Abstract
The effect of microstructures on fatigue and impact properties in high carbon steels was investigated using a rail steel to make welded joints in pearlite and tempered martensite structures.
The main results are as follows.
(1) In both properties the tempered martensite structure made by heat treatment or welding is superior to the pearlite structure, and in each of the two structures the finer structure exhibits better properties.
(2) The tempered martensite is superior to pearlite for both properties even if both of the structures change to pearlite after heating or welding and the tests are carried out at the pearlite states.
(3) Finally, the impact property increases as the grain size becomes finer while the hardness decreases.
