正火型V-N-Ti和Nb-V-Ti海工钢焊接粗晶热影响组织和韧性研究

用焊接热模拟方法研究了V-N-Ti和Nb-V-Ti微合金化正火型海工钢模拟粗晶热影响区(CGHAZ)组织和韧性的变化规律。结果表明，组织的不同使V-N-Ti设计正火型海工钢的模拟CGHAZ韧性比Nb-V-Ti钢的好。对于V-N-Ti钢，较高的N含量提高了富Ti(Ti, V)(C, N)粒子析出温度和铁素体形核能力，使模拟CGHAZ原始奥氏体晶粒和(取向差角为15°)晶粒细化，并生成能阻止或使解理裂纹的偏转细小多边形铁素体，因此具有良好的低温韧性。而Nb-V-Ti钢模拟CGHAZ原奥氏体晶界上的链状M-A、粗大的原始奥氏体晶粒和有效晶粒尺寸，是模拟CGHAZ韧性差的原因。

Study on Microstructure and Toughness of Simulated Coarse Grain Heated Zone in Normalized V-N-Ti and Nb-V-Ti Marine Steel

The microstructure and toughness of the simulated coarse grain heat affected zone (CGHAZ) of the normalized microalloying offshore steels V-N-Ti and Nb-V-Ti were investigated by means of a welding thermal simulator. The results show that the perculiar microstructure led to better CGHAZ toughness for the V-N-Ti steel. For V-N-Ti steel, the high N content increases the precipitation temperature of Ti-rich (Ti, V)(C, N) particles and the ferrite nucleation ability, so that refines the original austenite grain and decreases the effective grain size with high boundary tolerance angle 15^o, hence, the fine polygonal ferrite could efficiently deflect or even arrest the propagation of cleavage microcracks, so it had good low temperature CGAHZ toughness. While there exist chain-like M-A on original austenite grain boundaries, coarse original austenite grains and larger amount of fine grains with high boundary tolerance angle 15^o that may be responsible to the lower simulated CGHAZ toughness of Nb-V-Ti steel.