Papers by Keyword: Heat Input

Abstract: Nowadays the most perspective, high-tech and productive process is friction stir welding. The most important part of this technology is to determine the temperature of the material in the stir zone. This parameter is easily counted by the amount of the heat input, put in the welding zone. We made experimental researches about the relation of the heat input, therotation speed and thediameter of the working tool. For that purpose an experimental scheme was chosen, which models a welding material (aluminum alloy AMg5) as an experimental tube 20 mm in diameter. The tool (shear steel P6M5) is modeled as a working plate. Measurements of the frictional moments depending on the rotation speed of the experimental working tube during the constant temperature are made on the prepared stand. By the experimental data the specific heat input and the heat power were counted on every concentric ring, 2 mm in width, in the end of the working tool, 20 mm in diameter. Also, the sum of the heat power for the whole tool during various rotation speed terms was counted too. On the stand throughout the experiment were determined all the thermal conductivity heat losses along the rod, which the experimental tube was pinned on, all the working plate heat losses through the gasket towards the working desk and the convection from the surface of the rotating experimental tube to the environment. According the data, any of these losses is from 3 to 10 percent. This is shown in the heat input counting.

Abstract: The reactions of the base material, during the welding process, consist in chemical composition, volume, structure and granulation changes. There are multiple problems which can occur by welding two steels with totally different chemical composition, i.e. carbon steel S235JR + AR and austenitic stainless X2CrNiMo17-12-2. The process used for making the heterogeneous joint was flux cored arc welding (FCAW), numerically coded 136. The paper presents the effects of welding through heat input, on the structural characterization of welded seam and heat affected zone. It also focuses on the structural characterization of the welded joint obtained using the flux cored wire T 23 12 L P C/M 1, and determining how the base materials participate at the formation of the welding joint.

Abstract: Two kinds of industry trial X90 pipeline steels which have different chemical composition were chosen as test objects, and the grain coarsening, microstructural characteristics and the variation rules of low-temperature impact toughness in weld CGHAZ of this two steel under different welding heat input were studied by physical thermal simulation technology, SEM, optical microscope and Charpy impact tests. The results showed that the microstructure in weld CGHAZ of 1# steel was mainly bainite ferrite (BF) and most of the M/A constituents were blocky or short rod-like; the grains of 2# steel were coarse and there was much granular bainite (GB). Meanwhile M/A constituents became coarser and their morphology changed from block to long bar; alloy content of X90 pipeline steel under different weld heat input had great effect on the grain size of original austenite. When heat input was lower than 20KJ/cm, the impact toughness in CGHAZ of lower alloy content pipeline steel was good; as heat input increased, impact toughness in CGHAZ of 1# steel increased to the values between 260J and 300J when heat input was between 20KJ/cm and 25KJ/cm and the dispersion of impact energy was small. The impact toughness of 2# steel decreased gradually and the impact energy had the obvious dispersion.

Abstract: Aluminum alloys exhibit poor weldability by conventional fusion welding process. The heat treatable aluminum alloy AA2014 is extensively used in the aircraft industry because it has good ductility and high strength to weight ratio. In this paper the effects of welding parameters and tool profile on the mechanical properties of friction stir welded butt joints of dissimilar aluminum alloy sheets AA6082 and AA2014. The process parameters such as rotational speed, transverse speed and axial forces were considered. The effect of parameters on weld quality was analyzed. Hardness and tensile tests are carried out at room temperature to examine the mechanical properties of the welded joints. The joints produced with straight square tool pin profile have higher ultimate tensile strength, whereas the straight cylindrical tool pin profile results in lower tensile strength.

Abstract: The paper explores laser welding of high-strength CP-W^® 800 steel and forged steel. Dissimilar welds were produced with different welding parameters. Two welding beam diameters were used. The microstructure and mechanical properties of the resulting welds were examined. Metallographic sections were prepared and microhardness and tension tests were carried out. Fatigue tests were conducted on the weld specimens to map the effects of welding parameters on the fatigue behaviour of the dissimilar weld between the CP steel and the forged steel. Greater amount of heat input impairs the strength of the joint but improves its resistance to initiation of fatigue cracks.

Abstract: A series of experiments have been done to evaluate the way an electrode wire feed affects residual stresses in welded joints. It was found that an electrode wire pulse feed combined with shielding gases decreases residual stresses up to two times in comparison with welding with a continuous feed of an electrode wire.

Abstract: This paper presents an investigation on the influence of varying heat input during friction stir welding of Ti6Al4V alloy, with respect to static and dynamic joint integrity. Weld heat input was controlled by varying the rotational-and tool travel speed. In the absences of large defects the welded samples failed predominately in the parent plate, while percentage elongation for all welds was lower than that of the original material. To quantify the influence of joint geometry on dynamic joint integrity, the test samples were categorised into “as-welded” and “polished” conditions for ease of comparison. Welds done at medium heat input exhibited improved fatigue strength in both conditions, while crack initiation sites for the as-welded condition was predominantly from tool shoulder marks whereas the polished sample initiation sites could be mainly linked to subsurface defects in the weld nugget. The relationship between welding tool geometry, weld defects and-process parameters is also discussed in an attempt to identify interrelationships that could be linked to joint integrity.

Abstract: 316LN stainless steel is a material with excellent mechanical properties, good resistance to intergranular corrosion and good weldability, and it has been used in many fields of industry. Welding quality has great influence on the strength and corrosion resistance of weldment. In this study, one group of submerged arc welding and three groups of shielded metal arc welding were taken to study the influence of heat input on grain size in the structure of 316LN welded joints. The results show that the microstructures of the weld zones in experiment were all consist of austenite and a small amount of banding or dendritic δ-ferrite and the amount of ferrite decrease with the increase of heat input. It also can be concluded from the experiment that with the increase of welding heat input the grain size of overheated zone decrease.

Abstract: Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

Abstract: The article describes a method of increasing the efficiency of heat energy. The method is based on installation of heat metering system and automatic controlled domestic heating plant in residential building. An example of comparative calculation of the heat input and estimation for heat energy in a typical residential building, according to different methods which are used for the calculation of extra charge by the energy supplier, in the presence of the heat metering system and automatic controlled domestic heating plant and without. Calculated payback period of the proposed activities.