Mechanical and corrosion properties of welded duplex stainless steel structures are of paramount consideration in many engineering applications. This innovative steel, which exhibits a dual-phase constitution of austenite–ferrite, can be achieved by selecting appropriate compositions, physico-chemical and thermo-mechanical refining. In comparison to the one-phase grade of stainless steel, DSSs have higher yield strength and an exceptional ability to withstand SCC5,. In harsh environments containing acids, acid chlorides, seawater, and caustic chemicals, the dual-phase structure confers unrivalled strength, toughness, and enhanced corrosion resistance to these steels. DSS structures especially the low nickel-containing type (lean DSS) have recorded numerous exceptional achievements in comparison to face-centred cubic (FCC) iron due to the yearly fluctuation in nickel (Ni) alloy prices in the general market. The main issue with ASS structures is that they are vulnerable to a variety of harsh conditions12. As a result, various engineering sectors and businesses are attempting to promote replacement stainless steels with reduced nickel content that perform as well as or better than traditional ASSs having suitable weldability characteristics with application in industrial fields such as the manufacture of seawater heat exchangers and chemical containers for use in chloride environments with high concentrations13. In modern technological advancement, fabrication by welding plays a critical role. Generally, the DSS steel structural components are joined by gas metal arc welding or shielded metal arc welding technique. The weld is majorly influenced by the composition of the welding electrode used for the welding. The welding electrode consists of two components; metal and flux. Most commonly the electrode is coated with flux, a metal mixture that emits gases and generates protective slag as it decomposes to shield the weld from contamination, increase arc stability, and also provide alloying components to improve weld quality14. Cast iron, aluminium, stainless steel, mild steel, high-tensile steel, copper, brass, and bronze are some of the weld electrode metals and cellulose, iron powder, and hydrogen are some of the flux materials that are being used. Sometimes sodium, titanium, and potassium are also added to the flux mixtures. Nigeria’s Air Force Institute of Technology Mechanical Engineering Department’s Ibrahim Momoh-Bello Omiogbemi, Nigeria’s Ahmadu Bello University Mechanical Engineering Department’s Shell Professorial Chair Danjuma Saleh Yawas, Emmanuel Toi Dauda and India’s CSIR-National Metallurgical Laboratory, Jamshedpur’s Ibrahim Momoh-Bello Omiogbemi, Atanu Das, Sudhakar Rao Gorja & Sandip Ghosh Chowdhury in a recently published paper “Mechanical Properties And Corrosion Behaviour of Duplex Stainless Steel Weldment Using Novel Electrodes” in Nature have investigated the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, using optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715–732 MPa and that of the E2 electrode was found to be 606–687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with E1 electrode coated with basic flux has better mechanical properties. The steel structure in 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed on the basis of the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes.
Mechanical and corrosion properties of welded duplex stainless steel structures are of paramount consideration in many engineering applications. This innovative steel, which exhibits a dual-phase constitution of austenite–ferrite, can be achieved by selecting appropriate compositions, physico-chemical and thermo-mechanical refining. In comparison to the one-phase grade of stainless steel, DSSs have higher yield strength and an exceptional ability to withstand SCC5,. In harsh environments containing acids, acid chlorides, seawater, and caustic chemicals, the dual-phase structure confers unrivalled strength, toughness, and enhanced corrosion resistance to these steels. DSS structures especially the low nickel-containing type (lean DSS) have recorded numerous exceptional achievements in comparison to face-centred cubic (FCC) iron due to the yearly fluctuation in nickel (Ni) alloy prices in the general market. The main issue with ASS structures is that they are vulnerable to a variety of harsh conditions12. As a result, various engineering sectors and businesses are attempting to promote replacement stainless steels with reduced nickel content that perform as well as or better than traditional ASSs having suitable weldability characteristics with application in industrial fields such as the manufacture of seawater heat exchangers and chemical containers for use in chloride environments with high concentrations13. In modern technological advancement, fabrication by welding plays a critical role. Generally, the DSS steel structural components are joined by gas metal arc welding or shielded metal arc welding technique. The weld is majorly influenced by the composition of the welding electrode used for the welding. The welding electrode consists of two components; metal and flux. Most commonly the electrode is coated with flux, a metal mixture that emits gases and generates protective slag as it decomposes to shield the weld from contamination, increase arc stability, and also provide alloying components to improve weld quality14. Cast iron, aluminium, stainless steel, mild steel, high-tensile steel, copper, brass, and bronze are some of the weld electrode metals and cellulose, iron powder, and hydrogen are some of the flux materials that are being used. Sometimes sodium, titanium, and potassium are also added to the flux mixtures. Nigeria’s Air Force Institute of Technology Mechanical Engineering Department’s Ibrahim Momoh-Bello Omiogbemi, Nigeria’s Ahmadu Bello University Mechanical Engineering Department’s Shell Professorial Chair Danjuma Saleh Yawas, Emmanuel Toi Dauda and India’s CSIR-National Metallurgical Laboratory, Jamshedpur’s Ibrahim Momoh-Bello Omiogbemi, Atanu Das, Sudhakar Rao Gorja & Sandip Ghosh Chowdhury in a recently published paper “Mechanical Properties And Corrosion Behaviour of Duplex Stainless Steel Weldment Using Novel Electrodes” in Nature have investigated the mechanical properties and corrosion integrity of duplex stainless-steel weldment in a simulated 3.5% NaCl environment using specially developed novel electrodes without the addition of alloying elements to the flux samples. Two different types of fluxes having basicity indexes of 2.40 and 0.40 were used to coat E1 and E2 electrodes respectively for DSS plate welding. The thermal stability of the formulated flux was evaluated using thermogravimetric analysis. The chemical composition, using optical emission spectroscopy, and the mechanical and corrosion properties of the welded joints were evaluated as per different ASTM standards. X-ray diffraction was used to find out the phases present in the DSS welded joints while a scanning electron equipped with EDS was used for microstructural examination of the weldments. The ultimate tensile strength of welded joints made using the E1 electrode was in the range of 715–732 MPa and that of the E2 electrode was found to be 606–687 MPa. The hardness was increased with increased welding current from 90 to 110 A. The welded joint with E1 electrode coated with basic flux has better mechanical properties. The steel structure in 3.5% NaCl environment possesses substantial resistance to corrosion attack. This validates the performance of the welded joints made by the newly developed electrode. The results are discussed on the basis of the depletion of alloying elements such as Cr and Mo observed from the weldments with the coated electrodes E1 and E2 as well as precipitation of the Cr2N in the welded joints made by E1 and E2 electrodes.
