BRITTLE FRACTURE RESISTANCE OF HAZ METAL IN ARC-WELDED JOINTS OF HIGH-STRENGTH STEELS WITH CARBON CONTENT OF 0.55-0.65%

摘要

Modeling methods were used to study the influence of structural-phase composition and diffusible hydrogen on brittle fracture resistance of HAZ metal of high-strength steel with carbon content of 0.55-0.65 %. It is shown that to achieve comparatively high resistance of the joints to crack propagation, it is necessary to ensure formation in the HAZ metal of bainitic-martensitic structure, in which upper bainite is absent, and martensite volume fraction does not exceed lower bainite fraction. At saturation of HAZ metal with hydrogen, which diffuses from deposited metal during arc welding or surfacing, its brittle fracture susceptibility increases markedly. To reduce metal embrittlement, it is necessary to apply special welding techniques, at which hydrogen saturation is minimum (less than 0.2 ml/100 g), or special technological methods, allowing improvement of ductile properties of HAZ metal.