[Demented]

I know acetylene would be ideal, but I'm living in an apartment complex and it's a bit off limits. Never gotten into heavy wall 4130 before so preheat used to never be a worry. I know it will likely take way longer to get up to the 300*F preheat I'm after, but would the prolonged heating cause any issues in thr 4130? My biggest concern is just where the 4130 roll cage will be welded to the mild steel truck frame.
I do have an induction furnace i'm wilking to use for parts, but would rather not as I still use it occasionally for casting.

[smithdoor]

I know acetylene would be ideal, but I'm living in an apartment complex and it's a bit off limits. Never gotten into heavy wall 4130 before so preheat used to never be a worry. I know it will likely take way longer to get up to the 300*F preheat I'm after, but would the prolonged heating cause any issues in thr 4130? My biggest concern is just where the 4130 roll cage will be welded to the mild steel truck frame.
I do have an induction furnace i'm wilking to use for parts, but would rather not as I still use it occasionally for casting.

I use rosebud torch or wed burner
Simlpe and low cost

Dave

Sent from my SAMSUNG-SM-J320A using Tapatalk

[smithdoor]

I know acetylene would be ideal, but I'm living in an apartment complex and it's a bit off limits. Never gotten into heavy wall 4130 before so preheat used to never be a worry. I know it will likely take way longer to get up to the 300*F preheat I'm after, but would the prolonged heating cause any issues in thr 4130? My biggest concern is just where the 4130 roll cage will be welded to the mild steel truck frame.
I do have an induction furnace i'm wilking to use for parts, but would rather not as I still use it occasionally for casting.

I use rosebud torch or wed burner
Simlpe and low cost

Dave

Sent from my SAMSUNG-SM-J320A using Tapatalk

[cj737]

You don't need a preheat for .120 wall 4130. Heat treatment and preheat typically only come into play on thick, solid material. As for welding the cage (new) to the existing frame, MIG or TIG is perfectly fine and strong enough with ER70, or better still, ER80. ER80 is less common and more expensive, but is emerging as new preference for many CroMo cages.

I am fortunate to be well aquatinted with a race car chassis builder who builds spec frames and cages for Nascar, Sprint Series, Truck, etc. He only uses 4130, and they MIG everything, no preheat. And his cars pass Tech Inspection every time and win races (often).

[Demented]

Well damn, I always thought once you got up to .120 wall preheat was needed. ER70 is what I'll be using. 2 pass TIG for the most part. MIG for some reason gives me migranes so I never go that route. I was looking into ER80 but from what I've been reading, ER70 has a little more flexibility to it, which will be good for me because I'm likely to crash the dang thing 637395639202736 times a race.

[cj737]

I’m not going to tell you what or how to do it, but, a double pass may actually hurt you more than help you. You’re increasing the heat effected area and run a risk of making the surrounding area of the weld more susceptible to cracking or failure. A single, good pass on a tight fit run in would be my choice.

[Demented]

I've got some 4130 coming to practice on so I'll go the single pass route. There's been an ongoing argument for years over single or multipass on 4130 cages in offroading. Seems the general consensus, at least since 2009, has been a quick root pass with no filler to fuse the joint then a second pass with filler. I've seen some the trucks welded that way handle some pretty nasty crashes with no issue so figured it was probably the norm by now.

[cj737]

I've got some 4130 coming to practice on so I'll go the single pass route. There's been an ongoing argument for years over single or multipass on 4130 cages in offroading. Seems the general consensus, at least since 2009, has been a quick root pass with no filler to fuse the joint then a second pass with filler. I've seen some the trucks welded that way handle some pretty nasty crashes with no issue so figured it was probably the norm by now.

Exactly how I’d do it (fuse, and filler). This approach requires a good fit up though.

[Demented]

Fitup will definitely be spot on. I'd rather scrap a length of tube and start over than deal with even a blonde one of a gap. The finished truck will likely be 6000-7000lbs. Last thing I want is any suspect joints.

[Poland308]

I wouldn’t consider it heavy wall unless the wall thickness is over .5
But here is a chart
http://www.tempil.com/assets/1/31/weldi ... _chart.pdf