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Microalloying Strengthens Steel

Adding small amount of alloying elements can dramatically boost the strength and hardness of carbon steels.

Microalloying—the art of adding incredibly small amounts of alloying elements (0.15% or less) to steel, and getting a big change—began in the late 1970s. It created a new category of forging steels positioned in cost and performance midway between carbon steels and the alloy grades. It started with sheet steel and quickly moved on to include bar stock. With bar stock, the technique eliminated the need for heat treating after parts are forged. Microalloyed steels have been used since then in autos, construction hardware, and many other applications.

Microalloying creates new properties and characteristics through controlled chemistry in basic steelmaking. Most modified grades contain less than 0.5% of the added elements, and sometimes as little as 0.03%. The most commonly used microalloying elements are niobium (Nb) and vanadium (V). Silicon is sometimes used in higher carbon steels, and nitrogen can be added to some grades to a level higher than that found in steel to increase strength,particularly in combination with vanadium.

Microalloying affects steel‘s microstructure in three ways:

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