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Re: Straightening a weldment

Originally Posted by farmersammm

Water...…….Whether you use water, or let it air cool, it's all the same. The advantage of water is a rapid change..

Probably more accurate to say that either way works, but chilling the "restraining material" with water (or whatever) will upset the hot material faster than chilling it only with air, simply because water chills more effectively than air.

To paraphrase McDonalds, "You need the hot side hot, and the cool side cool" to effectively upset the metal to be bent/moved. Chilling with water will generally create a bigger temperature differential than chilling with air. The less the restraining material expands while the heated material expands and softens/weakens, the better.

Re: Straightening a weldment

Originally Posted by 12V71

I did one like this in a processing plant, 2 water headers for a bunch of condensers, they were 60' long with a pair 1.5" thredolets 10" apart every 36" on 8" schedule 40. After all the welding they looked like a banana. Turned them 180 degrees and heated a spot the size of a silver dollar opposite each weld and they came out as straight as a stringline.

thanks, i'll keep that in mind. funny how we can remember measurents and size pipe from jobs long ago, but i have hard time reembering a measuent from 5 min ago, or what i was supposed to remeber to walk out the door that morning w/. hell, i still remeber locker combos/friends phone numbers from jr high still.

yea, banana is the word. one thing that helps w/ bananaing a lil too, is, if they drill there hole after i weld thredolet, instead of before

Re: Straightening a weldment

Originally Posted by 123weld

it works doing this way like dave said, but individually before/during weld

I did one like this in a processing plant, 2 water headers for a bunch of condensers, they were 60' long with a pair 1.5" thredolets 10" apart every 36" on 8" schedule 40. After all the welding they looked like a banana. Turned them 180 degrees and heated a spot the size of a silver dollar opposite each weld and they came out as straight as a stringline.

Re: Straightening a weldment

It's common when welding pipe with fittings coming off the side, like above, to have to heat the back side to straighten it. Upper critical temp. is the key. You don't want to heat something up glowing orange and quench it. A few years ago I had a discussion with someone (an over confident CWI) over weave width of vertical up welds on steel plate or pipe. He was trying to say max. of 3 times rod diameter. Not finding a definitive answer I sent an e-mail to Walter Sperko who is one of the top people who works with ASME codes. He said there is no limit to weave width and more heat is actually better. The difference in grain structure is negligible. He said he would challenge any procedure limiting the weave width of a weld on standard grades of steel. He basically said it's something they did years ago that has no merit. On stainless where you want less heat input it applies.

I had to straighten the 1 1/2" thick bottom swing mount on my backhoe. I ended up Veeing it out and welding it but being such a thick piece I couldn't brace it in position because it would have had too much internal stress from being restrained. I had it bent down about 20 deg's and after welding up the V and letting it contract some I used a piece of flat bar to limit that last bit of contraction close to where it was straight. Still had a friend come over with rosebud to tweak it a bit but it was fairly close and thankfully everything went back together. I think heating it to get it exact may have stress relieved it somewhat.

Re: Straightening a weldment

it works doing this way like dave said, but individually before/during weld
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Re: Straightening a weldment

I had a situation where a 1.5 inch plate was distorted by a weld. I had to remove the bend in the plate. The plate was about six inches wide so I heated the top side and use a siphon gun spraying air and water continuously on the underside. The rosebud was able to heat the top surface to red while the under surface as cold from the water spray. I took the rosebud away and continued to spray the underside until it shrunk upwards and became straight. Without the cold spray I doubt I would have been able to create the red heat on the top surface without the heat going through the thickness.

Re: Straightening a weldment

Originally Posted by ronsii

I think a large dose of ultracool would have solved your problem permanently

...

If not, then the hammer Opus mentioned would have done the trick.

Re: Straightening a weldment

Originally Posted by Lis2323

Long ago.....I had a girl friend with long hair who chewed bubble gum. One time a bubble went astray and got stuck in her hair. What a mess.

Wish I had known about the spray liquid nitrogen trick.....she was like a boomerang. Kept coming back.

I think a large dose of ultracool would have solved your problem permanently

We used to use propane upside down to cool stuff all the time.... and it seemed plenty safe at the time...

Re: Straightening a weldment

There's been some posts that allude to damage to the base metal when heating, and cooling. I would direct those folks to literature developed by various highway administrations across the country. I won't include a link. Y'all ought to be interested enough to do it on yer own. Hint...……..highway bridge straightening.

Mild steel has incredible properties. One of which, is tolerance to welding, and heat straightening. You will NOT create the mythical HAZ when straightening with heat. Straightening has only one limitation...…………..critical temperature...……...1200*

The weld, on the other hand, is more subject to heat damage. Keep your heat out of the weld area if possible.

Water...…….Whether you use water, or let it air cool, it's all the same. The advantage of water is a rapid change.

Heat shrinking works best when the steel is restrained during heating. It likes to expand, then contract to its normal dimensions. When you restrain it from expanding, it will shrink to what you want it to be. This is called "upset", read up on it. Heat shrinking means heat shrinking...…..again...…..read up on it.

Straightening a weldment

Originally Posted by OPUS FERRO

ronsii



I've used spray liquid Nitrogen to remove chewing gum
in carpet. Freeze - hammer to a powder - and vac . . .


Opus

Long ago.....I had a girl friend with long hair who chewed bubble gum. One time a bubble went astray and got stuck in her hair. What a mess.

Wish I had known about the spray liquid nitrogen trick.....she was like a boomerang. Kept coming back.

Re: Straightening a weldment

ronsii

Originally Posted by ronsii

Cool!!!!

I've used spray liquid Nitrogen to remove chewing gum
in carpet. Freeze - hammer to a powder - and vac . . .


Opus

Re: Straightening a weldment

Originally Posted by Lis2323

I have often wondered for welding smaller heat critical projects if something like this would work to minimize distortion.




Obviously if it worked it may not be cost effective on bigger jobs but has anyone ever tried something similar?

Cool!!!!

Re: Straightening a weldment

You wouldn't want to quickly cool a critical weld unless it was certain types of stainless where a water quench can anneal it. Would need to use jigs and fixtures and carful distortion control. Was reading about huge diesel engines with welded construction and distortion control takes on a whole new meaning.

Re: Straightening a weldment

While the cooling spray boils at a low temperature, I'm pretty sure the amount of energy required to boil it off is WAY less than the same amount of water. Using something that boils at -51C rather than +100C is probably little help when the amount is so limited (not like you can dop something in it), and you start out with a weld closer to +1500C. A wet rag would probably cool things down much quicker - if that gives less distortion or not is another matter.

Re: Straightening a weldment

I have often wondered for welding smaller heat critical projects if something like this would work to minimize distortion.




Obviously if it worked it may not be cost effective on bigger jobs but has anyone ever tried something similar?

Re: Straightening a weldment

Originally Posted by Lis2323

Clamping it down securely and taking your time with the welds allowing them to cool will help. Skip around also. Do one leg near an end and then perhaps one halfway up the length. Don’t do them consecutively.

Also, welding hotter so you can get in and get out faster (with less total heat input) can help, too.

Re: Straightening a weldment

Being it's only 1/8" it will warp much easier with enough weld for 1/2" thick material. I think your racks could be bent into pretzel shapes before they broke. Clamping them back to back when welding them would help and like said above don't weld one section all at once.

Re: Straightening a weldment

Clamping it down securely and taking your time with the welds allowing them to cool will help. Skip around also. Do one leg near an end and then perhaps one halfway up the length. Don’t do them consecutively.

Re: Straightening a weldment

Originally Posted by Welder Dave

Glad it worked. How many pounds are your clamps rated for?

The big one is 2000 lb according to Kant Twist. It felt like I was going to have an easier time with the press so I went with that.

Originally Posted by BD1

Glad you got it straightened out.
You do know what caused that right ?
So it will be avoided on future projects.

Well, I thought it was inherent to welding on one side of the long piece. I’d love to hear more about how to avoid it.

Re: Straightening a weldment

Originally Posted by SlowBlues

If you don't have a torch or press, just match every weld (with another weld) on the opposite side of the bowed angle iron (to balance the shrink forces) and then grind them down (or don't).

Match every weld and then you can go back and add more weld (shrink) if needed. Easy, and time consuming, but a torch setup is ~$300, a hydraulic press is ~$150 and takes up quite a bit of room.

Since your racks look straight in one dimension i would heat in the purple areas, but only on the bowed side (not the triangular bit on the "top" side in the pic). If it is bowed in both dimensions then heat both sides to straighten in two directions (up and to the right in orientation to the colored "where to heat" pic).

I was about to say this, but you beat me to it, this is the way to do it.
I did some stainless steel fabrication with 2x2 tubing, the way it was laid out made it warp, I had to weld on the opposite side to straighten it out, it works fast too,

Re: Straightening a weldment

Glad you got it straightened out.
You do know what caused that right ?
So it will be avoided on future projects .


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Re: Straightening a weldment

That's pretty impressive, it can be pretty tough to get a warped angle that straight. Looks great

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Re: Straightening a weldment

Glad it worked. How many pounds are your clamps rated for?

Re: Straightening a weldment

I first tried some clamps on my table but it seemed pretty hard to move the metal:


So I built a frame to support my weldment at two points and hold it from twisting:


I overdid it a bit on the first two but the third came out pretty straight:

Re: Straightening a weldment

Originally Posted by BD1

What is this getting mounted to?

To a 2x6 wall, with tabs that I will weld on to each bracket.

Originally Posted by tapwelder

In this case I would Bend it cold. Concentrate the bending force on the flange. Angle likes to twist. You could also weld a bead opposite the welds.

Originally Posted by cwby

To straighten it cold, you can set it on top of a hydraulic jack on your table. Center of bend. Chain each end to the table, jack it past true & let pressure off to check it. It may have to go an inch or two past true to make it relax back straight.

Originally Posted by Welder Dave

Do you have some strong Bessey clamps or C clamps? Maybe you could put them back to back with 2x4's or 4x4's in the middle and use clamps at the ends to try and straighten them out some. Will have to go a little more than required. This would be relatively inexpensive to try. If the racks are bolting on a wall will probably straighten out when bolting on.

Thanks I have a press it’s just an awkward shape to fit in there. These are some helpful ideas on how to get around that. I appreciate the help.

Originally Posted by SlowBlues

If you don't have a torch or press, just match every weld (with another weld) on the opposite side of the bowed angle iron (to balance the shrink forces) and then grind them down (or don't).

I thought about this too, thanks. I’ll try some mechanical methods first and then maybe some additional beads.

Originally Posted by Lis2323

And be patient. It might get worse before it gets better. And when things start going the way you want, DON’T get greedy. Take slow steps and try to remember what works and what doesn’t.

You’ll get it. Have fun!

I appreciate the encouragement and useful guidance. I knew before I f’ed it up I should ask people who have done it. I was kind of hoping the only solution was to buy a torch and oxygen tank (it would be about time) but I’ll give the mechanical methods a go first. Thanks all. I’ll report back.