[enlpck]

Many materials can be fused without filler. In addition to the stainless and titanium, pure copper, some aluminum alloys, low carbon steel, some copper alloys (brasses and bronzes), and a few others.

Virtually all low carbon can be fused without a problem. A few alloys give problems with cracking, in particular those meant for easy machining. Common hot roll (A36, etc) and cold rolled alloys are fine.

Any stainlesses that can be welded using a matching filler can be fused to the same or similar alloys. Stainlesses that need non-matching filler (reduced carbon, modified alloy chemistry, etc) to avoid cracking, carbide precipitation, and other ills, shouldn't be fused. For example, most of the 300-series alloys can be fused successfully with the proper procedure.

Most aluminums NEED a non-matching filler to control the chemistry in the weld zone, or cracking will occur, and shouldn't be welded without filler.

Etc......


Basicly, if the filler is the same chemistry as the base metal, and there arn't special additives in the fillers (like extra deoxidizers, trace elements to refine the melt, etc), fusing is fine, and the weld will have the same properties as if welded with filler.

Cleanlinedd is MORE important than when using filler, as most fillers will have a small amount of additive to deal with trace impurities in the weld. Clean is critical for TIG. Cleaner yet is needed for fusing.

 

[enlpck]

Not a metallurgist (sp?). Just an (oh no, here comes the admission of guilt) engineer. (ducks to avoid the pitchforks. I don't mind the torches, but the pitchforks sting )

I do a bit of many things: hold current papers (ASME shop) for GTAW and SMAW all positions (1G through 4G, didn't bother with small pipe 6G as we have other people that can do it better), am the engineer for pressure vessel repair, assist our level-3 on NDE (learning a lot, don't know much yet), do job planning (despite the best efforts of the powers that be to thwart any plan), do diesel and heavy equip maintainance when needed, electrical work when needed, am a satisfactory machine operator when pressed (not machinist, but I have cut 48TPI on 0.040 wall tubing), and am still skinny enough, barely, to go through a small manway to drive pins and buck rivets. Been getting away from some of this as other people sign on that are more qualified to do some of this... I'v even had a few weekends off in the last six months! Oh, and I teach engineering (been doing that for 15 years).

 

[enlpck]

You could fuse it, though I wouldn't. Typical applications for fusing are thinner pipe, like stainless process pipe in a brewery, sheet metal joints, etc. Usually butt welds or lap welds (where you can melt the corner down). They are a special purpose type weld.

I would have no qualms about tacking without filler, but unless you want to spend some time doing practice welds and cutting them apart to be sure you are getting sufficient penetration, and want to do the welds from both sides, I would use filler for the final welds. It is tougher to get a good weld fusing.

Experiment, and you'll see a) how easy it can be, and b) how tough it can be to get consistant, quality welds this way.

 

[enlpck]

Whoops.... I should have caught the misuse of terminology. I'm so used to seeing and writing "fuse with no filler" in procedures, I didn't even think about it. Half the people I have worked with would ask "who's Otto, and whys he so smart?" or tell me not to talk dirty is I said 'autogeneous'

tresi: not an impressive resume. You do what you need to do. I'd rather work than take vacation, and take what opportunities I can to build skill. I look at times when I'm not teaching as opportuities to do something different, and don't tend to take jobs that are just for the cash- I'd have more money if I did. I prefer to do something interesting and, if possible, a little different. Just because someone else can do something better doesn't mean I can't learn to do it well enough.