Microstructural and mechanical properties of dissimilar SMAW process joints of DP Steels obtained by intercritical heat treatment from AISI 1010 steel

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Abstract Dual phase steel is a kind of advanced high strength steel used in automotive industry to reduce a fuel consumption. The present study assesses the microstructural and mechanical behavior of a dissimilar butt-welded dual-phase steel by Shielded Metal Arc Welding process. The ferrite phase with variable martensite fraction from 27–70% was obtained by water quenching at different inter-critical temperatures from a plate carbon steel AISI 1010 having a microstructure consisting of ferrite and pearlite. The mechanical properties, strength and ductility of DP steels were influenced by martensite volume fraction (MVF). When MVF reached value of 70%, the strength was improved by 28% and the elongation was decreased by 25%. Additionally, the DP steels obey to the two-stage strain hardening behavior. The obtained DP steels were welded by a shield metal arc weld (SMAW) process in a single pass while maintaining a constant heat input. Systematic analysis of dissimilar welded joints, microstructure and microhardness, revealed that the fusion zones remain unchanged. Tensile test of weld joints showed lower ultimate tensile strength (UTS), elongation and strain hardening exponent compared to the dual phase (DP) steel. The DP700/DP900 welded joint have the highest ultimate tensile strength compared to the other welded joints due to its higher martensite volume fraction.

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