Ultra-pure high-homogeneity ultra-high-strength wire rod for rare earth alloy wire and preparation method

Abstract

The invention belongs to the technical field of metal manufacturing, and particularly relates to a preparation method of a wire rod for an ultrahigh-strength rare earth alloy wire. According to the method, material components are optimized based on a collaborative change relation established in a cluster mode, and production of the high-strength wire rod for the rare earth alloy wire with the strength improved by 1350 MPa or above and the area shrinkage larger than 35% is completed through process control. The technological process comprises the steps that ZH90Re steel serves as a raw material, and an LF furnace and a VD furnace are used for refining molten steel; electroslag remelting is carried out through die casting, and annealing and surface cleaning treatment are carried out; heating forging and annealing and surface cleaning of a forging stock are carried out; and finally, heating and rolling to obtain the wire rod. The tensile strength, the inclusion size and the number of the obtained wire rod reach the international leading level, and reliable technical support is provided for replacing import of the wire rod and achieving localization.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal wire rods, and particularly relates to a wire rod for ultra-pure, highly homogeneous, ultra-high-strength rare earth alloy wires and a preparation method thereof. Background Art

[0002] Rare earth alloy wires are a type of ultra-high-strength, ultra-fine-diameter diamond-coated wire saws, with characteristics such as a low wire breakage rate, good mechanical properties (tensile strength, breaking force), high dimensional accuracy, and sufficient length. They are mainly used for cutting and forming polycrystalline, monocrystalline silicon for solar cells and other ultra-hard wire rods. Rare earth alloy wires play an irreplaceable role in the production process of solar wafers, and ultra-fine, high-strength rare earth alloy wires are essential tools for wafer production. High-carbon steel wire rods are mostly selected for rare earth alloy wires. To reduce silicon loss during cutting, rare earth alloy wires are developing towards finer diameters and higher strengths. In recent years, new breakthroughs have been continuously made in the wire diameter of rare earth alloy wires at home and abroad. The thinnest wire diameter has reached 35μm, and the tensile strength exceeds 5000MPa.

[0003] In the rare earth alloy wire industry, Japanese wire rods are the most recognized. The wire rods produced by them have the most stable quality and represent the world's leading level. In terms of purity control, the inclusion size can be stably controlled to ≤10μm, the quantity is small, and the inclusions are easy to plastically deform or break. The wire rods produced by domestic steel enterprises cannot stably control the inclusion size, quantity, and composition, and the wire drawing diameter of the steel wire is ≥0.12mm. In terms of wire rod microstructure control, due to its unique on-line salt bath treatment process, not only can the pearlite lamellar spacing be refined, but also the formation of network cementite in hypereutectoid steel can be inhibited. Domestic steel enterprises mostly use the on-line Stelmor air-cooling process for producing wire rods for rare earth alloy wires. The cooling at the lap joints and intermediate points is uneven, and there are significant differences in the microstructure and properties of the wire rods in the same coil. Problems such as a tensile strength fluctuation of about 100MPa, low sorbitization rate, and excessive network cementite affect the wire breakage rate and final diameter of rare earth alloy wire drawing.

[0004] At present, the drawing and heat treatment process of domestic rare earth alloy wire production has achieved a breakthrough, but the wire rod is still completely dependent on imports from Japan. The wire rods produced by domestic steel enterprises cannot meet the requirements in terms of purity and homogenization, and the wire breakage rate and stability are poor during the processing of downstream users. Solving the problem of localization of wire rods for rare earth alloy wires is of great significance to the high-quality development of my country's manufacturing industry. In addition, current domestic research is limited to discussing the influence of a single element on the properties of alloys, so the current technical standards are limited to specifying the composition range of a single element, lacking the interaction between elements. In fact, even if the widely accepted composition standards in industry are followed, the properties of alloys vary greatly, and the comprehensive performance cannot be guaranteed. In actual industrial production, each enterprise usually manufactures alloys according to empirical compositions, and due to the complexity of the preparation process, excellent performance alloys are often not obtained. In fact, this is also a common problem faced by all industrial alloys, that is, the types of elements and composition ranges are derived from engineering practice, and their theoretical basis is missing. Mechanistically speaking, the above engineering problems originate from people's understanding of solid solution structure. As we all know, industrial alloys are all based on solid solutions, which have chemical proximal processes as their structural characteristics and have both order and disorder. The alloy components must be implicit in this proximal process structure, but the academic community lacks a structural model for the chemical proximal processes of solid solutions.

[0005] In view of this, the present invention introduces a cluster composition design method (hereinafter referred to as cluster method) that describes the chemical near-program structure, especially considering the synergistic effect of elements in the alloy to clarify the composition range of various elements in the alloy and the combination range of similar elements. This standard also has a demonstration effect, and its significance can be extended to any industrial alloy system. Summary of the invention

[0006] In view of the above shortcomings of the prior art, the present invention provides a wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire and a preparation method thereof, specifically, a wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire and a preparation method thereof by adding rare earth elements and combining components in a synergistic change relationship, so as to improve the existing domestic wire rods for rare earth alloy wires, such as insufficient purity and homogenization, high wire breakage rate during drawing, and poor stability.

[0007] To achieve the above and other related purposes, the present invention provides a wire rod for pure, highly homogeneous, ultra-high strength rare earth alloy wire, using steel with the grade ZH90Re as the raw material. The chemical composition of the ZH90Re steel is as follows: C: 0.90 - 0.93 wt%, Mn: 0.28 - 0.34 wt%, Si ≤ 0.25 wt%, P ≤ 0.015 wt%, S ≤ 0.010 wt%, Al ≤ 0.003 wt%, Re(La): 0.02 - 0.04 wt%, Cr ≤ 0.05 wt%, Ni ≤ 0.05 wt%, Mo ≤ 0.02 wt%, Sn ≤ 0.005 wt%, As ≤ 0.005 wt%, Cu ≤ 0.05 wt%, O ≤ 0.001 wt%, N ≤ 0.005 wt%, and the rest is iron and inevitable impurities. The chemical composition of the ZH90Re steel is strictly controlled within a specific range, which is crucial for manufacturing the wire rod for ultra-pure, highly homogeneous, ultra-high strength rare earth alloy wire. If deviating from these proportional ranges, the following effects will occur on the performance parameters of the wire rod: Carbon (C) content: Carbon is one of the main elements to strengthen the iron matrix. If the carbon content is lower than 0.90 wt%, it will lead to insufficient strength, low hardness, and poor hardenability; while higher than 0.93 wt% will increase brittleness, reduce toughness and plasticity, and increase the risk of quenching cracks during the heat treatment process. Manganese (Mn) content: Manganese helps to improve the strength and hardness of the steel and at the same time reduces the hot brittleness caused by sulfur. If the Mn content is too low, its beneficial effects cannot be effectively exerted, while too high will lead to poor weldability and difficult hot working. Silicon (Si) content: Silicon is used as a deoxidizer, but too high a Si content will reduce the ductility and toughness of the steel. Phosphorus (P) and sulfur (S) content: These two elements are harmful impurities, which cause cold brittleness and hot brittleness respectively. Strictly restricting P ≤ 0.015 wt% and S ≤ 0.010 wt% is to ensure that the material has good processing performance and mechanical properties. Exceeding this range will cause the material to become brittle and easily break. Aluminum (Al) content: Aluminum is mainly used for deoxidation. Excessive aluminum will affect the purity of the steel, form oxide inclusions, and affect the drawing performance. Rare earth element lanthanum (Re(La)) content: Lanthanum can improve the morphology of inclusions, refine grains, and enhance the strength and toughness of the material. Lack of sufficient rare earth elements or excessive amounts will affect the microstructure and mechanical properties of the material. Trace elements such as chromium (Cr), nickel (Ni), molybdenum (Mo), tin (Sn), arsenic (As), copper (Cu), etc.: Although these elements are within the specified limit values, even minor changes will affect the corrosion resistance, hardness, strength and other properties of the steel. For example, a higher Cr content can improve the corrosion resistance but also increase the material cost; Ni and Mo can enhance the strength and toughness of the steel, but excessive amounts will lead to unnecessary cost increases and greater processing difficulties. Oxygen (O) and nitrogen (N) content: Strict control of the O and N content is to avoid the formation of harmful oxide and nitride inclusions, which will affect the purity and mechanical properties of the steel.Going beyond the specified range will result in more non-metallic inclusions and reduce the quality of the wire rod. In short, any change deviating from the above chemical composition range will have an adverse impact on the purity, homogeneity, strength, toughness, and drawing performance of the final wire rod, thereby affecting the final use effect of the rare earth alloy wire.

[0008] Optionally, the diameter of the wire rod for the rare earth alloy wire is 5.5 mm - 10.0 mm. The wire rod within this size range needs to have sufficient strength and toughness to withstand the stress during the subsequent drawing process without fracture or deformation. Strengthening elements such as C and Mn play a key role in this process. They not only increase the basic strength of the material but also act together with the grain refinement mechanism (such as adding an appropriate amount of rare earth elements) to further enhance the tensile strength of the wire rod.

[0009] Optionally, the inner diameter of the coil of the wire rod for the rare earth alloy wire is ≥ 800 mm, the outer diameter is ≤ 1500 mm, and the coil weight is 1000 - 2000 Kg. These specifications require the wire rod to maintain good shape stability during the coiling process, which depends on the uniformity of the internal structure of the wire rod and a low level of residual stress. Through electroslag remelting and annealing treatments, non-metallic inclusions in the molten steel can be effectively removed, and the distribution of alloying elements can be homogenized, reducing the risk of deformation caused by local stress concentration.

[0010] Optionally, the size of the inclusions in the wire rod for the rare earth alloy wire is ≤ 8 μm, and the number of inclusions is ≤ 10 per mm 2 , and the rating of network cementite is ≤ 1 level. Fine and well-dispersed inclusions help improve the purity of the material and reduce the crack initiation points. Rare earth elements (such as La) react with oxygen and sulfur to form stable compounds, reducing the presence of harmful inclusions. In addition, by strictly controlling the dosage of deoxidizers such as Si and Al and optimizing the refining process of the VD furnace, the size and quantity of inclusions can be effectively reduced, thereby improving the overall quality of the material.

[0011] Optionally, the tensile strength of the wire rod for the rare earth alloy wire is ≥ 1220 Mpa, and the reduction of area is ≥ 34%. To achieve such high strength and good plasticity, in addition to the strengthening effects of C and Mn mentioned above, the precipitation strengthening effects brought by microalloying elements such as Ti and Nb also need to be considered. These elements can form fine precipitation phases during the cooling process, hinder the movement of dislocations, enhance the material strength without affecting its ductility. In addition, appropriate heat treatment processes (such as temperature control during forging and rolling) are also key factors to ensure the desired microstructure and mechanical properties.

[0012] The present invention also provides a method for preparing a wire rod for a pure, highly homogeneous, and ultra-high-strength rare earth alloy wire, comprising the following steps:

[0013] According to the chemical composition requirements, steel with the grade ZH90Re is applied for use as raw material. The chemical composition of the ZH90Re steel is as follows: C: 0.90 - 0.93 wt%, Mn: 0.28 - 0.34 wt%, Si ≤ 0.25 wt%, P ≤ 0.015 wt%, S ≤ 0.010 wt%, Al ≤ 0.003 wt%, Re(La): 0.02 - 0.04 wt%, Cr ≤ 0.05 wt%, Ni ≤ 0.05 wt%, Mo ≤ 0.02 wt%, Sn ≤ 0.005 wt%, As ≤ 0.005 wt%, Cu ≤ 0.05 wt%, O ≤ 0.001 wt%, N ≤ 0.005 wt%, and the rest is iron and inevitable impurities. Based on the composition co-variation relationship established by the cluster method, the above alloying elements are divided into Ni-like elements (austenite stabilizing elements) entering the cluster: Mn; Cr-like elements (ferrite stabilizing elements), including: Cr, Si, Mo, Al; matrix element Fe; and trace elements not entering the cluster, including: C, S, P, H, O, N, and rare earth element La. The co-variation relationship (mass percentage) of each element satisfies: 0.28 ≤ Mn ≤ 0.34; 0.18 ≤ Cr + 1.83Si + 0.55Mo + 1.91Al ≤ 1.37; 96.18 ≤ Fe ≤ 98.40.

[0014] The raw material is subjected to melting and refining, ingot casting, electrode blank annealing, electroslag remelting, electroslag ingot annealing, forging, and rolling treatments to obtain wire rods for rare earth alloy wires.

[0015] In the present invention, during the melting and refining process, 0.02% - 0.04% rare earth La is added, and after the melting and refining are completed, the molten steel is subjected to ingot casting treatment.

[0016] In the present invention, after the ingot casting is completed, electrode blank annealing treatment is carried out. During the alloying process, different elements are unevenly distributed inside the wire rod, forming a segregation phenomenon. Annealing can homogenize the distribution of alloying elements through high-temperature diffusion, thereby avoiding performance differences.

[0017] In some preferred embodiments, the annealing temperature is 600 - 700 °C, and the holding time is 10 - 15 h. In some more preferred embodiments, the annealing treatment is carried out at a temperature of 640 °C, and the holding time is 12 h.

[0018] In the present invention, since atomic diffusion accelerates at high temperatures, it is beneficial to the effect of diffusion annealing and shortens the time. However, too high a temperature will cause overburning, resulting in melting or serious defects at the grain boundaries and deteriorating the performance, while insufficient temperature will cause the structure of the wire rod to be unable to be effectively homogenized, and the distribution of carbides or other phases is still uneven, deteriorating the performance of the wire rod. Therefore, in the present invention, the annealing temperature and time are limited within the above ranges.

[0019] In the present invention, after the annealing treatment of the electrode blank, the electrode blank is subjected to electroslag remelting treatment to obtain an electroslag ingot.

[0020] In the present invention, electroslag remelting treatment is adopted after the annealing treatment of the electrode blank. Since during the electroslag remelting process, non-metallic inclusions will be absorbed by the slag and separated from the molten steel, and gases such as oxygen, nitrogen, and hydrogen in the molten steel are removed through the process of slag covering and slow solidification, thereby improving the purity of the wire rod and enhancing the mechanical properties of the wire rod.

[0021] In some preferred embodiments, the melting rate of the electroslag remelting is 0.5D - 1.0D kg / h, where D is the diameter of the mold, in units of mm. In some more preferred embodiments, the melting rate of the electroslag remelting is 0.7D - 0.8D kg / h.

[0022] In the present invention, electroslag remelting can refine grains and improve the toughness, strength, and fatigue performance of the wire rod. However, too fast a melting rate will cause an increase in the depth of the molten pool, insufficient diffusion of solutes in the molten pool, resulting in composition segregation, and prone to axial or radial composition non-uniformity, affecting the mechanical properties of the wire rod; too low a molten pool temperature and poor fluidity will lead to insufficient metallurgical reactions of the metal, an increase in the consumption of slag materials, and an increase in production costs. Therefore, in the present invention, the melting rate of the electroslag remelting is limited within the above range.

[0023] In the present invention, after the completion of the electroslag remelting process, the electroslag ingot is subjected to annealing treatment.

[0024] In the present invention, electroslag ingot annealing treatment is adopted after the completion of the electroslag remelting process. Since the cooling process after electroslag remelting will introduce residual internal stresses in the electroslag ingot, annealing can release these stresses through a slow heating and cooling process, preventing cracking and deformation during subsequent processing. Additionally, during the annealing process, some grains will recrystallize, thereby refining the grains and improving the strength and toughness of the wire rod.

[0025] In some preferred embodiments, the annealing temperature is 800 - 900 °C, and the holding time is 10 - 15 h. In some more preferred embodiments, the annealing treatment is carried out at a temperature of 860 °C for a holding duration of 12 h.

[0026] In the present invention, since atomic diffusion accelerates at high temperatures, which is beneficial to the effect of diffusion annealing and shortens the time, but too high a temperature will cause abnormal grain growth, destroying the fine grain structure of the wire rod and reducing the strength, toughness, and fatigue resistance of the wire rod. Too low a temperature is insufficient to activate the stress release mechanism of the metal, and the residual internal stresses still remain in the wire rod. During processing or use, the internal stresses cause the wire rod to deform, crack, or even fail. Therefore, in the present invention, the annealing temperature and time are limited within the above range.

[0027] In the present invention, after the electroslag ingot is annealed, the electroslag ingot is forged to obtain a forging blank.

[0028] In some preferred embodiments, the starting forging temperature of the forging process is ≥1000 °C, the final forging temperature is ≥850 °C, and the cooling method is air cooling, slow cooling or red-hot annealing. In some more preferred embodiments, the starting forging temperature of the forging process is ≥1050 °C, the final forging temperature is ≥850 °C, and the cooling method is slow cooling or red-hot annealing.

[0029] In the present invention, the starting forging and final forging temperatures can effectively control dynamic recrystallization, dynamic recovery and grain refinement, so as to obtain the required microstructure; if the starting forging temperature is too high, it will cause melting at the grain boundaries (burning phenomenon) or increased oxidation, resulting in the loss of plasticity of the wire rod or internal defects, and if the starting forging temperature is too low, recrystallization will be insufficient and the grains will be coarse; if the final forging temperature is too low, the wire rod enters the low-plasticity zone, resulting in uneven deformation, cracks or even failure. Therefore, in the present invention, the starting forging temperature and the final temperature are limited within the above ranges.

[0030] In the present invention, after the forging process, the forging blank is rolled to obtain a wire rod.

[0031] In some preferred embodiments, the rolling process includes: heating and rolling the forging blank, the preheating section temperature is ≤1000 °C, the heating section temperature is 1100 - 1250 °C, the soaking section temperature is 1100 - 1250 °C, the hot rolling temperature is 800 - 900 °C, and the cooling method after rolling is air cooling or slow cooling; in some more preferred embodiments, the preheating section temperature is ≤950 °C, the heating section temperature is 1130 - 1200 °C, the soaking section temperature is 1180 - 1220 °C, the hot rolling temperature is 840 - 890 °C, and the cooling method after rolling is slow cooling.

[0032] In the present invention, controlling the temperature within the above ranges is crucial for ensuring the deformation performance of the wire rod, optimizing the microstructure, reducing defects and improving the performance of the final product; too high a temperature will cause problems such as grain coarsening, burning, oxidation, etc., affecting the mechanical properties and surface quality of the wire rod, and too low a temperature will increase the deformation resistance, resulting in incomplete recrystallization and crack defects. Therefore, in the present invention, the temperature during the rolling process is limited within the above ranges.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] From the perspective of the preparation process, the present invention realizes the fragmentation and plasticization of oxide inclusions, improves the size and distribution of inclusions in steel, the inclusions are fine and dispersed, the size of inclusions in the wire rod is ≤8 μm, and the number of inclusions is ≤10 per mm 2, the center segregation rating is ≤ level 1. The wire rod for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wire prepared by the present invention has reached the international advanced level in terms of the main indicators such as the final drawing diameter of the steel wire, breaking force, tensile strength, and wire breakage rate, successfully realized the localization of the wire rod for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wire, and broken the foreign technology monopoly.

[0035] This method combines composition design and processing to enhance the strength and toughness of the wire rod for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wire, and obtains excellent performance, including the technological processes: smelting, forging, and hot rolling. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 It is a schematic flow chart of a method for preparing a wire rod provided by an embodiment of the present application.

[0038] Figure 2 It is a flow chart of electrode blank annealing provided by an embodiment of the present application.

[0039] Figure 3 It is a flow chart of electroslag ingot annealing provided by an embodiment of the present application.

[0040] Figure 4 It is a flow chart of electroslag ingot heating provided by an embodiment of the present application.

[0041] Figure 5 It is a drawing of a finished cutting wire drawn from a wire rod provided by an embodiment of the present application. Detailed Embodiments

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following specific embodiments will be used for illustration. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. All other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0043] The present invention provides a method for preparing a wire rod for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wire. The specific steps include: arc furnace melting → LF furnace refining → VD furnace refining → die-casting electrode blank → electrode blank annealing and surface cleaning → electroslag → electroslag ingot annealing and surface cleaning → forging and blooming → forged billet annealing and surface cleaning → rolling wire rod → finished product inspection and warehousing.

[0044] As an alternative embodiment, the present application uses steel with the brand number ZH90Re as the raw material. The chemical composition of the ZH90Re steel is as follows: C: 0.90 - 0.93 wt%, Mn: 0.28 - 0.34 wt%, Si ≤ 0.25 wt%, P ≤ 0.015 wt%, S ≤ 0.010 wt%, Al ≤ 0.003 wt%, Re(La): 0.02 - 0.04 wt%, Cr ≤ 0.05 wt%, Ni ≤ 0.05 wt%, Mo ≤ 0.02 wt%, Sn ≤ 0.005 wt%, As ≤ 0.005 wt%, Cu ≤ 0.05 wt%, O ≤ 0.001 wt%, N ≤ 0.005 wt%, and the rest is iron and inevitable impurities. Based on the composition co-variation relationship established by the cluster method, the above alloying elements are divided into Ni-like elements (austenite stabilizing elements) entering the cluster: Mn; Cr-like elements (ferrite stabilizing elements), including: Cr, Si, Mo, Al; matrix element Fe; and trace elements not entering the cluster, including: C, S, P, H, O, N, and rare earth element La. The co-variation relationship (mass percentage) of each element satisfies: 0.28 ≤ Mn ≤ 0.34; 0.18 ≤ Cr + 1.83Si + 0.55Mo + 1.91Al ≤ 1.37; 96.18 ≤ Fe ≤ 98.40. This effectively ensures that the wire rod for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wire has reached the international advanced level in terms of the main indicators such as the final drawing diameter, breaking force, tensile strength, and wire breakage rate of the steel wire, realizing domestic substitution.

[0045] A reasonable ratio of Cr, Si, Mo, and Al helps to form a stable oxide film, improving the oxidation resistance and corrosion resistance of the steel; at the same time, the addition of these elements helps to refine the grains, thereby enhancing the strength and toughness of the material. In addition, such a combination can also improve the hardenability of the steel, enabling it to obtain more uniform and excellent mechanical properties during the heat treatment process. If the total content of the above elements is lower than the lower limit (0.18), it will lead to insufficient corrosion resistance and oxidation resistance of the steel, affecting its service life and application scenarios. On the contrary, if the total content exceeds the upper limit (1.37), the steel will become brittle, reducing its toughness and weldability, and due to the formation of excessive hard phases (such as carbides), it will increase the cracking risk during the processing of the material and also increase the manufacturing cost. Therefore, strictly controlling the ratio of these elements is crucial for ensuring the quality of the final wire rod.

[0046] As an alternative embodiment, the diameter of the wire rod for pure, high-homogeneity, ultra-high-strength rare earth alloy wire is 5.0 mm - 11.0 mm, the inner diameter of the coil is ≥ 700 mm, the outer diameter is ≤ 1600 mm, and the coil weight is 500 - 2500 Kg.

[0047] More preferably, the diameter of the pure high-homogeneity ultra-high-strength rare earth alloy wire wire rod is 5.5mm-10.0mm, the inner diameter of the coil is ≥800mm, the outer diameter is ≤1500mm, and the coil weight is 1000-2000Kg.

[0048] As an optional implementation, the phosphorus content in the final composition of electric arc furnace smelting is not more than 0.05wt%, the carbon content is 0.01-0.50wt%, and the tapping temperature is 1600±50℃.

[0049] More preferably, the phosphorus content in the final composition of electric arc furnace smelting is not more than 0.034wt%, the carbon content is 0.07-0.40wt%, and the tapping temperature is 1640±20℃.

[0050] The reason for controlling the phosphorus content in the arc furnace smelting endpoint composition to be no more than 0.034wt% is that phosphorus is a significant embrittlement element, which will significantly reduce the toughness and plasticity of the wire rod; phosphorus is easy to segregate at the grain boundary to form a low-melting point phosphide film, which causes the weakening of the grain boundary at high temperature, resulting in an increase in the hot brittleness of the wire rod and affecting the processing performance.

[0051] The reason for controlling the carbon content in the arc furnace smelting endpoint composition to 0.07-0.40wt% is that the increase of carbon will increase the strength and hardness of the wire rod, but too high a carbon content will make the wire rod brittle and lose its toughness and plasticity.

[0052] If the carbon content is less than 0.07wt%, it will cause insufficient strength: lower carbon content will lead to insufficient strength of steel, because carbon is one of the main elements to strengthen the iron matrix. Low carbon steel is usually softer and has poor wear resistance. Low hardness: the hardness will also be reduced accordingly, which will affect the wear resistance and abrasion resistance of the wire rod during use. Poor hardenability: the hardenability of low carbon steel is poor, and it is difficult to achieve the required high strength and hardness through heat treatment.

[0053] Carbon content above 0.40wt% will cause increased brittleness: Higher carbon content will make the steel more brittle, lose toughness and plasticity, thus affecting the processing performance of the material and the service life of the final product. This is because too much carbon will form a large amount of cementite. These hard and brittle phases will become the source of cracks when subjected to stress, causing the material to break easily. Difficulty in cold working: As the carbon content increases, the cold working performance of the steel decreases, and it is more likely to crack or other processing defects during subsequent processes such as drawing and rolling. Increased risk of quenching cracks: For applications that require heat treatment to increase hardness and strength, excessively high carbon content increases the risk of cracks during quenching, especially when the cooling rate is faster.

[0054] The reason for controlling the tapping temperature at 1640 ± 20 °C is that within this temperature range, the molten steel has enough time to remain in a molten state, which is conducive to the full mixing of alloying elements, avoiding composition segregation. It can also prevent the increase in gas dissolution caused by too high a temperature or incomplete deoxidation and alloying due to too low a temperature.

[0055] If the tapping temperature is too high, the solubility of gases (such as oxygen, nitrogen, hydrogen, etc.) in the molten steel will increase significantly, resulting in excessive dissolution of these gases in the molten steel and the formation of bubbles or inclusions during the cooling process, seriously affecting the purity and mechanical properties of the material. In addition, too high a temperature will also accelerate the erosion of refractory materials, increase non-metallic inclusions in the molten steel, and further reduce the quality of the molten steel. At the same time, too high a temperature leads to unnecessary energy consumption increase and causes operation safety problems.

[0056] On the contrary, if the tapping temperature is too low, the fluidity of the molten steel becomes poor, and alloying elements are difficult to dissolve and distribute evenly, easily causing composition segregation and affecting the homogeneity and consistency of the final product. The lower temperature also results in incomplete deoxidation and alloying reactions, and residual oxides and other impurities cannot be effectively removed, thus damaging the purity of the molten steel. In addition, too low a temperature will cause the molten steel to solidify prematurely, bringing difficulties to subsequent refining and casting, and even leading to production interruption or product defects.

[0057] As an alternative implementation method, during the electric arc furnace melting process, when deoxidation and alloying treatment are carried out on the molten steel and the tapping amount is about 1 / 4, alloys and slag materials are added in the order of "refining slag → lime → ferromanganese aluminum → alloying alloy"; the addition amount of the slag material is 5 - 10 kg / t in the tapping ladle for adding refining slag; the deoxidizer uses ferromanganese aluminum, which is added according to the C content in the tapping: 0.07% ≤ C ≤ 0.15%, 2 - 3 Kg / t, C > 0.15%, 1 - 3 Kg / t.

[0058] More preferably, the addition amount of the slag material is 6 kg / t in the tapping ladle for adding refining slag; the deoxidizer uses ferromanganese aluminum and is added according to the following ratio according to the carbon content in the molten steel: 0.07% ≤ C ≤ 0.15%, 2.5 Kg / t, C > 0.15%, 2 Kg / t.

[0059] The reason for controlling the addition amount of the refining slag to 6 kg / t is that the addition amount of the refining slag directly affects the production cost. Adding it at a ratio of 6 kg / t can achieve refining goals such as desulfurization, deoxidation, and inclusion removal, while avoiding waste of slag materials and improving economic benefits; this ratio has been verified by practice, which can meet the refining requirements without increasing unnecessary additional costs.

[0060] The reason for controlling the addition of deoxidizer in proportion to the carbon content in the molten steel is that an appropriate amount of aluminum-manganese-iron deoxidizer helps to generate fine and easily floating non-metallic inclusions, which can be removed through the stirring of the molten steel and the adsorption of the refining slag; excessive deoxidizer leads to the formation of supersaturated inclusions, which is not conducive to the control of the purity of the molten steel. Therefore, it is more reasonable to adjust the addition amount of deoxidizer according to the carbon content.

[0061] As an alternative implementation, the LF furnace inlet temperature ≥ 1400 °C; 630 - 770 Kg of silica is added at the inlet. After the silica melts, 490 - 510 Kg of lime is added. If the slag amount is small, silica and lime can be supplemented, and the ratio is added at 7:5.

[0062] More preferably, the LF furnace inlet temperature ≥ 1500 °C; 700 Kg of silica is added at the inlet. After the silica melts, 500 Kg of lime is added. If the slag amount is small, silica and lime can be supplemented, and the ratio is added at 7:5.

[0063] The reason for controlling the LF furnace inlet temperature ≥ 1500 °C is that high temperature can accelerate processes including desulfurization, deoxidation, and alloy composition adjustment, improving the refining efficiency; in addition, under high temperature conditions, the alloying elements in the molten steel can dissolve and distribute better, ensuring the uniformity of the composition.

[0064] The reason for controlling the ratio of silica and lime for the slag amount to be added at 7:5 is that the slag basicity affects the melting point, fluidity, and desulfurization ability of the slag. Adding silica and lime in a ratio of 7:5 can maintain the slag basicity within an appropriate range, which is beneficial for desulfurization and can also maintain good fluidity for easy operation.

[0065] As an alternative implementation, during the LF furnace refining process, diffusion deoxidation and precipitation deoxidation treatments are adopted; during the diffusion deoxidation treatment, carbon powder and silicon powder are used for diffusion deoxidation, and the ratio is added at 1:1, avoiding the use of aluminum beans; during the precipitation deoxidation treatment, Al wire precipitation deoxidation is avoided.

[0066] The reason for controlling the use of carbon powder and silicon powder for diffusion deoxidation during the diffusion deoxidation treatment and adding them in a ratio of 1:1 is that adding them in a 1:1 ratio can balance the deoxidation rate, preventing excessive gas evolution and splashing risks caused by too much carbon powder, or increasing inclusions in the slag due to too much silicon powder.

[0067] The reason for controlling the avoidance of Al wire precipitation deoxidation during the precipitation deoxidation treatment is that when the Al wire is added, the oxygen content in the local area decreases rapidly, causing over-deoxidation, generating a large amount of alumina inclusions, and increasing the metallurgical burden of the molten steel.

[0068] As an alternative implementation, the LF furnace refining treatment time is 40 - 100 minutes, and no raw and auxiliary materials are added in the last 5 minutes before the end of refining; after the refining is completed, the molten steel is softly blown, and the soft blowing time ≥ 10 minutes.

[0069] More preferably, the refining time in the LF furnace is 45 - 90 minutes, and any raw and auxiliary materials are avoided to be added within 5 minutes before the end of refining; after the refining is completed, the molten steel is softly blown, and the soft blowing time is ≥ 15 minutes.

[0070] The reason for controlling the refining time in the LF furnace to be 45 - 90 minutes is to ensure the effects of deoxidation, desulfurization, and inclusion removal, maintain the uniformity of the molten steel composition and the temperature stability, avoid the secondary absorption of inclusions, gas absorption, and equipment loss caused by too long refining time, and improve the production efficiency.

[0071] The reason for controlling the soft blowing of the molten steel to be ≥ 15 minutes after the refining is completed is that soft blowing can further promote the discharge of gases in the molten steel, reduce inclusions, and at the same time contribute to the uniform distribution of the molten steel temperature, improve the process stability, and avoid undercooling and non-uniformity while ensuring the quality of the molten steel.

[0072] As an alternative implementation method, before the ladle is lifted off, carbonized rice husk is added for heat preservation, which is required to cover the entire slag surface and be evenly spread, and the ladle temperature is 1550 - 1580 °C.

[0073] The reason for controlling the ladle temperature to be 1550 - 1580 °C is that this temperature range can effectively reduce the formation of nitrides in the molten steel, avoid poor fluidity and ladle bottom caking caused by too low molten steel temperature, and too high temperature will lead to ladle lining erosion and increased operation risks, ensuring the safety and the quality of the molten steel during the ladle lifting process.

[0074] As an alternative implementation method, after the refining in the LF furnace is completed, the converter is transferred to the VD furnace for refining, and the ultimate vacuum degree in the VD furnace is controlled to be ≤ 70 Pa, the ultimate vacuum holding time is ≥ 5 min, and the weak argon blowing time is ≥ 10 min.

[0075] More preferably, after the refining in the LF furnace is completed, the converter is transferred to the VD furnace for refining, and the ultimate vacuum degree in the VD furnace is controlled to be ≤ 67 Pa, the ultimate vacuum holding time is ≥ 10 min; the weak argon blowing time is ≥ 20 min.

[0076] The reason for controlling the ultimate vacuum degree in the VD furnace to be ≤ 67 Pa and the ultimate vacuum holding time to be ≥ 10 min is to improve the degassing efficiency of the molten steel, remove harmful gases such as hydrogen, nitrogen, and oxygen, reduce the solubility of gases in the molten steel, avoid gas reabsorption, and at the same time promote the floating and removal of non-metallic inclusions, thereby improving the purity of the molten steel.

[0077] The reason for setting the weak argon blowing time to be ≥ 20 minutes is as follows: to promote the floating of inclusions and improve the purity of the molten steel; to homogenize the molten steel composition and temperature, ensure the consistency and stability of the material; to enhance the degassing effect and further reduce the content of harmful gases in the molten steel; to improve the quality of the continuous casting billet, reduce internal defects, and enhance the performance of the final product.

[0078] This process setting not only improves the quality of molten steel, but also optimizes the production efficiency, ensuring that the wire rod for ultra-high strength rare earth alloy wires finally produced has excellent mechanical properties and reliability.

[0079] As an alternative implementation, 0.02%-0.04% rare earth La is added during the VD furnace refining process, and Si-Ca wire is fed at 1-5 m / t after the ladle is opened; the soft blowing argon time after VD is ≥15 minutes; the tapping temperature of the VD furnace is 1500-1600 °C.

[0080] More preferably, rare earth and microalloying are added during the VD furnace refining process, and Si-Ca wire is fed at a speed of 2-4 m / t after the ladle is opened; the soft blowing argon time after VD is ≥15 minutes; the tapping temperature of the VD furnace is 1540-1560 °C.

[0081] Adding rare earth is an important step to improve the purity of steel, improve the microstructure and enhance the material properties. The rare earth element lanthanum (La) can react with oxygen and sulfur in the steel to form stable oxides and sulfides. These compounds usually have a relatively high melting point and are easily separated from the molten steel, thereby reducing the oxygen and sulfur content in the steel. Rare earth elements can also change the morphology and distribution of existing inclusions in the steel, making them smaller and more dispersed, reducing the negative impact of large particle inclusions on the material properties. Rare earth elements help to refine the grains. By inhibiting the grain boundary migration rate during the recrystallization process, the grains become finer and more uniform, thereby improving the strength and toughness of the material. Rare earth elements can promote the formation of beneficial precipitation phases, such as carbonitrides, etc. These precipitation phases can play a strengthening role in the subsequent heat treatment process.

[0082] The reason for controlling the feeding speed of Si-Ca wire at 2-4 m / t is to ensure that it can be fully decomposed and diffused in the molten steel, and react effectively with the molten steel for deoxidation, desulfurization and inclusion modification reactions. At the same time, it can avoid the floating of unreacted Si-Ca wire or splashing caused by too fast feeding speed, which may cause molten steel disturbance, or uneven local composition and extended smelting time caused by too slow speed.

[0083] The reason for controlling the soft blowing argon time after VD to be ≥15 minutes is to ensure the uniformity and purity of the molten steel, and further remove the residual gas and inclusions.

[0084] The reason for controlling the tapping temperature of the VD furnace to be 1540-1560 °C is to ensure the fluidity and composition uniformity of the molten steel, so as to obtain good casting effect in the subsequent casting process; this temperature range can effectively avoid insufficient fluidity caused by supercooling of the molten steel, and at the same time helps to maintain the stability of the chemical composition of the molten steel and reduce the loss of alloying elements.

[0085] As an alternative embodiment, after VD furnace refining, MT-1 protective slag is used to cast the electrode blank with molten steel, and the casting temperature is 1500 - 1600 °C; argon protection casting is adopted, and the argon pressure range is 0.01 - 1.50 MPa, and the flow rate is 3 - 12 m 3 / h.

[0086] More preferably, the addition time of the rare earth element during the smelting process is after the molten steel is melted, and the temperature is controlled between 1540 - 1560 °C to ensure the full dissolution and distribution of the rare earth element. After VD furnace refining, MT-1 protective slag is used to cast the electrode blank with molten steel, and the casting temperature is 1535 - 1555 °C; argon protection casting is adopted, and the argon pressure range is 0.05 - 1.00 MPa, and the flow rate is 5 - 10 m3 / h. The annealing step of the electrode blank includes: heating from room temperature to 600 - 700 °C in 4 - 6 h and holding for 10 - 15 h, and then cooling in the furnace to 150 °C - 250 °C and taking out of the furnace.

[0087] The reason for controlling the casting temperature to be 1535 - 1555 °C is to ensure that the molten steel has good fluidity and formability. Within this temperature range, it can effectively avoid the aggravation of oxidation, the increase of die loss, and the rise of energy consumption caused by too high temperature.

[0088] The reason for controlling the argon pressure range to be 0.05 - 1.00 MPa and the flow rate to be 5 - 10 m 3 / h is to provide a stable protection environment during the casting process, prevent the molten steel from contacting with air and causing oxidation and inclusion defects; within this pressure range, argon can evenly cover the surface of the melt, form an effective isolation layer, avoid the intrusion of oxygen and nitrogen, and at the same time maintain an appropriate flow rate to ensure the fluidity and coverage of the protective gas in the casting area, and prevent the protection failure caused by local stagnation.

[0089] As an alternative embodiment, after casting, the electrode blank is demolded, and the demolding time is ≥ 1 hour; after demolding, the electrode blank is annealed while it is still hot. The annealing step includes: heating from room temperature to 600 - 700 °C in 4 - 6 h and holding for 10 - 15 h, and then cooling in the furnace to 150 - 250 °C and taking out of the furnace; after the electrode blank is annealed, it is subjected to surface sandblasting treatment to remove surface scale, slag inclusions, etc.

[0090] More preferably, after casting, the electrode blank is demolded, and the demolding time is ≥ 2 hours; after demolding, the electrode blank is annealed while it is still hot. The annealing step includes: heating from room temperature to 640 °C in 5 h and holding for 12 h, and then cooling in the furnace to 200 °C and taking out of the furnace; after the electrode blank is annealed, it is subjected to surface sandblasting treatment to remove surface scale, slag inclusions, etc.

[0091] The reason for controlling the demolding time to be ≥ 2 hours is to ensure that the molten steel is fully cooled and solidified in the mold, and avoid deformation, cracking or surface defects caused by premature demolding.

[0092] The reason for controlling the annealing holding temperature at 640 °C is to promote the recrystallization and microstructure homogenization of the electrode blank, effectively eliminate the residual stress, thereby improving the toughness and plasticity of the wire rod; at the same time, as an economically reasonable process temperature, this temperature not only meets the requirements of optimizing the performance, but also effectively controls the energy consumption and improves the process efficiency.

[0093] The reason for controlling the furnace cooling to 200 °C before discharging is to ensure that the internal stress of the electrode blank is fully released during the cooling process, and at the same time avoid the thermal stress concentration or structural damage caused by rapid cooling; before 200 °C, the electrode blank is still in a relatively high temperature range, and the grain structure and microstructure are not yet fully stable. The furnace cooling method can provide a slow and uniform cooling environment, reducing the risk of deformation or cracking caused by temperature difference; in addition, 200 °C is lower than the recrystallization temperature and the main phase transformation temperature of the electrode blank, ensuring that the performance of the electrode blank has stabilized when it is discharged, and will not be affected by the rapid change of the subsequent ambient temperature.

[0094] As an optional implementation method, after the casting demoulding is completed, electroslag treatment is carried out to obtain an electroslag ingot. The slag system is CaF2:Al2O3:CaO = 65%:30%:5%; the melting rate is 0.7D - 0.8D kg / h, where D is the diameter of the mold, in mm. The annealing step of the electroslag ingot includes: heating from room temperature to 850 °C - 870 °C in 4h - 6h and holding for 10 - 15h, and then furnace cooling to 150 °C - 250 °C before discharging.

[0095] The reason for controlling the melting rate at 0.7D - 0.8D kg / h is that controlling the melting rate can stabilize the molten pool temperature, avoid excessive temperature causing excessive consumption of the electrode or unstable molten pool, extend the service life of the electrode and improve the production efficiency.

[0096] As an optional implementation method, after the electroslag treatment is completed, annealing and surface cleaning treatment are carried out on the electroslag ingot; the annealing step includes: heating from room temperature to 800 - 900 °C in 4 - 6h and holding for 10 - 15h, and then furnace cooling to 150 - 250 °C before discharging; after the electroslag ingot is annealed, surface sandblasting treatment is carried out to remove surface scale, slag inclusions, etc.

[0097] More preferably, after the electroslag treatment is completed, annealing and surface cleaning treatment are carried out on the electroslag ingot; the annealing step includes: heating from room temperature to 860 °C in 5h and holding for 12h, and then furnace cooling to 200 °C before discharging; after the electroslag ingot is annealed, surface sandblasting treatment is carried out to remove surface scale, slag inclusions, etc.

[0098] The reason for controlling the annealing holding temperature at 860 °C is to promote the homogenization of the structure of the electroslag ingot, fully release the residual stress generated during the processing, improve the plasticity and toughness, and refine the grains. At a temperature of 860 °C, the electroslag ingot enters the complete austenitization range, causing partial dissolution of carbides, optimizing the hardness and wear resistance, while avoiding problems such as grain coarsening or overburning due to excessive temperature.

[0099] The reason for controlling the furnace cooling to 200 °C before discharging is to prevent thermal cracks and internal residual stress in the electroslag ingot during the cooling process, and at the same time ensure the structural uniformity and surface quality. Slow cooling can effectively reduce the risks of oxidation and deformation.

[0100] As an alternative implementation, after the annealing treatment of the electroslag ingot, forging treatment is carried out to obtain a forging billet; before forging, the electroslag ingot is heated, and the heating steps include: holding at 400 °C for 2 h, heating from 400 °C to 800 °C in 4 h and holding for 2 h, heating from 800 °C to 1160 - 1180 °C in 4 h and holding for 4 h, then discharging for forging; the starting forging temperature ≥ 1050 °C, and the final forging temperature ≥ 850 °C.

[0101] The reason for controlling the starting forging temperature ≥ 1050 °C and the final forging temperature ≥ 850 °C is to ensure the processing performance and final mechanical properties of the forging billet during plastic deformation; a higher starting forging temperature can improve the plasticity of the wire rod, reduce the deformation resistance, promote dynamic recrystallization and refine the grains, thus preventing the generation of cracks and defects; maintaining the final forging temperature above 850 °C can avoid the reduction of plasticity, work hardening and excessive elongation of grains caused by too low temperature, and at the same time prevent the occurrence of low-temperature brittleness or adverse phase transformation.

[0102] As an alternative implementation, after forging, annealing and surface cleaning treatments are carried out on the forging billet; the forging billet is slowly cooled or annealed in hot charging, and the annealing process is the same as the annealing steps of the electrode billet; after annealing of the forging billet, all are subjected to flaw detection inspection, surface inspection and grinding one by one to remove defects such as cracks and laps that affect rolling.

[0103] The reason for controlling the forging billet to enter slow cooling or hot charging annealing is to regulate the structure and properties of the metal forging billet, reduce the residual stress, prevent the generation of cracks and deformation, and at the same time optimize the grain size and structural uniformity.

[0104] As an alternative implementation, after the forging billet is annealed and surface cleaned, rolling treatment is carried out on the forging billet to obtain a wire rod; before rolling, the forging billet is heated, and the heating steps include: the temperature of the preheating section ≤ 1000 °C, the temperature of the heating section is 1100 - 1250 °C, and the temperature of the soaking section is 1100 - 1250 °C; the temperature when entering the finishing mill during rolling is 800 - 900 °C; the wire rod is slowly cooled after being taken off the production line.

[0105] More preferably, after the forging billet is annealed and surface cleaned, it is rolled to obtain wire rods; before rolling, the forging billet is heated, and the heating steps include: the temperature in the preheating section is ≤950°C, the temperature in the heating section is 1130 - 1200°C, and the temperature in the soaking section is 1180 - 1220°C; the temperature when entering the finishing mill during rolling is 840 - 890°C; after the wire rods are taken off the production line, they are slowly cooled.

[0106] The reason for controlling the temperature in the preheating section ≤950°C is to avoid phase transformation, grain coarsening or performance degradation of the forging billet at high temperatures, while reducing the impact of surface oxidation on the quality of the forging billet, and preventing excessive thermal expansion or uneven change of the microstructure.

[0107] The reason for controlling the temperature in the heating section to be 1130 - 1200°C is to meet the requirements of the process for the performance and microstructure of the forging billet, achieve sufficient heating of the forging billet, promote the homogenization of the microstructure, and improve the plasticity and workability of the forging billet.

[0108] The reason for controlling the temperature in the soaking section to be 1180 - 1220°C is to ensure the tissue uniformity and performance stability of the forging billet at this stage. Within the said temperature range, the forging billet can be fully recrystallized, internal stress can be eliminated, the microstructure can be made more uniform, which is beneficial to improving the mechanical properties of the forging billet.

[0109] The reason for controlling the temperature when entering the finishing mill during rolling to be 840 - 890°C is to avoid cracks or other defects during the rolling process, control the grain size, promote dynamic recrystallization, optimize the microstructure, and thus improve the mechanical properties of the wire rods.

[0110] The rare earth element is La. The addition of the rare earth element can significantly improve the grain refinement and tissue uniformity of the steel, deoxidize the steel, and reduce inclusions in the steel.

[0111] The method of this application uses a co-variation relationship established based on clusters to optimize the material composition, and through process control, it completes the production of high-strength rare earth alloy wire products with a minimum wire diameter of 35μm and a tensile strength exceeding 5000MPa by improving the strength.

[0112] Next, the wire rods for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wires and their preparation methods of this application will be described in detail with reference to examples and specific data.

[0113] Percentages in the examples are all mass percentages.

[0114] Example 1

[0115] This application uses steel with the brand ZH90Re as raw material. The chemical composition of the ZH90Re steel is as follows: C: 0.90 wt%, Mn: 0.28 wt%, Si: 0.25 wt%, P: 0.015 wt%, S: 0.010 wt%, Al: 0.003 wt%, Re(La): 0.02 wt%, Cr: 0.05 wt%, Ni: 0.05 wt%, Mo: 0.02 wt%, Sn: 0.005 wt%, As: 0.005 wt%, Cu: 0.05 wt%, O: 0.001 wt%, N: 0.005 wt%, and the rest is iron and inevitable impurities.

[0116] The production process of the wire rod in this application is as follows: electric arc furnace melting → LF furnace refining → VD furnace refining → die-casting electrode blank → annealing and surface cleaning of the electrode blank → electroslag → annealing and surface cleaning of the electroslag ingot → forging and blooming → annealing and surface cleaning of the forging blank → rolling wire rod → finished product inspection and warehousing.

[0117] In the electric arc furnace melting process, the C content of the molten steel at the end of the electric arc furnace melting is 0.07 wt%, the P content is 0.034 wt%, and the tapping temperature is 1640 °C. When about 1 / 4 of the tapping amount is reached, alloying agents and slag materials are added in the order of "refining slag → lime → ferromanganese-aluminum → alloying alloy". Among them, the addition amount of the slag material is 6 kg / t of refining slag in the tapping ladle. The deoxidizer is ferromanganese-aluminum, and it is added according to the following ratio based on the carbon content in the molten steel: 0.07%, 2.5 Kg / t.

[0118] In the LF furnace refining process, the temperature when entering the LF furnace is 1500 °C. 700 Kg of silica is added when entering the furnace, and 500 Kg of lime is added after the silica melts. Diffusion deoxidation and precipitation deoxidation are adopted, and the refining treatment time is 45 minutes. No raw and auxiliary materials are added in the last 5 minutes before the end of refining. After the refining is completed, the molten steel is softly blown, and the soft blowing time is 15 minutes. Before the ladle is lifted, carbonized rice husk is added for heat preservation. The carbonized rice husk covers the entire slag surface and is evenly spread, and the ladle lifting temperature is 1550 °C.

[0119] In the VD furnace refining process, the ultimate vacuum degree of the VD furnace is 67 Pa, the ultimate vacuum holding time is 10 min, and the weak argon blowing time is 20 min. 0.02% of rare earth La is added, and the Si-Ca wire is fed at 3 m / t after the ladle is opened. The soft argon blowing time after the VD furnace refining is completed is ≥15 minutes, and the VD tapping temperature is 1540 °C.

[0120] In the die-casting electrode blank process, MT-1 protective slag is used to cast the electrode blank, and the casting temperature is 1535 °C. Argon protection casting is adopted, and the argon pressure range is 0.05 MPa, and the flow rate is 5 m 3 / h.

[0121] In the annealing and surface cleaning process of the electrode blank, the demolding time of the electrode blank is ≥ 2 hours, and it is annealed with red heat. The annealing steps include: heating from room temperature to 700 °C in 6 hours and holding for 10 hours, then cooling in the furnace to 250 °C and taking out of the furnace, as Figure 2 shown; after the electrode blank is annealed, it is subjected to surface sandblasting to remove surface scale, slag inclusions, etc.

[0122] In the electroslag process, the slag system is CaF2:Al2O3:CaO = 65%:30%:5%; the melting rate is 0.7D kg / h, where D is the diameter of the mold, in mm.

[0123] In the annealing and surface cleaning process of the electroslag ingot, the annealing steps of the electroslag ingot include: heating from room temperature to 860 °C in 5 hours and holding for 12 hours, then cooling in the furnace to 200 °C and taking out of the furnace, as Figure 3 shown; after the electroslag ingot is annealed, it is subjected to surface sandblasting to remove surface scale, slag inclusions, etc.

[0124] In the forging and blooming process, first heat the electroslag ingot. The heating steps include: holding at 400 °C for 2 hours, heating from 400 °C to 800 °C in 4 hours and holding for 2 hours, heating from 800 °C to 1160 °C in 4 hours and holding for 4 hours, then taking out of the furnace for forging, as Figure 4 shown; the forging start temperature is 1050 °C, and the forging end temperature is 850 °C.

[0125] In the annealing and surface cleaning process of the forged blank, after forging, the forged blank is slowly cooled or annealed with red heat. The annealing process is the same as that of the electrode blank, as Figure 2 shown; after the forged blank is annealed, all are subjected to flaw detection inspection, and each piece is inspected and ground on the surface to remove defects such as cracks and laps that affect rolling.

[0126] In the process of rolling wire rods, before rolling, heat the forged blank. The heating steps include: the temperature of the preheating section is 950 °C, the temperature of the heating section is 1130 °C, and the temperature of the soaking section is 1180 °C; the temperature when entering the finishing mill during rolling is 840 °C, and the steel discharging speed is not limited; after the wire rods are taken off the production line, they are slowly cooled.

[0127] In the finished product inspection and warehousing process, samples of wire rods produced by hot rolling technology are taken to analyze the chemical composition, non-metallic inclusions, mechanical properties, grain size, decarburization, macrostructure, microstructure, ultrasonic flaw detection and surface quality of the steel. After passing the inspection, they are warehoused. The finished cutting wires are drawn from the wire rods prepared in Example 1 as Figure 5 shown. The test results of the prepared product performance are shown in Table 1.

[0128] Example 2

[0129] In this embodiment, the remaining parameters are the same as those in Embodiment 1, except that the chemical composition of the steel with the grade of ZH90Re is as follows: C: 0.93 wt%, Mn: 0.34 wt%, Si: 0.20 wt%, P: 0.010 wt%, S: 0.08 wt%, Al: 0.002 wt%, Re(La): 0.04 wt%, Cr: 0.03 wt%, Ni: 0.03 wt%, Mo: 0.01 wt%, Sn: 0.003 wt%, As: 0.003 wt%, Cu: 0.04 wt%, O: 0.001 wt%, N: 0.004 wt%, and the rest is iron and inevitable impurities. The product performance test results prepared in this embodiment are shown in Table 1.

[0130] Embodiment 3

[0131] In this embodiment, the remaining parameters are the same as those in Embodiment 1, except that the electrode blank annealing step includes: heating from room temperature to 600 °C in 4 h and holding for 15 h, and then cooling in the furnace to 150 °C and taking out of the furnace.

[0132] The product performance test results prepared in this embodiment are shown in Table 1.

[0133] Embodiment 4

[0134] In this embodiment, the remaining parameters are the same as those in Embodiment 1, except that the forging billet is heated before rolling. The heating steps include: the preheating section temperature is 930 °C, the heating section temperature is 1200 °C, and the soaking section temperature is 1220 °C; the temperature when entering the finishing mill during rolling is 890 °C; the wire rod is slowly cooled after being taken off the production line.

[0135] Table 1 Product performance test results of the embodiments

[0136]

[0137]

[0138] It can be seen from Table 1 that the solutions of the embodiments of the present application can successfully obtain wire rods for ultra-pure, high-homogeneity, ultra-high-strength rare earth alloy wires. This method optimizes the material composition by using a co-variation relationship established based on clusters, and through process control, it completes the production of wire rods for high-strength rare earth alloy wires with a strength increase of more than 1350 MPa and an area reduction exceeding 35%. Its tensile strength, inclusion size and quantity have reached the international leading level, meeting the user's requirements. The wire rods prepared by the present application are drawn into finished cutting wires as Figure 5 shown.

[0139] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire, characterized in that: The method includes: Preparing ZH90Re steel as raw material; Melting the raw material to obtain molten steel, and adding deoxidizer and slag material; Using an LF furnace and a VD furnace to refine the molten steel to obtain refined molten steel; Carrying out die casting on the refined molten steel to obtain an electrode blank, and annealing and surface cleaning the electrode blank; Carrying out electroslag remelting on the electrode blank to obtain an electroslag ingot, and annealing and surface cleaning the electroslag ingot; Heating and forging the electroslag ingot to obtain a forging blank, and annealing and surface cleaning the forging blank; Heating and rolling the forging blank to obtain a wire rod.

2. The preparation method of the wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire according to claim 1, characterized in that, The chemical composition of the ZH90Re steel is: C: 0.90 - 0.93 wt%, Mn: 0.28 - 0.34 wt%, Si ≤ 0.25 wt%, P ≤ 0.015 wt%, S ≤ 0.010 wt%, Al ≤ 0.003 wt%, Re(La): 0.02 - 0.04 wt%, Cr ≤ 0.05 wt%, Ni ≤ 0.05 wt%, Mo ≤ 0.02 wt%, Sn ≤ 0.005 wt%, As ≤ 0.005 wt%, Cu ≤ 0.05 wt%, O ≤ 0.001 wt%, N ≤ 0.005 wt%, and the rest are iron and inevitable impurities; Based on the component co-variation relationship established by the cluster method, the above alloying elements are divided into Ni-like elements entering the cluster: Mn; Cr-like elements, including: Cr, Si, Mo, Al; matrix element Fe; And trace elements not entering the cluster, including: C, S, P, H, O, N and rare earth element La; the mass percentage of the co-variation relationship of each element satisfies: 0.28 ≤ Mn ≤ 0.34; 0.18 ≤ Cr + 1.83Si + 0.55Mo + 1.91Al ≤ 1.37; 96.18 ≤ Fe ≤ 98.

40.

3. The preparation method of the wire rod for super-pure, highly homogeneous and ultra-high strength rare earth alloy wire according to claim 1, characterized in that, The rare earth element is La; the C content of the molten steel at the end of melting is 0.07 - 0.40 wt%, the P content is not more than 0.034 wt%, and the tapping temperature is 1640 ± 20 °C.

4. The preparation method of the wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire according to claim 1, characterized in that, The refining inlet temperature of the LF furnace ≥ 1500 °C; the refining time of the LF furnace is 45 - 90 minutes, after refining, the molten steel is softly blown, and the soft blowing time ≥ 15 minutes; the ladle hanging temperature is 1550 - 1580 °C.

5. The preparation method of the wire rod for ultra-pure, highly homogeneous and ultra-high strength rare earth alloy wire according to claim 1, characterized in that, The ultimate vacuum degree of the VD furnace refining ≤ 67 Pa, the ultimate vacuum holding time ≥ 10 min, the weak argon blowing time ≥ 20 min; the soft argon blowing time after VD furnace refining ≥ 15 minutes, and the tapping temperature of the VD furnace is 1540 - 1560 °C.

6. The preparation method of the wire rod for ultra-pure, high-homogeneity and ultra-high-strength rare earth alloy wire according to claim 1, characterized in that, The addition time of the rare earth element during smelting is after the molten steel is melted, and the temperature is controlled between 1540 - 1560 °C to ensure the full dissolution and distribution of the rare earth element. For continuous casting, MT-1 mold powder is used to pour the electrode blank, and the pouring temperature is 1535 - 1555 °C; the argon pressure range is 0.05 - 1.00 MPa, and the flow rate is 5 - 10 m 3 / h; The annealing step of the electrode blank includes: heating from room temperature to 600 - 700 °C in 4 - 6 h and holding for 10 - 15 h, and then cooling in the furnace to 150 °C - 250 °C and taking out of the furnace.

7. The preparation method of the wire rod for super-pure, high-homogeneity and ultra-high-strength rare earth alloy wire according to claim 1, characterized in that, The electroslag slag system is CaF2:Al2O3:CaO = 65%:30%:5%; the melting rate is 0.7D - 0.8D kg / h; the annealing step of the electroslag ingot includes: heating from room temperature to 850 - 870 °C in 4 - 6 h and holding for 10 - 15 h, and then cooling in the furnace to 150 - 250 °C and taking out of the furnace.

8. The preparation method of the wire rod for super-pure, high-homogeneity and ultra-high-strength rare earth alloy wire according to claim 1, characterized in that, The electroslag ingot heating step includes: holding at 400°C for 2 h, heating from 400°C to 800°C in 4 h and holding for 2 h, heating from 800°C to 1160 - 1180°C in 4 h and holding for 4 h, and then taking out of the furnace for forging; the forging starting temperature ≥ 1050°C, and the final forging temperature ≥ 850°C; the annealing process of the forged billet is the same as that of the electrode billet.

9. The preparation method of the wire rod for ultra-pure, highly homogeneous and ultra-high strength rare earth alloy wire according to claim 1, characterized in that, The heating step includes: the temperature of the preheating section ≤ 950°C, the temperature of the heating section is 1130 - 1200°C, and the temperature of the soaking section is 1180 - 1220°C; the rolling temperature entering the finishing mill is 840 - 890°C.

Images