The invention comprises a structural member formed from iron alloyed with 0.15% to 0.20% carbon, 1.00% to 1.80% manganese, 1.00% to 1.60% silicon, 1.50% to 2.50% chromium, 2.50% to 3.50% nickel, 0.40% to 0.70% molybdenum and 0.0025% to 0.0005% boron, all by weight. Preferably, alloy is subjected to a two-level thermal processing to confer a bainitic structure to the steel. Also preferably, the structural member is a frog for a railway track switch.