Daido Steel Co., Ltd. (President Tetsuya Shimizu) has become the first domestic manufacture to produce a low elastic modulus titanium alloy1) Ti-15Mo (ASTMF2066), and begun accepting purchase orders from major overseas customers in October 2023.
Ti-15Mo constitutes of titanium and molybdenum, those elements are good bio-compatibility, and is expected to have high recovery properties2) because it has a pliability that is close to that of bone among metal materials ( its elastic modulus is closer to that of bone than conventional alloys). This alloy is used for medical use.
Our company has been selling medical use titanium alloys such as Ti-6Al-4V ELI and Ti-6Al-7Nb, and now we have added a medical use titanium alloy with low elastic modulus closer to those of bone to our repertoire.
Demand for medical titanium alloys is expected to expand over the medium to long term due to the global population increase and the growing need for advanced medical care.
As a strategic investment to respond to the high order environment for medical titanium products, which is a growing field, in January 2024, we will introduce an ultrasonic inspection device as AMS specifications at the Hosizaki Plant (Nagoya), in addition, by March 2025, one new vacuum arc remelting furnace (VAR) for titanium will be established at the Chita No.2 Plant (Chita City, Aichi), bringing the total to two. With a total investment of approximately 2.2 billion yen, we plan to increase production by 20%.
By increasing our manufacturing capacity and promoting overseas sales expansion activities, we will approximately double the amount of titanium orders we receive by 2030 compared to 2018, and increases our global share of medical titanium products from the current 10% to 2030. We aim to increase this to 20% a year.
1.Background
For many years, our company has been providing titanium and titanium alloys that meet a variety of needs, including medical applications, automobiles, an eyeglass frame materials, and is the top domestic manufacture of titanium bars and wire rod products.
Ti-15Mo is a medical use titanium alloy with a history of more than 20 years, having been registered as ASTMF2066 by ASTM international (American society for Testing and Materials)3) in 2000.
Because it contains more molybdenum than other titanium alloys, it is difficult to manufacture, and there were no manufactures in Japan who could manufacture it.
Therefore, we introduced the LIF furnace (Levitation Induction Furnace)4) an advanced melting technology, to improve the un-melted molybdenum, marking us the manufacture to mass produce Ti-15Mo.
2.Characteristics of Ti-15Mo
(1)components
Ti-15Mo is constituted of titanium and molybdenum with little toxicity, and is not contain nickel and vanadium.
(2)Standard alloy registered with ASTM International
Ti-15Mo is a standard alloy registered with ASTM International (American Society for Testing and Materials) and has a prove track record in the market for medical applications, so it is easy to expand its use.
3.Flexibility
Its elastic modulus (Young’s modulus) is closer to that of bone than ASTMF136 (Ti-6Al-4V) and ASTMF1295(Ti-6Al-7Nb), which are alpha plus beta type alloys5) that have been conventionally used for artificial bones (Fig.1)., it has a flexibility similar to that of bone, and is less likely to cause stress shielding of bone tissue or bone atrophy.
4.High toughness
i-15Mo is soft and has good cold formability in solution treatment, and can be made stronger than ASTMF136 by adding aging6), so the strength can be adjusted as necessary.
Fig.1 Tensile strength and Young's modulus of various titanium alloys
3.Applications
Various medical device parts including artificial bones
Terminology
| *1 Low elastic modulus titanium alloy for medical device |
Low elastic titanium alloy for medical use has higher flexibility than those of conventional titanium alloy. Elastic modulus is a parameter of flexibility that deformation occurs by loading. |
| *2 High recovery properties |
When they are implanted into human body, metal materials that have a higher elastic modulus than that of bone, the implants take on most of force, and the bone is unable to perform its function (called stress shielding). With Ti-15Mo, the elastic modulus is close to that of bone, the force is transferred to both the implant and the bone. As a result, it is expected that recovery will be faster, and bone atrophy is less. |
| *3 AMS(Aerospace Material Specifications) | Standards for aerospace materials standardized by SAE International, a US non-profit organization. |
| *4 LIF(Levitation Induction Furnace) | Melting can be done without contacting the furnace wall using electromagnetic force, and the melting also uses strong Stirring in the molten metal, making it possible to melt without leaving molybdenum undissolved. |
| *5 Alpha plus beta type titanium alloy |
Titanium is hexagonal closed-pack lattice called α phase at room temperature, and body centered cubic lattice called β phase at high temperatures. Titanium alloys can be made even at room temperature, by adding alloying elements. A two-phases mixture of α and β phases occurs, and this alloy is called α+β type titanium alloy. The α+β type titanium alloy is characterized by moderate strength and heat resistance. |
| *6 Solution treatment and aging |
Solution treatment and aging are types of heat treatments. Solution treatment is a heat treatment witch dissolves α phase in β matrix phase by heating near β transus temperature. Here, β transus is a temperature at which the α phase completely dissolve in the β matrix and fully disappears. Aging is a heat treatment that increases strength by precipitated fine α phase at a lower temperature than solution treatment. |