Comparative Study of Droplet Transfer Modes on Appearance, Microstructure, and Mechanical Properties of Weld during Pulsed GMAW

Droplet transfer plays a crucial role in welding stability and quality of pulsed gas metal arc weld (GMAW), referring to the process of heat and mass transition. In this work, the appearance, microstructure, microhardness, tensile properties, and impact toughness with three typical modes of droplet transfer in pulsed GMAW (ODMP: one drop per multiple pulses; ODPP: one drop per pulse; MDPP: multiple drops per pulse) were studied and compared. The results showed that the better welding appearance, the deeper penetration, and the less fume covered on the steel plate could be found during the ODPP welding process. At the same wire feeding speed and arc length, the average current was similar in ODPP and MDPP conditions. However, the average current in the ODMP condition was about 15 A larger than the other two, contributing to the higher heat input. Compared with MDPP and ODMP, the longest elongation and impact energy of the welded joint were found in the ODPP condition. Furthermore, the decrease of elongation and impact toughness in the ODMP condition might result from the higher heat input and the coarsen microstructure, like the proeutectoid ferrite and ferrite side plate.

Effect of Protective Coatings in Welded Constructions on Welding Stability and Electrode Metal Transfer into a Weld Pool in MMA

The paper presents data of experimental research into the importance of protective surface coatings in welded products for MMA stability; heat field distribution patterns on their surfaces, and structure and phase composition of the welded metal. The study has revealed that a protective surface coating in a welded item in MMA has a positive effect on shortcut duration, increasing it by 5-11 %, raising its formation and transformation time by 10-12 %; 15% dimensional increase of a welded metal grain is registered as well, and a heat impact zone expands by 25%.

Effect of Arc Pressure on the Digging Process in Variable Polarity Plasma Arc Welding of A5052P Aluminum Alloy

The keyhole digging process associated with variable polarity plasma arc (VPPA) welding remains unclear, resulting in poor control of welding stability. The VPPA pressure directly determines the dynamics of the keyhole and weld pool in the digging process. Here, through a high speed camera, high frequency pulsed diode laser light source and X-ray transmission imaging system, we reveal the potential physical phenomenon of a keyhole weld pool. The keyhole depth changes periodically corresponding to the polarity conversion period if the current is same in the electrode negative (EN) phase and electrode positive (EP) phase. There exist three distinct regimes of keyhole and weld pool behavior in the whole digging process, due to the arc pressure attenuation and energy accumulation effect. The pressure in the EP phase is smaller than that of the EN phase, causing the fluctuation of the weld pool free surface. Based on the influence mechanism of energy and momentum transaction, the arc pressure output is balanced by separately adjusting the current in each polarity. Finally, the keyhole fluctuation during the digging process is successfully reduced and welding stability is well controlled.

ANALISA TEKNIS PENGUJIAN KEKEDAPAN PENGELASAN PADA TANGKI TONGKANG DENGAN MEMBANDINGKAN METODE CHALK TEST, AIR PRESSURE TEST DAN VACUUM TEST

PT. Dock & amp; perkapalan kodja nautical ( persero ) shipyard banjarmasin is a company that move in ship industry, development for shipbuilding industry large enough aims to meet the needs of countries will ships as a country maritime .In doing their activities, company got a job as the construction of ships new, work a serviceman a ship etc. The field of that is associated with welding, welding identical also with a flaw and fraud especially on the part affected a serviceman . Testing impermeability a tank were done in order to the examination of the possibility of mismanagement of a connection is welding and why ensure the quality of welds, an adequate number of qualified to leakage in the connection las can be seen from that there was an indication who occuring when testing done in the same manner .There are several a method of testing, and among the companies were a method of lime oil , water test and a vacuum test drives in .Chalk test drives in / lime oil is a method of welding stability testing traditional tank , water pressure test drives in is a method of welding stability testing a tank by the principle of the compressed air and a vacuum test drives in also made use of of the nature of soapy water , only on the implementation of the activity a method of testing is provided by way of an instrument a vacuum box shaped with one of the sides open and one of the sides made from the materials of glass . In the process of testing kekedapan welding a method of the most accurate in a reading of a point to leakage in connection las that is a method of water pressure test/the compressed air with flattened flattened a reading of a point leakage is more than 1 in any its testing. A method of tests need time in at least the process that is a method of vacuum test and water pressure test.Testing first method vacuum test 1.15 hours and water pressure test by 0.47 hours. Testing second method vacuum test 1.30 hours and water pressure test 1.20 hours. Testing third method vacuum test 0.40 hours and water pressure test 0.50 hours. Testing fourth method vacuum test 1.15 hours and water pressure test 1.20 hours. Testing fifth method vacuum test .30 hours and water pressure test 0.37 hours. Testing sixth method vacuum test 1.40 hours and water pressure test 1.30 hours.