Microalloyed Steels

Microalloyed Steels Microalloyed steels are a type of alloy steels that contains small amounts of alloying elements (usually 0.05 % to 0.15 %). These steels are also sometimes called high strength low alloy (HSLA) steels. Though the work of strengthening steels through addition of small percentage of alloying elements started as early as 1916 in USA, the term ‘Microalloying’ (believed to be of Russian origin) was adopted by Prof. T. M. Noren-Brandel in 1962 and became pervasive as a result of the landmark conference ‘Microalloying 75’.  Strengthening by microalloying elements permits a dramatic reduction in carbon content which greatly improves weldability and notch toughness. Microalloyed steels have been developed originally for large diameter oil and gas pipelines. The technology of microalloying involves the addition of a fraction of a percent of the microalloying elements to simple low carbon mild steel. The use of ‘micro’ alloy concentrations, which produce remarkable changes in mechanical properties, distinguishes the technology from ‘alloying’ in the conventional sense (low alloy steels family) where concentration of the alloying elements may range from 0.25 % to one or two or possibly several percent. Microalloyed steels are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels. They are not considered to be alloy steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition. Microalloyed steels are a family of steels that contain 0.07 % to 0.12 % carbon, upto 2 % manganese and are strengthened by the elements niobium, vanadium and titanium added either singly or in combination. These elements are sometimes used in conjunction with other strengtheners such as boron, molybdenum and chromium, nickel, copper and rare earth metals. The microalloying elements are used to refine...