An apparatus for the heat-treating of a heat-hardenable steel cruciform article having a weld seam includes a heating element to heat the weld seam to a point that an austenitic transformation occurs, and a quenching chamber to cool the weld seam, causing the formation of Martensite and an associated expansion. The quenching is rapid since slow quenching may allow a crystalline phase other than martensite to form. The apparatus may comprise rollers operable to convey the welded cruciform article through the apparatus at a speed such that the weld seam is subjected to heating for a predetermined heat time sufficient to cause a formation of martensite there within, and such that the heated portion reaches the quenching chamber and is quenched to create a substantial amount of martensite, e.g., an amount sufficient to cause expansion of the part.