Abstract
This investigation was planned for researching the properties of local martensite formed by the impact loading friction on the 0.6%C cold drawn steel wire and the effect of this local martensite upon the fatigue strength under rotary bending.
The specimens were adopted from a lead patenting wire drawn with 82.5% reduction and two air patenting wires drawn with 82.5% and 89% reductions, and the diameter of these wires was 1.05mm. The experimental apparatus was composed of the rotating disk and the pendulum. The specimen attached to the pendulum was made to collide with the rotating disk, and as the result of this impact loading friction the martensite layer was formed to the surface of specimen.
The results of fatigue test were as follows:
1) For the plain specimen, the fatigue strength of lead patenting wire was higher than those of both air patenting wire drawn with the same reduction and that having the same tensile strength.
2) Fatigue strength of partial notched specimen with tangential cracks formed in the local martensite layer by static bending was remarkably below than that of plain specimen. And its decrement increased remarkably as the crack deepens up to 35μ, but over this depth this rate of increase decreased as the crack deepens further.
3) Fatigue strength of this steel wire having the same depth of crack in the local martensite layer was not affected by the wire patenting method. And its fatigue limit was found having no relation with number of bending to rupture.
