RU2833653C1 - Hot-rolled steel sheet and high-pressure vessel made from it - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, specifically to hot-rolled steel sheet with thickness of 5-150 mm, used as material for making vessels or boilers operating under high pressure in media containing hydrogen sulphide at temperatures from minus 60 °C to plus 110 °C. Sheet has the following chemical composition, wt.%: carbon is not more than 0.10, manganese 1.0-2.0, silicon 0.1-0.45, chrome not more than 1.0, nickel not more than 0.5, copper not more than 0.5, sulphur is not more than 0.005, phosphorus not more than 0.015, aluminium 0.02-0.06, titanium 0.001-0.15, niobium 0.001-0.15, vanadium 0.001-0.15, nitrogen not more than 0.010, boron not more than 0.0015, iron and unavoidable impurities – the rest. Steel sheet has the following mechanical properties at a temperature of plus 20 °C: yield point is not less than 360 MPa, ultimate strength is not less than 490 MPa, relative elongation is not less than 19%, hardness HB is not more than 220. Steel sheet has the following mechanical properties at a temperature of plus 110 °C: yield point of not less than 310 MPa, ultimate strength of not less than 440 MPa, hydrogen induced cracking (HIC) CLR of not more than 6%, resistance to hydrogen induced cracking (HIC) CTR of not more than 3%, resistance to hydrogen sulphide stress cracking (SSC) of not less than 80% of the minimum yield strength, KCV at minus 40 °C not less than 29 J/cm², KCU at minus 60 °C is not less than 39 J/cm².

EFFECT: improved operational properties of petrochemical equipment made from steel sheet.

6 cl, 2 tbl, 1 ex

Description

The invention relates to the field of metallurgy, more specifically to vessels or boilers operating under high pressure (or vacuum) in environments containing hydrogen sulfide, at temperatures from minus 60°C to plus 110°C and made of low-alloy steel.

Currently, steel grade 20YuCh (according to TU 14-1-4853-2017) is mainly used for the manufacture of vessels operating in environments with increased hydrogen sulfide content under excess pressure. This steel does not meet modern requirements for steels for the further production of vessels or devices operating under pressure in a wet hydrogen sulfide environment, namely: the steel is characterized by a low set of mechanical properties and does not have sufficient corrosion resistance.

A method is known for producing hot-rolled sheet metal from low-alloy steel used in the production of boilers and vessels operating under high pressure. In this case, the sheets are obtained from a slab containing the following elements, wt. %: C = 0.22-0.26, Si = 0.30-0.40; Mn = 0.75-1.10, Al = 0.01-0.035, Nb = 0.03-0.05, Cr no more than 0.3, Ni no more than 0.3, Cu no more than 0.3, S no more than 0.010, P no more than 0.015, N no more than 0.008, V no more than 0.05, Ti no more than 0.05, Fe - the rest [patent RU 2613262, C21D8 / 02, C22C38 / 58, B21B1 / 26, 2017].

The disadvantage of sheets obtained using this method is their low corrosion resistance.

An ultra-thick steel sheet for a vessel and a method for its production are known. The sheet has a chemical composition containing in wt.%: C: 0.13-0.20, Si: ≤ 0.40, Mn: 1.00-1.60, P: ≤ 0.015, S: ≤ 0.005, Als: 0.01-0.05, Nb + V + Ti: ≤ 0.080, Ni: 0.20-0.50, Cu: ≤ 0.30, H: ≤ 2 ppm, the rest is Fe and inevitable impurities [patent RU 2797390, C22C38/14, C22C38/12, C21D8/02, 2023].

Another disadvantage of this sheet is that it does not have sufficient corrosion resistance, and is also available in a narrow range of thicknesses - 60-100 mm.

The technical task of the invention consists in increasing the operational properties of petrochemical equipment (including high-pressure vessels) operated in a hydrogen sulfide environment, due to their production from steel sheets with increased strength and corrosion-resistant properties, in a thickness range from 5 to 150 mm.

The stated objective is achieved by the fact that the hot-rolled steel sheet with a thickness of 5–150 mm, according to the invention, has the following chemical composition, wt.%:

Carbon no more than 0.10 Manganese 1.0 – 2.0 Silicon 0.1 – 0.45 Chromium no more than 1.0 Nickel no more than 0.5 Copper no more than 0.5 Sulfur no more than 0.005 Phosphorus no more than 0.015 Aluminum 0.02 – 0.06 Titanium 0.001 – 0.15 Niobium 0.001 – 0.15 Vanadium 0.001 – 0.15 Nitrogen no more than 0.010 Boron no more than 0.0015

Iron and inevitable impurities are the rest,

Moreover, the steel sheet has the following mechanical properties at a temperature of plus 20°C:

yield strength not less than 360 MPa,

tensile strength not less than 490 MPa,

relative elongation not less than 19%

hardness HB, no more than 220,

and the following mechanical properties at a temperature of plus 110 °C:

yield strength not less than 310 MPa,

tensile strength not less than 440 MPa,

and also:

resistance to hydrogen induced cracking (HIC) CLR not more than 6%,

resistance to hydrogen induced cracking (HIC) CTR not more than 3%,

resistance to hydrogen sulphide stress cracking (SSC) of at least 80% of the minimum yield strength,

KCV at minus 40°C is not less than 29 J/ ^cm2 ,

KCU at minus 60°C is not less than 39 J/ ^cm2 .

Hot rolled steel sheet has a ferrite-bainite structure with a grain size no larger than number 10.

The content of oxide non-metallic inclusions in hot-rolled sheet does not exceed 2.5 points on average, and the content of silicate non-metallic inclusions does not exceed 3.0 points on average.

The stated objective is also achieved by the fact that, according to the invention, the high-pressure vessel is made of a steel sheet with a thickness of 5–150 mm and has the following chemical composition, wt.%:

Carbon no more than 0.10 Manganese 1.0 – 2.0 Silicon0.1 – 0.45 Silicon0.1 – 0.45 Chromium no more than 1.0 Nickel no more than 0.5 Copper no more than 0.5 Sulfur no more than 0.005 Phosphorus no more than 0.015 Aluminum 0.02 – 0.06 Titanium 0.001 – 0.15 Niobium 0.001 – 0.15 Vanadium 0.001 – 0.15 Nitrogen no more than 0.010 Boron no more than 0.0015

Iron and inevitable impurities are the rest,

Moreover, the steel sheet has the following mechanical properties at a temperature of plus 20°C:

yield strength not less than 360 MPa,

tensile strength not less than 490 MPa,

relative elongation not less than 19%

hardness HB, no more than 220,

and the following mechanical properties at a temperature of plus 110 °C:

yield strength not less than 310 MPa,

tensile strength not less than 440 MPa,

and also:

resistance to hydrogen induced cracking (HIC) CLR not more than 6%,

resistance to hydrogen induced cracking (HIC) CTR not more than 3%,

resistance to hydrogen sulphide stress cracking (SSC) of at least 80% of the minimum yield strength,

KCV at minus 40°C is not less than 29 J/ ^cm2 ,

KCU at minus 60°C is not less than 39 J/ ^cm2 .

The steel sheet has a ferrite-bainite structure with a grain size no larger than number 10.

The content of oxide non-metallic inclusions in the steel sheet does not exceed 2.5 points on average, and the content of silicate non-metallic inclusions in the steel sheet does not exceed 3.0 points on average.

The essence of the invention.

The content of chemical elements in the specified ratios ensures the necessary mechanical properties of the sheets intended for production.

Carbon is necessary to achieve the required strength of steel, but its addition in an amount greater than 0.10% leads to a deterioration in the plastic properties of steel.

Manganese increases the degree of saturation of ferrite with dissolved elements involved in the dispersion hardening mechanism, deoxidizes and strengthens steel, and binds sulfur. In addition, manganese is also an element that stabilizes austenite at high temperatures. To achieve the required mechanical properties of the sheet, the manganese content in steel should be in the range of 1.0 - 2.0%.

Silicon deoxidizes and strengthens steel. To ensure the required level of deoxidation and strength, the silicon content in steel must be at least 0.10%. Increasing the silicon content above 0.45% increases the steel's tendency to crack formation.

Complex alloying with chromium, copper and nickel in the stated ranges contributes to increased strength characteristics, corrosion resistance and cold resistance.

When alloying with chromium, the corrosion products are enriched with chromium in the layers adjacent to the surface of the sheet metal, but at a concentration of more than 1.0%, the plasticity of the sheets decreases below the permissible level.

Nickel helps to increase the stability of austenite and prevents the sheets from softening when heated.

The introduction of copper leads to the formation of a protective film on the surface of the sheet, which prevents hydrogen from penetrating into the steel, thereby increasing the resistance of the rolled product to hydrogen embrittlement.

Sulfur and phosphorus are harmful impurities, therefore their designated values of no more than 0.005% and no more than 0.015%, respectively, are necessary to obtain high mechanical properties of steel.

Aluminum deoxidizes and modifies steel, binds nitrogen into nitrides. To reduce the oxygen content in molten steel, it is necessary to add at least 0.02% aluminum. When its content is more than 0.06%, the viscoplastic properties of steel decrease.

Niobium and titanium are strong carbonitride-forming elements. At the same time, they contribute to the formation of a cellular dislocation microstructure of steel, which provides a combination of high strength characteristics and high impact toughness. The content of titanium and niobium in an amount of more than 0.15% each contributes to the formation of an excess amount of poorly soluble impurities that tend to move to the boundaries, which are areas with lower density, enrich the grain boundaries and embrittle the steel. When the content of titanium and niobium in steel is less than 0.001% each, a decrease in the mechanical properties of steel is observed.

Microalloying with vanadium inhibits the growth of austenite grains during heating and rolling, and also strengthens the steel due to the formation of carbide and carbonitride inclusions. Vanadium content in the amount of 0.001 - 0.15% helps to obtain a developed fine-dispersed microstructure in steel and provides a combination of high strength and plastic properties.

Nitrogen is necessary for the release of finely dispersed nitrides to inhibit the growth of austenite grains. When the nitrogen content exceeds 0.010%, its concentration in the solid solution increases, which worsens the impact toughness and crack resistance of steel.

To increase low-temperature impact toughness, as well as to increase the hardenability of steel, boron is added in an amount of no more than 0.0015%.

A ferrite-bainite structure with a grain size no larger than number 10 is necessary to ensure a given set of mechanical properties of the sheet over its entire area and thickness.

The content of oxide non-metallic inclusions in the steel sheet should not exceed 2.5 points on average, and the content of silicate non-metallic inclusions in the steel sheet should not exceed 3.0 points on average.

Low content of non-metallic inclusions (no more than 2.5 points on average for oxide non-metallic inclusions and 3.0 points on average for silicate non-metallic inclusions) allows achieving in sheets the required set of strength and plastic properties at room temperature, the required set of strength properties at elevated temperature (110°C), as well as high impact toughness values in the entire range of test temperatures down to -60°C.

The test of sheet material for resistance to hydrogen induced cracking (HIC) is carried out according to NACE TM 0284 (environment A); for resistance to sulfide stress cracking in _H2S -containing environments (SSC) according to NACE TM 0177 (method A).

The declared thickness of sheets of 5 - 150 mm, as well as the complex of their mechanical properties both at a temperature of plus 20 °C and at a temperature of plus 110 °C, allow the production of vessels or boilers operating under high pressure (or vacuum) with increased consumer properties, of various sizes and purposes.

Example.

Under the conditions of PAO Severstal, sheets of various thicknesses were produced, from which vessels/boilers operating under high pressure (or vacuum) were then manufactured. The chemical composition of the sheets is given in Table 1. The parameters of the sheets are given in Table 2.

Subsequent operation of the vessel (absorber) made from the specified sheets showed that due to increased corrosion resistance, it was possible to extend the period of its operation without repairs, and it was also possible to reduce the metal consumption of the absorber (by more than 10%) due to the use of sheets with increased performance characteristics, which in turn made it possible to reduce the load on the foundation.

Table 1

Mass fraction of chemical elements, wt. %

Chemical composition C Si Mn P S Cr Ni Cu Al N ₂ V You Nb B Fe 1 0.055 0.17 1.6 0,008 0,0016 0.16 0.31 0.092 0.03 0.005 0.11 0,011 0.03 0,0003 rest 2 0.057 0.23 1.7 0,009 0,0016 0.73 0.01 0.32 0.05 0.008 0.003 0.006 0.06 0,0008 rest 3 0.079 0.31 1.8 0,009 0.0023 0.24 0.16 0,009 0.05 0,008 0,021 0.082 0.08 0,0003 rest

Table 2

Technological parameters of sheet production ^*

Chemical composition Sheet thickness, mm Yield strength at 20 °C, MPa Tensile strength at 20 °C, MPa Relative elongation at 20 °C, MPa Hardness, HB Yield strength at 110 °C, MPa Tensile strength at 110 °C, MPa (HIC) CLR, % (HIC) CTR, % SSC, % KCV at minus 40°C, J/ ^cm2 KCU at minus 60°C, J/ ^cm2 Micro-structure 1 12 500 620 25.0 184 470 540 0 0 80 446 431 F 40% + B 60% 2 12 523 650 23.3 189 492 570 0 0 80 429 420 F 35% + B 65% 3 12 553 671 21.5 196 519 596 1.82 0.15 80 404 407 F 30% + B 70% 1 105 460 560 28.0 177 420 500 0 0 80 450 440 F 50% + B 50% 2 105 487 585 26.5 181 442 525 0 0 80 438 420 F 45% + B 55% 3 105 515 613 22.0 187 465 555 2.14 0.17 80 424 397 F 40% + B 60%

* - in the experiments, the content of oxide non-metallic inclusions in the steel sheet did not exceed 2.0 points by average value, and the content of silicate non-metallic inclusions in the steel sheet did not exceed 2.5 points by average value.

- the structure was characterized by a grain size of 11-12 numbers.

Claims (36)

1. Hot rolled steel sheet with a thickness of 5-150 mm, characterized by having the following chemical composition, wt.%: carbon no more than 0.10 manganese 1.0-2.0 silicon 0.1-0.45 chrome no more than 1.0 nickel no more than 0.5 copper no more than 0.5 sulfur no more than 0.005 phosphorus no more than 0.015 aluminum 0.02-0.06 Titanium 0.001-0.15 niobium 0.001-0.15 vanadium 0.001-0.15 nitrogen no more than 0.010 boron no more than 0.0015 iron and inevitable impurities rest, Moreover, the steel sheet has the following mechanical properties at a temperature of plus 20°C: yield strength not less than 360 MPa, tensile strength not less than 490 MPa, relative elongation of not less than 19%, hardness HB no more than 220, and the following mechanical properties at a temperature of plus 110°C: yield strength not less than 310 MPa, tensile strength not less than 440 MPa, and also: resistance to hydrogen induced cracking (HIC) CLR not more than 6%, resistance to hydrogen induced cracking (HIC) CTR not more than 3%, resistance to hydrogen sulphide stress cracking (SSC) of at least 80% of the minimum yield strength, KCV at minus 40°C is not less than 29 J/ ^cm2 , KCU at minus 60°C is not less than 39 J/ ^cm2 . 2. A steel sheet according to item 1, characterized in that it has a ferrite-bainite structure with a grain size no larger than number 10. 3. A steel sheet according to paragraph 1, characterized in that the content of oxide non-metallic inclusions therein does not exceed 2.5 points by average value, and the content of silicate non-metallic inclusions does not exceed 3.0 points by average value. 4. A high-pressure vessel, characterized by the fact that it is made of a steel sheet 5-150 mm thick, having the following chemical composition, wt.%: carbon no more than 0.10 manganese 1.0-2.0 silicon 0.1-0.45 chrome no more than 1.0 nickel no more than 0.5 copper no more than 0.5 sulfur no more than 0.005 phosphorus no more than 0.015 aluminum 0.02-0.06 Titanium 0.001-0.15 niobium 0.001-0.15 vanadium 0.001-0.15 nitrogen no more than 0.010 boron no more than 0.0015 iron and inevitable impurities the rest, Moreover, the steel sheet has the following mechanical properties at a temperature of plus 20°C: yield strength not less than 360 MPa, tensile strength not less than 490 MPa, relative elongation of not less than 19%, hardness HB no more than 220 and the following mechanical properties at a temperature of plus 110°C: yield strength not less than 310 MPa, tensile strength not less than 440 MPa, and also: resistance to hydrogen induced cracking (HIC) CLR not more than 6%, resistance to hydrogen induced cracking (HIC) CTR not more than 3%, resistance to hydrogen sulphide stress cracking (SSC) of at least 80% of the minimum yield strength, KCV at minus 40°C is not less than 29 J/ ^cm2 , KCU at minus 60°C is not less than 39 J/ ^cm2 . 5. A vessel according to item 4, characterized in that the steel sheet has a ferrite-bainite structure with a grain size no larger than number 10. 6. A vessel according to item 4, characterized in that the content of oxide non-metallic inclusions in the steel sheet does not exceed 2.5 points on average, and the content of silicate non-metallic inclusions in the steel sheet does not exceed 3.0 points on average.