BN PRECIPITATION REINFORCED TYPE LOW CARBON FERRITIC HEAT RESISTING STEEL OF HIGH WELDABILITY

摘要

This invention provides a ferritic heat-resistant steel that can improve HAZ softening resistance, can omit heat-treatment after welding and can reduce the construction cost of a power generation plant.;This ferritic heat-resistant steel contains C: 0.01 to 0.06%, Si: 0.02 to 0.80%, Mn: 0.20 to 1.50%, Cr: 0.50 to 3.00%, Mo: 0.01 to 1.50%, W: 0.01 to 3.50%, V: 0.02 to 1.00%, Nb: 0.01 to 0.50%, N: 0.001 to 0.06%, B: 0.0003 to 0.008%, Ti: 0.001 to 0.5%, Zr: 0.001 to 0.5%, or containing one of Cu: 0.1 to 2.0%, Ni: 0.1 to 2.0% and Co: 0.1 to 2.0% either individually or in combination, and limiting P to not greater than 0.030%, S to not greater than 0.010% and O to not greater than 0.020%, wherein a weight ratio of TiN and BN in the steel is controlled to 1 to 100 in terms of a value (TiN + ZrN%)/(BN%), and a mean grain diameter of BN is not greater than 1 µm.