5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

The manufacturing of special steel forgings normally follows the basic technical process from casting, homogenization annealing, pre-heating, forging and post-heat treatment after forging. Such treatment obviouly is high-cost, energy dissipation and long manufacturing cycle. In terms of the formation mechanism of internal casting defects such as macrosegregation, shrinkage cavity and coarse grains in large steel ingot, this study proposes a novel casting-forging integrated technology (CFIT), in which the solidifying ingot is forged before its complete solidification. It was found that composition and microstructure were both inhomogeneous when deformed by CFIT with a higher liquid fraction above 0.5, and even A circle-like C, Cr, Mo and V macrosegregation band appeared in the forging. In contrast, a uniform microstructure and mechanical properties were obtained at the liquid fraction of 0.3. Further, to obtain the appropriate liquid fraction of 0.2 before forging and the time period of individual step, the plant-wide numerical simulations of CFIT by the arbitrary Lagrangian-Eulerian method and three-dimensional thermo-mechanical analysis were carried out when foring the 19t 16Mn thread tightening ring in industry. It shows that the forging by CFIT has slightly higher strength and hardness, and comparable impact energy and plasticity compared with the traditional processes. More significantly, the current technology presents highly economic, energy-conservation and short-period advantages in producing special steel forgings.