CN116574970A - Off-eutectoid transformation thinned crystal pressure vessel steel plate and manufacturing method thereof - Google Patents

Off-eutectoid transformation thinned crystal pressure vessel steel plate and manufacturing method thereof Download PDF

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CN116574970A
CN116574970A CN202310439649.2A CN202310439649A CN116574970A CN 116574970 A CN116574970 A CN 116574970A CN 202310439649 A CN202310439649 A CN 202310439649A CN 116574970 A CN116574970 A CN 116574970A
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percent
temperature
steel plate
rolling
steel
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Inventor
欧阳鑫
王储
胡昕明
邢梦楠
颜秉宇
高强
隋松言
苏小利
隋广雨
张坤
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Angang Steel Co Ltd
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Angang 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
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • 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
    • C21D1/26—Methods of annealing
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
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    • C21—METALLURGY OF IRON
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    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
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    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0231—Warm rolling
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • 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
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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    • 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
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    • 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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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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    • 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
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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    • 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
    • C21D2211/003—Cementite
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    • 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
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  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses a devitrification transformation and thinning crystal pressure vessel steel plate and a manufacturing method thereof, belonging to the technical field of steel preparation. The chemical components of the off-eutectoid transformation thinned crystal pressure vessel steel plate are as follows in percentage by weight: c:0.20 to 0.30 percent of Si:0.15 to 0.40 percent of Mn:0.90 to 1.50 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, and Cr:1.0% -2.0%, ni:0.20% -0.30%, mo:1.0 to 2.0 percent, nb:0.01 to 0.02 percent of Ti: 0.02-0.03%, cu:0.80 to 0.90 percent, V:0.02 to 0.03 percent, B: 0.001-0.002%, als:0.025 to 0.035 percent, N:0.06% -0.08%, the balance Fe and unavoidable impurities, adopting chromium-copper alloying, high-temperature short-time homogenization treatment, two-stage rolling, short-time normalizing and other tissue refining technologies to refine the microstructure of the medium carbon container steel plate, obtaining a fully spheroidized microstructure, wherein the grain size of cementite reaches 1.0-2.5 mu m, and the grain size of ferrite reaches 0.5-2.0 mu m, and simultaneously has good comprehensive mechanical properties, so that the medium carbon container steel plate is expected to be widely applied in the field of manufacturing pressure container equipment.

Description

Off-eutectoid transformation thinned crystal pressure vessel steel plate and manufacturing method thereof
Technical Field
The invention belongs to the technical field of steel preparation, and particularly relates to a devitrification eutectoid crystal-thinning pressure vessel steel plate and a manufacturing method thereof.
Background
Conventionally, it is thought that medium carbon steel can obtain high hardness and strength, and is suitable for use in the production of tool steels and die steels which are not highly required to toughness, but cannot be used for the production of structural materials such as pressure vessels because of its high brittleness. Along with the continuous development of the industry, the development direction of equipment tends to be large-scale, high-performance and long-term service, so that higher requirements are put on raw materials for equipment manufacture, and the toughness of the traditional low-carbon alloy container steel plate cannot meet the manufacturing requirements of high-end pressure container equipment. As is known, the performance of the material depends on the tissue type, the tissue is uniformly refined, the comprehensive mechanical property of the material is greatly improved, and the high matching degree of the toughness is realized.
The invention patent with the application number of 201710037112.8 discloses a manufacturing process of large-specification 42CrMo4 quenched and tempered steel for an outer main shaft of a wind power speed increasing box, wherein a die casting and 3500t rapid forging machine forging process is adopted in the patent, so that the manufacturing process has the advantages of higher production cost, high energy consumption, slow production rhythm and poorer plate shape and performance uniformity of products. The invention patent with the application number of CN201710919045.2 discloses a normalizing method for realizing the refinement of low-activation ferrite/martensitic steel structure, wherein the normalizing process is heated to 900-930 ℃ at 50-60 ℃/s, the temperature is kept for 1-2 s, and then the normalizing process is air-cooled to 20-25 ℃ at room temperature for refining the duplex stainless steel structure. The invention only provides a heat treatment process, does not definitely adopt a rolling process, and does not definitely propose the degree and grade of tissue refinement. At present, the tissue refinement of low carbon steel is successfully realized, but the related research of the tissue refinement of medium and high carbon steel is not reported yet.
Disclosure of Invention
In view of the above, the invention aims to provide a devitrification eutectoid transformation thinned crystal pressure vessel steel plate and a manufacturing method thereof, and the invention adopts the structure refining technologies of chromium-copper alloying, high-temperature short-time homogenization treatment, two-stage rolling, short-time normalizing and the like to refine the microstructure of the medium carbon vessel steel plate, so that the medium carbon steel plate not only has high room temperature strength, but also has good low-temperature toughness, and can obtain higher elongation after fracture through heat treatment. During the off eutectoid transformation, pearlite transformation does not occur, and carbide is precipitated in a spherical form on the austenite grain boundaries near undissolved carbide and inside the austenite grains. After the treatment, a fully spheroidized microstructure can be obtained, the grain size of cementite reaches 1.0-2.5 mu m, and the grain size of ferrite reaches 0.5-2.0 mu m, and the product has good comprehensive mechanical properties. The good technological property and mechanical property of the medium carbon steel make the medium carbon steel hopefully widely applied in the field of manufacturing pressure vessel equipment.
The invention aims at realizing the following steps:
the invention provides a steel plate for a devitrification transformation and thinning crystal pressure vessel, which comprises the following chemical components in percentage by weight: c:0.20 to 0.30 percent of Si:0.15 to 0.40 percent of Mn:0.90 to 1.50 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, and Cr:1.0% -2.0%, ni:0.20% -0.30%, mo:1.0 to 2.0 percent, nb:0.01 to 0.02 percent of Ti: 0.02-0.03%, cu:0.80 to 0.90 percent, V:0.02 to 0.03 percent, B: 0.001-0.002%, als:0.025 to 0.035 percent, N:0.06% -0.08%, and the balance of Fe and unavoidable impurities.
The action mechanism of the components is as follows:
c: c is a main constituent element of steel, the strength of the steel mainly depends on the content of C element in the steel, and the excessively high content of C element can lead to poor toughness, plasticity and welding performance of the steel; too low a content of C element results in lower strength of the steel and performance after simulated stress relief treatment. In order to ensure that the steel plate has good low-temperature impact toughness, strength and welding performance matching in the use process, the C content in the steel is required to be controlled within the range of 0.20-0.30 percent.
Si: si is added to the medium carbon steel, which affects the thermodynamics of the iron-carbon system and the kinetics of carbide formation and dissolution. Silicon as a ferrite stabilizing element will raise the Ac1 point of the steel. The addition of silicon causes the carbon content of the eutectoid composition to decrease, thereby increasing the amount of pre-eutectoid carbide, such that the volume fraction of carbide used to pin the grain boundaries in the gamma + theta two-phase region increases. Thus, not only the growth of ferrite and austenite grains is suppressed. Silicon is insoluble in carbide and when carbide precipitates, silicon is distributed around the carbide, locally forming a high concentration zone of silicon. Silicon is in turn an element that increases the activity of carbon. In the high concentration region of silicon, the activity of carbon is also improved correspondingly, so that the diffusion flow rate of carbon to carbide is reduced, and therefore, coarsening of carbide can be inhibited, and the Si content of the invention is controlled to be 0.15-0.40%.
Mn: mn element can strengthen ferrite in steel grade through solid solution strengthening, C-Mn strengthening is also a main mode for improving strength of low-carbon steel, but Mn content is too high, so that production cost is increased, mn element is easy to combine with S element to generate MnS, and hydrogen-induced cracking resistance of the material is reduced, so that the Mn content in the steel is required to be controlled to be 0.90% -1.50%.
P: phosphorus is a harmful element in steel, increases cold brittleness of the steel, worsens welding performance, reduces plasticity, worsens cold bending performance, and is particularly sensitive to irradiation embrittlement. The invention therefore requires that the lower the P content in the steel, the better, the invention requires less than 0.015%.
S: sulfur is a hazardous element in the usual case. S generally tends to form brittle sulfides with alloying elements in the steel, causing hot shortness to the steel, reducing the ductility and toughness of the steel, and S also tends to accelerate irradiation embrittlement. Therefore, the S content in the steel is required to be limited to below 0.005%.
Als: the Ac1 point of the steel can be increased by aluminum alloying, the proeutectoid cementite is thinned and uniformly distributed, the formation of network carbide is inhibited, and after aluminum is added, both grain boundary carbide and widmannstatten structure carbide disappear, so that a thinned complete pearlite structure is obtained. Therefore, the Al content in the steel is required to be 0.025% -0.035%.
V: v belongs to microalloy elements, and V microalloy in steel can form tiny second phase particles, plays roles of pinning grain boundary and precipitation strengthening, can effectively refine grains, and greatly improves comprehensive mechanical properties of steel such as strength, toughness, ductility, thermal fatigue resistance and the like, so that the range of V added in the steel is required to be 0.02-0.03%.
Ni: ni is a solid solution strengthening element in steel, can improve the strength of the steel, and reduces dislocation movement resistance of steel types to relax stress so as to change the substructure of a matrix structure, thereby improving the toughness of the steel, particularly the low-temperature toughness, so that the invention requires that the Ni content be controlled to be 0.20-0.30%.
Cr: chromium is an element that stabilizes the carbide, and the addition of chromium reduces the dissolution rate of the carbide. Therefore, when the thermal deformation tissue refining process is adopted, eutectoid transformation can be avoided even if the heating temperature is increased or the heating time is prolonged, and the refined tissue can be obtained. Chromium also inhibits graphitization of the silicon-containing, aluminum ultra-high carbon steel. The present invention therefore requires that the Cr content in the steel be controlled to 1.0-2.0%.
Cu: the outstanding effect of Cu in steel is to improve the corrosion resistance of common carbon low alloy steel, and also to improve the strength and yield ratio of steel without adversely affecting the welding performance. When the copper content exceeds 0.75%, the aging strengthening effect can be generated after solution treatment and aging. Meanwhile, the effect is similar to nickel, and the nickel-saving and cost-reducing effects can be achieved. However, when the content is high, copper embrittlement occurs during heat deformation processing. The present invention therefore requires that the Cu content in the steel be controlled to 0.80-0.90%.
Nb: nb is used as a strong carbide forming element to form NbC phase with large dispersity and good high-temperature stability in steel grade, plays a role of precipitation strengthening, can effectively refine grains through multi-stage rolling, and improves the toughness reduction caused by precipitation strengthening, so that the steel plate has the comprehensive performance of high strength and high toughness. In addition, in the steel added by Nb-Mo composite, mo can be partially polymerized on an NbC matrix interface, so that coarsening of NbC particles is prevented, and the high-temperature strength of the steel is greatly improved, and therefore, the Nb content in the steel is required to be controlled to be 0.01-0.02%.
Mo: mo mainly relies on solid solution strengthening and grain boundary strengthening to improve the strength of steel; secondly, mo increases the stability of supercooled austenite, so that the austenite moves to the right of a ferrite transformation curve, and finer ferrite tissues are obtained after transformation; in addition, ti and Mo are combined, nano-sized Ti-Mo (CN) carbide is greatly precipitated in the steel, and the refined carbide is used for pinning dislocation, so that the toughness of the steel is greatly improved, and the Mo content in the steel is required to be controlled to be 1.0-2.0%
Ti: adding proper amount of Ti to form a large amount of dispersed fine TiN or Ti 2 O 3 Particles which act as heterogeneous nucleation cores for the needle-shaped ferrite when the structure solidifies, thereby refining the structure. Ti also has deoxidizing effect, and ensures that B is not oxidized and nitrided. And B can reduce the transformation temperature from austenite to ferrite phase, promote the formation of acicular ferrite in the crystal grains and play a role in refining the crystal grains. However, when w (Ti) is not less than 0.09%, the acicular ferrite content is reduced to deteriorate the low-temperature toughness of the steel sheet, so that the Ti content in the steel is required to be controlled to 0.02 to 0.03% in the present invention.
B: and B can reduce the transformation temperature from austenite to ferrite phase, promote the formation of acicular ferrite in the grains and play a role in refining the grains. Therefore, the present invention requires that the B content in the steel be controlled to 0.001-0.002%.
N: n can be combined with Ti to form a large amount of tiny TiN which are dispersed and distributed, and can be used as heterogeneous nucleation cores of the needle-shaped ferrite when the tissue is solidified, so that the tissue is refined. The present invention therefore requires that the N content in the steel be controlled to 0.06-0.08%.
Based on the technical scheme, the microstructure of the steel plate is a fully spheroidized microstructure, the grain size of cementite reaches 1.0-2.5 mu m, and the grain size of ferrite reaches 0.5-2.0 mu m.
Based on the technical scheme, further, the tensile strength of the steel plate is 600-740 MPa, the yield strength is 360-500 MPa, the elongation after fracture is 40-50%, the impact power at minus 40 ℃ is 360-500J, the surface Brinell hardness is 290-360 HBW, and the high-temperature tensile yield strength at 450 ℃ is 265-405 MPa.
The second technical scheme of the invention is to provide a manufacturing method of the off-eutectoid transformation thinned crystal pressure vessel steel plate, which mainly comprises high-temperature short-time homogenization treatment, two-stage rolling and short-time normalizing treatment, and comprises the following steps:
(1) High-temperature short-time homogenization treatment: preserving heat of the continuous casting blank for 1-2h at 1130-1170 ℃, carrying out homogenizing annealing in a single-phase austenite region, and fully dissolving carbon elements;
(2) Two-stage rolling: the homogenized continuous casting billet is sent to a rolling mill for rolling at the initial rolling temperature of 1080-1110 ℃ and the final rolling temperature of 810-840 ℃ and the reduction rate of each pass of 15-25%, and is air-cooled to 600-650 ℃ for finish rolling at the final rolling temperature of 510-620 ℃ and the reduction rate of each pass of 5-15%;
(3) Short-time normalizing treatment: and (3) conveying the rolled steel plate to a continuous heat treatment furnace, austenitizing in a temperature range of 20-40 ℃ higher than Ac1, keeping the steel plate warm for 15-30 min, and air-cooling to room temperature.
Based on the technical scheme, the thickness of the continuous casting billet in the step (1) is 150-350mm.
Based on the technical scheme, the homogenization temperature in the step (1) is 1140-1160 ℃.
Based on the technical scheme, the thickness of the intermediate blank in the step (2) is 2-3 times of the thickness of the finished steel plate.
Based on the technical scheme, further, in the step (2), the rough rolling start temperature is 1093-1108 ℃, the finish rolling temperature is 813-838 ℃, the finish rolling start temperature is 640-650 ℃, and the finish rolling temperature is 514-613 ℃.
Based on the technical scheme, the austenitizing temperature in the step (3) is 820-840 ℃.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, chromium is adopted to improve the toughness matching of the steel plate, and chromium is used as an element for stabilizing carbide, so that the dissolution rate of the carbide is reduced, and therefore, when a two-stage rolling structure refinement process is adopted, eutectoid transformation can be avoided even if the heating temperature is increased or the heating time is prolonged, and a refined structure is obtained; homogenizing at high temperature for a short time, homogenizing and annealing in a single-phase austenite region, and fully dissolving carbon element; two-stage rolling is performed, which is helpful for breaking the proeutectoid cementite separated out from austenite, and avoiding forming net carbide; pearlite transformation does not occur in the short-time normalizing process, and carbide is precipitated in a spherical form on the austenite grain boundaries near undissolved carbide and inside the austenite grains. After the treatment, a fully spheroidized microstructure can be obtained, the grain size of cementite reaches 1.0-2.5 mu m, and the grain size of ferrite reaches 0.5-2.0 mu m. The final product steel plate has tensile strength of 600-740 MPa, yield strength of 360-500 MPa, elongation after fracture of 40-50%, impact power of 360-500J at minus 40 ℃, brinell hardness of 290-360 HBW at the surface and high-temperature tensile yield strength of 265-405 MPa at 450 ℃.
Drawings
In order to more clearly illustrate the embodiments of the present invention, the drawings to which the embodiments relate will be briefly described.
FIG. 1 is a golden phase diagram of a steel sheet prepared in example 1.
Detailed Description
The following detailed description of the invention is provided in connection with examples, but the implementation of the invention is not limited thereto, and it is obvious that the examples described below are only some examples of the invention, and that it is within the scope of protection of the invention to those skilled in the art to obtain other similar examples without inventive faculty.
Examples 1 to 6
The embodiment provides a manufacturing method of a steel plate of a devitrification transformation and thinning crystal pressure vessel, wherein the chemical compositions and weight percentages of the steel plate are shown in table 1;
TABLE 1 chemical composition and weight percent (wt%) of billets of examples 1-6
The method comprises the following steps:
(1) High-temperature short-time homogenization treatment: directly hot-charging a continuous casting billet with the thickness of 150-350mm into a heating furnace, preserving heat for 1.1-1.9h at 1145-1157 ℃, carrying out homogenizing annealing in a single-phase austenite region, fully dissolving carbon elements, and carrying out high-temperature short-time homogenizing treatment, wherein main technological parameters are shown in Table 2;
(2) Two-stage rolling: after homogenization treatment, the continuous casting blank is hot-rolled by a double-frame rolling mill, firstly, the continuous casting blank is rough-rolled and cogged, the proeutectoid cementite is formed in the form of fine particles in an austenite grain boundary and a high-density dislocation region in the crystal, the rough rolling start temperature is 1093-1108 ℃, the finish rolling temperature is 813-838 ℃, the reduction rate of each pass is ensured to be 17-24%, the thickness of an intermediate blank is 2-3 times of the thickness of a finished steel plate, the intermediate blank roller way is reciprocally swung and air-cooled until the temperature reaches 640-650 ℃ after rough rolling, continuous multi-pass quick finish rolling is carried out, the finish rolling temperature is 514-613 ℃, the reduction rate of each pass is ensured to be 5-15%, the thermal deformation in the process is beneficial to breaking the proeutectoid cementite precipitated in the austenite, the formation of net carbide is avoided, and the main technological parameters of two-stage rolling are shown in table 2;
TABLE 2 essential process parameters for high temperature short time homogenization treatment and two stage rolling of examples 1-6
(3) Short-time normalizing: after the steel plate is rolled, heat is sent to a continuous heat treatment furnace, austenitizing is carried out for a short time in a range of 20-40 ℃ higher than Ac1 temperature (800 ℃ measured), air cooling is carried out to room temperature after the steel plate is subjected to clean heat preservation for 17-30 min, and short-time normalizing heat treatment (the process is called off-eutectoid transformation) is completed. During the off eutectoid transformation, pearlite transformation does not occur, and carbide is precipitated in a spherical form on the austenite grain boundaries near undissolved carbide and inside the austenite grains. After the treatment, a fully spheroidized microstructure can be obtained, the steel plate has good mechanical properties, the main technological parameters of short-time normalizing are shown in Table 3, and the grain sizes and the comprehensive mechanical properties of the steel plates obtained in examples 1-6 are shown in Table 4.
TABLE 3 major process parameters for short-time normalizing of Steel sheets of examples 1-6
TABLE 4 grain size and comprehensive mechanical Properties of Steel sheets of examples 1-6
The present invention has been properly and fully described in the above embodiments by way of example only, and the present invention is not limited thereto, but various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention, and any modifications, equivalents, improvements, etc. should be included in the scope of the present invention.

Claims (9)

1. The off-eutectoid transformation thinned crystal pressure vessel steel plate is characterized by comprising the following chemical components in percentage by weight: c:0.20 to 0.30 percent of Si:0.15 to 0.40 percent of Mn:0.90 to 1.50 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, and Cr:1.0% -2.0%, ni:0.20% -0.30%, mo:1.0 to 2.0 percent, nb:0.01 to 0.02 percent of Ti: 0.02-0.03%, cu:0.80 to 0.90 percent, V:0.02 to 0.03 percent, B: 0.001-0.002%, als:0.025 to 0.035 percent, N:0.06% -0.08%, and the balance of Fe and unavoidable impurities.
2. The off-eutectoid rotary-grain pressure vessel steel sheet according to claim 1, wherein the microstructure of the steel sheet is a fully spheroidized microstructure, cementite grain size reaches 1.0 to 2.5 μm, and ferrite grain size reaches 0.5 to 2.0 μm.
3. The off-eutectoid rotary-grain pressure vessel steel plate according to claim 1, wherein the steel plate has tensile strength of 600-740 MPa, yield strength of 360-500 MPa, elongation after break of 40-50%, impact power of-40 ℃ of 360-500J, surface brinell hardness of 290-360 hbw, and high-temperature tensile yield strength of 450 ℃ of 265-405 MPa.
4. The method for producing an off-eutectoid transformation-thinned steel plate for a pressure vessel according to any one of claims 1 to 3, which is characterized by mainly comprising a high-temperature short-time homogenizing treatment, a two-stage rolling treatment and a short-time normalizing treatment, comprising the steps of:
(1) High-temperature short-time homogenization treatment: preserving heat of the continuous casting blank for 1-2h at 1130-1170 ℃, carrying out homogenizing annealing in a single-phase austenite region, and fully dissolving carbon elements;
(2) Two-stage rolling: the homogenized continuous casting billet is sent to a rolling mill for rolling at the initial rolling temperature of 1080-1110 ℃ and the final rolling temperature of 810-840 ℃ and the reduction rate of each pass of 15-25%, and is air-cooled to 600-650 ℃ for finish rolling at the final rolling temperature of 510-620 ℃ and the reduction rate of each pass of 5-15%;
(3) Short-time normalizing treatment: and (3) conveying the rolled steel plate to a continuous heat treatment furnace, austenitizing in a temperature range of 20-40 ℃ higher than Ac1, keeping the steel plate warm for 15-30 min, and air-cooling to room temperature.
5. The method according to claim 4, wherein the thickness of the continuous casting slab in the step (1) is 150 to 350mm.
6. The method according to claim 4, wherein the homogenization temperature in step (1) is 1140 to 1160 ℃.
7. The method of manufacturing according to claim 4, wherein the thickness of the intermediate blank in step (2) is 2 to 3 times the thickness of the finished steel sheet.
8. The method according to claim 4, wherein the rough rolling start temperature is 1093 to 1108 ℃, the finish rolling temperature is 813 to 838 ℃, the finish rolling start temperature is 640 to 650 ℃, and the finish rolling temperature is 514 to 613 ℃ in the step (2).
9. The method according to claim 4, wherein the austenitizing temperature in the step (3) is 820 to 840 ℃.
CN202310439649.2A 2023-04-23 2023-04-23 Off-eutectoid transformation thinned crystal pressure vessel steel plate and manufacturing method thereof Pending CN116574970A (en)

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