How the author started research and development of titanium alloys and the author’s subsequent development of research and development of titanium alloys over many years are described with hoping that it will be a reference for researchers and engineers who are about to start research and development of titanium alloys, or for researchers and engineers who have just started its research and development including topics.

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Light elements such as hydrogen, carbon, nitrogen, and oxygen interact with Ti and its alloys during manufacturing processes and in usage environments. These elements exhibit high affinity and high solubility in Ti as well as being interstitially dissolved, abundant, and inexpensive. Interactions between Ti and light elements are related to the reduction and refining process, alloy and surface design, microstructural control, and other functions. Thus, understanding interactions is necessary for constructing a reasonable Ti production process and expanding applications. The recent progress in our group on the interaction between Ti and light elements, including the experimental and computational approaches for the high-temperature oxidation of Ti alloys, preparation and antibacterial-activity evaluation of visible-light-responsive photocatalytically active TiO₂ layers formed by the surface reactions of Ti, and oxygen removal (deoxidation) from Ti melts using hydrogen plasma, are reported in this paper.

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Titanium and its alloys have high relative strength, excellent corrosion resistance and good biocompatibility. However, though they are expensive, application fields of them are not extended. To extend application fields, low cost titanium and its alloy are developed actively. Developments of Ti-Cr-Fe-Al and Ti-Mn-Fe-Al system alloys are explained in this text. Ti-13mass%Cr-1mass%Fe-3mass%Al system alloys was developed as commercial use, because those alloy had good mechanical properties. Ti-10mass%Mn-1mass%Fe-3mass%Al alloy was selected as a candidate for commercial use.

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The Japan Institute of Titanium (JITiT) was founded on April 20^th, 2021. The JITiT aims to promote the research and development of titanium and industry-academia collaboration by presenting research on the theory and application of titanium and its alloys, and by exchanging information among its members. The JITiT has already held two times lecture meetings on WEB based on this policy since been founded. Here after, it is expected that the JITiT would play big roles for creating the carbon neutral titanium rolled products producing process, reducing impurities or oxygen, iron, etc. from titanium scrap by reduction, and so on.

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The holding of the 11th World Conference on Titanium, 2007, and the establishment of the industry-academia collaboration committee, the foundation of the Titanium Research Grant for the young titanium researchers and engineers, and the exchange meeting for young titanium researchers and engineers of the Japan Titanium Society, which are thought to be the impetus for the establishment of the Japan Institute of Titanium (JITiT) are firstly described. Then, the establishment and launch of the JITiTi as well as the expectations for JITiT are described.

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3種類のカルシア粉末の特性を調べ, 鋳造用鋳型材およびルツボ材としての可能性を検討した.各カルシアは製法, 純度が異なるため, 粉末の粒度分布や活性度に差があることが認められた.特に, 焼成カルシア (CFQ-S, CSQ-S) は電融カルシア (CFQ-E) に比べて活性度が高いので硬化時間を大幅に短縮できることが判明した.焼成カルシアの生型強さは環境温度, 保存時間に影響を受け, 本実験では約10℃の環境下に24時間保存した場合に最も大きな値を示した.-方, 電融カルシアは低温の環境下では硬化が遅延され, 強さも小さかった.いずれのカルシアも粉末を添加して鋳型を作製すれば, 加熱時にの鋳造収縮を補償しうる膨張を有することが認められた.また, 高周波誘導融解鋳造機を用いて, 各カルシアで作製したルツボおよび鋳型より得られた鋳造体の硬さは, カルシアの純度に影響され, 純度99・9%のCFQ-Sで鋳造したものが最も硬さが小さかった.本実験の結果から, 高純度焼成カルシアが操作性, 物性に優れ, しかもとの反応性も低いので, 鋳造用鋳型材およびルツボ材として最も有望であると考えられた

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高温で安定なイットリアを用いて, 鋳造用鋳型材としての可能性を検討した.粒度の異なる2種類の高純度イットリア粉末を数種類の結合材により練和し, 硬化時間, 硬化時の寸法変化, 生型および焼成強度, 加熱膨張などを測定した.その結果, 平均粒径10μmの粗いイットリア粉末をイットリアゾル20wt%-ジルコニアゾル80wt%の混合溶液で練和した硬化体が硬化時間, 変形, 強度などの点から鋳型材として最も適していた.また金属ジルコニウム粉末を数%添加することにより数%程度の加熱膨張が得られ, の鋳造収縮を十分に補償できると考えられた.平均粒径2μmの細かい粉末は操作性に劣り, 硬化時に変形やひび割れを伴う大きな収縮が認められた.試作イットリア鋳型材中に鋳込まれた鋳造体は非常に型離れが良く光輝面を呈し表面粗さも小さかった.また, 表面の反応硬化層もビッカース硬さの結果から表層150μm程度に限局していることが認められた.また, 試作イットリア鋳型材を用いて臨床形態を有する全部鋳造冠を鋳造した結果, 鋳放しの状態で良好な適合を示した

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Since “Titanium” is lightweight and strong, and provides excellent corrosion-resistance performance and high formability, it has been used widely in each field at present as useful industrial material.
Weldability of pure titanium can be said to be extremely excellent as long as welding atmosphere is fully controlled. The following outlines the TIG welding procedures for titanium and titanium alloy and properties of typical joint example together with the practical application examples.

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難削材で知られるの歯科領域への利用に際し, 新たに結合材, 砥粒の粒度を変えたA-Dの4種類の焼結ダイヤモンドホイールを試作してその研削特性を評価した.市販のカーボランダムホイール (GC) を対照に用いて試験片に対する研削試験を行ったところ, 試作ホイールの研削量はGCと同等かあるいは若干劣っていた.しかし, ホイールの摩耗量はGCホイールに比べて著しく低く, 研削比が大きいため, 効率よくを研削できることが示唆された.4種類の試作ホイールの中では銅系の結合材で粗い砥粒で構成されているCホイールが最も研削効率に優れることが判明した.一方, は反応性に富むので, 研削中の試験片の発熱挙動についても検討を加えた.試験片の温度は荷重および使用ホイールの影響を受けることが明らかとなり・ホイール間の比較では試作ホイールの方がGCホイールよりも温度上昇が小さかった.また・試作ホイールで研削後の表面をEDX分析した結果, 研削面にホイールの成分は検出されなかった.以上のことから, 焼結ダイヤモンドホイールは効果的なの機械加工用工具になりうるものと期待された.

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Ballistic impact tests were conducted on intermediate purity titanium plate and Ti-6pctAl-4pctV-ELI alloy plate and newly developed Ti-Fe-O-N alloy plate using ogive-shaped projectile with 7. 62mm diameter to study relation between the fracture mechanisms and adiabatic shear band formation The plugging process was dominated by adiabatic shear deformation in localized bands.
Selected data and optical micrographs relating to the adiabatic shear band formation, the variation of depth of penetration and ballistic limit velocity were presented.
The fracture mechanisms associated with the shear localization and fracture process changed from bulging failure to plugging failure by a shocked pressure increase.
The results showed the differences of the fracture mechanisms between two high strength titanium alloys are responsible for significant differences in the elongation of their mechanical property and in the evolution of shear band patterns
It also showed evidence of the long shear band connected from the shocked surface to the bulging region was found in all target plates, but evidence of the long cracks connected did not be found in all target plates at impact velocity just near below each ballistic limits

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Properties of precision castings of Ti alloys were investigated in order to evaluate a newly developed casting process. This process is constituted of combination of levitation melting and counter-gravity low-pressure casting, named "LEVICAST". Cast specimens of commercial pure titanium (CP-Ti), Ti-6Al-4V and Ti-6Al-7Nb were prepared by LEVICAST process, and their mechanical properties and surface contamination were examined as compared with rolled and annealed bar. Sound surfaces of castings were obtained through LEVICAST process. Hard alpha case caused by oxygen contamination at surface of the cast specimens were very thin. Increases of carbon and nitrogen from melting atmosphere were negligible. Tensile properties of CP-Ti and Ti-6Al-4V in as-cast condition satisfied the specification of ASTM B367 C-2 and C-5 for ordinary cast use. HIP treatment improved ductility of the casts at the sacrifice of strength. Strength and ductility of HIP'ed Ti-6Al-7Nb casts were slightly lower than those of HIP'ed Ti-6Al-4V casts. Mechanical properties of the HIP'ed casts of both alloys satisfied the specification of ASTM F1108 of Ti-6Al-4V casts for surgical and implant use. Mechanical properties of the cast alloys were almost same as those of rolled and beta-annealed specimen which had coarse microstructures similar to cast one. This demonstrates that mechanical properties of the these alloys are essentially determined by microstructures such as prior beta grain size and lamellar spacing of alpha phases independent of production processes. It was confirmed that LEVICAST was a suitable precision casting process for Ti alloy casts which were free from contamination.

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Rolled titanium clad plates which Sumitomo metal industries, ltd. developed are characterized by Fe/Ni composite insert metal in Ti/ C-steel interface. These composite insert type-rolled titanium clad plates have better bonding strength than single (Fe) insert type-rolled clad plates and explosion bonded clad plates specially after heat treated condition. This excellent bonding characteristic is carried out by minimizing TiC precipitation in Fe/Ti interface where Ni insert hinders C deffusion from C-steel through Fe insert.
This paper presents these characteristics on bonding strength and the latest experiences on forming of rolled titanium clad and design data, especially relationship between drawing ratio and clad plate thickness in head forming and fatigue test results on T fillet welded joint.
Sumitomo metal industries, ltd. has already applied these titanium clad steel plates to various plants such as power plant condenser (tube sheets), pulp and paper industries (bleaching towers) and some chemical plant vessels, etc.

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鉱石類の化学分析における試料の溶融には過酸化アルカリ合剤法,および水酸化ナトリウム法が一般に用いられている.しかしながら前者はルツボの侵蝕が大きく,ルツボ材質の試料中への多量混入による定量への妨害,または影響の難点があり,後者はTiO₂の定量値が低値となる欠点を持っている.検討した結果,ホウ酸と水酸化カリウムの合剤を用いることによって,ルツボの侵蝕の少ない,しかもTiO₂定量値が正確に得られる方法を確立した.
この方法のホウ酸添加はルツボ内面を清浄な金属光沢の状態に保持し,水酸化カリウムによって,溶解度の大きい酸カリウムを生成させ,従来法の欠点を完全に解決し,その上操作が容易であり,迅速である利点も認められた.この方法によれば,スラッグ,ルチルは0.5～2分間,砂鉄,イルメナイトは粒度100メッシュの場合,2～3分間の溶融で完全に融解する.

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の骨に対する高い親和性の理由の一つとして, 疑似体液中に浸漬した場合に, 選択的にリン酸カルシウムの薄膜を生成する能力があることがあげられる.この能力は板表面の化学構造により影響される.本研究の目的は, 表面にTiO₂, TiO₂Ti₂Oと傾斜機能的に変化する厚い酸化層を有する, ワイヤ放電加工処理板のリン酸カルシウム薄膜の析出能を検討することである.ワイヤ放電加工処理板と, コントロールとしての研磨板を, 37℃の電解液 (無機成分のみのハンクス溶液) に30日間浸漬し, 板表面に析出するリン酸カルシウム薄膜の分析を行った.XPS分析およびFTIR分析からいずれの板表面においても, アパタイト様のリン酸カルシウム薄膜の存在が認められた.表面観察から両方の板表面には, 半透明の薄膜が形成され, ワイヤ放電加工処理板では, より厚い粒塊構造物が観察された断面の観察から, ワイヤ放電加工処理板表面には, 研磨板よりも厚いμmオーダの薄膜が形成されたことが確認された. 以上より, ワイヤ放電加工処理板では, 電解液中でのリン酸カルシウム薄膜の生成能が向上し, 骨に対する高い親和性を有していることが判明した.

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