MIG questions

[Moe]

My MM210......

I purchased a MM 210 with the spoolgun package a little over a month or so, mainly for welding marine aluminum. Neither me or my son has had any experience with welding aluminum before, so we rounded up some scrap and went to practicing.

About a week ago, we cut out some padeyes from 1/2" alum. plate. I needed to weld these to sch 80 alum pipe on my trawler. We used .035 wire. The welds looked perfect, but were not. As soon as I placed some considerable stress on the welds when lifting the trawl frames, the padeye popped off of the pipe like it was attached with cheap glue. I did backup the padeye with 1/4" SS cable as I do on all of my high stress areas as an added measure of safety. This time it came in handy as the 6 lb. SS pulley did not come off of the frame and blow through the cabin. At that point it was obvious that we had a serious lack of penetration on both of these welds. The first thing I thought was that I didn't have enough machine to achieve what I needed. I assumed wrong again.

A friend of mine was there when this happened. He has experience with aluminum welding. We went to the bench and he proceeded to instruct my son on the proper way to achieve good penetration when welding aluminum pieces with different thickness. My son test welded a piece of scrap 1/2" plate to some scrap pipe using his technique. The machine was set at a wire speed of 62 and 6 on the voltage (we find that the 7 setting instantly destroyed the contact tips). We also had the argon purge at max.. I locked the plate in a huge vice and tried to knock the piece of pipe off with a 5 lb mall and couldnt do it.

This evening we'll attempt to re-weld the padeyes back on the boat. Hopefully, I'll be catching shrimp tomorrow instead of thinking about catching shrimp.....

[HAWK]

Moe,

What did you do different? How did you get the necessary penetration?

[Moe]

When we originally cut and shaped the padeyes, the plate was not beveled, but shaped in a concave fashion to fit up to the pipe. Our thinking was that this would give us more surface area and a better end result. That was the first wrong assumption.

The second mistake was using a higher than needed wire speed. After the first thin pass, all we did was pile up aluminum, thinking we were tying in to both the pipe and the plate.

To correct it, we beveled the padeyes into a "V" and ran a thin root pass on both sides at a lower wire speed. From there we ran 2 additional passes, one concentrating the bulk of the heat on the plate and bringing it back to the pipe. We could see the plate "melting" and forming good fusion with the weld metal. The second pass concentrated more on the pipe, then overlapping the weld from the second pass. This method built up a pretty thick finished weld, but it is definitely much stronger than the first attempt...

I still backup these points with SS cable. Being caught in the water waiting for assistance with a trawl frame stuck in the down position because of a broken weld is not my idea of a good time.

If anyone has any better suggestions or ideas in welding 1/2" Alum plate to sch 80 alum. pipe with a machine like the MM210, please let me know your technique. I take constructive critisizm very well. Thanks in advance.