A short process for preparing high melting point niobium-titanium alloy ingot

Abstract

The present application relates to a kind of short process preparation high melting point niobium titanium alloy ingot method, comprising the following steps: step S1.Provide pure titanium hollow electrode and niobium rod, wherein pure titanium hollow electrode is selected from the hollow electrode of titanium sponge, rolled titanium tube electrode or as-cast titanium ingot hollow electrode;Nioium rod is inserted into titanium electrode coaxially, and forms the composite electrode of assembly close, gap uniform;Step S2.The composite electrode is melted once by VAR, and the ingot is obtained;Step S3.The ingot obtained in step S2 is melted second time using EB furnace, and high melting point niobium titanium alloy ingot is obtained.The present application is accurate and reliable in component control, and the composition fluctuation caused by Ti volatilization and uneven melting speed in EB melting is fundamentally alleviated by VAR pre-alloying and pre-compensation of Ti evaporation amount, combined with the homogenization effect of double-sided reverse arrangement, so that the composition deviation of Nb and Ti in the ingot is stabilized within ±0.5%.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting, and specifically discloses a short-process method for preparing high-melting-point niobium-titanium alloy ingots. Background Technology

[0002] Nb-Ti alloys have become a key material for manufacturing high-field superconducting magnets due to their excellent low-temperature superconductivity, good mechanical strength, and corrosion resistance. However, Nb has a melting point as high as 2468℃, while Ti has a melting point of 1668℃, a difference of 800℃. This presents significant challenges to the alloy's smelting and preparation. During the smelting process, if electron beam melting is used directly, the relatively low-melting-point Ti element is more likely to volatilize due to the high-temperature and high-vacuum environment. Furthermore, the large melting point difference between Nb and Ti results in a large difference in melting rates between the two elemental metals, making it impossible to accurately match the required ratio and easily leading to stratification, which makes it difficult to control the composition of the final ingot. Currently, the industrial preparation of Nb-Ti alloys mainly relies on multiple VAR melting processes. While vacuum consumable arc melting can help with alloying, it has limited ability to remove high and low density inclusions, makes it difficult to improve longitudinal concentration, and has a long production cycle and high energy consumption, affecting the purity and service reliability of the ingot.

[0003] Therefore, developing a short-process preparation method for Nb-Ti alloy ingots that can achieve precise composition control, efficient removal of inclusions, a compact process, and controllable cost has become a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a short-process method for preparing high-melting-point niobium-titanium alloy ingots. This method addresses the problems in existing technologies, such as the different melting rates of the two metals (Nb and Ti) in a single EB process due to the large difference in melting points, the long VAR (Vacuum-Aging Reduction) process, the difficulty in improving vertical concentration, the high cost, and the insufficient purity of the ingots. By designing a composite consumable electrode structure, introducing a Ti element evaporation compensation mechanism, and optimizing the VAR+EB dual-process and material arrangement, stable and efficient preparation of high-quality Nb-Ti alloy ingots is achieved.

[0005] This invention first prepares a pure titanium hollow electrode. The pure titanium hollow electrode can be selected from sponge titanium hollow electrodes, rolled titanium tube electrodes, or cast titanium ingot hollow electrodes. The sponge titanium hollow electrode can be formed by welding two tile electrodes together or by radially pressing them in one step. The rolled titanium tube electrode is made by a skew rolling process (forging an ingot obtained from VAR or EB furnace melting into the required size, and then drilling a central hole in the machined ingot) or by bending a pure titanium plate and then longitudinally welding it using inert gas shielded welding. The cast titanium ingot hollow electrode is formed in one step using an electron beam cold hearth furnace. Through water-cooled mandrel and directional solidification technology, the raw material is directly melted and cast into a hollow ingot with a central through hole. After minimal processing, it is ready for use. Subsequently, a high-purity Nb rod is coaxially inserted to form a composite electrode, wherein the amount of Ti element has been pre-increased by 0.2%. The pre-alloying of Nb-Ti is achieved by adding 0.6% to compensate for the volatilization loss during the subsequent EB melting process. Then, a VAR furnace is used for a first melting to achieve pre-alloying of Nb-Ti. The VAR ingot is then loaded into the EB furnace for a second melting, or it can be first free-forged into a billet before EB melting. This invention, through pre-alloying and composition compensation design, effectively suppresses excessive volatilization of Ti during EB melting, solving the composition control problem caused by uneven melting rates between high-melting-point Nb and relatively low-melting-point Ti due to the large difference in melting temperatures. Simultaneously, it fully utilizes the efficient impurity removal capability of the EB furnace, resulting in an ingot composition deviation ≤ ±0.5% and a high / low density inclusion removal rate ≥ 95%. This shortens the production process, reduces costs, and is suitable for the large-scale production of high-quality Nb-Ti alloy ingots in fields such as superconducting magnets and aerospace.

[0006] The technical solution adopted in this invention is: A method for preparing high-melting-point niobium-titanium alloy ingots via a short process, comprising the following steps: Step S1. Provide a pure titanium hollow electrode and a niobium rod; insert the niobium rod coaxially into the hollow hole of the sponge titanium electrode to form a tightly assembled composite electrode with uniform gap. The assembly gap between the niobium rod and the hollow electrode should be controlled within 0.05–0.10 mm, and the concentricity deviation should be ≤0.05 mm. Step S2. The composite electrode prepared in step S1 is melted once to obtain an ingot; Step S3. The ingot obtained in step S2 is smelted a second time to obtain a high melting point niobium-titanium alloy ingot.

[0007] Preferably, in the short-process method for preparing high-melting-point niobium-titanium alloy ingots, the pure titanium hollow electrode in step S1 is selected from one of sponge titanium hollow electrode, rolled titanium tube electrode, or cast titanium ingot hollow electrode. The sponge titanium hollow electrode is formed by welding two tile electrodes together or by radially pressing them in one go. The rolled titanium tube electrode is formed by oblique rolling through a tube process or by bending a pure titanium plate and then welding the longitudinal seam with inert gas shielded welding. The cast titanium ingot hollow electrode is formed in one step using an electron beam cold hearth furnace. Through water-cooled core mold and directional solidification technology, the raw material is directly melted and cast into a hollow ingot with a central through hole. Finally, the ingot head and tail are cut and the inner and outer skins of the hollow ingot are machined to obtain a cast titanium ingot hollow electrode adapted to niobium rods.

[0008] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, the skew rolling and piercing process specifically involves forging the ingot obtained from VAR or EB furnace melting into the required size, and then turning the ingot and piercing its center.

[0009] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, the outer diameter of the sponge titanium electrode in step S1 is φ250~380mm, and the purity of the niobium rod is ≥99.9%.

[0010] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots via a short process, the mass percentage of titanium in the high-melting-point niobium-titanium alloy ingot in step S2 is 0.2%-0.6% lower than the mass percentage of titanium in the composite electrode.

[0011] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, step S2 specifically includes the following steps: adding the composite electrode prepared in step S1 into a melting furnace for primary melting, which includes three stages: arc initiation, normal melting, and feeding. The current in the arc initiation stage is 2-5kA and the voltage is 24-28V; the current in the normal melting stage is 8-30kA and the voltage is 30-40V, and the vacuum degree before melting is not higher than 5.0Pa; the current in the feeding stage is gradually reduced to 6-15kA; after primary melting, the ingot is cooled, and the ingot cooling time is not less than 3 hours. Finally, the ingot is obtained by flattening the end to remove end defects.

[0012] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, step S3 specifically includes the following steps: The ingots are washed and then stacked in a horizontal double-sided reverse arrangement. Finally, the stacked ingots are smelted a second time in an EB furnace to obtain high-melting-point niobium-titanium alloy ingots.

[0013] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, step S3 specifically includes the following steps: The ingots are free-forged into square billets, which are then assembled in a horizontal double-sided reverse arrangement and vertical stacking manner. The assembled ingots are then melted a second time in an EB furnace to obtain high-melting-point niobium-titanium alloy ingots.

[0014] Preferably, in the short-process method for preparing high-melting-point niobium-titanium alloy ingots, the accelerating voltage of the electron beam cold hearth furnace is 30-40kV, the single-gun power is 180-350kW, and the vacuum degree inside the furnace is 1×10⁻⁶. - ³-5×10 -4 Pa, molten pool temperature is 1750-2000℃, ingot pulling speed is 5-15mm / min, and smelting rate is 700-800kg / h.

[0015] Preferably, in the short-process method for preparing high-melting-point niobium-titanium alloy ingots, the forging temperature is 900-1000℃ and the single-pass processing rate is 50%-70%.

[0016] Preferably, in the method for preparing high-melting-point niobium-titanium alloy ingots using the short-process method, the horizontal double-sided reverse arrangement is specifically as follows: one row in the horizontal direction is arranged alternately with the head and tail, and the other row is arranged alternately with the tail and head on the side closest to the head and tail.

[0017] The present invention has the following advantages: (1) The method for preparing high melting point niobium-titanium alloy ingots in the present invention has precise and reliable composition control. Through VAR pre-alloying and pre-compensation for Ti evaporation, the composition fluctuation caused by Ti volatilization and uneven melting rate in EB melting is fundamentally alleviated. Combined with the homogenization effect of double-sided reverse arrangement, the composition deviation of Nb and Ti in the ingot is stabilized within ±0.5%.

[0018] (2) The method for preparing high melting point niobium-titanium alloy ingots in the present invention has high purity. The high vacuum and local high temperature characteristics of the EB melting stage are fully utilized, which can effectively remove various non-metallic inclusions. The inclusion removal rate reaches more than 95%, which significantly reduces the internal defect rate.

[0019] (3) The method for preparing high melting point niobium-titanium alloy ingots in the present invention has a short process flow and low cost. It only requires one VAR melting and one EB melting, avoiding multiple remelting in the traditional process. The production cycle is shortened by about 30%, the utilization rate of titanium-based raw materials is increased to 85%-90%, and the overall production cost is reduced by about 30%.

[0020] (4) The method for preparing high melting point niobium-titanium alloy ingots in the present invention is flexible and adaptable, providing two options: direct melting and melting after forging. It can be flexibly selected according to different performance requirements (such as short process priority or high uniformity priority), thus broadening the scope of application of the process.

[0021] (5) The method for preparing high melting point niobium-titanium alloy ingots in the present invention is suitable for industrial production: the electrode assembly accuracy is high, the process parameters are optimized and matched, the melting success rate is high, and it has good repeatability and stability, making it easy to achieve large-scale mass production. Attached Figure Description

[0022] Figure 1 This is a flowchart of the short-process method for preparing high-melting-point niobium-titanium alloy ingots according to the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Unless otherwise stated, the terminology used herein should be understood in accordance with the conventional usage of those skilled in the art.

[0024] Example 1 like Figure 1 A method for preparing φ530mm high-melting-point niobium-titanium alloy ingots via a short process, comprising the following steps: Step S1. In this example, the pure titanium hollow electrode is obtained by radially pressing sponge titanium with a hydraulic press and welding it. Sponge titanium and niobium rods with a purity >99.9% and a diameter of φ168mm (dimensional tolerance ±0.03mm) are provided. The sponge titanium is pressed into a tile shape into electrode blocks using a hydraulic press, and the tile-shaped electrode blocks are welded to prepare a sponge titanium electrode with an outer diameter of φ280mm. A hollow hole is formed in the middle of the sponge titanium electrode along the axis. The niobium rod is coaxially inserted into the hollow hole of the sponge titanium electrode with an assembly gap of 0.08mm and a concentricity deviation of 0.05mm, forming a tightly assembled composite electrode with a uniform gap. The typical evaporation rate of titanium is 0.5%, and the mass percentage of titanium in the composite electrode is 0.5% higher than that in the high melting point niobium-titanium alloy ingot. Step S2. The composite electrode prepared in step S1 is added to a vacuum arc furnace for primary melting. A φ380mm crystallizer is used. The primary melting includes three stages: arc initiation, normal melting, and feeding. The arc initiation stage lasts for 2 minutes, with a current of 3kA, a voltage of 26V, and a DC stabilizing current of 3A. The normal melting stage has a current of 18kA, a voltage of 35V, a DC stabilizing current of 10A, a vacuum degree of 5.0Pa before melting, and a leakage rate of 1.0Pa / min. The feeding stage lasts for 3 minutes, with the current gradually decreasing to 10kA, a voltage of 28V, and a DC stabilizing current of 5A. The initial feeding weight is 90kg, and the final feeding weight is 10kg. After the primary melting is completed, the ingot is cooled for 4 hours. Finally, the ingot is flattened to remove end defects. Step S3. The ingots obtained in Step S2 are washed, and then stacked using a double-sided reverse arrangement of horizontal head-tail-head-tail and reverse tail-head-tail-head, stacking two layers vertically. Finally, the stacked ingots are smelted a second time in an EB furnace. The electron beam cold hearth furnace has an accelerating voltage of 35kV, a 7-gun configuration, a single gun power of 350kW, and a vacuum degree of 3×10⁻⁶. -4 Pa, molten pool temperature 1900℃, ingot pulling speed 8mm / min, smelting rate 750kg / h, to obtain φ530mm high melting point niobium-titanium alloy ingot.

[0025] The high-melting-point niobium-titanium alloy ingot prepared in Example 1 was tested. The ingot had a Nb content of 47.5%, a Ti content of 53%, a composition deviation of ±0.4%, a high and low density inclusion removal rate of 96%, and no obvious defects.

[0026] Example 2 A method for preparing high-melting-point niobium-titanium alloy ingots via a short process, comprising the following steps: Step S1. Provide sponge titanium and niobium rods with a purity >99.9% and a diameter of φ168mm (dimensional tolerance ±0.03mm). The electrode preparation method is the same as in Example 1. The sponge titanium is pressed into a tile shape using a hydraulic press to form electrode blocks, and the tile-shaped electrode blocks are welded to prepare a sponge titanium electrode with an outer diameter of φ280mm. A hollow hole is formed in the middle of the sponge titanium electrode along the axis. The niobium rod is coaxially inserted into the hollow hole of the sponge titanium electrode with an assembly gap of 0.08mm and a concentricity deviation of 0.05mm, forming a tightly assembled composite electrode with a uniform gap. The typical evaporation rate of titanium is 0.5%, and the mass percentage of titanium in the composite electrode is 0.5% higher than the mass percentage of titanium in the high melting point niobium titanium alloy ingot. Step S2. The composite electrode prepared in step S1 is added to a vacuum arc furnace for primary melting. A φ380mm crystallizer is used. The primary melting includes three stages: arc initiation, normal melting, and feeding. The arc initiation stage lasts for 2 minutes, with a current of 3kA, a voltage of 26V, and a DC stabilizing current of 3A. The normal melting stage has a current of 18kA, a voltage of 35V, a DC stabilizing current of 10A, a vacuum degree of 5.0Pa before melting, and a leakage rate of 1.0Pa / min. The feeding stage lasts for 3 minutes, with the current gradually decreasing to 10kA, a voltage of 28V, and a DC stabilizing current of 5A. The initial feeding weight is 90kg, and the final feeding weight is 10kg. After the primary melting is completed, the ingot is cooled for 4 hours. Finally, the ingot is flattened to remove end defects. Step S3. The ingot obtained in step S2 is subjected to free forging at a forging temperature of 950℃ and a single-pass processing rate of 60% to form a square billet. The billets are then assembled in a horizontal, double-sided, reverse arrangement and can be stacked in three layers. The assembled ingots are then subjected to a second melting in an EB furnace. The accelerating voltage of the electron beam cold hearth furnace is 35kV, with a 7-gun configuration, a single-gun power of 350kW, and a vacuum degree of 3×10⁻⁶. -4 Pa, molten pool temperature 1900℃, ingot pulling speed 8mm / min, smelting rate 750kg / h, to obtain φ530mm high melting point niobium-titanium alloy ingot.

[0027] The high-melting-point niobium-titanium alloy ingot prepared in Example 2 has better microstructure uniformity than that in Example 1, with a composition deviation of ±0.3% and an inclusion removal rate of 97%, meeting the requirements for high uniformity.

[0028] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method, characterized in that, Includes the following steps: Step S1. Provide a pure titanium hollow electrode and a niobium rod; insert the niobium rod coaxially into the hollow hole of the pure titanium hollow electrode to form a tightly assembled composite electrode with uniform gaps; Step S2. The composite electrode prepared in step S1 is subjected to a VAR melting process to obtain an ingot; Step S3. The ingot obtained in step S2 is smelted a second time using an EB furnace to obtain a high-melting-point niobium-titanium alloy ingot.

2. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, In step S1, the pure titanium hollow electrode is selected from one of sponge titanium hollow electrode, rolled titanium tube electrode, or cast titanium ingot hollow electrode. The sponge titanium hollow electrode is formed by welding two tile electrodes together or by radially pressing them in one go. The rolled titanium tube electrode is formed by skew rolling through a tube or by bending a pure titanium plate and then welding the longitudinal seam with inert gas shielded welding. The cast titanium ingot hollow electrode is formed in one step in an electron beam cold hearth furnace. Through water-cooled core mold and directional solidification technology, the raw material is directly melted and cast into a hollow ingot with a central through hole. Finally, the ingot head and tail are cut and the inner and outer skins of the hollow ingot are machined to obtain a cast titanium ingot hollow electrode that is compatible with niobium rods.

3. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 2, characterized in that, The skew rolling tube-piercing process is as follows: the ingot obtained from VAR or EB furnace melting is forged into the required size, and the ingot is machined and then pierced at the center.

4. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, In step S1, the outer diameter of the sponge titanium electrode is φ250~380mm, and the purity of the niobium rod is ≥99.9%.

5. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, In step S2, the mass percentage of titanium in the high-melting-point niobium-titanium alloy ingot is 0.2%-0.6% lower than that in the composite electrode.

6. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, Step S2 specifically includes the following steps: The composite electrode prepared in step S1 is added to a melting furnace for primary melting. Primary melting includes three stages: arc initiation, normal melting, and feeding. The current in the arc initiation stage is 2-5kA and the voltage is 24-28V; the current in the normal melting stage is 8-30kA and the voltage is 30-40V, and the vacuum degree before melting is not higher than 5.0Pa; the current in the feeding stage is gradually reduced to 6-15kA. After primary melting, the ingot is cooled, and the ingot cooling time is not less than 3 hours. Finally, the end defects are removed by flattening to obtain the ingot.

7. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, Step S3 specifically includes the following steps: The ingots are washed and then stacked in a horizontal double-sided reverse arrangement. Finally, the stacked ingots are melted a second time in an EB furnace to obtain high-melting-point niobium-titanium alloy ingots.

8. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 1, characterized in that, Step S3 specifically includes the following steps: The ingots are free-forged into square billets, which are then assembled in a horizontal double-sided reverse arrangement and vertical stacking manner. The assembled ingots are then melted a second time in an EB furnace to obtain high-melting-point niobium-titanium alloy ingots.

9. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 7 or 8, characterized in that, The accelerating voltage of the electron beam cold hearth furnace is 30-40kV, the single-gun power is 180-350kW, and the vacuum degree inside the furnace is 1×10⁻⁶. - ³-5×10 -4 Pa, molten pool temperature is 1750-2000℃, ingot pulling speed is 5-15mm / min, and smelting rate is 700-800kg / h.

10. The method for preparing high-melting-point niobium-titanium alloy ingots using a short-process method as described in claim 7, characterized in that, Forging temperature is 900-1000℃, and single-pass machining rate is 50%-70%; The horizontal double-sided reverse arrangement is as follows: one row in the horizontal direction is arranged alternately with the head and tail, and the other row is arranged alternately with the tail and head on the side closest to the head and tail.

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