A liquid flow recasting method for preparing titanium steel laminated composite material by vacuum induction levitation melting

Abstract

The application discloses a liquid flow re-casting method for preparing a titanium-steel layered composite material by vacuum induction suspension melting, and comprises the following steps: performing surface cleaning on a steel base plate, and sequentially forming a diffusion barrier layer and a wetting buffer layer on a surface to be compounded of the steel base plate; performing vacuum induction suspension melting on a titanium or titanium alloy raw material in a melting cavity to obtain a liquid titanium base melt; placing the steel base plate in a re-casting cavity for preheating, introducing the liquid titanium base melt from the melting cavity into the re-casting cavity, and pouring and spreading the liquid titanium base melt on the surface to be compounded of the steel base plate in a preheated state; and cooling and solidifying the compounded plate to obtain a titanium-steel layered composite plate. The liquid flow re-casting method for preparing a titanium-steel layered composite material by vacuum induction suspension melting can effectively inhibit the formation of a brittle phase layer of the titanium-steel layered composite material, and can prepare a high-quality titanium-steel composite plate with a uniform thickness of an interface transition layer and a dense interior.

Description

Technical Field

[0001] This application belongs to the field of metal composite material preparation technology, specifically, it relates to a liquid flow recasting method for preparing titanium-steel layered composite materials using vacuum induction suspension melting. Background Technology

[0002] Titanium and titanium alloys are characterized by corrosion resistance and high specific strength, while steel is characterized by low cost, good strength and rigidity. By combining titanium / titanium alloys with steel to form layered composite plates, material costs can be reduced while maintaining both corrosion resistance and load-bearing capacity, thus finding wide application in fields such as chemical containers and marine engineering.

[0003] Currently, the main methods for preparing titanium-steel layered composite materials include explosive bonding, rolling bonding, and casting bonding. Among these, casting bonding, especially liquid-solid bonding, has attracted much attention due to its high production efficiency and good interfacial bonding strength. However, titanium and iron are highly reactive elements, and under high-temperature liquid contact conditions, they readily undergo diffusion reactions to form various brittle intermetallic compounds, such as FeTi and Fe2Ti. The presence of these brittle phase layers not only leads to a significant decrease in the bonding strength of the composite interface and makes delamination easy, but also becomes a weak point for crack initiation and propagation, seriously affecting the mechanical properties and reliability of titanium-steel composite materials.

[0004] To suppress the formation of brittle phases, existing technologies often employ methods such as adding an interlayer or controlling the cooling rate. For example, copper foil, nickel foil, or titanium-based coatings are used as interlayers. However, copper interlayers may introduce oxide impurities under high temperature and residual oxygen conditions; traditional nickel interlayers or titanium-based coatings often struggle to effectively prevent the rapid diffusion of elements in a short time during the liquid-solid composite process where liquid titanium is in direct contact with the steel substrate. Furthermore, existing equipment has limited temperature and cooling rate control capabilities, making it difficult to meet the precise temperature difference control and stability requirements of titanium-steel liquid-solid composites.

[0005] Furthermore, a series of process challenges exist in actual production, especially when using a combination of vacuum induction levitation melting and liquid flow casting. The melt from induction levitation melting needs to be transferred and coated within a very short time. Even minor leaks, splashes, slag inclusions, or temperature fluctuations can lead to defects such as incomplete filling and interface slag inclusions, further exacerbating the problem of brittle phases at the interface. Additionally, when the steel substrate or mold is close to the levitation melting coil, the magnetic permeability of the steel may cause electromagnetic field distortion in the melting zone, resulting in poor melt temperature uniformity and further affecting the stability of the composite quality.

[0006] In summary, effectively controlling interfacial reactions, inhibiting the formation of the FeTi / Fe2Ti brittle phase layer, and improving batch stability are key technical issues that urgently need to be addressed in the current field of titanium-steel layered composite plate preparation technology. Summary of the Invention

[0007] The technical effect to be achieved by this application is to provide a liquid flow recasting method for preparing titanium-steel layered composite materials using vacuum induction suspension melting, thereby solving the problems existing in the prior art.

[0008] To achieve the above-mentioned technical effects, this application provides a liquid-flow recasting method for preparing titanium-steel layered composite materials using vacuum induction suspension melting, comprising the following steps: S1: Clean the surface of the steel substrate plate, and sequentially form a diffusion barrier layer and a wetting buffer layer on the surface of the steel substrate plate to be laminated; S2: Vacuum induction levitation melting of titanium or titanium alloy raw materials is carried out in the melting chamber to obtain liquid titanium-based melt; S3: The steel substrate plate is placed in the recasting chamber for preheating, and the liquid titanium-based melt is introduced from the melting chamber into the recasting chamber, and poured and spread on the surface of the steel substrate plate to be composited in the preheated state. S4: Cool and solidify the composite plate to obtain a titanium-steel layered composite plate.

[0009] As a preferred option, the diffusion barrier layer is an Nb, V, or Ta metal layer with a thickness of 10-40 μm.

[0010] As a preferred option, the wetting buffer layer is a Ni metal layer or a Ni-based alloy layer with a thickness of 5-30 μm.

[0011] Preferably, the diffusion barrier layer and the wetting buffer layer are formed in any of the following ways: The diffusion barrier layer and the wetting buffer layer are deposited sequentially by vacuum magnetron sputtering, ion plating or vacuum arc deposition. Alternatively, the diffusion barrier layer can be formed by applying metal foil and then vacuum fixing, and the wetting buffer layer can be formed by electroplating or chemical plating.

[0012] As a preferred option, the preheating of the steel substrate plate within the casting cavity includes: The steel substrate plate is heated as a whole to 650°C to 900°C; Within 0.2-2.0 s before introducing the liquid titanium-based melt into the recasting cavity, the surface of the steel substrate plate to be composited is heated to form a semi-solid paste layer with a thickness of 5-50 μm.

[0013] As a preferred option, the melting chamber and the recasting chamber are isolated from each other, and the two chambers are connected by a gate valve or an openable and closable guide channel.

[0014] Preferably, in step S3, the recasting cavity is maintained in a vacuum state or continuously filled with inert protective gas during the casting process.

[0015] As a preferred option, in step S4, the cooling and solidification of the composite board includes: gradient cooling and solidification of the composite board, wherein the equivalent cooling rate of the gradient cooling and solidification is 50-100 ℃ / s.

[0016] As a preferred option, in step S2, the titanium alloy raw material includes TiAl alloy; the vacuum degree of the vacuum induction levitation melting is not less than 1×10⁻⁶. -3 Pa, with a melting temperature of 1600-1800℃.

[0017] As a preferred option, in step S1, the surface cleaning of the steel substrate plate includes: The steel substrate plate was subjected to pickling, deionized water rinsing and drying in sequence; The dried steel substrate plate is then ground or sandblasted.

[0018] The beneficial effects of this application are as follows: 1. The solution provided in this application constructs a composite intermediate layer of diffusion barrier layer and wetting buffer layer on the surface of steel substrate, especially using Nb, V or Ta as diffusion barrier layer, which can effectively physically block the direct contact and interdiffusion of titanium and iron elements, thereby inhibiting the formation of brittle phases such as FeTi and Fe2Ti; at the same time, the outer Ni wetting buffer layer provides good wettability and venting channels, improves the spreading of liquid titanium, and reduces the risk of defects such as local unbonding and gas entrapment caused by insufficient wetting during the casting process.

[0019] 2. The solution provided in this application employs a "cavity-isolated" vacuum induction suspension melting and recasting process, avoiding interference from the steel substrate to the melting electromagnetic field and ensuring the uniformity of the titanium liquid temperature. Furthermore, by subjecting the steel substrate to "overall preheating + secondary surface heating," a micron-sized semi-solid paste layer is formed on its surface. This process activates the steel substrate surface before casting, significantly improving the spreadability of liquid titanium, reducing rapid solidification defects caused by excessive temperature differences, and enhancing the stability of the composite process.

[0020] 3. The solution provided in this application achieves rapid transfer and casting of liquid titanium through a short-path flow channel, and combined with a gradient cooling solidification process, which not only reduces temperature loss and secondary oxidation during the casting process, but also prevents excessive growth of brittle phases through rapid cooling, thereby obtaining a high-quality titanium-steel composite plate with uniform interface transition layer thickness and dense interior. Detailed Implementation

[0021] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0022] This application provides a liquid-flow recasting method for preparing titanium-steel layered composite materials using vacuum induction suspension melting, characterized by comprising the following steps: S1: Clean the surface of the steel substrate plate, and sequentially form a diffusion barrier layer and a wetting buffer layer on the surface of the steel substrate plate to be laminated; Specifically, this step aims to provide a clean, moderately active substrate with interfacial reaction inhibition capabilities for the subsequent liquid-solid composite of titanium-based melt and steel substrate by performing multi-stage surface treatment and functional layer preparation on the steel substrate plate.

[0023] Preferably, the diffusion barrier layer is an Nb, V, or Ta metal layer with a thickness of 10-40 μm. Nb, V, and Ta, as refractory metals, exhibit good chemical stability at high temperatures and have relatively low interdiffusion rates with iron and titanium. Therefore, they can effectively suppress direct elemental exchange between iron and titanium at the composite interface, reducing the formation and growth of brittle intermetallic compounds. This is crucial for improving interfacial bonding strength and fatigue reliability.

[0024] Preferably, the wetting buffer layer is a Ni metal layer or a Ni-based alloy layer with a thickness of 5-30 μm. Ni has good solid solubility for both iron and titanium, which can effectively reduce the surface tension of liquid titanium on the diffusion barrier layer, promote the spreading and wetting of liquid titanium, and thus facilitate the formation of a continuous, defect-free metallurgical interface. The Ni layer can also serve as a thermal stress buffer layer to alleviate thermal stress caused by the difference in thermal expansion coefficients between titanium and steel.

[0025] In one implementation, the diffusion barrier layer and the wetting buffer layer are formed in any of the following ways: The diffusion barrier layer and the wetting buffer layer are deposited sequentially by vacuum magnetron sputtering, ion plating or vacuum arc deposition. Alternatively, the diffusion barrier layer can be formed by applying metal foil and then vacuum fixing, and the wetting buffer layer can be formed by electroplating or chemical plating.

[0026] Specifically, physical vapor deposition (PVD) technologies such as vacuum magnetron sputtering, ion plating, and vacuum arc deposition can achieve atomic-level deposition of diffusion barrier layers (such as Nb layers) and wetting buffer layers (such as Ni layers) in a high vacuum environment, thereby obtaining dense, uniform, and strongly bonded thin film layers while controlling their thickness to avoid introducing impurities. Another approach is to use appropriate metal foils (such as Nb foils) to be applied to the diffusion barrier layer via spot welding or vacuum holding in a vacuum environment, achieving initial bonding with the steel substrate; subsequently, a Ni wetting buffer layer is prepared on the foil surface using wet processes such as electroplating or electroless plating. Both of these methods can obtain a dense and firmly bonded intermediate layer structure on the steel substrate surface, providing a good foundation for subsequent composite processes.

[0027] Optionally, the surface cleaning of the steel substrate plate includes: The steel substrate plate was subjected to pickling, deionized water rinsing and drying in sequence; The dried steel substrate plate is then ground or sandblasted.

[0028] Specifically, pickling removes oxide scale and rust from the steel surface, ensuring its chemical purity. Subsequently, deionized water is used for rinsing to thoroughly remove pickling residues, followed by drying. Mechanical grinding or sandblasting increases surface energy, which is beneficial for the adhesion of the intermediate layer and the spread of liquid titanium. Optionally, the surface roughness Ra of the steel substrate to be laminated reaches 1μm-20μm.

[0029] To further reduce the risk of interfacial porosity, it is preferable to bake the steel substrate plate in a vacuum environment at 200℃-450℃ for 0.5h-3h after the above cleaning to remove adsorbed water and other volatile gases.

[0030] S2: Vacuum induction levitation melting of titanium or titanium alloy raw materials is carried out in the melting chamber to obtain liquid titanium-based melt; Specifically, this step employs vacuum induction levitation melting to melt titanium or titanium alloy raw materials. A high-frequency electromagnetic field suspends the metal raw material in the air or melts it within a water-cooled copper crucible, preventing contamination of the melt by the crucible material. The melting process is carried out under a high vacuum or inert atmosphere, effectively preventing titanium from reacting with elements such as oxygen and nitrogen in the air, ensuring the purity of the melt. For example, the melting temperature is typically set at 1600-1800℃, with a superheat of 25-60K maintained to ensure the fluidity of the melt while avoiding excessively high temperatures that could lead to element volatilization or equipment damage.

[0031] Preferably, the titanium alloy raw material includes TiAl alloy; the vacuum degree of the vacuum induction levitation melting is not less than 1×10⁻⁶. -3 Pa, with a melting temperature of 1600-1800℃.

[0032] Specifically, because TiAl alloys contain highly reactive aluminum, it is prone to volatilization loss during vacuum melting, leading to alloy composition segregation and performance fluctuations. To effectively control Al volatilization, a vacuum level of not less than 1×10⁻⁶ is required. -3 Melting under high vacuum conditions (Pa) can effectively reduce the vapor pressure of Al. The melting temperature should be controlled at 1600-1800℃, and the melting time (e.g., ≤30 min) should be controlled to minimize the time Al is exposed to the high-temperature vacuum environment. Optionally, to further suppress aluminum volatilization, the TiAl alloy raw material can be wrapped with aluminum foil before melting. The aluminum foil can create a localized high Al vapor pressure environment during melting, suppressing additional Al volatilization in the TiAl alloy. Furthermore, during melting, a low-pressure, high-purity inert gas (such as argon) can be introduced as needed to further reduce Al evaporation loss by increasing the local total pressure.

[0033] S3: The steel substrate plate is placed in the recasting chamber for preheating, and the liquid titanium-based melt is introduced from the melting chamber into the recasting chamber, and poured and spread on the surface of the steel substrate plate to be composited in the preheated state. Specifically, the steel substrate is preheated within the casting chamber to reduce the temperature difference between the liquid titanium and the steel substrate, thereby minimizing thermal shock and stress. After melting, the liquid titanium-based melt in the melting chamber is rapidly introduced into the casting chamber through a bottom outlet structure or a guide channel. This liquid flow is poured and spread in a laminar manner onto the preheated steel substrate surface to be composited, utilizing the spreadability of liquid titanium to metallurgically bond with the semi-solid surface of the steel substrate, forming an initial composite.

[0034] In one implementation, the step of placing the steel substrate plate in the casting cavity for preheating includes: The steel substrate plate is heated as a whole to 650°C to 900°C; Within 0.2-2.0 seconds before introducing the liquid titanium-based melt into the recasting cavity, the surface of the steel substrate plate to be composited is heated to form a semi-solid paste layer with a thickness of 5-50 μm.

[0035] Specifically, within 0.2-2.0 seconds before the introduction of the liquid titanium-based melt, the steel substrate surface to be composited is rapidly reheated, for example through localized induction heating, infrared heating, or laser heating, to bring its surface to a semi-solid paste-like temperature range above the solidus line and below the liquidus line. This control aims to form a semi-solid paste-like layer or locally micro-melted layer with a thickness of approximately 5-50 μm on the steel substrate surface. This semi-solid paste-like layer can significantly activate the interface, promote rapid wetting and spreading of liquid titanium, and form good mechanical intercalation and initial metallurgical bonding. Due to its extremely thin thickness and extremely short heating time, it can effectively limit the diffusion time of iron and titanium at high temperatures, thereby inhibiting the excessive growth of brittle intermetallic compounds.

[0036] In one implementation, the melting chamber and the recasting chamber are isolated from each other, and the two chambers are connected by a gate valve or an openable and closable flow channel.

[0037] Specifically, this compartmentalized design avoids interference from the steel substrate plate to the electromagnetic field of the induction coil during the suspension melting process, thus ensuring the uniformity and stability of the titanium-based melt temperature within the melting chamber and solving the problem of magnetic field distortion caused by the magnetic permeability of steel in existing technologies. Simultaneously, the gate valve or flow channel between the melting chamber and the recasting chamber can be quickly opened after melting, enabling the transfer of the melt over a very short distance, reducing heat loss, oxidation, and the risk of secondary contamination during the transfer process.

[0038] Preferably, the recasting chamber is maintained under vacuum or continuously filled with inert protective gas during the casting process. Maintaining a vacuum or filling the recasting chamber with an inert protective atmosphere such as argon with a purity higher than 99.99% during the casting stage effectively isolates the melt from contact with reactive gases such as oxygen and nitrogen in the air, preventing oxidation and nitriding of the titanium-based melt, reducing the generation of defects such as inclusions and porosity, and ensuring the purity of the interface bonding.

[0039] S4: Cool and solidify the composite plate to obtain a titanium-steel layered composite plate.

[0040] Specifically, after the liquid titanium-based melt is poured onto the surface of the steel substrate to form a composite, it is immediately cooled and solidified to transform it from a liquid to a solid state, thus completing the final solidification and molding.

[0041] Preferably, the cooling and solidification of the composite board includes: The composite board is subjected to gradient cooling solidification, and the equivalent cooling rate of the gradient cooling solidification is 50-100℃ / s.

[0042] Specifically, immediately after casting, the liquid-solid composite is introduced into a gradient cooling mold or a reverse solidifier for rapid cooling. Gradient cooling solidification can establish a controlled temperature gradient, allowing the solidification front to pass through the interface region at a faster speed, thereby minimizing the time the interface is in a high-temperature diffusion reaction state, thus inhibiting the excessive growth of brittle intermetallic compounds and controlling the thickness of the target interface transition layer within a more ideal range (e.g., 2μm-14μm).

[0043] The technical solutions and beneficial effects of this application are further illustrated below through specific embodiments and comparative examples. Experimental methods not specifying specific conditions in the embodiments are generally performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products available on the market.

[0044] Example 1 This embodiment provides a method for preparing a layered composite plate of TA2 industrial pure titanium and Q235 carbon steel.

[0045] S1: Preparation of steel substrate and composite intermediate layer.

[0046] A Q235 steel plate with dimensions of 300 mm × 200 mm × 20 mm was selected as the steel substrate. The surfaces of the steel plate to be laminated were pickled (using a 10% hydrochloric acid solution, immersed at room temperature for 5 min) to remove oxide scale, followed by rinsing with deionized water and drying. After drying, sandblasting was performed to achieve a surface roughness Ra of approximately 8 μm. The sandblasted steel plate was then placed in a vacuum baking oven at 250 ± 10℃ and a vacuum degree of 5 × 10⁻⁶. -2 Insulate at Pa for 2 hours to remove adsorbed gases and moisture.

[0047] The treated steel plate was transferred to a multi-target vacuum magnetron sputtering system. First, using an Nb target under an argon atmosphere, a 20 μm thick Nb layer was deposited as a diffusion barrier. Maintaining vacuum, the Ni target was replaced, and a 10 μm thick Ni layer was deposited in the same system as a wetting buffer.

[0048] S2: Titanium alloy smelting.

[0049] Within a separate melting chamber, TA2 industrial pure titanium raw material is loaded into a water-cooled copper crucible induction levitation melting furnace. The melting chamber is then evacuated to a vacuum level of 3 × 10⁻⁶. -3 Pa, then start the induction heating power supply. Control the melting power to completely melt the titanium raw material and reach 1700±20℃. At this temperature, electromagnetic stirring and holding for 10 minutes will obtain a liquid titanium-based melt with uniform composition.

[0050] S3: Preheating of steel matrix and liquid recasting.

[0051] The prepared Q235 steel plate with the intermediate layer is placed on the composite platform inside the casting chamber. The casting chamber is isolated from the melting chamber by a water-cooled gate valve. The steel plate is heated to 800±20℃ by a resistance heater inside the casting chamber and held at that temperature. Before casting is completed and before lamination is prepared, a high-frequency induction rapid heater positioned above the steel plate is activated to locally and rapidly heat the surface of the steel plate to be laminated for 0.5 seconds, raising the surface temperature (approximately 10-20μm deep) to a semi-solid range between the solidus line (approximately 1480℃) and the liquidus line (approximately 1520℃) of Q235 steel, forming a semi-solid paste layer.

[0052] The outlet at the bottom of the melting chamber and the gate valve between the two chambers are quickly opened. Under the influence of gravity and pressure difference, liquid titanium flows into the recasting chamber at a speed of approximately 0.8 m / s through a short-distance (approximately 200 mm long) insulated guide channel. The recasting chamber is filled with 99.999% high-purity argon gas at a pressure of 200 Pa. The liquid titanium smoothly spreads and covers the entire composite surface of the steel plate within 3 seconds.

[0053] S4: Cooling and solidification.

[0054] After casting, the platform supporting the composite plate is quickly moved to the gradient cooling mold below. This mold is circulated with cooling water, and forced heat exchange causes the composite plate to solidify rapidly from the steel substrate side. The equivalent average cooling rate of this process is approximately 70°C / s.

[0055] After complete solidification, a TA2 / Q235 titanium steel layered composite plate is obtained.

[0056] Example 2 This embodiment provides a method for preparing a layered composite plate of TC4 titanium alloy and No. 20 carbon steel, focusing on high-strength composite.

[0057] S1: A No. 20 carbon steel plate with dimensions of 400 mm × 250 mm × 25 mm was selected. Surface cleaning and baking degassing were the same as in Example 1. The surface roughness Ra after sandblasting was approximately 10 μm.

[0058] The intermediate layer was prepared using a foil lamination and electroplating method: a 35μm thick pure Nb foil was laminated onto the steel plate to be laminated, and then fixed in a vacuum environment using micro-beam plasma spot welding along the perimeter and center. Then, a dense Ni layer with a thickness of 20μm was electroplated onto the Nb foil surface using a conventional electroplating process.

[0059] S2: Melting TC4 (Ti-6Al-4V) alloy raw material in the melting chamber. The melting vacuum degree is 5×10⁻⁶. -3 Pa, the melting temperature is controlled at 1720±20℃, and the melting and holding time is 15 minutes.

[0060] S3: Preheat the entire steel plate to 820±20℃. One second before casting, rapidly heat the composite surface using a high-energy infrared focusing heater to form a semi-solid paste layer approximately 20-30 μm deep. Liquid TC4 melt is poured at a speed of 1.0 m / s, spreading within 4 seconds. The atmosphere in the casting chamber is high-purity argon at 200 Pa.

[0061] S4: Cooling is achieved using a reverse solidifier. After the composite plate enters the reverse solidifier, directional strong cooling is applied from the titanium layer side, with an equivalent cooling rate of approximately 80°C / s.

[0062] After complete solidification, a titanium-steel layered composite plate is obtained.

[0063] Example 3 This embodiment provides a method for preparing a layered composite plate of TiAl intermetallic compound and 304 stainless steel, focusing on the control of the active system.

[0064] S1: 304 stainless steel plate with dimensions of 200 mm × 150 mm × 15 mm is selected. After surface cleaning, a V layer (diffusion barrier layer) with a thickness of 30 μm and a Ni-5%Cr alloy layer (wetting buffer layer) with a thickness of 15 μm are prepared sequentially by vacuum arc deposition.

[0065] S2: The raw material for smelting is a Ti-48Al-2Cr-2Nb alloy. To suppress Al volatilization, the alloy ingot is tightly wrapped in 0.05 mm thick aluminum foil before being placed in the crucible. The smelting chamber is evacuated to an ultimate vacuum of 5 × 10⁻⁶. -3 After Pa, high-purity argon gas is introduced to a pressure of 0.5 Pa, and then induction suspension melting is carried out. The melting temperature is controlled at 1680±20℃, and the total time from melting to preparation for casting is controlled within 25 minutes.

[0066] S3: Preheat the entire stainless steel plate to 780±20℃. 0.3 seconds before casting, rapidly heat the composite surface using laser scanning (2 kW power, 5 mm spot diameter, 2 m / s scanning speed) to form a semi-solid layer with a depth ≤20 μm. Liquid TiAl melt is then poured at a speed of 0.9 m / s, spreading within 2.5 seconds. The casting chamber is maintained under dynamic high-purity argon gas protection.

[0067] S4: The gradient cooling mold uses high-pressure gas injection to achieve an equivalent cooling rate of 90 ℃ / s.

[0068] After complete solidification, a titanium-steel layered composite plate is obtained.

[0069] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step S1, no Nb diffusion barrier layer was prepared; instead, a 30 μm thick Ni layer was directly deposited as an intermediate layer on the sandblasted Q235 steel plate. All other steps and parameters are identical to those in Example 1.

[0070] Comparative Example 2 The only difference between this comparative example and Example 1 is that in step S3, the secondary heating of the steel substrate surface is omitted. The steel substrate is only preheated to 800±20°C, and no semi-solid paste layer is formed on the surface; that is, liquid titanium is poured onto the completely solid steel substrate surface. The parameters of the remaining steps are exactly the same as in Example 1.

[0071] Comparative Example 3 The only difference between this comparative example and Example 1 is that gradient cooling is omitted in step S4. After casting, the composite plate and composite platform are allowed to cool naturally in the casting cavity with the furnace, and the estimated equivalent average cooling rate is less than 10°C / s. The parameters of the remaining steps are exactly the same as in Example 1.

[0072] Effect testing and data analysis The titanium-steel layered composite plates prepared in Examples 1-3 and Comparative Examples 1-3 were sampled and analyzed to examine their interfacial bonding performance and microstructure. The test items and methods included: 1) Wire cutting was used to cut samples from the center area of ​​each composite board.

[0073] 2) Interface shear strength test: According to GB / T 6396-2008 "Test methods for mechanical and technological properties of composite steel plates", standard shear specimens were prepared and the interface shear strength was tested on a universal testing machine. Three specimens were tested under each condition and the average value was taken.

[0074] 3) Interface microstructure analysis: The microstructure of the interface region was observed using a scanning electron microscope and an attached energy dispersive spectrometer, the total thickness of the interface reaction transition layer (including the diffusion layer and possible compound layers) was measured, and the elemental distribution was analyzed.

[0075] 4) Defect statistics: The composite board is subjected to non-destructive testing using ultrasonic C-scanning, and the area percentage of defects such as interface non-bonding and pores is statistically analyzed.

[0076] The test results are shown in Table 1 below: Table 1 Test results of Examples 1-3 and Comparative Examples 1-3

[0077] Results analysis: As can be seen from the test results in Table 1, Examples 1-3 all achieved high interfacial shear strength, thin and uniform interfacial transition layers, and extremely low internal defect rates, demonstrating the effectiveness and stability of the technical solution of this application. Among them, Example 2 exhibits the best overall performance due to its thicker intermediate layer and moderate cooling rate.

[0078] In Comparative Example 1, the interfacial shear strength decreased significantly, the transition layer thickness increased to 25.5 μm, and a large number of brittle Fe-Ti intermetallic compounds formed internally, leading to an increased defect rate. This directly demonstrates the crucial role of diffusion barrier layers such as Nb / V in physically isolating Fe and Ti elements and suppressing the formation of harmful brittle phases.

[0079] Comparative Example 2 exhibited lower interfacial shear strength, the highest defect rate (3.5%), and unbonded areas at the interface. This indicates that overall preheating alone is insufficient to achieve effective spreading and initial bonding of liquid titanium; "surface semi-solidification" is crucial for achieving active wetting and mechanical interlocking in a very short time.

[0080] Comparative Example 3 showed the thickest interfacial transition layer, and microcracks due to coarse microstructure and stress concentration were observed, leading to a decrease in strength. This confirms the necessity of rapid gradient cooling for limiting element diffusion, refining interfacial microstructure, preventing excessive growth of brittle phases, and alleviating thermal stress.

[0081] In summary, the technical solution of this application effectively solves the problems of interfacial brittleness control, wetting and spreading, and process stability in titanium-steel liquid-solid composites, resulting in high-performance, high-yield titanium-steel layered composite plates. The above embodiments and comparative examples fully verify the outstanding beneficial effects of the technical solution of this application.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid-flow recasting method for preparing titanium-steel layered composite materials using vacuum induction suspension melting, characterized in that, Includes the following steps: S1: Clean the surface of the steel substrate plate, and sequentially form a diffusion barrier layer and a wetting buffer layer on the surface of the steel substrate plate to be laminated; S2: Vacuum induction levitation melting of titanium or titanium alloy raw materials is carried out in the melting chamber to obtain liquid titanium-based melt; S3: The steel substrate plate is placed in the recasting chamber for preheating, and the liquid titanium-based melt is introduced from the melting chamber into the recasting chamber, and poured and spread on the surface of the steel substrate plate to be composited in the preheated state. S4: Cool and solidify the composite plate to obtain a titanium-steel layered composite plate.

2. The method as described in claim 1, characterized in that, The diffusion barrier layer is an Nb, V, or Ta metal layer with a thickness of 10-40 μm.

3. The method as described in claim 1, characterized in that, The wetting buffer layer is a Ni metal layer or a Ni-based alloy layer with a thickness of 5-30 μm.

4. The method according to any one of claims 1 to 3, characterized in that, The diffusion barrier layer and the wetting buffer layer are formed in any of the following ways: The diffusion barrier layer and the wetting buffer layer are deposited sequentially by vacuum magnetron sputtering, ion plating or vacuum arc deposition. Alternatively, the diffusion barrier layer can be formed by applying metal foil and then vacuum fixing, and the wetting buffer layer can be formed by electroplating or chemical plating.

5. The method as described in claim 1, characterized in that, The step of placing the steel substrate plate in the casting cavity for preheating includes: The steel substrate plate is heated as a whole to 650°C to 900°C; Within 0.2-2.0 s before introducing the liquid titanium-based melt into the recasting cavity, the surface of the steel substrate plate to be composited is heated to form a semi-solid paste layer with a thickness of 5-50 μm.

6. The method as described in claim 1, characterized in that, The melting chamber and the recasting chamber are isolated from each other, and the two chambers are connected by a gate valve or an openable and closable guide channel.

7. The method as described in claim 6, characterized in that, In step S3, the recasting cavity is maintained under vacuum or continuously filled with inert protective gas during the casting process.

8. The method as described in claim 1, characterized in that, In step S4, the cooling and solidification of the composite board includes: The composite board is subjected to gradient cooling solidification, and the equivalent cooling rate of the gradient cooling solidification is 50-100 ℃ / s.

9. The method as described in claim 1, characterized in that, In step S2, the titanium alloy raw material includes TiAl alloy; The vacuum degree of the vacuum induction suspension melting is not less than 1×10⁻⁶. -3 Pa, with a melting temperature of 1600-1800℃.

10. The method as described in claim 1, characterized in that, In step S1, the surface cleaning of the steel substrate plate includes: The steel substrate plate was subjected to pickling, deionized water rinsing and drying in sequence; The dried steel substrate plate is then ground or sandblasted.

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