I'm becoming more satisfied with my tig practice and am paying more attention to details - some probably irrelevant- which raise some questions.
Does a tungston "absorb" base/filler metal if dipped? Since they are made with powder technology and fracture easily, it made me wonder. Also, if the contamination just appears to be on the prepared (pointed) section, will regrinding be sufficient or must the end be broken off and reground?
Can sandpaper and nylon abrasive pads be used to prepare stainless? I suspect they may be contraindicated for Al since the abrasive material in the nylon pad or on the paper may become imbedded in the Al. Is that a reasonable assumption? If these materials can be used as a replacement or adjunct for SS wool/brushes are there certain brands/specs that are recommended?
With respect to technique and 12ga SS, I have tried a continuous movement progression with filler dip at intervals related to movement speed. I have also used a move, pause, dip type of progression. I seem to get better penetration with the latter. Is one technique preferred/mandated?
With respect to approx .065 Al, I seem to get better results with a fairly rapid continuous movement and quick dips of the filler. That results in a smooth bead and good penetration. Are any of these approaches considered "poor form?" I've heard some say you should pump the pedal as you progress. It begins to feel like you are rubbing you stomach while patting your head and tapping your right foot while shuffling your left! And I am using a chin lift helmet so I have to open and close my mouth too. I have a new appreciation for one man bands now.
Thanks
Ken
Ken,
I have watched a welder with a broken left arm tape the filler rod to his helmet and dip it by nodding his head. Give that a try!
Regards,
Ken,
Good questions!
Tungsten is dense and its solubility while manual Tig welding is not really a concern. Now aluminum will tend to "climb" up your electrode when you dip it into the molten pool or stab it with your filler wire, when this happens its best to stop and remove all visible traces from your tungsten. I like an 80 grit 2' belt sander to prep my electrodes for aluminum. Stay away from mounted grinding wheels as they will "load up".
Surface prep: Aluminum oxide discs are my choice for edge prep for both stainless and aluminum under 0.090 thickness. 1 and 3 inch disks with 36 grit for the heavy stuff and 80-120 grit for blending. I prefer a pneumatic angle grinder with a stock mandrel. A good brand to look at would be http://www.standardabrasives.com/consumer/consumer.html .
Technique. Lots of ways to address this. Here is a simple way to look at it. With thin stainless (under 0.90 square groove joint) and a quality argon backup the weld should for the most part look the same on the bottom as it does on the top. The weld reinforcement on the bottom will be more silver-shiney but the pattern of dips should look almost like a mirror image. With your 0.065 Aluminum I see no reason for aggressive pumping the foot pedal. Your observation that aluminum likes to be welded fast is a good one. Penetration (reinforcement) on aluminum sheet is generally greater than with stainless so don't be dismayed if your penetration (in a square groove joint) is as much as twice the thickness of your sheet metal in the situation you describe. As you see the puddle widen and become concave add your wire, this will cool the puddle and you may progress. The addition of wire to cool the puddle rather than pedal manipulation will make you go much faster and with less chance of inconsistent heat input. As you become more and more accustomed to what your seeing in the puddle you will be able to make bead profile adjustments with travel speed, filler wire diameter, heat sinks, balance control and torch angle.
Thank you. Very informative and helpful info. I'll put it to good use.
Ken
Lawrence had some good tips for you.
I would say that there is no need to break off the tungsten, that sanding like Lawrence suggested would be adequate.
I never use abrasives to prep aluminum. X-rays always show lots of pores whenever I used to. I always scrape or file, then don't touch it, not even with a wire brush. The brush can only make it dirtier.
The reason you use a pause dip move technique is that the pause gives the puddle time to penetrate, the dip adds in the filler to replace the metal that has dropped through, then you move on. It is kind of like a series of overlapping spot welds. If you are penetrating all the way through without pausing, there is no need to pause. The pedal rocking that some folks do is designed to limit the overall amount of heat that they are putting into the metal. They are punching the pedal to penetrate, then backing off to allow the weld metal to cool so that the weld pool does not become too big or too hot. Use the technique that works for you on a given material, position or thickness. One is not "better" or "poor form."
Roger
Roger,
Thank you very much for the additional information. The relationship of cleaning to x-ray inspection was particularly interesting. I'm also glad to have opinions about technique, especially since I was becoming quite satisfied with how my Al bead/penetration was progressing with a continuous movement technique.
Ken
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