Acid Etch & Penetration

[Bede]

Been dabbling around with setting and tests on 40mm plate with my 320 amp mig. Ran a few runs initially with 1.0mm wire then stepped upto 1.2 and the difference is quite noticable.

The first couple of pics are of multi-runs at just shy of 300 amps on 1.0mm mig wire. Nowhere near enough penetration. The next couple are of 1.0mm wire at 320 amps, wire feed at about 14 m/min - penetrates well into the smaller block of 40mm but just sits on the wider plate. Still not enough juice.

The final couple of pics are of 40mm, root one side, root and two caps on the other, at 320 amps with 1.2mm wire fed at 13 m/min. Acceptable levels of penetration but to be honest I'd rather a touch deeper.

Anyway, just thought I'd stick up some examples. I'll also show a couple of roots from the lower settings on 1.0mm wire. Upon imnspection they look fine, until you etch them and discover inadequate penetration.

 

[Bede]

And here's the root runs from the first two photos of etch tests above. Look a tad cold as the thickness of the material is sucking out the power but I was surprised at how little those welds had penetrated.

 

[galooph]

Interesting (and a bit scary!) how little those welds penetrated, as they look good on the surface. What do you etch the surface with?

Just had a look at your web site - didn't realise you were only in Chesterton. I'm in Alsager and my parents both used to teach around Chesterton

 

[Bede]

Random - teach where?!

It's etched with Nital solution. 3% Nitric Acid in Methanol solution.

 

[Richard.]

Can you not prep the joint slightly to get in there deeper or is that not permitted.

 

[Richard.]

Random - teach where?!

It's etched with Nital solution. 3% Nitric Acid in Methanol solution.

I etch with exactly the same mixture and ratios.

 

[Bede]

I have a square joint to weld from the design so just running some test pieces before I do the job. Don't want to start straying from their design although I'd have preferred a weld prep on some parts.

 

[Bede]

So this is a 7 run, 14mm fillet. 320 amp 1.2mm G3Si1wire, Ferromaxx 15 gas.

The root penetration is around 4.5mm deep into the parent metal.

 

[TechnicAl]

320 amps on a 1.2mm seems a bit excessive and 300 Amps on a 1.0mm is definitely excessive

The 300 on 1.0mm is almost a third higher than 320 on 1.2.........when you measure it as amps/mm2

So the 1.0mm should be much deeper than the 1.2mm

There might be something else at play here

 

[Bede]

The 1mm wire at 300 should give deeper penetration than the 1.2 at 320 amps?

 

[TechnicAl]

yes.........calculate the cross sectional area and then divide the current...........300 on 1.0mm is 380 amp/mm2...............320 on 1.2mm is 280 amp/mm2

 

[Kent]

On that joint on that sort of thickness I should expect to be pre-heating. Long way away from what I do now mind you, can you tell us what it is?

 

[Bede]

It's an 8 metre 24 tonne lifting beam.

I suspect I may have a problem with the set I'm using.

Gonna run a test with another set tomorrow. If I'm not happy im gonna hire a 400 amp Lorch.

Never had an issue with this kind of thing before, never failed an MPI or load test but this'll be an expensive lump of scrap if it's not right.

Considered preheat but this seems borderline for the thickness?

 

[galooph]

Random - teach where?!

Dad taught at St. Chad's primary, Red Street and Mum was a bit further out at Wood Lane. Going back a bit now though!

 

[Richard.]

I personally would pre heat something of that size and thickness. I know your using a lot of amps but in general it is a low heat input process and you can still get hardness in the HAZ.
It wouldn't hurt to warm it up before you weld it.

 

[Jim Davey]

You need Force Arc from EWM in your life

 

[Ed.]

If you can, to try a gas mix which has 20% to 25% CO2 which might help, assuming that you have a bottle of it lying around, or else as others have mentioned preheat and bevel the joint.

 

[backpurge]

Interesting stuff and great photos, that second root photo looks as if you've used a "sawing" technique rather than a straight forward stringer bead

 

[Bede]

It's just the light. I've always welded with a very very tiny weave. The weld is smooth and flat but when I take pics on my iPhone directly under the light above me it reflects off the construction of the weld and exaggerates it.

I'm gonna run a test piece on a different welder this morning to start with.

Jim - that's the level of penetration I'm looking for. I'm not a million miles away with the root weld but not enough to be satisfied to crack on with the job.

I actually looked you up on Facebook but you're all the way down in Southampton!

I guess a lack of investment in upto date kit has taken a big bite out of my ****. I hate being restricted by equipment. Damn recession.

 

[Jim Davey]

There are other EWM dealers, where are you based?