Modelling of Transient Temperature Field and Phase Transformation Change: A way for Residual Stress Management in Large Scale Forgings

The paper is devoted to development of the modelling approach based on 3D finite-element (FE) analysis of the transient temperature fields and the thermally induced phase transformations as a way towards residual stress management in large size forgings. Heating, holding and cooling stages are under consideration and modelling of both the austenite formation and decomposition are taken into account. The thermal-mechanical FE model capable of taking into account changes in the specific volume during ferrite/austenite transformation is coupled with the relevant phase transformation model in order to allow simulation of the transient stresses due to both thermal contraction and the dilatometric effect. The model is capable of taking into account different boundary conditions for the heat transfer problem based on the available data. To improve the predictive abilities, the following two commercial FE codes, such as MSC Marc 2013.1.0 and Abaqus/Standard 6.12, are used for solving the non-steady state 3D problem of the metal expansion/contraction during consecutive heating, holding and cooling stages. Although all the mentioned process steps are considered, the model is dedicated to be used for modelling the cooling stages of large forgings and castings

A Comprehensive Case Study of Macrosegregation in a Steel Ingot

This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s11663-015-0386-yA case study is presented that examines the macrosegregation and grain structure present in a 12-tonne steel ingot, which was cast for experimental purposes. Details of the casting procedure were well documented and the resulting ingot was characterized using a number of techniques that measured chemical segregation, shrinkage, and porosity. The formation of the porosity and segregation patterns is discussed in reference to the particular grain structure observed in the ingot. It is hoped that this case study can be used as a tool for the validation of future macromodels.This work was undertaken as part of a Project sponsored by Rolls-Royce Power Nuclear plc in collaboration with Sheffield Forgemasters International

Rolling of aluminium 2: practical aspects for finite element model development

The finite element technique has been selected to study the hot rolling process because it offers the best alternative to analyse the complexities of the process. These include: non-linearity of the material behaviour, boundary conditions and contact. It has been shown from the previous chapter that the method is capable of handling these non-linearities and has been used successfully to analyse a wide range of metal forming operations. This chapter aims to point out the modelling techniques and methodologies (steps) involved in undertaking thermo-mechanical simulations of the rolling process. This is done by means of a series of case studies

Rolling of aluminium 1: thermomechanical processing and FEM simulation

This chapter is intended to introduce new users to the practical aspects of the thermo-mechanical processing and the finite element method. The hot rolling of aluminium alloys is the topic chosen to illustrate these aspects. This is because rolling is used worldwide and the final product from this kind of operation is the primary material for a wide range of industrial sectors including shipbuilding, construction, automobile, and manufacturing. During this practice, a piece of material is plastically deformed using rotating rolls, which deliver a product with a specific transversal section. According to their shape they can be classified into flat and long products (shape rolling). [Introduction

A parametric study on the effects of process conditions on dehydrogenation, wall shear and slag entrainment in the vacuum arc degasser using mathematical modelling

The effect of vacuum pressure and argon flow rate on hydrogen degassing of molten steel in a triple plug, 100 tonne vacuum arc degasser has been examined using a three phase Eulerian CFD-mass transfer coupled model. The model takes into account the interaction between the slag, steel and argon phases over a 20-minute degassing period. Increasing the argon flowrate from 13-29 Nm3hr−1 produces a 10% increase in the hydrogen removal ratio, generating a faster melt velocity and larger slag eye. This also results in the maximum shear stress on the ladle walls increasing by a factor of 2.2 and the shear stress integrated across the wall increasing by a factor of 3.75, thus contributing to enhance refractory erosion. Within the same flowrate range the volume of entrained slag also increases by a factor of 1.4, which may result in increased nitrogen/oxygen pickup. Reducing the vacuum pressure maintains a low equilibrium hydrogen concentration and allows more efficient hydrogen removal, with a 38% reduction in the removal ratio between 102−104 Pa

A Comprehensive Case Study of Macrosegregation in a Steel Ingot

This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s11663-015-0386-yA case study is presented that examines the macrosegregation and grain structure present in a 12-tonne steel ingot, which was cast for experimental purposes. Details of the casting procedure were well documented and the resulting ingot was characterized using a number of techniques that measured chemical segregation, shrinkage, and porosity. The formation of the porosity and segregation patterns is discussed in reference to the particular grain structure observed in the ingot. It is hoped that this case study can be used as a tool for the validation of future macromodels.This work was undertaken as part of a Project sponsored by Rolls-Royce Power Nuclear plc in collaboration with Sheffield Forgemasters International

Hybrid modelling of aluminium-magnesium alloys during thermomechanical processing in terms of physically-based, neuro-fuzzy and finite element models

For modern metals industries using thermomechanical processing, off-line modelling and on-line control based on physical knowledge are highly desirable in order to improve the quality of existing materials, the time and cost efficiency, and to develop new materials. Neural network and neuro-fuzzy models are the most popular tools, but they do not embed physical knowledge. On the other hand, current physically-based models are too complex for industrial application and are less efficient than neural networks. A combination of neuro-fuzzy and physically-based models has therefore been developed, which is termed a “hybrid model”. The hybrid model has been applied to predict flow stress and microstructural evolution during thermomechanical processing. Comparison with experimental data shows generally good agreement for Al–1% Mg alloy deformed under thermomechanical processing conditions. The hybrid model was then embedded into a finite element model and the simulated results show a very similar distribution to those calculated using empirical models