Vacuum induction melting ODS steel system capable of achieving lifting feeding and application method

Abstract

The invention provides a liftable feeding vacuum induction melting ODS steel system and an application method, and relates to the technical field of oxide dispersion strengthening (ODS) steel. The vacuum induction melting ODS steel system capable of achieving lifting feeding comprises a vertical lifting type feeding mechanism. The vertical lifting type feeding mechanism comprises two stepping motors, a vertically-arranged ball screw, a ball screw nut and a ball spline nut. Wherein the structures of the stepping motor, the ball screw and the nut are arranged to realize lifting and synchronous rotating motion of the ball screw; a disc with the diameter of 20 cm is installed at the bottom of the lead screw, and two yttrium-titanium thin iron rods are fixed to the two sides of the disc. According to the invention, a liftable feeding technology is developed, so that yttrium and titanium are uniformly dissolved in the molten steel pouring process and are distributed in a solidified cast ingot in the form of fine and dispersed oxides, and quantitative preparation of ODS steel is realized; the preparation method is simple and easy to operate, green and environment-friendly, low in cost, short in process, high in efficiency and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of oxide dispersion strengthened steel (ODS), and in particular to a vacuum induction melting system for ODS steel with lifting and feeding capabilities and an application method thereof. Background Art

[0002] Fusion energy, due to its abundant resources and environmental friendliness, has become humanity's ideal energy source for the future. It is one of the most promising fundamental solutions to the energy crisis and holds strategic significance for the sustainable development of my country's economy and society. It represents a fundamental frontier field crucial for long-term development. The blanket, a core component of a fusion reactor, lies within the reactor core, subject to extremely harsh operating environments. It must withstand high-flux particle and heat fluxes, as well as high-energy and high-dose fusion neutron irradiation. It also faces numerous critical events, particularly plasma disruption, boundary localized mode instabilities, and vertical displacement events, posing significant challenges to materials and heat exchange fittings. Maintaining the integrity of materials and components not only requires withstanding the reactor's high temperatures, high temperature gradients, and intense radiation, but also coolant corrosion and erosion, complex mechanical loads, and, in particular, resistance to permeation of hydrogen isotopes from the fusion fuel. This poses significant challenges to the compositional design, microstructure control, and manufacturing processes of the materials and fittings.

[0003] Ferritic / martensitic steels (F / M steels) with 9-12% chromium content have become candidate materials for fusion reactor blankets due to their excellent high-temperature strength, high thermal conductivity, low radiation swelling, and low stress corrosion cracking susceptibility. Oxide dispersion-strengthened (ODS) steels, developed based on F / M steels, exhibit excellent high-temperature mechanical properties and radiation resistance by incorporating nanoparticles into the steel matrix. Y2O3, due to its high melting point, thermal stability, and ability to trap radiation-induced defects, has become the mainstream additive phase in ODS steels for fusion reactor blankets. Complex oxides such as Y2Ti2O7 further enhance the mechanical properties of ODS steels by refining the nanoparticle size (2-4 nm).

[0004] At present, the mainstream technology for preparing ODS steel is powder metallurgy. Powder metallurgy uses mechanical alloying (MA) to evenly disperse ultrafine nano-oxides (such as Y2O3 and Y2Ti2O7) into the steel matrix, forming submicron-sized grains and high-density nano-dispersed phases (number density of 10 23 m -3 ), which can significantly improve the high temperature strength, creep resistance and radiation resistance of steel.

[0005] However, the main technical defects of preparing ODS steel by powder metallurgy are as follows:

[0006] (1) Process complexity and cost issues. The powder metallurgy process requires multiple steps, including powder making, mechanical alloying, canning, and hot forming (such as hot isostatic pressing or forging). The process cycle is long, energy consumption is high, and batch-to-batch stability is poor. The single-batch output of ODS steel produced by powder metallurgy is low, making it difficult to meet the large-scale demand for fusion reactor blanket materials (for example, 1,140 tons are required for a blanket over a 30-year operation period), limiting industrial production.

[0007] (2) Bottlenecks in economic efficiency and large-scale production. Powder metallurgy equipment requires large investments, and the storage and transportation of ultrafine powders are susceptible to contamination, further increasing costs. Powder metallurgy is difficult to produce large-scale components and requires complex post-processing processes such as sheath welding and composite rolling.

[0008] In addition to powder metallurgy, the methods for preparing ODS steel also include liquid metal method. The main advantages and technical difficulties of this method are as follows:

[0009] The preparation of ODS steel by liquid metal method has the advantages of short process flow, large single batch output, good stability between batches, and low manufacturing cost. However, because yttrium oxide has poor wettability in molten steel and its density is lower than the density of molten steel, if yttrium oxide is directly added to molten steel, it will easily cause it to agglomerate and float, and cannot be dispersed in the molten steel. The difficulty in using liquid metal method to prepare ODS steel is to shorten the contact time between molten steel and rare earth yttrium as much as possible. When yttrium and titanium are dissolved in molten steel, they will react with the dissolved oxygen in the molten steel to form yttrium titanium oxide. At this time, it is necessary to make the molten steel solidify quickly to avoid the agglomeration and growth of yttrium titanium oxide in the molten steel, but to be able to form small (size <10nm), dispersed (number density >10 23 m -3 ) is evenly distributed in the ingot after solidification. Summary of the Invention

[0010] To address the technical problems of ODS steel production in the prior art, such as complex processes, poor batch-to-batch stability, high costs, and difficulty in large-scale production, the present invention proposes a vacuum induction melting system for ODS steel with a lifting and feeding mechanism and its application method. The technical solution is as follows:

[0011] A vacuum induction melting system for ODS steel with liftable feeding, comprising a vertical lift feeding mechanism arranged directly above a pouring gate in a vacuum induction melting furnace chamber, the vertical lift feeding mechanism comprising two 1 kW stepper motors, a vertically arranged ball screw, a ball screw nut, and a ball spline nut; wherein: the structure of the two stepper motors, the ball screw, the ball screw nut, and the ball spline nut is arranged to realize vertical lift and synchronous rotation of the ball screw; a disc with a diameter of 20 cm is installed at the bottom of the screw, and two steel pipe clamps with an inner diameter of 20 mm, a wall thickness of 10 mm, and a length of 50 mm are symmetrically installed at the edge of the disc.

[0012] Optionally, the vertical lifting and synchronous rotation motion structure of the ball screw is set: the structure of one stepper motor and the ball screw is used to drive the screw to lift and lower in the vertical direction, and the structure of another stepper motor and the ball screw is used to drive the screw to rotate at a constant speed around its own vertical axis. The coordinated setting of the two stepper motors can enable the ball screw to achieve synchronous lifting and rotation motion.

[0013] Optionally, by turning on two stepper motors at the same time, the lead screw will achieve coupled movement of lifting and rotating.

[0014] Optionally, a stepper motor drives the ball screw nut to rotate, converting the rotational motion into the vertical lifting of the screw, thereby realizing the lifting and lowering feeding function; another stepper motor drives the ball spline nut to rotate, transmitting the rotational motion to the screw, so that it can rotate at a constant speed around its own vertical axis; the rotation of the screw drives the yttrium-titanium-containing thin iron rod to stir in the molten steel, so that the yttrium and titanium can be evenly dissolved in the molten steel.

[0015] Optionally, a small hole with a diameter of 7.5 mm is opened in the side wall of the steel pipe using a hole opener, and a thin iron rod containing yttrium titanium is fixed in each steel pipe fixture. The diameter of the thin iron rod containing yttrium titanium is 5-15 mm and the length is 1-1.5 m.

[0016] Alternatively, use a hole opener to create a 7.5mm diameter hole in the side wall of the steel pipe. Use an M8 tap to tap the hole and insert an M8 screw. Insert a thin yttrium-titanium iron rod into the steel pipe and tighten the screw to secure it.

[0017] Optionally, two 1KW stepper motors are set on the side wall of the vacuum furnace chamber, and are engaged with the ball screw nut and the ball spline nut through bevel gears, so that the bevel gears drive the ball screw nut and the ball spline nut to rotate respectively. The ball screw nut can convert its own rotational motion into linear motion of the screw, and the ball spline nut transmits its own rotational motion to the screw, so that it can rotate around its own vertical axis.

[0018] Optionally, a ball spline nut engages with the ball screw, allowing the nut to rotate the screw about its vertical axis, thereby rotating a thin yttrium-titanium iron rod on a circular disc at the bottom of the screw. When the yttrium-titanium iron rod comes into contact with molten steel, it dissolves in the steel while stirring, achieving uniform dissolution of yttrium and titanium in the steel.

[0019] Optionally, the vacuum furnace's charging bin is equipped with interfaces for installing sampling cups and temperature and oxygen measurement probes. Sampling and temperature and oxygen measurement are both performed from the charging bin. Before and after refining, approximately 200g of sample is obtained from the molten steel using an alumina sampling cup for composition uniformity analysis. The alloying element content in the sample is measured using a direct reading spectrometer and compared with the designed composition to determine compositional uniformity. Before pouring, the dissolved oxygen content in the molten steel is measured using a molten steel temperature and oxygen measurement probe to ensure that it is within the range of 50-1000ppm. This ensures that the dissolved oxygen reacts with the yttrium and titanium dissolved in the molten steel in the pouring gate to form a Y-Ti-O dispersed phase.

[0020] An application method of the vacuum induction melting ODS steel system with liftable feeding is carried out in the chamber of a vacuum induction melting furnace. A thin iron rod containing yttrium and titanium is fixed on the bottom disc of the screw. During pouring, the thin iron rod containing yttrium and titanium descends at a uniform speed into the pouring gate to contact the molten steel, thereby achieving continuous feeding. The synchronous rotation of the screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, thereby achieving uniform dissolution of yttrium and titanium in the molten steel and reacting with the original dissolved oxygen in the molten steel to form Yttrium titanium oxide, the molten steel in the final pouring mouth flows into a flat steel ingot mold of 40 cm long × 10 cm wide × 60 cm high and is rapidly solidified to obtain an ODS steel ingot with fine and dispersed yttrium titanium oxide. Optionally, before the experiment, a thin yttrium titanium iron rod is fixed on the bottom disc of the screw, and two thin yttrium titanium iron rods with a diameter of 5-15 mm and a length of 1-1.5 m are respectively inserted into two steel pipe clamps, and the bolts on the side wall of the steel pipe are tightened to tighten the thin yttrium titanium iron rods.

[0021] Optionally, during the refining process, the vacuum degree in the induction furnace is controlled at 10-200 MPa, and the temperature of the molten steel is controlled at 1530-1680° C.; before tapping, the temperature of the molten steel is controlled at 1530-1580° C. so that the molten steel can solidify rapidly after entering the ingot mold; the composition of the molten steel without the addition of the yttrium-titanium thin iron rod is C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si 0.6-1.4%, Mn 0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, O 0.005-0.10%, and the balance is Fe.

[0022] Optionally, the yttrium-titanium-containing thin iron rod contains 1-20% Y, 0.2-5% Ti, and the balance Fe. The yttrium-titanium-containing thin iron rod descends at a speed of 0.5-1.5 m / min to ensure that the molten steel in the crucible is poured and the yttrium-titanium-containing thin iron rod is fed. The yttrium-titanium-containing thin iron rod rotates around the lead screw at a speed of 30-90 r / min to ensure that the yttrium and titanium are evenly dissolved in the molten steel.

[0023] Optionally, the composition of the final steel ingot is: C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si0.6-1.4%, Mn 0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, Y 0.05-0.3%, Ti0.01-0.1%, O 0.005-0.10%, and the balance is Fe.

[0024] Optionally, the prepared alloy ingot is heat treated by forging at 1050-1200°C for 2-4 hours, rolling at 1050-1150°C for 1-3 hours, water cooling at 950-1100°C for 0.5-2 hours, and air cooling at 700-780°C for 1-3 hours. The microstructure is fully tempered martensite, with the tempered martensite accounting for 100%, and the original austenite grain size is 20-50μm.

[0025] Optionally, the prepared ingot is heat treated by forging after being kept at 1050-1200°C for 2-4h, rolling after being kept at 1050-1150°C for 1-3h, water cooling after being kept at 950-1100°C for 0.5-2h, and air cooling after being kept at 700-780°C for 1-3h, and the tensile strength is ≥800MPa, the yield strength is ≥700MPa, the yield strength ratio is ≥0.85, the micro Vickers hardness is ≥250HV, the elongation after fracture is ≥17%, the strength-ductility product is ≥13GPa·%, and the room temperature impact toughness is ≥150 J.

[0026] Alternatively, the production cost of 1,000 kg alloy steel ingot is 60,000 to 90,000 yuan.

[0027] Technical principle of the present invention:

[0028] The preparation of ODS steel by liquid metal method has the advantages of short process flow, large single batch output, good stability between batches, and low manufacturing cost. However, because yttrium oxide has poor wettability in molten steel and its density is lower than the density of molten steel, if yttrium oxide is directly added to molten steel, it will easily cause it to agglomerate and float, and cannot be dispersed in the molten steel. The difficulty in using liquid metal method to prepare ODS steel is to shorten the contact time between molten steel and rare earth Y as much as possible. When yttrium and titanium are dissolved in molten steel, they will react with the dissolved oxygen in the molten steel to form yttrium titanium oxide. At this time, it is necessary to make the molten steel solidify quickly to avoid the agglomeration and growth of yttrium titanium oxide in the molten steel, but to be able to form small (size <10nm), dispersed (number density >10 23 m -3 ) is evenly distributed in the ingot after solidification.

[0029] In this invention, we first control the dissolved oxygen content in the molten steel within the range of 0.005-0.10% by controlling the vacuum level within the induction furnace, while a thin iron rod containing yttrium and titanium is fixed above the pouring gate. The chemical reaction between the dissolved oxygen and yttrium and titanium occurs only when the molten steel is poured after refining is completed, thus preventing the dissolved oxygen and yttrium and titanium from directly interacting and reacting during the induction melting stage, which could cause yttrium and titanium oxides to agglomerate and float in the molten steel.

[0030] Secondly, we use a lead screw to drive a thin iron rod containing yttrium and titanium downward vertically during pouring. This device synchronizes the pouring of molten steel with continuous feeding. When the oxygen in the molten steel reacts with the yttrium and titanium dissolved in the molten steel during the feeding phase, the molten steel flows into a flat ingot mold (40cm long, 10cm wide, and 60cm high) and solidifies into an ingot at the fastest cooling rate, effectively shortening the existence time of yttrium and titanium oxide in the molten steel.

[0031] Finally, the rotation of the screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, allowing yttrium and titanium to dissolve more evenly in the molten steel.

[0032] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0033] The above scheme, the present invention proposes a vacuum induction melting ODS steel system with lifting feeding and application method, which can solve the technical problems of the existing powder metallurgy technology for preparing ODS steel, such as complex process, poor stability between batches, high cost and difficulty in large-scale production.

[0034] The present invention prepares ODS steel by separating dissolved oxygen in molten steel from yttrium-titanium raw materials during vacuum induction melting, and reacting them during the molten steel pouring stage to form yttrium-titanium oxide. The yttrium-titanium oxide is evenly distributed in the ingot in a fine, dispersed form, and can achieve low-cost, large-scale, and stable preparation of nuclear-grade ODS steel.

[0035] The present invention uses a structural arrangement in which a lead screw drives a thin iron rod containing yttrium titanium to rise and fall vertically, thereby enabling the pouring of molten steel and continuous feeding to be carried out synchronously. After the dissolved oxygen in the molten steel reacts with the yttrium titanium raw material to form oxides, the ingot can be quickly solidified, thereby avoiding the long-term presence of yttrium titanium oxide in the molten steel, which causes agglomeration and floating.

[0036] The invention adopts a structural arrangement in which a thin iron rod containing yttrium and titanium is driven to stir in molten steel by the rotation of a lead screw, thereby enabling yttrium and titanium to be uniformly dissolved in the molten steel.

[0037] In summary, compared with other traditional methods, the method of the present invention develops a lifting feeding technology, which allows yttrium and titanium to be uniformly dissolved in molten steel and exist in the form of fine, dispersed oxides, so as to realize the quantitative preparation of ODS steel; this preparation method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 This is a TEM image of an alloy steel ingot produced by an application method of a vacuum induction melting ODS steel system with liftable feeding in Example 1 of the present invention;

[0040] Figure 2 This is a three-dimensional distribution diagram of O, Ti, Y and YTiO3 in the molten-cast ODS steel obtained by the isoconcentration surface method of the alloy steel ingot prepared by the application method of the vacuum induction melting ODS steel system with lifting feeding in Example 1 of the present invention;

[0041] Figure 3 3 is a comparison chart of the room temperature tensile stress-strain curves of Examples 1-2 of the present invention and the comparative example. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0043] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0044] In the embodiments of the present invention, “image” and “picture” may sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings they intend to express are consistent.

[0045] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0046] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0047] A vacuum induction melting system for ODS steel with liftable feeding includes a vertical lift feeding mechanism arranged directly above the pouring gate of a vacuum induction melting furnace, the vertical lift feeding mechanism comprising two 1KW stepper motors, a vertically arranged ball screw, a ball screw nut and a ball spline nut; wherein: the structure of the two stepper motors and the ball screw is configured to achieve vertical lift and synchronous rotation of the ball screw; a 20cm diameter disc is installed at the bottom of the screw, and two steel pipe clamps with an inner diameter of 20mm, a wall thickness of 10mm and a length of 50mm are symmetrically installed at the edge of the disc.

[0048] In particular, the vertical lifting and synchronous rotation motion structure of the ball screw is set up: the structure of one stepper motor and the ball screw is used to drive the screw to lift and lower in the vertical direction, and the structure of another stepper motor and the ball screw is used to drive the screw to rotate at a constant speed around its own vertical axis. The coordinated setting of the two stepper motors can enable the ball screw to achieve synchronous lifting and rotation motion.

[0049] In particular, by turning on the two stepper motors at the same time, the lead screw will achieve coupled movement of lifting and rotating.

[0050] In particular, a stepper motor drives the ball screw nut to rotate, converting the rotational motion into the vertical lifting of the screw, realizing the lifting and lowering feeding function; another stepper motor drives the ball spline nut to rotate, transmitting the rotational motion to the screw, so that it can rotate at a constant speed around its own vertical axis; the rotation of the screw drives the yttrium-titanium-containing thin iron rod to stir in the molten steel, so that yttrium and titanium can be evenly dissolved in the molten steel.

[0051] In particular, a small hole with a diameter of 7.5 mm is opened on the side wall of the steel pipe using a hole opener, and a thin iron rod containing yttrium titanium is fixed in each steel pipe fixture. The thin iron rod containing yttrium titanium has a diameter of 5-15 mm and a length of 1-1.5 m.

[0052] Specifically, a hole with a diameter of 7.5 mm was opened in the side wall of the steel pipe using a hole opener. An M8 tap was used to tap the hole and an M8 screw was inserted. A thin iron rod containing yttrium titanium was inserted into the steel pipe and the screw was tightened to secure it.

[0053] In particular, two 1KW stepper motors are installed on the side walls of the vacuum furnace chamber, and are respectively engaged with the ball screw nut and ball spline nut through bevel gears, so that the bevel gears drive the ball screw nut and ball spline nut to rotate respectively. The ball screw nut can convert its own rotational motion into linear motion of the screw, and the ball spline nut transmits its own rotational motion to the screw, so that it can rotate around its own vertical axis.

[0054] Specifically, the ball spline nut engages the ball screw, allowing it to rotate about its vertical axis, thereby rotating a thin yttrium-titanium iron rod attached to a disc at the screw's base. When the yttrium-titanium iron rod comes into contact with molten steel, it dissolves while stirring, achieving uniform dissolution of yttrium and titanium in the molten steel.

[0055] Specifically, the vacuum furnace's charging hopper is equipped with interfaces for installing sampling cups and temperature and oxygen measurement probes. Sampling and temperature and oxygen measurement are both performed from the charging hopper. Before and after refining, approximately 200g of samples are collected from the molten steel using an alumina sampling cup for compositional uniformity analysis. A direct reading spectrometer is used to measure the alloying element content in the samples and compare them with the designed composition to confirm compositional uniformity. Before pouring, a molten steel temperature and oxygen measurement probe is used to measure the dissolved oxygen content in the molten steel to ensure it is within the range of 50-1000ppm. This ensures that the dissolved oxygen reacts with the yttrium and titanium dissolved in the molten steel in the pouring gate to form a Y-Ti-O dispersion phase.

[0056] An application method of the vacuum induction melting ODS steel system with liftable feeding is provided. The application method is carried out just above the pouring gate in the chamber of a vacuum induction melting furnace. A thin iron rod containing yttrium and titanium is fixed on the bottom disc of the screw. When pouring starts, the thin iron rod containing yttrium and titanium descends at a uniform speed into the pouring gate to contact the molten steel, thereby achieving continuous feeding. The synchronous rotation of the screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, thereby achieving uniform dissolution of yttrium and titanium in the molten steel and reacting with the original dissolved oxygen in the molten steel to form yttrium titanium oxide. Finally, the molten steel in the pouring gate flows into a flat steel ingot mold with a length of 40 cm, a width of 10 cm, and a height of 60 cm and rapidly solidifies to obtain an ODS steel ingot with fine and dispersed yttrium titanium oxide.

[0057] In particular, before the experiment, a thin yttrium-titanium iron rod was fixed on the bottom disc of the screw, and two thin yttrium-titanium iron rods with a diameter of 5-15 mm and a length of 1-1.5 m were inserted into two steel pipe clamps respectively, and the bolts on the side walls of the steel pipes were tightened to tighten the thin yttrium-titanium iron rods.

[0058] In particular, during the refining process, the vacuum degree in the induction furnace is controlled at 10-200 MPa, and the temperature of the molten steel is controlled at 1530-1680°C. Before tapping, the temperature of the molten steel is controlled at 1530-1580°C so that the molten steel can solidify quickly after entering the ingot mold. The composition of the molten steel without the addition of the yttrium-titanium thin iron rod is C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si 0.6-1.4%, Mn 0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, O 0.005-0.10%, and the balance is Fe.

[0059] Specifically, the yttrium-titanium thin iron rods contain 1-20% Y, 0.2-5% Ti, and the balance Fe. The rods are lowered at a speed of 0.5-1.5 m / min to ensure that the molten steel in the crucible is poured and the rods are fed into the crucible simultaneously. The rods are rotated around the lead screw at a speed of 30-90 r / min to ensure that the yttrium and titanium are evenly dissolved in the molten steel.

[0060] In particular, the composition of the final steel ingot is: C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si0.6-1.4%, Mn 0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, Y 0.05-0.3%, Ti0.01-0.1%, O 0.005-0.10%, and the balance is Fe.

[0061] In particular, the prepared alloy ingot is heat treated by forging at 1050-1200°C for 2-4 hours, rolling at 1050-1150°C for 1-3 hours, water cooling at 950-1100°C for 0.5-2 hours, and air cooling at 700-780°C for 1-3 hours. The microstructure of the alloy ingot is fully tempered martensite, with the tempered martensite accounting for 100% and the original austenite grain size being 20-50μm.

[0062] In particular, the prepared ingot, after heat treatment at 1050-1200°C for 2-4 hours, forging, at 1050-1150°C for 1-3 hours, rolling, at 950-1100°C for 0.5-2 hours, water cooling, and air cooling at 700-780°C for 1-3 hours, has a tensile strength ≥800MPa, a yield strength ≥700MPa, a yield strength ratio ≥0.85, a micro-Vickers hardness ≥250HV, an elongation after fracture ≥17%, a strength-ductility product ≥13GPa·%, and a room temperature impact toughness ≥150 J.

[0063] In particular, the production cost of 1,000 kg alloy steel ingot is 60,000 to 90,000 yuan.

[0064] Example 1

[0065] A vacuum induction melting system for ODS steel with liftable feeding includes a vertical lift feeding mechanism arranged directly above the pouring gate of a vacuum induction melting furnace, the vertical lift feeding mechanism comprising two 1KW stepper motors, a vertically arranged ball screw, a ball screw nut and a ball spline nut; wherein: the structure of the two stepper motors and the ball screw is configured to achieve vertical lift and synchronous rotation of the ball screw; a 20cm diameter disc is installed at the bottom of the screw, and two steel pipe clamps with an inner diameter of 20mm, a wall thickness of 10mm and a length of 50mm are symmetrically installed at the edge of the disc.

[0066] Among them, a small hole with a diameter of 7.5mm is opened on the side wall of the steel pipe using a hole opener, and a thin iron rod containing yttrium titanium is fixed in each steel pipe clamp. The diameter of the thin iron rod containing yttrium titanium is 5mm and the length is 1.5m.

[0067] Among them, two 1KW stepper motors are installed on the side wall of the vacuum furnace chamber, and are respectively engaged with the ball screw nut and ball spline nut through bevel gears, so that the bevel gears drive the ball screw nut and ball spline nut to rotate respectively. The ball screw nut can convert its own rotational motion into the linear motion of the screw, and the ball spline nut transmits its own rotational motion to the screw, so that it can rotate around its own vertical axis.

[0068] The ball spline nut engages the ball screw, allowing it to rotate around its vertical axis, thereby rotating a thin yttrium-titanium iron rod attached to a disc at the screw's base. When the yttrium-titanium iron rod comes into contact with molten steel, it dissolves while stirring, achieving uniform dissolution of yttrium and titanium in the molten steel.

[0069] The vacuum furnace's charging hopper is equipped with interfaces for installing sampling cups and temperature and oxygen measurement probes. Sampling and temperature and oxygen measurement are both completed from the charging hopper. Before and after refining, approximately 200g of samples are collected from the molten steel using an alumina sampling cup for compositional uniformity analysis. The alloying element content in the samples is measured using a direct reading spectrometer and compared with the designed composition to confirm compositional uniformity. Before pouring, the dissolved oxygen content in the molten steel is measured using a molten steel temperature and oxygen measurement probe to approximately 300ppm, ensuring that the dissolved oxygen reacts with the yttrium and titanium dissolved in the molten steel in the pouring gate to form a Y-Ti-O dispersion phase.

[0070] An application method of the described vacuum induction melting system for ODS steel with liftable feeding is performed directly above the pouring gate in the chamber of a vacuum induction melting furnace. Before the experiment, a thin yttrium-titanium iron rod is fixed to the bottom disc of the screw, and two thin yttrium-titanium iron rods with a diameter of 10 mm and a length of 1.5 m are respectively inserted into two steel pipe clamps, and the bolts on the side walls of the steel pipes are tightened to fasten the thin yttrium-titanium iron rods.

[0071] During the refining process, the vacuum degree in the induction furnace is controlled at 150 MPa, and the temperature of the molten steel is controlled at 1580°C. Before tapping, the temperature of the molten steel is controlled at 1550°C to ensure rapid solidification after the molten steel enters the ingot mold. The composition of the molten steel without the addition of the yttrium-titanium thin iron rod is C 0.10%, N 0.03%, Cr 9.0%, Si 1.0%, Mn 0.6%, W 1.5%, V 0.25%, Ta 0.2%, O 0.03%, and the balance is Fe.

[0072] A thin iron rod containing yttrium and titanium is fixed on the bottom disc of the screw. When pouring starts, the thin iron rod containing yttrium and titanium descends at a uniform speed into the pouring gate to contact the molten steel, realizing continuous feeding. The synchronous rotation of the screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, so that yttrium and titanium are uniformly dissolved in the molten steel and react with the original dissolved oxygen in the molten steel to form yttrium titanium oxide. Finally, the molten steel in the pouring gate flows into a flat steel ingot mold with a length of 40 cm, a width of 10 cm, and a height of 60 cm and rapidly solidifies to obtain an ODS steel ingot with fine and dispersed yttrium titanium oxide.

[0073] The yttrium-titanium thin iron rods contain 12% Y, 2% Ti, and the balance Fe. They descend at a speed of 1 m / min, ensuring that the molten steel in the crucible is poured and the rods are fed simultaneously. They rotate around the lead screw at 60 r / min to ensure uniform dissolution of yttrium and titanium in the molten steel.

[0074] The composition of the final steel ingot prepared in this example is: C 0.10%, N 0.03%, Cr 9.0%, Si 1.0%, Mn 0.6%, W 1.5%, V 0.25%, Ta 0.2%, Y 0.05%, Ti 0.01%, O 0.02%, and the balance is Fe.

[0075] The alloy ingot prepared in this embodiment was heat treated by forging at 1150°C for 4 hours, rolling at 1100°C for 2 hours, water cooling at 1050°C for 1 hour, and air cooling at 750°C for 2 hours to obtain a heat-treated steel billet.

[0076] The microstructure of the heat-treated steel billet is fully tempered martensite, with tempered martensite accounting for 100% and the original austenite grain size being 29μm.

[0077] The tensile strength of the heat-treated steel billet is 827 MPa, the yield strength is 709 MPa, the yield strength ratio is 0.86, the micro-Vickers hardness is 275 HV, the elongation after fracture is 18%, the strength-ductility product is ≥14.9 GPa·%, and the room temperature impact toughness is 169 J.

[0078] The production cost of preparing 1000kg alloy steel ingot in this embodiment is RMB 90,000.

[0079] Example 2 (Compared with Example 1, the yttrium and titanium contents in the yttrium-titanium thin iron rod are increased, and the dissolved oxygen content in the molten steel is increased)

[0080] A vacuum induction melting system for ODS steel with liftable feeding includes a vertical lift feeding mechanism arranged directly above the pouring gate of a vacuum induction melting furnace, the vertical lift feeding mechanism comprising two 1KW stepper motors, a vertically arranged ball screw, a ball screw nut and a ball spline nut; wherein: the structure of the two stepper motors and the ball screw is configured to achieve vertical lift and synchronous rotation of the ball screw; a 20cm diameter disc is installed at the bottom of the screw, and two steel pipe clamps with an inner diameter of 20mm, a wall thickness of 10mm and a length of 50mm are symmetrically installed at the edge of the disc.

[0081] Among them, a small hole with a diameter of 7.5mm is opened on the side wall of the steel pipe using a hole opener, and a thin iron rod containing yttrium titanium is fixed in each steel pipe clamp. The diameter of the thin iron rod containing yttrium titanium is 10mm and the length is 1.5m.

[0082] Among them, two 1KW stepper motors are installed on the side wall of the vacuum furnace chamber, and are respectively engaged with the ball screw nut and ball spline nut through bevel gears, so that the bevel gears drive the ball screw nut and ball spline nut to rotate respectively. The ball screw nut can convert its own rotational motion into the linear motion of the screw, and the ball spline nut transmits its own rotational motion to the screw, so that it can rotate around its own vertical axis.

[0083] The ball spline nut engages the ball screw, allowing it to rotate around its vertical axis, thereby rotating a thin yttrium-titanium iron rod attached to a disc at the screw's base. When the yttrium-titanium iron rod comes into contact with molten steel, it dissolves while stirring, achieving uniform dissolution of yttrium and titanium in the molten steel.

[0084] The vacuum furnace's charging hopper is equipped with interfaces for installing sampling cups and temperature and oxygen measurement probes. Sampling and temperature and oxygen measurement are both completed from the charging hopper. Before and after refining, approximately 200g of samples are collected from the molten steel using an alumina sampling cup for compositional uniformity analysis. The alloying element content in the samples is measured using a direct reading spectrometer and compared with the designed composition to confirm compositional uniformity. Before pouring, the dissolved oxygen content in the molten steel is measured using a molten steel temperature and oxygen measurement probe to approximately 400ppm, ensuring that the dissolved oxygen reacts with the yttrium and titanium dissolved in the molten steel in the pouring gate to form a Y-Ti-O dispersed phase.

[0085] An application method of the described vacuum induction melting system for ODS steel with liftable feeding is performed directly above the pouring gate in the chamber of a vacuum induction melting furnace. Before the experiment, a thin yttrium-titanium iron rod is fixed to the bottom disc of the screw, and two thin yttrium-titanium iron rods with a diameter of 10 mm and a length of 1.5 m are respectively inserted into two steel pipe clamps, and the bolts on the side walls of the steel pipes are tightened to fasten the thin yttrium-titanium iron rods.

[0086] During the refining process, the vacuum degree in the induction furnace is controlled at 150 MPa, and the temperature of the molten steel is controlled at 1580°C. Before tapping, the temperature of the molten steel is controlled at 1550°C to ensure rapid solidification after entering the ingot mold. The composition of the molten steel without the addition of the yttrium-titanium thin iron rod is C 0.10%, N 0.03%, Cr 9.0%, Si 1.0%, Mn 0.6%, W 1.5%, V 0.25%, Ta 0.2%, O 0.04%, and the balance is Fe.

[0087] A thin iron rod containing yttrium and titanium is fixed on the bottom disc of the screw. When pouring starts, the thin iron rod containing yttrium and titanium descends at a uniform speed into the pouring gate to contact the molten steel, realizing continuous feeding. The synchronous rotation of the screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, so that yttrium and titanium are uniformly dissolved in the molten steel and react with the original dissolved oxygen in the molten steel to form yttrium titanium oxide. Finally, the molten steel in the pouring gate flows into a flat steel ingot mold with a length of 40 cm, a width of 10 cm, and a height of 60 cm and rapidly solidifies to obtain an ODS steel ingot with fine and dispersed yttrium titanium oxide.

[0088] The yttrium-titanium thin iron rods contain 18% Y, 3% Ti, and the balance Fe. They descend at a speed of 1 m / min to ensure the crucible is filled with molten steel and the rods are fed simultaneously. They rotate around the lead screw at 60 r / min to ensure uniform dissolution of yttrium and titanium in the molten steel.

[0089] The composition of the final steel ingot prepared in this example is: C 0.10%, N 0.03%, Cr 9.0%, Si 1.0%, Mn 0.6%, W 1.5%, V 0.25%, Ta 0.2%, Y 0.07%, Ti 0.015%, O 0.025%, and the balance is Fe.

[0090] The alloy ingot prepared in this embodiment was heat treated by forging at 1150°C for 4 hours, rolling at 1100°C for 2 hours, water cooling at 1050°C for 1 hour, and air cooling at 750°C for 2 hours to obtain a heat-treated steel billet.

[0091] The microstructure of the heat-treated steel billet is fully tempered martensite, with tempered martensite accounting for 100% and the original austenite grain size being 25μm.

[0092] The tensile strength of the heat-treated steel billet is 841 MPa, the yield strength is 732 MPa, the yield strength ratio is 0.87, the micro-Vickers hardness is 283 HV, the elongation after fracture is 18%, the strength-ductility product is 15.1 GPa·%, and the room temperature impact toughness is 157 J.

[0093] The production cost of preparing 1000kg alloy steel ingot in this embodiment is RMB 90,000.

[0094] Comparative Example

[0095] This comparative example uses vacuum induction melting technology to prepare traditional low-activation steel. Compared with the ODS steel in Example 1, the traditional low-activation steel preparation process does not use a lifting feeding device to add yttrium titanium raw materials. The rest of the process and molten steel composition are the same as Example 1.

[0096] The final composition of the conventional low-activation steel prepared in the comparative example is: C 0.10%, N 0.03%, Cr 9.0%, Si 1.0%, Mn 0.6%, W 1.5%, V 0.25%, Ta 0.2%, and the balance is Fe.

[0097] The low-activation steel ingot prepared in the comparative example was heat-treated by forging at 1150°C for 4 hours, rolling at 1100°C for 2 hours, water cooling at 1050°C for 1 hour, and air cooling at 750°C for 2 hours to obtain a heat-treated steel billet.

[0098] The microstructure of the heat-treated steel billet is fully tempered martensite, with tempered martensite accounting for 100% and the original austenite grain size being 33μm.

[0099] The tensile strength of the heat-treated steel billet is 692 MPa, the yield strength is 521 MPa, and the elongation after fracture is 22%. The room temperature tensile properties of the comparative example and the embodiment are compared in the following Tables 1 and Figure 3 shown.

[0100] Table 1 Comparison of room temperature tensile properties between comparative examples and examples

[0101] Tensile strength / MPa Yield strength / MPa Elongation after fracture / % Comparative Example 692 521 22 Example 1 827 709 18 Example 2 841 732 18

[0102] The above scheme, the present invention proposes a vacuum induction melting ODS steel system with lifting feeding and application method, which can solve the technical problems of the existing powder metallurgy method for preparing ODS steel, such as complex process, poor stability between batches, high cost and difficulty in large-scale production.

[0103] The present invention prepares ODS steel by separating dissolved oxygen in molten steel from yttrium-titanium raw materials during vacuum induction melting, and reacting them during the pouring stage to form yttrium-titanium oxide. The yttrium-titanium oxide exists uniformly in the ingot in a fine, dispersed form, and can achieve low-cost, large-scale, and stable production of nuclear-grade ODS steel.

[0104] The present invention uses a structural arrangement in which a lead screw drives a thin iron rod containing yttrium titanium to rise and fall vertically, thereby enabling the pouring of molten steel and continuous feeding to be carried out synchronously. After the dissolved oxygen in the molten steel reacts with the yttrium titanium raw material to form oxides, the ingot can be quickly solidified, thereby avoiding the long-term presence of yttrium titanium oxide in the molten steel, which causes agglomeration and floating.

[0105] The invention adopts a structural arrangement in which a thin iron rod containing yttrium and titanium is driven to stir in molten steel by the rotation of a lead screw, thereby enabling yttrium and titanium to be uniformly dissolved in the molten steel.

[0106] The room temperature tensile strength and yield strength of the ODS steel prepared by the present invention using the liftable feeding device are significantly higher than those of the low-activation steel prepared by the traditional smelting process.

[0107] In summary, compared with other traditional methods, the method of the present invention develops a lifting feeding technology, which allows yttrium and titanium to be uniformly dissolved in molten steel and distributed in the solidified ingot in the form of oxides, so as to realize the quantitative preparation of ODS steel; this preparation method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, and high in efficiency, which is conducive to large-scale industrial production and promotion.

[0108] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0109] In this disclosure, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0110] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0111] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A vacuum induction melting ODS steel system with lifting and feeding, characterized in that: The liftable feeding vacuum induction melting ODS steel system includes a vertical lifting feeding mechanism arranged directly above the pouring gate inside the vacuum induction melting furnace chamber, and the vertical lifting feeding mechanism includes two 1KW stepper motors, a vertically arranged ball screw, a ball screw nut and a ball spline nut; wherein: the structure of the two stepper motors, the ball screw, the ball screw nut and the ball spline nut is arranged to realize the vertical lifting and synchronous rotation motion structure of the ball screw; a 20 cm diameter disk is installed at the bottom of the screw, and two steel pipe clamps with an inner diameter of 20 mm, a wall thickness of 10 mm and a length of 50 mm are symmetrically installed at the edge of the disk.

2. The vacuum induction melting ODS steel system with liftable feeding according to claim 1 is characterized in that: The vertical lifting and synchronous rotation motion structure setting of the ball screw: the structural setting of one stepper motor and the ball screw nut is used to drive the ball screw to lift in the vertical direction, and the structural setting of another stepper motor and the ball spline nut is used to drive the ball screw to rotate at a constant speed around its own vertical axis. The coordinated setting of the two stepper motors can enable the ball screw to achieve synchronous lifting and rotation motion.

3. The vacuum induction melting ODS steel system with liftable feeding according to claim 1 is characterized in that: A small hole with a diameter of 7.5 mm is opened on the side wall of the steel pipe using a hole opener. A thin iron rod containing yttrium titanium is fixed in each steel pipe fixture. The diameter of the thin iron rod containing yttrium titanium is 5-15 mm and the length is 1-1.5 m.

4. The vacuum induction melting ODS steel system with liftable feeding according to claim 1 is characterized in that: Two 1KW stepper motors are arranged on the side wall of the vacuum furnace body and are respectively engaged with the ball screw nut and the ball spline nut through bevel gears.

5. The vacuum induction melting ODS steel system with liftable feeding according to claim 1 is characterized in that: The ball screw nut and the ball spline nut are respectively engaged with the ball screw.

6. The vacuum induction melting ODS steel system with liftable feeding according to claim 1 is characterized in that: The charging bin of the vacuum furnace is provided with an interface for installing a sampling cup and a temperature and oxygen measuring instrument probe.

7. An application method of the vacuum induction melting ODS steel system with liftable feeding according to any one of claims 1 to 6, characterized in that: The application method is carried out just above the pouring gate in the chamber of a vacuum induction melting furnace. A thin iron rod containing yttrium and titanium is fixed on a disc at the bottom of a lead screw. When pouring starts, the thin iron rod containing yttrium and titanium descends at a uniform speed into the pouring gate to contact the molten steel, thereby achieving continuous feeding. The synchronous rotation of the lead screw drives the thin iron rod containing yttrium and titanium to stir in the molten steel, thereby achieving uniform dissolution of yttrium and titanium in the molten steel and reacting with the original dissolved oxygen in the molten steel to form yttrium titanium oxide. Finally, the molten steel in the pouring gate flows into a flat steel ingot mold with a length of 40 cm, a width of 10 cm, and a height of 60 cm, and is rapidly solidified to obtain an ODS steel ingot with fine and dispersed yttrium titanium oxide.

8. The application method of the vacuum induction melting ODS steel system with liftable feeding according to claim 7 is characterized in that: During the refining process, the vacuum degree in the induction furnace is controlled at 10-200 MPa, and the temperature of the molten steel is controlled at 1530-1680°C. Before tapping, the temperature of the molten steel is controlled at 1530-1580°C so that the molten steel can solidify quickly after entering the ingot mold. The composition of the molten steel without the addition of the yttrium-titanium thin iron rod is C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si 0.6-1.4%, Mn 0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, O 0.005-0.10%, and the balance is Fe.

9. The application method of the vacuum induction melting ODS steel system with liftable feeding according to claim 7 is characterized in that: The yttrium-titanium thin iron rod contains Y 1-20%, Ti 0.2-5%, and the balance is Fe. The yttrium-titanium thin iron rod descends at a speed of 0.5-1.5 m / min and rotates around the lead screw at a speed of 30-90 r / min.

10. The application method of the vacuum induction melting ODS steel system with liftable feeding according to claim 7, characterized in that: The composition of the final steel ingot is: C 0.06-0.12%, N 0.02-0.06%, Cr 8.0-12.0%, Si 0.6-1.4%, Mn0.2-0.8%, W 1.2-2.2%, V 0.1-0.3%, Ta 0.05-0.25%, Y 0.05-0.3%, Ti 0.01-0.1%, O0.005-0.10%, and the balance is Fe.

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