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Vertical welding on a C channel frame. Fact or fiction.


li7in6

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I've heard from several places for and against welding vertically on a C channel. The idea is that a vertical weld across even 50% of the vertical width of the frame will weaken it dangerously. Supposedly due to the annealing of the metal surrounding the weld, causing it to get brittle and weaker. Possibly leading to a crack or other failure. Welding across the entire vertical width of it will create a sure fire failure point on the otherwise strong frame. The only way to solve this is to normalize and possibly temper the entire frame to the desired hardness(damn near impossible with a truck frame).

On the other hand I've heard its all nonsense and welding across a length of metal will not weaken it.

So, whats you're guy's take? If I were to want to attach link mounts, or longer leaf mounts, the recommended method of welding would be to weld along the length of the frame and leave front/back ends unwelded? or just weld the whole thing up, or forget welding and bolt it up.
 


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When welding to the frame you should try and keep all pieces being welded on in a Diamond patter, stay away from vertical welds. Never bring any welds to a sharp point, try and make them round so as not to create a stress point.
 

Iron Ranger

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The frame of a truck is not special in any way, it's still a strip of mild steel put into a series of brakes and dyes to get it into shape. Tempering and annealing is pointless because it's not high carbon and it's not an alloy steel, and as long as you don't put 6 passes of super hot welds over each other, you'll be fine.


If you're welding a step side or some attachment stuff, then as long as the plates being welded are round or diamond shaped(like what sasquatch was saying), you'll get the most possible amounts of strength out of it.

Welding is always stronger than bolting, if it's possible, weld it vertical UP, this reqires some extra skill, but it is as strong, if not, stronger than a regular flat weld(I did this on 1" plate and bend tested it for college, solid across the board). A nice hot bead will more than get the job done
 
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DRanger024

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The frame of a truck is not special in any way, it's still a strip of mild steel put into a series of brakes and dyes to get it into shape. Tempering and annealing is pointless because it's not high carbon and it's not an alloy steel, and as long as you don't put 6 passes of super hot welds over each other, you'll be fine.


If you're welding a step side or some attachment stuff, then as long as the plates being welded are round or diamond shaped(like what sasquatch was saying), you'll get the most possible amounts of strength out of it.

Welding is always stronger than bolting, if it's possible, weld it vertical UP, this reqires some extra skill, but it is as strong, if not, stronger than a regular flat weld(I did this on 1" plate and bend tested it for college, solid across the board). A nice hot bead will more than get the job done
Agreed 100% from the viewpoint of another professional welder.
 

li7in6

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Thanks for the info guys. Some of the 'pros' on race-dezert, pirate 4x4, and other places make it out to be a safety concern.

Can you guys elaborate on a few things you mentioned?

try and keep all pieces being welded on in a Diamond patter
Having a bit of trouble visualizing this. Do you mean cut the plate that is to be welded in a jagged diamond pattern to increase the length of the weld without increasing the overall length of the piece?

stay away from vertical welds.
Does this mean you believe there is some truth to the vertical weld weakening subject?

Tempering and annealing is pointless because it's not high carbon and it's not an alloy steel
I'm no metallurgist, so forgive my ignorance, but I'm under the impression that you can anneal and temper all kinds of steel. Since fusion welding requires bringing the metal to its melting point, and ends with letting the metal (of the weld itself, and surrounding it) cool on its own to room temperature. This is very similar to the annealing process, albeit less controlled. So is it out of the question that the steel in/around the weld could be softer/more ductile? If any annealing is taking place, could simply cooling the site down more quickly with a wet rag help prevent this?

don't put 6 passes of super hot welds over each other, you'll be fine.
This leads me to believe if a properly executed weld will not instill enough heat into the base metal to cause any significant annealing or change its ductility.

if it's possible, weld it vertical UP, this reqires some extra skill, but it is as strong, if not, stronger than a regular flat weld
Can you elaborate on this a bit please?

Again, thanks for the help guys.:icon_thumby:
 

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It's always made sense to me that any time you apply sudden red to white-hot heat to a piece of metal that was cold-formed (stamped), you change the molecular structure of the metal enough than some type of change in it's fatigue resistance will be inevitable (that area of the metal will now be under tension from contraction upon cooling as well). Combine this with how a C-channel frame constantly flexes more than something that is boxed, this "bump" in the frame's molecular structure seems much more likely to induce a crack forming around it.

I've always just avoided this whole chance of failure by simply making a long "L-bracket" that bolts against the outside and bottom of the frame, then weld my suspension (or rockslider) attachment point to that. Never have had any issues with bolts loosening or the plate shifting on the frame.
 

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I'll agree with Shawn's (Junkie's) post.

Agreed 100% from the viewpoint of another professional welder.
As a professional engineer, I'll disagree. Perhaps from a macroscopic level, things may not be effected; but microscopically and molecularly, they are. You may not see any failure immediately, but you are reducing the fatigue life of the c-channel frame in these locations. The radpid heating and cooling can cause microscopic fissures to form which can propagate into larger cracks over time (fatigue failure). Welds are typically more brittle than the surrounding base metals, hence why they are often said to be "stronger".

I don't like vertical welds, but in some instances they are unavoidable. I suggest that you try to avoid them by using rounded plates or fish-eyed plates wherever possible.
 

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All service manuals tell you what you can and cannot do to a frame. I could scan and post the pages from the ones I have, and I may. But the thing that sticks in my head is #1 don't mess with the flanges and #2 avoid the area near the flanges. You can drill all you want as long as you don't have more than three holes in a vertical line or something. I installed a generator in my bus by bolting L-brackets to the frame rail so I definately read the pertinent section of the manual. Drilling and bolting takes longer than clamping and welding, but it's better.

The end of the frame past the rear leaf spring mount doesn't matter. You are allowed to do whatever you want back there pretty much. Which is why a receiver hitch can be bolted to the flange, and the bus has the recovery hooks welded there as well.
 

Iron Ranger

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I can elaborate some of your questions.

1. A diamond(stop sign) shape eliminates sharp 90 degree corners, which spreads the stress points to 8 corners rather than 4, or a round platform which has no corners so the stress is spread as evenly as possible.

2. Vertical(or down-hand) welding is the weakest of all the positions. It flows nice and may look nice, but it doesn't penetrate into the steel worth jack-squat. The only times where this is admissible is if you have a corner to corner joint with a hairline gap, that way it'll still fill in nice, and penetrate to the joint's full potential. Or on anything under 1/8" plate, the thin plate should heat up enough for proper penetration. If it's not turning blue on the other side of your work piece, you're not hot enough.

It's not a matter of weakened steel, it's a matter of poor penetration.

3. Any and all welds(excluding aluminum) should be stronger than the base metal. Tempering and annealing are necessary in high carbon and alloy metals to reconfigure the HAZ(Heat Affected Zone), and the crystal base structure. In low carbon/alloy steel(mild steel), it's really pointless to do this because the HAZ is usually under control(unless excessive heat/welds are excecuted). At the steel mill, they can actually "burn" steel, it gets too hot and forms perminant, brittle, useless grain structures. I've read where they had to throw away 280 tons of burnt steel, no good.

4. The weld should be the thickness of the thinner piece being joined(EX. 1/8" to 1/4" plate, an 1/8" bead is all you need). What happens when you overheat steel with weld is the weld metal and the base metal form huge crystals that are inline with each other(they should be out of sync), and that makes it brittle and finally, failure. Had an example done at the college, took a stick welder, used 10 sticks to weld a 4" joint, and cut it in half. You could see the actual grains of the metal separating from each other.

On a truck frame, I wouldn't worry about it. I trust you have good judgement on what's strong and what's not.

5. Vertical up is one of the hardest welds to do. As you weld, gravity is constantly trying to pull the weld puddle down, which if done incorrectly, will look like the aftermath of an expired TV dinner.

It takes the right amount of heat, wire speed, travel, epecially gun angle, and travel speed. A slight weave is acceptable, but not too much, it'll cause unwanted stresses in the weld. The uphill travel heats up the metal as you go, making the weld penetrate better. This is what's used in the field for repairs on heavy objects, when moving or turning it is impossible, so multiple welding positions are required, and down-hand is a big no-no.

It's easiest on flux-cored wire, because the flux creates an instant "mold" that holds the liquid metal in place as it cools, forming a flawless bead. Solid MIG wire is a little more erratic, takes a lot of practice to get that one figured out.

Whoo, that was a lot of typing. I'm going to bed.:icon_thumby:
 
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Iron Ranger

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One more thing. Those other places that you said was a safety concern, they probably have to say that because Joe Shmo who hasn't welded before is now trying to put a weight-bearing item on his frame and is going to go extreme off-roading suddenly breaks something. The slogan "WARNING, PROFESSIONALS ONLY" apply's here too. If you don't know how to weld, there is always someone who is more than willing to give you a hand.

Or some frames are different than others? Shouldn't be, but I could be wrong.
 
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li7in6

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You've been tons of help and that answers a lot of my questions.

I have a few more. How do the 'pros' feel about brazing when it come's to suspension mounts and pieces that would see similar loads. I've heard of entire race car chassis' being brazed together, and I have read that a braze joint can be stronger than the base steel (I believe I read this in 'Welders Handbook' by Richard Finch). Obviously fusion welding is the prefered joining method for every offroad fabricator I've known or heard of, just wondering how you feel about brazing on a properly prepared surface for load bearing parts. I would think that brazing would be weaker per unit of area, but because you can get so much better penetration between two flat surfaces (due to capillary action) it might make for a stronger joint overall.

Also given the relative cheapness between a oxyacetylene setup and a MIG setup. What are your thoughts on fusion welding with a torch. I understand typically both are needed and MIG is a much cleaner method, but are there guys out there building trucks with an acetylene torch?

A little background on me. I've welded both MIG and oxyacetylene for my previous job, but no where near a professional level I assure you. Very little actual training, most metal repair/fabrication was done with the oxyacetylene or propane torches we used for torching glass, I was the one who convinced them to actually get the MIG. Mostly did general fabrication for tables, sheet metal patching, making cabinets, supports for in ceiling air evacuation systems, etc. I've also worked with my dad in welding and minor fabrication with his sand toys when i was a kid. I think I can lay down a decent bead in both (MIG/oxyacetylene). I've read a few books on MIG/TIG and plan on taking a few coarses this coming semester. In effect I have very little experience with STRUCTURAL welds. I did do scrap weld bend/smash testing for fun but I'd hate to weld something like a leaf mount and have it break off due to what i think is a fine weld but has too little penetration. Or worse, crack my truck frame in half due to an improperly performed vertical weld :icon_confused:. Obviously I'm not going to start boogering up critical parts of my truck without faith in my welding so I'm just trying to take it all in.

Anyway, thanks for the help so far and any in the future.
 

Iron Ranger

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I don't have a lot of experience with brazing, I only do a little silver soldering at work. The shop next to us does a ton of brazing on copper to brass applications. Maybe the frames are soldered because everything can be set at once and run through a furnace which solders all the joints in one motion.

Oxy welding would get the job done, BUT, it needs massive amounts of heat for the filler to melt into the puddle properly, and massive amounts of heat will warp the truck frame, which is a very bad thing.

I wouldn't worry about cracking the truck's frame in half. Like I said, the amount of heat needed to mess with the grain structure of the metal towards failure is massive.

If you are not confident in your welds, then bolting it with 1/2" Grade 8 bolts will be fine also. That's what I did with mine, not because I'm not confident in my welds, but the new mount goes in the same exact spot as the old one.

Here's some pics of the work:







All was done with a Handler180 110V welder. Best graduation gift I ever received.
 
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AllanD

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I've heard from several places for and against welding vertically on a C channel. The idea is that a vertical weld across even 50% of the vertical width of the frame will weaken it dangerously. Supposedly due to the annealing of the metal surrounding the weld, causing it to get brittle and weaker. Possibly leading to a crack or other failure. Welding across the entire vertical width of it will create a sure fire failure point on the otherwise strong frame. The only way to solve this is to normalize and possibly temper the entire frame to the desired hardness(damn near impossible with a truck frame).

On the other hand I've heard its all nonsense and welding across a length of metal will not weaken it.

So, whats you're guy's take? If I were to want to attach link mounts, or longer leaf mounts, the recommended method of welding would be to weld along the length of the frame and leave front/back ends unwelded? or just weld the whole thing up, or forget welding and bolt it up.
Good greif! Could you atleast try to look up words in a dictionary before you try using them?

"annealing" metal may weaken it, but it does so by making it SOFTER not "more brittle"

Welds often create a hardness gradient nearby and this results in failure near the weld but not necissarily because it is more "brittle"
it is usually because the weld was poorly planned relative to the load that was going to be applied to it.

Frames are NOT heat treated at all, simply because they aren't the
right kind of steel to BE "hardened", they are low carbon "mild steel"

the pieces are cold formed.


Next it's the weld that is subject to brittle failure for one simple reason a weld by definition is cast metal, cast in place as the weld melts and then solidifies.

Frankly welding on the top and bottom flange of the frame is far more compromising to the strength.

any welding should be done with doubling plates to spead the load
as far as possible.

More metal is always a good thing if you design things so that they are bolted as well as welded you have insurance against a broken weld.

Also to be remembered welds are weaker under tension, less so in shear
and essentially a non worry under compression

you also need to consider that the frame rails ar subject to both bending load and torsional load so you really need to look at the entire structure and consider how it is going to be stressed under load in different situation.

But the welds to REALLY worry about are the ones across the narrow flange at the top or bottom of the frame.

The thing is which flange is more critical changes depending on
exactly where on the frame you are talking about and how you
are talking about applying load to the frame...

but welds are by definition cast metal.


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li7in6

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Good greif! Could you atleast try to look up words in a dictionary before you try using them?

"annealing" metal may weaken it, but it does so by making it SOFTER not "more brittle"
Give a guy a break. I meant ductile, not brittle. :annoyed:

welds are by definition cast metal.
Any insight as to why welding to a cast peice of metal isn't a good idea?
 

AllanD

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Give a guy a break. I meant ductile, not brittle. :annoyed:



Any insight as to why welding to a cast peice of metal isn't a good idea?
The usual issue is that most Iron castings are made of alloys that simply aren't weldable.

There are four common kinds of cast iron
"Grey Iron"
"Malleable Iron" (Includes "white Iron")
"Nodular Iron" (Aka "Ductile Iron")

when you weld cast iron there is a tndency for Martensite formation
(different form of carbon crystal formation) near the weld because of rapid cooling near the weld thus you have a hardness gradient across the material

the real problem is that each of the different forms of cast iron have different preheat and cooldown requirements, not to mention the fact that anealing after the welding is done...

Welding to cast iron is quite simply a job that is an unforgiving bitch.

a bitch that enjoys slapping back

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"Ductile iron"


Some are, most aren't.
 

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