MIG Welding of JIS A2P7 Aluminum Alloy

Abstract

In the U.S.A. the modified aluminum alloy filler metals such as 5183, 5356 and 5556 have been developed for welding Al-4-55/, Mg base metals so that they may have their own uses for the spe cified base metals as seen in the examples of 5183 filler metal to 5083 alloy and 5556 filler metal to 5456 alloy, though in some cases they seem to be handled as a group because of their approximately equal Mg contents, while in the U.K. and Canada only NG 6 and Alcan 56S filler metals are available respectively for welding these base metals.
This study has been made to compare the properties of welds in JIS A 2 P 7 (A. A. 5083, B. S. N5/6) alloy made with 5083, 5183 (only for cracking test) 5056, Alcan 56S, AWCO NG 6, 5356 and 5556 filler metals.
The results obtained are summarized as follows.
(1) The chemical analyses of the deposited metals made on 99.85% Al plate showed that Mg loss increased with welding current and seemed to be affected by arc voltage. Mg loss estimated from weld metals in A 2 P 7 alloy made with various filler wires was 5 to 8 % of the Mg content in the wire. Regarding minor alloying elements, Ti seemed to be lost, but no Mn and Cr losses occurred.
(2) The fish-bone cracking tests for A 2 P 7 and A 2 P 1 (A. A. 5052) alloys indicated that A 2 P 1 was apparently more susceptible to cracking than A 2 P 7 alloy, but the cracking suscepti-bilities in both alloys were little affected by the filler rods used. Whether Ti is of any significance or not for cracking sensitivity remains to be investigated.
(3) There was little difference in the gas contents between the mechanically finished AWCO NG6, as well as the gas contents of their weld metals. Therefore, it is difficult to point out which type of filler metal is more desirable. But the chemically finished filler metals excet NG 6 contained a large amount of gases. This means that care should be taken in performing the chemical clea-ning method.
(4) The total gas and hydrogen contents of filler metals reduced to 4.82-6.49 cc/100 g and to 1.35-2.33 cc/100 g in the weld metals respectively. These values of gas contents had no effect on the X-ray grade porosity.
(5) The tensile and bend tests, and hardness measurements of the welded joints showed no differences in the results obtained with various filler metals.