Abstract
In this study, we address the challenge of obtaining high strength at ambient and elevated temperatures in fire-resistant Ti–Mo–V steel with ferrite microstructures through thermo-mechanical controlled processing (TMCP). Thermally stable interphase precipitation of (Ti, Mo, V)C was an important criterion for retaining strength at elevated temperatures. Electron microscopy indicated that interphase precipitation occurred during continuous cooling after controlled rolling, where the volume fraction of interphase precipitation was controlled by the laminar cooling temperature. The interphase precipitation of MC carbides with an NaCl-type crystal structure indicated a Baker–Nutting (B–N) orientation relationship with ferrite. When the steel was isothermally held at 600 °C for up to 3 h, interphase precipitation occurred during TMCP with high thermal stability. At the same time, some random precipitation took place during isothermal holding. The interphase precipitation increased the elastic modulus of the experimental steels at an elevated temperature. It is proposed that fire-resistant steel with thermally stable interphase precipitation is preferred, which enhances precipitation strengthening and dislocation strengthening at elevated temperatures.
Highlights
Precipitation strengthening is an effective approach to increase the strength of steels and has received significant attention
A study has shown that interphase precipitation is easier at higher temperatures during the continuous cooling process [17]
The objective of the present study is to explore the effect of interphase precipitation on the fire-resistance of steel
Summary
Precipitation strengthening is an effective approach to increase the strength of steels and has received significant attention. Studies have shown that a number of precipitate-forming elements can form interphase precipitation, such as carbonitrides of. There have been two main approaches to obtain interphase precipitation up to now. One is isothermal treatment and the other is continuous cooling [5,6,7,13,14,15]. Some studies have shown that interphase precipitation always takes place at the beginning of phase transformation during isothermal treatment [16]. A study has shown that interphase precipitation is easier at higher temperatures during the continuous cooling process [17]. A reasonable match between the migration rate of the interface and the enrichment of precipitating elements can effectively promote the nucleation of interphase precipitation. There are many studies on the orientation relationship between interphase precipitation and ferrite matrix, generally showing a Baker–Nutting
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