Development And Research On DH36Hot-rolled H-beams

Due to the rapid development of world economy, the demand of oil has been increasing. At present, the marine oil exploitation is becoming more and more important. With the development of oil exploitation, the research and development of H-beams excrusively used for offshore oil platform has been paid more attention than ever before. Ordinarily, people fabricate the traditional H-beams used for offshore oil platform by weldding shipbuilding steel plates together, but because of the weld and the heat affected zone, the H-beams fabricated as outlined above can not be used in the sea where the tough and harsh conditions are common, as the result of which, it will be meaningful to develop the hot-rolled H-beams dedicated for offshore oil platform which can both improve the performance of H-beams and save resources.This issue is the important technical item of Shandong Iron&Steel Group. In this issue, we produce the qualified products by proper microalloying and optimized process of steel-making and rolling. In this research, the microstructure of the H-beams were studied by optical microscope (OM); the micro fractographs were carefully observed by scanning electron microscopy (SEM); the microstructure morphology and composition analysis of the inclusions in the steel were studied by scanning electron microscopy (SEM) and energy spectrum analyzer (EDS). All the above explore the influencing factors to the low temperature impact toughness of the DH36hot-rolled H-beams.The results indicates that the FATT is-40℃or so, which has reached the requirement of national standard(-20℃).Some conclusions in our research are summarized as followed:(1) The combination of Ti with other elements is uncertain, so getting rid of the Ti from the steels can eliminate ill effects of the compounds generated by Ti with other elements.(2) The finishing rolling temperature controlled at910℃, can guarantee that the recrystallization of austenite grains do not grow to a large size so as to avoid producing widmanstatten structures and that the grains can generate relatively small ferrites after cooling, both of which can promote the strength and impact toughness of DH36; at the same time, non-recrystallized austenite grains after rolled by9times, can accumulate large amounts of deformation energy on one hand, and can improve the volume fraction of recrystallization on the other hand, both of which can generate small ferrite during the phase transition so as to promote the strength and impact toughness of DH36.(3) The inclusions in steel have an adverse effect on comprehensive performance of steel, especially on the impact toughness, as the result of which, controlling the production process strictly can decrease the inclusion amount in the steel so as to promote the strength and impact toughness of DH36.