The heavy-duty circuit-breaker having an axis (A) which defines an axial coordinate (z) parallel to the axis and a radial coordinate (r) at right angles to the axis, and having an arcing contact piece, a current-carrying element and an erosion protection element, with the arcing contact piece having an opening in order to carry an essentially axial flow of a gas which has been heated by an arc which may be based on the arcing contact piece, and together with the current-carrying element forms a flat contact (F) in order to carry a short-circuit current (I) which flows through the arcing contact piece and the current-carrying element for the time during which the arc burns, and with the erosion protection element essentially shielding the current-carrying element from the flow close to the flat contact (F), is characterized in that the current-carrying element has an axial area in which a radial internal dimension (d2) of the current-carrying element increases in steps or continuously as the distance from the flat contact (F), measured parallel to the axis (A), increases. The axial area is advantageously intended, to hold the erosion protection element.