In present research, a three dimensional welding process phenomenon is simulated using a commercial finite element package ANSYS® in order to study the heat distribution and residual stress in SAE 1020 fillet joint.

Heat distribution in different points of weldment shows that peak temperature at the nods near weld line is higher than peak temperature at nods which are located further. Also, temperature shapely increases when it subject to heat input and then falls down with a relatively lower rate after peak temperature.

Longitudinal residual stress which is most important stress field in the specimen, in HAZ region and near the weld line is tensile with maximum values but with increase of distance from weld line the stresses decrease. Contractual resistance of material at the beginning of cooling process is a reason for generating the tensile stress.

Transverse residual stresses perpendicular to the weld line, at the beginning and end of fillet joint is compressive due to constraints and changes to tensile in the middle of weld line. Maximum transverse residual stress will be happened at the middle and by increasing the distance the stress values approach to zero. Although, transverse residual stress values are lower than longitudinal residual stress but those should be considered as a main factor in weld deign.

As a matter of fact, in present research maximum longitude stress (100 MPa) and transverse stress (30 MPa) satisfy AWS D1.1 weld design code requirements. According to Structural Welding Code-Steel, AWS D1.1, tension or compression parallel to axis of weld shouldn't exceed base metal tensile strength i.e 420 MPa for SAE 1020. Further, shear on effective area should be less than 0.3 of nominal tensile strength of filler material i.e 126 MPa