Melting furnace of a rigid structure

A melting furnace of a rigid structure includes a hollow body for receiving a material to be melted, the body comprising bricks joined together. A shell of iron surrounds the brick body so as to restrain a thermal expansion of the brick body during an operation of the furnace. A heating device is mounted around the iron shell for heating it to control the degree of thermal expansion of the iron shell, thereby controlling compressive forces exerted by the iron shell on the brick body when the brick body is thermally expanded during the operation of the furnace.