The effect of N on the properties of steel is similar to that of carbon and phosphorus. With the increase of nitrogen content, the strength of steel can be significantly improved, the plasticity, especially the toughness, is also significantly reduced, the weldability is deteriorated, the cold and brittleness is intensified, and the aging tendency is increased. Cold brittleness and hot brittleness, damage to the weldability and cold bending properties of steel. Therefore, the nitrogen content in the steel should be minimized and limited. Generally, the nitrogen content should not be higher than 0.018%.
Nitrogen can reduce the adverse effects of aluminum, antimony, vanadium and other elements, improve the properties of steel, and can be used as an alloying element of low alloy steel. Some grades of stainless steel, appropriate increase in the content of N, can reduce the amount of Cr used, can effectively reduce costs.