Influence of heat input on corrosion resistance of SAW welded duplex joints

Purpose: Purpose of this paper is description of influence of the heat input of submerged arc welding (SAW) of duplex steel UNS S31803 on welded butt joints corrosion resistance. Design/methodology/approach: Butt joints on plates of 9-30 mm thickness were executed where the applied heat input of welding exceeded the 2.5 kJ/mm value. Maximum heat input level was HI ≤ 3.0; HI ≤ 3.5; HI ≤ 4.0; HI ≤ 4.5; HI ≤ 5.0. Analysis of welding heat input influence on mechanical properties, value of ferrite share, and corrosion of test joints has been done. Non-destructive and destructive testing, e. g. visual examinations, microstructure examination, corrosion resistance tests according to ASTM G48 Method A, HV5 hardness tests, impact and tensile test were carried out. For analysis of welding heat input influence on creation of welding imperfections, there were executed welding of sheet of thickness 9, 14, 28 mm. Findings: It was shown that submerged arc welding of duplex steel with the heat input from 2.5 kJ/mm up to 5.0 kJ/mm has no negative influence on properties of the joints. Based on the performed tests the conclusion is that according to DNV Rules the welding heat input exceeding the recommended values has no negative impact on strength properties and corrosion resistance of the executed welded joints. Research limitations/implications: Research implications the welding heat input exceeding the recommended values should influenced the precipitation processes in the HAZ, what need further experiments. Practical implications: Application of high value of the welding heat input will be profitable in terms of the welding costs. Originality/value: An original value of the paper is to prove that a usage of high value welding heat input provides the best joints quality.