Research On Gas Shielded Flux-cored Wire For Cargo Oil Tank(COT)

The designing of Flux-Cored Wire for Cargo Oil Tank(COT)anti-corrosion steel was studied on the paper.1、Principal Slag TiO2-SiO2 was choosed,perfect all position welding procedure was achieved in 100%CO2 gas shield by adding supplementary slag of ZrO2、MgO、NaF、Al-Mg、Si-Mn,Electrolytic Mn.2、In order to achieve mechanical and corrosion resistant property,alloy system of Ti-B microalloying C-Mn-Cu-Ni was adopted;in gas shielded 100%CO2,element Ti was transferred to deposited metal by reduction reaction of rutile in welding process and the amount of rutile was remain unchanged.The best match value of element B and Ni was achieved by the adjustment of alloy composition,thus excellent mechanical property was got(σs:491Mpa,σb:568Mpa,A:24.0%,KV2,-40℃:112J).3、According to the《Guide of COT Corrosion Resistant Steel》passed by CCS in February,2013,homemade corrosion device of stimulating COT upper and bottom deck plate corrosion environment was used to study Flux-Cored Wire deposited metal and welding joint of COT anti-corrosion steel,the result revealed that ECL25 of deposited metal in stimulating COT upper deck plate corrosion environment was 1.72182mm that less than 2mm;corrosion loss of deposited metal in stimulating COT bottom deck plate corrosion environment was 0.94223mm that less than lmm;the corrosion deep of welding joint were both less than 30 μm.Optical microscope(OM)and Scanning Electron Microscopy(SEM)were used to analyze toughning mechanism of gas sheiled Flux-Cored Wire,Focusing on studying the effect of element B and Ni on the microstructure of Flux-Cored Wire deposited in gas shielded 100%CO2 which the Ti Wt%unchanged.4.Proeutectoid ferrite and Ferrite Side-plate(FSP)were restrained and ting、diffuse distribution acicular ferrite was generated by adding element B to Flux-Cored Wire,thus improving the-40 ℃ low tempature toughness.5、Proeutectoid ferrite was retrained and acicular ferrite was promoted by adding element Ni;the acicular ferrite was predominant in Flux-Cored Wire deposited metal when content of Ni was 0.29,further,the acicular ferrite with cross shape was seen to make-40 ℃ low tempature toughness the maximum value.6.Martensite that caused by dendritic segregation was observed in Ac1～Ac3 of reheated area of Flux-Cored Wire deposited metal adding element Ni,the amount of Martensite was increased with highly adding element Ni,thus causing the phenomen of stress concentration and reducing toughness.