Bainite

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

Ultra high strength, secondary hardening steels with superior toughness and weldability

Abstract: High strength steel is produced by a first rolling of a steel composition, reheated above 1100 °C, above the austenite recrystallization, a second rolling below the austenite recrystallization temperature, water cooling from above AR to less than 400 °C and followed by tempering below the AC transformation point. The steel comprises predominantly martensite/bainite phase containing precipitates of the carbides, nitrides, or carbonitrides of vanadium, niobium, and molybdenum, wherein the concentrations of vanadium +niobium ⊃ 0.1 wt.%, the carbon content ranges from about 0.03 to 0.12 wt.%, and chromium is present in amounts ranging from 0.3-1.0 wt.%.

High strength hot rolled steel sheet and method for manufacturing the same

Abstract: The present invention relates to a high strength hot rolled steel sheet consisting of 004 to 015% C, 15% or less Si, 05 to 16% Mn, 004% or less P, 0005% or less S, 004% or less Al, 003 to 015% Ti, 003 to 05% Mo, by mass, and balance of Fe and inevitable impurities, and having a microstructure consisting of ferrite containing precipitates, second phase of bainite and/or martensite, and other phase, wherein the percentage of the ferrite containing precipitates is 40 to 95%, and the percentage of the other phase is 5% or less For example, the high strength hot rolled steel sheet having a thickness of 14 mm shows a tensile strength of 780 MPa or higher, an elongation of 22% or higher elongation, and a hole expansion ratio of 60% or higher, thus the steel sheet is suitable for reinforcing members automobile cabin and crash worthiness members of automobile

Effect of Nb on the microstructure and properties of Ti-Mo microalloyed high-strength ferritic steel

Abstract: The effects of Nb on the microstructure and mechanical properties of Ti-Mo microalloyed high strength ferritic steel were systematically investigated It was found that Nb addition inhibited the bainite transformation and was beneficial for obtaining ferritic steel Further, Nb accelerated the precipitation in austenite and finer ferrite grains were obtained in Ti-Nb-Mo steel The strengthening mechanism analysis results of experimental steels showed that the precipitation hardening effect of the (Ti, Mo, Nb)C particles was remarkable due to their larger volume fraction, although their average particle size was greater than that of (Ti, Mo)C in Ti-Mo steel With the decrease of coiling temperature from 650 °C to 550 °C, the grain refinement strengthening and precipitation hardening of experimental steels increased When the coiling temperature was 550 °C, the ferritic steel with superior mechanical properties was obtained by means of Ti-Nb-Mo complex microalloying And the tensile strength, yield strength, and elongation of the Ti-Nb-Mo ferritic steel were 755 MPa, 712 MPa, and 22%, respectively

Morphology change of retained austenite during austempering of carbide-free bainitic steel

Abstract: A change in the mechanical properties of a carbide-free bainitic steel was observed during prolonged holding at austempering temperature after termination of the bainitic transformation. To determine the origin of the property change, the microstructure was investigated by correlative electron microscopy. Although the retained austenite content remains the same during prolonged holding, its morphology changes from thin films separating the individual bainitic sub-units to a more globular structure. Since films of austenite contain a higher C concentration, the blocky austenite becomes gradually enriched in C during this morphology change. The more homogeneous distribution of the C after prolonged austempering leads to higher deformability as a result of a more pronounced TRIP effect.