CN1291056C

CN1291056C - High-strength and toughness steel for conveying pipeline and manufacturing method thereof

Info

Publication number: CN1291056C
Application number: CNB2004100132651A
Authority: CN
Inventors: 孔君华; 郑琳; 郭斌; 刘昌明; 刘小国
Original assignee: Wuhan Iron and Steel Group Corp
Current assignee: Wuhan Iron and Steel Group Corp
Priority date: 2004-06-04
Filing date: 2004-06-04
Publication date: 2006-12-20
Anticipated expiration: 2024-06-04
Also published as: CN1584097A

Abstract

The present invention relates to high strength and toughness pipeline steel which is particularly suitable for conveying the oil and the gas of large pipe diameter, high pressure and high density at a long distance, and a production method thereof. The present invention solves the defects that the thickness of the existing producing material is only 8 millimeters, strength and wall thickness for conveying high pressure and high density mediums are obviously insufficient, a pipeline is easy to generate fracture, low elongation rate and poor machine forming performance, etc. The present invention has the technical measure that the chemical composition of the high strength and toughness pipeline conveying steel comprises by weight percentage: 0.01 to 0.06 of C, 0.15 to 0.40 of Si, 1.61 to 2.0 of Mn, 0.0031 to 0.018 of P, at most 0.003 of S, 0.051 to 0.09 of Nb, at most 0.025 of Ti, 0.10 to 0.40 of Mo, 0.10 to 0.40 of Cu, 0.10 to 0.40 of Ni and Fe as the rest. The preparation method of the high strength and toughness pipeline steel comprises: 1150 to 1199 DEG C of heating temperature, 750 to 830 DEG C of finishing temperature, 450 to 629 DEG C of winding temperature, and 15 to 30 DEG C /S of cooling control speed.

Description

The preparation method of high-intensity high-tenacity line of pipes steel

Technical field

The invention belongs to the high-intensity high-tenacity Alloy And Preparation Method, be particularly useful for big caliber, high pressure, highdensity oil, the long production method of using the high-intensity high-tenacity pipe line steel apart from conveying of gas.

Technical background

According to country formulate " the grand strategic objective of West-east Gas is with the line of pipes of laying thousands of kilometers.Because its line of pipes major part all will pass through ice box, and region complexity on the way, in order to reduce the conveying cost, raising oil and gas transport efficiency, its transport pipe is rapidly to big caliber, and medium is to high pressure, high-density developer conveying direction.At present, ", could reduce the construction and the operation cost of pipeline in order to satisfy in the West-east Gas to the requirement of line of pipes material; the intensity rank of pipe line steel develops into X70 by X60; it has satisfied the pressure of delivery medium and the requirement that density improves; but can not satisfy medium; and, have only the grade of steel of further raising pipe line steel along with the raising of delivery medium pressure to high pressure more, high-density length demand apart from developer conveying direction.As application number is 00123185.5, name is called " a kind of Ultra-low carbon high tenacity anti-H 2 S steel for gas delivering pipeline ", its deficiency is: because production material thinner thickness has only 8 millimeters according to specification sheets, as carrying high pressure, high-density medium, its intensity and wall thickness are obviously not enough, make pipeline very easily cause rupture failure, poor stability, and its unit elongation is lower, have only 20.9～24.5%, processing forming is bad.The deficiency that its process system exists is the finishing temperature height, at 900 ℃～830 ℃, promptly can not give full play to the advantage of carrying out process strengthening by low temperature rolling.Application number is 00123128.6, and name is called " a kind of preparation method of high-cleanness, high-strength and high-toughness steel for gas delivering pipeline ", and its deficiency is with above-mentioned patent.Though Baosteel, Anshan iron and steel plant carried out the production of X80, the coiled sheet thickness of producing (≤10mm) and index such as fracture toughness property all can't satisfy the engineering requirement.The Europe X80 steel that goes out of steel pipe's production because of its carbon content 0.07～0.11%, its fracture toughness property is obviously not enough.And Korea S Pu Xiang Ze has been owing to added v element in steel, and vanadium makes dropping hammer of heavy wall steel tear (DWTT) unstable properties to toughness inherent disadvantageous effect.

Owing to the purity requirement of the pipeline steel to steel of carrying high pressure, high-density medium is high, the alloying element addition is restricted, and therefore studying the pipe line steel by appropriate ingredients and rational process system production with high-intensity high-tenacity is that the X80 steel is imperative.

Summary of the invention

The objective of the invention is to overcome above-mentioned deficiency, provide can satisfy carry high pressure, highdensity medium length apart from the heavy wall of delivery requirements at 10～20 millimeters, heavy caliber, and not easy fracture and destruction, safe reliability is strong, unit elongation is high, processing forming is good high-intensity high-tenacity line of pipes steel and production method thereof.

Realize the technical measures of above-mentioned purpose:

The preparation method of high-intensity high-tenacity line of pipes steel, to be by chemical component weight per-cent: C0.01～0.06, Si 0.15～0.40, Mn 1.61～2.0, P 0.0031～0.018, S≤0.003, Nb0.051～0.09, Ti≤0.025, Mo 0.10～0.40, Cu0.10～0.40, Ni0.10～0.40, the steel billet that all the other are formed for iron, it is 1150～1199 ℃ of the Heating temperatures of steel billet, 750～830 ℃ of finishing temperatures, 450～629 ℃ of coiling temperatures, 15～30 ℃/S of controlled chilling speed.

The effect of its each composition is as follows:

The composition design: it is the basis that the chemical composition design of X80 steel is taked with low-carbon (LC) (or Ultra-low carbon)-manganese-niobium-molybdenum, auxiliary again method of adding other alloying element.Low or ultralow C content can reduce the C element to the flexible disadvantageous effect, and by alloying element Mn, Mo be used for suppress proeutectoid ferrite and change, guarantee to obtain acicular ferrite type tissue.Adopt Nb, Ti microalloying to improve recrystallization temperature, obtain to contain the tissue of more deformed belts, realize refined crystalline strengthening, dislocations strengthening and precipitation strength.By adding anti-hydrogen embrittlement corrosion (HIC) ability that Cu improves high-strength line-pipe steel.And by adding the ductile-brittle transition temperature that nickel reduces steel.

C: carbon is the principal element that influences pipe line steel obdurability, weldability.Carbon content increases, and weldability worsens, and toughness descends, simultaneously, and segregation aggravation, anti-hydrogen embrittlement corrosion (HIC) ability drop.Along with the raising of the intensity rank of steel, the C content in the pipe line steel is downward trend gradually, and X80 pipe line steel carbon content of the present invention is controlled in 0.01～0.06 scope.

Mn: manganese is the basic alloy element of pipeline with high-strength low-alloy steel.In the present invention manganese is controlled in 1.61～2.0 scopes, to help improving the yield strength and the impelling strength of steel.

P, S: phosphorus brings segregation easily in pipe line steel, worsen welding property, significantly reduce steel low-temperature impact toughness, improve disadvantageous effect such as brittle transition temperature.Sulphur is to influence the anti-hydrogen embrittlement corrosion (HIC) of pipe line steel and the principal element of resisting sulfide stress corrosion (SSC) ability, and sulphur easily combines generation MnS and is mingled with manganese, and sulphur also influences the low-temperature impact toughness of pipe line steel.Therefore, high grade of steel pipe line steel should reduce P, the S element disadvantageous effect to the performance of steel as far as possible.0.0031～0.018, S content is below 0.003 by P content in the control X80 steel, and uses conventional inclusion modification treatment technologies such as feeding the Ca-Si line and make the steel inclusion nodularization, be evenly distributed and reduce its disadvantageous effect.

Nb: add niobium can more significantly improve steel than vanadium recrystallization temperature T _RX,, show the ductile-brittle transition temperature that improves steel, so this steel does not add V because vanadium has disadvantageous effect to the toughness of steel.Contain the Nb steel owing to obtain high T _RXMake in the course of hot rolling that a large amount of strains is able to carry out being lower than below its recrystallization temperature, thereby obtain tissue tiny, that contain a large amount of deformed belts.Simultaneously Nb content is controlled in 0.051～0.09% scope, can in rolling process of cooling, makes and separate out tiny Nb (C, N) particle precipitation strength, thus the intensity of raising steel.

Ti: in controlled rolling low-carbon (LC) pipe line steel, but add, improve the yield strength and the toughness of steel less than 0.025% titanium crystal grain thinning.The improvement of this performance is main to improve the recrystallization temperature and the AUSTENITE GRAIN COARSENING temperature of steel with titanium, thereby it is relevant with the grain-size in the heat-processed to control continuous casting.Simultaneously, Ti adds in the Nb steel can prolong separating out incubation period of NbC, make the carbide of Nb-Ti clad steel separate out the time opening and want evening than the Nb steel, thereby precipitate is more tiny, disperse.Because Ti at high temperature can combine with N, form the TiN particle, so the crystal grain control of the adding of Ti heat affected zone when helping welding, this also is very favorable to the toughness of improving welded heat affecting zone.

Mo: molybdenum can prolong the incubation period of perlitic transformation effectively, and ferrite and perlitic range are moved to right, but very little to the phase transformation influence of bainite.Therefore make steel through behind the austenitizing continuously fast during cooling, can obtain bainite structure.When carbon content in the steel was very low, the bainite of this microtexture and acicular ferrite structure can guarantee that steel has good ductility.The High-Strength Low-Alloy pipe line steel that contains Nb-Mo can have much higher intensity than containing the Nb-V steel, and this is because Mo can reduce the diffusibility of carbide forming element such as Nb etc., thereby hinders the formation of carbide, postpones the precipitation process of carbide.In high-strength low-alloy steel, yield strength improves with the increase of Mo add-on.

Ni: nickel can reduce the ductile-brittle transition temperature of pipe line steel, improves the impelling strength of steel.

Cu: copper can improve the resistance to corrosion of steel.

The present invention compared with prior art has following advantage:

1, yield strength (R _T0.5) 580～690MPa, tensile strength (Rm) 〉=621MPa;

2 ,-20 ℃ v-notch Charpy-V impact power 〉=220J;

3 ,-15 ℃ Drop-Weight Tear Test (DWTT) (DWTT) fracture fiber rate (SA) 〉=85%;

4, corrosion resistance (HIC): CSR (crackle area occupation ratio)≤2%, CLR (crack length rate)≤15%, CTR (crack thickness rate)≤5%;

5, thickness of pipe is 10～20 millimeters, not easy fracture and destruction, safe reliability is strong, unit elongation is high, processing forming is good.

Embodiment

The chemical ingredients such as the table 1 of specific embodiment 1～3:

Wuhan Iron and Steel Plant X80 steel finished product chemical ingredients (Wt%) table 1

Sequence number	C	Si	Mn	P	S	Nb	Ti	Cu	Mo	Ni
Sequence number	C	Si	Mn	P	S	Nb	Ti	Cu	Mo	Ni	1	0.02	0.30	1.88	0.007	0.003	0.071	0.023	0.20	0.20	0.37
2	0.03	0.27	1.80	0.007	0.003	0.057	0.022	0.20	0.30	0.35	1	0.02	0.30	1.88	0.007	0.003	0.071	0.023	0.20	0.20	0.37
2	0.03	0.27	1.80	0.007	0.003	0.057	0.022	0.20	0.30	0.35	3	0.05	0.28	1.85	0.012	0.001	0.068	0.012	0.23	0.30	0.28

Concrete preparation method and test-results such as table 2 and table 3:

The stretching of X80 steel, cold bending test be table 2 as a result

Sequence number	Heating temperature, ℃	Finishing temperature, ℃	Coiling temperature, ℃	Water-cooled speed, ℃/s	Thickness/mm	Tension test				180 ° of clod washes
						Tension test				180 ° of clod washes	R _t0.5/MPa	Rm/MPa	A ₅₀/％	Yield tensile ratio	D＝2a
						1	1180	780	550	10	R _t0.5/MPa	Rm/MPa	A ₅₀/％	Yield tensile ratio	D＝2a	15	580	655	39	0.89	Qualified
2	1180	780	550	10	15	1	1180	780	550	10	590	670	38	0.88	Qualified	15	580	655	39	0.89	Qualified
2	1180	780	550	10	15	3	1200	790	560	15	590	670	38	0.88	Qualified	17.5	615	680	37.5	0.90	Qualified

The fracture toughness test of X80 steel is table 3 as a result

Sequence number	Thickness/mm	-20 ℃ of V-type shock tests								-15 ℃ of DWTT tests
		-20 ℃ of V-type shock tests								-15 ℃ of DWTT tests			Akv/J				SA/％				SA/％
		1	2	3	On average	1	2	3	On average	1	2	On average	Akv/J				SA/％				SA/％
		1	2	3	On average	1	2	3	On average	1	2	On average	1	15	295	295	295	295	100	100	100	100	100	100	100
2	15	285	300	305	297	100	100	100	100	100	100	100	1	15	295	295	295	295	100	100	100	100	100	100	100
2	15	285	300	305	297	100	100	100	100	100	100	100	3	17.5	327	327	336	330	100	100	100	100	100	100	100

Annotate: 1～3 in table 2,3 1～3 data and the table 1 is corresponding relation.

Claims

1, the preparation method of high-intensity high-tenacity line of pipes steel, to be by chemical component weight per-cent: C0.01～0.06, Si 0.15～0.40, Mn 1.61～2.0, P 0.0031～0.018, S≤0.003, Nb 0.051～0.09, Ti≤0.025, Mo 0.10～0.40, Cu 0.10～0.40, and Ni 0.10～0.40, the steel billet that all the other are formed for iron, 1150～1199 ℃ of Heating temperatures that it is characterized in that steel billet, 750～830 ℃ of finishing temperatures, 450～629 ℃ of coiling temperatures, 15～30 ℃/S of controlled chilling speed.