Study On The Behavior Of Inclusions Of Deep Punching Steel In Guo Feng

With the successful development of MRT3-BA deep punching steel, the technologysystem of Tangshan Guofeng Iron and Steel CO.,LTD is still in the exploration andperfection. Quality problems of products in production process happen from time to tome;the major reason is that steel sheet has poor deep drawability especially unevendeformation and crack.To solve the above problems, some study means including tracer addition,systematical sampling and laboratory analysis are introduced to research on the origin,type, size and distribution of inclusions in billet in three processes of the current MRT3-BA deep punching steel of Guofeng. The three processes include BOFâ†'LFâ†'CC（process1）, BOFâ†'RHâ†'CC （process2）and BOFâ†'LFâ†'RHâ†'CC （process3）. Thebest production process of MRT3-BA steel is defined and corresponding improvementmeasures of technology is put forward for improving billet quality. The influence ofcasting speed and nozzle submerged depth on flow field in mould is studied by mouldflow field physical simulation experiment.The results of the study show that the contents of T[O] respectively are20.8×10^-6,14.3×10^-6and13×10^-6in billet of process1, Process2, Process3. Therefore, control ofT[O] has reached a high level in MRT3-BA deep punching steel of Guofeng. Through thecomparison with production data of other manufacturers, the numbers of microsco-inclusions respectively are6.8/mm²,5.66/mm²and5.36/mm²in billet; the control level inMRT3-BA steel of Guofeng has reached domestic advanced level. Large inclusioncontents respectively are72.2mg/10kg,75.38mg/10kg and30.35mg/10kg in billet, farhigher than similar steel producted by domestic advanced steel plants. Analysis showsthat large inclusion>300μm accounts for69.8%⁸5%of total inclusion in billet in threetechnological processes, and inclusion containing K and Na is the most; wrapping slag inmould is really serious. Steel cleanliness and production cost taken into account, thebetter technological process of MRT3-BA stamping steel for Guofeng is BOF-RH-CC.Tracer analysis shows that inclusions containing K, La, Ce, Mg, respectively account for62%,44%,44%,15%of total inclusion in process2. Therefore, the source of largeinclusion in billet is from mould fluxes, ladle slag, tundish covering flux and trefractorycorrosion.The physical simulation experiment determines casting speed and corresponds thebest nozzle submerged depth suitable for mould whose section is180×1270mm². Castingspeeds respectively are1.0m·min^-1,1.2m·min^-1and1.4m·min^-1, and the best nozzlesubmerged depths are140¹50mm,150¹60mm and160¹70mm.