Steel for gas and oil pipelines

 

The invention relates to ferrous metallurgy, in particular to alloyed steels for steel products, and can be used in the production of gas and oil pipelines. The objective of the invention: improvement of mechanical properties of steel products operating at very low temperatures under conditions of corrosive environments that cause hydrogen cracking. Steel for gas and oil pipelines contains, by weight. %: carbon 0,02-0,07, manganese of 1.45 and 1.80, silicon 0,03-0,10, vanadium 0,10-0,12, aluminum 0,03-0,05, sulfur0,010, phosphorus0,012, nitrogen 0,003-0,005 (calcium + barium + magnesium) 0,07-0,10, iron - rest. We offer steel provides high impact strength at very low temperatures (-70)oC and a high level of mechanical properties and corrosion resistance against hydrogen cracking exposed to corrosive environments containing hydrogen sulfide. table 2.

The invention relates to ferrous metallurgy, in particular to alloyed steels for steel products, and can be used in the production of gas and oil pipelines operating at very low temperatures under conditions of corrosive environments, calls the Mac. %: carbon - 0,11, manganese - 1,61, silicon - 1,30, sulfur - 0,004, phosphorus - 0,014, chrome - 0.03, Nickel - 0,02, copper - 0,01, aluminum - 0,021, titanium - 0,14 (C. I. Alimov, V. N. NEPAD, Century, Onoprienko and other Local properties of rolled sheet large diameter. Metallurgical and mining industry, 1998. - 3 - C. 20-21).

Known steel X70 specified structure provides the following mechanical properties: ultimate strengthin= 590 H/mm2yield strengtht= 580 H/mm2, elongation5= 24%, toughness KCV-60=146 j/cm2.

The disadvantages of the known steel is a poor machinability by cutting edges of the sheets before they are formed into tubes and susceptibility to hydrogen cracking when used in corrosive environments, especially at very low temperatures of the order of (-70)oC. in Addition, steel is expensive and scarce.

The closest analogue of the present invention is a steel for main oil and gas pipelines that contains components in the following ratio, wt.%: carbon 0.05 to 0.15, silicon - 0,30-0,90, manganese - 0,40-0,90, vanadium - 0,05-0,20, niobium 0,01-0,08, al.02.2002).

Signs nearest analogue, coinciding with the essential features of the claimed invention: available in carbon steel, manganese, silicon, vanadium, aluminum, iron, and sulfur and phosphorus.

Known steel for the nearest similar after corresponding processing is characterized by the following properties: ultimate strengthin= 510-630 H/mm2yield strengtht=360 N/mm2, elongation5= 24%, toughness KCV-60=59 j/cm2the General corrosion rate Q=0.5 mm/year, the value of the threshold load P70%tthe ratio of crack length CLR 3%, the ratio of the width of the crack P 6%.

The disadvantages of the known steel is insufficient impact strength at very low temperatures (-70)oWith insufficient corrosion resistance and susceptibility to hydrogen embrittlement, especially in corrosive environments containing hydrogen sulfide. The heterogeneity of the fine crystal structure in this steel, which is expressed in an inhomogeneous distribution of dislocations leads when operating in such environments, the pre is here.

The basis of the invention is the task of such improvements composition of steel for gas and oil pipelines, mainly 500-800 mm in diameter, which would increase the impact strength at very low temperatures (-70)oWith a high level of mechanical properties and corrosion resistance against hydrogen cracking exposed to corrosive environments containing hydrogen sulfide due to the optimum content of components in steel and its structure in the finished products.

The problem is solved in that the steel for gas and oil pipelines containing carbon, manganese, silicon, vanadium, aluminum, iron, and impurities of sulfur and phosphorus, according to the invention additionally contain nitrogen and a group of alkaline earth metals calcium, barium and magnesium in the following ratio, wt.%: Carbon - 0,02-0,07 Manganese - Of 1.45 And 1.80 Silicon - 0,03-0,10 vanadium - 0,10-0,12 Aluminum - 0,03-0,05 Sulfur - 0,010 Phosphorus - 0.012 Nitrogen - 0,003-0,005 (calcium + barium + magnesium) - 0,07-0,10
Iron - Rest
We offer steel for gas and oil pipelines, mainly 500-800 mm in diameter has an impact strength at (-70)oWith KCV-70=45 j/cm2at a high level of other mechanical yield strengtht=560 N/mm2, elongation5=23%, the rate of General corrosion Q=0.35 mm/year, the value of the threshold pressure that leads to hydrogen cracking due to hydrogen embrittlement P75%t. In addition, steel has good weldability and satisfactory cutability, which is important when handling edges billets.

The carbon content in the inventive steel and low is 0.02-0.07 wt. %. It provides high ductility and weldability of steel, including at very low temperatures. To get less than 0.02 wt.% carbon in the smelting difficult and it is not necessary, as and when declared carbon content is not blocked by the moving dislocations, providing high ductility and toughness. This is not guaranteed when the carbon content is more than 0.07 wt.% and therefore, a higher carbon content in the steel is impractical.

Manganese is contained in the range of 1.45 and 1.80 wt.%. In such quantities it dissolves in the ferrite, is included in the cementite and carbides as alloying element and thereby provides high strength steel. When the content of men who, is use which because of the tendency to segregation can produce highly enriched in manganese microvolumes, which results in subsequent to the receipt of non-equilibrium structures, especially in the post-weld cooling and, consequently, to the formation of cracks, and reduced toughness at very low temperatures.

The silicon in the inventive steel is contained within the boundaries of 0.03-0.10 wt.%. Sufficient recyclenet steel at such a low content of silicon is achieved by a high content of aluminum and manganese, and technological methods of treatment of liquid steel, but it is not sensible reduction in silicon content below 0.03 wt.%. When the content is more than 0.10 wt.% silicon increases the amount of silicate inclusions, and it reduces the impact strength especially at very low temperatures, contributes to the embrittlement of the steel and increase the amount of corrosion microgalvanic elements.

The vanadium content in the inventive steel is 0.10 and 0.12 wt.%, that provides fine grain steel, the formation of hardening carbonitrides and additional deoxidation. When the content is less than 0.10 wt.% vanadium, these effects are insufficient, and the properties of the steel are reduced. The excess of vanadium in excess of 0.12 wt.% n the AC.% introduced in the inventive steel as rescissory and the modifying element; it also forms a nitrogen nitrides, reinforcing steel. When the content of aluminum is less than 0.03 wt.% the lack of effect of deoxidation in combination with other elements, when the content exceeds 0.05 wt. % aluminum can be a lot of alumina inclusions, which reduces the ductility and toughness of steel at low temperatures.

In the inventive steel sulfur content is limited to the upper limit 0,010 wt. % and the phosphorus - 0,012 wt.%. At a higher sulfur content increases the amount of sulfides, reduced the ductility of the steel deteriorates corrosion resistance, increased susceptibility to hydrogen embrittlement. When the content is more of a 0.012 wt.% phosphorus steel becomes more prone to brittle fracture at very low temperatures.

The nitrogen in the steel is limited to within 0.003 to 0.005 wt.%. When the content of nitrogen is less of 0.003 wt. % not provided a sufficient amount of carbonitrides in the role of hardening phases. When the nitrogen content of more than 0.005 wt. % may show the effect of aging leads to a decrease in the ductility of steel.

The group of alkaline earth metals calcium, barium and magnesium is entered in the total amount of 0.07 to 0.10 wt.%. These elements enhance the action of each other and obespecivaet the 7 wt.% the effect is not achieved and elongated sulfides play the role of hubs voltage, when the total content of elements greater of 0.10 wt.% steel polluted with excessive amounts of non-metallic inclusions, which reduces the impact strength, especially at low temperatures.

Variant implementation of the invention, not excluding other options in the scope of the claims.

Experienced steel smelted in a semi-industrial induction crucible furnace with crucible capacity 30 kg In the preparation of the charge used a scrap of low-carbon steels with small and controlled amount of impurities. For comparison, in the same conditions smelted steel with chemical composition as the nearest equivalent. The chemical composition of the steels are given in table 1.

The obtained ingots weighing 25-28 kg forged into billets 35160 mm, and then rolled into strips of a thickness of 18 mm From strips produced samples for heat treatment, mechanical, corrosion testing and evaluation of weldability. Mechanical testing was performed according to current standards. Corrosion tests were carried out in tap water, which was previously saturated with hydrogen sulfide to 15-15 mg/l and pH was 7.45. Evaluated the rate of General corrosion and the value of the threshold stress at which at which reflect the quality of the weld and heat-affected zone.

Comparative properties experienced and known are shown in table 2, which shows that mechanical properties and corrosion resistance of the inventive steel is substantially outweighed known at high values of impact strength at very low temperatures. The inventive steel is well welded at low temperatures.


Claims

Steel for gas and oil pipelines containing carbon, manganese, silicon, vanadium, aluminum, iron, and impurities of sulfur and phosphorus, characterized in that it further contains nitrogen and the group of the alkaline earth metals calcium, barium and magnesium in the following ratio, wt.%:

Carbon 0,02-0,07

Manganese is 1.45 and 1.80

Silicon 0,03-0,10

Vanadium 0,10-0,12

Aluminum 0,03-0,05

Sulfur0,010

Phosphorus0,012

Nitrogen 0,003-0,005

Calcium + barium + magnesium 0,07-0,10

Iron Rest

 

Same patents:

The invention relates to ferrous metallurgy and can be used in the disc brake device of the cars and other vehicles

The invention relates to rolling production, particularly modes of rolling strips of low-alloy steels in continuous broadband mill

The invention relates to metal finish the wire and to a method of manufacturing the wire

The invention relates to metallurgy and can be used in the manufacture of welded hot rolled bar reinforcement class AS for concrete structures

The invention relates to high-strength steel and its manufacture

Steel // 2100470
The invention relates to ferrous metallurgy, in particular to steel used in chemical engineering for parts and welded steel elements

Maraging steel // 2073738
The invention relates to the field of metallurgy, namely the composition of Maraging high strength steel loaded for critical parts

Steel // 2064522
The invention relates to the field of ferrous metallurgy, in particular to the composition of steel and can be used in the production of high-strength rod deformed bars, as well as for the manufacture of prestressed concrete structures

Die steel // 2041968
The invention relates to metallurgy, in particular to steel for the manufacture of cold forming dies, and can be used in mechanical engineering, aviation and other industries

The invention relates to metallurgy, in particular to the structural steel for the manufacture of shells of containers for storage and transportation of spent nuclear fuel

FIELD: metallurgy; precision casting alloys at low thermal expansion; flying vehicles; opto-electronic engineering; laser engineering precision instrumentation engineering.

SUBSTANCE: proposed method is used for manufacture of parts working in contact with quartz, silicon, silicon carbide and other non-metals. Iron-based casting alloy contains the following constituents, mass-%: nickel, 31.0-32.5; cobalt, 9.4-11.0; molybdenum, 0.4-0.6; rare-earth elements: cerium, lanthanum, praseodymium, neodymium, total 0.04-0.25; the remainder being iron. Proposed casting alloy has reduced average temperature linear expansion coefficient within the following temperature ranges: 20-400°C, 20-450°C and 20-500°C.

EFFECT: enhanced resistance to cracking; enhanced homogeneity to temperature of minus 60°C.

5 tbl

FIELD: ferrous metallurgy; production of dispersion-hardening austenitic steel with memory of the form.

SUBSTANCE: the invention is pertaining to the field of ferrous metallurgy, in particular, to production of dispersion-hardening austenitic steel with effect of memory of the form (EMF), which may be used, for example, at manufacture of couplings at the seamless connection of the pipelines, fuel pipes and at manufacture of power units in the different types of security and fire-fighting automation. The stated steel contains ingredients in the following ratio (in mass %): Carbon - 0.25-0.5; manganese - 16-25; silicon - 1-3; vanadium - 1.1-3; tungsten - 0.1-3; niobium - 0.1-1 and iron - the rest. At that the ratio of (V+Nb) to carbon should be not less than 6, and the total amount of carbide-forming elements (V+Nb+W) - not less than 1.8 %. At that the steel may additionally contain 0.1-3 mass % of molybdenum. The technical result of the invention is an increased EMF and the strength of the steel. Alloys with the EMF based on iron are the most low-cost and technologic in the production.

EFFECT: the invention ensures an increased effect of memory of the form (EMF) and the strength of the steel and production of alloys with the EMF based on iron as the most low-cost and technologic in the field.

2 cl, 2 dwg, 2 tbl

FIELD: metallurgy; production of round calibrated bars from medium-carbon steel of high machinability for manufacture of shock absorber rods.

SUBSTANCE: proposed method includes making steel in electric-arc furnace, off-furnace treatment, micro-alloying with sulfur, continuous teeming at protection of jet with argon, hot rolling of continuously cast billet making use of mechanical heat treatment modes, hot calibration and winding merchant shape in bundles, unwinding bars, cutting and straightening bars. Steel contains the following components, mass-%: carbon, 0.42-0.50; manganese, 0.50-0.80; silicon, 0.17-0.37; sulfur, 0.020-0.040; phosphorus, 0.001-0.030; aluminum, 0.03-0.05; calcium, 0.0010.010; oxygen, 0.001-0.015; chromium, no more than 0.25%; nickel, up to 0.35%; copper, no more than 0.25%; molybdenum, no more than 0.10%; arsenic, no more than 0.08%; nitrogen, no more than 0.015%. The remainder being iron and unavoidable admixtures. Ratio of oxygen and calcium content is determined by the following ratio: oxygen/calcium =1-4.5 and calcium-sulfur ≥0.065. At tapping from melting unit, metal is subjected to deep deoxidation, alloying with silicon, manganese, chromium etc. After bringing the chemical composition of metal to specified level pertaining to all elements, but for aluminum and sulfur, metal and slag are subjected to repeated oxidation with gaseous oxygen or oxidized pellets. Then aluminum is added followed by treatment with calcium and alloying with sulfur.

EFFECT: enhanced conditions for machining articles made from this steel; improved ductility and toughness characteristics of steel.

1 ex

FIELD: metallurgy; production of round calibrated merchant shapes in form of bars from medium-carbon steel of enhanced machinability for manufacture of shock absorbers.

SUBSTANCE: proposed method includes melting of steel in electric furnace, off-furnace treatment of steel, micro-alloying with sulfur, continuous teeming at protection of jet with argon shield, hot rolling of continuously cast billet in modes of thermo-mechanical treatment and winding of bars in bundles, unwinding of bars, cutting and straightening of bars and special finishing of their surfaces. Proposed steel contains the following components, mass-%: carbon, 0.42-0.50; manganese, 0.50-0.80; silicon, 0.17-0.37; sulfur, 0.020-0.040; phosphorus, 0.001-0.030; aluminum, 0.03-0.05; calcium, 0.001-0.010; oxygen, 0.001-0.015; chromium, no more than 0.25; nickel, no more than 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; nitrogen, no more than 0.015; the remainder being iron and unavoidable admixtures; ratio of oxygen to calcium, as well calcium to sulfur is determined by the following dependence: oxygen/calcium=1-4.5 and calcium/sulfur≥0.065. In tapping metal from melting unit, it is deeply de-oxidized by aluminum and is alloyed by silicon, manganese and chromium. After bringing the chemical composition of metal to normal in all components but for aluminum and sulfur, metal and slag are subjected to repeated oxidation by oxidized pellets; then, aluminum is added and metal is treated with calcium and is alloyed with sulfur. Machined bars, 6 m long are obtained from bundles of hot-rolled shapes at accuracy of cutting of ±5 mm. Finishing of shapes includes straightening, monitoring of surfaces for defects and ultrasonic monitoring of internal surfaces for defects, random abrasive dressing, continuous abrasive grinding and machining of round bars.

EFFECT: enhanced machinability by wide cutting tools; improved ductility and toughness of steel.

1 ex

FIELD: metallurgy; making steel for large items of mining and smelting processes under high shock loading and abrasive wear, for example cone-type crushers for coarse crushing and cone-type funnels of filling apparatus.

SUBSTANCE: proposed cast wear-resistant steel contains the following components, mass-%: carbon, 0.80-0.95; silicon, 0.20-0.40; manganese, 8.50-10.0; nickel, 0.50-0.85; tungsten, 0.10-0.30; nitrogen, 0.025-0.045; vanadium, 0.05-0.10; phosphorus, no more than 0.070; sulfur, no more than 0.012, the remainder being iron. Steel may also contain molybdenum in the amount of 0.10-0.30 mass-%.

EFFECT: enhanced wear resistance of large items made from proposed steel.

2 cl, 2 tbl

FIELD: welding wire composition for welding and surfacing articles of low-alloy construction steels operating at high sign-variable loads and low temperature values.

SUBSTANCE: welding wire contains next relation of ingredients, mass %: carbon, 0.06 - 0.12; silicon, 0.2 - 0.8; manganese, 0.9 - 1.6; vanadium, 0.05 - 0.009; sulfur, no more than 0.025; phosphorus, no more than 0.030; nickel, no more than 0.25; titanium, no more than 0.05; nitrogen, no more than 0.012; iron, the balance. Relation of carbon content of vanadium content being in range 0.4 - 1.2 allows receive stable structure of seam metal with uniformly distributed in it finely dispersed carbides. Relation of sulfur content to total content of calcium and manganese being in range 0.015 - 0.030 provides lowered quantity of non-metallic inclusions along grain boundaries.

EFFECT: improved resistance against cracking in near-seam zone of welded seam, combination of optimal strength and impact strength values of welded seam at high corrosion resistance.

Steel // 2312922

FIELD: ferrous metallurgy.

SUBSTANCE: invention proposes steel comprising the following components, wt.-%: carbon, 0.3-0.7; silicon, 0.2-0.4; manganese, 10.0-12.0; vanadium, 1.8-2.3; nitrogen, 0.08-1.2; niobium, 1.0-1.5; aluminum, 0.08-0.12; nickel, 1.5-3.0; molybdenum, 5.0-5.5, and iron, the balance. Invention provides enhancing strength of steel and can be used in machine engineering.

EFFECT: improved and valuable technical property of steel.

1 tbl

FIELD: metallurgy, in particular, manufacture of steel used in automobile building.

SUBSTANCE: method involves smelting steel containing components used in the following ratio, wt%: carbon 0.002-0.015; silicon 0.005-0.050; manganese 0.05-1.0; phosphor 0.005-0.09; sulfur 0.003-0.020; aluminum 0.02-0.07; nitrogen 0.002- 0.007; titanium 0.0005-0.040, niobium no more than 0.060; iron and unavoidable impurities the balance, on condition that Cef=[C]-CTi-CNb≥0.0006%, where Cef is effective content of titanium or niobium non-bound carbon, [C] is total content of carbon in steel, CTi is content of titanium bound carbon, with titanium [Ti] to nitrogen [N] content ratio making [Ti]/[N]<3.43; CTi=0, with [Ti]/{N]≥3.43 CTi={[Ti]-3.43N}/4; CNb is content of niobium bound carbon, CNb=Nb/7.74; Cef+0.05[P]≥0.003%, where [P] is phosphor content in steel; providing steel casting; hot rolling; winding strips into rolls; in case of necessity, providing etching and/or tempering after winding into rolls; in case of necessity, providing thermal processing and coating after etching process.

EFFECT: increased tendency to BH-effect and provision for keeping of high formability.

2 cl, 1 tbl, 4 ex

FIELD: metallurgy, in particular, manufacture of steel used in automobile building.

SUBSTANCE: method involves smelting steel containing components used in the following ratio, wt%: carbon 0.002-0.015; silicon 0.005-0.050; manganese 0.05-1.0; phosphor 0.005-0.09; sulfur 0.003-0.020; aluminum 0.02-0.07; nitrogen 0.002- 0.007; titanium 0.0005-0.040, niobium no more than 0.060; iron and unavoidable impurities the balance, on condition that Cef=[C]-CTi-CNb≥0.0006%, where Cef is effective content of titanium or niobium non-bound carbon, [C] is total content of carbon in steel, CTi is content of titanium bound carbon, with titanium [Ti] to nitrogen [N] content ratio making [Ti]/[N]<3.43; CTi=0, with [Ti]/{N]≥3.43 CTi=([Ti]-3.43N)/4; CNb is content of niobium bound carbon, CNb=Nb/7.74; Cef+0.05[P]≥0.003%, where [P] is phosphor content in steel; providing steel casting; hot rolling; winding strips into rolls at temperature not in the excess of 650 C; performing cold rolling and recrystallization on annealing in cover furnace with regulated heating: first to temperature of 450-500 C at heating rate of at least 50 C/hour, then to temperature of up to 550-600 C at heating rate not in the excess of 30 C/hour, then at heating rate not in the excess of 50 C/hour to temperature of 700 C, and, when necessary applying coating.

EFFECT: increased tendency to BH-effect, including after thermal processing in cover furnaces, and provision for keeping of high formability.

3 cl, 1 tbl, 7 ex

Construction steel // 2313610

FIELD: ferrous metallurgy, machine building.

SUBSTANCE: the construction steel in question contains the components in the following ratio, weight%: carbon 0.2-0.4; silicon 0.17-0.37; manganese 0.4-0.8; vanadium 1.0-2.0; boron 0.001-0.005; aluminum 0.2-0.4; niobium 1.0-2.0; nickel 12.0-14.0; iron - the rest. The innovation provides increased impact strength and fatigue strength of the construction steel.

EFFECT: increased impact strength and fatigue strength.

1 tbl

Up!