Effect of pre-processing annealing and ram speed on mechanical properties for low carbon steel processed by constrained groove pressing

摘要

Constrained groove pressing (CGP) has emerged for producing ultra-fine-grained materials with distinguished properties. Low carbon steel sheets were subjected to severe plastic deformation by constrained groove pressing process. The effect of pre-processing annealing temperature, ram speed and number of passes on microstructure, mechanical properties and wear behaviour of the sheets were investigated. The 3 mm thick sheets were deformed by a constrained groove pressing die at ram speeds: 5 mm/min, 10 mmmin 1 and 20 mmmin 1. Furthermore, the as received sheets were annealed at 600 degrees C and 900 degrees C, then deformed at ram speed 20 mmmin 1. The annealing temperature 900 degrees C led to slightly coarser grains, lower strength and larger ductility compared to those obtained after annealing at 600 degrees C. With lowering the ram speed to 5 mmmin 1, the number of passes could be increased to 10 passes while increasing ram speed from 5 mmmin 1 to 20 mmmin 1 improved the mechanical properties; after 3 constrained groove pressing passes, the ultimate tensile strength increased from 420 MPa to 490 MPa, the hardness from 174 HV 1 to 190 HV 1 and the elongation from 7.6 % to 9.5 %. Finer grains were also obtained by increasing ram speed. Wear resistance was greatly enhanced by constrained groove pressing and by the increase in ram speed.