Study On Behavior Of Inclusions In Near-Net-Shape CC Of Beam Blank

Jinxi Iron&Steel Co.Ltd adopts Near-Net-Shape CC of Beam Blank to produce H-beam. Merits of simplified procedure, high yield, low energy loss and less investment are possessed by this mode of production. There is no experience to use for reference because it is the first time to use this mode of production in our nation. At the same time, a few problems appeared in course of producing. Crack in abdomen plank is one of extrusive deficiencies. One–third of the cracks in abdomen plank are caused by quality of steel, especially caused by high content of inclusions in steel.For the present techniques and condition of the company, the non-metallic inclusions type, quantity, dimension and distribution are studied with the method of tracer addition,systemic sampling and synthetic analysis. Semi-open casting is adopted to produce beam blank. The result of research shows that: (1) the average content of T[O] in beam blank is 70.8×10-6. Volume ratio of micro-inclusion is 0.15%. Amount of inclusion are quite great when semi-open casting is adopted and it is also difficult to improve steel quality and enlarge steel breed. (2) The content of inclusion is high in inner arc of beam blank. The inclusions aggregated in the area of apart from 1/5 to 3/5 of inner arcs. This trait of distribution is mainly worked by inclusions which diameter is less than 10μm. (3) Inclusions whose diameter is less than 10μm account for about 60%, inclusions whose diameter is between 10μm and 20μm account for 15%, and inclusions whose diameter are more than 20μm account for 20%. (4) Inclusions that contain Ba account for 66.7%, inclusions that contain La account for 38.9%, inclusions that contain Ce account for 27.8% and inclusions that contain K and Na account for 100%. More than two kinds tracing element are contained in 83% inclusions. There is more than one source for mostly inclusions. Two or more kind components that exist in ladle slag, tundish covering, and stamp mass and protective slag of crystallizer assemble to form inclusion in molten steel. (5) The content of macro-inclusion is 78.75 mg/10kg in state of steady casting, and is 130.09 mg/10kg in state of unsteady casting. Non-metallic inclusions whose diameter is less than 100μm account for 98%, the percent of inclusions whose diameter is between 0 and 50μm is 47, and the percent of inclusion whose diameter is between 50μm and 100μm is 51. Source of inclusion in steel and effects of inclusion to crack in abdomen plank are confirmed by research. Rational advice is also brought forward to reduce non-metallic inclusion and control crack in abdomen plank.