Nitrogen Content
Nitrogen content is an important indicator to measure the quality of carbon additives. Ordinary calcined petroleum coke recarburizer, the calcination temperature is low, and the nitrogen and sulfur content is high. When producing gray iron castings, since the scrap steel itself in the furnace charge will bring a part of nitrogen, if the scrap steel is added in a large proportion, the amount of carburant will increase accordingly. Excessively dissolved N in molten iron will hinder graphitization, increase the stability of carbides, promote the formation of D-type graphite, increase hardness, and deteriorate the processing performance of castings. For gray cast iron, an appropriate amount of N element can shorten the length of graphite flakes, increase the bending degree, passivate the end, reduce the aspect ratio, stabilize the pearlite in the matrix, refine the grain structure, and improve the tensile strength of the casting. and hardness. When N>0.012% in molten iron, castings may have nitrogen porosity defects. Nitrogen pores are often found inside, on the surface or near the surface of castings. They are round, rectangular and irregular in different sizes. They are one of the common defects in casting production.