Vacuum Induction Melting Research Articles

A Future for Vacuum Arc Remelting and Electroslag Remelting—A Critical Perspective

In the secondary metals refining processes, vacuum arc remelting (VAR) and electroslag remelting (ESR), the consumable electrode is commonly produced by vacuum induction melting (VIM) which employs the regrettably primitive casting technique of simply pouring into the open top of the mold. Despite the vacuum, the resulting oxidizing conditions and the immensely powerful turbulence accompanying the top-pouring of the electrode is now known to create a substantial density of serious cracks. The cracks in the cast electrode are bifilms (double oxide films), which in turn are proposed to be responsible for the major faults of the VAR ingot, including undetectable, horizontal macroscopic cracks, white spots (clean and dirty varieties) and in-fallen crown. The remedial action to solve all these issues at a stroke is the provision of a counter-gravity cast electrode, cast in air or vacuum, or provision of any similar electrode substantially free from bifilm defects. The ESR process is also described, explaining the reasons for its significantly reduced sensitivity to the top-poured VIM electrode, but indicating that with an improved electrode, this already nearly reliable process has the potential for perfect reliability. The target of this critical overview is an assessment of the potential of these secondary refining processes to produce, for the first time, effectively defect-free metals, metals we can trust.

Effect of solid solution tungsten on the radiation-induced amorphization in bulk M23C6 fabricated by vacuum induction melting

To provide a mechanistic understanding of the stability of the M23C6 phase under irradiation, the crystalline to amorphous (c-a) transition behavior in bulk M23C6 specimens with a variation in tungsten (W) content subjected to helium ion irradiation was investigated. The Cr-W-C ternary ingots with a W concentration range of 0–11.6 at.% were fabricated by vacuum-induced furnace melting. Microstructure characterization revealed that the dominant phase in the ingots was M23C6 regardless of the W concentration, and a small amount of metallic-Cr, (Cr, W), and W-rich carbide co-existed as the minor phase. The lattice parameter of M23C6 increases with an increase in W concentration, and the maximum value is 1.083 nm when the W content is 11.6 at.%. Based on this, the chemical formula of the M23C6 particle in F82H steel was represented by Cr20W3C6 or Cr19W4C6 because its lattice parameter was estimated to be 1.08–1.09 nm. From the grazing incident X-ray diffraction analysis before and after irradiation, the amorphous peak was only observed in the specimen of W concentration 11.6 at.% after irradiation, which was further confirmed by transmission electron microscopy analyses. It is clarified that the c-a transition behavior in M23C6 is dependent on the W content, the amorphization of M23C6 can be mitigated when the W concentration is 6.8 at.% or less under the present study condition.

Evolution of inclusions in vacuum induction melting of superalloys containing 70% return material

Evolution of inclusions in vacuum induction melting of superalloys containing 70% return material

Effect of rare earth Er on discontinuous precipitation and mechanical properties of Cu-15Ni-8Sn-0.3Fe alloy

The Cu-15Ni-8Sn-0.3Fe-xEr (wt%, x = 0.1–0.4) alloy was prepared by vacuum induction melting. The microstructure evolution, mechanical properties and discontinuous precipitation (DP) growth kinetics during solidification and heat treatment were systematically investigated. The results show that the added Er leads to the formation of micrometer-sized ErNiSn2 phase and nanometer-sized ErNi phase in the Cu-15Ni-8Sn-0.3Fe alloy, which suppresses the formation of the discontinuous precipitation phases. Compared to alloys with other compositions, the Cu-15Ni-8Sn-0.3Fe-0.3Er alloy exhibits superior mechanical properties during aging at different temperatures. Specifically, after aging for 13 h at 723 K, the alloy achieved a peak hardness of 383.5 HV. In addition, the growth kinetics of the DP in Cu-15Ni-8Sn-0.3Fe-xEr (wt%, x = 0.1–0.4) alloys were evaluated using the Johnson-Mehl-Avrami-Kolmogorov equation. The activation energy (Q) of DP in the Cu-15Ni-8Sn-0.3Fe-0.3Er alloy is 178.4 kJ/mol, which is 39.2 kJ/mol higher than that of the Cu-15Ni-8Sn alloy.

High throughput construction for the deformation mechanism diagram and dynamic recrystallization of a bimodal‐sized particle‐reinforced Ti‐2.5Zr‐2Al‐1(Si,C) titanium alloy

AbstractAn in situ autogenous particle‐reinforced Ti‐2.5Zr‐2Al‐1(Si,C) titanium alloy is prepared by vacuum induction melting. The wide range of an effective strain between 0.2 and 1.2 and the corresponding microstructure are obtained by the double‐cone high‐throughput compression test and finite element simulation. The deformation mechanism diagram with strains of 0.2–1.2 and strain rates of 0.7–1.5 s−1 at 900°C is constructed. When the strain rate is 1.3 s−1, dynamic recovery occurs in the small strain range (<0.377), dynamic recrystallization (DRX) occurs in the medium strain range (0.377–1.182), and deformation instability occurs in the large strain range (>1.182), resulting in the deformation bands. High‐angle annular dark field and high‐resolution transmission electron microscopy are used to determine the existence of bimodal particle distribution, namely micron‐scale TiC particles and nano‐scale Ti5Si3 and (Zr, Si) particles. The average radius of the (Zr, Si) nanoparticles measured by small angle neutron scattering is 19.3 nm, and the volume fraction is 0.35%. DRX grains with an average size of 0.49 μm are obtained at 900°C, strain rate of 1.3 s−1, and strain of about 0.6. Micron‐scale particles stimulated DRX nucleation, while nanoscale particles hindered the growth of new grains, resulting in grain refinement.

Phase evolution, hydrogen storage thermodynamics, and kinetics of ternary Mg98Ho1.5Fe0.5 alloy

Rare earth elements and transition metals have been found to improve the hydrogen storage characteristics of magnesium-based alloys. This study investigated the Mg-Ho-Fe (MHF) ternary alloy prepared using the vacuum induction melting technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), pressure-composition-temperature (PCT), and differential scanning calorimetry (DSC) were used to analyze the alloy's phase transitions, microstructure, thermodynamics, and kinetic properties. The results reveal that the Mg98Ho1.5Fe0.5 alloy forms a solid solution with Ho and Fe in the magnesium matrix. Upon hydrogen absorption, the activated alloy transforms into a mixture of Mg/MgH2 phases and nanoscale HoH2 phases. Notably, only the MgH2 phase decomposes during hydrogen desorption, while the HoH2 phase remains unchanged, exhibiting a positive catalytic effect. The alloy demonstrates excellent hydrogen absorption kinetics, achieving a capacity of 5.56 wt% H2 within 10 min at 360 °C, owing to the combined catalytic effects of Ho and Fe. The activation energy for hydrogen desorption is found to be 135.87 kJ/mol, which is lower than that of the activation energies of pure MgH2 and MgFe alloys, indicating an enhancement in desorption kinetics. Moreover, the enthalpy and entropy changes for hydrogen absorption and desorption are determined to be –70.51 kJ/mol H2, –125.62 J/(K·mol) H2, 72.83 kJ/mol H2, and 128.95 J/(K·mol) H2, respectively. Furthermore, it is worth noting that the thermodynamic properties of the alloy are improved due to the catalytic effect of Ho and Fe.

Formation and aggregation behavior of inclusions in Ni-based alloys with different Mg contents

Large non-metallic inclusions affect the mechanical properties and service life of nickel-based superalloys. This study investigates the effects of magnesium elements on non-metallic inclusions in K4169 nickel-based superalloys, exploring the formation mechanisms and aggregation relationships of the inclusions. Four gradients of the magnesium content were used to simulate the erosion of MgO refractories on inclusions in the vacuum induction melting of nickel-based superalloys. The observed inclusions mainly comprised MgO, TiN, MgAl2O4, and MgAl2O4–TiN composites. To study the formation mechanism of inclusions in Ni-based alloys with different Mg contents, the predominance diagram of Mg–Al–Ti–O inclusions in nickel-based superalloy systems was calculated using Factsage thermodynamics software and classical thermodynamics separately. The aggregation behavior of MgAl2O4 and MgO inclusions on the surface of molten nickel-based superalloys was observed in situ under a high-temperature confocal laser scan microscope. The capillary force acting on inclusions in nickel-based superalloys was calculated using the Kralchevsky–Paunov model (K–P model), the calculation was verified with experimental results, and the influencing factors were analyzed. The capillary force acting on inclusions on the surface of molten nickel-based superalloys weakened in the order of MgAl2O4 > MgO > Al2O3, which is the opposite of the order for the force acting on inclusions in molten steel. Minimizing the magnesium content in the alloy is crucial to preventing the formation of large inclusions in nickel-based superalloys, and the use of magnesium-containing materials in the smelting process should thus be avoided.

Coarsening of needle-shaped precipitates in CoNiCrAl alloys during isothermal heat treatment: Kinetics in length and thickness

This paper investigated the coarsening kinetics of needle-shaped γ precipitates in CoNiCrAl alloys after isothermal heat treatments at 900 °C and 1100 °C. The CoNiCrAl alloys were prepared by vacuum induction melting and casting process. They were characterised to exhibit a two-phase γ + β structure and some needle-shaped secondary γ precipitates were formed within the primary β phase during isothermal heat treatments. The coarsening of the needle-shaped secondary γ precipitates occurred with heat treatment time and became more rapid at elevated temperatures. In particular, the coarsening kinetics of needle-shaped γ precipitates in length and thickness were specifically studied. It was found that the coarsening kinetics in length and thickness was a volume diffusion governed process and generally followed the classic Lifshitz-Slyozov-Wagner (LSW) theory. An analytical model was proposed to estimate the lengthening and thickening of the precipitates, which considered the aspect ratio and volume fraction of the precipitates. The calculated coarsening rate in thickness agreed well with the experimentally determined value. But some discrepancies were found between the predicted and measured coarsening rate in length. This might be due to the termination migration effects of the needle-shaped precipitates which restricted the coarsening rate in length.

Effects of heat treatment on the precipitation behaviors and mechanical properties of Nb-doped CrMnFeCoNi0.8 high-entropy alloy

In this work, the CrMnFeCoNi0·8Nb0.2 high-entropy alloys (HEAs) were fabricated through vacuum induction melting and subsequently annealed at various temperatures (namely, 900 °C, 1000 °C, and 1100 °C). The microstructure and mechanical properties of the HEAs following heat treatment were investigated systematically. It reveals that the annealed alloys demonstrate the coexistence of the face-centered cubic (FCC) matrix phases and Laves phases, wherein partial dissolution of primary NbCo2 phases into the matrix while the remaining part precipitation as secondary phases. The alloy annealed at 1000 °C exhibits a ductility of 13.2%, along with high yield strength of 497.8 MPa, ultimate tensile strength of 851.1 MPa and hardness of 393.9 HV. The high strength of the alloy primarily originates from the hetero-deformation induced (HDI) strengthening of the eutectic-like structure, while additional strengthening is provided by precipitation strengthening caused by nano-sized second precipitates and solution strengthening.

Microstructural refinement and tensile properties of Fe65.7Ni11.7Ti1Mo6.6Co15 HEA undergoing multiple LSP

Seeking for the Fe65.7Ni11.7Ti1Mo6.6Co15 high entropy alloy (HEA) with well-performed mechanical properties is indispensable for its wide applications. Herein, the HEA was fabricated via vacuum induction melting at 1923 K, and then subject to LSP treatment by one to three coverage layers. The corresponding microstructure features were observed and a systematic work of the strengthening mechanism were revealed. Moreover, the uniaxial tensile testing was performed and the fracture behaviors of the tensile specimens as a function of the coverage layer are also determined. It evidently shows that, the significant LSP-generated grain refinement process attributes to the following two modes: (i) interactions of multidirectional dislocation motion subdividing the β phases into refined equiaxed grains, and (ii) numerous new formed parallel lath martensite in γ phases divided by vertical DWs resulting in slender lath grains. In addition, the tensile properties and fracture behaviors of the HEA subjected to LSP treatment strongly depend on the coverage layer. With increasing the coverage layer of LSP, both the ultimate tensile strength and the ductility of the material are improved. Thus, the typical cleavage fracture pattern gradually evolves into the brittleness and ductility mixed fracture pattern.

Effect of annealing treatment on microstructural evolution and compressive behavior of Al0.5CrFeNi2.5Si0.25 high-entropy alloy

Dual or multi-phase high-entropy alloys (HEAs) with nano-precipitates are of great importance to overcome the strength-ductility tradeoff of structural materials. In this work, Al0.5CrFeNi2.5Si0.25 HEAs were designed and fabricated using vacuum induction melting. The microstructure, phase evolution and compressive behavior of Al0.5CrFeNi2.5Si0.25 HEAs before and after annealing at various temperatures (750 °C, 850 °C, 1050 °C, and 1200 °C) were investigated. The as-casted and annealed Al0.5CrFeNi2.5Si0.25 HEAs constitute a dual-phase (FCC and BCC) composition with L12 and σ phases. With increasing annealing temperature (750 °C–1200 °C), the proportion of the BCC matrix containing Cr-rich nanoparticles and strip-shaped σ phases gradually increased. The Cr-rich nanoparticles were gradually refined. Partial σ phase dissolved after heat treatment at 1050 °C and 1200 °C. The variation of the precipitated phases at different temperatures led to the occurrence of strengthening, which makes the alloys overcome the tradeoff between compressive strength and ductility. Under the 750 °C–1200 °C annealing, the compressive strength increased from 2288 MPa to 2584 MPa, accompanied by an increase in fracture strain from 14.9% to 23.4%.

Effects of Heat Treatment on Microstructure and Mechanical Properties of Weldable Al-Mg-Zn-Sc Alloy with High Strength and Ductility.

A weldable Al-Mg-Zn-Sc alloy was produced using vacuum induction melting and an argon-protected casting method to achieve high strength and ductility, and the effects of heat treatment on the microstructure evolution and mechanical properties of Al-Mg-Zn-Sc alloys were comparatively investigated. The results reveal that fine equiaxed grains with an average grain size of 40 μm in an as-cast Al-Mg-Zn-Sc alloy change little after heat treatments, bringing about a grain-boundary strengthening of 46.1 MPa. The coarse T-Mg32(Al, Zn)49 phases at grain boundaries are completely dissolved into the matrix through solid-solution treatment, and T-Mg32(Al, Zn)49 with diameters ranging from 10 to 25 nm and Al3Sc with diameters ranging from 5 to 20 nm gradually precipitate during the artificial aging process. The Mg solid solubility is 4.67% in the as-cast Al-Mg-Zn-Sc alloy, and it increased to 5.33% after solid-solution treatment and dramatically decreased to 4.15% after post-aging treatment. The contributions of solid-solution strengthening to as-cast, post-solid-solution and post-aging Al-Mg-Zn-Sc alloys are 78.2 MPa, 85.4 MPa and 72.3 MPa, respectively. The precipitation strengthening of the post-aging alloy is 49.7 MPa, which is an increase of 21% in comparison to that of both as-cast and post-solid-solution alloys. The alloy achieves an optimal tensile strength of 355.3 MPa, yield strength of 175 MPa and elongation of 22% after undergoing solid-solution treatment.

Effect of Er2O3 on kinetic and thermodynamic properties of RE-Mg based hydrogen storage alloys

In this paper, Mg90Ce5Y5 alloy was prepared by vacuum induction melting and Er2O3 catalyst was doped by high energy ball milling. The phase structure and microstructure were characterized by XRD, TEM, EDS, and the results showed that the ball-milled samples contained CeMg12, Ce2Mg17, Y5Mg24, Mg and Er2O3. After hydrogen absorption, the phase composition is MgH2, CeO2, YH2, Er2O3 and ErH3. Only MgH2 and ErH3 participated in the dehydrogenation reaction to form Mg and ErH2 phase, and other phases have excellent thermodynamic stability. Moreover, there are abundant defects inside the composite particle. In the process of hydrogenation, the E6 sample absorbs 84.3% of maximum hydrogen (4.65 wt % H2) in 573 K within 2 min, which has more excellent hydrogen absorption kinetics than the others, especially Mg90Ce5Y5 (64.7%). The E6, E8 and E10 composites desorbs 3 wt %H2 at 20.2, 22.2 and 19.9 min in 573 K, respectively, and the Edes of them is 76.9 ± 1.8, 80.4 ± 0.4 and 78.4 ± 1.2 kJ/mol, respectively. The kinetics of dehydrogenation does not increase with the increase of catalyst content. The thermodynamic properties have not been significantly improved, but because the existence of ErH2 ↔ ErH3 reversible reactions has been weakly improved.

Formation mechanism of titanium solid solution and its influence on equiaxed behavior of α phase of Ti–5Al–5Mo–5Cr–2Zr-xNb alloys

To clarify the formation mechanism of titanium solid solution (Tiss) and its effect on the microstructure, Ti–5Al–5Mo–5Cr–2Zr-xNb alloys are prepared by vacuum induction melting and multi-directional forging (MDF). The results show that the alloy phase is composed of grain boundary α (αGB), primary α (αp), secondary α (αs) and residual β phases. The crystal structure of Tiss is consistent with that of the β phase. Nb atoms rapidly spread along the dislocations and aggregated to the α phase boundary during MDF, and Nb atoms dissolved in the lattice of the β phase to form Tiss. There are (0002)α∥(3¯21¯)Tiss and (011¯0)α∥(121¯)Tiss orientation between titanium solid solution and equiaxed αp phase. Therefore, the equiaxed behavior of the αp phase is characterized by the formation of new phase boundaries caused by dislocations captured by Tiss. The tensile strength and toughness increased when the Nb content increased from 3 to 9%, which is attributed to the increase in the α phase content and the solid solution strengthening of Nb. When the Nb content increased to 12 wt.%, the tensile strength and toughness decreased due to the debonding of the lamellar αp phase. The equiaxed αp phase improves the plasticity of the titanium alloy, so the strain decreases with decreasing content.

Microstructure evolution of as-cast CoNiCrAl bond coat alloys after isothermal heat treatments

In this paper, the microstructure evolution of two as-cast CoNiCrAl bond coat alloys after various isothermal heat treatments were investigated. The CoNiCrAl bond coat alloys were prepared by vacuum induction melting and casting process. The as-cast alloys were subjected to heat treatments from 550 °C to 1300 °C for periods up to 100 h to study the effects of temperature on the microstructure and phase distribution. The microstructure of heat treated CoNiCrAl bond coat alloys was characterised by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). The CoNiCrAl alloys exhibited a two phase γ + β structure, with the β phase acting as the primary phase. It was shown that the precipitation of needle-like secondary γ phase was slow at temperatures below 600 °C but became rapid above 900 °C. It was found that the morphology of the secondary γ phase changed from needle-like to rod-like at 1100 °C. A homogeneous γ + β two phase structure was obtained at 1300 °C even after 2 h heat treatment. It was revealed that the heat treatment temperature had a significant influence on the formation and distribution of the secondary γ phase. In addition, the precipitation of sub-micron Cr-rich particles occurred at 1300 °C in both CoNiCrAl alloys, which was due to the low solubility of Cr in the β phase and rapid coalescence of γ phase at elevated temperatures.

Microstructure and mechanical behaviour of Nb- containing high Al ferritic low density steels

Two high Al ferritic low density steels, Fe-11Al-5Mn-1Nb-1C (Alloy 1) and Fe-11Al-10Mn-1Nb-1C (Alloy 2) were prepared by vacuum induction melting. Their recrystallization behaviour is investigated. Hot rolling of the steels was carried out at 1100 °C. The temperature was chosen to ensure that the alloys were hot rolled in the intercritical region. Hot rolling led to a ferritic microstructure which was only partially recrystallized even after 92% rolling reduction. Annealing of hot rolled alloys at 1000 °C for 1 h results in a significant Static Recrystallization of the ferrite matrix. This suggests that dynamic recrystallization is difficult in these high Al ferritic steels. A further reduction of 33% was given to the hot rolled and annealed alloys by cold rolling. Annealing of cold rolled alloys at 1000 °C for 1 h leads to almost complete recrystallization. The hot rolled alloys exhibit better Yield and Ultimate Tensile Strength whereas the annealed alloys show higher total elongation. The best combination of properties is obtained in cold rolled and annealed samples. Alloy 2 exhibit superior tensile properties in comparison to Alloy 1. NbC precipitates pin the grain boundaries and may delay recrystallization. This necessitates further cold working and annealing to achieve complete recrystallization. NbC precipitates result in a significant refinement in grain size in annealed alloys. Nb addition also permits cold rolling without edge cracking. Thus, Nb may be an important alloying addition for high Al ferritic low density steels.

Microstructure Characteristics and Hydrogen Storage Kinetics of Mg77+xNi20-xLa3 (x = 0, 5, 10, 15) Alloys.

Mg77+xNi20-xLa3 (x = 0, 5, 10, 15) alloys were successfully prepared by the vacuum induction melting method. The structural characterizations of the alloys were performed by using X-ray diffraction and scanning electron microscope. The effects of nickel content on the microstructure and hydrogen storage kinetic of the as-cast alloys were investigated. The results showed that the alloys are composed of a primary phase of Mg2Ni, lamella eutectic composites of Mg + Mg2Ni, and some amount of LaMg12 and La2Mg17. Nickel addition significantly improved the hydrogen-absorption kinetic performance of the alloy. At 683 K, Mg77Ni20La3 alloy and Mg82Ni15La3 alloy underwent hydrogen absorption and desorption reactions for 2 h, respectively, and their hydrogen absorption and desorption capacities were 4.16 wt.% and 4.1 wt.%, and 4.92 wt.% and 4.69 wt.%, respectively. Using the Kissinger equation, it was calculated that the activation energy values of Mg77Ni20La3, Mg82Ni15La3, Mg87Ni10La3 and Mg92Ni5La3 alloys were in the range of 68.5~75.2 kJ/mol, much lower than 150~160 kJ/mol of MgH2.

Machine learning assisted optimization of tribological parameters of Al–Co–Cr–Fe–Ni high-entropy alloy

ABSTRACT High-entropy alloys (HEA) have become increasingly important in the materials world due to their ability to combine multiple principal elements in an alloy system to achieve desired mechanical and tribological properties. In this study, Al–Co–Cr–Fe–Ni HEA alloy is synthesized using vacuum induction melting and its tribological properties are analyzed under dry conditions, which is important since dry sliding is a common mode of wear in many engineering applications. To enhance its tribological performance, evolutionary data-driven modeling and optimization techniques are applied to determine the best possible solutions for the loading condition at different frequency levels. A neural net-based algorithm (EvoNN) is utilized in the data-driven modeling process to generate and train models, which are then used in the optimization process. The reference vector-based algorithm (cRVEA) is incorporated with the EvoNN to evaluate the optimum wear, coefficient of friction (COF), and surface roughness results in multidimensional hyperspace. The results obtained from this study fall within the experimental data range and satisfy the tribological requirements under optimum conditions. The excellent wear resistance of HEAs due to their high hardness, strength, and resistance to deformation makes them suitable for use in various wear applications, including cutting tools, bearings, and gears. Overall, this study highlights the potential of HEAs and data-driven modeling techniques for the development of advanced materials with superior properties and performance.

Development of an Al rich Ti–Al alloy with better ductility

In this work, structural and mechanical properties of Ti–56Al–4Zr–2Nb (wt.%) alloy have been investigated by first-principles calculations based on density functional theory and experimentally. Theoretical studies have been performed with the crystal structures created with the Virtual crystal approximation approach. Ti–56Al–4Zr–2Nb (wt.%) alloy have been synthesized first time by vacuum induction melting. The phases in the microstructure were examined by scanning electron microscopy and X-Ray diffraction. Simulated alloy is found as mechanically stable by first-principles calculations. Elastic modulus and hardness results of theoretical and experimental studies are in good agreement with each other, and acceptable difference shows the reliability and success of the theoretical results in this study. Ti–56Al–4Zr–2Nb (wt.%) alloy is suggested as a promising new Ti–Al alloy for industrial applications.

Properties of various CaO-Al2O3-TiO2 refractories and their reaction behaviours in contact with Ti6Al4V melts

Vacuum induction melting technology is an important method for producing high-quality titanium alloy. The key challenge lies in the development of refractories with excellent chemical stability for titanium alloy corrosion. In this work, CaO-Al2O3-TiO2 refractories are proposed as the potential materials for Ti6Al4V alloy smelting. Four CaO-Al2O3-TiO2 refractories with different TiO2 contents were prepared and their reaction behaviours in contact with titanium aluminum melts were investigated in detail. When the refractory has a suitable content of CaTiO3 phase, it promotes the diffusion and mass transfer rate of ions and improves the sintering reaction activity, leading to good high temperature mechanical properties and corrosion resistance to titanium aluminum alloy. However, when the TiO2 component is excessive, CA6 has been completely wrapped by CaTiO3, and some CA6 grows abnormally, resulting in a decrease in high temperature mechanical properties of the refractory. Moreover, during the smelting of Ti6Al4V alloy, Al component reacts with CaTiO3 to produce metallic Ti and calcium aluminate phase with low melting point, resulting in degradation of refractory.