Phosphorus transfer behaviours have been elucidated by employing designed CaF2–Ca3(PO4)2 fluxes, and influences upon microstructural and mechanical responses have been documented in EH36 shipbuilding steel subjected to submerged arc welding. As the equivalent P2O5 content in the flux grows from 0 to 0.664 wt-%, corresponding P and O contents in the weld metals increase from 0.013 to 0.076 wt-% and from 0.012 to 0.020 wt-%, respectively. Additionally, the amount of inclusions is significantly enhanced, with number density being boosted from 1.73 × 103 to 5.15 × 103 mm–2. A closer examination reveals that the microstructures of the weld metal are primarily composed of bainite. Consequently, a reduction in Charpy impact energy is observed, characterised by a distinct brittle fracture mode across all weld metals.
WangCZhangJ. Fine-tuning weld metal compositions via flux optimization in submerged arc welding: an overview. Acta Metall Sin2021; 57: 1126–1140.
2.
ZhongMLiTBasuS, et al.Phosphorus transfer behaviors induced by CaF2–TiO2–CaO fluxes in EH36 shipbuilding steel subject to high heat input submerged arc welding. Metall Mater Trans B2022; 53: 2774–2778.
3.
YuanHZhangYWangC. Influence of MnO upon electrical conductive mechanisms of submerged arc welding fluxes: insights from ab initio molecular dynamics simulations. Acta Metall Sin2025. doi:https://doi.org/10.11900/10412.11961.12025.00065
4.
ZhongMMatsuuraHTsukihashiF. Thermodynamic properties of phosphorus oxide in the 2CaO·SiO2–3CaO·P2O5 solid solution saturated with MgO. Metall Mater Trans B2016; 47: 1745–1752.
5.
MatsuuraHHamanoTZhongM, et al.Energy and resource saving of steelmaking process: utilization of innovative multi-phase flux during dephosphorization process. JOM2014; 66: 1572–1580.
6.
ZhongMMatsuuraHTsukihashiF. Activity of phosphorus pent-oxide and tri-calcium phosphate in 2CaO·SiO2–3CaO·P2O5 solid solution saturated with CaO. Mater Trans2015; 56: 1192–1198.
7.
ZhongMMatsuuraHTsukihashiF. Activity of P2O5 in solid solution between di-calcium silicate and tri-calcium phosphate at 1823 and 1873K. ISIJ Int2015; 55: 2283–2288.
8.
DallamCLiuSOlsonD. Flux composition dependence of microstructure and toughness of submerged arc HSLA weldments. Weld J1985; 64: 140–151.
9.
MillsARThewlisGWhitemanJA. Nature of inclusions in steel weld metals and their influence on formation of acicular ferrite. Mater Sci Technol1987; 3: 1051–1061.
10.
HanCZhongMKaldreI, et al.Role of SiO2 upon weld metal inclusion characteristics in EH36 shipbuilding steels treated by CaF2–SiO2 fluxes. Metall Mater Trans B2023; 54: 989–995.
11.
ZhongMGuoDBasuS, et al.Impact toughness variations of EH36 weld metal treated by CaF2–SiO2–MnO submerged arc welding flux. J Iron Steel Res Int2023; 30: 1873–1878.
12.
PowncebyMIHapugodaSManuelJ, et al.Characterisation of phosphorus and other impurities in goethite-rich iron ores – possible P incorporation mechanisms. Miner Eng2019; 143: 106022.
13.
IndacocheaJEBlanderMChristensenN, et al.Chemical reactions during submerged arc welding with FeO–MnO–SiO2 fluxes. Metall Trans B1985; 16: 237–245.
14.
CoetseeTMostertRJPistoriusPGH, et al.The effect of flux chemistry on element transfer in submerged arc welding: application of thermochemical modelling. J Mater Res Technol2021; 11: 2021–2036.
15.
XieXZhongMZhaoT, et al.Probing microstructural evolution in weld metals subjected to varied CaF2–TiO2 flux cored wires under high heat input electro-gas welding. J Iron Steel Res Int2023; 30: 150–157.
16.
YuanXWuYMaJ, et al.Acicular ferrite growth behaviors in the weld metal of EH36 shipbuilding steel subjected to CaF2–30wt pct TiO2 flux. Metall Mater Trans B2023; 54: 2889–2894.
17.
XieXZouXZhongM, et al.Understanding element transfer behaviors of CaF2–TiO2 flux-cored wires under high heat input electro-gas welding. Metall Mater Trans B2024; 55: 1202–1207.
18.
ZhongMHuDGuoD, et al.Ferrite features in simulated transition zone of EH36 shipbuilding steel submerged arc welded by CaF2–SiO2–MnO fluxes. J Iron Steel Res Int2024; 31: 790–796.
19.
YuanXWuYZhongM, et al.Inclusion size dependency of acicular ferrite formation in EH36 shipbuilding steel weld metal treated by CaF2–TiO2 flux. Metall Mater Trans B2024; 55: 1991–1995.
20.
WuYYuanXZhongM, et al.Penetration-dependent microstructures in TiO2-induced weld metal of EH36 shipbuilding steel. Metall Mater Trans A2024; 55: 1295–1301.
21.
WuYYuanXZhongM, et al.Revealing planar to cellular transition in the weld metal of EH36 shipbuilding steel subjected to CaF2–TiO2 flux. Metall Mater Trans B2024; 55: 1975–1983.
22.
MaJZhongMCaoM, et al.Elucidating inclusion-induced microstructural responses of EH36 shipbuilding steels with varied Ti contents. Metall Mater Trans A2024; 55: 3178–3184.
23.
WuYYuanXKaldreI, et al.TiO2-assisted microstructural variations in the weld metal of EH36 shipbuilding steel subject to high heat input submerged arc welding. Metall Mater Trans B2023; 54: 50–55.
24.
YuanXZhongMWuY, et al.Characterizing inclusions in the weld metal of EH36 shipbuilding steel processed by CaF2–30 wt pct TiO2 flux. Metall Mater Trans B2022; 53: 656–661.
25.
YuanXWuYZhongM, et al.Profiling inclusion characteristics in submerged arc welded metals of EH36 shipbuilding steel treated by CaF2–TiO2 fluxes. Sci Technol Weld Joi2022; 27: 683–690.
26.
XieXHanSZhongM, et al.In situ observation of acicular ferrite growth behavior differences in weld metals subjected to varied CaF2–TiO2 flux-cored wires. Metall Mater Trans A2025; 56: 7–13.
27.
ChaiCSEagarTW. Slag metal reactions in binary CaF2–metal oxide welding fluxes. Weld J1982; 61: 229–232.
28.
YuanHWangZZhangY, et al.Elucidating electrical conductive mechanisms for CaF2–SiO2–Al2O3–MgO welding fluxes in liquid and crystalline states. Metall Mater Trans B2024; 55: 5068–5079.
29.
BaiHZhangYZhaoY, et al.Numerical analysis of slag viscosity effects mechanism in submerged arc welding pool. Metall Mater Trans B2025; 56: 1659–1671.
30.
ZhongMJiangLBaiH, et al.Simulating molten pool features of shipbuilding steel subjected to submerged arc welding. J Iron Steel Res Int2023; 30: 569–579.
31.
YuanHZhangYLiuH, et al.Bond characteristic-dependent viscosity variations in CaF2–SiO2–Al2O3–MgO welding fluxes. Weld J2025; 104: 107–118.
32.
LiuHZhangYZhaoY, et al.Unveiling the amphoteric behavior of TiO2 in fused CaF2–TiO2–MgO–SiO2 submerged arc welding fluxes. Metall Mater Trans B2025; 56: 699–710.
33.
YuanHZhangYZhaoY, et al.Structural role of CaF2 upon welding flux viscosity. Weld J2025; 104: 164–174.
34.
NatalieCAOlsonDLBlanderM. Physical and chemical behavior of welding fluxes. Annu Rev Mater Sci1986; 16: 389–413.
35.
XieXWanYZhongM, et al.Optimizing microstructures and properties of electro-gas welded metals for EH36 shipbuilding steel treated by CaF2–TiO2 fluxes. Acta Metall Sin2025. doi:https://doi.org/10.11900/10412.11961.12025.00028
36.
TurkdoganET. Assessment of P2O5 activity coefficients in molten slags. ISIJ Int2000; 40: 964–970.
37.
YamasueEShimizuKNagataK. Direct determination of standard gibbs energies of the formation of 4CaO·P2O5 and 3CaO·P2O5 by transpiration method. ISIJ Int2013; 53: 1828–1835.
38.
SchenckH. Introduction to the physical chemistry of steelmaking. London: UK, 1945.
39.
HinoMItoK. Thermodynamic data for steelmaking. Sendai: Japan, 2010.
40.
MitraUEagarTW. Slag-metal reactions during welding: part II. Theory. Metall Trans B1991; 22: 73–81.
41.
FieldDMMagagnoscDJHornbuckleBC, et al.Tailoring γ-austenite stability to improve strength and toughness of a medium-Mn steel. Metall Mater Trans A2022; 53: 2530–2543.
42.
BhattacharyaABiswalSBarikRK, et al.Comparative interplay of C and Mn on austenite stabilization and low temperature impact toughness of low C medium Mn steels. Mater Charact2024; 208: 113658.
43.
FattahiMNabhaniNHosseiniM, et al.Effect of Ti-containing inclusions on the nucleation of acicular ferrite and mechanical properties of multipass weld metals. Micron2013; 45: 107–114.
44.
SarmaDSKarasevAVJönsson PG.On the role of non-metallic inclusions in the nucleation of acicular ferrite in steels. ISIJ Int2009; 49: 1063–1074.
45.
WangQZouXMatsuuraH, et al.Evolution of inclusions during the 1473K (1200°C) heating process of EH36 shipbuilding steel. Metall Mater Trans B2018; 49: 18–22.
46.
ZouXSunJMatsuuraH, et al.Unravelling microstructure evolution and grain boundary misorientation in coarse-grained heat-affected zone of EH420 shipbuilding steel subject to varied welding heat inputs. Metall Mater Trans A2020; 51: 1044–1050.
47.
JungYCKimSJOhmoriY. Morphology and growth process of bainitic ferrite in steels. Met Mater1998; 4: 125–134.
48.
WangZGaoJZhongM, et al.Revealing charpy impact toughness variations of EH36 shipbuilding steel weld metals processed by CaF2–Al2O3–TiO2 fluxes under high heat input submerged arc welding. J Mater Eng Perform2024; 33: 2809–2816.
49.
LeeTKKimHJKangBY, et al.Effect of inclusion size on the nucleation of acicular ferrite in welds. ISIJ Int2000; 40: 1260–1268.
50.
LoderDMichelicSKBernhardC. Acicular ferrite formation and its influencing factors – a review. J Mater Sci Res2017; 6: 24–43.
51.
ChenXMSongSHWengLQ, et al.Relation of ductile-to-brittle transition temperature to phosphorus grain boundary segregation for a Ti-stabilized interstitial free steel. Mater Sci Eng A2011; 528: 8299–8304.
52.
ErhartHGrabkeHJ. Equilibrium segregation of phosphorus at grain boundaries of Fe–P, Fe–C–P, Fe–Cr–P, and Fe–Cr–C–P alloys. Met Sci1981; 15A: 401–408.
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