CN115449714A - High-toughness thick-wall seamless steel pipe and preparation method thereof - Google Patents

High-toughness thick-wall seamless steel pipe and preparation method thereof Download PDF

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CN115449714A
CN115449714A CN202211141883.9A CN202211141883A CN115449714A CN 115449714 A CN115449714 A CN 115449714A CN 202211141883 A CN202211141883 A CN 202211141883A CN 115449714 A CN115449714 A CN 115449714A
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steel pipe
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CN115449714B (en
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冯莹
邓叙燕
高辉
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Dalipal Pipe Co
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Dalipal Pipe Co
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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
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B19/00—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work
    • B21B19/02—Tube-rolling by rollers arranged outside the work and having their axes not perpendicular to the axis of the work the axes of the rollers being arranged essentially diagonally to the axis of the work, e.g. "cross" tube-rolling ; Diescher mills, Stiefel disc piercers or Stiefel rotary piercers
    • B21B19/04—Rolling basic material of solid, i.e. non-hollow, structure; Piercing, e.g. rotary piercing mills
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
    • 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
    • C22C38/06—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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • 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
    • C21D2211/009—Pearlite
    • 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
    • Y02P10/00—Technologies related to metal processing
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Abstract

The invention particularly discloses a high-toughness thick-wall seamless steel pipe and a preparation method thereof, wherein the thick-wall seamless steel pipe comprises the following components in percentage by weight: c is more than or equal to 0.20 percent and less than or equal to 0.30 percent, si is more than or equal to 0.15 percent and less than or equal to 0.35 percent, mn is more than or equal to 1.45 percent and less than or equal to 1.70 percent, V is more than or equal to 0.05 percent and less than or equal to 0.10 percent, N is more than or equal to 0.013 percent and less than or equal to 0.020 percent, alt is more than or equal to 0.010 percent and less than or equal to 0.040 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.020 percent, ni is less than or equal to 0.25 percent, cu is less than or equal to 0.20 percent, nb is less than or equal to 0.03 percent, and the balance is Fe and inevitable impurities. The invention obviously improves the mechanical property of the seamless steel tube through reasonable component design and unique preparation process of large diameter expansion and large diameter reduction, enables the strength and the toughness to be matched, does not need rolling normalizing treatment or normalizing treatment in the preparation process, has simple process and lower energy consumption, and has higher popularization and application value.

Description

High-toughness thick-wall seamless steel pipe and preparation method thereof
Technical Field
The invention relates to the technical field of seamless steel pipe manufacturing, in particular to a high-toughness thick-wall seamless steel pipe and a preparation method thereof.
Background
According to the design of a well column, the guide sleeve and the surface casing pipe are more large K55 steel grades with the specification of more than 177.8mm, and the raw material for connecting the coupling is a thick-wall seamless steel pipe with the wall thickness of more than 20 mm. Along with the gradual development of the oil and gas exploitation environment to the regions with severe environment and complex geology, the requirement of higher toughness is put forward for a technical casing and an oil layer casing, and meanwhile, the requirement of higher toughness is correspondingly put forward for the casing which plays a role in sealing the surface geology. In order to ensure good coupling connection effect, the strength and toughness requirement of the seamless steel pipe for the butt coupling is improved.
The thick-wall seamless steel pipe prepared by adopting the hot rolling process generally has the problems of coarse grains, uneven inner and outer wall structures and the like of the rolled seamless steel pipe, so that the impact toughness is poor, and therefore, better obdurability matching cannot be obtained. At present, one of the main measures for improving the toughness of the seamless steel pipe is to improve the strength and toughness of the seamless steel pipe by adjusting components, namely increasing the content of alloy elements, but the seamless steel pipe for coupling is required to have good welding performance, and the increase of the alloy elements can cause the welding crack index CE Pcm Is increased. The other method is a normalizing treatment method in the rolling process or a heat treatment method after rolling, and the normalizing treatment method in the rolling process needs to adopt an accelerated cooling mode after sizing, so that the composition proportion of bainite is difficult to control, and if the proportion is improperly controlled, the impact toughness is also obviously reduced; furthermore, the thick-walled pipe has a large heat storage capacity, so that it is difficult to ensure uniform cooling inside and outside the steel pipe, and the cooling of the inner surface is not uniformThe bainite transformation temperature is easy to reach, and the unevenness of internal and external structures is increased. Therefore, at present, a mode of post-rolling heat treatment, namely a method of off-line normalizing heat treatment, is adopted, but the method has high energy consumption and increases the manufacturing cost of the seamless steel pipe. Therefore, it is necessary to develop a new method for manufacturing thick-walled seamless steel tubes, which effectively reduces the production cost on the premise of ensuring the matching of strength and toughness.
Disclosure of Invention
Aiming at the problems that the existing thick-wall seamless steel pipe for coupling has high content of alloy elements, high energy consumption of production process and unmatched obdurability of the prepared seamless steel pipe, the invention provides a high-toughness thick-wall seamless steel pipe and a preparation method thereof.
In order to solve the technical problem, the embodiment of the invention provides the following technical scheme:
a high-toughness thick-wall seamless steel pipe comprises the following components in percentage by weight: c is more than or equal to 0.20 percent and less than or equal to 0.30 percent, si is more than or equal to 0.35 percent and less than or equal to 0.15 percent, mn is more than or equal to 1.70 percent and less than or equal to 1.45 percent, V is more than or equal to 0.10 percent and less than or equal to 0.05 percent and less than or equal to 0.020 percent, N is more than or equal to 0.013 percent and less than or equal to 0.020 percent, alt is more than or equal to 0.010 percent and less than or equal to 0.040 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.020 percent, ni is less than or equal to 0.25 percent, cu is less than or equal to 0.20 percent, nb is less than or equal to 0.03 percent, and the balance is Fe and inevitable impurities.
Compared with the prior art, the high-toughness thick-wall seamless steel pipe provided by the invention has a simple alloy component system, and the strength of the thick-wall seamless steel pipe is improved by adding V element refined crystal grains, but the toughness of the thick-wall seamless steel pipe is reduced by adding the V element, so that the V in a solid solution state is converted into a VN and V (C, N) precipitation state by adding N element with a specific content, and a precipitation strengthening effect is realized, so that the toughness of the thick-wall seamless steel pipe is improved, meanwhile, the dissolution of alloy carbonitride in high-temperature austenite can be reduced by adding a proper amount of N element, the growth of alloy carbonitride crystal grains is hindered, the effect of refining the crystal grains is realized, and the toughness of the thick-wall seamless steel pipe is further improved. The components of the invention are mutually matched and cooperated, so that the prepared thick-wall seamless steel pipe has excellent comprehensive performance and stable mechanical property, the tensile strength can reach 669-712 MPa, the yield strength can reach 481-523 MPa, and the yield ratio can reach 0.70-0.75.
In the present invention, the thick seamless steel pipe means a seamless steel pipe having a wall thickness of 20mm to 30 mm.
Preferably, the microstructure of the high-toughness thick-walled seamless steel pipe is ferrite and pearlite, and the grain size is 8-9 grade.
The invention also provides a preparation method of the high-toughness thick-wall seamless steel pipe, which comprises the following steps:
using scrap steel as a raw material, and preparing a continuous casting round billet through the working procedures of electric arc furnace smelting, ladle refining and continuous casting; heating a continuous casting round billet by using an annular furnace, perforating to prepare a capillary, rolling the capillary to obtain a pierced billet, and reducing the diameter of the pierced billet by using micro-tension and cooling to obtain a high-toughness thick-wall seamless steel pipe; wherein the chemical composition of the continuous casting round billet is the same as that of the high-toughness thick-wall seamless steel pipe.
Preferably, in the ladle refining process, lime, aluminum particles and silicon carbide are added for slag mixing for 2 times, the first time of adding is the beginning of refining power transmission, the time of the first power transmission is more than or equal to 15min, power is cut to measure temperature, sampling is carried out, then secondary power transmission is started, the lime, the aluminum particles and the silicon carbide are added for the second time, the alkalinity of refining slag is 5-6, meanwhile, argon is blown from the bottom to ensure that a molten pool is well stirred, and the soft blowing time is more than or equal to 15min.
The optimized refining process can make the non-metallic inclusion in the steel float sufficiently, reduce the level of the inclusion in the steel and make the total sum of the inclusions in the prepared seamless steel pipe less than or equal to 2.0.
Preferably, in the continuous casting process, argon is adopted for protection between a ladle nozzle and a sliding plate, when the liquid level of the molten steel in the tundish reaches 300-450 mm, a covering agent is quickly added to the surface of the molten steel for isolating air, and the tundish and the crystallizer are subjected to protective casting by adopting an integral submerged nozzle.
The preferable continuous casting process can effectively reduce the contents of H and O in the steel, so that the content of H in the molten steel is less than or equal to 2.5ppm and the content of O in the molten steel is less than or equal to 30ppm.
Preferably, in the heating procedure of the annular furnace, the annular heating furnace is sequentially divided into a preheating section, a heating section and a soaking section according to the conveying direction of the continuous casting round billet, the heating section is divided into a first heating section, a second heating section and a third heating section, and the temperature of each section is controlled respectively; wherein the temperature of the preheating section is controlled to be 800-1000 ℃, the temperature of the heating section is controlled to be 1000-1200 ℃, the temperature of the heating section is controlled to be 1240-1270 ℃, the temperature of the heating section is controlled to be 1260-1290 ℃, and the temperature of the soaking section is controlled to be 1240-1270 ℃.
The preferable control mode of the heating temperature of the annular furnace can promote the full solid solution of V, avoid the coarsening of austenite crystal grains in the heating process, is favorable for controlling the continuous casting round billet to roll in an ideal deformation temperature range, and improves the surface quality, the dimensional precision and the performance of the seamless steel tube.
Preferably, the preheating section is heated in a mode of nozzle-free combustion, and the heating section and the soaking section are heated in a mode of pulse-type nozzle combustion.
The preferred heating mode can realize the accurate control to each section temperature of annular furnace.
Preferably, the hole-expanding ratio in the piercing step is 24% to 26%.
Further, in the punching step, punching was performed using a two-roll guide plate type puncher.
Preferably, in the perforating step, the diameter is expanded by using an expanding guide plate, the outlet angle of the expanding guide plate is 6.0-7.0 degrees, the outlet angle of the perforating roller is 6.0-6.5 degrees, the distance between the expanding guide plates is 230-245 mm, the diameter of the circular section of the perforating head is 224-230 mm, and the distance between the perforating rollers is 205-215 mm.
The preferable perforation process can enable the steel pipe to achieve the effect of expanding the diameter by 24% -26%, and the strength of the steel pipe is effectively improved through deformation strengthening.
Preferably, equal-diameter rolling is adopted in the rolling process, and the temperature of the rolled pierced billet is 1030-1050 ℃.
Preferably, the perforated tubular billet is rotated and naturally cooled on the front stage of the rolling mill, the total time interval of perforation and rolling is 65s, and the oxide skin on the surface of the tubular billet is removed by removing phosphorus through water before entering the rolling mill.
Further, in the rolling step, an ACCU-ROLL rolling mill was used for rolling.
Preferably, in the micro-tension reducing process, the diameter is reduced by 5 to 7 micro-tension reducing machines, the reducing rates from the first micro-tension reducing machine to the third micro-tension reducing machine are sequentially increased, the reducing rates from the third micro-tension reducing machine to the last micro-tension reducing machine are sequentially reduced, and the total reducing rate is 5.0 to 7.5 percent.
Further, in the micro-tension reducing process, 6 micro-tension reducing machines are adopted for reducing, wherein the single-frame reducing rate of the first micro-tension reducing machine is 0.8% -1.2%, the single-frame reducing rate of the second micro-tension reducing machine and the third micro-tension reducing machine is 1.2% -1.6%, the reducing rate of the fourth micro-tension reducing machine is 0.5% -0.7%, and the reducing rate of the fifth micro-tension reducing machine and the sixth micro-tension reducing machine is 0.2% -0.3%.
The preferred micro-tension reducing process avoids the problem of dimensional accuracy affected by the internal hexagonal shape due to uneven metal flow during the reduction of thick-walled steel pipes, so that the ovality of the final finished steel pipe is less than or equal to 0.5% D (D is the nominal outer diameter) and the wall thickness unevenness is less than or equal to 12% t (t is the nominal wall thickness).
Preferably, in the micro-tension reducing step, the temperature of the steel pipe after the completion of the micro-tension reducing is 860 to 920 ℃.
The optimized micro-tension diameter reducing temperature and diameter reducing rate can improve the nucleation rate during phase change, inhibit the aggregation and growth of precipitated phases, facilitate the refinement of crystal grains and the improvement of tissues, and further obviously improve the strength and toughness of the material.
The invention provides a thick-wall seamless steel tube, which has a simple alloy component system, increases the phase transformation ratio from austenite to ferrite through reasonable component design and a unique preparation process of large diameter expansion and large diameter reduction, so that the prepared seamless steel tube has a fine and uniform ferrite and pearlite structure, the ferrite crystal grains are fine and uniform, the grain size reaches 8-9 levels, the mechanical property of the seamless steel tube is obviously improved, the strength and the toughness are matched, the tensile strength of the seamless steel tube can reach 669-712 MPa, the yield strength can reach 481-523 MPa, and the yield ratio is 0.70-0.75; the elongation is 22-31%, the room-temperature transverse Charpy impact energy is 66-145J, the rolling normalizing treatment or normalizing treatment is not needed in the preparation process, the process is simple, the energy consumption is low, the production efficiency of the thick-wall seamless steel tube can be effectively improved, the production cost is reduced, the market competitiveness of enterprises is remarkably improved, and the popularization and application value is high.
Drawings
FIG. 1 is a metallographic structure diagram of a high-toughness thick-walled seamless steel pipe produced in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
In order to better illustrate the invention, the following examples are given by way of further illustration.
Example 1
The embodiment of the invention provides a high-toughness thick-wall seamless steel pipe which comprises the following chemical components:
0.25% of C, 0.25% of Si, 1.55% of Mn, 0.06% of V, 0.016% of N, 0.020% of Alt, 0.012% of S, 0.010% of P, 0.15% of Ni, 0.13% of Cu, 0.01% of Nb, and the balance of Fe and inevitable impurities.
The preparation steps of the high-toughness thick-wall seamless steel pipe are as follows:
using scrap steel as a raw material, and preparing a continuous casting round billet (with the section diameter of 230 mm) with the same chemical composition as the thick-wall seamless steel pipe through the procedures of electric arc furnace smelting, ladle refining and continuous casting; heating the continuous casting round billet by an annular furnace, perforating to prepare a capillary, rolling the capillary to obtain a pierced billet, and performing micro-tension diameter reduction and natural air cooling on the pierced billet to prepare the thick-wall seamless steel tube with the outer diameter of 269.88mm and the wall thickness of 22mm.
In the ladle refining process, lime, aluminum particles and silicon carbide are added for slag adjustment for 2 times, the first time of adding is the beginning of refining power transmission, the time of the first power transmission is 18min, power is cut to measure temperature and sample, then secondary power transmission is started, the lime, the aluminum particles and the silicon carbide are added for the second time, the alkalinity of refining slag is 5-6, meanwhile, argon is blown from the bottom to ensure that a molten pool is well stirred, and the soft blowing time is 20min.
In the continuous casting process, argon protection is adopted between a ladle nozzle and a sliding plate in the continuous casting process, when the liquid level height of the molten steel in the tundish reaches 350mm, a covering agent is quickly added to the surface of the molten steel to isolate air, and the tundish to the crystallizer adopts an integral submerged nozzle for protective casting.
The method comprises the following steps of (1) a circular heating furnace procedure, wherein in the circular heating furnace heating procedure, the circular heating furnace is sequentially divided into a preheating section, a heating section and a soaking section according to the conveying direction of a continuous casting round billet, the heating section is divided into a heating section, a heating section and a heating section, and the temperature of each section is controlled respectively; the preheating section is heated in a non-nozzle combustion mode, the heating section and the soaking section are heated in a pulse nozzle combustion mode, the temperature of the preheating section is controlled to be 900 ℃, the temperature of the heating section is controlled to be 1100 ℃, the temperature of the heating section is controlled to be 1260 ℃, the temperature of the heating section is controlled to be 1275 ℃, the temperature of the soaking section is controlled to be 1250 ℃, and the furnace heating time is 125min.
In the perforating process, a two-roller guide plate type perforating machine is adopted for perforating, the outlet angle of an expanding guide plate is 6.7 degrees, the outlet angle of a perforating roller is 6.3 degrees, the distance between the expanding guide plates is 237mm, the diameter of an even area of a perforating top is 226mm, the distance between perforating rollers is 211mm, the outer diameter of a capillary tube obtained after perforating is 285 mm-290 mm, and the wall thickness is 24-26 mm.
In the rolling process, an ACCU-ROLL rolling mill is adopted for equal-diameter rolling, before the rolling mill, water is used for removing phosphorus and removing oxide skin on the surface of the hollow billet, the hollow billet is rotated and naturally cooled on the front table of the rolling mill after perforation, the total time interval of perforation rolling is 65s, the temperature of the rolled hollow billet is 1040 ℃, the outer diameter of the rolled hollow billet is 285-295 mm, and the wall thickness is 20-22 mm.
In the micro-tension reducing process, 6 micro-tension reducing machines are adopted for reducing the diameter in the micro-tension reducing process, the pass ovality is 1.0-1.02, wherein the single-stand reducing rate of the first micro-tension reducing machine is 0.97%, the reducing rate of the second micro-tension reducing machine is 1.32%, the single-stand reducing rate of the third micro-tension reducing machine is 1.38%, the reducing rate of the fourth micro-tension reducing machine is 0.64%, the reducing rate of the fifth micro-tension reducing machine is 0.29%, the reducing rate of the sixth micro-tension reducing machine is 0.21%, and the temperature of the steel pipe after the micro-tension reducing is finished is 880 ℃.
Example 2
The embodiment of the invention provides a high-toughness thick-wall seamless steel pipe which comprises the following chemical components in parts by weight:
0.2% of C, 0.35% of Si, 1.45% of Mn, 0.05% of V, 0.020% of N, 0.040% of Alt, 0.015% of S, 0.015% of P, 0.23% of Ni, 0.18% of Cu, 0.03% of Nb, and the balance of Fe and inevitable impurities.
The preparation method of the high-toughness thick-wall seamless steel pipe comprises the following steps:
using scrap steel as a raw material, and preparing a continuous casting round billet (with the section diameter of 230 mm) with the same chemical composition as the thick-wall seamless steel pipe through the procedures of electric arc furnace smelting, ladle refining and continuous casting; heating the continuous casting round billet by an annular furnace, perforating to prepare a capillary, rolling the capillary to obtain a pierced billet, and performing micro-tension diameter reduction and natural air cooling on the pierced billet to prepare the thick-wall seamless steel tube with the outer diameter of 269.88mm and the wall thickness of 22mm.
In the ladle refining process, lime, aluminum particles and silicon carbide are added for slag adjustment for 2 times, the first time of adding is the beginning of refining power transmission, the time of the first power transmission is 16min, power is cut to measure temperature and sample, then secondary power transmission is started, the lime, the aluminum particles and the silicon carbide are added for the second time, the alkalinity of refining slag is 5-6, meanwhile, argon is blown from the bottom to ensure that a molten pool is well stirred, and the soft blowing time is 18min.
In the continuous casting process, argon protection is adopted between a ladle nozzle and a sliding plate in the continuous casting process, when the liquid level height of the molten steel in the tundish reaches 450mm, a covering agent is quickly added to the surface of the molten steel to isolate air, and the tundish to the crystallizer adopts an integral submerged nozzle for protective casting.
A circular heating furnace process, wherein in the circular heating furnace heating process, the circular heating furnace is sequentially divided into a preheating section, a heating section and a soaking section according to the conveying direction of the continuous casting round billet, the heating section is divided into a first heating section, a second heating section and a third heating section, and the temperature of each section is controlled respectively; the preheating section is heated in a non-nozzle combustion mode, the heating section and the soaking section are heated in a pulse nozzle combustion mode, the temperature of the preheating section is controlled to be 800 ℃, the temperature of the heating section is controlled to be 1000 ℃, the temperature of the heating section is controlled to be 1240 ℃, the temperature of the heating section is controlled to be 1260 ℃, the temperature of the soaking section is controlled to be 1240 ℃, and the heating time in the furnace is 130min.
In the perforating process, a two-roller guide plate type perforating machine is adopted for perforating, the outlet angle of an expanding guide plate is 6.7 degrees, the outlet angle of a perforating roller is 6.3 degrees, the distance between the expanding guide plates is 230mm, the diameter of an average area of a perforating top is 226mm, the distance between perforating rollers is 209mm, the outer diameter of a capillary tube obtained after perforating is 285 mm-290 mm, and the wall thickness is 24-26 mm.
In the rolling process, an ACCU-ROLL rolling mill is adopted for equal-diameter rolling, before the rolling mill, water is used for removing phosphorus to remove oxide skin on the surface of the hollow billet, the hollow billet is rotated and naturally cooled on the front stage of the rolling mill after perforation, the total time interval of perforation rolling is 65s, the temperature of the hollow billet after rolling is 1030 ℃, the outer diameter of the hollow billet obtained after rolling is 285-295 mm, and the wall thickness is 20-22 mm.
In the micro-tension reducing process, 6 micro-tension reducing machines are adopted for reducing the diameter in the micro-tension reducing process, the pass ovality is 1.0-1.02, wherein the single-stand reducing rate of the first micro-tension reducing machine is 0.89%, the reducing rate of the second micro-tension reducing machine is 1.32%, the single-stand reducing rate of the third micro-tension reducing machine is 1.38%, the reducing rate of the fourth micro-tension reducing machine is 0.64%, the reducing rate of the fifth micro-tension reducing machine is 0.29%, the reducing rate of the sixth micro-tension reducing machine is 0.21%, and the temperature of the steel pipe after the micro-tension reducing is finished is 860 ℃.
Example 3
The embodiment of the invention provides a high-toughness thick-wall seamless steel pipe which comprises the following chemical components in parts by weight:
0.3% of C, 0.15% of Si, 1.70% of Mn, 0.10% of V, 0.013% of N, 0.010% of Alt, 0.008% of S, 0.020% of P, 0.19% of Ni, 0.16% of Cu, 0.02% of Nb and the balance of Fe and inevitable impurities.
The preparation steps of the high-toughness thick-wall seamless steel pipe are as follows:
using scrap steel as a raw material, and preparing a continuous casting round billet (with the section diameter of 230 mm) with the same chemical composition as the thick-wall seamless steel pipe through the procedures of electric arc furnace smelting, ladle refining and continuous casting; heating the continuous casting round billet by an annular furnace, perforating to prepare a capillary, rolling the capillary to obtain a pierced billet, and performing micro-tension diameter reduction and natural air cooling on the pierced billet to prepare the thick-wall seamless steel tube with the outer diameter of 269.88mm and the wall thickness of 22mm.
In the ladle refining process, lime, aluminum particles and silicon carbide are added for slag mixing for 2 times, the first time of adding is the beginning of refining power transmission, the time of the first power transmission is 15min, power failure temperature measurement and sampling are performed, then secondary power transmission is started, the lime, the aluminum particles and the silicon carbide are added for the second time, the alkalinity of refining slag is 5-6, meanwhile, argon is blown in from the bottom to ensure that a molten pool is well stirred, and the soft blowing time is 16min.
In the continuous casting process, argon protection is adopted between a ladle nozzle and a sliding plate in the continuous casting process, when the liquid level height of the molten steel in the tundish reaches 300mm, a covering agent is quickly added to the surface of the molten steel to isolate air, and the tundish to the crystallizer adopts an integral submerged nozzle for protective casting.
The method comprises the following steps of (1) a circular heating furnace procedure, wherein in the circular heating furnace heating procedure, the circular heating furnace is sequentially divided into a preheating section, a heating section and a soaking section according to the conveying direction of a continuous casting round billet, the heating section is divided into a heating section, a heating section and a heating section, and the temperature of each section is controlled respectively; the preheating section is heated in a non-nozzle combustion mode, the heating section and the soaking section are heated in a pulse nozzle combustion mode, the temperature of the preheating section is controlled to be 000 ℃, the temperature of the heating section is controlled to be 1200 ℃, the temperature of the heating section is controlled to be 1270 ℃, the temperature of the heating section is controlled to be 1290 ℃, the temperature of the soaking section is controlled to be 1270 ℃, and the furnace is heated for 120min.
In the perforating process, a two-roller guide plate type perforating machine is adopted for perforating, the outlet angle of an expanding guide plate is 6.7 degrees, the outlet angle of a perforating roller is 6.3 degrees, the distance between the expanding guide plates is 245mm, the diameter of an average area of a perforating top is 226mm, the distance between perforating rollers is 215mm, the outer diameter of a capillary tube obtained after perforating is 285 mm-290 mm, and the wall thickness is 24-26 mm.
In the rolling process, an ACCU-ROLL rolling mill is adopted for equal-diameter rolling, before the rolling mill, water is used for removing phosphorus to remove oxide skin on the surface of the hollow billet, after the hollow billet is punched, the hollow billet rotates on the front stage of the rolling mill for natural cooling, the total time interval of punching and rolling is 65s, the temperature of the hollow billet after the rolling is 1050 ℃, the outer diameter of the hollow billet obtained after the rolling is 285-295 mm, and the wall thickness is 20-22 mm.
In the micro-tension reducing process, 6 micro-tension reducing machines are adopted for reducing the diameter in the micro-tension reducing process, the pass ovality is 1.0-1.02, wherein the single-stand reducing rate of the first micro-tension reducing machine is 1.13%, the reducing rate of the second micro-tension reducing machine is 1.32%, the single-stand reducing rate of the third micro-tension reducing machine is 1.38%, the reducing rate of the fourth micro-tension reducing machine is 0.64%, the reducing rate of the fifth micro-tension reducing machine is 0.29%, the reducing rate of the sixth micro-tension reducing machine is 0.21%, and the temperature of the steel pipe after the micro-tension reducing is finished is 920 ℃.
The seamless steel pipes prepared in examples 1 to 3 had a structure mainly comprising ferrite plus pearlite, fine crystal grains, and a grain size of 8 to 9 grades, wherein the metallographic structure of the seamless steel pipe prepared in example 1 is shown in fig. 1.
The seamless steel pipes prepared in examples 1 to 3 were arbitrarily sampled and analyzed for yield strength (Rt) according to the API Spec 5CT version 10 standard requirements 0.5 ) Tensile strength (R) m ) The results of statistical analysis of the elongation (a) and the room temperature transverse impact energy (21 ℃, TV sample size 10 × 55mm) are shown in table 1, in which the number of samples is the number of seamless steel pipes to be sampled, and random sampling is performed.
TABLE 1
Figure BDA0003853859490000101
Figure BDA0003853859490000111
In conclusion, the thick-wall seamless steel pipe has the advantages of simple component system, low manufacturing cost, high matching degree of strength and toughness, wide application in oil well exploitation in severe environment and complicated geological regions, and wide market prospect.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. A high-toughness thick-wall seamless steel pipe is characterized by comprising the following components in percentage by weight: c is more than or equal to 0.20 percent and less than or equal to 0.30 percent, si is more than or equal to 0.35 percent and less than or equal to 0.15 percent, mn is more than or equal to 1.70 percent and less than or equal to 1.45 percent, V is more than or equal to 0.10 percent and less than or equal to 0.05 percent and less than or equal to 0.020 percent, N is more than or equal to 0.013 percent and less than or equal to 0.020 percent, alt is more than or equal to 0.010 percent and less than or equal to 0.040 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.020 percent, ni is less than or equal to 0.25 percent, cu is less than or equal to 0.20 percent, nb is less than or equal to 0.03 percent, and the balance is Fe and inevitable impurities.
2. A high toughness thick wall seamless steel pipe as claimed in claim 1, wherein its microstructure is ferrite and pearlite with a grain size of 8 to 9 grade.
3. A method for producing a high toughness thick wall seamless steel pipe as claimed in claim 1 or 2, characterized by comprising the steps of: using scrap steel as a raw material, and preparing a continuous casting round billet through the working procedures of electric arc furnace smelting, ladle refining and continuous casting; heating a continuous casting round billet by using an annular furnace, perforating to prepare a capillary, rolling the capillary to obtain a pierced billet, and reducing the diameter of the pierced billet by using micro-tension and cooling to obtain a high-toughness thick-wall seamless steel pipe; wherein the chemical composition of the continuous casting round billet is the same as that of the high-toughness thick-wall seamless steel pipe.
4. The method for producing a high-toughness thick-walled seamless steel pipe as claimed in claim 3, wherein in the annular furnace heating step, the annular furnace is divided into a preheating section, a heating section and a soaking section in this order in the direction of conveyance of the continuously cast round billet, the heating section is divided into a first heating section, a second heating section and a third heating section, and each section is subjected to temperature control; wherein the temperature of the preheating section is controlled to be 800-1000 ℃, the temperature of the heating section is controlled to be 1000-1200 ℃, the temperature of the heating section is controlled to be 1240-1270 ℃, the temperature of the heating section is controlled to be 1260-1290 ℃, and the temperature of the soaking section is controlled to be 1240-1270 ℃.
5. A method for producing a high toughness thick-walled seamless steel pipe as claimed in claim 3, wherein the hole-expanding ratio in the piercing step is 24 to 26%.
6. A method for producing a high-toughness thick-walled seamless steel pipe as claimed in claim 5, wherein in the piercing step, the diameter of the pipe is increased by using a diameter-increasing guide plate, the outlet angle of the diameter-increasing guide plate is 6.0 to 7.0 degrees, the outlet angle of the piercing rolls is 6.0 to 6.5 degrees, the pitch of the diameter-increasing guide plates is 230 to 245mm, the diameter of the entire piercing plug area is 224 to 230mm, and the piercing roll pitch is 205 to 215mm.
7. A method for producing a high toughness thick-walled seamless steel tube as claimed in claim 3, wherein the rolling step is constant diameter rolling, and the temperature of the rolled pierced billet is 1030 ℃ to 1050 ℃.
8. A method for producing a high toughness thick-walled seamless steel pipe as claimed in claim 3, wherein in the micro-tension reducing step, the reducing is performed by using 5 to 7 micro-tension reducing mills, and wherein the reducing ratios from the first micro-tension reducing mill to the third micro-tension reducing mill are sequentially increased, and the reducing ratios from the third micro-tension reducing mill to the last micro-tension reducing mill are sequentially decreased, and wherein the total reducing ratio is 5.0% to 7.5%.
9. The method for producing a high-strength seamless steel pipe according to claim 8, wherein in the micro-tension reducing step, the reducing is performed by using 6 micro-tension reducing machines, wherein the single-stand reducing ratio of the first micro-tension reducing machine is 0.8% to 1.2%, the single-stand reducing ratios of the second micro-tension reducing machine and the third micro-tension reducing machine are both 1.2% to 1.6%, the reducing ratio of the fourth micro-tension reducing machine is 0.5% to 0.7%, and the reducing ratios of the fifth micro-tension reducing machine and the sixth micro-tension reducing machine are both 0.2% to 0.3%.
10. The method of producing a high-strength seamless steel pipe according to claim 3 or 9, wherein in the micro-tension reducing step, the temperature of the steel pipe after the completion of the micro-tension reducing is 860 ℃ to 920 ℃.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101658879A (en) * 2008-08-27 2010-03-03 宝山钢铁股份有限公司 Method for manufacturing seamless steel pipe
CN113106346A (en) * 2021-04-12 2021-07-13 达力普石油专用管有限公司 High-strength seamless line pipe and preparation method thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101658879A (en) * 2008-08-27 2010-03-03 宝山钢铁股份有限公司 Method for manufacturing seamless steel pipe
CN113106346A (en) * 2021-04-12 2021-07-13 达力普石油专用管有限公司 High-strength seamless line pipe and preparation method thereof

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