The microstructure and mechanical properties of HSLA-100 steel WELD joints was investigated. WELDing with three HEAT INPUT of 0. 820, 1. 176 and 1. 392 kJ / mm was performed using E12018 electrode. Microstructural studies were performed using scanning electron and optical microscopes. The mechanical properties of WELDed joints were evaluated by impact and microhardness tests. Microstructural studies showed that with increasing the HEAT INPUT, the amount of acicular ferrite in the WELD metal decreased and the amount of polyhedral and quasi-polygonal ferrite increased. It was found that with increasing the HEAT INPUT, the amount of layered bainite in the HEAT affected zone increased and the amount of granular bainite decreased. Due to the decrease in the amount of acicular ferrite in the WELD metal microstructure with increasing inlet temperature, the amount of hardness and impact energy decreased. The results showed that the increase in HEAT INPUT due to the reduction of the acicular ferrite of the WELD metal and the dissolution of precipitates in the coarse grain HEAT affected zone has caused a decrease in hardness in these zones. It was found that with increasing the HEAT INPUT due to decreasing the acicular ferrite, the impact energy of the WELD metal decreased by 29% (from 45 joules at an HEAT INPUT of 0. 82 to 32 joules at an HEAT INPUT of 1. 392 kJ / mm). It was found that at all HEAT INPUTs, the impact energy of the base metal is greater than the impact energy of the WELD metal.

Usage in low temperatures causes embrittlement of many structures; consequently, selection of WELDing parameters for maintaining the toughness of WELDed structures is crucial. In this paper, effects of arc HEAT INPUT and WELDing speed on the cryogenic impact strength of type 304L austenitic stainless steel WELD metal are investigated. For this purpose, 304L austenitic stainless steel sheet with 5 mm thickness was WELDed with gas tungsten arc WELDing process and by changing the parameters of arc HEAT INPUT and WELDing speed, the effect of these parameters on the microstructure, WELD metal ferrite content and low temperature, charpy impact energy of samples was determined. The arc HEAT INPUT range applied was between 1.04 and 3.23 kW, and the WELDing speed varied between 30 and 240 mm/min. It was found that increasing arc HEAT INPUT can reduce WELD metal ferrite content, which improves low temperature impact strength, but on the other hand, slow cooling due to increasing HEAT INPUT results in coarser dendritic structures in the WELD metal, and can adversely affect impact strength. Changes of WELDing speed can also affect the amount of ferrite and microstructure and thus have an influence on the impact strength. Finally, having carried out the numerous tests, optimum impact properties at low temperature were obtained at 1.67 kW arc HEAT INPUT and 120 mm/min WELDing speed.

In this study, the effect of WELDing HEAT INPUT on microstructure and mechanical properties of dissimilar joints of API-X42 and API-B pipeline steels was investigated. Evaluation of the microstructures showed that increasing the WELDing HEAT INPUT decreased acicular ferrite in WELD metal microstructure, while amount of Widmanstatten ferrite, polygonal ferrite and grain boundary ferrite increased. Also, results of microhardness test showed that by increasing the HEAT INPUT, hardness of WELD metal and the HEAT affected zone decreased. Tensile test results showed that as the HEAT INPUT increased, fracture transferred from base metal of API-B to the HEAT affected zone. Impact test results also showed that increasing the WELDing HEAT INPUT could sharply drop the impact energy of the HEAT affected zone for both base metals due to extensive grain growth.

In this article, thermal analysis of sheet metals during arc WELDing is studied by an adaptive finite element method to construct a WELDing process simulator. This simulator can be developed to reduce the cost of WELD training. By increasing the calculation speed of HEAT transfer in comparison with the usual methods, this approach analyzes the process in real-time and permits the development of the simulator. So, it can be used as the main calculation engine of a WELDing simulator. The most crucial parameter in evaluation of real-time analysis is the calculation accuracy. Hence an adaptive mesh method based on H-refinement is applied and the HEAT transfer is analyzed by both constant and adaptive mesh methods. First, the HEAT transfer equations will be derived and solved, then the stiffness and capacity matrix and the other parameters will be obtained. The linear 3D tetrahedral elements are used and considered by means of 3 dimensional cartesian coordinates. The HEAT flux of the arc is studied through Pavelic model. The parameters of interest in the equations are WELDing voltage, current, speed and sheet specifications which are time dependant. A comparison between the calculation times and accuracy of the results demonstrates that an adequate calculation speed is achieved without any considerable effect on the accuracy.

In a shell and tube HEAT exchanger, the failure of tube-to-tubesheet WELDs results in high-pressure water jet which erodes the refractory in front of the tubesheet. Finite element method was employed to simulate the WELDing process and post WELD HEAT treatment (PWHT) to find the factors affecting the failure in tube-to-tubesheet WELDments. Residual stresses in two different geometries of tube-to-tubesheet WELDment were calculated through uncoupled thermal-structural analysis. The results showed that the values of residual stresses are higher in HEAT exchanger of site 1 than site 2 due to more WELD passes and geometry of connection. Also, the maximum stress in site 1 occurs at the shellside face of tubesheet while it is on the WELD toe in site 2. High tensile residual stresses, especially in Site 1, reduce the tubesheet life. Therefore, performing an efficient PWHT is vital. The PWHT simulation indicated that the process designed is effective for both sites by reducing the residual stress significantly. In addition, the effect of stress concentration was examined on both sites. Moreover, the stress concentration factor in site 1 is as twice as in site 2 and it is the main reason for more failures in site 1.

In the present study, 5083 aluminium alloy sheets by tungsten inert gas WELDing --brazing were joined to galvanized steel sheets with 4043 and 4047 filler wires. The amount of the WELD HEAT and filler metal type influence the mechanical and microstructural properties of the resultant joint. The results obtained from microstructural observation showed that with equal WELD HEAT INPUT the thickness of brittle intermetallic compound layer for the joint produced with 4047 filler metal was approximately half of that for joint produced with 4043 filler metal. Energy dispersive x- ray spectrometry analysis results showed that the IMCs layer formed in interface of steel-WELD seam consisted of Fe (Al, Si) 3 phase in side of steel and Al7.3Fe1.7 Si phase in side of WELDed seam. It was found that the joint produced with 4047 filler metal exhibit ed higher mechanical resistance of 170 MPa than that produced with 4043 of 120 MPa. The results of x-ray diffraction analysis conducted on the fracture plane showed the presence of Al0.5Fe3Si0.5 phase. Moreover, for joints produced with 4047 filler metal, the FeSi2 phase created from enriching of Si atoms in IMCs layer was seen.

This research deals with the effect of HEAT INPUT on microstructure and mechanical properties of a sheet WELDed joints made of low alloy quenched and tempered steel (AISI 4340). Samples were prepared by manual gas tungsten arc WELDing (GTAW) with the low carbon consumable and also pre and post-WELD HEAT treatment has been applied. Macro etch analysis showed that as the HEAT INPUT increases, the HAZ area widespread. Indeed, the primary austenite grain phase grows up. The microstructure of HAZ consists of bainite and different ferrite morphology. The martensite and ferrite can be seen in the WELD section. The volume fraction of ferrite increases as HEAT INPUT increases. Furthermore, the ferrite morphology changes to acicular ferrite due to reduced cooling rate in the WELD. Tensile strength decreases from 1078 Mpa to 970 Mpa correlatively coarsening in the HEAT-affected zone. Impact energy results vary with HEAT INPUT correspondingly, the toughness increases in the WELD and was reduced in HAZ. However, for conclusion, improved mechanical properties of the WELD joints were achieved using low HEAT INPUT and low carbon consumable.

An experimental study on pulsating HEAT pipe (PHP) is presented in this work. A closed loop PHP with a single U turn is fabricated and tested. The transient and steady state experiments are conducted and operating temperatures are measured. The experiments are carried out for different working fluids, HEAT INPUT and for different evacuation levels. The derived parameters include thermal resistance and HEAT transfer coefficient of PHP. The results of these experiments show an intermittent motion of the working fluid at lower HEAT INPUT. The temperature difference between evaporator and condenser at steady state is found lower for acetone compared to water, ethanol and methanol. Lower value of thermal resistance and higher value of HEAT transfer coefficient are observed in case of acetone compared to water, ethanol and methanol. Lower values of temperature difference between evaporator and condenser and thermal resistance and higher value of HEAT transfer coefficient are observed at atmospheric conditions of operation of PHP compared to evacuation conditions. The Power Spectral Density Analysis is also carried out on the results of these experiments using FFT technique to analyse the pulsating motion of the fluid in a PHP. In the Power Spectral Density analysis, the frequency distribution of temperature variation in PHP was observed over a wider range, signifying the periodic motion in the fluid flow of the liquid slug and vapour plug. This characteristic frequency corresponded to the characteristic time for a couple of adjacent vapour plug and liquid slug passing through a specific local wall surface in a PHP.

In this work the effect of preHEAT and post WELD HEAT treatment on the properties of AISI 4140 steel was evaluated. The Experements were carred out on three different conditions:1-without preHEAT and without post WELD HEAT treatment.2-with preHEAT and without post WELD HEAT treatment.3-with pre HEAT and with post WELD HEAT treatment. WELDing process was SMAW. The effect of preHEAT and post WELD HEAT treatment on mechanical properties was evaluated by mechanical testes such as impact test, tensile test, hardness test and bend test. The changing of microstructure was studied by optical microscope. With preHEAT and post WELD HEAT treatment the mechanical properties of WELD area should be controlled. The post WELD HEAT treatment can improve the fracture toughness.