Investigation of Hot Workability of Steel at High Strain Rates

A plane strain tensile test for determining hot workability of steel at high strain rates was studied. Below the incipient melting temperature, the fracture was transgranular. Above the incipient melting temperature, the fracture was intergranular. The ideal workability temperature was the highest temperature before local incipient melting. Lower strain rates and austenite finer grains were observed to improve workability.

Using experimental data and FEM, the true strain at fracture and the modified Cockroft-Latham criteria predicted similar results in terms of steel workability. The plane strain test results used to define the modified Cockroft-Latham criterion were compared to past torsion tests of a similar material. The findings demonstrated a higher than expected workability to fracture in torsion. This higher workability can be attributed to cracks initiated only on the surface of the twisted specimen which allowed for more twists prior to complete failure.