Welding mild steel to chromoly?

[lifeofwelding]

Does anyone know how this works out? any special filler rods needed? Any other special needs for this process?

Shawn

[kcstott]

Works fine just don't expect the mild steel to do the work that the chromoly should be doing. You may run into the weld cracking due to the lack of similarities between the two metals but over all it's fine.
Filler rod is not a big issue but it would help if you use a chromoly rod

What is it exactly you are doing?

[lifeofwelding]

Im building a mini dune buggy. I wanted to make the frame out of 4130 and all the mounts from mild steel. I was curious as to how the mounts will work since they arent the same type of metal.

[Broccoli1]

http://www.aws.org/wj/apr03/AWfeature.html


Some info

[kcstott]

If in "mounts" you mean engine mounts, shock, axle, steering mounts. Sure I've done it for a few friends with buggies. Weld prep the heck out of them and burn them in. I've used a mig every time and that seems to be the best way.
Just be sure your mounts are either prefabed (store bought) or are stout enough where needed. Overkill is a good thing in this aspect

[Laiky]

mild steel rod NOT chromoly rod, er70s2 or 6, do a search and you will find all the 4130 info you need.

[kcstott]

Originally Posted by Laiky

mild steel rod NOT chromoly rod, er70s2 or 6, do a search and you will find all the 4130 info you need.

What he said yeah yeah that's it. Guess I should have been more specific.
Yes mild steel filler is fine for welding mild steel mounts to 4140 4130 tube

[Broccoli1]

Originally Posted by Laiky

mild steel rod NOT chromoly rod, er70s2 or 6, do a search and you will find all the 4130 info you need.

That's the info in the Link I posted

[Blue Collar Moto]

Actually I think the chromoly will crack before the mild steel. The moly is stronger but at the welded joint without pre and post heat can be verry brittle after welding. About 1/4" away from the weld will be the weakest spot. (assuming your using 1 1/2 tubing) Im sure theres alot of people on here that know much more about this than I do. Just my .o2

[kcstott]

Yes this is true but on small pieces for what ever reason pre and post heat is not used and works fine. Is this to say that pre and post heating would not help?? No just that it almost makes no difference with the kind of loads these parts will see. and it just plain not practical to pre and post heat a buggy frame. lots of little flanges and pieces that need to be attached by the time you pre and post heated one part you could have had half of them done. This is also why a lot of the mounts are made from 5/16" 3/8" and up to 1/2" and bigger plate. once again OverKill but it get the job done.