| Recently, with the domestic department of industry&manufacturing developed rapidly, steel plates manufactured by the steel industry are important materials used in large welded structures, such as shipbuilding, large span bridges, offshore structures, large oil tanks, super-high rise building. The high heat input welding of plate steel has became a new direction of iron and steel technology under the promotion of industrial development and scientific research. In the paper, in order to find the optimal technology of oxide metallurgy, the toughness and micro structure of investigated EH40steel, which is based on the oxidation metallurgical technology, were studied after high heat input thermal cycle simulation. The investigated steel proves well weldability by Vibrative Electron Gas Arc welding (EGW), which may benefit to the regulation for industrial productions.The contents and conclusion in this paper are summarized as follows:(1) The deoxidation equilibrium and precipitation between [Al],[Ti] and [Mg] and [O] was simply analyzed using the simplified molten model on the based of the theory of metallurgical thermodynamics. The optimal particle will precipitate with the weight mass ratio W(Ti)/W(Al)≥13-16through analyzing the theory of competition in Al-Ti-O molten. It will prefer to precipitate MgO·Al2O3and MgO from the low aluminium content steel, when Mg is properly added into the liquid steel. At last the theory is proved by analyzing the investigated steel in the lab.(2) High heat input welding thermal cycle simulation has been carried on MMS-300thermal/mechnical simulation tester. As a result, when the peak temperature was1400℃and the heat input energy was among100-380kJ/cm, the E-3investigated steel’s microstructure and low temperature impact toughness is the best among the investigated steels by analyzing with OM and SEM.(3) According to the thermal expansion method, microstructure observation and Vickers hardness testing. The CCT curves of two investigated steels were plotted. The law of cooling rate and reheat treatment rate after elevated temperature deformed austenite was studied by OM and TEM with M/A constituent and precipitation.(4) The mechanical properties of the investigated20mm thickness plate steel get the targets of the CCS by Vibrative Electron Gas Arc welding experiment. The E-3investigated steel reveals fine acicular ferrite, correspondent with the thermal cycle simulation test. |
