Papers by Keyword: Toughness Degradation

Abstract: The mechanism of toughness degradation during slow cooling in the austenite range was studied in CA6NM stainless steel, 13% Cr-4% Ni soft martensitic stainless steel. The variation of toughness, fracture mode and microstructural features were examined by means of cooling rate and isothermal heating in the austenite range together with chemical composition. Toughness degradation was referred to as the increases of FATT and intergranular fracture when those steels were cooled slowly after austenitizing and isothermally heated in the austenite range. The embrittlement was found to be related the intergranular fracture and the precipitation of carbide along prior austenite grain boundaries. Its fracture surface was characterized by mosaic-like markings when the carbide precipitation got to increase. Reducing carbon, silicon and phosphorus and increasing molybdenum improve the toughness degradation.

Abstract: Many researchers have been interested in the nondestructive measurement methods for examining the microstructural changes and components damage in order to assure the safe operation of steel structure. It has been recognized that the techniques based on magnetic measurement offered a great potential because of high susceptibility to the change of several metallurgical factors. In this study, the effect of isothermal heat treatments, which simulate the microstructural changes observed in reactor vessel material at the service temperature, on the magnetic properties was investigated. 2.25Cr-1Mo steel specimens with several different kinds of aging were prepared by an isothermal heat treatment at three different temperature levels. Magnetic property such as coercive force was measured. The coercive force at room temperature monotonously increased with the extent of degradation of the material. The correlation between the measured magnetic property and the mechanical properties was studied. In addition, the applicability of magnetic properties measurements to the evaluation for toughness degradation of reactor vessel was discussed.