Hey..

I started making my own subframe today...
Thought I'd make it out of chromoly... just because i thought i could...

I live in Holland... and the material is called 25crmo4 over here... dont know if it's the same as 4130..

anyway... i'm using a lincoln wire to tig weld it... LNT 25... which is ER 70S-3 wire..

I'm getting cracks along the weld as soon as i stop welding...
I'm trying to weld the tube to some mild steel bushes...
I'm welding it at 130 amps on pulse... square pulse...

Does any1 have any tips for me? or a solution to the problem?
I have a 309 filler rod lying around... gonna try that next... see if that works out better...

 

post heat to keep it from cracking.

 

I would skip the chromoly.

You're using mild steel parts and welding it with mild steel filler rod.

That is defeating the purpose of even using chromoly.

Use mild steel. Do some more research on chromoly and do some more practice on some non critical/practice weldments.

Just jumping in and welding up a mission-critical part using a material you are inexperienced with is not the best plan I've ever heard.

 

problem is i have dies for bending this size tubing.... i cant get mild steel tubing in this size here in holland... so i have to make it work...

post heating wont work... as it's already cracked the moment i take off my helmet...

 

That's odd. The filler should be fine for what you're doing. I can't say I have ever had any mild steel stuff crack on me like that. Are you welding at 130amps or is the machine set to 130? Are you cleaning everything first?

 

the machine is set to 130 amps... maybe a bit higher... but on pulse...
maybe that's a problem?... too many temp differences?

i usually weld stainless like that... maybe a bit less amps... but this is thicker material...

i clean everything with brake cleaner... nasty stuff... but works every time..

i have a lot of experience with welding stainless... but want to get into cage building... so i want to get this right...

 

what is the wall thickness on the chromoly? i have welded .063,.083 and some smaller stuff in chromoly and 130amps is way to much even if you are pulsing it..try turning the amps down.and are you using the correct filler rod? i use er70s for chromoly instead of er80s because it is more ductile and lessens the chance of cracking.

 

Pulse is cheating anyway. Try it without.

 

filler size, material thickness? post pictures.

if it is undercut i could see it cracking.

 

i'm using er70 filler wire...
material thickness is .98 inch.. 2,5mm
the mild steel bushes i'm welding it to are 5mm thick...
I'll try to get some pics..

 

i tried less heat... no pulse... and it seems to work out fine...

110 amps now... set on the machine...

 

what SIZE filler?

also get those pictures up

 

filler is 2 mm...

camera is not working along... i'll get pics as soon as it is cooperating..

 

Hey man, glad you could figure out what your issue was. But you need to read this!!! Its very imperative to your health. I would hate to read a thread about someone getting hurt.

https://honda-tech.com/forums/welding-fabrication-53/just-note-all-you-welders-out-there-2611372/

 

Filler is fine, amps are high. Back off on the heat, move @ a steady pace, dont overheat the material, and let it cool gradually or you'll run into further problems.

 

the 110 amps is still to high?

@vtecspeed1320.. thnx for that... looks like i need to find another type of cleaner..!!

 

Denatured alchohol works great for me. Glad you figured it out.

 

thnx for the help

 

i can't even see how you're not blowing holes in the material! you need to turn your amps down to about 50-70 amps and use a gas lense for better coverage. if you really need to run that high of an amprage, you need a trailing gas to shield your weld. i think you may have to travel really fast cause of the heat and your weld is still red hot when the shielding is gone, thus causing it to crack.

 

Should be 1 amp per .001, +/- a speed and material factor (no more then 10% though). So 90-100 amps would be fine. Could be technique. Could be contamination. Could be wierd metal that doesn't like standard rod.

 

I'd be using 1mm filler, 1.5mm tops!

 

50 - 70 amps is waaaayy to low... cant even get it to melt properly... let alone have some penetration..
and i'm using a gas lense already...

i feel that if i turn the amps to 100 it still takes to long to heat op the metal and form a decent pool...
110 is on the low side... but it works... but that's my feeling...

i also noticed the 2mm filler is a bit on the large side yeah...

 

then turn the pulser off, and 70 amps should work, if 100 on pulse is not cutting it.

reguardless of amperage turn the pulser off.

 

chromoly does not like alot of heat it will crack..heres some chromoly i welded when i first started about 6 months ago. it is .083 wall at about 75amps.

 

I haven't had a ton of chromoly experience, but I've done some trophy truck parts and some chromo wheelie bars and it welds fine for me. It takes a second or two longer to puddle up then mild (kind of seems like it has a hard coating on the outside) but once you've established a puddle it doesn't like heat, so move quick, and keep the temp low. I stab the peddle all the way to puddle, then back off to about 1/2-3/4. I used 309 stainless wire to weld it, maybe a no-no ? but it worked great for me, and all the parts I welded have held up (even the trophy truck, and all those parts got magna fluxed and x-ray'd).
Good luck.