جوشکاری اینکونل 625 و فولاد زنگ‎نزن L 304 با پرتوی الکترونی

Microstructure and hardness studies of electron beam

welded Inconel 625 and stainless steel 304L

مطالعه ریزساختار و سختی اینکونل 625 و فولاد زنگ‎نزن L 304

جوشکاری شده با پرتوی الکترون

ABSTRACT

In this study, electron beam welding of dissimilar Inconel 625 and SS 304L alloys was successfully performed by employing optimized electron beam welding parameters. The welded joint was characterized using SEM/EDS, XRD and micro-hardness tester. The welded joint was found homogeneous, well bonded and defect free. Two types of microstructure i.e. columnar dendritic and cellular dendritic were observed in the fusion zone. The development of different microstructures in the fusion zone was attributed to the localized cooling effects during solidification. Few micro-cracks along with dendrites splitting were observed in the vicinity of end crater that was mainly due to the segregation of S element. A significant variation of Ni and Fe was observed across Inconel/FZ and FZ/SS interfaces due to their fast diffusion in the melt pool. Micro-hardness measurements across Inconel/FZ and FZ/SS interfaces showed an increasing trend in the FZ from SS 304L towards Inconel base alloy.

  

اثر سرعت جوشکاری بر تنش پسماند در طول جوشکاری قوس با الکترود تنگستن تحت پوشش گاز

Influence of welding speed and power on residual stress during gas tungsten arc welding (GTAW) of thin sections

with constant heat input: A study using numerical simulation and experimental validation

اثر سرعت جوشکاری و توان بر تنش پسماند

در طول جوشکاری قوسی الکترود تنگستن (GTAW) مقاطع نازک با ورودی گرمای ثابت

مطالعه ای با استفاده از شبیه سازی و اعتبارسنجی تجربی

ABSTRACT

The temperature distribution and residual stresses for a GTAW circumferential butt joint of AISI 304 stainless steel using numerical simulation have been evaluated. For evaluation of weld induced residual stresses, the analysis of heat source fitting was carried out with heat inputs ranging from 200 to 500 J/mm to arrive at optimal heat input for obtaining proper weld penetration and heat affected zone (HAZ). For this chosen heat input, the influence of different weld speeds and powers on the temperature distribution and the residual stresses is studied. The heat source analysis revealed the best choice of heat input as 300 J/mm. The residual stresses on the inner and outer surfaces, and along the radial direction were computed. Increase in temperature distribution as well as longitudinal and circumferential residual stresses was observed with the increase in weld speed and power. The validity of the results obtained from numerical simulation is demonstrated with full scale shop floor welding experiments.

   

اثر عملیات حرارتی در جوشکاری انفجاری فولاد زنگ نزن/مس

Effect of heat treatment on bonding interface in explosive welded
copper/stainless steel

اثر عملیات حرارتی روی فصل مشترک اتصال در جوشکاری انفجاری فولاد زنگ نزن/مس

ABSTRACT

In this investigation, explosive welding and heat treatment processes provided an effective method for manufacturing high-strength and high-ductility copper/ austenitic stainless steel couple. In order to improve diffusion in the interface of copper/stainless steel, first the tensile samples were provided from the welded part, then they were subjected to annealing at 300 C (below recrystallization temperature) for 8–32 h with 8 h intervals and then samples were cooled in the furnace. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to evaluate the possibility of diffusion in the joints. Moreover, in order to measure the hardness of the samples, microhardness test was performed. Microstructural evaluations showed that the stainless steel 304L had a wavy interface. Furthermore, the post heat treatment process resulted in great enhancement of diffusion. Microhardness measurements showed that the hardness of the sample near to the interface is greatly higher than other parts; this is due to plastic deformation and work hardening of copper and stainless steel 304L in these regions. The interface of samples with and without the post heat treatment was exhibited ductile and brittle fracture, respectively.

 

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.

 

اتصال نفوذی آلیاژ مس به فولاد زنگ نزن تحت فشار ناگهانی

Impulse pressuring diffusion bonding of a copper alloy to a stainless

steel with/without a pure nickel interlayer

اتصال نفوذی آلیاژ مس به فولاد زنگ نزن تحت فشار ناگهانی همراه با یک لایه ی نیکل خالص بین آن ها و یا بدون آن

ABSTRACT

Impulse pressuring diffusion bonding of a copper alloy to a stainless steel was performed in vacuum. Using Ni interlayer of 12.5 lm, the joint produced at 825 C under 5–20 MPa for 20 min exhibited lower strength, which could result from the insufficient thermal excitation and plastic deformation. At 850 C under 5–20 MPa for 5–20 min, the strength of the joint improved with time. An optimized joint strength reached up to 217.2 MPa. Fracture occurred along the Cu–Ni reaction layer and the Ni layer and almost plastic fracture was confirmed by extensive dimples on the fracture surface. Using the interlayer of 50 lm, the fracture surface was similar. Without Ni assistance, under the same bonding condition, the joint strength was about 174.2 MPa. The lowered strength might be attributed to the appearance of some unbonded zones in the joint. Lots of brittle fracture areas appeared on the fracture surface.

  

ساختار اتصالات جوشکاری شده فولادهای هاردوکس

Structure and hardness changes in welded joints of Hardox steels

ساختار و تغییرات سختی در اتصالات جوشکاری شده فولادهای هاردوکس (Hardox)

ABSTRACT

In the article, the structure and change in hardness of the welded Hardox 400 and Hardox 500 steels have been presented. It has been shown that structures of lower wear resistance are being created as a result of welding those materials in the “as delivered” state (i.e. with the tempered martensite structure) within the heat-affected zones. They are as much as up to 90 mm wide, and that causes their non-uniform and fast wear in the anticipated applications. Based on microscopic tests and hardness measurements a method of thermal joints treatment has been proposed, consisting in their hardening and low-temperature tempering (self-tempering) at the heat-affected zones. It leads to reproduction of that area structure, similar to the native material structure. In the laboratory conditions, a heat treatment differing from the usual practice (stress-relief annealing or normalizing) has not led to welding incompatibilities (cracks).