Investigation of the multi-pass drawing process for steel thin-walled ribbed tube using Taguchi-grey relational analysis optimisation

Ribbed tubes are characterised by specialised geometries that offer benefits such as enhanced structural strength and improved heat transfer performance, making them widely adopted as functional components across various applications and industries. On the other hand, multi-pass drawing (MPD) has proven to be an effective forming method for fabricating ribbed tubes with complex cross-sectional geometries using high strength materials. However, due to the extensive workload involved in determining the optimal geometries of drawing tool and billet size, the efficiency of MPD design largely depends on trial and error as well as experimental experience. To address this challenge, this study presents an optimisation method that combines the Taguchi-grey relational analysis and numerical simulation for MPD of 316L stainless steel thin-walled ribbed tubes. By utilising this method, optimal parameter sets for billet size and drawing tool geometries in the drawing passes are determined to fabricate ribbed tube with required ultimate section with acceptable divergences in the key cross-sectional geometries. Furthermore, the efficiency and effectiveness of this method are verified through MPD experiments using the derived optimal parameter sets. Additionally, the mechanism of ribbed tube forming and the correlation between forming quality and material flow in the MPD process are further investigated based on the results generated by this method.