Study On Slab Inclusion For TANG Steel

The quality of steel products are greatly influenced by nonmetallic inclusion,inclusion’s size and type and source and distribution and crack of steel products is studiedin SPHC and IF and TWG800bearing steel produced by TangShan Iron&Steel Co.Ltd.Utilizing tracer method follows the inclusion source, electrolytic sample analyses large-sized inclusion’s content, metallographic analysis observes micro-inclusions and utilizeSEM/EDS to make further analyses. The source of inclusions in steel and slag andrefractory material in the steel which bad to quality of slab are studied in the paper.The result of study shows：1) The content of inclusion is high in inner arc of beamblank. The inclusions aggregated in the area of apart from1/6to1/3of inner arcs. Thistrait of distribution is mainly worked by inclusions which diameter is less than10μm.2)Inclusions whose diameter is less than5μm account for about7%，inclusions whosediameter is between5μm and10μm account for9%，and inclusions whose diameter arebetween10μm and15μm account for80%. In the large non-metallic inclusions, K, Naand Mg, Ca are detected the main elements, therefore, that inclusions source is not asingle, large non-metallic inclusion is mainly composed of ladle slag, slag and moltensteel deoxidation products which in collision aggregation formation.3) The content ofmacro-inclusion in thin slab is45mg/10kg in state of steady casting，and is56mg/10kgin medium thickness slab. Non-metallic inclusions whose diameter is less than140μmaccount for10%，inclusions whose diameter is between140and300μm account for20%，and inclusions whose diameter are more than300μm account for70%.4) Internalcracks in continuous casting is slim and curing, but it is formed in mould and growed upin soft reduction process.Inclusions in steel are mainly come from deoxidating process, secondly come frommould flux and tundish cinders cover. But most sources of inclusions in steel is not single,which is mainly composed of oxidation products and a variety of slag and refractorymaterial in liquid steel interactions assembled grew to form the composite inclusions.