CN116732452A - High-corrosion-resistance high-carbon austenitic stainless steel for nuclear power and manufacturing method thereof - Google Patents

High-corrosion-resistance high-carbon austenitic stainless steel for nuclear power and manufacturing method thereof Download PDF

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CN116732452A
CN116732452A CN202310621122.1A CN202310621122A CN116732452A CN 116732452 A CN116732452 A CN 116732452A CN 202310621122 A CN202310621122 A CN 202310621122A CN 116732452 A CN116732452 A CN 116732452A
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steel
stainless steel
temperature
nuclear power
austenitic stainless
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王爽
胡海洋
颜秉宇
孙殿东
王勇
陈捷
张瀚宁
高天宇
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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
    • C22C38/18—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
    • 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
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • 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
    • C22C38/48—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
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
    • 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
    • C21D2211/001—Austenite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses a high corrosion resistance high carbon austenitic stainless steel for nuclear power and a manufacturing method thereof, wherein the chemical components of the steel comprise C:0.20% -0.35%; si:2.0% -3.0%; mn:5.50% -7.50%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; ni:3.80% -4.50%; cr:16.75% -18.25%; co:0.75% -1.00%, nb:0.10% -0.20%; zr:0.05% -0.08%. Production by combining smelting, continuous casting, heating, rolling and heat treatment processes ensures steel plateHas high comprehensive performance level, room temperature yield strength (R) p0.2 ) And tensile strength (R) m ) Respectively reaching more than 530MPa and 735 MPa; yield strength (R) at high temperature of 550 DEG C p0.2 ) And tensile strength (R) m ) Respectively reaching more than 325MPa and 527 MPa; when the impact energy reaches more than 150J at the low temperature of 20 ℃ below zero, and the accumulated loss weight is less than or equal to 2.53mg after 40h vibration cavitation test, so that the corrosion resistance is excellent.

Description

High-corrosion-resistance high-carbon austenitic stainless steel for nuclear power and manufacturing method thereof
Technical Field
The invention belongs to the technical field of metal materials, and particularly relates to high-corrosion-resistance high-carbon austenitic stainless steel for nuclear power and a manufacturing method thereof.
Background
The austenitic stainless steel has good mechanical property, processability, corrosion resistance and neutron irradiation resistance, and is widely applied in industry, and the austenitic stainless steel accounts for more than 60% of the total yield of the stainless steel in the world.
With the rapid development of the nuclear power industry, the demand for equipment materials is also higher and higher, and the large-scale and high-temperature and high-pressure equipment are important development trends in the future. In the liquid flowing in the nuclear power unit, when the pressure in a local area suddenly drops below the vaporization pressure corresponding to the temperature of the liquid in the area for some reason, part of the liquid is vaporized, and the gas dissolved in the liquid escapes, so that bubbles in the liquid flow are formed. When the bubble enters the region with higher pressure along with the liquid flow, the bubble is suddenly collapsed due to the loss of existing conditions, and the pressure of the local region is suddenly increased due to the movement of the liquid around the original bubble. If the gas bubbles which are formed and grow up in the liquid flow are collapsed frequently near the solid wall surface, the wall surface can be subjected to repeated impact of huge pressure, so that fatigue damage and even surface degradation of the material are caused. In order to prevent excessive precipitation of Cr carbide, the conventional austenitic stainless steel is generally low in carbon content, so that the strength is not high, the development requirement of the industry is influenced, and the technical problem to be solved in the field is urgent.
Patent application number CN202110727249.2, "high carbon austenitic stainless steel plate with uniform intergranular corrosion resistant structure and manufacturing method thereof," comprises the following components in percentage by weight: c:0.07% -0.11%, si:0.49% -0.97%, mn: 1.53-2.51%, P is less than or equal to 0.035%, S is less than or equal to 0.015%, ni:7.90% -9.40%, cr:19.10% -19.90%, V:0.32% -0.53%, W:0.03% -0.06%, N:0.04% -0.12%, and the balance of Fe and unavoidable impurities; the manufacturing method comprises smelting, casting, heating, rolling, heat treatment and cold straightening; the invention adopts a mode of combining a two-stage controlled rolling mode with a three-stage solution treatment to produce the austenitic stainless steel plate with the maximum thickness of 100mm, the grain size of the section of the whole thickness of the produced steel plate meets the 3-5-grade requirement, no mixed crystal phenomenon occurs, and the steel plate has good intergranular corrosion resistance. The carbon content in the steel plate is low, the strength grade of the steel plate is difficult to meet the development requirement of the industry, and the high-temperature performance and cavitation erosion resistance of the steel plate are not researched and discussed.
Patent application number CN202110725422.5 discloses a high-carbon low-ferrite austenitic stainless steel plate and a production method thereof, wherein the steel plate comprises the following components in percentage by weight: c:0.15% -0.20%, si:0.4% -0.6%, mn:1.20 to 1.40 percent, less than or equal to 0.010 percent of P, less than or equal to 0.002 percent of S, and Cr:21.0% -22.0%, ni:10.5% -11.5%, mo:2.0% -3.0%, N:0.035% -0.055%, and the balance of Fe and unavoidable impurities; the delta ferrite content in the steel plate is less than 1%. The manufacturing method comprises smelting, casting, electroslag remelting, heating, forging, homogenizing heat treatment, rolling and grain boundary engineering control; the steel plate produced by the method has good mechanical properties and good comprehensive properties, is suitable for a long-term service environment of nuclear power plant core components, and ensures the high efficiency and the safety of the operation of nuclear power equipment. The invention adopts electroslag remelting and forging processes, has high cost and low yield, and is not suitable for industrial production.
Patent application number CN202210848609.9, a method for improving corrosion resistance of super austenitic stainless steel, comprises the following components in percentage by weight: less than or equal to 0.02 percent of C, less than or equal to 0.5 percent of Si, less than or equal to 0.50 percent of Mn, less than or equal to 0.03 percent of P, less than or equal to 0.01 percent of S, and less than or equal to Ni:18.5% -25.5%, cu:0.7% -0.8%, N:0.20% -0.35%, cr:19.5% -22.5%, mo:4.5% -7.0%, B:0.002% -0.006% and the balance of Fe. The invention carries out solution treatment on the high-molybdenum super austenitic stainless steel, then carries out water cooling, and carries out low-temperature heat preservation treatment and medium-temperature heat preservation treatment after water cooling. The trace B is added, so that the corrosion resistance of the steel is improved, but the obtained finished product is small in size and specification, and meanwhile, the process is complex and has limitation in use.
Disclosure of Invention
The invention aims to provide high corrosion resistance high carbon austenitic stainless steel for nuclear power and a manufacturing method thereof, and designs an alloy component with proper process so as to have good mechanical property and corrosion resistance.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the high corrosion resistance high carbon austenitic stainless steel for nuclear power comprises the following chemical components in percentage by weight: 0.20% -0.35%; si:2.0% -3.0%; mn:5.50% -7.50%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; ni:3.80% -4.50%; cr:16.75% -18.25%; co:0.75% -1.00%, nb:0.10% -0.20%; zr:0.05% -0.08%, and the balance of Fe and unavoidable impurities.
Further, nb+Zr in the chemical components of the steel is more than or equal to 0.2%; ni+Cr is more than or equal to 21 percent.
Further, the thickness of the steel plate is 10-100mm, and the room temperature yield strength R p0.2 Reach more than 530MPa, and the tensile strength R m Reaching over 735 MPa; yield strength R when stretched at 550 DEG C p0.2 Reaching more than 325MPa, the tensile strength R m Reaching above 527 MPa.
Further, the stainless steel impact energy reaches more than 150J at the low-temperature impact of minus 20 ℃.
Further, after 40h vibration cavitation test, the cumulative loss weight of the stainless steel is less than or equal to 2.53mg.
The method for manufacturing the high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein the production process comprises the following steps: smelting, continuous casting, heating, rolling and heat treatment, wherein,
heating: heating the casting blank along with a furnace, wherein the heating speed is less than or equal to 50 ℃/h, the heating temperature is 1140-1180 ℃, and the total furnace time is 6-7h;
rolling: adopting two-stage controlled rolling, wherein the initial rolling temperature of the steel plate in the first stage is 1100-1140 ℃, the steel plate is stretched by transverse rolling, the average rolling reduction rate of the previous 3 passes is 20-25%, and when the thickness is stretched to 2-2.5T, the temperature is kept for 1-2min; in the second stage, longitudinal rolling is adopted, the initial rolling temperature is more than 1030 ℃, and the average reduction rate of the last 5 passes is 5-7%; naturally cooling the steel plate after rolling; the T is the thickness of a finished product;
and (3) heat treatment: adopting two-stage solid solution, preserving heat for 1-2.5h at 630-670 ℃, then quickly raising the temperature to 1030-1070 ℃ for 10-30min, discharging, and cooling to room temperature.
Further, an induction furnace, LF and RH are adopted for smelting, the induction furnace uses industrial pure iron and alloy to jointly finish melting and component adjustment, the tapping temperature of the induction furnace is more than or equal to 1650 ℃, the LF finishes controlling S and removing impurities, and the RH carries out vacuum treatment on molten steel, and the treatment vacuum degree is 0.2-0.5kPa.
Further, before the RH is carried out, if the Mn content does not reach the lower limit, mn is alloyed and then the target value is reached.
Further, in the smelting process, the content of FeO+MnO in slag of the LF furnace is controlled to be less than or equal to 1.0 percent.
Further, the continuous casting is carried out at the casting temperature of 1490-1510 ℃ and the superheat degree of the tundish is 15-25 ℃; the continuous casting end adopts an electromagnetic stirring or light pressing mode, the pulling speed is controlled to be 1.0-1.3m/min, and the electromagnetic stirring parameters are selected to be 800-1200A and 3-5Hz; the soft reduction is selected to be 6-8mm, the continuous casting blanks are stacked and slowly cooled for more than 48 hours after being off line, and the thickness of the casting blanks is 300-350 mm.
The invention adopts the design of high Mn and low Ni components, the combined action of Nb and Zr and the combined action of Cr, mn, co and Si, and simultaneously, the higher carbon content in the steel ensures that the steel has good corrosion resistance on the basis of higher strength and toughness. The production process of the combination of smelting, continuous casting, heating, rolling, straightening, slow cooling and heat treatment ensures that the steel plate has good performance and good key indexes, and completely meets the manufacturing requirements of subsequent equipment. After solution heat treatment, the steel grade of the invention has higher comprehensive performance level and room temperature yield strength (R) p0.2 ) And tensile strength (R) m ) Respectively reaching more than 530MPa and 735 MPa; yield strength (R) at high temperature of 550 DEG C p0.2 ) And tensile strength (R) m ) Respectively reaching more than 325MPa and 527 MPa; when the impact is carried out at the low temperature of minus 20 ℃, the impact energy reaches more than 150J, and simultaneously hasHas excellent corrosion resistance, and the accumulated loss weight is less than or equal to 2.53mg after 40h vibration cavitation test. The austenitic stainless steel for nuclear power completely meets the comprehensive performance requirements of the current industry.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other. The described embodiments are only some, but not all, embodiments of the invention. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides high corrosion resistance high carbon austenitic stainless steel for nuclear power, which comprises the following chemical components in percentage by weight: comprising C:0.20% -0.35%; si:2.0% -3.0%; mn:5.50% -7.50%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; ni:3.80% -4.50%; cr:16.75% -18.25%; co:0.75% -1.00%, nb:0.10% -0.20%; zr:0.05% -0.08%; nb+Zr is more than or equal to 0.2%; ni+Cr is more than or equal to 21%, and the balance is Fe and unavoidable impurities.
The reason for adopting the components is as follows:
c: the strength of the steel can be obviously improved through solid solution, is the most basic strengthening element in the steel, and has obvious influence on the yield strength, the tensile strength and the welding performance of the steel. Some of the carbon in the steel enters the matrix of the steel causing solid solution strengthening and some of the carbon will combine with the carbide forming elements in the alloying elements to form alloy carbides. However, too high a content of carbon causes various negative effects such as degradation of the welding performance and corrosion resistance of the steel. According to the use requirement and performance requirement, the invention selects and adds C with the content of 0.20-0.35%.
Si: is an important reducing agent and deoxidizer in the steelmaking process, can be dissolved in ferrite and austenite to improve the hardness and strength of steel, and can also form SiO on the surface of steel 2 At the same time as the passivation film of (a)With Cr 2 O 3 And a composite passivation film is formed, so that the high-temperature oxidation resistance of the steel is remarkably improved. However, too high a Si content will significantly reduce the plasticity and toughness of the steel. The element segregation phenomenon can be promoted, obvious dendrite structures are formed and a large amount of harmful phases are separated out, the uniformity of casting blank structures and components can be seriously influenced, and meanwhile, the grain boundary strength can be weakened, so that cracking is caused in the subsequent rolling process. Comprehensively considering, the Si content of the invention is selected to be 2.0% -3.0%.
Mn: the strength of the steel can be improved in a solid solution strengthening mode, the defect caused by the reduction of C is overcome, and the steel is a main alloy element affecting the strength, the hardenability and the weldability, and meanwhile, the cost is low. However, too high Mn content adversely affects toughness and high temperature properties, and segregation tends to occur to make the matrix material composition and structure nonuniform. The invention adds proper amount of Mn to play a role in stabilizing austenite, and enables more carbide to be dissolved into a matrix during high-temperature solid solution, thereby inhibiting the formation of delta ferrite and fully playing the beneficial effects, so that the Mn content is 5.50-7.50% in the invention.
P, S: the steel of the invention is harmful element, which has adverse effect on the thermoplasticity and corrosion resistance of the steel, P is easy to segregate at austenite grain boundary to weaken interatomic bonding force on the grain boundary of the matrix material, so that the tempering brittleness of the material is large, S is distributed in the steel in the form of MnS, the anisotropy of the steel is increased, the thermal stability of the steel is reduced, and in addition, the uniformity and purity of the steel are influenced by excessive S, P. Therefore, the lower the control content, the better, but the invention requires control of P.ltoreq.0.015% and S.ltoreq.0.005% in steel in view of steelmaking conditions and costs.
Ni: the main synthetic elements of the stainless steel are added with a proper amount of Ni to help to obtain a single-phase austenitic structure, the corrosion resistance and the plasticity are obviously improved, and the Ni can also form a spinel oxide film NiO-Cr with good protectiveness through coaction with Cr in a certain temperature range 2 O 3 And the composite oxide film and the like can effectively improve the corrosion resistance and the high-temperature oxidation resistance of the steel. However, excessive Ni can increase the cost, reduce the diffusion speed of carbon in the matrix, delay the dissolution process of undissolved carbide into austenite and make the dissolution process strongThe degree decreases. Therefore, the content of the modified starch is set to 3.80% -4.50%.
Cr: the most important alloying elements in the stainless steel interact with Ni to form a stable austenitic structure of the steel, so that the steel can be passivated and has good corrosion resistance and stainless property, and when the chromium content in the stainless steel exceeds 13 percent, the steel has good high-temperature oxidation resistance and corrosion resistance. However, the excessive Cr has high cost and can lead to ferrite structure in the steel, so the Cr content is 16.75-18.25 percent.
Co: the austenite stabilizing element, co element, can improve the strength of steel, is mainly dissolved in a matrix to play a very strong solid solution strengthening role, improves the structural stability of the steel when the steel is heated at high temperature, can also increase the relative content of Cr in an oxide film, promotes the alloy to generate a continuous protective oxide film, can enhance the adhesiveness and compactness of the oxide film, delays the rupture time of the oxide film, and prolongs the hot corrosion inoculation period. Co can also effectively delay the diffusion of S element in stainless steel, and reduce the vulcanization-oxidation speed in the hot corrosion process, thereby improving the hot corrosion resistance of the alloy. Considering the cost factor of adding Co in the invention, the alloying cost is high, so the Co addition content of the invention is 0.75-1.00%.
Nb: formation of stable NbC or Nb in steel 4 C 3 And the particles are distributed in fine dispersion on the matrix, thereby playing a role in precipitation strengthening. An appropriate amount of Nb can improve the strength of the steel without affecting the plasticity or toughness of the steel. The impact toughness of the steel can be improved and the brittle transition temperature of the steel can be reduced due to the effect of grain refinement. Inter-crystal corrosion of the steel by the oxidizing medium can also be prevented. The high temperature properties of the steel can be improved due to the fixed carbon and precipitation hardening. In consideration of cost, the content of Nb is selected to be 0.10% -0.20%.
Zr: the high-strength carbide forming element is added with a small amount of zirconium to have the effects of degassing, purifying and refining grains, oxide can be formed in molten steel, the steel can be used as a non-spontaneous nucleation core, austenite grains are refined, the austenite grains are precipitated on the austenite grain boundaries, the growth of the austenite grains is prevented by using the pinning effect of dispersed fine inclusions, so that the structure generated by phase transformation of the austenite grains is refined, the strength and toughness of the material are improved, the low-temperature performance of the steel is facilitated, the stamping performance is improved, a part of the steel acts together with Cr element, an oxidized rust layer can be prevented from being formed on the surface, the inward diffusion of oxygen atoms and the combination of iron ions are reduced, and the pinning base metal is jointly acted, so that the oxidation resistance of the steel is greatly improved, and the high-temperature oxidation resistance of the steel is improved. Considering cost factors, the invention selects to add Zr:0.05% -0.08%.
The Nb+Zr is more than or equal to 0.20 percent for composite use, not only can refine casting blank tissues, but also can refine steel plate tissues after hot rolling, has more precipitated phases in steel, finer precipitated particles and stronger refining effect, plays a role in fine grain strengthening, and improves the strength of the steel on the premise of not affecting plasticity and processability. Meanwhile, a proper amount of Cr, mn, co and Si elements are added to perform combined action, so that the fault energy of the steel is reduced, gamma austenite is converted into epsilon martensite under the stress action condition, a great amount of faults are easy to occur, the probability of dislocation slip is reduced, the epsilon martensite grows up by means of fault nucleation, and the corrosion resistance of the material is improved.
The invention relates to a manufacturing method of high corrosion resistance high carbon austenitic stainless steel for nuclear power, which comprises the following steps: smelting, continuous casting, heating, rolling and heat treatment, and the concrete contents are as follows:
smelting: and smelting molten steel is completed by adopting induction furnace, LF and RH three-step treatment. The induction furnace uses industrial pure iron and alloy to finish melting and component adjustment together, the tapping temperature of the induction furnace is more than or equal to 1650 ℃, LF finishes controlling S and removing impurities, RH carries out vacuum treatment on molten steel, the vacuum degree is 0.2-0.5kPa to remove gases such as oxyhydrogen, mn is controllable in vacuum burning loss, and before RH is carried out, if the component of Mn does not reach the lower limit, mn is alloyed and supplemented to a target value. In the smelting process of high manganese steel, the content of (FeO+MnO) in slag of an LF furnace is strictly controlled to be less than or equal to 1.0 percent so as to ensure the desulfurization effect, prevent sulfur from being separated out on a grain boundary after molten steel is solidified and cause the steel to become brittle.
Continuous casting: the casting temperature is 1490-1510 ℃, and the superheat degree of the tundish is 15-25 ℃. The continuous casting end adopts an electromagnetic stirring or light pressing mode, the temperature of secondary cooling water and the blank pulling speed are strictly controlled, the pulling speed is controlled to be 1.0-1.3m/min, and if electromagnetic stirring is used, the stirring parameters are selected to be 800-1200A and 3-5Hz; if soft reduction is selected, the reduction is 6-8mm, and the internal and external quality of the casting blank is fully ensured. The casting temperature is controlled mainly, and as the casting temperature increases, the shrinkage stress of the casting blank increases, more importantly, the crystal grains are coarse, the columnar crystals are serious, and the strength of the steel is greatly weakened. And stacking and slowly cooling the continuous casting blanks for more than 48 hours after the continuous casting blanks are off line. The thickness of the continuous casting billet is preferably 300-350 mm.
Heating: the casting blank is charged, and the heating rate of the preheating section is less than or equal to 50 ℃/h, so that the generation of cracks caused by overlarge temperature difference between the furnace temperature and the casting blank is prevented; the temperature of the heating section is 1140-1180 ℃; the total furnace time of the casting blank is 9-10 hours, the alloy content of the invention is higher, the heating temperature of the casting blank is required to be higher, and the longer heat preservation time ensures that alloy elements are fully dissolved in a matrix, thus improving the non-uniformity of the components of the casting blank and further reducing the subsequent tissue segregation.
Rolling: the rolling is controlled by adopting two stages, the initial rolling temperature of the steel plate in the first stage is 1100-1140 ℃, the steel plate is stretched by adopting transverse rolling, the high-temperature and high-pressure process is adopted, the average reduction rate of the first 3 passes is 20% -25%, and the high-temperature stage adopts high pressure, so that the dynamic recrystallization is promoted under the conditions of higher deformation temperature and higher reduction rate, the continuous dynamic recrystallization of the core is ensured, and the whole thickness of the steel plate is enabled to obtain a uniform and fine grain structure. When the thickness is widened to 2-2.5T (the thickness of a finished product), the temperature is kept for 1-2min, high-temperature rolling is carried out firstly, then the temperature is kept, dynamic recrystallization and dynamic recovery are promoted, and the growth of grains is avoided, so that the temperature keeping effect is better on the premise of ensuring a certain total rolling reduction. In the second stage, longitudinal rolling is adopted, the initial rolling temperature is higher than 1030 ℃, the last 5 passes adopt small deformation, the average reduction rate is 5-7%, the hot rolling orientation gradient is kept, the later large deformation easily causes the recrystallized grain orientation to be consistent, and the abnormal growth of the grains is caused. The transverse performance can be improved by adopting transverse rolling and longitudinal rolling in the rolling process, and the anisotropism of the steel plate is reduced. And naturally cooling the steel plate after rolling. After rolling, a steel plate with the thickness of 10-100mm is obtained.
And (3) heat treatment: because of the high Mn content in the steel, the heat conductivity of the steel is poor, the stress is high and the steel is easy to crack during heating, and the heating rate is slow in order to reduce the deformation or cracking of the steel plate during heating. The two-stage solid solution is adopted, the temperature is kept for 1 to 2.5 hours at 630 to 670 ℃ in advance, after the temperature in the furnace is uniform, the temperature is raised to 1030 to 1070 ℃ to ensure complete dissolution of carbide in the tissue and homogenization of austenite, the heat-preservation time is 10 to 30 minutes, the high-temperature stage is relatively short in the furnace time, and the method is a main reason for finer overall grain size. And discharging the material, and cooling the material to room temperature.
A high corrosion resistance high carbon austenitic stainless steel for nuclear power and a manufacturing method thereof, the specific implementation mode is as follows:
wherein, table 1 is the composition of each example, table 2 is the smelting and continuous casting process parameters of each example, table 3 is the rolling and heat treatment process parameters of each example, and table 4 is the comprehensive performance of each example.
Table 1 chemical composition (%)
Table 2 smelting and continuous casting process parameters of each example
Table 3 process parameters for rolling and heat treatment of various examples
Table 4 overall performance of each example
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (10)

1. The high-corrosion-resistance high-carbon austenitic stainless steel for nuclear power is characterized by comprising the following chemical components in percentage by weight: 0.20% -0.35%; si:2.0% -3.0%; mn:5.50% -7.50%; p is less than or equal to 0.015 percent; s is less than or equal to 0.005%; ni:3.80% -4.50%; cr:16.75% -18.25%; co:0.75% -1.00%, nb:0.10% -0.20%; zr:0.05% -0.08%, and the balance of Fe and unavoidable impurities.
2. The high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein Nb+Zr is not less than 0.2%; ni+Cr is more than or equal to 21 percent.
3. The high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein the thickness of the steel plate is 10-100mm, and the room temperature yield strength R p0.2 Reach more than 530MPa, and the tensile strength R m Reaching over 735 MPa; yield strength R when stretched at 550 DEG C p0.2 Reaching more than 325MPa, the tensile strength R m Reaching above 527 MPa.
4. The high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein the steel has an impact energy of 150J or more when impacted at a low temperature of-20 ℃.
5. The high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein the cumulative loss weight of the steel after 40h vibration cavitation test is less than or equal to 2.53mg.
6. The method for manufacturing the high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 1, wherein the production process comprises the following steps: smelting, continuous casting, heating, rolling and heat treatment, and is characterized in that,
heating: heating the casting blank along with a furnace, wherein the heating speed is less than or equal to 50 ℃/h, the heating temperature is 1140-1180 ℃, and the total furnace time is 6-7h;
rolling: adopting two-stage controlled rolling, wherein the initial rolling temperature of the steel plate in the first stage is 1100-1140 ℃, the steel plate is stretched by transverse rolling, the average rolling reduction rate of the previous 3 passes is 20-25%, and when the thickness is stretched to 2-2.5T, the temperature is kept for 1-2min; in the second stage, longitudinal rolling is adopted, the initial rolling temperature is more than 1030 ℃, and the average reduction rate of the last 5 passes is 5-7%; naturally cooling the steel plate after rolling; the T is the thickness of a finished product;
and (3) heat treatment: adopting two-stage solid solution, preserving heat for 1-2.5h at 630-670 ℃, then quickly raising the temperature to 1030-1070 ℃ for 10-30min, discharging, and cooling to room temperature.
7. The method for manufacturing high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 6, wherein an induction furnace +LF+RH is adopted for smelting, the induction furnace uses industrial pure iron and alloy to jointly complete melting and component adjustment, the tapping temperature of the induction furnace is more than or equal to 1650 ℃, LF is used for controlling S and removing inclusions, and RH is used for carrying out vacuum treatment on molten steel, and the treatment vacuum degree is 0.2-0.5kPa.
8. The method for producing a high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 6, wherein if the Mn content does not reach the lower limit before the RH is carried out, mn is alloyed to the target value.
9. The method for manufacturing high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 6, wherein the content of FeO+MnO in slag of the LF furnace is controlled to be less than or equal to 1.0% in the smelting process.
10. The method for manufacturing high corrosion resistance high carbon austenitic stainless steel for nuclear power according to claim 6, wherein the casting temperature is 1490-1510 ℃ and the tundish superheat is 15-25 ℃ by continuous casting control; the continuous casting end adopts an electromagnetic stirring or light pressing mode, the pulling speed is controlled to be 1.0-1.3m/min, and the electromagnetic stirring parameters are selected to be 800-1200A and 3-5Hz; the soft reduction is selected to be 6-8mm, the continuous casting blanks are stacked and slowly cooled for more than 48 hours after being off line, and the thickness of the casting blanks is 300-350 mm.
CN202310621122.1A 2023-05-30 2023-05-30 High-corrosion-resistance high-carbon austenitic stainless steel for nuclear power and manufacturing method thereof Pending CN116732452A (en)

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