Niobium in engineering bar steels

The use of niobium as a microalloying addition to hot rolled and cold finished bars offers many opportunities to achieve enhanced mechanical properties in a very cost effective manner. By the addition of niobium (sometimes in combination with vanadium) to selected carbon steel grades, it is possible to produce hot rolled bars with minimum yield strengths up to 689 MPa (100 ksi) and cold finished bars with yield strengths up to 1035 MPa (150 ksi). These high-strength-low-alloy bars have a myriad of applications particularly for automotive parts such as shafts, stabilizer bars, tie rods, piston rods, fasteners such as U-bolts, brackets, and various transmission parts. Of particular value has been the specification of Nb-microalloyed steels for such hot forgings as connecting rods and caps, and weld yokes a situation which has permitted elmination of post-forging heat treatment (quenching and tempering). Significant reductions in cost and energy consumption have been realized. (AU)