Effect of titanium and nitrogen content on the microstructure, hardenability and mechanical properties of direct quenched and tempered ultra-high strength structural steel

Ari Saastamoinen, Antti Kaijalainen, David Porter, Pasi Suikkanen

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientific

2 Citations (Scopus)

Abstract

textcopyright 2016, ThermoMechanical Processing (TMP). All rights reserved. The effect of titanium and nitrogen content on the austenite grain structure, hardenability and mechanical properties of laboratory-scale direct-quenched and tempered martensitic 0.16C-0.2Si-1.1Mn-0.40Mo-0.60Cr-0.04Al-16B steels have been studied. Titanium (0.01-0.03 wt.%) and nitrogen (30-60 ppm) contents have been varied resulting different levels of excess titanium above the stoichiometric amount for TiN. CCT-diagrams of the 5 different test compositions were determined using a Gleeble 1500. Furthermore, two tempering temperatures (210 and 600°C) were applied for laboratory hot rolled and direct-quenched steels. Austenite grain structure investigations have been performed with light optical microscopy and general microstructure investigations using field emission scanning electron microscope. It was found that Ti/N ratios close to stoichiometry, i.e.2.4-4.2, provided both the finest austenite grain structure and the best impact toughness after hot rolling and direct quenching. Excess of titanium was shown to contribute to secondary hardening during high-temperature tempering, while excess of nitrogen had a significant negative effect on the hardenability.
Original languageUndefined/Unknown
Title of host publicationTMP 2016 - 5th International Conference on ThermoMechanical Processing, Advance Programme
Publication statusPublished - Oct 2016
Externally publishedYes
Publication typeB3 Article in conference proceedings

Keywords

  • Direct quenching,Martensite,Nitrogen,Strength,Tempering,Titanium,Touhghness

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