Welding 6061

[doorsRus]

This is the problem I have. I need the advice of experienced welder
I have a project to build an aluminum door for an aircraft. It is an airstair door. Approx. 4 ft by 5 ft. It is made up of many sheetmetal parts all 6061. All the same thickness .063. Some parts will be bent to shape on a brake. Others will be cold formed to shape using a shrinker stretcher. All the parts will then be put in a jig fixture for welding, which will result in essentially a shell. The problem that a previous manufacturer had was warping.
I saw at one time a welder first tacking together, than welding little sections (approx 1 inch) at time at opposing locations. I think it was for allowing even heating of the aluminum. I would think with the addition of "clamping until cooling" that this might reduce the warpage.
Is this correct?
Karl

 

[Ron]

Thin 6061 aluminum can be welded successfully using either of the methods you described. One reason for not clamping is that the amount of "warp" can be seen during the welding process and compensated accordingly. This is pretty subjective and depends greatly on the experience of the welder. Clamping induces residual stresses that may or may not hurt your finished part. Most likely with the shapes you are welding, there will be little detriment to clamping. You should use the GTAW welding process to maintain low, concentrated heat input and affect a smaller stress area of the alloy.