Advanced Materials Research Vol. 1157

Abstract: Dissimilar metal welding (DMW) is frequently used to join stainless steels to other metals in Thermal Power Plants (TPP) and industries. DMW process has been shown to have great advantages for many years. This approach is most often used where a transition in mechanical properties and/or performance in service are required. The objective of this research is to review the basic principles of fusion welding of dissimilar metals.In experiments, the two seamless pipes with 18 mm thick, one modified SS 304L austenitic stainless steel was welded to another modified carbon steel A 106B by means of shielded metal arc (SMAW) and gas tungsten arc (GTAW) welding processes using ER309L and E 309L-16 type of filler metal. Before welding, essential variables were analysed so that creating preliminary welding procedure specifications (pWPS). After welding, weldment was tested by NDT such as visual, penetrant and radiography. Microstructural examinations were carried out including macro and micrographs, grain size analysis, and hardness measurements. Transverse tensile, and face/ root bend testing were carried out. Finally, WPS was established conformance to standards of TPP structure toward to building Nuclear Power Plant in Vietnam.

Abstract: This paper contains results of tests performed in order to determine mechanical properties of steel P460NL1, used as filler material during the execution of welded joints. Arc welding of samples from which the specimens were taken was carried out through the application of welding process 111, because it is one of the processes for the execution of pipelines for pressure equipment. Microspecimens with diameter of Ø1,5 mm were tested in order to determine tensile properties of material taken from the heat-affected zone and weld metal, while specimens with diameter of Ø6 mm were tested in order to determine tensile properties of parent material. Standard Charpy V-notch specimens were used in order to determine impact energy. Results of metallographic tests which refer to the structure of a pipe welded joint are also presented.

Abstract: The paper proposes the analysis of an alternative technology for manufacturing deodorant roll-on balls of polypropylene. With the current extrusion-blowing technology, the manufacturing of these balls results in an uneven wall thicknesses and a large technological runner of material that needs to be grinded and reintroduced into the injection equipment, which involves additional raw material and energy consumption.The proposed alternate method of manufacturing these balls (as spherical objects) is to form the ball from two ball halves joined together by infrared radiation welding. This process will result in significant savings in raw materials and energy.Further improvements of dimensional capabilities and control of welding parameters are required prior the transfer on high productivity manufacturing lines. Additionally, this technology can be assimilated into other applications where hollow balls of plastic are used.

Abstract: The paper presents the assembling flux of thermocouple-instrumented nuclear fuel element for research reactor, from the point of view of the welding / brazing engineer, considering nuclear quality and safety requirements: fuel element structural reliability (no radioactive leaks through joints) and temperature signal reliability (thermocouple sheath integrity), this signal being an essential parameter for reactor normal operation and emergency shut-down. The paper is a real case study for an experimental instrumented element recently developed at INR-Pitesti describing technology choices as balance between fabrication complexity and risk of failure in joining processes, especially in later stages when added value increases. All joints (welded or brazed) fall into microjoining category, and it is shown how some special provisions may influence reliability. Focus is put on brazing thin-walled Inconel sheathed thermocouples, where erosion and local loss of ductility are known issues, leading to sheath rupture. Choosing as filler the less aggressive BNi-9 helped too little. A simple but efficient technique has been developed to address this matter adequate to narrow spaces inside a nuclear fuel element, where no room is available for solutions described in literature e.g. distal preplacing of filler. The solution prevents sheath from having prolonged contact with large volume of molten filler by using locally a miniature barrier (thin stainless-steel coil or sleeve) which only allows capillary wetting, being also a perfect real-time visual indicator of brazing progress and completion. As proved in the present paper, this method along with using filler formulation with lower Carbon content (without organic binder) enhances significantly, 8 times at least, resistance to bending fatigue. A particular vacuum brazing chamber design is employed: narrow quartz tube with external induction coil and top fitting letting outside the long thermocouples attached, reducing much the chamber volume and degassing. Careful impedance match is therefore required to overcome induction power loss due to the larger coil-to-workpiece gap. Additional joining problems are discussed e.g. inherent differential expansion of long parts during induction heating which afterwards may put tension upon braze during solidification and determine delayed cracking, this being avoided through wise order of operations. Another concern is the final precision weld between instrumentation segment having attached the hard-to-handle long thermocouples bunch and nuclear segment with the heavy Uranium pellets. The result of this research is successful assembling of first Romanian prototype with joints exhibiting He leak rate bellow 1E-09 std.cc/sec and overall reliability proved during reactor irradiation testing.

Abstract: Experiments have been performed for the butt welding of 160 mm x 90 mm x 2 mm sheets of EN AW 5754 aluminium alloy, where the friction stir welding (FSW) has been used.Referring to the parent metal, the chemical composition and the form of wrought products of the aluminium alloy EN AW 5754 is presented, according to the standard EN 573-1:2005, respectively EN 573-3:2013. The mechanical properties of EN AW-5754 (Al Mg3) sheets are presented, according to EN 485-2:2016. The experiments have been conducted on the own equipment for friction stir welding, type FSW-4kW-10kN, to execute 8 (eight) FSW test pieces, according to EN ISO 25239-4. A quenched FSW tool, own-made of C 45 grade steel, EN 10083, has been used. The parameters of the FSW tests are shown. As main parameters, the rotational speed of the FSW tool was in the range n = 800 – 1200 rev/min, respectively the travel speed was in the range v = 50 – 200 mm/min. The run of the joining experiments is described and the joining test pieces are presented in figures. The ultimate tensile strength of the parent metal (σ_min,pm) is based on the specified minimum tensile strength of the ”O” condition of the parent material, respectively this value is also required for the weld, that is σ_min,w = 190 MPa. The specimens T1.0, T1.1, T2.1, T2.2, T3.1, T3.2, T4.1, T4.2, T5.1, T5.2 și T6.1 are adequate and accepted by this tensile test. The specimens T1.2, T6.2, T7.1, T72. and T8.1 can be accepted, if higher properties are achieved with a full postweld treatment. Another possibility is a lower extent of the minimum tensile strength of the weld that shall be in accordance with another design specification, for example σ_min,w = 145 MPa. By the correlation of the FSW parameters with the results of the tensile test, the ranges for the main parameters with adequate values of the ultimate tensile strength are established: n = 800 – 1000 rev/min and v = 50 – 100 mm/min. By the conclusions, the main aspects of the execution of the FSW test pieces, as well as the results of the tensile tests are selected. The involved industrial areas of the applications are: electro-technique, electronics, manufacturing, shipbuilding and automotive industries. The FSW process is ecological, because it neither uses, nor produces hazardous substances. The references consist of 12 titles.

Abstract: Inconel 718 is a very difficult metal for machining because of its high plasticity. Lately, more and more researchers are interested in using it for cavitation parts, such as the plugs and drawers of the valves. For this purpose, thermal volumetric treatments have been initiated to facilitate mechanical machining, aiming simultaneously to obtain good compression and cavitation resistance results. Therefore, this paper presents the results of cavitation erosion behavior and cavitation resistance of ICONEL 718, subjected to two thermal treatment regimes, differentiated by the duration (temperature 800 °C and residence times 5 hours, and respectively 10 hours). The assessment of the cavitation resistance provided by each heat treatment regime is based on the average durability cavitation parameter, as defined by K. Steller. The research is achieved by using the standard vibrator device with piezo - ceramic crystals from the Cavitation Laboratory of the Politechnica University of Timisoara.

Abstract: Among the uses of stainless steel GX5CrNi18-10 one mentions the hydraulic machine blades and the rotors, which are highly susceptible to cavitation. To achieve a long life service under cavitation conditions, the pieces made of this steel are subjected to volumetric thermal treatments, which change the structure and mechanical properties. In this paper, one presents the results of the research concerning the behavior and the resistance to the cavitation erosion of the thermally sensitized GX5CrNi18-10 stainless steel, applying four different temperature regimes (two at 650°C and two at 750°C) and different durations (30 minutes and respectively 60 minutes). The results are presented in the form of cumulative mass loss curves M (t) and erosion rate v (t). The assessment of the cavitation resistance provided by each heat treatment regime is based on the average durability cavitation parameter, as defined by K. Steller. The research was conducted on the standard vibrator with piezo-ceramic crystals from the Cavitation Laboratory of the Politechnica University of Timisoara.

Abstract: Ultrasonic welding is a fast and economical solution for plastic parts. This article proposes Ultrasonic Welding as an alternative technology for manufacturing deodorant roll-on plastic balls. With the current technology, the manufacturing of these balls results in an uneven wall thicknesses and a large technological runner of material that needs to be grinded and reintroduced into the injection equipment.The proposed method of manufacturing these deodorant balls is to form the ball from two ball halves joined together by ultrasonic welding. This process will result in significant savings in raw materials and energy.Further improvements of welding parameters and dimensions are required prior the transfer on high productivity manufacturing lines. This technology can be assimilated into other applications where hollow balls of plastic are used.

Abstract: In this paper, heat affected zone characteristics of DP1000 steels was investigated during diode laser beam welding (LBW). A butt-welded joint of specimen in dimension of 300 x 150 mm each (according to EN15614-11:2002) with 1 mm thickness is used for the experimental purpose. The welding thermal cycle and the cooling circumstances in the HAZ was determined by real experiment and the physical simulation. A Gleeble 3500 thermo-physical simulator was used to physically simulate the coarse grain heat affected zone (CGHAZ) on the base material specimens by the utilization of the thermal cycles for t_8/5 =2.5 s. The results of the physical simulation were validated by real welding experiments. The properties of the simulated and the real HAZ was examined by optical microscopic, scanning electron microscope and hardness tests.