nzjetboating Web Board. Forums => Tech Library => Jet Units & Driveline => Topic started by: callan FNQ on August 14, 2013, 10:28:52 AM

Title: crack in intake housing
Post by: callan FNQ on August 14, 2013, 10:28:52 AM

hi fellas
A mate has found a crack in his intake housing on his 770
he has no idea how old it is but its not leaking. its an ex sprint jet so i dare say she's seen a fair bit of load up it over the years.

he wanted to know how well the intake housings take to welding, and what filler rod to use ?

Title: Re: crack in intake housing
Post by: dhs_42 on August 14, 2013, 11:29:27 AM
The castings seem to be really nice to weld. Must be a reasonable quality I guess. I've used 5356 filler wire on them (not sure if its the correct one or not thou - just what we had).
Title: Re: crack in intake housing
Post by: callan FNQ on August 15, 2013, 14:00:22 PM
okay thanks mate will let him know : )
Title: Re: crack in intake housing
Post by: PM on August 15, 2013, 14:06:23 PM
4043 is designed for welding 6xxx series aluminum alloys. It may also be used to weld 3xxx series alloys or 2xxx alloys. 4043 has a lower melting point and more fluidity than the 5xxx series filler alloys, and is preferred by most welders because it "wets and flows better" and it's less sensitive to weld cracking with the 6xxx series base alloys. 4043 can also be used for welding castings. 4043 also makes brighter looking MIG welds with less smut because it doesn't contain magnesium. 4043 gives more weld penetration than 5356, but produces welds with less ductility than those made using 5356. However, 4043 is not well suited for welding Al-Mg alloys and should not be used with high Mg content alloys such as 5083, 5086 or 5456 because excessive magnesium-silicide (Mg2Si) can develop in the weld structure to decrease ductility and increase crack sensitivity. (One exception to this rule is 5052, which has a low magnesium content.)

5356 wire has become the most commonly used of all aluminum filler alloys because of its good strength and its good feed-ability when used as a MIG electrode wire. It is designed to weld 5xxx series structural alloys and 6xxx series extrusions, basically anything other than castings, because castings are high in silicon. Its one limitation is that 5356 is not suitable for service temperatures exceeding 65 degrees Celsius. The formation of Al2Mg at elevated temperatures at the grain boundaries makes the alloys prone to stress corrosion. For components that will be anodized after welding, 5356 is recommended over 4043, which turns jet black when anodized.