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Thread: Welding aluminum: how different is it from steel?

  1. #11
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    Quote Originally Posted by Sparky_NY View Post
    First time I tried my spool gun I had horrible results. Went through about 4 tips in just the first couple minutes, the wire stuck in the tip and plugged it. THEN.... I fell back and regrouped... did some reading.... I was running the spoolgun in the same manner as doing steel..... the biggest difference is the stickout !!!! About a inch stickout is close to what you want and of course with steel its about 1/3 that amount. Once I went to the proper stickout, things improved radically.

    As for cleaning the metal... I have friends with a fab shop that constantly mig aluminum. They do not clean new extruded material at all, just weld it and it comes out fantastic. Textbook says cleaning is a lot more important than it is in the real world. Now IF the material is all corroded and nasty then yes you must clean it up but if its shiny new it should mig weld nicely as-is.

    As stated, pure argon is the correct gas for aluminum mig. IF you try it with the blend used for steel you will have zero success.

    With all the problems you describe, my bet is the stickout was your major problem and possibly the wrong gas also. Its not much more difficult than mig welding steel from what I seen. You DO move along faster too.
    I struggled with a spool gun for ages, but I kept at it because that's what I had and I had aluminum that needed welding. I'm not good by any means, but I can make two pieces of aluminum stick together. I've patched a few boats including one of my own and when I was short on cash for new stock I welded up miss cut molds and recut them. I didn't actually want to weld aluminum when I started. I just couldn't get the local welding shops to remember to do my projects right after putting me off for two more weeks for 4-6 months.

    Part 1:
    My Rig. I'm running spool gun on straight DCEP MIG with 100% Argon. I burned up a lot of tips to start with. So rather than fight it I bought a couple huge bags of spare tips. Remember I had things I wanted to get done. Then somebody suggested cutting back the wire feed tube and threading it back a little deeper. I started by just screwing the gas nozzle out and wrapping it with tape. I found an 1/8" extra recess on the tip reduced my burn backs by 60%. So I cut the tube back and 1/8 inch and threaded it an 1/8 inch deeper. The next thing that helped was taking the extra few seconds to cut off the ball on the end of the wire every single time when I stop. I just make it part of my stopping habit. Even before I look at the weld. That cut the remaining burn backs by another 50%. Instead of burning up half dozen tips for every small project I was burning 1 or 2 for smallish projects and 2 or 3 for larger ones. There is one more mechanical thing. I didn't get this one for years, but recently I decided to "feel" my gas flow. I put my hand in front of the nozzle and I could feel that it always seemed like there was more gas on one side than the other. I put a little piece of mesh back inside the gun to act as a sort of a gas spreader. As soon as I did it I got less soot, and my welds improved.

    Part 2:
    Clean, Clean, Clean, and when you think its clean enough clean some more. I found if I didn't brush down to shiny metal and wipe down with acetone (some guys think DNA is better) within 30 minutes prior to the weld I needed to brush again. This means on long welds with lot of clamping and setup I can not just clean the whole thing and then weld it. I found if I brushed and cleaned the whole part of the project I was working on at that time, and then brushed each section again right before I welded it I got much better results. If I took a break to get some water or have lunch brush again. Guys who run AC TIG don't understand how OCD I am about cleaning when welding aluminum with my plane old DC MIG welder, but I get welds that stick, and I have made tanks that don't leak. I think the type of rig makes a difference in cleaning, but the issue is not always just crud on the material. Its just as much the fact that aluminum oxide (which coats all aluminum directly exposed to air) melts at a higher temperature. From what I understand AC welding aluminum has a cleaning action on the aluminum oxide on one side of the cycle and a penetrating action on the other side of the cycle. I also noticed on thicker materials that it doesn't melt through and drop out as quickly so it seems like I don't have to clean as much as the textbooks or my experience says. I've welding one more than one 1/4" thick brace that I knew I didn't clean as well as I should have.


    Part 3:
    Practice. When I got my welder (Miller 212 Dual gun) I practiced with a lot. In fact I ran almost exclusively aluminum with it. In another thread you can read about my stupidity with the steel stinger. Anyway I tried welds on things as small as .043 to as thick as .375. Both kind of outside the supposed range of the machine. I found with lots of preheat I could weld .375, and for one project I welded .125 bulkheads to .375 structural pieces. It wasn't pretty. I wasted a lot of flap discs cleaning up welds and chasing pin holes. I found with .043 I could weld about half way around a 1/2" tube if I moved the gun about as fast as I could go. Of course I then promptly blew a hole in it, but it showed me it was possible. Practice isn't a one time thing though. I keep all my scrap aluminum so I can practice a weld before I do the actual weld. If I welded aluminum every day I might not have to, but I 've found that my projects come out 200% better when I do. I get some raw stock scraps the same thickness as my project. Using the correct wire I make a couple short practice welds until I have a feel for the right speed to move the gun. Then I go over to the actual work piece and make a couple more practice runs with my finger off the trigger. When it feels right I check my gun, clean the work piece again, and pull the trigger on the next pass.


    Part 4:
    I found on 1/4 inch plate I could wallow around like I was welding steel, but on anything thicker I had to crank it up and keep the heat on it or I would lose my preheat. On thinner than 1/8" my best practice is to make a bunch of short one inch (or shorter on even thinner stock) welds and space them out skipping back and forth all over the work piece until I have a little stitch weld about every 4 to 6 inches. On smaller work pieces I would sometimes just walk away and let it cool after a couple stitches because if I didn't it would build heat and burn through. On bigger pieces I like to have every weld a couple feet away from the last if I can. When its all jacked up looking I jump around again filling in between the stich welds. I start on a stich weld and I finish on a stitch weld. Its not pretty, but it sticks and it doesn't have start and stop craters that way. Then the next one is several fee away again. If the work piece isn't that big I'll walk away and let it cool between welds.

    Is DCEP MIG with a spool gun or a push pull gun the best way to weld aluminum? No absolutely not. AC TIG will give you the prettiest welds, and pulse MIG will allow you to make the longest fastest welds. I bought what I thought was going to be the most flexible welding rig for the most different things at the time and then I had to learn to weld aluminum with what I had.

    Are there guys who can make good looking welds without all that effort. Sure there are. They do it every day. I'm not one of them.

    A lot of folks have a one dimensional view of welding aluminum. You have to use AC TIG. No you don't. If you practice with it AC Pulse TIG might be the easiest way to weld aluminum, but you can weld aluminum with DC TIG, DC MIG, Pulse MIG, Aluminum arc rod, and even with a torch and one of those torch rods with flux. They will have different results of course. I have used the torch rod, and my first welds looked really good, but since I didn't really understand the process I proceeded to burn up my project on the next few welds. Now I bet I could do better just applying some of what I learned from learning to DC MIG weld aluminum and practicing some good heat management.

    When it comes to welding I'm a total hack, but in the end I get one piece of metal to stick to the next. I hope this helped.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

  2. #12
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    Bob,
    In your first paragraph you told we what you are doing wrong, and none of the things you did were necessary. You said you cut the round ball off the wire each time. The fact you have the round ball and not a point tells me you are welding using shrt arc and aluminum should be welded in spray arc. Your welds are smoky, and not because the metal isn’t clean. There are little white balls all over the floor, and penetration is poor with sharp ripples in the weld. The sound of welding is crackling. Sound about right?

    Turn the voltage up to about 21 volts while welding. Start with a long stickout and keep turning up the wire speed, way faster than for steel, until the sound changes to what a spray gun makes. You’ll see the ball disapear, the arc will become fan shaped and weld bead smooth out, with very little spatter at all.

  3. #13
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    Quote Originally Posted by garyhlucas View Post
    Bob,
    In your first paragraph you told we what you are doing wrong, and none of the things you did were necessary. You said you cut the round ball off the wire each time. The fact you have the round ball and not a point tells me you are welding using shrt arc and aluminum should be welded in spray arc. Your welds are smoky, and not because the metal isn’t clean. There are little white balls all over the floor, and penetration is poor with sharp ripples in the weld. The sound of welding is crackling. Sound about right?

    Turn the voltage up to about 21 volts while welding. Start with a long stickout and keep turning up the wire speed, way faster than for steel, until the sound changes to what a spray gun makes. You’ll see the ball disapear, the arc will become fan shaped and weld bead smooth out, with very little spatter at all.
    I get very little spatter when welding aluminum. I get a nice sizzling sounding like slowly frying bacon. I run aluminum wire at about 3/4 inch stickout per the advice of multiple welding experts. I am getting spray arc the vast majority of the time. If I get short circuit its purely accidental and momentary. I would note that I am welding 5052 with 5356 90% of the time and it DOES weld differently than 6061 with 4043. When using 4043 on 6000 series aluminum its much cleaner and easier. Ultimately spool guns are notorious for poor gas coverage and as I stated when I I made some adjustments to force the spool gun to provide more uniform coverage the cleanliness and the quality of the weld improved. Even when welding 5052 with 5356 wire. I recessed the wire tip, and added a fiber insert to improve evenness of gas coverage.

    I am sure people never get a ball on the end of the wire, but I get it all the time. Sometimes its pretty small and has little or no affect, but by clipping it off every single time I get no problems from it. Thick, thin, high power, low power. It gets a little ball on the end of the wire. It requires increased current to burn that ball and then you sometimes get flash back into the tip. By always clipping that off even if its very small it virtually eliminates start up flash back and tip melting from that.

    Some of the steps I took to cure the problems and get acceptable welds were because of the advice of guys with lots of welding experience and multiple certifications who experienced very similar problems and told me what they did to cure them. I never would have thought of adding a fibrous gas spreader inside the nozzle, or trimming back the tip holder inside the gun on my own. Those things made huge differences in soot and weld quality.

    I am aware that there are people who can urinate on two pieces of metal from across the room and make them look like they were tig welded by a 35 year veteran. They can make mediocre equipment perform like top notch equipment. I get it, but as I detailed ad nauseum I was able to learn to get acceptable welds with a bottom of the line Miller spool gun. I might have learned how faster if I hadn't just assumed because it said Miller on the side of it everything was top notch. It surely was not.
    *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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