METHOD OF MAKING FINE CRYSTAL GRAIN BY ADDING B, ZR IN STEEL

摘要

PURPOSE: A method is provided to obtain a compound having a low gravitational segregation, reduced size of crystal grain, improved yield strength and superior tensile strength. CONSTITUTION: In the manufacturing process of carbon steel having a composition containing 0.02 to 0.5% C, 0.05 to 2.0% Si, and the residual part of F3, to make the crystal grain fine, 0.01 to 0.3% B and 0.05% to 0.8% Zr are simultaneously added to produce ZrB2 compound which has a high gravity of approximately 6.2. The size of the crystal grain is reduced by 1/3 approximately, while the yield strength and tensile strength are increased by 60 to 100MPa approximately.