Investigation into the hot cracking of filler metals usedin pad welding

The preliminary method, manual TIG padding of GA8 magnesium alloy plates with cast IM rods, and, also, the results of the investigationinto the tendency to hot cracking of eight fillers (filler materials) of different chemical compositions (Table 2) carried out by the Tekken, Fisco, and wedge-plate tests showed that: 1 There exists a range of optimal padding parameters within which the weld has a straight and smooth face with no undercutting (Table 4). With cast welding rods, gas pores may be present in the welds because of the saturation of the rod-metal with hydrogen and oxygen during casting, and, also, because of the existence, on rod surfaces, of difficult to remove impurities; 2 The 8C filler metal, in the form of an extruded rod, 3.2 mm in diameter, did not show a tendency to the generation of gas pores within the weld because the degree of saturation with hydrogen and oxygen was low, and the rod surface was very clean; 3 The Tekken test did not create conditions necessary for the generation of hot cracks in the investigatedfillers which would propagate to the surfaces ofpadding welds. The rigidity of test joints was too low; 4 The lowest tendency to hot cracking was displayed by IM and 8C filler metals of chemical compositions close to that of GA8 alloy; 5 For all of the tested filler metals, the use of the craterfilling method prevented incidence of hot cracking in the wedge-plate test for the current intensity of 200 A, and with the IM and 8C fillers for even the current of 280 A.