CN111593265B - Nanostructured low-activation martensitic steel and preparation method thereof - Google Patents

Nanostructured low-activation martensitic steel and preparation method thereof Download PDF

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CN111593265B
CN111593265B CN202010519485.0A CN202010519485A CN111593265B CN 111593265 B CN111593265 B CN 111593265B CN 202010519485 A CN202010519485 A CN 202010519485A CN 111593265 B CN111593265 B CN 111593265B
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邱国兴
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Xian University of Architecture and Technology
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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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
    • 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
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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    • 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
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    • C21D2211/008—Martensite

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Abstract

The invention discloses a nano-structure low-activation martensitic steel and a preparation method thereof, wherein the nano-structure low-activation martensitic steel comprises the following chemical elements in percentage by mass: 0.08 to 0.12 percent of C, 0.1 to 0.25 percent of Si, 0.4 to 0.5 percent of Mn, 8.5 to 9.5 percent of Cr, 1 to 1.5 percent of W, 0.18 to 0.22 percent of V, 0.01 to 0.05 percent of Ti, 0.0050 to 0.01 percent of N, and the balance of Fe. The preparation process comprises the following steps: the method comprises the processes of consumable electrode preparation, protective electroslag remelting and refining, high-temperature forging, medium-temperature rolling and microstructure shaping heat treatment.

Description

Nanostructured low-activation martensitic steel and preparation method thereof
Technical Field
The invention belongs to the technical field of metal materials, and particularly relates to a nano-structure low-activation martensitic steel and a preparation method thereof.
Background
The nuclear fusion reactor is used as a clean energy source, has great strategic significance in ensuring energy safety and coping with global climate change and environmental pollution, and has become a hot spot of competitive research at home and abroad. Because the working environment in the fusion reactor is far harsher than fission, the temperature in the reactor is higher, the pressure is higher, and the neutron irradiation intensity is higher, higher requirements are provided for fusion reactor materials. The development of high performance structural materials becomes the key to whether a fusion reactor can be finally used commercially.
At the beginning of the design of the fusion reactor, the concept of 'low-activation material' is introduced, namely, the radioactivity of the material after service needs to be reduced to the limit level (10mSv/h) of recycling within 100 years. The content of high active elements such as Al, Ni, Cu, Nb, Mo, and Sn in the material is strictly limited. Therefore, conventional austenitic steels or nickel-based superalloys are no longer taken into consideration for materials of fusion reactor construction due to the high activation of Ni, and low activation steels are produced. The Chinese patent discloses a preparation method (CN 109594009A) of nano precipitated phase reinforced anti-radiation low activation steel, which firstly prepares FeTaC intermediate alloy, and then adds the FeTaC alloy into the steel, and the preparation of the intermediate alloy improves the preparation cost of the low activation steel. Meanwhile, C in FeTaC is adopted for deoxidation, and the mass fraction of oxygen in the alloy liquid in the smelting process of the induction furnace is uncertain, so that the method has the advantages of simple process, low cost and high yieldIt is difficult to produce low activation steel with controllable C and Ta components. The related research results show that most of Ta exists in a solid solution form in the steel, which is the main reason for the rise of ductile-brittle transition temperature (DBTT) of the experimental steel after irradiation, so that the use of Ta element should be reduced. Chinese patent publication "a low activation steel structure material for fusion reactor (CN 102560257B)" which uses Ti element instead of Ta element. In the chemical components of the invention, W is 2.0-2.5%, N is 0.01-0.05%, and excessive W can cause Laves phase (Fe) in steel2W) further deteriorates the high-temperature mechanical properties of the steel, and excessively high N content leads to generation of large-sized TiN-type inclusions during the melting process, thereby deteriorating the impact mechanical properties of the steel. The annealing treatment is carried out after the hot working is cooled to the room temperature, so that the generation of cracks can not be effectively avoided, and the cracks are generated in the process of cooling the hot working to the room temperature. Meanwhile, the conventional heat treatment process of the Ta-containing low-activation steel is adopted, and the precipitation strengthening effect of Ti cannot be fully exerted. Meanwhile, in view of the development of low-activation steel, a plurality of researchers at home and abroad put forward urgent needs on a metallurgical preparation technology, and the preparation technology has obvious influence on the purity, the structure and the performance of the low-activation steel. There is therefore a need to develop a new nanostructured low activation steel and to propose a complete manufacturing process comprising melting, hot working and heat treatment.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a nano-structure low-activation martensitic steel and a preparation method thereof, so as to improve the service performance of a low-activation steel structure material.
The technical scheme adopted by the invention is as follows:
a nanostructured low activation martensitic steel whose chemical elements comprise, in mass percent:
0.08 to 0.12 percent of C, 0.1 to 0.25 percent of Si, 0.4 to 0.5 percent of Mn, 8.5 to 9.5 percent of Cr, 1 to 1.5 percent of W, 0.18 to 0.22 percent of V, 0.01 to 0.05 percent of Ti, 0.0050 to 0.01 percent of N, and the balance of Fe.
The preparation method of the nano-structure low-activation martensitic steel comprises the following steps:
preparation of a consumable electrode: proportioning according to components, firstly carrying out vacuum melting on Fe, Cr, W and C, and refining after the alloy is melted down, wherein the refining temperature is 1600-1610 ℃; after refining is finished, reducing the temperature of the alloy liquid to 1540-1550 ℃, and then sequentially adding Si, Mn, V and Ti into the alloy liquid; after the alloy is melted down, introducing nitrogen, keeping the pressure at 2000-4000 Pa, and casting at 1510-1530 ℃ in a nitrogen environment; forging the cast steel ingot into an electrode bar;
protective electroslag remelting and refining: carrying out electroslag remelting refining on the electrode bar in a nitrogen atmosphere to obtain a refined steel ingot;
high-temperature forging: forging the refined steel ingot to obtain an intermediate forging piece capable of being rolled, wherein the forging temperature is 1000-1150 ℃;
rolling at medium temperature: rolling the intermediate forging piece to obtain an original rolled piece, wherein the rolling temperature is 760-940 ℃, austenitizing the intermediate forging piece before rolling, and slowly cooling the original rolled piece to room temperature after rolling;
and (3) setting and heat treatment of the microstructure: carrying out primary quenching on an original rolled piece, wherein the quenching temperature is 1000-1050 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; carrying out secondary quenching on the original rolled piece after the primary quenching, wherein the quenching temperature is 950-1000 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; and tempering the original rolled piece after the secondary quenching to obtain the low-activation martensitic steel with the nano structure.
Preferably, when Si, Mn, V and Ti are sequentially added into the alloy liquid, Mn is added at an interval of 1-1.5 min after the Si is added, V is added at an interval of 1-1.5 min after the Mn is added, and Ti is added at an interval of 1-1.5 min after the V is added.
Preferably, the refining time is 50-70 min when the consumable electrode is prepared.
Preferably, when the consumable electrode is prepared, the cast steel ingot is subjected to diffusion annealing at the temperature of 1150-1200 ℃ for 1-2 hours, and then forged into an electrode rod at the temperature of 1000-1150 ℃.
Preferably, protectiveWhen electroslag remelting refining is carried out, firstly removing iron oxide scales on the surface of an electrode rod; the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO。
Preferably, during high-temperature forging, the defective parts at the top and the bottom of the refined steel ingot are removed, then the refined steel ingot is subjected to heat preservation treatment to eliminate stress generated in the solidification process, the temperature of the heat preservation treatment is 1150-1200 ℃, and the time is 1.5-2 hours; and then forging the refined steel ingot to obtain an intermediate forging which can be used for rolling.
Preferably, when the intermediate forging is austenitized, the intermediate forging is placed at 1100-1150 ℃ for heat preservation for 1-1.5 h, and austenitization is realized.
Preferably, the slow cooling speed is 1-2 ℃/s during medium-temperature rolling.
Preferably, during the micro-structure shaping heat treatment, the tempering temperature is 650-700 ℃, the heat preservation time is 1.5-2 h, and the cooling mode is water cooling.
The invention has the following beneficial effects:
in the nano-structure low-activation martensitic steel, the use of Ta element is avoided, and the DBTT can be effectively prevented from greatly rising after the material is irradiated; meanwhile, the W content in the steel is controlled at a lower level, the tungsten content is only 1 to 1.5 percent and is lower than the tungsten content of 2.0 to 2.5 percent in the prior art, so that the Fe content in the high-temperature operation process can be avoided2The precipitation of the W phase further deteriorates the overall mechanical properties of the steel.
According to the preparation method of the nano-structure low-activation martensitic steel, the addition amount of Fe, Cr and W is large, so that the Fe, Cr and W are melted firstly; because the melting point of W is very high, W can be completely dissolved by refining at 1600-1610 ℃; the temperature of 1540-1550 ℃ later is the alloying temperature, Si, Mn, V and Ti can react with oxygen, a large amount of burning loss is easily caused due to overhigh temperature, nitrogen is introduced to ensure the nitrogen content in steel, the casting temperature is controlled to ensure the compactness of a solidification structure, and the lower the casting temperature is, the better the solidification structure is. When the protective electroslag remelting refining is carried out, the electroslag remelting refining is carried out in a nitrogen atmosphere, and the purpose of preventing the absorption of the previous step is toAnd (4) separating out nitrogen. Forging at 1000-1150 ℃ at high temperature, and mainly aiming at forging steel ingots into plates so as to facilitate subsequent rolling; the purpose of medium temperature rolling is to enable the steel to have higher strength, work hardening can occur at low rolling temperature, so that the strength of the steel is higher, before rolling, the intermediate forging is austenitized, so that austenite phase transformation occurs in the steel, an austenite structure is obtained, slow cooling is performed to prevent cracks caused by stress concentration, and stress-induced nucleation can promote precipitation of nano-scale Ti (C, N) and (Ti, W) (C, N). Because the middle-temperature rolling in the front and the reduction of the plasticity of the material caused by work hardening, the quenching is needed to release the stress in the material, and the purpose of twice quenching is as follows: the first quenching is to release the stress caused by warm rolling work hardening and to precipitate a part of nano-scale MX phase (VC or TiC or (W, Ti) (C, N)) from the steel, the second quenching is to refine austenite grains and to precipitate a large amount of nano-scale MX phase (VC or TiC or (W, Ti) (C, N)) from the steel, the size of the precipitated MX phase is small because the second quenching temperature is lower than the first quenching temperature, and the tempering is to obtain tempered martensite structure by releasing the quenching stress and to precipitate nano-scale M in the steel23C6(M ═ Fe or Cr).
Further, since Si, Mn, V and Ti all have a deoxidizing function and are combined with oxygen in steel, and the addition of V and Ti is mainly capable of generating carbide, the addition of Si and Mn consumes oxygen in steel, so that V and Ti do not generate oxide, the content of V in steel is higher (0.18% -0.22%), so that the addition of V is earlier than that of Ti, otherwise, oxygen consumes Ti, and the addition of Ti is 0.01% -0.05%. Therefore, based on the consideration, when Si, Mn, V and Ti are added into the alloy liquid in sequence, Mn is added at an interval of 1-1.5 min after the Si is added, V is added at an interval of 1-1.5 min after the Mn is added, and Ti is added at an interval of 1-1.5 min after the V is added.
Furthermore, when the consumable electrode is prepared, the cast steel ingot is subjected to diffusion annealing at 1150-1200 ℃ for 1-2h, so that the electrode is prevented from being forged and wasted, and cracks are easy to generate due to low temperature.
Further, when the protective electroslag remelting refining is carried out, the iron scale on the surface of the electrode rod is removed firstly, so that the iron scale is prevented from carrying oxygen; the pure iron scrap is used for arc striking, so that the steel is prevented from being polluted; the refining slag is a matched slag system, and the purpose of adopting the slag system is to prevent excessive high-activation element Al from being brought in.
Furthermore, during high-temperature forging, the head and the tail are removed to obtain a steel ingot with a compact structure, and heat preservation treatment is performed before forging to eliminate stress generated in the solidification process.
Furthermore, when the intermediate forging piece is austenitized, the intermediate forging piece is placed at 1100-1150 ℃ for heat preservation for 1-1.5 h, austenitization can be realized at the temperature, meanwhile, crystal grains can be prevented from being coarsened, and the rolling performance is improved.
Further, during medium-temperature rolling, the slow cooling speed is 1-2 ℃/s, and under the slow cooling speed, phase change cracks can be effectively prevented.
Further, when the microstructure is subjected to setting heat treatment, the tempering temperature is 650-700 ℃, and the heat preservation time is 1.5-2 hours, so that tempered martensite is obtained, and the mechanical property of the steel is improved.
Drawings
FIG. 1 is a flow chart of a process for preparing a nanostructured low-activation martensitic steel of the present invention.
Detailed Description
The invention is further described below with reference to the figures and examples.
The components of the nano-structure low-activation martensitic steel comprise C, Si, Mn, Cr, W, V, micro-alloying elements, N and Fe;
wherein the microalloying element is Ti;
the nano-structure low-activation steel comprises the following components in percentage by mass: 0.08 to 0.12 percent of C, 0.1 to 0.25 percent of Si, 0.4 to 0.5 percent of Mn, 8.5 to 9.5 percent of Cr, 1 to 1.5 percent of W, 0.18 to 0.22 percent of V, 0.01 to 0.05 percent of Ti, 0.0050 to 0.01 percent of N, and the balance of Fe;
the preparation method of the nano-structure low-activation martensitic steel comprises the following steps:
(1) preparation of consumable electrodes
Compounding according to low activation steel compositionAnd (4) smelting. Firstly, placing Fe, Cr, W and C in a vacuum induction furnace for smelting, and refining after the alloy is melted down. The refining time is 50-70 min, the refining temperature is 1600-1610 ℃, and the vacuum degree is 10-20 Pa. After refining, reducing the power of the induction furnace, reducing the temperature of the alloy liquid to 1540-1550 ℃, and adding the rest of alloys into the alloy liquid from an alloy bin according to the following sequence: si → Mn → V → Ti at the time interval of 1-1.5 min. And after all the alloys are melted down, introducing nitrogen into the induction furnace to keep the pressure in the induction furnace at 2000-4000 Pa, and casting under the nitrogen environment at 1510-1530 ℃. The steel ingot prepared by smelting is placed at 1150-1200 ℃ for heat preservation for 1-2h for diffusion annealing, and then the steel ingot is forged into
Figure GDA0002947393350000061
The forging temperature of the electrode bar is 1000-1150 ℃;
(2) protective electroslag remelting refining
And carrying out electroslag remelting refining on the consumable electrode. Turning off iron scales on the surface of the electrode before refining; the remelting protective atmosphere is nitrogen; the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO；
(3) High temperature forging
And removing the top (1/5-1/4) and the bottom (1/5-1/4) of the electroslag steel ingot to obtain an original blank with compact structure and less defects. And (3) insulating the blank at 1150-1200 ℃ for 1.5-2 h to eliminate stress generated in the solidification process. Then forging to obtain an intermediate forging piece, wherein the forging temperature is 1000-1150 ℃, and the forging ratio is more than or equal to 5: 1;
(4) rolling at moderate temperature
Rolling the intermediate forging piece to obtain an original rolled piece, wherein the rolling temperature is 760-940 ℃, the intermediate forging piece is placed at 1100-1150 ℃ for heat preservation for 1-1.5 h before rolling, the rolled piece is placed in a slow cooling pit to be slowly cooled to room temperature after rolling, the slow cooling speed is 1-2 ℃/s, and the precipitation of nanoscale Ti (C, N) and (Ti, W) (C, N) is promoted through medium-temperature rolling;
(5) heat treatment for setting microstructure
And carrying out heat treatment on the original rolled piece to obtain the nano-structure low-activation steel. The heat treatment mode is quenching-tempering process. The first quenching temperature is 1000-1050 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; the secondary quenching temperature is 950-1000 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; the tempering temperature is 650-700 ℃, the heat preservation time is 1.5-2 h, and the cooling mode is water cooling, so that the nano-structure low-activation martensitic steel is finally obtained.
Example 1
In the nanostructured low-activation martensitic steel of the present embodiment, the contents of the components are, in mass percent: 0.1% of C, 0.1% of Si, 0.45% of Mn, 9.0% of Cr, 1.45% of W, 0.20% of V, 0.015% of Ti, 0.0075% of N and the balance of Fe.
The preparation process of the nano-structured low-activation martensitic steel comprises the following steps:
(1) preparation of consumable electrodes
The low-activation steel components are proportioned and smelted. Firstly, placing Fe, Cr, W and C in a vacuum induction furnace for smelting, and refining after the alloy is melted down. The refining time is 60min, the refining temperature is 1605-1610 ℃, and the vacuum degree is 10-15 Pa. After refining, reducing the power of the induction furnace to reduce the temperature of the alloy liquid to 1545-1550 ℃, and adding the rest alloys into the alloy liquid from an alloy bin according to the following sequence: si → Mn → V → Ti with 1min interval. And after all the alloys are melted down, introducing nitrogen into the induction furnace to keep the pressure in the induction furnace at 3000-3500 Pa, and casting under a nitrogen environment at 1510-1520 ℃. The steel ingot prepared by smelting is placed at 1150 ℃ for heat preservation for 1h for diffusion annealing, and then is forged into
Figure GDA0002947393350000071
The forging temperature of the electrode rod is 1100-1150 ℃;
(2) protective electroslag remelting refining
And carrying out electroslag remelting refining on the consumable electrode. Turning off iron scales on the surface of the electrode before refining; the remelting protective atmosphere is nitrogen;the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO；
(3) High temperature forging
And removing the top and the bottom of the electroslag steel ingot to obtain a blank with compact structure and less defects. And (3) insulating the blank at 1200 ℃ for 1.5h to eliminate stress generated in the solidification process. Then forging to obtain an intermediate forging piece, wherein the forging temperature is 1100-1150 ℃, and the forging ratio is 5: 1;
(4) rolling at moderate temperature
Rolling the intermediate forging to obtain an original rolled piece, wherein the rolling temperature is 800 ℃, the intermediate forging is placed at 1100 ℃ for heat preservation for 1h before rolling, the rolled piece is placed in a slow cooling pit after rolling and is slowly cooled to room temperature, the slow cooling speed is 1-2 ℃/s, and the precipitation of nanoscale Ti (C, N) and (Ti, W) (C, N) is promoted through medium-temperature rolling;
(5) heat treatment for setting microstructure
And carrying out heat treatment on the original rolled piece to obtain the nano-structure low-activation steel. The heat treatment mode is quenching-tempering process. The first quenching temperature is 1050 ℃, the heat preservation time is 0.5h, and the cooling mode is water cooling; the secondary quenching temperature is 980 ℃, the heat preservation time is 0.5h, and the cooling mode is water cooling; the tempering temperature is 650 ℃, the heat preservation time is 1.5, and the cooling mode is water cooling, so that the nano-structure low-activation martensitic steel is finally obtained.
The table of the performance test of the nanostructured low-activation martensitic steel prepared in this example is shown in table 1.
Example 2
In the nanostructured low-activation martensitic steel of the present embodiment, the contents of the components are, in mass percent: 0.12% of C, 0.2% of Si, 0.4% of Mn, 9.5% of Cr, 1.0% of W, 0.18% of V, 0.01% of Ti, 0.01% of N and the balance of Fe.
The preparation process of the nano-structured low-activation martensitic steel comprises the following steps:
(1) preparation of consumable electrodes
The low-activation steel components are proportioned and smelted. Firstly, Fe, Cr, W and C are placed in a vacuum induction furnaceSmelting the alloy in the furnace, and refining the alloy after the alloy is melted down. The refining time is 60min, the refining temperature is 1600-1605 ℃, and the vacuum degree is 10-15 Pa. After refining, reducing the power of the induction furnace to reduce the temperature of the alloy liquid to 1545-1550 ℃, and adding the rest alloys into the alloy liquid from an alloy bin according to the following sequence: si → Mn → V → Ti with 1min interval. And after all the alloys are melted down, introducing nitrogen into the induction furnace to keep the pressure in the induction furnace at 3000-3500 Pa, and casting under a nitrogen environment at 1510-1520 ℃. The steel ingot prepared by smelting is placed at 1180 ℃ and is kept warm for 2 hours for diffusion annealing, and then the steel ingot is forged into
Figure GDA0002947393350000081
The forging temperature of the electrode rod is 1100-1150 ℃;
(2) protective electroslag remelting refining
And carrying out electroslag remelting refining on the consumable electrode. Turning off iron scales on the surface of the electrode before refining; the remelting protective atmosphere is nitrogen; the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO；
(3) High temperature forging
And removing the top and the bottom of the electroslag steel ingot to obtain a blank with compact structure and less defects. And (3) insulating the blank at 1200 ℃ for 1.5h to eliminate stress generated in the solidification process. Then forging to obtain an intermediate forging piece, wherein the forging temperature is 1100-1150 ℃, and the forging ratio is 5: 1;
(4) rolling at moderate temperature
Rolling the intermediate forging to obtain an original rolled piece, wherein the rolling temperature is 760 ℃, the intermediate forging is kept at 1100 ℃ for 1.5h before rolling, the rolled piece is slowly cooled to room temperature in a slow cooling pit after rolling, the slow cooling speed is 1-2 ℃/s, and the precipitation of nanoscale Ti (C, N) and (Ti, W) (C, N) is promoted through medium-temperature rolling;
(5) heat treatment for setting microstructure
And carrying out heat treatment on the original rolled piece to obtain the nano-structure low-activation steel. The heat treatment mode is quenching-tempering process. The first quenching temperature is 1000 ℃, the heat preservation time is 1h, and the cooling mode is water cooling; the secondary quenching temperature is 980 ℃, the heat preservation time is 0.5h, and the cooling mode is water cooling; the tempering temperature is 680 ℃, the heat preservation time is 1.8h, and the cooling mode is water cooling, so that the nano-structure low-activation martensitic steel is finally obtained.
The table of the performance test of the nanostructured low-activation martensitic steel prepared in this example is shown in table 1.
Example 3
In the nanostructured low-activation martensitic steel of the present embodiment, the contents of the components are, in mass percent: 0.08 percent of C, 0.25 percent of Si, 0.50 percent of Mn, 8.5 percent of Cr, 1.5 percent of W, 0.22 percent of V, 0.05 percent of Ti, 0.0050 percent of N and the balance of Fe.
The preparation process of the nano-structured low-activation martensitic steel comprises the following steps:
(1) preparation of consumable electrodes
The low-activation steel components are proportioned and smelted. Firstly, placing Fe, Cr, W and C in a vacuum induction furnace for smelting, and refining after the alloy is melted down. The refining time is 60min, the refining temperature is 1605-1610 ℃, and the vacuum degree is 10-15 Pa. After refining is finished, reducing the power of the induction furnace, reducing the temperature of the alloy liquid to 1540-1545 ℃, and adding the rest alloys into the alloy liquid from an alloy bin according to the following sequence: si → Mn → V → Ti with 1min interval. And after all the alloys are melted down, introducing nitrogen into the induction furnace to keep the pressure in the induction furnace at 3000-3500 Pa, and casting under a nitrogen environment at 1510-1520 ℃. The steel ingot prepared by smelting is placed at 1200 ℃ for heat preservation for 1.5h for diffusion annealing, and then is forged into
Figure GDA0002947393350000101
The forging temperature of the electrode rod is 1100-1150 ℃;
(2) protective electroslag remelting refining
And carrying out electroslag remelting refining on the consumable electrode. Turning off iron scales on the surface of the electrode before refining; the remelting protective atmosphere is nitrogen; the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO；
(3) High temperature forging
And removing the top and the bottom of the electroslag steel ingot to obtain a blank with compact structure and less defects. And (3) insulating the blank at 1200 ℃ for 1.5h to eliminate stress generated in the solidification process. Then forging to obtain an intermediate forging piece, wherein the forging temperature is 1100-1150 ℃, and the forging ratio is 5: 1;
(4) rolling at moderate temperature
Rolling the intermediate forging to obtain an original rolled piece, wherein the rolling temperature is 940 ℃, the intermediate forging is placed at 1100 ℃ for heat preservation for 1.2h before rolling, the rolled piece is placed in a slow cooling pit after rolling and is slowly cooled to room temperature, the slow cooling speed is 1-2 ℃/s, and the precipitation of nanoscale Ti (C, N) and (Ti, W) (C, N) is promoted through medium-temperature rolling;
(5) heat treatment for setting microstructure
And carrying out heat treatment on the original rolled piece to obtain the nano-structure low-activation steel. The heat treatment mode is quenching-tempering process. The first quenching temperature is 1030 ℃, the heat preservation time is 0.5h, and the cooling mode is water cooling; the secondary quenching temperature is 980 ℃, the heat preservation time is 0.8h, and the cooling mode is water cooling; the tempering temperature is 700 ℃, the heat preservation time is 2, and the cooling mode is water cooling, so that the nano-structure low-activation martensitic steel is finally obtained.
The table of the performance test of the nanostructured low-activation martensitic steel prepared in this example is shown in table 1.
TABLE 1
Figure GDA0002947393350000111
As can be seen from Table 1, the nanostructured low-activation martensitic steel of the present invention has excellent normal temperature and high temperature mechanical properties before irradiation, and the DBTT has been reduced to below-100 ℃; after irradiation, the material still has higher normal-temperature yield strength, the DBTT rising amplitude is smaller and still lower than minus 90 ℃, and the service performance of the low-activation steel structure material is improved.

Claims (9)

1. A preparation method of a nano-structure low-activation martensitic steel is characterized in that the chemical elements of the nano-structure low-activation martensitic steel in percentage by mass comprise:
0.08 to 0.12 percent of C, 0.1 to 0.25 percent of Si, 0.4 to 0.5 percent of Mn, 8.5 to 9.5 percent of Cr, 1 to 1.5 percent of W, 0.18 to 0.22 percent of V, 0.01 to 0.05 percent of Ti, 0.0050 to 0.01 percent of N and the balance of Fe
The method comprises the following steps:
preparation of a consumable electrode: proportioning according to components, firstly carrying out vacuum melting on Fe, Cr, W and C, and refining after the alloy is melted down, wherein the refining temperature is 1600-1610 ℃; after refining is finished, reducing the temperature of the alloy liquid to 1540-1550 ℃, and then sequentially adding Si, Mn, V and Ti into the alloy liquid; after the alloy is melted down, introducing nitrogen, keeping the pressure at 2000-4000 Pa, and casting at 1510-1530 ℃ in a nitrogen environment; forging the cast steel ingot into an electrode bar;
protective electroslag remelting and refining: carrying out electroslag remelting refining on the electrode bar in a nitrogen atmosphere to obtain a refined steel ingot;
high-temperature forging: forging the refined steel ingot to obtain an intermediate forging piece capable of being rolled, wherein the forging temperature is 1000-1150 ℃;
rolling at medium temperature: rolling the intermediate forging piece to obtain an original rolled piece, wherein the rolling temperature is 760-940 ℃, austenitizing the intermediate forging piece before rolling, and slowly cooling the original rolled piece to room temperature after rolling;
and (3) setting and heat treatment of the microstructure: carrying out primary quenching on an original rolled piece, wherein the quenching temperature is 1000-1050 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; carrying out secondary quenching on the original rolled piece after the primary quenching, wherein the quenching temperature is 950-1000 ℃, the heat preservation time is 0.5-1 h, and the cooling mode is water cooling; and tempering the original rolled piece after the secondary quenching to obtain the low-activation martensitic steel with the nano structure.
2. The method for preparing the nanostructured low-activation martensitic steel as claimed in claim 1, wherein when Si, Mn, V and Ti are added to the alloy liquid in sequence, Mn is added at an interval of 1-1.5 min after the Si is added, V is added at an interval of 1-1.5 min after the Mn is added, and Ti is added at an interval of 1-1.5 min after the V is added.
3. The method for preparing the nanostructured low-activation martensitic steel as claimed in claim 1, wherein the refining time is 50-70 min when the consumable electrode is prepared.
4. The preparation method of the nanostructured low-activation martensitic steel as claimed in claim 1, characterized in that when preparing the consumable electrode, the cast steel ingot is diffusion annealed at 1150-1200 ℃ for 1-2h, and then forged into an electrode bar at 1000-1150 ℃.
5. The method for preparing the nanostructured low-activation martensitic steel as claimed in claim 1, wherein the protective electroslag remelting refining is performed by removing iron scales on the surface of the electrode bar; the arc striking agent is pure scrap iron; the slag system for refining is 55 wt% CaF2-20wt.％CaO-20wt.％Al2O3-5wt.％MgO。
6. The preparation method of the nanostructured low-activation martensitic steel as claimed in claim 1, characterized in that during high-temperature forging, the defective parts at the top and bottom of the refined steel ingot are removed, and then the refined steel ingot is subjected to heat preservation treatment to eliminate the stress generated in the solidification process, wherein the temperature of the heat preservation treatment is 1150-1200 ℃, and the time is 1.5-2 h; and then forging the refined steel ingot to obtain an intermediate forging which can be used for rolling.
7. The preparation method of the nanostructured low-activation martensitic steel as claimed in claim 1, wherein when austenitizing the intermediate forging, the intermediate forging is kept at 1100-1150 ℃ for 1-1.5 h to realize austenitizing.
8. The method for preparing the nanostructured low-activation martensitic steel as claimed in claim 1, wherein the slow cooling rate is 1-2 ℃/s during medium temperature rolling.
9. The method for preparing the nanostructured low-activation martensitic steel as claimed in claim 1, wherein the tempering temperature is 650-700 ℃ and the holding time is 1.5-2 h during the microstructure shaping heat treatment, and the cooling mode is water cooling.
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