12Cr13 forged rod for nuclear power plant reactor control rod driving mechanism and manufacturing method thereof

Abstract

The invention relates to a 12Cr13 forged rod for a nuclear power plant reactor control rod driving mechanism and a manufacturing method thereof, and aims to improve the mechanical property and reliability of the forged rod. The method comprises the following steps that firstly, smelting is conducted through a medium-frequency induction furnace in combination with AOD, the content of all elements in molten steel is controlled, and the content of five-harm elements is limited; and secondly, the purity and uniformity of the steel are further improved by adopting an electroslag remelting technology, the inclusion content is reduced, and the impact toughness is remarkably improved. And then, the forming technology of'fast forging and radial forging 'is implemented, and the physical performance is enhanced. And finally, high-temperature tempering treatment is carried out, so that the strength and toughness are optimized. By comprehensively controlling the chemical components, the smelting process, the forging process and heat treatment, the problem that in the prior art, the strength and toughness of a forged rod are unstable is solved, it is ensured that the manufactured 12Cr13 forged rod can meet the strict requirement of a nuclear power station for material performance, and the 12Cr13 forged rod has important engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy preparation, and in particular to a 12Cr13 forged rod for a control rod driving mechanism of a nuclear power plant reactor and a manufacturing method thereof. Background Art

[0002] The control rod drive mechanism of a nuclear power plant reactor is a crucial component in the operation of a nuclear power plant. Its core function is to control and stop the nuclear reaction, so the performance requirements of the material are extremely stringent. In the manufacture of this mechanism, 12Cr13 stainless steel forging rods have been widely used in the manufacture of components such as magnetic poles, armatures, adjustment plates and protective sleeves in the control rod drive mechanism due to their good corrosion resistance and medium strength. However, with the increasingly complex operating conditions of nuclear power plant equipment, the performance requirements for 12Cr13 forging rods have gradually increased. Not only are they required to have high strength, but they are also required to have excellent low-temperature impact toughness at medium strength. To achieve this, the composition, smelting process, forging and heat treatment processes of the steel must be strictly controlled to ensure that the steel has good purity and uniform microstructure.

[0003] In the existing technology, the production of 12Cr13 stainless steel mainly adopts the smelting process of "medium frequency induction furnace + electroslag remelting" or "arc furnace + external refining (LF+VOD) + electroslag remelting", and is formed by forging or rolling, and finally delivered in the state of "quenching / quenching + tempering". Although this process route can produce materials that meet the basic requirements of nuclear power plants, as the harshness of the operating environment of nuclear reactors increases, some problems that cannot meet actual needs are exposed in the existing process.

[0004] First, although the 12Cr13 stainless steel forging rods produced by the existing technology have high strength, their low-temperature impact toughness is low and unstable. This problem of insufficient toughness is manifested as weak impact resistance in the actual operation of the control rod drive mechanism. Especially under low temperature conditions, the material is prone to brittle fracture, which greatly limits the application of this material in nuclear reactors. The lack of impact toughness will not only lead to early failure of the material during use, but also bring safety hazards, affecting the safe operation of the entire nuclear power plant.

[0005] Secondly, in the existing process of smelting, although the purity of steel has been improved to a certain extent through electroslag remelting technology, the traditional process does not control the chemical composition and impurity elements in a precise manner, resulting in a serious problem of component segregation of the material. In particular, the content of impurity elements such as phosphorus and sulfur in steel is high. The presence of these non-metallic inclusions in the material greatly weakens the uniformity of the material and reduces the stability of the mechanical properties of the material.

[0006] In addition, although the traditional forging and rolling processes can form the basic product form, the uniformity of the material structure is insufficiently controlled. During the forging process, improper deformation control leads to uneven internal structure of the steel and unsatisfactory grain size distribution. This organizational defect further affects the comprehensive mechanical properties of 12Cr13 stainless steel, especially key indicators such as toughness and plasticity. In addition, the traditional tempering process often cannot accurately control the precipitation of carbides in the material, resulting in unstable material properties and difficulty in adapting to the needs of complex working conditions of nuclear power plants in the long term.

[0007] Therefore, the existing 12Cr13 stainless steel forging rod production process cannot fully meet the actual requirements of the control rod drive mechanism, and the material still has a lot of room for improvement in toughness, purity, and uniformity of structure. The existing technology urgently needs an improved manufacturing method to effectively improve the comprehensive performance of 12Cr13 forging rods, especially in low temperature toughness and impact performance, to ensure that it can operate stably in nuclear reactors for a long time. Summary of the invention

[0008] One of the technical problems to be solved by the present invention is to provide a 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor, so as to solve the problem that the existing 12Cr13 stainless steel forged rod production process cannot fully meet the actual requirements of the control rod drive mechanism and the material has poor toughness, purity and structural uniformity.

[0009] In order to solve the above technical problems, the present invention provides a 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor. The composition of the 12Cr13 forged rod includes, by mass ratio: C: 0.080-0.150%, Si: ≤1.00%, Mn: ≤1.00%, P: ≤0.030%, S: ≤0.030%, Cr: 11.50-13.50%, Co: ≤0.10%, Ni: 0.05-0-50%, and the balance is Fe and unavoidable impurities.

[0010] Compared with the prior art, the 12Cr13 forged rod for the control rod drive mechanism of the reactor of a nuclear power plant in the present application has the following advantages: through the formula design of the forged rod, the alloy elements and impurity content of the forged rod are regulated, thereby ensuring the high strength and high toughness of the material. The adoption of the above technical scheme can effectively reduce the impurity content in the material, and by controlling the appropriate component ratio, the toughness and strength of the material can be kept stable in a wider working environment. By precisely controlling the chemical composition, the impact toughness of the material at medium and low temperatures is significantly enhanced, and at the same time, the uniformity of the material is improved, meeting the harsh use requirements of the reactor equipment for the material. Ultimately, the technical effect achieved is to ensure the long-term stable use of the 12Cr13 forged rod in harsh environments, extend the service life of the reactor equipment, and the forged rod has excellent low-temperature impact toughness and mechanical properties. The control of the above components ensures the uniformity and grain size of the steel, improves the impact resistance and fatigue resistance, thereby solving the problems of uneven organization and poor toughness mentioned in the background technology.

[0011] In a possible implementation manner, the composition of the 12Cr13 forged rod includes, by mass ratio: C: 0.095-0.120%, Si: 0.20-0.60%, Mn: 0.30-0.65%, P: ≤0.029%, S: ≤0.002%, Cr: 11.70-12.30%, Co: ≤0.08%, Ni: 0.08-0-3 0%, and the balance is Fe and unavoidable impurities.

[0012] Another technical problem to be solved by the present invention is to provide a method for manufacturing 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor, so as to solve the problem that the deformation amount is improperly controlled during the forging process in the existing method for manufacturing 12Cr13 forged rods, resulting in uneven internal structure of the steel and unsatisfactory grain size distribution.

[0013] In order to solve the above technical problems, the present invention provides a method for manufacturing the 12Cr13 forged rod for the control rod drive mechanism of the nuclear power plant reactor, comprising the following steps:

[0014] S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is cast into electrode rods to obtain electrode rods;

[0015] S2: remelting the electrode rod by electroslag;

[0016] S3: The raw material after electroslag remelting in step S2 is subjected to rapid forging and radial forging forming treatment in sequence, and the conditions of the rapid forging and radial forging forming treatment are: the electroslag ingot is heated to a temperature of 1140-1170°C, and then rapid forging is performed, and then the product after rapid forging is placed in a heating furnace, and then kept warm at 950-1000°C for waiting for materials, and after all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for keeping warm, and then a radial forging machine is used for one-fire forming, and the final forging temperature is ensured to be ≥880°C, and the rod is obtained after cooling;

[0017] S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

[0018] Compared with the prior art, the manufacturing method of 12Cr13 forged rods for the control rod drive mechanism of a nuclear power plant reactor in the present application has the following advantages: the manufacturing method in the present invention changes the single smelting step in the prior art into a combination of multi-stage smelting and refining, and optimizes the forging and heat treatment steps, further refines the grain size, and ensures the uniformity of the internal structure of the steel. The direct technical principle is to remove impurities through multiple smelting, refining and electroslag remelting technology to improve the purity of the steel, and make the internal structure of the material more dense and uniform through the combination of fast forging and radial forging; through the combination of chemical composition control and multi-stage heat treatment, it can ensure that the material still maintains excellent mechanical properties and organizational stability under complex working conditions. Finally, the technical effect achieved is to further improve the impact resistance and ductility of the material, ensure the long-term reliable operation of the reactor control rod drive mechanism, and solve the problems of insufficient toughness and uneven organization in the prior art.

[0019] In a possible implementation manner, in step S1, the raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the tapping temperature of the medium frequency induction furnace is ≥1600°C.

[0020] Compared with the existing technology, the above technical solution can further reduce the content of harmful elements in steel, ensure the purity and consistency of steel, especially the toughness and strength under complex working conditions, remove harmful elements through refining and deoxidation technology, directly improve the corrosion resistance and fatigue resistance of steel, and achieve high-purity 12Cr13 forging rods, ensuring long-term and reliable application in the control rod drive mechanism of nuclear power plant reactors.

[0021] In a possible implementation, in step S1, in the AOD furnace, the AOD refining conditions are: first dephosphorizing the raw steel until the mass ratio of phosphorus is less than 0.015%, and then decarburizing, reducing, and alloying.

[0022] Compared with the existing technology, the above technical solution can improve the toughness and plasticity of the material by effectively controlling the phosphorus content. By controlling the phosphorus content at an extremely low level, the brittle tendency of the material is reduced and the stability of the material under high stress conditions is improved. Through the refining process, the 12Cr13 forged rod can maintain good mechanical properties in various extreme environments and extend the service life of the material.

[0023] In a possible implementation, in step S1, the smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include:

[0024] LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing;

[0025] VD degassing: The vacuum in the VD vacuum furnace should be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process should be controlled at 1560-1580℃;

[0026] Compared with the existing technology, the above technical scheme can effectively remove residual oxygen and other gas impurities in the raw materials by strictly controlling the deoxidation process and vacuum degassing process, ensure the purity of the steel, and reduce the pores and inclusions in the material through the combined refining method of LF and VD, and make the structure denser, further improving the mechanical properties and fatigue life of the material, so that the durability and toughness of 12Cr13 forging rods in high load and high stress environments can be significantly enhanced.

[0027] In a possible embodiment, in the step S1, after the AOD refining, the composition of the molten steel includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the remainder is Fe and unavoidable impurities.

[0028] After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

[0029] Compared with the prior art, the above technical solution can ensure the stability of the material by precisely controlling the content of each element. By further controlling the appropriate proportions of elements such as C, Cr, Ni, etc., the material can maintain high strength while also having good toughness and corrosion resistance. Further synergistic effects enable the 12Cr13 forged rod to exhibit extremely high stability and fatigue resistance in harsh environments.

[0030] In a possible embodiment, in step S2, the conditions of the electroslag remelting include: crystallizer specifications: Φ500-Φ550mm; slag ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in the normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min and then air-cooled after hood cooling for ≥48h.

[0031] Compared with the existing technology, the above-mentioned electroslag remelting technology can effectively remove impurities in steel and improve the microstructure and composition uniformity of the material by precisely controlling the current, voltage and slag composition. The electroslag remelting process eliminates the segregation phenomenon within and between grains, further improving the organizational uniformity of the material. Through this optimized electroslag remelting process, the 12Cr13 forged rods produced have higher impact toughness, mechanical stability and ductility, meeting the high performance requirements of key parts of nuclear power plants.

[0032] In a possible implementation manner, in step S3, the conditions of the rapid forging treatment are: upsetting once by a rapid forging machine to lengthen to an octagonal blank, and leaving 60-70% deformation; the conditions of the cooling are: air cooling the bar to ≤100°C after forging.

[0033] Compared with the prior art, the above technical solution can complete the upsetting and drawing processes at one time through the fast forging machine, while controlling the deformation amount and avoiding the damage of the organization caused by excessive processing. By controlling the deformation amount of 60-70%, the internal organization of the bar is uniformly deformed under controlled conditions, reducing the accumulation of internal stress. The bar after fast forging has a good grain structure and uniform grain size. After air cooling, the thermal stress caused by rapid cooling is avoided, and the fatigue resistance and low-temperature toughness of the material are further enhanced, so that the 12Cr13 forged rod shows a balance of high strength and high toughness in subsequent processing or use, which fully meets the stringent requirements of the control rod drive mechanism of the nuclear power plant on the mechanical properties of the material.

[0034] In a possible implementation manner, the tempering process includes:

[0035] Initial temperature control stage: The initial temperature of the forging rod is controlled below 350℃, and then the temperature is increased, and the heating rate does not exceed 80℃ per hour to ensure uniform heating.

[0036] Heating and holding stage: The forging rod is heated to 760℃ to 800℃ and kept in this temperature range for at least 8 hours to ensure the uniformity and stability of the internal structure of the forging rod.

[0037] The first cooling stage: from the holding temperature of 760°C to 800°C to about 600°C at a cooling rate not exceeding 50°C per hour.

[0038] The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

[0039] Compared with the prior art, the above-mentioned tempering treatment scheme can accurately control the temperature and cooling rate, avoid the abnormal structure of the material caused by too fast or too slow cooling, and fully release the stress inside the forged rod by controlling the heating rate, holding time and cooling rate, while the structure is refined and the carbide is evenly distributed. After the tempering treatment, the low-temperature toughness, impact resistance and fatigue resistance of the forged rod are improved, and the residual stress inside the material is significantly reduced, which ultimately enhances its long-term service life under the high-strength and high-load conditions of the nuclear power plant. Such high-temperature tempering treatment ensures the uniformity of the structure of the forged rod in different temperature ranges, so that the material has extremely high strength and toughness, which is particularly suitable for the high-demand parts of the control rod drive mechanism of the nuclear power plant. This multi-stage, finely controlled tempering process further optimizes the performance of the 12Cr13 forged rod, especially under high stress and extreme environmental conditions, it can maintain performance stability for a long time, and is not prone to problems such as material fatigue and fracture, which fully meets the special requirements of materials for nuclear power plants mentioned in the background technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the heat treatment process diagram for tempering treatment. DETAILED DESCRIPTION

[0041] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0042] The invention provides a 12Cr13 forged rod for a control rod driving mechanism of a reactor of a nuclear power plant. The 12Cr13 forged rod comprises, by mass ratio, the following components: C: 0.080-0.150%, Si: ≤1.00%, Mn: ≤1.00%, P: ≤0.030%, S: ≤0.030%, Cr: 11.50-13.50%, Co: ≤0.10%, Ni: 0.05-0-50%, and the balance is Fe and inevitable impurities.

[0043] As a preferred solution, the composition of the 12Cr13 forged rod includes, by mass ratio: C: 0.095-0.120%, Si: 0.20-0.60%, Mn: 0.30-0.65%, P: ≤0.029%, S: ≤0.002%, Cr: 11.70-12.30%, Co: ≤0.08%, Ni: 0.08-0-3 0%, and the balance is Fe and unavoidable impurities.

[0044] The present invention also provides a method for manufacturing the 12Cr13 forged rod for the control rod drive mechanism of a nuclear power plant reactor, comprising the following steps:

[0045] S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is cast into electrode rods to obtain electrode rods;

[0046] S2: remelting the electrode rod by electroslag;

[0047] S3: The raw material after electroslag remelting in step S2 is subjected to rapid forging and radial forging forming treatment in sequence, and the conditions of the rapid forging and radial forging forming treatment are: the electroslag ingot is heated to a temperature of 1140-1170°C, and then rapid forging is performed, and then the product after rapid forging is placed in a heating furnace, and then kept warm at 950-1000°C for waiting for materials, and after all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for keeping warm, and then a radial forging machine is used for one-fire forming, and the final forging temperature is ensured to be ≥880°C, and the rod is obtained after cooling;

[0048] S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

[0049] As a preferred solution, in step S1, the raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the tapping temperature of the medium frequency induction furnace is ≥1600°C.

[0050] As a preferred solution, in step S1, in the AOD furnace, the AOD refining conditions are: first dephosphorizing the raw steel until the mass ratio of phosphorus is less than 0.015%, and then decarburizing, reducing and alloying.

[0051] As a preferred solution, in step S1, the smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include:

[0052] LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing;

[0053] VD degassing: The vacuum in the VD vacuum furnace should be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process should be controlled at 1560-1580℃;

[0054] As a preferred scheme, in step S1, after the AOD refining, the composition of the molten steel includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the remainder is Fe and unavoidable impurities.

[0055] After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

[0056] As a preferred scheme, in step S2, the conditions for electroslag remelting include: crystallizer specifications: Φ500-Φ550mm; slag ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in the normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min and then removed, and air-cooled after hood cooling for ≥48h.

[0057] As a preferred solution, in step S3, the conditions of the rapid forging treatment are: upsetting once by a rapid forging machine to draw the blank into an octagonal shape, and leaving 60-70% deformation; the conditions of the cooling are: air cooling the bar to ≤100°C after forging.

[0058] As a preferred solution, Figure 1 As shown, the tempering process includes:

[0059] Initial temperature control stage: The initial temperature of the forging rod is controlled below 350℃, and then the temperature is increased, and the heating rate does not exceed 80℃ per hour to ensure uniform heating.

[0060] Heating and holding stage: The forging rod is heated to 760℃ to 800℃ and kept in this temperature range for at least 8 hours to ensure the uniformity and stability of the internal structure of the forging rod.

[0061] The first cooling stage: from the holding temperature of 760°C to 800°C to about 600°C at a cooling rate not exceeding 50°C per hour.

[0062] The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

[0063] After the tempering treatment, the mechanical properties of the forged rods are required to meet the requirements of Table 1.

[0064] Table 1 Mechanical properties of rods used in control drive mechanisms

[0065]

[0066] In combination with the above technical solution, embodiments are further given below to explain the technical solution of the present invention in more detail:

[0067] Embodiment 1:

[0068] Embodiment 1 provides a 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor and a manufacturing method thereof, comprising:

[0069] The invention discloses a 12Cr13 forged rod for a control rod driving mechanism of a nuclear power plant reactor. The components of the 12Cr13 forged rod include, by mass ratio, 0.115% C, 0.31% Si, 0.47% Mn, 0.013% P, 0.002% S, 12.55% Cr, 0.003% Co, 0.14% Ni, 0.011% N, and the balance is Fe and unavoidable impurities.

[0070] The manufacturing method of the 12Cr13 forged rod comprises the following steps:

[0071] S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is used to cast electrode rods. The electrode rod of Φ360 is cast by the pouring method, and argon protection is used during the casting process to obtain the electrode rod;

[0072] The raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the steel tapping temperature of the medium frequency induction furnace is ≥1600°C.

[0073] In the AOD furnace, the AOD refining conditions are as follows: firstly, the raw steel is dephosphorized to a phosphorus mass ratio of less than 0.015%, and then decarburized, reduced, and alloyed;

[0074] After the AOD refining, the molten steel composition includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the balance is Fe and unavoidable impurities.

[0075] The smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include:

[0076] LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing;

[0077] VD degassing: The vacuum in the VD vacuum furnace should be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process should be controlled at 1560-1580℃;

[0078] After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

[0079] S2: The electrode rod is remelted by electroslag; the conditions of the electroslag remelting include: crystallizer specification: Φ500-Φ550mm; slag ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in the normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min to be removed, and the ingot is cooled in the air after hood cooling for ≥48h.

[0080] S3: The raw materials after electroslag remelting in step S2 are subjected to quick forging and radial forging forming treatments in sequence. The conditions of the quick forging and radial forging forming treatments are: heating the electroslag ingot to a temperature of 1140-1170°C, and then performing quick forging treatment. The conditions of the quick forging treatment are: using a quick forging machine to upset once and stretch it to an octagonal billet, and leaving 60-70% deformation; the cooling conditions are: after forging, the bar is air-cooled to ≤100°C; then the product after quick forging is placed in a heating furnace, and then kept warm at 950-1000°C for material waiting. After all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for insulation, and then a radial forging machine is used for one-fire forming to ensure that the final forging temperature is ≥880°C, and the bar is obtained after cooling;.

[0081] S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

[0082] The process of the tempering treatment comprises:

[0083] Initial temperature control stage: The initial temperature of the forging rod is controlled below 350℃, and then the temperature is increased, and the heating rate does not exceed 80℃ per hour to ensure uniform heating.

[0084] Heating and holding stage: The forging rod is heated to 760℃ to 800℃ and kept in this temperature range for at least 8 hours to ensure the uniformity and stability of the internal structure of the forging rod.

[0085] The first cooling stage: from the holding temperature of 760°C to 800°C to about 600°C at a cooling rate not exceeding 50°C per hour.

[0086] The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

[0087] Embodiment 2:

[0088] Embodiment 2 provides a 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor and a manufacturing method thereof, comprising:

[0089] The invention discloses a 12Cr13 forged rod for a control rod driving mechanism of a nuclear power plant reactor. The components of the 12Cr13 forged rod include, by mass ratio, 0.116% C, 0.38% Si, 0.45% Mn, 0.010% P, 0.003% S, 12.50% Cr, 0.002% Co, 0.11% Ni, 0.014% N, and the balance is Fe and unavoidable impurities.

[0090] The manufacturing method of the 12Cr13 forged rod comprises the following steps:

[0091] S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is used to cast electrode rods. The electrode rod of Φ360 is cast by the pouring method, and argon protection is used during the casting process to obtain the electrode rod;

[0092] The raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the steel tapping temperature of the medium frequency induction furnace is ≥1600°C.

[0093] In the AOD furnace, the AOD refining conditions are as follows: firstly, the raw steel is dephosphorized to a phosphorus mass ratio of less than 0.015%, and then decarburized, reduced, and alloyed;

[0094] After the AOD refining, the molten steel composition includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the balance is Fe and unavoidable impurities.

[0095] The smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include:

[0096] LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing;

[0097] VD degassing: The vacuum in the VD vacuum furnace should be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process should be controlled at 1560-1580℃;

[0098] After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

[0099] S2: The electrode rod is remelted by electroslag; the conditions of the electroslag remelting include: crystallizer specification: Φ500-Φ550mm; slag ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in the normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min to be removed, and the ingot is cooled in the air after hood cooling for ≥48h.

[0100] S3: The raw materials after electroslag remelting in step S2 are subjected to quick forging and radial forging forming treatments in sequence. The conditions of the quick forging and radial forging forming treatments are: heating the electroslag ingot to a temperature of 1140-1170°C, and then performing quick forging treatment. The conditions of the quick forging treatment are: using a quick forging machine to upset once and stretch it to an octagonal billet, and leaving 60-70% deformation; the cooling conditions are: after forging, the bar is air-cooled to ≤100°C; then the product after quick forging is placed in a heating furnace, and then kept warm at 950-1000°C for material waiting. After all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for insulation, and then a radial forging machine is used for one-fire forming to ensure that the final forging temperature is ≥880°C, and the bar is obtained after cooling;.

[0101] S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

[0102] The process of the tempering treatment comprises:

[0103] Initial temperature control stage: The initial temperature of the forging rod is controlled below 350℃, and then the temperature is increased, and the heating rate does not exceed 80℃ per hour to ensure uniform heating.

[0104] Heating and holding stage: The forging rod is heated to 760℃ to 800℃ and kept in this temperature range for at least 8 hours to ensure the uniformity and stability of the internal structure of the forging rod.

[0105] The first cooling stage: from the holding temperature of 760°C to 800°C to about 600°C at a cooling rate not exceeding 50°C per hour.

[0106] The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

[0107] Embodiment 3:

[0108] Embodiment 3 provides a 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor and a manufacturing method thereof, comprising:

[0109] The invention discloses a 12Cr13 forged rod for a control rod driving mechanism of a nuclear power plant reactor. The components of the 12Cr13 forged rod include, by mass ratio, 0.109% C, 0.35% Si, 0.49% Mn, 0.015% P, 0.002% S, 12.43% Cr, 0.002% Co, 0.10% Ni, 0.013% N, and the balance is Fe and unavoidable impurities.

[0110] The manufacturing method of the 12Cr13 forged rod comprises the following steps:

[0111] S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is used to cast electrode rods. The electrode rod of Φ360 is cast by the pouring method, and argon protection is used during the casting process to obtain the electrode rod;

[0112] The raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the steel tapping temperature of the medium frequency induction furnace is ≥1600°C.

[0113] In the AOD furnace, the AOD refining conditions are as follows: firstly, the raw steel is dephosphorized to a phosphorus mass ratio of less than 0.015%, and then decarburized, reduced, and alloyed;

[0114] After the AOD refining, the molten steel composition includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the balance is Fe and unavoidable impurities.

[0115] The smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include:

[0116] LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing;

[0117] VD degassing: The vacuum in the VD vacuum furnace should be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process should be controlled at 1560-1580℃;

[0118] After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

[0119] S2: The electrode rod is remelted by electroslag; the conditions of the electroslag remelting include: crystallizer specification: Φ500-Φ550mm; slag ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in the normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min to be removed, and the ingot is cooled in the air after hood cooling for ≥48h.

[0120] S3: The raw material after electroslag remelting in step S2 is subjected to rapid forging and radial forging forming treatment in sequence. The conditions of the rapid forging and radial forging forming treatment are: the electroslag ingot is heated to a temperature of 1140-1170°C, and then rapid forging is performed. The conditions of the rapid forging treatment are: the bar is upset once and drawn to an octagonal billet by a rapid forging machine, and a deformation amount of 60-70% is left; the cooling conditions are: the bar is air-cooled to ≤100°C after forging; the product after rapid forging is then placed in a heating furnace, and then kept warm at 950-1000°C for material waiting, and after all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for insulation, and then a radial forging machine is used for one-fire forming, ensuring that the final forging temperature is ≥880°C, and the bar is obtained after cooling;

[0121] S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

[0122] The process of the tempering treatment comprises:

[0123] Initial temperature control stage: The initial temperature of the forging rod is controlled below 350℃, and then the temperature is increased, and the heating rate does not exceed 80℃ per hour to ensure uniform heating.

[0124] Heating and holding stage: The forging rod is heated to 760℃ to 800℃ and kept in this temperature range for at least 8 hours to ensure the uniformity and stability of the internal structure of the forging rod.

[0125] The first cooling stage: from the holding temperature of 760°C to 800°C to about 600°C at a cooling rate not exceeding 50°C per hour.

[0126] The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

[0127] The chemical compositions of the forgings prepared in Examples 1-3 are shown in Table 2 below:

[0128] Table 2: 12Cr13 chemical composition wt%

[0129]

[0130] The 12Cr13 forgings of Examples 1-3 were tested for non-metallic inclusions, grain size, and mechanical properties of the bars. The test results are shown in Tables 3 and 4. In the table, 1#, 2#, and 3# correspond to Examples 1 / 2 / 3, respectively, and Φ is the diameter of the forging:

[0131] Table 3 Non-metallic inclusions and grain size of 12Cr13 forged rods

[0132]

[0133] Table 4 Mechanical properties of 12Cr13 bars

[0134] serial number <![CDATA[R P0.2 / MPa]]> Rm / MPa A / ％ Z / ％ KV(0℃) / J HBW 1#-Φ155 592 / 588 430 / 438 25.5 / 26.0 72 / 75 155 / 149 / 140 197 / 198 / 197 2#-Φ145 550 / 561 356 / 362 29.5 / 30.0 76 / 75 146 / 138 / 136 173 / 168 / 170 3#-Φ145 582 / 575 432 / 425 26.0 / 25.0 74 / 72 153 / 127 / 154 192 / 195 / 190

[0135] The above tests and embodiments further prove that the present invention overcomes the problem of unstable strength and toughness of forged rods in the prior art by comprehensively controlling the chemical composition, smelting process, forging process and heat treatment, ensuring that the manufactured 12Cr13 forged rods can meet the strict requirements of nuclear power plants on material properties and have important engineering application value. The prepared rods have excellent mechanical properties, uniform grain size and few inclusions.

[0136] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0137] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor, characterized in that: In terms of mass ratio, the composition of the 12Cr13 forged rod includes: C: 0.080-0.150%, Si: ≤1.00%, Mn: ≤1.00%, P: ≤0.030%, S: ≤0.030%, Cr: 11.50-13.50%, Co: ≤0.10%, Ni: 0.05-0-50%, and the balance is Fe and inevitable impurities.

2. The 12Cr13 forged rod for a control rod drive mechanism of a nuclear power plant reactor according to claim 1, characterized in that: In terms of mass ratio, the composition of the 12Cr13 forged rod includes: C: 0.095-0.120%, Si: 0.20-0.60%, Mn: 0.30-0.65%, P: ≤0.029%, S: ≤0.002%, Cr: 11.70-12.30%, Co: ≤0.08%, Ni: 0.08-0-30%, and the balance is Fe and inevitable impurities.

3. A method for manufacturing 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: Electrode rod smelting: After selecting the raw material of 12Cr13 forging rod, the raw material is smelted in a medium frequency induction furnace, an AOD furnace, an LF furnace and a VD vacuum furnace in sequence, and the raw material is cast into electrode rods to obtain electrode rods; S2: remelting the electrode rod by electroslag; S3: The raw material after electroslag remelting in step S2 is subjected to rapid forging and radial forging forming treatment in sequence, and the conditions of the rapid forging and radial forging forming treatment are: the electroslag ingot is heated to a temperature of 1140-1170°C, and then rapid forging is performed, and then the product after rapid forging is placed in a heating furnace, and then kept warm at 950-1000°C for waiting for materials, and after all the products are loaded into the furnace, the temperature is raised to 1100-1150°C for keeping warm, and then a radial forging machine is used for one-fire forming, and the final forging temperature is ensured to be ≥880°C, and the rod is obtained after cooling; S4: Tempering the rod obtained in step S3 to obtain 12Cr13 forged rods for a control rod drive mechanism of a nuclear power plant reactor.

4. The manufacturing method according to claim 3, characterized in that: In the step S1, the raw material of the 12Cr13 forged rod is raw steel with low content of five harmful elements, the five harmful elements include Pb, Sn, As, Sb, and Bi, and in the raw steel, the mass content of any one of the five harmful elements is less than 0.015%, and the total mass content of the five harmful elements is less than 0.035%; the tapping temperature of the medium frequency induction furnace is ≥1600°C.

5. The manufacturing method according to claim 3, characterized in that: In the step S1, the AOD refining conditions in the AOD furnace are as follows: firstly, the raw steel is dephosphorized to a phosphorus mass ratio of less than 0.015%, and then decarburized, reduced, and alloyed.

6. The manufacturing method according to claim 3, characterized in that: In the step S1, the smelting conditions of the raw materials in the LF furnace and the VD vacuum furnace include: LF refining: use aluminum particles and calcium silicon powder for deoxidation, control the white slag time ≥ 30min, adjust the composition of the raw materials, and electrically adjust the temperature in the LF furnace to above 1650℃, and carry out bag processing; VD degassing: The vacuum in the VD vacuum furnace is required to be evacuated to ≤67Pa and maintained for ≥15min; the temperature during the bag hanging process is controlled at 1560-1580℃.

7. The manufacturing method according to claim 3, characterized in that: In the step S1, after the AOD refining, the molten steel composition includes: C: 0.04-0.09%, Cr: 12.10-12.40%, Ni: 0.06-0.15%, Si: 0.20-0.30%, Mn: 0.40-0.50%, P: ≤0.020%, S: ≤0.002%, N: ≤0.015%, and the balance is Fe and unavoidable impurities; After the electrode rod is cast, the composition of the electrode rod includes: C: 0.095-0.12%, Cr: 12.00-12.60%, Ni: 0.08-0.30%, Si: 0.30-0.55%, Mn: 0.40-0.65%, Co≤0.08%, P≤0.022%, S≤0.005%, N:≤0.010%, and the balance is Fe and unavoidable impurities.

8. The manufacturing method according to claim 3, characterized in that: In step S2, the electroslag remelting conditions include: crystallizer specifications: Φ500-Φ550mm; slag material ratio: CaF2∶Al2O3∶CaO∶MgO=65∶15∶15∶5 or pre-melted slag with the same composition; power parameters in normal remelting stage: current 10500~9000A, voltage 62~56V; and after the electroslag remelting is completed, the ingot is cooled in the crystallizer for 40~50min to be removed, and then air-cooled after hood cooling for ≥48h.

9. The manufacturing method according to claim 3, characterized in that: In step S3, the conditions of the rapid forging treatment are: upsetting once by a rapid forging machine to lengthen to an octagonal blank, and leaving 60-70% deformation; the conditions of the cooling are: air cooling the bar to ≤100°C after forging.

10. The manufacturing method according to claim 3, characterized in that: In the step S4, the tempering process includes: Initial temperature control stage: the initial temperature of the forged rod is controlled below 350°C, and then the temperature is increased, and the heating rate does not exceed 80°C per hour; Heating and holding stage: heat the forging bar to 760-800℃ and keep it in this temperature range for at least 8 hours; The first cooling stage: cooling from the holding temperature of 760-800°C to about 600°C at a cooling rate not exceeding 50°C per hour; The second cooling stage: At 600°C, the forged bars are taken out of the furnace and air-cooled to room temperature in the air.

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