Study On The Mechanism Of Microstructure Refinement Of Different Welded Wire Energy

Wide and thick plate used in shipbuilding has always been one of the important strategic products of steel products,and the steel used in shipbuilding industry which can adapt to large line energy welding is the most urgent demand in recent years.Because in the process of weld line energy welding near long time high temperature process,steel plate welding heat affected zone microstructure occurred serious degradation,lead to toughness fell sharply,seriously affect the mechanical properties of steel plate,so to improve the welding haz toughness has become the iron and steel metallurgy,one of the most important research topics in material field.At present,the oxide metallurgy technology of introducing fine particles into steelmaking process is the most effective method to improve the toughness in the heat affected zone of wide and thick plate welding.This paper mainly aimed at the research using the third generation of the oxide metallurgy technology is strong calcium magnesium deoxidizing technologies together with some domestic steel smelting of DH36 ship plate steel experiment analysis,around the two refining mechanism of oxide metallurgy technology is induced to micron grade inclusions in steel nail IAF refining and nano-scale second phase particles rolling researches on the two aspects of the original austenite grain boundary,explore the micron grade inclusions and nanoscale of second phase particles after big line energy welding detailed rules of the organization.In this paper,the comparison test of DH36 billet steel containing Mg and traditional DH36 billet steel smelted by the third-generation oxide metallurgy technology was carried out.The comparison study found that the addition of Mg element not only changed the composition of the microstructure of the billet steel,but also had an impact on the type,size and dispersion distribution of microscopic inclusions.The addition of Mg element not only produced more IAF to refine the organization,and make the particle size of steel in concentrated between 2?m⁴?m,which induce the IAF nucleation of mixed main ingredients for Al₂O₃-Ti₂O₃?Al₂O₃-Ti₂O₃-MnS?Al₂O₃-Ti₂O₃-MnS-SiO₂ composite inclusions class,center parts with small size MgO style as the core,and the micro inclusions in steel species more rich,more fine particle size,narrow distribution more diffuse.Then,when analyzing the mechanism of IAF nucleation refining induced by micron inclusion in oxide metallurgy technology,it is found that there is a certain matching relationship between the size of inclusion inducing IAF nucleation and the size of the original austenite grain.In this paper,systematic data statistics and analysis are conducted.The results show that there is a linear functional relationship between the size of IAF induced inclusions and the original austenite grain size in test steels.With the increase of austenite grain size,the size of ferrite induced inclusions will decrease to some extent.In the end,the simulated welding tests of different welding line energies were carried out on shipboard steel,and the post-welding structure was analyzed.Moreover,the nano-level second phase particles of the post-welding sample were analyzed and statistically analyzed by means of the extraction compound experiment,so as to explore and analyze the nailing effect of nano-level second phase particles on the austenite grain boundary during the welding process.Figere:36;Table:11;Reference:63.