Steel: The strategic material

There is a bit of steel in every person's life. The humble rickshaw and a luxury car are both made out of steel. Steel reinforces the mansions of the wealthy and a steel sheet is the roof for the modest abode of the poor. Bridges and flyovers and skyscrapers obviously require vast quantities of steel and so does electrical power generation equipment and transmission towers. Steel is a finite and scarce resource. Iron ore and steel scrap prices have more than doubled in the last decade. This has led to a technological quest for newer and better forms of steel to conserve the use of this scarce material. The Industrial Revolution in the 19th century began with the mass production of steel in Great Britain by Henry Bessemer. Germany and the United States quickly emulated Britain's initial success in steel making. Thereafter, Europe and the United States became the leading industrial and economic powers of the world. Today, China's awesome economic growth is based on the fact it accounts for 46.4 per cent of the global steel production of 1,224 million tonnes. China's per capita consumption of steel is 405.2 kilogramme (kg) while Bangladesh consumes a meagre 9.5 kg. By contrast, Vietnam consumes 128 kg per capita. If our country wants to attain the status of a middle income country by 2025 annual export figures must climb to at least U.S. $ 70 billion (in today's $ value) and our export items have to shift from a primarily textile base to light manufactured goods, and fabricated steel articles such as ocean vessels. The textile sector will attain saturation with annual exports of US $. 30 - 40 billion. The next phase of our economic development will require enormous quantities of steel to fuel future growth. Our per capita consumption of steel must rise over 100 kg if we want to cross $70 billion per annum export figures and become a middle income nation like Thailand. If our country aspires to become a great manufacturing export power house which will create sustainable employment for our teeming millions it requires a world class physical infrastructure: roads, bridges, sea and air ports, energy and power generation and factory buildings. It will also need a social infrastructure under the broad categories of housing, health and education to build and sustain a world class human resource base. Both the infrastructures need quality steel products to transform this vision in to a reality. To achieve this noble end Bangladesh must become a steel manufacturing and steel consuming nation. Bangladesh has a small steel industry primarily engaged in the manufacture of concrete reinforcing steel bars or 'rebar' for brevity. Colloquially rebar is widely known as 'Iron rod' or MS Rod. This is the type of steel most commonly seen by our people at various building sites of the country. Reinforcing Steel Bars or rebar is manufactured in various sizes from as small as 8mm in diameter to 32mm in diameter is available in several grades or strength category in our country. The second most recognized grades are Grade 300 commonly known as Grade 40 and Grade 400 commonly known as Grade 60. In the last four years several manufacturers have introduced Grade 500 rebar which has become very popular as less steel is required in construction. The grade of the bar designates the yield strength or the useful strength of the steel. It is also known as the 'elastic limit' of the steel. The high strength of the steel implies less consumption in construction. As steel rebar is widely used product by anyone building a house the most common query among consumers is what we should look for in buying steel rebar. As high strength steel has been so widely accepted by the general public the most important property of steel is 'ductility'. Ductility is the ability of a steel to elongate beyond its elastic limit and gain strength before final rupture. There are several measures of ductility which is best understood by following the graph below. The above graph highlights the elastic and plastic behavior and limits of steel and the 2 types of elongation. The most important is the "Elongation at Max. Force" which is a measure of the true safety of the steel. The Total elongation is a measure of the total ductility of the steel before rupture. As steel is a vital element of building construction and the safety and permanence of the building depends on the quality of the steel used it is wise to test the steel for compliance to strength and ductility. In Bangladesh the tests conducted by the Bangladesh University of Engineering & Technology commonly known as the "BUET Test" is the most reliable and trustworthy. The writer, Engineer M Firoze PE, is the Head of Product Development and Marketing at BSRM. He can be reached at E-mail : firozemohammad@gmail.com