View Full Version : Please critique my welding.
11-14-2008, 08:45 PM
I am building a Lotus Seven and this are my first few welds. Fortunately they won't be seen as I have ground them down and the steel floor panel will cover them. What do you think?
These were my first few welds this morning. Later in the day I flipped the frame over and did a few more on the other side and they came out much nicer. I'll see if I can post those too.
Last night I was welding a couple of spots where the 16 gauge tubes butt together and I suffered a nasty hole where the tubes end melted. My solution was to tack weld, let it cool, tack weld, let it cool, until the hole was filled. Is this the correct procedure to fix a problem like that?
11-14-2008, 09:00 PM
Here are a few pics later in the day. I sped a little and made sure my arm was better supported.
11-14-2008, 09:15 PM
Pause briefly at the end of your weld beads and allow the metal to build up just a little bit. This will minimize the crater left a the end of the weld bead. The craters at the end of your beads are potential weak spots where fatigue cracks can start.
your later welds definitely look better than the earlier beads.
Make sure to go back with a wire brush or wheel and clean all those silicon islands(glassy deposits) off the welds. They'll ruin any paint job you do if you leave them on. Either the paint won't stick to them, or they'll pop off after you painted and leave lots of little places where bare metal will show. I wouldn't grind the beads flush unless you need to for clearance reasons. The face reinforcement gives you a little insurance with regards to weld strength. A perfect weld is fine if it's flush, but the face and root reinforcement helps overcome small imperfections in the welded joint.
I don't see any obvious undercut or cold lap, but some of the others on here are better judges of that. You posted two photos of fitted joints that had not been welded. One showed 0 root opening, and the other showed ~1/8"(I guess). I recommend using some root opening rather than butting the joints flush. The wider root opening will give you better penetration and a stronger weld joint.
Your jig looks like it gives good support to the frame in 2 dimensions. But welds will distort in 3 dimensions. I hope you're using some good clamps to hold the frame down on the jig base. Otherwise you might see some distortion up/down relative to the jig base.
I don't know what your level of expertise is, but short circuit MIG welding is sensitive to welding technique. Stay at the leading edge of the puddle or you run the risk of making good looking, but poor performing, welds.
If you're a novice, post what equipment, filler metal, shielding gas, and settings you're using so others can factor that into their constructive criticisms.
11-14-2008, 10:33 PM
I think the first weld was run a bit cold, maybe more importantly, it looks like you were bouncing the wire a bit, and did not have a good braced stance when you started that weld. The material looks like the rest of the welds are much better; I was thinking if you are burning through the thin material, turn the speed up just a little bit. It may help that. As for grinding down the welds?? I would keep that to a bare minimal, as these are going to be structural welds, and the good book says you should not be grinding down strucutural welds. Here is a link for you: http://weldingweb.com/showthread.php?t=11271&highlight=42ft+raceboat This shows some pics of the basics for filling a bigger gap, and also, it gives the basic of filling a hole. Considering the thin material you are welding, I would not be trying to have a gap that you will need to fill with a root pass. On material that thin, you should be able to fuse it completely with good tight fit-up. And, the fact that you're burning through will tell you that; you have plenty of penetration. Also, if you have a gap that you fill, you are likely to see a lot more weld distortion, and it will defeat the jig work you have done. Pretty decent welds, the latter ones.
11-15-2008, 11:19 AM
My problem was that I hadn't practiced any welds where the tubes butted together and the position of the weld was difficult as it was an inside vertical weld with the tube resting on the jib table. As I said I think I my problem was too slow travel. Supporting my arm and speeding up really improved my welds. The tubing is 1 inch square and the weld just happens so quickly it's hard to adjust speed.
The reason for me grinding the welds down is that the floor panel gets plug welded on the bottom of the frame so there will be added support for those welds.
On the top side of the bottom frame vertical uprights must be added to these areas. The "book" suggests that the frame be completely tack welded before the finishing welds are made but I didn't like to try and join three pieces of metal with one weld.
And if you notice I am using wire to hold down the frame to the building board.
vBulletin® v3.8.7, Copyright ©2000-2013, vBulletin Solutions, Inc.