UA124766C2 - High chromium martensitic heat-resistant steel with combined high creep rupture strength and oxidation resistance - Google Patents

Abstract

Martensitic heat-resistant steel for boiler applications with a unique combination of enhanced creep strength and excellent oxidation resistance upon high temperature exposure in steam containing environments., having the following melt analysis (in wt.-%): C: 0.10 to 0.16 %, Si: 0.20 to 0.60 %, Mn: 0.30 to 0.80 %, P P0.020 %, S 00.010 %, Al 00.020 %, Cr: 10.5 to 12.00 %, Mo: 0.10 to 0.60 %, V: 0.15 to 0.30 %, Ni: 0.10 to 0.40 %, B: 0.008 to 0.015 %, N:0.002 to 0.020 %, Co: 1.50 to 3.00 %, W: 1.50 to 2.50 %, Nb: 0.02 to 0.07 %, Ті: 0.001-0.020 %. The balance of the steel consists of iron and unavoidable impurities. The steel is normalized for a period of about 10 to about 120 minutes in the temperature range between 1050 °C and 1170 °C and cooled down in air or water to room temperature, and then tempered for at least one hour in the temperature range between 75OCC and 820 °C. It exhibits martensitic microstructure with average 5-ferrite content of less than 5 vol.-%.

Description

from 10.5 to 12.00, Mo: from 0.10 to 0.60, Y: from 0.15 to 0.30, Mi: from 0.10 to 0.40, B: from 0.008 to 0.015, M : from 0.002 to 0.020, Co: from 1.50 to 3.00, MU: from 1.50 to 2.50, MB: from 0.02 to 0.07, Ti: 0.001-0.020. The rest of the steel consists of iron and unavoidable impurities. The steel is normalized for a period of about 10 to about 120 minutes at a temperature range of 1050 to 1170°C and cooled in air or water to room temperature, and then quenched for at least one hour at a temperature range of 750 to 820°C. It shows a martensitic microstructure with an average b-ferrite content of less than 5 95 by volume. ! y y : 3 nos : N

Ex 1 Characteristics according to and J. Intermediate and IN. Characteristic for the nobleness of desire and five characteristics! in the presence of protection 2 from mm I 5-1 mgcm" and "with mgom" to Ko i

Eh! sha : : and and ; !

And oh! and Che! and y and nya: in y

The content of the

Fk.

The present invention relates to martensitic high-chromium heat-resistant steels for components operating at elevated temperatures, for example from 550 to 750 "C, and under high stresses. The steel according to the present invention can be used in the field of energy production, chemical and oil and gas industries.

Materials based on ferritic/martensitic high-chromium steel are widely used in modern power plants as materials for intermediate superheater/superheater pipes and steam pipes. To further improve the overall efficiency of thermal power plants, it will be necessary to increase steam parameters, pressure and temperature. Thus, the implementation of more efficient cycles in power plants will require stronger materials with improved resistance to oxidation from the steam side.

Known attempts to create a new martensitic high-chromium steel that combines exceptional long-term strength properties with excellent oxidation resistance have so far been unsuccessful due to the formation of the so-called 72-phase. The 2-phase is a complex nitride, which rapidly solidifies with the absorption of the surrounding strengthening precipitates МХ, where М is MB, М, and Х is C, М.

The expression "material based on high chromium steel" usually means grades of steel containing more than 9 95 St by weight. However, increased chromium content, i.e., containing more than 9 95 Cg by weight, which is necessary for adequate resistance to oxidation in water vapor, accelerates the formation of the 2-phase and also increases the rate of coarsening of chromium carbide precipitates. The loss of the microstructure stabilization effect of both MH deposits and chromium carbide together ultimately lead to a decrease in the long-term strength of martensitic high-chromium heat-resistant steel grades. As a result, a major challenge for further steel development is to resolve the apparent contradiction between long-term strength and oxidation resistance.

Today, for high-temperature applications, i.e., applications at operating temperatures higher than 550 "С, grades 91 and 92 according to A5TM are widely used, both of which contain 9 95 Cg by weight, with a long-term strength of more than 109 h . at 600 "C, at 90 and 114 MPa, respectively. The main difference between the two grades is that grade 92 contains M/ in the range of 1.8 95 by weight and a lower amount of Mo in the range of 0.4 95 by weight compared to 1 96 by weight in the case of grade 91. In addition, the grade 92 contains small amounts of B, less than 0.005 95 by weight.

Both grades of steel are characterized by insufficient resistance to oxidation in steam atmospheres at temperatures higher than 600 "C, which significantly limits the range of application temperatures.

In particular, in the components of the boiler unit with heat transfer, scale performs the function of a heat-insulating material, which thus increases the temperature of the metal and, as a result, reduces the service life of the corresponding components. In addition, scale chipping during operation or entering the steam turbine - on the turbine blades and guide vanes - will lead to erosive destruction of subsequent steam transfer components. Chipped scale can clog the pipe, especially in the bend area, which impedes the flow of steam, often resulting in localized overheating and catastrophic failure. х20биМоМ11-1 is a reliable high-chromium ferritic/martensitic steel for use in high-temperature conditions, containing 0.20 o C by weight, 10.5-12 95

Sg by weight, 1 95 Mo by weight and 0.2 95 M by weight. This steel shows better oxidation properties than steel grades 91 and 92 according to A5TM due to the higher content of Cg, but worse long-term strength (long-term strength greater than 105 hours at 600 "C is about 59

MPa). In addition, hot workability and weldability are impaired due to the high C content of 0.20 95 by weight. Brand 122 according to ABTM contains 10-12 95 St, 1.8 96

M, 1 95 Cy, as well as the addition of M, Mb and M to cause the precipitation of strengthening particles

МХ. The long-term strength is significantly lower than that of grade 92 of A5TM, which shows a long-term strength of 98 MPa after more than 105 h. at 600 "C.

Hot workability is also controversial due to the increased content of Si.

There is another steel with a content of St 11-12 95 by weight. It is used mainly for thin-walled pipe and is called steel MM12-5НС, which combines proper resistance to oxidation from the steam side and long-term strength at the level of grade 91 according to A5TM. The definition of such steel is known from the patent application M/O 02081766, which discloses steel for use at high temperatures, containing by weight: from 0.06 to 0.20 95 C, from 0.10 to 1.00 95 51, from 0.10 to 1.00 95

Mp, not more than 0.010 95 5, from 10.00 to 13.00 95 St, not more than 1.00 95 Mi, from 1.00 to 1.80 95

M, Mo in such a way that (M/24Mo) is no more than 1.50 95, from 0.50 to 2.00 95 Co, from 0.15 to 0.3595 M, from 0.040 to 0.150 95 MB, from 0.030 to 0.12 95 M, from 0.0010 to 0.010095 V and 60 optionally up to and including 0.0100 95 Sa, and the rest of the chemical composition consists of iron and impurities or residues obtained after preparatory processes or steel casting or necessary for them. The content of chemical components mainly confirms such a relationship that steel after normalization of heat treatment in the range from 1050 to 1080 C and tempering is characterized by the structure of tempered martensite, which does not contain or practically does not contain delta-ferrite.

Compared to this steel, the long-term strength can be further improved under storage conditions without changing other properties, such as corrosion resistance and mechanical properties.

Thus, the object of this invention is to provide a seamless tubular product made of martensitic heat-resistant steel with significantly better long-term strength than that of steel grade 92 by

A5TM, for nozzles and pipes, and with characteristics of high-temperature corrosion and oxidation in water vapor, which are comparable or better than those of steels Х2ОСгтМоМм11-1 и ММ12-5НС, described in the prior art.

An additional object of this invention is to obtain a steel that exhibits a martensitic microstructure with a content limitation of delta-ferrite, also known as b-ferrite, to an average of 5 95 by volume.

Another object of the present invention is to provide a steel suitable for the manufacture of small or large diameter seamless tubular products such as seamless pipes or seamless fittings, and steel suitable for the manufacture of welded pipes and fittings, stamped products and plates using known and reliable manufacturing methods. processes.

Steel is suitable as a manufacturing material for a range of components operating under stress at elevated temperatures, including seamless and welded pipes/tubes, stampings and plates in the power, chemical and petrochemical industries. In addition, the steel according to the present invention is resistant to tempering, after prolonged tempering up to and including 30 hours at 800 "C, the yield strength is greater than or equal to 440 MPa, the tensile strength is greater than or equal to 620 MPa, and the impact toughness at 20 "C greater than or equal to 40 J when tested in the longitudinal direction and 27 J when tested in the transverse direction.

According to the present invention, the object can be achieved by means of a seamless tubular product for high temperature applications made of steel characterized by the following chemical composition in percent by weight:

C: from O.10 to 0.16 95, from: from 0.20 to 0.60 95,

MP: from 0.30 to 0.80 Fo,

R.x 0.020 95, 5:50.010 96,

AI x 0.020 95,

C: from 10.50 to 12.00 95,

Mo: from 0.10 to 0.60 95,

In: from 0.15 to 0.30 9,

Mi: from 0.10 to 0.40 95,

B:fromO, 008 to 0.015 95,

M: from 0.002 to 0.020 95,

So: from 1.50 to 3.00 95,

MU: from 1.50 to 2.50 95,

M: from 0.02 to 0.07 o,

Those: from 0.001 to 0.020 95, and the rest of the specified steel is iron and inevitable impurities.

Preferably, the ratio of boron and nitrogen is as follows: M 71.5, to achieve hot workability.

Preferably, the following equation is satisfactory: 1.00 95 x MozhO.5UM x 1.50 95 (in 95 by weight). in my preferred version of garan, the following equation satisfies (in 9o by weight): в-( 14 (m-105 77y57s9 Ve 48771) 2 0007

In another preferred embodiment, the following equation satisfies (in 95 by weight): 2.6 24. (MinSozhO,5-Mp) - 20-(С-М) 5 11.2

In a preferred embodiment, the carbon content is from 0.13 to 0.16 95.

In another preferred embodiment, the Mo content is from 0.20 to 0.60 95.

Preferably, the content of B is from 0.0095 to 0.013 95.

In a preferred embodiment, the Ti content is from 0.001 to 0.005 95.

In another preferred embodiment, the microstructure contains, on average, at least 95% tempered martensite, and the remainder is delta ferrite.

In an even more preferred embodiment, the microstructure contains on average at least 98 95 of tempered martensite, and the rest is delta ferrite.

In the most preferred embodiment, the microstructure is martensitic and does not contain delta-ferrite.

The present invention also relates to a production method, which involves the following stages: - casting steel with a chemical composition according to the present invention, - hot forming of the specified steel, - heating the specified steel and holding the specified steel for a period of time ranging from 10 to 120 minutes, in temperature range from 1050 "C to 1170 C, - cooling of the specified steel to room temperature, - reheating of the specified steel to the tempering temperature of TT and keeping it at this temperature, which is from 750 "C to 820 "C, for at least one hour, - cooling of the specified steel to room temperature.

Preferably, the cooling stage is carried out using air cooling or water cooling.

The cooling stage after the reheating stage can be carried out by means of water cooling.

The cooling stage after the heating stage can be carried out by means of water cooling.

The present invention may also relate to the manufacture of a welded pipe, pipe or plate using a steel such as steel for a seamless tubular product according to the present invention or according to a method according to the present invention.

In fig. 1 shows a diagram of mass gain due to oxidation plotted against chromium content.

The essence of this invention

According to this invention, a martensitic high-chromium heat-resistant steel is created, which is characterized by the following chemical composition: (1) C: from 0.1O to 0.16 vol, while C must be added to at least 0.1095 to obtain sufficient precipitation of carbides. In addition, C is also an austenitic stabilizing element. A C content lower than 0.10 95 would suggest a higher amount of β-ferrite in the microstructure. The upper limit for carbon is 0.16 95, as excess addition of C limits impact strength and weldability properties. (2) 51: from 0.20 to 0.60 95, while Z is used for deoxidation during the implementation of the steel production method.

In addition, it is one of the key elements that determines the oxidation characteristics of steels.

To achieve the effect of improving the complete oxidation of additives, the amount of 5i should be at least 0.20 95. The upper level of bi should preferably be limited to 0.60 95, since the excess addition of 5i accelerates sediment thickening and reduces impact viscosity. Preferably, the lower limit is 0.25 95. (3) Mp: 0.30 to 0.80 95, where Mp is an effective deoxidizing element. It binds sulfur and reduces the formation of b-ferrite. At least 0.30956 MP can be added. The upper limit should be 0.8 95, since excess additives reduce the long-term strength of steels at elevated temperatures. (4) P. x 0.020 9, while P is an active grain boundary element that reduces the impact toughness properties of steels. The content should be limited to 0.020 95 to prevent negative impact of P on impact properties. P may be present in an amount equal to or greater than 0.00 95 as it may be a permanent impurity. (5) 5:0.010 9, while Z forms sulfides and reduces the impact toughness and hot workability properties of steels. Limiting the upper limit of the 5 content to 0.010 prevents the formation of defects during hot working and the negative impact on impact strength. 5 may be present in an amount equal to or greater than 0.00 95 because it may be a permanent impurity. (6) A x 0.020 95, while A! is an effective deoxidizing element used in the process of steel production. Excessive addition of AI, higher than 0.02 95, may cause the formation of AIM, which thus reduces the amount of strengthening nitride deposits

МХ (M represents MB, MU, and X represents C, M) in steel and, as a result, properties regarding long-term strength. AI may be present in an amount equal to or greater than 0.00 95 as it may be a permanent impurity. (7) Cg: from 10.5 to 12.00 95, while Cg forms carbides that form on the boundaries of the martensitic microstructure.

Chromium carbides are important for stabilizing the martensitic microstructure when exposed to elevated temperatures. St improves the characteristics of high-temperature oxidation of steels.

The content, which is at least 10.5 95, is necessary to reveal the improving effect of complete oxidation of Cg additives. The content of Cg, higher than 12 95, leads to increased formation of b-ferrite. (8) Mo: from 0.10 to 0.60 9,

Mo is an important element for improving long-term strength, which is also responsible for solid solution strengthening. This element is also found in carbides and intermetallic phases.

Mo may be added up to a content of 0.10 95. Mo additions higher than 0.60 95 will impair impact toughness and cause an increase in b-ferrite content. It should be noted that the content of M and M/ must satisfy the ratio (in 9o by weight) 1 x Mozh0O,5 x

UM x 1.5 to ensure sufficient separation of carbides and intermetallic phases. (9UM: from 0.15 to 0.30 Ob, while M in combination with M forms coherent nitrides МХ (М represents: МБ, У, and Х represents: С, М), which contributes to the improvement of properties in terms of long-term durability .

A content lower than 0.15 95 is not sufficient to achieve this property improvement effect on long-term durability, while a content of 0.30 95 reduces impact toughness and increases the risk of b-ferrite content higher than 5 95 in medium volume. (10) Mi: from 0.10 to 0.40 Ob, and Mi is an important element that improves impact toughness. Thus, a minimum content of 0.10 95 is necessary. However, it lowers the As temperature and tends to reduce long-term strength when added in amounts greater than 0.40 9. (11) B: 0.008 to 0.015 obo, while B is the key element responsible for the stabilization of MgzSv carbides and

Due to the delay in the restoration of the martensitic microstructure. It strengthens the grain boundaries and improves the long-term stability of long-term strength. In addition, B is responsible for significantly improving the ability to deform at long-term strength. To achieve the maximum strengthening effect, additives in the amount of at least 0.008 95 are necessary. However, the content higher than 0.015 95 significantly reduces the maximum processing temperature of steels and is considered harmful. Additives B and M satisfy a ratio of B/M x 1.5 to ensure conversion using known methods of hot treatment. Moreover, this ratio

V/M makes it possible to manufacture seamless and welded pipes, fittings and plates of small or large diameters using the production method according to this invention. Preferably, the B content should be in the range of 0.0095 to 0.0130 (95 by weight). (12) M: from 0.002 to 0.020 Ob, while nitrogen is necessary for the formation of nitrides and carbonitrides of MX (M is:

MB, M, and X represents C, M), responsible for achieving long-term strength. At least 0.002 965 can be added. However, excess M additives, i.e. higher than 0.020 95, lead to increased formation of VM, due to which the strengthening effect of B additives decreases. 14 Khm-107 ug,45 sa BB 481) 20007. (13) Co: from 1.50 to 3.00 95, where Co is an extremely effective austenite-forming element and is used to limit the formation of b-ferrite. Moreover, it causes only a slight effect on the Asi temperature. In addition, it is this element that improves long-term strength properties by reducing the size of the initial precipitates after heat treatment. Therefore, a minimum amount of 1.50 95 should be added. Preferably, a minimum content of 1.75 95 . However, excessive additions of Co can cause embrittlement as a result of increased intermetallic phases during high-temperature operation. At the same time, Co is extremely expensive. Thus, limiting additions to 3.00 95, per important to 2.50 905, is necessary.

It is preferable that the content of Mi, Co, Mn, C and M (in 95 by weight) corresponds to the following equation: 2.654. (MinSo-0.5. Mp) - 20. (S-M) 2 11.2. 60 (14) MU: from 1.50 to 2.50 Ob,

at the same time, UM is known as an effective tool for increased concentration of the solution. At the same time, it is contained in carbides and forms the Laves C14 phase, which can also contribute to increased long-term strength. Therefore, a minimum content of 1.50 95 is required. However, this element is expensive, is highly delaminated during the steelmaking and casting process, and forms intermetallic phases that lead to significant embrittlement. Therefore, the upper limit for UM additives can be brought to 2.50 95. It should be noted that the content of Mo and M/ (in 9o by weight) must satisfy the ratio of 1.00 x Mo-0.5UM x 1.50 to guarantee sufficient separation of carbides and intermetallic phases. (15) MB: from 0.02 to 0.07 Or.

MO forms stable MC carbonitrides, which are important not only for long-term strength properties, but also for austenite grain size control. A minimum amount of 0.02 95 may be added. Mo content greater than 0.07 956 results in the formation of coarse Mo carbides, which can reduce long-term strength properties. Therefore, the upper limit is set to 0.07 95. (16) Ti: 0.001-0.020 Fo, while Ti is a strong nitride-forming element. It contributes to the protection of B in the free form by the formation of nitrides. For this purpose, a minimum content of 0.001 95 is necessary. However, excess Ti content above 0.020 95 can reduce the impact strength properties as a result of the formation of large blocking deposits of TIM.

The rest of the steel contains iron and the usual residual elements obtained as a result of the steelmaking and casting process. The casting technologies used are known to a specialist in this field of technology. Impurities mean elements such as tantalum, zirconium and any other elements that cannot be avoided. It should be noted that tantalum and zirconium are not intentionally added to the steel, but they may be present in amounts of less than 50 ppt in total as unavoidable impurities.

In one embodiment of steel, unavoidable impurities may include one or more of copper (Si), arsenic (A5), tin (5p), antimony (55) and lead (RB).

Si may be present in an amount equal to or less than 0.20 95.

Element Ah may be present in an amount equal to or less than 150 ppm; 5p can

To be present in an amount equal to or less than 150 ppt; ZB may be present in an amount equal to or less than 50 ppt; Pb may be present in an amount equal to or less than 50 ppm and the total content of Ae-5p-ZBrAPb is equal to or less than 0.04 95 by weight.

The steel is normalized for a period of from about 10 to about 120 minutes at a temperature range of 1050 "C to 1170 "C and cooled in air or water to room temperature and then quenched for at least one hour at a temperature range of 750 "C to 820 WITH.

It was found that the resulting steel is characterized by significant and absolutely exceptional strength at elevated temperatures and excellent resistance to oxidation in water vapor.

Moreover, it has been found that at a Steq./Misq ratio of less than 2.3, the average b-ferrite content can be limited to less than 5 95 by volume to prevent impact toughness problems, while SGeq. and Miske. defined as St-6b5in4Mon-1.5M/-11U-5M0B-8tii Ki 40S-30M-2Mp4Min2SozhvSy, respectively. Unexpectedly, it has been found that a W/M ratio of 1.5 or less must be maintained in order to provide hot work using known conversion methods.

The delta ferrite content should not exceed 5 95 by volume, as a content higher than 5 95 by volume will degrade the impact toughness properties.

By hot forming methods are meant: hot rolling, pilgrim rolling, hot drawing, stamping, tube rolling on a mandrel, the method of pushing on rail mills, where a piercing rod pushes an elongated recess through several in-line work cages to obtain a hollow continuous rolling, and other methods of rolling are also known. Pipes and nozzles can be formed from steel according to the present invention. Numerous attempts have been made to obtain steel grades exhibiting satisfactory properties such as oxidation characteristics, long-term strength, but these steel grades have not been able to produce a satisfactory product using these hot forming methods. In particular, sometimes it was even impossible to obtain seamless pipes or nozzles.

The steel according to the present invention provides the production of seamless tubular products with satisfactory properties and the possibility of production of seamless tubular products or slabs by means of hot forming methods, and these products meet the requirements for compliance with dimensions.

EXAMPLES

The advantages of the steel according to the present invention will be explained in more detail on the basis of the following examples. Steels according to the present invention (steel 1, steel 2, steel 3), as well as comparative illustrative steels (steel 4, steel 5), which have the chemical composition indicated in Table 1, were cast in 100-ks casting molds using a vacuum induction melting furnace, then subjected to hot rolling to obtain plates (thickness 13-25 mm) and then normalized and subjected to tempering. Normalizing heat treatment was carried out in the temperature range from 1060"C to 1100"C for 30 minutes, followed by air cooling to room temperature. Annealing was carried out at 780" for 120 minutes, again followed by air cooling.

Comparative illustrative steels 4 and 5 have a B content lower than 0.008 and thus do not meet the present invention.

In the case of steel 4, additions of Mi, Co, Mp, C and M do not satisfy the equation weight). stele does not correspond to the following MINE v-(/14)um-lo bisa Vb8) 748) Ti) 2 0007 (v 9; by weight) also.

Table 1

Element Steel 1 Steel2 Steel C Steel 47 Steel 57 (95 by weight) (95 by weight) (95 by weight) (95 by weight) (95 by weight)

Shi 0.001 0.015 0.015 0.005 0.001 0.002 0.001 0.002 0.001 0.002 0.007 -0.002 0.007 0.007 0.006 Shi 0.0145 0.011 0.0100 0.0040 0.0052 0.011 0.0088 0.0103 0.042 0.042

Continuation of table 1 0.048 0.038 0.033 0.038 0.043 0.001 0.003 0.001 0.001 0.001 "in Comparative grades of steel

For two illustrative steels (Steel 1, Steel 2, Steel 3), the results shown in Table 2 were obtained at room temperature for tensile strength, yield strength, elongation, relative reduction in surface area, and fracture energy of a Charpy M-cut specimen .

Table 2 xia xuo xia" St. 77 in 17775

Long-term strength tests conducted according to ISO SIM EM 204 on samples of two illustrative steels additionally demonstrated a significant improvement in long-term strength. This is reflected in the failure time, which is at least almost twice that of prior art steels such as ROY, ROY, MM12-5H5S, P1I22 and X2OStMoMm11-1, during the long-term endurance test at 130 MPa and 100 MPa. The results are shown in Table 3.

Also, the comparative illustrative steels did not achieve the long-term strength of the steels of the present invention.

Table C

Destruction time per hour. at 650 "C under tension

Steel grade 130 MPa 100 MPa umta-vNo 2vov

Continuation of table C 7) Average values calculated on the basis of the strength values specified in the technical data sheet

ESSS

"») K. Kitiga eigai. Proceedings of the conference on RUR AZME (RMR2012), 2012, Toronto, Canada

In fig. 1 shows a diagram of the increase in mass due to the oxidation of water vapor in the atmosphere at elevated temperatures, plotted as a function of the chromium content. The basis for building the scheme is oxidation tests in the atmosphere of water vapor, which were carried out in accordance with IBO 21608:2012.

In fig. 1, three areas that reflect different characteristics of oxidation in water vapor are defined as follows. (I) Characteristics in the absence of protection for mass gain greater than 10 mg/cm after 5000 h. (II) Intermediate characteristic for mass gain in the range of 5-10 mg/sme (PI) Characteristic in the presence of protection for values of mass gain less than 5 mg/cm-.

Accordingly, the classification of various high-chromium martensitic heat-resistant steels with regard to oxidation characteristics is carried out in Table 4 below. Areas Я, ЯІ and ІІ correspond to the values of mass gain, as shown in fig. 1. Two illustrative steels absolutely prevail over РО1, Р92,

РИ22 ии Х2О0СтМоМ11-1 in terms of resistance to oxidation in water vapor. The steel according to this invention shows characteristics comparable to those of MM12-5НО.

Table 4

Mass gain (mg/cm) 600 s 65070

Test temperature (C)

UMm12-5NS a ve hostMoM 1 p Po

RI22 (one phase) no

FRI A THROUGH MON

According to the present invention, it is possible to obtain high-chromium martensitic heat-resistant steel with improved long-term strength properties and resistance to oxidation in water vapor, which can be used for the manufacture of pipes, stamped products, nozzles and plates operated at high temperature in the field of energy production, chemical and oil and gas chemical industries.

Claims (12)

FORMULA OF THE INVENTION 1. Seamless tubular product for use in high temperature conditions, made of steel characterized by the following chemical composition, wt. 90: C: fromO.10 to 0.16, with: from 0.20 to 0.60, Mp: from 0.30 to 0.80, P:x0.020, 5:0.010, Aik0.020, Sg: from 10.50 to 12.00, Mo: from 0.10 to 0.60, M: from 0.15 to 0.30, Mi: from 0 .10 to 0.40, B: from O.008 to 0.015, M: from 0.002 to 0.020, Co: from 1.50 to 3.00, MU: from 1.50 to 2.50, Mr: from 0.02 to 0.07, Ti: from 0.001 to 0.020, while the rest of the specified steel consists of iron and inevitable impurities, and the microstructure is martensitic due to delta-ferrite. 2. Seamless tubular product. 1, where: /M' 1.5. 3. Seamless tubular product according to claim 1 or claim 2, where, wt. 95: 1.00:Mo-0.5Uuk1.50. 4. A hollow tubular product according to any of claims 1-3, where, wt. 90: in La ) (this is a frequent word with Y schy ) Li) x0007. and 5. A seamless tubular product according to any of claims 1-4, where, wt. 95: 2.6:4-(Mi-bozhO,5-Mp)-20(С--М)211.2. 6. Seamless tubular product according to any one of claims 1-5, where the carbon content is from 0.13 to 0.16. 7. A seamless tubular product according to any one of claims 1-6, where the Mo content is from 0.30 to 0.60. 8. A seamless tubular product according to any one of claims 1-7, where the content of B is from 0.0095 to 0.013. 9. A seamless tubular product according to any one of claims 1-8, where the Ti content is from 0.001 to 0.005. 10. A seamless tubular product according to any one of claims 1-9, where the specified product is a seamless pipe. Zo 11. The method of obtaining a seamless tubular product according to any of claims 1-9, which involves the following stages: - casting of steel with the chemical composition specified in any of claims 1-9, - hot forming of the specified steel, - heating of the specified steel and holding the specified steel for a period of time ranging from 10 to 120 minutes, in the temperature range from 1050 to 1170 C, - cooling the specified steel to room temperature, - reheating the specified steel to the tempering temperature of TT and holding it at this temperature, which is from 750 to 820 "С, for at least one hour, - cooling of the specified steel to room temperature. 12. The method of obtaining a seamless tubular steel product according to claim 11, where the cooling stages are carried out using air cooling or water cooling.