EFFECT OF PHOSPHORUS ON THE RESISTANCE TO BRITTLE AND DUCTILE FRACTURE OF LOW-ALLOY STEELS FOR CASTINGS.

The application of a special etching method to three low-alloy casting steels made it possible to reveal the formation, along the boundaries of former austenite grains, of phosphorus segregations which are resorbed during subsequent normalization. In the cast state phosphorus has no effect on the strength properties of the steel. In the post-normalization state an increase in the phosphorus content to 0. 04% leads to an increase in the strength properties. The results of impact tests showed that in the cast state with an increase in the phosphorus content the fracture toughness during completely ductile fracture decreases. This is especially noticeable at phosphorus concentrations above 0. 04%. In the normalized state the harmful effect of phosphorus is noticeable only in one of the three steels investigated at P concentrations higher than 0. 04%.