Corrosion resistance of SAW duplex joints welded with high heat input
J. Nowacki*, P. Rybicki
Institute of Materials Science and Engineering, Szczecin University of Technology, Al. Piastow 19, 70-310 Szczecin, Poland
Received 19.03.2007; published in revised form 01.08.2007
Abstract
Purpose: test if the welding heat input exceeding the recommended values has negative impact on strength properties and corrosion resistance of the executed welded joints as well as description of influence of the heat input of submerged arc welding (SAW) of duplex steel UNS S31803 (0.032%C, 23.17%Cr, 9.29%Ni, 3.48%Mo, 0.95%Mn, 0.7%Si, 0.16%N, 0.017P, 0.006%S, 0.11%Cu) on welded joints microstructure, particularly average values of ferrite volume fraction, mechanical properties, and corrosion resistance.
Design/methodology/approach: 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. Butt joints on plates of different thickness were made 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.
Findings: 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. 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.
Research limitations/implications: the welding heat input exceeding the recommended values may 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.
Regards,
Limesh
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