Papers by Author: Horia Mateiu

Abstract: The paper presents an application according the reliability and remining life assessment of the reactor (coxing box) from a petrochemical plant, after failure in welding joint of plated shell from W1.5423 (16Mo5) steel with 25 mm thickness, plated with W1.4002 stainless steel with 3 mm thickness. The reactor failure it has associated with initial flaws from welding process, which have accelerated remaining life exhaustion. The assessment made in two steps. It has used VII section of ASME code specifications and iRiS-Thermo expert system for preliminary remaining life assessment. Concomitantly, it was performed the experimental creep and thermal fatigue testing. The program results have defined creep and thermal fatigue exhaustion and its remaining life at common creep-fatigue action, in condition of safety exploitation. It was emphasized the possibility of use an extra 40,000 hours of rehabilitated reactor in the safety condition of normal parameters.

Abstract: The paper presents the experimental results regarding the influence of the multiple thermal cycles on the structural and mechanical characteristics of the weldable C-Mn steel used in energetic. Macro- and microscopic examinations, and mechanical testing made on the intersection welds show that the structural and mechanical characteristics are within the reference range of CMn (type S355JR) steel. So, the hardness of the pearlitic – ferritic structures in the welded joints characteristic zones is less than 216 HB; the tensile strength of the welded joints is more than 430 [N /mm2], imposed value for the C-Mn steel. Also, the weld toughness is between 38 [J] and 52 [J] (at 20 °C), more than 27 [J], value what must be assured for the investigated steel. So, the tendency to brittle fracture of the welded joints is diminished. The presence of some imperfections within the intersection welds imposes a carefully monitoring of all these welded joints by adequate nondestructive examinations.