A computational model is presented in this article for the prediction of microstructural development during heat treating of steels and resultant room-temperature hardness. This model was applied in this study to predict the hardness distribution in end-quench bars (Jominy hardness) of heat treatable steels. It consists of a thermodynamics model for the computation of equilibria in multicomponent Fe-C-M systems, a finite element model to simulate the heat transfer induced by end quenching of Jominy bars, and a reaction kinetics model for austenite decomposition. The overall methodology used in this study was similar to the one in the original work of Kirkaldy. Significant efforts were made to reconstitute the reaction kinetics model for austenite decomposition in order to better correlate the phase transformation theory with empiricism and to allow correct phase transformation predictions under continuous cooling conditions. The present model also expanded the applicable chemical composition range. The predictions given by the present model were found to be in good agreement with experimental measurements and showed considerable improvement over the original model developed by Kirkaldy et al.

A computational model for the prediction of steel hardenability

Analysis of published data demonstrates that the start temperatures of bainite (Bs) and martensite (Ms) formation exhibit an exponential carbon dependence. Empirical models are proposed to describe this specific carbon dependence. The models are relatively simple and sufficiently accurate for conventional steels with 0·1–1·9 wt-% carbon and less than 7 wt-% in total of other alloying elements. Predictions of the Bs and Ms temperatures show a better accuracy than those obtained with equations from literature. An improved prediction of the Ms temperature is important to accurately determine of the amount of martensite at a certain arrest temperature using the Koistinen and Marburger (KM) equation. Predictions of the volume fraction martensite are also influenced by the rate parameter αm controlling the kinetics of martensite formation. Based on the improved models for the composition dependence of Ms and αm, the volume fraction of retained austenite at room temperature has been calculated for Fe–C a...

Bainite and martensite start temperature calculated with exponential carbon dependence

Modelling the correlation between processing parameters and properties of maraging steels using artificial neural network

Weld residual stresses often approach, or exceed, the yield strength of the material, with serious implications for the integrity of engineering structures. It is not always feasible to measure residual stresses, so integrity assessments often rely heavily on numerical models. In ferritic steels, the credibility of such models depends on their ability to account for solid-state phase transformations, which can have a controlling effect on the final residual stress state. Furthermore, a better understanding of weld transformations provides an opportunity to engineer the weld stress state and microstructure for improved life. In this article, the complementary merits of synchrotron X-ray and neutron diffraction are exploited both to verify and refine weld models and to inspire the development of weld filler metals to control weld stresses. In terms of weld filler metal design, X-ray diffraction is used to characterize phase transformations in real time during realistic weld cooling cycles, for understanding small-scale behavior and identifying features that need to be incorporated into finite-element models. Meanwhile, neutron diffraction is used to elucidate the practical consequences of solid-state phase transformations on the macroscopic scale, thereby providing crucial validatory structural integrity data.

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Characterizing Phase Transformations and Their Effects on Ferritic Weld Residual Stresses with X-Rays and Neutrons

Effect of thermal cycles on the corrosion and mechanical properties of UNS S31803 duplex stainless steel

The most comprehensive collection of time-temperature diagrams for irons and steels ever collected. Between this volume and its companion, Atlas of Time Temperature Diagrams for Nonferrous Alloys, you'll find the most comprehensive collection of time-temperature diagrams ever collected. Containing both commonly used curves and out-of-print and difficult-to-find data, these Atlases represent an outstanding worldwide effort, with contributions from experts in 14 countries. Time-temperature diagrams show how metals respond to heating and cooling, allowing you to predict the behavior and know beforehand the sequence of heating and cooling steps to develop the desired properties. These collections are a valuable resource for any materials engineer Both Collections Include: Easy-to-Read Diagrams Isothermal transformation Continuous cooling transformation Time-temperature precipitation Time-temperature embrittlement Time-temperature ordering Materials Included in the Irons and Steels Volume: Low-carbon High Strength Low Alloy Stainless (Maraging, austenitic, ferritic, duplex) Chromium, molybdenum, vanadium, silicon Structural Quenched and tempered Spring and Rail High-temperature creep-resistant Tool and die Eutectoid, hypereutectoid carbon Deep hardening Titanium bearing Irons: Gray cast, malleable, white, white cast, ductile.

Vander Voort

Papers

Atlas of time-temperature diagrams for irons and steels