Fusion Welding

[atmal]

I am fusion welding a rail that is approximately 8ft long. It has multiple components being welded with approximately 118 fusion welds. The parts are all within tolerance and I am welding from one end to the other. I find that the part is reaching thermal expansion. What is the best way to counteract this?

 

[patprimmer]

Start from the middle and work out, making each weld on alternate sides.

Allow cooling time between welds.



Regards

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[atmal]

Thank for the response. Based on cycle time cooling is not viable. Any other suggestions?

 

[TVP]

Create a proper weld fixture and alternate the side to be welded as patprimmer mentioned. Cooling can be improved by using fans if necessary.

 

[HDS]

1) preheating and a good fixture
maintain a very consistent environment such as room temp

2) If you are very consistent environment and still have problems just adjust the positions until the parts come out right.

 

[dkelly]

This is very common when welding frame rails, and is one of the reasons why some trucks only have three wheels in contact with the road. Try these.
1. document weld procedure very closely
2. repeat weld process exactly the same each time
3. as mentioned earlier try to alternate or balance welds to reduce the effect of thermal expansion as much as possible.
4. once you have a stable part/process and you can predict how much the part is moving during the weld process, now you can go back to your weld fixture and introduce a little "pre-bend" in the opposite direction so that your parts come out straight.

Been there, done that, got the scars

danno

 

[Tmoose]

I think "thermal expansion" is what happens whenever metal gets warm, and "goes away" when things get back to room temp. I >think< Atmal's dilemma may be the rail is no longer straight enough after the welding is done and back to room temp, and may indicate the residual weld stresses are at least partially the cause.

There are some good hints here about avoiding weld distortion, many already mentioned by others.

http://www.lincolnelectric.com/knowledge/articles/content/distortion.asp