The metallurgist explains: The trade-off between hardness and toughness Discs
Life involves compromises, even with wear parts on your Väderstad machine. While hard parts last longer, they don’t need to be as hard as possible. Material hardness measures resistance to permanent deformation, tested by pressing specimens against materials with varying loads.
Material hardness should be balanced to avoid brittleness, which reduces effectiveness in wear parts. Toughness, the ability to resist crack growth, is crucial. Steel’s hardness is controlled by its composition and heat treatment. Higher carbon content leads to harder steel but risks brittleness. Suppliers must offer consistent quality and clean steel for reliable wear parts.The great thing about steel is that it can be hardened. If we heat it up to a bright red-orange colour, the iron atoms rearrange themselves inside the material in a way that allows the carbon to fit into small spaces that don’t exist at room temperature. If the steel is then cooled rapidly, for example in a water bath, the carbon atoms do not have time to move back and are forced to remain in these places. We then have a hard phase called martensite, which unfortunately is also very brittle.
Hardened wear parts can become too brittle for use and may crack during mounting. Tempering steel after hardening is crucial, as it reduces brittleness while sacrificing some hardness for increased toughness. This challenge is common for wear part manufacturers, as creating functional items that withstand soil preparation conditions requires balancing hardness and toughness. For example, steel in a Carrier disc is slightly harder than in a cultivator point to maximize longevity, highlighting the need for varying hardness levels in different parts.
Do not ask for the hardest possible wear parts, but for the best possible wear parts for your Väderstad machine.
