Welding problems

[TheJoker]

Guys,

Here's a pic of one of my recent welds;

I'm wondering what makes these pits in the weld and why it turns out this bad.
My primary suspect is that this material isn't very good and it contains impurities. To get rid of it I'll either have to a) blast it with a lot of power, b) weld and filler on top until it's nice, or best alternative c) get the grinder out and get rid of the dirt and weld it again.

Any other takers on why this might happen?

Thanks!!

 

[Paul.]

The material doesn't look that dirty, what filler rod are you using, that effect is typical of using oxy acetylene welding rods with tig, A15 or A18 triple deoxidised is what you need, could also be a gas flow problem, or being a box section is it rusty inside, although the weld looks clean, usually impurities float to the surface.

 

[scott0031]

Agree with paul it looks typical of using gas welding rods.


A note on the ' material not being good':

I will add to that whilst the material isnt that dirty as such, its still 'black', Black being the mill scale from 'hot' formed material. Mill scale being a by product of the way the material is produced.

You cant weld mill scale its not the base material your trying to weld. Always prep the area to be welded to remove the mill scale and any remaining pits those pits you see will contain mill scale. Its all impurities that will end up in the weld. If you prep the area every time you can 'always be sure' thats not causing you a problem. Its not always essential but its a good sound practice to follow in my book.

Its a practice i use on everything, be it mig or tig so i know the weld is always clean.


Kind regards,


Scott (ward eng)

 

[carlcall]

Try and find a video called 'TIG Welding Basics' by Ron Covell.....it may be basic but it gives you some good advice on how to get a clean weld and what you can actually do with a TIG, plus it also shows you some of the problems you may encounter.

Just remember Google is your friend.

 

[the snooper]

i agree clean clean clean weld nice shinny steel get rid of those impurities on the surface

 

[TheJoker]

Most of the other welds on the same material are just perfect. Sadly I've painted the stuff now, so I can't take any good pictures of those. The rods are TIG rods, A15 in fact.

Most of the bad welds seemed to be when welding just that way. A box section at 90 degrees to another box section. The L-welds on the sides all went in just fine. In other spots I had 45 degrees box section welded to another 45 degrees box section, these also went in just fine.

All welding was done on the same equipment, on the same evening.

Forgot to say that the cleaning has been done with an SS wire brush on a drillling machine and filing of the weld-areas.

 

[scott0031]

Well those bad welds if there is any strength required i would suggest you go do them again. There is no strength in those at all. A good impact will detach those welds.

I would suggest you use an angle grinder with a flap disk or normal grinding disk to remove the scale. Wire brushes wont touch scale all it will do is take off the surface dusty like deposits. That scale is 'glass hard'. Files and all that a lot of hard work that can be done in a few min with an angle grinder, plus you still wont remove all of it with a file. As mentioned is not essential but is more important with tig compared to mig. All that scale burns off gets in the weld flares up ruins the tungsten and dissapates dirt into it, which in tun effects the weld.

The other thing i noticed in the pic is that upstand looks like you have tried to clean the end of it. You can see from the pics your not really de-scaling enough area. Dont be worried about attacking the area clean it well back from where your going to weld, An inch plus. If you only get back to bare metal on that 3mm area you intend to weld, you will still be dragging crap into the weld pool. If you have been getting like mini flare ups and lots of black smoke when welding thats cos its not clean, thats the scale burning. So take it back to clean metal well back from the inended weld.


You have to look at what you did different to the other welds to find a cause. For instance was there a draught coming from somewhere that could run through the tube effecting gas flow. Were you trying to weld these in a different position. All things have to be considered and by a process of elimination you can always find the answer.

Its a bit hard to note what size that tube is by a picture. I personally, if i had to tig black tube with rads on the edges would up my rod size if you have been using 1.6 rods try using 2.4 for a better quicker fill. Rod choice is an each to their own type thing. Some prefer smaller rods and feed more, some prefer less feeding with larger diam rod . It can do no harm to try to find what your most comfortable with.


My Kind regards,


Scott (ward eng)

 

[TheJoker]

Well those bad welds if there is any strength required i would suggest you go do them again. There is no strength in those at all. A good impact will detach those welds.

I would suggest you use an angle grinder with a flap disk or normal grinding disk to remove the scale. Wire brushes wont touch scale all it will do is take off the surface dusty like deposits. That scale is 'glass hard'. Files and all that a lot of hard work that can be done in a few min with an angle grinder, plus you still wont remove all of it with a file. As mentioned is not essential but is more important with tig compared to mig. All that scale burns off gets in the weld flares up ruins the tungsten and dissapates dirt into it, which in tun effects the weld.

After the welding went that bad, I have indeed used an angle grinder to get rid of the bad weld. I just want to figure out why it happened.
When I mentioned filing and wire brushing I meant it as preparations before welding, not repairing the bad weld.

The other thing i noticed in the pic is that upstand looks like you have tried to clean the end of it. You can see from the pics your not really de-scaling enough area. Dont be worried about attacking the area clean it well back from where your going to weld, An inch plus. If you only get back to bare metal on that 3mm area you intend to weld, you will still be dragging crap into the weld pool. If you have been getting like mini flare ups and lots of black smoke when welding thats cos its not clean, thats the scale burning. So take it back to clean metal well back from the inended weld.

I cleaned it all with the aforementioned wirewheel on the drill. I did all of the metal as it made my hands go black from simply handling it. I also filed most areas, but I don't think I used the file on the flat bit of the box section. Just the ends. The photo does reveal quite a lot of dirt being left in place despite wire brushing it. I think emery cloth would be a bit more efficient where I will be welding, and up to 30mm around it, just as you say.

You have to look at what you did different to the other welds to find a cause. For instance was there a draught coming from somewhere that could run through the tube effecting gas flow. Were you trying to weld these in a different position. All things have to be considered and by a process of elimination you can always find the answer.

This is where I'm failing to see any real changes. I was in the garage, doors closed so no drafts. I put the project in the vice and welded all welds on one side, then turned it around and welded that side, and so forth. Some of the welds (mostly these types) went bad, most of them perfect.

Its a bit hard to note what size that tube is by a picture. I personally, if i had to tig black tube with rads on the edges would up my rod size if you have been using 1.6 rods try using 2.4 for a better quicker fill. Rod choice is an each to their own type thing. Some prefer smaller rods and feed more, some prefer less feeding with larger diam rod . It can do no harm to try to find what your most comfortable with.

I think the wall thickness is about 2mm, so you're right that a 2.4rod and 2.4 tungsten would have been a bit more appropriate than the 1.6 and 1.6 that I used. This doen't, however, explain how some welds were good and some not.

Thanks very much for your insights!

 

[scott0031]

When i say use a angle grinder, I mean prior to welding, scurf the whole area off so its clean steel. Again emery cloth wont get it out of deep pits. By all means use a angle grinder to take out bad welds, its what angle grinders are for.

It help a lot if you can go study how materials are made and formed. It gives you a big insight to the animal your dealing with.
I will give you some info on hot worked materials such as black mild steels:

Its made exactly as its described Hot! When i say hot i mean red hot. This action between the red hot material and the atmosphere causes the scale or oxidasation to occur. When they form these materials into the shapes we see such as box or tube they have to be formed. To do this requires applying mechanical pressure of some kind to form the shape. When this pressure is applied the scale trying to form is engrained into the steel due to the pressures needed to form it. Whist a lot of the scale is on the surface of the material, a lot also isnt. Its actually embedded into the steel. In exagerated terms its like you drilling a 3 mm hole a few mm deep then filling it with muck, you wont be able to get that out with a file (especially on a flat surface) or emery cloth or wire brushes. You have to take that top layer of material off.

If you look at your pic you can see these tiny dots of black and indentations where you have cleaned the area. Those areas still contait the scale. Again its not essential to remove it all, all of the time. You have to remember in technical terms its still muck thats present.

When you prep prior to welding especially tig, get rid of it if you can. An angle grinder and rip it off. Its sometimes hard for people to get their head round working with new materials. You have to keep in mind its not a lump of timber or a sheet of wall paper. Its a lump of steel and you have to treat it as such. obviously you dont wont to be silly and grind half the material thickness away, but you can attack it with some vigor. Its still a lump of steel.

It still really looks like a rod problem the only other option is a gas problem, Its typical of one of the two. You should also consider the cup size you are using and the area the gas has to cover for the width of weld. It doesnt look typical of this but it could be a filling problem on your part. If you are paying enough attention to the weld pool when welding and you see its not filling, obviusly you alter torch/amps /speed and fill rate to accomodate. If you did that and then found these viods still appear it can only be rod problem or a gas problem. If it is either of those no matter how much you try to adjust how your welding the problem re-occurs.


Might be a good idea to do some trial runs on scrap and see how you get on.


Kind regards,

Scott (ward eng)

 

[TheJoker]

Thanks Scott. I think my first port of call is more cleaning, but I'll definitely keep an eye on the filler and gas. Appreciated!

 

[scott0031]

Your welcome mate.

 

[NTwoO]

What angle are you holding the torch? If the angle is too flat, then the argon sucks in air from the back. This looks like air getting to the weld.

 

[TheJoker]

What angle are you holding the torch? If the angle is too flat, then the argon sucks in air from the back. This looks like air getting to the weld.

I'm trying to hold it as all litteraure is telling me to, but it might be a bit flat though. Maybe a bit more tungsten stick-out would allow me to tilt it back a bit more..

Thanks!

 

[NTwoO]

Well, it must pretty square, not too much in line with the weld. At about 75-80 degr is fine.

 

[runnach]

I'm with TIG Paul, looks like gas flow, too little will cause problems, same for too much, 10 lpm should be suffice, if there are still quality problems, check you are getting 10 lpm leaving torch. Also check around gas solenoid area, could be a ruptured pipe drawing in air?

 

[rodofgod]

Hi All!

TheJoker,

My first impression was wrong filler wire, this is what I would expect to see with Oxy-Acy filler wire and TIG welding! However, you have stated that you are using the correct wire! If this is just a problem on these configuration of joints, up the gas flow, use a larger 'Cup'. ideally a gas lens!
Typically, fillet welds will concentrate the gas and porosity problems are less likely. Once away from the typical fillet weld configuration, with the same gas flow, cup size etc. these type of problems can arise! Your pictures show mill scale which needs to be removed prior to welding and in extreme conditions even from the inside of the parts to be welded. However, I would think use of a larger Cup, increased gas flow and grinding the parent material back to 'silver' finish would solve your problems!

Regards

 

[TheJoker]

Thank you, rodofgod! I'll keep that in mind.