Mat-for-Build-03-Metals.pdf

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2 3 METALS MATERIALS FOR Metallic bond BUILDINGS  Strong bond  Sharing of valence electrons among several contiguos Inorganic compounds made of metallic atoms elements (i.e.: Fe, Cu, Al,...).  Crystalline structure Metals Very high thermal and electric conductivity Prof. Sara Goidanich Dip. di Chimica, Materiali e Ingegneria chimica “G.Natta” [email protected] Tel. 02.23993148 - http://midar.chem.polimi.it/ Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 4 5 6 ALLOYS Two general types of “alloying” are used today STRENGHTENING MECHANISMS Pure metals are scarcely used due their mechanical and physical  inclusion of one or more elements into the body of another metal properties This change in the bulk composition of the metal results in an alteration of Are used to increase the materials resistance Alloys are widely diffues and may display rather different the host metal's properties throughout its matrix. This kind of alloying is characteristics respect to those of the original metals used to affect bulk material properties such as overall stiffness, tensile  Addition of alloy elements strength, toughness and many other attributes and also surface characteristics such as corrosion resistance  Work hardening through cold plastic deformation Different features: mechanical, physical, chemical, fluidity...  Thermal treatments Pure copper  alteration of the chemical composition of the surface of a metal (plating, hot dip galvanizing, nitriding, carburizing, etc.)  Control of the grains dimension Cu Cu Copper alloys This kind of alloying affects only the attributes of the surface of the host metal and is therefore used to improve such properties as corrosion resistance, hardness, color and other surface-related properties N.B. strenghtening may interfere with some of the Zn material characteristics (ductility, toughness, corrosion Cu E.g galvanized steel resistance) Brass Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 7 9 10 Addition of ALLOYS ELEMENTS WORK HARDENING WORK HARDENING EFFECT OF PLASTIC DEFORMATION  (MPa) A (%) 100 Grain morphology RESISTANCE OR DEFORMATION Ultimate strenght Tensile Strength ts ELECTRIC CONDUCTIVITY 500 Mechanical cold working (T 12% Other alloy elements: nichel (Ni) e molybdenum (Mo) AISI 304. to be used in not particularly aggressive atmosphere, urban or non urban environment, as Several uses in civil engineering panels, in façades, windows… (urban design, finishing, restoration) 7-8 times more expensive than steel for general AISI 316. to be used in marine or industrial highly aggressive use atmosphere High corrosion resistance Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 72 73 74 Burj Khalifa Dubai Stainless steel - superficial finishing Stainless steel and restoration RESTORATION thermal dilation coefficient is critical San Francesco Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 75 Stainless Steel for long-life buildings and civil 76 78 Restoration fire-resistant cast steel alloys structures Long-life buildings and civil works value durability above  Fire-resistant cast steel alloys that retain a much greater many other criteria proportion of their service strength at higher To avoid galvanic coupling temperatures A calculation is made that a longer life will return a net benefit to society, therefore the inevitable premium to be paid  These steel alloys retain a little over two-thirds of the upfront is amortized over a very long period of time. service strength at elevated temperatures as high as 600°C  Cast steels have been improved to provide metals that are better at resisting the kinds of stresses endured during violent events like earthquakes Cathedral of Our Lady of the Cathedral of Our Lady of the Angels by Angels by Rafael Moneo Rafael Moneo Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148  82 83 MATERIALS FOR Nonferrous alloys Nonferrous alloys BUILDINGS The lighter metals (aluminum, magnesium and titanium) are Many of the heavier nonferrous alloys – copper, tin, zinc, lead – attractive to industry generally because of: have been used for architectural applications for millennia  low densities because of:  good strength to weight and stiffness to weight ratios  Ductility  good to excellent corrosion resistance  corrosion resistance  wear tolerance Aluminium is commonly used in many architectural applications For example, copper is dense and quite ductile, possessing an Nonferrous alloys extremely valuable set of properties useful to many purposes in Titanium will most likely retain a small market as an exterior building construction. finish material. Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 85 86 MATERIALS FOR Aluminium and Aluminium alloys Main Characteristics BUILDINGS  Aluminium (or aluminum) is the third most abundant element of the Earth's crust and the second most consumed metal on Earth, behind iron  Low density  However it is a late arrival behind all of the major metals  Good strength/density and stiffness/density ratios known today because of the difficulty of extracting it pure from the ores in which it is found  High ductility: it can be easily worked and deformed also in  Aluminum has been known for slightly more than 200 very complex shapes years Aluminium and Aluminium alloys  Good conductibility  the modern process of electrolytic refinement that led to the economical separation of aluminum from bauxite was  Good corrosion resistance but not in all environments developed in the late 19th century Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 87 88 90 Environmental impacts  Environmental impacts   Application in Architecture The environmental ramifications of aluminum extraction extend well  Aluminum is a highly recycled material, currently 60-90 percent of all  Aluminum is now the primary metal for use in curtainwalls: beyond the energy used in its refinement: aluminum produced is reclaimed and recycled into second generation use. The process of melting Aluminum down to its molten form does not mullions restraining glazing  Typical aluminum ore deposits are located in “blanket-type” deposits, change any properties of the metal. Therefore, like steel, aluminum can that is, in horizontal layers that necessitate mining of large areas of be recycled infinitely. Aluminum is one of the most widely recycled surface finish panel land, a great deal of the landscape is violently and often materials and through the recycling process it saves 95% of the energy permanently disturbed that it would cost to produce new aluminum. Producing secondary  Aluminum is also being used in numerous products to form aluminum ingot requires 5 percent of the energy of primary structural monocoque assemblies using sheet Al  Regeneration techniques are available to repair this damage but the aluminum. sandwiching an interior honeycomb or folded plate structure largest bauxite mines are found in the tropics, the Caribbean and the Mediterranean, areas in which regeneration is not always  However, even with recycling, studies show that the substitution of accomplished aluminum for steel in typical building superstructures is not an  Recently, aluminum has also been used as a flooring material environmentally sound strategy. in several buildings  As a result, large tracts of rain forest have been spoiled by the need to completely clear land of its upper layers of soil in the mining process.  The use of aluminum is certainly worthwhile for the superstructure of vehicles, especially automobiles where the weight reduction contributes to significant fuel savings over the lifetime of the automobile Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148  94 95 MATERIALS FOR Copper and copper alloys Copper and copper alloys BUILDINGS  Copper is in use as early as 2200 BC, and possibly before, for  During the 18th century copper started to be used to sheath roofing, scuppers, sinks, fixtures and implements the bottoms of boats and ships to protect the oak outer planking  Seven hundred years later bronze was developed  In buildings, copper has played an important role for  As with most useful metallic ores, copper is not found freely environmental durability and water management available in nature but as minerals  copper has been used as a flashing material and sheathing on  Today copper is alloyed with zinc, tin, aluminum, beryllium, dormers, roofing sheets, gutters, canopies, windows, copings chromium, manganese and others and many other conditions where water needs to be directed Copper and copper Alloys away from the building.  Most common alloys are bronzes and brasses Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 96 97 Copper and copper alloys Recycle Copper and copper alloys PATINAS Copper - Stockholm  Copper, like aluminum, is also a highly recycled material 1997 2023  When exposed to the atmosphere they interact with oxygen  For metals like copper, recycling and the recovery of scrap and humidity forming PATINAS metal have been an integral part of its material flow from its first use  Natural patinas  Artificial patinas (preweathered or prepatinated sheets)  Copper, in particular, is known to have been reused because of its ease of mechanical workability. The reclamation of  High aesthetical value hammered sheets of copper was easily achieved without the  Historical and artistic value need for additional chemical or thermal treatment.  Copper release: environmental issues  Hygienic material: biocide properties Gustaf Vasa church (Odenplan) Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 99 102 103 Prewaethered panels Titanium London planetarium Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148  104 105 106 Titanium Titanium is: Guggenheim Bilbao  exceptionally corrosion resistant  Lightweight (low density)  High mechanical resistance and toughness Perugia Facoltà del Design  Low thermal expansion coefficient Politecnico di Milano  It can be “electrochemically colored” 12 – 28 Novembre 2003  Non magnetic Used in aerospace and other high performance applications in which structural performance at high temperatures is a requirement, titanium has nevertheless seen use in several buildings recently, mainly for cladding Partenone Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 107 108 109 Pietro Pedeferri Lead Nowadays forbidden A lead tile roof surfaces Renzo Piano Auditorio Roma giro Duodecedron expansus (Leonardo – Pacioli) Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 110 117 119 Other non-ferrous metals Emergent Metals Ultralight Metals Tin became highly useful as one of the components of bronze The rate of the development of new metallic alloys has been Mainly related to the automotive industries. before it was refined for use as a separate metal. The first decreasing these past few decades. At the moment very far from being applied to implements date from about 2000BC but the smelting of tin Superplastic alloys, shape memory alloys, metal matrix architecture, nevertheless they form an important set of wasn't widespread until 500 years later. Confused with lead composites are all recent developments. research interests that may be relevant to architectural form. by the Romans, who called both metals plumbum , it was The maturation of the science of metals has only recently been fully rarely used alone. It is highly malleable and highly resistant realized in architectural assemblies. Metallic alloys once to corrosion. developed for higher performance scenarios, for example high strength aluminum alloys for aeronautical applications, are Zinc is primarily used for surfacing for improved durability, now available for architectural assemblies often laminated with copper. Frequently used is the Improved corrosion resistance, better strength with ductility, GALVANISED STEEL reliable coatings and other surface treatments and a better understanding of the behavior of metals, especially at high Chromium and Nickel are both important alloy metals for temperatures, have been a benefit to improving the quality of imparting good corrosion resistance to ferrous metals. metals used in architecture. Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148  120 121 Cellular metals: METFOAMS Cellular metals: METFOAMS ALUMINIUM FOAM - Fondazione Prada - Milan The most innovative form of cellular metals includes the The set of novel material properties includes: metallic foams, known as metfoams. Metfoams are Lightweight cellular materials processed from a solid metal to encapsulate Stiff voids within the body of the material. These are very new materials currently being examined by researchers and good thermal and acoustic control. Aluminium Foam industry for their novel set of properties A few metfoams are commercially available, most being either Cellular metal foams may very well be useful in roofing aluminum or nickel (Duocel 2005). At the moment, these applications where weight becomes a critical issue materials are rather expensive compared with their solid particularly in long span situations. metal precursors. Mirrored Glass Wall A metal foam interlayer between sheets of aluminum would provide rigidity at a good strength to weight Golden Leafs ratio. Plaster Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 ALUMINIUM FOAM - DEFINITION Production Fondazione Prada applications Gas input Internal wall Foam sheet solidification PODIUM Rotor Cutting Estetical reasons Conveyor belt Format availability: sheets Cellular structure made up of Al-melt alu- minium, containing a large Propeller volume fraction of gas-filled Gas output pores. FAÇADE First time that aluminium foam is used as a facade cladding Used to create a sort of illusion: it seems to be concrete but it Thickening Foaming Cooling Foamed block Slicing guarantees a sense of lightness instead Direct foaming of melts by adding gas-releasing powders (ALPORAS) Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148 COMPOSITION AND STRATIGRAPHY 43mm External walls 25mm Internal walls CAUTION 12mm False Ceiling ALL PICTURES IN THIS FILE BELONG TO THE PHOTO ARCHIVE OF TEACHERS AND COLLEAGUES OR THEY WERE ACQUIRED FROM BOOKS AND MAGAZINES OR DOWNLOADED FROM WEBSITES: THEREFORE, THEY ARE PROTECTED BY COPYRIGHT. THEY CAN ONLY BE USED IN UNIVERSITY TEACHING PVC Layer 4mm No effect of stag- ENVIRONMENT AND FOR NO REASON THEY CAN BE Aluminium Layer 3mm nancy: water can REPRODUCED AND DISCLOSED IN ANY OTHER WAY. flow through the Aluminium Foam 43 mm panel reaching the Elevation and Section of the panel ground Sara Goidanich http://midar.chem.polimi.it Sara Goidanich – [email protected] – tel. 02 2399 3148 Sara Goidanich – [email protected] – tel. 02 2399 3148