A direct smelting vessel and a hearth cooler element are disclosed. The vessel includes a refractory lined hearth. An inner surface of an upper part of the hearth extends upwardly and outwardly to side walls of the vessel. The upper part of the hearth incorporates a hearth cooler disposed outwardly behind the refractory lining of that part of the hearth and below the cooling panels on the side walls of the vessel. The hearth cooler comprises a plurality of cooler elements. Each cooler element has a hollow open-backed shell structure having base, top and side walls formed integrally in a cast structure and incorporating coolant flow passages.