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What materializes architecture for tomorrow

Potential of titanium louver

-Tetsuma Chiken (NIPPON STEEL Corporation)
-Hiroshi Shimizu (Nihon Teppan Co., Ltd.)
-Satoshi Ueda (Sanwa Tajima Corporation)
-Kazuhiko Miyazawa (Kengo Kuma & Associates)
-Moderator: Takashi Nakasaki

-From Magazine for Architects and Engineers, “Detail”

Lightweight, rust-resistant, highly-durable titanium

Nakasaki: Steel, aluminum, and copper have been widely used as metallic building materials for a very long time. Recently, titanium, which has different features than those of these materials, has evolved as building material and has been replacing conventional materials in some areas. With the aim of promoting more use of titanium, there is an ongoing titanium project, in which architect Kengo Kuma was invited to get involved.
 Today, I am pleased to have this opportunity to hear from representatives of three companies participating in this project, as well as Mr. Kazuhiko Miyazawa who is in charge of the project at Kengo Kuma & Associates. I am delighted to learn about titanium and to explore the potential of titanium in future architecture, together with you.

Chiken: Titanium is a relatively new material compared to copper with about 6,000 years of history, steel with 4,000 years, and aluminum with 200 years. Only about 70 years have passed since the industrial production of titanium began. While titanium ore was found before that, it was so difficult to extract the material, as being suggested by its naming after Titans, who were imprisoned in the underworld in Greek mythology. Use of titanium in architecture began merely about 45 years ago.
 As a metal, titanium has three distinctive features of being lightweight, rust-resistant, and highly-durable, and is mainly used for products for aerospace, special industrial plants, and certain equipment such as heat exchangers.
 “Being lightweight” helps ensure safety and (important for some countries) quake-resistance, and helps reduce burden in processing and construction. “Being rust-resistance” means to contribute to reduction in the life cycle cost (LCC), as compared to metals it replaces there is no need for maintenance and no limitation in where it is to be used. Finally, “being strong” enables, for example, a titanium sheet to be thinner than an aluminum sheet for the same application. Titanium imparts virtually no impact to the environment. As titanium is also a biocompatible material, it has been adopted in medical applications for artificial bones and artificial joints.
 Moreover, as a great design-related feature, titanium shows interference colors. Titanium does not rust due to the protective, colorless, and transparent oxide layer that forms on its surface but various colors are produced due to light interference phenomena when the light passes through the film. In case of exterior cladding made of titanium, the wall colors change with differences of incident light in the morning, at noon, and in the evening, and depending on where you stand and look at the material. Such interesting effects can be created with titanium.

Expanding application of titanium building materials overseas

Chiken: The basic material of titanium is glossy but a matte texture can be created by using the aluminum blast process to blast-finish alumina grains. This type of titanium was used as replacement for ceramic tiles (kawara) of Japanese traditional architecture, such as various parts of the Sensoji Temple in Asakusa, Tokyo (Hozomon Gate in 2007, Hondo Main Hall in 2009, and Five-story Pagoda in 2017). The products are also being used to replace roofing made of copper, Japanese cypress bark, and shingles. Ion deposition to produce gold-titanium is also beginning to be used as alternative to gold.

Shimizu: Use of titanium in modern architecture is particularly gaining popularity overseas. It was triggered by architect Frank O. Gehry who extensively used titanium in the Guggenheim Museum Bilbao (1997) in Spain. Gehry likes interference colors and adopted titanium made by NIPPON STEEL Corporation in the Hotel Marqué de Riscal (2004) in Spain. Then, French architect Paul Andrew saw the titanium used in the Bilbao and asked NSSMC to supply titanium products for National Centre for the Performing Arts (2007) in China.
The first titanium project I was personally involved in Japan was the spherical observation platform of Fuji TV’s headquarters building (1996) in Odaiba, Tokyo, designed by Kenzo Tange. The roll dull finish (ND20) product was adopted there. Architect Kiyonori Kikutake also uses various titanium products in his works. We supplied pickled-surface white titanium for roofing of the Shimane Art Museum (1998) and glossy blue titanium for roofing of the Kyushu National Museum (2004). Our titanium product was adopted for the first time in exterior cladding of a large-scale structure at the National Showa Memorial Museum (1998) in Tokyo. The titanium sheet was 1.5mm in thickness and 7m in length with no surface strain. I believe this is a representative case of using titanium in architecture.

Chiken: NSSMC has recently started branding development of TranTixxii, with the aim to accelerate its applications in various products ranging from architecture to consumer products from a perspective of promoting both superior features and aesthetic quality.
 As a recent example, a residential tower, M6B2 Tower of Biodiversity, (2016) in the suburbs of Paris has adopted our Hyperbeta green titanium material for cladding. Responding to a request from French architect Edouard François to provide a Japanese moss-like aesthetic, we have realized such texture and color with the titanium product after extensive trials and errors.
 Now we are working at developing titanium louvers as a ready-made product, together with architect Kengo Kuma, as one of the projects to further exploit the architectural design potential of titanium.

Making louvers made of titanium

Nakasaki: Looking at Mr. Kuma’s architecture portfolio of the past two decades, I notice that louver has been used as one of his distinctive designs. Mr. Miyazawa, as the person in charge of it at Kengo Kuma’s office what was your initial thought on titanium louvers?

Miyazawa: Without having used titanium material in architecture, I initially thought of titanium as an expensive material compared to aluminum, for example. I therefore thought that this was the first obstacle to overcome.
 In addition, various competing aluminum louvers were already available in the market. Being an extruded material, aluminum louvers are manufactured with a uniform cross-sectional surface. This means that the horizontal surface can be designed but the lateral surface cannot. I thought this can be one of factors to be considered in designing titanium louvers.
 In our office, with regard to architecture that emphasizes materials, louvers are one of the main parts deserving consideration. Similar to koshi grating in old days, in Japan louvers are used not only for design reasons but also as functional components of structures. In that sense, I think we can say that louvers are not a temporary fad.
 According to architect Kuma, the light which “particulates” through louvers can be incorporated in architecture. The louver thus plays a role of a filter. Rather than being simply a frame with panels, the louver can be one of methods to intentionally control the “particulated” light so as to obtain a desired effect on the surface where it falls.
 When I talked with Kuma for the project, he showed interest in soft reflection of the roll dull finish. As one of the issues is how thin the panel can be, I have asked Sanwa Tajima to actually make louver mock-ups at their plant.

Ueda: At Sanwa Tajima we have recently made exterior cladding of the Nakameguro Ventilation Tower (2014) in Tokyo. Leveraging such experiences, we have made the mock-ups with additional stainless material on the back side to ensure strength. This is because it was difficult to make it durable with a titanium part, which were also required to be thin and lightweight from a cost perspective.

Miyazawa: Sanwa Tajima made two types of mock-ups with different thickness for us. We then found that slight strain was generated in the mock-up panel with 0.6mm in thickness. We therefore verified that the panel needs thickness of 1mm for being produced commercially.

Ueda: Another issue for titanium is its higher springback power compared to other metals. Titanium tends to be very stiff and hard to be formed after being pressed. These aspects also need to be resolved.

Chiken: Young’s modulus, or the modulus of elasticity, of titanium is low. Titanium, once bended, tends to try to return to its original shape due to its springback feature. Even in such a case, we provided advice such as how to easily process the original material for our customers.
 At present, most titanium materials can be formed in a press. I believe that the titanium material has improved significantly in the past two decades in this connection.

Improvement in materials enable complex forming

Shimizu: With regard to material improvement, we have endeavored to realize a shape that befits titanium while appearing like a kawara tile for Sensoji Temple’s roof tiles. In manufacturing onigawara (Japanese demon roof tile), we produced a particularly soft, easy-to-use titanium material. I don’t think anybody could have imagined making such a complex product as onigawara from titanium, as titanium materials, in general, are difficult to be formed into a complex shape.

Miyazawa: I think titanium is the superb in replacing kawara tiles and creating onigawara tile for temples and other buildings as the material has distinctive features well. Given the present status in material improvement, I am thinking of what can be possible in case of louvers. I would say that molding, or imparting a visual impression by pattern pressing, can be doable as one of the methods.

Ueda: That sounds like a good direction that may satisfy our desire. In fact, while we were asked to make it simple at the launch of the project, we have found it difficult to differentiate it to be sold as ready-made products. We are therefore thinking of asking you to consider differentiation in design, such as in differentiation in texture. If the louver has a certain expression on its surface, it can be differentiated from aluminum louvers and other materials, even when seen from afar, for example.

Chiken: It would be great to have basic simple models as well as special products. Then, the application potential will also be widened.

Miyazawa: Undoubtedly a broad product line-up will make it easy to call for use of titanium. We are also working on the possibility of imparting the texture of burned cedar bark and the cedar bark to a louver for an overseas project.

Titanium’s easy-to-handle advantage overwhelms its disadvantage in price.

Miyazawa: The cost hurdle of titanium may be cleared by making it thinner. We are also thinking about raising surface strength of thinner products by controlling the texture.
 Someone told me that at present, plastic molding is available for pattern pressing on metals. If so, the price of molds becomes cheaper and, by taking into account of durability, a small-lot production can be doable cost-wise. This could really satisfy need to use titanium louvers in small or medium-scale architectural works. In the sense of eliminating a barrier, I can see great potential in such new technology.

Ueda: Indeed, we are also working on issues such as costs and ensuring of strength. We also intend to look at how to locate and attach a louver to the wall and how to cope with issues raised by the wall materials, among other issues.

Chiken: ln fact, I would say that titanium is not as expensive as people think. I feel strongly that if the price of titanium product can be close to the price of existing general materials per unit area or per part, if you take into account the titanium’s lightweight or make all kinds of efforts to make the product thinner.
 Compared to magnesium and other materials, titanium stands out as being so easy to handle. It does not rust and can be pressed. All kinds of titanium products, including plates, sheets, bars, pipes, and pattern pressed products, are all available and they are easy to handle just like general-purpose products.
 A touch of class and design attractiveness are additional features of titanium, leading to a cost-benefit performance that more than justifies the price. Being light also means reduction of the burden of the structure, resulting ultimately in cost reduction. I thus think titanium can contribute in various ways.
 I hope that many designers and contractors will better understand titanium and use titanium louvers and other advanced titanium building materials more to further expand exploiting the potential of titanium.

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