Hi all, I just finished welding a frame for a minibike and noticed that some of my welds are shiny and others are dull. I'm using tig DCSP,
18 cfh pure argon, ars702 filler rod on 4130 to mild steel. What can I do
to improve this or be more consistent. Thanks,
O. Sanchez
Heres a guess
This is probably related to gas shielding. Some welds may heat the
based metal more or take longer. When you complete the welds the gas shielding may be stopping before the welds have cooled enough.
A little more gas flow with a gas lens and a large cup may help.
I'm not real experienced with GTAW on lightgauge tubing soo someone else may have some better info.
Have a nice day.
Gerald Austin
Hi All!
I agree with Pipewelder on this one!, always use a gas lens whenever possible!The bigger the 'cup the better! Make sure you don't withdraw the wire before it's had time to cool whilst still under the protection of the 'Gas', other wise it'll oxidise and next time you put it into the weld pool, you'll 'contaminate' the weld with oxides!!
If you do get a 'lens' and larger cup, make sure you increase gas flow accordingly!
the reason why that is happening is because when you are making fillet welds your shielding gas is contained and your getting good gas coverage. In some of those tight angles you might have bad gas coverage. Lucky for you it's a carbon steel and you CAN make good welds with a smaller cup!
At one time I made thousands of small airplane motor mounts out of 4130 steel. I used a #5 cup for every weld. 90% of the welds were dull looking in appearance. That has little to do with quality of welds.
As long as your welds are tied in good and there is no porosity then you don't have much to worry about.
Magnetic particle is a great way to inspect weld quality.
A large "gas lens" is not the answer. Steel sometimes pops and berries will stick to the screen and mess up your coverage. You also can't get into tight spots with a gas lens. You would have to compromise gas coverage with tungsten length.
Try sandblasting your welds and take another look at them.
As has been mentioned, gas coverage is very important. But tell me, are you wire brushing your welds when you are done?
The "dull" looking welds sure sound like high temperature oxidation(the weld and base metal were still hot enough for high temperature oxidation to occur when the shielding gas was removed, resulting in a scale over the weld and adjacent base metal)
Try wire brushing both shiny and dull looking welds, and see if they don't look the same after brushing. If they do, then I wouldn't worry about it. After all, your probably going to paint the frame afterwards, aren't you?
Hope this helps,
Dale Simonds
I also have to agree with pipewelder and rodofgod. Your best chance of gas coverage is to use a gas lens and preferably the larger the better.
I'm currently using one more like those used for titanium for the best results. It has a nozzle 3/4" in diameter and leaves my 4130 welds all shiney with good colour. I weld 4130 every day on lots of small diameter tubing junctions on sprintcar chassis' and I've found that gas lenses give far better results than normal ceramic nozzles. As for gas flow I don't bother changing the flow, just so that I get between 7.5 litres/minute and 9.0 litres/minute but this is measured at the torch and that's very important! What you set your flowmeter at the bottle has very little relationship to what you get at the torch, so measure your gas flow at the nozzle.
I also use this large gas lens for stainless steel and the results are outstanding. Provided you have adequate post flow the welds are either straw coloured or silver with no trace of blue.
Regards Andrew.
Several opinions here, so I’ll chime in too.
Gas lenses are nice, and can be of benefit when *unbrushed* weld bead appearance is a factor, Oxide discoloration in both carbon steels and stainless steels have NO effect on the mechanicals and are acceptable according to AWS D17.1 (Table 6.1). In fact, when I see a shiney top on a GTA weld on 4130 at thicknesses greater than 0.050 I suspect a cold weld.
If the joint is multi-pass I would remove the oxide before subsequent passes.
My preference is to use gas lenses in groove and surfacing welds and standard cups in fillets. The extra coverage gained in the groove welds is nice but in tight fillets and awkward positionings I like to see what I’m dong and this is best accomplished with a small standard cup. 6AL makes the valid point that often with gas lenses you must increase the stickout to get the electrode where it ought to be thus risking contamination.
Gas flow is important. With a small standard cup you can run from 10 to 15 cfh, any more and your just going to suck air into the weld zone.
With some gas lenses you can run up to 30 cfh or more. I like these for Titanium groove welds.
could be something simple like one weld you make you might be moving faster while adding more rod thus getting a shiny weld vs the next weld you may be moving slower and not adding more rod thus getting the weld too hot. I like to pull my rod out of the hot zone in between dips when I weld because it seems to add a much cooler puddle to my weld vs leaving your rod right next to the puddle. I am a 10 year tig welder of industrial coils (304 SS and 316 SS .049wall) so I am by no means an expert with 4130 Moly but I can not believe it is that much different then steel or SS is it? anyway thanks
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