Hi, I am new to this forum. I have a query regarding tig welding mild steel - I am self taught. We normally do stainless and use argon, but need to do something in mild steel. I have been using ER 80 filler rods and argon. Some welds come out perfectly but with most others there is occasional bubbling in the puddle which leaves holes when cooled and when finishing the run there is a huge(approx dia. 4mm) bubble that stays upon cooling. I have even tried sanding the weld area to bare/shiny metal and cleaning the surfaces with laquer thinners. Any help or URL links most appreciated. Thanks Paul
Are you experiencing porosity just at the ends of your welds? You might be loosing the gas shielding by pulling away too fast after you break the arc, before the puddle has set up. John Wright
if you're using a copper coated rod, it may be causing some porosity as you describe.
In my experience some coated rods have caused a similar problem. ER70S-2 (copper coated) have always produced consistently good results. If you need ER80, there may be an 80S-2 ?
also make sure that your HF is set to "start" if you use it. I have seen welders get a bubbly/stirring effect when they have inadvertently put HF to continuous setting when welding with DCEN.
Several possible reasons for what you have happening.
Unkilled steel http://metals.about.com/library/bldef-Unkilled-Steel.htm has a natural tendency to bubble while being GTA welded. The best solution is to use better steel. If you must work with what you have than choose a filler wire with good deoxidizing properties such as ER70S-6. The fact that your getting bubbles at the end of the weld as well as the beginning is kind of strange..
There is at technique that involves getting that first dip of filler in as quickly as possible. With the addition of the deoxidizers in the filler wire you should reduce the popping and mini-volcanos by a good bit.
Torch angles and gas flow should be similar to the stainless your used to.
With respect to Jerry's responce.... Superimposed High Frequency will not have an effect on the weld puddle. It is unnessary except for arc starting in DC- operations, but It won't stirr or in any other way have an effect on the weld puddle.
thanks guys! I'll try ER70S-6 filler rods. Will they give the desired effect using argon or will I need another gas? I have actually tried welding Corten and Domex550 (both are better steels than MS) to see if they behave differently ....BUT NO they did the same. I checked my rods again they are ER80S-G, would this make a difference? I'll also try using uncoated rods - will sanding the copper coating off be sufficient? Would preheating perhaps help - this would certainly remove any liquid contaminants?
Unless you see visible corrosion the copper is negligable and will cause no difference.
Argon gas only for GTAW
GTAW does not like to weld over rust but if you have prepped your material to a "bright" condition with an abrasive, that should be good enough. Even a power wire brush may not remove enough mill scale to make Good GTA welds.
At the end of your welds. As your tailing off your arc add a last dab of wire as your puddle is beginning to shrink, just a little, not enough for a stress riser, it should blend smoothly with the rest of the weld. This will help cool the puddle and add a last bit of deoxidizer that might have good effect on your endings. If you slam off your power at the end of a GTA weld, you can run into all kinds of bad conditions. Look at the ends under 10X magnification and see if there is a difference when you employ this technique.
Have you cleand off all the mill scale with a grinder or flapper disc? The area of the weld joint has to be very clean before welding or tacking. Also, at the end of the weld, you need to deposit metal and then pull off (kill the arc)....if you linger around (with the arc) and are not depositing metal, then this could be your trouble.
haven't been at it again and will only get to this particular job in a few days - going to do the prep and get a couple of filler rod samples from our supplier. Flow rate is set at 8 litres per minute and the cup size is about 1/4 inch (I am assuming you are refering to the diameter of the opening); these are the settings I use on stainless. I use a 1.6mm thoriated electrode. I have tried playing with the gas flow rate, different cup sizes and electrode diameters but haven't had any luck.
keep the ideas coming - I'll let you know when I hit the jack-pot.
The flow rate sounds OK. 8 liter per minute is 17 cubic feet per hour. I usually run 15-20 CFH with a #5 or #6 cup. You are using a #4, which seems a bit small but should work. You should check the torch connections and hose for leaks.
What is the lenght of the tungsten prodtruding from the end of the gas cup?? Good rule of thumb unless using a gas lense, is half the diameter of the cup. Also, holding the tungsten too far away from the base metal causes gas coverage loss. I agree that a #4 cup is a little small.
This may seem like a dumb question, after reading this thread again, but are you sure you have 100% argon and not a mix of 75 argon 25 Co2? I have seen this happen, personaly, after having my son pick up a cylinder of gas, and not checking it myself, just hooking it up to the regulator and trying to weld. I tried everything, grinding, flapper wheeling, different tungsten, different cups, changing hoses, torches, etc, to find out I had the wrong gas.
Paul, you could use a 309L s/s filler wire which is compatable w/many mild steels. It is a low carbon stainless.it may be cost prohibitive to some companies compared to a steel filler. I use it almost exclusively when welding mild steel(A36) mainly, and cast iron. It provides great strength and low corrosion. The small cup size could create a problem with some flow rates causing a venturi affect drawing in o2 to the weld area. 8 lpm should be sufficient. Saw some of the other posts and a larger cup with that flow rate could help as stated. The E70s-6 has silicon in the wire which may help also. You see the result of the 70s-6 w/ silicon when mig welding as a brown glassy scale in areas of the weld. the bubble is a gas pocket caused when the weld pool solidifies gases are trapped and before the weld pool cools the gases expand an cause the bubbles.hope you get the problems worked out! Mike
Are you experiencing porosity just at the ends of your welds? You might be loosing the gas shielding by pulling away too fast after you break the arc, before the puddle has set up.
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