快削ステンレス鋼SUS303同種摩擦圧接継手の疲労特性
1997 年 46 巻 9 号 p. 1051-1056
詳細
1997 年 46 巻 9 号 p. 1051-1056
Fatigue tests were conducted on the free cutting stainless steel SUS303/SUS303 friction welded joints under pulsating zero-tension load to study the effect of microstructure produced by friction welding process. The specimens with circumferential notch which was machined near the welding interface were used in the fatigue tests. Fatigue crack initiation and propagation were examined by using DC potential drop method.
The fatigue limit of the friction welded joints was almost the same as that of the base metal. But the difference in fatigue strength between the base metal and the joints increased with increasing stress level. The crack initiation strength of the joints was lower than that of the base metal and the non-propagating cracks were found in the specimens of the joints which did not fracture above 107 stress cycles. The fatigue crack growth rate of the joints decreased and reached the minimum value near crack length of 0.2mm. The crack growth rate of the joints was smaller than that of the base metal in the low stress intensity factor range, while it increased and gained upon that of the base metal. The degradation of fatigue strength of the joints, especially for the fatigue crack initiation strength, was mainly caused by the shape, size, direction and distribution of non-metallic inclusions which differed from those of the base metal.
