Foam formation upon TIG welding of steel

By plombaer Date 03-13-2004 10:30

Good morning,

I have some troubles when welding steel plate (2 mm) in TIG-mode. On some pieces I get excessive formation of foam. Also, when a weld looks just great and you make a second pass, the root weld gets really foamy.

Parameters: clean steel sheet, 2 mm, DC-Tig 2 or 2.4 mm electrode, approx. 65 A, Ar-gas 9 litres/min, dedicated TIG rods as filler metal, 3 s downslope, 6 s post-gas.

If anyone can give some hints on how to avoid this problem, I would be pleased.

Thanks,

P.

By GRoberts (***)

Date 03-14-2004 02:25

When you say the weld gets "foamy", are you talking about porosity? If you are, the reason weld metal gets porosity is that it is trying to get rid of gas as it solidifies. There are several ways that the liquid weld metal can absorb gas, which it later needs to evolve during cooling. First, make sure your steel and filler metal are clean. Grease, mosture or other foreign materials can cause porosity. Second, make sure your sheilding is adequate. Too high or too low of a gas flow, improper torch angle, or contaminated gas could be the culprit. Also make sure wind or drafts aren't blowing away your shielding gas. Another possible problem is if you are not using deoxidized steel, such as rimmed steel. The base metal itself can be providing too much dissolved gas. The best solution for that would be to use ER70S-6 which is high in de-oxidizing elements.

By plombaer Date 03-14-2004 16:38

I am indeed talking about porosity, which is not always seen at first sight. The filler metal is clean, I even tried to clean the filler metal by using a bit of sandpaper, a common practice in aluminum work. Shielding should also be good. The #1 reason could be the 'messiness' of the plate. In moste cases, the plates we are using are protected with a paraffin layer. It would probably be advisable to degrease these plates prior to welding.

Also, we will try to use this different filler metal as you stated.

Once we've tried these solutions, I will post my comments.

Thanks,

P.

By welder_guy2001 (***)

Date 03-15-2004 06:20

I'd say that is your problem...parafin will contaminate a weld.

By jmfmicroweld Date 03-17-2004 03:26

whats your flow rate and what gas are you using........pure argon.....98/2 mix?

By plombaer Date 03-19-2004 16:30

Hi,

The flow rate is 10 litres/min and the gas is pure Ar.