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Thread: Cleaning 4130 for TIG welding...

  1. #1

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    Cleaning 4130 for TIG welding...

    My first fuselage was 4130 and gas welded. I am starting a new project and decided this time to do it with TIG. Basically, I am relearning to weld so I haven't really started yet. My question is this; with gas the mill scale wasn't a problem and just burned off during welding. Now with TIG everyone says to clean the tubing of mill scale. Now maybe I am mistaking the grey coating the tube has with mill scale OR I am to make the tube bright and shiny? Just what do I use to clean the tube? How clean should I get it? I assume a pneumatic grinder with a steel brush on it would damage the tube. What is best practice? What is clean for 4130?

    Thanks!

  2. #2

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    Quote Originally Posted by subnoize View Post
    My first fuselage was 4130 and gas welded. I am starting a new project and decided this time to do it with TIG. Basically, I am relearning to weld so I haven't really started yet. My question is this; with gas the mill scale wasn't a problem and just burned off during welding. Now with TIG everyone says to clean the tubing of mill scale. Now maybe I am mistaking the grey coating the tube has with mill scale OR I am to make the tube bright and shiny? Just what do I use to clean the tube? How clean should I get it? I assume a pneumatic grinder with a steel brush on it would damage the tube. What is best practice? What is clean for 4130?

    Thanks!
    I use a fine wire wheel on a bench grinder to clean the areas being welded with TIG. Partly I do this to de-burr the ends of the tubes.
    Some of the 4130 I have received has a real scale issue and his has to be removed get a really good weld. The surface on good quality 4130, bluish in color does not cause issue when TIG welding.

    Bottom line, cleaning the weld area is always a good practice.

  3. #3

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    Quote Originally Posted by lathropdad View Post
    I use a fine wire wheel on a bench grinder to clean the areas being welded with TIG. Partly I do this to de-burr the ends of the tubes.
    Some of the 4130 I have received has a real scale issue and his has to be removed get a really good weld. The surface on good quality 4130, bluish in color does not cause issue when TIG welding.

    Bottom line, cleaning the weld area is always a good practice.
    I finally googled mill scale and its apparent that I am mistaking the finish for mill scale. I guess that is the danger of learning from books and videos, right? I always assumed the 4130 bluish finish was the mill scale. Amazing I have gotten this far without knowing that. I guess its forgivable since I've only ever welded aircraft grade metals. I am such a spoiled person!

  4. #4
    Dana's Avatar
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    My friend who's TIG welding a new landing gear for my Starduster says TIG is more tolerant of dirty surfaces than gas. I'm still cleaning everything (solvent and Scotchbrite) before tack welding.

  5. #5

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    Quote Originally Posted by Dana View Post
    My friend who's TIG welding a new landing gear for my Starduster says TIG is more tolerant of dirty surfaces than gas. I'm still cleaning everything (solvent and Scotchbrite) before tack welding.
    I have discovered that most TIG welders have never gas welded. Or if they did, they did it for a week in the classes and never touched it after that. Most have had a bad experience with it on top of it all.

    Gas is certainly no where near as fickle as TIG when it comes to surface prep. Gas is harder to master, faster welding and is easier to set up. TIG is easier to weld, slower welding though and requires a lot of prep and setup time.

    Gas seems to have less warping, probably because I take the torch and run it up and down the parts before I dig in. TIG makes these incredibly tiny little welds that make you wonder if is will be strong enough (it will but you start questioning it when you are use to huge gas welds).

    Anyways! TIG is a clean freak. Gas doesn't care.

    --jb

  6. #6
    Spencer_Gould's Avatar
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    You want to have your metal as clean as possible at & near the weld sight. Clean metal will be something working for you, dirty / crud / rust / mil scale will be working against you. I learned TIG the hard way and this is one of the many factors in making airworthy welds vs. booger welds.

    Its not too hard to do with a bit of elbow grease but you want the right tools for the job. 150 - 200 grit sand paper wrapped around a foam sanding sponge works quite well for general areas, for tighter spots a Dremel with a sanding drum. A Dual Action "DA" sander with the same grit is another option. If you have a Lathe or access to one you can chuck raw stock, spin and use sand paper on it. It usually does not take too much effort to get it clean. Do be careful to only use Isopropyl Alcohol for cleanup, more harsh chemical residues vaporize into toxic fumes when welded.

    Here is a post on making a Elevator Idler for my plane (TIG welded 4130)
    https://gouldaero.wordpress.com/sp-5...levator-idler/

    Since your new to TIG I would get to making airworthy welds on scrap before you go for the real deal. I went thru quite a few test welds before I made the above flight control part.

    Hope this helps,

    Spencer Gould

    EAA 466275
    Technical Counselor
    Chapter 203 VP
    Aerospace Engineer
    Author: TIG Welding: GTAW need to know for beginners & the DIY home shop
    ASIN: B06ZZCLYHY / ISBN: 1548233722

  7. #7

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    Quote Originally Posted by Spencer_Gould View Post
    Since your new to TIG I would get to making airworthy welds on scrap before you go for the real deal. I went thru quite a few test welds before I made the above flight control part.
    Well thank you, Spencer!

    That is the info I needed! I am certainly relearning to weld. The eye, hand and now foot coordination don't match between the two different processes. I keep doing this thing where I try to lift my TIG torch to reduce heat as oppose to backing off the foot pedal. I never knew I was doing it when gas welding (it works there). Now when I do it with TIG I get these lightening bolts shooting out and blowing holes in surrounding parts!

    I will certainly spend a lot more time perfecting TIG before I start welding my fuselage. No question about that. I have plenty of 4130 scrap tube. I will say I am having much better time learning TIG than I had with gas. I just need to find more time to stick parts together though!

    Thanks again,
    Spencer!

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