scholarly journals Numerical Modelling Of Thermal And Structural Phenomena In Yb:YAG Laser Butt-Welded Steel Elements

2015 ◽  
Vol 60 (2) ◽  
pp. 821-828 ◽  
Author(s):  
M. Kubiak ◽  
W. Piekarska ◽  
S. Stano ◽  
Z. Saternus
Keyword(s):  
Phase Transformations ◽  
Numerical Models ◽  
Welding Process ◽  
Source Model ◽  
Welded Steel ◽  
Heating And Cooling ◽  
Real Distribution ◽  
Classical Models ◽  
Volume Method ◽  
Cct Diagrams

AbstractThe numerical model of thermal and structural phenomena is developed for the analysis of Yb:YAG laser welding process with the motion of the liquid material in the welding pool taken into account. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using Chorin projection method and finite volume method. Phase transformations in solid state are analyzed during heating and cooling using classical models of the kinetics of phase transformations as well as CTA and CCT diagrams for welded steel. The interpolated heat source model is developed in order to reliably reflect the real distribution of Yb:YAG laser power obtained by experimental research on the laser beam profile.On the basis of developed numerical models the geometry of the weld and heat affected zone are predicted as well as the structural composition of the joint.

Numerical Investigation of the Influence of Microstructure on the Residual Stress Distribution and Distortion in DP600 Welds

2011 ◽  
Vol 681 ◽  
pp. 79-84 ◽  
Author(s):  
A.M.Akbari Pazooki ◽  
M.J.M. Hermans ◽  
I.M. Richardson
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Dual Phase Steel ◽  
Ferrite Matrix ◽  
Volume Changes ◽  
Heating And Cooling ◽  
Distortion Level ◽  
Martensitic Phase Transformations ◽  
Cct Diagrams

Dual phase steel consists of martensite embedded in a ferrite matrix. The material experiences high heating and cooling rates during welding, which alter the microstructure significantly. In this work the effects of solid state phase transformations on the prediction of residual stresses and distortion during welding of DP600 steel is investigated. Phase fractions have been calculated implicitly using continuous cooling time (CCT) diagrams. The results of the model are compared with experimental measurements for bead-on-plate welds made on DP600 sheets. It is found that the volume changes and the increase of the strength due to the martensitic transformation have both a significant effect on the residual stress and distortion level although in opposite directions. Martensitic phase transformations in DP600 steel tend to reduce tensile residual stresses in the weld metal.

The Effect of Phase Transformations on Predicted Values of Residual Stresses in Welded Ferritic Components

2006 ◽  
Vol 524-525 ◽  
pp. 827-832 ◽  
Author(s):  
Alex P. Warren ◽  
Steve K. Bate ◽  
Richard Charles ◽  
C.T. Watson
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Welding Process ◽  
Heating And Cooling ◽  
Test Pieces ◽  
Property Data ◽  
Finite Element Package ◽  
Predicted Values ◽  
Welding Processes

The accurate prediction of the residual stresses present in welded structures can be of great importance to the fracture assessment of such components. Therefore, a large amount of benefit can be gained from improving techniques for measuring and numerically analysing these stresses. In recent years many advances have been made in the field of analysing residual stresses using finite element methods. That said, very little work has been conducted on the accurate modelling of welded ferritic components. This is largely due to the added complication of phase transformations that occur during the heating and cooling of such steels. The objective of the work presented in this paper was to improve understanding of the effect that phase transformations have on residual stresses present within welded ferritic structures. This was conducted by simulating such welding processes using the finite element package SYSWELD. An investigation was conducted to determine how phase transformations, and therefore residual stresses, are affected by the welding process used. Phase transformation and material property data available within SYSWELD were used for this analysis. An autogenously welded beam provided a simple basis for this qualitative investigation. In the future the manufacture and measurement of suitable test-pieces will enable these simulations to be validated.

Modeling the Welding Process of the Low Alloy Ferritic Steels T/P23 and T/P24

2012 ◽  
Vol 476-478 ◽  
pp. 642-649 ◽  
Author(s):  
José Adilson de Castro ◽  
Carlos Roberto Xavier ◽  
Luciano Pessanha Moreira ◽  
Yasushi Sazaki
Keyword(s):  
Cooling Rate ◽  
Thermal Evolution ◽  
Welding Process ◽  
Source Model ◽  
Ferritic Steels ◽  
Heat Source Model ◽  
Metal Thickness ◽  
Preheating Temperature ◽  
Volume Method ◽  
Good Agreement

In this paper a model based on transport equations is proposed to study the weldability of low alloy ferritic steels T/P23 and T/P24. The model was numerically implemented by using the finite volume method (FVM) in an open source computational code to simulate the influence of the heat input, base metal thickness and preheating temperature on the thermal evolution and the cooling rate during the welding process. Meanwhile, it was possible to evaluate qualitatively the microstructure at the heat affected zone (HAZ) of these steels when a single weld bead was deposited on their surface and calculate the maximum hardness reached at this region. A double-ellipsoid heat source model for power density distribution was used in order to obtain a good estimate of the cooling rate and evolution of the fusion zone (FZ). The results are discussed and good agreement between experimental and simulated results was obtained for temperature distribution

Numerical Modelling of Thermal and Structural Strain in Laser Welding Process / Modelowanie Numeryczne Odkształceń Cieplnych I Strukturalnych W Procesie Spawania Techniką Laserową

2012 ◽  
Vol 57 (4) ◽  
pp. 1219-1227 ◽  
Author(s):  
W. Piekarska ◽  
M. Kubiak ◽  
Z. Saternus
Keyword(s):  
Numerical Modelling ◽  
Welded Joints ◽  
Base Material ◽  
Welding Process ◽  
Thermomechanical Properties ◽  
Continuous Heating ◽  
Heating And Cooling ◽  
Cct Diagrams ◽  
Kinetics Of ◽  
Structural Strain

This work concerns numerical modelling of thermal and structural strain, resulting in heating and cooling of laser butt-welded joints. Numerical analysis of strain is carried out in Abaqus FEA. Through the use of additional author’s subroutines, the structural strain caused by phase transformations during heating and cooling of welded elements is taken into account in the analysis. V.I. Machnienko models as well as Continuous Heating Transformation (CHT) and Continuous Cooling Transformation (CCT) diagrams for S355 steel are implemented into UEXPAN subroutine in order to determine the kinetics of phase transformation in the solid state. The model takes into account thermomechanical properties of the base material varying with temperature. The paper presents results of numerical simulation of temperature field, predicted structural composition, thermal and structural strain in laser butt-welded joints.

Modeling of Thermomechanical Phenomena of Welding Process of Steel Pipe / Modelowanie Zjawisk Termomechanicznych Procesu Spawania Rury Stalowej

2012 ◽  
Vol 57 (4) ◽  
pp. 1229-1238 ◽  
Author(s):  
A. Kulawik
Keyword(s):  
Phase Transformation ◽  
Solid State ◽  
Numerical Models ◽  
Welding Process ◽  
Macroscopic Model ◽  
The Finite Element Method ◽  
Welded Steel ◽  
Solidification Model ◽  
The Individual ◽  
Thermal Phenomena

In this paper an analysis of phenomena of laser welding of steel thin-walled element is presented. Coupled mathematical and numerical models of thermal phenomena, mechanical and phase transitions in solid and liquid state are proposed. To the modeling of phase transformation in the solid state the macroscopic model based on the analysis of the CTP diagrams are used. In the simulation of thermal phenomena the solution of heat transport equations with melting and solidification model is applied. Mechanical phenomena using the stress model for a elastic-plastic range and the isotropic strengthening of material are simulated. In order to solve analyzed problem the software using the finite element method (3D problem)has been developed. The influence of the individual elements of the model on the stress field and the plastic deformation field of welded steel element is determined. A comparative analysis of the results of numerical calculations for the case: the dependence of material properties on the temperature, the inclusion of phase transformation in the solid state, the dependence of the yield strength on the phase composition of the material are made.

Numerical Models of Hardening Phenomena of Tools Steel Base on the TTT and CCT Diagrams

2011 ◽  
Vol 56 (2) ◽  
pp. 325-344 ◽  
Author(s):  
T. Domański ◽  
A. Bokota
Keyword(s):  
Finite Elements ◽  
Phase Transformations ◽  
Tool Steel ◽  
Numerical Models ◽  
Stress And Strain ◽  
Steel Base ◽  
Thermal Phenomena ◽  
Cct Diagrams ◽  
Mechanical Phenomena

Numerical Models of Hardening Phenomena of Tools Steel Base on the TTT and CCT DiagramsIn work the presented numerical models of tool steel hardening processes take into account thermal phenomena, phase transformations and mechanical phenomena. Numerical algorithm of thermal phenomena was based on the Finite Elements Methods in Galerkin formula of the heat transfer equations. In the model of phase transformations, in simulations heating process, isothermal or continuous heating (CHT) was applied, whereas in cooling process isothermal or continuous cooling (TTT, CCT) of the steel at issue. The phase fraction transformed (austenite) during heating and fractions of ferrite, pearlite or bainite are determined by Johnson-Mehl-Avrami formulas. The nescent fraction of martensite is determined by Koistinen and Marburger formula or modified Koistinen and Marburger formula. In the model of mechanical phenomena, apart from thermal, plastic and structural strain, also transformations plasticity was taken into account. The stress and strain fields are obtained using the solution of the Finite Elements Method of the equilibrium equation in rate form. The thermophysical constants occurring in constitutive relation depend on temperature and phase composite. For determination of plastic strain the Huber-Misses condition with isotropic strengthening was applied whereas for determination of transformation plasticity a modified Leblond model was used. In order to evaluate the quality and usefulness of the presented models a numerical analysis of temperature field, phase fraction, stress and strain associated hardening process of a fang lathe of cone shaped made of tool steel was carried out.

scholarly journals Failure Analysis of Premature Corrosion of HF Seam-Welded Steel Pipe in Central Heating System

2021 ◽  
Author(s):  
Dorota Tyrala ◽  
Bogdan Pawlowski
Keyword(s):  
High Frequency ◽  
Energy Dispersive Spectrometry ◽  
Weld Line ◽  
Welding Process ◽  
Heating System ◽  
Bond Line ◽  
Steel Pipe ◽  
Huge Number ◽  
Welded Steel ◽  
Central Heating

AbstractPremature corrosion in the form of longitudinal cracking in a high-frequency (HF) induction seam-welded steel pipe occurred after just 24 months in service. The failed pipe was investigated to reveal the main cause of its failure, and the results of microstructural examinations (light optical microscopy, scanning electron microscopy with energy-dispersive spectrometry) suggest that the failure resulted from an HF induction welding process defect—a so-called cast weld, that is, a huge number of iron oxides in the weld line caused by insufficient ejection of the molten metal from the bond line.

scholarly journals Process Stability, Microstructure and Mechanical Properties of Underwater Submerged-Arc Welded Steel

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1249
Author(s):  
Maofu Zhang ◽  
Yanfei Han ◽  
Chuanbao Jia ◽  
Shengfa Dong ◽  
Sergii Maksimov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Water Glass ◽  
Welding Process ◽  
Process Stability ◽  
Surrounding Water ◽  
Welded Steel ◽  
Underwater Wet Welding ◽  
Marine Engineering ◽  
High Level

In underwater wet welding, the unstable welding process caused by the generation and rupture of bubbles and the chilling effect of water on the welding area result in low quality of welded joints, which makes it difficult to meet the practical application of marine engineering. To improve the process stability and joining quality, a mixture of welding flux with a water glass or epoxy resin was placed on the welding zone before underwater welding. In this paper, welds’ appearance, geometry statistics of welds’ formation, welding process stability, slag structure, microstructure, pores and mechanical properties were investigated. It was found that with the addition of water glass in the mixture, the penetration of weld was effectively increased, and the frequency of arc extinction was reduced. Though the porosity rose to a relatively high level, the joints’ comprehensive mechanical properties were not significantly improved. Notably, the applied epoxy resin completely isolated the surrounding water from the welding area, which greatly improved process stability. Furthermore, it benefited from the microstructure filled with massive acicular ferrite, the average elongation and room temperature impact toughness increased by 178.4%, and 69.1% compared with underwater wet welding, respectively, and the bending angle of the joint reaches to 180°.

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