Abstract: During the assembly of a gas circulation block, encased in sheet metal, a conical sheet-metal sleeve is placed onto a shaped block which is in the form of a truncated cone and made of a refractory material, then a sheet-metal cover provided with a gas supply tube is laid onto the larger end face of the shaped block and then the sheet-metal sleeve is welded onto the sheet-metal cover. In order to reduce the assembly effort and at the same time to create an improved gas circulation block, the conical sheet-metal sleeve is heated up before placing onto the shaped block and is then shrunk onto the shaped block. By the shrinking of the sleeve, every type of dimensional inaccuracy is compensated for, whether on the shaped block or on the sheet-metal sleeve, so that the sheet-metal sleeve, in the shrunk-on condition, sits uniformly and tightly against the shaped block over its entire periphery and its entire length.