Showing 9 results for Mostaan
Dr M. Safari, Dr H. Mostaan,
Volume 1, Issue 1 (Journal OF Welding Science and Technology of Iran 2016)
Abstract
Weldability of high carbon steels due to the high percentage of carbon and consequently formation of martensitic structure is very poor. In this research, resistance spot welding of eutectoid high carbon steel 1075 is experimentally and numerically investigated from various points of view. The effect of welding current as one of the most effective parameters on failure mode, mechanical properties and nugget size diameter in resistance spot welding is analyzed with experimental tests and numerical simulations. The results show that with increase of welding current, the diameter of nugget size is increased and consequently the failure mode changes from interfacial mode to pull out mode.
M. Safari, H. Mostaan, A. Bakhtiari,
Volume 2, Issue 1 (Journal OF Welding Science and Technology of Iran 2016)
Abstract
In this research, lap joint frictionstir welding of IF sheets with thickness of 0.7 mm is investigated. For this purpose, mechanical properties of joints and also microstructural evolutions are studied. It was found that increase in tool rotational speed and decrease in travel speed results in increase in fracture stress of welded joints. Texture study indicates that no changes can be observed in texture components after friction stir welding. This phenomenon in texture components can be related to high stacking fault energy of IF steel and consequently severe dynamic recrystallization during welding. The results show with increase in the tool rotational speed between 900-1400 Rev/min, ultimate force of fracture of friction stir welded joints is increased. Also, it is concluded from results that with increase in tool travel speed between 50-160 mm/min, ultimate force of fracture of welded joints is decreased. Finally it is proved from results of this paper that in the frictionstir welding of IF sheets with thickness of 0.7 mm, maximum force of fracture of welded joints is achieved in rotational speed of 1400 Rev/min and travel speed of 105 mm/min.
M. Safari, H. Mostaan,
Volume 2, Issue 2 (Journal OF Welding Science and Technology of Iran 2016)
Abstract
In this paper, resistance spot welding process of AISI 201 stainless steel is studied experimentally. For this purpose, effect of welding current on quality of weld is investigated and relationships between welding current and fusion zone characteristics are examined. For determining mechanical properties such as maximum load and fracture mode, tensile - shear test of spot welds is performed. Hardness and microstructural examinations are performed for study the influence of welding current on characteristics of welded joints. The results show that strength of resistance spot welds of AISI 201 stainless steel is increased with increase in welding current. Transition of fracture mode from interfacial to pullout and then pullout with tearing of sheet mode during tensile-shear tests of AISI 201 spot welds is investigated through experimental and theoretical approaches. It is concluded from results that increasing in welding current leads to change in fracture mode from interfacial to pullout mode due to increase in fusion zone size (weld nugget size). Also, it is observed that increasing in fusion zone size is accompanied by an increase in load carrying capacity of resistance spot welds. The minimum required fusion zone size to ensure pullout fracture mode is estimated using an analytical model.
H. Mostaan, M. Safari, A. Sonboli, M. Haddadi, A. Taherkhani,
Volume 4, Issue 1 (Journal OF Welding Science and Technology of Iran 2018)
Abstract
In this paper, numerical and empirical investigations of the effect of AISI 347 stainless steel interlayer on the microstructure, mechanical properties and fracture mode of AISI 321 stainless steel resistance spot welds have been conducted. For this purpose, two types of joints, the first free from inter layer and the second contains interlayer with 0.05 mm thickness as well as difference currents and times,were evaluated. In order to examine the mechanical properties including maximum force and tensile mode, tensile – shear test of the spot welds was done. The obtained results indicated that an increase in the welding time and current resulted in a change in fracture mode from interfacial to peripheral owing to an increase in fusion zone volume. The change in the chemical composition because of the presence of interlayer and an increase in cooling rate caused the formation of different phases as well as observation of the dispersed Martensite phase in fusion zone.
M. Gholami, H. Mostaan, A. Sonboli, ,
Volume 4, Issue 2 (Journal OF Welding Science and Technology of Iran 2019)
Abstract
In this research, gas tungsten arc welding of dissimilar joint between 4130 low alloy steel and AISI 201 austenitic stainless steel was investigated. Four filler metals i. e. ERNiCr-3, ER 309L, ER 308L and ER 80SB2 were used. After welding, microstructural features of various areas and also fracture surfaces were examined using optical microscopy and scanning electron microscopy. Tensile test was conducted in order to study the mechanical properties of each joint. It was found that ERNiCr-3 is fractured from fusion zone and the others were fractured from 4130 base metal. Also, some second phase particles such as NbC were seen in the ERNiCr-3 weld joint. SEM observation showed that the fracture behavior of ERNiCr-3 weld joint is semi brittle and the others are ductile. The fusion zone of ERNiCr-3 weld joint was fully austenitic and consisted of equiaxed grains and no crack was seen in this area. The fusion zone of ER 308L and ER 309L were composed from cellular dendrite and finally ER 80S-B2 weld joint was consisted of lath martensite.
M. Emadi, H. Mostaan, M. Rafiei,
Volume 5, Issue 2 ((Journal OF Welding Science and Technology) 2020)
Abstract
Dissimilar weld joints between stainless steels and nickel based super alloys are extensively used in petrochemical, gas and oil applications. These joints jave great challenges from metallurgical transformations point of view. In this research, microstructural evolutions and corrosion behavior of laser weld joint between Inconel 625 and AISI 430 ferritic stainless steel were investigated. Ferritic stainless steels are less expensive and have magnetic properties in comparison with austenitic stainless steels. Scanning electron microscope and optical microscope were used in order to study the microstructures of weld metal and heat affected zone. It was found that fine dendritic microstructuresare formed in the weld metal which isgrown in a competition manner. An epitaxial growth was observed in the interface between AISI base metal and weld metal. No considerable grain growth was observed in the heat affected zone on Inconel 625. Corrosion resistance of weld joint was investigated in 3.5 % wtNaCl solution using potantiodynamic polarization test. It was concluded that corrosion resistance is increased from AISI 430 base metal toward Inconel 625 base metal.
M.r. Samadi, H. Mostaan, M. Rafiei , M. Salehi,
Volume 6, Issue 1 (Journal OF Welding Science and Technology 2020)
Abstract
Nowadays, aluminum and its alloys have extensive applications in marine and aerospace industrious owing to their excellent properties. Among these alloys, 5xxx series of aluminum alloys have also excellent corrosion resistance, high toughness and strength and also good weldability. Decrease in yield strength and also tensile strength due to the grain growth in the heat affected zone is of the main problems in the welding of these series of Al alloys. In this research work, gas tungsten arc weld joints in two modes i. e. direct current and pulsed current were compared in order to study the effect of this parameter on the microstructure, mechanical properties and corrosion resistance of weld joints. Also, the effect pulsed current parameters such as peak current and basic current were investigated. Microstructural evolutions and fracture surfaces of weld joints were examined by optical microscope and scanning electron microscope, respectively. It was found that the fracture behavior of all joints is in a ductile manner. Also, tensile test and electrochemical polarization were conducted in order to study the mechanical properties and corrosion behavior of weld joints.
M. M. Taghvaei, H. Mostaan, A. Sonboli, H. R. Mansouri Gavari,
Volume 8, Issue 1 (Journal OF Welding Science and Technology 2022)
Abstract
In this study, DIN 34CrAlNi7 Nitriding steel in two states before and after nitriding, were welded by tungsten-gas arc welding process using two types of fillers (ER309L and ER312). The aim of this research was to investigate the best conditions for welding (before or after nitriding) and also to choose the best filler metal. The microstructure of the joint was examined using an optical microscope. A tensile strength test was also used to evaluate the mechanical properties. Fracture surfaces were also studied using a scanning electron microscope (SEM). According to the results Welding of these steels with ER309L filler is allowed only in the pre-nitriding state. If the base metal is nitriding, due to microstructural changes in the weld metal, filler metal ER309L cannot be used. However, the results of samples welded with ER312 filler metal show that if the base metal mixing percentage is less than 30%, this filler can be used for welding base metals in both before and after nitriding.
M. M. Taghvaei, M. Shamanian, Behzad Niroumand, H. Mostaan,
Volume 8, Issue 2 (Journal OF Welding Science and Technology 2023)
Abstract
Joining of Hastelloy C276 nickel-base superalloy to AISI316 Stainless Steel using BNi-2 interlayer performed by transient liquid phase process (TLP) at 1150°C for 5 and 30 minutes. Bonding microstructure was studied using an Optical microscope and a scanning electron microscope (SEM). Vickers hardness test and shear strength test have been used to evaluate the mechanical properties. Microstructural studies showed that at 5 and 30 minutes of bonding time, isothermal solidification is completely formed, and the Center of the joint is free of any eutectic intermetallic compounds. Also, Findings showed that the DAZ of Hastelloy C276 nickel-base superalloy contains rich borides of Ni, Cr, Mo, and W, and the DAZ of 316 austenitic stainless steel contains borides rich in Fe, Cr, and Ni.
