Application of Quenching and Partitioning (Q%26P) Processing to Press Hardening Steel

作者：Seo Eun Jung^*; Cho Lawrence; De Cooman Bruno Charles

来源：Metallurgical and Materials Transactions A-Physical Metallurgy and Materials Science, 2014, 45A(9): 4022-4037.

DOI：10.1007/s11661-014-2316-z

Press hardening steel (PHS) has been increasingly used for the manufacture of structural automotive parts in recent years. One of the most critical characteristics of PHS is a low residual ductility related to a martensitic microstructure. The present work proposes the application of quenching and partitioning (Q%26P) processing to improve the ductility of PHS. Q%26P processing was applied to a Si- and Cr-added Q%26P-compatible PHS, leading to a press hardened microstructure consisting of a tempered martensite matrix containing carbide-free bainite and retained austenite. The simultaneous addition of Si and Cr was used to increase the retained austenite fraction in the Q%26P-compatible PHS. The Q%26P processing of the PHS resulted in a high volume fraction of C-enriched retained austenite, and excellent mechanical properties. After a quench at 543 K (270 A degrees C) and a partition treatment at 673 K (400 A degrees C), the PHS microstructure contained a high volume fraction of retained austenite and a total elongation (TE) of 17 pct was achieved. The yield strength (YS) and the tensile strength were 1098 and 1320 MPa, respectively. The considerable improvement of the ductility of the Q%26P-compatible PHS should lead to an improved in-service ductility beneficial to the passive safety of vehicle passengers.

• 出版日期2014-8