenitic to a temperature Tm of between Ms +100 ° C and Ms -20 ° C is. The forging is then held for at least two minutes at a temperature which is between the temperature Tm and a temperature Tf, for which Tf> Tm -100 ° C. In this way, one should obtain a steel component having a substantially bainitic structure comprising at least 15% lower bainite and preferably at least 20% bainite formed between Tm and Tf.

Practical experiments with steel materials of the type described above have shown that such bainitic steels are unsuitable for components with large cross-sectional changes due to their tendency to warp and greatly fluctuating mechanical properties.

Against this background, the object of the invention to provide a steel which has a high strength, without the need to complete complex heat treatment process, which has a low tendency to warping and as such in particular for the forging production of forgings with their length has large cross-sectional changes.

Likewise, a forged part should be specified, which has an optimal combination of properties without complex heat treatment process.

Finally, a method for producing a forging should be proposed, which allows the production of forgings with optimized property combination by simple means.

With respect to the steel, the invention has achieved the object mentioned above by the structural steel specified in claim 1.

With regard to the forging component, the solution according to the invention of the abovementioned object consists in that such a steel component is produced from a steel according to the invention.

With regard to the method, the invention has finally achieved the abovementioned object by carrying out the operations recited in claim 13 during the production of a forging component.

Advantageous embodiments of the invention are specified in the dependent claims and are explained below as the general inventive concept in detail.

An inventive structural steel has at a yield strength of at least 750 MPa and a tensile strength of at least 950 MPa and at least 80% by volume bainitic structure, the remaining 20% by volume of the microstructure being retained austenite, ferrite, pearlite or martensite.

In this case, the steel according to the invention is characterized by a high elongation at break A of at least 10%, in particular at least 12%, whereby it is shown in practice that steels according to the invention regularly achieve an elongation at break A of at least 15%.

According to the invention, the engineering structural steel consists of (in% by weight) up to 0.25% C, up to 1.5% Si, in particular up to 1% Si or up to 0.45% Si, 0.20-2, 00% Mn, up to 4.00% Cr, 0.7-3.0% Mo, 0.004-0.020% N, up to 0.40% S, 0.001-0.035% Al, 0.0005-0.0025% B, up to 0.015% Nb, up to 0.01% Ti, up to 0.50% V, up to 1.5% Ni, up to 2.0% Cu and balance iron and unavoidable impurities, the Al Content% Al, the Nb content% Nb, the Ti content% Ti, the V content% V and the N content% N of the noble structural steel each satisfy the following condition:

% Al / 27 +% Nb / 45 +% Ti / 48 +% V / 25>% N / 3.75

The unavoidable impurities due to production include all elements which are present in terms of alloying inefficiencies with regard to the properties of interest here and which enter the steel on the basis of the respectively selected melting route or the respective selected starting material (scrap). In particular, the unavoidable impurities also include levels of P of up to 0.0035% by weight.

A steel according to the invention and the forging components produced therefrom are characterized by a particularly uniform property distribution, even if, due to changing component dimensions during cooling from forging heat over the Forged part volume considered locally very different cooling conditions prevail. This insensitivity to the cooling conditions is achieved in that the noble structural steel according to the invention has a homogeneous, largely exclusively bainitic microstructure with a low variance of the hardness. At the same time, this homogeneous microstructure contains low residual stresses, which has a positive effect on the distortion behavior.

Accordingly, steel according to the invention is particularly suitable for the production of forged components in which sections of very different volumes and diameters abut one another. Examples of such forgings, for whose forging technology production of the steel according to the invention is particularly suitable, are crankshafts, connecting rods and the like, which are intended in particular for internal combustion engines.

Furthermore, steel parts according to the invention in the area of the undercarriage and the suspension can be manufactured reliably with very different cross-sections without much subsequent reworking by grinding while maintaining the predetermined strength properties.

As based on the as Fig. 1 From the point of view of material technology, it can be understood that a particularly wide window can be used for bainitizing a noble structural steel according to the invention if the engineering steel according to the invention is continuously cooled from forging heat. The alloy of the structural steel according to the invention is chosen so that in the course of cooling do not affect its properties affecting amounts of martensite or ferrite or perlite in the structure. Noble structural steel according to the invention is thus distinguished by the fact that it is predominantly, ie has at least 80 vol .-% bainic microstructure, wherein the content of non-bainitic microstructure constituents in steels of the invention is typically minimized so much that the steel according to the invention has a completely bainitic structure in the technical sense.

Here, the noble steel steel according to the invention largely independent of the cooling rate in bainite an almost constant hardness. The constant hardness is a consequence of the almost complete transformation of the former austenite into bainite, preferably into a bainitic transformation stage.

By limiting the C content to at most 0.25% by weight, on the one hand it is achieved that a noble structural steel according to the invention has good elongation and toughness properties despite its maximized strength. The low C content also contributes to the acceleration of the bainite transformation in a steel according to the invention, so that the formation of undesired structural constituents is avoided.

At the same time, however, a certain amount of carbon in the engineering steel according to the invention can also contribute to the strength. For this purpose, contents of at least 0.09 wt .-% C can be provided in the steel. An optimized effect of the presence of C in the steel according to the invention can thus be achieved by adjusting the C content to 0.09-0.25% by weight.

The Si content of a steel according to the invention is limited to 1.5% by weight, in particular 1% by weight or 0.75% by weight, in order to allow the bainite transformation to proceed as early as possible. In order to achieve this effect particularly reliably, the Si content can also be limited to at most 0.45 wt .-%.

Mo is present in the noble structural steel according to the invention in contents of 0.6-3.0% by weight, in order to delay the transformation of the microstructure into ferrite or perlite. This effect occurs in particular when at least 0.7 wt .-%, in particular more than 0.70 wt .-% Mo, are present in the steel. At contents of more than 3.0% by weight, no economically viable further increase in the positive effect of Mo occurs in the steel according to the invention. In addition, above 3.0 wt% Mo, there is a risk of forming a molybdenum-rich carbide phase which may adversely affect the toughness properties. Optimum effects of Mo in the steel of the present invention can be expected when the Mo content is at least 0.7 wt%. Mo contents of not more than 2.0% by weight have proved to be particularly effective.

Manganese is present at levels of 0.20-2.00% by weight in the steel of the present invention to adjust the tensile strength and yield strength. A minimum content of 0.20% by weight of Mn is required in order to increase the strength. If this effect is to be achieved particularly reliably, then an Mn content of at least 0.35 wt .-% can be provided. Too high Mn contents lead to the delay of the bainite transformation and thus to a predominantly martensitic transformation. Therefore, the Mn content is limited to at most 2.00 wt%, especially 1.5 wt%. Negative influences of the presence of Mn can be avoided particularly reliably by limiting the Mn content in the steel according to the invention to a maximum of 1.1% by weight.

The sulfur content of a steel according to the invention can be up to 0.4 wt .-%, in particular max. 0.1% by weight or max. 0.05 wt .-% to assist the machinability of the steel.

The fine-grade alloying with respect to the mechanical properties and the texture of a structural steel according to the invention is carried out according to the inventive alloying concept via a combined microalloying of the elements boron in amounts of 0.0005-0.0025% by weight, nitrogen in contents of 0.004-0.020% by weight, in particular at least 0.006% by weight N or up to 0.0150% by weight % N, aluminum in amounts of 0.001-0.035% by weight and niobium in amounts of up to 0.015% by weight, titanium in contents of up to 0.01% by weight and vanadium in contents of up to 0, 10% by weight.

The contents% Al,% Nb,% Ti,% V and% N of Al, Nb, Ti, V and N are on the condition

% Al / 27 +% Nb / 45 +% Ti / 48 +% V / 25>% N / 3.75

linked together so that the nitrogen contained in the structural steel over the respective existing contents of Al and the addition of necessary additionally added levels of Nb, Ti and V is fully bonded and boron can thus delay conversion. At the same time, the inventively provided and matched to each other and the N content levels of microelements to increase the fine grain stability and strength.

Moreover, the setting of N according to the invention makes it possible for boron to become effective as a dissolved element in the matrix and to suppress the formation of ferrite and / or perlite.

In order to safely utilize the advantages of the presence of the micro-alloying elements and of aluminum, it may be expedient to set the Al content to at least 0.004% by weight, the Ti content to at least 0.001% by weight, the V content to at least 0 , 02 wt .-% or the Nb content to at least 0.003 wt .-% set. In this case, the micro-alloying elements V, Ti, Nb on the one hand and Al on the other hand may be present in each case in combination with one or more elements of the group "Al, V, Ti, Nb" or alone in amounts above said minimum contents.

At levels of up to 0.008 wt.% Ti, up to 0.01 wt.% Nb, up to 0.075 wt.% V or up to 0.020 wt.% Al, the effects of these elements can be seen in Use particularly effective construction steel according to the invention. At the same time, the nitrides or carbonitrides formed increase the strength and contribute to fine grain stability. Again, the stated upper limits of the contents of Ti, Nb, V or Al can be maintained alone or in combination with each other in order to achieve the optimum effect of the respective alloying element.

Optionally present contents of Cr of up to 4.00 wt .-%, in particular up to 3 wt .-% or up to 2.5 wt .-%, contribute to the hardenability and corrosion resistance of the steel according to the invention. For example, at least 0.5% by weight or at least 0.8% by weight of Cr may be provided for this purpose.

Also optionally present levels of Ni of up to 1.5 wt .-% may also contribute to the hardenability of the steel.

Among the alloying elements which pass through the starting material into the steel according to the invention or which have been deliberately added, is Cu, whose content, in order to avoid negative influences in the steel according to the invention, is limited to max. 2.0 wt .-% is limited. A positive effect of the optional presence of copper in the alloy of a structural steel according to the invention consists in the formation of finest Austenitfilmen and the associated significant increase in the toughness level. This effect can be achieved by providing at least 0.3% by weight of Cu, in particular more than 0.3% by weight of Cu, in the structural steel according to the invention. By limiting the Cu content to at most 0.9 wt%, an optimized positive effect of the copper content can be obtained.

If steel according to the invention is heated to thermal temperatures of at least 100.degree. C. above the respective Ac.sub.3 temperature, in particular more than 900.degree. C., then heat-deformed and finally regulated or uncontrolled to quiescent or agitated air to a temperature of less than 200 ° C, in particular cooled to room temperature, so sets itself at an extremely wide range of cooling rate after the transformation, a uniform bainitic structure. The Ac3 temperature of the steel may be determined in a manner known per se based on its composition. The upper limit of the range of the heat temperature is typically 1300 ° C, especially 1250 ° C or 1200 ° C.

As a measure of the range of cooling rates, the t8 / 5 time can be used here, ie the time within which each thermoformed part cools from 800 ° C to 500 ° C. This t8 / 5 time should be at 10 - 1000 s in the cooling of manufactured from inventive steel components.

The specific cooling time selected should be selected as a function of the respective heat temperature. The influence of the heat temperature can be calculated using the Fig. 2 enclosed ZTU diagram is reproduced, in which for the heat temperatures 900 ° C (solid line), 1100 ° C (dashed line) and 1300 ° C (dotted line) the respective position of the respective bainite over the cooling time is shown. Thus, at low heat temperatures of 900 ° C, shorter t8 / 5 times should be selected to achieve the desired bainite texture, whereas at higher heat temperatures, cooling may be slower. A high certainty that the cooling of steel according to the invention, the bainite is made regardless of the respective heat temperature exists for Steels according to the invention at a temperature in the range of 900 - 1300 ° C heat temperatures therefore when the t8 / 5 time is 100 - 800 s.

The alloying concept according to the invention thus permits high thermoforming temperatures of more than 1150 ° C., as a result of which the forming forces during hot forming can be reduced without undesired grain growth occurring.

1. a) Bereitstellen eines Schmiedehalbzeugs, das aus einem in der voranstehend erläuterten Weise erfindungsgemäß zusammengesetzten Edelbaustahl besteht;
2. b) Erwärmen des Schmiedehalbzeugs auf eine Schmiedetemperatur von mindestens 100 °C über der Ac3-Temperatur des jeweiligen Edelbaustahls, wobei die Ac3-Temperatur in konventioneller Weise in Abhängigkeit von der jeweiligen Zusammensetzung des Edelbaustahls bestimmt wird;
3. c) Schmieden des auf die Schmiedetemperatur erwärmten Schmiedehalbzeugs zu dem Schmiedestück;
4. d) Abkühlen des Schmiedestücks aus der Schmiedehitze auf eine unterhalb von 500 °C liegende Temperatur, wobei die t8/5-Zeit bei der Abkühlung 10 - 1000 s beträgt.

The inventive method for the production of forgings with a yield strength of at least 750 MPa and a tensile strength of at least 950 MPa and at least 80 vol .-% bainitic structure, in total up to 20 vol .-% retained austenite, ferrite, pearlite or martensite can therefore contain the following steps:

1. a) providing a forging tool, which consists of a composite according to the invention in the above-explained construction engineering steel;
2. b) heating the forging die to a forging temperature of at least 100 ° C above the Ac3 temperature of the particular engineering steel, the Ac3 temperature being determined in a conventional manner depending on the particular composition of the engineering grade steel;
3. c) forging the forging temperature heated forging to the forging;
4. d) cooling the forging from forging heat to a temperature below 500 ° C, the t8 / 5 time during cooling being 10-1000 sec.

To reduce the forming forces, it may also be in the course of the inventive method with a view to minimizing the required forging forces prove to be advantageous if the respectively the starting point of forging deformation forming semi-finished forging is heated to a forging temperature of more than 1150 ° C.

A further adjustment of the mechanical properties, in particular the strength and toughness, of the hot-formed steel according to the invention, in particular forged components can be carried out by means of a tempering treatment in which the respective part over a tempering time of 0.5 - 2 h in the temperature range of 180 - 375 ° C is held.

In practice, tensile strengths of at least 950 MPa, a yield strength of at least 750 MPa, and an elongation at break A of at least 15% can be reliably determined in the steel according to the invention, with it being found in practice that even higher elongation values A of at least 17% are regularly achieved become. This combination of properties in existing from steel according to the invention forgings, especially if they have been produced in the manner according to the invention.

The invention will be explained in more detail by means of exemplary embodiments.

Steel melts E1-E6 according to the invention and a comparative melt V1 having the compositions specified in Table 1 were melted and cast into semi-finished products which were blocks, as are customarily made available for forging technology further processing.

The semi-finished products are heated to a forging temperature Tw for a forging temperature, then thermoformed in a conventional manner by drop forging to forgings and then in air cooled to room temperature. For some of the obtained forgings a tempering treatment was then carried out.

In Table 2, the heat temperatures used in the examples are Tw, the t8 / 5 time required for the passage of the critical temperature range of 800-500 ° C, the temperature and duration of the tempering treatment, if any, and the bainite content in the microstructure, the tensile strength Rm, the yield strength Re, the elongation A and the impact energy W of the forging obtained after forging indicated.

The examples show that forgings can be produced when the specifications according to the invention are adhered to, which make it possible to vary the operating parameters set during their production over a wide range and thereby reliably obtain thermoformed components with optimized mechanical properties. Table 1 stole C Si Mn Cr Not a word N S al B Nb Ti V Ni Cu P (1) (2) (1)> (2) E1 0.13 0.4 0.55 2.37 1.04 0.0069 0,003 0,015 0.0012 0,003 0,002 0.03 0.24 0.19 0.019 0.006864 0.00184 YES E2 0.17 0.25 0.72 2.05 0.71 0.0100 0.005 0,020 0.0012 0,021 0.001 0.10 0.24 0.23 0,021 0.005228 0.002667 YES E3 0.17 0.24 0.90 1.72 0.74 0.0082 0,003 0.031 0.0008 0,007 0.001 0.03 0.22 0.62 0,017 0.002525 0.002187 YES E4 0.23 0.27 0.43 1.23 0.77 0.0076 0.034 0,017 0.0013 0,003 0.001 0.04 0.17 0.21 0,017 0.002317 0.002027 YES E5 0.16 0.73 1.49 0.94 0.78 0.0077 0,004 0.027 0.0013 0,003 0.001 0.06 0.21 0.17 0.016 0.003488 0.002050 YES E6 0.19 0.67 0.89 1.47 0.79 0.0092 0.005 0,035 0.0012 0,003 0.001 0.03 0.22 0.13 0,020 0.002584 0.002453 YES V1 0.24 0.10 1.50 2.00 0.03 0.0100 0,002 0.023 - 0,020 0,015 0.02 0.40 0.50 0,018 0.002409 0.002667 NO Data in wt .-%, balance iron and unavoidable impurities
(1):% Al / 27 +% Nb / 45 +% Ti / 48 +% V / 25
(2):% N / 3.75 stole tw t8 / 5 tempering treatment Bainite content in the structure rm re A According to the invention? [° C] [S] [° C], [h] [Vol .-%] [MPa] [MPa] [%] E1 1050 320 without > 97% 965 763 22 YES E2 1080 580 without > 97% 1225 972 17 YES E3 1080 640 without > 97% 1174 840 25 YES E4 1150 500 300 ° C, 1.5 h > 97% 1192 1034 24 YES E5 950 100 without > 97% 1353 1112 24 YES E6 950 200 without > 97% 1367 1167 22 YES V1 1075 500 without 75% (rest of MS) 1352 897 8th NO

Claims (15)

Noble structural steel with a yield strength of at least 750 MPa, a tensile strength of at least 950 MPa and a microstructure consisting of at least 80% by volume of bainite and not more than 20% by volume of retained austenite, ferrite, pearlite and / or martensite where the steel is (in% by weight) C: 0 - 0.25%, Si: 0 - 1.5%, Mn: 0.20 - 2.00%, Cr: 0 - 4.00%, Not a word: 0.6 - 3.0%, N: 0,004 - 0.020%, S: 0 - 0.40%, al: 0.001 - 0.035%, B: 0.0005 - 0.0025%, Nb: 0 - 0.015%, Ti: 0 - 0.01%, V: 0 - 0.10%, Ni: 0 - 1.5%, Cu: 0 - 2.0%, Residual iron and unavoidable impurities,
exists and
the Al content% Al, the Nb content% Nb, the Ti content% Ti, the V content% V and the N content% N of the noble structural steel each satisfy the following condition:

% Al / 27 +% Nb / 45 +% Ti / 48 +% V / 25>% N / 3.75

Noble structural steel according to claim 1, characterized in that its C content is at least 0.09 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its Al content is at least 0.004 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its Al content is at most 0.020 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its Nb content is at least 0.003 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its Nb content is at most 0.01% by weight. Noble structural steel according to one of the preceding claims, characterized in that its Ti content is at least 0.001 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its Ti content is at most 0.008 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its V content is at least 0.02 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its V content is at most 0.075 wt .-%. Noble structural steel according to one of the preceding claims, characterized in that its breaking elongation A is at least 10%. Forgings consisting of a steel obtained according to one of the preceding claims. A method for producing a forging having a yield strength of at least 750 MPa and a tensile strength of at least 950 MPa and a minimum of 80 vol .-% bainitic structure, the remaining maximum 20 vol .-% of other microstructural fractions be retained austenite, ferrite, pearlite or martensite can, comprising the following steps: a) providing a forging tool, which consists of a according to one of claims 1 - 10 composite engineering steel; b) heating the forging die to a forging temperature of at least 100 ° C above the Ac3 temperature of the engineering grade steel; c) forging the forging temperature heated forging to the forging; d) cooling the forging from forging heat to a temperature below 200 ° C, the t8 / 5 time during cooling being 10-1000 sec. A method according to claim 12, characterized in that the forging temperature is more than 1150 ° C. Method according to one of claims 12 or 13, characterized in that the forging after cooling undergoes a tempering treatment in which it is maintained over a tempering period of 0.5 - 2 h at a tempering tempering 180 - 375 ° C.

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