Still the Iron Age

by Vaclav Smil

  McKinsey (2013) estimated the following consumption shares for China in 2015: 20% each for residential buildings, commercial buildings, and machinery, 12% for public infrastructures, and 11% for transportation, while Stahlinstitut VDEh (2014) offers the following major shares for German steel demand: 25% each for construction and cars; 13% each for machinery and pipes; and 9% for metal products. There is one thing that all of these diverse final uses have in common: as the variety of steel applications has grown, users have begun to demand higher consistence, higher quality (virtual absence of both surface and internal defects), and specific functionality, such as lighter weight, better workability, and greater strength (Iwasaki & Matsuo, 2012). The need for minimum compositional deviation led to the development of procedures that allowed mass production of steels with uniformly low contents of phosphorus (<50 ppm), sulfur (<5 ppm), hydrogen (<1.5 ppm), and carbon (<10 ppm).

  New steels have filled many high-performance niches, with alloys needed for vehicles, ships, machinery, components, and tools for exacting applications ranging from mass transportation of liquids and gases to chemical syntheses and energy conversions. Their desirable physical properties include increased strength, tolerance of high temperatures, high ductility, abrasion, and corrosion resistance, easy weldability, and ability to arrest crack propagation. Better steels have also been developed for military equipment, particularly for heavy armor (steel-encased depleted uranium for tank bodies). Another notable long-term trend has been the rising demand for smaller amounts of specialty steels, including stainless steel. Besides its traditional uses for cutlery, cookware, surgical tools, and medical and food processing equipment, stainless steel has found many new uses wherever there is a need for extended corrosion resistance: in the construction of tunnels and for outdoor furniture, wastewater treatment, seawater desalination, nuclear engineering, and production of biofuels (Team Stainless, 2014).

  I will look at final steel demand in some detail, focusing on three commonly used consumption categories, or subcategories (construction, vehicles, and appliances), as well as on steel used in energy systems; those uses cut across standard consumption categories as they include major infrastructural projects (such as pipelines and transmission lines), mechanical and electrical equipment (boilers, turbogenerators, transformers), and different means of mass-scale transportation (giant oil and LNG tankers, unit trains transporting coal). These surveys will be done both in global terms and by focusing on a few leading steel consumers, mostly on the United States and China.

  Infrastructures and Buildings

  Certainly the most fundamental, as well as the most important (when judged by annual global consumption), use of steel products is in construction, as well as maintenance and upgrading, of buildings and key infrastructures that create housing and commercial and industrial enterprises, that underpin the functioning of modern economies, including a high degree of mobility, and that ensure public safety and private well-being. As already noted, construction of buildings and infrastructure now claims about 50–55% of annual global steel production, with national shares in low-income, rapidly modernizing economies ranging from close to, and even above, 60%, while the shares in affluent economies range mostly between 30% and 35%.

  Despite the sector’s importance there is no systematic reliable information on how construction uses steel. Moynihan and Allwood (2012) attempted to estimate this breakdown for the United Kingdom and on the global level. For the United Kingdom, in 2006 they concluded that infrastructure consumed 24% of all construction steel, while buildings consumed the rest, with industrial structures claiming 31% of the total. In contrast, their global allocation of 480 Mt of construction steel used in 2006 shows about 36% going into infrastructure: this expected higher share is largely explained by the urbanization and modernization in Asia. In the building sector (64% of the total), industries dominated with about 23% of all construction steel, and residential uses were only about 11%. Reinforcing steel accounts for 50–60% of all steel used in construction (Fig. 8.1); the rest is in a variety of structural shapes, sheets and plates, rails and pipes, and tubes. As for the origins of end-use steel products in construction, the global mapping by Cullen et al. (2012) shows that about 40% of their total originated in hot- and cold-rolled coils, 28% are reinforcing bars, and about 20% become wire rods.

  Figure 8.1 Heavy reinforcing bars for massive pylon foundations of a bridge in Incheon, South Korea. Corbis.

  The list of critical infrastructures dependent on steel ranges from transportation (roads, railways, tunnels, bridges, ports, canals, airports) to environmental protection (flood and erosion control, fire suppression, air and water pollution control, solid waste disposal), and from energy systems (power plants, dams, refineries, pipelines, transmission lines) to the backbones of high-density urban living (high-rise buildings, apartment blocks, subways, industrial and commercial establishments, parks, sport facilities). Building these infrastructures de novo is invariably associated with the largest increase of steel consumption. But there is a fundamental difference between the past episodes of infrastructural expansion and their modern version.

  In the past, as exemplified by the British, American, or German experience, these additions came in successive waves. Before 1900 the United States had seen rapid extension of railways and modern ports, its first pipelines, transmission lines, high-rises, and subways; after WW I came paved highways, the first airports, more subways, more skyscrapers, extensive pipelines, refineries, large dams, and power plants; and only after WW II did the country get its system of interstate highways, a large network of airports, and an intensive wave of electrification. In contrast, in China construction of all of these infrastructural necessities has been compressed into less than two generations.

  In 1980, 4 years after Mao’s death, China still had an impoverished look, with most of its technical advances traceable to the transfer of Soviet techniques of the 1950s (which, in turn, had their origin in the US advances of the 1930s). Large-scale infrastructural development began only during the 1990s and since that time the length of China’s multilane highways has far surpassed the total of the US interstates (about 112,00 km vs. about 77,000 km). The country has about 16,000 km of high-speed trains (more than the rest of the world combined), and, perhaps the most telling example of the frenzied pace of its infrastructure creation, it has produced more cement (4.9 Gt) to emplace new concrete in just 3 years, between 2008 and 2010 (NBS, 2013), than did the United States (4.56 Gt) during the entire twentieth century (Smil, 2013)! And the total for the first 3 years of the second decade of the twenty-first century was even higher (USGS, 2014).

  This is impressive—but also worrisome because the rapid pace of building Chinese infrastructures has not always gone hand in hand with the best achievable quality, and this will create higher-than-usual demand for maintenance and, for some structures in just two or three decades, for upgrading or replacement. Keeping all of these infrastructures safe is predicated on adequate inspection and replacement of their steel components or on their complete periodic reconstruction requiring better new steel and more advanced steel-based designs, and abundant evidence shows that even the world’s richest countries have mounting deficiencies in this respect. These investment deficits have been comprehensively documented by bi-annual reports by the American Society of Civil Engineers (ASCE) that grade all infrastructures divided into four categories: water and environment, transportation, public facilities, and energy.

  The latest report card awards D+as the overall average, with solid waste disposal as the only B−grade and the rest being various Cs and Ds (ASCE, 2015). Among the six most steel-intensive categories that also require relatively frequent upkeep, only bridges and rails got a less-than-humiliating C+, while energy got a D+and roads, transit, and wastewater treatment got a barely passable D. But a closer look at the state of American bridges makes that C+a rather generous award. The Federal Highway Administration classifies more than 25% of the country’s almost 60
0,000 bridges as either functionally obsolete or structurally deficient, and it estimated the investment backlog as totaling $121 billion, while ASCE (2015) calculated the need for annual investment of $20.5 billion in order to eliminate the maintenance backlog by 2028. And more steel should also be used in all seismically active regions to enhance the resilience of buildings likely to be subjected to strong earthquakes, something that has been done, so far, on a large scale only in a few affluent countries, mostly in Japan and in California (Kanno et al., 2012; USGS, 2012).

  Certainly the most spectacular, that is, visually most captivating, uses of steel in construction are skyscrapers, towers, and bridges. In buildings up to 25% of all steel is structural sections, up to 44% is reinforcing bars, and up to 31% is sheet products (including roofs, interior and exterior walls, and cladding), with heating and cooling ducts, fixtures, fittings, rails, shelves, and stairs being among common nonstructural steel uses (WSA, 2012). Steel use creates larger open spaces, allowing unprecedented spans, light access, and good cross-ventilation, and these qualities have been used to the maximum in designing skyscrapers.

  Construction of skyscrapers has proceeded in waves, with notable New York additions coming during the 1930s: the Chrysler building (319 m) in 1930 and the Empire State building (381 m) a year later (Landau & Condit, 1996). The World Trade Center’s twin towers, destroyed in the 9/11 attacks, were 417 m tall. The tallest US structure, the Sears Tower 443 m in Chicago, was finished in 1973, and in 2015 the four tallest buildings (including spires) in the world were Burj Khalīfa in Dubai (828 m), Makkah Clock Royal Tower Hotel in Saudi Arabia (601 m), One World Trade Center in New York (541.3 m), and Taipei 101 (508 m) in Taiwan (SkyscraperPage.com, 2015).

  Except for the Makkah structure, which is a steel-and-concrete complex of buildings with a central tower, all of the world’s tallest 12 buildings are variations on a fundamental structural theme, with steel skeletons covered mostly by walls of glass, also with some aluminum and steel—and a large number of similarly tall, and even taller, buildings are under construction or in planning stages. These efforts have required not only high-quality, high-strength steels but also fireproof products and construction methods that guarantee flawless welding and bolting, as well as appropriate measures to limit the lateral motion of these tall structures, a goal achieved by installation of tuned dampers.

  As for the world’s tallest broadcasting tower, the latest record-setter is Tokyo’s Sky Tree completed in 2012, an ingenious 634-m tall structure inspired by the form of an ancient Chinese tripod kettle that is built of circular pipes, with the largest bottom trusses having a diameter of 2.3 m and thickness of 10 cm, while most of the tower’s outer tubing is high-strength (780 MPa) steel pipe 110 cm in diameter with a thickness of 2.5 cm (Keii et al., 2010; Fig. 8.2). The second tallest tower, in Guangzhou, is also a steel structure, in the form of a hyperboloid (twisted shape), 600 m tall, while the third highest freestanding structure, Toronto’s 553.3-m tall CN Tower, is built of reinforced concrete.

  Figure 8.2 Tōkyō Tree. Corbis.

  Bridges have been another class of steel structure with steadily advancing record measures, both for spans and overall lengths. The longest pre–WW II suspension span was San Francisco’s famous Golden Gate Bridge completed in 1937 (1280 m). By 2015 there were 11 suspension bridges with longer spans, with Japan’s Akashi Kaikyo (linking Honshu and Awaji island by both road and railway, completed in 1998) holding the record with 1991 m, and cabling strength of 1800 MPa (HSBEC, 2015; Kanno et al., 2012; Fig. 8.3). The world’s three longest cable-stayed bridges (in Vladivostok, Suzhou, and Hong Kong) have spans in excess of 1000 m, while Ikitsuki bridge (since 1991 in Nagasaki prefecture) has the world’s longest (400 m) continuous steel truss span.

  Figure 8.3 Akashi Kaikyō Bridge linking Honshū to Awaji Island in Japan. Corbis.

  In contrast to these highly visible structural sections, construction steel has also been increasingly used for pile foundations—with hat-type sectioned steel piles having end-bearing capacity as good as a steel pipe pile (Kanno et al., 2012)—as well as for steel studs (bearing and nonbearing) for external and interior partition walls of residential, commercial, and industrial buildings. Cold-formed C-shaped studs and U-shaped tracks are the most common profiles; studs are connected to track flanges with screws and in American houses are spaced at 24 inches rather than at 16 inches as with wooden studs (Steel Framing Alliance, 2007). Framing steel studs used to have a thickness of 1.2 mm; now, with stronger steels, they are just 0.6 mm thick.

  Fuels and Electricity

  Modern civilization depends on incessant flows of affordable fuels and electricity—and not only is the entire energy system heavily dependent on steel, but this dependence has been increasing in both quantitative and qualitative terms, and none of the accomplishments of our advanced energy supply would have been possible without increased supply of higher-quality steels (Ginley & Cahen, 2012; Uemori et al., 2012). Laplace Conseil (2013) estimated the global steel consumption in energy sectors at 178 Mt or 12 % of the total sales of finished steel products, with oil and gas production (45 Mt) and transportation (55 Mt) as the largest markets.

  Large-scale underground coal mining became possible only thanks to mechanization using steel cutters and loaders, and the most efficient modern long-wall technique uses large drum-shaped cutting steel heads to extract coal from the length of a seam and dump it onto conveyors, with the miners protected under a jack-supported steel roof that advances along a seam as the cutting progresses (Osborne, 2013). And the most productive surface mining (as practiced in lignite regions of Germany or in large bituminous coal mines in the Western United States or Australia) is unthinkable without massive bucket and bucket-wheel excavators and trucks.

  Extraction, transportation, storage, and use of oil and gas and refining of crude oil are no less dependent on ubiquitous uses of steel. In 1965 most hydrocarbons came from wells less than 2 km deep, offshore drilling was common only in shallow near-shore waters, the largest pipelines were the US lines from Texas to the Northeast, the largest tankers had a capacity of less than 200,000 tonnes, there were only two small liquefied natural gas (LNG) tankers. Half a century later hydrocarbon extraction commonly involves drilling wells deeper than 4 km, including many complex and long horizontal wells; offshore drilling is done in deep ocean waters (about 2.5 km); the longest pipelines carry natural gas from Northwestern Siberia all the way to Western Europe and from Turkmenistan to Xinjiang and then to Shanghai (total length of nearly 7700 km); the largest tankers carry more than 400,000 tonnes of crude oil; and the largest LNG tankers have capacities in excess of 200,000 m3. And refineries are essentially giant assemblages of steel pipes, processing columns, and storage tanks.

  Deep drilling for hydrocarbons relies on seamless steel pipe and electric resistance-welded pipe whose gastight threaded joints are coupled together to form long and heavy drill strings. These high-strength pipes must also be corrosion- and collapse-resistant as they are exposed to high temperatures, high pressures, and acidic environments deep underground and, in offshore drilling, as they hang several kilometers in seawater before reaching the ocean bottom; moreover, in directional and horizontal drilling pipes face even greater stresses as they are contorted into bends, while drilling in the Arctic exposes the rigs, pipes, and machinery to temperatures as low as −60 °C, conditions that would readily embrittle ordinary steels. Offshore extraction also requires the construction of massive drilling and production platforms whose high-strength, high-toughness steel must be particularly resistant to fracture in order to avoid catastrophic collapse of those heavy structures.

  Because the volume of gas transported by a pipeline can be increased by using higher operating pressure, modern, long-distance, large-diameter trunk lines must use new kinds of ultra-high-strength pipes that also have the necessary low-temperature toughness and good field weldability. For pipelines laid at the ocean’s bottom (now often in depths exceeding 2 km) collapse resistanc
e is a key consideration, while pipelines in the regions of discontinuous permafrost or in areas affected by landslides must guard against accidental fracturing of circumferential welds and pipe buckling. And all pipelines transporting oil or gas with traces of hydrogen sulfide must be protected against hydrogen-induced cracking.

  Many advances in steels for giant oil tankers and large bulk cargo carriers originated in Japan during the decades when the country was the leader in global shipbuilding, and Japanese steelmakers have continued to improve their products even after South Korea and China emerged as the world’s largest builders of oceangoing vessels. The maximum strength of steel plates for shipbuilding rose from less than 250 N/mm2 in the 1960s to 460 N/mm2 by 2010, and the new steels have higher crack arrestability and better abrasion and corrosion resistance (Uemori et al., 2012). Besides plates tanker construction also requires various steel shapes, pipes, and bars. LNG tanks are exposed to temperatures of −160 °C: plates of 9% Ni steel (up to 5 cm thick) have sufficient brittle fracture resistance and crack propagation arrest to form large gas containers for intercontinental shipment.