Complex sentence: In material science terms, harder steels take sharper edges, but are more brittle and hence chip more easily, while softer steels are tougher, and are used for knives such as cleavers which must be tough but do not require a sharp edge.
Split into simpler sentences: In material science terms, harder steels take sharper edges, but are more brittle and hence chip more easily, whereas softer steels are tougher. The latter are used for knives such as cleavers, which must be tough but do not require a sharp edge.