In this study, we investigated the effect of shot blasting on the corrosion properties after electrodeposition and the fatigue properties of the arc welds in automotive steel sheets. The corrosion properties of arc welds after electrodeposition were signi cantly improved by shot blasting due to the removal of slag and fume, which can cause painting defects. Also, the fatigue strength of welded joints was enhanced by shot blasting, because the mean stress effect due to compressive residual stress improved the fatigue properties. These results suggest that shot blasting has the potential to reduce the thickness of arc welded steel parts in automobile chassis.

The stretch flangeability of tailor-welded blank depends on the angle between weld line and the tangential line of blank edge, which is generally the tensile direction in stretch flanging. This effect was studied by uniaxial tensile testing of tailor-welded high-strength-steel specimens with a weld line at 45, 60, or 90 degrees from the tensile direction. The 60-degree-weld-line specimen provides the highest elongation at the maximum load. This is the angle at which the strain component in the weld-line direction is close to zero. At the other angles, the weld lines, of which hardness sufficiently increases by welding, play a role as a constraint for vicinal base metal. This leads to early strain localization and low elongation. Furthermore, the elongation at the maximum load can, in some cases, exceed the uniform elongation of base metal. This is pronounced by a base metal with a low n-value.

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To decrease car body weight and improve crash safety, tailor-welded blanks are often used for the car body materials. In the past, little research has been conducted on the formability of the weld metal (WM). This study focuses on the bendability of the WM and evaluates it by the bending test. The main results are as follows. (1) The bendability of the laser-welded specimens was better than that of the plasma-welded specimens. (2) The bendability of the weld line (WL) was related to the homogeneity of the WM structure, and it increased with increasing homogeneity. (3) The surface roughness of the WL has no effect on the bendability of the WL. (4) The deformation of the bent surface of the WL changed with the WL width, and the bendability increased as the WL narrowed because the bent surface showed increasing uniaxial stretching deformation.

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