اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

Studies on the Effect of Mechanical Vibration on 

the Microstructure of the Weld Metal

تحقیقات در مورد اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

ABSTRACT

The solidification process in the weld metal produces solidification structure. The solidification process depends on the thermal gradient, solidification speed and the alloy content. These structures can be planar, cellular, columnar dendritic and equiaxed dendritic. The solidification process may change from planar to cellular, columnar dendritic and equiaxed dendritic across the weld metal zone as shown in fig.1. Three grains are shown to grow epitaxially from the fusion line. A short distance away from the fusion line, solidification changes to the cellular mode. Further away from the fusion line, the solidification changes to columnar dendritic mode. Near the weld centre line equiaxed dendrites nucleate and grow, blocking off the columnar dendrites. Each one of these structures would affect the hot cracking susceptibility in greater or smaller extent.

تنش‌های پسماند در جوش‌های لب به لب اتصالات لوله غیرمشابه

Effect of the welding heat input on residual stresses in butt-welds of dissimilar pipe joints

اثر ورودی حرارت جوشکاری بر تنش‌های پسماند در جوش‌های لب به لب اتصالات لوله غیرمشابه

ABSTRACT

This study used finite element techniques to analyse the thermo-mechanical behaviour and residual stresses in dissimilar butt-welded pipes. The residual stresses at the surface of some weld specimens were measured experimentally by using the hole-drilling method. The results of the finite element analysis were compared with experimentally measured data to evaluate the accuracy of the finite element modelling. Based on this study, a modelling procedure with reasonable accuracy was developed. The developed finite element modelling was used to study the effects of welding heat input on magnitude and distribution of welding residual stresses in butt-welded pipes made of ferritic and austenitic steels. The hoop and axial residual stresses in dissimilar pipe joints of 8 mm thick for V-groove shape were studied. It is shown that the welding heat input has a significant effect on magnitude and distribution of residual stresses in the stainless steel side of the studied joints.

  

ارزیابی ساختار در اتصال نفوذی آلیاژ تیتانیوم/فولاد زنگ نزن

THE EVOLUTION CHARACTERISTICS AND NUMERICAL
ANALYSIS OF DIFFUSION BONDING INTERFACE
STRUCTURE OF TITANIUM ALLOY/Cu/STAINLESS STEEL

ارزیابی خصوصیات و آنالیز عددی ساختار در فصل مشترک اتصال نفوذی آلیاژ تیتانیوم/فولاد زنگ نزن

ABSTRACT

Carries on the investigation to the titanium alloy/Cu/stainless steel intermetallic compound of bonding interface in the meantime, to make a thermodynamic model of the interface element diffusion to have a numerical simulation of the diffusion distance and diffusion temperature, time. Using analysis methods of stretching test, microhardness test, SEM and EDS, to investigate and research the mechanical properties, the interface structure characteristic, the principal element atomic diffusion mechanism of joints thermal simulation and the vacuum diffusion bonding of Ti-6Al-4V/Cu/304, the reacting phases are produced and the distribution range . The results show that when bonding prssere is 5.0 MPa ، the joints tensile strength first increase and then decreases, with bonding temperature and time rising, When bonding temperature is 1223K, bonding time is 3.6 ks, there is a maximum tensile strength that is 162.73 MPa. However, it will is disadvantageous to performance of the joints, when bonding temperature and time extended overly. It formed multi-phase transition organizations by solid solution, intermetallic compounds in the bonding interface, such as Ti2Cu, TixCuy , Ti2Fe, TiFe2 and TiFe. Effect of TixFey on strength of the joints is slightly inferior the TixCuy compound. The fracture is mainly by the titanium alloy side region III for the source dehiscence, developing in the weak diffusion layer.