Manifold Flange Warping....

[Coo]

I was asked to weld up a mild steel exhaust manifold where it had cracked around the pipes, in position shown on pic:

Using my Clarke 150 I managed to put enough heat in it to warp the flange...
Welded the pipes okay though, certainly wont fall off.

Don't have an actual pic, it'll be on the stock car by now heading to practice!

Question is, how could I minimize/avoid warping next time ?

I was thinking:

A) Weld part at time allow to fully cool - only this is a long process!
B) Bolt it tightly to a bit of 10mm thick plate that I have to transfer heat to the plate.

I welcome your advice

Cheers

 

[roofman]

I was asked to weld up a mild steel exhaust manifold where it had cracked around the pipes, in position shown on pic:

Using my Clarke 150 I managed to put enough heat in it to warp the flange...
Welded the pipes okay though, certainly wont fall off.

Don't have an actual pic, it'll be on the stock car by now heading to practice!

Question is, how could I minimize/avoid warping next time ?

I was thinking:

A) Weld part at time allow to fully cool - only this is a long process!
B) Bolt it tightly to a bit of 10mm thick plate that I have to transfer heat to the plate.

I welcome your advice

Cheers

bolt the flange to a piece of scrap plate..going nowhere

 

[Coo]

Will do that next time, Cheers

 

[rtbcomp]

Just make sure the scrap you use is flat.

 

[Wallace]

As above and the thicker the better. You can also pre-heat the plate to prevent it drawing the welding heat off to get better penetration with a smaller welder.

 

[octo0072000]

or just do it the old fashioned way let it warp and then file it flat

 

[rtbcomp]

^^ That's fine if the holes still line up with the studs. My Landrover manifold warped in use so much I couldn't get it to fit back on.

 

[Coo]

He did have another manifold just in case !

Although little more work drilling holes...I will definitely clamp it next time.
...and let it cool naturally.

Cheers all.

 

[Richard.]

As with the comments above clamping that down will help a lot. Distortion is caused by localised heat input. Another thing I would suggest is crank up your machine to a setting that allows you to whip round them nice and quickly. Having your set turned down low and dribbling it in slowly creates more heat input than wacking things up a bit and picking up the travel. Clamp it down and pick things up a bit.

 

[KemppiFrog]

As with the comments above clamping that down will help a lot. Distortion is caused by localised heat input. Another thing I would suggest is crank up your machine to a setting that allows you to whip round them nice and quickly. Having your set turned down low and dribbling it in slowly creates more heat input than wacking things up a bit and picking up the travel. Clamp it down and pick things up a bit.

Like that approach. Got a Lotus S 7 four branch in right now. Corroded and warped flanges. Going to mig extra plates (3mm) onto the face of each after grinding them a bit flatter. Odd thing is, the original joints are all brazed?
Nice bit of flat 12mm plate to clamp the whole thing to while welding. Bit like when I used to gas weld the monal pipes for Gypsy Majors, as used in DH Tiger Moths and assorted Austers and others.

 

[Coo]

Nice one Richard, combination of both sound like perfect solution...

Cheers

 

[Richard.]

Definatly. Distortion is a problem I help out a lot with to reduce. Design and mechanical restraint play a big part in keeping things from pulling along with heat input reduction. Tell someone to reduce heat input and more often than not the power is turned down. But naterally the travel has to go down too in order to weld it. This increases the localisation of the heat input by keeping it in one place for a long time and then distortion becomes worse. By cranking it up a gear you can ensure good weld fusion while you whip round the joint at a decent pace ensuring the heat doesn't become too localised.

 

[Chris Stevens]

I would think that would be pretty straightforward job to do with a 200amp pro standard set, but might be problematic with something which simply doesnt have the power for thicker materials?