Mechanical properties and microstructure transformation for welded joints in EH40 ship plate steel were investigated after an electro-gas vertical welding and welding thermal simulation. Effect of the inclusions on the prior to austenite grain size and nucleation of intragranular ferrites (IGFs) was examined. Results indicated that the experimental steel has a good ability for high-heat input welding. Excellent impact toughness at testing temperature of − 20 °C was obtained. An increase in impact energies at − 20 °C for the position away from fusion line (FL) is observed. The average impact energy (177 J) for heat-affected zone by simulation with heat input of 120 kJ/cm is similar with that (165 J) for FL+1 mm by electro-gas vertical welding with heat input of 207 kJ/cm. The TiN particle lost the pinning effect when the peak temperature reached 1400 °C. However, the titanium oxide particles play an important role in inhibiting the austenite grain growth because of the high melting point. Three IAFs nucleated on the TiO_x-Al₂O₃-MgO-MnS particle with the size of 7.6 μm were observed. The inclusion size is not the dominant requirement for the nucleation of IGFs and IAFs. The MnAl₂O₄ and TiO particle have good lattice matching with ferrite, they have a strong ability to promote the nucleation of IAF.

通过电-气立焊和焊接热模拟，研究了 EH40 船板钢焊接接头的力学性能和组织转变。检查了夹杂物对前奥氏体晶粒尺寸和晶内铁素体 (IGF) 形核的影响。结果表明，试验钢具有良好的高热输入焊接能力。在 - 20 °C 的测试温度下获得了优异的冲击韧性。观察到远离熔合线 (FL) 的位置在 − 20 °C 时的冲击能量增加。热输入120 kJ/cm模拟热影响区平均冲击能(177 J)与热输入207 kJ/cm FL+1 mm FL+1 mm的平均冲击能(165 J)相近. 当峰值温度达到 1400 °C 时，TiN 颗粒失去钉扎效应。然而，氧化钛颗粒由于熔点高，在抑制奥氏体晶粒长大方面起着重要作用。三个 IAF 在 TiO 上成核观察到尺寸为7.6 μm的_x -Al ₂ O ₃ -MgO-MnS颗粒。夹杂物尺寸不是 IGF 和 IAF 成核的主要要求。MnAl ₂ O ₄和TiO 颗粒与铁素体具有良好的晶格匹配，它们具有很强的促进IAF成核的能力。