Effect Of Trace Ce On Microstructure And Properties Of FH40 Ship Plate Steel

High strength,high toughness and excellent welding performance were necessary features of modern high-strength ship plate steel,however,large line energy welding might reduce the performance of steel.Oxide metallurgy could improve the properties of steel by controlling the formation of inclusions in steel which serves as the nucleation core of intragranular acicular ferrite(IAF).Through smelting FH40 steel with different content of Ce,the author studied the influence of Ce.The results can enrichment and improvement of oxide metallurgy technology and the development of rare earth steel.Based on the national standard chemical composition of FH40 ship plate steel,FH40 ship plate steel with different Ce content was prepared,the size and composition of inclusions in the steel was studied,the influence of inclusions in the as cast microstructure of the steel was analyzed and the effect of inclusions on inducing IAF nucleation was analyzed.The inclusions in steel are changed from Al-O to Ce-O-S and Ce-Al-O-S,which average particle size decreases from 1.274 μm to 1.081 μm and the particle size distribution is between 0.4~2.0 μm.Al-O doesn’t induce IAF.Ce-O-S and Ce-Al-O-S induce IAF to some extent.With experimental steel forged and rolled,microstructure and properties of the rolled steel plate were studied,and the mechanism of IAF nucleation induced by inclusions in the rolling process and explores the strengthening mechanism of the rolled steel plate were analyzed.The results show that the Al-O doesn’t induce IAF,while the Ce-O-S and Ce-O-S+Ti N induce IAF.After adding Ce element,the properties of the experimental steel are improved to some extent.Gleeble3800 welding thermal simulator was being used to simulate welding of steel plate with heat input of 50 k J/cm.The effect of inclusions in the experimental steel on the microstructure and properties of CGHAZ in the heat affected zone of FH40 ship plate welding was studied.The results show that the microstructure of the experimental steel is refined and the weldability is improved.Figure 36;Table 14;Reference 66...