by Vaclav Smil
In a more recent analysis, Takamatsu et al. (2014) used worldwide statistics to calculate the changes in accumulated global steel stock since 1870. The total reached 1 Gt around 1930 and 5 Gt in 1970, and by the century’s end, as the net annual addition reached 500 Mt, it was about 12.5 Gt, or about 15% less than my approximation. By 2010 global steel stocks reached 24 Gt, and a year later they stood at 25.1 Gt, with net annual addition in excess of 1 Gt. Other published estimates offer totals that are significantly higher or lower than the range of 12.5–15 Gt for the year 2000. Müller et al. (2006) put the global anthropogenic iron stocks at 25–30 Gt in the year 2000. Kozawa and Tsukihashi (2011) estimated the global steel stocks at 27.8 Gt for 2005. And Fujitsuka et al. (2013) concluded that the global in-use steel stock had doubled between 1980 and 2010, when it reached 16 Gt.
Some researchers have tried to overcome the lack of steel consumption statistics for many countries by using nighttime satellite light images to estimate steel stock in use in engineering infrastructures and buildings. Hsu et al. (2011) analyzed first the link between steel stocks and lights for every Japanese prefecture and then they applied the results to Japan, South Korea, Taiwan, and China. Their totals were 495 Mt for Japan and 974 Mt for China. Hattori et al. (2013) extended this approach globally, and their total for 2010 was 11.3 Gt of steel (about 21% above the 2006 level), almost equally split between infrastructures (5.5 Gt) and buildings (5.8 Gt). And Hsu, Elvidge, and Matsuno (2015) ended up with a nearly identical total of about 11 Gt of global infrastructural and building steel stocks.
National totals should be more reliable, but substantial differences are common. Müller et al. (2006) put the US total at 200 Mt in 1920, 1.25 Gt in 1950, 2 Gt in the early 1960s, 3 Gt in the year 2000, and 3.2 Gt in 2004, with per capita stocks leveling off, or even slightly declining, after 1980, when they reached just over 12 t/person. At 3.2 Gt the US steel stocks in use were just 30% less than the domestic resource base and 50% more than the reserves (at 2.1 Gt) and represented the second largest iron reservoir (after the ores in the American share of the lithosphere), followed by landfills (containing about 700 Mt), tailing ponds (with roughly 600 Mt of iron), and repositories of slag from blast and other furnaces (about 100 Mt), but errors in estimating the last three totals are particularly large (up to 50%). In contrast, Sullivan (2005) estimated the total US steel stocks in use at 4.13 Gt in 2002, and Buckingham (2006) took a closer look at steel stocks in automobiles in use and put them at 217 Mt in 2001, or just 5.3% of all steel stocks in use, implying the total of 4.09 Gt in 2001. Laplace Conseil (2013) put the total “reserves” in the US scrap “mines” at nearly 3 Gt in 2010 and the EU total at about 3.2 Gt.
Estimates of national per capita steel stocks for the world’s most populous modernizing countries in 2005 ranged from just around 0.1 t for Pakistan and Nigeria and 0.4 t for India to 2.2 t for China and 3.1 t for Brazil, while the stocks in leading affluent economies were 7.5 t in France, 8.5 t in the United Kingdom, 9.0 t in Germany, 10.5 t in the United States, 12.1 t in Canada, and 13.6 t in Japan (WSA, 2012). The global average was 2.7 t, and secular trends show that, as must be expected, relatively rapid additions to stocks (prevailing until the levels reach 5–8 t/capita) are followed by much slower growth as the stocks tend toward saturation plateaux whose levels indicate substantial variation depending on the country’s size and economic structure, but the range of 7–14 t/capita will accommodate all but a few economically mature outliers.
China’s extraordinary post-1995 growth of steel production resulted in a rapid accumulation of the nation’s steel stock. America’s cumulative steel production amounted to 2 Gt during the first 50 years of the twentieth century, and during its peak production decade (1966–1975) the United States added about 1.2 Gt of domestic steel to its stock. In contrast, China added 6.5 Gt during the 10 years between 2006 and 2015, accumulating the metal’s stock faster than any nation in history. China became the first nation whose total in-use stock reached 5 Gt, most likely before the end of 2010, and its stock increased to more than 7 Gt by 2015.
As just noted, the best US estimate shows that the country reached no more than 4.1 Gt between 2000 and 2002, which means that with net additions of less than 700 Mt since 2002, the US in-use steel stocks were most likely still below 5 Gt by 2015. Whatever the actual nationwide totals of steel stocks in use in the United States and China may be, there is no doubt that these two nations have created the largest anthropogenic stocks of steel, new, and largely urban and industrial, metal deposits to be “mined” profitably during the coming decades as they yield an increasing share of overall steel demand in the two countries.
Some recent publications have also focused on steel stocks in major consumption sectors. Moynihan and Allwood (2012) looked at steel use in the global and British construction sector, and Hu et al. (2010) traced the incorporation of iron and steel into Chinese residential buildings, finding the expected large difference between the steel intensity of rural and urban dwellings: the former averaged only about 5 kg of steel per m2 of living area, while the latter incorporated about 40 kg/m2 by the year 2010. Material flow analysis by Kawahara et al. (2012) estimated the global in-use steel stock of ships at 540 Mt in 2009 and predicted that the total will reach 900 Mt by 2035, when the annual steel demand for ship construction should increase to 41 Mt.
Chapter 10
Looking Ahead
The Future of Iron and Steel
Abstract
Future use of any material will be affected by the progress of substitutions and the advances of relative, and eventually also absolute, aggregate dematerialization on national and global scales and by the emergence and adoption of new production processes. Even as steel has conquered new markets, it has had to cede some of its market shares to competing materials, most notably to aluminum and plastics. This process will continue, and the combination of acceptable physical attributes and substitution costs—higher for both aluminum and plastics, and much higher for new composite materials—will determine how fast and how far it will go in the future. This is also an apposite place to appraise the possibilities of another substitution, the use of modern charcoal to replace coke as part of the quest to reduce CO2 emissions from the iron and steel industry.
Keywords
Coke; charcoal; dematerialization; GDP; material substitutions; future steel demand
Future use of any material will be affected by the progress of substitutions and the advances of relative, and eventually also absolute, aggregate dematerialization on national and global scales and by the emergence and adoption of new production processes. Even as steel has conquered new markets, it has had to cede some of its market shares to competing materials, most notably to aluminum and plastics. This process will continue, and the combination of acceptable physical attributes and substitution costs—higher for both aluminum and plastics, and much higher for new composite materials—will determine how fast and how far it will go in the future. This is also an apposite place to appraise the possibilities of another substitution, the use of modern charcoal to replace coke as part of the quest to reduce CO2 emissions from the iron and steel industry.
Given the world’s still growing population and huge unmet demand for steel in low- and medium-income countries of Asia, Latin America, and Africa (associated with the transition to modern, high-energy urbanized societies), there is no early possibility of any lasting absolute dematerialization on the worldwide scale: there may be temporary declines but in the long run global steel consumption will continue to grow. At the same time, relative dematerialization (per unit mass of a final product or per unit of national GDP) will continue, and societies will be able to derive more value and enjoy higher standards of living with progressively lower inputs of steel.
All principal iron- and steelmaking methods—blast furnaces (BFs), basic oxygen furnaces (BOFs), electric arc furnaces (EAFs), continuous casting—are now technically mature, as are the processes required to produce raw materials (e
xtraction of coal, iron ore, and fluxing materials, production of coke, sinter, and pellets). All of these techniques will see further efficiency gains and further reductions of environmental impacts, but all of these improvements will be relatively small, and new techniques will be needed to bring fundamental technical and economic departures. I will look at the options and their likely commercial success in the chapter’s penultimate section.
Finally, I will take a brief look at future steel consumption levels, and although I will cite some published near- and longer term estimates, I will not offer my specific (and inevitably inaccurate) forecasts but instead I will review some key factors whose combination will determine the future rates of demand and production. Existing ironmaking and steelmaking processes and their continuing gradual improvements could supply all the steel needed by the middle of the twenty-first century. Beyond that time the fortunes of the world’s most fundamental metal industry will greatly depend on the pace of the unfolding global warming and on the state of our efforts to transit to economies that use the Earth’s resources more rationally.
Substitutions
In 1900, steel had virtually no competition for many exacting, durable, or heavy-duty uses for which its mass production had been originally developed. A century later this has changed with large-scale production of aluminum and of its alloys, and with reliance on other metals for some critical applications. Titanium, 45% less dense than steel but with ultimate tensile strength only 20% lower, has been favored in alloys with aluminum, molybdenum and steel that are used above all in aerospace industry (also in bicycles, crutches, golf clubs, and hip replacements). The post-1950 world has seen a spreading use of a wide variety of plastics, and the emergence of new composite materials has cut into steel demand as they have replaced many components used to make machinery, appliances, pipes, parts, and tools. Relative steel dematerialization (share of steel in total mass of specific products) has thus been an unmistakable trend in modern manufacturing, and it has resulted in absolute steel dematerialization in many mature economies with slowly growing populations—but it has yet to translate into absolute dematerialization in global terms.
Substitution is usually seen as using an entirely different material but one of the most important trends in modern steel use has been the displacement of ordinary varieties of steel by superior alloys whose attributes translate into overall reduction in weight (and hence increased efficiency of performance when higher strength steels are used in cars or ships) or in greater longevity (with new crack- and abrasion-resistant steels). This substitution, as already noted, has made a great difference in reducing the weight of cars. Shift toward high-tensile steels is shown by the Japanese trends: during the 1990s minimum tensile strengths were below 400 MPa, by the year 2000 they rose to 600 MPa, and maxima are now near or above 1000 MPa (Takahashi, 2015).
This trend will continue. The latest concept design of Ultra Light Steel Auto Body (ULSAB) uses 100% high-strength steel (HSS), of which more than 80% is advanced high-strength steel (AHSS) (Galán et al., 2012). A WorldAutoSteel (2011) study of FutureSteelVehicle (FSV) considered more than 20 AHSS grades (expected to be commercially available by 2020) whose deployment (making up 97% of all steel in a car), combined with new design and manufacturing methods, would save up to 39% of the mass and nearly 70% of total lifetime cycle greenhouse gas emissions compared to today’s designs and, given aluminum’s inherently higher energy intensity, do so at a fraction of the lighter metal’s cost and result in lower aggregate environmental impacts. Compared to the total vehicle masses of, respectively, 1199 and 1483 kg for smaller and larger 2010 cars powered by internal combustion engines, WorldAutoSteel (2011) sees the future steel vehicles (plugged-in hybrids) weighing 990 and 1279 kg, weight reductions of, respectively, 18% and 16%.
Lightweighting
Several lighter materials are available to replace automotive steel. Magnesium steel alloys and carbon fiber and polymer composites have the lowest density of all structural materials used in vehicles, and their widespread use has the potential to reduce component weight by more than 60%—but their widespread adoption is not imminent. Magnesium’s tensile yield strength is similar to that of aluminum, but the metal has lower ultimate tensile, fatigue, and creep strength and its alloys have lower modulus and hardness, are prone to exhibit low-ductility failure, create problems with corrosion and recycling, and are difficult to be formed as sheets at low temperature (USDOE, 2013). As a result, they have been used for only about 1% of average vehicle mass. Carbon fibers and polymer composites are still fairly expensive (that is why they have been used more in airplanes rather than in cars) and also highly energy intensive.
Aluminum alloys are seen as a middle ground of the lightweighting spectrum, heavier than magnesium alloys but lighter than steel; moreover, long experience with their use in airplanes and vehicles makes their applications and limitations well understood. Car parts made of aluminum alloys include not only hoods and panels but also engine blocks and other power-train components and even entire vehicle bodies. Further use of these materials is limited due to their cost, formability, premature corrosion, and multimaterial complications in joining, painting, repairing after accidents, and recycling (USDOE, 2013). That is why HSS and AHSS are the most appealing options: their relatively high density is compensated by exceptional strength and ductility, a combination that allows weight-saving designs, and their new automotive applications have been growing faster than the substitutions by aluminum or plastics (WorldAutoSteel, 2011).
All suitable materials lighter than ordinary steel offer significant weight advantages but at higher costs. Recent costs of substitutes compared to their weight advantages (with both relative numbers for ordinary steel at 100) have been 100 and 80 for plastics (but their structural use is obviously very limited), 115 and 80 for HSS, 130 and 60 for aluminum, and 570 and 50 for carbon fiber (Heuss et al., 2012). Carbon fiber has the highest potential for weight reduction in many automotive applications, but its costs (up to six times more expensive than ordinary steel) prohibit its wide use (they are much less of an obstacle in airplane construction, with Boeing 787 being the first plane using mostly carbon fiber).
But cheaper precursor materials and their more efficient processing are expected to lower the cost of automotive carbon fiber rather significantly by 2030: conservative estimates see it down by 45%; optimistic forecasts are for reductions as high as 66%, bringing it much closer to the current cost of aluminum. In terms of weight reduction for a medium-sized car, the amount of steel substituted by lightweighting may be only 250 kg when using only HSS (and steel would still make up 63% of car mass), 420 kg when deploying more aluminum and magnesium in conjunction with HSS (all steel just 21%), and 490 kg when carbon fiber would be about 36% of the total mass and steel would account for just 16% (Heuss et al., 2012). Competitiveness of aluminum relative to steel has increased due to the falling difference in prices, and in the EU the net cost for some applications is less than 1 EU/kg, clearly a very competitive price (McKinsey, 2013a).
Consequences of a more aggressive pace of steel substitutions would be enormous, with the market for ordinary automotive steel cut by 30–50% in just a decade and even more during the next generation. Production of HSS would, of course, rise, but its future would depend on the success of lowering the cost of carbon fiber. In contrast, McKinsey (2013a) sees only negligible role for carbon fiber by 2030. Comparisons of material shares for 2010 with its modeled shares for 2030 are as follows: all steel 67% and 51% (HSS 15% and 38%), aluminum 15% and 12%, magnesium unchanged at 5%, plastics 9% and 12%, and carbon fiber 0% and 0.5%.
Lightweighting was the top emerging trend identified by leading car experts in 2014, second only to efficiency in its overall importance (Prime Research, 2014). Engine downsizing was judged to be the most promising approach, with more aluminium in second place (new Ford F-150 with high Al content is seen as shifting the metal’s perception from relatively exclusive to a standard high-volume materia
l), clever material mix in third, and, surprisingly, carbon fiber in fourth, ahead of HSS, whose role was seen as already peaking; this rise has come mainly because the experts felt that the BMW i3 could change the perception of carbon fiber from an expensive and exclusive material to one that might offer an affordable, mass-market solution for weight saving.
That remains to be seen as HSS may soon offer 25% weight reduction at no extra cost compared to ordinary steel and, importantly, when compared to other light automotive materials it will retain the advantages of component formability, durability, and safety performance; and AHSS parts can be readily repaired (Baltic & Hilliard, 2013). Another lightweighting option, particularly suitable for car roofs, is to use a sandwich material with improved stiffness: two steel sheets (0.2–0.3 mm thick) cover a layer (>