Impact-fatigue strength of medium-carbon high-nickel steel
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Medium-carbon nickel steels with σb = 180–190 kgf/mm2 have high impact-fatigue strength and can be recommended as structural materials for machine parts subject to cyclic impact loads.
Raising the nickel content of medium-carbon steel (0.4%) from 10 to 14% permits a substantial increase of the impact-fatigue strength.
The γ→α transformation occurs in medium-carbon nickel steels with cyclic impact loading. This substantially increases the number of cycles to failure of steel 40N14 at cyclic stresses σmax ≤ 240 kgf/mm2.
With σmax> 240 kgf/mm2 the presence of a large quantity of retained austenite in steel 40N14 leads to a reduction of resistance to repeated impact, since relaxation processes occur to a lesser extent in newly formed crystals of martensite with high rates of crack propagation.
KeywordsNickel Austenite Martensite Structural Material Relaxation Process
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