TIG WELDING for MS

Dirt or some foreign material in the defect you are trying to weld, or, loss of shielding gas. Make sure to mechanically clean and properly prepare the defect prior to welding. For much more than this, I'd have to examine a sample.

Dear FKIA,

I had shot blast the job prior to salvage or fill the cavities, again, so far as filler wire that i used was ER 70 S quality. Again, the shielding gas i.e. ARGON, was kept at 3.5bar and than i reduced to 1bar for checking the effect. But consistently, the porosity or pin holes, were there.

Thank you,

RAJIV DAMANI

Would recommend using a carbide bur to remove the original surface of your porosity.

The dross that caused your imperfection is also interfering w/ your weld repair, too.

Unless the pour was too cold, or somebody screwed up the alloy, the pin holes or pits have to be caused by foreign material which caused the original defect. You must remove this foreign material. Shot blasting is not the best choice for cleaning in this case. I'd opt for the carbide burr as suggested by others. Shielding gas pressure is not as important as flow rate which should be fast enough to keep the weld area shielded, but slow enough to avoid aspirating air into the gas stream. You may also try a slower weld progression rate to try and let any foreign material boil out of the weld pool before it freezes. This should be a simple, straight forward, weld repair.

Dear FKIA,

Well, the pour can't be too cold, as in casting process, I am sure you are aware of it. Secondly, yesterday, I tried the same TIG process by changing the machine, instead of 150amps I tried with heavier machine in the sense of amps. I set the amp to 160+ amp, and tried with the same procedure, I did got some improvement, meaning which the porosity or the pin holes were lesser or almost nill, in many cases, so a new development, is that would the current range or ampere setting could be the cause, of this pin holes in my prior attempt where I had set the ampere range to 150+.

Do guide.

Thanks for all suggestions

Rajiv Damani

Is the casting a sand casting? What method of cleaning prior to welding did you use? Cast steel can have lots of impurities that will cause pin hole porosity. Grinding to remove the defect and proper cleaning prior to welding is most important. Good luck.

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I have been successfully using TIG /Argon welding procedure for precision casting, for salvaging, casting defects. The castings are of ALLOY STEEL [SS304, SS 316, SS410etc.] Recently I did some MS [Carbon steel] casting, on which I used this procedure, I came across some pin holes, or bubbles in the welding or salvaging. Could any one guide me as to what could be the problem and how to eliminate it.

Thank you, all,

Dear AV8RJIM,

As posted the reply, the job is not a sand cast, its investment precision cast and I had shot blast done prior to the salvaging procedure. Kindly assist

Thank you

RAJIV DAMANI

Have you tried any preheat?

I have repaired steel castings in the past with the same problem. Had to weld then grind out and reweld to get sucess.

Glass shot will embed powder into the weld area bad idea. You will need to grind the weld area with a burr not a rock, clean it with acetone or something that will not leave a residue, and weld using a flood method for the weld pool. The object is to create a weld pool that covers the base casting with clean pure welding rod. Do not dip the rod into the weld pool. This will not be as strong a weld as the conventional tig method but it will not have pin holes.

Hello,

Pre heating a casting to a an accurate temprature is very important when welding castings, your filler rod supply house should have pre heat temp charts for you to assist.

TIG is an amazingly clean process, however there are a number of settings which can affect the weld quality - Are you using AC or DC welding? What other settings does your machine have. The correct combination of settings can be vital here.

Also talk to your Gas supply source, as they may be able to recommend the best gas for your application. Sometimes shielding gases react and cause weld problems.

As previously mentioned V-Grove with a carbide burr.

When applying the filler Rod assure that you "DAB" into the molten pool with a frequency of about 1.5 dabs/ sec or similar - do not hold the filler into the puddle steadily this will give you a poor incosistant weld and may cause inclusions and pin holes. Depending on your current settings, thickness of casting etc. angle the tig head about 15 - 20 degrees, pointing the tip towards the filler. Then when dabbing with your "filler feed hand" try to dab as close to below the Tungsten tip as possible without hitting it, removing the filler about .5" from the pudle at each dab.

The tungsten tip must be in near perfect shape otherwise you`ll get a poor weld and inclusions. The tip shape will depend on your welding machines settings and capabilities, AC / DC welding. Discuss the right filler with your supply expert, it would seem to me that your filler rod can be improved.

During Tungstes Inert Gas (TIG) welding most all impurities leave the weld area and will not be inclusions in the weld, which is why TIG welding is so clean and strong and can be used on virtually all metals. If the welding is done properly with the correct settings, filler, and Gas.

Best of luck.

Dear MICROCONSULTANT,

I am moved and appreciate your guidance, if you origin from my country,[India] do let me know, your address, I would definitely like to meet one fine day, of life. Again, coming back to your suggestions, rest assure, the angel of the filler wire, and the filler wire itself have been perfectly matched, I can say for sure, because, when I fill the cavities of Alloy cast, with the same machine, and relevant filler wire, there seems to be no problems of any sort. In fact, as you suggested, TIG is the ultimate in welding alloy steel. Creating a V groove, is out of question, as the porosity generated are very minute or say approximately of 2mm average in size, with no fix shape. Its basically the defects created in the investment precision castings. So, the job is well shot blasted before i bring them to weld floor shop for filling the cavities and salvaging them. The machine I am using is SINGLE PHASE, inverter [IGBT MOSPHATE] type TIG welding machine, of 150amps.

Hope my stand with this description, would bring you closer to the fact at where i am making the mistake or what the problem persist.

Thanks again

RAJIV DAMANI

Dear Rajiv,

Thank you for the remarks. Current Country - Canada, origin Germany.

I am unfortunately not familiar with your machine.

Do the techniques I described help, or is this pretty much what you are doing?

Dear MICROCONSULTANT

Oui, the process that you described i think would be very much be applicable with the process of welding where a sheet has to be welded, where you have to draw weld line joining two sheet or similar application, so far as my job or particularly speaking where i am facing the problem is, while welding small spots or pin holes made by the air bubbles developed during the casting process. Now, prior to finishing, this castings, I have to fill the holes which actually is a defect some where in the process. Now, doing so, I use TIG machine. which is INVERTER base ,so straight AC. Now, when the alloy cast is salvaged I do not face any problem, but while doing the procress with MS cast. the weld beads it self gives air bubbles. i am stuck up there.

Thanks again

RAJIV DAMANI

Is there a control for both + and - portions of the AC wave? (Wave balance) -- I am beginning to believe that a more advanced welding machine will enable you to "crater fill"

I understand what you are facing the bubble keeps on surfacing. Have you tried DC TIG with a stainless filler?

I still believe you need to grind out the defect and then fill it for best results.

What type of tungsten are you using ? (Thoriation)?