An Experiment on the Effect of Induction Hardening on Fatigue Strength (Report 4)

Abstract

The authors have conducted fatigue tests on induction hardened V-notched specimens (ρ=0.25;0.5;1 and 5 mm) of C=0.40%, 0.34% and C=0.29% steel. Induction heating temperature was chosen at 700, 800, 900 and 1000°C, the same as in the 3rd report (experiment on C=0.13% steel). The experimental results may be summarized as follows : (i) There is some difference between σw1 and σw2 of notched specimen, but the differences in C=0.40%, C=0.34%, and C=0.29% steels are smaller than that in C=0.13% steel. The difference between σw1 and σw2 becomes larger when a becomes larger, the same as in the 3rd report. (ii) Maximum value of σw1 at ρ=0.25mm, d=10mm of specimen is 50kg/mm2, under the conditions of C=0.34% in steel, and heating temperature 1000°C. And this value is nearly equal to (2σw0/α). As yet the authors cannot understand clearly the reason why σw1 becomes (2σw0/α). (iii) According to the authors' past experimental data on notched specimen (ρ=0.25 mm, d=10 mm), the values of σw1 are almost proportional to the hardness at the notched-bottom, but the values of σw2 are almost proportional to the Vicker's hardness in the ranme lower than Hv≅500 and are nearly constant in the range over Hv≅500.