微合金钢中氧化物夹杂对焊接热影响区组织、性能的影响

研究了一种微合金钢中夹杂物与模拟焊接热影响区微观组织以及低温冲击韧性的关系.结果发现:实验钢夹杂物以类球状Ti2O3-Al2O3-MnS型复合夹杂为主,分布较为均匀且尺寸小于3μm;在相变冷却时间较短(T8/5=40s)时,试样微观组织以针状铁素体和沿晶铁素体为主,板条贝氏体束较少,原奥氏体晶粒尺寸在50μm左右,低温冲击性能优良;随着相变冷却时间的延长(T8/5=60,80s),原奥氏体晶粒尺寸也随之增大,相变温度的提高和相变区域的变宽使得位于原奥氏体晶界附近的夹杂物对晶界处多边形铁素体的诱导促进作用更加明显,沿晶铁素体长大剧烈,一定程度上消耗了晶内针状铁素体对组织的分割细化作用,使得低温冲击韧性有所降低.

Influence of oxide inclusions on the microstructure and properties of weld-heat-affected zones in a microalloyed steel

The relationship between inclusions and the microstructure of the simulated weld-heat-affected zone (HAZ) in a microalloyed steel as well as low-temperature impact toughness was investigated. The results show that inclusions in the steel are mainly Ti_2O_3-Al_2O_3-MnS, these complex inclusions are well distributed and their size is less than 3μm. The microstructure of HAZ consists of acicular ferrite, intergranular ferrite and small amount of lath bainite while the cooling time during phase formation is short (T_(8/5)=40s), the prior austenite grain size is about 50μm and the samples have good impact toughness under this welding thermal simulation condition. The size of prior austenite grains increases with the increase of transformation cooling time (T_(8/5)=60 and 80s), the increase of transformation temperature and the broadening of the transformation region make the promotion effect on polygonal ferrite induced by inclusions in the vicinity of the grain boundaries become more obviously, the intergranular ferrite grows up rapidly, the refinement effect of intragranular acicular ferrite is lowered to some extent, and the low-temperature impact toughness is decreased.