In a webinar held recently, chemicals industry leader, D S Ravindra Raju, President, Deepak Fertilisers & Petrochemicals Corp, spoke about implementing the ‘proof of concept’ in a plant in a large chemicals company under his charge. He and his group are working on improvements in the Environment, Health and Safety (EHS) area, capacity & reliability, quality, productivity and efficiency. The change is to be brought about by using digital and IT-oriented technologies. And the issues that the change initiative is covering are to be addressed through engineering, technology and human ingenuity. These three interconnected mechanisms have been at the forefront of industrial advancements over the years since the industrial revolution began in the late 1700s.
Engineering materials have been the instrument through which all improvements due to engineering developments have been implemented. It all began with the use of iron and steel to make large machines, like flywheels, forging presses and railway engines. Over time, aluminium, copper, tin & a few other metals came into use. Magnetism, electrical conductivity and generation & transportation of electric power led to major advances in the way machines worked. The source of energy, which used to be water (in the form of steam), human hands & animals, was extended to include electric power, magnetic mobility, followed by electro magnetism. Then came nuclear materials, piezo electric crystals, carbon, composites, ceramics, electronic components, sensors and newly synthesised materials, which extended & expanded the use of engineering materials. In the global engineering materials journey, steel has been and will continue to be the leading material, never mind the competition from aluminium, carbon, etc.
Stage 1: The capital goods era
In the initial stages of the industrial revolution, steel was used to build equipment to manufacture other assets. For example, forging presses, EOT cranes, chemical reactor vessels and so on. These capital equipment manufacturing applications were possible due to the increasing availability of steel, alloy steels, cast iron and related engineering materials. The sintering plants, blast furnaces, coke ovens, open hearth furnaces, ingot making mills, blooming mills, rolling mills, which were all built using various amounts of steel & iron, produced millions of tons of steel, a lot of which was used to build capital equipment.
The steel that was produced in the shape of slabs, plates and sheets was used to make capital equipment through cutting, shaping, welding (joining), machining and fitting. Over the years, the demand for high strength steels, especially of the alloys variety, has increased substantially. In fact, for some of the applications, like aerospace, VLCC ships and Antarctic ice breakers, which are special purpose, infrequent applications have challenged materials science engineers. Such equipment is usually large, works in extreme temperatures and is expected to work to very high safety standards. Alloying elements, like chromium, nickel (for stainless steels), high nickel (for low temperature applications),low to very low carbon (for corrosion free steels), vanadium (for high strength & ductility), are typically used to expand the scope of engineering properties of steel. Of late, like high-speed fighter aircraft, large and very large planes (which all demand high strength, with malleability & ductility over severe temperature ranges) use stainless steels that are versatile, utilitarian and maraging steels. The era of capital equipment will continue to be an integral part of the iron & steel industry. The newer applications, like the Mars Voyager, the high-speed trains, Mag Lev trains, will all call for very high strength to weight ratios, good machinability and wide temperature range tolerance.
Stage 2: The products era
The line between capital equipment and products is not airtight. Products are those which are manufactured in large volumes & numbers and are used in domestic & consumer applications for ultimate end-use. For example, while a ship can be considered capital equipment, in that it costs a lot and is used only for transportation. A domestic appliance, like a fan or an electric iron, is small in size and used for household applications. These products are produced by using capital assets and use steel for providing properties, such as low weight, high strength, corrosion resistance and superior aesthetics. The product era is another facet of the development of applications of steel for human usage. Rapid advancements in testing of steel also aided product development. For example, NDT, magnetic particle testing and testing of weldments made steel a versatile engineering material for daily use. The range of steel usage in day-to-day products has developed over the years through advancements in material composition, material testing, metal joining techniques, metal working & machining techniques. Refinements and enhancements in product chemistry expanded application areas. Alloy additions were critical in making steels & cast iron serve complex product applications, such as, Ni Hard castings, Hadfield Manganese steels for work hardening applications in military vessels (tanks), cryogenic steels for the manufacturing of liquid oxygen and nitrogen & high temperature steels for automobile rotating parts, like bearings.
Stage 3: The construction era
Bulk of steel is used in the construction and infra industries. From the engineering standpoint, load bearing capacity, strength & torsion capacity are the metrics which determine the suitability & usage. Steel sheets in building facades, trusses and channels in airport & railway stations, stainless steels in elevators, steels in bridges of all shapes & sizes are all major engineering applications. One must see the Terminal 2 at Mumbai airport or the new terminal at Indira Gandhi airport in Delhi to appreciate how steel trusses can be aesthetically functional. In any economy, steel & iron are considered the basic foundational materials. Along with electric power, water, roadways & railways, the iron & steel industry forms the core for building an industrial economy. In the iron & steel sector, the use of flat products increases as more steel is used in the construction sector. In advanced economies, the production of flat steel products is as much as 60–70% of the total production & usage. This is because steel flats are the most engineering-friendly materials. The superior surface finish, corrosion resistance, strength to weight ratio and the comparatively lower cost are all factors in its favour. Easy availability, in terms of cost & sales outlets, easy maintainability & repairability, abundant supply of parts & services all make construction steel the most versatile engineering material.
Skill levels needed to install and maintain are again available in plenty. In terms of cost, flat steel currently costs ₹50,000 per ton, whereas a ton of flat aluminium costs ₹200,000 and up. Of course, aluminium scores in terms of lower weight per running foot but steel is endowed with better tensile strength. Moreover, the surface finish of aluminium can never be as good as steel, especially stainless steel, whose shiny surface is long-lasting as well.
Steel – The most preferred engineering material
Finally, when looking at the usage of a material for engineering applications, one must carefully weigh several pros and cons. The table above is a comparison of some of the commonly used materials in the world.
Clearly, steel is favourable from most angles important for engineering use because –
It is produced in abundance and at an affordable cost. The availability of steel is universal, and many countries in the world produce it.
It can be shaped to any requirement and rolled to a thicknesses as low as 0.01 cm, with carbon content as low as 0.01%. This is important as the low carbon, with alloying elements, gives steel the drawability & strength combination which is unbeatable.
Weldability, joinability & testability are all well developed, thereby, increasing the applications.
Special properties like hardenability, work hardening, magnetism & electrical conductivity make it usable in many diverse areas.
Its ability to alloy with almost any other important metal makes it versatile & adaptable to complex uses.
Its ability to work under very wide temperature ranges endows it with a superior panorama of applications.
Thus, overall, steel is the most important & widely used engineering material in the world, and there is nothing else in sight to change this situation.