Abstract
It is well known that the fatigue strength of a welded joint with reinforcement is considerably decreased below that of base metal or of a smooth surface welded joint without reinforcement.
Some methods are proposed to improve the fatigue strength of a welded joint with reinforcement, that is, local heating and rapid cooling, synthetic resin coating, grinding or machining of reinforcement bead etc.
The authors also carried out some experiments to improve the fatigue strength of a steel welded joint by metallic coating.
Butt-welded joint with reinforcement was coated with various metalls. Zinc, copper and cadmium film were precipitated by electroplating. Zinc film was formed by hot galvanizing, too. In hot galvanizing process, the welded joint was dipped in zinc bath at 470°C for 70 sec and immediately cooled in water bath. Aluminium molten bath dipping and tin film soldering were also used as coating methods. In these cases, specimens were cooled in air.
Fatigue tests of welded joint specimens with various metal coatings were carried out under reversed plane bending load, to be compared with as-welded joint specimens. As a result, the fatigue strength of hot galvanized joint was improved over that of non-treated joint and was higher than that of smooth machined welded joint. Other metallic coatings had no effects.
