T Joint woes

[anth510]

Hi all, just joined up, here's my intro thread:

http://www.mig-welding.co.uk/forum/showthread.php?t=35373

I'm currently making a new lower alternator mount, here it is before welding:

I comprises of 3 parts. A lower mounting plate, and two vertical tabs. I need to weld those two vertical tabs onto the bottom mounting plate, and then probably add some sort of a gusset for strength between them. The material is 5mm steel.

I am using a Uni Mig 180 amp mig welder, with .08mm wire and BOC Argoshield Light gas.

My problem is that I can get nice welds on 5mm steel when doing practice runs on flat sheets, but then using the same settings on a T joint doesn't give me the same results. I welded the piece in the photo above last night and wasn't happy with it, plus I welded it all without letting it cool down between runs so it's slightly warped, therefore I'll be making another one!

I noticed that at times it appeared I wasn't getting enough penetration, the welds were tall and not "sticking" to both pieces of metal at some points (more heat?), but then when I get near the edges of the piece (end of the run) the metal goes bright red and starts to melt (less heat?) This is where I'm confused. Should I pull the welder slightly further away from the piece at the end of the run?

Any help is appreciated

 

[Lawnmowerboy]

180a is enough to get decent penetration on 5mm imo.

 

[pedrobedro]

I replied in your other thread but I'll put a bit here as well. Just use a few good fillet tacks where the weld will not obstruct the bolts, the alternator adjuster will hold it as well. Start at the edge instead of finishing there if it's a problem.

 

[stuvy]

rather than replying on the other thread, i think you need alot more practise mate, theres no short cut to start welding!

straight looking car though

 

[anth510]

not looking for a short cut, just advice I'm going to get into the garage tonight after work and re-make a new mount, then practice a bunch on scrap pieces, I'll post up pictures of how I go.

 

[F.J.]

It sounds like you need to turn the power up in your welder. You mention getting nice runs on flat sheet and looking at your other post some if them are up to the mark. The thing is your now trying to weld two components together which means more power to create penetration. Full runs probably wont be needed either, as stated, two good stitches either end of the braces should do it. Good look and awesome motor

 

[anth510]

I'm currently welding at a power setting of 5 out of a possible 6, I think 6 might be a bit too hot?

I got part way through making a new mount tonight but I had a curse of flat battery syndrome (4 cordless drill batteries all died on me!) so I used the time to do some practice welds on two T-joints. The metal was sanded down with a sanding bit on a Dremel before I welded. Let me know what you think...

Piece number 1:

other side:

underneath:

Piece number 2:

other side:

underneath:

Can anyone tell me why I'm getting those craters above the bead of the weld? Any advice on how to improve is appreciated, you guys can probably see heaps of things that I can't

 

[ChrisJohnsSculpture]

When you're welding a fillet joint you will often find that the two pieces heat up at different rates, simply because one is bigger than the other and can conduct heat away from the weld faster.

This means you need to put more heat into one side of the joint than the other to compensate (in this case the lower part requires more heat). This is exacerbated by teh fact that the upper edge of the weld will tend to slump down under gravity if it doesn't freeze fast enough. It's the combination of these two factors which causes the undercut on the top edge of the fillet.

The solution is to compensate by a combination of the weave you use and the angle of the torch eg angle the torch slightly towards the bottom plate rather than the dead centre of the joint and use a weave which pauses longer on the bottom plate and quickly laps the puddle onto the top plate.

Basically it's something which takes a bit of practice and careful observation of the weld puddle as you go.

 

[anth510]

thanks mate that's a huge help! thanks for taking the time to explain it so well, I'll have another shot with that technique as best I can and see how it goes.

 

[Justme]

With that brown deposit it looks like a touch more gas would not go amiss either.

Oh & what gas / mix are you using? (forget that just read your other thread)


Your getting quite a bit of splatter, If I remember right you need to turn the volts down a touch or up the wire speed a smidgeon (or its the other way round lol).

 

[backpurge]

Don't weave, point the wire right into the corner and keep your travel speed up

 

[dickie bell]

Don't weave, point the wire right into the corner and keep your travel speed up

can I ask why you say not to weave I have always weaved on 5mm+ mtl

 

[backpurge]

When you weave there is a real danger you wont get fusion in the root of the joint, people tend to fall into the trap of thinking "if I weave it around and lay lots of metal down the weld will be stronger", when in fact the opposite is true, with MAG you are far better off laying stringer beads

 

[anth510]

I thought I needed to weave to tie in the two pieces of metal? Especially since I'm nearing the max thickness of metal recommended for my machine (max is 6mm structural). That's what I gathered from everything I've read/watched so far. I'll try running a straight bead on a test piece and see how it differs.

backpurge: If I try no weave + faster travel speed, would I need to increase wire-speed to compensate?

 

[backpurge]

See how it goes first, judge your travel speed by keeping the wire feeding into the front edge of the weldpool, if the welpool starts to overtake the wire speed up a bit. You want to be looking for a mitred weld with a reasonably flat face and a minimal of spatter. If you need to lay a bigger weld build it up with stringers not by weaving.

 

[anth510]

Well I had a couple more practice runs today without weaving and I have to say I like these results much better, I've written the power and wirespeed settings next to the welds, 4/6 came up really well.

Straight off the mig...





After a quick wire brush...





Comparing my last attempt (on top)...



A closer look at the neatest weld...



So yeah, I know it looks nicer, but I'm keen to hear if it's actually better. I like the idea that it's down a notch in power compared to my last try because it'll help me keep the distortion down.

 

[Engineer1964]

This is the type of weld you want to try and achive, These are some test pieces i did when i did my coding

You want to try and learn to keep the tourch in a striaght line, it looks like your going all over the show, Keep it fairly hot for good penatration but when your getting undercut you need to turn up the wirespeed or slow down with your travel.

Looking at your last effort it looks like your getting better

 

[backpurge]

Spot on example Gerry.
Anth, looking a lot better but I think you may still be travelling too slow, just because you are letting the weld size build up doesn't mean it's stronger

 

[Engineer1964]

Spot on example Gerry.
Anth, looking a lot better but I think you may still be travelling too slow, just because you are letting the weld size build up doesn't mean it's stronger

Thanks,

Alot of it is just practice and trial and error, we were all newbies at one time.

 

[anth510]

Thanks guys, loving the feedback.