Instrumented indentation testing and FE analysis for investigation of mechanical properties in structural steel weld zone

• An indentation test series of 5×25 points across SS400 steel weld zone were performed.
• Mechanical properties were extracted from indentation test and FE analysis results.
• Tension test of steel and welded specimens and its FE simulation were conducted for verification.
• Material within HAZ exhibited a significant gradient of the mechanical properties.
• Ferrite grain size and shape are mainly responsible for the mechanical properties changes in HAZ.

In this paper, a procedure for determining mechanical properties in structural steel weld zone using indentation test and finite element (FE) analysis was established and applied for investigating mechanical properties in an SS400 steel weld zone. Instrumented indentation tests were performed across the weld zone and the mechanical properties (E, H, σy, and n) were then determined from their load–depth data with the aid of FE analysis. The obtained mechanical properties in the weld zone were verified to be reliable by comparing with the results from tensile tests and their FE simulations of both steel and welded specimens. It is shown that in the investigated weld zone, base metal has lower values of mechanical properties (E, H, σy, and n) than does the weld metal, and mechanical properties within heat affected zone (HAZ) gradually increase from the base metal to weld metal regions. Based on the optical microscopy examination results, the gradient of mechanical within HAZ is found to be associated with the change of grain sizes from base metal to weld metal regions.