Continuous ECAP process design for manufacturing a microstructure-refined bolt

In this paper, split dies combined with a spring-loaded auto-fastening system are newly proposed to continuously apply an equal channel angular pressing (ECAP) process to a multi-pass bolt forming process. The proposed spring-loaded ECAP set-up was used to produce microstructure-refined materials in a continuous manner. Experiments for a single pass of the ECAP followed by four stages of the bolt forming process were carried out to manufacture a microstructure-refined bolt made of an aluminum alloy 6061 by using the multi-stage former at room temperature. The present study clearly showed that manufacturing the microstructure-refined bolt is possible with the proposed die set-up with a conventional material. The proposed process design might be beneficial in using the ECAP as part of a continuous process sequence to increase the mechanical strength of the material without adding more alloying elements in industry.

► A continuous manufacturing system to apply an ECAP to bolt forming was developed.
► A spring-loaded auto-fastening system with split-dies for the ECAP was devised.
► The UTS of the microstructure-refined bolt was 6.2% higher than the conventional one.