Mower blades today are made of low-carbon alloy steel. Most of the latest mower blades are rigid in nature but softening makes them bendable if they strike a rock or piece of wood. Because these blades are designed for being soft, it makes lawn mowing safer. The blades made from a harder steel alloy do not bend, but instead break. This can lead to steel bits flying around, especially when the blades spin at very high RPMs.