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  • Donald Branscom
    replied
    Originally posted by Miller B. Hemmert View Post
    Color changes in stainless steel are indications that one or more of three factors are not quite right. Heat input, gas coverage, or travel speed are the main factors that affect the color of your stainless steel weld bead.

    -Heat input - If stainless is anything but a shiny silver color it means that the material has been exposed to temperatures above 540 degrees F. without proper gas shielding coverage. At this point the material will begin to turn a yellowish color. As the material outside of the shielded zone reaches higher temperatures the weld bead will become darker in color. Typical color order (lower temp. to higher temp.) is light yellow, yellow, salmon, reddish, purple, blue, and then grey. Once the material has reached the grayish color the corrosion resistance properties of the material are pretty much non-existent. Obviously the welding amperage is the main factor affecting overall heat input. If your bead is a grayish color the amperage is a good place to start adjusting. Another thing that will affect your heat input is your arc length. Your arc is shaped like a cone. If your arc length is long the puddle will be larger than if the arc length is held tight. A larger weld pool means a need for better gas shielding.

    -Gas Coverage – Any time you are welding stainless steel proper gas coverage is essential. As mentioned above, the material needs to be shielded until it reaches an acceptable temperature. This does not mean that your gas flow needs to be set higher to get better coverage (your gas flow should be set between about 12-15 CFH or about 20 PSI). Setting your shielding flow too high will actually cause turbulence in the arc zone, cause your arc to wander, and potentially suck outside contaminants (ex – Oxygen, Hydrogen) into the shielded area. Having your gas flow set too high can cause worse contamination than just a grayish color. Something that is often overlooked is proper coverage at the end of your weld. When you are finished with a bead, and you crater out, leave the TIG torch at the end of the weld until the post flow stops (post flow should be about 1 second post-flow per 10 amps of welding current). This will ensure that you are getting proper coverage at the crater of your weld. Try an experiment... Make a spot weld for about 3-5 seconds on that material and hold the torch in place after you stop welding until the post flow stops. Your spot weld should be nice and shiny, and probably a yellowish/salmon red color. If you do the same spot weld and pull the torch away right after you stop welding you most likely have a gray contaminated spot weld. This is just basically showing how critical it is to maintain proper shielding.
    No Gas Lens
    http://i45.photobucket.com/albums/f1...ogaslens-1.jpg
    <a href="http://s45.photobucket.com/albums/f100/kermienut/?action=view&amp;current=Shieldingflownogaslens-1.jpg" target="_blank"><img src="http://i45.photobucket.com/albums/f100/kermienut/Shieldingflownogaslens-1.jpg" border="0" alt="no gas lens"></a>
    With a Gas Lens
    http://i45.photobucket.com/albums/f1...lowgaslens.jpg
    <a href="http://s45.photobucket.com/albums/f100/kermienut/?action=view&amp;current=Shieldingflownogaslens-1.jpg" target="_blank"><img src="http://i45.photobucket.com/albums/f100/kermienut/Shieldingflownogaslens-1.jpg" border="0" alt="no gas lens"></a>

    -Travel Speed - Slower travel speeds will increase heat input, widen your heat affected zone (HAZ), and increase the temperature of the part after it is welded. The more heat you put into a weld joint, the more gas shielding is required for the weld area. If you travel too slow, the area that you just finished welding is so hot that you are not going be able to provide enough shielding coverage to reach the material temperatures that we talked about above.
    Here are some things that you can try to help out in your situation –
    Use the smallest tungsten size you can for the best arc control. I would also use the smallest filler that you can get away with. If you use filler material that is too large it takes too much amperage to melt the filler which means that the area where you are placing the filler is too hot.

    -Other Thoughts - Some people achieve better gas coverage by using a slightly larger diameter cup, or by using a gas lens. A gas lens will definitely make your flow of shielding gas more consistent and provide better coverage. Gas lenses are a beautiful thing but not a necessity! The picture below shows the difference between gas flows that the two provide. Obviously the gas lens provides more consistent flow.
    If you increase your travel speed you reduce heat input in the area near the bead. This means that the gas coverage is not needed for such a long period of time due to the material’s temperature being lower, It will also reduce distortion while welding on thinner material.
    Any of the points made above will help on Stainless, Titanium, Inconel, or pretty much any other material that can be welded. The same basic concepts also apply to Aluminum and magnesium.
    I respectfully disagree about the coloration of the weld.
    If you are getting rainbow colors on the weld it means that after the weld was completed that oxides in the weld area from surface contaminants, even dust,
    Make smoke and that is reducing the surface oxides and producing the rainbow colors. Just as in ceramics production. At 975º these colors will be produced.
    It does mean that at least the weld has not been overheated and turned to grey.
    If the weld area is perfectly clean and the travel speed and amperage is near perfect you can get a weld that is silver or chrome like but it is rare.
    You can get all yellow color but most of the time the colors will be rainbow colors.
    I TIG welded stainless for 6 hours per day for 11 years on stainless steel and had lots of time to notice these effects and colors. If the stainless is 302 instead of 304 that can change the colors too because of the lead in the stainless to make machining easier.

    If you do not believe me do this:
    Take a piece of stainless that is polished and just heat it to dull red and then
    take any burnable smoke producing material like newspaper,sawdust etc.,. and apply it to the stainless area after the red heat goes away. After a minute or two lift the clump of newspaper or sawdust and you will see the colors.

    Another easy way is take a piece of stainless or copper and pass a propane torch over the surface and immediately press a wad of newspaper or saw dust on the surface and notice the rainbow colors.

    This same process is used to produce the colors on RAKU pottery.
    These oxides on the surface of metal or pottery with copper carbonate solution now are being used by NASA to make electronic chips work better.

    BTW if you are going to electropolish the stainless weldment do not wire brush the weld area. It will show up after electropolishing and look scratched. You will notice that if wire brushed when hot, the brush really drags and scratches on the hot surface as opposed to when the weld is cold.
    Last edited by Donald Branscom; 03-12-2011, 12:57 PM.

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  • popspipes
    replied
    Another thing to watch is contaminated tungsten, if dipped always reprep the tungsten, welding with a contaminated tungsten will degrade the quality of the weld severley.

    Get the tecnique down on the bench on flat work, then work on your out of position welds.
    Gold or reddish color can usually be removed with a ss wire brush while the work is still warm, too hot and it will reappear as a shade of brown,too cold and it takes forever to brush it off. If you get carbide precipitation on one or both edges of the weld, it is too hot for the travel speed or the tungsten is contaminated, this will not brush off, 3m wheel or sanding means is required to remove it, and the corrosion resistance is all but destroyed.
    In my experience if a tubing weld was too narrow or pure silver in color it usually didnt penetrate 100%, in the Dairy field this is unacceptable on any weld that comes in contact with the product.
    When stopping a weld on tubing, speed up the travel before pulling off so that it isnt getting 100% penetration or it will leave a crater that sometimes goes thru to the inside.
    With a foot control, keep the travel speed the same and let off the pedal gradually as you go over the starting point of the weld, this gives the same effect.Walking the cup helps with the appearance as well, this wasnt my thing so I really cant coment much on it.
    Tigging stainless isnt difficult, but it takes some serious practice to get the 100% penetration and out of position down and make a nice looking tube weld.

    I hope some of this may be useful..........

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  • tawelding
    replied
    Try upping the amps a bit and speeding up your travel speed. Also your filler rod could be dirty try cleaning it with a rag and some acetone Good Luck
    Last edited by tawelding; 03-11-2011, 04:20 PM. Reason: day dreaming ....lol

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  • ®@©E®
    replied
    This thread is great!
    One thing I'd like to add, is about thermal wraps for turbo headers mentioned here. Please don't! 304L is wonderful material, but with max service temp around 1650F it's kinda risky to put that insulation around runners. I used to make thin stainless heatshields for my exhaust works. this downpipe shield for example

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  • Donald Branscom
    replied
    Great workmanship on that intake manifold JEEBUS!

    POST # 3 (Dipsomaniac) was on the money!!!! IT was the right track. Read why.

    The engineer covered the subject very well, but left too much info.LOL

    You said that the welds look rainbow colored and nice when using no filler rod.
    Then when you used filler that they got grey looking.

    This is what is going on....

    When you see the rainbow colors, those colors are oxides that are formed at about 975º.
    The colors form from reducing materials on the metal, tiny amount of oil or other contaminants. Even if it was clean.


    When your welding with filler rod turned grey it was because you slowed down too much and the metal got too hot.

    The "secret" to TIG welding is hot close fast.

    You need to use .045 filler rod so that you can travel faster. If the filler rod diameter is too large ,like 1/16 it will melt slower ,slow you down and overheat the metal.

    For that thickeness of tubing and with a 3/32 tungsten ,use the .045 filler even if you have to order it. Many welding stores do not carry it. You can get a one pound container at ARC ZONE. Ebay has (.045)308L it but they all want to sell you a $100. 10 pound box. Forget that.

    That is also "secret" info. Right filler diameter =correct welding travel speed for that thickness.


    BTW if you get a perfect TIG weld on a really clean piece of stainless,
    it may appear all gold in color or all silver!!
    Last edited by Donald Branscom; 02-08-2011, 09:27 AM.

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  • mooseye
    replied
    After reading more reply's, I though I would mention something mostly for the newer welders, but also something alot of old timers forget.
    When discussing welding you will always hear the word "heat" in many different contexts. If we tell someone the weld was to hot, the first thing they think is turn the amps down. It can be a little confusing.
    A good part of the time, if a weld looks like the base material has been overheated, it is not because the amperage is set too high. It is the exact opposite.
    Some posters have already said to turn the "heat" up. This does not mean get the metal hotter, of course. As said, turning the amps up allows you to travel faster. This lowers the amount of time you have an arc going on any given spot on your base metal which will naturally keep it cooler. The worst thing you can do is turn the amps down. This will cause you to have to linger waiting on the puddle to flow which will cause higher temperatures and a larger haz.
    I hope this makes sense to some of you more recent tiggers and maybe some help.

    Edit Also for the OP< You are on the right track, but, You are going to find a whole different ball of wax when you start on pipe. Especially the tight areas you have to work in. You will want to get some scrap pipe and just cut angles on it and weld them back up for some cheap practice.
    Last edited by mooseye; 02-08-2011, 09:21 AM.

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  • mooseye
    replied
    Dude,
    You need to stop worrying about color. It is a side effect.
    Lay your wire in the groove and turn the heat up a little. You will be able to weld over the wire in effect duplicating a pass with no wire. You have to increase the amperage to compensate for the added heat sink (the filler). You should not have to move the filler much at all if the heat and travel speed are correct.
    Try this and see if the color doesn't come on its own. It only means that your are getting even atmospherical contamination. Stainless is silver not red, salmon, ect...
    Those colors are caused by the gasses in the atmosphere reacting with the haz. No cup can keep it all out but if all things are right you get the same color on the entire bead. No color at all other than original material color would be the best possible.

    edit When I say weld over the wire, I don't mean spread it like peanut butter. You should have a puddle in the base metal groove and the filler should melt away and flow into this puddle as you walk the cup along the groove. If you don't walk the cup you can accomplish the same thing freehand with a controled motion. Just make sure you are filling the puddle and leaving no undercut due to lack of filler. If you have excessive undercut use a larger filler or slightly more angle on the filler rod.

    Originally posted by Jeebus View Post
    Alright I tried it again... this time with a bit more success.

    Here's all the info I think you guys would require.

    1/8th Stainless flat bar
    3/32 308 filler rod
    1/16 Tungsten Lanthanated
    # 8 Gas Lens
    14 CFM
    120 Amps

    -Before starting I cleaned both sides of the flat bar with a wire wheel attached to a drill. The wire wheel is only used on stainless.
    -I cleaned all pieces with acetone before staring, including the bench.
    -I used a brand new set of tig cloves

    It appears I did a bit better. The two things that I know I changed from tyring this yesterday was I believe I have the heat a bit higher then I did, and the other thing which I believe was a lot of the fix was I kept the filler in contact with the base metal. Basically never moving the filler rod and just melting it in as I went.

    That last step I mentioned is a major difference from what I was doing with aluminum. Aluminium I was always puddle, dip, move, puddle, dip, move. It appears if I tried to dip and move with stainless it turns grey.

    Anyways this is by no means perfect. Please ignore the pin holes and all the inconsistency. I was strictly focusing on not pulling the rod out away from the material.

    Please any suggestions you may have is much appreciated. Please keep in mind I'm a rookie when it comes to this so I'm sucking all this stuff in like a sponge.

    It was extremely hard to take pics of these but I tried my best.

    Bottom right in this picture is where I started, used no filler rod just to see if things were looking correct. I then moved on adding filler from there. Each length there's three seperate attempts. Each time trying I tried to change my control just a little bit. Settings all stayed the same.





    Last attempt I just used no filler rod again.


    Back side
    Last edited by mooseye; 02-08-2011, 08:54 AM.

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  • Hillbilly69
    replied
    SS Tig

    Welding without filler is different than with filler

    The addition of filler cools the puddle Therefore requiring either higher Amps for the same travel speed or Slower travel speed at the same Amps......??? Think about it you're trying to melt a lot more SS per inch of weld.

    Usually you do not want to slow down cause your heat inputs will get too high.
    When adding filler increase your amperage!

    Believe it or not sometimes you need to increase your amperage to reduce your heat inputs (You lower your heat by getting a quicker puddle and travelling faster).

    I would say the gray color is slightly overheated chrome (Burnt chrome) from travelling too slow because you are waiting on the puddle. Bump up your Amps by 5-10 when using filler.

    Usually the biggest problem with overheated SS is Carbide precipitation next to the HAZ that will crack when in service.

    Make sure to back purge with Argon or use Solar Flux.

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  • grizzquad
    replied
    Hi, Check out this website, and I think you will get some very helpful information and videos.
    www.weldingtipsandtricks.com

    Good Luck, Steve

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  • Guest's Avatar
    Guest replied
    I've heard some people mention how hard aluminum is to weld but in reality I found stainless to be more difficult to get a "proper" weld. Aluminum is rather simple as long as you can move fast and steady enough. Stainless is like someone said earlier.....it doesn't take much in either direction to make a too hot or too cold weld. And being that the welds are so much smaller than with aluminum applying the proper amount of filler is key as well. I've only messed with .065 stainless plate and 1.5"x .065" stainless square tube but TOO MUCH HEAT is most likely the culprit. Dave

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  • Maggie
    replied
    Thanks for the advice, I just got back from the repair job. Luckily the break was not in the place where I thought it might be but a much easier spot to repair. My co-workers went a little to far when grinding the welds smooth on the first go around and didn't leave much actual wall thinkness! Yeesh. Anyways, I think I'll post some pictures of my stainless beads in this thread so you all can give me some feedback on what I am doing wrong.

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  • Dipsomaniac
    replied
    Originally posted by Maggie View Post
    Oh, okay. Well it is all 308, is there a way to tell the difference? What is the difference in those classifications?
    308 is an austenitic stainless steel that is very stable throughout the entire welding process.

    Take a look at this link for the classification.

    http://ajh-knives.com/metals-ss.html

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  • Maggie
    replied
    Originally posted by Dipsomaniac View Post
    That would depend on if it is Martensitic, Ferritic, or Austenitic stainless steel.

    Martensitic stainless is subjected to becoming brittle at the affected areas but if you over heat Austenitic stainless steel and rapidly cool it, that actually softens the affected area...

    Oh, okay. Well it is all 308, is there a way to tell the difference? What is the difference in those classifications?

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  • Dipsomaniac
    replied
    Originally posted by Maggie View Post
    I am learning this process and I am having this same problem with the color. My question is, though it has been stated that once the stainless turns grey it has little to no corrosion resistance, is it still strong as far as from a breakage perspective? I have to do an onsite repair of a piece made using a MIG machine, but my only option is my TIG because it runs on 115 and that is all that is available...
    That would depend on if it is Martensitic, Ferritic, or Austenitic stainless steel.

    Martensitic stainless is subjected to becoming brittle at the affected areas but if you over heat Austenitic stainless steel and rapidly cool it, that actually softens the affected area...

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  • Maggie
    replied
    I am learning this process and I am having this same problem with the color. My question is, though it has been stated that once the stainless turns grey it has little to no corrosion resistance, is it still strong as far as from a breakage perspective? I have to do an onsite repair of a piece made using a MIG machine, but my only option is my TIG because it runs on 115 and that is all that is available...

    Leave a comment:

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