Preparation method of low-cost titanium-based hydrogen storage alloy and product thereof

Abstract

The application provides a preparation method of low-cost titanium hydrogen storage alloy and a product thereof, and belongs to the field of non-ferrous metal smelting. The steps are as follows: (1) mechanical activation and pre-reduction of titanium raw materials to obtain low-valence titanium oxide; (2) calcium-magnesium composite hot reduction of the low-valence titanium oxide and addition of cheap furnace charge for alloying, and separation of gold slag to obtain a primary melt; (3) secondary reduction refining, introduction of the primary melt into a vacuum induction furnace for further refining, purification and deoxidization; (4) online detection of components and fine adjustment; and (5) vacuum casting and rapid solidification of thin strips (sheets), crushing, powdering and annealing treatment to obtain hydrogen storage alloy powder. The application has the advantages that expensive metals such as vanadium and titanium are not used as raw materials, but the alloy is directly prepared from metal oxides, the process flow is short, and the energy consumption is low. Gold slag separation and control of the content of elements such as Al and O are easy to realize. The hydrogen storage alloy prepared by the application has high hydrogen storage density, is easy to activate and has low production cost.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting, specifically a method for preparing low-cost titanium-based hydrogen storage alloys and its products. Specifically, it relates to a method for preparing binary or multi-element hydrogen storage alloys containing elements such as Ti, V, Fe, Cr, and Mn based on calcium-magnesium composite thermal reduction-vacuum refining. Background Technology

[0002] Hydrogen storage alloys possess advantages such as high safety under low pressure, high hydrogen storage density, small size, mild hydrogen absorption and desorption conditions, good reversibility, and long lifespan. Furthermore, their preparation technology is mature and can be scaled up for application, making them one of the most promising hydrogen storage materials. Hydrogen storage alloys comprise five major series: rare earth alloys (LaNi5, La2MgNi9), magnesium alloys (Mg2Ni), titanium alloys (TiFe, TiMn, TiCr2), zirconium-titanium alloys (Ti-Zr-(Cr, Fe, Mn)), and vanadium-titanium alloys (V-Ti-(Cr, Fe)). Because the alloy contains a large amount of expensive and rare elements such as rare earth (RE), nickel (Ni), cobalt (Co), vanadium (V), titanium (Ti), and zirconium (Zr), raw materials usually account for 40% to 60% of the total cost. In particular, the V content (high price of 2500 to 2800 yuan / kg) in vanadium-based hydrogen storage alloys is as high as 20 to 60 wt.%, and the raw material cost accounts for more than 70% of the total cost. The high raw material cost and market price are the main reasons that limit its widespread application and restrict the rapid development of the hydrogen energy industry chain.

[0003] Traditional methods typically employ a mixed melting process using materials such as sponge titanium, sponge zirconium, and Fe-V to prepare alloy ingots. This method suffers from drawbacks including the use of high-purity raw materials, high energy consumption, and high costs. To significantly reduce production costs, it is essential to bypass expensive raw materials such as Kroll sponge titanium, metallic vanadium, or Fe-V. New technologies are needed to directly extract vanadium and titanium from titanium dioxide (TiO2) and vanadium pentoxide (V2O5) for alloy preparation. Therefore, in recent years, new methods have emerged that directly prepare alloys using titanium concentrate (FeTiO3), high-titanium slag, or titanium dioxide (TiO2), vanadium pentoxide (V2O5), and other titanium concentrates and metal oxides as raw materials. Examples include metallothermic reduction-refining and hydrogenation combustion methods. These methods offer a wide range of raw material sources, shorter processes, lower energy consumption, and production costs that are 30%–40% lower than traditional mixed melting methods, demonstrating a significant cost advantage. However, the high oxygen content and incomplete gold slag separation are two major factors hindering the industrialization of these new methods. Currently, the key technologies and processes utilizing these methods focus on reducing impurities such as Al, O, and Si, and enhancing gold slag separation.

[0004] A search of existing patents revealed that patent application CN02813035.9 discloses a method using aluminothermic reduction with Cr2O3, V2O5, and Al reducing agents as reactants to obtain a Cr-V melt, which is then smelted with sponge titanium to obtain a Cr-Ti-V alloy. The Al content in the alloy is >1 wt.%, which reduces the hydrogen storage density. Controlling the Al content within the target range is challenging, hence the Al dosage is below 90% of the theoretical value. However, due to insufficient aluminum, the aluminothermic reaction exothermics are insufficient, requiring the addition of large amounts of chlorine-based exothermic agents (KClO3 and NaClO3), and also necessitating deoxidation using rare earth elements such as La and Ce. Patent application CN201510338166.9 uses metal oxides as raw materials and employs an aluminothermic reduction-slag washing refining method to prepare a V-Ti-Fe hydrogen storage alloy. The Al content in the alloy reaches 1.1–2.3 wt.%, affecting the hydrogen storage performance. Patent application CN201310385946.X uses a similar method to prepare V... (2-x) Ti (1-y) M y NiO x To prevent aluminum residue from reducing hydrogen storage performance, the hydrogen storage electrode was also designed for use under aluminum-deficient conditions.

[0005] However, there are still several challenges to overcome in preparing titanium-based hydrogen storage alloys using the aluminothermic reduction method. First, it is difficult to control the Al content in the aluminothermic reduction method. When the Al content exceeds a certain level, it will lead to an increase in the slope of the hydrogen absorption and desorption plateau and a decrease in the hydrogen storage density, making it extremely difficult to prepare alloys with high hydrogen storage density using the aluminothermic reduction method. Second, the enthalpy of the aluminothermic reaction is low (3TiO2+4Al=3Ti+2Al2O, ΔH=-1437kJ / kg). Without an external heat source and insulation, it is insufficient to sustain the entire reaction spontaneously. Rapid cooling after the reaction ends leads to the failure of the gold slag to separate and excessive oxygen content. The reaction heat of chlorine-based exothermic agents is much higher, but the reaction between the exothermic agent and aluminum will increase aluminum consumption and slag production (KClO3+2Al=Al2O3+KCl↑, ΔH=-10119kJ / kg; 3KClO4+8Al=4Al2O3+3KCl↑, ΔH=-9470kJ / kg). Therefore, more aluminum must be added for deoxidation, which inevitably increases the amount of slag production and the risk of non-separation of gold slag, resulting in higher inclusion and oxygen content in the alloy. Finally, chlorine-based exothermic agents and igniters have complex compositions, which may introduce impurity elements and release toxic gases such as Cl2 and KCl. Potassium hypochlorite is a key hazardous chemical, which is inconvenient to purchase and poses safety hazards, making it unsuitable for industrial-scale production. Summary of the Invention

[0006] To address the shortcomings of existing methods for preparing hydrogen storage alloys using the melting and mixing method, and to overcome the technical difficulties of excessive aluminum and oxygen content and incomplete gold-slag separation in existing aluminothermic reduction methods, this invention provides a method for preparing titanium-based hydrogen storage alloys based on a combination of calcium-magnesium composite thermal reduction and vacuum refining. This method replaces the existing aluminothermic reduction with calcium-magnesium composite thermal reduction, utilizes external electric heating during the reduction process, and pre-reduces the titanium raw material to reduce the consumption of reducing agents and slag-forming agents, significantly reducing slag production. This reduces slag at the source, which is beneficial for promoting gold-slag separation and reducing oxygen content. Secondary refining under vacuum using a water-cooled copper roller spinning method allows for rapid solidification of the melt, promoting uniform composition. Furthermore, modification with high-density elements such as Fe, Cr, and Mn enhances gold-slag separation by increasing the melt's specific gravity, while simultaneously achieving multi-element alloying. Through the implementation of these multiple technological innovations, various types of low-cost, high-performance titanium-based hydrogen storage alloys have been prepared.

[0007] This invention is achieved through the following technical solution:

[0008] As a first aspect of the present invention, a method for preparing a low-cost titanium-based hydrogen storage alloy is provided. The method comprises a calcium-magnesium composite thermal reduction-vacuum refining process, and includes the following steps:

[0009] (1) Mechanical activation treatment of titanium raw materials, followed by pre-reduction of the activated titanium raw materials with carbon powder under a reducing atmosphere to reduce high-valence TiO2 to low-valence titanium oxide Ti. n O 2n-1 Where n = 4, 3, 2 or 1, the pre-reduction product is obtained;

[0010] (2) After crushing the pre-reduction product obtained in step (1), calcium-magnesium composite thermal reduction is carried out in the reduction furnace. Alloy furnace charge, reducing agent, and slag-forming agent are added. After the reduction reaction is completed, the melt is released once at the bottom water outlet of the reduction furnace. The slag floats on the upper layer and remains in the furnace for separation. The mass ratio is: pre-reduction product in step (1): reducing agent: alloy furnace charge: slag-forming agent = 1: 0.45~0.65: 0.1~0.15: 0.15~0.35. The reducing agent is a calcium-magnesium alloy with a mass ratio of Mg:Ca = 50%~80%: 20%~50%.

[0011] (3) The primary melt obtained in step (2) is introduced into a vacuum induction furnace for secondary reduction refining, kept warm and stirred, further purified and deoxidized to obtain a secondary melt with a composition close to the target; the reactants are a mixture of primary melt, titanium residue, alloy furnace charge, reducing agent and slag-forming agent.

[0012] (4) Take online samples to test the composition, add alloy furnace charge again to fine-tune the composition so as to meet the target composition range, and take online samples of the melt that meets the target composition range to test the composition.

[0013] (5) Vacuum casting to obtain a rapidly solidified thin strip (sheet), which is then crushed, powdered and annealed to obtain the final product titanium-based hydrogen storage alloy powder; specifically, the melt is cast onto the surface of a water-cooled copper roller in a vacuum environment, and a rapidly solidified thin strip is obtained through the quenching effect of the water-cooled copper roller. The rapidly solidified thin strip is then crushed, powdered and annealed to finally obtain titanium-based hydrogen storage alloy powder.

[0014] The titanium raw material is high-titanium slag or titanium dioxide, preferably high-titanium slag smelted in an electric furnace with high calcium and magnesium impurities, to minimize the cost of titanium raw materials. Since calcium and magnesium are used as the metal reducing agent, the magnesium and calcium impurities in the high-titanium slag have no effect on the alloy. Because the alloy contains modifying elements such as vanadium, iron, chromium, and manganese, these elements in the high-titanium slag can all participate in alloying. The high-titanium slag contains 85%–92% TiO2 by weight, 3.5%–5% calcium and magnesium impurities (CaO+MgO), 3%–9% total iron (TFe), 1.5%–2.5% SiO2, and 1.5%–2.2% Al2O3.

[0015] Preferably, in step (1), the reducing atmosphere uses a reducing gas containing H2 and CO in a volume ratio of 1:2 to 2:1, with a supply pressure range of 0.2 MPa to 5 MPa and a flow rate of 0.5 to 5 m³ / h. 3 / m 2 •min; the carbon powder is selected from any one or at least two of coke, activated carbon, and graphite; the pre-reduction temperature is 1050℃~1150℃, and the reduction time is 0.5h~3h.

[0016] Preferably, the reactants in step (2) include the pre-reduction product, reducing agent, alloy charge, and slag-forming agent from step (1). The chemical formula of the reaction is Ti. n O 2n-1 +Mg→Ti+MgO, Ti n O 2n-1 +Ca→Ti+CaO. (Molar ratio of Ti) n O 2n-1 The reactants are Mg (or Ca) in a ratio of 1:1 to 2, and the mass ratio of the reactants is pre-reduction product: reducing agent: alloy charge: slag-forming agent = 1:0.45 to 0.65:0.1 to 0.15:0.15 to 0.35. The slag-forming agent is a CaO-CaF2 binary slag, with a mass ratio of CaO:CaF2 of 70% to 90%:30% to 10%.

[0017] In the embodiments provided by the present invention, the titanium raw material is subjected to ball milling activation treatment to refine the titanium raw material and introduce cracks and defects to facilitate hydrogenation reduction, thereby providing favorable conditions for subsequent thermal reduction and refining.

[0018] The alloy furnace charge is a combination of one or more of the following: stainless steel, manganese steel, etc., with Fe, Cr, and Mn as the main elements; ferrochrome master alloy (Fe-Cr); ferromanganese master alloy (Fe-Mn).

[0019] The reducing agent is a magnesium-calcium alloy with a mass ratio of Mg:Ca = 50%–80%: 20%–50%. To prevent aluminum residue from affecting the alloy's performance, a calcium-magnesium alloy with stronger reducing properties than aluminum is selected.

[0020] Preferably, the reduction furnace in step (2) is a DC electric arc furnace, the top center electrode is hollow, the top of the hollow electrode is a feeding port, the hollow electrode serves as both a plasma arc initiation device and a feeding device, the electrode material is graphite or tungsten, the side wall of the reduction furnace is provided with a slag outlet and a melt outlet, the slag outlet is higher than the melt outlet in the vertical direction.

[0021] Furthermore, the reduction temperature in step (2) is 1400℃~1600℃, and the time is 0.1~0.5h.

[0022] Preferably, the reactants in the secondary reduction refining step (3) are in the following mass ratio: primary melt: titanium residue: reducing agent: slag-forming agent = 1: 0~0.2: 0.05~0.15: 0.1~0.15; the reducing agent is a calcium-magnesium alloy with a mass ratio of Mg:Ca = 50%~80%: 20%~50% and a particle size range of 0.5mm~5mm.

[0023] Step (3) is carried out in a vacuum induction furnace. The secondary reduction temperature is 1400℃~1600℃ and the secondary reduction holding time is 0.1h~0.5h.

[0024] Preferably, in step (5), the product of the secondary reduction refining in step (4) is poured into a water-cooled copper roller under vacuum to obtain a rapidly solidified strip or sheet. The rapidly solidified strip is then subjected to mechanical crushing, hydrogen explosion, pulverization, and annealing to obtain hydrogen storage alloy powder. Specifically, in step (5), the melt of the secondary reduction refining in step (4) is poured into a rotating water-cooled copper roller under vacuum through an intermediate ladle at a pouring temperature of 1400℃~1550℃. It is rapidly cooled on the rotating water-cooled copper roller to become a rapidly solidified strip, which is then crushed into small rapidly solidified sheets by a crushing device to accelerate cooling. After the rapidly solidified sheets are cooled to room temperature, they are removed from the vacuum and then subjected to HD hydrogen explosion, crushing, pulverization, and annealing to finally obtain hydrogen storage alloy powder.

[0025] Rapidly solidified strip is a common term in this field. Because this type of strip is obtained by rapid solidification, it is called rapidly solidified strip, or simply SC strip (strip casting). Strips that are very small in size or coarsely ground are called rapidly solidified flakes.

[0026] As a second aspect of the present invention, it is to provide a product of the method for preparing a low-cost titanium-based hydrogen storage alloy, wherein the hydrogen storage alloy type includes a Ti-Cr-Mn-Fe alloy having a C14 Reves phase, a Ti-Fe-Mn-V alloy having a CsCl structure, and a Ti-Zr-Mn-Cr-Fe alloy having a C14 Reves phase, and the specific composition of each type of alloy can be adjusted, including but not limited to the component ratios in the embodiments.

[0027] In the embodiments provided by this invention, the component is TiCr 1.6-x Mn 0.1 Fe x The hydrogen storage alloy (atomic ratio at.%, x = 0.1–1.0) has an effective hydrogen storage density of 1.69 wt.% at 25 °C; its composition is TiFe. 0.8-0.9 Mn 0.15 V x The hydrogen storage alloy with x = 0 to 0.15 achieved a hydrogen storage density of 1.89 wt.% at 25 °C; its composition is Ti. 0.9 Zr 0.1 Mn 0.2 Cr 1.8-x Fe x The hydrogen storage alloy with (x = 0 to 0.5) has a hydrogen storage density of 1.65 wt.% at 25°C, which is no lower than that of existing technologies. The initial activation times are much lower than those of similar products produced by traditional methods. At the same time, the production cost can be reduced by more than 40% by using this method.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] 1. The titanium raw materials of this invention are widely available, with low requirements for grade and calcium and magnesium impurities. The alloy furnace charge is recycled material such as titanium scrap and waste stainless steel, which has the advantage of low raw material cost.

[0030] 2. The advantages of using calcium-magnesium composite thermal reduction in this invention are threefold: First, calcium and magnesium do not alloy with titanium, thus avoiding the problem of aluminum residue reducing hydrogen storage performance; second, calcium and magnesium have stronger reducing properties, which is beneficial for reducing the oxygen content in the alloy; and third, the slag CaO and MgO generated by calcium and magnesium are easy to separate, which is beneficial for reducing inclusions in the alloy and improving the vanadium-titanium yield.

[0031] 3. This invention pre-reduces titanium raw materials, ensuring that the oxygen in the metal oxides is ultimately discharged directly in gaseous form. This pre-reduction treatment reduces the burden on the calcium-magnesium composite thermal reduction and refining processes. By reducing the amount of metal reducing agent used at the source, the amount of slag produced is naturally reduced significantly. Therefore, this invention is beneficial for enhancing gold slag separation and reducing oxygen content.

[0032] 4. This invention is based on refining under external electric heating and vacuum conditions, which provides sufficient thermodynamic conditions for the reaction. The reaction temperature and energy density in the furnace are easy to control, which is beneficial to maintaining the temperature and uniformity of the alloy melt, promoting the separation of gold slag, and thus reducing the oxygen content. In addition, it has low requirements for the shape, particle size distribution and proportion of the furnace charge, and allows the furnace charge to be in powder or block form, which further reduces the raw material cost.

[0033] 5. The alloying elements of this invention are Fe, Cr, Mn and other high-density elements. By increasing the specific gravity of the alloy melt, the separation of gold slag is enhanced, and the composition ratio and alloying are achieved at the same time.

[0034] 6. This invention does not use any chlorine-based, phosphate, peroxide, or other exothermic or igniting agents, thus avoiding the introduction of impurity elements due to exothermic and igniting agents, and further reducing raw material costs, making it suitable for safe industrial production. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of the present invention;

[0036] Figure 2 This is a schematic diagram of the reduction furnace structure of the present invention;

[0037] Among them, 101. Furnace body, 102. Gold outlet, 103. Slag outlet, 104. Hollow electrode, 105. Feeding port, 106. Bottom electrode;

[0038] Figure 3 This is a schematic diagram of the vacuum induction furnace structure of the present invention;

[0039] Among them, 201. Melting chamber, 202. Crucible, 203. Induction coil, 204. Vacuum feeding hopper, 205. Feeding vacuum valve, 206. Observation hole, 207. U-shaped bell jar, 208. Buffer bag, 209. Filter screen, 210. Intermediate ladle, 211. Water-cooled copper roller, 212. Rapid solidification strip, 213. Crushing device, 214. Rapid solidification sheet, 215. Receiving bucket;

[0040] Figure 4 It is an oxygen potential diagram of several substances;

[0041] Figure 5 It is the ΔG-T curve of the reduction reaction of carbon with titanium oxide;

[0042] Figure 6This is a schematic diagram illustrating the mechanism by which oxide particles affect the initial activation of hydrogen storage alloys;

[0043] Figure 7 These are the PCT curves of Example 3 and Comparative Example 3. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solution of the present invention, this embodiment is based on the technical solution of the present invention and further illustrates the present invention in conjunction with comparative examples. The specific implementation methods and operation steps described are only used to illustrate the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0045] The flowchart of this invention is as follows Figure 1 As shown, it includes the following steps:

[0046] Step (1): Pre-restore

[0047] The titanium raw material is mechanically activated, and then pre-reduced with carbon powder in a reducing atmosphere. The titanium raw material is high-titanium slag and / or titanium dioxide. The titanium raw material is widely available and relatively inexpensive.

[0048] The titanium raw material is a high-titanium slag, preferably a high-calcium-magnesium titanium slag, to minimize the cost of titanium raw materials. The high-titanium slag contains 85%–92% TiO2, 3.5%–5% CaO+MgO, 3%–9% TFe (total iron), 2%–3% MnO, 0.4%–0.6% V2O5, and 0.25%–0.3% Cr2O3.

[0049] The titanium dioxide is selected from standard grades, with low-grade sulfuric acid process titanium dioxide being preferred.

[0050] The carbon powder is not particularly limited, for example, any one or at least two of coke, activated carbon, and graphite, wherein typical but non-limiting combinations are: coke and activated carbon, coke and graphite, activated carbon and graphite, and a mixture of coke, activated carbon, and graphite.

[0051] The pre-reduction is carried out in a reducing atmosphere, and carbon powder is used to convert the high-valence TiO2 in the titanium raw material into low-valence titanium oxide Ti. n O 2n-1 (n = 4, 3, 2, 1).

[0052] according to Figure 4 The provided ΔG-T oxygen potential diagram shows the hydrogen line positioned near the top, with a small negative Gibbs free energy, indicating it cannot reduce titanium oxide. Above the intersection of the carbon and titanium lines, carbon can reduce titanium oxide. This process involves complex chemical reactions, including solid-solid and gas-solid reactions. The solid-solid reaction is TiO2(s) + C(s) → Ti n O 2n-1TiO2(s) + CO(g)↑, the gas-solid reaction is TiO2(s) + CO(g) → Ti n O 2n-1 (s) + CO2(g)↑, where Ti n O 2n-1 The titanium oxides are low-valence oxides (n = 4, 3, 2, 1). Other metal oxides in the titanium raw material can also be reduced to elemental metals: Fe₂O₃ + 3CO = 2FeO + 3CO₂↑, FeO + CO = Fe + CO₂↑, MnO₂ + 2CO = Mn + 2CO₂↑. After pre-reduction, some oxygen in the oxides is continuously extracted as CO and CO₂ gases, thus almost entirely producing slag. The proportion of titanium oxides is increased after pre-reduction, which is beneficial for the next thermal reduction step. More importantly, the low-valence titanium oxide Ti-HO with dissolved hydrogen is structurally and thermodynamically unstable than TiO₂; the higher the H content, the higher the structural instability, which is more conducive to further deoxidation. This reduces the consumption of reducing agent at the source, correspondingly reducing the amount of slag and providing favorable conditions for subsequent thermal reduction and secondary reduction steps.

[0053] Before implementing step (1), the titanium raw material is first mechanically activated to introduce cracks and defects, thereby increasing the diffusion rate at the solid-solid and gas-solid reaction interfaces. This helps to lower the reduction reaction temperature and maximizes the reduction of TiO2 to low-valent titanium oxide Ti. n O 2n-1 The conversion rate (in order of reaction priority: Ti4O7, Ti3O5, Ti2O3, TiO, etc.).

[0054] There are no special restrictions on the form of mechanical activation, and any method known to those skilled in the art can be used, such as eccentric vibratory mill, planetary ball mill, drum mill, vertical / horizontal ball mill, etc.

[0055] The mechanical activation time is 0.5h to 3h, for example, 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, preferably 1.0h to 2.5h, and more preferably 1.5h to 2.0h.

[0056] The particle size of the mechanically activated high-titanium slag is 80μm to 150μm, for example 80μm, 90μm, 100μm, 110μm, 130μm, 140μm, 150μm, preferably 90μm to 140μm, and more preferably 110μm to 130μm.

[0057] The pre-reduction equipment is not particularly limited and can be any type well known to those skilled in the art, such as an atmosphere sintering furnace, an HDH hydrogenation furnace, a microwave pyrolysis furnace, or a simple resistance furnace.

[0058] The reducing gas is a mixture of H2 and CO, specifically industrial by-product ash hydrogen; the volume fraction of H2 and CO is not less than 95%, the volume ratio of H2 to CO is 1:2 to 2:1, the supply pressure ranges from 0.1 MPa to 5 MPa, and the flow rate is 0.5 to 5 m³ / s. 3 / m 2 •min. The supply of the reducing gas can be either a non-closed continuous supply or a closed intermittent supply.

[0059] The pre-reduction temperature is 1050℃~1150℃, for example, it can be 1050℃, 1070℃, 1090℃, 1110℃, 1130℃, 1150℃, but is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable. Figure 5 The ΔG-T curve of the carbon-titanium oxide reduction reaction shown indicates that, in order to avoid producing TiC hard particles at excessively high temperatures, the reduction temperature should not exceed 1150℃, preferably 1050℃~1130℃, and more preferably 1050℃~1100℃.

[0060] The pre-reduction time is 0.5h to 3h, for example, 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, but is not limited to the values ​​listed above. Other values ​​not listed in the above range are also applicable. Preferably, it is 1.0h to 2.5h, and more preferably, it is 1.5h to 2.0h.

[0061] The conversion rate of the low-cost titanium oxide is 50% to 95%, for example 50%, 60%, 70%, 80% or 95%. The conversion rate should take into account the balance between the degree of conversion and energy consumption and cost, preferably 70% to 95%, and more preferably 80% to 90%.

[0062] Step (2): Calcium-magnesium complex thermal reduction

[0063] The product of step (1) is subjected to calcium-magnesium composite thermal reduction (or "primary reduction"). The reactants include the pre-reduction product, reducing agent, alloy furnace charge and slag-forming agent from step (1).

[0064] The reactants for the calcium-magnesium composite thermal reduction are in the following weight ratio: pre-reduction product: reducing agent: alloy furnace charge: slag-forming agent = 1: 0.45~0.65: 0.1~0.15: 0.15~0.35.

[0065] The pre-reduced product undergoes ball milling treatment, with a particle size of 50μm to 200μm and D50 = 110μm. For example, it can be 80μm, 100μm, 125μm, 150μm, 180μm, or 200μm, preferably 80μm to 180μm, and more preferably 100μm to 125μm.

[0066] The reducing agent is a calcium-magnesium alloy, and any national standard grade well known to those skilled in the art can be used. Preferably, the weight ratio of Mg to Ca is Mg:Ca = 50%–80%: 20%–50%. The magnesium-calcium-magnesium alloy has no specific shape, with a maximum size range of 0.5mm–5mm, for example, 0.5mm, 1mm, 2mm, 3mm, 4mm, or 5mm, preferably 2mm–4mm.

[0067] The alloy furnace charge is scrap or recycled material containing Fe, Cr, and Mn as the main elements, such as scrap iron, scrap stainless steel, manganese steel, and / or one or more of micro-carbon ferrochrome and low-carbon ferromanganese master alloys.

[0068] The scrap stainless steel is common ferritic or martensitic stainless steel (400 series) with Fe and Cr as the main elements, such as SUS436L, SUS410L, and SUS430. The alloy charge contains ≤0.03% carbon by weight, as well as unavoidable trace elements such as Ni, Si, Mo, and C, but the content is very low and the amount added to the charge is small. Therefore, the influence of other non-main elements in the recycled material is negligible.

[0069] The waste stainless steel is cut into blocks without a specific shape, and the maximum size range is 0.5mm to 5mm. For example, it can be 0.5mm, 1mm, 2mm, 3mm, 4mm, or 5mm, preferably 2mm to 4mm.

[0070] There are no special limitations on the ferrochrome alloy used, and any alloy well known to those skilled in the art can be used, such as, but not limited to, any one or at least a combination of two of the micro-carbon ferrochrome FeCr69C 0.25-0.5 and FeCr69C 0.03-0.15 specified in industry standards. The ferrochrome alloy has no specific shape, and its maximum size ranges from 10mm to 150mm, for example, it can be 10mm, 20mm, 50mm, 100mm, 120mm, or 150mm, preferably 10mm to 50mm.

[0071] There are no special limitations on the ferromanganese alloy used, and any alloy well known to those skilled in the art can be used, such as, but not limited to, any one or at least a combination of two of the low-carbon ferromanganese FeMn88C0.2 and FeMn84C0.4 specified in industry standards. The micro-carbon ferromanganese alloy has no specific shape, and the maximum size range is 10mm to 150mm, for example, it can be 10mm, 20mm, 50mm, 100mm, 120mm, or 150mm, preferably 10mm to 50mm.

[0072] The slag-forming agent is based on CaO and forms a binary slag with CaF2. CaO-CaF2 binary slag is a commonly used slag-forming agent in the industry. CaO acts as a flux, forming a low-melting-point, low-viscosity slag with Al2O3. Adding CaF2 can promote gold slag separation. The mass fraction ratio of the CaO and CaF2 slag-forming agent is CaO:CaF2 = 70%–90%:30%–10%, preferably 75%–85%:25%–15%. The particle size range of the slag-forming agent is 0.2mm–2mm, D50 = 1.0mm, for example, it can be 0.2mm, 0.5mm, 1.0mm, 1.2mm, 1.5mm, 1.8mm, or 2mm, preferably 0.5mm–1.5mm, and more preferably 0.8mm–1.2mm.

[0073] The thermal reduction temperature of the calcium-magnesium composite is 1400℃~1600℃, for example 1400℃, 1450℃, 1500℃, 1550℃ or 1600℃, but is not limited to the values ​​listed above. Other values ​​not listed in the above range are also applicable, preferably 1500℃~1550℃.

[0074] The thermal reduction time of the calcium-magnesium composite is 0.1h to 0.5h, for example, 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, preferably 0.2h to 0.4h, but not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0075] The form of the calcium-magnesium composite thermal reduction device is not particularly limited, and any electric heating furnace well known to those skilled in the art can be used, which should be understood as an industrial furnace with electric heating and heat preservation functions. For example, a DC electric arc furnace, an AC electric arc furnace, an electromagnetic induction heating furnace, or a (vacuum, hot pressing) sintering furnace, an electron beam or plasma heating furnace, or a simple resistance furnace. A DC electric arc furnace is preferred.

[0076] The reduction furnace used in this embodiment is a DC electric arc furnace, with the structure as follows: Figure 2As shown, the furnace includes a furnace body 101, and a gold outlet 102, a slag outlet 103, a hollow electrode 104, a charging port 105, and a bottom electrode 106 disposed on the furnace body 101. The gold outlet 102 and the slag outlet 103 are located on the side wall of the furnace body 101. The gold outlet 102 serves as the melt outlet and is vertically lower than the slag outlet 103. The hollow electrode 104 is hollow inside, with the charging port 105 at its top. The hollow electrode serves as both a plasma arc initiation device, providing heat to the molten pool, and a charging device. Furthermore, the DC hollow electrode features no yielding effect, a long arc, strong molten pool stirring, and low heat loss, and allows for rapid adjustment of the input current and reduction temperature. The molten pool level is higher than the gold outlet, and the melt is discharged from the gold outlet, while the uppermost slag is removed from the slag outlet. After removing most of the slag, a primary melt is obtained, achieving the effect of gold-slag separation. The structure can continuously feed, reduce, and remove slag, enabling continuous or semi-continuous production.

[0077] Step (3): Secondary reduction and refining

[0078] The primary melt obtained in step (2) is introduced into crucible 202 in a vacuum induction furnace, and then deeply deoxidized with a calcium-magnesium alloy that has stronger reducing properties. A slag-forming agent is added, and the mixture is kept warm and refined to obtain a secondary melt with a composition close to the target.

[0079] Vacuum induction furnace, such as Figure 3 As shown, the system includes a melting chamber 201 and a crucible 202 disposed within the melting chamber 201. An induction coil 203 is installed outside the crucible 202 to heat it. A feeding hopper 204 is connected to the top of the melting chamber 201, and a feeding vacuum valve 205 is installed between the feeding hopper 204 and the melting chamber 201. An observation hole 206 and a U-shaped bell jar 207 are also provided on the top of the melting chamber 201. The melting chamber 201 includes a buffer bag 208 and an intermediate ladle 210. The buffer bag 208 and the intermediate ladle 210... 10 are connected together, and a filter screen 209 is provided at the overlapping position; the intermediate ladle 210 is in frictional contact with the water-cooled copper roller 211, and the secondary melt flows to the water-cooled copper roller 211 through the buffer ladle 208 and the intermediate ladle 210; the water-cooled copper roller 211 rapidly cools the secondary melt into a quick-solidifying thin strip 212; the quick-solidifying thin strip 212 is peeled off the copper roller and falls, and is crushed into small quick-solidifying flakes 214 by the crushing device 213; the quick-solidifying flakes 214 are collected in the receiving bucket 215 below the melting chamber 201 for secondary cooling.

[0080] The vacuum induction furnace is pre-evacuated, then cleaned with inert gas, and the operation is repeated 1 to 2 times. Finally, inert protective gas is introduced to prevent the volatilization of elements with high saturated vapor pressure. As one of the means to further reduce costs, a layer of pure titanium residue not exceeding 20% ​​of the weight of the primary melt is evenly distributed at the bottom of the crucible 202 beforehand, and the primary melt is introduced into the crucible 202 by tilting upward pouring.

[0081] The reactants in the secondary reduction refining process include titanium residue, with a weight ratio of primary melt: titanium residue: calcium-magnesium alloy: slag-forming agent = 1: 0~0.2: 0.05~0.15: 0.1~0.2.

[0082] The temperature for the secondary reduction is 1400℃~1600℃, for example 1400℃, 1450℃, 1500℃, 1500℃, 1550℃ or 1600℃, but is not limited to the values ​​listed above. Other values ​​not listed in the above range are also applicable, with 1500℃~1550℃ being the preferred value.

[0083] The secondary refining and heat preservation time is 0.1h to 0.5h, for example, 0.5h, 0.1h, 0.2h, 0.3h, 0.4h, but not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable. Preferably, it is 0.2h to 0.4h. The refining time should not be too long, and it is even more preferably 0.2h to 0.3h.

[0084] There are no special restrictions on the calcium-magnesium alloy used; any alloy well-known to those skilled in the art can be employed, with a preferred composition of 50%–80% Mg and 50%–20% Ca. According to the ΔG-T oxygen potential diagram, the magnesium and calcium lines are located lower than those of aluminum. The larger the negative ΔG value or the smaller the oxygen potential, the more stable the oxide, meaning it has a stronger ability to combine with oxygen. Calcium and magnesium have higher reducing properties than pure aluminum, stronger deoxidizing capabilities, and do not form alloys with titanium, thus also reducing slag viscosity and melting point.

[0085] The calcium-magnesium alloy is fed in as irregularly shaped fragments with a particle size ranging from 30mm to 120mm. Unlike existing methods that use pure calcium and pure magnesium blown in with steam, this calcium-magnesium alloy is added in multiple batches in small quantities. To prevent excessively high reduction temperatures leading to boiling, splashing, burn-off, and severe volatilization, it is pressed into the furnace bottom using high-temperature resistant tools such as inverted U-shaped bell jars made of alumina or molybdenum. The calcium-magnesium alloy melts inside the molten metal, and the bubbles generated during the reaction rise to the surface, carrying away some of the slag.

[0086] The secondary reduction refining process is not particularly limited and can employ any electrically heated furnace well-known to those skilled in the art. This should be understood as an industrial furnace with electric heating and heat preservation functions in a vacuum environment. Examples include vacuum induction furnaces, vacuum electroslag furnaces, vacuum consumable remelting furnaces, vacuum shell-forming furnaces, vacuum electromagnetic levitation furnaces, and simple vacuum resistance furnaces or atmosphere resistance furnaces, with a vacuum induction furnace being the preferred option.

[0087] Step (3) also includes titanium scrap. To utilize this pure and economical titanium raw material, titanium scrap is preferred. The titanium scrap is machining chips and scraps of industrial pure titanium material, with few impurity elements, oxygen content ≤0.5wt.%, and relatively cheap price. It should be cleaned, dried and magnetically separated before use. The amount added should not exceed 20% of the weight of a single melt. The addition of titanium scrap is not necessary. It can be omitted if there is no stock or insufficient stock.

[0088] The size range of the titanium residue is 0.5mm to 5mm, for example, it can be 0.5mm, 1mm, 2mm, 3mm, 4mm, or 5mm, preferably 2mm to 4mm.

[0089] The titanium residue is added as follows: a layer of titanium residue is pre-distributed evenly at the bottom of the crucible, and the melt is introduced into the crucible through an inclined top pouring method via an intermediate ladle. Then the melt melts and mixes the titanium residue evenly.

[0090] Step (4): Online component detection and fine-tuning

[0091] Alloy furnace charge is used to adjust the alloy composition to meet the target range. This includes pure metals and commonly used intermediate alloy furnace charge, with one or at least two added based on composition analysis results. The alloy furnace charge is used for fine-tuning the composition and is added in small quantities; preferably, it consists of scraps of pure titanium, iron, chromium, manganese, or Fe-80%V alloy, with a purity preferably between 99.9% and 99.99%.

[0092] The alloy charge is pre-stored in the vacuum charging chamber 205. The charging vacuum valve 205 is opened and the charge is added to the melting chamber 201 in batches in small quantities. The charge is pressed into the bottom of the crucible 202 through the inverted U-shaped bell jar 207 made of alumina material, so as to accelerate the uniform mixing of alloy elements and melt and also to stir the melt.

[0093] Step (5): Vacuum casting

[0094] The vacuum casting is carried out in a vacuum, and the casting temperature is 1400℃~1550℃ depending on the alloy composition and liquidus temperature. The casting process is completed within 5~10 minutes from the start to the end.

[0095] like Figure 3 As shown, in one embodiment, the secondary melt is poured from the upper furnace opening through the buffer ladle 208 and the intermediate ladle 209 onto the rotating water-cooled copper roller 211 via a tilting furnace body. The secondary melt rapidly solidifies on the surface of the water-cooled copper roller 211 into a rapidly solidified thin strip 212. The rapidly solidified thin strip 212 is peeled off from the surface of the water-cooled copper roller 211 and forms a rapidly solidified sheet 214 after passing through the crushing device 213. The rapidly solidified sheet 214 falls into the receiving bucket 215 and is accelerated to room temperature under water cooling. Then, after subsequent hydrogen explosion crushing, powdering and annealing, hydrogen storage alloy powder is obtained.

[0096] As another implementation method, it can also be cast into an ingot. The molten material is poured into a mold, and after the mold is opened, a square or V-shaped thin plate ingot is obtained. The composition and structure of the ingot are different from those of the rapidly solidified flakes, requiring long-term high-temperature homogenizing annealing. However, the composition and structure of the rapidly solidified strips (flakes) are uniform, so the high-temperature homogenizing annealing process can be omitted.

[0097] The following is a detailed description with reference to specific embodiments:

[0098] The list of material parameters processed in this embodiment of the invention is as follows:

[0099] Table 1 Chemical composition of titanium raw materials (mass percentage)

[0100] type <![CDATA[TiO2]]> TFe MgO CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MnO TZ92-2 High Titanium Slag ≥92 3.50 2.56 0.57 1.98 2.09 2.50 Titanium dioxide 92～98 / / / / 0.2～0.4 /

[0101] Table 2-1 Chemical composition range of alloy furnace charge containing Fe, Cr, Mn, and V (mass percentage %)

[0102] type Fe Cr Mn Ni Mo V Si C Used SUS 436L margin 16～19 ≤1 ≤0.6 ≤1.5 / ＜1 ≤0.025 FeCr69C0.03 margin 63～75 / / / / / ≤0.03 FeMn88C0.2 margin / 85～92 / / / ＜1 ≤0.2 FeV80 margin / ≤1.5 / / 78～82 ≤1.5 ≤0.15

[0103] Table 2-2 Chemical composition range of Ti-containing alloy charge (mass percentage %)

[0104] type Ti Fe Cr Mn Si O Titanium residue TA1-TA4 margin ≤0.50 / / / ≤0.5 Titanium sponge MHT-200 ≥98.5 ≤0.40 / ≤0.08 ≤0.06 ≤0.3

[0105] Example 1:

[0106] The hydrogen storage alloy is designed with TiCr as its composition. 1.6-x Mn 0.1 Fe x (atomic ratio at.%, x = 0.1 to 1.0).

[0107] Step (1) Mechanical activation-pre-reduction

[0108] The TZ92-2 high-titanium slag was mechanically activated in a ball mill for 2.0 h, resulting in a particle size of 110 μm–130 μm. The activated high-titanium slag was then reduced in hydrogen at a pre-reduction temperature of 1100℃–1140℃ for 2.0 h, ultimately converting high-valence TiO2 into low-valence titanium oxide TiO.

[0109] Step (2) Calcium-magnesium composite thermal reduction

[0110] The reactants for the calcium-magnesium composite thermal reduction are a mixture of various furnace materials, with a weight ratio of pre-reduced titanium raw material: reducing agent: alloy furnace material: slag-forming agent = 1:0.5:0.08:0.2. After pre-reduction, the average particle size of the titanium raw material is <120μm, and the particle size range of the calcium-magnesium alloy is <5mm. The furnace material consists of recycled SUS436L scrap, ferrochrome alloy, and ferromanganese alloy, with a particle size not exceeding 5mm. The slag-forming agent is used at a mass ratio of CaO:CaF2 = 75%:25%, with a particle size <1mm. The calcium-magnesium composite thermal reduction is carried out in a DC electric arc furnace at a reduction temperature of 1500℃~1600℃ for 0.25h. The DC electric arc furnace can be continuously fed from the top, with slag discharged from the upper opening of the side wall and primary melt extracted from the lower opening, achieving semi-continuous production.

[0111] Step (3) Secondary reduction and refining

[0112] The primary molten metal is introduced into a vacuum induction furnace, and alloy charge, reducing agent, and slagging agent are added for secondary reduction refining. The secondary reduction temperature is 1550℃~1580℃, and the reduction time is 0.2h. The slagging agent has a mass ratio of CaO:CaF2 of 75%:25%. The reducing agent is MgCa30 alloy lumps with an average particle size not exceeding 50mm.

[0113] Step (4) Online component detection and fine-tuning

[0114] After the secondary reduction refining is completed, the chemical composition of the melt is tested. Based on the test results, alloy charge is added to the melt to fine-tune the composition to the target range. The alloy charge consists of pure titanium, pure iron, pure chromium, and electrolytic manganese, with an average particle size of no more than 5 mm.

[0115] Step (5) Vacuum casting

[0116] After the secondary reduction and refining process is qualified, the material is cast into a rapid solidification sheet under vacuum at a temperature of 1520℃~1550℃. After cooling to room temperature, the material is removed to obtain a rapid solidification sheet of hydrogen storage alloy. Then, after multiple subsequent processing stages, titanium-based hydrogen storage alloy powder is obtained.

[0117] Table 3 TiCr 1.6-x Mn 0.15 Fe x (x = 0.1~1.0) Alloy composition and properties:

[0118]

[0119]

[0120] In this embodiment 1, the nominal composition TiCr is used. 1.6-x Mn 0.15 Fe xWith a (x = 0.1~1.0) ratio, the actual composition is close to the nominal composition. The phase structure is a C14 Laves single phase. The Mn content was measured to be 0.14 at.%-0.16 at.%. After adjusting the Fe and Cr contents, the room temperature plateau pressure of the PCT curve gradually increased with increasing Fe content, while the effective hydrogen storage density gradually decreased from 1.69 wt.% to 1.4 wt.%.

[0121] Example 2:

[0122] The hydrogen storage alloy is designed with a TiFe composition. 0.8-0.9 Mn 0.15 V x (atomic ratio at.%, x = 0 to 0.15).

[0123] Example 2's alloy composition contains a maximum of 0.15 at.% V, therefore a certain proportion of FeV80 alloy (210 yuan / kg) was added to the alloy charge. Since metallic V is expensive (2500 yuan / kg), its use should be avoided. Other process steps are basically the same as in Example 1, only the alloy composition ratio and main and auxiliary materials differ, and will not be repeated here.

[0124] Table 4 TiFe 0.8-0.9 Mn 0.15 V x (x=0~0.15) Alloy composition and properties:

[0125]

[0126]

[0127] In this embodiment 2, according to the nominal component Fe 0.8-0.9 Mn 0.15 V x (x = 0~0.15) The actual composition is close to the nominal composition. The phase structure is a single CsCl phase. The Ti-Fe based alloy has two distinct hydrogen absorption and desorption plateaus. After modification with V element, the pressure of both the first and second plateaus is significantly reduced, and the maximum and effective hydrogen storage densities are significantly increased.

[0128] Example 3:

[0129] The hydrogen storage alloy is designed with a Ti composition. 0.9 Zr 0.1 Mn 0.2 Cr 1.8-x Fe x (atomic ratio at.%, x = 0 to 0.5).

[0130] In Example 3, a certain proportion of sponge zirconium (Zr) was added to the alloy charge at a ratio of 0.1 at.%. Other process steps were basically the same as in Example 1, and will not be repeated here.

[0131] Table 5 Ti 0.9 Zr 0.1 Mn 0.2 Cr 1.8-x Fe x (x=0~0.5) Alloy composition and properties:

[0132]

[0133] In this embodiment, the nominal composition of alloy 3 is Ti. 0.9 Zr 0.1 Mn 0.2 Cr 1.8-x Fe x (x = 0-0.5), the phase structure is a single-phase C14Laves. Adding Zr increases the alloy's cell volume and intercellular spacing due to the larger atomic radius of Zr compared to Ti, affecting the hydrogen absorption / desorption equilibrium pressure. The hydrogen absorption / desorption plateau is lower than that of Zr-free TiCr. 1.6-x Mn 0.1 Fe x The alloy content decreased significantly.

[0134] Examples 4-6:

[0135] The titanium raw material used in Examples 4-6 is titanium dioxide, with a TiO2 content of 92-98 wt.%. Examples 4-6 correspond to Examples 1-3, respectively, with the same operating steps and process parameters. High-titanium slag is an intermediate raw material for preparing titanium dioxide. After acid and alkali leaching, MgO, CaO, FeO, MnO, and SiO2 are removed, resulting in a higher TiO2 content in the titanium dioxide. However, high-density elements such as Fe and Mn are also removed, which is not conducive to the separation of the titanium dioxide from the slag. Additional addition of Fe and Mn is required for alloying. On the other hand, due to the low SiO2 content in titanium dioxide, the Si content in the alloy is also low. Si has both advantages and disadvantages in its effect on hydrogen storage performance. The disadvantage is that Si reduces the hydrogen storage density, increasing the plateau slope; the advantage is that it can improve the activation of the alloy and increase the hydrogen absorption and desorption rate. However, compared with high-titanium slag, the change in hydrogen storage density is less than 5%, and the changes in activation and hydrogen absorption rate are not significant. However, in terms of raw material prices, titanium dioxide is 2,000-5,000 yuan / ton more expensive than high-titanium slag, making it less cost-effective. Therefore, low-Si high-titanium slag is preferred as the raw material.

[0136] Table 6 Comparison of the effects of titanium raw materials in Examples 1-3 and Examples 4-6:

[0137]

[0138] Comparative Example 1:

[0139] The process flow and operation steps of Comparative Example 1 are basically the same as those of Example 1, and will not be repeated here. In this example, step (2) is changed to aluminothermic reduction, and aluminum powder and / or aluminum granules are used as reducing agents instead of calcium-magnesium alloy. Since aluminothermic reduction produces calcium aluminate slag (Al2O3-CaO), which has a high melting point and high viscosity, in order to ensure the fluidity of the slag, the reduction temperature must be increased to 1800℃~2000℃, and an appropriate amount of CaF2 must be added to reduce the viscosity of the slag. This makes it very difficult to separate the gold slag, resulting in an excessively high content of inclusions in the alloy (≤10wt.%). In addition, since the reducing power of aluminum is weaker than that of calcium-magnesium alloy, the slag also contains a certain amount of suboxide Ti. n O 2n-1 This reduces the yield of metallic titanium. In step (3), the reducing agent is replaced with aluminum powder and / or aluminum granules, and the secondary reduction temperature is 1700℃~1900℃. The main and auxiliary materials and proportions of other operating steps are the same as in Example 1.

[0140] The nominal composition of the alloy in Comparative Example 1 is TiCr 1.6-x Mn 0.1 Fe x (x = 0.1-1.0) The actual composition and properties are shown in Table 6.

[0141] Table 7 TiCr 1.6-x Mn 0.1 Fe x (x = 0.1 ~ 1.0) Actual composition and properties of the alloy:

[0142]

[0143] Analysis of the data in Table 7 shows that the aluminothermic reduction process forms a difficult-to-separate slag, with some titanium oxides remaining unreduced and entering the slag, resulting in an inclusion content close to 10 wt.%. The alloy phase obtained from aluminothermic reduction is not a single Laves phase; due to the alloying of Al and Ti, a non-hydrogen-absorbing Ti-Al phase is formed, leading to a decrease in hydrogen absorption and desorption density. Furthermore, the influence of Al on titanium-based hydrogen storage alloys has been extensively studied, and the mechanism of its influence on the hydrogen storage performance is relatively clear. Al can improve alloy kinetics to some extent, but excessive Al will increase the hydrogen absorption and desorption equilibrium pressure, increase or eliminate the slope of the PCT plateau, thereby inhibiting the formation of γ-hydrides and causing a sharp decrease in the hydrogen capacity of the material.

[0144] Comparative Example 2:

[0145] The comparative operation steps are basically the same as those in Example 2, and will not be repeated here. Step (2) is changed to aluminothermic reduction, with aluminum powder and / or aluminum granules replacing the calcium-magnesium alloy as the reducing agent. Since aluminothermic reduction produces calcium aluminate slag (Al2O3-CaO), which has a high melting point and high viscosity, the reduction temperature must be increased to 1800℃~2000℃. In step (3), the reducing agent is also changed to aluminum powder and / or aluminum granules, with a secondary reduction temperature of 1700℃~1900℃. Other operation steps, main and auxiliary materials, and proportions are the same as in Example 1.

[0146] The nominal alloy composition of Comparative Example 2 is TiFe 0.8-0.9 Mn 0.15 V x (x = 0 to 0.15) The actual composition and properties are shown in Table 8.

[0147] Table 8 shows the actual composition and properties of the alloy in Comparative Example 2:

[0148]

[0149] In the aluminothermic reduction process of Comparative Example 2, the high-viscosity, high-melting-point slag produced made gold slag separation difficult, resulting in an inclusion content in the alloy exceeding 10 wt.%. Incomplete reduction of vanadium-titanium oxides led to a decrease in Ti and V content in the alloy, especially a significant decrease in V. Al participated in alloying and was present in a relatively high amount, resulting in a large difference between the actual and nominal compositions. Testing revealed an actual Al weight ratio of 5.5–6.1 wt%. During the aluminothermic reduction process, Al alloyed with Ti to form α2-Ti3Al and / or γ-TiAl phases. Since the Ti-Al phase is a non-hydrogen-absorbing phase, the effective hydrogen storage density of the alloy was significantly reduced, decreasing by 48%–78% compared to Example 2. Furthermore, research indicates that Al can increase the hydrogen absorption / desorption equilibrium pressure of the alloy, abnormally increase or eliminate the plateau slope, thereby inhibiting the formation of γ-hydrides and causing a sharp decrease in the material's hydrogen capacity.

[0150] Comparative Example 3:

[0151] To compare the effects of different preparation methods on the PCT properties of the alloy, Comparative Example 3 was set up. The alloy composition of Comparative Example 3 was the same as that of Example 3, but Comparative Example 3 used conventional vacuum electric arc furnace melting. The PCT curves of the alloys prepared by the two different methods at 25°C were compared (e.g., Figure 7The differences are significant. The effective hydrogen storage density of Example 3 is slightly lower than that of Comparative Example 3, while the plateau pressure of Example 3 is slightly higher than that of Comparative Example 3. The initial activation of Example 3 is the same as that of Comparative Example 3, but the number of activation cycles in Example 3 is significantly less than that in Comparative Example 3. Furthermore, the effective hydrogen storage density of Example 3 after the third activation cycle is greater than 80% of the maximum hydrogen storage density, while the number of activation cycles in Comparative Example 3 is more than 10, and the effective hydrogen storage density after the third activation cycle is only 60% of the maximum hydrogen storage density. The reason for the significant difference in hydrogen storage performance between the alloys prepared by the two methods may be that the metallothermic reduction method used in Example 3 is conducive to the activation of the alloy, and the residual oxygen and oxide particles in the alloy affect the hydrogen absorption kinetics and the characteristics of the PCT curve.

[0152] Table 9. Effects of two different preparation methods on alloy properties

[0153]

[0154] By comparing Example 3 and Comparative Example 3, although the preparation methods are different, the hydrogen storage densities of the alloys prepared by the two methods are basically similar after the initial activation treatment. The conventional method uses expensive, high-purity raw materials, resulting in a slight improvement in hydrogen storage performance; however, in terms of raw material costs, it is estimated that the production cost of Example 3 is reduced by more than 40%, meaning that the new method of directly preparing titanium-based hydrogen storage alloys from titanium dioxide using the calcium-magnesium composite thermal reduction method can completely replace the conventional method.

[0155] Comparative Example 4:

[0156] The alloying methods for high-density elements such as Fe, Cr, and Mn in the alloys of Comparative Examples C4-1, C4-2, and C4-3 differ. In the two hot reduction processes of steps (2) and (3), alloy charge containing Fe, Cr, and Mn is not added, but is added in step (4) after refining. Since the melt from hot reduction and refining is almost pure titanium, the melt density (4.51 g / cm³) is... 3 ) with a slag density of 2-3 g / cm³ 3 The differences are not significant. Due to the similar density of the gold slag, the slag cannot float, making gold slag separation difficult. The slag volume fraction in the alloy reaches up to 15%, and the oxygen content in the alloy is as high as close to 2.0 wt%. However, in Examples 1-3, the alloying charge is added in advance during the primary reduction stage, which not only helps with gold slag separation but also achieves preliminary alloying. The advantage of these examples is that they combine the two processes of gold slag separation and alloying.

[0157] Table 10 Effect of alloying charge addition method on alloy properties

[0158]

[0159]

[0160] Literature review revealed that the effect of oxygen content on hydrogen storage performance is complex. Generally, high oxygen content reduces hydrogen storage density, but an appropriate amount of oxygen not only has little effect on reducing hydrogen storage density but can also improve the hydrogen absorption kinetics of the alloy and reduce the difficulty of alloy activation. Figure 6 As shown, oxygen in the alloy exists in the form of oxides such as Ti3Fe3O, Fe2O3, TiO2, V2O5, and Ti4(FeMn)2O. This not only promotes hydrogen dissociation on the surface but also forms microcracks on the alloy surface and grain boundaries. During hydrogen absorption and desorption, more cracks and fresh surfaces are generated, providing diffusion channels for hydrogen atoms and making alloy activation easier or even unnecessary. For example, some literature has shown that introducing 0.78 wt.% oxygen into the alloy resulted in an effective hydrogen storage capacity reduction from 1.7 wt.% to 1.6 wt.% without activation treatment (Davids, MW et al., International Journal of Hydrogen Energy 46.25(2021):13658-13663). Therefore, to improve the initial activation conditions of the alloy and accept a smaller loss in hydrogen storage capacity, a suitable amount of oxygen or intentional introduction of oxygen (<1 wt.%) is permissible. During the research and development process, the inventors unexpectedly discovered that the metallothermic reduction method has limited deoxidation capacity (lower limit range of 0.2wt.% to 1wt.%), which is basically equivalent to the oxygen content required to improve the activity of the alloy. Therefore, the preparation of titanium-based hydrogen storage alloys by metallothermic reduction is very feasible and suitable.

[0161] The basic principles, preparation process, and advantages of the present invention have been described above with reference to specific embodiments and accompanying drawings. However, the present invention is not limited to the details of the above embodiments. Those skilled in the art should understand that any transformations, modifications, and combinations of the present invention, as well as equivalent substitutions and additions to the main and auxiliary materials and equipment components of the present invention, without departing from the principles and spirit of the present invention, fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-cost titanium-based hydrogen storage alloy, characterized in that, Includes the following steps: (1) Mechanical activation treatment of titanium raw materials, followed by pre-reduction treatment of activated titanium raw materials with carbon powder under a reducing atmosphere to reduce high-valence TiO2 to low-valence titanium oxide Ti. n O 2n-1 Where n = 4, 3, 2 or 1, the pre-reduction product is obtained; (2) After crushing the pre-reduced product obtained in step (1), calcium-magnesium composite thermal reduction is carried out in the reduction furnace. Alloy charge, reducing agent, and slag-forming agent are added. After the reduction is completed, the melt is released once at the bottom of the reduction furnace, and the slag floats on the upper layer and remains in the furnace for separation. The mass ratio is: pre-reduced product in step (1): reducing agent: alloy charge: slag-forming agent = 1: 0.45~0.65: 0.1~0.15: 0.15~0.

35. The reducing agent is a calcium-magnesium alloy with a mass ratio of Mg:Ca = 50%~80%: 20%~50%. (3) The primary melt obtained in step (2) is introduced into a vacuum induction furnace for secondary reduction refining, kept warm and stirred, further purified and deoxidized to obtain a secondary melt with a composition close to the target; the reactants are a mixture of primary melt, titanium residue, alloy furnace charge, reducing agent and slag-forming agent; (4) Component detection online, sample and detect components online and make fine adjustments to the components to meet the target component range; (5) Vacuum casting: the melt is rapidly solidified into a rapidly solidified strip or sheet, which is then crushed, powdered and annealed to obtain the final product, titanium-based hydrogen storage alloy powder. The titanium raw material mentioned in step (1) is a high-titanium slag smelted in an electric furnace with high calcium and magnesium impurities. The titanium raw material is activated by ball milling and has a particle size of 50-200 μm and D50 = 100 μm-110 μm. The reducing agent in step (2) has a particle size range of 0.5 mm to 5 mm; The alloy furnace charge is one or a combination of at least two of the following: scrap stainless steel, ferrochrome master alloy, and ferromanganese master alloy, with Fe, Cr, and Mn as the main elements, and a maximum particle size range of 0.5 mm to 5 mm; the slag-forming agent has a particle size range of 0.2 mm to 2 mm and a D50 of 1.0 mm. The alloy furnace charge also includes FeV80 alloy; The reduction furnace described in step (2) is a DC electric arc furnace. The side wall of the reduction furnace is provided with a slag outlet and a melt outlet. The height of the slag outlet is higher than that of the melt outlet. The reactants in the secondary reduction refining step (3) are in the following mass ratio: primary melt: titanium residue: reducing agent: slag-forming agent = 1: 0~0.2: 0.05~0.15: 0.1~0.

15. The reducing agent in the secondary reduction refining reaction is the same as that in step (2).

2. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, The high-titanium slag mentioned in step (1) has a TiO2 content of 85% to 92% and a CaO+MgO content of 3.5% to 5%.

3. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, Step (1) The reducing atmosphere is a mixture of H2 and CO, with a volume ratio of H2 to CO of 1:2 to 2:

1. The gas supply pressure ranges from 0.2 MPa to 5 MPa, and the flow rate is 0.5 to 5 m³ / s. 3 / m 2 •min; the carbon powder is selected from any one or at least two of coke, activated carbon, and graphite; the pre-reduction temperature is 1050℃~1150℃, and the reduction time is 0.5h~3h.

4. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, The slag-forming agent mentioned in step (2) is a CaO-CaF2 binary slag with a mass ratio of CaO:CaF2 = 70%~90%:30%~10%.

5. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, The calcium-magnesium composite thermal reduction temperature in step (2) is 1400℃~1600℃, and the time is 0.1h~0.5h.

6. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, In step (3), the maximum particle size range of the reducing agent in the secondary reduction refining reaction is 0.5 mm to 5 mm; the temperature of the secondary reduction refining is 1400℃ to 1600℃; and the holding time of the secondary reduction refining is 0.1 h to 0.5 h.

7. The method for preparing a low-cost titanium-based hydrogen storage alloy according to claim 1, characterized in that, Step (5) The melt refined by the secondary reduction in step (4) is poured into a water-cooled copper roller under vacuum and quickly solidified to obtain a rapidly solidified strip or sheet. Then, it is subjected to mechanical crushing, hydrogen explosion crushing, powdering and annealing to obtain hydrogen storage alloy powder.

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