The paper deals with computer-aided repair welding of a damaged metal-working tool, i. e., a stamping tool. To repair an uncomplicated tool, TIG (Tungsten Inert Gas) welding with a filler material was used. In the process of welding, the welding parameters and the temperature at the workpiece were measured. The major part of the paper describes the use of a personal computer as an aid to calculate the temperature distributions in the workpiece in the process of welding and after welding, and the cooling rate after welding. To this end, the Microsoft Excel software was used. The cooling curves obtained for the individual parts of the workpiece after welding were plotted in a TTT (Time Temperature Transformation) diagram to determine the workpiece structure, hardness and, indirectly, other mechanical properties. The most important finding is that the method described permits to find the locations of maximum stresses in the workpiece that may be potential sources of crack formation.