Improvement in hole expansion ratios of dual phase DP 980 steels for holes prepared by electrical discharge machining by micro-plasma heat treatment
Aman Mohtta, Murugaiyan Amirthaligam, Uday Chakkingal
Abstract. Advanced high-strength steels (AHSS) like dual phase (DP) steels are increasingly used in autobody parts for improved crash performance and weight reduction. However, dual phase (DP) steels have poor stretch flangeability, which can result in edge cracking during stamping operations. Stretch flangeability is usually expressed in terms of hole expansion ratios (HER) obtained from standard hole expansion testing (HET). In this study, local heat treatment of the hole edge has been investigated as a tool to increase HER. Holes were prepared in HET specimens by electrical discharge machining (EDM) and a micro-plasma heat source was used to locally heat treat the hole edges. Different heat inputs were used during the local micro-plasma source-based heat treatment to get different temperature profiles and hence different hardness and microstructures at the hole edge. Hole expansion testing was carried out on as-received and heat-treated specimens. It is observed that HER varied as a function of heat input and resultant microstructure and mechanical properties at the hole edge. The HER in the as-received condition was 51 ± 2. HER varied as a function of heat input and resultant microstructure and mechanical properties at the hole edge. Maximum value of HER of 62 ± 2 was obtained for a heat input of 61 J/mm.
Keywords
Hole Expansion Ratio, Micro-Plasma, Dual Phase Steel (DP) 980
Published online 5/7/2025, 9 pages
Copyright © 2025 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: Aman Mohtta, Murugaiyan Amirthaligam, Uday Chakkingal, Improvement in hole expansion ratios of dual phase DP 980 steels for holes prepared by electrical discharge machining by micro-plasma heat treatment, Materials Research Proceedings, Vol. 54, pp 980-988, 2025
DOI: https://doi.org/10.21741/9781644903599-105
The article was published as article 105 of the book Material Forming
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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