純チタン鍛造材の引張および疲労強度に及ぼす鍛錬成形比および結晶粒径の影響

概要

論文の詳細を見る
Pure titanium is expected to be used in high-speed ships in light of its corrosion resistance, high specific strength, ability to reduce ship-dismantling costs, and recyclability. Titanium rudder forgings, each of which is an integrated combination of a rudder plate and a rudder stock, have been used for high-speed ships. Fatigue fractures have often been observed in the rudder stocks. In the context of these fractures, tensile and fatigue tests were per-formed using forgings with forging ratios of 2 and 4 and different grain sizes. Typical results obtained are summarized as follows: (1) 0.2% proof stresses in the tensile test agreed with the Hall-Petch equation; (2) their slope was approximately equal to that for low-carbon steels ; (3) S-N curves showed that forgings with a forging ratio of 4 were obviously superior in fatigue strength to those with a forging ratio of 2 ; (4) fatigue crack initiation was observed at grain boundaries between large grains, indicating that the decrease in fatigue strength is caused by an inhomogeneous microstructure; and (5) the forging ratio had an obvious effect on fatigue strength rather than on tensile properties.
社団法人日本材料学会の論文
2005-01-15