Study on Prevention of Microcracking on the Fillet Weld between the Lowest Course Shell Plate and the Annular Plate in Oil Storage Tank

Abstract

Various forms of microcrackings are found in mild steel weld metal under same limited circumstances. A kind of microcrackings occurs on the surface after grinder dressing in the fillet weld of the lowest course shell plate and the annular plate in Oil Storage Tank. Compressive stress by grit blasting is effective for prevention of these crackings. Many efforts are made on the determination of optimum blasting conditions. They are as follows.
Exhaust pressure: 0.49MPa
Working speed : 1.5m/min
Grit : MGH30
Grinder dressing and grit blasting under optimum conditions are conducted on the surface of weld metal after welding. Microcrack susceptibility by MT of the latter is less than that of the former. Blasting is effective for prevention of microcrackings.