Formability of steels subjected to cold ECAE process

Extensive researches have been conducted on mechanical property and microstructure after severe plastic deformation (SPD) processes, i.e. ECAE, ARB, HPT and so on. The study on mechanical properties, such as the tensile strength, the hardness and the fatigue were conducted, however the formability of materials after SPD processes was little studied. Therefore we investigated the formability of steels subjected to different cold forming processes, the one is the ECAE process and the other is the cold rolling and followed swaging. The evaluation of formability was judged by forming micro screws (M1.6), whether it was possible or not. Four different materials, Ultra low Carbon, 0.15%C, 0.25%C steel and SWCH18A (0.16%C with spheroidizing treatment) were used. The formability test was conducted to product micro screws by a cold header that was commonly used in factory production. The formability was checked with eyes to examine crack or not at the first pre-forming and second recess forming. The materials subjected to ECAE process and as-received were able to manufacture the micro screw except ECAE processed 0.25%C steel. On the contrary no materials subjected to the cold rolling followed by swaging were able to manufacture the micro screw. It was found that formability of steel subjected to ECAE process was little decreased from as-received.