Can't get nice-looking TIG welds on steels

Date 01-17-2007 14:31

Scaley looking welds are usually a product of impurities in the puddle that float to the top of the puddle and solidify. Are you cleaning the filler wire prior to welding? As well as cleaning the oxidation off of the base metal?

By SWP

Date 01-17-2007 15:17

Assuming a shielding problem.
1. This may sound crazy, but make sure you are using Argon shielding gas, I've heard of several beginner TIG welders that have mistakenly been sold or somehow end up using a MIG gas mixture with CO2 or O2 additions.
2. Plug off gas flow at the torch gas nozzle, pressurize the gas system, and check every possible connection for leaks with a bubble solution (windex will work).
3. Check your gas flow rate, experiment with a range of flow rates, higher flow is not better, excessive flow can cause turbulence and contamination of shield gas with air.
4. Try to keep a minimum electrode-to-work distance, ie. arc length maximum around 1/16". The electromagnetic field of the arc produces a strong gas jet towards the weld pool that greatly amplifies the shield gas flow. The driving force for this is enhanced at longer arc lengths and thus this may play a part in entraining air contamination.
5. Set a minimum electrode stickout distance beyond the end of the gas nozzle, just enough so you can see what your doing.
6. Try a larger diameter gas nozzle.
7. Use a gas lens.
8. Hold the torch very near perpendicular to the weld joint, a slight tilt of 10 to 20 degree push will help in seeing the puddle and in adding filler to the puddle without hitting the electrode.
9. When adding filler, dab it into the puddle to melt, do not melt off balls with the arc. When dabbing filler in and out of puddle, try to keep the hot end protected in the shield gas envelope, other wise you will add oxide via the filler end.
10. Ensure the base metal is absolutely clean hydrocarbons and oxide.
11. Do not try to make a huge weld bead in one pass. An excessively hot weld will oxidize rapidly as you travel forward and the trailing edge loses protection from the shielding gas. Notice that a small bead on relatively thick material will be rapidly chilled by the base metal and will look much cleaner than a big hot weld.

By mike944 (*)

Date 01-17-2007 15:26

Ok, thanks for the tips guys.

I did clean the filler rod, and the base metal, but i'm not sure how well i did that. I'll try again on some scrap.

I assume it's argon, it says so on the bottle. I'm almost out, so when I replace the tank, i'll see if that helps.
I'll also check the system for leaks.

I have tried both higher, and lower flows. I do understand the whole turbulence thing.

I do probably keep longer arc distances, than that. If i try to keep them that short, i find i ocasionally touch the tungsten to the pool, while i'm adding wire, so i keep them longer to prevent that.

All the rest of the stuff (with the exception of the gas lens) i either do, or i've tried.

I'll let you know.

By jwright650 (*****)

Date 01-17-2007 15:41

Hi Mike,

I'm throwing this out there just in case(I was reading very quickly, but I didn't see any mention of which gas you were using, yet you described welding several different materials)....just be sure you're using the correct gas mix for the materials being joined.

By mike944 (*)

Date 01-17-2007 15:51

correct gas mix for the metal? I use argon for everything. is that wrong?

By jwright650 (*****)

Date 01-17-2007 16:24

No Argon is not wrong, but you can optimize with blends or mixes....

Sparx and Lawrence summed it up pretty good here....http://aws.org/cgi-bin/mwf/topic_show.pl?pid=22999;hl=#pid22999

By ssbn727 (*****)

Date 01-17-2007 19:47

Hi Mike!
SWP gave you some great tips to use and all I want to do here is to add on to the already great advice you're getting already!

The next time you strike your arc, position your head & line of sight so that you can clearly see the weld pool... this will definitely help you better gauge whether or not your tungsten is either too close or too far away from the joint in question. Position yourself ahead of the starting location so that you can clearly see the weld pool towards your line of sight but, make sure that you're close enough to clearly see the weld pool form... when you position your torch, does it have a slight "drag" or "push" angle towards the direction of travel? I ask this because, you want to have a slight "push" angle... In other words, the torch is ever so slightly angled towards the direction of travel - around 5 to 15 degrees from being perpendicular to the surface of the material being welded. When you introduce the filler metal to the weld pool, is the pool fluid? Does the filler "ball up" on you and do you feed it into the leading edge of the puddle? Do you feed the filler in a constant motion, continuously feeding the filler into the puddle or do you dab the filler in and out of the puddle? If you dab in and out, you must be aware that if you pull the filler out of the gas shield before the end of the filler solidifies, you'll contaminate the end of the filler and the next time you dab the filler into the puddle, you'll introduce contaminated filler inot the molten pool so make sure that the end of the filler is always shielded with the gas coverage envelope coming out from the torch also!

Also just to be sure, always CLEAN, CLEAN, CLEAN, the joint surfaces and the filler wire being used... this way you clearly eliminate the possibility of contamination from either of the two potential sources.
Make sure your torch parts are clean... I did'nt see you mention what was your gas flow rate from the regulator mounted on the tank, could you let us know what it's set at? Also, what is the distance of your tungsten stick out? I ask this because if it's sticking out too far and you did'nt compensate for it by increasing your gas flow rate then, you could be contaminating the tungsten if it's sticking out too far when combined with a longer arc length and while we're at it, what type of tungsten are you using for ferrous metals? What's the thickness of the material, what size tungsten are you using, what is the power source current set at? are you using DCSP or AC?

I know I gave you another set of questions to ponder through but, if you eliminate these potential issues then you'll be on your way to producing consistant high quality GTAW deposits.
I hope that some of this helps...

Respectfully,
SSBN727
Run silent... Run Deep!!!

By Molten Metal (**)

Date 01-17-2007 23:12

Make sure you are using a filler rod designed for tig.OAW rod,like say,RG-45,sure looks like ER70S-2,but it wont work with tig.You can however use er70-s2,etc. for gas welding.You can also use stainless filler on carbon steel's,but not the other way around.If all that stuff is right,my guess is that you are moving too slow.

By Blaster (***)

Date 01-17-2007 23:49 Edited 01-18-2007 00:12

Great tips above.

I also think you are likely moving too slow. You are likely contaminating the puddle from the backside - excessive exposure of the root to the air. With stainless you need a backing gas or Solar Flux on the back. Steel is more tolerant, but excessive exposure to air will also cause a steel weld to degrade.

You want low total heat input, and you don't want the bead to reamain molten longer than necessary. You lessen heat input by using high current levels and moving fast. Also keep the puddle as narrow as the joint depth will allow, again by using plenty of current and moving fast, and also by keeping the electrode as close to the puddle as you can get it without touching.

One more obvious thing that I don't remember seeing mentioned - don't waste any time attempting to weld with an electrode you have dipped in the puddle. The contaminated end needs to be cut completely off, and the end resharpened. Welding with contamination on the electrode will both contaminate the puddle and cause a significant loss of arc control.

By mike944 (*)

Date 01-18-2007 03:20

Well thanks for all the suggestions!!!

Most of the stuff you guys have suggested, it looks like i'm doing that stuff correctly.   Even though this isn't my buisness, i've been tig'ing on and off for 10 years or more, so i'm pretty sure i've got the basic and obvious stuff correct, my difficulty is probably poor technique.   (that's what i need a class for, that class that i can't find ARRRRGH!)

I think it's probably either lack of cleanliness, or moving too slow.

SSBN727 - On steel, i tend to feed the rod continuiously. On aluminum i dab.   Flow rate 20-25 CFH, and my work area is free of drafts. Thoriated, but i've tried ceriated, and lanthinated. they all seem to work about the same for me. Tungsten stickout is less than the diameter of the gas cup. Both materials are .062, but it's a lap joint, tungsten is 3/32, DCSP, and i tried varying the current from 80-100A.

All the filler is definitely tig filler. 308L.   I don't think it's backside contamination, because as i said above, it's a lap joint, so the molten metal is never actually is exposed to the backside.

As soon as i have a chance, i'll post a link to some pictures.

Thanks!
Mike

By Blaster (***)

Date 01-18-2007 03:45

Didn't catch the part about it being a lap joint.

BTW, you might want to try 1/16" Tungsten.

Also BTW, I don't care too much for Cerium or Lanthanum alloys on DC, and I stopped using Thoriated a few years ago as a health precaution - I now use a lot of Diamond Ground Products' "Tri-Mix" tungsten. It works well on a variable output frequency / extended balance control AC output powersource, such as with a Dynasty 300, as well.

Couple more thoughts - sometimes gas is contaminated in the bottle, we get 1 or 2 a year. Don't know if you have tried more than one bottle on your machine. Also, I have seen TIG torch argon lines that had been contaminated from coolant during installation that would never weld cleanly even after being dried out.

By Lawrence (*****)

Date 01-18-2007 04:41

Aluminum is like a canary in a coal mine... If you can weld it with no surface flaws than that pretty much ensures your gas is good for carbon or stainless steels... So we can count bad gas out.

Try a few lap welds with no filler. Try to get a slightly convex bead contour that still ties in to the lower leg.. This exercise will help you to understand your heat input a bit better... Make these fusion joints only 1 inch at a time and check the color of the welds as you go, keep practicing until your start/stop tie ins are almost impossible to see. Do not remove the cup from the weld, allow gas coverage for 10 seconds after the arc is off. Keep your torch perpendicular for this with no push or drag angle at all.

When you have this mastered then start adding filler and attempt to keep that same slightly convex bead profile and smooth tie in at the bottom leg

By mike944 (*)

Date 01-18-2007 13:43

I like the "practice exercise" above. I'll try it, and see how i do.

On the Thoriated / health topic, i only "use up" about 3-5 full tungstens a year. I read somewhere that if you're using less than 10-20 a year, you have nothing to worry about, therefore it never really concerned me. I like the way it welds, and the exposure risk seems extremely low, due to my low usage.

By Lawrence (*****)

Date 01-18-2007 13:48

Right Mike,

There has never been in the history of medicine, a proven case of radiation poisining caused by thoriated welding electrodes.

Plenty of cases of toxiscity from tungsten in general.

I simply view all tungstens as toxic.... because they are.

By Blaster (***)

Date 01-18-2007 15:16

"Aluminum is like a canary in a coal mine... "

Good point Lawrence, missed the part about welding aluminum without contamination - That is what I get for answering a techincal post after a 14 hour work day.

By PaulusNZ Date 01-28-2007 22:38

Can I also ask for some advice with tig welding please? Would it be better to start a new thread? Im practising welding gussets onto a 55 gallon steel drum. There will be two gussets, both angled inwards towards each other. In between them will go a galvanised iron pipe (with the galvanising cleaned off) as one of four legs I want to put onto the drum to lift it off the floor. The gussets are angled inwards for lateral strength.

I can weld the outside of the gusset onto the drum okay, bearing in mind the need for the smallest bead possible. But I feel for strength the inside acute angle of each gusset of maybe 60 degrees needs to be welded.

What is the procedure for welding into an acute angle? I've tried 1.6mm stainless rod but found a lot was needed. I had a go with 3.2mm black ferrox rod but got the balling problem described to Mike. Have yet to try 1.6mm black ferrox rod. My welder is an AC arc welder with a rectifier box with scratch start. Pretty crude but it works. Normal flow rate is 6 litre a minute of argon, I tried increasing the tungsten stickout and raising argon flow to 8 litre a minute. Tungsten is thoriated 2.4mm (3/32 I think). I'm a real home welder with not much experience.

By ssbn727 (*****)

Date 01-29-2007 02:06

Hey PaulusNZ! Have you properly cleaned that 55 gallon tank before you start to practice on it???
I ask this because, if you do'nt know what was in it - prior to welding on it, you just might be welding on a potentially explosive device and not know it!!! Now if you already know about these potential hazards and have already taken the necessary precautions, then please disregard my query but, if you have'nt, DO NOT WELD ON THE 55gallon DRUM UNTIL YOU KNOW FIRST WHAT WAS IN IT AND YOU TAKE THE NECESSARY STEPS TO PREVENT IT FROM IGNITING OR EXPLODING ON IT!!! CAPISH???

I'm being very adamant about this issue, and I cannot emphasize enough how important it is for you to make darn sure the 55 gallon drum's internal atmosphere and inner wall & surfaces are free of any combustable gas vapor, material or film that can ignite or explode!!!

Why am I being adamant about this??? Because you yourself mentioned that: "I'm a real home welder with not much experience." Well PaulusNZ! You are the very type of individual that is more prone than others to prematurely cease to exist on account of your inexperience in working with such potentially lethal objects as the 55 gallon drum!!! Once again, If you are already aware of the potential dangers involved when working around or on 55 gallon drums, and have already taken the necessary precautions then please disregard my rather blunt warning to you and accept my apology but, if you're not sure then listen to what I've said and have the 55 gallon drum checked out before you even strike another arc on it - UNDERSTAND???

Respectfully,
Henry

By PaulusNZ Date 01-29-2007 09:23

Lol, sure, thanks for pointing that out. The practise drum held some sort of paint solvent which is long gone. My "good" drum (which Ive cut the end off ready to weld on a cone) held motor oil. I'll clean the inside surface before welding there.

By jwright650 (*****)

Date 01-29-2007 12:16

Explosive is just one thing......another thing to think about when using an old drum...fumes....you can breathe some very toxic fumes without realizing it, if you are unsure of it's former contents, don't heat on it or weld on it.

edit: another thought to add...folks are quick to use drums for cookers....be very carefull about using one for a cooker.

By PaulusNZ Date 01-29-2007 13:35

Your concerns are appreciated. Perhaps you could tell me if welding onto a steel drum that contained motor oil is dangerous, or whether the oil is likely to interfere. I hasten to add that I am not completely without experience. I have over 30 years' experience with soldering as an electronics hobbyist, and have owned my own oxy-acetylene set for almost 20, and have done a limited amount of arc welding.

Tig or GTAW is of course a very precise skill and I love the tiny clean welds that it can make with minimal deformation.

My friend Jason is a professional welder - a real ace - and has already made up the cone to go on the drum. It's in 2mm electrogalv and a beautiful job he made of it. Good welding always humbles and thrills me and when I can produce my own it brings a real sense of accomplishment and pleasure. I have the utmost respect for craftsmen in this field.

I am expected to tack the cone onto the drum and Jason will finish it probably with Mig and I just was hoping to go back to him with something really neat and tidy. At the same time the legs have to be attached, and although Jason suggested angle iron the original plan was to use the gussets and I'd like to stick with that It will be a more attractive finish.

It occurs that maybe the gusset could have an exaggerated L-like fold in it where it contacts the drum - ie a foot - and that would spread the load and make my welding easier. The foot could go either outwards or inwards.

By the way, the purpose of all this is to make a 150 litre-plus biodiesel reactor similar to this one http://biodiesel.infopop.cc/eve/forums/a/tpc/f/959605551/m/8711096081 (the reactor is on the left and it has gussets). Murphy has been giving me some pointers. Here is another project by Fabricator http://biodiesel.infopop.cc/eve/forums/a/tpc/f/419605551/m/4041052971/p/1 using an old propane vessel. Everyone is really impressed with this.

Thanks for your help!
Paul

By jwright650 (*****)

Date 01-29-2007 15:28

The paint on the outside of the drum, or the oil from within the drum will give you welding problems, so the immediate areas where it will be welded needs to be cleaned.

By PaulusNZ Date 01-31-2007 00:40

OK. So to weld two flat surfaces together at an acute angle of, say, 60 degrees, the procedure is to increase the tungsten stickout and maybe turn up the argon a little? All other things being equal, that is.

By PaulusNZ Date 03-26-2007 23:30

Well, I'm pleased to say that my welding is very much better since reading the advice given by you people on this web page. My welds are smaller, tidier and stronger and also very pleasing! Thank you everyone for your advice, it proved to be excellent.

Paul