Research On High Heat Input Welding And Composition Design Of E36Ship Plate Steel

In recent years, the sharp growth of trade volume with shipping brought shipbuilding industry an unprecedented prosperity. Demand of ship steel especially marine thick plate rose rapidly year by year with the rapid growth of the world shipping industry and the moving of shipbuilding industry center towards the east. In the shipbuilding industry, welding accounts for about30%～40%of the shipbuilding time and the cost on welding time takes half that of welding. Efficient multiplewire submerged-arc welding and electrogas welding are widely used in order to improve the efficiency and reduce the cost, which welding energy is as high as500kJ/cm above. At present for this kind of high heat input welding steel plate, a tight technology blockade is taken by foreigners, and our country mainly depend on imports. Therefore, the research and development of domestic high heat input welding ship steels with high strength is imminent. This paper started research from the thermodynamics, chemical composition design, metallurgy process, controlled rolling&controlled cooling process, welding toughness, and many other aspects, and developed in laboratory a kind E36senior steel suitable for high heat input welding. The main work of this paper are as follows:(1) The activity coefficients of each element in ship steel ware calculated through first class activity interaction coefficient, and the order of deoxidizing ability of alloy elements was determined:Zr>Ca>Al>Ti>B. The thermodynamic separational conditions of Ti2O3and Ti3O5are separately:[%Ti]/[%Al]>6.27and [%Ti]/[%Al]>5.03. Additive amount of Ca, Ce, Ti, Al were calculated by thermodynamic calculation software, which offered a reference to designing a best E36steel.(2) An appropriate rolling and cooling process were determined in laboratory: recrystallization rolling with an accumulative pressure of41.7%at1100～1000℃, nonrecrystallization rolling with a62.8%accumulative pressure at920～880℃, and direct water cooling to650℃with a cooling speed of12to15℃/s, in which way the rolled plate can meet mechanics requirements of GB712-2000standard.(3) Welding simulation experiment shows that-20℃impact energy of the senior Ca-Ti-Ce steel present first increases and then decreases with100kJ/cm to700kJ/cm linear energy. The maximum impact energy is332J when welding energy reaches400kJ/cm. All samples’ toughness is much higher than the national standard47J when welding energy is within700kJ/cm.(4) The relationship between inclusions and acicular ferrite is:MnS inclusion cannot be nucleating agent of AF until combined with other substances together; the most important role of Ce element is to help AF nucleate; complex inclusion with form of Al2O3-TiOx-CaO-MnS is the most beneficial for AF nucleation.