Microalloyed steel

About: Microalloyed steel is a research topic. Over the lifetime, 2183 publications have been published within this topic receiving 33586 citations.

Artificial neural networks for hardness prediction of HAZ with chemical composition and tensile test of X70 pipeline steels

Abstract: A neural network with feed-forward topology and back propagation algorithm was used to predict the effects of chemical composition and tensile test parameters on hardness of heat affected zone (HAZ) in X70 pipeline steels. The mass percent of chemical compositions (i. e. carbon equivalent based upon the International Institute of Welding equation (CEIIW), the carbon equivalent based upon the chemical portion of the Ito-Bessyo carbon equivalent equation (CEPcm), the sum of the niobium, vanadium and titanium concentrations (CVTiNb), the sum of the niobium and vanadium concentrations (CNBV), the sum of the chromium, molybdenum, nickel and copper concentrations (CCrMoNiCu) ), yield strength (YS) at 0.005 offset, ultimate tensile strength (UTS) and percent elongation (El) were considered as input parameters to the network, while Vickers microhardness with 10 N load was considered as its output. For the purpose of constructing this model, 104 different data were gathered from the experimental results. Scatter diagrams and two statistical criteria, i. e. absolute fraction of variance (R2) and mean relative error (MRE), were used to evaluate the prediction performance of the developed model. The developed model can be further used in practical applications of alloy and thermo-mechanical schedule design in manufacturing process of pipeline steels.

Effect of austenite pancaking on texture formation in a plain carbon and A Nb microalloyed steel

Abstract: The way in which texture development is affected by austenite pancaking was studied in a plain carbon and a niobium steel. Three processing parameters (austenitizing temperature, finish rolling temperature and amount of reduction) were varied, and their influence on the state of the austenite was analyzed. It was found that the presence of niobium, which leads to pancaking of the austenite when low finishing temperatures are employed, strengthened the transformation products produced from the copper, brass, S and Goss orientations in the austenite. Larger reductions resulted in sharper textures, especially in the microalloyed steel. The effect of austenitizing temperature was not particularly strong. Several f.c.c. ideal orientations were transformed according to the Kurdjumov-Sachs relationship, and the b.c.c. products resulting from this analysis are compared with the experimental results. When recrystallized austenite transforms, it is shown that the cube component transforms preferentially into the {001} rotated cube orientation, with lower than expected intensities displayed by the Goss and rotated Goss components. Similar trends are observed with respect to the four main deformation components; these tendencies are interpreted in terms of variant selection and selective growth.

Precipitation and clustering in a Ti-Mo steel investigated using atom probe tomography and small-angle neutron scattering

Abstract: The isothermal evolution of nanometre-sized precipitates formed in a Ti-Mo microalloyed steel through interphase precipitation has been investigated using atom probe tomography and small-angle neutron scattering. The coiling time and applied strain have been varied to observe the precipitate evolution at a constant coiling temperature of 650 °C, where various evolution parameters such as particle radius, number density, volume fraction and chemical composition have been evaluated and compared. The possibility of early stage solute clustering and its effect on precipitate formation have also been investigated. Clustering of Ti, Mo and C atoms as Ti-C and Mo-C has been observed at the shortest coiling time of 5 min. These clusters are assumed to be precursors to the carbide precipitates observed in the system, which exhibit a metastable composition, containing a carbon fraction (C/Ti+Mo ratio) in the range of 0.2–1. In particles having a Guinier radius > 3 nm, however, the average chemical composition approached the stable MC carbide stoichiometry with Ti/Mo ratio ~2.5 and C/(Ti+Mo) ratio ~0.55. This study reveals that the precipitate coarsening kinetics are very slow, with average particle diameter 10 h) in both the undeformed and deformed conditions. This is believed to be due to the reduction in equilibrium Ti content in the matrix as a result of partial replacement of Ti by Mo (Ti/Mo ratio > 2) in the precipitate lattice, in the presence of excess C in the system.

Microstructure and properties of ferritic steel welds containing Al and Ti

Abstract: The combined effect of Al and Ti, in the range 5 to 500 ppm, on the microstructure and properties of C-Mn shielded metal arc welds has been studied. It was found that Ti, in contrast to Al, dramatically enhanced the formation of acicular ferrite and improved notch toughness. A strong interactive effect was encountered, with Al at low concentrations tending to diminish the influence of Ti. Unless a critical balance is achieved, with regard to oxygen content, it is concluded that Ti be optimized at 30 to 40 ppm and that Al be kept as low as possible.