CN117305704A - Thick-wall seamless steel tube steel for high-strength high-crack tip-opening displacement LNG receiving station and method for producing seamless steel tube - Google Patents

Thick-wall seamless steel tube steel for high-strength high-crack tip-opening displacement LNG receiving station and method for producing seamless steel tube Download PDF

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CN117305704A
CN117305704A CN202311238441.0A CN202311238441A CN117305704A CN 117305704 A CN117305704 A CN 117305704A CN 202311238441 A CN202311238441 A CN 202311238441A CN 117305704 A CN117305704 A CN 117305704A
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seamless steel
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杨志强
汪开忠
胡芳忠
陈恩鑫
庄振
金国忠
吴林
杨少朋
陈世杰
王自敏
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Maanshan Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium

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Abstract

The invention provides a thick-wall seamless steel tube steel for an LNG receiving station with high strength and toughness and high crack tip opening displacement and a method for producing the seamless steel tube, wherein the components of the steel tube are as follows: 125.0.ltoreq.A.ltoreq.150.0, A=467× (% C+% N) +35×% Mn+30× (% Cr+% Ni) +10×% Mo+3×0% V+15×1% Si+28×2% Cu; y is equal to or greater than 1.0%, y=10×% ni+6×% v+5×% mo+15×% N-20×% C-3×% mn+8×% Cu-2×% Si. The invention produces the seamless steel pipe with the wall thickness of 40-60 mm for the LNG receiving station by the component design, the production method and the heat treatment design, the tensile strength of the 1/2 wall thickness of the product is more than or equal to 720MPa, the yield strength is more than or equal to 640MPa, and the KV at minus 50℃ is more than or equal to 640MPa 2 And (3) the thick-wall seamless steel tube for the LNG receiving station with high strength, toughness and high crack tip opening displacement is obtained.

Description

Thick-wall seamless steel tube steel for high-strength high-crack tip-opening displacement LNG receiving station and method for producing seamless steel tube
Technical Field
The invention belongs to the field of alloys, relates to the field of steel for seamless steel pipes, and in particular relates to steel for thick-wall seamless steel pipes for LNG receiving stations with high strength and toughness and high crack tip opening displacement and a method for producing the seamless steel pipes.
Background
Liquefied Natural Gas (LNG) is recognized as the cleanest fossil energy source on earth, and is colorless, odorless, nontoxic, and noncorrosive, and is the primary energy source substance. In LNG pipeline transportation, the LNG station is needed to be convenient for operations such as transportation maintenance, pressurization and the like every a certain distance, the scale of the LNG receiving station is larger at present, and the scale of the receiving station is further expanded along with the increase of the LNG demand.
As LNG transfer pressure increases, the strength, toughness, and cracking resistance requirements for LNG transfer pipelines increase. Because the service environment of the LNG conveying pipeline is changed, when the pipeline is knocked by external objects, steel pipe micro defects are easy to generate, and crack sources are easy to form by the micro defects, so that the steel pipe is broken and damaged. Therefore, how to improve the crack resistance tip displacement capability of the steel pipe and the improvement of the cracking resistance of the steel pipe are key to the improvement of the performance of the steel pipe.
The traditional method considers that the improvement of the tip displacement resistance of the steel pipe requires strict requirements on the purity of the steel, but the method increases smelting difficulty. In addition, the toughness of the material is improved by adopting more toughening element Ni so as to improve the tip displacement resistance, but the method directly increases the cost, and the economical efficiency is in need of consideration. Therefore, it is becoming urgent how to obtain an LNG seamless steel pipe that is easy to realize and that achieves high crack tip displacement capability.
Patent CN 102581553a published in 2012, 7 and 18 indicates a manufacturing method of an X80-grade large-caliber seamless steel pipe, alloy refined molten steel is cast and centrifugally cast to obtain a large-caliber pipe blank, a carbon steel round part is fixedly connected to the head end and the tail end of the pipe blank, the inner surface and the outer surface of the whole pipe are machined by cutting, after heating and dephosphorization, a core rod is inserted into the hollow pipe blank and positioned, and then the hollow pipe blank is sent into a periodical rolling mill to be rolled back and forth to obtain the pipe with the required size. Removing the core rod, cutting the head and the tail, heating, sizing and finishing to obtain the finished pipe fitting with qualified size. But the wall thickness of the steel pipe is 35mm and the diameter is 650mm. The key point of the product is still the production process of the seamless tube blank, and the inspection, evaluation, heat treatment and the like of the steel tube are all related. The crack tip opening displacement performance is not mentioned, so the application environment of the steel pipe is not considered.
Patent CN 110306120A published in 10.8.2019 indicates an elbow pipe of an X80-grade diameter 1422 seamless steel pipe and a manufacturing method thereof, an electroslag ingot blank is obtained, and the electroslag ingot blank is sequentially heated, insulated and forged to obtain a rod-shaped pipe blank; carrying out first normalizing heat treatment, annealing heat treatment and machining on the rod-shaped tube blank to obtain a steel tube blank; sequentially carrying out cold centering, heating, perforating, pipe rolling, expanding, fine shaping and second normalizing heat treatment on the steel pipe blank to obtain an X80 steel grade D1422mm seamless steel pipe; and (3) performing whole-course induction heating bending forming and tempering heat treatment on the seamless steel pipe by adopting an intermediate frequency induction heating pipe bending machine to obtain the X80 steel grade D1422mm seamless bent pipe. However, the patent adopts electroslag ingots which have the problem of high cost. And the maximum wall thickness of the steel pipe is 36mm, the performance fluctuation is large, the maximum fluctuation of the strength is 70MPa, and the use requirement of the seamless steel pipe for the large-diameter thick-wall LNG receiving station cannot be met.
Therefore, it is necessary to develop a steel for seamless steel pipe with high strength, high diameter, large wall thickness and high Crack Tip Opening Displacement (CTOD) for manufacturing a seamless steel pipe for large diameter thick wall LNG receiving stations.
Disclosure of Invention
The steel for the thick-wall seamless steel tube for the LNG receiving station with high strength and toughness and high Crack Tip Opening Displacement (CTOD) can obtain excellent strength and toughness and high Crack Tip Opening Displacement (CTOD) performance through component design and component matching, and can be used for manufacturing the thick-wall seamless steel tube for the LNG receiving station with large diameter.
The invention also aims to provide a method for producing the seamless steel pipe by using the steel for the thick-wall seamless steel pipe for the LNG receiving station with high strength, high crack tip opening displacement, a production method and a heat treatment process which are designed and matched with components, and the method for producing the seamless steel pipe with the wall thickness of 40-60 mm for the LNG receiving station, wherein the tensile strength of 1/2 wall thickness of the product is more than or equal to 720MPa, the yield strength is more than or equal to 640MPa and the KV of minus 50 DEG C 2 More than or equal to 200J; the hardness difference of the cross section uniformity is less than or equal to 20HBW; and simultaneously has good Crack Tip Opening Displacement (CTOD) performance.
The specific technical scheme of the invention is as follows:
the thick-wall seamless steel tube steel for the LNG receiving station with high strength and toughness and high crack tip opening displacement comprises the following components in percentage by mass:
0.05 to 0.10 percent of C, 0.20 to 0.40 percent of Si, 1.40 to 1.70 percent of Mn, 0.60 to 0.90 percent of Cr, 0.50 to 0.70 percent of Mo, 0.20 to 0.50 percent of Ni, 0.010 to 0.030 percent of Cu, 0.20 to 0.35 percent of V, less than or equal to 0.012 percent of P, less than or equal to 0.008 percent of S, 0.0030 to 0.0070 percent of N, less than or equal to 0.0020 percent of T.O, and the balance of Fe and other unavoidable impurities.
The components of the steel for the thick-wall seamless steel tube for the high-strength high-crack tip opening displacement LNG receiving station also meet the following conditions:
125.0≤A≤150.0，A＝467×(％C+％N)+35×％Mn+30×(％Cr+％Ni)+10×％Mo+3×％V+15×％Si+28×％Cu；
the components of the steel for the thick-wall seamless steel tube for the high-strength high-crack tip opening displacement LNG receiving station also meet the following conditions:
Y≥1.0％，Y＝10×％Ni+6×％V+5×％Mo+15×％N-20×％C-3×％Mn+8×％Cu-2
×％Si。
the invention provides a method for producing a seamless steel tube by using thick-wall seamless steel tube steel for an LNG receiving station with high strength and toughness and high crack tip opening displacement, which comprises the steps of hot forming and heat treatment of the seamless steel tube steel.
In the hot forming of the steel for the seamless steel tube, the heating temperature of the tube blank is controlled to 1050-1150 ℃, the deformation of the tube penetrating is 15-30%, and the tube penetrating speed is 0.30-0.50 s -1 Single deformation of the expanded pipe is 10-20%, and the rate of expanding pipe is 0.15-0.25 s -1 ；
The wall thickness of the produced seamless steel pipe is more than or equal to 40mm; preferably, the wall thickness is 40 mm-60 mm;
the heat treatment comprises quenching and tempering;
the quenching: the furnace charging temperature is less than or equal to 400 ℃ and the heating temperature T Quenching and heating 820-980 ℃; time t of incubation Quenching heat preservation From the wall thickness S and the heating temperature T of the steel pipe Quenching and heating Determination, 180+ (S/2) - (T) Quenching and heating /9)≤t Quenching heat preservation ≤200+(S/2)-(T Quenching and heating 9), water cooling; wherein the unit of the wall thickness S of the steel pipe is mm, and the heating temperature T Quenching and heating The unit of (C) is the temperature and the heat preservation time t Quenching heat preservation The unit of (2) is min, and when the formula is calculated, the data before the unit is directly carried into the formula for calculation;
the tempering: tempering temperature T Tempering and heating 600-720 ℃ and heat preservation time t Tempering and heat preserving From the wall thickness S and the tempering temperature T of the steel pipe Tempering and heating Determining, 460+ (S/2) - (T) Tempering and heating /3)≤t Tempering and heat preserving ≤500+(S/2)-(T Tempering and heating 3) water cooling, wherein the unit of the wall thickness S of the steel tube is mm, and the heating temperature T Tempering and heating The unit of (C) is the temperature and the heat preservation time t Tempering and heat preserving In units of min, when calculated by the above formula, the above units are calculatedThe previous data is directly brought into formula calculation.
Through the production process flow, the thick-wall seamless steel tube for the LNG receiving station is produced by using the high-strength and high-toughness high-crack tip opening displacement thick-wall seamless steel tube for the LNG receiving station through the production method and the heat treatment method.
The inner wall, 1/2 wall thickness and the outer wall of the produced seamless steel pipe are all 100% tempered sorbite; the grain size is 20-27 mu m, and the difference between the grain sizes of the structures of the inner wall, the 1/2 wall thickness and the outer wall is less than or equal to 0.5 mu m;
the tensile strength of the produced seamless steel pipe at 1/2 wall thickness of the steel pipe is more than or equal to 720MPa, the yield strength is more than or equal to 640MPa and the KV at-50℃ is more than or equal to 50 DEG C 2 More than or equal to 200J, more than or equal to 22 percent of A and more than or equal to 50 percent of Z; the cross section uniformity is good, the cross section hardness difference is less than or equal to 20HBW, and the preferable cross section hardness difference is less than or equal to 15HBW; CTOD test is carried out according to GB/T21143, CTOD (delta) is more than or equal to 1.10mm at minus 20 ℃ and CTOD (delta) is more than or equal to 0.65mm at minus 40 ℃ and the high-pressure conveying requirement of an LNG receiving station is met.
The steel with the above components has excellent toughness and high Crack Tip Opening Displacement (CTOD) performance, and is suitable for manufacturing a seamless steel pipe (wall thickness 40-60 mm) for a large-diameter (diameter 965-1500 mm) thick-wall LNG receiving station. The design idea is as follows:
c: c is a strengthening element in steel, and each time 0.01% of solid solution C is increased, the strength can be increased by about 45MPa, and C and an alloy element in the steel form a precipitated phase to play a role in precipitation strengthening. And C can obviously improve the hardenability, so that the center of the steel pipe with large wall thickness can obtain a martensitic structure. However, as the content increases, the plasticity and toughness decrease, so the C content is controlled to be 0.05-0.10%.
Si: si is an effective solid solution strengthening element in steel, improves the strength and the hardness of the steel, can play a deoxidizing role in steelmaking, and is a common deoxidizer. However, si tends to be biased to have austenite grain boundaries, so that the bonding force of the grain boundaries is reduced, and brittleness is induced. In addition, si tends to cause element segregation in steel. Therefore, the Si content is controlled to be 0.20% to 0.40%.
Mn: mn can play a solid solution strengthening role, the solid solution strengthening capability is weaker than that of Si, mn is an austenite stabilizing element, the hardenability of steel can be obviously improved, decarburization of steel can be reduced, and the combination of Mn and S can prevent hot shortness caused by S. However, excessive Mn reduces the plasticity of the steel. Therefore, the Mn content is controlled to be 1.40-1.70%.
Cr: cr is a carbide forming element, and Cr can improve both hardenability and strength of steel, but is liable to cause temper embrittlement. Cr can improve the oxidation resistance and corrosion resistance of steel, but when the Cr content is too high, crack sensitivity is increased. The Cr content should be controlled to be 0.60% -0.90%.
Mo: mo can effectively reduce segregation of P, S, as and other impurity elements at the grain boundary, so that the toughness of steel is improved, and the tempering brittleness is reduced. Mo decreases M 7 C 3 Is higher, needle-like Mo is formed 2 C, will result in a reduced Mo content of the matrix. Mo can improve the strength of steel by the combined action of solid solution strengthening and precipitation strengthening, and can also change the toughness of steel by changing the precipitation of carbide. So that the Mo content is controlled to be 0.50-0.70%.
Ni: ni can form infinite mutual-soluble solid solution with Fe, is an austenite stabilizing element, has the effect of expanding a phase area, increases the stability of supercooled austenite, makes a C curve move right, and improves the hardenability of steel. Ni can refine the width of the martensite lath and improve the strength. Ni obviously reduces the ductile-brittle transition temperature of steel, improves low-temperature toughness, and can effectively control the deformation of a steel foundation after the toughness of the steel is improved, so that no sharp crack is generated after external force is received, thereby reducing the crack formation rate and reducing the crack tip expansion risk. The Ni element is a noble metal element, and excessive addition results in excessive cost. The Ni content is controlled to be 0.20-0.50%.
V: v is a strong C, N compound forming element, and V (C, N) is finely dispersed and maintains a coherent relation with the matrix, so that the effects of strengthening and refining tissues can be achieved. The V content is controlled to be 0.25-0.35%.
Cu: cu expands an austenite phase region, and a simple substance Cu can be used as a second phase to obviously improve strength, and can improve the tempering stability and strength of a structure. However, too high Cu will result in Cu embrittlement. Therefore, the Cu content is controlled to be 0.010-0.030 percent.
T.o and N: T.O forms oxide inclusion in steel, and the T.O is controlled to be less than or equal to 0.0020 percent.
N can form fine precipitated phase refined structure with nitride forming element in steel, and can precipitate Fe 4 The diffusion rate of N is low, so that the timeliness of the steel is generated and the processing performance is reduced, and therefore, the N is controlled to be 0.0030-0.0070 percent.
Thick-walled seamless steel pipes are superior to those with wall thicknesses exceeding 40mm, and require high toughness and high Crack Tip Opening Displacement (CTOD) performance for service in LNG environments. The strength of the steel can be improved through the addition of beneficial alloy elements, the toughness of the steel can be improved through the effective proportion of the elements, and the Crack Tip Opening Displacement (CTOD) performance is improved through effectively improving the crack propagation resistance of the steel in the corrosion ring. According to the research of the alloy system, under the condition of the component system, mn in alloy elements improves hardenability and strength effectively, so that the coefficient is 35; mo contributes significantly to hardenability and strength by improving tempering stability and interaction with Mn, and has a coefficient of 10; cr is a main substitution solid solution element and a carbide forming element, and has a contribution coefficient to strength of 30; ni and Cu do not form carbide in steel, and the hardenability and strength of the steel are improved by changing the crystal lattice morphology through solid solution strengthening, and the coefficients are 30 and 28 respectively; c and N are nonmetallic elements, are the most main interstitial solid solution strengthening elements in steel, and have influence on strength and toughness, so the coefficient is 467; si is a nonmetallic element and is also a main solid solution strengthening element in steel, and the contribution to the performance of the steel is 15; v is the microalloying element that increases the strength of the steel by interacting and forming a second phase, and therefore has a coefficient of 3. Because the strength, plasticity and toughness of the steel have inverse proportion relation, and the plasticity and toughness are reduced when the strength is high, the strength cannot be improved at the same time in order to ensure the comprehensive performance of the steel. The strengthening factor in the steel is expressed by A, so that A is more than or equal to 125.0 and less than or equal to 150.0,
A＝467×(％C+％N)+35×％Mn+30×(％Cr+％Ni)+10×％Mo+3×％V+15×％Si+28
×％Cu。
the seamless steel pipe for the LNG receiving station needs better Crack Tip Opening Displacement (CTOD) performance in the service process, so the proportion of C, N, si, mn, mo, ni, cu, V needs to be limited. The strength of the steel can be obviously improved by C, si and Mn, but the elements are easy to deviate to cause uneven structure, so that the entropy of the material is increased, and the local weakness of a material matrix is caused, so that cracks are aggravated. Mo, V can form a second phase with C, N in steel, which can control dislocation slip and migration in microstructure in steel, thereby improving crack propagation resistance. Ni can improve the stacking fault energy of steel, improve the dislocation density of steel and reduce the dislocation slip rate, thereby improving the hydrogen induced cracking resistance. Cu can be well combined with steel at nano scale to form a semi-coherent relation, thereby playing a role in fixing harmful elements, controlling the displacement of crack tips and being capable of preventing cracks. The crack resistance expansion factor in the steel is expressed by Y, and then Y is more than or equal to 1.0 percent,
y=10× ni+6× v+5× mo+15× N-20× C-3× mn+8× Cu-2× Si. The outer diameter of the large-diameter steel pipe is larger than 965mm, and the production of the steel pipe has difficulty: 1. the deformation of the steel pipe manufactured by adopting the continuous casting round billet is small, and the structure of the steel is not easy to be uniform. 2. The external diameter is large, the pipe diameter needs to be expanded, and the requirement on the plasticity and toughness of the material is high. The invention reduces segregation effect of steel in smelting process and makes steel uniform through reasonable proportion of elements. In addition, through the mutual coordination of elements, the plasticity and toughness of the steel are improved, thereby meeting the production process of expanding the pipe diameter.
Compared with the prior art, the invention adopts reasonable component design and heat treatment process design, on one hand, the steel material obtains higher toughness, and the crack expansion work of the material is improved; on the other hand, the crack propagation resistance is improved by improving the crack threshold value of the material, and the produced thick-wall seamless steel tube for the LNG receiving station has the tensile strength of more than or equal to 720MPa, the yield strength of more than or equal to 640MPa and the yield strength of-50 ℃ KV at 1/2 wall thickness (the wall thickness of more than or equal to 40 mm) of the steel tube 2 More than or equal to 200J; the hardness difference of the cross section uniformity is less than or equal to 20HBW; CTOD test is carried out according to GB/T21143, CTOD (delta) is more than or equal to 0.65mm at minus 40 ℃ and high-pressure conveying requirement of an LNG receiving station is met.
Drawings
FIG. 1 is a microstructure and IPF reconstruction of the outer wall, 1/2 radius and inner wall of the seamless steel tube of example 1;
FIG. 2 is a low temperature impact fracture morphology of the outer wall, 1/2 radius and inner wall of the seamless steel tube of example 1;
FIG. 3 is a microstructure and IPF reconstruction of the outer wall, 1/2 radius and inner wall of a seamless steel tube of comparative example 2;
FIG. 4 shows the low temperature impact fracture morphology of the outer wall, 1/2 radius and inner wall of the seamless steel pipe of comparative example 2.
Detailed Description
The present application will be further described with reference to several specific examples and comparative examples.
Example 1-example 3
A thick-wall seamless steel tube steel for a high-strength high-crack tip-opening displacement LNG receiving station comprises the following components in percentage by mass: as shown in table 1, the balance not shown in table 1 is Fe and other unavoidable impurities.
Comparative example 1-comparative example 3
The steel for the seamless steel pipe comprises the following components in percentage by mass: as shown in table 1, the balance not shown in table 1 is Fe and other unavoidable impurities.
Table 1 chemical composition (wt%) of each of examples and comparative examples
A production method for producing thick-wall seamless steel pipes for high-strength and high-crack tip-opening displacement LNG receiving stations by using thick-wall seamless steel pipes for high-strength and high-crack tip-opening displacement LNG receiving stations comprises the steps of hot forming and heat treatment of the steel for the seamless steel pipes, and specifically comprises the following process flows:
electric furnace smelting, LF furnace refining, RH or VD vacuum degassing, round billet continuous casting, round billet slow cooling, round billet blanking, round billet heating, perforation, sizing, stretch reducing, heat treatment, flaw detection, grinding, packaging and warehousing.
Smelting in an electric furnace: oxygen is fixed before tapping, and steel retaining operation is adopted in the tapping process, so that slag discharging is avoided;
refining in an LF furnace: C. si, mn, cr, ni, mo, V, cu and other elements to target values; the LF adopts strong stirring to carry out desulfurization and decarburization, argon is adopted for stirring, and the gas flow is 400L/min-800L/min; adding 100-150 m calcium wire for inclusion denaturation; making white slag, wherein the white slag time is controlled to be 20-30 minutes; the LF outlet temperature is controlled to be 1580-1620 ℃.
Vacuum degassing: the pure degassing time is more than or equal to 15 minutes, the H content after vacuum treatment is less than or equal to 1.5ppm, and the phenomenon of hydrogen embrittlement caused by white spots in steel is avoided;
round billet continuous casting: the target temperature of the ladle molten steel is controlled to be 10-40 ℃ above the liquidus temperature, and the diameter phi=700 mm of round billet is continuously cast.
The manufacturing route of the seamless steel tube comprises the following steps: blanking round billets (with the diameter of 700 mm), heating the round billets, perforating, sizing, reducing the diameter by stretching, heat treatment, flaw detection, grinding, packaging and warehousing.
The seamless steel tube forming process comprises the following steps: the heating temperature is 1050-1150 ℃, the deformation of the penetrating pipe is 15-30%, and the penetrating pipe speed is 0.30-0.50 s -1 Single deformation of the expanded pipe is 10-20%, and the rate of expanding pipe is 0.15-0.25 s -1 。
Heat treatment of a seamless steel tube: heating by a trolley furnace, heat preservation, quenching, tempering, heat preservation and air cooling.
The heat treatment method comprises quenching and tempering.
The quenching: the furnace charging temperature is less than or equal to 400 ℃ and the heating temperature T Quenching and heating 820-980 ℃; time t of incubation Quenching heat preservation From the wall thickness S and the heating temperature T of the steel pipe Quenching and heating Determination, 180+ (S/2) - (T) Quenching and heating /9)≤t Quenching heat preservation ≤200+(S/2)-(T Quenching and heating 9), water cooling; wherein the unit of the wall thickness S of the steel pipe is mm, and the heating temperature T Quenching and heating The unit of (C) is the temperature and the heat preservation time t Quenching heat preservation The unit of (2) is min, and when the formula is calculated, the data before the unit is directly carried into the formula for calculation;
the tempering: tempering temperature T Tempering and heating 600-720 ℃, and heat preservationTime t Tempering and heat preserving From the wall thickness S and the tempering temperature T of the steel pipe Tempering and heating Determining, 460+ (S/2) - (T) Tempering and heating /3)≤t Tempering and heat preserving ≤500+(S/2)-(T Tempering and heating 3) water cooling, wherein the unit of the wall thickness S of the steel tube is mm, and the heating temperature T Tempering and heating The unit of (C) is the temperature and the heat preservation time t Tempering and heat preserving When the unit of (2) is min, the data before the unit is directly brought into the formula for calculation.
The performance detection method comprises the following steps:
tissue: samples were taken from the seamless steel tube body, and metallographic, grain size, hardness difference analysis were performed at the outer wall, 1/2 thickness (thickness: 56 mm) and inner wall positions.
Performance: samples were taken from a seamless steel pipe body, and tensile, impact and hydrogen induced cracking samples were taken at a thickness of 1/2 (thickness: 56 mm), and performance tests were conducted with reference to GB/T228, GB/T229 and GB/T21143. The heat treatment process is shown in Table 2, and the mechanical properties are shown in Table 3.
Table 2 list of process conditions for the examples and comparative examples of the present invention
TABLE 3 list of Performance test cases for examples and comparative examples of the present invention
The fluctuation of the section hardness is to measure the Brinell hardness at the outer wall thickness, the 1/2 wall thickness and the inner wall 3 positions respectively in the wall thickness direction of the steel pipe, and the calculated difference of the hardness is the maximum value.
The underlined data above are data which do not satisfy the requirements of the present invention.
The chemical composition and the production method of the steel in the examples 1-3 are properly controlled, and the chemical composition ensures that the strength, the plasticity, the toughness and the CTOD performance of the steel with A being more than or equal to 125.0 and 150.0,1.0 percent and Y being more than or equal to 150.0,1.0 percent are better. Comparative examples 1, 2 and 3 are unsuitable in chemistry, and the pipe making process and the heat treatment process of comparative example 3 are both unsuitable and poor in performance.

Claims (9)

1. The steel for the thick-wall seamless steel tube for the high-strength high-crack tip-opening displacement LNG receiving station is characterized by comprising the following components in percentage by mass:
0.05 to 0.10 percent of C, 0.20 to 0.40 percent of Si, 1.40 to 1.70 percent of Mn, 0.60 to 0.90 percent of Cr, 0.50 to 0.70 percent of Mo, 0.20 to 0.50 percent of Ni, 0.010 to 0.030 percent of Cu, 0.20 to 0.35 percent of V, less than or equal to 0.012 percent of P, less than or equal to 0.008 percent of S, 0.0030 to 0.0070 percent of N, less than or equal to 0.0020 percent of T.O, and the balance of Fe and other unavoidable impurities.
2. The steel for thick-walled seamless steel pipe for high-strength high-crack-tip-opening displacement LNG receiving station according to claim 1, wherein the composition of the steel for thick-walled seamless steel pipe for high-strength high-crack-tip-opening displacement LNG receiving station further satisfies:
125.0≤A≤150.0，A＝467×(％C+％N)+35×％Mn+30×(％Cr+％Ni)+10×％Mo+3×％V+15×％Si+28×％Cu。
3. the steel for thick-walled seamless steel pipe for high-strength high-crack-tip-opening displacement LNG receiving station according to claim 1, wherein the composition of the steel for thick-walled seamless steel pipe for high-strength high-crack-tip-opening displacement LNG receiving station further satisfies:
Y≥1.0％，Y＝10×％Ni+6×％V+5×％Mo+15×％N-20×％C-3×％Mn+8×％Cu-2
×％Si。
4. a method of producing a seamless steel pipe from a thick-walled seamless steel pipe for an LNG receiving station according to any of claims 1-3, wherein the production method comprises hot forming and heat treating the steel for a seamless steel pipe.
5. The method according to claim 4, wherein the heat forming of the steel for the seamless steel tube is performed by controlling the heating temperature of the tube blank to 1050-1150 ℃ and the tube penetrating deformation to 15-30% and the tube penetrating speed to 0.30-0.50 s -1 Single deformation of the expanded pipe is 10-20%, and the rate of expanding pipe is 0.15-0.25 s -1 。
6. The method of claim 4 or 5, wherein the heat treatment comprises quenching and tempering; the quenching: the furnace charging temperature is less than or equal to 400 ℃ and the heating temperature T Quenching and heating 820-980 ℃; time t of incubation Quenching heat preservation From the wall thickness S and the heating temperature T of the steel pipe Quenching and heating Determination, 180+ (S/2) - (T) Quenching and heating /9)≤t Quenching heat preservation ≤200+(S/2)-(T Quenching and heating 9), water cooling; wherein the unit of the wall thickness S of the steel pipe is mm, and the heating temperature T Quenching and heating The unit of (C) is the temperature and the heat preservation time t Quenching heat preservation In minutes.
7. The method of claim 6, wherein the tempering: tempering temperature T Tempering and heating 600-720 ℃ and heat preservation time t Tempering and heat preserving From the wall thickness S and the tempering temperature T of the steel pipe Tempering and heating It is decided that the method comprises the steps of,
460+(S/2)-(T tempering and heating /3)≤t Tempering and heat preserving ≤500+(S/2)-(T Tempering and heating 3) water cooling, wherein the unit of the wall thickness S of the steel tube is mm, and the heating temperature T Tempering and heating The unit of (C) is the temperature and the heat preservation time t Tempering and heat preserving In minutes.
8. The method according to any one of claims 4 to 7, wherein the inner wall, 1/2 wall thickness and outer wall of the seamless steel pipe produced are all 100% tempered sorbite; the grain size is 20-27 μm, and the difference between the grain sizes of the inner wall, the 1/2 wall thickness and the outer wall is less than or equal to 0.5 μm.
9. The method according to any one of claims 4 to 7, wherein the seamless steel pipe produced has a tensile strength of 720MPa or more at 1/2 wall thickness, a yield strength of 640MPa or more, and a KV of-50 DEG C 2 More than or equal to 200J, more than or equal to 22 percent of A and more than or equal to 50 percent of Z; the section hardness difference is less than or equal to 20HBW; CTOD test is carried out according to GB/T21143, and CTOD (delta) at minus 20 ℃ is more than or equal to 1.10mm and CTOD (delta) at minus 40 ℃ is more than or equal to 0.65mm.
CN202311238441.0A 2023-09-25 2023-09-25 Thick-wall seamless steel tube steel for high-strength high-crack tip-opening displacement LNG receiving station and method for producing seamless steel tube Pending CN117305704A (en)

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