ABSTRACT

The effects of coarse TiN particles, prior austenite grains, and intragranular microstructures on the impact toughness in heat-affected zone of Mg deoxidation steel plates without Al (0Al) or with 0.02 wt-% Al (200Al) were studied from the cleavage initiation and propagation. The coarse particles are mainly TiN. 0.02 wt-% Al addition increases coarse TiN particles (>0.5 μm) from 124 to 151 mm^–3, increases brittle microstructures from 25% to 78%, and increases dislocations between ferrite laths, which impairs the toughness, although the austenite grain size is reduced from 213 to 184 μm. Coarse TiN particles alone can’t govern the brittle fracture with the additional effect of microstructures in the case of intragranular acicular ferrites (IAFs). The importance of intragranular microstructures on preventing crack propagation is greater than that of austenite grain boundaries when the grain size is smaller than a critical size to suppress the IAF formation for ferritic steels.

摘要

研究了粗TiN颗粒、原奥氏体晶粒和晶粒内显微组织对不含Al(0Al)或含0.02wt-%Al(200Al)的Mg脱氧钢板热影响区冲击韧性的影响。传播。粗颗粒主要是TiN。添加 0.02 wt-% Al 将粗 TiN 颗粒（>0.5 μm）从 124 增加到 151 mm ^–3, 将脆性组织从 25% 增加到 78%，并增加铁素体板条之间的位错，这会损害韧性，尽管奥氏体晶粒尺寸从 213 减小到 184 μm。在晶内针状铁素体 (IAF) 的情况下，单独的粗 TiN 颗粒不能通过微观结构的额外影响来控制脆性断裂。当晶粒尺寸小于铁素体钢 IAF 形成的临界尺寸时，晶粒内显微组织对于防止裂纹扩展的重要性大于奥氏体晶界的重要性。