Jaromír Moravec

Numerical Simulations of Heat Treatment Processes

Welding and heat treatment are a modern, high efficient production technologies. During last few years requirements for quality of the welded joints have been constantly increasing in all production areas. Unfortunately, this approach increases the cost of production due to demand of intense experimental or prototype work prior the use of technology to make a final product. Preliminary experiments have to take into account proper chose of welding technology, materials, welding parameters, clamping and final optimization the welding conditions. All of these activities can be supported or even replaced by numerical simulations based on finite elements method. Tremendous advance in field of numerical simulation, facilitates very high correlation of simulation and experimental results bringing this new approach to common use. This paper highlight to usefulness of numerical simulation in heat treatment of bulk materials in various production stages. It was shown that it is possible to predict formation of metallurgical phases, hardness distribution, strains and stresses during and after quenching process. Simulations of different heating conditions and cooling media makes it possible to simulate processes such as heating, quenching, carburizing and nitriding.

Numerical Analysis of Residual Stresses and Distortions in Aluminium Alloy Welded Joints

Simulation software based on a finite element method have significantly changed the possibilities of determining welding strains and stresses at early stages of product design and welding technology development. But the numerical simulation of welding processes is one of the more complicated issues in analyses carried out using the Finite Element Method. A welding process thermal cycle directly affects the thermal and mechanical behaviour of a structure during the process. High temperature and subsequent cooling of welded elements generate undesirable strains and stresses in the structure. Knowledge about the material behaviour subjected to the welding thermal cycle is most important to understand process phenomena and proper steering of the process. The study presented involved the SYSWELD software-based analysis of MIG welded butt joints made of 1.0 mm thickness, 5xxx series aluminium alloy sheets. The analysis of strains and the distribution of stresses were carried out for several different cases of fixing and releasing of welded elements.

The Selection of Appropriate Process Parameters of Diffusion Bonding in Heterogeneous Weld of 355J2/AISI 316L Steels

The aim of this article is to present possibilities of diffusion bonding utilization at creation heterogeneous joints where strength properties are taken into account. The joint was implemented to low-alloy structural ferrite-pearlite S355J2 steel and high-alloy austenitic AISI 316L steel. The fundamental theory of diffusion and also design and realisation of experimental creation of diffusion joint in thermal-mechanical simulator Gleeble 3500 is described in the article. Furthermore, procedure of technological parameters selection, when optimisation of strength properties of heterogeneous joint including metallographic evaluation are taken into account, are presented.

APPLICATION OF NUMERICAL SIMULATIONS ON X10CRWMOVNB9-2 STEEL MULTILAYER WELDING

Creep-resistant martensitic steel X10CrWMoVNb9-2 (P92) is suitable for high-temperature application used in the ultrasupercritical (USC) power plants at temperatures within the limits from 600 to 620°C and pressures about 26 MPa. It is steel alloyed with vanadium and with controlled content of boron and nitrogen. The aim of this paper is to describe how can be optimized welding processes by means of the numerical simulations mainly with respect to the structural changes and hardness in the HAZ. On the real multilayer weld will be described how to arrange whole experiment in order to obtain not only relevant input data but also verification data. Additional aim of this paper is to propose mathematical description of the computational model that is usable for simulation computations of welding and heat treatment of real structure components.

Application of Numerical Simulations on 10GN2MFA Steel Multilayer Welding

10GN2MFA steel is used to produce wire and manufacturing of steam generators, pressure compensators, collectors and other equipment for nuclear power plants. In this area, there is no place to do any mistakes during manufacturing or carrying out extensive tests and producing a lot of prototypes. It is the main reason why we used modern software for numerical simulation of welding and heat treatment processes also on the very early stage of development. The aim of this paper is to describe how can welding processes be optimized by means of the numerical simulations mainly with respect to the structural changes, stresses and hardness distribution in the Heat Affected Zone (HAZ). On the real multilayer weld how to arrange whole experiment in order to obtain not only relevant input data but also verification data will be described. Additional aim of this paper is to propose mathematical description of the computational model that is usable for simulation computations of welding and heat treatment of real structure components.

APPLICATION POSSIBILITIES OF THE DIFFUSION BONDING FOR MATERIAL 10GN2MFA USED IN THE NUCLEAR POWER INDUSTRY

The aim of this paper is to demonstrate the application possibilities at using diffusion bonding for creation the homogenous joints regarding their strength properties in comparison with the fusion MMAW method and with the parent material. Connection was carried out for low-alloyed bainitic steel 10GN2MFA that is designed for production shells and bodies of the primary steam-generators collectors which are used in the nuclear power industry. In the paper are theoretically described the basics of diffusion. Moreover, there is described also the proposal and optimization of the diffusion bonding process parameters and optimization of the thermal treatment procedure. Experiments were carried out by means of the thermal-mechanical simulator Gleeble 3500. Welded joints were subsequently evaluated in light of mechanical properties by hardness measurement and metallography.

The Increase in Effectivity of Material Processing with Employment of Liquid CO 2 during Aluminium Die Casting

The article is focused on monitoring the cooling effect of the liquid CO2. This unconventional cooling system was used as a supplement method added to the standard tempering system of the die casting mould particularly intended for aluminium alloy castings. Standard tempering system of die casting moulds enables preheating the mould to operating temperature before the particular production starts and then the tempering system regulates the temperature balance between the mould and the casting during individu al production cycles. Conventional cooling system is based on drilled or milled interconnected channels with predominantly parallel orientation to the parting line, through which a tempering medium (oil, water etc.) flows. This system has some limitations that can be overcame with utilizing of special approaches. One of these approach is employment of liquid CO2.This study revealed the positive impact of this additive cooling on homogeneity of temperature field distribution on the mould cavity surface, which assures first of all the uniform coating the cavity surface by separating agent and sticking the melt on the cores. The products were analysed using the metallographic and CT analyses and the leak tightness was tested.

THE IMPACT OF SELECTED PROCESSES AND TECHNOLOGICAL PARAMETERS ON THE GEOMETRY OF THE WELD POOL WHEN WELDING IN SHIELS GAS ATMOSPHERE

This paper is focused on welding with a consumable electrode in a gas shield atmosphere and its main aim is to show the influence of selected processes and technological parameters on the geometry of the weld pool in terms of theoretical and experimental views. For this purpose, the parametric areas defined by the change of the welding current and welding rate were determined. Apart from the influence of these parametric areas, the influence of other technological input variables, including the wire diameter and preheating temperature, was also studied. The experimentally obtained geometric data of the weld pool can be used for technological welding procedures WPS and especially for simulation calculations to obtain a more accurate numerical model of the heat source. This makes it possible to get accurate simulation results and to better understand the impact of other variables that influence the welding process. This all helps to the optimization of the welding process for several applications.

INFLUENCE OF THE PRESSURE TANKS REPEATED ENAMELLING ON THE BASIC MATERIAL DEGRADATION

Pressure tanks with the enamel surfaces play an important role mainly in the food industry and pharmacy. As the best advantage of these enamels there is very good resistance against aggressive environment at keeping the required mechanical properties of low-alloyed steels which are used for these applications. Enameling is generally applied as several particular layers whereas every of these layers has to undergo the pre-defined temperature cycle. Because of increasing device service life there is very often applied repeated enameling. The paper deals with the monitoring influence of the temperature exposition on the change of mechanical properties and structure of the basic material P265GH regarding its initial properties. The aim was to identify whether and eventually how these repeated emailing can influence the basic material degradation and based upon this to determinate their possible maximal number.

IMPROVEMENT OF MODEL OF ALUMINIUM ALLOYS BEHAVIOUR FOR APPLICATION IN NUMERICAL SIMULATIONS OF WELDING

1370 IMPROVEMENT OF MODEL OF ALUMINIUM ALLOYS BEHAVIOUR FOR APPLICATION IN NUMERICAL SIMULATIONS OF WELDING MOJMIR VANEK, JAROMIR MORAVEC, JAN RIHACEK Brno University of Technology, Faculty of Mechanical Engineering, Institute of Manufacturing Technology Brno, Czech Republic Technical University of Liberec, Faculty of Mechanical Engineering, Department of Engineering Technology Liberec, Czech Republic