The static and dynamic strength of a carbon steel at low temperatures

Abstract

Abstract Previous investigations of the effect of temperature on the static and dynamic strength of steel are briefly reviewed. A description is given of tests in which small specimens of a medium-carbon steel were compressed at high rates of strain and at temperatures ranging from 15°c to −121°c. Dynamic stress-strain curves obtained from these tests are compared with stress-strain curves obtained from tests at normal rates of strain, at temperatures from 15°c to −183°c. The results indicate that the effect on the stress-strain curve of increasing the average strain rate to 600 see−1 is comparable to that of lowering the test temperature to −183°c, the upper yield stress being multiplied some 2½ times and the lower yield strain being increased considerably. The effect of testing at high rates and low temperatures is to raise the curve still further. Metallographic examination shows that the slip occurring in the ferrite at low temperatures and normal rates is finer than that obtained at room temperature; also there is less multiple slip. These characteristics have also been observed at high strain rates. No twinning took place in the static tests, even at the lowest temperature. In the dynamic tests, twins were not formed at room temperature, but were formed at the lower test temperatures.