Abstract: The invention discloses an object comprising at least one part made of steel, the composition of which comprises, the contents being expressed by weight, carbon with a content of between 0.005 and 0.27%, manganese between 0.5 and 1.6%, silicon between 0.1 and 0.4%, chromium in a content of less than 2.5%, Mo in a content of less than 1%, optionally one or more elements chosen from nickel, copper, aluminum, niobium, vanadium, titanium, boron, zirconium and nitrogen, the balance being iron and impurities resulting from the smelting, said steel part including at least one zone welded by a high-energy-density beam, characterized in that said welded zone has a microstructure consisting of 60 to 75% self-tempered martensite and, to complement this, 40 to 25% lower bainite, and preferably 60 to 70% self-tempered martensite and, to complement this, 40 to 30% lower bainite.