Ti Powder Research Articles

Large‐scale fabrication of TiC@C powders and its effect on the properties of Al2O3‐MgO‐C castables

AbstractHigh performance carbon containing castables have always been pursued by researchers and steelmaking producers, unfortunately, poor water‐wettability of graphite flakes was greatly limited their application in castables. To respond this, we proposed a large‐scale and low‐cost modified molten salt shielding synthesis technique for fabricating TiC coated graphite in air atmosphere using graphite flake and Ti powder as raw materials. Microstructure, wettability and oxidation resistance of TiC@C powders, and effect of TiC@C powders on the properties of Al2O3‐MgO‐C castables were investigated. The results demonstrate that TiC coated graphite was synthesized via modified molten salt shielding synthesis route in air atmosphere. A uniform and continuous TiC layer was formed on the surface of graphite, thereby significantly improving the water‐wettability and oxidation resistance of graphite flakes. The castables with 5% TiC@C powders possessed lower apparent porosity, higher cold strength, good oxidation resistance, and slag resistance in comparison with the castables with graphite flakes, and slag resistance were also better than Al2O3‐MgO castables. The as‐fabricated TiC@C powders have good water‐wettability and oxidation resistance, making them as a prime carbon source for producing carbon containing castables for steel ladle linings.

Effect of particle size on initial reaction temperature of Ti and Zr powders

In order to study the effect of particle size on the initial reaction temperature of reactive metal powders, thermogravimetric analysis- differential scanning calorimetry (TG-DSC) experiments and hot plate combustion tests were performed on Zr and Ti powders with an average particle size of 13±2, 25±5, 48±3, 75±5, 150±10 μm. Differential scanning calorimetry (DSC) results show that the initial reaction temperature of the metal powder with smaller particle size is lower. The heat flow rate and reaction rate are negatively correlated to the particle size. The hot plate combustion test shows that the initial reaction temperature of the metal powder increased with the increasing particle size. The heating rate also has a certain influence on the initial reaction temperature of the reactive metal powder. The initial reaction temperature is lower with a faster heating rate, for Ti and Zr particles of this study.

Analyzing the Sintering Kinetics of Ti12.5Ta12.5Nb Alloy Produced by Powder Metallurgy

The focus of this work is to analyze the sintering kinetics of Ti12.5Ta12.5Nb alloy by dilatometry. The mixture of powders was achieved by mixing individual powders of Ti, Ta and Nb, which were then axially pressed. Sintering was performed at 1260 °C using different heating rates. The microstructure was determined by X-ray diffraction and scanning electron microscopy. Results show that densification is achieved by solid state diffusion and that the relative density increased as the heating rate was slow. Due to the full solubility of Ta and Nb in Ti, the relative density reached was up to 93% for all samples. Activation energy was estimated from the densification rate and it was determined that two main diffusion mechanisms were predominant: grain boundary and lattice self-diffusion. This suggests that Ta and Nb diffusion did not affect the atomic diffusion to form the necks between particles. The microstructure shows a combination of α, β and α′, and α″ martensitic phases as a result of the diffusion of Ta and Nb into the Ti unit cell. It was concluded that the heating rate plays a major role in the diffusion of Ta and Nb during sintering, which affects the resulting microstructure.

Experimental and thermodynamic modeling of Al2O3 corundum and TiO2 rutile structures forming on Ti-6Al-4V powder during oxidation

The high affinity of Ti-6Al-4 V (Ti64) powder to oxygen impacts the quality of the powder during additive manufacturing. The oxide scale consists of a double layer with α-Al2O3 in the outer part and TiO2 in the inner one. Experimental and thermodynamic results are used to further understand the formation of these two oxide layers. Inert marker revealed the anionic growth of the duplex oxide scale. The thermodynamic results highlighted that interstitial aluminum enters and diffuses fast within TiO2 (rutile) to form Al2O3 as the surface layer. Moreover, α-Al2O3 is considered as a non-stoichiometric oxide with a very small excess of oxygen as dumbbells at high partial pressures of oxygen. A remarkable effect of the impurities on the concentration of native point defects is observed in this phase. Finally, a reactional mechanism with elementary steps for the oxidation of Ti64 powder is proposed.

Cryomilling of Isotope-Enriched Ti Powders for HIVIPP Deposition to Manufacture Targets for Nuclear Cross Section Measurement.

The realization of isotopically enriched Ti targets for nuclear cross-section measurements requires particular attention, from the starting material preparation up to the deposition technique. In this work, a cryomilling process was developed and optimized, aimed at reducing the size of 49,50Ti metal sponge as provided by the supplier (size up to 3 mm), to the optimal size of 10 µm, to fit the High Energy Vibrational Powder Plating technique used for target manufacturing. The optimization of the cryomilling protocol and the HIVIPP deposition using natTi material was thus performed. The scarce amount of the enriched material to be treated (about 150 mg), the need to obtain a non-contaminated final powder and a uniform target thickness of about 500 µg/cm2 were taken into account. The 49,50Ti materials were then processed and 20 targets of each isotope were manufactured. Both powders and the final Ti targets produced were characterized by SEM-EDS analysis. The amount of Ti deposited was measured by weighing, indicating reproducible and homogeneous targets, with an areal density of 468 ± 110 µg/cm2 for 49Ti (n = 20) and 638 ± 200 µg/cm2 for 50Ti (n = 20). The uniformity of the deposited layer was also confirmed by the metallurgical interface analysis. The final targets were used for the cross section measurements of the 49Ti(p,x)47Sc and 50Ti(p,x)47Sc nuclear reaction routes aimed at the production of the theranostic radionuclide 47Sc.

Fabrication of nanostructured non-stoichiometric TiO2-x by spark plasma sintering for enhancing its thermoelectric properties

In this study, nanostructured non-stoichiometric TiO2-x compacts were prepared by the in-situ reduction of rutile titanium oxide (TiO2) powder with urea powder via spark plasma sintering (SPS). The crystal structure and particle size of the prepared compacts were examined. The XRD patterns revealed that TiO2 could be reduced easily by the urea powder to obtain non-stoichiometric TiO2-x, and the compacts still possessed rutile crystal structures. The average particle sizes of the compacts were less than 250 nm, successfully obtaining the non-stoichiometric TiO2-x with uniform nanostructures at the sintering temperature of 1073 K. In addition, nanostructured TiO2-x compacts with Magnéli phase TinO2n-1 (n = 2, 4, 8) were fabricated by varying the volume fraction of Ti powder in a urea environment via SPS. The results suggested that addition of Ti powder contributed to the formation of Magnéli phases TinO2n-1, and the value of n decreased with an increase in the volume fraction of the Ti powder. Furthermore, the thermoelectric properties of the compacts sintered with and without Ti powder were both investigated. The TiO2–U13.3-Ti10 compact displayed the highest power factor of 5.04 μWcm−1K−2 at 973 K. A lower thermal conductivity was achieved by TiO2–U13.3-Ti10 compact in the temperature range of 373–973 K, approximately 3 Wm−1K−1, due to the nanostructures and Magnéli phases. The highest ZT value of 0.146 was obtained for the TiO2–U13.3-Ti10 compact at 973 K, achieving a reasonable enhancement of thermoelectric properties.

Microstructure evolution and reaction mechanism of reactive plasma sprayed Ti–C–N coatings

This investigation focuses on the feasibility of the reaction synthesis of Ti–C–N phase using plasma spraying powder mixture of Ti and graphite under nitrogen ion flame flow. To regularize the microstructure and properties of the sprayed Ti–C–N coating, the microstructure evolution of the Ti-graphite-N2 system was analyzed based on water quenching tests. The reaction pathway of the Ti-graphite-N2 system has been investigated by thermodynamic calculations and thermal analysis, revealing the mechanisms of the reaction during plasma spraying. The results show that the as-deposited coatings exhibit a typical layered structure consisting mainly of TiCxNy and TiO2. The quenched powders exhibit a melting process from irregular particles to smooth spherical particles, forming complete droplets with increasing spray distance. Based on phase evolution of the quenched powders and the thermal analysis of Ti powders or Ti/graphite powders under N2/Ar atmosphere, it found that the Ti powder can reacted with graphite or N2 by solid-solid or solid-gas reaction to form TiCx and TiNy, and TiNy can be formed preferentially as compared with TiCx phase. As the spraying distance increases, the Ti and graphite reactions are enhanced, and a pronounced TiCx phase can be detected once a large liquid Ti phase is formed. As the spray distance increases, formed TiNy and TiCx phases aggregate into droplets and rapidly transform into TiCxNy phase by solid-solution reactions. In addition, titanium oxide coexists in lamellae of Ti–C–N coatings due to the absorption and dissociation of O₂ from the atmosphere at the droplet surface.

Green synthesis, formation mechanism and oxidation of Ti3SiC2 powder from bamboo charcoal, Ti and Si

Using low-cost and highly reactive bamboo charcoal, Ti and Si elemental powders as starting materials, Ti3SiC2 powder was synthesized via a simple and cost-efficient pressureless sintering technique in argon atmosphere. The influences of synthesis temperature, holding time and Si content on the Ti3SiC2 content of the synthesized products were investigated, and the analysis indicated that the relative content of Ti3SiC2 reached 98.9 wt% with a molar ratio of 3Ti/1.2Si/2.2C at 1400 °C for 1.5 h. The Ti3SiC2 with good crystallinity and homogeneous nanolayered structure was synthesized at lower temperatures due to the high reactivity and high specific surface area of bamboo charcoal. The non-isothermal oxidation behavior showed that Ti3SiC2 powder was stable in air below 540 °C. With the temperature increasing up to 1300 °C, continuous and dense TiO2 and SiO2 oxidation layers were formed on the surface of Ti3SiC2 particles, which conferred good oxidation resistance to Ti3SiC2 powder.

Tritium release behavior from neutron-irradiated FLiNaK mixed with Ti powder

• FLiNaK mixed with Ti powder was irradiated by mainly thermal neutrons. • Amounts of TF, T2 and T2O released from the FLiNaK by heating were investigated. • Chemical form ratio of released tritium was approximately TF:T2:T2O = 5:70:25. • Approximately 70% of tritium was released as T2O from the FLiNaK exposed to air. • Ti powder mixed to the FLiNaK contributed to the suppression of tritium release. FLiNaK is used as a simulant of FLiBe and FLiNaBe which are promising candidates of liquid blanket material in fusion reactors. In this study, to obtain useful knowledge for tritium release behavior from molten salts such as FLiBe and FLiNaBe, tritium release experiments were carried out for neutron-irradiated FLiNaK containing Ti powder. The solid-state samples were irradiated by mainly thermal neutrons at Kyoto University Research Reactor, and tritium release behavior as TF and T 2 by heating in Ar gas flow was observed and additionally total amount of released T 2 O was obtained. Most of the tritium generated inside the FLiNaK was released to the gas phase even when the FLiNaK was in a solid state at a temperature below its melting point. From the molten FLiNaK unintentionally exposed to air, approximately 70% of tritium was released as tritiated water vapor. The amount of TF released from the molten FLiNaK was considerably less than that of T 2 . This result is consistent with the tendency of tritium release from neutron-irradiated FLiNaBe in our previous study. The ratio of chemical form was approximately TF:T 2 :T 2 O = 5:70:25. It was experimentally confirmed that the Ti powder added to the salt contributes to the suppression of tritium release from the molten salt.

Effect of ball mill time and wet pre-milling on the fabrication of Ti powders by recycling Ti machining chips by planetary milling

In this study, Cp-Ti particles were fabricated from titanium turning chips by wet-pre milling assisted mechanical milling with different ball to powder ratio and milling time. The minimum particle size fabricated with a ball to powder weight ratio of 15:1 is approximately 15 times smaller than powders produced with 5:1. TiO2 (Anatase and Rutile) peaks were found in the structure of Cp-Ti particles fabricated after 4 h of milling at a ball-to-powder ratio of 15:1. However after the milling with low ball to powder ratios (5:1 and 10:1) the oxidation was not observed in results of XRD analysis. The lowest apparent density and hardness was measured as 2.45 g/cm3 and 126 HV for 0.5 h milled powders, respectively. The maximum apparent density and hardness was measured as 3.45 g/cm3 and 325 HV for 7 h milled powders, respectively.

Effect of micro particle addition to the resin on the mechanical behavior of fiber reinforced composite plates

Abstract In this study, laminated composite plate was produced from fiber reinforced fabric by vacuum infusion method. Composite plate was produced using glass fiber and epoxy resin. During production, B4C, TiC, TiO2, Al, Fe, and Ti powders were added to the resin in micro size and at 3 to 5 wt%. Test samples were obtained from the produced plate and subjected to wear test on pin-on disc type bench. For samples with 3 wt% additives, the wear rate increased significantly as the wear distance increased for each sample. In the case where the wear distance is maximum, the wear rate decreased the most in the TiC added sample. At the same time, TiC additive gave the lowest wear rate at 900–1800 m wear distance. For each sample with non-additive and 5 wt% additive, the wear rate increased linearly as the wear distance increased. When the wear distance is maximum, the wear rate decreased the most in the TiO2 added sample. The highest tensile strength reduction was obtained in B4C added sample as 50 wt% for 3 wt% additive and 61 wt% for 5 wt% additive.

Effects of content and particle size of TiH2 powders on the energy output rules of RDX composite explosives

In order to improve the detonation characteristics of RDX, a RDX-based composite explosive with TiH2 powders was prepared. The effects of content and particle size of TiH2 powders on thermal safety, shock wave parameters and thermal damage effects of RDX-based composite explosive were studied with the C80 microcalorimeter, air blast experiment system and colorimetric thermometry method. Experimental results showed that TiH2 powders could enhance the thermal stability of RDX-based composite explosive and increase its ultimate decomposition heat. The content and particle size of TiH2 powders also had significant effects on the thermal safety, detonation velocity, shock wave parameters, fireball temperature and duration of RDX-based composite explosives. Furthermore, the differences of TiH2 and Ti powders on the detonation energy output rules of RDX-based composite explosives were also compared, showing that TiH2 powders had better influences on improving the explosion power and thermal damage effect of RDX-based composite explosives than Ti powders, for the participation of free H2 released by TiH2 powders in the detonation process. TiH2 powders have important research values as a novel energetic additive in the field of military composite explosives.

In situ fabrication of spherical oxide dispersion strengthened Ti powder through gas atomization

Oxide dispersion strengthened (ODS) alloys exhibit excellent mechanical properties due to fine oxide dispersion, but they have great limitations due to utilizing powder fabrication via mechanical alloying. Therefore, this study examined the alloy composition and process that can fabricate ODS titanium (Ti) powder in situ through a gas atomization method. The composition and content of the oxide, which can dissolve in molten Ti during melting and precipitate inside powders during cooling in the gas atomization, were derived through thermodynamic calculations. The ODS Ti alloy composition of Ti + 1 wt% yttria (Y2O3) was derived, and the alloy was prepared as a powder through an electrode induction melting gas atomization (EIGA) method. First, rod-shaped ingots were prepared through vacuum arc remelting (VAR), and Y2O3 was coarsely precipitated along the grain boundaries due to the slow cooling rate. Then, the ODS Ti powder was fabricated by EIGA using the rod ingot and spherical powders could be continuously fabricated. The cross-section microstructure of the powder was observed, and the Y2O3 particles with several tens of nm were uniformly distributed inside the powder. These thermodynamic calculations and experiments confirmed that ODS Ti powder could be fabricated in situ using the gas atomization method.

Processing of hydroxyapatite (HA)–Ti–6Al–4V composite powders via laser powder bed fusion (LPBF): effect of HA particle size and content on the microstructure and mechanical properties

This research study examines the influence of hydroxyapatite (HA) powder particle size and content on the processability, microstructure, and mechanical properties of the laser powder bed fusion (LPBF) fabricated Ti–6Al–4V (Ti64)-HA composites. For this purpose, various Ti64-HA composite powders were produced, and the effects of the HA particle size and content on the optical reflectance were investigated. Composite powders and the monolithic Ti64 powder (as the reference) were subjected to the LPBF process within a wide range of volumetric energy densities by varying the LPBF process parameters. Parts with the highest relative density for each material were assessed by studying their microstructure, nanohardness, and nanoindentation-derived yield strength. Results revealed that the incorporation of the highly reflective HA powder into the Ti64 slightly enhanced the reflectance of Ti64-HA composite powders over that of the monolithic Ti64 powder. The LPBF processability of the composite powders was found to highly depend on the content of the HA constituent. For any given volumetric energy density employed in this study, composites containing 1 wt%HA were crack-free. However, composite systems containing higher HA content (2.5 wt%) featured randomly distributed transgranular cracks. Addition of 1 and 2.5 wt%HA to the Ti64 resulted in a significant improvement in the nanohardness (∼30 and 75%) and yield strength (∼20 and 37%). The dominant strengthening mechanisms in composite samples were the Hall-Petch and geometrically necessary dislocations strengthening, accounting for 57–66% and 13–20% of the total yield strength improvement.

Effect of Ti content on the cell structure and compressive and energy absorption properties of Al3Ti/Al6061 foam composite

Aluminium alloy foams are often used as cushioning parts for automobiles because of their excellent energy absorption properties and lightweight characteristics. Their energy absorption properties mainly depend on the cell structure of the foam, but the cell structure of aluminium alloy foams prepared by the powder metallurgy method is usually difficult to control. In this work, Al3Ti/Al6061 foam composite (AT-FC) was prepared by powder metallurgy using TiH2 as the blowing agent and a mixture of Al6061 and Ti powder as the foaming matrix. The effects of different Ti contents on the cell structure, cell distribution and morphology of AT-FC were focused on, and their mechanical properties under quasi-static compressive loading were investigated. The experimental results showed that different Ti contents could regulate the cell size and improve the cell morphology and distribution, in which AT-FC contains 7.5 wt% Ti had the best cell structure with an average cell size of about 1.56 mm and an average circularity of 0.82. By comparing the compressive yield strength, energy absorption and specific energy absorption of AT-FC with different Ti contents, the AT-FC with 10 wt% Ti had the best compressive yield strength of 8.96 MPa and AT-FC with 7.5 wt% Ti had the best energy absorption of 6.50MJ/m3.

Synthesis and characterization of novel NiTi–Ni3Ti/SiC nanocomposites prepared by mechanical alloying and microwave-assisted sintering process

Equiatomic Ni–Ti alloy reinforced with 0, 2.5, 5, and 10 vol % SiC nanoparticles was synthesized through mechanical alloying and microwave sintering process. In this method, a mixture of Ti and Ni powders and SiC nanoparticles (0–10 vol%) were mechanically milled for 30 h, compressed under 1 GPa pressure, and then sintered at 900–1100 °C by microwave heating. Microstructural analysis of the synthesized samples was performed using X-ray diffraction and scanning/transmission electron microscopy, and their hardness was determined using a Vickers microhardness tester. Structural studies revealed the formation of a complex phase structure consisting of the austenite (B2–NiTi), the martensite (B19′-NiTi), and the nickel-rich (Ni3Ti) and titanium-rich (NiTi2) phases. HR-TEM investigations confirmed an increased Ni3Ti phase in the austenitic NiTi matrix nearby the martensitic NiTi phase. It was found that adding SiC nanoparticles to Ni–Ti increased the amount of hard Ni3Ti phase, promoted the stability of the martensite phase at room temperature, and retarded the matrix grain growth during the sintering process. Microhardness tests showed that when the content of SiC nanoparticles increased up to 5 vol %, the microhardness increased considerably to 9 GPa and then declined. The high microhardness of synthesized nanocomposites is due to the formation of Ni3Ti and NiTi martensitic phases and their nanocrystalline structure.

Novel titanium matrix composites reinforced by NiCoCr medium entropy particles

Titanium matrix composites (TMCs) reinforced with 2–8.3 wt.% NiCoCr medium-entropy alloy particles (NiCoCrp/Ti) were synthesized through an in-situ reaction between NiCoCr and Ti powders during a spark plasma sintering process at 850 °C and 1000 °C. At 850 °C, there are obvious interdiffusion layers with Ti3(Ni, Co) intermetallic around NiCoCr particles. At 1000 °C, the sufficient diffusion of Ni, Co and Cr away from the prior NiCoCr particles results in clusters of granular intermetallic (Ti3(Ni, Co) and Ti2(Ni, Co)) in the Ti matrix. Besides, the addition of NiCoCr particles leads to a significant improvement in tensile strength and hardness. Ti-2wt.%NiCoCr sintered at 1000 °C has a combination of high tensile strength (788 MPa) and good ductility (23.4%). Furthermore, the mechanical properties are mainly correlated to the amount and distribution of the intermetallic compounds in TMCs.

Micro-hydroxyapatite reinforced Ti-based composite with tailored characteristics to minimize stress-shielding impact in bio-implant applications

Biomaterials having higher strength and increased bioactivity are widely researched topics in the area of scaffold and implant fabrication. Metal-based biomaterials are favorably suitable for load-bearing implants due to their outstanding mechanical and structural properties. The issue with pure metallic material used for bio-implant is the mismatch between the mechanical properties of the human body parts and the implant. The mismatch in modulus and hardness values causes damage to muscles and other body parts due to the phenomena of ‘stress-shielding’. As per the rule of mixture, combining a biocompatible ceramic with metals will not only lower the overall mechanical strength, but will also enhance the composite's bioactivity. In the present work, a Metal-Ceramic composite of Ti and μ-HAp is processed through high-energy mechanical alloying. The μ-HAp powders (in a weight fraction of 1%, 2%, and 3%) were alloyed with Pure Ti powder sintered using microwave hybrid heating (MHH). The homogeneously alloyed materials were inspected for chemical and elemental characteristics using XRD, SEM-EDX, and FTIR analyses. Nano-mechanical and micro-hardness properties were inspected for the fabricated Ti- μ-HAp composites and it shows a decreasing trend. Elastic modulus declined from 130.8 GPa to 50.11 GPa for 3 wt% μ-HAp compared to pure-Ti sample. The mechanical behaviour of developed composites confirms that it can minimize the stress-shielding impact due to comparatively lesser strength and hardness than pure metallic samples.

Study of the influence of the parameters of the TI-C-Al-SiO2-Al2O3-Fe2O3-PT-NA-01 charge stock mechanical activation on the duration of the modifying composites synthesis

Abstract. Problem. The paper is devoted to one of the urgent problems of modern materials science – the creation of materials with predetermined properties, methods of their production and practical application. Goal. This work is devoted to the study of the influence of mechanical activation parameters on the synthesis duration and morphology of the Ti-C-Al-SiO2-Al2O3-Fe2O3-PT-NA-01 charge intended for the production of a modifying composite material obtained by self-propagating high-temperature synthesis. Methodology. Powders Ti, C, Al, SiO2, Al2O3, Fe2O3, PT-NA-01 are used as starting materials. Mechanical activation of the charge with variation of process parameters was carried out in a ball mill of the KM-1 model, developed by the authors of this work, of the intermittent principle of operation with a working steel drum volume of 1.5‧10-4m3. The ball mill weighs 5.8 kg and has dimensions (W-H-D) of 190-180-230 mm. The duration of mechanical processing of the charge was from 1 to 25 minutes, with a drum rotation speed of 50 to 180 rpm. The ratio of the charge weight to the grinding media weight (steel balls with a diameter of 6 mm) was 1 : 20 and 1 : 40. Results. Studies have established that the recommended mode of mechanical activation of the Ti-C-Al-SiO2-Al2O3-Fe2O3-PT-NA-01 charge is treatment for 15 minutes at a drum rotation speed of 130 rpm and a ratio of 1:40 charge weight to steel ball weight. The particle size distribution of the charge is reduced from a maximum size of 100 microns to 40 microns. Originality. Based on the studies conducted, it can be concluded that such treatment of this charge leads to an increase in the chemical activity of the components and increases the efficiency of the SHS process by reducing the duration of its initiation and synthesis. Practical value. The developed modified composite material is recommended for arc surfacing and gas thermal spraying of strengthening and restoring coatings of machine parts.

Production of Titanium Hydride Powder from Titanium Tetrachloride Using Magnesium Metal in Hydrogen Gas Atmosphere

The development of titanium (Ti) powder production process is important because Ti powder metallurgy (PM) is a promising method that can result in large cost savings by reducing material loss and the number of steps in the conventional manufacturing process of Ti metal and its alloys. This study investigated the process of producing Ti hydride powder directly from titanium tetrachloride (TiCl4) using magnesium (Mg) metal and hydrogen gas (H2). The experiments were conducted at 1073–1173 K when the TiCl4 feeding rate was in the range of 19.16–57.42 g·min−1 with the use of cooling gas as Ar or H2 gas. A mixture of Ti and Ti hydride (TiH1.5) was obtained in an iron (Fe) crucible by the dehydrogenation of Ti hydride as the TiCl4 reduction proceeded. The concentration of oxygen (O) decreased with a decrease in the specific surface area and/or an increase in the proportion of TiH1.5 in the powder. As a result, the concentration of O of the mixture of Ti and TiH1.5 decreased to 0.116 mass% under a certain condition.