Effect of Titanium on Microstructure and Phase Composition of High Boron Alloyed Stainless Steel

High boron alloyed stainless steel(HBASS) with different Ti content were fabricated by vacuum induction furnace and their microstructure and boride phase were analyzed. The boride phase of HBASS do not contain Ti element is mainly (Fe,Cr)(2)B phase with slender rod-shape. After adding Ti into steel, because Ti and B preferentially combines into TiB2 phase with petals or small block shape which can stop the formation of hard and brittle (Fe,Cr)(2)B, so the number of (Fe,Cr)(2)B phase is reduced. And after adding Ti, many crisscross cracks appeared in internal large (Fe,Cr)(2)B phase, which will be effective to break into small pieces of boride to improve steel plasticity and shielding thermal neutron performance during hot rolling process. Stainless steel itself has certain shielding effect to gamma-ray, and after adding B element into the steel, it has good comprehensive shielding performance to gamma-ray and neutron. But even more important, the radiation has little effect on its properties, so the stainless steel is not only used for shielding materials, but also can be act as structural materials[1]. However, during casting process, HBASS could crystallize hard and brittle boride (Fe,Cr)(2)B, whose amount will increase with the increasing of boron content, this will bring rather difficulty to work the HABSS during hot rolling[2]. Ti element which has stronger affinity with B has priority to react with B to form boride TiB2 with small piece or petal shape, this can stop the formation of (Fe,Cr)(2)B phase, so the plasticity and shielding thermal neutron performance can be improved[3].