In the early 20th century, researchers around the world worked to develop new, stainless, and acid resistant steels, especially for the chemical industry. At that time, already known nickel and chromium steels, with increased demands from the chemical industry, were prone to corrosion and brittleness.
Strauss and Maurer, the fathers of stainless steel, reduced the carbon content to below one percent. They combined chromium and nickel as alloying elements and developed a suitable method for heat treatment to improve corrosion resistance and strength of the steel. Thus began the worldwide success of stainless steels.
The rapid success of the stainless steel market in 1920s can be credited to the development of an economic process to produce and process stainless steels. Earlier, stainless steels were produced in oil-fired, tilting pans. The invention of induction melting furnaces later simplified the process.
Early 60s saw the introduction of a melting technique with optional vacuum (VOD) or argon (AOD). The new production technique lowered the cost of production and at the same time extended the range of properties sustainably. The 80s witnessed another quality and commercial milestone for stainless steel making with the introduction of the continuous casting method, the conditions for a near net shape casting. Computer-aided control engineering drove the reproducibility of stainless steel products, thus advancing towards new application areas.
The study for materials resistant to overheated gases and vapours in the chemical industry was the driving force behind the invention of stainless steel. Increasingly, weldability and formability of stainless steel gained importance.
Growing system sizes in the chemical industry demanded boilers, columns, heat exchangers, centrifuges, transport and storage tanks, valves and pumps to come up in acid-and heat-resistant stainless steels in the market.
This application range today is almost limitless; from production and processing of acids, hydrogenation of coal or tar, distillation of liquid mixtures, textile fiber production, petrochemicals, mineral recovery, solid-liquid separation in wastewater treatment plants, and food and beverage industry.
Only a few years after its invention, stainless steel inspired architects and planners as a building material. Being weather resistant, strong, and durable, stainless steel makes itself through long life with minimum maintenance costs. It forms an essential part of a wide array of architecture ranging from structurals, corrosion-resistant concrete and masonry reinforcement, protective facades, conventional roof covers, green roofs, lightning protection, ceilings or floors, swimming pools, elevators, escalators, doors or gates, balustrades, car parks, hotels, stadiums, train stations, airports, etc.
In 1929, the Chrysler Building in New York adorned 4,500 large-sized stainless steel shingles. Later, the Petronas Towers in Kuala Lumpur, the Atomium in Brussels, the Burj Khalifa in Dubai or the new landmark of New York, the One World Trade Center, all employed stainless steel showcasing its remarkable aesthetics. The tallest buildings of the past 100 years carried a distinctive stainless steel touch. Today, stainless steel is a synonym for creative expression and sustainability.
The automotive and railway industries quickly recognized the potential of stainless steel. In 1936, Ford produced 6 prototypes using stainless steel bodies in Detroit. Since the 1950s, exhaust parts are made of stainless steel. In the late 1960s, Porsche's legendary 911 came in a stainless steel variant, which is showcased in the German Museum in Munich. In 1934, Edward G. Budd, Philadelphia, built the famous, only 104-tonne Pioneer Zephyr (previously known as Burlington Zephyr) with diesel locomotive and three carriages. Today, latest high quality automotive and railway components are manufactured entirely in stainless steel.
In systems for fuel injection, particulate filtration or gas treatment of high-performance material has long been indispensable - stainless steel is the best suited metal for the job. The precise and light-weight stainless steel components reduce material costs, vehicle weight, and fuel consumption.
For rail vehicles of the latest generation, the concept of innovative light-weight construction became more relevant than ever. Given its strength at low thickness and crash and fire resistance, stainless steel today has become the leading material for all kinds of sophisticated and economic body structures.
The decisive factor for stainless steel applications in medical industry was its resistance to high temperatures and aggressive chemicals, withstanding sterilization and disinfection problems. In 1926, the first body implants were developed in stainless steel. Even today, artificial knee joints of stainless steel meet the current state of research.
The strict hygiene regulations for surgical instruments and surgical equipment apply analogously in the food and beverage industry. Here also, stainless steel ensures a smooth, aseptic, easy to clean, and reliably inert surface. In the dairy and meat industry, stainless steel makes for hygienic engineering and economic production processes. Kitchens, dairies, breweries, wineries and juice manufacturers have been using stainless steel for decades. Its extraordinary chemical and thermal stability - even under extreme temperature fluctuations allows for an extensive use of stainless steel in manufacturing, storage, and transport of acidic products.
In 1921, the first stainless steel cutlery came into being. Since then, more and more everyday objects in stainless steel followed. In the 1950s, a variety of legendary commodities were designed in stainless steel by the pioneer of industrial design, Wilhelm Wagenfeld. The organic shape of industrially produced stainless steel cutlery, bowls, egg cups, salt and pepper shakers, butter dishes, and vases brought him worldwide recognition.
The year 1956 revolutionized beard trimming with the invention of the first stainless steel razor blades from Wilkinson Sword. Soon, stainless steel assumed a leading role as a material for cookware, fittings, sanitary ware, radiators, appliances and accessories for the kitchen and bathroom. Its timeless aesthetics, durability, and easy-care functionality made it the wonder of modern life.
In the energy industry, clean room technology, environmental technology, and telecommunications and electronics, the resistance of stainless steel against corrosion and a variety of stress regularly set new standards. Stainless steel is a prime choice for crucial applications in power plants like in heat exchangers or flue gas filters for solar panels or biogas plants. In telecommunications, paper-thin stainless steel foils and precision strips, coated with nickel and gold in the nanometer range, are constantly used.
Stainless Steel grades are essentially alloys of iron with more than 10.5% chromium. These grades may contain additional elements of nickel, manganese, carbon, nitrogen and silicon. They can further be modified for special purposes by addition of molybdenum, titanium, niobium, silicon, sulphur etc. A wide range of these grades have been developed based on specific requirements. These are classified into following categories based on their micro structure:
Austenitic Stainless Steel grades are characterized by superior corrosion and oxidation resistance, weldability, ductility and toughness compared to ferritic and martensitic stainless steel grades for similar levels of chromium. These grades exhibit excellent resistance to atmospheric corrosion, withstand attack of organic acids (e.g. acetic, lactic, citric etc.), exhibit good resistance to oxidizing acids (e.g. nitric acid), and fair resistance to mineral acids (e.g. sulfuric acid). They are well suited for severe forming. Austenitic Stainless Steel grades are nonmagnetic in annealed condition but depending on composition, they may become mildly magnetic when cold worked. They also exhibit excellent low temperature ductility and impact strength. Austenitic Stainless Steel grades can be readily fabricated by bending, drawing, spinning, punching, drilling, machining and welding and can be readily polished to a high finish. These attributes make them very versatile and popular for diverse applications in a variety of industries.
Martensitic Stainless Steel grades are plain chromium grades containing 11.5 % to 18% of chromium with relatively high carbon content (0.1% - 1.2%). Initially developed for cutlery, these are well suited for applications requiring high hardness and resistance to abrasion and erosion. These grades are magnetic and display fair cold forming characteristics. Although these can be hardened by air cooling, oil quenching is sometimes used to assure uniform hardening. These grades can be welded but require stress relieving after welding. They exhibit their best corrosion resistance in the hardened condition and perform well in mildly corrosive, environments. Martensitic Stainless Steel grades are commonly used for knife blades, turbine blades, surgical instruments, fasteners, shafts,
Ferritic Stainless Steel grades are non-hardenable plain chromium grades with chromium content varying from 10.5% to 28% and with low carbon content. These are magnetic and exhibit a better resistance to corrosion than martensitic grades. These grades are employed in applications where the desired formability, weldability and corrosion resistance is between those of martensitic, and austenitic types. The ferritics can be polished or buffed to achieve high luster.
Duplex Stainless Steel grades contain relatively high chromium (between 18% and 28%) and moderate amounts of nickel (1% to 8%). This combination of ferritic and austenitic structures is called duplex. Many of these grades contain molybdenum (1% to 5%) and nitrogen (0.05% to 0.3%). Some duplex Stainless Steel grades also contain manganese (up to 5%), copper (up to 2%) and tungsten (up to 2%. These grades exhibit high resistance to stress, corrosion cracking and chloride ion attack and have higher yield strength than that of austenitic or ferritic steel grades. These properties combined with suitable design lead to material saving. High quality fabrication and welding are possible if the operator is trained well. These grades are used in marine applications, offshore platforms, paper and pulp industry, chemical, petrochemical and desalination plants.
Stainless steel is often confused with mild steel or carbon steel. While carbon steel is a less flexible alloy of steel, stainless steel is an alloy of iron and has minimum 10.5% Chromium as a chief component.
The increased resistance to corrosion in stainless steel is due to the naturally occurring chromium-rich oxide film formed on its surface. Although extremely thin, this inert film is adherent to the metal and is extremely protective in a wide range of corrosive media. The film is rapidly self repairing, in the presence of oxygen, if damaged by any external force.
Speaking strictly in economic terms, cost is always associated with Value of Money. The cheapest alternative may not always be the best option to choose when the entire life of the product is taken into account. Therefore, life cycle costing becomes an important key.
Life Cycle Cost (LCC) analysis is a means of quantifying the choice of materials for a product or construction, with the aim of selection of the most economic alternative. Stainless steel normally comes with an initially higher cost of material, but its longer life due to excellent wear and corrosion resistance, low requirement of maintenance, and recyclability compensate for the higher initial cost and make it an environment friendly material or ‘Green Material’.
With the advent of new technology in every stream of engineering and the fast pace of the infrastructural and industrial progress, engineers are faced with daunting challenges in designing and constructing robust structures and machineries that are long lasting and low in maintenance. It is therefore necessary that engineers take the total life cycle costing for their designed structures into account.
Corrosion is the major culprit for loss of value and reduction in useful life of any structure. It causes plant shut downs, waste of valuable resources, loss or contamination of products, reduction in efficiency and costly maintenance. Awareness with respect to corrosion is very less in our country. A NACE International study estimates the global cost of corrosion to be USD 2.5 trillion, equivalent to roughly 3.4% of the global Gross Domestic Product (GDP).
Stainless steel, by virtue of its special chemical composition, is one such value added material for construction that offers long lasting and low maintenance structures. A good understanding of life cycle costing (LCC) is important to make informed choices and create values that will serve for years to come.
Corrosion is the major culprit for loss of value and reduction in useful life of any structure. Material costs are assessed with their implications. For example, initial outlay, maintenance and its frequency, downtime effects, production losses, repair, replacement, and other operationally related costs such as manpower and energy consumption.