Fatigue crack propagation in a structural steel after flash welding

A study has been made concerning the affect of tempered martensite volume fraction on the fatigue behavior of a quenched and tempered R4 grade structural steel, largely adopted for fabricating offshore mooring chains. As the chain links are fabricated by flash welding, the study also included welded joints. Martensite content was varied by using different austenitization temperatures and fatigue resistance of quenched and tempered specimens was determined by following crack growth during constant amplitude cyclic loading. The results indicated that an increase in the ferrite volume fraction was associated with an increase in the number of cycles to failure and that for a given microstructural condition, the fatigue life of the welded joint was invariably shorter than that of the base material. Finally, the fatigue behavior is presented and discussed considering the mechanical properties and the toughness of the fatigued specimens