CN117248163A - Production method of high-strength low-temperature toughness pipe fitting steel - Google Patents

Production method of high-strength low-temperature toughness pipe fitting steel Download PDF

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CN117248163A
CN117248163A CN202311486271.8A CN202311486271A CN117248163A CN 117248163 A CN117248163 A CN 117248163A CN 202311486271 A CN202311486271 A CN 202311486271A CN 117248163 A CN117248163 A CN 117248163A
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equal
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temperature
steel
low
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陈奇明
高擎
罗登
史术华
熊祥江
李中平
范明
彭宁琦
张勇伟
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Hunan Valin Xiangtan Iron and Steel Co Ltd
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Hunan Valin Xiangtan 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract

The invention discloses a production method of high-strength low-temperature toughness pipe fitting steel, which comprises the following technological processes of converter smelting, refining, continuous casting, heating and rolling, cooling, checking and warehousing. The steel comprises, by mass, C=0.07-0.08, si=0.15-0.30, mn=1.40-1.60, P.ltoreq.0.012, S.ltoreq.0.002, nb=0.035-0.045, ti=0.015-0.02, al.ltoreq.0.005, ni=0.12-0.20, cr=0.15-0.20, mo=0.16-0.20, V=0.045-0.055, ca/S=0.9-2.1, and the balance Fe and unavoidable impurities. The steel produced by the method has the advantages of high strength, good toughness, excellent low-temperature toughness, excellent processability and excellent welding performance, the yield strength of the steel is 490-780 mpa, the tensile strength is 500-600 mpa, the yield ratio is less than or equal to 0.88, the plate thickness low-temperature impact toughness is minus 40 ℃, and the Akv is more than or equal to 300J.

Description

Production method of high-strength low-temperature toughness pipe fitting steel
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a production method of high-strength pipe fitting steel with good welding performance, high strength and toughness and good hardening and tempering performance.
Background
With the change of energy structures and the increase of energy demands, inland energy sources are gradually reduced, and the exploitation of energy sources by various countries is gradually extended from inland to ocean and polar regions. This greatly facilitates the development of long distance transfer lines. Ocean and polar natural conditions are severe, ocean currents, frozen soil, earthquakes and low temperatures greatly increase the risk of damaging materials, and therefore higher requirements are put on the materials. In order to improve the conveying efficiency and reduce the engineering cost, the steel for long-distance petroleum and natural gas conveying pipelines is promoted to develop towards the high-steel-grade, large-diameter, large-wall-thickness and low-temperature toughness direction, and the requirement for high-strength and low-temperature toughness steel is generated.
The high-strength low-temperature ductile steel is a new steel grade with high technical content and high added value, and has good elongation property, cold bending property, welding property and low-temperature crack arrest property besides higher yield strength and tensile strength. The high-strength low-temperature toughness pipeline steel is used for manufacturing pipes such as natural gas conveying elbows, reducing joints, tee joints, four-way joints, pipe caps and the like, so as to adapt to more complex service environments, effectively resist damage of materials caused by landslide, earthquake, faults and low-temperature environments, prolong the service life of the steel, increase engineering safety coefficients and save resources.
Disclosure of Invention
The invention aims to provide a production method of steel for petroleum and natural gas pipelines, which has high strength, good toughness, excellent low-temperature toughness, excellent processability and excellent welding performance, wherein the yield strength of the steel is 485-630 mpa, the tensile strength is 570-730 mpa, the yield ratio is less than or equal to 0.88, the plate thickness is 1/2, the low-temperature impact toughness is minus 40 ℃, and the Akv is more than or equal to 300J. The class A coarse system/fine system of the inclusion is less than or equal to 0.5 level; class B coarse system/fine system is less than or equal to 0.5 level; class C coarse system/fine system is less than or equal to 0.5 level; class D coarse/fine system is not more than 1.0 level.
The invention is realized by the following technical scheme:
the production method of the high-strength low-temperature toughness pipe fitting steel comprises the following process flows of converter smelting, refining, continuous casting, heating and rolling, cooling, checking and warehousing, wherein C=0.07-0.08, si=0.15-0.30, mn=1.40-1.60, P is less than or equal to 0.012, S is less than or equal to 0.002, nb=0.035-0.045, ti=0.015-0.02, al is less than or equal to 0.005, ni=0.12-0.20, cr=0.15-0.20, mo=0.16-0.20, V=0.045-0.055, ca/S=0.6-2.1, and the balance of Fe and unavoidable impurities; the key process steps comprise:
(1) And (3) a converter: controlling oxygen of the converter to be more than or equal to 400ppm, adopting a slide plate device, and adding lime and Al after the converter is heated 2 O 3 Slag treatment and aluminum-free deoxidation are carried out; stirring for 4-8 min by using large argon gas after the furnace to perform full carbon-oxygen reaction, wherein the final carbon content is less than or equal to 0.045;
(2) Refining: adding lime and refined slag to deoxidize and sulfur, wherein the alkalinity CaO/SiO2 of the refined slag is less than or equal to 4.5-6.0, and controlling the aluminum content in molten steel to be less than 0.008% in the whole process, so that Al2O3 inclusion is avoided; maintaining the vacuum for more than 18 minutes under the vacuum degree of 0.5 torr; performing denitrification, hydrogen and oxygen treatment on the molten steel, and controlling H to be less than or equal to 1.5 and O to be less than or equal to 13ppm;
(3) Continuous casting: the whole process of low superheat degree protection casting is performed, the casting temperature is less than or equal to 1534 ℃, the superheat degree is controlled to 8-12 ℃, the secondary cooling adopts a method of dynamically proportioning water, the specific water amount is 0.25-0.45L/kg, the rolling reduction of a casting blank by a dynamic soft reduction technology is 6-8 mm, the bridging behavior in the process of breaking and solidification is reduced, the center segregation and the looseness of the casting blank are reduced, a casting blank quenching device is adopted for quenching the casting blank to less than or equal to 600 ℃ after flame cutting, and the casting blank is put into a heat preservation device for slow cooling to less than or equal to 350 ℃ for charging and rolling;
(4) Rolling: the low-temperature pipe steel with the yield strength of 550-650 mpa, the tensile strength of 630-730 mpa, the yield ratio of less than or equal to 0.88, the thickness of a blank to be heated being more than 3h, the initial rolling temperature of 840-930 ℃, the final rolling temperature of 770-810 ℃, and the on-line quenching is adopted, the initial cooling temperature of 780-820 ℃, the final cooling temperature of 240-320 ℃ and the cooling rate of 25-35 ℃/s, and the low-temperature impact toughness of 1/2 of the low-temperature pipe steel with the Akv of more than or equal to 300J is obtained.
The principle of the invention is as follows:
regarding the step (1), stirring a molten pool by using large oxygen jet flow to manufacture high-alkalinity slag, so that the oxygen content of steel is more than or equal to 400ppm, the carbon oxygen volume=0.0023% and the P is less than or equal to 0.010%, adopting a sliding plate to stop slag tapping, reducing the mixing out of the high-oxidation slag, not deoxidizing and alloying, keeping the high oxygen content of molten steel, stirring for 4-8 min by using large argon after the furnace, and further generating carbon oxygen reaction to produce CO 2 Discharging, further reducing carbon content of molten steel, and eliminating Al from molten steel 2 O 3 The inclusion content is stably controlled to be less than or equal to 0.04 percent, and conditions are created for subsequent refining.
Regarding the step (2), deoxidizing and deoxidizing the lime and the refined slag, sulfur is adopted to produce high-alkalinity fluidity slag, and the alkalinity CaO/SiO of the refined slag is adopted 2 : 4.5-6.0, no aluminum-containing material is added in the whole process, and Al is avoided 2 O 3 The generation of inclusions is convenient for CaO-AL 2 O 3 -SiO 2 The MgO composite inclusion is converted, so that the floating and the removal of the inclusion are facilitated, and the class A thickness/fineness system of the inclusion is stably controlled to be less than or equal to 0.5 level; class B coarse system/fine system is less than or equal to 0.5 level; class C coarse system/fine system is less than or equal to 0.5 level; class D coarse/fine system is not more than 1.0 level.
Regarding the step (3), ladle automatic casting, long nozzle argon blowing protection, argon flow (20-60) L/min, avoiding secondary oxidation of molten steel, controlling ladle temperature in casting to be less than or equal to 1534 ℃, controlling superheat degree to 8-12 ℃, performing whole-course protection casting to effectively reduce secondary oxide generation, controlling continuous casting two-stage cold dynamic water distribution technology, solidifying end three-stage dynamic soft reduction technology, reducing reduction of 7-9 mm, reducing formation of center bridge chain, reducing center segregation and looseness, and ensuring that center segregation C is less than or equal to 0.5 level; and after the casting blank is cut by flame, the casting blank is chilled to be less than or equal to 600 ℃ by a casting blank quenching device, the casting blank tissue is uniformly cooled in a lower line protective cover to be less than or equal to 350 ℃ and then is charged and rolled, so that the diffusion and precipitation of hydrogen are facilitated, the segregated casting blank tissue is further stabilized, and the fine equiaxed crystal tissue is obtained.
In the step (4), through the execution of low-temperature heating at 1140-1180 ℃, initial austenite is tiny, center segregation is diffused, and the mixed structure of a large amount of needle-shaped ferrite middle part bainite on the surface is obtained by matching with rolling under high pressure, further crushing crystal grains and ultra-high cooling speed. The ferrite structure is intertwined, and a large number of dislocation exists, so that the extension of fracture is prevented, and the crack stopping performance of the material is improved.
The invention has the advantages that: simple production flow, low alloy cost and no aluminum component control, and can effectively avoid Al 2 O 3 The generation of inclusions reduces the amount of large-sized inclusions in steel and improves the performance of the steel. The unique furnace decarburization technology omits the traditional RH decarburization process, reduces the working procedures, saves the production cost, saves the energy and reducesLow CO content 2 The emission reduces the converting pressure of the converter, protects the converter lining, prolongs the converter life, and can stably control 0.035-0.045% of carbon elements by further generating argon stirring carbon-oxygen reaction after the converter. The quenching and chilling of the continuous casting blank and the heat preservation technology of the heat preservation cover lead the casting blank to obtain as many tiny equiaxed crystal tissues as possible. Ferrite and bainite are wound to obtain excellent low-temperature crack-stopping performance. The low-temperature pipe fitting steel Q485PF produced by the invention has casting blank segregation C less than or equal to 1.0, the steel plate has uniform and stable performance, excellent crack arrest performance, yield strength of 550-630 Mpa, tensile strength of 650-730 Mpa, yield ratio less than or equal to 0.88, impact at-40 ℃ of 260-450J, inclusion A coarse system/fine system less than or equal to 0.5 level, B coarse system/fine system less than or equal to 0.5 level, C coarse system/fine system less than or equal to 0.5 level, D coarse system/fine system less than or equal to 1.0 level.
Drawings
FIG. 1 is a metallographic structure diagram of a steel sheet produced in example 1.
Detailed Description
The invention is further illustrated below with reference to examples.
Example 1: production of 24mmQ485PF pipe steel
The chemical components of the alloy elements in percentage by weight are C=0.07, si=0.18, mn=1.52, P=0.010, S is less than or equal to 0.0014, nb=0.038, ti=0.016, ni=0.16, cr=0.18, mo=0.17, V=0.048, ca/S=1.3, and the balance of iron and unavoidable impurities, and the key process steps are as follows:
smelting in a converter: the oxygen content of the tapping of the converter is 430ppm, the carbon content is 0.063%, the argon stirring is controlled after the converter, the argon flow is 10L/min, the argon blowing time is 6min, the carbon-oxygen reaction further occurs, and the carbon=0.042% of the argon blowing station is discharged;
(2) Refining in an LF furnace: the refining temperature is 1500-1650 ℃; no aluminum pill or aluminum wire is added in the whole process, thereby avoiding Al 2 O 3 The generation of inclusions is convenient for CaO-AL 2 O 3 -SiO 2 MgO composite inclusion transformation, which is beneficial to floating and removing the inclusion, class A coarse/fine system 0 grade; class B coarse/fine 0.5 grade; class C coarse/fine class 0; class D coarse/fine system 0.5 grade, vacuum maintaining at 0.5 torr for 18 minutes; denitrifying, hydrogen and oxygen treatment of molten steel, and oxygen contentThe purity of the molten steel is improved and is less than or equal to 13ppm;
(3) Continuous casting: controlling the superheat degree to 10 ℃, blowing argon protection flow at a long nozzle to 40L/min, continuously casting secondary cooling water distribution ratio water quantity to 0.2L/kg, solidifying an end three-section dynamic soft reduction technology, reducing the formation of a center bridge chain by 8mm, and relieving center segregation and looseness, wherein the center segregation is of 0.5 level; quenching the casting blank by a quenching device at 580 ℃ after flame cutting, cooling to 330 ℃ in a lower line protective cover, and then charging and rolling, wherein hydrogen of the casting blank is diffused and separated out, and the casting blank state structure is further stabilized to obtain a fine equiaxed crystal structure;
(4) Rolling: the heating temperature is 1140-1180 ℃, the heating time is 290min, the thickness of a blank to be heated is 100mm, the initial rolling temperature is 860 ℃, the final rolling temperature is 740-780 ℃, the online quenching is adopted, the initial cooling temperature is 720 ℃, the final cooling temperature is 240-320 ℃, and the cooling rate is 26.3 ℃/s.
The steel properties were measured as shown in Table 1.
Example 2: production of 52mmQ485PF pipeline steel
The chemical components of the alloy elements are c=0.07, si=0.20, mn=1.54, p=0.011, s.ltoreq.0.0014, nb=0.038, ti=0.016, ni=0.17, cr=0.18, mo=0.17, v=0.048, ca/s=1.3, the balance being iron and unavoidable impurities. The key process steps are as follows:
(1) Smelting in a converter: the tapping oxygen content of the converter is 420ppm, the carbon content is 0.06%, argon stirring is controlled after the converter, the argon flow is 10L/min, the carbon-oxygen reaction further occurs, and the carbon of an argon blowing station is 0.034%;
(2) Refining in an LF furnace: the refining temperature is 1500-1650 ℃; no aluminum pill or aluminum wire is added in the whole process, thereby avoiding Al 2 O 3 The generation of inclusions is convenient for CaO-AL 2 O 3 -SiO 2 MgO composite inclusion transformation, which is beneficial to floating and removing the inclusion, class A coarse/fine system 0 grade; class B coarse/fine 0.5 grade; class C coarse/fine class 0; class D coarse/fine system 0.5 grade, vacuum maintaining at 0.5 torr for 18 minutes; the molten steel is subjected to denitrification, hydrogen and oxygen treatment, the oxygen content is less than or equal to 13ppm, and the purity of the molten steel is improved;
(3) Continuous casting: controlling the superheat degree to 10 ℃, blowing argon protection flow at a long nozzle to 40L/min, continuously casting secondary cooling water distribution ratio water quantity to 0.2L/kg, solidifying an end three-section dynamic soft reduction technology, reducing the formation of a center bridge chain by 8mm, and relieving center segregation and looseness, wherein the center segregation is of 0.5 level; quenching the casting blank by a quenching device at 580 ℃ after flame cutting, cooling to 330 ℃ in a lower line protective cover, and then charging and rolling, wherein the casting blank state structure is further stabilized, and a fine equiaxed crystal structure is obtained;
(4) Rolling: the heating temperature is 1140-1180 ℃, the heating time is 290min, the thickness of a blank to be heated is 140mm, the initial rolling temperature is 830 ℃, the final rolling temperature is 760-780 ℃, the online quenching is adopted, the initial cooling temperature is 730 ℃, the final cooling temperature is 240-320 ℃, and the cooling speed is 23.7 ℃/s.
The steel properties were measured as shown in Table 2.
Table 1 table of properties of 24mmQ485PF pipe steel produced in example 1
Table 2 table of properties of 52mmQ485PF pipeline steel produced in example 2

Claims (1)

1. A production method of high-strength low-temperature toughness pipe fitting steel is characterized by comprising the following steps: the steel comprises, by mass, C=0.07-0.08, si=0.15-0.30, mn=1.40-1.60, P.ltoreq.0.012, S.ltoreq.0.002, nb=0.035-0.045, ti=0.015-0.02, al.ltoreq.0.005, ni=0.12-0.20, cr=0.15-0.20, mo=0.16-0.20, V=0.045-0.055, ca/S=0.6-2.1, and the balance Fe and unavoidable impurities; the key process steps comprise:
(1) And (3) a converter: controlling oxygen of the converter to be more than or equal to 400ppm, adopting a slide plate device, and adding lime and Al after the converter is heated 2 O 3 Slag treatment and aluminum-free deoxidation are carried out; stirring for 4-8 min by using large argon gas after the furnace to perform full carbon-oxygen reaction, wherein the final carbon content is less than or equal to 0.045;
(2) Refining: adding lime and refined slag to deoxidize and sulfur, wherein the alkalinity CaO/SiO2 of the refined slag is less than or equal to 4.5-6.0, and controlling the aluminum content in molten steel to be less than 0.008% in the whole process, so that Al2O3 inclusion is avoided; maintaining the vacuum for more than 18 minutes under the vacuum degree of 0.5 torr; performing denitrification, hydrogen and oxygen treatment on the molten steel, and controlling H to be less than or equal to 1.5 and O to be less than or equal to 13ppm;
(3) Continuous casting: the whole process of low superheat degree protection casting is performed, the casting temperature is less than or equal to 1534 ℃, the superheat degree is controlled to 8-12 ℃, the secondary cooling adopts a method of dynamically proportioning water, the specific water amount is 0.25-0.45L/kg, the rolling reduction of a casting blank by a dynamic soft reduction technology is 6-8 mm, the bridging behavior in the process of breaking and solidification is reduced, the center segregation and the looseness of the casting blank are reduced, a casting blank quenching device is adopted for quenching the casting blank to less than or equal to 600 ℃ after flame cutting, and the casting blank is put into a heat preservation device for slow cooling to less than or equal to 350 ℃ for charging and rolling;
(4) Rolling: the low-temperature pipe steel with the yield strength of 550-650 mpa, the tensile strength of 630-730 mpa, the yield ratio of less than or equal to 0.88, the thickness of a blank to be heated being more than 3h, the initial rolling temperature of 840-930 ℃, the final rolling temperature of 770-810 ℃, and the on-line quenching is adopted, the initial cooling temperature of 780-820 ℃, the final cooling temperature of 240-320 ℃ and the cooling rate of 25-35 ℃/s, and the low-temperature impact toughness of 1/2 of the low-temperature pipe steel with the Akv of more than or equal to 300J is obtained.
CN202311486271.8A 2023-11-09 2023-11-09 Production method of high-strength low-temperature toughness pipe fitting steel Pending CN117248163A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114855060A (en) * 2022-05-30 2022-08-05 湖南华菱湘潭钢铁有限公司 Pipeline steel X80 and production method thereof
CN114921727A (en) * 2022-06-21 2022-08-19 湖南华菱湘潭钢铁有限公司 Production method of acid-resistant pipeline steel X65MS
CN114959496A (en) * 2022-06-25 2022-08-30 湖南华菱湘潭钢铁有限公司 Production method of container steel Q345R resistant to hydrogen sulfide corrosion
CN116970865A (en) * 2023-07-22 2023-10-31 湖南华菱湘潭钢铁有限公司 Production method of aluminum-free pipe fitting steel Q555PF

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114855060A (en) * 2022-05-30 2022-08-05 湖南华菱湘潭钢铁有限公司 Pipeline steel X80 and production method thereof
CN114921727A (en) * 2022-06-21 2022-08-19 湖南华菱湘潭钢铁有限公司 Production method of acid-resistant pipeline steel X65MS
CN114959496A (en) * 2022-06-25 2022-08-30 湖南华菱湘潭钢铁有限公司 Production method of container steel Q345R resistant to hydrogen sulfide corrosion
CN116970865A (en) * 2023-07-22 2023-10-31 湖南华菱湘潭钢铁有限公司 Production method of aluminum-free pipe fitting steel Q555PF

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