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  1. #16
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    Your beads are lumpy and the edges of the bead where it meets the parent metal is standing up and not blending in. Also check your angle of the torch as "pipeclay" mentioned, pushing it is generally the preferred method of MIG welding as the super heated gas is pushed ahead of the arc, substantially heating and melting the base metal to be welded. It can be done both ways as pulling will give you a taller narrower but more penetrating bead if done correctly and pushing the torch will give a shallower wider penetration. But as I said before pulling is not normally done and also not recommended. Also the distance from the wire to the torch will also influence on how good the bead is.

    In my Pic 1 the toes blend in to the base metal but in Pics 2 and 3 the weld is fine except for the very start of the weld, if you look at the start of the right hand side of the bead in Pic 3 you should be able to see that a bit of the weld has just pooled there without really biting into the parent metal. After starting the bead I should have backtracked a bit over the start with the arc to fix it, bear in mind that pic is of 25mm thick steel and the first one is I think about 18mm. That thin darker line on the toes isn't undercut but a very fine line of molten silicon slag that flowed there. As that weld wasn't that crucial in that section I did not worry about that little bit of bead start.
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  2. #17
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    Quote Originally Posted by Ed.. View Post
    pushing it the preferred method of MIG welding as the super heated gas is pushed ahead of the arc, substantially heating and melting the base metal to be welded. It can be done both ways as pulling will give you a taller narrower but more penetrating bead if done correctly and pushing the torch will give a shallower wider penetration. But as I said before pulling is not normally done and also not recommended. Also the distance from the wire to the torch will also influence on how good the bead is.
    As well as being the inert shielding component of the welding process, the Gas is also a cooling agent for an air cooled MIG torch, it actually has a chilling effect on the MIG consumable package/front end. It does Ionize in the arc, but my understanding is that most of the parent metal heating effect is via the weld pool and arc, not 'superheated gas'. On balance, and more broadly speaking, gas is a poor conductor, and not an ideal method for transfer of heat.

    I've never heard of the push/pull direction effecting penetration profile- although I know it effects bead profile. Interested to know more... unless you mean that a higher bead profile at a set voltage gives less arc heat into the joint, and less penetration as a result?
    I know the Choke effect/ inductance settings on the mig are probably your best drivers of arc characteristics (narrow/penetrating vs wide/shallow). Only applicable to short circuit transfer mode, as this setting chokes the current rise at short circuit, and can also help with tuning out spatter on the job.


    My advice, FWIW:
    Unlike stick or TIG, MIG gives you your voltage, and your amperage is manipulated through your wire speed and contact tip to work distance (CTWD). Try and strike an arc wtih 300mm of wire hanging out of the end of the torch and you'll get the idea how important arc length is. The other consideration for an operator is travel speed. This takes a bit of muscle memory to get right.

    Many beginners try to be too fast. Slow it down. Watch your weld puddle and watch as it wets the edge of your joint. This is the driver for your travel speed.
    I notice your welds have that 'stack of pennies' look - desirable for weldporn, but oftentimes you want a weld free of the stop/start look which can trap any glassy silicone inclusions or create wormhole voids in the weld where insufficient penetration into the weld occurs. Aim to move your torch only as fast as is needed, and as consistently as you can.
    Torch angle of approx 20 degrees on the push is about right, might need to modify if you have obstacles in the way, 'in the real world'.

  3. #18
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    Quote Originally Posted by Commander_Keen View Post

    I've never heard of the push/pull direction effecting penetration profile- although I know it effects bead profile. Interested to know more... unless you mean that a higher bead profile at a set voltage gives less arc heat into the joint, and less penetration as a result?
    I know the Choke effect/ inductance settings on the mig are probably your best drivers of arc characteristics (narrow/penetrating vs wide/shallow). Only applicable to short circuit transfer mode, as this setting chokes the current rise at short circuit, and can also help with tuning out spatter on the job.
    There quite a few test examples on the internet comparing the effects of both methods, I did find one good video about a week ago which I was going to link but unfortunately can't find it now, typical! and a couple I did find, showed the weld which mainly looked like short circuit, I think that it has a greater effect when done in spray mode. I usually do push welding but have done done a couple of pull welds in the past, although now can't remember why as it has been a very long time ago. I find that the push method gives a better looking bead overall but each to his own I suppose.

    Here is a link I found just now, have a look at this one.

    https://www.youtube.com/watch?v=QRht...tbChannel=null

    As for the heating effect of the gas, when doing the spray transfer method, you can see the metal melting in front of the arc from the combination of arc heat and the gas preheating the metal directly in front of the pool. I use a 95/3/2 mix, as the CO2 dissociates into CO and O2 and combined with the 2%O2, it stabilizes the arc as well giving extra heat energy to the arc temp. The temp can be many thousands of degrees C and when directed towards the front of the weld and will significantly heat up the metals going forward, whereas pulling the bead will not direct as much heat towards the back, most likely due to the torch angle, think of it as similar to an extreme hot air gun blowing forward. Most of the heat is going forward over the area to be welded and preheating it, whereas pulling the bead, most of the heat is being directed over where you just welded and a little towards where it's going.

    Personally, I doubt that the shielding gas at ambient temps from the torch itself would make any significant cooling difference to the Arc or Plasma temps when talking about these sort of temps. Maybe for the torch itself though. That is why if you use straight argon for steel (MIG) you have to substantially increase the voltage to get more heat and stabilize the arc as Argon is not reactive, but add the CO2 and O2 gases and they dissociate and greatly increase the plasma temp (MAG).

    Actual how or why is probably best left up to the scientists or engineers who study these sort of things as this sort of explanation is way above my pay grade if you know what I mean! I just press the trigger and weld.

    Cheers

  4. #19
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    So I had another little go this afternoon at some beads with slightly more voltage and wire feed speed. im not sure if they are an improvement ill let you blokes be the judge.

    I also learnt another couple of valuable welding lessons, the first being the importance of welding gloves when I picked up a piece of metal that burnt me through the gloves can only imagine the pain if I wasn't wearing them. Secondly to from now on always where pants that cover the opening at the top of my shoes getting hot metal in my shoe with no hope of getting it out is not fun

    IMG_2230.jpg

    IMG_2231.jpg

    IMG_2232.jpg
    A lot of spatter on this last one sounded a bit funny (can't put my finger on why)

  5. #20
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    The top pic has under cut where the arc has meted the top edge and still wobbly, just had a thought, are you holding the torch with one hand? If you are, use two hands, place one hand on the bench to steady the torch, hold the torch with the other hand and rest it on the hand that is on the bench, position the wire from the torch and then use the bottom gloved hand as a slide to give a consistent travel speed, it will also help to keep the wire height constant which in turn will help to stop the the arc/bead from going up and down. Do a couple of dry runs to test for any jerkiness or problems.

    As for the gloves, had to laugh, after 48 years I still occasionally do the same, you know the story..... I know it's very hot, but I need to move it so I will just quickly pick it up and move it before the heat goes though the glove, proceed, half way through, ouch, ouch, drop, swear. You would think that one would learn! but it's called complacency, guarantee you it won't be the last time you do it either. Another thing you have to look out for when the time comes to actually make something largish, it is accidentally touching something while it's still hot or leaning over to get a better view, at welding temps it takes just a split second of contact to make your skin blister even through a shirt, by the time you feel it it will be too late.
    As for shoes, you really need to get into the habit of wearing safety boots, not so much for really thin stuff but definitely if the metal has any weight to it. Ask yourself, if the metal I am working on or anything on the bench were to drop on my toes, would it hurt me, if the answer is yes then you know what you have to wear, and do not wear just a T'shirt or shorts.

    Heaps of other stuff you should know but you will find them out as you start welding. Have fun!

  6. #21
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    Quote Originally Posted by Ed.. View Post
    The top pic has under cut where the arc has meted the top edge and still wobbly, just had a thought, are you holding the torch with one hand? If you are, use two hands, place one hand on the bench to steady the torch, hold the torch with the other hand and rest it on the hand that is on the bench, position the wire from the torch and then use the bottom gloved hand as a slide to give a consistent travel speed, it will also help to keep the wire height constant which in turn will help to stop the the arc/bead from going up and down. Do a couple of dry runs to test for any jerkiness or problems.

    As for the gloves, had to laugh, after 48 years I still occasionally do the same, you know the story..... I know it's very hot, but I need to move it so I will just quickly pick it up and move it before the heat goes though the glove, proceed, half way through, ouch, ouch, drop, swear. You would think that one would learn! but it's called complacency, guarantee you it won't be the last time you do it either. Another thing you have to look out for when the time comes to actually make something largish, it is accidentally touching something while it's still hot or leaning over to get a better view, at welding temps it takes just a split second of contact to make your skin blister, by the time you feel it it will be too late.
    As for shoes, you really need to get into the habit of wearing safety boots, not so much for really thin stuff but definitely if the metal has any weight to it. Ask yourself, if the metal I am working on or anything on the bench were to drop on my toes, would it hurt me, if the answer is yes then you know what you have to wear, and do not wear just a T'shirt or shorts.

    Heaps of other stuff you should know but you will find them out as you start welding. Have fun!
    I am using both hands but still have problems with fluid movement get caught at times etc. I'm sure it will come with time, I am enjoying welding and cant wait to start fabricating a few things, I have a rather large 6 car shed that needs to be decked out with shelving etc and all the other fun stuff. I just want to get to a point where I can be certain anything I make isn't going to fall apart, especially the benches because they will cop a fair bit of vibration etc.

    Always wear safety boots but unfortunately the work pants I wear have cuffed bottoms which sit above the top of the boot leaving a nice opening for drops of hot metal. Will probably invest in a set of heavy long sleeved overalls for welding so I don't burn holes in all my work clothing lol.

  7. #22
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    Quote Originally Posted by Ed.. View Post
    Personally, I doubt that the shielding gas at ambient temps from the torch itself would make any significant cooling difference to the Arc or Plasma temps when talking about these sort of temps. Maybe for the torch itself though. That is why if you use straight argon for steel (MIG) you have to substantially increase the voltage to get more heat and stabilize the arc as Argon is not reactive, but add the CO2 and O2 gases and they dissociate and greatly increase the plasma temp (MAG).

    Actual how or why is probably best left up to the scientists or engineers who study these sort of things as this sort of explanation is way above my pay grade if you know what I mean! I just press the trigger and weld.

    Cheers
    Cheers for the video.

    As a quick aside for the shielding gas piece:
    Cylinder gas is at high pressure (up to 300BAR), but used at a much low pressure (liters per minute at STP). This change in pressure brings with it a change in temp (this is how refrigeration works). Also, this is the reason why a cylinder in use is colder than ambient, or why valves can frost up.
    So, shielding gas flow is a cooling mechanism for the contact tip, via the diffuser and out the nozzle, before it's primary use as an inert shielding barrier for the weld. Contact tips which contain a lot of copper, when they get hot, anneal, go soft, and prematurely wear (ovalise), and lead to feed issues and erratic arc conditions. While shielding gas alone will not do the job, it plays a not insignificant part in cooling. The secondary torch cooling is the heatink fins which are on the side of many torches (binzel 36's, and 24's for example). Otherwise the swan neck.

    As for ionization, I might need to read up on that. I know it ionizes, but I thought that was just a charged gas particle which assists electron flow thru the arc, not disassociation of CO2 into C and O2. Maybe only differences with different gases like O2 and CO2 is their ability to ionize mre or less easily? ...

    ...I'm no engineer, could be considered a scientist but in a completely unrelated field to material science.

  8. #23
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    No problem, as for the video, it sounded a bit like it was short circuit to me, which from memory doesn't have as noticeable a difference as what you get when in spray deposition. At about 7min in or so, the guy did an etch test and you could see that the pull weld bead was higher and had a slightly deeper penetration. It wasn't a bad video as it removed the human error from the test by using the auto rail device.

    As for the disassociation, from what I have been told, only a certain percentage of the CO2 breaks down, adding to the O2 already in the mix, maybe the rest breaks down into CO, anyway as I said before, I just press the trigger and weld, so long as it works! the how's and why's, that is for other smarter people than me to concern themselves with.

    Cheers

    Ed.

  9. #24
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    Just found another post regarding push or pull MIG welding.

    https://www.youtube.com/watch?v=jtlO...tbChannel=null

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