A process for producing a honeycomb body includes a) producing a tubular casing from sheet metal; b) introducing a hole, delimited by a rim, into the sheet metal; c) fitting a flange piece for a measurement sensor to the hole rim; d) introducing a honeycomb structure into the tubular casing; and e) joining the tubular casing to the honeycomb structure and the flange piece by brazing or welding in a single, common, heat treatment process. Steps a), b) and c) are carried out in any desired order. A honeycomb body includes a honeycomb structure. A tubular casing surrounds the honeycomb structure, has a hole delimited by a rim, and has a necked region surrounding the hole. A flange piece for a measurement sensor is brazed to the hole rim. The process allows a flange piece to be connected to the tubular casing in an advantageous manner as part of an on-going heat treatment process, resulting in a simple and fast production and consequently a reduction of costs.