The effect of heat input on the fracture behaviour of surface weld metal of rail steel

Surface welding of rail steel with self-shielded wire was conducted with different heat inputs, and the influence of welding heat input on the total impact energy and its components, crack growth rate and fracture mechanism was systematically investigated. It is shown that toughness decreases as heat input increases, but, with a temperature decrease, these differences are not so marked. An increase of heat input leads to increasing the share of transgranular brittle fracture, what is in complete accordance with the obtained energy values. It is established that fatigue life increases when increasing the welding heat input, while resistance to crack growth decreases in the final deposit layer up to the HAZ at all heat inputs. Based on obtained results, the optimal value of heat input is defined for the selected welding procedure.