UA82568C2 - Steel with high corrosion resistance and pipes, made of it - Google Patents

Abstract

The invention relates to ferrous metallurgy, namely to the composition of steel with high corrosion resistance and seamless pipes made of it. The steel contains: carbon 0.04-0.065, manganese 0.40-0.65, silicon 0.15-0.40, chromium 1.03-1.30, columbium 0.02-0.60, vanadium 0.02-0.06, aluminium 0.02-0.06, nickel no more than 0.25, copper no more than 0.25, sulfur no more than 0.020, phosphorus no more than 0.020, and the rest – ferrous and inevitable impurities, mass %. The content of chromium, columbium, vanadium, carbon and manganese should correspond to ratio ([Cr]+[Nb]+[V])/([C]+0,2[Mn])>6.5. The seamless pipes are made of declared steel that has value of the carbon equivalent calculated under the formula:, no more than 0.40, and streak structures are not more than 1,5 mark. The technical result is the increasing of corrosion resistance of steel and pipes.

Description

Description of the invention

The invention relates to metallurgy, namely to the composition of low-alloy steel of increased corrosion 2 resistance for the production of pipes and seamless pipes made of it and can be used in the construction of pipelines, in particular oil and gas pipelines of high corrosion resistance in water oil production environments with an increased content of carbon dioxide, carbon dioxide, chlorides, hydrogen sulfide, mechanical impurities and other components, as well as for the transportation of formation waters, oil, petroleum products and hydrated gas and for other purposes. 70 Ordinary carbon steels under the specified conditions can be subject to general and local corrosion, stress corrosion cracking, hydrogen sulfide corrosion cracking, hydrogen embrittlement, etc., which leads to through corrosion damage to the pipeline. Therefore, the main requirements for such steels are high resistance against various types of corrosion damage with sufficient strength required for pipelines operating under pressure, as well as high viscosity, cold resistance and satisfactory 12 weldability. In connection with the significant volumes of use of such pipes, their cost should be relatively low, which excludes the possibility of using steels with a high content of precious alloying elements.

Well-known steel for the manufacture of pipes, containing the following components, wt. 9o:

Carbon 0.06-0.13

Silicon 0.15-0.40

Manganese 0.30-0.60

Chrome 0.40-0.70

Molybdenum 0.08-0.15

Aluminum 0.01-0.07 and.

Titanium 0.005-0.09 Ge)

Cerium 0.002-0.05

Iron is the rest, while the content of cerium, titanium, and aluminum in the steel corresponds to the condition: (patent of the Russian Federation Mo2122045, IPC C22С38/28, publ. 11/20/1998Y1. "about

This steel is used for the manufacture of main pipes for pumping oil products in conditions of northern latitudes and ensures resistance of pipes to sulphide corrosion cracking, good weldability in conditions of low temperatures while ensuring wear resistance. However, due to the insufficient content of chromium, the resistance of such steel, and therefore of pipes made of it, against local corrosion in water environments containing chlorine is low. In addition, alloying with chromium and molybdenum, as well as microalloying with titanium and cerium leads to to increase the cost of steel and pipes made of it.

Also known is steel for the manufacture of pipes, which contains, wt. 9b:

Carbon 0.24-0.28 "

Manganese 1.30-1.50 - s Silicon 0.15-0.35 s» Copper no more than 0.20

Chromium 0.13-0.20

Molybdenum 0.15-0.60

Aluminum 0.007-0.05 so Nitrogen no more than 0.02 ke Titanium 0.02-0.04

Boron 0.0007-0.0025 o Niobium 0.02-0.10 (ex) 50 Sulfur no more than 0.01

Phosphorus is no more than 0.03 so Iron is the rest (US patent Mo4784704, NKY 148/334, IPC C22С38/22, publ. 11/15/1998). This steel is used for 59 production of high-strength welded seamless pipes. The minimum yield strength of steel is 94.5 kg/mm 2,

F! minimum elongation 1595. Despite the high strength and satisfactory plasticity, the corrosion resistance of such steel, and therefore of its pipes, in the environments of oil fields, especially those containing chlorides and hydrogen sulfide, is insufficient. In addition, due to the high total content of carbon, chromium and manganese, steel and pipes made of it have a high carbon equivalent, which impairs their weldability, especially at negative temperatures, which limits their use.

Also known is steel for the manufacture of pipes, which contains, wt. 9b:

Carbon 0.13-0.17

Manganese 0.45-0.65 b5 Silicon 0.17-0.37 -Д-

Sulfur not more than 0.015

Phosphorus is not more than 0.015

Chromium 0.4-0.7

Vanadium 0.04-0.06

Aluminum 0.02-0.04

Nickel no more than 02

Zalizo reshta, 70 YiKirsanov V., Krutsan R., Radkevich 0. and others. / Effect of heat treatment on corrosion resistance of 20HF type pipe steel in hydrogen sulfide environments. // Physico-chemical mechanics of materials. Lviv. - 20021.

This steel and seamless pipes made of it have higher corrosion resistance, as well as high strength and resistance to hydrogen sulfide stress cracking and hydrogen cracking after special heat treatment. However, the resistance against general and local corrosion in water/5 Environments containing chlorine ions and in some others is not high enough. In addition, in order to ensure resistance against hydrogen sulfide corrosion cracking, steel and pipes made of it must be subjected to a special heat treatment - hardening and tempering, which leads to significant energy consumption and an increase in the price of the specified metal products, which limits its use.

The closest analogue of the claimed invention is steel for the manufacture of pipes, containing the following components, wt.9o:

Carbon 0.07-0.30

Manganese 0.35-1.50

Silicon 0.15-0.70

Chrome 0.05-1.00 cm

Niobium 0.01-0.06 o

Nickel 0.05-0.50

Copper 0.05-0.50

Aluminum 0.01-0.05 s

Sulfur not more than 0.010

Phosphorus no more than 0.020 (Ce)

Calcium 0.0008-0.0020 and iron and inevitable impurities, including oxygen, the rest. with

Moreover, the content of carbon, manganese and silicon corresponds to the condition: 2(С1-0.1|(Мп|нО,4(|51)«0.63, where |СИ, ИМп) and (ЗИ со - the content of carbon, manganese and silicon respectively, by mass, while the content of calcium aluminates in the steel does not exceed 1 mm of inclusions, the oxygen content is no more than 0.3 of the aluminum content, and the sulphide score is no more than 1.0. Seamless pipes made of this steel, which has a striation of the structure no higher than 2 points (Patent

RF Mo2243284. MKY C22C38/42. 27.12.2004). "

Steel and seamless pipes made of it have increased corrosion resistance while maintaining strength, viscosity, cold resistance at satisfactory cost indicators. However, the presence of calcium aluminates and structural inhomogeneity in the steel (the striation of the structure is up to 2 points according to GOST 5640), as well as insufficient chromium content can lead to pitting and pitting corrosion in 5 aqueous chloride-containing environments (containing up to 150g/l chlorine ions), and at the same time contain carbon dioxide and, as a result, are characterized by increased acidity (pH less than 6.0). The result of this can be premature failure of pipelines due to local through corrosion damage. In addition, the declared ratio of the content of carbon, manganese and silicon (2ИС1-0.1|Мп1но,4(5И1«:0.63) does not ensure resistance against hydrogen sulfide corrosion cracking. ko Cold resistance and welding of steel and pipes made of it at temperatures below minus 6092С is not sufficiently high, which limits their use in the conditions of the Far North.

The basis of this invention is the solution to the problem of improving steel and pipes made of it by (22) changing the composition of steel, the ratio of its components and structural state - as a result of which it is ensured: c increased resistance against local corrosion of steel and pipes made of it, in highly aggressive oil industry environments that have high mineralization and contain up to 150 g/l of sodium chloride in combination with carbon dioxide at high acidity (pH less than 6.0), increased resistance to hydrogen sulfide corrosion cracking, resistance to hydrogen embrittlement, as well as increased cold resistance and improvement of weldability during the installation of pipelines, including in conditions of northern latitudes, (F) at a satisfactory cost of steel and pipes made of it. with The task is solved by the fact that according to item 1. steel containing carbon, manganese, silicon, chromium, niobium, aluminum, nickel, copper, sulfur, phosphorus, iron and inevitable impurities, according to the invention, additionally contains vanadium because with the following ratio of components, mass. 90:

Carbon 0.04-0.065

Manganese 0.40-0.65

Silicon 0.15-0.40 65 Chromium 1.03-1.3

Niobium 0.02-0.06

Vanadium 0.02-0.06

Aluminum 0.02-0.06

Nickel is no more than 0.25

Copper not more than 0.25

Sulfur not more than 0.020

Phosphorus is not more than 0.020

Iron and other inevitable impurities. 70 At the same time, the content of chromium, niobium, vanadium, carbon, and manganese should correspond to the ratio: of carbon equivalent, calculated according to the formula: с (3- са Мп уст in Меж Сы not more than 0.40, and -kE. B 5 157 striation of the structure is not higher than 1.5 points.

The ratio of the declared components was obtained experimentally.

The difference between the proposed steel and the closest analogues is in the reduction of the carbon content, the increase of the chromium content, and the introduction of vanadium into the composition while observing the ratio (dsp AMTY STO, 2|Mp1)26.5. Seamless pipes, which are made of steel according to p.i. with a carbon equivalent value of no more than 0.40 and striation of the structure no higher than 1.5 points.

The technical result of using the proposed composition is an increase in the corrosion resistance of steel and pipes made from it in aggressive oil industry environments with a high content of carbon dioxide, carbon dioxide, chlorides, hydrogen sulfide, mechanical impurities and other components, an increase in cold resistance at temperatures up to minus 602C, and an improvement in weldability when installing pipelines - while maintaining high mechanical and viscoplastic properties, as well as reducing the number of technological operations during the production of pipes and reducing their cost. As a result, it makes it possible to operate pipes in aggressive oil production environments without the use of expensive corrosion inhibitors, to expand the areas of use of steel and pipes made of it, including in the conditions of the Far North, to significantly increase the period of trouble-free operation of pipelines and to improve working conditions and the environment.

This is due to the fact that an increase in the chromium content, a decrease in the carbon content and the introduction of vanadium in the composition with the fulfillment of the ratio (Сп(Ме|АМИИС1О0.2|Мпии)) 26.5 contributes to: the formation of a homogeneous (with a banding lower than 1.5 points) of a structure clean of non-metallic inclusions, personally, of manganese sulfides; the formation of a passive protective oxide film with an increased approx. 2 times compared to the base metal with chromium content, which increases resistance against local and general c 3З5 Corrosion, as well as resistance against hydrogen sulfide corrosion cracking and hydrogen embrittlement, in addition, c increases the strength characteristics of steel and pipes while maintaining high viscosity and plasticity and satisfactory weldability at negative temperatures - due to the low value of the carbon equivalent of no more than 0.40.

Steels were obtained with the content of components that correspond to what is declared, as well as those that go beyond the "limits that are declared and the composition that corresponds to the closest analogues. The specified compositions are shown in Table 1. 2. The molten steels were poured into ingots with a diameter of 200 mm, rolled into pipe blanks with a diameter of 120 mm, and then rolled on an automatic TPA 140 machine into seamless hot-deformed pipes with dimensions "» w114xX9, mm. Pipes made of steels corresponding to those declared were manufactured using the energy-saving technology of normalization rolling, without heat treatment from separate heating. Steel pipes of the closest analogues were additionally subjected to normalization at a temperature of 900-9302С from separate heating. со с 175 1 z | 3 5 g 5

F Mavenshe 1111111111101091 St. Blo | ol | sli about these 00000001 56014301 lay 0 lav0bmv dev 00011111 0060061 about 0002 00100 zv Your 00000001 007010о60оок ооо длюмны 11110011 002 10560002 00757 боків1701 7" 009 035 05 yu vo vi 1101-01-11 11-11 ov field assimilation; 01570156 182 | with | 58 | 20 bo Value of carbon equivalent (Ce) 0.44 0.39 0.38 0.39 0.53 0.47 zskolmieyavi 33333331 - 1-1 1-1 | o5 in 1mmZ 1.5 - compositions with a ratio that exceeds the proposed limits; 6 - steel composition corresponding to the closest analogues.

The striation of the structure was determined on the pipes according to GOST 5640, and samples were also taken for 7/0 Comprehensive mechanical and corrosion tests and weldability tests. Tensile tests were carried out according to GOST 10006 on turned samples of round section with a diameter of the working part of 5 mm and a length of

B5 Ohm, impact toughness tests at a temperature of minus 60 "С were carried out according to GOST 9454 on longitudinal samples with a sharp cut ("Sharpy" type) made of the base metal, and on welded samples; special corrosion tests for resistance against local corrosion, general corrosion, hydrogen sulfide cracking 75 | hydrogen embrittlement - was carried out according to the following methods: 1) proposed in the work of V.M. Lipovskikh,

Kashinskogo V.I., Reformatskaya I.I. etc. "Protection of metals". 1999, vol. 35 Mob, p. 653-655 (we determined the rate of development of pitting in hot water (steam) at a temperature of (135 -15)2С, containing B5Omg/l of chlorine ions, 5Omg/l of sulfate ions and 2Omg/ l of oxygen, at a pH of 8.5-9.5, the duration of the tests is 3 months); 2) by determining the corrosion potentials of steels in a 1N solution of sodium chloride by an electrochemical method - on flat samples with a working surface of 1-1 cm -; 3) according to the MACE TM 0177 method (testing for resistance to hydrogen sulfide stress corrosion cracking in an environment of composition: 595 sodium chloride, 0.595 acetic acid,

ZbbOmg/l of hydrogen sulfide, at pH-4-5 and a tensile stress equal to 70905 from the yield point of steel (0.7 b02), for 720 hours - on circular cross-section samples with a diameter of the working part of 6.2 mm; 4) according to the MACE TM 0284 method (testing of flat samples for hydrogen embrittlement in a solution of the MACE TM 0177 method for 92 hours); 5). C test for general corrosion of flat samples in the solution of the MACE TM 0177 method, but without hydrogen sulfide; 6) in the oil industry environment of the oil and gas production management "Okhtyrka-naftogaz" of the Sumy region, Ukraine (chlorcalcium type water composition (g/l): НСОз- - 0.40; SI- - 146; (Ma"K") - 54 ,2; Ca 2" - 29.8; Ma" - 52; 50.27 - 0.66; (Vg" yan") - 0.35; total mineralization - 235; CO" - 58.2 mg/l; Noz - 5-10mg/l; pH-4.8) - within 120 days. The results of the tests are presented in Tables 2-3. oo (Se)

Metal! 11111101 The result of the corroder produced 1110 y and (rate (potential to cracking (coefficients of length and (rate (rate of local corrosion, corrosion, mV) samples, hours) width of cracks, 95) corrosion, mm/year) corrosion, mm/year) s mm/rii) 90 I enter the blshet 00010000 blo? 0 won 781 ovhyuvy 1 zv3000vlshetyu 10001010 oovoi 0 bogom « 4 40 zvo 100300 ticket 110 ooeolo 0 ootosyu From c. in | oyavogyu lm //17BBO 01 zib bozo! | what? about Ma 10000110 Mekanyai vlasmyut 1000

Strength limit of st; N/mm2 Yield strength, N/mm2 Relative elongation 55 96). Impact viscosity of KSU, Jim? and (welded seam)

Fi

FO syu sv 81000100 vv 01000050 tva avu zro i 7" - fragile fracture of samples. co

The analysis of the presented data shows that the steel compositions of options 2-4, corresponding to the claims of the invention, 60 provide high mechanical properties (strength limit, yield limit, relative elongation), high viscoplastic characteristics (impact strength at negative temperatures and 80- 10095 of the viscous component in the fracture of the samples after the tests), high corrosion resistance - against local corrosion (the rate of local corrosion is no more than 0.4 mm/year, the corrosion potential of samples in a chloride-containing environment is more positive than minus 400mV), against general corrosion (the rate corrosion depending on the environment is 0.07-0.12 mm/year), against 65 hydrogen sulphide stress corrosion cracking (the samples did not collapse in the environment of the MACE standard

TM 0177, containing hydrogen sulfide, for the basic test time of 720 hours at a voltage equal to 0.7 so)

and against hydrogen embrittlement (longitudinal and transverse cracks on the samples after tests in a hydrogen sulfide environment were absent), as well as satisfactory weldability and high viscoplastic properties of the welded seam at negative temperatures.

Compositions of steel and pipes with out-of-bounds values (compositions 1 and 5) have 1.5-2 times lower resistance against local corrosion, 2-5 times lower resistance against general corrosion in an aggressive oil industry environment, do not pass resistance tests against hydrogen sulfide cracking according to the MACE TM 0177 method. In addition, composition 5 has insufficient impact toughness of steel, pipes made of it, and welded joints at negative temperatures, which limits their use. 70 The steel corresponding to the closest analogues (steel 6) has reduced resistance against local and general corrosion and against hydrogen sulfide corrosion cracking, as well as steel, its pipes and welded joints have insufficient viscoplastic characteristics at negative temperatures, which limits their use.

Thus, the use of the proposed steel of increased corrosion resistance and pipes made of it provides a significant increase in resistance against local and general corrosion in highly aggressive 7/5 oil production environments, as well as resistance against hydrogen sulfide cracking in combination with high mechanical and viscoplastic properties and high cold resistance, with satisfactory weldability, including at temperatures down to minus b02С and the low cost of steel and seamless pipes made from it.

Ultimately, this will lead to a significant increase in the period of trouble-free operation of pipelines, improvement of working conditions and the environment.

Claims (1)

The formula of the invention 1. Steel of increased corrosion resistance, which contains carbon, manganese, silicon, chromium, niobium, aluminum, nickel, copper, sulfur, phosphorus, iron and inevitable impurities, which is distinguished by the fact that it additionally contains vanadium with the following ratio of components, mass . 90: (o) carbon 0.04-0.065 manganese 0.40-0.65 (ge) silicon 0.15-0.40 and chromium 1.03-1.30 (se) niobium 0.02-0.06 n Io) vanadium 0.02-0.06 aluminum 0.02-0.06 s nickel no more than 0.25 so copper no more than 0.25 sulfur no more than 0.020 phosphorus no more than 0.020 iron and inevitable impurities the rest, " , WHAT . with 2. Seamless pipes of increased corrosion resistance, which are distinguished by the fact that they are made of steel according to claim 1, which has the value of the carbon equivalent calculated by the formula: y My St M Mia Su ; no more than 0.40, and striation of the structure no higher than 1.5 points. Seq (а) - ЯК - Я 5 СЯ Ж 8 65 Ж i 6 Ж - - (c) В 5 15 ko triigya i " : " " : : po Official bulletin "Industrial property". Book 1 "Inventions, useful models, topography of integrated Ge) microcircuits", 2008, M 8, 25.04.2008. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. Fuks of Ukraine") ko 60 b5