RU2254394C1 - High-strength austenitic stainless steel and method of final hardening of articles made from such steel - Google Patents

Abstract

FIELD: production of high-strength austenitic stainless steel for casing pipes and oil tubing of gas and oil fields at high content of hydrogen sulfide.

SUBSTANCE: proposed steel includes the following components, mass-%: C≤0.05; Cr, 24-28; Ni25-40; Mo, 2-5; Cu, 1-3; W≤3; Mn≤2.5; Si≤0.2; V≤0.15; Nb≤0.1; Ti≤0.2; Al≤0.1; rare-earth metals≤0.05; N≤0.11; S≤0.01; P≤0.02; the remainder being iron. Mo+W≤6 mass-%; V+Nb≤0.2 mass-% and 1.10<%Ni[%Cr+0.8(%Mo+%W)]<1.25. Method of final hardening of articles made from proposed steel includes preliminary plastic deformation at reduction no less than 40% and temperature not exceeding the temperature of beginning recrystallization, hardening to solid solution from temperature not below 1020°C and final plastic deformation at degree of 30-70% at temperature below temperature of beginning of recrystallization by 150°C.

EFFECT: increased toughness and ductility of steel; improved technological and corrosion-resistant properties.

3 cl, 4 tbl

Description

The invention relates to metallurgy, and in particular to high-strength austenitic stainless steels used in the cold-deformed state, and can be used in the manufacture of products used for arranging wells in oil and gas fields, for example, casing and tubing.

Known dispersion hardening alloy with high resistance against corrosion cracking for high-strength oil pipes (US Pat. Japan No. 57203739, C 22 C 19/05, C 22 C 30/00, C 22 C 38/50, publ. 14.12. 1982) containing, mac. %: C not more than 0.1; Ni 25-60; Cr 22.5-35; Si no more than 1; Mn no more than 2; S no more than 0.005; P no more than 0.03; Al no more than 0.5; Nb, Ti, Ta, Zr, V 0.5-4; Mo is not more than 7.5; W no more than 15, the rest is iron and impurities.

The alloy after quenching and aging is characterized by high strength - more than 600 MPa and is not susceptible to corrosion cracking at temperatures up to 200 ° C, but contains in large quantities alloying elements required to achieve strength, which makes it difficult to apply for mass production due to the high cost and low technology.

Known corrosion-resistant steel for castings intended for oil and gas equipment operating in a hydrogen sulfide-containing medium (US Pat. RF No. 2016133, C 22 C 38/58, publ. 15.07.1994), containing, wt.%: C 0.04-0 , 08; Cr 23-27; Ni 3.5-5; Mn 3.5-6; Mo 2.5-3.5; Ci 1.5-2.5; Si 0.8-1.5; N, 0.15-0.35; Nb 0.20-0.40; Zr, Hf, La, P3M, the rest is iron and impurities.

However, this steel contains a large amount of nitrogen, hardening a solid solution, forming nitrides, stabilizing the austenitic structure. Due to the high nitrogen content, this steel is not technologically advanced in smelting and hot plastic deformation, which makes it difficult to apply for the manufacture of hot and cold-deformed pipes.

Known cold-deformed high nickel alloy with a high nitrogen content, hardened in a combined way by grinding grain below 8.5 microns, the selection of nitrides based on niobium and molybdenum, as well as due to nitrogen in solid solution (US Pat. US No. 4559090, C 21 D 6 / 02, C 21 D 8/00, C 22 C 38/00, C 22 C 38/40, publ. 12/17/1985). This alloy contains, wt.%: C not more than 0.12; N, 0.075-0.55; Nb no more than 0.75; Cr 16-32; Ni 7-55; Mn no more than 8.5; Mo is not more than 6.5; Si no more than 3.0; Cu no more than 4.0; W is not more than 3.0 and is quenched from temperatures above 1000 ° C, then it is deformed to cold by 40-85% in one or more passes, and then annealed between 800 and 1050 ° C. When the nitrogen content of 0.22-0.45% in this alloy, the yield strength is not lower than 730-850 MPa.

A significant drawback of this alloy is the low ductility during hot deformation necessary to obtain a workpiece, therefore, reduced processability, as well as a decrease in corrosion resistance due to the binding of part of the chromium to nitrides, resulting in a decrease in the concentration of chromium in the solid solution. In addition, the limits of changes in the chemical composition required to achieve high strength and resistance to corrosion and embrittlement in a hydrogen sulfide-containing medium have not been determined.

Among steels of increased strength with a high nitrogen content (0.35-0.8%) in solid solution and resistant to corrosion in sulfuric environments and environments enriched with chlorine ions, steel containing Cr 20-30% and Ni 25-32% is known (US Pat. No. 5480609, C 22 C 38/44, C 22 C 38/42, C 22 C 30/00, publ. 02/01/1996). In the absence of strong nitride-forming elements, the processability of this steel increases slightly during pressure processing, however, in general, its processing is difficult. In addition, the strength properties are relatively low, the yield strength with a nitrogen content of 0.45% is 490 MPa, the resistance to corrosion cracking is not defined, although the corrosion resistance in these environments is high. The stability of the austenitic structure is ensured due to the high concentration of nitrogen and nickel, which avoids the formation of embrittle phases during processing.

The closest technical solution, selected as a prototype, is steel (brand XlNiCrMoCu31-27-4), described in European Standard EN 10088-3: 1995, Tab. 3, containing elements in the ratio, wt.%: C - not more than 0,020; Si - not more than 0.70; Mn - not more than 2.0; P no more than 0.03; S - not more than 0.010; N, not more than 0.11; Cr 26-28; Ni 30-32; Mo 3-4; Ci 0.7-1.5. This steel is usually used in the state of annealing (quenching) on a solid solution, that is, in an unhardened state (yield strength not lower than 220-250 MPa). For hardening, cold plastic deformation is used, which provides a significant increase in yield strength and temporary resistance with a natural decrease in viscosity and ductility.

The disadvantage of steel of this composition is the tendency to form sigma-like intermetallic phases, which requires high heating temperatures for deformation and quenching in solid solution at relatively high cooling rates. High heating temperatures for solid solution quenching before final deformation lead to excessive grain growth. In addition, the high content of Cr, Mo, and Si leads to the development of twinning deformation instead of sliding at relatively low speeds and compression ratios lower than those required to achieve a yield strength of 760–910 MPa. The formation in the cold-deformed state of twins reduces the stock of both ductility and toughness, negatively affects the corrosion resistance.

A known method of hardening austenitic stainless steel using cold plastic deformation. Moreover, an increase in strength can be achieved without a significant reduction in corrosion properties (US Pat. EPO No. 0789089, C 22 C 38/00, C 22 C 38/54, C 21 D 8/00, C 21 D 6/00, publ. 13.08 .1997). To increase the strength and resistance to corrosion cracking in hot water under intense neutron radiation, the steel after quenching on a solid solution is subjected to deformation by 30% at a temperature below the recrystallization temperature, and then aging at 600-750 ° C for up to 100 hours. However, this treatment provides only moderate hardness (yield strength of about 400 MPa) and does not guarantee resistance to hydrogen sulfide.

The closest solution adopted for the prototype is a method for processing austenitic stainless steel (US Pat. No. 2000017396, C 22 C 38/00; B 21 J 5/00; C 22 C 38/58; C 22 C 38/60, publ. . January 18, 2000), which consists in the fact that the final deformation of steel hardened by a solid solution is carried out at a temperature from room temperature to 350 ° C. This prevents cracking during deformation and provides high strength.

The disadvantage of this method is the inability to determine the degree of deformation necessary to achieve the specified properties, and the lack of pre-treatment before final deformation, which does not guarantee the required initial structure and does not provide the necessary set of properties of steel of the proposed composition. In addition, a relatively narrow strain temperature range implies significant strain during deformation and limits the ability to control riveting.

The technical problem solved by the inventions is to increase the viscosity and ductility of the material, to increase technological and anticorrosion properties during hardening treatment.

The problem is solved due to the fact that high-strength austenitic stainless steel containing carbon, chromium, nickel, molybdenum, copper, manganese, silicon, sulfur, phosphorus, nitrogen and iron, according to the invention, additionally contains vanadium, niobium, aluminum, titanium, tungsten and rare earth metals in the following ratio of components, wt.%:

Carbon no more than 0,05 Chromium 24-28 Molybdenum 2-5 Copper 1-3 Tungsten no more than 3 Manganese no more than 2.5 Silicon no more than 0.2 Vanadium no more than 0,15 Niobium no more than 0.1 Titanium no more than 0.2 Aluminum no more than 0.1 REM no more than 0,05 Nitrogen no more than 0.11 Sulfur no more than 0,01 Phosphorus no more than 0,02 Iron rest

the total content of molybdenum and tungsten is not more than 6 wt.%, vanadium and niobium - not more than 0.2 wt.%, and the nickel content is determined from the ratio, (wt.%):

In addition, the problem is also solved due to the fact that in the method of final hardening of products from high-strength austenitic stainless steel, including hardening by solid solution and plastic deformation, according to the invention, preliminary hardening is carried out before hardening in one or several passes with a degree of less than 40% at a temperature not exceeding the temperature of the onset of recrystallization, quenching on a solid solution is carried out at a temperature not lower than 1020 ° C, and the final plastic kuyu deformation is carried out with a degree of 30-70% at a temperature below the recrystallization start temperature of not less than 150 ° C.

The proposed steel is characterized by the presence of vanadium, niobium, aluminum, titanium, tungsten and rare earth metals, lower lower limit of chromium, wider limits of molybdenum content, higher upper limits of copper and manganese, lower upper limits of silicon and phosphorus.

The presence of vanadium, niobium and titanium in the composition contributes to the production of fine grains, provides an increased rate of hardening deformation, the binding of carbon and nitrogen to sparingly soluble carbonitrides, which improves the resistance of the composition to intergranular corrosion.

The presence of aluminum provides the most complete deoxidation of steel.

To provide the necessary stability in acidic aggressive environments with dissolved hydrogen sulfide and chlorine ions, a sufficiently high chromium content of up to 24-28% is necessary.

The introduction of tungsten increases the resistance of the composition against the formation of pits.

Molybdenum additives up to 5% provide increased resistance against pitting. An increase in the molybdenum content increases the anticorrosive and strength properties of steel, but at the same time its cost increases significantly. In addition, the total content of molybdenum and tungsten should not exceed 6%, since at a higher content they contribute to the formation of sparingly soluble intermetallic phases that impair ductility and corrosion resistance.

A copper content of up to 3% improves the behavior of the metal in acidic media, and increases the rate of strain hardening.

Nickel stabilizes the austenitic structure and increases resistance to corrosion cracking, the introduction of at least 25% nickel is especially beneficial. An excessive increase in its concentration leads to an increase in the cost of steel.

To ensure high corrosion resistance, the carbon content should be as low as possible when using modern manufacturing metallurgical technologies. Additives of niobium, vanadium, and titanium bind residual carbon to carbides and carbonitrides, preventing the formation of chromium carbides. However, the total content of nitrogen and carbon should not lead to the formation of large carbonitrides that facilitate local corrosion and reduce the ductility and toughness of steel.

The sulfur content, as in the prototype, is limited to 0.01% to ensure resistance to hydrogen embrittlement.

Proposed Ratio

justified by the following:

- an increase in the concentration of nickel is possible due to a decrease in the iron content, which ensures an increase in the stability of the austenitic structure, facilitates the dissolution of intermetallic phases upon heating under quenching, reduces its temperature, but at the same time leads to an increase in the cost of steel;

- the high mechanical properties of the final product provide a fine grain, which is almost impossible in the case of steels with a low nickel content, requiring an elevated heating temperature for quenching, but in addition, with an increase in the nickel content, the cooling rate required to suppress the release of intermetallic compounds decreases, which eliminates the need for accelerated cooling after hot deformation, firmware and other operations;

- an increase in the nickel content also favors a decrease in the tendency of these steels to form twins during cold plastic deformation, which ensures an increase in the ductility and toughness of the final product.

Thus, an increase in the nickel content is favorable for service and technological properties, which requires the establishment of upper and lower limits for its content relative to the content of elements that have the opposite effect.

However, a high complex of properties cannot be achieved only due to the optimal chemical composition. The processing parameters providing the necessary characteristics of the structure are of decisive importance.

Conducting preliminary plastic deformation in one or several passes with a degree of at least 40% at a temperature not exceeding the temperature of the onset of recrystallization, provides the possibility of the formation of fine grain, recrystallized by heating under quenching. Under these conditions of deformation, the necessary plastic properties of steel are provided. An increase in the deformation temperature above 600 ° С seems undesirable due to a decrease in the hardening intensity, a decrease in the stored energy necessary for recrystallization, and the possibility of the formation of intermetallic sigma-like phases, especially in nickel-doped formulations.

Carrying out quenching on a solid solution from a temperature of at least 1020 ° C provides the dissolution of the "second" phases that can reduce operational and technological properties, and the formation of recrystallized grains with an average size of 15-25 microns. At higher heating temperatures, accelerated grain growth is observed, which is undesirable for subsequent processing by plastic deformation. The required high strength is achieved by carrying out the final deformation with a degree of 30-70% at a temperature below the temperature of the onset of recrystallization by at least 150 ° C. Deformation at temperatures closer to the temperature of the onset of recrystallization may be accompanied by dynamic softening and polygonization, which make it difficult to achieve high strength. In addition, with prolonged exposure in the temperature range close to the temperature of the onset of recrystallization and above, the development of embrittling phases is possible. Heating during deformation also avoids the formation of twins, which indicates a decrease in ductility and viscosity.

The proposed method is implemented as follows. An ingot of steel of the required composition is subjected to hot deformation in one or several stages with intermediate heating. The resulting intermediate is subjected to cold or warm deformation with a degree of at least 40% at a temperature of from room temperature to 600 ° C. Providing temperatures above room temperature is carried out by heating in any way, for example, in a continuous or chamber furnace, followed by heating to a quenching temperature, which is at least 1020 ° C. Exposure at a heating temperature for hardening is determined by the cross section of the workpiece and the dissolution rate of the "second" phases at a selected temperature. However, excessive exposure, as well as an increase in temperature, are undesirable due to the possible growth of grain. Hardening consists in accelerated cooling to temperatures that exclude the release of "second" phases. The choice of cooling medium is determined by the cross section of the workpiece. After quenching, final plastic deformation is performed with a degree of 30-70% at a given temperature, which is lower than the temperature of the onset of recrystallization by at least 150 ° C. When choosing a deformation temperature, it is necessary to take into account possible heating due to the work of plastic deformation.

To determine the optimal chemical composition of steel and its physicomechanical and technological properties, 7 steel options were smelted (table 1). The value of the relative concentration of Nickel, wt. % equal to

provided below 1.11, above 1.25 and between these values varied the concentration of chromium.

As a prototype, steel of the type XlNiCrMoCu31-27-4 (composition 1) was selected. Steel was melted in an induction 100 kg furnace with a main lining on low-carbon charge materials with a low content of impurities in an argon atmosphere. After step homogenization with a final temperature of 1200 ° C, ingots were forged onto a square with a side of 18 × 18 mm. The temperature of the start of forging was 1180 ° С, of the end - 950 ° С. Cold and warm deformations were carried out by rolling in a laboratory mill 200 with a rhomb-square calibration. The temperature was controlled by a type XA thermocouple. The dissolution temperature of the intermetallic phases was determined metallographically using electrolytic etching in a saturated aqueous solution of oxalic acid. Corrosion tests were carried out in a solution with an initial pH of 2.7 when the solution was saturated with hydrogen sulfide by continuously passing gas. Samples of cylindrical shape were weighed before and after the test to determine the rate of general corrosion. The rate of general corrosion V _k at elevated temperature (90 ° C) was determined in a saturated aqueous NaCl solution with continuous transmission of hydrogen sulfide. Samples for mechanical testing were subjected to stretching in the state after final processing and after saturation in a solution of the second type. Embrittlement as a result of exposure in a medium saturated with hydrogen sulfide was evaluated by the decrease in elongation D relative to the level in the initial state, i.e. without exposure in an environment saturated with hydrogen sulfide. The cold-forming ability of steel was evaluated by the drawing coefficient K _tr during rolling in a closed gauge to form cracks, as well as by the values of the transverse narrowing ψ and impact strength KCV, by measuring on samples with a sharp notch.

The results of measuring the ductility and toughness of steels depending on the hardening temperature (table 2) showed that the known steel, characterized by a lower relative nickel content, has low viscosity and limited ductility during rolling when using low tempering heating temperatures. As shown by metallographic studies, this corresponds to a significant amount of intermetallic particles in the structure. At the same time, to achieve high ductility of steel, it is necessary to heat it under hardening to higher temperatures, which is accompanied by intensive grain growth. In this case, the plastic characteristics of the steels, characterizing the ability to deformation by rolling and to the perception of peak loads during impact loading, are aligned.

To achieve high mechanical properties in the final product, it is necessary to dissolve the embrittling phases and the formation of the minimum grain possible for each given composition. To ensure approximately equal initial grain, all compositions were quenched from 1125 ° С, and deformation was carried out by 20-100% (degree of drawing 1.2-2.0) at temperatures from room temperature to 700 ° С. Then, heating was carried out under hardening to a temperature minimally necessary to ensure the drawing coefficient during rolling without cracking of more than 3.5 (table 2). It was found that the most effective grain grinding is observed in steel of the proposed composition with a deformation of more than 30% and a deformation temperature below 600-650 ° C. At lower degrees of deformation, the steel partially recrystallizes, especially when using elevated temperatures. At the same time, an increase in the degree of deformation of more than 70% does not lead to significant changes in the nature of recrystallization. Increasing the strain temperature significantly complicates the grinding of grain due to the occurrence of polygonization and reduce the excess energy introduced by the deformation. In addition, prolonged heating under deformation to 600-650 ° C leads to a decrease in the ductility of steels of all compositions, which consists in the appearance of surface cracks when drawing more than 1.8. This is especially evident in steel composition 1, which is associated with the onset of the formation of intermetallic compounds.

The mechanical properties after the final deformation at various temperatures with different degrees of deformation, are shown in table 3, showed that the steel of the proposed compositions, in comparison with the prototype, have a higher combination of mechanical properties. In this case, the advantages of the high-nickel composition 7 over the compositions 2-6, the relative nickel content k in which is in the range of 1.11-1.25, are not observed. An increase in the deformation temperature in excess of 600 ° C leads to insufficient rolling strength and somewhat reduces the viscosity and ductility. Deformation with a small degree of compression in the optimal temperature range does not provide sufficient strength, and exceeding the degree of deformation of more than 80% affects the ductility and toughness.

The tests showed that the proposed steel has higher mechanical and corrosion properties than the known steel, which is achieved due to the high pre-treatment efficiency (table 4), while the steel of composition 7 with a higher relative nickel content does not have a noticeable advantage over the compositions with suggested relative nickel content.

The use of the proposed steel and the method of final processing of products from it allows, while saving alloying elements, to provide increased viscosity and ductility in the cold-deformed state, to increase technological and anticorrosion properties and to apply in products for arranging and operating wells in oil and gas fields, including casing and tubing.

Table 1.
The chemical composition of the studied steels Compositions options) The content of elements, wt.% k FROM Mn Ni Cr Mo W Si S R Ti Al Cu N 1 * (prototype) 0.012 1.72 30.41 27.88 3.30 0.05 0.45 0.002 0.018 0.02 0,03 0.91 0,037 0.99 2 0,022 1.78 29.31 24.22 2,53 0.12 0.15 0.004 0.016 0.09 0.06 1,62 0,023 1,11 3 0,025 1,61 32.34 25.38 3,51 0.16 0.16 0.005 0.015 0.05 0.04 1.48 0.012 1.14 4 0.015 1.92 33.91 25.63 3.22 0.05 0.12 0.004 0.016 0.08 0,03 1.35 0.013 1.20 5 0.018 2.05 36.86 27.83 2.62 2.11 0.14 0.003 0.018 0.12 0.04 1.72 0.008 1.16 6 0.015 2.21 37.73 27.39 3.18 0.01 0.17 0.004 0.014 0.11 0.05 1.05 0.013 1.25 7 0,021 0.58 38.76 25.35 3.21 0.06 0.18 0.001 0.018 0,03 0,03 1.22 0,021 1.38 Note: * - Steel, with the exception of composition 1, is microalloyed with Nb and V in the amount of up to 0.10%

table 2
Indicators of ductility and toughness of the studied steels depending on the hardening temperature Quenching temperature, ° C Mechanical properties Compositions (options) 1 2 3 4 5 6 7 K _tr 2.2 3,5 3,1 3.4 3.3 3.6 3,5 1050 δ ₅ ,% 25,4 38,2 39.3 39.8 38,4 39.1 38.9 KCV, 1.25 2.86 2.96 3.21 3.13 3.21 3.02 MJ / m ² K _tr 2,8 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 1075 δ ₅ ,% 30,2 42.3 44.8 45.6 44,2 43,2 44.3 KCV, 2.06 2.92 3.20 3.08 2.98 3.12 3.15 MJ / m ² K _tr 3.4 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 1100 δ ₅ ,% 39.5 44.6 43.8 44,2 43.9 44,2 45.1 KCV, 2.7 3.12 3.4 3.02 2.96 3.16 3.05 MJ / m ² K _tr > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 > 3.5 1125 δ ₅ ,% 44,2 44.6 43.1 46.8 45.8 44.3 44.9 KCV, 3.12 3.30 3.15 3.18 3.19 3.08 3.05 MJ / m ²

Table 3
The influence of temperature and the degree of final deformation on the mechanical properties of the studied steels Composition The degree of deformation,% T = 20 ° C T = 250 ° C T = 500 ° C T = 700 ° C σ _0.2 MPa δ ₅ ,% KCV, MJ / m ² σ _0.2 MPa δ ₅ ,% KCV, MJ / m ² σ _0.2 MPa δ ₅ ,% KCV, MJ / m ² σ _0.2 MPa δ ₅ ,% KCV, MJ / m ² 1* twenty 620 24.2 2.6 610 25.6 2.65 550 27,2 2.82 480 26.5 2.12 40 745 16.6 1.83 732 17,2 1.88 687 18.1 2.21 496 25.8 1.81 60 875 12.3 1,52 808 13,4 1,56 746 15,5 1.76 534 25,2 1.32 80 925 10,2 1.33 898 11.2 1.38 862 13.1 1.68 586 22.9 1.19 100 990 7.6 1,07 963 8.4 1.12 856 8.8 1.43 645 20.1 1,02 2 twenty 632 26.1 2.86 642 26.3 2.75 562 28,2 3.02 502 28.5 2.82 40 769 22.6 2.12 761 22.4 2.08 735 23.1 2.64 523 26.3 2.61 60 878 18,4 1.75 826 18.8 1.86 754 19.3 2.25 536 26.1 2,32 80 932 14.2 1,66 896 14.6 1.71 862 15.0 1.92 595 25.8 2.13 100 1020 9.7 1.47 977 10.6 1.42 875 10.8 1.63 667 25.7 2.05 3 twenty 628 26.7 2.82 621 27,2 2.83 568 27,2 3.02 478 26.5 2,52 40 761 23,2 2.23 763 21,2 2.27 752 22.1 2.83 516 25.8 2.11 60 886 17.1 1.82 857 17.9 1.91 766 18,4 2,36 541 25,2 2.02 80 948 13.1 1,61 912 14.2 1.79 878 14.8 1.86 588 24.9 1.86 100 996 9.6 1,58 983 10,4 1,56 912 10.8 1.62 642 24.3 1,64 4 twenty 637 27,2 2.81 618 26.9 2.89 560 29.1 2.96 492 28.1 2.41 40 762 19.6 2,33 774 21.6 2.66 726 24.0 2.45 514 22.8 2.16 60 882 16.3 1.88 831 18.1 2.16 765 19.5 2.04 544 25.9 1.96 80 952 12,2 1,69 898 14.2 1,62 873 13.1 1.98 586 24.3 1.87 100 992 9.7 1.43 974 11,4 1,58 884 10.6 1,63 613 23.8 1.82 5 twenty 628 26.2 2.85 623 26.6 2.91 582 27,2 3.04 502 27.8 2,53 40 761 22.2 2,38 768 21.5 2.06 7355 18.1 2.71 538 26.3 2.11 60 893 17.3 1.72 838 17.3 1.88 796 16,2 1.96 562 25.9 1.86 80 954 16,2 1,69 921 14.2 1.72 891 14.8 1.88 596 23.9 1.75 100 1032 11.1 1,53 981 11.6 1.48 902 10.8 1,62 626 22.3 1.65 6 twenty 639 27.3 2.87 615 27.3 2.91 562 28,2 2.94 520 27.1 2,51 40 769 19.5 2.43 765 21.5 2.71 752 23.0 2.54 546 24.8 2,32 60 892 17.3 1.83 836 18,4 2.22 785 18.5 2.08 575 25,2 2.06 80 962 13,2 1.71 888 14.1 1.65 893 14.1 1.83 602 23.3 1.82 100 998 9.9 1.48 984 11.3 1,53 913 10.7 1,56 632 22.7 1.73 7 twenty 631 26.6 2.78 635 27.1 2.78 572 28.1 2.98 492 27.1 2.62 40 768 21,4 2.69 762 28,2 2,37 699 23.1 2.78 522 25.3 2.23 60 892 16.1 2.06 855 16.8 2.10 776 17.6 2.42 553 24.6 2.05 80 953 13,4 1.71 915 14.3 1.85 882 14.7 2.01 594 23.9 1.92 100 998 10.6 1,62 981 10,4 1,62 936 11.2 1.72 651 22.8 1,53 Note: All compositions after preliminary cold rolling by 50%;
* in order to achieve sufficient ductility, steel of composition 1 was tempered in air from 1125 ° С before the final deformation; the remaining compositions were from 1070 ° С.

Table 4
Mechanical properties and resistance to corrosion and hydrogen embrittlement of the studied steels hardened by solid solution and subjected to final rolling with compression of 50% at 200 ° C depending on the degree of preliminary deformation at room temperature Composition Degree of pre-deformation 0% fifty% 70% σ _0.2 MPa δ ₅ ,% V _to , g / m ² h D% σ _0.2 MPa δ ₅ ,% V _to , g / m ² h D% σ _0.2 MPa δ ₅ ,% V _to , g / m ² h D% 1 776 14.5 0.85 29th 783 14,4 1.06 32 772 15.1 1.24 42 2 783 16,2 0.94 23.5 805 17.8 0.78 21 803 17.7 0.96 25 3 793 15.8 0.92 26 813 17.3 0.94 24.5 822 17.5 1,02 27 4 786 16,0 0.88 eighteen 809 16.8 0.92 25 812 17.3 1.12 24 5 769 15,5 0.92 22 801 17,2 0.88 27 806 17.8 0.93 19 6 775 15,2 0.72 fifteen 790 17.3 0.73 17 810 17 0.81 16.5 7 760 14.8 0.76 eighteen 802 16.8 0.91 21.5 799 17.4 0.78 eighteen

Claims (2)

1. High-strength austenitic stainless steel containing carbon, chromium, nickel, molybdenum, copper, manganese, silicon, sulfur, phosphorus, nitrogen and iron, characterized in that it additionally contains vanadium, niobium, aluminum, titanium, tungsten and rare earth metals the following ratio of components, wt.%: carbon no more than 0,05 chromium 24-28 molybdenum 2-5 copper 1-3 tungsten no more than 3 manganese no more than 2.5 silicon no more than 0.2 vanadium no more than 0,15 niobium no more than 0.1 titanium no more than 0.2 aluminum no more than 0.1 REM no more than 0,05 nitrogen no more than 0.11 sulfur no more than 0,01 phosphorus no more than 0,02 iron rest the total content of molybdenum and tungsten is not more than 6 wt.%, vanadium and niobium - not more than 0.2 wt.%, and the nickel content is determined from the ratio, (wt.%):

2. The method of final hardening processing of products from high-strength austenitic stainless steel, including hardening by solid solution and plastic deformation, characterized in that prior to hardening, preliminary plastic deformation is performed in one or several passes with a degree of at least 40% at a temperature not exceeding the start temperature recrystallization, quenching on a solid solution is carried out at a temperature not lower than 1020 ° C, and the final plastic deformation is carried out with a degree of 30-70% at a temperature below the rate perature onset of recrystallization of not less than 150 ° C.