ばね鋼の腐食疲労寿命におよぼす合金元素の影響

概要

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The weight saving in automotive parts is a keenly undertaken subject for the improvement in fuel efficiency of automobiles. To meet the demand, the number of coil and/or the diameter of vehicle suspension springs have been reduced by increasing the design stress of the springs, maintaining endurance to corrosive fatigue in a service environment. We developed series of high strength spring steels and succeeded in applying them to practical use by means of optimizing the content of alloying elements in spring steels. In this study a new fatigue test was carried out to investigate the influence of each alloying element on corrosive fatigue strength using shot-peened spring steels whose basic composition and tensile strength were 0.45%C-2.0%Si and 1900 MPa, respectively. And it was clarified: 1) Corrosive fatigue lives were prolonged by the addition of Cu or Ni into steels, while the lives deteriorated with the Cr or V addition. 2) There was a good relation between the fatigue lives and he depth of corrosive pits, which were formed during corrosive treatment before the fatigue test: The depth of pits in Cr or V added steels were deeper than those of Cu or Ni added steels.