Bainite

About: Bainite is a research topic. Over the lifetime, 9520 publications have been published within this topic receiving 145305 citations.

A nanoindentation study on the micromechanical characteristics of API X100 pipeline steel

Abstract: The hardness characteristics of constituent micro-phases (ferrite and bainite) in a dual-phase API X100 pipeline steel were analyzed by nanoindentation experiments. The measured nano-hardness of the bainite phase is from 3.8 GPa to 4.9 GPa, which is much higher than that of the ferrite phase, which ranged from 1.75 GPa to 2.3 GPa. With the hardness and volume fraction of each micro-phase, attempts were made to predict the overall hardness by applying a simple rule-of-mixture. A comparison between the predicted overall hardness value and the experimentally measured value revealed that the rule-of-mixture can be successfully applied for prediction purposes. The results are discussed in terms of the grain boundary strengthening effect and the indentation size effect.

Influence of cooling rate on microstructure and properties of high strength steel weld metal

Abstract: Microstructures, and hence mechanical properties, of high strength steel weld metals are affected by cooling rate. Weld metal microstructures for a nominal composition of Fe–0·05C–0·3Si–2Mn–3Ni–0·5Cr–0·6Mo (wt-%) were therefore characterised for a range of cooling rates using high resolution scanning electron microscopy, and transformation behaviour, assessed from cooling curves, is presented as a continuous cooling transformation diagram. As deposited last bead microstructure changes gradually from lower bainite and martensite interspersed with coalesced bainite, via a mixture of relatively fine upper and lower bainite, to coarse upper bainite as cooling rate decreases. The microstructure of reheated beads follows the as deposited structure closely and becomes coarse with slower cooling. Mechanical properties correlate with observed microstructure and transformation behaviour. Results suggest high strength and good toughness for cooling rates between 800 and 500°C of about 3–13 s. A fine microstr...

High-strength hot-dip zinc coated steel sheet excellent in workability and process for production thereof

Abstract: This invention provides a high strength galvanized steel sheet having a TS of 590 MPa or more and excellent processability, and a method for manufacturing the same. The component composition contains, by mass%, C: 0.05% to 0.30, Si: 0.7% to 2.7%, Mn: 0.5% to 2.80, P: 0.1% or lower, S: 0.01% or lower, Al: 0.1% or lower, and N: 0.008% or lower, and the balance: Fe or inevitable impurities. A microstructure contains, in terms of area ratio, ferrite phases: 30% to 90%, bainite phases: 3% to 30%, and martensite phases: 5% to 40%, in which, among the martensite phases, martensite phases having an aspect ratio of 3 or more are present in a proportion of 30% or more. Preferably, retained austenite phases are contained in a proportion of 2% or more in terms of volume fraction and the average crystal grain diameter of the retained austenite phases is 2.0 µm or lower.